U.S. patent application number 14/259076 was filed with the patent office on 2014-10-23 for lift gate load elevator with columnar power assemblies.
This patent application is currently assigned to MAXON INDUSTRIES, INC., dba MAXON LIFT CORP.. The applicant listed for this patent is MAXON INDUSTRIES, INC., dba MAXON LIFT CORP.. Invention is credited to Karapet Ablabutyan.
Application Number | 20140314534 14/259076 |
Document ID | / |
Family ID | 46047899 |
Filed Date | 2014-10-23 |
United States Patent
Application |
20140314534 |
Kind Code |
A1 |
Ablabutyan; Karapet |
October 23, 2014 |
LIFT GATE LOAD ELEVATOR WITH COLUMNAR POWER ASSEMBLIES
Abstract
A lifting system includes a vertically extending parallel pair
of fixedly spaced apart guide surfaces, a linear actuator suspended
vertically between said pair of guide surfaces, a vertically
elongate runner member having a pivotal connection to a lower end
of said linear actuator to be vertically reciprocated by said
actuator, a load bearing member at a lower end of said runner
member at a location spaced downwardly from said pivotal connection
and a vertically spaced apart pair of sliding contact members on
said runner member for relatively slidable contact with said pair
of guide surfaces during vertical reciprocation of said runner
member by said actuator. Each of said contact members comprises a
projecting contact pad having a concave surface for slidable
contact with one of said guide surfaces.
Inventors: |
Ablabutyan; Karapet;
(Glendale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAXON INDUSTRIES, INC., dba MAXON LIFT CORP. |
Santa Fe Springs |
CA |
US |
|
|
Assignee: |
MAXON INDUSTRIES, INC., dba MAXON
LIFT CORP.
Santa Fe Springs
CA
|
Family ID: |
46047899 |
Appl. No.: |
14/259076 |
Filed: |
April 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12945628 |
Nov 12, 2010 |
8740539 |
|
|
14259076 |
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Current U.S.
Class: |
414/545 |
Current CPC
Class: |
B60P 1/4421
20130101 |
Class at
Publication: |
414/545 |
International
Class: |
B60P 1/44 20060101
B60P001/44 |
Claims
1. A lift comprising: a vertically extending parallel pair of
fixedly spaced apart guide surfaces; a linear actuator suspended
vertically between said pair of guide surfaces; a vertically
elongate runner member having a pivotal connection to a lower end
of said linear actuator to be vertically reciprocated by said
actuator; a load bearing member at a lower end of said runner
member at a location spaced downwardly from said pivotal
connection; and a vertically spaced apart pair of sliding contact
members on said runner member for relatively slidable contact with
said pair of guide surfaces during vertical reciprocation of said
runner member by said actuator, a first one of said sliding contact
members being mounted at an upper end of said runner member, a
second of said sliding contact members being mounted on an
intermediate portion of said runner member between said first
sliding contact member and said pivotal connection, wherein said
pair of sliding contact members are mounted on opposite sides of
said runner member for contact with opposite ones of said pair of
guide surfaces; wherein each of said sliding contact members
comprises a projecting contact pad having a curved surface for
slidable contact with one of said guide surfaces; wherein each of
said sliding contact members comprises a self-adjusting mounting
mechanism configured such that each of said contact pads is
pivotally mounted on the runner member, allowing axial displacement
of each sliding contact member relative to the corresponding one of
said guide surfaces, for maintaining substantial uniform contact
therebetween substantially throughout the axial width of the
contact pad of that sliding contact member.
2. The lift of claim 1, wherein: each of said pair of sliding
contact members comprises a spaced apart tandem pair of contact
pads on a support member pivotally mounted on said runner member,
each of the contact pads having a curved surface for slidable
contact with one of said guide surfaces.
3. The lift of claim 2, wherein: a first one of said sliding
contact members is at a rear side of said lift; a second one of
said sliding contact members is at a forward side of said lift; and
said load bearing member is configured to support a load at said
rear side of said lift for biasing, via said runner member, said
second contact member against a front one of said guide surfaces
and biasing said second contact member against a rear one of said
guide surfaces.
4. The lift of claim 3, wherein: each of said guide surfaces
comprises a curved track surface for contact with one of said
contact pads; each of said contact pads and each of said track
surfaces has substantially the same radius for substantially
uniform mating contact therebetween essentially throughout the
axial width of said contact pad; said contact pads and said track
surfaces having the centers of their respective radii within a
common vertical plane substantially bisecting said contact pads and
said track surfaces.
5. The lift of claim 4, wherein: said pair of sliding contact
members and said pivotal connection of said runner member are so
oriented relative to one another such that said longitudinal axis
of said runner member is misaligned relative to a longitudinal axis
of said guide surfaces.
6. The lift of claim 5, further comprising: a pair of clearance
contact members corresponding to the sliding contact members, each
clearance contact member mounted on the runner member essentially
opposite a corresponding sliding contact member, each clearance
contact member configured for slidable contact with one of said
guide surfaces.
7. The lift of claim 6, wherein: each clearance contact member
comprises a clearance pad having a substantially planar surface for
slidable contact with one of said guide surfaces.
8. The lift of claim 5, wherein: each of said guide surfaces
comprises an arcuately convex track surface for contact with one of
said contact pads; and each of said contact pads comprises an
arcuately concave surface for mating contact with one of said
convex track surfaces.
9. The lift of claim 5, wherein: said actuator is pivotally
suspended on an axis transverse to a plane including said pair of
guide surfaces; and said pivotal connection of said runner member
and said actuator has an axis parallel to said transverse pivot
axis of said actuator and horizontally offset from a longitudinal
axis of said runner member.
10. The lift of claim 5, wherein: wear between said contact pads
and said track surfaces permits displacement of said longitudinal
axis of said runner member toward alignment with said longitudinal
axis between said tracks while maintaining substantially uniform
contact between said contact pads and said track surfaces.
11. A liftgate comprising: a vertically spaced apart parallel pair
of vertically extending columns having inner open sides confronting
one another, each column including: a linear actuator suspended
vertically between said pair of guide surfaces; a vertically
reciprocable runner mechanism telescopically mounted within the
column, the runner mechanism comprising a vertically elongate
runner member having a pivotal connection to a lower end of said
linear actuator to be vertically reciprocated by said actuator; a
load bearing member at a lower end of said runner member at a
location spaced downwardly from said pivotal connection; a
vertically extending parallel pair of fixedly spaced apart guide
surfaces; and a vertically spaced apart pair of sliding contact
members on said runner member for relatively slidable contact with
said pair of guide surfaces during vertical reciprocation of said
runner member by said actuator, a first one of said sliding contact
members being mounted at an upper end of said runner member, a
second of said sliding contact members being mounted on an
intermediate portion of said runner member between said first
sliding contact member and said pivotal connection, wherein said
pair of sliding contact members are mounted on opposite sides of
said runner member for contact with opposite ones of said pair of
guide surfaces; wherein each of said sliding contact members
comprises a projecting contact pad having a curved surface for
slidable contact with one of said guide surfaces; wherein each of
said sliding contact members comprises a self-adjusting mounting
mechanism configured such that each of said contact pads is
pivotally mounted on the runner member, allowing axial displacement
of each sliding contact member relative to the corresponding one of
said guide surfaces, for maintaining substantial uniform contact
therebetween substantially throughout the axial width of the
contact pad of that sliding contact member.
12. The liftgate of claim 11, further comprising: a platform
section having a pivotal connection along a forward edge thereof to
lower ends of said pair of runner members at the load bearing
members for movement between a substantially vertically erect
position and a rearwardly projecting horizontal load bearing
position.
13. The liftgate of claim 11, wherein: each of said pair of sliding
contact members comprises a spaced apart tandem pair of contact
pads on a support member pivotally mounted on said runner member,
each of the contact pads having a curved surface for slidable
contact with one of said guide surfaces; a first one of said
sliding contact members is at a rear side of said lift; a second
one of said sliding contact members is at a forward side of said
lift; said load bearing member is configured to support a load at
said rear side of said lift for biasing, via said runner member,
said second contact member against a front one of said guide
surfaces and biasing said second contact member against a rear one
of said guide surfaces.
14. The liftgate of claim 13, wherein: each of said guide surfaces
comprises a curved track surface for contact with one of said
contact pads; each of said contact pads and each of said track
surfaces has substantially the same radius for substantially
uniform mating contact therebetween essentially throughout the
axial width of said contact pad; said contact pads and said track
surfaces having the centers of their respective radii within a
common vertical plane substantially bisecting said contact pads and
said track surfaces; said pair of sliding contact members and said
pivotal connection of said runner member are so oriented relative
to one another such that said longitudinal axis of said runner
member is misaligned relative to a longitudinal axis of said guide
surfaces.
15. The liftgate of claim 14, further comprising: a pair of
clearance contact members corresponding to the sliding contact
members, each clearance contact member mounted on the runner member
essentially opposite a corresponding sliding contact member, each
clearance contact member configured for slidable contact with one
of said guide surfaces; wherein each clearance contact member
comprises a clearance pad having a substantially planar surface for
slidable contact with one of said guide surfaces.
16. The liftgate of claim 15, wherein: each of said guide surfaces
comprises an arcuately convex track surface for contact with one of
said contact pads; and each of said contact pads comprises an
arcuately concave surface for mating contact with one of said
convex track surfaces.
17. The liftgate of claim 15, wherein: said actuator is pivotally
suspended on an axis transverse to a plane including said pair of
guide surfaces; and said pivotal connection of said runner member
and said actuator has an axis parallel to said transverse pivot
axis of said actuator and horizontally offset from a longitudinal
axis of said runner member.
18. The liftgate of claim 15, wherein: wear between said contact
pads and said track surfaces permits displacement of said
longitudinal axis of said runner member toward alignment with said
longitudinal axis between said tracks while maintaining
substantially uniform contact between said contact pads and said
track surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/945,628 filed on Nov. 12, 2010, the disclosure of which
is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to load elevators or
lifts and, more particularly, to hydraulically operated
synchronized dual lift systems.
BACKGROUND OF THE INVENTION
[0003] A dual lift system may comprise a parallel pair of
vertically extending standards, posts or columns, each having a
vertically disposed hydraulic cylinder for vertically raising and
lowering a load carried by the pair of cylinders. The pair of
cylinders are actuated from a single source of hydraulic power and
the hydraulic circuit contains a flow divider distributing
hydraulic flow to each of the cylinders. Typically, the flow
divider comprises a spool valve spanning the outlets to the pair of
cylinders, the spool being counter-balanced by opposing springs at
its opposite ends. This type of flow divider tends to lose its
initial stabilizing setting over time, requires frequent
readjustment, and is often unreliable in operation under conditions
where the load is off-center relative to the pair of columns.
[0004] A load elevator has been used in the form of a liftgate
comprising a rigid H-frame having a parallel pair of upstanding
columns. The columns contain a corresponding pair of vertically
disposed hydraulic cylinders having runners interconnected by a
transverse heavy stabilizing bar typically supporting a two-section
foldable platform actuated on each side by an actuating linkage
system. However, the resulting H-frame is difficult to transport,
and the heavy stabilizing bar prevents folding of the platform
sections into a fully recessed condition wherein neither the
platform sections nor the linkage system parts protrude beyond a
rear plane of the pair of columns (requiring the driver to
frequently reposition the vehicle away from a dock surface for
added clearance to lower the folded platforms into a dock loading
position). Further, the stabilizing bar typically results in a
large gap between the dock and the interior of the vehicle body
requiring use of a dock plate to span the gap.
[0005] There are also liftgates comprising a vertical pair of
columns each containing a runner assembly mounted for vertical
reciprocation within the columns. Each runner is typically engaged
with interior tracks or surfaces of the companion column by means
of rollers. The contact is typically steel on steel and thus
induces high wear on the contacting parts and resulting
misalignment of the runner assembly relative to its column.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention provides a lifting system with
columnar power assemblies. In one embodiment the lifting system
comprises a vertically extending parallel pair of fixedly spaced
apart guide surfaces, and a linear actuator suspended vertically
between said pair of guide surfaces. The lifting system further
comprises a vertically elongate runner member having a pivotal
connection to the lower end of said linear actuator to be
vertically reciprocated by said actuator. The lifting system
further comprises a load bearing member at a lower end of said
runner member at a location spaced downwardly from said pivotal
connection.
[0007] The lifting system further comprises a vertically spaced
apart pair of sliding contact members on said runner member for
relatively slidable contact with said pair of guide surfaces during
vertical reciprocation of said runner member by said actuator, a
first one of said contact members being mounted at an upper end of
said runner member. The second of said contact members being
mounted on an intermediate portion of said runner member between
said first contact member and said pivotal connection, wherein said
pair of contact members are mounted on opposite sides of said
runner member for contact with opposite ones of said pair of guide
surfaces.
[0008] Wherein each of said contact members comprises a projecting
contact pad having a curved surface for slidable contact with one
of said guide surfaces. Wherein each of said contact members
comprises a self adjusting mounting mechanism configured such that
each of said contact pads is pivotally mounted on the runner
member, allowing axial displacement of each contact member relative
to the corresponding one of said guide surfaces, for maintaining
substantial uniform contact therebetween substantially throughout
the axial width of said contact pad.
[0009] The lifting system further comprises a pair of clearance
contact members corresponding to the sliding contact members, each
clearance contact member mounted on the runner member opposite a
corresponding sliding contact member, each clearance contact member
for slidable contact with one of said guide surfaces.
[0010] In another embodiment the lifting system comprises a
vertically extending parallel pair of fixedly spaced apart guide
surfaces, a linear actuator suspended vertically between said pair
of guide surfaces, a vertically elongate runner member having a
pivotal connection to a lower end of said linear actuator to be
vertically reciprocated by said actuator, and a load bearing member
at a lower end of said runner member at a location spaced
downwardly from said pivotal connection.
[0011] The lifting system further comprises a vertically spaced
apart pair of sliding clearance members mounted on said runner
member for relatively slidable contact with said pair of guide
surfaces during vertical reciprocation of said runner member by
said actuator, a first one of said sliding clearance members being
mounted at an upper end of said runner member, a second of said
sliding clearance members being mounted on an intermediate portion
of said runner member between said first sliding clearance member
and said pivotal connection, wherein said pair of sliding clearance
members are mounted on opposite sides of said runner member for
contact with opposite ones of said pair of guide surfaces.
[0012] Wherein each of said sliding clearance members comprises a
projecting contact pad having a surface for slidable contact with
one of said guide surfaces. Further, each of said sliding clearance
members comprises an adjustable mounting mechanism for adjustably
mounting the sliding clearance member on the runner member to
maintain substantial uniform contact therebetween essentially
throughout the axial width of said contact pad.
[0013] These and other features, aspects and advantages of the
present invention will become understood with reference to the
following description, appended claims and accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a lift gate mounted at the
rear of a freight vehicle, according to an embodiment of the
invention.
[0015] FIG. 2 is a fragmentary perspective view of the lower end
portion of the curb side column assembly of FIG. 1 and the
corresponding corner of the load platform, according to an
embodiment of the invention.
[0016] FIG. 2A is a view, partly in section, taken on the line A-A
of FIG. 2, according to an embodiment of the invention.
[0017] FIG. 2B is a partial exploded perspective view of the
platform pivot hinge construction at one side of the platform,
according to an embodiment of the invention.
[0018] FIG. 2C is a partial perspective view of the general area
shown in FIG. 2B, but from the opposite side, according to an
embodiment of the invention.
[0019] FIG. 3 is a partial perspective view of substantially the
same area as depicted in FIG. 2, but with the parts in different
relative positions, according to an embodiment of the
invention.
[0020] FIG. 4 is a partial elevational view of the inside of the
curb side columnar assembly and the fully raised and folded
platform assembly but also showing, in dotted outlines, fully
horizontally extended and intermediate partly folded positions of
the partially lowered platform assembly, according to an embodiment
of the invention.
[0021] FIG. 5 is a partial elevational view on the line 5-5 of FIG.
4, with parts broken away, showing a clearance recess at one side
of the folded platform, according to an embodiment of the
invention.
[0022] FIG. 6 is a perspective view of the liftgate of FIG. 1 but
with the platform sections in substantially the intermediate
position indicated in dotted outline in FIG. 4, according to an
embodiment of the invention.
[0023] FIG. 7 is a partial perspective view of the area of pivotal
interconnection of the two platform sections, particularly showing
portions utilized in constraining the corresponding chain during
folding and unfolding movement of the two platform sections,
according to an embodiment of the invention.
[0024] FIG. 8 is a partial elevational view taken in the direction
of the arrow 8 of FIG. 7, according to an embodiment of the
invention.
[0025] FIG. 9 is a partial sectional view taken on the line 9-9 of
FIG. 8, according to an embodiment of the invention.
[0026] FIG. 10 is a partial perspective view of the curb side
columnar assembly and corresponding side of the platform assembly,
the latter being shown on a fully closed and raised condition,
according to an embodiment of the invention.
[0027] FIG. 11 is a partial perspective view similar to FIG. 10,
but showing parts in their relative positions during lifting of the
platform assembly into the fully raised condition of FIG. 10,
according to an embodiment of the invention.
[0028] FIG. 12 is a side elevational view of the foldable platform
sections in an angularly separated condition, portions being cut
away to illustrate interior details of construction, according to
an embodiment of the invention.
[0029] FIG. 13 is a partial sectional view of a bumper pad area of
the main platform section shown in FIG. 12 and showing, in phantom
outline, a fully compressed condition of the bumper pad upon
complete closing of the outer platform section, according to an
embodiment of the invention.
[0030] FIG. 14 is a rear elevational view of a columnar assembly,
portions being cut away to show interior details of construction,
according to an embodiment of the invention.
[0031] FIG. 14A shows a perspective view of a loading bearing pad
for a columnar assembly, according to an embodiment of the
invention.
[0032] FIG. 14B shows an end view of a load bearing pad for a
columnar assembly, according to an embodiment of the invention.
[0033] FIG. 14C shows a perspective view of a mounted loading
bearing pad for a columnar assembly, according to an embodiment of
the invention.
[0034] FIG. 14D shows a perspective view of another mounted loading
bearing pad for a columnar assembly, according to an embodiment of
the invention.
[0035] FIG. 14E shows a perspective view of a mounted clearance pad
for a columnar assembly, according to an embodiment of the
invention.
[0036] FIG. 14F shows a perspective view of another mounted
clearance pad for a columnar assembly, according to an embodiment
of the invention.
[0037] FIG. 14G shows a perspective view of mounted load bearing
and clearance pads for a columnar assembly, according to an
embodiment of the invention.
[0038] FIG. 15 is an elevational view of the inside of the curb
side columnar assembly when its runner assembly is in a fully
retracted position, with parts cut away to show interior details of
construction and the curb side power mechanism for folding and
unfolding of the platform sections, according to an embodiment of
the invention.
[0039] FIG. 16 is a rear elevational view of the columnar assembly
of FIG. 15, portions being cut away to illustrate interior details
of construction, according to an embodiment of the invention.
[0040] FIG. 17 is a top view taken on the direction 17-17 of FIG.
15, the top cover of the assembly having been removed, according to
an embodiment of the invention.
[0041] FIG. 18 is a transverse sectional view taken on the line
18-18 of FIG. 15, according to an embodiment of the invention.
[0042] FIG. 19 is a partial sectional view taken on the line 19-19
of FIG. 16, according to an embodiment of the invention.
[0043] FIG. 20 is a partial vertical sectional view taken of the
area 20 of FIG. 16, according to an embodiment of the
invention.
[0044] FIG. 21 is a top view taken in the direction 21 of FIG. 14,
the cover of the assembly having been removed, according to an
embodiment of the invention.
[0045] FIG. 22 is a sectional view taken on the line 22-22 of FIG.
14, according to an embodiment of the invention.
[0046] FIG. 23 is a partial sectional view taken on the line 23-23
of FIG. 14, according to an embodiment of the invention.
[0047] FIG. 24 is a partial elevational view of the lower end
portion of the forward face of a column assembly, according to an
embodiment of the invention.
[0048] FIG. 25 is a partial elevational view of the lower end of
the forward side of a column assembly, according to an embodiment
of the invention.
[0049] FIG. 26 is a schematic vertical sectional view illustrating
interaction of a runner assembly relative to its corresponding
support column, the parts being illustrated in phantom outline in
an exaggerated condition under conditions of displacement due to
stress, according to an embodiment of the invention.
[0050] FIG. 27 is a staggered section taken on the line 27-27 of
FIG. 26 showing the relative relationship of the parts in a normal
condition, according to an embodiment of the invention.
[0051] FIG. 28 is a view similar to FIG. 27, but showing the parts
in the exaggerated stress condition shown in phantom outline in
FIG. 26, according to an embodiment of the invention.
[0052] FIGS. 29 and 30 show partial elevational views of opposite
faces of a runner showing the mounting of slider pads thereon,
according to an embodiment of the invention.
[0053] FIG. 31 shows a left side view of fixed angle load bearing
pads, and adjustable clearance pads mounted on a runner, in
relation to tracks, according to an embodiment of the
invention.
[0054] FIG. 32 shows an end view of fixed angle load bearing pads,
and adjustable clearance pads mounted on a runner, in relation to
tracks, according to an embodiment of the invention.
[0055] FIG. 33 shows a right side view of fixed angle load bearing
pads, and adjustable clearance pads mounted on a runner, in
relation to tracks, according to an embodiment of the
invention.
[0056] FIG. 34 shows an end view opposite to FIG. 32, according to
an embodiment of the invention.
[0057] FIG. 35 shows a perspective view of a load bearing pad with
mounting brackets, according to an embodiment of the invention.
[0058] FIG. 36 shows a perspective view of a load bearing pad
without mounting brackets, according to an embodiment of the
invention.
[0059] FIG. 37 shows a perspective view of an adjustable clearance
pad, having a contact pad with an essentially rectangular shape and
tapered profile and planar contact surface for contact with tracks,
according to an embodiment of the invention.
[0060] FIG. 38 shows another perspective view of an adjustable
clearance pad, according to an embodiment of the invention.
[0061] FIGS. 39A-39B show side views of mountings for adjustable
clearance pads, according to an embodiment of the invention.
[0062] FIGS. 39C-39D show top views of a mounted adjustable
clearance pad and a fixed angle contact pad, respectively,
according to an embodiment of the invention.
[0063] FIGS. 40A-40C show side views of mounted adjustable
clearance pads, according to an embodiment of the invention.
[0064] FIG. 41 shows a schematic drawing of the equalizing circuit
for the main power cylinders of the curb side and street side
columnar power assemblies, according to an embodiment of the
invention.
[0065] FIG. 42 shows a schematic representation of the several
components of a liftgate of the invention as bundled for shipment
to a point of application to a vehicle or other point of use,
according to an embodiment of the invention.
[0066] FIG. 43 is an elevational view of the inside of a columnar
assembly similar to FIG. 15, but showing a combination of contact
pads and rollers on a runner assembly, according to an embodiment
of the invention.
[0067] FIG. 44 is a sectional view similar to FIGS. 21 and 22
wherein guide surfaces are disposed on runner and the sliding
contact members are disposed on the inner walls of the column,
according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0068] The present invention provides a lifting system with
columnar power assemblies. In one embodiment the lifting system
includes a vertically extending parallel pair of fixedly spaced
apart guide surfaces, a linear actuator suspended vertically
between said pair of guide surfaces, a vertically elongate runner
member having a pivotal connection to a lower end of said linear
actuator to be vertically reciprocated by said actuator, a load
bearing member at a lower end of said runner member at a location
spaced downwardly from said pivotal connection and a vertically
spaced apart pair of sliding contact members on said runner member
for relatively slidable contact with said pair of guide surfaces
during vertical reciprocation of said runner member by said
actuator.
[0069] A first one of said contact members is mounted at an upper
end of said runner member. The second of said contact members is
mounted on an intermediate portion of said runner member between
said first contact member and said pivotal connection, wherein said
pair of contact members are mounted on opposite sides of said
runner member for contact with opposite ones of said pair of guide
surfaces. Each of said contact members comprises a projecting
contact pad having a curved surface, such as concave or convex
surface, for slidable contact with one of said guide surfaces.
[0070] FIG. 1 shows an embodiment of the invention implemented in
liftgate L. The liftgate is shown mounted on the rear vertical
corner posts of the rear end opening of a truck, van, or trailer
body 40. The liftgate L comprises a right hand or curb side
columnar power assembly C, a left hand or street side columnar
power assembly S, and a platform assembly P. The curb side columnar
power assembly C mounts a downwardly extendable and upwardly
retractable curb side runner assembly RC. The street side columnar
power assembly S includes a companion downwardly extendable and
vertically retractable street side runner assembly RS. Further,
telescopically mounted runner assemblies RS and RC are
hydraulically operable in unison for raising and lowering the
platform assembly P between ground level and the level of a bed 41
of the truck, van, or trailer body 40. The liftgate L further
comprises a threshold plate T secured in horizontally extending
position to the rear edge of the bed 41. The threshold plate T has
a triangular profile (i.e., cross-sectional configuration) rigidly
secured, as by welding, to the sill of the truck bed such that one
flat face of the plate comprises a flush extension of the bed
41.
[0071] FIG. 4 shows a partial elevational view of the inside of the
curb side columnar power assembly C and the fully raised and folded
platform assembly P but also showing, in dotted outlines, fully
horizontally extended and intermediate partly folded positions of
the partially lowered platform assembly P, according to an
embodiment of the invention. Generally, the columnar power
assemblies C and S may be mirror image assemblies of identical
components. In one embodiment, the curb side power assembly C
differs however, in that the lower end portion of its runner
assembly RC is fitted with a preferably hydraulically powered crank
mechanism, designated generally by the numeral 42, to effect
rotation of the platform sections through the various stages
indicated in FIG. 4. Accordingly, in the ensuing description, like
components of the pair of columnar power assemblies C and S will be
identified by the same numeral.
[0072] The platform assembly P is illustrative of one of several
different kinds of platforms that may be employed with the lift of
this invention. FIG. 5 is a partial elevational view on the line
5-5 of FIG. 4, with parts broken away, showing a clearance recess
at one side of the folded platform assembly P, according to an
embodiment of the invention. In the illustrated case, the platform
assembly P comprises a main or forward platform section 78 and a
rear platform section 79 that, along its rear edge, is fitted with
a retention ramp 80.
[0073] At opposite sides of its forward edge the main section 78 is
pivotally supported by the bearings 75 (FIG. 15) for rotation
between the horizontally extending position illustrated and a
vertically erect position between the runner assemblies RC and
RS.
[0074] The adjoining edges of the main platform section 78 and rear
platform section 79 are pivotally interconnected by a butt hinge
means 81 (FIG. 5) so oriented that when the main platform section
78 is turned upwardly from the FIG. 1 position, the underside of
the rear platform section 79 swings toward the underside of the
main platform section 78 as indicated in FIG. 4. The retention ramp
80 may be of the type that is invertible and latchable over the top
or load surface at the rear end of the rear platform section 79.
However, it should be understood that the pair of lifting columns
of this invention have utility with single piece platforms and
types of multi-piece platforms other than that depicted in FIG.
1.
[0075] As shown in FIG. 5, the main platform section 78 comprises a
rigid rectangular frame, preferably made of structural tubing of a
square cross section, including opposite side frame members 82 and
a transverse pair of forward and rear edge frame members 83. FIG.
12 is a side elevational view of the foldable platform sections 78,
79, in an angularly separated condition, portions being cut away to
illustrate interior details of construction, according to an
embodiment of the invention. The rear platform section 79 has a
similar frame, including a pair of opposite side frame members 82,
84. Both frames are covered on their top side by a rectangular
sheet metal skin 85, which may be diamond plate, welded to the
underlying frame.
[0076] Each of the platform sections 78 and 79 is further
structurally reinforced by a single seamless rectangular sheet 86
of corrugated metal on the underside thereof, congruently fitted
within and, at peripheral portions, welded to the corresponding
platform frame. Thus, the corrugated metal sheet 86 preferably is
of the section or profile shown in FIG. 12 comprising flat crests
and flat roots 86-1, the root sections being welded at spaced
intervals therealong to the underside of the platform skin 85. The
effect is thus one of a plurality of laterally spaced apart
transverse hollow beams defined by the corrugated sheet that
rigidly support loads placed on the platform surface.
[0077] Rotation of the main platform section 78 between vertical
and horizontal positions is effected by the powered crank means 42.
In order to effect corresponding rotation of the rear platform
section 79, a collapsible linkage system is provided that is
interconnected between the platform sections 78,79 and the runner
assemblies RC and RS.
[0078] FIG. 15 is an elevational view of the inside of the curb
side columnar power assembly C when its runner assembly RC is in a
fully retracted position, with parts cut away to show interior
details of construction and the curb side power mechanism for
folding and unfolding of the platform sections 78, 79 (FIG. 4),
according to an embodiment of the invention. FIG. 16 is a rear
elevational view of the curb side columnar power assembly C of FIG.
15, portions being cut away to illustrate interior details of
construction, according to an embodiment of the invention.
[0079] FIG. 18 is a transverse sectional view taken on the line
18-18 of FIG. 15, according to an embodiment of the invention. FIG.
19 is a partial sectional view taken on the line 19-19 of FIG. 16,
according to an embodiment of the invention. FIG. 20 is a partial
vertical sectional view taken of the area 20 of FIG. 16, according
to an embodiment of the invention.
[0080] Referring to FIGS. 1, 4 and 18-20, each of the columnar
power assemblies C and S comprises a vertically elongate metal
channel or column 45 having a block C-shaped profile. Each column
has a web section 45-1, a front or forward wall 45-2, and a rear
wall 45-3. The walls 45-2 and 45-3 are parallel to another and,
along their edges remote from the web section 45-1, are integrally
formed with inwardly turned flanges 45-4 and 45-5, respectively,
disposed parallel to the web 45-1.
[0081] As is shown in FIG. 18, the flanges 45-4 and 45-5 are
relatively narrow and thus define a wide clearance gap between the
confronting parallel edges thereof. When the components of the
liftgate are mounted on a truck body 40, the front or forward wall
45-2 of the corresponding column is fitted on the rear face of the
corresponding rear corner post of the rear end opening of the
vehicle as by welding or bolting thereto. Further, as indicated in
FIGS. 18-19, when mounted in place, the rear wall 45-3 of the
column 45 is substantially flush with the corresponding side of the
van body 40 and the elongate clearance gaps between flanges 45-4
and 45-5 of the parallel pair of columnar power assemblies C and S
confront one another (FIG. 1).
[0082] Under a box-like column cap 44 (FIG. 14), the upper end of
each column 45 rigidly mounts a parallel spaced apart pair of
upstanding power cylinder support plates 46 (FIG. 16), oriented
parallel to the major axis of the column profile having opposite
ends resting on the column front and rear walls 45-2 and 45-3. The
power cylinder support plates 46 are formed with coaxial holes to
seat opposite ends of a transversely oriented cylinder support pin
47. The cylinder support pin 47 pivotally supports a cap 48
comprising the butt end of an elongate fluid-powered linear
actuator or cylinder 49 (FIG. 15) that is thus suspended from the
cylinder support pin 47 to hang within the cavity of the column 45
so that the lower end of the power cylinder is displaceable in a
direction parallel to said major axis of the column 45. The
cylinder 49 may be of either the single or double acting type and
encloses a piston-powered rod 57 (FIG. 16) that is extendable and
retractable through the lower end of the cylinder 49.
[0083] Also mounted within each column 45 is a tubular runner
member 50 preferably having the rectangular cross-sectional
configuration shown in FIG. 22. The vertically elongate runner
member 50 is of a length such that when it is in the fully extended
position of FIG. 1 a major portion of the length of the runner
remains supported within the corresponding column 45. The runner
member 50 is suspended from the piston-powered rod 57 by means of a
runner support pin 51 having opposite ends journalled in an
opposite pair of sidewalls of the runner member 50 on an axis
parallel to that of the cylinder support pin 47. As is indicated in
FIGS. 14, 15 and 16, the runner support pin 51 is located within a
lower end portion of the runner member 50.
[0084] The major axis of the profile of tubular runner member 50 is
parallel to the major profile axis of the corresponding column 45
so that an opposite parallel pair of sidewalls 50-1 and 50-2 of the
runner are parallel to the web section 45-1 of the corresponding
column 45. The major axis of the runner member 50 is substantially
shorter than that of the profile of the corresponding column 45
such that there is a substantial clearance between the front and
rear faces 50-3 and 50-4 (FIG. 18) of the runner member 50 and
corresponding front and rear faces 45-2 and 45-3 respectively of
the corresponding column 45. Within these clearances, the column 45
is fitted with an elongate front guide track 52 and a rear guide
track 53 (FIG. 15).
[0085] The front and rear guide tracks 52, 53 extend over
substantially all of the vertical length of the corresponding
column 45. The front guide track 52 is fitted between and within
the internal corners of the front wall 45-2 of the column 45 as by
having opposite edges of the track welded to the internal corners
of the column 45. The track is of uniform arcuate cross-sectional
configuration from end-to-end having an outwardly convex track
surface 52-1 of a uniform radius (e.g., about 3 inches or 7.62
centimeters), from side-to-side or edge-to-edge of the member. At
the same time, a clearance passage 54 is defined between the front
guide track 52 and the front wall 45-2 of the channel 45 through
which hydraulic conduits and electrical wires can be passed from
one end to the other of the track.
[0086] Similarly, the rear guide track 53 is fitted into the
internal opposite corners at the rear wall 45-3 of the
corresponding channel 45. The rear guide track 53 also has an
outwardly convex track surface 53-1, preferably of the same uniform
radius from side-to-side as the track surface 52-1. However,
opposite longitudinal edges of the rear guide track 53 develop into
an opposite pair of straight flanges 55 (FIG. 20) whereby the track
defines a clearance passage 56 relative to the rear wall 45-3 of
the channel 45 that is of a larger cross-sectional area than the
clearance passage 54 at the front wall 45-2.
[0087] In order to support the platform assembly P on the runner
assemblies RC and RS, the lower end of each runner assembly RC, RS
is provided on the lower end of its inside face with a bearing
designated generally by the numeral 75. It will be understood that
the pair of bearings 75 are coaxially related. As shown in FIG. 15,
each bearing 75 has its axis closer to the front wall 50-3 of the
corresponding canted runner such that its axis, the axis of the
runner support pin 51 and the axis of the cylinder support pin 47
are all aligned substantially along the mid-line of the
corresponding columnar assembly C or S.
[0088] Referring to FIGS. 1, 4 and 6, the inside face of each
runner and cover assembly has an inwardly projecting pin 89 that
pivotally supports the root end of an arm 90 whose free end is
swingable on an axis 91 that is parallel to the axes of the
bearings 75 and platform hinge 81. The swingable free end of each
arm 90 is connected to an upper end of an elongate flexible member
such as link chain 92 whose other end is connected via a shackle to
a bracket 87 affixed to and upstanding from a rear platform side
frame member 84. An actuator arm 93 has a root end pivotally
connected at actuator axis 94 to the rear platform side frame
member 84 adjacent to the hinge 81 interconnecting the two platform
sections while an intermediate portion of the link chain 92 is
pivotally connected with a pin through a link at actuator axis 95
to a yoke comprising the outer end of the actuator arm 93. The
actuator axes 94 and 95 are parallel to the platform hinge 81.
[0089] The geometry of this linkage mechanism is substantially that
shown in FIG. 4 and effects co-rotation of the two platform
sections 78 and 79 substantially in the manner depicted therein in
solid and dotted outlines. FIG. 6 depicts an intermediate phase of
the folding of the two platform sections 78 and 79 while the link
chain 92 on each side remains in tension. As the forward platform
section advances farther toward the fully erect position, a chain
section 92-1 between the arm 90 and the actuator arm 93 and the
other chain section 92-2 between the actuator arm 93 and bracket 87
will become slack. Accordingly, the linkage system is adapted on
each side for maintaining both chain sections 92-1 and 92-2 in
substantial parallelism with the corresponding platform side frame
members 82 and 84.
[0090] FIG. 7 is a partial perspective view of the area of pivotal
interconnection of the two platform sections, particularly showing
portions utilized in constraining the corresponding chain during
folding and unfolding movement of the two platform sections,
according to an embodiment of the invention. FIG. 8 is a partial
elevational view taken in the direction of the arrow 8 of FIG. 7,
according to an embodiment of the invention. FIG. 9 is a partial
sectional view taken on the line 9-9 of FIG. 8, according to an
embodiment of the invention. As shown, the root end portion of the
actuator arm 93 has a generally L-shaped bracket 98 affixed
thereto. The bracket 98 has an upstanding flange 99 oriented
parallel to the actuator arm 93 for retaining the link chain 92
against sideward displacement outwardly of the platform sections.
The bracket 98 also includes a base portion 100 formed on one edge
with a notch 101 adapted to capture a link of the chain section
92-1 as the platform sections approach the fully closed condition.
As the chain section 92-1 slackens upon continued closing of the
platform sections, the actuator arm 93 is gravitationally biased
into substantial parallelism with the rear platform section 79,
coming to rest against a compressible pad 102 carried by a flange
of an L-shaped bracket 103 affixed to the corresponding side frame
member 84.
[0091] As is indicated by the two dotted outline positions in FIG.
4, folding and unfolding of the two platform sections 78 and 79 is
performed when they are at a lower position than their fully raised
condition shown in solid outline. In this connection, a means is
provided for biasing the two platform sections slightly apart when
in the partly lowered condition, while a camming means or the like
is provided for wedging the two platforms together into substantial
parallelism as they are raised into the fully elevated
condition.
[0092] FIG. 13 is a partial sectional view of a bumper pad area of
the main platform section shown in FIG. 12 and showing, in phantom
outline, a fully compressed condition of the bumper pad upon
complete closing of the outer platform section, according to an
embodiment of the invention. Referring to FIGS. 12 and 13, a
cup-like bracket 105 is seated and affixed, as by welding, on the
flat root section 86-1 of one of the valleys of the corrugated
metal sheet 86 of the main platform section 78. The bracket has a
flat dome portion 106, preferably protruding slightly above the
level of the crests of the corrugated sheet that centrally mounts a
fastener means 107 having a head portion externally of the dome to
secure a base portion of an annular cushion 108. The cushion 108 is
made of an elastomeric material and the axial dimension of the
cushion supporting structure is such that the annular face of the
cushion 108 protrudes into the space occupied by the rear platform
section 79 when it swings into parallelism with the forward
platform section 78.
[0093] In somewhat similar fashion the rear platform section 79 and
a root portion 86-1 of a transverse valley of its corrugated metal
sheet 86 is fitted with a cup-like bracket 110 on a radius relative
to the platform connection hinge 81 like that of the annular
cushion 108. The bracket 110 is configured with a preferably flat
dome section 111 for engagement with the annular surface of the
annular cushion 108 when the two platform sections are swung
together in the manner indicated by the directional arrow of FIG.
12. The bracket 110 has an axial dimension such that when the two
platform sections are brought into parallelism, as indicated in
phantom outline in FIG. 13, the annular cushion 108 is axially
compressed so that when the two platform sections are released from
the restraint holding them into parallelism, the annular cushion
108 expands to bias the rear platform section 79 away from the
forward platform section 83.
[0094] As shown in FIG. 4, a wedge block 114 is secured to the
outside of the actuator arm/bar 93 of the rear platform section 79
at a location intermediate its opposite ends. The wedge block 114
extends above an edge of the actuator arm 93 to present an exposed
flared surface 115 (FIG. 11).
[0095] FIG. 10 is a partial perspective view of the curb side
columnar power assembly C and corresponding side of the platform
assembly P, the latter being shown on a fully closed and raised
condition, according to an embodiment of the invention. FIG. 11 is
a partial perspective view similar to FIG. 10, but showing parts in
their relative positions during lifting of the platform assembly
into the fully raised condition of FIG. 10, according to an
embodiment of the invention. As shown in FIG. 11, the flange 45-5
of the column 45 has a vertically disposed cam block 117 secured
thereto, having a forward face 118 that inclines downwardly and
rearwardly in interfering alignment with the profiled wedge block
flared surface 115. Thus, when the two platform sections are lifted
from the position of FIG. 11 into the fully elevated position shown
in solid outline in FIGS. 10 and 4, the rear platform section 79 is
wedged into parallelism with the forward platform section 78 to
compress the annular cushion 108 of the forward platform section
78.
[0096] As shown in FIG. 3, the forward platform section 78 on each
of its side frame members 82 is fitted with a block 112 while each
of the runner assemblies RS and RC is fitted on its inner face with
a corresponding stop member 113. Each stop member 113 and the pair
of blocks 112 are on the same radius relative to the platform hinge
such that when the forward platform section 78 moves into the
vertical position the stop member 113 engages an elastomeric pad
116 fitted on the block 112.
[0097] When the two platform sections have been folded together and
raised and wedged together into the transit position, all of the
pads 102, 108, and 116 are in a compressed state. Thus, when the
folded platform sections are lowered to an extent that the wedge
block 114 is released from contact with the cam block 117, the
accumulated compressive forces are released by displacing the rear
platform section 79 rearwardly relative to the forward platform
section 78. This arrangement is adequate for partially opening the
platform sections before actuation of the crank means 42 in most
attitudes of the truck. However, a torsion spring 119 coaxially
supported on the bearing 75 is primarily relied on for this
purpose, particularly when the truck points downhill.
[0098] The powered crank means 42 (FIGS. 1-2) for effecting
rotation or turning of the platform sections is mounted at the
lower end of the curb side runner assembly RC. The crank means 42
comprising a preferably single acting fluid powered cylinder 120
having an upper butt end pivotally connected to the inside faces of
the runner member 50 by a pin 121 (FIG. 15) fixedly projecting
therebetween. The pin 121 is positioned adjacently beneath the
runner support pin 51 and slightly closer to the front wall 50-3 of
the runner 50 (FIG. 18). The cylinder 120 inclines downwardly
rearwardly and has a piston rod 122 projecting axially therefrom to
terminate in an eye 123 that is coaxially rotatably seated on a
crank pin 124.
[0099] FIG. 2A is a view, partly in section, taken on the line A-A
of FIG. 2, according to an embodiment of the invention. FIG. 2B is
a partial exploded perspective view of the platform pivot hinge
construction at one side of the platform, according to an
embodiment of the invention. FIG. 2C is a partial perspective view
of the general area shown in FIG. 2B, but from the opposite side,
according to an embodiment of the invention. Referring to FIGS. 2,
2A-2C, on opposite sides of the piston rod eye 123, opposite ends
of the crank pin 124 are journalled in aligned holes of a companion
pair of crank arms 126, which have an integral root crank hub 127
coaxially mounted on a platform pivot pin 128. The crank hub 127 is
keyed to the platform pivot pin 128 for co-rotation by a
diametrically oriented bolt 131. Inwardly of the crank hub 127 the
platform pivot pin 128 coaxially mounts a tubular member 132. A
concentric annular spacer 135 bears against the inside face of
crank hub 127. The tubular member 132 projects inwardly through the
bearing 75 mounted on the inside face of the runner member 50 at
its lower end. Coaxially with the bearing 75, the outer wall of the
runner member 50 mounts a bearing 136 that receives the outer end
of the platform pivot pin 128.
[0100] The inner end of the platform pivot pin 128 is keyed to the
platform by a fastener means 139 through a sleeve 138 fixed in the
adjacent end of the forward edge frame member 83 of the forward
platform section 78. The inner end of the tubular member 132 is
integrally formed with a radially extending tear drop crank arm 140
that is oriented in flush engagement with a plate 141 fixed on the
corresponding platform sideframe member 82. The outer end of the
crank arm 140 receives a bolt 142 that is anchored within the
platform side frame member 82. Accordingly, the forward platform
section 78 is keyed to the piston rod 122 of the power cylinder 120
such that they undergo movement simultaneously.
[0101] In order to provide clearance for actuation of the crank
means 42, the rear wall 50-4 (FIG. 18) and portions of the opposite
side walls 50-1 and 50-2 of the curb side runner member 50 are cut
away to provide a relief 145, in combination with the open lower
end of the runner member 50. The pivotal platform connection of the
runner assembly RS of the street side columnar power assembly S is
essentially the same as that of the runner assembly RC of the curb
side columnar power assembly C, except that, as the former is not
equipped with another platform operating cylinder, it has no
similar relief 145, nor the parts associated with the cylinder 120
such as the crank arms 126 and crank hub 127.
[0102] As will appear, the platform power cylinders 49 of the
columnar power assemblies S and C are operated synchronously in
order to maintain a horizontal attitude of the platform P during
raising and lowering thereof. However, to ensure a substantially
level attitude of the platform from side-to-side, notwithstanding
off-center loads or any lack of synchronicity between the pair of
cylinders, coating means are provided at each of the forward
corners of the forward platform section 78 such that any lagging of
one runner assembly behind the other is compensated for.
[0103] More specifically, as shown in FIG. 2, the corner plate 141
at each side of the forward platform section 78 projects above the
platform skin and has a channel gusset 143 welded between its
inside face and the platform sheet metal skin 85. At its forward
upper edge, the plate 141 has a laterally outwardly directed flange
146 that is substantially parallel to the platform skin and whose
underside is reinforced by another gusset 147 welded between the
underside of the flange 146 and the outer face of the plate 141. At
its free edge, the flange 146 has an integral upstanding flange 148
reinforced by a gusset plate 149 interposed between forward edges
of the flange 146 and flange 148.
[0104] Each of the runner assemblies is provided at the lower end
of its inner face with a box-like structure 152 into and out of
which the flange structure of the plate 141 is rotated by turning
of the forward platform section between vertical and horizontal
positions. Thus, at a position just above the bearing 75, each
runner member 50 is provided with a horizontally inwardly
projecting fixed plate 155 that is enclosed on its underside by
vertically depending rear plate 156 and an inside plate 157, the
parts being welded to each other and to the corresponding runner.
The rear plate 156 may be formed with a hole 159 to anchor an end
of torsion spring 119. Internally, the box-like structure 152 is
rigidly fitted with a plate or plates to define an internal slot
160 (FIG. 2A) that is open at the bottom and at the forward side of
the block structure 152.
[0105] As indicated in FIG. 2A, the internal slot 160 is oriented
such that rotation of the forward platform section 78 rotates the
flange 148 carried by the platform into and out of the internal
slot 160, the flange having tapered leading edges. Preferably,
there is only a small clearance between opposite sides of the
flange 148 and the internal walls of the box-like structure 152
defining the internal slot 160 so that the two parts are in effect
locked against lateral displacement when mutually engaged. The
engaged surfaces, being radially offset from the axis of the pair
of platform pivot pins 128, provide mechanical advantage to
stabilize the forward platform section 78 in a horizontal attitude
from side-to-side.
[0106] The curb side runner assembly C has a length of hydraulic
tubing 164 extending vertically through the clearance passage 56
within the rear guide track 53 alongside an electrical harness 165.
A clip assembly 166 is interiorly mounted on the rear wall 45-3 of
the column 45 at its lower end to support an assembly of fittings
167 and 168 providing fluid communication between the lower end of
the hydraulic tubing 164 and the lower end of a length of flexible
hose 169 (FIG. 20). The clip assembly 166 also supports and
restrains a portion of the harness 165 which passes therethrough to
turn upwardly to be trained alongside the flexible hose 169. The
flexible hose 169 and the companion portion of the harness 165 are
trained upwardly and reversely bent through a bight 174 with the
hose terminating at an elbow 170 providing fluid communication to
the interior of the cylinder to deliver fluid under pressure to the
underside of the piston therein (FIG. 15).
[0107] In order to control the flexure of the hose 169 and the
companion length of harness 165, during reciprocation of the runner
assembly, they are wrapped by a helically coiled wire 173 and
guided in an opposing pair of channels formed in the lower end of
the runner member 50 and column 45. More specifically, referring to
FIGS. 18 through 20, portions of the runner walls 50-1 and 50-4 are
cut away at an intermediate portion of their common corner to
fixedly mount a vertical length of channel 175 (FIG. 19) whose open
side faces the column 45. A similar channel is formed in the column
45 by removal of an edge portion of the rear guide track 53 in its
lower end portion adjacent to the flange 45-5 and by fixedly
mounting an elongate strip 176 extending between the inside face
rear wall 45-3 and the cut-away edge of the rear guide track 53. In
order to anchor one end of the helical wire 173, a fastener means
177 is connected between the column flange 45-5 and the strip 176
adjacent their lower ends to capture adjacent end coils of the wire
173.
[0108] The vertical extent of the channel 175 of the runner is so
oriented relative to the vertical extent of the opposing channel
formed by the strip 176 on the column 45 that when the runner is in
the raised position an upper end portion of the column channel
confronts a lower end portion of the channel 175 of the runner. A
portion of the electrical harness 165 extends upwardly through an
open upper end of the channel 175 and is trained interiorly through
the runner to terminate at a switch 178 at the upper end of the
runner operable externally of the runner as by an operator standing
on the platform or the bed of the truck to raise or lower the
platform. As will now be evident, the composite structure
comprising the companion portions of the flexible hose 169 and
harness 165 encased in the wire coil 173 flex through the running
bight 174 during reciprocation of the runner while the opposite leg
portions of the composite structure are protectively shielded
within their respective channels.
[0109] FIG. 24 is a partial elevational view of the lower end
portion of the forward face of a column assembly (such as the
street side column assembly S), according to an embodiment of the
invention. FIG. 25 is a partial elevational view of the lower end
of the forward side a column assembly (such as the street side
column assembly C), according to an embodiment of the invention.
Referring to FIGS. 24 and 25, the forward wall 45-2 of each of the
columns 45 is formed at its lower end with a window or aperture
180. Access is thus provided to the interior of the clearance
passage 54 under the corresponding front guide track 52 for the
electrical harnesses and fluid conduits appropriate for the
corresponding column assembly C or S. The accessible ends of the
electrical harnesses accessible at the aperture 180 are fitted with
plugs or receptacles for connection to and disconnection from an
external source of electrical power. Similarly, the ends of the
hydraulic conduits accessible through the aperture 180 are fitted
with couplings for connection to and disconnection from an external
source of pressurized hydraulic fluid.
[0110] As is shown in FIGS. 18 and 22, the corresponding conduits
and harnesses are trained vertically through the clearance passage
54. In the case of both column assemblies the fluid power circuit
includes a length of tubing 182 (FIG. 15) extending the length of
the corresponding cylinder 49 having valve controlled fluid
communication with the lower end of the corresponding cylinder
49.
[0111] FIG. 14 is a rear elevational view of a columnar assembly,
portions being cut away to show interior details of construction,
according to an embodiment of the invention. FIG. 21 is a top view
taken in the direction 21 of FIG. 14, the cover of the assembly
having been removed, according to an embodiment of the invention.
Referring to FIGS. 18 and 21, one electrical harness is trained
through the upper end of the corresponding column and thence
downwardly through the clearance passage 56 under the rear guide
track 53 for connection to the housings of a vertically spaced
apart series of lamps 190, 191 and 192 (FIG. 1) internally mounted
on and protected by the rear wall 45-3 of the corresponding channel
45. The lamp lenses protrude slightly rearwardly beyond the
external surface of the channel 45 but are protected against
breakage by a vertically extending flange 193 (FIG. 23), having
arcuate opposite end portions, externally affixed to the rear wall
45-3 of the channel 45, protruding rearward a dimension slightly
greater than the lenses. Preferably, the vertical array of lamps
190-192 is positioned above the level of the truck bed 41 (FIG. 1).
The lamps 190-192 may comprise stop lights, warning lights and turn
signals and, as is evident, because of their relationship relative
to the platform assembly P are not subject to being blanked out in
any phase of operation of the liftgate.
Self-Adjusting Load Bearing Pads and Fixed Angle Clearance Pads
[0112] As shown in FIGS. 16 and 22, the axis of pivotal connection
51 between the piston rod 57 and the runner member 50 is laterally
offset relative to the longitudinal axis of the runner to be more
adjacent to the forward wall 50-3 of the runner member 50. As shown
in FIG. 15, above the runner support pin 51, an upper portion of
the runner member 50 is fitted at the front and rear walls thereof
with vertically spaced apart self-adjusting load bearing, sliding
contact pads 59 and 60 (load pads), having sliding contact with
surfaces of the parallel tracks 53 and 52 (FIG. 14G),
respectively.
[0113] As can be seen from an inspection of FIGS. 15 and 18, the
longitudinal axis of the runner member 50 is slightly canted
relative to the vertical axis of the power cylinder 49 by virtue of
the location of the runner support pin 51 such that the runner
member 50 inclines slightly rearwardly and downwardly, which canted
attitude is maintained during reciprocation of the runner member 50
by the spaced self-adjusting sliding load pads 59 and 60 (FIG. 21).
In heavier duty applications, each load pad may be replaced by
multiple load pads.
[0114] As shown in FIGS. 18 and 22, at the upper end of the runner
member 50 portions of the rear face 50-4 and opposite side walls
50-1 and 50-2 are cut away to provide relief (clearance) for a
mounting means for the upper load pad 59. FIG. 26 is a schematic
vertical sectional view illustrating interaction of a runner
assembly relative to its corresponding support column, the parts
being illustrated in phantom outline in an exaggerated condition
under conditions of displacement due to stress, according to an
embodiment of the invention. In the example shown in FIG. 26, said
relief may take the form of the profile 61 which leaves a pair of
rearwardly projecting ears 62 formed in the opposite side walls
50-1 and 50-2 of the runner member 50. The confronting pair of ears
62 are formed with coaxial holes for the reception of opposite ends
of a pin 63, opposite ends of which pivotally support brackets 64
that mount/support contact pads 64C. Each pin 63 passes co-axially
through the hub of the corresponding bracket 64 to rotatably
support the same. Similarly, for mounting the lower lad pad 60, the
forward wall 50-3 and opposite side walls 50-1 and 50-2 of the
runner member 50 are relieved to define the profile 66 and spaced
ears 67 also seen in FIG. 26. As before, the ears 67 support
opposite ends of another pin 63 whose opposite ends, in turn,
pivotally support a bracket 64 mounting a respective contact pad
64C. In one example, each contact pad 64C has a rectilinear
footprint about 2 inches by 2 inches or 5.08 centimeters by 5.08
centimeters.
[0115] FIG. 14A shows a perspective view of a load pad 58
comprising tandem contact pads 64C supported by a bracket 64,
according to an embodiment of the invention. FIG. 14B shows an end
view of a load pad 58. Each of the contact pads 64C has a periphery
of concave configuration formed on a radius matingly complementary
to that of the surfaces of the guide tracks 52 and 53. FIG. 14C
shows a perspective view of a load pad 59 resting against rear
guide track 53, wherein the load pad 59 is an example of the load
pad 58. Further, FIG. 14D shows a perspective view of the load pad
60 resting against front guide track 52, wherein the load pad 60 is
an example of the load pad 58.
[0116] The contact pads 64C and guide tracks 52, 53, have the
centers of their respective radii within a common vertical plane
substantially bisecting the contact pads 64C and the track
surfaces. Load pads 59 and 60 are thus matingly engaged by the
track surfaces throughout their axial width. It should also be
observed that each of the load pads 59 and 60 is shorter in axial
length than the pins 63 and the space between confronting surfaces
of the corresponding pair of said ears 62, 67 (FIGS. 14C, 26). As a
result, each of the load pads 59, 60 is automatically axially
displaceable with respect to the pin 63 on which it is supported
relative to the corresponding track surfaces for maintaining
substantial uniform contact therebetween substantially throughout
the axial width of said contact pad 64C (e.g., upon deflection of a
track surface or wear of the load pads and/or track surfaces).
[0117] The contact pads 64C have a low coefficient of friction and
are adapted to cushion the runner member 50 during reciprocation
and against vibration, and may be made of a hard plastic material
or a high density polymer although a metallic material can also be
used.
[0118] FIG. 14G shows a perspective view of mounted load bearing
(contact) pads 59, 60 and clearance pads 70, for the runner member
50, according to an embodiment of the invention. Specifically, FIG.
14G shows a perspective view of an example assembly with the load
pads 59, 60 from FIG. 14A, and essentially rectangular and uniform
thickness clearance pads 70 from FIGS. 14E-F, mounted in relation
to the runner member 50 and the guide tracks 52, 53, according to
another embodiment of the invention. FIGS. 29 and 30 show partial
elevational views of opposite faces of the runner member 50 showing
the mounting of clearance pads (slider pads) 70 thereon, according
to an embodiment of the invention.
[0119] Specifically, the front face 50-3 of the runner member 50,
at a location opposite to the area of the upper load pad 59 mounted
on the rear face 50-4, is fitted with a clearance pad 70 of a
thickness to slidably engage the confronting front guide track 52.
As indicated in FIG. 30, the clearance pad 70 may be offset from
the midline of the runner and has beveled upper and lower edges.
FIG. 14E shows a perspective view of a mounted clearance pad 70 for
a columnar assembly, according to an embodiment of the
invention.
[0120] Similarly, the rear face 50-4 of the runner member 50, in an
area opposite the general area of the lower load pad 60, is fitted
with a similar clearance pad 70, the pads being held in place by
appropriate fastening means 71. FIG. 14F shows a perspective view
of another embodiment of the clearance pad 70. The clearance pads
70 are preferably made of a hard plastic material, having a low
coefficient of friction and are adapted to cushion the
corresponding runner during its reciprocation and against
vibration.
[0121] In one embodiment, the inside face of each runner member 50
is partially covered by a rectangular cover sheet 74 (FIGS. 1, 17)
having a slight clearance between its opposite vertical edges and
the inside flanges 45-4 and 45-5 of the corresponding column 45. In
vertical extent, the cover sheet 74 extends from about the upper
end of the corresponding runner member 50 downwardly to at least
cover the lower load pad 60.
[0122] In one embodiment, the side face 50-2 of the runner member
50 is externally fitted over a major portion of its vertical extent
with a wide pad 72 of a thickness to slidably engage the inside
face of the confronting web section 45-1 of the corresponding
column 45 (FIGS. 17, 18). In one embodiment, the side face 50-1 of
the runner member 50 is externally fitted over a major portion of
its vertical extent with a wide pad 72 of a thickness to slidably
engage the inside face of the cover sheet 74 of the column 45. The
wide pads 72 are preferably made of a hard plastic material, having
a low coefficient of friction and are adapted to cushion the
corresponding runner during its reciprocation and against
vibration.
[0123] According to an embodiment of the invention, the geometry of
the columnar power assemblies C and S automatically compensates for
wear occurring in the load pads 59 and 60. Also, the geometry of
the load pads 59 and 60 and guide tracks 53 and 52 maintain their
mutual contact irrespective of load pad wear and deflection of the
column walls supporting the guide tracks 53 and 52.
[0124] More particularly, as a result of the heretofore described
alignment of the cylinder butt end cylinder support pin 47 (FIG.
17), runner support pin 51 (FIG. 18), and platform bearings 75
(FIG. 15) and the resulting slightly canted attitude of the runner
member 50 within the column 45 (FIGS. 18, 26), loads on the
platform P are transmitted to the lower load pad 60 (FIG. 15) to
react against the front guide track 52, and to react the upper load
pad 59 against the rear track 53 through the upper load pad 59.
Accordingly, as wear occurs on the concave surfaces 64S of the load
pads 59 and 60, the runner member 50, by virtue of its support pin
51 to the piston rod of the cylinder 49 (FIGS. 14, 15, 41), at all
times biases load pads 59 and 60 into uniform contact with their
respective guide tracks 53, 52, regardless of reduction in load pad
thickness (e.g., diameter).
[0125] In this connection, the mounting of each load pad 59 and 60,
pivotally mounted via pin 63 (FIGS. 14C, 14D), uniformly
distributes the load from the runner member 50 on each load pad 59,
60. As wear occurs on the load pads 59, 60, the runner member 50
moves towards parallelism of its longitudinal axis with the
vertical axis of the corresponding column 45. Excessive wear of the
load pads may be indicated by the runner 50 coming into a reversely
canted attitude such that it slopes downwardly and forwardly of the
column 45, thereupon signaling an occasion for replacement of the
load pads 59, 60.
[0126] FIG. 26 is a schematic vertical sectional view illustrating
interaction of the runner assembly 50 relative to its corresponding
support column 45, the parts being illustrated in phantom outline
in an exaggerated condition under conditions of displacement due to
stress, according to an embodiment of the invention. FIG. 27 is a
staggered section taken on the line 27-27 of FIG. 26 showing the
relative relationship of the parts in a normal condition, according
to an embodiment of the invention. FIG. 28 is a view similar to
FIG. 27, but showing the parts in the exaggerated stress condition
shown in phantom outline in FIG. 26, according to an embodiment of
the invention.
[0127] Specifically, FIG. 26 shows in dotted outline a greatly
exaggerated depiction of the deflection of the opposite column
walls mounting the guide tracks 52 and 53, which is depicted in
solid outline in FIG. 28. Notwithstanding such deflection, load
pads 59 and 60 are mounted on the pins 63 to be shifted axially
therealong so that each load pad 59 and 60 maintains contact
between its concave surfaces 64S and the convex surface of the
corresponding track uniformly from one end to the other.
[0128] Referring to FIG. 27, it will be seen that there is an
appreciable clearance between each end of the load pads 59 and 60
and the inside faces of the support environment. Thus, as shown in
FIG. 28, upon any appreciable deflection of the column walls 45-2
or 45-3 relative to the web section 45-1 of the column 45, each
load pad 59 or 60 automatically shifts axially of its supporting
pin 63 (indicated by dashed arrows) to maintain uniform contact
from one side to the other with a convex surface of the
corresponding guide track 53, 52. This automatic self-adjusting,
including automatic self-centering, of each of the load pad 59, 60
with respect to corresponding guide tracks 53, 52, respectively,
occurs regardless of wear on the load pads 59, 60 and distortion of
the supporting column 45, and is maintained because as described,
runner member 50 is mounted in a way to alter its canted
attitude.
[0129] According to an embodiment of the invention, two or more
contact pads maybe deployed at each location on the runner member
50. According to an embodiment of the invention, the surfaces of
the contact pads may have features (not shown) such as
dimples/grooves on them to reduce friction and/or greasing and/or
cleaning. Such features may also reduce coefficient of friction
against track surfaces and reduce harmonic vibrations. For example
the pad surfaces may include V-shaped grooves, or holes to vary the
coefficient of friction against the surfaces of the tracks.
[0130] According to an embodiment of the invention, a combination
of load pads 58 and rollers 60R on a runner member 50, maybe used
as shown by example in FIG. 43 (an example of such rollers 60R is
described in U.S. Pat. No. 5,513,943, incorporated herein by
reference).
[0131] As shown in FIG. 44, according to an embodiment of the
invention, the location of the load pad 59 and the corresponding
guide track 53 may be switched, such that the load pad 59 may be
located on the inner surface of the rear wall 45-3 of the column
45, and the guide track 53 may be located on the rear face 50-4 of
the runner member 50. Similarly, the location of the load pad 60
and the corresponding track 52 may be switched, such that the load
pad 60 may be located on the inner surface of the front wall 45-2
of the column 45, and the guide track 52 may be located on the
front face 50-3 of the runner member 50. As such, load pads 59, 60
may be located on the inner walls of the each column 45 and the
guide tracks 52, 53 may be located on the runner member 50. The
tracks 52 and 53 may be components or walls of the runner member
50. Further, clearance pads 70 may be located on the inner walls of
the column 45 instead of on the runner member 50. In a similar
fashion, when the guide tracks 52, 53 are located on the runner
member 50, the clearance members 258, 261 may be positioned on the
inner walls of the column 45, and the contact member 259, 260 may
be positioned on the inner walls of the column 45.
Fixed Angle Load Bearing Pads and Adjustable Clearance Pads
[0132] Referring to FIGS. 31-40, embodiment of the present
invention provide fixed angle load bearing pads 259, 260, and
manually adjustable clearance pads 258, 261. Specifically, FIG. 31
shows a left side view of the load pads 259, 260, and adjustable
clearance pads 258, 261 mounted on the runner member 50, in
relation to the guide tracks 52, 53, in a column 45. As described
in more detail further below, the clearance pad 258 is manually
adjustable to allow changing the distance between the pad 258C and
the guide track 52, and similarly, the clearance pad 261 is
manually adjustable to allow changing the distance between the pad
261C and the guide track 53. In one embodiment, the clearance pad
258 is adjusted to maintain minimal gap between the pad 258C and
the guide track 52 to ensure substantial contact therebetween, and
the clearance pad 261 is adjusted to maintain minimal gap between
the pad 261C and the guide track 53 to ensure substantial contact
therebetween. In one example, each pad 258C, 259C, 261C and 260C
has a rectilinear footprint about 2.5 inches by 2.5 inches or 6.35
centimeters by 6.35 centimeters.
[0133] FIG. 32 shows an end view of the runner member 50 with the
clearance pad 258 in front of the load bearing pad 260 against the
guide track 52, and the clearance pad 261 (not shown) behind the
load bearing pad 259 against the guide track 53. FIG. 33 shows a
right side perspective view of the assembly of FIGS. 31-32. FIG. 34
shows an opposite end view to FIG. 32, depicting an assembly of the
runner member 50 with the clearance pad 261 in front of the load
bearing pad 259 against the guide track 53, and the clearance pad
258 (not shown) behind the load bearing pad 260 against the guide
track 52.
[0134] FIG. 35 shows a perspective view of a load bearing pad 259
with mounting brackets 259B, 259E. The load bearing pad 259 is
essentially rectangular and includes a support/mounting bracket
259B, for fixedly attaching the load bearing pad 259 to the runner
member 50. The load bearing pad 259 includes a contact pad 259C,
having a periphery of concave surface configuration formed on a
radius matingly complementary to that of the surfaces of the guide
tracks 52 and 53. FIG. 36 shows another perspective view of the
load bearing pad 259 without the support bracket 259B. The contact
pad 259C is substantially rectangular having a thickness, and
concave contact surface 259S formed on a radius matingly
complementary to that of the surfaces of the guide tracks 52, 53.
The contact pad 259C is connected to a support base 259D having an
attachment mounting bracket 259E.
[0135] Referring to FIGS. 31, 33, the load bearing pad 260 is
similar to the load bearing pad 259, and therefore not shown in
detail. For example, FIG. 39D shows a top view of the load bearing
pad 260 on the runner member 50, wherein similar to the load
bearing pad 259, the load bearing pad 260 includes a contact pad
260C, support bracket 260B, and attachment bracket 260E (FIG. 33).
Preferably, the pads 259C and 260C (FIG. 35) are of the same
material as the pads 64C of the load pads 59, 60, above.
[0136] The contact pads 259C, 260C, for the load bearing pads 259,
260, respectively, and the corresponding guide tracks 53, 52, have
the centers of their respective radii within a common vertical
plane substantially bisecting the contact pads and the track
surfaces. Load bearing pads 259 and 260 are thus matingly engaged
by the track surfaces throughout their axial width. The contact
pads 259C, 260C for load bearing pads 259, 260 have a low
coefficient of friction and are adapted to cushion the
corresponding runner during reciprocation and against vibration,
and may be made of a hard plastic material or a high density
polymer although a metallic material can also be used.
[0137] FIG. 37 shows a perspective view of an adjustable clearance
pad 258, having a contact pad 258C with an essentially rectangular
shape and a thickness that in one example has a tapered profile in
one dimension. The contact pad 258C further has a planer contact
surface 258S for contact with the surface of the guide track 52. As
shown in FIGS. 37 and 38, the clearance pad 258 includes a mounting
member comprising an adjustment system including an L-shaped
support base 258B having a spaced apertures 258A to adjustably
connect the clearance pad 258 to the runner member 50.
[0138] In one embodiment of the invention, an essentially
wedge-shaped (tapered) spacer 505 is used for the adjustable
clearance pad 258 (also shown in perspective view in FIGS. 33, 37,
and side view in FIG. 39A), wherein the spacer 505 includes
multiple apertures 50A spaced along its length in sequence similar
to the spacing of the apertures 258A. The edge 50G of the spacer
505 has a downward slope (transverse angle) in relation to right
edge 50R of the runner member 50. As shown in FIG. 39A, moving down
along the dashed arrow (along the lengths of the spacer 505 and the
runner member 50), there is a decrease in distance between
apertures 50A and to the bottom of the spacer 505 adjacent to the
right edge of the runner member 50. As such, the apertures 50A
closer to the bottom of the drawing page are nearer to the right
edge of the runner member 50 than the apertures 50A closer to the
top of the drawing page. The apertures 50A along said downward
slope of the spacer 505 towards the runner member 50, allow
adjusting the clearance (distance) between the clearance pad 258C
and the track 52 (FIGS. 40A-40C), as described below.
[0139] According to embodiments of the invention, changing the
number of apertures 50A on the spacer 505 and/or the changing the
angle of said downward slope on the spacer 505 towards the runner
member 50, provides variation in the successive amounts of
clearance that can be achieved between the pad 258C and the guide
track 52. The higher the number of apertures 50A and the smaller
the slope angle of the spacer edge 50G in relation to the runner
edge 50R, the higher the number of incremental clearance
adjustments possible.
[0140] For example, referring to FIGS. 40A and 40B, to increase the
distance between the contact pad 258C and the guide track 52, the
clearance pad 258 is shifted down along dashed arrow in FIG. 40B,
and lined up with selected apertures 50A on the spacer 50S. To
decrease clearance between the clearance contact pad 258C and the
guide track 52, the clearance pad 258 is shifted up in the opposite
direction and lined up with selected apertures 50A on the spacer
50S. In one embodiment, the clearance pad 258 is shifted up until
the pad 258C is jammed against the guide track 52. Then, the
clearance pad 258 is shifted down slightly until the apertures 258A
on the support base 258B lineup with the closest pair of apertures
50A on the spacer 50S. The clearance pad 258 is attached to the
spacer 50S with screws through the apertures 258A and selected
apertures 50A, thereby providing a desired clearance between the
clearance pad 258C and the guide track 52.
[0141] The distance between the clearance pad 261 and the guide
track 53 is similarly adjustable, as described below. As shown in
FIGS. 33 and 39B, the runner member 50 includes multiple apertures
50B for the adjustable clearance pad 261, wherein the apertures 50B
are spaced along the length of the runner member 50. The clearance
pad 261 includes spaced apertures 261A in a support base 261B (FIG.
39C), allowing the support base 261B of the clearance pad 261 to be
connected to the runner member 50 at different positions on the
apertures 50B along the length of the runner member 50. As shown in
FIG. 39B, the apertures 50B have a reduced distance to the left
edge of the runner member 50 moving down (dashed arrow in FIG.
39B), along the length of the runner member 50. As such, the
apertures 50B closer to the bottom of the drawing page are nearer
to the left edge of the runner member 50, than the apertures 50B
closer to the top of the drawing page. The apertures 50B along a
downward slope on the runner member 50 towards the left edge of the
runner member 50, allow adjusting the clearance (distance) between
the clearance pads 261 and the guide track 53. Further, as shown in
FIGS. 31, 33 and 39C, a wedge shaped spacer 51S may be used in
between the base of the clearance pad 261 and the runner member
50.
[0142] To increase the distance between the clearance contact pad
261C and the guide track 53 (FIG. 33), as shown in FIG. 39B the
clearance pad 261 is shifted down (along dashed arrow in FIG. 39B)
and lined up with selected apertures 50B. To decrease clearance
between the clearance contact pad 261C and the guide track 53, the
clearance pad 261 is shifted up in the opposite direction and lined
up with selected apertures 50B. The clearance pad 261 is attached
to the runner member 50 with screws through the apertures 261A and
selected apertures 50B.
[0143] FIG. 40C shows example distances between the apertures 50A
of the spacer 50S and the guide track 52 based on location of each
aperture 258A for the clearance pad 258. In this example, there are
four apertures 50A, at 0.0656 inch or 1.6662 centimeter distance
increments relative to the guide track 52, providing distances of
1.0726, 1.007, 0.9414, and 0.8758 inches or 2.7244, 2.5578, 2.3915,
and 2.50845 centimeters, respectively. In this example, the sloped
(tapered) spacer edge 50G of the spacer 505 forms about
3.75.degree. angle with the runner edge 50R, and similarly a
3.75.degree. angle with the top line of the convex guide track 52.
In one example, said angle can range from about 2.degree. to
5.degree.. Other ranges are possible. Similar or different
dimensions and angles may be used for the clearance pad 261. Such
adjustability in clearance eases manufacturing and allows ability
for more tolerance for assembly.
[0144] When the clearance between the pads and the tracks increases
due to pad wear in use, the runner member 50 may work eventually
itself out of the retaining column (C or S). In one embodiment, the
clearances between the pads and the tracks can be adjusted while
the liftgate is in the field. As needed, additional spacers/plates
may be placed between spacer 505 and the runner member 50 for
additional adjustment range and maintaining a desired clearance
between the pads and the tracks to maintain proper operation of the
runner member 50 in the retaining column 45.
[0145] In one embodiment, the clearance pads utilize a wedge design
wherein the clearance pad position allows change in clearance
between pad and the track. A load bearing pad such as 59 or 259 is
self-adjusting for the load bearing surface to have maximum contact
with the track surfaces. Such adjustability eases manufacturing and
allows ability for more tolerance for assembly.
[0146] According to an embodiment of the invention, adjustment of
the distance between the clearance pads and the tracks can be
accomplished using springs, wherein the clearance pads are spring
loaded against the tracks.
[0147] According to an embodiment of the invention, the load
bearing pad surfaces such as 258S may have curved (concave/convex)
surfaces.
[0148] FIG. 41 is a schematic diagram of the hydraulic circuit
employed in a lift gate system, according to an embodiment of the
invention. The circuit comprises a reservoir 200 communicating with
a supply line 201 that passes through a motor and pump assembly
202. The downstream end of the supply line 201 communicates with a
selector valve 203 by means of which fluid under pressure can be
communicated alternatively to either a conduit 204 leading to the
lower end of the platform power cylinder 120 or a conduit 206
communicating with the input port of a flow divider 207. An
opposite pair of outlet ports of the divider have fluid
communication via conduits 210 and 211, respectively, with the
piston rod ends of the pair of power cylinders 49. Each of the
conduits 210 and 211 incorporates a solenoid controlled normally
open hydraulic lock valve 212, fitted with a manual override, as
well as a pressure compensated velocity control valve 213.
[0149] When the selector valve 203 is actuated in a mode for
lifting the load carried by the piston rods of the cylinders 49, a
solenoid controlled check valve 215 in the conduit 206 is opened to
supply pressurized fluid to the input port of the flow divider 207.
The flow divider body has an inlet communicating with a pair of
passages for dividing the flow of hydraulic fluid between the inlet
and the pair of power cylinders 49. Each of the pair of passages
communicating to the power cylinders is fitted with a means for
positively displacing and being positively displaced by the fluid
flowing therethrough. The flow divider 207 may be Model No. PM6,
obtainable from MTE Hydraulics, Inc., of Rockford, Ill., which
contains two pairs of spur-toothed idler rotors 217 and 218, there
being one such pair within the flow passage to each of the conduits
210 and 211. Each idler rotor 217 meshes with its companion idler
rotor 218. At the same time, the two idler rotors 217, 218 are
keyed together for synchronous rotation, as by mounting on a common
shaft, as are the two idler rotors 218 at the diametral plane of
the flow passage. The resulting synchronized rotation of each
companion pair of idler rotors 217 and 218 occurs simultaneously in
either direction, as driven by and depending on the direction of
flow through the outlet ports. Associated with each outlet to
conduits 210 and 211, spanning opposite sides of the companion pair
of idler rotors 217 and 218, is a shunt conduit incorporating a
relief valve 220 that opens in response to a pre-determined back
pressure from the associated cylinder 49 to recirculate fluid
through the shunt.
[0150] Between the check valve 215 and fluid divider 207, the
conduit 206 has a shunt circuit including a return line 222 having
a relief valve 223 on one side and a solenoid controlled valve 224
on the other side of an inlet to a return line 222 to the reservoir
200.
[0151] When the selector valve 203 is set into a mode to
communicate fluid pressure to the conduit 204 for the platform
cylinder 120, a solenoid check valve 226 in the conduit 204 is
opened to pass pressurized fluid to the lower end of the platform
cylinder 120. The conduit 204 also incorporates a pair of flow
control valves 227 and 228, one of which is adjusted to vary the
rate of movement of the cylinder piston in one direction while the
other may be adjusted to vary the rate of movement of the cylinder
piston in the other direction.
[0152] The hydraulic circuit may also incorporate a known auxiliary
circuit 230 incorporating a relief valve and hand-pump mechanism in
order to operate the liftgate in the event of failure of the motor
and pump assembly 202. In the interest of clarity, return lines
from the butt ends of the cylinders 49 and 120 to the reservoir 200
have not been shown. However, it will be understood that return
lines comprise normal parts of the circuit. In a case where the
cylinders are of the single acting type, the return lines will
comprise low pressure breather lines. In a case where double acting
cylinders are desired, high pressure lines will be employed and the
selector valves accordingly modified.
[0153] The mode of operation of the invention should be apparent to
those of ordinary skill in the art from the foregoing description
and the drawings. Summarizing, let it be assumed that the platform
sections are in the fully folded and raised transit position of
FIG. 4. Upon actuation of the electrical control system in a mode
to open the valves 203 and 215, fluid is evacuated through the
lower ends of the pair of cylinders 49 through conduits 210 and
211, normally open valves 212, conduit 206, valves 215 and 203 and
into a reservoir return line 231 as the platforms descend under the
influence of gravity. During descent of the platform, after the
wedge block 115 clears the cam block 117 both platform sections are
maintained in a substantially erect position by the hydrostatic
head under the piston of the platform cylinder 120 as checked by
the normally closed solenoid check valve 226. Assuming it is
desired to maintain the platforms in dock loading position, the
folded platforms are then lowered to ground level.
[0154] Assuming the platform sections are to be opened into a
common horizontal plane for loading and unloading, after the wedge
block 114 has cleared the cam block 117, further downward movement
of the platforms is arrested by release of the control switch to
thereby effect closure of the valves 203 and 215. Thereupon, the
electrical control circuit is operated in a mode to open the valve
203 into communication with the conduit 204 while obturating the
conduit 206. Simultaneously, the solenoid check valve 226 is
opened. As the pump and motor 202 is idle in this phase and as the
weight of the platform sections is rearwardly over-center with
respect to the platform pivot/hinge pins 128, the platforms are
gravitationally biased into the full open position as fluid drains
from the bottom end of the platform cylinder 120 through the
conduit 204, conduit 206, selector valve 203, and reservoir return
line 231. The rate of opening may be altered by means of the flow
control valve 228.
[0155] Thereafter, each bracket flange 148 now being seated in its
internal slot 160, loading and unloading operations can be carried
out on the open platform assembly P by appropriate actuation of the
valve 203 and motor and pump assembly 202. During raising and
lowering synchronized movement of the piston rods of the pair of
cylinders 49 and a substantially horizontal attitude of the
platform assembly P is maintained by the pair of idler rotors 217,
218 or by the combination of the operation of the idler rotors and
the mutual interaction of the platform hinge flanges 148 and runner
bracket internal slots 160. Thus, the keyed together pairs of idler
rotors 217, 218, while operating synchronously, nevertheless appear
to permit leakage therearound internally of the body of flow
divider 207 in a manner to equalize or stabilize hydraulic
pressures within the pair of cylinders 49. At the same time, each
of the platform/hinge contacts 148, 160 at each side of the
platform at all times operate to maintain or force the adjoining
side portion of the forward platform section 78 into an orthogonal
relationship relative to the vertical axis of the companion column
assembly, which force is translated through the structural beam
forward edge of the forward platform section 78 to the bracket
combination 148, 160 on the other side of the platform. Thus, if
one side of the platform tends to lag behind the other side, the
first side is borne along by virtue of the bracket interconnection,
via the platform, to the opposite side runner member 50. The
converse is equally true in that a runner assembly on one side of
the platform moving in advance of the runner assembly on the other
side tends to carry along the runner assembly of the other side via
the interaction of the brackets and platform hinge connections 148,
160.
[0156] To close the platform assembly P and raise it to transit
position, the open platform is first elevated to a slightly above
ground position sufficient to provide clearance for movement of the
rear platform section 79 in the mode shown in FIG. 6. The valve 203
is then energized to pass fluid pressurized by the pump 202 through
the conduit 204 into the lower end of the cylinder 120. The two
platform sections are thus folded together into the substantially
vertically erect condition shown in FIG. 11 while the actuator arms
93 and their corresponding link chains 92 are simultaneously
restrained into alignment with their respective clearances at
opposite sides of the platform (e.g., FIG. 5). Thereafter, the
selector valve 203 is operated in a mode to close the conduit 204
and to pass pressurized fluid into the conduit 206 for raising the
collapsed platform sections and squeezing them together by the
action of the cam block 117 and wedge block 114 in the manner
previously described. The platform sections are thus raised from
the FIG. 11 condition into the FIG. 10 condition to an upper limit
shown in FIG. 15. Raising of the platform sections to the upper
limit effects closure of the normally open valves 212 (FIG. 15)
thus effecting a hydraulic lock at each side of the raised
platforms to maintain their transit position.
[0157] As shown in FIG. 42, the components of the liftgate may be
packed for shipment to an end-user as an unassembled package of
components. Thus, the package may comprise street side and curb
side columnar power assemblies C and S, a threshold plate T, a
platform assembly P of one or more sections, a power pack 245, and
a parts box 246, all conventionally strapped to a conventional
pallet 247. In order to maintain its runner assembly and power
cylinder in a fully retracted condition during shipping and
handling, each columnar power assembly may have a shipping strap
248 tack welded thereto to engage the underside of the bearing 75
(FIG. 15). The package may include special mounting fixtures
whereby the threshold plate T is first secured in place followed by
attachment of the street side and curb side column assemblies S and
C to the rear of the truck to be squared up relative to the
threshold plate T and indexed on pins T-1 projecting from opposite
ends of the threshold plate. The platform assembly P can then be
positioned in place for the reception of the pair of platform pivot
pins 128 after which the upper ends of the pair of link chains 92
are connected to the pivot arms 90 of the pair of runner
assemblies.
[0158] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0159] While certain exemplary embodiments have been described and
shown in the accompanying drawings, it is to be understood that
such embodiments are merely illustrative of and not restrictive on
the broad invention, and that this invention not be limited to the
specific constructions and arrangements shown and described, since
various other modifications may occur to those ordinarily skilled
in the art.
* * * * *