U.S. patent number RE31,157 [Application Number 06/010,616] was granted by the patent office on 1983-02-22 for self-folding platform.
This patent grant is currently assigned to Maxon Industries, Inc.. Invention is credited to William V. Perkins.
United States Patent |
RE31,157 |
Perkins |
February 22, 1983 |
Self-folding platform
Abstract
A load lifting and lowering platform comprises a pair of
hingedly interconnected platform sections that are foldable between
a horizontally extending, load bearing position and a vertically
extending collapsed position. A forward one of the platform
sections is hingedly connected at its forward edge to lower ends of
a pair of runner assemblies that are vertically movably mounted in
a supporting framework. A pair of chains are interconnected between
upper ends of the pair of runner assemblies and outer ends of the
outer one of the platform sections. Cooperating cam elements,
interposed between the forward edge of the forward platform section
and the supporting framework, translate vertical movement of the
runner assemblies into angular movement of the platform sections,
in cooperation with the chains, for folding and unfolding of the
platform sections.
Inventors: |
Perkins; William V. (Marina Del
Rey, CA) |
Assignee: |
Maxon Industries, Inc.
(Huntington Park, CA)
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Family
ID: |
26681377 |
Appl.
No.: |
06/010,616 |
Filed: |
February 9, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
654334 |
Feb 2, 1976 |
04007844 |
Feb 15, 1977 |
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Current U.S.
Class: |
414/545 |
Current CPC
Class: |
B60P
1/4421 (20130101) |
Current International
Class: |
B60P
1/44 (20060101); B60P 001/44 () |
Field of
Search: |
;414/545,557
;187/9R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Edbro Lift (Diesel Equipment Ltd.), Ontario, Canada. .
USI Hydraulic Tail Lift; U.S. Industries Inc., Engineering Ltd.;
Hertfordshire, England..
|
Primary Examiner: Paperner; Leslie J.
Attorney, Agent or Firm: Mueller; Frederick E.
Claims
I claim:
1. A self-folding and unfolding platform lift comprising:
a supporting framework;
a vertically elongate runner assembly mounted on said framework for
vertical movement;
an inner platform section having a forward edge horizontally
pivotally connected to a lower end of said runner assembly;
an outer platform section having a forward edge connected to a rear
edge of said inner platform section by a horizontal hinge means
positioned for folding an underside of said outer platform section
into superposition over an underside of said inner platform
section;
a finite length of a flexible member having one end connected at a
rear edge of said outer platform section and another end connected
to an upper end of said runner assembly;
.Iadd.whereby when said platform lift is unfolded, said finite
length of said flexible member forms a straight line; .Iaddend.
means intermediate said inner platform section and said framework
to translate vertical movement of said runner assembly into folding
or unfolding movement of said inner platform section;
and means .[.defining a rigid rearward extension of.].
.Iadd.extending from the rear of .Iaddend.said inner platform
section .Iadd.defining a bearing in spaced relation to said
horizontal hinge means .Iaddend.for .[.contacting and.]. seating an
intermediate portion of said flexible member for effecting folding
or unfolding movement of said outer platform section, relative to
said hinge means, as a function of corresponding folding or
unfolding movement of said inner platform section.
2. A self-folding and unfolding platform lift as in claim 1 in
which said means to translate movement of said runner assembly into
movement of said inner platform section is selectively actuable
between operative and inoperative positions.
3. A self-folding and unfolding platform lift as in claim 1 in
which said means to translate movement of said runner assembly into
movement of said inner platform section comprises cam means.
4. A self-folding and unfolding platform lift as in claim 3 in
which said cam means comprises a cam follower carried on said
forward edge of said inner platform section and a vertically
extending cam affixed to said framework.
5. A self-folding and unfolding platform lift as in claim 1 in
which said inner platform section and said outer platform section
have cooperating means limiting further unfolding movement of said
platform sections when said platform sections have been unfolded to
a common horizontal plane.
6. A self-folding and unfolding platform lift as in claim 5 in
which said cooperating means comprise shape characteristics of said
rear edge of said inner platform section and said forward edge of
said outer platform section defining a butt joint overlying said
hinge means.
7. A self-folding and unfolding platform lift as in claim 1 in
which said .[.rigid rearward.]. .Iadd.means defining a bearing
comprises an .Iaddend.extension of said inner platform section
.Iadd.that .Iaddend.is coplanar with .Iadd.and rigidly secured to
.Iaddend.said inner platform section.
8. In a platform lift having a horizontal hinge interconnecting
inner and outer platform sections for folding the unfolded sections
out of a common horizontal load bearing plane into vertically
extending superposed relationship of the undersides of the folded
sections, a vertically elongate runner assembly to whose lower end
the forward edge of the inner platform section is horizontally
pivotally connected, the runner assembly being vertically movably
mounted on a supporting framework, the improvement comprising;
a finite length of a flexible member having one end connected at
the rear edge of the outer platform section and having another end
connected to the upper end of the runner assembly;
.Iadd.whereby when said platform lift is unfolded, said finite
length of said flexible member forms a straight line; .Iaddend.
means intermediate the inner platform section and the framework to
translate vertical movement of the runner assembly on the framework
into folding or unfolding movement of the inner platform
section;
and means defining a rigid rearward extension of the inner platform
section for contacting and seating an intermediate portion of said
flexible member for effecting folding or unfolding movement of the
outer platform section, as a function of the corresponding folding
or unfolding movement of the inner platform section.
9. The improvement of claim 8 in which said means to translate
movement of the runner assembly into movement of the inner platform
section is selectively actuable between operative and inoperative
positions.
10. The improvement of claim 8 is which said means to translate
movement of the runner assembly into movement of the inner platform
section comprises cam means.
11. The improvement of claim 10 in which said cam means comprises a
cam follower carried on the forward edge of the inner platform
section and a vertically extending cam affixed to the
framework.
12. The improvement of claim 8 in which said rigid rearward
extension is coplanar with the inner platform section.
13. A self-folding and unfolding platform lift for the tailgate of
a truck comprising:
a support framework having a laterally spaced apart pair of
vertically extending guide channels;
a pair of vertically elongate runner assemblies mounted on said
guide channels for vertical movement in unison;
an inner platform section having a forward edge horizontally
pivotally connected to lower ends of said runner assemblies;
an outer platform section having a forward edge connected to a rear
edge of said inner platform section by a horizontal hinge means
positioned for folding an underside of said outer platform section
into superposition over an underside of said inner platform
section,
said inner platform section and said outer platform section having
cooperating means limiting further unfolding movement of said
platform sections when said platform sections have been unfolded to
a common horizontal plane;
a pair of lengths of a flexible member on opposite sides of said
platform lift, each flexible member having one end connected at a
rear edge of said outer platform section and having another end
connected to an upper end of the corresponding one of said pair of
runner assemblies;
.Iadd.whereby when said platform lift is unfolded said pair of
lengths of said flexible member on opposite sides of said platform
lift each form a straight line; .Iaddend.
means intermediate said inner platform section and said framework
to translate vertical movement of said pair of runner assemblies
into folding or unfolding movement of said inner platform
section;
and a pair of means, .[.on.]. .Iadd.extending from
.Iaddend.opposite sides of .Iadd.the rear of .Iaddend.said platform
lift, defining a .[.rigid rearward extension of.]. .Iadd.bearing on
.Iaddend.the corresponding side of said inner platform section
.Iadd.in spaced relation to said horizontal hinge means
.Iaddend.and positioned in a common vertical plane with the
corresponding one of said pair of flexible members for
.[.contacting and.]. seating an intermediate portion of said
flexible member for effecting folding or unfolding movement of said
outer platform .[.sections.]. .Iadd.section.Iaddend., relative to
said hinge means, as a function of corresponding folding or
unfolding movement of said inner platform section.
14. A self-folding and unfolding platform lift as set forth in
claim 13 in which one of said runner assemblies carries a
selectively engageable and disengageable latch means for holding
said platform sections in vertically extending collapsed folded
position against said pair of runner assemblies, one of said guide
channels fixedly mounting a vertically extending bar for slidable
engagement with said latch means for retaining said latch means in
either of engaged or disengaged positions, the upper end portion of
said retaining bar defining a clearance for effecting movement of
said latch means between engaged and disengaged positions.
15. A platform lift as in claim 13 in which said means to translate
movement of said runner assemblies into movement of said inner
platform section is selectively actuable between operative and
inoperative positions.
16. A platform lift as in claim 13 in which said means to translate
movement of said runner assemblies into movement of said inner
platform section comprises cam means.
17. A platform lift as in claim 16 in which said cam means
comprises a cam follower carried on said forward edge of said inner
platform section at one side of said platform and a vertically
extending cam affixed to the corresponding one of said guide
channels in vertical alignment with said cam follower.
18. A platform lift as in claim 17 in which said cam follower is
pivotally connected to said inner platform section.
19. A platform lift as in claim 18 in which said cam follower is
biased towards a retracted position out of vertical alignment with
said cam, said cam follower being released for movement to said
retracted position upon downward movement of said inner platform
section and cam follower downwardly beyond the lower end of said
cam.
20. A platform lift as in claim 13 in which said cooperating means
limiting unfolding movement of said platform sections comprise
shape characteristics of said rear edge of said inner platform
section and said forward edge of said outer platform section
defining a butt joint overlying said hinge means.
21. A platform lift as in claim 13 in which said .[.rigid rearward
extensions.]. .Iadd.means defining a bearing .Iaddend.on opposite
sides of said inner platform section are coplanar with .Iadd.and
rigidly secured to .Iaddend.said inner platform section.
Description
BACKGROUND
This invention relates to load elevators of the collapsible type, a
common example of which is a truck tailgate lift.
For some types of freight a load lifting and lowering platform of
large area, e.g., 6.times.6 feet, is required by trucks for
tailgate mounting. For such use there is a species of lift whose
supporting framework includes a pair of laterally spaced apart
channels framing the sides of the truck's tailgate opening to
vertically movably mount a pair of lifting legs on or in the guide
channels. The lifting legs pivotally carry a forward platform
section that, in turn, hingedly carries an outer platform section.
Erlinder U.S. Pat. No. 3,831,788 discloses a lift of this type
which is only partially self-folding in response to actuation of
the power means for the lift, in that it employs two pairs of
chains, one set of which must be detached in an intermediate step
of folding or unfolding the lift. Martin U.S. Pat. No. 3,795,329
discloses another lift of this class which is manually movable for
folding and unfolding, which is a very great disadvantage
considering the weight of the platform sections. The prior art
devices are comparatively complex and have several other
operational disadvantages.
SUMMARY OF THE INVENTION
In this invention, a supporting framework includes a laterally
spaced apart vertically disposed pair of guide channels vertically
movably mounting a vertically elongate pair of runner assemblies.
At their lower ends the pair of runner assemblies pivotally mount
the forward edge of a forward platform section whose rear edge is
hingedly interconnected to the forward edge of a rear or outer
platform section. A pair of chains are mounted on opposite sides of
the assembly, each extending between a point of connection to the
upper end of one of the runner assemblies and a point of connection
at the rear end of the rear platform section on the corresponding
side. At both sides, the forward platform section is provided with
rigid rearward extensions in vertical alignment with the chain of
the corresponding side. Cooperating cam elements intermediate the
forward edge of the forward platform section and the lower end of
the guide channel or channels translate powered vertical movement
of the runner assemblies into corresponding folding or unfolding
movement of the forward platform section to, in turn, effect
sequential corresponding folding or unfolding movement of the outer
platform section. Apart from the fact that one of the cam elements
is manually movable into and out of interfering alignment with the
other of the cam elements, the operation is entirely automatic.
Contrasted to the prior art, but a single pair of chains is
employed, the chains having the dual function of not only
supporting the unfolded platform in cantilevered, horizontally
extending, load bearing position but, also, functioning as
operative elements in the folding and unfolding operations.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a self-folding tailgate lift
platform of the present invention incorporated on the rear-end of a
truck, illustrating the platform in horizontally extending, load
bearing position.
FIGS. 2-5 inclusive are schematic side elevational views
illustrating different relative positions of platform components of
the invention in their sequence of movement between folded and
unfolded configurations.
FIGS. 6-9 inclusive are schematic partial side elevational views of
cam components of the lift in different relative positions in their
sequence of movement between the folded and unfolded configurations
of the platform.
FIG. 10 is a partial plan view on the line 10--10 of FIG. 9, on a
larger scale, of one of the cam elements of FIGS. 6-9.
FIG. 11 is a partial side elevational view, on a larger scale, of
the hinge connection between the inner and outer platform
sections.
FIG. 12 is a partial top plan view of the mechanism shown in FIG.
13.
FIG. 13 is a horizontal sectional view, on a larger scale, of one
of the lifting column assemblies taken on the line 13--13 of FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the invention is illustrated as affixed to the
rear-end of a freight truck 20. In the illustrated case, the
supporting framework for the load elevator includes a box-like
cross frame 21 having its upper face flush with the floor 22 of the
van body. At the opposite ends of the cross frame 21 are a pair of
vertically extending frame members 23, which may comprise box beam
members secured to or defining the tailgate opening of the van
body. Rigidly secured to the rear face of frame members 23 are
elongate, vertically extending lift guide channels 24 and 25, which
may be of essentially C-shaped cross sectional configuration as
shown in FIG. 13, the rear face of each guide member having
rearwardly opening, full length, vertically extending slot 26. It
will be noted that the lower ends of the pair of hollow guide
members 24 and 25 terminate in a common horizontal plane spaced
vertically downwardly beneath the horizontal plane of the floor 22
of the van body.
Briefly, the load elevator comprises an inner or forward platform
section 30 and an outer or rear platform section 31, a pair of
runner assemblies 32 vertically movable in the pair of guide
channels 24 and 25 and to which the forward edge of the inner
platform section 30 is hingedly connected, a pair of chains 33, and
a selectively actuable means for translating vertical movement of
the platform assembly into angular movement of the inner platform
section to, in turn, effect folding or unfolding of the platform
sections.
Referring to FIG. 13, each of the runner assemblies 32 includes a
vertically elongate bar 35 mounted on the slotted rear face of the
corresponding one of the guide members 24 or 25. Within the guide
member the bar 35 carries a longitudinally spaced apart series of
pairs of wheels 36 for vertically rolling engagement with the inner
surface of the corresponding guide member. By way of example, each
pair of wheels may be mounted on a common axle means 37 that, in
turn, is carried on an inner end of a stud 38, or the like, which
projects through the channel's slot 26 and is secured, as by
welding, to the forward face of the runner bar 35.
While not illustrated, it will be understood that the pair of
runner assemblies 32 are connected to a common source of power to
effect raising and lowering of the pair of runner assemblies in
unison. Such means could take the form of a pulley and cable system
with a power source housed in the transverse box frame 21 and
having the cables reeved through the pair of frame members 23 and
hollow guide members 24 and 25 with the pair of cable ends secured
to upper ends of the pair of runner assemblies 32. This and a
variety of other platform power mechanisms are well known in the
art.
At their lower ends, the pair of runner assemblies 32 carry
coaxially aligned hinge means 40 interconnected to the forward edge
of the inner or forward platform section 30. The latter platform
section, in turn, has its rear edge interconnected by a hinge means
41 to the forward edge of the outer platform section 31. The pair
of chains 33 are mounted at opposite sides of the platform assembly
with one end connected, as at 42, adjacent the rear edge of the
outer platform section 31 and the other end connected, as at 43, to
a fitting at the upper end of the corresponding runner assembly 32.
If desired, a loading ramp 44 may be secured to the rear edge of
the outer platform section 31 as either a foldable or rigid
extension of the outer platform section.
The articulation of the platform components is such that the inner
platform section 30 is angularly movable, relative to the hinge
means 40, between a rearwardly horizontally extending position and
a vertically upwardly extending position. The outer platform
section 31 is angularly movable, relative to its pivot axis 41
between a rearwardly horizontally extending position, as a rigid
extension of the platform section 30, and a vertically downwardly
extending position, in which the underside of the outer platform
section closely overlies or abuts the underside of the inner
platform section 30.
Turning of the forward platform section 30 between vertical and
horizontal positions is accomplished by a cam means responsive to
vertical movement of the pair of runner assemblies 32. A pair of
similar cam means can be provided for each side of the platform
assembly. However, in the illustrated case only the curbside guide
member 25 is provided with a fixed cam member 46 mounted in
vertical alignment with a cam follower element 47 carried by the
forward platform section 30 on the corresponding curbside thereof.
As is shown in FIG. 10, the cam follower 47 has one end connected
to a shaft 48 that is journalled between a pair of frame members 49
and 50 of the forward platform section 30. The shaft 48 is fitted
with a torsion spring 51 normally biasing the cam follower 47 to
the protruding position thereof illustrated in FIG. 1. In FIG. 10,
the cam follower 47 is illustrated as having been manually turned
into a position in which it extends beyond the forward edge of the
platform section 30, i.e., the position indicated in FIGS. 6-9. As
is shown in FIG. 10, one side of the cam follower 47 has a stop
member 52 secured thereto, as by welding, which upon coming into
abutment with the upper surface of the platform frame member 49
defines the position of the cam follower illustrated in FIGS.
6-9.
The profiles of the cam member 46 and cam follower 47 are best seen
in FIGS. 6-9. As shown, the cam 46 has a vertically extending
straight edge 46a merging into lowermost curved cam section 46b,
the cam follower 47 having a straight edge 47a that is slidable
over the surfaces of the cam 46.
The relative positions of the cam elements 46 and 47 illustrated in
FIG. 6 correspond to the fully folded condition of the platform
sections 30 and 31, illustrated in FIG. 2, in which the underside
of the outer platform section 31 overlies the underside of the
forward platform section 30. It will be understood that in this
position of the parts the platform assembly is gravitationally
biased to unfold but is held in check against unfolding movement by
the engagement of the cam follower straight edge 47a with the
straight vertical edge 46a of the cam 46. Upon movement downwardly
of the platform assembly and, therefore, of the cam follower 47,
the cam follower comes into sliding engagement with the curved
section 46b of the cam to gradually unfold the inner platform
section 30 in a positively restrained manner, due to the check
provided by the contact of the cam follower against the curved cam
section 46b, until the platform section 30 attains the horizontal
condition illustrated in FIG. 9. Subsequently, upon further
lowering movement of the runner assemblies 32, the cam follower
spring 51 turns the cam follower to the retracted, upwardly
projecting position depicted in FIG. 1, in which the cam follower
is out of interfering alignment with the cam 46.
The relative positions of the cam elements 46 and 47 in FIG. 7
correspond, approximately, to the relative positions of the
platform sections illustrated in FIG. 3. In this phase of movement
the outer platform section 31 is freely gravitationally suspended
about the pivot axis 41 between the two platform sections. However,
as the angle included between the cam element 46 and the forward
platform section 30 increases to that depicted in FIGS. 4 and 8,
the slack in the pair of chains 33 is taken up in a manner to
effect unfolding of the outer platform section 31.
More specifically, both sides of the forward platform section 30
are provided with rigid extensions projecting rearwardly, relative
to the platform hinge 41, for engaging the pair of chains 33 in
order to translate a portion of the unfolding or folding movement
of the forward platform section into corresponding unfolding or
folding movement of the rearward platform section 31. Referring to
FIGS. 11 and 12, wherein the curbside bracket assembly is shown, a
parallel, laterally spaced apart pair of bracket bars 53 and 54 are
rigidly secured, as by welding, to the corresponding forward
platform side frame members, comprising essentially linear rearward
extensions thereof projecting rearwardly relative to the hinge axis
41. Adjacent the outermost ends of the pair of bracket bars 53 and
54 they are rigidly interconnected by a pin 55 over which a roller
sleeve 56 is journalled.
As is best illustrated in FIG. 4, the spacing of the roller
supporting pins 55 relative to the platform hinge interconnection
41 is such that the rollers 56 .[.come into engagement with.].
.Iadd.define bearings about which .Iaddend.the corresponding chains
33 .Iadd.bend .Iaddend.after an initial angular increment of
opening movement by the forward platform section 30. Thereafter,
.[.upon.]. the slack of the chain 33 .[.being.]. .Iadd.having been
.Iaddend.taken up, further unfolding movement of the forward
platform section is translated into unfolding movement of the outer
platform section 31. As the two platform sections approach the
horizontal, fully unfolded position of FIG. 5, the rollers 56 move
out of engagement with the chains 33 but further unfolding movement
of both platform sections continues as a function of the straight,
tensioned chains 33 and the cam elements 46 and 47 translation of
further downward movement of the runner assemblies 32. As is shown
in FIG. 11, the confronting edges of the platform sections 30 and
31 at the hinge line 41 define a butt joint upwardly offset
relative to the hinge axis. Accordingly, when the platform sections
are in the horizontal position they are suspended by the pair of
chains 33 as essentially a single horizontally rigid platform
cantilevered relative to the hinge 48. While not necessary, it will
be observed from FIGS. 11 and 12 that the bracket arm 54 may be
projected rearwardly beyond the rear end of the other bracket bar
53 to provide for the mounting of a removable safety pin 57 through
aligned apertures of the bracket bar 54 and the confronting edge of
the framework of the outer platform section 31.
In FIG. 2, the platform is shown in fully collapsed and raised
position. As will now be apparent, the forward platform section 30
is so locked by the engagement of the cam follower 47 with the
straight edge portion 46a of the cam, while the rearward or outer
platform section 31 is so maintained by virtue of its
gravitationally depending from the platform hinge 41. However, a
latch means is provided to maintain the platform sections in the
collapsed folded condition during lowering of the runner assemblies
32 in order to facilitate dock loading of the vehicle on which the
apparatus is mounted.
Referring to FIGS. 1-3, such latch means may take the form of a
manually operable hook 60, carried by one of the runner assemblies
32, and a cooperating hook locking bar 61 on the corresponding
stationary guide channel. In the illustrated case, the bar 61 is an
elongate vertically extending member, of sufficient length to cover
the range of vertical movement of the hook 60, affixed to the
curbside face of the curbside guide channel 25. A lock pin 62 is
mounted on the curbside edge of the forward platform section 30 for
selective engagement and disengagement by the hook 60, the latter
being mounted intermediate the ends of the runner assembly 32. An
upper end portion 63 of the hook lockbar inclines forwardly
upwardly so that when the collapsed platform is in the fully raised
position of FIG. 2 the hook 60 can be freely swung between the
latching position of FIG. 2 and the unlatched position illustrated
in FIG. 1, the inclined portion 63 providing clearance for this
purpose.
When the hook 60 is in the latching position of FIG. 2, one edge 64
thereof is aligned with the vertically extending straight rear face
of the hook locking bar 61 to be slidable thereover. Accordingly,
if the hook 60 is allowed to remain latched the platform will
remain securely locked in the collapsed position upon lowering of
the runner assemblies 32, since unlatching pivotal movement of the
hook is prevented throughout the vertical extent of the straight
rear face of the locking bar 61. On the other hand, when it is
desired to unfold the platform sections in response to lowering of
the runner assemblies 32, the hook 60 can be moved to the open
position (shown in FIG. 1) wherein another edge 65 of the hook
comes into engagement with the clearance section 63 of the bar, the
center of gravity of the hook going forwardly over-center of its
pivot axis. As a result, upon downward movement of the runner
assemblies relative to the supporting framework, the edge 65 of the
hook 60 comes into sliding engagement with and is held against
pivotal movement by the vertically straight run portion of the
locking bar 61.
To summarize operation of the invention for purposes of loading and
unloading freight, let it first be assumed that the load platform
is in the collapsed and raised position illustrated in FIG. 2. The
hook 65 is first turned out of engagement with the lock pin 62 and
the power means then energized to permit lowering of the runner
assemblies 32. Upon the cam follower 47 coming into engagement with
the curved segment 46b of the cam 46 the forward platform section
30 gradually commences unfolding and is thereafter positively
constrained throughout its unfolding movement by the mutual
engagement of the camming surfaces. Initially, the outer platform
section 31 is gravitationally biased to vertically depending
position relative to the hinge 41, until the pair of rollers 56
come into .Iadd.bearing .Iaddend.engagement with the pair of chains
33, which have been slack to this point. Thereafter, as indicated
in FIG. 4, upon further unfolding movement of the forward platform
section 30 the tensioned pair of chains 33 effect angular unfolding
movement of the outer platform section 31 relative to the platform
hinge 41. In the final increment of unfolding movement of the
forward platform section 30 by the cam elements 46 and 47, the pair
of rollers 56 are swung downwardly out of engagement with the now
straight and fully tensioned chains 33 until the butt joint of the
platform sections overlying the hinge 41 is made. Thereafter, upon
continued lowering movement of the runner assemblies 32 both
platform sections are in a common horizontal plane.
Upon the horizontally disposed platform sections 30 and 31 coming
to ground level, the spring biased cam element 47 is biased to the
vertically extending position indicated in FIG. 1, out of
interfering alignment with the cam 46, whereby the unfolded load
platform is in readiness for load lifting or lowering in the usual
manner. In order to refold the platform, when it is raised to
approximately the position shown in FIG. 9 the cam follower 47 is
manually turned forwardly into alignment with the cam 46 so that
upon continued upward movement of the runner assemblies 32 the
platform sections are folded one upon the other in the reverse of
the sequence of positions shown in FIGS. 2-5.
As will now be apparent, a variety of modifications of the
invention are possible. Thus, as indicated previously, both sides
of the supporting framework may be provided with cams 46 and a
corresponding pair of cam elements 47 may be mounted on a common
shaft for operation in unison. A spring loaded stop may be
employed, if desired, to hold the cam element 47 in the erect
position of FIG. 1. It will also be apparent that use of the
invention is not limited to the tailgate environment of a truck but
may be employed independently as a self contained unit with its own
supporting framework. It will be understood that these and other
modifications are possible without departing from the
invention.
* * * * *