U.S. patent application number 09/783488 was filed with the patent office on 2002-10-10 for apparatus for monitoring loading of a lift.
Invention is credited to Engvall, David P., Sumsion, Stanley R..
Application Number | 20020144862 09/783488 |
Document ID | / |
Family ID | 25129407 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020144862 |
Kind Code |
A1 |
Engvall, David P. ; et
al. |
October 10, 2002 |
APPARATUS FOR MONITORING LOADING OF A LIFT
Abstract
A load lift comprising a lifter and a linkage on the lifter
carrying a load support for movement therewith to different
elevations. The linkage is a four-member linkage which includes a
first vertical side member carried by the lifter, a second vertical
side member carrying the load support, a third member constituting
an upper member of the linkage pivotally connected to the first and
second members, and a fourth member constituting a lower member of
the linkage pivotally connected to the first and second members. An
interconnection between the first and second members holds up the
second member and load support and is thereby subject to loading on
account of the load support and load thereon. Instrumentation
senses the loading on the linkage indicative of the load on the
load support.
Inventors: |
Engvall, David P.; (St.
Joseph, MO) ; Sumsion, Stanley R.; (St. Joseph,
MO) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT AND ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
US
|
Family ID: |
25129407 |
Appl. No.: |
09/783488 |
Filed: |
February 14, 2001 |
Current U.S.
Class: |
182/18 ;
182/2.1 |
Current CPC
Class: |
B66F 11/046 20130101;
B66F 17/006 20130101; G01G 3/14 20130101; G01G 19/12 20130101 |
Class at
Publication: |
182/18 ;
182/2.1 |
International
Class: |
E04G 001/00 |
Claims
What is claimed is:
1. A load lift comprising a lifter, a linkage on the lifter
carrying a load support for movement therewith to different
elevations, said linkage comprising a first member carried by the
lifter, a second member carrying the load support, said first and
second members constituting side members of the linkage extending
generally vertically, a third member constituting an upper member
of the linkage pivotally connected to the first and second members,
a fourth member constituting a lower member of the linkage
pivotally connected to the first and second members, and an
interconnection between said first and second members holding up
said second member and load support, said lifter further comprising
instrumentation for sensing the loading on said linkage indicative
of the loading on said load support.
2. A load lift as set forth in claim 1 wherein said interconnection
is a tension-taking interconnection subject to strain in tension by
said loading.
3. A load lift as set forth in claim 2 wherein said instrumentation
is operable for sensing the tension load in said
interconnection.
4. A load lift as set forth in claim 3 wherein the interconnection
comprises a tension member pivotally connected at one end
constituting its upper end with said first member and at its other
end constituting its lower end with said second member, and wherein
the instrumentation is in the tension member.
5. A load lift as set forth in claim 1 wherein said instrumentation
is operable to sense a horizontal component of shear force
indicative of a moment force exerted on the load support.
6. A load lift as set forth in claim 5 wherein said instrumentation
is further operable for sensing a vertical component of shear force
indicative of the weight of a load on the load support.
7. A load lift as set forth in claim 1 wherein said linkage is
generally a parallelogram linkage.
8. A load lift as set forth in claim 7 wherein said interconnection
comprises a tension member extending diagonally with respect to the
parallelogram linkage.
9. A load lift as set forth in claim 8 wherein said tension member
is pivotally connected at one end constituting its upper end with
said first member and at its other end constituting its lower end
with said second member, said instrumentation being operable for
sensing the load in said tension member.
10. A load lift as set forth in claim 1 wherein said first member
comprises an elongate first bracket attached to the lifter
extending generally vertically and movable up and down with the
lifter in the direction of its length and generally vertically
throughout its up and down movement, said second member comprises
an elongate bracket attached to the load support extending
generally vertically generally parallel to the first bracket
between the first bracket and load platform, said third member
comprising an upper link pivotally connected to said brackets and
said fourth member comprises a lower link pivotally connected to
said brackets.
11. A load lift as set forth in claim 10 wherein said upper link is
pivotally connected to said brackets on upper pins mounted on said
brackets and said lower link is pivotally connected to said
brackets on lower pins mounted on said brackets.
12. A load lift as set forth in claim 11 wherein said
interconnection comprises a tension member connected between an
upper pin of the first bracket and a lower pin of the second
bracket.
13. A load lift as set forth in claim 12 wherein said
instrumentation is in the tension member.
14. A load lift as set forth in claim 13 wherein said
instrumentation is operable for sensing a component of shear force
on at least one of said upper and lower pins, said component being
indicative of the loading on the load support.
15. A load lift as set forth in claim 14 wherein said
instrumentation is operable to sense a horizontal component of
shear force indicative of a moment force exerted on the load
support.
16. A load lift as set forth in claim 15 said instrumentation
comprises a strain gauge system on at least one of said upper or
lower pins on the interconnection.
17. A load lift as set forth in claim 11 wherein said
instrumentation is operable for sensing a horizontal component of
shear force indicative of a moment force exerted on the load
support, and also for sensing a vertical component of shear force
indicative of the weight of a load on the load support.
18. A load lift as set forth in claim 17 said instrumentation
comprises a strain gauge system on at least one of said upper or
lower pins for sensing said horizontal and vertical components of
shear force.
19. A load lift as set forth in claim 11 wherein the upper and
lower pins are spaced generally the same distance and wherein the
upper and lower links have generally the same effective length so
that the linkage constituted by said brackets and links is
generally a parallelogram linkage.
20. A load lift as set forth in claim 19 wherein the effective
length of the upper and lower links is a fraction of the distance
between the upper and lower pins.
21. A load lift as set forth in claim 20 having interengageable
stops on the brackets limiting the up and down movement of the
second bracket relative to the first.
22. A load lift as set forth in claim 11 wherein each bracket is of
channel shape in horizontal cross section having a web and flanges
extending from the web, each of the pins extending on a generally
horizontal axis between the flanges, each upper and lower link
comprising a sleeve and a pair of eyes spaced lengthwise of the
sleeve on an axis parallel to that of the sleeve, the upper link
having the eyes thereof on the upper pin of the first bracket and
the sleeve thereof on the upper pin of the second bracket, the
lower link having the eyes thereof on the lower pin of the second
bracket and the sleeve thereof on the lower pin of the first
bracket, the load cell having a pivotal connection with the upper
pin of the first bracket between the eyes of the upper link and a
pivotal connection with the lower pin of the second bracket between
the eyes of the lower link.
23. An aerial work platform lift comprising a boom carrying the
work platform pivotable to move the work platform to different
elevations, said boom having an end carrying the work platform for
pivotal movement of the work platform about a generally horizontal
axis to maintain the work platform generally level as it is moved
up and down by the boom, a linkage on the boom end carrying the
work platform, said linkage comprising a generally vertical first
bracket attached to said boom end and movable up and down with the
boom in the direction of length of said first bracket, a second
bracket attached to the work platform extending generally parallel
to the first bracket between the first bracket and work platform,
an upper link pivotally connected to said brackets, a lower link
pivotally connected to said brackets, an interconnection between
the first bracket and the second bracket holding up said second
bracket and work platform, and instrumentation for sensing the
loading on said linkage indicative of the loading on the work
platform.
24. An aerial work platform lift as set forth in claim 23 wherein
said interconnection is a tension-taking interconnection subject to
strain in tension by said loading.
25. An aerial work platform lift as set forth in claim 24 wherein
said instrumentation is operable for sensing the tension load in
said interconnection.
26. An aerial work platform lift as set forth in claim 25 wherein
the interconnection comprises a tension member pivotally connected
at one end constituting its upper end with said first member and at
its other end constituting its lower end with said second member,
and wherein the instrumentation is in the tension member.
27. An aerial work platform as set forth in claim 23 wherein said
instrumentation is operable to sense a horizontal component of
shear force indicative of a moment force exerted on the load
support.
28. An aerial work platform as set forth in claim 27 wherein said
instrumentation is further operable for sensing a vertical
component of shear force indicative of the weight of a load on the
load support.
29. An aerial work platform lift as set forth in claim 23 wherein
said linkage is generally a parallelogram linkage.
30. An aerial work platform lift as set forth in claim 29 wherein
said interconnection comprises a tension member extending
diagonally with respect to the parallelogram linkage.
31. An aerial work platform lift as set forth in claim 30 wherein
said tension member is pivotally connected at one end constituting
its upper end with said first member and at its other end
constituting its lower end with said second member, said
instrumentation being operable for sensing the load in said tension
member.
32. An aerial work platform lift as set forth in claim 21 wherein
said first member comprises an elongate first bracket attached to
the lifter extending generally vertically and movable up and down
with the lifter in the direction of its length and generally
vertically throughout its up and down movement, said second member
comprises an elongate bracket attached to the load support
extending generally vertically generally parallel to the first
bracket between the first bracket and load platform, said third
member comprising an upper link pivotally connected to said
brackets and said fourth member comprises a lower link pivotally
connected to said brackets.
33. An aerial work platform lift as set forth in claim 32 wherein
said upper link is pivotally connected to said brackets on upper
pins mounted on said brackets and said lower link is pivotally
connected to said brackets on lower pins mounted on said
brackets.
34. An aerial work platform lift as set forth in claim 33 wherein
said interconnection comprises a tension member connected between
an upper pin of the first bracket and a lower pin of the second
bracket.
35. An aerial work platform lift as set forth in claim 34 wherein
said instrumentation is in the tension member.
36. An aerial work platform lift as set forth in claim 35 wherein
said instrumentation is operable for sensing a component of shear
force on at least one of said upper and lower pins, said component
being indicative of the loading on the load support.
37. An aerial work platform lift as set forth in claim 36 wherein
said instrumentation is operable to sense a horizontal component of
shear force indicative of a moment force exerted on the load
support.
38. An aerial work platform lift as set forth in claim 37 said
instrumentation comprises a strain gauge system on at least one of
said upper and lower pins.
39. An aerial work platform lift as set forth in claim 33 wherein
said instrumentation is operable for sensing a horizontal component
of shear force indicative of a moment force exerted on the load
support, and also for sensing a vertical component of shear force
indicative of the weight of a load on the load support.
40. An aerial work platform lift as set forth in claim 39 said
instrumentation comprises a strain gauge system on at least one of
said upper and lower pins for sensing said horizontal and vertical
components of shear force.
41. An aerial work platform lift as set forth in claim 33 wherein
the upper and lower pins are spaced generally the same distance and
wherein the upper and lower links have generally the same effective
length so that the linkage constituted by said brackets and links
is generally a parallelogram linkage.
42. An aerial work platform lift as set forth in claim 41 wherein
the effective length of the upper and lower links is a fraction of
the distance between the upper and lower pins.
43. An aerial work platform lift as set forth in claim 41 having
interengageable stops on the brackets limiting the up and down
movement of the second bracket relative to the first.
44. An aerial work platform lift as set forth in claim 33 wherein
each bracket is of channel shape in horizontal cross section having
a web and flanges extending from the web, each of the pins
extending on a generally horizontal axis between the flanges, each
upper and lower link comprising a sleeve and a pair of eyes spaced
lengthwise of the sleeve on an axis parallel to that of the sleeve,
the upper link having the eyes thereof on the upper pin of the
first bracket and the sleeve thereof on the upper pin of the second
bracket, the lower link having the eyes thereof on the lower pin of
the second bracket and the sleeve thereof on the lower pin of the
first bracket, the load cell having a pivotal connection with the
upper pin of the first bracket between the eyes of the upper link
and a pivotal connection with the lower pin of the second bracket
between the eyes of the lower link.
45. A load sensor mounting for the load support of a load lift
having a lifter, said mounting comprising a linkage including a
first side member for attachment to the lifter in generally
vertical position, a second side member for attachment to the load
support in generally vertical position, an upper member pivotally
connected to the side members, a lower member pivotally to the side
members, an interconnection between the side members for holding up
the second side member and the load support, said mounting further
comprising instrumentation for sensing the loading on said linkage
indicative of the load on said load support.
46. A load sensor mounting as set forth in claim 45 wherein said
interconnection is a tension-taking interconnection subject to
strain in tension by said loading.
47. A load sensor mounting as set forth in claim 46 wherein said
instrumentation is operable for sensing the tension load in said
interconnection.
48. A load sensor mounting as set forth in claim 47 wherein the
interconnection comprises a tension member pivotally connected at
one end constituting its upper end with said first member and at
its other end constituting its lower end with said second member,
and wherein the instrumentation is in the tension member.
49. A load sensor mounting as set forth in claim 45 wherein said
instrumentation is operable to sense a horizontal component of
shear force indicative of a moment force exerted on the load
support.
50. A load sensor mounting as set forth in claim 49 wherein said
instrumentation is further operable for sensing a vertical
component of shear force indicative of the weight of a load on the
load support.
51. A load sensor mounting as set forth in claim 45 wherein said
linkage is generally a parallelogram linkage.
52. A load sensor mounting as set forth in claim 45 wherein said
interconnection comprises a tension member extending diagonally
with respect to the parallelogram linkage.
53. A load sensor mounting as set forth in claim 52 wherein said
tension member is pivotally connected at one end constituting its
upper end with said first member and at its other end constituting
its lower end with said second member, said instrumentation being
operable for sensing the load in said tension member.
54. A load sensor mounting as set forth in claim 45 wherein said
first member comprises an elongate first bracket attached to the
lifter extending generally vertically and movable up and down with
the lifter in the direction of its length and generally vertically
throughout its up and down movement, said second member comprises
an elongate bracket attached to the load support extending
generally vertically generally parallel to the first bracket
between the first bracket and load platform, said third member
comprising an upper link pivotally connected to said brackets and
said fourth member comprises a lower link pivotally connected to
said brackets.
55. A load sensor mounting as set forth in claim 54 wherein said
upper link is pivotally connected to said brackets on upper pins
mounted on said brackets and said lower link is pivotally connected
to said brackets on lower pins mounted on said brackets.
56. A load sensor mounting as set forth in claim 55 wherein said
interconnection comprises a tension member connected between an
upper pin of the first bracket and a lower pin of the second
bracket.
57. A load sensor mounting as set forth in claim 56 wherein said
instrumentation is in the tension member.
58. A load sensor mounting as set forth in claim 57 wherein said
instrumentation is operable for sensing a component of shear force
on at least one of said upper and lower pins, said component being
indicative of the loading on the load support.
59. A load sensor mounting as set forth in claim 58 wherein said
instrumentation is operable to sense a horizontal component of
shear force indicative of a moment force exerted on the load
support.
60. A load sensor mounting as set forth in claim 59 said
instrumentation comprises a strain gauge system on at least one of
said upper and lower pins.
61. A load sensor mounting as set forth in claim 55 wherein said
instrumentation is operable for sensing a horizontal component of
shear force indicative of a moment force exerted on the load
support, and also for sensing a vertical component of shear force
indicative of the weight of a load on the load support.
62. A load sensor mounting as set forth in claim 61 said
instrumentation comprises a strain gauge system on at least one of
said upper or lower pins for sensing said horizontal and vertical
components of shear force.
63. A load sensor mounting as set forth in claim 55 wherein the
upper and lower pins are spaced generally the same distance and
wherein the upper and lower links have generally the same effective
length so that the linkage constituted by said brackets and links
is generally a parallelogram linkage.
64. A load sensor mounting as set forth in claim 63 wherein the
effective length of the upper and lower links is a fraction of the
distance between the upper and lower pins.
65. A load sensor mounting as set forth in claim 64 having
interengageable stops on the brackets limiting the up and down
movement of the second bracket relative to the first.
66. A load sensor mounting as set forth in claim 55 wherein each
bracket is of channel shape in horizontal cross section having a
web and flanges extending from the web, each of the pins extending
on a generally horizontal axis between the flanges, each upper and
lower link comprising a sleeve and a pair of eyes spaced lengthwise
of the sleeve on an axis parallel to that of the sleeve, the upper
link having the eyes thereof on the upper pin of the first bracket
and the sleeve thereof on the upper pin of the second bracket, the
lower link having the eyes thereof on the lower pin of the second
bracket and the sleeve thereof on the lower pin of the first
bracket, the load cell having a pivotal connection with the upper
pin of the first bracket between the eyes of the upper link and a
pivotal connection with the lower pin of the second bracket between
the eyes of the lower link.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to apparatus for monitoring the
loading of a lift, such as the loading of the work platform of an
aerial work platform lift, and the loading of a forklift; and more
particularly for sensing the load on the work platform of the
aerial work platform lift or the tines of the forklift.
[0002] As to the monitoring of the loading of the work platform of
an aerial work platform lift, reference may be made to U.S. Pat.
No. 5,913,379 of Paul E. Young and David P. Engvall issued Jun. 22,
1999 entitled Articulated Aerial Work Platform System for a
disclosure of the type of aerial work platform lift in which the
monitoring apparatus or "load sensor mounting" apparatus of this
invention is incorporated, with the understanding that the
apparatus of the invention may be incorporated generally in aerial
work platform lifts other than that shown in said U.S. Pat. No.
5,913,379, which is incorporated herein by reference. A problem
which has existed with regard to such lifts has been that of
detecting overloading (i.e. excessive weight) on the work platform
of the lift, so that unsafe conditions due to overloading may be
avoided. Excessive weight may be due to the weight of the workman
(or workmen) standing on the work platform plus equipment and items
being used, additive to the weight of the work platform itself.
Attempts to solve this problem have been made; see, for example
such prior U.S. Pat. No. 3,952,879 issued Apr. 27, 1976 entitled
Overload Control for Lifting Boom and U.S. Pat. No. 4,456,093
issued Jun. 26, 1984 entitled Control System for Aerial Work
Platform Machine and Method of Controlling an Aerial Work Platform
Machine. Other attempts have involved the use of multiple load
sensors at various locations on the work platform. However, these
systems are expensive and not particularly accurate. This invention
is regarded as representing an improvement over such systems and
what is disclosed in such prior U.S. patents.
[0003] In addition to being applicable to monitoring the loading of
the work platform of an aerial work platform lift, the invention is
also applicable to the monitoring of the loading of other lifts, in
particular a forklift, and especially a type of forklift referred
to as a rough terrain forklift, such as used on construction sites
to lift construction materials, for example. In such usage, the
forklift may encounter the problem of a load being picked up on the
tines of the forklift in a way as to result in a dangerous
situation which, if not remedied, may cause the forklift to tip
over. An adjunct of the invention involves detection of a potential
tip-over condition.
[0004] Reference may also be made to the following U.S. Patents as
of interest re the forklift application of the invention and re
other potential applications thereof:
1 Pat. No. Date Title 3,724,679 April 3, 1973 Indicator or Control
for Cranes 4,068,773 Jan. 17, 1978 Lift Vehicle with Fail- Safe
Overload Protection System 4,093,091 June 6, 1978 Load Movement
Sensing System for Lift Trucks 5,557,526 Sep. 17, 1996 Load
Monitoring System for Booms
[0005] In general, a load lift of this invention comprises a lifter
(e.g. the boom of an aerial work platform lift, the lifter of a
forklift, or the like) and a linkage on the lifter carrying a load
support (e.g. the aerial work platform, the tines of the forklift,
or the like) for movement therewith to different elevations. The
linkage comprises a first member carried by the lifter, a second
member carrying the load support, said first and second members
constituting side members of the linkage extending generally
vertically, a third member constituting an upper member of the
linkage pivotally connected to the first and second members, and a
fourth member constituting a lower member of the linkage pivotally
connected to the first and second members. An interconnection
between said first and second members holds up said second member
and load support. Instrumentation is provided for sensing the load
on the load support.
[0006] This invention is also directed to a load sensor mounting
per se (a unit for incorporation in a lift). The mounting generally
comprises the linkage and instrumentation described above.
[0007] Other objects and features will be in part apparent and in
part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a view in perspective showing the extensible boom
and work platform of an aerial work platform lift incorporating the
load sensor mounting of this invention, the boom being shown in a
longitudinally extended upwardly angled position;
[0009] FIG. 2. is a side elevation of the boom work platform and
load sensor mounting of FIG. 1, the boom being shown in a retracted
condition and in a downwardly angled position;
[0010] FIG. 3 is a view in elevation of one side of the load sensor
mounting per se, the other side being a mirror image thereof;
[0011] FIG. 4 is a view in elevation of one face of the load sensor
mounting, the other face appearing the same;
[0012] FIG. 5 is a top plan view of the load sensor mounting;
[0013] FIG. 6 is a bottom view of the load sensor mounting;
[0014] FIG. 7 is a vertical section taken generally on line 7-7 of
FIGS. 4 and 5 showing in phantom certain framework on the end of
the boom (to which one side of the load sensor mounting is
fastened) and also showing in phantom the work platform (which is
fastened to the other side of the load sensor mounting);
[0015] FIG. 8 is an exploded view of the load sensor mounting per
se in perspective;
[0016] FIG. 9 is a view, partly broken away, of a load cell per se
of the mounting;
[0017] FIG. 10 is a view of a shear-sensing pin which may be used
in the load sensor mounting;
[0018] FIG. 11 is an enlarged fragment of FIG. 10;
[0019] FIG. 12 is a cross-section generally on line 12-12 of FIG.
11;
[0020] FIG. 13 is a fragmentary elevation illustrating the mounting
of the FIG. 10 pin;
[0021] FIG. 14 is generally an end view of FIG. 13;
[0022] FIG. 15 is a view of a modification of the FIG. 10 pin used
in a modification of the mounting of FIGS. 1-8;
[0023] FIG. 16 is an enlarged fragment of FIG. 15; and
[0024] FIG. 17 is a cross-section generally on line 17-17 of FIG.
16.
[0025] Corresponding reference characters indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Referring first to FIGS. 1 and 2 of the drawings, there is
generally indicated at 1 the boom of an aerial work platform lift
such as disclosed in the aforesaid U.S. Pat. No. 5,913,379, for
example, the boom constituting in a broad sense a lifter for the
load support constituted by the work platform, the latter being
identified in its entirety by the reference numeral 3. The boom 1
and work platform 3 are conventional, the boom being shown as the
conventionally telescopically extensible boom comprising base
section 5, mid-section 7 and tip or end 9. The end 9 of the boom
includes a framework 11 (e.g., a rotation bracket assembly) carried
by leveling apparatus 13 including a hydraulic cylinder 15 for
pivotal movement of the framework 11 about a generally vertical
axis indicated generally at A--A and for further pivotal movement
with apparatus 13 about a generally horizontal axis 17 for
maintaining the framework 11 in a position for keeping the work
platform 3 level as the boom 1 pivots up and down and for enabling
the work platform to be pivoted from side-to-side on axis 17. All
this is standard and well-known at this time; reference may be made
to said U.S. Pat. No. 5,913,379 for details. The invention resides
in means mounting the work platform 3 on the end of the boom; which
means may be referred to as noted as the "load sensor mounting" for
the work platform, and which is referred to in its entirety by the
reference numeral 19. As shown in FIG. 2, means 19 mounts the work
platform 3 on the framework 11, but it will be understood that
framework 11 could be eliminated and means 19 used to mount the
work platform directly on the leveling apparatus 13.
[0027] In general, the load sensor mounting 19 comprises a linkage,
generally designated 20, which includes a first member 21 carried
by the framework 11 on the end of the boom 1 (the lifter), a second
member 23 carrying the work platform 3 (the load support), said
members 21 and 23 constituting side members of the linkage, and
third and fourth members 25 and 27 constituting upper and lower
members of the linkage. The stated first and second members extend
generally vertically in close proximity one to the other, member 21
having upper and lower ends 21a, 21b, and member 23 having upper
and lower ends 23a, 23b. The third (upper) member 25 is pivotally
connected to the first and second members 21 and 23 adjacent their
upper ends as indicated at 29 and 31 (FIG. 5) and the fourth member
is pivotally connected to the first and second members 21 and 23
adjacent their lower ends as indicated at 33 and 35 (FIG. 6). At 37
(FIG. 4) is indicated in its entirety an interconnection between
the first and second members 21 and 23 functioning to hold up said
second member 23 and the work platform 3 (the load support), the
interconnection 37 thereby being subject to loading on account of
holding up the work platform (the load support) and the load
thereon. As will be described in detail later, instrumentation is
provided for sensing the load on the linkage 20 indicative of the
loading on the work platform 3.
[0028] In the preferred embodiment, the side member 21 of the load
sensor mounting 19 comprises an elongate metal bracket generally of
channel shape in transverse (horizontal) cross- section, thereby
having a web 39 and flanges 41 and 43 extending at right angles to
the web (FIG. 8). The web has openings indicated at 45 and 47 and
holes 49 for reception of fasteners such as indicated at 50 (see
FIG. 7) for fastening it in position extending vertically on the
framework 11. The flanges 41 and 43 have notches indicated at 51
and 53 (FIG. 8) generally midway of the length (height) thereof,
the notch 51 having upper and lower horizontal edges 51a, 51b and
the notch 53 having upper and lower horizontal edges 53a, 53b.
Adjacent the upper end 21a of the bracket 21, its flanges 41, 43
have holes 55 and 57 in transverse alignment for reception of a pin
59a for establishing the pivotal connection 29. Adjacent the lower
end 21b of bracket 21 its flanges 41, 43 have holes 61 and 63 in
transverse alignment for reception of a pin 59b for establishing
the pivotal connection 33.
[0029] The side member 23 of the load sensor mounting 19 also
comprises an elongate metal bracket generally of channel shape in
transverse (horizontal) cross-section, thereby having a web 69 and
flanges 71 and 73 extending at right angles to the web (FIG. 8).
The web has openings indicated at 75 and 77 and holes 79 for
reception of fasteners such as shown at 50 for fastening it in
position extending vertically on the work platform 3. The flanges
71 and 73 have noses indicated at 81 and 83 generally midway of the
length (height) thereof, the nose 81 having upper and lower
horizontal edges 81a, 81b and the nose 83 having upper and lower
horizontal edges 83a, 83b. Adjacent the upper end of the bracket
23, its flanges 71, 73 have holes 85 and 87 in transverse alignment
for reception of a pin 89a for establishing the pivotal connection
29. Adjacent the lower end of bracket 23 its flanges 71, 73 have
holes 91 and 93 in transverse alignment for reception of a pin 89b
for establishing the pivotal connection 35.
[0030] The aforesaid third (upper) member 25, which constitutes a
link linking the work platform bracket 23 and the bracket 21
adjacent the upper ends of the brackets comprises a sleeve or tube
95 having a pair of eyes thereon each designated 97 spaced
lengthwise thereof on an axis parallel to the axis of the sleeve.
The sleeve and eyes are of suitable metal, each eye being welded to
the sleeve by welding, as indicated at 25w (FIG. 5), the effective
length of the upper member or link 25 (the distance between the
axis of the eyes 97 and the axis of the sleeve 95), being short in
relation to the height of the brackets 21, 23 and the vertical
distance between the axes of the pins 59a, 59b and 89a, 89b. The
sleeve and eyes could be made integral instead of being welded
together. Each pin 59a, 59b, 89a, 89b is retained in the respective
pin holes by means of C- clips 99 snapped into annular grooves in
the pins adjacent their ends.
[0031] The aforesaid fourth (lower) member 27, which constitutes a
link linking the work platform bracket 23 to the bracket 21
adjacent the lower ends of the brackets, like link 25 comprises a
sleeve or tube 105 having a pair of eyes thereon each designated
107 spaced lengthwise thereof on an axis parallel to the axis of
the sleeve. Here again, the sleeve and eyes are of suitable metal,
each eye being welded to the sleeve by welding, as indicated at 27w
(FIG. 6), the effective length of the upper member or link 27 (the
distance between the axis of the eyes 107 and the axis of the
sleeve 105), being short in relation to the height of the brackets
21, 23 and the vertical distance between the axes of the pins 59a,
59b and 89a, 89b. Here again, the sleeve 105 and eyes 107 could be
made integral instead of being welded together.
[0032] The upper link 25 has its eyes 97 pivotally encircling the
pin 59a at the upper end of bracket 21 and its sleeve 95 pivotally
encircling the pin 89a at the upper end of bracket 23. The lower
link 27 has its eyes 107 pivotally encircling the pin 89b at the
lower end of bracket 23 and its sleeve 105 pivotally encircling the
pin 59b at the lower end of bracket 21. The arrangement is such as
to permit some degree of up and down movement (essentially vertical
movement) of bracket 23 relative to bracket 21 in the direction of
the length of bracket 23. Since the upper and lower links 25 and 27
are identical (and of the same effective length), permitted
movement of bracket 23 is generally vertical in the direction of
its length and parallel to bracket 21. The effective length of each
of the upper and lower links 25, 27 (which is relatively short) is
such that bracket 23 is disposed in close proximity to bracket 21
with the edges of the flanges 71, 73 of bracket 23 close to the
edges of flanges 51, 53 of bracket 21 and with the noses 81, 83 on
flanges 71, 73 extending into the notches 51, 53 in flanges 51,
53.
[0033] Suitable bushings (139 in FIG. 13) are provided in sleeves
95, 105 and in eyes 97, 107 to insure smooth rotation of these
members relative to pins 89a, 89b, 59a, 59b. The bushings may be
self-lubricating bushings, bronze bushings or other types of
suitable bushings. Roller bearings may also be used.
[0034] Referring to FIGS. 7 and 8, the interconnection 37 is a
tension-taking interconnection pivotally connected at one end
constituting its upper end to the boom end bracket 21 and at its
other and lower end to the work platform bracket 23. Preferably,
the tension-taking interconnection comprises a commercially
available elongate tension load cell 109, more particularly a Model
ST-F tension load cell sold by Strainsert, Union Hill Industrial
Park, West Conshohocken, Pa., 19428. For a work platform weighing
generally from 100 to 200 lbs. which is to carry safely loads up to
500 lbs. The Strainsert Model ST-F load cell is one comprising a
3/8 inch diameter 16 NC 61/2 inch long rod (capable of safely
carrying at least 4500 lbs.) having load-sensing instrumentation
comprising a strain gauge 111 (FIG. 9) incorporated therein at the
inner end of an axial bore 113 extending from one end thereof (the
upper end as illustrated). The load cell 109 is generally similar
to the force sensing stud disclosed in U.S. Pat. No. 2,873,341
issued Feb. 10, 1959 entitled Electric Strain Gauge and Resistance
Units Therefor except for having eyes 115 threaded on each end. The
strain gauge is connected in an electrical circuit, wiring thereof
being indicated at 117, and acts to provide an electrical output
signal via the wiring representative of the strain to which the
load cell is subjected and thus serving as a measure of the weight
of the work platform 3 and load carried thereby, and utilized for
detecting the load on the work platform (e.g. loading thereof
totaling more than 500 lbs.). The wiring extends from the upper end
of the load cell through the opening 47 in bracket 21.
[0035] The upper eye 115 is hooked on a hook 119 extending down
from a sleeve 121 (a short metal tube) pivotally mounted on pin 59a
between the eyes 97 of the upper link 25, and the lower eye 115 is
hooked on a hook 123 extending up from a similar sleeve 125
pivotally mounted on pin 89b between the eyes 107 of the lower link
27. Thus, the interconnection 37 of linkage 20 may generally be
considered as comprising (in order from the top of the mounting 19
down as viewed in FIG. 8) sleeve 121 on pin 59a, upper hook 119,
upper eye 115, load cell 109, lower eye 115, lower hook 123, sleeve
125 and pin 89b. In the absence of a load on the work platform, the
interconnection holds the bracket 23 carrying the work platform in
the position wherein the upper edges 81a, 83a of the noses 81 and
83 on flanges 71 and 73 of the bracket 23 are slightly (e.g. 0.13
inch) spaced down from the upper edges 51a and 53a of notches 51
and 53 and the lower edges 81b and 83b of the noses 81, 83 and are
spaced a somewhat greater but still small distance (e.g. 0.25 inch)
up from the lower edges 51b and 53b of the notches. Said edges act
as interengageable stops (on brackets 21 and 23) limiting the up
and down movement of bracket 23 relative to bracket 21.
[0036] The load cell 109 of interconnection 37 continuously
monitors the loading of the work platform 3, being stressed and
strained in tension according to the weight of the platform and the
loading which the platform is subject to (e.g. the weight of a
workman or workmen on the platform plus items thereon and dynamic
forces), acting to transmit electrical current via wiring 117
depending in value on the strain in the load cell and thus
depending in value on the loading. Overloading, for example,
loading in excess of 700 lbs. static load (200 lbs. platform
weight) results in the current being of overload-detecting value,
thereupon acting via suitable and well-known means to trigger an
audible overload alarm, such as a siren, or a visual alarm, such as
a red light, or to effect movement of the work platform to a safe
position. An alternative is to have the load cell output interfaced
with a computer acting to trigger the alarm or to effect movement
of the work platform to a safe position if the load cell detects an
overload condition more than a predetermined portion of a
predetermined period of time (e.g. 50% of such period). The latter
mode may be preferred on account of the platform being subject to
dynamic load exceeding whatever static load is set as the overload
(e.g. 700 lbs. including platform weight of 200 lbs.).
[0037] With the effective length of each of links 25 and 27 short
in relation to the distance between the axes of pins 59a, 59b (and
the distance between the axes of pins 89a, 89b), preferably less
than 50% of that distance, and more preferably less than 25% and
most preferably less than 15% (e.g., 12.5%), the load cell 109 is
inclined off vertical only a small angle and accurately reflects
the loading. Thus, the tension on the load cell is generally equal
to the loading divided by the cosine of the angle off vertical,
e.g. for an angle of 5.degree. off vertical for the load cell, the
tension thereon is the load divided by 0.996. The mounting 19 is
sufficiently rigid to forces tending to twist the boom about its
axis (e.g., forces resulting from a person moving from side to side
on the work platform) that the load cell 109 is not affected by
such forces and essentially does not react to them.
[0038] It will be observed from the foregoing that links 21, 23, 25
and 27 form a parallelogram linkage, with the upper and lower links
being short compared to the side links 25 and 27. It will be
understood that other four-member linkages may also be used to
practice the present invention, and that the lengths of the
respective links may vary. For example, the upper and lower links
may be substantially longer than links 21 and 23 as shown in the
drawings. Also, the construction of the links may vary from that
shown. Further, the construction of the interconnection 37 may also
vary. For example, the load cell 109, eyes 115, hooks 119, 123 and
sleeves 121, 125 could be formed as an integral member machined
from a piece of suitable metal. Instrumentation other than strain
gage 111 could also be used for sensing the tension load in the
linkage 20.
[0039] As an adjunct to the above, the load sensor mounting 19 may
be modified to detect not only a vertical load on the load support
3 but also an overhung load on the load support. This modification
has particular (albeit not exclusive) application to forklifts,
such as a rough terrain forklift, where loads substantially
overhanging the tines of the forklift may create large moment
forces tending to tip the forklift. In these circumstances, it is
desirable to measure such forces to prevent tipping. As illustrated
in FIGS. 10-14, the interconnection 37 of the load sensor mounting
19 is modified so that the pin 59a of the bracket 23 is
instrumented to measure the shearing force thereon. (This shear
force is indicative of the tension in the upper member 25 and thus
the magnitude of the overhung load). The pin used in place of 59a,
designated 59c in FIGS. 10-14, has strain gauges 131 incorporated
therein connected in an electrical circuit the wiring of which is
indicated at 133 extending out of one end of the pin through an
axial bore 135 in the pin. In the event the strain gages 131 sense
a shear force indicative of an overhung load which exceeds a
predetermined maximum load, an alarm or lift shut-off is
triggered.
[0040] As shown in FIG. 12, the preferred embodiment includes four
strain gages 131, two at each end of the pin 59c arranged on
diametrically opposite upper and lower sides of the pin on a
neutral vertical axis Al of bending moment. These strain gages
measure the horizontal force component of a shear force F exerted
on the pin at an angle .omega. (FIG. 12). This force component (F
cos .omega.) is representative of the moment or "overhung" load on
the load support 3. The pin 59c has a circumferential groove 137
adjacent each of its ends at the location of the strain gages 131
to provide a reduced pin cross-section for sensing the shear forces
with greater accuracy. It is important that these grooves 137 (and
the associated strain gages 131) be located at positions where the
shear load is greatest, such as the locations shown in FIG. 13
where the ends of the eyes 97 (and bushings 139 therein) are
centered widthwise of the grooves. The pin is held in this position
by a keeper plate 141 fastened to a flange 41 of side member 21 of
the load sensor mounting 19. An edge of the keeper plate 141 is
received in a slot 143 in the pin 59c. The opposite end of the pin
has an enlarged head 145 which engages flange 43 of the side member
21, the end result being that the pin is held in fixed axial
position in which the ends of the eyes 97 and/or bushings 139 are
generally in registry with the grooves 137 in the pin. The keeper
plate 141 also holds in the pin 59c in a predetermined angular
position in which the neutral axis Al of bending moment is
generally vertical to provide an accurate reference from which to
quantify the output signals of the strain gages 131. (When the
strain gages are positioned on a neutral axis which is vertical,
the strain gages will sense only the horizontal component (F cos
.omega.) of shear force on the pin, which is the component
representative of the overhung load; the strain gages will not
sense the vertical component (F sin .omega.) of the force F. An
instrumented pin suitable for use is commercially available from
Strainsert, Union Hill Industrial Park, West Conshohocken,
Pennsylvania, 19428.
[0041] FIGS. 15-17 illustrate an alternative embodiment capable of
measuring both the weight of the load on the platform and the
"overhung" load, but without the need to use a tension load cell
109. In this embodiment, pin 59c is replaced by an instrumented pin
59d which is similar to pin 59c except that there are two pairs of
strain gages at each end of the pin, a pair of upper and lower
strain gages 125a for measuring the horizontal component (F cos
.omega.) of any shear force on the pin, indicative of the overhung
load, and a pair of left and right strain gages 125b for measuring
the vertical component (F sin .omega.) of any such shear force
indicative of the weight of the load on the load support 3. The
upper and lower strain gages 125a are located on a vertical neutral
axis Al of bending moment, and the left and right strain gages 125b
are located on a horizontal neutral axis A2 of bending moment. In
this embodiment the load cell 109 is replaced by a simple
structural member which functions solely to support the load of the
platform. An instrumented pin 59d of suitable manufacture may be
obtained from the aforementioned Strainsert company.
[0042] It will be understood that the interconnection 37 between
the first and second members 21, 23 described can have
configurations other than those described above without departing
from the scope of this invention, which is intended to cover any
type of linkage interconnection between the first and second
members 21, 23 instrumented for sensing the load on the work
platform 3 (i.e., the load support). Further, the instrumentation
used for sensing the loads may be different from the strain gage
systems described above. For example, the instrumentation could be
a spring system comprising a spring (in lieu of a tension member
such as 109) and a device for measuring the deflection of the
spring under a load on the work platform 3. The measuring device
could be a dial load indicator, or a linear potentiometer or
encoder providing a digital readout of the load, or a set-point
device such as a proximity switch for signaling an alarm or
shut-off of the machine in the event of a predetermined load
condition. Another method for measuring the force in the diagonal
would be to use a hydraulic cylinder with a pressure transducer or
pressure switch.
[0043] Regardless of how the load is sensed, the load sensor of the
present invention can have various outputs, as noted above. For
example, the output of the load sensor can be displayed as an
analog or digital readout of the actual load on the platform, or it
can be used to signal an alarm or to shut off the machine if a
predetermined load condition is met.
[0044] The load sensing system represents an improvement over prior
systems. Not only is the system more economical, due in large part
to the fact that only a single bracket and load sensor is used, it
is also accurate and capable of measuring various load conditions,
including the weight on the work platform and the overhung
load.
[0045] In view of the above, it will be seen that the several
objects of the invention are achieved and other advantageous
results attained.
[0046] As various changes could be made in the above constructions
without departing from the scope of the invention, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *