Load cell and weighing system

The present invention is directed to a novel load cell for weighing heavy loads and a weighing system using the novel load cells on a vehicle, such as a refuse truck. More specifically, the present invention is directed to a weighing system on a front-end loader refuse truck for weighing scrap metals or trash in boxes or containers lifted by arms or forks on which a plurality of the novel load cells are mounted. In addition, a protection mechanism may be activated to protect the load cells from a falling container when the container is lifted over the truck for dumping the contents into the truck or when the arms or forks are placed into the sleeves of the container to be weighed.

FIELD OF THE INVENTION 
The present invention is directed to a novel load cell for weighing heavy 
loads and a weighing system using four of the load cells on a scrap or 
trash truck. More specifically, the present invention is directed to a 
weighing system on a front-end loader refuse truck for weighing scrap 
metals or trash in containers lifted by arms or forks on which a plurality 
of the novel load cells are mounted. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 2,935,213 discloses a weighing scale using strain gage 
networks carried in certain load cells disposed in the tines of a fork 
type lift vehicle. A bar disposed in the tines with a central raised 
portion permits deflection in a vertical plane and four load cell 
assemblies are provided for the bar. 
U.S. Pat. No. 3,059,710 discloses a fork lift weighing apparatus employing 
electrical strain response means for weighing a load with a reasonable 
degree of accuracy regardless of where the load is placed on the fork 
tines. 
U.S. Pat. No. 3,063,576 discloses the use of two load cells each having a 
single tension gauge and two load cells having a single compression gauge 
connected where each cell is one of the four legs of a Wheatstone bridge 
so that the summation of the responses from the four cells indicates the 
correct total weight of a given load. 
U.S. Pat. No. 3,196,966 discloses load measuring devices on a fork lift 
truck which has spaced front and back plates with the front plate carrying 
the forks and the back plates secured to a mounting plate or mounting 
straps on a truck. Relative vertical and horizontal movement of the front 
and back plates is limited to avoid damage to the flexure strips and to 
the load cell. 
U.S. Pat. No. 3,910,363 discloses a weighing device for use with a fork 
lift truck having a stationary plate and a moveable plate and at least one 
load cell interposed between the moveable and stationary plates. 
U.S. Pat. No. 4,323,132 discloses a mounting adapter which provides a quick 
attachment for mounting or removing an electro-mechanical scale with 
respect to the lift frame of a fork lift truck. 
U.S. Pat. No. 4,420,053 discloses a weighing apparatus for fork lifts 
comprising a weight bridge supported at each end by load cells, the weight 
bridge and load cells are built into the fork. 
U.S. Pat. No. 4,421,186 discloses a fork lift scale which consists of 
horizontally disposed load sensors connecting a crossbar frame to the 
crossbars of a fork lift truck. 
U.S. Pat. No. 4,638,876 discloses a weighing apparatus for weighing 
eccentric loads for use with a forklift which has a weighing plate, three 
weight measuring systems or weighing cells engage the weighing plate. 
U.S. Pat. No. 4,666,004 discloses a pallet truck with a fork member movable 
in an up-and-down manner which is provided with a plurality of load cells 
on the tines of the fork member. 
U.S. Pat. No. 4,714,122 discloses pressure load cells with "an upwardly 
extending sensing element 56 which protrudes from the main body of the 
load cell . . . . Each sensor 56 is biased upwardly relative to the main 
body of the load cell and is forced into the main body of the load cell by 
the downward pressure on the sensing element. The greater the weight or 
pressure on the sensing element, the greater the movement of the sensing 
element into the body of the load cell." Also disclosed, a limit switch is 
operatively connected to the transducer so that the transducer is 
energized at a point when a full container is supported by the lifting 
means and when an empty container is supported by the lifting means for 
the purpose of determining the weight of the refuse in the container. 
U.S. Pat. No. 4,771,837 discloses a weighing system on a refuse truck which 
has a hydraulically actuated lifting means and a fluid pressure transducer 
which is operatively connected to the hydraulically actuated lifting means 
for sensing the weight of a refuse container when the container is lifted 
and lowered by the lifting means. 
U.S. 4,854,406 discloses the weighing systems of U.S. Pat. No. 4,714,122 
and U.S. Pat. No. 4,771,837 with emphasis on the electrical control 
system. 
U.S. Pat. No. 4,899,840 discloses a weighing apparatus for a vehicle having 
tines in which a ramp is mounted on each tine in front of and in spaced 
relation to a weighing load bearing plate. 
U.S. Pat. No. 5,245,137 discloses a method for determining a weight of 
material being emptied from a container. 
SUMMARY OF THE INVENTION 
The present invention is directed to a novel load cell for weighing heavy 
loads and a weighing system using the novel load cells on a vehicle, such 
as a refuse truck. More specifically, the present invention is directed to 
a weighing system on a front-end loader refuse truck for weighing scrap 
metals or trash in boxes or containers lifted by arms or forks on which a 
plurality of the novel load cells are mounted. In addition, a protection 
mechanism may be activated to protect the load cells from a falling 
container when the container is lifted over the truck for dumping the 
contents into the truck or when the arms or forks are placed into the 
sleeves of the container to be weighed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is directed to a weighing system for a vehicle having 
a pair of forwardly-extending arms or tynes to weigh any load lifted by 
the arms. The major problem of the weighing systems of the prior art is 
that the design of the load cells could not withstand the dropping of 
heavy weigh on the cells or weighing structure. The present invention 
utilizes a novel load cell which by its construction is sturdy and can 
withstand the rigors of a field weighing system. The load cell of the 
present invention has a bearing plate above that part of the load cell 
having the electrical and mechanical system (the bridge) which largely 
overcomes the problem of the prior art and protects the load cells of the 
present invention. More specifically, the present invention is directed to 
a weighing system on a front-end loader refuse truck for weighing scrap 
metals or trash in boxes or containers lifted by arms or forks on which a 
plurality of the novel load cells are mounted. In this preferred 
embodiment of the present invention, a further protection mechanism is 
utilized which protects the load cells especially from the dropping of 
large boxes on the surface of the cell in the dumping cycle. 
Referring to FIG. 1, the weighing system 10 in the prefered embodiment of 
the present invention is attached to the pair of front-end extending arms 
12 of a front end loading refuse truck 14. Truck 14 has a lifting 
mechanism 16 which includes a pair of hydraulically operated actuators 18 
on each side of the truck 14 which raises and lowers boom 20. The boom 20 
is pivotally connected to the side of truck 14 by a pivot pins 22. The 
front-end extending arms 12 are pivotally connected to the boom 20 by pins 
24 and moved by hydraulically operated actuators 26. The truck driver can 
control the operation of the actuators 18 and 26 independently throughout 
a dumping operation. 
The truck 14 is driven toward a container or box 30 to be serviced which 
may be filled with scrap metal or trash which is to be placed in a 
container 28 on the truck 14. The container 28 on the truck 14 has an 
opening (not shown) into which the scrap metal or trash in the box 30 is 
dumped. The dumping operation is no different than practiced 
conventionally, i.e. the arms 20 are positioned by the driver so they are 
in horizontal alignment with the sleeves 32 on the box 30 and the truck 
moved toward the box 30 until the arms 20 enter the sleeves 32. The boom 
20 is activated to lift the box 30 above the truck 14 and when it reaches 
the dumping position the arms 12 are activated by the driver so that the 
open top of the box 30 faces down toward the opening in the container 28. 
One aspect of the present invention is the novel load cells used in the 
weighing system. Referring to FIGS. 2 and 3, the load cell 40 of the 
present invention is a modification of a load cell manufactured by Coti, 
Inc. identified as ST 3 as set forth in their brochure, which is 
incorporated herein by reference. The preferred cell is a 10K load 
capacity and is calibrated for positive polarity in compression. The Coti 
load cell is the bottom portion of the cell as shown in the side view of 
FIG. 2 and consists of the stainless steel body 41 which is rectangular in 
shape. At one end 42, a foot 43 provides a solid base when bolted to a 
foundation by bolts placed through openings 44 to cantilever the other end 
45 from the foundation. The cell has a bridge 40' within the body 41, 
having covers 46 to secure the strain gages and electrical circuits of the 
bridge. A conductor cable 47 from the bridge conducts the electrical 
signal which is proportional to the compression (weight) placed on the end 
45. The load cell of the present invention modifies the Coti load cell by 
adding a bearing plate 50 welded to the upper surface 48 of the body 41. 
The plate 50 extends over the upper surface 48 beyond the weld 49 and 
protects the body 41 from any load. The upper surface 52 of the bearing 
plate 50 thus provides the only surface for any load placed on the load 
cell and protects the body 41 from any dropped load. In the event of a 
very large load such as the scrap iron or trash boxes 30, more than one 
cell 40 is utilized to provide sufficient bearing surfaces 52 of the 
bearing plates 50 to support the large load. Each load cell 40 measures 
the compression (weight) on the bearing surface 52 and the accumulation of 
the weights will provide the total weight of the load placed on the load 
cells. The utilization of the load cells 40 is illustrated in the 
preferred embodiment of the weighing system of the present invention. 
Referring now to FIGS. 4, 5 and 6, one of the front-end extending arms 12 
of a refuse truck has two load cells 40 mounted outside and adjacent the 
arm 12 on a foundation 60. The foundation is a metal bar welded between 
the arm 12 and a housing 62 which surrounds and protects the weighing 
system. The bar or foundation 60 may have an indentation (not shown) in 
which the cell 40 seats so there is no rotation of the cell 40 when the 
cell is bolted to the bar by bolts placed through openings 44. As 
illustrated, the cells 40 are positioned so that the bearing surfaces 52 
are above the upper surface 13 of arm 12 and preferably positioned so that 
the bearing surfaces 52 are nearest the front end and back end of arm 12, 
providing the greatest distribution of bearing surface area on which the 
box 30 will sit when weighed. To weigh the contents of a box 30, the arm 
12 is inserted into the sleeve 32 and the box 30 lifted from the ground so 
that the total weight of the box is on the four bearing surfaces 52 of the 
four load cells 40, two on each arm 12. After the contents of the box 30 
are dumped into the container 28 of truck 24, the empty box 30 is again 
weighed and the difference in weight is the weight of the contents dumped. 
A serious problem which is present in the systems of the prior art is that 
when the box 30 is lifted over the truck 14 to be dumped, the box 30 drops 
from being supported on the bottom of sleeve 32 to a position of being 
supported on the top of arm 12. The drop is only inches but the weight of 
a box 30 is such that even that drop will over time seriously affect the 
calibration of any load cell on which such a weight is repeatedly dropped. 
The load cells 40 of the weighing system of the present invention can 
withstand this problem; however, additional protection is provided by 
protection mechanism 70. Protection mechanism 70 preferably includes a 
pair of blocks 71 and 72 mounted in housing 62 adjacent arm 12, one block 
71 positioned in front of the load cells 40 and the other block 72 
positioned in back of both load cells 40. The blocks 71 and 72 are 
connected by a first member 74 which may be a rod or bar. A second member 
76, which also may be a rod or bar, is connected to the first member 74 by 
two link plates 77 and 78 which are pivotally around pins 80 and 82, 
respectively. Rods 80 and 82 extend from the outside of housing 62 to the 
opposite side of arm 12. A hydraulic actuator 84 which may be a piston 
with a cylinder 85 and a rod 86 is attached to the second member 76 by a 
pin 79. When the actuator 85 is activated by the driver of the truck 14, 
the members 74 and 76 are moved from the position of FIG. 5 to that of 
FIG. 6 where member 76 moves until it abuts stop 88 and the connections 
link plates 77 and 78 to the members 74 and 76 are vertically aligned to 
the rods 80 and 82. In this position, the blocks 71 and 72 are raised and 
the upper surfaces 71' and 72' are above the upper surface 52 of the 
bearing plates 50 of the load cells 40. The driver of the truck activates 
the actuator 85 during the dumping cycle after the weighing of the 
contents and before the box 30 starts downward after dumping the contents 
in the container 28 of truck 14. The actuator 85 may also be activated at 
any time to protect the load cells 40, such as lifting a full box 30 which 
may be bumped or jarred when it is carried by the extending arms 12 of the 
truck 14. There are many situations where the load cells 40 should be 
protected and the protection mechanism 70 provides such protection. There 
may be other alternatives to the specific protection mechanism 70 
illustrated such as hydraulic jacks mounted within housing 62. 
The individual cables 47 from each of the four load cells 40 are collected 
at a juncture box 90 on the boom 20 of truck 14. The juncture box 90 has 
chips which collect the individual analog signals from each load cell 40 
and a collective signal is transferred to the cab of the truck 14 by cable 
92. As illustrated in FIG. 7, the collected signal may to connected to a 
digital weigh read out device 94, such as a Model Programmable Weigh 
Indicator (PWI) available from GSE Scale Systems, or a panel mounted 
controller and printer 96, such as a PLI80RM series panel mount printer 
for instrumentation and data logging available from TEL, INC., Addison, 
Tex. With these devices in the cab of the truck 14 a driver can record the 
weight of the material dumped into the container 28 on the truck 14, 
provide the information to a person at the site of the box 30 and record 
the information for billing purposes.