Portable scale with load cell

A load cell for scales and the like has an elongated bar having opposite sides, sloped ends and a removable top portion. A pair of load cells are mounted within the housing with each load cell comprising an elongated bar having opposite ends, opposite sides, a center portion, and top and bottom surfaces. The bar has cavity openings extending into the sides thereof adjacent each of the opposite ends. A strain gauge is mounted in each of the cavity openings and is sensitive to deflection of the bar caused by weight exerted on the top surface of the bar. Each of the strain gauges are connected to a visual readout apparatus which collectively reflects the loads imposed upon the bars. A cantilever support element is positioned on the bottom surface of the bars and has a length less than the bars to create a space below the bottom thereof and a support surface upon which the cantilever support bar is positioned to suspend the ends of the bar in cantilever fashion.

BACKGROUND OF THE INVENTION 
Portable scales using strain gauge load cells are common in the prior art. 
A typical device of the prior art is shown in U.S. Pat. No. 4,714,121. 
These devices are adapted to support the wheels of a vehicle. The downward 
weight of the vehicle on the scale and the load cells thereof is 
transmitted electronically to a visible data readout system whereby the 
weight of the vehicle can be ascertained. 
The load cells of such portable scales utilize conventional strain gauges 
whereupon the deflection of the load cells is measured by the strain 
gauges and is transmitted to the readout apparatus which assimilates the 
collective readings from the individual portable scales located under the 
various wheels of the vehicle. 
The load cells of the prior art are normally comprised of an elongated bar. 
U.S. Pat. No. 4,775,018 shows such a bar having an elongated slot therein. 
When weight deflects the bar and compresses the slot, strain gauge therein 
measure the deflection of the bar and this data is transmitted to the 
readout apparatus. 
Other load cells of the prior art utilize an elongated bar which is 
supported on one end and which has the other end suspended in cantilever 
fashion. A strain gauge is placed within a cavity in the cantilevered end 
of the bar, and the strain gauge measures deflection of the cantilever end 
of the bar in conventional fashion. Load cells of this type are commonly 
used in pairs with the bars being positioned in alignment, and the 
cantilevered ends thereof extend in opposite directions from the inner 
ends which support the bar on a supporting surface. 
Among the shortcomings of the prior art devices is that they do not possess 
the strength which is often required to weigh large and heavy vehicles. 
Further, the top plate of the scales of the prior art using these load 
cells often engage the load cells in such a manner that the top plates are 
damaged as the vehicle wheels are supported thereby. In addition, a 
plurality of load cells are often required for each portable scale 
(sometimes four in number) and this large number of load cells often 
exceeds the capacity of the readout equipment. The portable scales of the 
prior art are often very heavy even though they can be manually moved from 
one place to another. 
It is therefore a principal object of this invention to provide a load cell 
for a portable scale which is strong, relatively light in weight, easily 
mounted in a scale housing, and capable of operationally housing more than 
one strain gauge. 
A further object of this invention is to provide a portable scale utilizing 
a load cell that can assume the weight being imposed thereon by the top 
plate of the scale without resulting in deformation or other damage to the 
top plate of the scale. 
A still further object of this invention is to provide a portable scale 
utilizing load cells which minimizes the number of load cells required per 
scale, and wherein the load scale is easily installed in the scale housing 
and easily serviced. 
These and other objects will be apparent to those skilled in the art. 
SUMMARY OF THE INVENTION 
A portable scale with a load cell of this invention has a housing with a 
bottom, opposite sides, sloped ends and a removable top portion. A pair of 
load cells are mounted within the housing with each load cell comprising 
an elongated bar having opposite ends, opposite sides, a center portion, 
and top and bottom surfaces. The bar has cavity openings extending into 
the sides thereof adjacent each of the opposite ends. A strain gauge is 
mounted in each of the cavity openings and is sensitive to deflection of 
the bar caused by weight exerted on the top surface of the bar. Each of 
the strain gauges are connected to a visual readout apparatus which 
collectively reflects the loads imposed upon the bars. A cantilever 
support element is positioned on the bottom surface of the bars and has a 
length less than the bars to create a space below the bottom thereof and a 
support surface upon which the cantilever support bar is positioned to 
suspend the ends of the bar in cantilever fashion.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The numeral 10 designates the portable scale of this invention which is 
comprised of housing 12 having an interior compartment 12A. Housing 12 has 
a bottom 14, side 16, sloping ends 18, and a removable top 20. An 
outwardly extending handle 22 is welded or otherwise secured to one of the 
sides 16. As shown in FIGS. 2, 3 and 4, an electrical connector 24 is also 
mounted in one of the sides 16. A stabilizer wall 26 extends across the 
center of interior compartment 12A (FIGS. 3 and 4). 
Two load cells 28 (FIGS. 3 and 4) are mounted within compartment 12A. These 
load cells are identical in structure and function. The load cells 28 are 
comprised of a bar 30 (see FIGS. 5 and 6) having a top surface 32, a 
bottom surface 34, sides 36, ends 38, and a center portion 40. Cavity 
openings 42 extend inwardly in the sides 36 adjacent the opposite ends 38 
of the bar 30 to create a narrow web 44 (FIG. 6). Strain gauges 46 of 
conventional construction are mounted in two of the cavity openings 42 
adjacent web 44. A cantilever plate 48 is positioned on the bottom surface 
34 of bar 30 and has a length less than the length of bar 30. Plate 48 
could be made integral with bar 30. A bar pad 50 is welded or otherwise 
secured to the bottom 14 of housing 12 on the upper portion thereof, and 
the bars 30 are supported on the bar pads 50 through the engagement of 
cantilever plates 48 on the bottom 14. 
With reference to FIGS. 5 and 6, apertures 52 extend vertically through the 
center portion 40 of bars 30 to receive countersunk bolts 54. Apertures 52 
also extend through cantilever plate 48 as best shown in FIG. 5. The lower 
ends of bolts 54 are threaded and are threadably received within apertures 
56A which are positioned in alignment with apertures 56. 
Vertically disposed apertures 58 extend through the ends 38 of bars 30, and 
washers 60 are positioned on the top surface 32 of bar 30 around the upper 
ends of these apertures. Bolts 62 extend through suitable apertures in top 
plate 20 and extend downwardly through washers 60 and are threadably 
mounted within apertures 58. As a result, the top plate 20 is suspended on 
the load cells 28 by resting on the washers 60. 
With reference to FIG. 4, a wiring harness 64 is electrically connected to 
each of the strain gauges on the load cell 28 shown on the right hand side 
of the drawing. The wiring harness extends through the stabilizer wall 26 
and the wires contained therein are conventionally connected to connector 
66. Similarly, leads 68 extend from the strain gauges 46 in the load cell 
28 on the other side of the device as shown in FIG. 4, and the opposite 
ends thereof are also connected to the connector 66. Lead 70 then extends 
from connector 66 to the electrical connector 24 on the side 16 of housing 
12 as shown in FIG. 4. A conventional lead 72 then extends from connector 
24 to the digital readout apparatus 74 as best shown in FIG. 1. 
In operation, the portable scale as shown in FIG. 2 is carried to the 
desired location by manually grasping the handle 22. For a four-wheeled 
vehicle, four of the scales 10 would be spaced to support the four wheels 
of the vehicle. Each scale would have a lead 72 which is connected to the 
readout apparatus 74. With reference to FIG. 1, a feed mixing wagon 76 
having at least a pair of wheels 78 will utilize two of the scales 10 with 
one scale being under each of the wheels 78. With the readout apparatus 74 
being connected to a conventional source of power (not shown) the 
conventional readout apparatus 74 receives the data from each of the 
portable scales 10 through the leads 72, assimilates this data, and 
visually displays the total weight being imposed on the collection of 
scales 10. 
It is therefore seen that the device of this invention will provide load 
cells which overcome the shortcomings of the prior art, and which will 
achieve all of the stated objects of this invention.