Weighing scales – Structural installation – Geographic
Reexamination Certificate
1999-04-09
2001-01-23
Gibson, Randy W. (Department: 2859)
Weighing scales
Structural installation
Geographic
C177S255000, C177SDIG009
Reexamination Certificate
active
06177639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of load cell mounts.
2. Description of the Background Art
Scales are devices that are used to determine a weight of an object by measuring the gravitational pull exerted on that object. Scales are commonly used to determine the physical amount or quantity of an item, such as a foodstuff, for example. Scales are therefore a necessary component of commerce, and aid in the smooth flow of commerce by ensuring fairness and accuracy in any transactions requiring a weight or amount measurement.
Modern scales have benefitted greatly from improvements in technology. One device that has revolutionized scales is the load cell. Load cells are widely used in scales designed to weigh large quantities, such as scales for weighing trucks, train cars, tanks, hoppers, or other large loads or machinery. A load cell is a piece of steel that contains a strain gauge. The strain gauge is an electronic transducer that changes resistance when it is stressed. It measures a strain imposed on the load cell by measuring an almost imperceptible deformation of the load cell under a load. Typically, in a load cell multiple strain gauges are connected in a Wheatstone bridge configuration. When an input voltage is applied to the bridge, the bridge outputs a voltage proportional to the force on the load cell. By varying the size and strength of the steel comprising the load cell body, the load cell can be designed to accommodate different load capacities.
One type of load cell is a shear or shear beam type (also referred to as compression type) load cell. This type of load cell is a device that is placed horizontally under a load, with the force of the scale directed onto a small area, or “sweet spot,” on the top of the load cell.
In use, multiple load cells may be used in a scale application. Multiple load cells may be placed under a weigh bridge of a scale, and the outputs of all load cells may be summed to provide a total weight of the weight bridge and load.
Load cells offer several advantages over the traditional mechanical scale apparatus. Because load cells are electronic, they can provide an electronic output and can be calibrated electronically, with no moving parts to wear out. Load cells are resistant to dirt and moisture.
In scale applications, load cells are only a component, and must be mounted within the scale so as to receive the full weight of the scale and the load. In order to generate accurate readings, the weight must be imparted to the load cell with only a vertical force component, and with no horizontal force component. This means that any horizontal motion or sway must be reduced or eliminated. One of the biggest drawbacks of related art load cell mounts is the inability to accommodate and minimize motion of the weigh bridge relative to the load cell. In related art load cell mounts, external devices were employed in order to limit or reduce sway of the weigh bridge due to movement of a vehicle onto the weigh bridge. These external devices often took the form of bumpers that limited sway. In an effort to solve this problem, one related art mount employed a pivoting mount that pivoted on the top surface of the load cell (U.S. Pat. No. 4,549,622 to Leiman). Unfortunately, the Leiman load cell mount thereby imparted a torsional force to the load cell, with the resulting torsional force affecting the accuracy of measurements.
There remains a need in the art for improvements in load cell mounts.
SUMMARY OF THE INVENTION
A swing and roll load cell mount for a weigh scale is provided according to a first aspect of the invention. The swing and roll load cell mount comprises a weigh bridge, a saddle mounted to the weigh bridge, the saddle having an upper surface adapted for attachment to the weigh bridge, and having a pair of downwardly extending arms having substantially semi-circular cut-outs in bottom edges of the arms, a bottom pin on which the cut-outs of the arms rest, the arms being freely rotatable on the bottom pin, a pair of link plates having a top hole and a bottom hole, with the bottom pin extending through the bottom hole of the pair of link plates and being freely rotatable within the link plates, with the link plates being spaced apart, a top pin, the top pin extending through the top hole of the pair of link plates and being freely rotatable within the link plates, a base, and a compression type load cell mounted on the base and having a substantially hourglass shaped medial groove, with the top pin resting in the medial groove of the load cell and the bottom pin passing below the load cell, wherein the saddle is supported in a manner that allows the saddle and the weigh bridge to swing longitudinally on a combination of the top and bottom pins and the pair of link plates, and further allows the top pin to roll transversely on the medial groove of the load cell while maintaining a load force in a substantially centered position on the load cell.
A swing and roll load cell mount for a weigh scale is provided according to a second aspect of the invention. The swing and roll load cell mount comprises a weigh bridge, a saddle mounted to the weigh bridge, the saddle having an upper surface adapted for attachment to the weigh bridge, and having a pair of downwardly extending arms having substantially semi-circular cut-outs in bottom edges of the arms, a bottom pin on which the cut-outs of the arms rest, the arms being freely rotatable on the bottom pin, a pair of link plates having a top hole and a bottom hole, with the bottom pin extending through the bottom hole of the pair of link plates and being freely rotatable within the link plates, with the link plates being spaced apart, a top pin, the top pin extending through the top hole of the pair of link plates and being freely rotatable within the link plates, the top pin further having a substantially hourglass shaped medial groove, a base, including two piers, with each pier of the pair of piers receiving an end of the load cell, with each pier having a cut-out on a side of each pier facing a center of the load cell, with the cut-out allowing the load cell more ability to deform, and a compression type load cell mounted on the base and having a substantially hourglass shaped medial groove, with the hourglass shaped medial groove of the top pin resting in and substantially matching the substantially hourglass shaped medial groove of the load cell, with the bottom pin passing below the load cell, wherein the saddle is supported in a manner that allows the saddle and the weigh bridge to swing longitudinally on a combination of the top and bottom pins and the pair of link plates, and further allows the top pin to roll transversely on the medial groove of the load cell while maintaining a load force in a substantially centered position on the load cell.
The above and other features and advantages of the present invention will be further understood from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3797593 (1974-03-01), Conley
patent: 4066140 (1978-01-01), Conley
patent: 4248317 (1981-02-01), Rahav
patent: 4280576 (1981-07-01), Smith, Jr.
patent: 4516645 (1985-05-01), Wetzel
patent: 4549622 (1985-10-01), Leiman
patent: 4601356 (1986-07-01), Muccillo, Jr.
patent: 4627507 (1986-12-01), Powell et al.
patent: 4828055 (1989-05-01), Hamilton et al.
patent: 4955441 (1990-09-01), Mills et al.
patent: 6046412 (2000-02-01), Rockwell
patent: 0 161 103 A2 (1985-11-01), None
Gibson Randy W.
Rothwell Figg Ernst & Manbeck
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