Load cell scale

• US 4,020,911 A
• Filed: 06/14/1974
• Issued: 05/03/1977
• Est. Priority Date: 08/10/1973
• Status: Expired due to Term

• Current Assignee: Structural Instrumentation, Inc. (Vishay Intertechnology Incorporated)
• Original Assignee: Structural Instrumentation, Inc. (Vishay Intertechnology Incorporated)
• Inventors: McCauley, Jerry L., English, David C., Holmstrom, Godfrey A.
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Miska, Vit W.
• Application Number:
  US05/479,474
• Time in Patent Office: 1,054 Days
• Field of Search: 177/136, 177/211, 73/141 R, 73/141 A
• US Class Current: 177/136
• CPC Class Codes: G01G 19/12 having electrical weight-sensitive devices
• CPC Class Codes: G01G 3/1406 combined with special measuring circuits

Abstract

Several load cell fixed beams transmit the weight of the useful load of a truck or a scale device from the useful load support to the base structure, such as a truck chassis, or a trailer chassis. The load cell fixed beam carries two compression sensitive strain gauges and two tension sensitive strain gauges connected in a Wheatstone bridge circuit to actuate a digital display. An amplifier or a variable gain amplifier can be provided to intensify the bridge circuit signal. Calibration controls can be provided for setting the readout of the useful load to zero, and further controls can alter the sensitivity of the circuitry to alter the ratio between useful weight and readout.

Claims

1. A system for measuring the weight of a load carried by a truck having planar load supporting members above opposing planar portions on the underlying frame of the truck,

load cells positioned between said load supporting members and planar portions and being operatively connected to weight indicating means for providing an indication of the sum of the individual loads carried by said load cells, each of said load cells comprising:

a single, elongated, rectangular measurement beam having two end portions separated from a central portion by respective, relatively thin intervening portions, said end portions being relatively thick and projecting below the central and intervening portions of said beam such that said central and intervening portions can deflect downwardly when said end portions are supported on a planar surface and a load is applied to said central portion, and said central portion being relatively thick and projecting above the end and intervening portions of said beam with the top surface of said central portion being welded to a respective said planar load supporting member thereby spacing said planar load supporting member above the end portions of said beam such that said load supporting member does not contact said end portions when said central and intervening portions of said beam deflect downwardly responsive to a load applied to the central portion of said beam;

an elongated, planar support plate extending beneath said beam from one end portion to the other end portion, said beam having its lower surface contacting the respective planar portion of said underlying frame and its upper surface contacting the lower surface of said beam end portions, said end portions being welded to said support plate so that said measurement beam constitutes a fixed ended beam forming an S-shaped curve upon deflection; and

a pair of strain gauges secured to the underside of each intervening portion of said beam, said strain gauges being spaced apart from each other such that as the center portion of said beam deflects, the portion of said beam contacting one strain gauge undergoes compression while the portion of said beam contacting the other strain gauge undergoes tension.

2. The system of claim 1, wherein said truck is a logging truck with log supporting bunks and said support plates are secured to the frame of the truck at locations spaced beneath respective ends of said bunks, and the central portions of said measurement beams are welded to respective planar support plates which are bolted at the underside of said bunks, the axes of said measurement beams extending along the longitudinal axis of said truck such that said load cells effectively restrain shifting of said load responsive to forces exerted on said bunks in a longitudinal direction.