Electronic force sensing load cell

• US 5,336,854 A
• Filed: 04/03/1992
• Issued: 08/09/1994
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Avery Weigh-Tronix LLC (Illinois Tool Works Inc.)
• Original Assignee: Weigh-Tronix, Inc. (Illinois Tool Works Inc.)
• Inventors: Johnson, Thomas H.
• Primary Examiner(s): MILLER JR, GEORGE
• Application Number:
  US07/862,827
• Time in Patent Office: 858 Days
• Field of Search: 177/211, 177/229, 177/210 FP, 338/6, 73/862.627
• US Class Current: 177/210.0FP
• CPC Class Codes: G01G 21/24 Guides or linkages for ensuring parallel motion of the weigh-pans
• CPC Class Codes: G01G 3/1412 the supports being parallelogram shaped
• CPC Class Codes: G01L 1/162 using piezoelectric resonators
• CPC Class Codes: G01L 1/2243 the supports being parallelogram-shaped
• CPC Class Codes: G01P 15/097 by vibratory elements

Abstract

A load cell device includes a load cell structure formed of a suitable metal and including vertically spaced apart, generally parallel horizontal elements integrally formed with longitudinally spaced apart, generally parallel vertical elements. Flexures interconnect each horizontal element with the vertical elements. A bending beam extends between and is interconnected with the horizontal or vertical elements. When a load is applied vertically and perpendicularly to one of the horizontal elements, the load cell structure will elastically deform as a parallelogram to thereby transfer shear force to the bending beam to cause shear-induced bending of the latter. Strain gages or frequency resonator crystal elements sense the shear-induced bending and are embodied in electronic circuitry which produces an output signal caused by deformation of the bending beam. The electronic circuitry is operable to convert the output signal to a perceptive force readout.

Claims

1. A load cell device for measuring loads applied thereto as a weight determination, comprising:

a single-piece load cell structure including a pair of vertically spaced apart horizontal elements, a pair of longitudinally spaced apart opposed vertical elements, and flexures, integral with said horizontal and vertical elements, for connecting each horizontal element with said vertical elements,

a bending beam integrally connected with said pair of horizontal elements of said load cell and being spaced from said flexures, said bending beam being symmetrically spaced from and substantially parallel to said pair of vertical elements and being disposed substantially normal to said pair of horizontal elements, said bending beam having opposed vertical surfaces, each vertical surface having a pair of vertically spaced apart recesses therein,

electronic sensor means mounted on said bending beam, said sensor means including a pair of frequency resonator crystal elements, each bending beam having opposed vertical surfaces, each vertical surface having a pair of vertically spaced apart recesses therein,

electronic sensor means mounted on said bending beam, said sensor means including a pair of frequency resonator crystal elements, each being positioned across one of said recesses, whereby, when a load is applied vertically and perpendicularly to the plane of one of said horizontal elements, said load cell structure will elastically deform at said flexures as a parallelogram to thereby transfer shear force to said bending beam and cause shear-induced bending of said bending beam, and

electronic circuitry including said sensor means producing an output signal caused by deformation of said bending beam and being operable to convert said output signal to a perceptive weight readout.