Pancake load cell

• US 3,874,229 A
• Filed: 03/11/1974
• Issued: 04/01/1975
• Est. Priority Date: 03/11/1974
• Status: Expired due to Term

• Current Assignee: Alfred Newman Ormond
• Original Assignee: Alfred Newman Ormond
• Inventors: Ormond, Alfred Newman
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/449,901
• Time in Patent Office: 386 Days
• Field of Search: 73/88E,141R,141A,398AR 177/208,211 338/5,4
• US Class Current: 73/862.581
• CPC Class Codes: G01G 19/10 having fluid weight-sensitive devices
• CPC Class Codes: G01G 5/00 Weighing apparatus wherein the balancing is effected by fluid action
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction

Abstract

A load cell is formed in the shape of a pancake so as to be readily accommodated beneath objects to be weighed wherein the vertical clearance is low. The body includes a pancake shaped inner chamber filled with oil, a wall portion of the chamber being thinned to define a diaphragm. Strain gauges connect to the diaphragm which is responsive to pressure changes in the chamber as a consequence of weight tending to squeeze the pancake configuration, the strain gauges providing electrical signals constituting a function of the weight or force applied to the cell.

Claims

1. A load cell comprising:

a. an upper flat circular plate member having an upper shallow circular cavity on its underside;

b. a lower flat circular plate member having a lower shallow circular cavity on its top side opposing said upper shallow circular cavity;

c. means securing said upper plate member on top of said lower plate member such that the shallow cavities define an hermetically sealed circular chamber of inside diameter D'"'"''"'"' and inside thickness T'"'"''"'"' within said members, the overall configuration resulting in a general pancake shaped load cell of outside diameter D and outside central area of thickness T, the peripheral portion of the members radially beyond the central area of thickness T having a reduced outside thickness of T'"'"''"'"''"'"''"'"', the diameter of the end of the reduced outside thickness being D'"'"''"'"''"'"''"'"';

wherein;

2. A load cell according to claim 1, in which:

D/T 15.5 + or - 0.5 D'"'"''"'"'/T'"'"''"'"' 13.0 + or - 0.5 D/D'"'"''"'"' 1.035 + or - 0.002 T/T'"'"''"'"' 8.75 + or - 0.25 D'"'"''"'"'/d 13.2 + or - 0.5 d/t 25.0 + or - 1.0 D/D'"'"''"'"''"'"''"'"' 1.150 + or - 0.025 T/T'"'"''"'"''"'"''"'"' 4.75 + or - 0.25

3. A load cell according to claim 1, in which said means securing said upper plate member on top of said lower plate member comprises welding of the peripheral edge of the upper plate member to the peripheral edge of the lower plate member over 360* and wherein said substantially incompressible fluid comprises oil.

4. A load cell according to claim 1 including stop means limiting the movement of the plates towards and away from each other whereby when given compression and tension forces on the load cell exceed given values, the flexing of the peripheral portion of the cell is limited.