FORCE MEASURING APPARATUS

• US 3,693,425 A
• Filed: 04/30/1970
• Issued: 09/26/1972
• Est. Priority Date: 04/30/1970
• Status: Expired due to Term

• Current Assignee: Rheometrics, Inc.
• Original Assignee: Christopher W. Macosko, Joseph M. Starita
• Inventors: Starita, Joseph M., Macosko, Christopher W.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/033,251
• Time in Patent Office: 880 Days
• Field of Search: 73/133,117.4,517R,136R,147 308/2A
• US Class Current: 73/862.044
• CPC Class Codes: G01L 1/2262 involving simple electrical bridges
• CPC Class Codes: G01L 5/162 of piezoresistors
• CPC Class Codes: G01L 5/1627 of strain gauges using piezoresistors G01L5/162
• CPC Class Codes: G05G 2009/04762 Force transducer, e.g. strain gauge

Abstract

Apparatus for independently measuring mutually perpendicular forces and torque about the line of action of one said force. A set of four cantilevered beams extends along a pair of X-Y coordinate axes and supports a rigid platform in the X-Y plane. A force receiving means above said X-Y plane and on the Z-axis intersecting the origin of said X-Y axes, is rigidly coupled to said platform, whereby forces applied thereto produce bending in said beams in accordance with the direction of the force. Strain gauge means and bridge circuit means are arranged to detect only strains in said beams resulting from the force desired to be measured.

Claims

1. Apparatus for independently measuring mutually perpendicular forces applied to a force receiving means and torque about the line of action of one said force, comprising:

a set of four cantilevered support beams extending along a pair of orthogonal X-Y coordinate axes, the cantilevered ends of each pair of opposite beams being equidistantly spaced from the origin of said axes;

a rigid platform means secured and suspended by said cantilevered ends of said beams, said platform means being centered at the origin of said axes;

force receiving means spaced from the plane of said X-Y coordinates on a Z-axis orthogonal to said X-Y axes, said means being rigidly coupled to said platform means whereby X or Ydirected forces applied to said force receiving means equidistantly but oppositely deflects the cantilevered ends of onlY the pair of said beams extending along the coordinate axis parallel to said force by bending said beams, whereby a Zdirected force applied to said force receiving means deflects said cantilevered ends equidistantly along said Z-axis, and whereby torque about said Z-axis upon said force receiving means deflects equidistantly the said cantilevered ends of said beams in directions parallel to said X-Y plane; and

means for measuring the strain in said beams resulting only from the deflections effected by the force desired to be measured, and deriving therefrom the magnitude of said desired force.

2. Apparatus in accordance with claim 1 wherein said beams are reduced in cross-section at said cantilevered ends adjoining said platform to define hinge-like connections between said platform and beams.

3. Apparatus in accordance with claim 1 wherein said force receiving means is coupled to said platform by a columnar member secured to said platform and extending along said Z-axis to said force receiving means.

4. Apparatus in accordance with claim 1 wherein said beams are provided with a configuration which concentrates said strains-to-be-measured in localized portions thereof, said measuring means being adapted to measure said strains in said localized portions.

5. Apparatus in accordance with claim 4 wherein said strain measuring means comprises matched sets of four strain gauges affixed to each of the opposed surfaces of the localized portions of said beams, and bridge circuit means connected to said strain gauges such that bridge-unbalancing electrical changes thereof detected by said bridge circuit means are effected only by the force desired to be measured.

6. Apparatus in accordance with claim 4 wherein said localized portions are proximate the supported ends of said beams.

7. Apparatus in accordance with claim 6 wherein said beams are hollow in at least said localized portions.

8. Apparatus in accordance with claim 6 wherein said beams are of rectangular cross-section at at least said localized portions.

9. Apparatus in accordance with claim 6 wherein said strain measuring means comprises matched sets of four strain gauges affixed to each of the opposed surfaces of the localized portions of said beams, and bridge circuit means connected to said strain gauges such that bridge-unbalancing electrical changes thereof detected by said bridge circuit means are effected only by the force desired to be measured.

10. Apparatus in accordance with claim 9 wherein said beams are reduced in cross-section at said cantilevered ends adjoining said platform to define hinge-like connections between said platform and beams.

11. Apparatus in accordance with claim 10 wherein said force receiving means includes a flat surface parallel to said X-Y plane, said surface being adapted to receive material thereon for subjection to force testing.

12. Apparatus in accordance with claim 10 wherein the cantilevered ends of each of said beams are equidistantly spaced from the origin of said axes and said force receiving means is positioned along said Z-axis at a spacing from the origin of said coordinate axes equal to the spacing of the cantilevered ends of said beans from said origin.