Strain gauge transducer force or weight measurement arrangement and touch tablet

• US 5,447,074 A
• Filed: 12/19/1994
• Issued: 09/05/1995
• Est. Priority Date: 11/18/1992
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Maniguet, Francois, Polaert, Remy
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): Olsen, James M.
• Application Number:
  US08/358,637
• Time in Patent Office: 260 Days
• Field of Search: 73/763, 73/781, 73/755, 73/862.04
• US Class Current: 73/862.041
• CPC Class Codes: G01G 3/1402 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports

Abstract

A strain-gauge transducer (5) comprising a substrate (10) provided with strain gauges and pressure members (11, 12) which deform the substrate (10) via transfer elements (1a, 4a) which transmit an applied force (F). The transfer elements comprise bars (1a, 1b, 4a, 4b) molded from an elastomer in a common molding operation. A material (2a, 3a) having a higher compressibility than the bars may be interposed between the bars. This material may form elastic stops (54a) provided to preclude breakage of the substrate. This results in a transducer whose sensitivity is linear for small loads and which is very insusceptible to overloading. The transducer can be used for the construction of scales or touch tablets.

Claims

1. A strain-gauge transducer, comprising:

two pressure members which are deformable in response to an applied force;

at least one strain gauge having a substrate disposed between the two pressure members; and

a plurality of strain detectors and transfer means comprising segments of an elastic material integrally molded to the substrate and located between the substrate and the pressure members to transmit the applied force.

2. A transducer as claimed in claim 1, wherein the segments are alternately disposed at opposite sides of the substrate.

3. A transducer as claimed in claim 1, wherein opposite each segment, on the surface opposite to that where it is situated, a stop is disposed to limit the deflection of the substrate.

4. A transducer as claimed in claim 3, wherein the stop is made of an elastic material.

5. A weight or force measurement arrangement, wherein it includes at least one transducer as claimed in claim 1.

6. A strain-gauge transducer, comprising:

at least one strain gauge including a substrate;

a strain detector in contact with a side of the substrate;

two pressure members each one of which is disposed adjacent an opposing side of the substrate which deform the strain gauge under the influence of an applied force;

transfer means disposed between each said pressure member and the substrate for transmitting the applied force, including segments of an elastic material molded on the substrate in a single molding operation for positioning and dimensioning said segments on the substrate; and

a stop attached to an opposite surface of the substrate that the segment is molded to and located opposite the segment, having a higher compressibility than an adjacent segment, to limit the deflection of the substrate.

7. A transducer as claimed in claim 6, wherein the higher compressibility of the stop is obtained by forming air chambers in the elastic material during molding.

8. A strain-gauge transducer, comprising:

at least one strain gauge including a substrate;

a strain detector in contact with a side of the substrate;

two pressure members each one of which is disposed adjacent an opposing side of the substrate which deform the strain gauge under the influence of an applied force;

transfer means disposed between each said pressure member and the substrate for transmitting the applied force, including segments of an elastic material molded on the substrate in a single molding operation wherein the segments are positioned and dimensioned during the single molding operation for positioning and dimensioning said segments on the substrate; and

a stop attached to an opposite surface of the substrate that the segment is molded to and located opposite the segment wherein the stop is positioned and dimensioned during the single molding operation.

9. A touch tablet, comprising:

at least one transducer including

two pressure members which are deformable in response to an applied force;

at least one strain gauge having a substrate disposed between the two pressure members; and

a plurality of strain detectors and transfer means comprising segments of an elastic material integrally molded to the substrate and located between the substrate and the pressure members to transmit the applied force.

10. A method for producing a strain gauge transducer, comprising the steps of:

positioning and dimensioning a plurality of strain detectors and transfer means comprising segments of an elastic material on a surface of a substrate by molding the elastic material on the substrate in a single molding operation; and

disposing at least one strain gauge including the substrate between two deformable pressure members.

11. The method of claim 10 in which the step of positioning and dimensioning the strain detectors and transfer means on a surface of a substrate comprises alternately disposing the segments on opposing surfaces of the substrate.

12. The method of claim 10 further comprising the step of disposing a stop on the surface of the substrate opposite each segment to limit a deflection of the substrate due to an applied force.

13. The method of claim 12 wherein disposing a stop on the surface of the substrate comprises disposing a stop having a compressibility that is higher than a compressibility of the segment adjacent the stop.

14. The method of claim 12 wherein disposing a stop having a compressibility that is higher than a compressibility of the segment adjacent the stop comprises forming an air chamber in the elastic material during the single molding operation.

15. The method of claim 12 wherein disposing a stop on the surface of the substrate comprises positioning and dimensioning the stop in the single molding operation of positioning and dimensioning the strain detectors and transfer means.