Load sensor using a piezoelectric S.A.W. device

• US 4,623,813 A
• Filed: 12/24/1984
• Issued: 11/18/1986
• Est. Priority Date: 12/22/1983
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Ishida KOKI
• Original Assignee: Kabushiki Kaisha Ishida KOKI Seisakusho
• Inventors: Naito, Kazufumi, Utsunomiya, Mitito
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US06/685,779
• Time in Patent Office: 694 Days
• Field of Search: 310/313 R, 310/339, 310/313 B, 310/338, 310/313 C, 310/313 D, 333/150-154, 333/193, 333/195, 333/196, 73/763, 73/774, 73/778, 73/781, 73/754, 73/514, 73/517 R, 73/517 AV, 73/703, 73/708, 73/723, 73/DIG. 4, 177/210 R, 177/210 FP, 177/210 EM
• US Class Current: 310/313.00R
• CPC Class Codes: G01G 3/13 having piezoelectric or piezoresistive properties
• CPC Class Codes: G01G 3/16 measuring variations of frequency of oscillations of the body
• CPC Class Codes: G01L 1/165 with acoustic surface waves
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

A load sensor includes a fixed rigid portion, a movable rigid portion spaced from the fixed rigid portion and adapted to receive an applied load, and a shear-deformable member provided between the two rigid portions. The shear-deformable portion is provided with a transmission and a reception transducer constituting an elastic surface-wave oscillator. When a load is applied to the movable rigid portion, weight is sensed based on a deviation in the oscillation frequency of the elastic surface-wave oscillator. The fixed and movable rigid portions, as well as upper and lower beams interconnecting these portions, constitute a load-sensitive element. The latter has a side face which is closed off by a pliable membrane for sealing the shear-deformable element disposed within the load-sensitivie element. Alternatively, a corrugated bellows is connected across the fixed and movable rigid portions to seal the shear-deformable member within the bellows.

Claims

1. A load sensor for sensing a load based on an oscillation frequency deviation of an elastic surface-wave oscillator having an elastic surface-wave resonator and an amplifier, comprising:

a fixed rigid portion fixedly secured to a stationary object;

a movable rigid portion disposed in spaced relation from said fixed rigid portion for receiving an applied load;

a shear-deformable member having one end portion fixedly secured to said fixed rigid member and an opposite end portion fixedly secured to said movable rigid member;

a shear-deformable portion provided on said shear-deformable member;

an elastic surface-wave resonator provided on said shear-deformable portion;

a first beam interconnecting an upper end of said fixed rigid portion and an upper end of said movable rigid portion; and

a second beam interconnecting a lower end of said fixed rigid portion and a lower end of said movable rigid portion, said first and second beams each having an arcuate cut-out at end portions thereof to form flexible portions of said end portions.

2. A load sensor according to claim 1, wherein said fixid rigid portion, said movable rigid portion and said first and second beams constitute a load-sensitive element, said load-sensitive element having a side face closed off by a sheet member to seal said shear-deformable member.

3. A load sensor according to claim 1, wherein said shear-deformable portion has a front side surface and a back side surface and an elastic surface-wave resonator is provided on each of said front and back side surfaces of said shear-deformable portion.

4. A load sensor according to claim 1, wherein said shear-deformable portion has a front side surface and a back side surface and a plurality of elastic surface-wave resonators are provided on each of said front and back side surfaces of said shear-deformable portion.

5. A load sensor according to claim 1, wherein said elastic surface-wave resonator comprises one transducer.

6. Aload sensor according to claim 3, wherein said elastic surface-wave resonators provided on said shear-deformable portion are oriented at an angle with respect to the longitudinal direction of said shear-deformable member.

7. A load sensor according to claim 6, wherein said shear-deformable portion has a front side surface and a back side surface and an elastic surface-wave resonator is provided on each of said front and back side surfaces of said shear-deformable portion.

8. A load sensor according to claim 7, wherein the elastic surface-wave resonators provided on the front and back side surfaces of said shear-deformable portion are oriented in mutually opposing directions and define identical angles with respect to the logitudinal direction of said shear-deformable member.

9. A load senosr according to claim 7, wherein a plurality of elastic surface-wave resonators are formed on each side of said shear-deformable portion.

10. A load sensor according to claim 1, wherein said shear-deformable member is sealed between said fixed rigid member, said movable rigid member and said first and second beams.

11. A load sensor according to claim 1, wherein a plurality of elastic surface-wave resonators are provided on said shear-deformable portion.

12. A load sensor according to claim 1, wherein said elastic surface-wave resonator is oriented at an angle to the logitudinal direction of said shear-deformable member.

13. A load sensor for sensing a load based on an oscillation frequency deviation of an elastic surface-wave oscillator having an elastic surface-wave resonator and an amplifier, comprising:

a fixed rigid portion fixedly secured to a stationary object;

a movable rigid portion disposed in spaced relation from said fixed rigid portion for receiving an applied load;

a shear-deformable member having one end portion fixedly secured to said fixed rigid member and an opposite end portion fixedly secured to said movable rigid member;

a shear-deformable portion provided on said shear-deformable member;

an elastic surface-wave resonator provided on said shear-deformable portion, and a corrugated bellows extending between said fixed rigid portion and said movable rigid portion, said shear-deformable member being sealed within said bellows.