Force sensing device and method

• US 4,856,350 A
• Filed: 10/22/1987
• Issued: 08/15/1989
• Est. Priority Date: 10/22/1987
• Status: Expired due to Term

• Current Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Original Assignee: Richard A. Hanson
• Inventors: Hanson, Richard A.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/112,409
• Time in Patent Office: 663 Days
• Field of Search: 73/862.59, 73/517 AV, 73/704, 73/778, 73/DIG. 1, 73/DIG. 4
• US Class Current: 73/862.59
• CPC Class Codes: G01L 1/162 using piezoelectric resonators
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: Y10S 73/01 Vibration

Abstract

A force sensing device especially suitable for use in an accelerometer or a pressure transducer, depending upon its particular design. This device includes at least one and preferably two adjacent and parallel, elongated vibratable tines and means for vibrating the tines back and forth in a direction normal to their axes of elongation. These tines are supported for vibration by an arrangement including an array of interconnected links and mounting means adapted to be connected to an external member capable of applying a variable external force to the support arrangement along an axis normal to the axes of elongation of the tines. The support arrangement is configured so as to apply to the tines its own internal force in response to and varying with the external force in a way which causes the tines to vibrate at a frequency that varies with the magnitude of the internal force and therefore the external force. In this way, the vibrating frequency of either or both tines can be sensed for determining therefrom the magnitude of the external force applied to the support arrangement.

Claims

1. A force sensing device, comprising:

(a) at least one elongated, vibratable tine;

(b) means for vibrating said tine back and forth in a direction normal to its axis of elongation;

(c) an arrangement supporting said tine for said vibration and including mounting means adapted for connection to an external member capable of applying a variable external force to the support arrangement along an axis not parallel to the axis of elongation of said tine, said support arrangement being configured so as to apply to said tine its own internal force in response to and varying with said external force in a way which causes the tine to vibrate at a frequency that varies with the magnitude of said internal force and therefore said external force, said support arrangement including four links of substantially equal lengths and means interconnecting the links to one another and to opposite ends of said tine so as to form a parallelogram such that the elongation axis of the tine extends between a first pair of opposing corners of the parallelogram and such that the direction along which the external force is applied extends between a second pair of opposing corners of the parallelogram and normal to the elongation axis of said tine; and

(d) means for sensing the vibrating frequency of said tine and for determining therefrom the magnitude of said external force.

2. A device according to claim 1 including a second substantially identical vibratable tine supported by said arrangement for vibration adjacent to and parallel with said first-mentioned tine and vibrated by said vibrating means such that its vibration frequency varies with the magnitude of said external force.

3. A device according to claim 2 wherein said vibrating means vibrates said tines at the same frequency but 180°

out of phase with one another in a direction normal to the elongation axes of said tines and parallel with the axis along which said external force is applied.

4. A device according to claim 1 including only said one tine and wherein its direction of vibration is parallel to the axis along which said external force is applied.

5. A device according to claim 1 wherein the corners of said parallelogram containing the ends of said tine are each less than 90°

such that said internal force is greater than its associated external force, whereby to make the device especially suitable for measuring small external forces such as acceleration forces.

6. A device according to claim 1 wherein the corners of said parallelogram containing the ends of said tine are each greater than 90°

such that said internal force is less than its associated external force, whereby to make the device especially suitable for measuring large forces such as large pressures.

7. A device according to claim 1 wherein said tine, said links and said interconnecting means are integrally formed as of a single unit of quartz crystal material.

8. A device according to claim 1 wherein said support arrangement is configured such that said internal force is greater than said external force.

9. A force sensing device, comprising:

(a) at least one elongated, vibratable tine;

(b) means for vibrating said tine in a particular way;

(c) an arrangement including a plurality of links interconnected to one another and to said tine for supporting the latter for said vibration and further including means adapted for connection to an external member capable of applying a variable external force to the support arrangement which is configured so as to apply to the tine its own internal force in response to and varying with said external force in a way which causes the tine to vibrate at a frequency that varies with the magnitude of said internal force and therefore said external force, said support arrangement being configured such that the said external force is applied thereto along an axis which is normal to the axis of elongation of said tine and which bisects the tine, said support arrangement including four links of equal lengths and means interconnecting the links to one another and to opposite ends of said tine so as to form a parallelogram such that the elongation axis of the tine extends between a first pair of opposing corners of the parallelogram and such that said external force is applied to the arrangement along an axis extending between a second pair of opposing corners of the parallelogram; and

(d) means for sensing the vibrating frequency of said tine and for determining therefrom the magnitude of said external force.

10. A device according to claim 9 wherein said tine, said links and said interconnecting means are integrally formed of a single unit of quartz crystal material.

11. A device according to claim 9 including a second substantially identical vibratable tine supported by said arrangement of links for vibration adjacent to and parallel with said first-mentioned tine and vibrated by said vibrating means such that its vibration frequency varies with the magnitude of said external force.

12. A force sensing device, comprising:

(a) a pair of substantially identical, adjacent and parallel elongated vibratable tines;

(b) means for vibrating said tines back and forth at the same frequency but 180°

out of phase with one another in a common plane and in a direction normal to the elongation axis of the tines;

(c) an arrangement including four substantially identical links located in said common plane and means interconnecting the links to one another and to opposite ends of said tines so as to form a parallelogram such that the elongation axes of said tines extend between a first pair of opposing corners of the parallelogram, said arrangement including mounting means located at a second pair of opposing corners of said parallelogram for connecting the arrangement to an external member capable of applying a variable external force to the support arrangement along an axis extending through the second pair of corners of said parallelogram such that the arrangement applies to said tines its own internal force in response to and varying with said external force and causes the tines to vibrate at a frequency that varies with the magnitude of said internal force and therefore said external force; and

(d) means for sensing the vibrating frequency of at least one of said tines and for determining therefrom the magnitude of said external force.

13. A device according to claim 12 wherein said tines, said links and said interconnecting means are integrally formed as a single unit of quartz crystal material.

14. A device according to claim 12 wherein the corners of said parallelogram containing the ends of said tine are each less than 90°

, whereby to make the device especially suitable for measuring small external forces such as acceleration forces.

15. A device according to claim 12 wherein said corners of said parallelogram containing the ends of said tines are greater than 90°

, whereby to make the device especially suitable for measuring large forces such as large pressures.

16. A force sensing device, comprising:

(a) elongated vibratable tine means;

(b) means for vibrating said tine means back and forth in a direction normal to the elongation axis of the tine;

(c) an arrangement including four links and means interconnecting the links to one another and to opposite ends of said tine means so as to form a quadrangle such that the axis of elongation of said tine means extends between a first pair of opposing corners of the quadrangle, said arrangement including mounting means located at a second pair of opposing corners of said quadrangle for connecting the arrangement to an external member capable of applying a variable external force to the arrangement along an axis extending through the second pair of corners of said quadrangle such that the arrangement applies to said tine means its own internal force in response to and varying with said external force and causes the tine means to vibrate at a frequency that varies with the magnitude of said internal force therefore said external force; and

(d) means for sensing the vibrating frequency of said tine means for determining therefrom the magnitude of said external force.

17. A device according to claim 16 wherein said arrangement is configured such that said links and interconnecting means together form a parallelogram.

18. A device according to claim 17 wherein said arrangement is configured such that the said external force is applied thereto along an axis which is normal to the axis of elongation of said tine means.

19. A device according to claim 18 wherein said four links are of equal lengths, whereby the axis along which said external force is applied to said arrangement bisects said tine means.

20. A device according to claim 16 wherein said tine means consists of a single elongated vibratable tine.

21. A device according to claim 16 wherein said tine means includes a pair of substantially identical, adjacent and parallel elongated vibratable tines.

22. A force sensing device, comprising:

(a) elongated vibratable tine means;

(b) means for vibrating said tine means back and forth in a direction normal to the elongation axis of the tine;

(c) an arrangement including a number of structure links and means interconnecting the links to one another to formed a closed loop structure and to opposite ends of said tine means such that the elongation axis of said tine means extends between a first pair of opposing corners of the structure, said arrangement including mounting means located along said structure for connecting the arrangement to an external member capsule of applying a variable external force to the arrangement along an axis which is neither parallel with nor normal to any of the links of said structure such that the arrangement applies to said tine means its own internal force in response to and varying with said external force and causes the tine means to vibrate at a frequency that varies with the magnitude of said internal force and therefore said external force; and

(d) means for sensing the frequency of said tine means and for determining therefrom the magnitude of said external force.

23. A device according to claim 22 wherein said arrangement is configured such that said closed loop structure includes four links interconnected to form a parallelogram.

24. A device according to claim 23 wherein said four links are of equal lengths.

25. A device according to claim 22 wherein said mounting means are located at a second pair of opposing corners of the structure.