Force sensing device

• US 4,970,903 A
• Filed: 06/30/1989
• Issued: 11/20/1990
• Est. Priority Date: 10/22/1987
• Status: Expired due to Term

• Current Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Original Assignee: New SD, Inc.
• Inventors: Hanson, Richard A.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US07/374,968
• Time in Patent Office: 508 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) 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 forming part of said interconnecting means and 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 for determining therefrom the magnitude of said external force;

(e) said tines and links and said interconnecting means being integrally formed as a single unit of quartz crystal material; and

(f) said means interconnecting said links to opposite ends of said tines including a pair of quartz crystal members separate from but integrally formed with said tines and said links, each of said members connecting a respective one of the pair of adjacent ends of said tines together and to an adjacent one of said opposing corners.

2. A device according to claim 1 wherein each of said pair of quartz crystal members includes a segment transverse to said tines for connecting adjacent ends thereof and a segment parallel with said tines for connecting said transverse segment to the adjacent one of said opposing corners.

3. A device according to claim 1 wherein each of said quartz crystal members includes a first segment which is wider than the distance laterally across both of said tines for connecting adjacent ends of said tines and a second segment parallel with said tines and thinner widthwise than said first segment for connecting said first segment to the adjacent one of said opposing corners.

4. 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 a number of structure links and means interconnecting the links to one another to form a closed loop structure and to opposite ends of said tines such that the elongation axes of said tines extend between a first pair of opposing corners of the structure, said arrangement including mounting means forming part of said interconnecting means and located along said structure for connecting the arrangement to an external member capable of applying a variable external force to the arrangement along an axis which is neither parallel with or normal to any of the links of said structure 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 frequency of said tines and for determining therefrom the magnitude of said external force;

(e) said tines and links and said interconnecting means being integrally formed as a single unit of quartz crystal material; and

(f) said means interconnecting said links to opposite ends of said tines including a pair of quartz crystal members separate from but integrally formed with said tines and said links, each of said members connecting a respective one of the pairs of adjacent ends of said tines together and to an adjacent one of said opposing corners.

5. A device according to claim 4 wherein each of said pair of quartz crystal members includes a segment transverse to said tines for connecting adjacent ends thereof and a segment parallel with said tines for connecting said transverse segment to the corners.

6. A device according to claim 4 wherein each of said quartz crystal members includes a first segment which is wider than the distance laterally across both of said tines for connecting adjacent ends of said tines and a second segment parallel with said tines and thinner widthwise than said first segment for connecting said first segment to the adjacent one of said opposing corners.

7. A device according to claim 4, wherein said arrangement is configured such that said closed loop structure includes four links interconnected to form a parallelogram.

8. A device according to claim 7 wherein said four links are of equal widths.

9. A device according to claim 4 wherein said mounting means is located at a second pair of opposing corners of the structure.