Pressure sensing device and transducer arrangement

• US 4,142,175 A
• Filed: 06/12/1978
• Issued: 02/27/1979
• Est. Priority Date: 06/12/1978
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Panissidi, Hugo A., Herbst, Noel M., Liu, Chao N.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/914,651
• Time in Patent Office: 260 Days
• Field of Search: 340/146.3 SY, 73/141 A, 73/1 B, 73/4 R, 73/100, 73/89, 73/432 R, 73/37, 73/39, 274/23 R
• US Class Current: 382/314
• CPC Class Codes: G01L 1/22 using resistance strain gauges
• CPC Class Codes: G01L 5/00 Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
• CPC Class Codes: G06V 40/30 Writer recognition; Reading and verifying signatures
• CPC Class Codes: G06V 40/376 Acquisition
• CPC Class Codes: G07C 9/35 by means of a handwritten signature

Abstract

A pressure sensing device having applicability as a simple pressure sensor and which is particularly adapted for use as a pen in a Signature Verification System, said device including a unique mounting structure for the pressure sensing stylus by flexible support means mounted on a substantially rigid base. The support means has a pressure sensing element mounted thereon. The flexible support means comprises two spaced members so disposed that their deflections and the output of the pressure sensing element are substantially independent of the angle of pressure on the stylus. In the special purpose embodiment useful for Signature Verification the stylus comprises a pen and the device further includes two orthogonally disposed accelerometers for sensing accelerations of said pen during the writing of a signature.

Claims

1. A pressure sensing probe for producing a continuous pressure dependent signal as the probe is moved into contact with a surface, said probe comprising,

an elongated flexible pressure sensing element having a surface engaging tip at one end thereof,

a substantially rigid support means for carrying said pressure sensing element,

first and second flexible mounting means for attaching said pressure sensing element to said rigid support member at opposite ends thereof,

means for rigidly attaching the first mounting means to both the pressure sensing element and support member, means for rigidly attaching one end of the second mounting means to said support member and pivotally attaching said second mounting means to said pressure sensing element,

the relative stiffness of said mounting means being such that the majority of flexure occurs in the second of said mounting means whenever the distance between same decrease due to flexure of said flexible pressure sensing element when a transverse force is applied to same,

signal producing means located on said second mounting means having the greater flexibility for producing an electrical signal proportional to the degree of deflection of said mounting means.

2. A pressure sensing probe assembly as set forth in claim 1 wherein said flexible pressure sensing element and said rigid support means are substantially parallel.

3. A pressure sensing probe assembly as set forth in claim 2 wherein said second mounting means is located adjacent the surface engaging tip of said pressure sensing element and the first mounting means is located at the opposite end of said pressure sensing element, and

wherein said signal producing means is located on said second mounting means adjacent to the point at which said second mounting means is rigidly attached to said rigid support means.

4. A pressure sensing probe assembly as set forth in claim 3 wherein said elongated flexible pressure sensing element comprises a hollow flexible tube.

5. A pressure sensing probe assembly as set forth in claim 4 wherein said elongated flexible tube comprises a carrier for a writing pen and wherein said surface engaging tip comprises the writing stylus of said pen.

6. A pressure sensing probe assembly as set forth in claim 5 wherein the elongated flexible tube comprises the ink carrier cartridge of a ball point pen assembly and the writing stylus comprises a ball point pen tip.

7. A writing instrument for producing a continuous pressure dependent signal as the instrument is moved across a writing surface, comprising,

an elongated flexible stylus member having a writing tip at one end thereof,

a substantially rigid support member for carrying said elongated flexible stylus member,

first and second flexible mounting means for attaching said elongated flexible stylus member to said support member at opposite ends thereof,

means for rigidly attaching the first mounting means to both the elongated flexible member and support member at the end opposite from said writing tip,

means for rigidly attaching one end of the second mounting means to said support member, and means for pivotally attaching said mounting means to said elongated flexible member at the end adjacent to said writing tip,

the relative stiffness of said mounting means being such that the majority of flexure occurs in said second mounting means whenever the distance between same decreases due to flexure of said elongated flexible stylus member when a transverse force is applied to said writing tip, and

signal producing means located on said second mounting means for producing an electrical signal proportional to the deflection of said second mounting means.

8. A writing instrument as set forth in claim 7 including two orthogonally disposed accelerometers mounted on said support means for sensing accelerations of said writing instrument.

9. A writing instrument as set forth in claim 7 wherein said signal producing means located on said second mounting means comprises a strain gauge mounted thereon adjacent to the end of said mounting means rigidly fastened to said support means.