Angular displacement measuring apparatus

• US 4,940,063 A
• Filed: 02/23/1989
• Issued: 07/10/1990
• Est. Priority Date: 02/23/1989
• Status: Expired due to Fees

• Current Assignee: Twintec
• Original Assignee: Brian Challis
• Inventors: Challis, Brian
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): REICHLE, KARIN M
• Application Number:
  US07/314,441
• Time in Patent Office: 502 Days
• Field of Search: 128/774, 128/782, 33/1 C, 33/1 N, 33/1 PT, 33/177, 33/564, 33/DIG. 13, 33/511, 33/512, 33/534, 73/849
• US Class Current: 600/587
• CPC Class Codes: A61B 5/1071 measuring angles, e.g. using goniometers A61B5/1123 takes precedence
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes

Abstract

Angular displacement measuring apparatus includes a tightly-wound coil spring conduit which, when bent, elongates on the outside of the bend without substantially shortening on the inside of the bend. A wire is disposed within the conduit to extend from one end, where the wire is fixed so that it cannot slide longitudinally relative to the conduit, to the other end, where the wire is free to slide longitudinally relative to the conduit. A movement measuring device is mounted on the other end of the conduit and coupled to the wire for measuring movement of the wire. As the conduit is bent, the wire is caused to move an amount proportional to the degree of the bend and so measurement of the movement of the wire serves as a measure of the degree of the bend, i.e., angle of displacement of the conduit. Bending in an object is determined by attaching the conduit to the object to be measured.

Claims

1. An angular displacement measuring device comprising

a bendable conduit having a side wall which is stretchable in the direction parallel to the longitudinal axis of the conduit but is substantially noncompressible in the same direction so that when the conduit is bent, the portion of the side wall on the outside of the bend elongates while the portion of the side wall on the inside of the bend remains substantially unshortened,

a fiber having first and second ends disposed in the conduit so that the first end extends from one end thereof, where the fiber is fixed at the second end of said conduit so that it may not slide longitudinally relative to and out of the other end of the conduit and where the remainder of the fiber is free to slide relative to the remainder of the conduit, and

movement measuring means disposed at said other end of the conduit and coupled to said fiber for measuring movement of the fiber relative to the conduit as the conduit is bent to thereby measure the angle of bending of the conduit.

2. A device as in claim 1 wherein said conduit comprises a tightly wound coil spring.

3. A device as in claim 2 wherein said coil spring is comprised of stainless steel.

4. A device as in claim 2 wherein said coil spring is comprised of a composite material.

5. A device as in claim 2 further including an elongate sheath disposed snugly about the coil spring.

6. A device as in claim 5 wherein said sheath is comprised of a heat shrinkable, elastic material.

7. A device as in claim 5 wherein said sheath is comprised of polytetrafluoroethylene.

8. A device as in claim 1 further including an inner sleeve disposed in the conduit, said sleeve having an elongate central bore in which the fiber is positioned.

9. A device as in claim 8 wherein said inner sleeve comprises a flexible, synthetic material.

10. A device as in claim 9 wherein said synthetic material is polytetrafluoroethylene.

11. A device as in claim 9 wherein said synthetic material is fused silica.

12. A device as in claim 1 wherein said fiber is comprised of stainless steel.

13. A device as in claim 1 wherein said movement measuring means further comprises display means for producing a visual indication of the angle of displacement of the conduit.

14. A device as in claim 13 wherein said movement measuring means further comprises an alarm means for producing an audible signal when the conduit is bent to a predetermined angle.