Strain indicator

• US 3,908,508 A
• Filed: 09/23/1974
• Issued: 09/30/1975
• Est. Priority Date: 09/23/1974
• Status: Expired due to Term

• Current Assignee: RBS Industries, Inc.
• Original Assignee: William J. Payne
• Inventors: Payne, William J.
• Primary Examiner(s): Parsons, Jr., Marion
• Application Number:
  US05/508,211
• Time in Patent Office: 372 Days
• Field of Search: 85/62,61,1T,32T 73/88F,88E,88A,1B 116/DIG.34
• US Class Current: 411/14
• CPC Class Codes: F16B 31/025 with a gauge pin in a longitudinal bore in the body of the bolt
• CPC Class Codes: G01B 5/30 for measuring the deformation in a solid, e.g. mechanical strain gauge

Abstract

A strain indicator of the type wherein a change in length of a strain member produces movement of an indicator member. Such movement, in the elastic range of the fastener material, is essentially linear and in proportion to the stress being applied to the fastener. When, however, a preset strain limit within the fastener is exceeded the indicator element is biased in an upward direction giving an immediate visual indication of that fact.

Claims

1. An optical stress-strain indicator comprising in combination:

a first member subject to stress-strain and having a head and a recess extending from said head into said member;

a second member received within said first member and having a first end and a second end, said first end being secured to said first member;

a body member having a viewing area, said body member being secured to said first member with said viewing area substantially adjacent said head so as to be visible;

an indicator element disposed within said body member;

releasable connecting means interconnecting said indicator element and said second end of said second member;

bias means interposed between said indicator element and said second member, whereby;

a. as said first member undergoes an elastic change in length, said second end of said second member is caused to move with respect to said body with the result that said indicator element is caused to move inwardly with respect to said body, thereby giving a visual indication of the change of length of said first member;

b. as said first member undergoes a further change in length exceeding a preset limit of said first member, said indicator element becomes separated from said second member as said releasable connecting means is caused to release said indicator element from said second member and said bias means causes said indicator element to move to an extended position at least partially outside of said body member giving a visual indication of a load on said first member.

2. The invention of claim 1 in which said releasable connecting means is defined as interengaging, generally frustoconical surfaces, one surface defined at said indicator element and the other defined by a release element secured to said second member.

3. The invention of claim 1 in which said indicator element and said body are provided with generally radial stop shoulders with a clearance space initially provided between said shoulders.

4. The invention of claim 3 in which said clearance space has an axial dimension which approximates the strain limit of said first member.

5. The invention of claim 1 in which said indicator element and said body are provided with generally radial stop shoulders whereby travel of said indicator element outside of said body is limited.