OPTI-MECHANICAL STRESS-STRAIN INDICATOR

• US 3,602,186 A
• Filed: 08/06/1970
• Issued: 08/31/1971
• Est. Priority Date: 08/06/1970
• Status: Expired due to Term

• Current Assignee: Charles H. Popenoe
• Original Assignee: Charles H. Popenoe
• Inventors: Popenoe, Charles H.
• Primary Examiner(s): Capozi, Louis J.
• Application Number:
  US05/061,764
• Time in Patent Office: 390 Days
• Field of Search: 116/70,114,DIG.24 73/1,88E,88F,88,85.5 85/62
• US Class Current: 411/13
• CPC Class Codes: F16B 31/02 for indicating the attainment of a particular tensile load or limiting tensile load apparatus for, or method of, determining value of torque or twisting moment for tightening a nut or other member similarly stressed G01L5/24
• CPC Class Codes: G01L 5/24 for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
• CPC Class Codes: Y10S 116/34 Tension indicating

Abstract

A purely mechanical device for indicating the stress condition between two portions of a machine or structure, typically in the form of a threaded fastener or bolt used to fasten or connect the two points. In one form of the invention, an unstressed pin is inserted loosely in an axial bore in the bolt and fastened to it at one end; the free end of the pin terminates in an indicator head having an exposed area, preferably brightly colored, normal to the pin axis, which area in the unstressed condition of the bolt rests flush against the transparent or translucent window set into the head of the bolt, and the space surrounding the pin and head is filled with a preferably dark fluid which absorbs the color of the exposed indicator area. When stress is applied between the ends of the bolt, as by tightening it, the indicator head of the unstressed pin is retracted away from the window, and the colored fluid enters behind the window absorbing the color of the indicator area at a predetermined stress, and causing an apparent change of color of the indicator window. If the bolt later becomes loosened, the indicator window reverts to its original bright color, providing a warning of the looseness.

Claims

1. A. Optimechanical stress ro strain indicator comprising b. a first strain member and a second unstressed member fixed to each other at one point and movable relative to each other at another point when said first member is elastically deformed, c. said first member having a window aperture fixed thereto, d. said second member having an indicator area adjacent said window area and movable with respect to said window area under stress applied to said first member, e. a light-absorbing indicator fluid between said window area and said indicator area, the amount of said fluid visible between said two areas varying with the relative movement of said areas, f. means for fastening said first member near its window area to one part of a structure and near said unstressed member to another part of a structure to indicate the condition of stress or strain between said two parts.

2. a. Stress indicator comprising b. an elongated strain member having a axial bore therein, c. means for attaching the ends of said member to respective parts between which strain may occur, d. an elongated rodlike member loosely fitted in said axial bore, e. said rodlike member being fixed at one end of said axial bore to said strain member, f. the other end of said rodlike member having an indicator area substantially transverse to its longitudinal axis, g. a light-transmitting window closing the indicator-area end of said bore, h. said indicator area of said rodlike member in the unstressed condition of said strain member being very close to the inside of said window, i. a light-absorbing indicator fluid substantially filling the space in said axial bore not occupied by said rodlike member j. whereby when said strain member is strained by a stress between its opposing ends, the indicator-area end of the rodlike member moves away from said window, permitting the indicator fluid to enter between said window and said indicator area.

3. The invention according to claim 2, with both said indicator area and the inside surface of said window being planar and in close abutting contact.

4. The invention according to claim 2, said window having a planar interior surface, the indicator area having a slight curvature, or vice versa, so that the indicator area and window are not in contact at all points of their adjacent surfaces.

5. The invention according to claim 2, said indicator area having a number of stepped areas at slightly different distances from said window.

6. The invention according to claim 2, said elongated strain member being a threaded bolt, said window being in one end of the bolt.

7. The invention according to claim 2, said elongated strain member being a threaded stud, said window being in the threaded end of said stud.

8. The invention according to claim 1, said first member being an elastically deformable fastener head.

9. The invention according to claim 8, said head having a resilient disclike web element extending inwardly from the periphery of the head toward a central region, said second member extending from said central region toward said window.