Bolt head which measures and maintains preload

• US 3,886,840 A
• Filed: 06/22/1973
• Issued: 06/03/1975
• Est. Priority Date: 10/24/1972
• Status: Expired due to Term

• Current Assignee: Robert B. Bossler
• Original Assignee: Robert B. Bossler
• Inventors: Bossler, Robert B.
• Primary Examiner(s): Parsons, Jr., Marion
• Application Number:
  US05/372,667
• Time in Patent Office: 711 Days
• Field of Search: 85/61,62 73/88F,1B
• US Class Current: 411/14
• 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: F16B 31/025 with a gauge pin in a longitudinal bore in the body of the bolt
• 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 bolt providing an indication of pre-load and continuous load thereafter wherein the bolt head has recesses on both sides thereof leaving a central ring which functions as a diaphragm spring and deflects along the bolt axis as a function of load. In one embodiment, an indicator pin is mounted in or forms part of the ring so as to deflect with the ring, moving through a passage in a fixed indicator washer or ring which closes the top recess and which permits a ready determination, by comparison of the relative positions of pin and indicator ring, of bolt pre-load. A further embodiment of the pre-load indicating device eliminates the indicator pin and replaces the indicator washer with a transverse buckled column, which indicates load along the bolt axis by the deflected location of the buckled column. In a third embodiment both an indicator pin, which deflects with the ring, and a transverse buckled column are employed to increase sensitivity as the column and pin move in opposite directions with change in load.

Claims

1. A bolt comprising:

a first member having a shaft portion extending along a bolt axis and terminating in a head with a first annular recess on one side of said head between a surface for bearing against a clamped member and the juncture of said shaft and said head and a second annular recess on the opposite side of said head so as to define a ring between said recesses which deflects along the bolt axis with increasing and decreasing load and having an indicator pin with a portion joined to said defined ring for movement therewith and a portion extending out of said defined ring away from said shaft portion, and a transverse buckled column mounted in said second recess and having a central passage through which said indicator pin extends so that said column and indicator pin deflect in opposite directions with increasing and decreasing load and the relative position of said pin and said buckled column indicates the load on said bolt.

2. A bolt as in claim 1, wherein said first recess is concave, with the center of curvature falling on a line extending parallel to said bolt axis and said second recess extends from a maximum depth near the periphery of said head to a minimum depth near said bolt axis.

3. A bolt as in claim 2, wherein said pin is cylindrical with its axis coincident with said bolt axis.

4. A bolt as in claim 1, wherein said head has peripheral torque applying surfaces.

5. A bolt comprising:

a first member having a shaft portioN extending along a bolt axis and terminating in a head with a first annular recess on one side of said head between a surface for bearing against a clamped member and the juncture of said shaft and said head and a second annular recess on the opposite side of said head so as to define a ring between said recesses which deflects along the bolt axis with increasing and decreasing load and means joined to said defined ring for movement therewith so that the position thereof indicates the load on said bolt.

6. A bolt as in claim 5, wherein said first recess is concave, with the center of curvature falling on a line extending parallel to said bolt axis and said second recess extends from a maximum depth near the periphery of said head to a minimum depth near said bolt axis.

7. A bolt as in claim 6, wherein said means is cylindrical with its axis coincident with said bolt axis.