BOLT HEAD WHICH MEASURES AND MAINTAINS PRELOAD

• US 3,812,758 A
• Filed: 10/24/1972
• Issued: 05/28/1974
• Est. Priority Date: 10/24/1972
• Status: Expired due to Term

• Current Assignee: Robert B. Bossler Jr
• Original Assignee: Robert B. Bossler Jr
• Inventors: Bossler, Robert B. Jr.
• Primary Examiner(s): Parsons, Jr., Marion
• Application Number:
  US05/299,799
• Time in Patent Office: 581 Days
• Field of Search: 85/62,61 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

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. An indicator pin is mounted in or forms part of the ring so as to deflect with the ring, moving through a passage in an 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.

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 an annular indicator ring mounted in said head and having a central passage through which said indicator pin extends so that the relative position of said pin and said indicator ring 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 as in claim 1, wherein said indicator ring is mounted in a groove at the outer periphery of said second recess and substantially closes said second recess.

6. 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 a transverse buckled column mounted in said second recess so that the relative position of said buckled column indicates the load on said bolt.

7. A bolt as in claim 6, wherein said second recess is at least partially filled with protective material to shield said buckled column from damage.

8. A bolt as in claim 6, wherein said head has peripheral torque applying surfaces.