Two-part, two-material fastening element

Claim 2

A fastener indicator device which comprises a yielding section therein subject to plastic deformation on application of a predetermined compressive force and characterized by a groove or gap therein, which device is further characterized by the yielding section composed of a material which has been workhardened by the application of a loading force of the same character as that force to which the device is subject in use, such loading force slightly less than or equal to the said predetermined force, but greater than the force which would cause initial yielding of the material, whereby in use a change in the dimension of the groove or gap indicates that the fastener carries the predetermined force.

Claim 3

The device of claim 1 which includes an annular groove or gap which includes therein a flowable material, whereby the said predetermined force extrudes such material from such groove or gap as an indicator of such force level.

Claim 4

The device of claim 1 which is a bolt, the bolt comprising: a bolt head having a peripheral wrenching surface and a cylindrical extension terminating in a bearing face and having an inner surface, the inner surface of the cylindrical extension spaced apart from the outer surface of the bolt and defining therewith a radial clearance; and an annular groove formed on the outer wrenching surface of the cylindrical extension, said groove being less in axial width that twice the radial thickness between the bottom of the external groove and the inner surface of the cylindrical extension, thereby defining an annular section which plastically deforms redially inward with an essentially wedge-shaped cross section when said predetermined force acts on the bolt with resultant reduction of the axial width of the external groove.

Claim 5

The device of claim 1 which is a bolt, the bolt comprising: a. a first part which includes a bolt head integrally secured to said bolt, the bolt head having an outer wrenching surface, and includes a ring-like extension depending therefrom adjacent to said outer wrenching surface, and defining an axial extending inwardly directed surface; b. a second separate part having an outer wrenching surface, with one end thereof engaging said inwardly directed surface, and abuttingly secured to the extension of said bolt head and extending along said bolt, the other end thereof terminating in a bearing surface; c. said second part having an inner surface spaced apart from the outer surface of the bolt to define therewith a radial clearance; and d. an external radially directed annular groove defined by said outer wrenching surfaces, the external groove being less in axial width than twice the radial thickness between the bottom of the external groove and the inner surface thereby defining an annular section which plastically deforms radially inward with an essentially wedge-shaped cross section when said predetermined force acts on the bolt with resultant reduction of the axial width of the external groove.

Claim 8

The method of claim 5 which includes loading the device to produce in the yielding section a predetermined amount of reduction in the width of the groove or gap, which amount of reduction corresponds to the average deformation associated with a loading force equal to or slightly less than said predetermined force.

Claim 9

The method of claim 5 which includes loading the device to reduce the axial width of the groove or gap to a specified width, which width corresponds to the average width of said groove or gap associated with a loading force slightly less than or equal to said predetermined force.

Claim 10

The method of claim 6 which includes inserting in the groove or gap prior to loading and reduction of the groove or gap a load deformation-limiting means, and then loading the device to provide a reduction of the width of the groove or gap.

Claim 11

The method of claim 8 wherein the deformation-limiting means is a spacer, and which method includes insertion of the spacer in the groove or gap prior to loading, and removing of the spacer after loading.

Claim 12

The method of claim 5 which includes loading the device after manufacture and before use of the device.

Claim 13

The method of claim 5 which includes detecting the loading force by gauge detection of the decrease in dimension of the gap or groove.

Claim 14

The method of claim 5 which includes applying a loading force to the device slightly less than or equal to the level of the range of variations in the force level of the manufactured material of the yielding section of the device.

Claim 15

The method of claim 5 which includes employing as a loading force on the device an exteranl compressive force.