THREAD FORMING WIRE THREAD INSERT

Abstract

A wire thread insert (1) for forming a helical thread, comprising a wire (7) wound into a closed coil having an outer surface (9) and an inner surface (11), wherein the wire (7) has a first portion (13) defining the inner surface of the thread insert when coiled, said first portion having a cross-section at least substantially in the form of a standard thread, the wire having an opposing second portion (15) defining the outer surface of the thread insert and having a cross-section in the form of a tapered flange with at least one concave face (23).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

It will be convenient to further describe the invention with respect to the accompanying drawings which illustrate a preferred embodiment of the wire thread insert according to the present invention. Other embodiments of the invention are possible, and consequently, the particularly of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

In the drawings:

FIG. 1 is a side cross-sectional view of a wire thread insert according to the present invention installed within a bore; and

FIG. 2 is a detailed view designated “A” in FIG. 1.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, the thread forming wire thread insert 1 according to the present invention can be inserted into a bore 3 provided within a substrate 2. The bore 3 may be drilled into the substrate 2 or may be integrally formed together with the substrate 2 or may be integrally formed together with the substrate 2 prior to insertion of the wire thread insert 1, the internal walls 5 are relatively smooth without the need for any helical thread to be provided within the bore 3.

The wire thread insert 1 is installed into the bore 3 by means of an installation tool (not shown) which has a mandrel which allows the setting and maintaining of the thread pitch of the wire thread insert 1 during installation thereof. The mandrel dimensions are designed to maintain the gauge dimensions of the installed wire thread insert 1, and this may vary from a standard thread hole wire thread insert.

The wire thread insert 1 is formed by wrapping a wire 7 into a closed coil having an inner surface 9 providing an internal helical thread, and an outer surface 11 which provides the thread forming arrangement according to the present invention. The wire has a first portion 13 forming the inner surface 9 of the wire thread insert 1, and a second portion 15 forming the outer surface 11 thereof. The first portion 13 is in the form of a standard thread and is adapted to cooperate with the thread of a bolt or other threaded fastener. The second portion 15 has a cross-section in the shape of a tapered flange which extends from a base 17 defined by the interface between the first and second portions 13, 15 to a tip 19 of the tapered flange 25. The length 21 of the tapered flange 25 measured between the base 17 and tip 19 is directly proportional to the modulus of elasticity of the substrate 2 to which it is to be used increases. Each tapered flange 25 has opposing flat concave faces 23 as best shown by FIG. 2. The shape of the cross-section of the tapered flange 25, and therefore the curvature of the concave faces 23, is determined by on the basis of the “rule of thirds”. More specifically, the thickness of the tapered flange 25 measured in a pitch dimension (i.e. parallel to the base 17) varies as a function of the distance from the tip 19 in a 3:1 ratio.

The configuration of the tapered flange 25 allows the substrate material to plastically deform about the tapered flange 25 as the wire thread insert 1 is installed into the bore 3 without the need to pre-machine a helical thread within that bore.

Modifications and variations as would be deemed obvious to the person skilled in the art are included within the ambit of the present invention as claimed in the appended claims.

Claims

1. A wire thread insert for forming a helical thread, comprising a wire wound into a closed coil having an outer surface and an inner surface, wherein the wire has a first portion defining an inner surface of the thread insert when coiled, said first portion having a cross-section at least substantially in the form of a standard thread, the wire having an opposing second portion defining the outer surface of the thread insert and having a cross-section in the form of a tapered flange with at least one concave face.

2. A wire thread insert according to claim 1, wherein the cross-section of the tapered flange is provided with opposing concave faces.

3. A wire thread insert according to claim 2, wherein the thickness of the tapered flange measured in a pitch dimension varies as a function of the distance away from a free end of the tapered flange in a 3:1 ratio.