GB2210124A

GB2210124A - Tamper-proof fastening

Info

Publication number: GB2210124A
Application number: GB8722290A
Authority: GB
Inventors: Alan David Pitt
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-09-22
Filing date: 1987-09-22
Publication date: 1989-06-01
Anticipated expiration: 2007-09-22
Also published as: GB8722290D0; GB2210124B

Abstract

Two elements 10, 11 are secured to one another in a manner which is, to all intents and purposes, tamper-proof by means of a nut and bolt 16, 12 and two cups 20, 21. The drive head portion 17 of the nut 16 shears off at a neck 19 upon the application of a predetermined torque to leave a threaded annulus portion 18 in the cup 21. ln order to prevent rotation of the cup 21 relatively to the bolt, perhaps for the purpose of attempting to undo the annulus 18, the bolt may have at least one flat (151, Fig. 2) which is in contact with a corresponding flat (212) of the periphery of the aperture in the cup 21 (or 210). Alternatively, for the same purpose, the exterior surfaces of the closed ends of said cups 20, 21 may have serrations which will bite into the elements 10, 11 when the fastening has been tightened. <IMAGE>

Description

TAMPER-PROOF FASTENING This invention relates to a tamper-proof fastening system.

According to a first aspect thereof, the present invention consists in a tamper-proof fastening system securing a first element to a second element by means of a nut and bolt of which the entire axial extent of the head of the bolt is accommodated within a first cup and of which the entire axial extent of the nut is accommodated within a second cup.

According to a second aspect thereof, the present invention consists in a tamper-proof fastening system securing at least a first element to a second element, said system comprising a headed bolt whose threaded shank extends through both of said elements and a nut screwed onto said shank; said shank also extending through the closed ends of first and second cups, the closed end of the first cup being in contact with a surface of said first element and the closed end of the second cup being in contact with a surface of said second element; and the head of the bolt being accommodated wholly within the confines of said first cup and the nut being accommodated wholly within the confines of said second cup.

In a system as described in either of the two preceding paragraphs, the nut was equipped with an integral drive part which was adapted to be engaged by a tool (e.g. a spanner) and which sheared off when a predetermined level of torque was applied thereto, thus leaving the nut engaging the threaded shank of the bolt and in such a position as to prevent the speedy application of a simple tool thereto in order to undo the fastening system.

In a system as described in any one of the two preceding paragraphs, either (a) the exterior surface of the closed end of the second cup may be provided with serrations, whereby said serrations will tend to bite into the said surface of the second element; or (b) the threaded shank of the bolt may be provided with at least one flat and the aperture in the closed end of the second cup may be provided with at least one straight-line portion of its periphery, said flat on said threaded shank being in contact with said straight-line portion of the periphery of said aperture.

The present invention further consists in a tamper-proof fastening system constructed, arranged and adapted to operate substantially as hereinafter described with reference to the accompanying diagrammatic drawings, in which: Figure 1 illustrates a first embodiment of a tamper-proof fastening system according to the present invention; and Figure 2 illustrates one alternative embodiment thereof.

Referring to Figure 1 of the drawings, there is illustrated therein a first element 10 and a second element 11 which are secured to one another by means of a nut and bolt. The bolt is indicated by the reference numeral 12 and has a head 13 and a shank which consists of an unthreaded portion 14 and a threaded portion 15. The nut is indicated by the reference numeral 16 and has a drive head 17 of hexagonal configuration which is connected to an internally threaded annulus 18 by a shear neck 19.

The shank of the bolt 12 extends through (a) an aperture in the closed end or bottom of a first cup 20 and (b) an aperture in the closed end or bottom of a second cup 21. The other or top ends of said cups 20, 21 are, of course, open.

In order to effect the fastening to one another of the elements 10, 11 by means of the tamper-proof fastening system whose constituent parts have been briefly described above, the previously apertured elements 10, 11 are brought together so that the apertures therein are in axial alignment. The bolt 12 has its shank extending through the aperture in the closed end of the first cup 20 and said shank is then caused to extend through the aligned apertures in the elements 10, 11. Thereafter, the second cup 21 is slipped onto the threaded portion 15 of the bolt and the internally threaded annulus 18 is screwed onto said portion 15.When the free end of the annulus 18 touches the apertured base of the cup 21, it will be necessary to complete the tightening of the fastening system by the use of a spanner (not illustrated) on the drive head 17; when a predetermined torque, applied by said spanner, is reached, the shear neck 19 shears and said neck and the attached drive head 17 come away from the annulus 18. It will be seen from the drawing that the head 13 of the bolt is accommodated wholly within the confines of the first cup 20 because the axial length of said head is less than that of said cup. It will also be seen that the annulus 18 is accommodated wholly within the confines of the second cup 21 because the axial length of said annulus is slightly less than that of said cup 21.

Therefore, it is not possible for any tool to be applied quickly and/or simply to either the head 13 or the annulus 18 for the purpose of undoing the connected elements.

Referring briefly to Figure 2, there is illustrated therein a modified bolt 120 which has a head 130 and a threaded shank 150. The shank has diametrically opposed flats 151 of which one is clearly seen in the Figure. A modified second cup 210 has an aperture 211 in the closed or bottom end thereof, the periphery of said aperture having two diametrically opposed straight-line portions 212. In use, the portions 212 of the aperture periphery are in contact with the flats 151 of the bolt 120, and this prevents rotation of the cup 210 relatively to the bolt 120 about the longitudinal axis of the bolt.

Of course, only one flat 151 and one straightline portion 212 need be provided to achieve the same effect.

In a further alternative embodiment, the bolt 12 and cup 21 can be as illustrated in Figure 1 but the exterior surface of the closed end or bottom of said cup 21 may be serrated; the purpose of said serration would be to cause a more positive grip between the outer surface of the second element 11 and the exterior surface of said cup 21. The serrations, biting into the surface of the element 11, will tend to inhibit rotation of the cup 21 relatively to the bolt 12 about the longitudinal axis of said bolt.

Claims

CLAIMS:

1. A tamper-proof fastening system securing a first element to a second element by means of a nut and bolt of which the entire axial extent of the head of the bolt is accommodated within a first cup and of which the entire axial extent of the nut is accommodated within a second cup.

2. A tamper-proof fastening system securing at least a first element to a second element, said system comprising a headed bolt whose threaded shank extends through both of said elements and a nut screwed onto said shank; said shank also extending through the closed ends of first and second cups, the closed end of the first cup being in contact with a surface of said first element and the closed end of the second cup being in contact with a surface of said second element; and the head of the bolt being accommodated wholly within the confines of said first cup and the nut being accommodated wholly within the confines of said second cup.

3. A system as claimed in Claim 1 or Claim 2, wherein the nut was equipped with an integral drive part which was adapted to be engaged by a tool (e.g. a spanner) and which sheared off when a predetermined level.of torque was applied thereto, thus leaving the nut engaging the threaded shank of the bolt and in such a position as to prevent the speedy application of a simple tool thereto in order to undo the fastening system.

4. A system as claimed in Claim 2 or as claimed in Claim 3 when appended to Claim 2, wherein the exterior surface of the closed end of the second cup is provided with serrations, whereby said serrations will tend to bite into the said surface of the second element.

5. A system as claimed in Claim 2 or as claimed in Claim 3 when appended to Claim 2,wherein the threaded shank of the bolt is provided with at least one flat and the aperture in the closed end of the second cup is provided with at least one straight-line portion of its periphery, said flat on said threaded shank being in contact with said straight-line portion of the periphery of said aperture.

6. A tamper-proof fastening system constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying diagrammatic drawing.

7. Any features of novelty, taken singly or in combination, of the embodiments of the invention hereinbefore described with reference to the accompanying diagrammatic drawing.