GB2220723A

GB2220723A - Security means for use with a screwthreaded fastening

Info

Publication number: GB2220723A
Application number: GB8914919A
Authority: GB
Inventors: Graham Stokes; Carolyn Stokes
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-30
Filing date: 1989-06-29
Publication date: 1990-01-17
Also published as: GB8815580D0; GB8914919D0

Abstract

Security means for use with a nut and bolt type fastening 14, 15 comprises a first component 11 defining a recess within which the nut 15, in its tightened position, is received, and a closure component 12 shaped and dimensioned to be received as a non-removable force-fit in said recess so preventing access to the nut. The components 11, 12 may be made of hardened steel and the component 12 being provided with or without an aperture 12c. The components may also be used for the head of a bolt or screw. A particular use is on the fastenings for a ball hitch coupling to the draw-bar of a trailer. <IMAGE>

Description

SECURITY MEANS FOR USE WITH A SCREW THREADED FASTENING This invention relates to a security means for use with a screw threaded fastening arrangement, primarily but not exclusively of the kind wherein a nut is in screw threaded engagement with a shank or stud, or example the shank of a bolt.

Nut and bolt type fastenings are very widely used, and constitute a relatively cheap and convenient fastening device. However, in order to separate components secured together by a nut and bolt type fastening, usually all that is necessary is removal of the nut. There are of course self-locking arrangements which resist inadvertent or accidential unscrewing of the nut but such arrangements are of no use where the security required is of the anti-theft type. It is an object of the present invention to provide, in a cheap and convenient manner, means for preventing unscrewing of a nut and bolt type fastening.

In accordance with the present invention there is provided security means for use with a nut and bolt type fastening, comprising a first component defining a recess within which the nut, in its tightened position, is received, and a closure component shaped and dimensioned to be received as a non-removable, force-fit in said recess so preventing access to said nut.

Preferably said first component is a hollow cylindrical member having a radially inwardly directed flange at one axial end, said flange being trapped in use between the nut and one of the parts secured by the nut and bolt fastening, and said closure component is also a hollow cylindrical member at least partially closed at one axial end by a radial wall, the outer diameter of the closure component being so related to the inner diameter of the first component that the outer cylindrical wall of the closure component can engage as a non-removable force-fit within the first -component.

Desirably said radial wall of said closure component is an annular wall having a centrally disposed aperture through which the shank or stud associated with the nut, can protrude.

Preferably the lengths of the components are such that the closure component can be received in the first component with their outer ends flush.

In the accompanying drawings: Figure 1 is a diagrammatic, exploded perspective view of a security means in accordance with one example of the present invention, and Figure 2 is a diagrammatic longitudinal sectional view illustrating the security means of Figure 1 in use.

Referring to the drawings, there is provided a security means comprising first and second inter-engagable components 11, 12. Each of the components 11, 12 is conveniently formed from hardened steel and each is of circular cross-section comprising a cylindrical sleeve lla, 12a partially closed at one axial end by an integral, radially inwardly extending flange llb, 12b. The external diameter of the cylindrical sleeve 12a of the component 12 is equal to the internal diameter of the cylindrical sleeve ila of the component 11 so that the sleeve 12a can be driven (force-fitted) into the sleeve lia and thereafter will be virtually impossible to remove.If desired the external surface of the sleeve 12a and/or the internal surface of the sleeve lla can be knurled or otherwise roughened to enhance the fit of the component 12 within the component 11.

Figure 2 illustrates the use of the security means comprising the components 11, 12 as illustrated in Figure 1. Item 13 in Figure 2 is one of a pair of parts being secured together by a nut and bolt type fastening. The screw threaded, elongate shank of the bolt of the fastening is illustrated at 14 and the mating nut is illustrated at 15. The shank 14 of the bolt is introduced through aligned bores of the two parts to be interconnected (one of the bores being illustrated at 13a in Figure 2) and its free end protrudes beyond the part 13 in order to receive the nut 15. However prior to engaging the nut 15 with the protruding portion of the shank 14 the component 11 is threaded over the shank with the shank passing through the centrally disposed aperture llc defined by the flange llb.The component 11 is threaded over the shank 14 with the flange llb presented towards the part 13 and the internal diameter of the sleeve lla of the component 11 is substantially greater than the largest diameter of the nut 15. Thereafter, the nut 15 is engaged with the protruding portion of the shank 14 and is screwed down to trap the flange llb against the part 13, it being recognised that the aperture llc is of smaller diameter than the nut 15. After tightening of the nut 15 the component 12 is offered to the component 11 with the open end of the component 12 presented to the open end of the component 11.The matching of the external diameter of the sleeve 12a to the internal diameter of the sleeve lla ensures that in order to engage the component 12 within the component 11 the component 12 must be driven into the component 11 and this may be achieved by a mechanical press or, conveniently by means of hammering. Thus conveniently a hammer will be used to drive the component 12 into the component 11, the hammer blows being applied either directly to the flange 12b of the component 12 or more preferably to a disposable packing member interposed between the hammer and the component 12. The flange 12b of the component 12 defines a centrally disposed aperture 12c so that in the event that the protruding length of the shank 14 exceeds the axial length of the component 11, then the free end of the shank can extend through the aperture 12c.It is to be recognised however that if desired versions may be produced wherein the one axial end of the component 12 is completely closed so that both the nut 15 and the free end of the shank 14 are received within the security means 11, 12.

The internal diameter of the component 12 exceeds the maximum diameter of the nut so that if necessary the nut will rotate within the component 12.

Similarly the diameter of the aperture 12c is such that the shank 14 can pass therethrough with slight clearance, but desirably the clearance will not be sufficiently large to permit introduction of any form of tool through the clearance. In this respect it should be noted that in Figure 2 the clearance between the shank 14 and the wall of both the aperture llc and the aperture 12c is exaggerated.

In a security critical application it is probable that the nut 15 will be of the self-locking type, and thus should an attempt be made to remove the nut and bolt fastening by rotating the bolt relative to the nut then the nut will rotate with the bolt there being, as mentioned above, sufficient clearance between the nut and the interior of the component 12 to permit such rotation. Thus any attempt to remove the nut and bolt fastening by this method would be frustrated.

However, for additional security it is possible, if desired, to apply the components 11, 12 also to the head of the bolt so that after fitting of both the components 12 neither the head of the bolt, nor the nut 15 would be accessible for unscrewing.

It will be recognised that if desired the components 11, 12 can be produced in a range of sizes to suit different nut and bolt fasteners. Furthermore, while it is preferred that the components 11, 12 are of circular cross-section other cross-sectional shapes could be utilized if desired.

The term nut and bolt type fastening is intended to embrace the type of fastening where a nut is in screw threaded engagement with a protruding portion of a captive stud. Thus the stud may be rigidly secured to one of the parts to be interconnected by the fastening and may not have a bolt head.

It will be recognised that it is desirable that the axial length of the component 11 is slightly less than the internal axial length of the sleeve lla of the component 11 so that when the component 12 is driven into the component 11 it can be driven to a position such that the outer face of the flange 12b is flush with the free end of the sleeve lla. Such a relationship further hampers any attempt subsequently to withdraw the component 12 from the component 11. It will be recognised that generally it will be impossible to remove a component 12 from its mating component 11, and so should removal of the nut and bolt type fastening prove necessary then it is possible that this may only be accomplished by grinding away the outermost end of the sleeve lla and the flange 12b of the component 12.

A particular application of the components 11, 12 is the nut and bolt fastenings securing a ball hitch coupling to the draw-bar of a caravan or other trailer but of course use is not restricted to such an application. Moreover, the components 11, 12 could be applied to a one-ended screw fastening, for example the component could be applied to the head of a bolt the shank of which is received wholly within a bore in a part, or to the head of a woodscrew or self-tapping screw. Furthermore the end of the component 11 which engages the part 13 can be shaped to conform to the part 13. Thus where the part 13 is, for example, a cylindrical draw-bar then the end of the component 11 can have a matching, concave, part cylindrical face so as to seat on the draw-bar.

Claims

1. Security means for use with a nut and bolt type fastening, comprising a first component defining a recess within which the nut, in its tightened position, is received, and a closure component shaped and dimensioned to be received as a non-removable, force-fit in said recess so preventing access to said nut.

2. Security means as claimed in claim 1 wherein said first component is a hollow cylindrical member having a radially inwardly directed flange at one axial end, said flange being trapped in use between the nut and one of the parts secured by the nut and bolt fastening, and said closure component is also a hollow cylindrical member at least partially closed at one axial end by a radial wall, the outer diameter of the closure component being so related to the inner diameter of the first component that the outer cylindrical wall of the closure component can engage as a non-removable force-fit within the first component.

3. Security means as claimed in claim 2 wherein said radial wall of said closure component is an annular wall having a centrally disposed aperture through which the shank or stud associated with the nut, can protrude.

4. Security means as claimed in any one of claims 1 to 3 wherein the lengths of the components are such that the closure component can be received within the first component with their outer ends flush.

5. Security means as claimed in any one of claims 1 to 4 wherein said components are of hardened steels.

6. Security means substantially as hereinbefore described with reference to the accompanying drawings.