GB2259554A

GB2259554A - Anti-tamper cover for nut or bolthead

Info

Publication number: GB2259554A
Application number: GB9119559A
Authority: GB
Inventors: John Joseph Nolan
Original assignee: SECURITY FASTENERS AND FIXINGS
Current assignee: SECURITY FASTENERS AND FIXINGS
Priority date: 1991-09-13
Filing date: 1991-09-13
Publication date: 1993-03-17
Anticipated expiration: 2011-09-13
Also published as: GB2259554B; AU645235B3; GB9119559D0

Abstract

A nut or bolthead is protected against tampering by a cover which is deformed onto either the nut, the bolthead, or a portion of a threaded shank protruding from the nut, the cover having a narrow end and a wide end. In Figure 2, the cover 18 has a circular hole 15 which interferes with the corners of the bolthead 20. In Figure 9, the cover 110 is forced onto the threaded end 124; in Figure 12 the cover 310 is frusto-conical. <IMAGE>

Description

Title: Fastener and cover and method of covering a part of a fastener.

Descrintion of Invention From one aspect, the present invention relates to a combination of a cover with a two-part fastener comprising a threaded shank and a nut on the shank.

A variety of decorative and protective covers have been proposed for nuts. In some cases, these require nuts of special form for cooperation with the cover. Other known covers can be fitted onto a variety of nuts of known form There have also been proposed covers incorporating key-operated locks, which can be used to prevent access being gained to a nut by unauthorised persons. However, these lockable covers are relatively complex and expensive.

It is an object of the present invention to provide a simpler cover which can be used to make it difficult or impossible for an unauthorised person to remove a nut.

According to the first aspect of the invention, there is provided in combination with a two-part fastener comprising a threaded shank and a nut on the shank, a hollow cover which has a narrower end, a wider end and a respective opening at each of said ends, wherein a part of the fastener lies inside the cover, the cover grips the fastener and the cover has an external surface which extends substantially from the wider end to the narrower end.

The cover may cover either the nut or a head at an end of the threaded shank of the fastener. The cover may also cover a part of the threaded shank.

The cover preferably grips the fastener at at least a position adjacent to the narrower end of the cover. At its wider end, the cover may be spaced from the fastener.

Said external surface is preferably a surface of revolution having an axis of revolution which passes through both of said openings.

According to a second aspect of the invention, there is provided a cover for use in a combination according to the first aspect, the cover having the form of a dome with a hole at a crest of the dome and wherein an annular portion of the dome bordering the hole is interrupted to facilitate deformation of said portion.

The annular portion may be interrupted by one or more slits or by a recess or by a combination of these.

According to a third aspect of the invention, there is provided a method of covering a bolt head or a nut on a bolt wherein there is formed a hollow cover having a narrower end, a wider end and a respective opening at each of said ends, the cover is applied over the head or nut with the wider end of the cover leading, and wherein, during application, the cover is deformed by engagement with the nut or with the bolt to establish a gripping relation between the cover and at least one of the nut and the bolt.

Examples of combinations of fastener and cover embodying the invention and which are produced by a method embodying the invention will now be described, with reference to the accompanying drawings, wherein: FIGURE 1 shows a diametral cross section through a first cover, FIGURE 2 shows a cross section of the cover of Figure 1, in combination with a fastener, FIGURE 3 shows a plan view of the combination of Figure 2, FIGURE 4 is a view similar to Figure 2 illustrating an alternative arrangement in which the cover of Figure 1 is combined with a fastener, FIGURE 5 is a plan view of a second cover, FIGURE 6 shows a side elevation of the cover of Figure 5, FIGURE 7 shows a cross section of the cover of Figure 5, in combination with a fastener, at the commencement of application of the cover to the fastener, FIGURE 8 shows an intermediate stage in application of the cover to the fastener, FIGURE 9 shows the completed combination of cover and fastener, FIGURE 10 illustrates a modification of the cover of Figure 1, FIGURE 11 shows the modified cover of Figure 10, when applied to a head of a bolt, FIGURE 12 shows a modification of the cover of Figure 5 and FIGURE 13 shows the modified cover of Figure 12, applied to a fastener.

The cover illustrated in Figure 1 is a hollow body of annular form having a narrower end 11 and a wider end 12. The cover is circular and is symmetrical about an axis 13, which passes through the internal space defined by the cover. The cover is open at both of its ends 11 and 12, The cover 10 has a substantially flat wider end face 14 and a cylindrical internal surface 15. There is a chamfer 16 between the faces 14 and 15 of the cover. The axis of the surface 15 coincides with the axis 13 and the surface 14 is perpendicular to this axis. At its narrower end, the cover 10 may have a relatively small end face 17 which is parallel to the end face 14.

The cover 10 has an external surface 18 which is a surface of revolution about the axis 13. In the particular example illustrated in Figure 1, the surface 18 is frusto-conical and is generated by rotation of a straight line about the axis 13. Alternatively, the surface 18 may be generated by rotation of a curve about the axis 13. For example, the surface 18 may be domed. In the example illustrated, the generatrix of the surface 18 is inclined to the axis 13 at an angle of at least 25 and preferably an angle within the range 25 to 40".

The surface 18 extends substantially from the narrower end 11 of the cover to the wider end 12 thereof. However, in the example shown, there is a relatively small, cylindrical surface 19 between the surface 18 and the wider end of the cover.

The cover 10 is suitable for covering the flats of a hexagonal head 20 of a bolt shown in Figure 2. There is also shown in Figure 2 a member 21 which is a component of a structure to be secured together by means of the bolt and a nut. A shank 22 of the bolt extends through an aperture in the member 21 and the head 20 is seated on the member 21.

As shown in Figures 2 and 3, the cover 10 is applied to the head 20 so that the head is received inside the cover and the cover grips the head. The internal diameter of the cover, as manufactured, is slightly smaller than the distance across the head 20, as measured between diagonally opposite corners of the head. The chamfer 16 facilitates entry of the head into the cover and the cover is driven along the head until the cover is seated on the member 21. The force for driving the cover along the head can be applied to the cover by means of a hammer, possible through the intermediary of a tubular tool having an internal diameter which is slightly greater than the diameter of the cover 10 at its narrower end 11. During driving of the cover along the head, the cover is deformed to accept the corners of the head inside the cover.The head 20 may also suffer some deformation, depending upon the relative hardnesses of the cover and head.

When application of the cover 10 to the head 20 has been completed, the internal form of the cover will be such that the cover conforms to the shape of the head, in the vicinity of the corners of the head. In the vicinity of the corners, the cover will embrace the head tightly. In the vicinity of the middle of the flats of the head, there may be small clearances between the cover and the flats.

It will be noted that the depth of the cover 10 is similar to the depth of the head 20. In the example illustrated in Figure 2, the cover grips the head 20 substantially throughout the depth of the cover.

In Figure 4, there is illustrated an alternative arrangement incorporating the cover 10 of Figure 1.

In Figure 4, there is shown a hexagonal nut 23 which has been screwed onto a threaded shank 24 of a bolt until the nut 23 is seated on a member 25 of the structure which is to be held in assembled relation by the nut and bolt. The cover 10 has been applied by the procedure herein before described to the nut 23 until the cover also is seated on the member 25. Adjacent to its periphery, the nut 23 may be identical with the head 20 and the cover is engaged with the nut in the same manner as the cover is engaged with the head 20 of Figure 2.

It will be understood that the cover 10 of Figure 1 may be applied to nuts other than hexagonal nuts. Furthermore, the internal surface of the cover 10 may be slightly tapered, being wider adjacent to the wider end 12 of the cover.

In this case, only a portion of the cover adjacent to the narrower end 11 may be deformed during application of the cover to the head of the bolt or to the nut.

The cover may grip the head of the bolt or the nut only in a region adjacent to the narrower end of the cover. The wider end of the cover may be spaced from the head of the bolt or the nut, as the case may be.

An alternative cover is illustrated in Figures 5 to 9, Figure 9 illustrating the cover in combination with a bolt and nut. Certain parts illustrated in Figures 5 to 9 correspond to parts herein before described with reference to Figures 1 to 4. In Figures 5 to 9, such corresponding parts are identified by like reference numerals with the prefix 1 and the preceding description is deemed to apply, except for the differences herein after mentioned.

The wider end face 114 of the cover shown in Figure 6 is a relatively narrow annulus having a dimension measured radially of the axis 113 which is approximately equal to the wall thickness of the cover. The wall thickness is approximately uniform throughout the cover. The shape of the cover 110 is that of a dome and the external surface 118 may be a part of a sphere.

The hole at the narrower end 112 of the cover 110 is non-circular.

That portion of the cover which borders the hole is interrupted by a plurality of recesses, one of which is shown at 126, and by a number of slits, one of which is shown at 127. As shown, the slits may be arranged in mutually parallel pairs and there may be two such pairs. Each pair of slits may lie between a pair of recesses. Between the slits of the pair there is defined a tongue 128 which can flex relative to the remainder of the cover.

The diameter of the hole at the narrower end of the cover 110, as measured between the two tongues, is slightly less than the outside diameter of the threaded shank 124 of the bolt. Thus, the tongues can rest on the end of the shank, when the cover is placed over the shank. The cover 110 is driven along the shank with the wider end 112 leading, by means of a hollow tool having an internal diameter greater than the diameter of the shank 124. As the cover is driven onto the shank 124, the tongues 128 are flexed to admit the shank 124 between them.

When the cover 110 has been seated on the structure which is to be held in assembled relation by the nut and bolt, the tongues 127 may be driven further along the shank 124 by means of a hollow tool having an internal diameter which is only slightly greater than the diameter of the shank 124. This reverses the deformation of the tongues 127 and causes the tongues to bite into the shank 124, thereby deforming the thread of that shank locally. This local deformation of the thread prevents the cover being unscrewed from the shank.

The cover 110 grips only the shank 124. The cover may be spaced from the nut 123. During application to the fastener, the cover is deformed only in a region adjacent to its narrower end. This deformation may be partly or entirely reversed when applications is completed. It will be noted that the cover 110 is, before application to the bolt and nut, entirely open at both of its ends and that the cover 10, before application to the bolt and nut, also is entirely open at both of its ends. The cover 110 covers both the nut 123 and a part of the shank 124.

It will be understood that the covers herein before described may be used to cover a nut on the threaded shank of a stud which does not have a head at an end.

The covers of figures 1 and 5 may be modified to have an elliptical or other non-polygonal shape, at least at their wider ends.

Certain parts of the cover shown in Figures 10 and 11 correspond to those herein before described with reference to Figures 1 to 4. In Figures 10 and 11, such corresponding parts are identified by like reference numerals with the prefix 2. The preceding description is deemed to apply to the cover of Figures 10 and 11, except for the differences hereinafter mentioned.

The internal surface 215 of the cover of Figures 10 and 11 includes a step near to the narrower end face 217, the internal diameter of the cover between this step and the narrower end 211 of the cover being somewhat less than the internal diameter of the remainder of the cover. Thus, the cover has an inwardly projecting lip adjacent to its narrower end 211. The diameter of the opening defined by the lip is substantially equal to the distance between opposite flats of the head of the bolt.

The cover of Figure 10 is applied to the head 220 of a bolt in the same manner as the cover 10 is applied to the head 20. During the final stage of application, the lip adjacent to the narrower end of the cover is deformed where it engages the head of the bolt, primarily adjacent to corners of the head, so that the lip finally conforms to the shape of the head and there is no significant gap between the cover and the head of the bolt at the narrower end of the cover. At a position intermediate the ends of the cover, there will be gaps between the internal surface 215 of the cover and the flats of the bolt head but these gaps will be obscured from view by the lip of the cover.

Certain parts of the cover shown in Figures 12 and 13 correspond to parts of the cover herein before described with reference to Figures 5 to 9. In Figures 12 and 13, such corresponding parts are identified by like reference numerals with the prefix 3 substituted for the prefix 1 used in Figures 5 to 9. The preceding description is deemed to apply to these corresponding parts, except for the differences hereinafter mentioned.

The general shape of the cover shown in Figures 12 and 13 is frustoconical. The cover has a narrower end face 317 which is substantially flat and is of relatively large area, being presented by a substantially flat end portion of the cover which is formed to overlie an end face of a nut.

The smaller internal diameter of the frusto-conical portion of the cover 310 shown in Figure 12 is somewhat greater than the distance between opposite corners of the nut so that there is a clearance between the nut and the frustoconical portion of the cover. The substantially flat end portion of the cover grips the shank 324. The hole at the narrower end of the cover 310 preferably has the same form as that of the cover 110, there being tongues at opposite sides of the hole and recesses between the tongues. The cover 310 is applied to the fastener in the same manner as the cover 110 is applied.

The covers of Figures 10 and 12 may be further modified to have an elliptical or other non-polygonal shape, at least at their wider ends.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. In combination with a two-part fastener comprising a threaded shank and a nut on the shank, a hollow cover which has a narrower end, a wider end and a respective opening at each of said ends, wherein a part of the fastener lies inside the cover, the cover grips the fastener and the cover has an external surface which extends substantially from the wider end to the narrower end without interruption.

2. A combination according to Claim 1 wherein said external surface is a surface of revolution having an axis of revolution which passes through both of said openings.

3. A combination according to Claim 1 or Claim 2 wherein the cover grips the fastener at least at a position adjacent to the narrower end of the cover.

4. A combination according to any preceding claim wherein the nut lies inside the cover.

5. A combination according to Claim 4 wherein the cover grips the nut.

6. A combination according to Claim 5 wherein the nut has at its periphery flats which intersect at corners of the nut, the cover embraces the nut tightly at the corners and there are clearances between the flats and the cover.

7. A combination according to Claim 6 wherein the internal form of the cover, in the vicinity of the corners of the nut, conforms to the shape of the nut.

8. A combination according to any of Claims 1 to 3 wherein the fastener further comprises a head on an end of the shank, the head has at its periphery flat which intersect at corners of the head, the head lies inside the cover, the cover embraces the head tightly at the corners and wherein there are clearances between the flats and the cover.

9. A combination according to Claim 8 wherein the internal form of the cover, in the vicinity of the corners of the head, conforms to the shape of the head.

10. A combination according to any of Claims 1 to 3 wherein the cover grips the shank.

11. A combination according to Claim 10 wherein the thread of the shank is deformed where the shank is gripped by the cover.

12. A combination according to Claim 2 or according to Claim 3 as appendant to Claim 2 wherein said surface of revolution is frusto-conical.

13. A combination according to Claim 2 or according to Claim 3 as appendant to Claim 2 wherein said surface of revolution is domed.

14. A method of covering a bolt head or a nut on a bolt wherein there is formed a hollow cover having a narrower end, a wider end and a respective opening at each of said ends, the cover is applied over the head or nut with the wider end leading and wherein, during application, the cover is deformed by engagement with the nut or with the bolt to establish a gripping relation between the cover and at least one of the nut and the bolt.

15. A method according to Claim 16 wherein the cover is deformed only in a region adjacent to its narrower end during application.

16. A method according to Claim 14 wherein the cover is applied over the nut, during application, the cover engages a threaded shank of the bolt which protrudes from the nut, the cover is deformed only in a region adjacent to the narrower end of the cover and wherein deformation of a portion of the cover adjacent to the narrower end is subsequently reversed, either partly or entirely.

17. A cover for use in a combination according to Claim 1 which has the form of a dome with a hole at a crest of the dome and wherein an annular portion of the dome bordering the hole is interrupted to facilitate deformation of said portion.

18. A cover according to Claim 17 wherein said portion is interrupted by a plurality of slits.

19. A cover according to Claim 17 or Claim 18 wherein said portion is interrupted by a recess.

20. A cover according to any one of Claims 17 to 19 wherein the dome has a base defined by a circular edge and wherein the interior of the dome is entirely open at its base.

21. A cover substantially as herein described with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings.

22. A cover substantially as herein before described with reference to and as illustrated in Figures 5 to 9 of the accompanying drawings.

23. Any novel feature or novel combination of features disclosed herein or in the accompanying drawings.