GB2232218A

GB2232218A - Security fasteners for preventing theft or vandalism

Info

Publication number: GB2232218A
Application number: GB8912714A
Authority: GB
Inventors: Frederick John Yarrow
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-06-02
Filing date: 1989-06-02
Publication date: 1990-12-05
Anticipated expiration: 2009-06-02
Also published as: GB8912714D0; GB2232218B

Abstract

A bolt or screw (2) has an external screw thread (4) for screwing into an object, a first internal thread (6) of the same hand as the external thread (4) and engageable by an externally screw-threaded tool (not shown) for driving the bolt or screw (2), and a second internal thread (8) of opposite hand to the first and external threads (6, 4) and engageable by a different screw-thread of the same (or a separate) tool for unscrewing the bolt or screw (2). The end (10) of the screw or bolt (2) and the engaging end of the tool are convex or concave to avoid binding, or they may be flat. Where both the external tool threads are on the same tool, the central portion is of hexagonal cross-section. A release washer may be positioned between the head (10) and the tool or tools. <IMAGE>

Description

-A SECURITY FASTENER This invention relates to a security fastener.

Security fasteners are known. There is always a need for security fasteners for securing objects together such for example as door handles, light fittings, toilet roll holders and mirrors in public places. If security fasteners such for example as screws or bolts are employed with standard-type heads, experience has shown that members of the public tend to undo the security fasteners either for the purpose of stealing the unfastened object or for the purpose of vandalising the object.

Some known security fasteners are not sufficiently well designed substantially to hinder persons determined to undo the security fasteners.

other known security fasteners are unduly complex and this causes relatively expensive production costs.

It is an aim of the present invention to provide security fastener which gives a good degree of security in the fastening of objects together, whilst at the same time is of a relatively simple construction so that manufacturing costs can be kept to a minimum.

Accordingly, this invention provides a security fastener having an external thread for enabling the security fastener to be screwed into an object and to be unscrewed from the object, a first internal thread which is of the same hand as the external thread, and a second internal thread which is of an opposite hand to the external thread, the first and the second internal threads extending one after the other along the longitudinal axis of the security fastener.

Because of the positioning of the first and the second internal threads one after the other along the longitudinal axis of the security fastener, the first and the second internal threads can easily be formed. The security fastener operates to give a good degree of security when it is used to connect the object to another object.

Preferably, the security fastener is one in which the first internal thread starts at the end of the security fastener remote from the start of the external thread, and in which the second internal thread starts at the inner end of the first internal thread. If desired, the opposite arrangement may be employed.

Preferably, the security fastener is one in which the first internal thread defines a first bore, in which the second internal thread defines a second bore, and in which the first bore is of a larger diameter than the second bore. If desired, the second bore may be larger than the first bore.

Advantageously, the end of the security fastener remote from the start of the external thread is convex. The use of a convex end reduces the contact area of the end of the fastener available for being engaged by a tool or tools for screwing the security fastener into the object and for unscrewing the security fastener from the object. If too much binding occurs, difficulty may be incurred in releasing the tool after it has been used to screw the security fastener into the object. As an alternative to having the end of the security fastener remote from the start of the external thread convex, the end may be concave.

The end may also be flat but then care must be taken not to have too much binding between the end of the security fastener remote from the start of the external thread and the tool used to screw the security fastener into the object.

One way of reducing undesired binding is to have the mating face of the tool convex or concave. Such a mating face of the tool may be used with a concave or convex end of the security fastener. The convex or concave end of the tool can also be used with a flat end of the security fastener.

Usually, the fastener will comprise a head and a shank, the external thread being formed in the shank, and the first internal thread being formed in the head. The second internal thread will also usually be formed in the head.

The security fastener is preferably a screw or a bolt. The screw is preferably a machine screw which is machined to accept a machined thread in an object. The screw may however be a wood screw if desired. Other types of security fastener, for example security fasteners in the form of grub screws, may be employed.

The security fastener may be made in any desired lengths and thicknesses. Thus, for example, the fastener may be made as 5, 6, 8, 10 and 14mm screws.

The fastener may also be produced with a variety of threads so that the fastener may have British Standard fine threads, British Standard Whitworth threads, Unified National Course threads and Unified National Fine threads.

The security fastener may be made in a variety of materials. The security fastener may be made of brass, mild steel or stainless steel.

The security fastener may also be made of a plastics material. Plastics materials may be preferred where the security fastener is to be used, for example, in the automobile industry for securing, for example, vehicle registration plates to cars. The plastics material may be nylon. Other types of plastics materials may be employed.

The present invention also extends to the combination of the security fastener and a tool or tools for securing the security fastener into the object and for unscrewing the security fastener from the object.

Preferably, the combination is one in which there is one tool, the tool having a first end with a first external thread for mating with the first internal thread in the security fastener, a second end with a second external thread for mating with the second internal thread in the security fastener, and a central portion having flat sides for receiving a spanner.

Preferably, the central portion has six of the flat sides.

The tool or the tools may be made from any desired material such for example as mild steel.

The combination of the invention also includes a release washer positioned between the end of the security fastener remote from the start of the external thread and the tool or the tools.

As mentioned above, the use of a release washer will usually not be required since the end of the security fastener remote from the start of the external thread and/or the corresponding mating surface on the tool or the tools will be appropriately formed to reduce the point of contact to a minimum and thus to avoid the creation of excessive friction. If a release washer is employed, then this will usually be made of a plastics material or a fibre material. A presently preferred plastics material is nylon.

During use of the fastener, it is preferred that the fastener be countersunk into the object. The fastener then looks like a pop rivet but of course the fastener is removable.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a first security fastener; Figure 2 shows a first tool; Figure 3 shows a second tool; Figure 4 shows a second security fastener; and Figure 5 shows a third tool.

Referring to Figure 1, there is shown a security fastener 2 having an external thread 4 for enabling the security fastener 2 to be screwed into an object (not shown) and to be unscrewed from the object.

The security fastener 2 also has a first internal thread 6 which is a right hand thread and which is of the same hand as the external thread 4.

The security fastener 2 further has a second internal thread which is a left hand thread and which is thus of an opposite hand to the external thread 4.

As can be seen from Figure 1, the first and the second internal threads 6, 8 extend one after another along the longitudinal axis of the security fastener 2. The first internal thread 6 starts at the end 10 of~the security fastener 2 remote from the start 12 of the external thread 4. The second internal thread 8 starts at the inner end 14 of the first internal thread 6.

As can also be seen from Figure 1, the first internal thread 6 defines a first bore 16. The second internal thread 8 defines a second bore 18. The first bore 16 is of a larger diameter than the second bore 18.

The end 10 shown in Figure 1 is flat. In a preferred alternative construction, the end 10 is concave as shown in dotted lines in Figure 1.

The security fastener 2 comprises a head 20 and a shank 22. The external thread 4 is formed in a lower part of the shank 22. The first internal thread 6 and the second internal thread 8 are formed in the head 20. The security fastener 2 shown in Figure 1 is a machine screw. The machine screw is preferably made of brass but it may be made of other materials including steel and plastics materials.

Figure 2 shows a tool 24 for screwing the security fastener 2 into the object. The tool 24 has a body portion 26 and an appropriate right handed screw threaded portion 28. The body portion 26 has an end 30 which is flat as shown and which mates with the end 10. In a preferred alternative construction, the end 30 is concave as shown by the dotted lines.

With a concave end 10 and/or a concave end 30, the point of contact between the ends 10,30 is reduced to a minimum, sufficient to enable the tool 24 to screw the security fastener 2 into the object, but not sufficient to cause so much binding that the tool 24 cannot be released from the security fastener 2 when the security fastener 2 is in the object.

Figure 3 shows a tool 32 for unscrewing the security fastener 2 from the object. The tool 32 has a body portion 34, a screw threaded portion 36, and an end 38. The screw threaded portion 36 has the left hand thread for engaging the second internal thread 8. Because the bore 18 is smaller than the bore 16, the screw threaded portion 36 is of a smaller diameter than the screw threaded portion 28. The end 38 on the tool 32 can be concave as shown by the dotted lines if desired. Both the tools 24 and 32 are provided with a screw driver slot 40 for enabling the tools to be screwed in and out.

Figure 4 shows a security fastener 2 which is in the form of a bolt. For ease of comparison and understanding, similar parts as in Figure 1 have been given the same reference numerals and their precise construction and operation will not again be given. In Figure 4, the head of the bolt is frusto-conical as shown so that it cannot be gripped, for example by a pair of pliers.

Figure 5 shows a tool 42 having the thread 28 at one end and the thread 36 at the other end. The threads 28, 36 are separated by a central portion 44 which has flat sides and is hexagonal in cross section. The single tool 42 can replace the two tools 24, 32. The tool 42 can be used in a chuck of a drill.

The drill can be mainsor battery operated.

The security fasteners 2 can be used in public places or other appropriate places for securing objects such for example as door handles, light fittings, toilet roll holders and mirrors in place. Preferably the security fasteners are counter sunk to make it more difficult for thieves and vandals to remove the security fasteners 2. The security fasteners 2 can also be used to give good home security, for example to secure in position windows or to secure in position other items of valuable household equipment such for example as video and stereo equipment. The security fasteners 2 may be sold in boxes with the tools 24, 32 or the tool 42. Replacement boxes would normally only be provided with the security fasteners 2.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, the screw threaded portion 36 has been shown to be longer than the screw threaded portion 28 but this can be reversed or both screw threaded portions can be of the same size. Furthermore, convex ends 10, 30, 38 can be employed.

Claims

1. A security fastener having an external thread for enabling the security fastener to be screwed into an object and to be unscrewed from the object, a first internal thread which is of the same hand as the external thread, and a second internal thread which is of an opposite hand to the external thread, the first and the second internal threads extending one after the other along the longitudinal axis of the security fastener.

2. A security fastener according to claim 1 in which the first internal thread starts at the end of the security fastener remote from the start of the external thread, and in which the second internal thread starts at the inner end of the first internal thread.

3. A security fastener according to claim 1 or claim 2 in which the first internal thread defines a first bore, in which the second internal thread defines a second bore, and in which the first bore is of a larger diameter than the second bore.

4. A security fastener according to any one of the preceding claims in which the end of the security fastener remote from the start of the external thread is convex.

5. A security fastener according to any one of the preceding claims and comprising a head and a shank, the external thread being formed in the shank, and the first internal thread being formed in the head.

6. A security fastener according to claim 5 in which the second internal thread is formed in the head.

7. A security fastener according to any one of the preceding claims and which is a screw or a bolt.

8. A security fastener substantially as herein described with reference to Figures 1 and 4 of the accompanying drawings.

9. The combination of a security fastener as claimed in any one of the preceding claims and a tool or tools for securing the security fastener into the object and for unscrewing the security fastener from the object.

10. The combination according to claim 9 in which there is one tool, the tool having a first end with a first external thread for mating with the first internal thread in the security fastener, a second end with a second external thread for mating with the second internal thread in the security fastener, and a central portion having flat sides for receiving a spanner.

11. The combination according to claim 10 in which the central portion has six of the flat sides.

12. The combination according to any one of claims 9 to 11 and including a release washer positioned between the end of the security fastener remote from the start of the external thread and the tool or the tools.

13. The combination according to claim 9 and substantially as herein described with reference to Figures 2, 3 and 5 of the accompanying drawings.