BACKGROUND OF THE INVENTION

This invention relates to a security fastening.

The theft of portable petrol engined machines such as motor mowers, trimmers, chain saws, cultivators, etc. is a continuing problem. This is especially so with thefts from sellers (retailers) of such machines. Attempts to deter such thefts have largely been unsuccessful. For example, the chaining down of the machines creates little deterrent to the serious or professional thief as the chains can be simply cut or locks associated therewith broken/picked.

Those stealing such machines wish to guickly dispose of the machines by on-selling. Thus rendering the engine inoperative is a desirable deterrent as those involved in the theft do not wish to spend time and possibly money restoring a machine to its operative state. There thus exists a need for a disabling device which is simple, is easy to install and remove yet is effective.

SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a security fastening functionable as an engine disabling device which can be simply installed in a engine to render it inoperative but readily removable when operation of the engine is required.

There are, however, many other situations where a security fastening is required so as to prevent the unauthorised removal of an article. For example, wheels of motor vehicles are often stolen and to deter a thief it is known to provide a lockable wheel nut with each wheel of a vehicle. However, such lockable wheel nuts do not provide significant deterrent as the locks can either be picked or sufficiently damaged by an impact force to the locking region to enable the nut to be removed.

Therefore it is a further object of the present invention to provide a security fastening which is functionable as a nut or a bolt which can be applied to any mating fastening in order to prevent unauthorised removal or access.

Broadly the present invention consists of a security fastening comprising a first part having a threaded portion, a second part rotatably mounted with said first part, said first part having a tool engagement surface, said tool engagement surface and/or at least a portion of the second part being of such a construction that only a specially configured tool is locatable therewith such as to enable the tool to engage with the tool engagement surface and be used to apply a torque to said first part to remove same from its threaded engagement in or on an item.

In one form of the invention the security fastening is able to be screwed into a spark plug hole of an engine but only with the use of a specially configured tool.

According to a second form the security fastening can be screwed onto a threaded stud of a wheel and only be removable by the use of a specially configured tool. To this end the tool engagement surface is of a shape which cannot be gripped by conventional tools.

As the second part of the device which is readily accessible is only rotatably mounted with the first part any attempt to remove the device by manipulating the second part results simply in free rotation of the second part and no torque applied to the first part.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an elevation view of one form of the invention, Figure 2 is a further elevation view but taken at 90° to that of Figure 1,

Figure 3 is a top plan view,

Figure 4 is an elevation view of a second form of the invention, Figure 5 is a top plan view of the second form of the invention shown in Figure 4,

Figure 6 is a top plan view of the first part of the second form of the invention,

Figure 7 is a cross-sectional elevation view of the second form of the invention, Figure 8 is an elevation view of a tool for engagement with the second form of the invention,

Figure 9 is an end elevation view of the tool of Figure 8, and

Figure 10 is a cross-sectional elevation taken on line A-A of Figure 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The security fastening of the invention (which is shown in Figures 1 to 3 of the drawings as an engine disabling device) is formed of two basic parts. A first part 10 has a threaded shank 11 which extends from a body or tool engagement portion 12. The shank 11 has an external thread lla such that it can be screwed into a threaded opening such as the spark plug opening of an engine.

A second part 14 is formed with a projection or stud 15 which extends within bore 17 of the first part 10 so as to be rotatable therein. Due to the presence of fixing means 18 stud 15 is prevented from any substantial axial movement relative to the first part 10.

The fixing means 18 can, as shown in Figures 1 to 3 for example, be a headed fastening screwed into a threaded opening (not shown) in the end of stud 15. Alternatively the end of stud 15 can extend beyond the terminal or distal end 16 of shank 11 and be swaged or otherwise deformed into an enlarged head which prevents axial movement of the second part 14 relative to the first part 10.

With the second embodiment shown in Figures 4-7 a projection or stud 15' of first part 10 has towards its distal end a peripheral groove 25 while a corresponding groove 26 is formed in the wall of the bore 17 of second part 14. When the stud 15 is inserted into bore 17 the grooves 25 and 26 align. Accordingly, a circlip 27 can be fitted into groove 24 and compressed so that the stud 15' with circlip 27 can be inserted into bore 17. Upon the circlip reaching groove 26 the circlip expands into groove 26. Consequently the circlip

27 is captured between grooves 25 and 26 and the stud 15' is retained within bore 17. Stud 15' can, however, rotate within bore 17.

The or part of the peripheral surface of tool engagement portion 12 of the first part 10 forms a tool engagement surface 13. This is configured so that it is not able to be engaged by a conventional tool such as a fixed jaw or adjustable spanner. Thus, such a tool cannot be used to apply a torque to the first part about its longitudinal axis.

Thus in the illustrated form of Figures 1 to 3 the tool engagement surface 13 includes a pair of flats 21 forming a generally V shaped surface and a generally curved surface 22.

The peripheral surface of the second part 14 is likewise configured so that at least at its greatest cross sectional area it has corresponding flats 23 and curved surface 24.

With the second form of the security fastening as shown in Figures 4-7 the peripheral surface of the tool engagement surface 13 of body 12 is substantially polygonal in shape when the first part 10 is viewed in plan and is preferably a polygon having an odd number of sides, eg five, seven or nine. Preferably each side is of a curved shape. Also the apex between each side iε curved. This results in the peripheral engagement surface 28 being a shape of constant width. Thus, if a standard hexagonal socket, box, ring or open ended spanner is engaged over the peripheral surface 28 and turned it will only freely rotate and not apply any torque to the first part 10.

Likewise, the peripheral surface 28 of the second part 14 is of the same configuration but has a pair of spaced apart protrusions 30. The same spaced apart protrusions could also project from the tool engagement surface 13 of the first part 10 though this is not necessary.

The device iε thus inserted and removed from the screw threaded spark plug hole by a special tool configured to be able to fit over the first 10 and second 14 parts and apply a screwing torque via engagement with tool engagement portion 12 of the first part 10.

As shown in Figures 8, 9 and 10 the tool 31 for use with the second form of the invention consists of a socket having an open ended bore or cavity 32 which in cross section is shaped to conform with the peripheral shape of the tool engagement surfaces 13 and 28 of the first and second parts 10 and 14 when the cross sectional profiles of the two parts are aligned. The bore 32 additionally includes two open ended grooves 33 which are located so that they engage over the protrusions 30.

Thus, to remove the security fastening from, say, the spark plug hole of an engine the second part 14 is rotated relative to the first part 10 so that the cross sectional profiles are aligned whereupon the socket 31 is slid over engagement surface 28 of the second part 14 such that the protrusions slide along the grooves 33. When the socket 31 is pushed sufficiently onto the fastening that it also engages with the tool engagement surface 13 a torque can then be applied to the tool to unscrew the fastening from the spark plug hole.

The tool engaging surface 13 of the first part 10 is preferably of as little width as possible such that it nestles within the confines of that part of the engine from which the spark plug opening extends, eg within the cooling fins. This ensures that pliers type tools are not able to engage therewith and apply a screwing torque to remove the device. However, any attempt to remove the device by gripping the second part with pliers type tools will simply result in the second part freely rotating and hence no unscrewing torque being applied to the firεt part.

It is envisaged that with the device of Figures 1 to 3 a variety of configurations of tool engagement surfaces 12 for the first part 10 will be designed together with correspondingly εhaped toolε. Such tools will generally be of a socket type having an internal cross section corresponding to that of the tool engagement portion 12 of first part 10. A seller would thus be provided with a supply of identical devices and a tool of a configuration corresponding to the configuration of engagement portion thereof. As a result only that seller would be able to install and remove devices of that particular configuration.

With the device of Figures 1 to 7 the spatial array (and number) of protrusions 30 can be varied. Also for a greater number of different configured devices the size (ie the diameter of a circle which circumscribeε the apices of the

sides of surfaceε 12 and 28) can be varied. This would result in, say, two devices having protruεionε located in identical positions but the tool able to operate one device would not be suitable for the other device as it would either not be able to fit over surface 28 or would fit over but not be able to grippingly engage to cause a torque to be applied to surface 12.

As it would be unlikely or impractical for someone removing a machine without authority to have the specialist tool to remove the disabling device from the engine it is believed that the presence of the device will constitute sufficient deterrent to such unauthorised removal. However, as the authorised seller of the machine can by use of the specially configured tool simply install and remove a disabling device at will the ability to render an engine inoperative does not result in the inconvenience normally associated with other means of incapacitating an engine as a deterrent to theft.

The security fastening of the present invention can be readily adapted to function as, say, a lock nut for the wheel of a motor vehicle. To this end the shank 11 of the first part 10 will have an internal threaded bore with the thread being suited to engage on the threaded stud of a wheel hub. Once again, the security fastening could only be installed and removed by a special tool configured to fit with the security fitting. This tool would be in the form of a

εuitably configured εocket having meanε for engagement with a torque applying lever, eg a bar of circular cross section able to engage in a pair of diametrically opposed openings 34 in the end of the socket remote from that which has the configured opening in which the security fastening can engage.