Background to Invention The use of the threaded nuts and bolts is a universally recognised fixing means for the diverse range of components. Such threaded fixing tools generally rely on friction at the thread interface to secure a nut or bolt in the"locked"position. However, vibration, temperature fluctuations and many other environmental factors can act on such fixtures and cause them to loosen.

A vast range of clips, locking pins and other mechanical means have been devised to address these problems. Chemical means are also available in the form of thread locking solutions which also serve to lock such fixtures by effectively gluing the threaded region common to both components of the fixture.

However, to date no complete solution to the above problem has been satisfactorily provided. In particular, when such fixtures are used with tilt-lift concrete panels and similar heavy construction elements, such components must be manipulated involving heavy lifting, bracing and fixing of large concrete panels and similar structures. The fixing, lifting and bracing of such panels generally relies on threaded fixtures which can work loose on such panels if they are caused to rock during assembly or when exposed to wind etc. Such an uncalculated motion can cause structural fixing elements to work loose. Similarly, temporary bracing used to support panels can be subjected to vandalism and unauthorised interference, or untrained use. A locking device adapted for use with standard fasteners which can be readily fitted, without specialised tools, by single handed operation and which allow ready visual inspection of the state of tightening of a fixture would provide great benefits.

Statement of Invention Accordingly, in one aspect the invention provides a locking device for a rotation based fastener for fastening an object to a substrate said device comprising a washer

adapted for placement between said fastener head and said object and a locking plate adapted for removable placement over said fastener head for co-operation therewith to prevent relative rotation of said locking plate and said fastener head wherein said locking plate and said washer are connected by a common portion being an integral foldable tab wherein said foldable tab is flexible but substantially non-elastic.

The washer may be provided with a first aperture adapted to receive the shank of the fastener such that the fastener head will abut the washer face and upon tightening be drawn into tight contiguous contact with the substrate.

The locking plate may be provided with a second aperture of smaller size than said fastener head, wherein said locking plate must be forcibly fitted over said fastener head causing said aperture to distort in a manner to secure said locking plate onto the head thereof and prevent relative rotation between the head and the locking plate. The aperture may be circular and dimensioned to provide sufficient latitude to commence engagement with the fastener head, but require forcible fitting to fully engage said fastener head and once fitted over the head of the fastener prevent rotation thereof.

The locking device is preferably made from one piece and of unitary construction. The locking plate is preferably of greater dimension than the fastener head.

The second aperture formed in the locking plate is preferably circular and of a diameter less than the distance between opposing highs of a polygonal fastener head (major diameter) and greater than the distance between opposing lows of said polygonal fastener head (minor diameter). Where the fastener head is hexagonal in shape the highs occur at the corners of the hexagon and the lows occur at the flats of the hexagon Where the fastener head is non-hexagonal the aperture size can be between said average major and average minor diameters of said head.

The foldable tab is preferably formed as a narrow waist region between the larger washer and larger locking plate. The foldable tab may include a transverse creasable region to assist in the bending of the device; but any such folding aids will add little or no elasticity to the foldable tab.

The invention will now be described with reference to Figures 1 to 6 which detail particularly preferred embodiments of the invention and are not to be take as limiting.

Figure 1 Shows a plan view of the integral locking device in a first embodiment

Figure 2 Shows a plan view of the locking device in a second embodiment.

Figure 3 Shows a side elevation of the locking device fitted to a fastener prior to locking down.

Figure 4 Shows a side elevation of the locking device after locking down.

Figure 5 Shows a perspective view of the locking device applied to a fastener.

Detailed Description of Invention Referring firstly to Figures 1 and 2 an embodiment of the locking device of the invention is shown in two plan views where the locking device is adapted to co-operate with a rotation based fastener, for example, a bolt or nut or other threaded device having a fastener head (2), shown in phantom, and adapted for fixing an object to a substrate. The device comprises a washer (1) having an aperture (8) through which the shank of the fastener can pass such that the fastener head, once drawn down so as to bring the object into contact with the substrate, bears down on the washer face in the usual manner of operation of a washer. The device of the invention further comprises an integral locking plate (4) attached to the washer (1) by way of a foldable tab (5) having a foldable or crease region (6). The locking plate (4) is provided with a second aperture (9) dimensioned to allow forced fitting to and over the fastener head (2). The material of choice for the device is low carbon steel; but any suitably ductile and strond material could be used.

Referring now to Figures 3 and 4; in use, the locking device of the invention is fitted by placing the washer part on top of the object (3) to be fastened, and then securing the fastener head (2) onto the washer (1) through the first aperture (8). An optional standard washer (7) can be used between the device and the fastener if required. Once the fastener head is secured at the appropriate torque the locking plate (4) is drawn over by folding about the foldable tab (5) 180° such that the second aperture is placed onto and over the fastener head.

The second aperture is formed by way of a circular hole having a diameter between the major and minor diameters of the fastener head. In the example given, the fastener head is formed as a hexagonal bolt head or nut, with the major axis being the distance between opposing corners of the hexagonal fastener head and the minor diameter being the distance between the opposing flats of the hexagonal fastener head.

In this manner, the second aperture of the locking plate is readily able to be placed in juxtaposition to the fastener head, but requires forceful application in order to cause the locking plate to be drawn or impacted down onto the fastener head. The action of forcing the locking plate onto the fastener head causes the second aperture to distort

and comply to the form of the fastener head. In this manner, once the locking plate is positioned to a fastener head, the combination of the non-elastic nature of the foldable tab (5) and the swaging effect of forcing the second aperture to distort, which has the fastener head acting a swage block, elongates and stretches the circular hole over the fastener head. The force and swaging result assists in snugly engaging the locking plate to the fastener head by way of the coning effect thereby ensuring that the locking plate is securely fixed to the fastener head and cannot work loose.

The application of the locking plate requires the use of minimal tools including a maul hammer and a tubular punch.

Referring now to Figure 5, a perspective view of the applied locking device of the invention shows the simple and intuitive nature of the device and clearly demonstrates the swaging effect of the forced application of the locking plate to the fastener head. The combination of the non-elastic qualities of device's component material, which is preferably low carbon steel, and the coning effect of the forced application of the locking plate to the fastener head ensures that a secure, reliable and simplified locking device can now be applied to a wide range of situations The material used in the device can be selected from any suitable malleable material having the requisite strength and characteristics to allow bending without undue elasticity. The device of the invention provides many advantages over all of the known prior art. In particular, the known prior art includes a range of hinged locking plates, which generally include pre-formed poly sided apertures for the locking plate, which do not require forced application to the fastener head and must be secured by other means to prevent them working loose. In addition, the pre-formed configuration of the receiving aperture of the locking plate requires that the fastener head be rotated to specifically provide for the application of locking plate. Such rotations may well over or under torque the fastener head. In contrast to these problems as experienced by the prior art, the device of the invention requires no movement of the fastener head beyond the optimum torqued position as the locking plate aperture is formed in situ during the application process as the locking head is forced onto the fastener head in its optimal position. A further advantage of the locking device of the invention over the prior art results from the loop region (10) formed as the foldable tab is bent over the crease region (6). The action of folding the foldable tab results in an open access loop (10) which is available to assist in removal of the locking device where a suitable tool or pry bar is placed into the access loop, allowing ready leverage of the locking plate away from the fastener head.

The device of the invention is principally intended for one off use, although recycling of the product is possible, providing the aperture of the locking plate is reinstated prior to re-use.

The invention provides for the first time a highly secure and simplified means for locking a fastening device in a manner that prevents the device from becoming loose during operation, installation or use. The device of the invention is simple and intuitive to use and can be operated single handedly without the use of specialised tools. Once the device is in place, it is readily visible and provides a means of visual inspection confirming that the fastener under inspection is tight and secure without the need to check physically each fastener.

Whilst the device of the invention provides a highly secure means of locking a fastening device, it is readily removable without the use of specialised tools by the simple levering away of the locking plate from the fastener head.

In addition, the locking device of the invention can be colour matched to particular fasteners or situations so as to assist in inspection of finished work.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.