The present invention also relates to methods of installing fixing devices.

According to a first aspect of the invention there is provided a fixing device for a bolt which comprises at least two resiliently biased leaves which are adapted to engage with a pre-formed hole into which the fixing device is inserted, the leaves being resiliently biased to expand radially outwardly and a radially inner surface of each leaf being adapted to fixedly engage with the bolt which is received by the leaves, wherein on urging the fixing device into the pre-formed hole a sufficiently widened portion of the pre-formed hole is reached to allow the leaves to expand sufficiently so that the bolt can then be received by the leaves on urging the bolt into the hole.

By way of explanation the term'bolt'is also intended to include any generally elongate anchor member such as a screw, for example.

Preferably the radially inner surface of each leaf is provided with a threaded region which is adapted to engage with a threaded bolt.

Preferably each leaf comprises a radially outer surface which is adapted to engage with a respective wall surface of the pre-formed hole, the radially outer surface being arranged to be at an acute angle to the threaded region.

Preferably in an expanded condition the threaded regions define, at least in part, a substantially cylindrical space which is sized so as to threadably receive the bolt. Most preferably, in the expanded condition

the radially outer surface of each leaf bears against a respective wall surface of the pre-formed hole.

In the expanded condition the radially outer surfaces of the leaves desirably form a substantially frusto-conical outline.

Preferably a lowermost end of each leaf is provided with a resilient member. Preferably each resilient member comprises an elongate arm portion which extends longitudinally away from each leaf leading to a coiled portion. Most preferably distal ends of the resilient members attached together.

According to a second aspect of the invention there is provided a device of the first aspect of the invention which is provided with a sleeve to maintain the device in a contracted condition.

According to a third aspect of the invention there is provided a method of installing a fixing device, the fixing device comprising at least two resiliently biased leaves which are adapted to engage with a preformed hole, the leaves being resiliently biased to expand radially outwardly, each leaf being provided with a radially inner region which is adapted to fixedly engage with a bolt, the method comprising forming a hole into which the fixing device is to be inserted, inserting the fixing device into the pre-formed hole, the pre-formed hole comprising a widened portion to allow the leaves to expand radially outwardly to bear against respective wall surfaces of the hole and so allow the bolt to be received by the leaves and the method then comprising urging the bolt into the hole so as to be fixedly received by the leaves.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is partial cross-sectional side elevation of a fixing device in accordance with the invention in an outer sleeve to maintain the device in a contracted condition, Figure 2 is a partial cross-sectioned side elevation of the fixing device of Figure 1 being urged into a preformed hole, Figure 3 is a partial cross-sectional side elevation of the fixing device of Figures 1 and 2 in an expanded condition in the preformed hole, Figure 4 is an end view of the fixing device of the previous Figures in a contracted condition, Figure 5 is an end view of the fixing device of the previous Figures in an expanded condition, Figure 6 is a side view of a longitudinal cross-section of a second fixing device in a contracted condition, Figure 7 is a side view of a longitudinal cross-section of the fixing device shown in Figure 6, Figure 8 is an end view of the spring member of the fixing device shown in Figures 6 and 7, and, Figure 9 is a partial cross-sectional view of a further fixing device of the invention in an expanded condition in a pre-formed hole.

With reference to Figure 1 there is shown a fixing device 1 which comprises four leaves 2, the leaves 2 being connected at the lowermost

distal ends thereof by respective torsion springs 5. The torsion springs 5 act to bias the leaves 2 generally radially outwardly.

Each leaf 2 comprises a radially outermost surface 3 which is of a part frusto-conical shape and a radially innermost threaded portion 4 of substantially part-cylindrical shape. As best seen in Figure 3 the radially outermost surface is arranged to be at an acute angle A to the radially innermost threaded region 4.

A lowermost portion of each leaf 2 comprises a tapered portion 7 which tapers in a direction opposite to the direction of taper between the radially innermost threaded portion 4 and the radially outermost surface 3. Each lowermost tapered portion 7 comprises a radially extending throughbore 8.

Each throughbore 8 is adapted to receive a bent distal end 10 of a respective torsion spring 5. Each torsion spring 5 further comprises an elongate arm 11 which extends generally longitudinally away from each leaf. Each arm 11 ends in a coiled portion 12. The respective distal ends 13 of the coiled portions 12 are arranged to extend generally longitudinally inwardly of the leaves 2, said distal ends 13 being secured together in a bundle by a tie member 14. The action of the torsion springs 5 on the leaves is to resiliently bias said leaves radially outwardly.

In use the fixing device 1 is used to anchor a bolt 15 as follows. A hole of a substantially cylindrical shape is formed in a material 20. The hole is then reamed out to have a wall 21 of flared cross-section. The reaming drill of UK Patent No 2375062B would be suitable for forming the tapered hole. The reaming drill of the aforementioned patent ensures

that below the flared hole a hole section of cylindrical shape is provided which hole section is defined by a side wall 24 and a base 25.

The fixing device 1 is provided in a sleeve 6 so that it is maintained in a contracted condition in which the leaves 2 are urged radially inwardly against the bias action of the torsion springs 12. The fixing device 2, in the sleeve 6, is positioned on the mouth of the preformed hole so that the longitudinal axis of the fixing device 1 is co-incident with the longitudinal axis of the preformed hole. A bolt 15 is then placed on top of the fixing device 1 and head 16 of the bolt is rotated so that lower threads of the threaded shank 17 engage with upper threads of the radially inner threaded regions 4 of the leaves 2. The bolt 15 is then urged downwardly towards the preformed hole and in so doing the fixing device 1 is urged into the hole. As the fixing device 1 is urged further downwards and into the tapered portion of the preformed hole the leaves 2 progressively expand radially outwardly, the radially outer surfaces 3 of the leaves 2 bearing against the frusto-conical wall 21.

With continued downward force the leaves 2 eventually expand sufficiently so that the threaded regions 4 of the leaves 2 define a substantially cylindrical outline. In such an expanded condition base portions 28 of the fixing device 1 can be caused to bear against annular shoulder 29 of the preformed hole.

When the leaves 2 have fully entered the flared region of the preformed hole the head 16 is rotated so that the threaded shank 17 threadably engages with the threaded regions 4 of the leaves 2. As the bolt 15 is being screwed into the fixing device frictional engagement between the radially outer surfaces 3 of the leaves and the wall 21 of the flared section of the preformed hole is achieved as a result of the resilient biasing of the leaves, which ensures that the leaves do not rotate with the

bolt 15. Figure 3 shows that the bolt 15 has been fully screwed into position. The radial extent of the biasing of the leaves 2 is arranged such that when the bolt is fully screwed into the fixing device 1, the leaves 2 bear against the wall 21 so that the fixing device and bolt are held above the base 25 of the preformed hole.

Figures 6,7 and 8 show a second fixing device 32 which is similar to the fixing device 1 but the four torsion springs 5 have been replaced by a spring member 32 made of sheet metal.

The fixing device 30 comprises four leaves 31 of similar construction to the leaves 2 of the fixing device 1, each leaf 31 comprising a radially inner threaded region 33 and a lower portion of each leaf comprises a radially extending through bore 35. Each leaf also comprises radially outer surfaces 40 which are of a part frusto-conical shape.

The spring member 32 is of sheet metal construction and comprises four limbs 36 equally angularly spaced around a base portion 34. Each limb 36 is of serpentine profile to provide added resilience.

A distal end 38 of each limb is received in a through bore 35 of a respective leaf 31. The action of the spring member 32 is to urge the leaves 36 radially outwardly.

An uppermost end of the device is provided with a resilient ring 37 which maintains the integrity of that end of the device.

In use the device 30 operates and is installed in substantially the same manner as the fixing device 1.

In a modified embodiment of the invention the radially outermost surfaces of the fixing device are adapted to frictionally engage with the wall defining the widened portion of the hole such that on rotating the bolt into the leaves the leaves engage with said wall and are so further prevented from co-rotating with the bolt. In some instances it may be desirable to configure said outermost surfaces to prevent rotation of the leaves when the bolt is being urged into the leaves, but allow co-rotation of the leaves when it is attempted to unscrew the bolt-thus providing a security feature. Alternatively the outermost surfaces of the leaves may be configured to prevent co-rotation of the leaves when it is attempted to screw the bolt into the leaves and when it is attempted to unscrew the bolt from within the leaves. Alternatively or in addition it may be desirable to reduce the frictional engagement between the threaded portion of the bolt and the threaded portions of the leaves, for example by way of adding a lubricant.

In yet a further modified embodiment resilient means to urge the leaves radially outwardly is provided by a compressed resilient member which is located within the leaves and bears against the radially innermost portions of the leaves. Such a resilient member may be in the form of a plug made of foam or rubber for example An example of such a modified embodiment is shown in Figure 9 in which three leaves 50 are resiliently biased outwardly by a rubber bung 51 that is received by the lowermost portions of the leaves. An annular flange 52 is located adjacent the lowermost ends of the leaves 50 and a substantially cylindrical portion 53 is provided which is located in the lowermost region 57 of the hole 54. On urging the leaves 50 and bung 51 in to the hole 54 said bung will cause the leaves to expand radially outwardly when the widened region of hole 54 is reached. The

axial depth of the flange 52 is such that it will be seated on annular shoulder 55 of the hole 54 when the leaves have expanded sufficiently to allow receipt of threaded bolt 56. Advantageously on rotating the bolt 56 into the leaves 50 the flange 52 frictionally engages with the shoulder 55 to prevent co-rotation of the leaves.