MOUNTING ARRANGEMENT

This invention concerns mounting arrangements, and particularly but not exclusively mounting arrangements for sheet components.

On bolts there is usually an underhead blend radius or underhead blend portion between the bolt head and the bolt shank. This blend portion provides a stress relieving transition zone between the head and shank. When using such a bolt in a hole, steps are usually taken to prevent continuous hard contact between the hole edge and the blend portion.

One way of achieving this is to provide a washer. This however means that extra components are required increasing the part count and also potentially increasing weight. Moreover the bolt head will be raised up slightly relative to the component .

A further existing approach is to use a chamfered hole, such that the blend portion is received within the chamfer to substantially prevent contact between the hole edge and the blend portion. Providing such a chamfer involves a secondary manufacturing operation. In practice this operation is often carried out by hand meaning that different sizes of chamfer are often produced. This can significantly affect bolt tension in use due to the differences in frictional-torque between the underside of the bolt head and the surface surrounding a hole, resulting from the variations in mean friction-torque radius. This means that for a set torque tightening, different fixing tensions will be achieved dependent on the degree of chamfering of a hole.

According to the present invention there is provided a mounting arrangement for a component, the arrangement including a bolt with a head, shank and an underhead blend portion therebetween, and a substantially cylindrical hole in a face of the component into which hole the bolt shank is locatable, the hole having a diameter such that the bolt shank is slideably locatable therein and the underhead blend portion can be wholly contained therein, three or

more spaced projections are provided extending generally radially into the hole from the circumference thereof, the projections being configured such that the underhead blend portion is engageable therewith when the shank is fully located in the hole .

The projections may be configured such that when the bolt head is urged towards the component the projections will be plastically deformed by the underhead blend portion engaging thereagainst such that the underside of the bolt head can engage against the component face around the hole .

The projections may have a substantially constant cross section along the length of the hole.

The projections may be substantially equispaced around the circumference of the hole. Four projections may be spaced around the circumference of the hole.

The projections may be substantially identical to each other.

The hole and projections may be formed by any of laser cutting, wire cutting or punching.

The invention also provides a mounting arrangement for a sheet component, the mounting arrangement being according to any of the preceding seven paragraphs .

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: -

Fig. 1 is a diagrammatic part cross sectional view through a prior art mounting arrangement during assembly;

Fig. 2 is a similar view to Fig. 1 but with the arrangement fully assembled;

Fig. 3 is a diagrammatic plan view through part of the prior art mounting arrangement;

Fig. 4 is a diagrammatic cross sectional side view through part of the prior art mounting arrangement; Figs. 5 and 6 are similar views to Figs. 1 and 2 but of a mounting arrangement according to the invention, and with an additional component shown in Fig. 5; and

Figs. 7 and 8 are similar views to Figs. 3' and 4 but of the mounting arrangement of Figs. 5 and 6, and with Fig. 8 being a view along the line A-A in Fig. 7.

Figs. 1-4 diagrammatically illustrate a conventional mounting arrangement incorporating a bolt 10 mounted to a plate 12. The bolt has a head 14 with an appropriate formation to permit turning thereof and a shank 16. An underhead blend portion 18 is extends around the shank 16 beneath the head 14 to provide a stress relief transition zone between the head 14 and shank 16.

A cylindrical hole 20 is provided through the plate 12 and a chamfer 22 is provided around the upper part of the hole 20. The chamfer 22 receives the blend portion 18 when the head 14 engages against the plate 12. The chamfer 22 would often be formed by hand such that a relatively small chamfer 22 may be provided as shown for instance in Fig. 1 or a relatively large chamfer 22 as shown in Fig. 4.

Figs. 5-8 show a mounting arrangement according to the invention. This arrangement includes an identical bolt 10 to that in the conventional arrangement. In this arrangement a larger cylindrical hole 24 is provided in the plate 12, and is of a diameter to fully receive the shank

16 including the blend portion 18. The size of the hole 24 is chosen to provide control over the allowable eccentricity of the shank 16 within the hole 24.

Four substantially semi-circular equispaced projections 26 extend into the hole 24 for the whole depth thereof. The projections 26 are of a size to permit the shank 16 to pass therebetween, but for the blend portion 18 to engage thereagainst when the head 14 is brought against the plate 12. In practice as the head 14 is brought against the plate 12 the projections 26 will be plastically deformed, as shown at 28 (Fig. 6) , by the blend portion 18 engaging thereagainst such that the underside of the head 14 engages fully against the plate 12 around the hole 24.

In Fig. 5 two plates 12 are diagrammatically shown, an upper plate 12 being along the line A to A in Fig. 7 and a lower plate being along the line B to B in Fig. 7.

This arrangement provides for a number of advantages . For instance, the hole including the projections can be formed in a single straightforward manufacturing technique such as laser cutting, wire cutting or punching. No additional components such as washers are required. These features reduce manufacturing time and cost .

This arrangement means that the area under the bolt head can be accurately predicted in both size and position and repeated in a number of arrangements. This means that consistent bolt tensions can be achieved from the same torque tightening of a number of bolts. This greater reliability in torque to tension conversion may permit the total number of fixings or fixing sizes to be reduced. This can provide weight reduction and/or reduced build time. If fixing sizes are reduced this can lead to increased strain energy and a decreased risk of loss of fixing tension over time, providing greater integrity of mounting.

Various modifications may be made without departing from the scope of the invention. For example a different number of projections may be provided. Alternatively or in addition, the projections may be differently shaped and of relative sizes relative to the hole.