GB2057617A

GB2057617A - Bolt-retaining device

Info

Publication number: GB2057617A
Application number: GB7931010A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1979-09-06
Filing date: 1979-09-06
Publication date: 1981-04-01

Abstract

An assembly comprising a component having bolt holes 12 extending through it from a first face 15 against which the heads 16 of bolts 13 register, and a locking member 21 for restricting rotational and axial movements of the bolts 13. The component 10 is provided on the first face 15 with a projection 19. An elongate recess in the projection extends in a direction tangentially to the holes 12. The locking member 21 extends along the recess and has a set of first tabs 23 each of which is positioned to engage a respective one of the bolt heads 16 to restrict its axial movement. The member 21 has one or more second tabs 24 for preventing it moving along the recess. Rotational movement of the bolts 13 is restricted by the locking member 21 and by abutment faces 17 on the bolt heads 16 engaging abutment faces 18 on the component 10. <IMAGE>

Description

SPECIFICATION Apparatus for retaining bolts, or like members, in components This invention relates to methods of retaining bolts or like members in components and has particular relevance to assemblies where it is impossible to gain access to the heads of the bolts during or after fabrication of the assembly.

There are many instances in engineering where it is required to retain bolts, or like members, in a component and to prevent the bolts rotating or being displaced axially. For example, in the construction of aero engines there is a need to be able to secure a fan rotor assembly to its respective shaft by bolts and be able to remove it from the shaft without losing the bolts, or disturbing the shaft. In many designs of aero engines access to the bolt heads is impossible.

Any solution to this problem must be completely fool-proof and reliable and must also be easy to manufacture and cheap to fabricate.

An object of the present invention is to provide an assembly comprising a component with bolts extending through it with means to restrict the bolts from rotational or axial movement in bolt holes in the component.

According to the present invention there is provided an assembly comprising a component having bolt holes extending through it from a first face against which the heads of the bolts register, and bolts having an abutment face which registers with an abutment face on the component to prevent rotation of the bolts in the holes, wherein there is provided a projection on the first component which protrudes from the said first face of the component, an elongate recess in the projection extending in a direction tangentially to the holes, and a locking member extending along the recess and having a set of first tabs for engaging the heads of the bolts to restrict axial movement of the bolts in the holes and one or more second tabs which restrict the movement of the locking member along the recess.

The holes may be provided in a straight line or on a common pitch circle diameter. In the latter case, the projection and recess extend along a curved line.

Preferably the flange extends normal to the first surface and the recess is provided in a face of the flange that is normal to the first face and is adjacent the holes.

The locking member may comprise an elongate strip of sheet metal bent to form a body portion which will fit in the recess, and has tangs which are bent to form the tabs. Alternatively, the locking member may be formed from a solid bar to provide a body portion which will fit in the recess and a thin sheet-like portion from which the tabs are formed.

The invention will now be described, by way of an example, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional elevation of an assembly incorporating the present invention; and Figure 2 is an end view of part of the assembly of Figure 1 looking at the bolt heads.

Referring to the drawings the assembly comprises a shaft 10 having a flange 11 at one end. The flange 11 is provided with a plurality of holes 12 on a common pitch circle diameter concentric with the shaft 10. The holes 12 are provided for receiving bolts 13 by which further structure, for example the hub of a fan rotor 14 of a gas turbine engine of the bypass type, is bolted to the shaft. The holes 12 extend through the end plate 11 from a first face 1 5 against which the heads 1 6 of the bolts 13 register.

The heads 1 6 of the bolts 13 are generally right circular cylindrical with two parallel flats 1 7 machined on them. The flats 1 7 constitute abutment faces which co-operate with an abutment face on the flange 11 formed by a circular ledge 1 8 which stands proud of the first face 15 of the end plate 11.

The flange 11 is provided with a right circular cylindrical projection 1 9 which protrudes from the first face 1 5 of the end plate 11, and a recess 20 is formed in the inner circumferential surface of the projection 1 9. The projection 19 and recess 20 lie tangentially to all the holes 1 2.

One or more locking members 21 in the form of an arcuate strip extend along the recess 20. The, or each, locking member comprises a thin sheet of metal which is folded along an axis extending along the strip to form a double layer, or body portion, 22 which is the width and depth of the recess 20. The remaining part of the sheet is provided with a set of first tabs 23 spaced along the strip to coincide with the positions of the bolt heads around the pitch circle. The strip also has one or more second tabs 24 which are located so that in use the, or each, second tab 24 is positioned between two adjacent bolt heads 16.

The locking member 21 is inserted in the recess 20 with the set of first tabs 23 clear of the holes 12 and the bolts inserted in the holes before the tabs 23 are bent to contact each bolt head 1 6.

Alternatively, the tabs 23 may be bent before the locking member 21 is inserted in the recess 20. In this case the tabs 23 are bent to a position where, in use, they would contact the ends of the bolt heads 16, and the tabs 24 are positioned initially clear of contact of the bolt heads. The locking member 21 is then inserted into the recess 20 leaving the bolt holes 12 unobstructed. After the bolts 1 3 are inserted in the holes 12 the locking member 21 is indexed around the recess 20 to bring the tabs 23 into contact with the ends of the bolt heads 1 6 and then the tab 24 bent to a position where it is trapped between two bolt heads 16 to prevent further movement of the locking member 21 around the recess 20.

It will be seen that axial movement of the bolts is restricted by the tabs 23 whereas the flats on the bolt heads co-operate with the ledge 1 8 and the body portion 22 of the locking member 21 to prevent rotation of the bolts 1 3.

Instead of making the locking member from thin sheet material, it may be machined from the solid. In this case, the body portion 22 may be rectangular in cross-section and conform 'approximately to the cross-sectional size and shape of the recess 20 and the tabs 23 and 24 made of thinner section material. This enables the thickness of tabs 23 to be selected for maximum strength.

Although in the above examples, the bolt holes 12 are on a pitch circle and the projection 19 and recess 20 are curved to be tangentially to the bolt holes 12 it is to be understood that where the holes 12 lie in a straight line the projection 1 9 and recess 20 may be along a line extending tangentially to the holes 12.

A feature of the present invention is that should the locking tab 24 fail, the locking member 21 is retained in the recess 20 by the bolts 1 3. A further feature is that if only one bolt needs to be removed the locking tab or tabs 24 may be bent clear of the bolt heads and the locking member 21 indexed around the recess 20 without disturbing the other bolts. To facilitate indexing of the locking members 21, gaps are left between adjacent strips.

Claims

1. An assembly comprising, a component having bolt holes extending through it from a first face against which the heads of the bolts register, and bolts having an abutment face which registers with an abutment face on the component to prevent rotation of the bolts in the holes, wherein there is provided a projection on the first component which protrudes from the said first face of the component, an elongate recess in the flange extending in a direction tangentially to the holes, and a locking member extending along the recess and having a set of first tabs for engaging the heads of the bolts to restrict axial movement of the bolts in the holes and one or more second tabs which restrict the movement of the locking member along the recess.

2. An assembly according to claim 1 wherein the holes are provided on a common pitch circle diameter and the projection and recess extend along a curved line.

3. An assembly according to any one of the preceding claims wherein the projection extends normal to the first surface and the recess is provided in a face of the projection that is normal to the first surface and is adjacent the holes.

4. An assembly according to any one of the preceding claims wherein the locking member comprises an elongate strip of sheet metal bent to form a body portion which will fit in the recess and has tangs which are folded to form the first and second tabs.

5. An assembly according to any one of claims 1 to 3 wherein the locking member is formed from a solid bar to provide a body portion which will fit in the recess and a thin sheet-like portion from which the tabs are formed.

6. An assembly substantially as hereindescribed with reference to the accompanying drawings.