GB2381300A

GB2381300A - Self-centring washer

Info

Publication number: GB2381300A
Application number: GB0125818A
Authority: GB
Inventors: Ian Murray Garry
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2001-10-27
Filing date: 2001-10-27
Publication date: 2003-04-30
Also published as: GB0125818D0

Abstract

A washer (40) for a bolted assembly, the washer (40) comprising a body (28) which defines a bore (42) wherein the body (28) comprises at least three lands (46) projecting into the bore (42).

Description

SELF-CENTRING WASHER The present invention relates to a washer, particularly but not exclusively, for use with bolted joint.

It is well known to use a generally flat washer, defining a central hole therethrough and through which a bolt or similar passes, to assist in tightening together the bolt and nut of a bolted joint. Washers are often made by cutting a disc from a solid bar and then the hole is either punched or drilled. Between the head of the bolt and its shaft there is commonly a root radius. Where it is important for the washer to be centrally positioned to the bolt, the bore is a close fit to the diameter of the bolt.

When the bolt tightens against the washer the root radius engages the edge of the hole and a gap can be left between the head and the washer. This is undesirable and to avoid this it is common for the edges of the washer surrounding the hole to be chamfered so that the root radius does not engage the washer and the head sits flush. Chamfering is an additional process and adds significant cost and time to the manufacture of washers.

Accordingly the present invention seeks to provide a washer that may be formed without chamfers and that, in use, sits flush with a bolt and is self-centring to the bolt.

Accordingly the present invention provides a washer for a bolted assembly, the washer comprising a body which defines a bore wherein the body comprises at least two lands projecting into the bore. Preferably the body comprises a plurality of lands, the plurality of lands form a generally castellated profile around the bore and the washer is annular.

The present invention further provides a bolted assembly for securing at least two components together, the bolted assembly comprising a bolt, a nut and a washer, the washer comprising a body which defines a bore wherein the body comprises at least two lands projecting into the bore.

Preferably, the body comprises a plurality of lands, the plurality of lands form a generally castellated profile around the bore.

Preferably, the bolt comprises a shaft and a head, the shaft, in use, extends through a hole defined in each of the components and engages the nut to secure the components together, the washer disposed between the head and the components.

Preferably, the bolt further comprises a root radius between the shaft and the head, in use, the root radius engages and deforms the lands thereby the head sits flush and generally centrally with the washer.

The present invention will be more fully described by way of example with reference to the accompanying drawings in which :- Figure 1 is cross section of a bolted joint comprising a prior art washer; Figure 2 is cross section of a bolted joint comprising a washer in accordance with the present invention; Figure 3 is a plan view of the washer shown in Figure 2.

With reference to Figure 1, it is desired to secure

plates 10 and 12 together. The plates 10, 12 define holes 14, 16 respectively and which are aligned so that a conventional bolt 18 may extend therethrough. The bolt 18, comprises a head 20 and a shaft 22, the shaft 22 defines a thread 24 onto which, in use, is screwed a threaded nut 26.

The head 20 and nut 26 clamp and secure the plates 10,12 together. A washer 27, comprising an annular body 28 defining a bore 32, is provided between the head 20 of the bolt 18 and plate 12 to aid distribution of compressive force and to enable the bolt to be tightened as required. The bolt 18 also comprises a root radius 30 between the head 20 and the shaft 22.

It is necessary to provide a chamfer 32 around the periphery of the hole 32 so that the root radius 30 does not engage the washer 27. This is so that the head 20 of the bolt 18 is able to sit flush with the washer 27 when assembled. It should be noted that it is important for the bore 32 of the washer 27 to closely fit the shaft 22 of the bolt 20 so that it locates appropriately and is not positioned off-centre. However, providing the washer 27 with a chamfer 32 increases the time and cost of manufacture and it is the object of the present invention to obviate the chamfering process.

Referring to Figures 2 and 3, where like elements are given like reference numerals of Figure 1, a bolted assembly 39 incorporates a washer 40 in accordance with the present invention. The washer 40 is of generally conventional configuration except that its bore 42 comprises a castellated profile 44. The castellated profile 44 comprises a plurality of lands 46, each inwardly projecting from the annular body 28 into the bore 42. It is intended that the washer 40 does not have the chamfers of the prior art. Instead, it is intended for each land 46 of the castellations to be deformed or partially deformed by the root radius 30 during tightening of the bolt 20 and the nut 26. With this configuration the washer 40 is self-

centring as an interference fit, between the lands 46 and the root radius, is desirable.

Although Figure 3 shows eight lands 46 the number of lands 46 is governed by the circumference of bore 42 and the stiffness of the material the washer 40 is made from.

The dimensions of the lands 46 are also dependent on the stiffness and plastic deformation characteristics of the material of the washer 40. For the washer 40 to selfcentre it is important for there to be at least two lands 46 and the lands 46 spaced equidistant from one another around the circumference of the bore 42.

It is preferable that the washer 40 is cut from a plate by a laser, however, the washer 40 may be punched out or machined in a conventional manner. For each application of the washer 40 it is also desirable for the plate, from which the washer 40 is cut, is of a suitable size so that the washer 40 may be threaded onto the thread 24 of the bolt 18. In this way the washer 40 may be threaded up to the head 20 of the bolt 18 so that the bolt 20 and washer 40 are secured together thereby aiding ease of assembly of the joint 39. It is preferable for the thickness of the washer 40 to coincide with the washer 40 It should be apparent that the root radius 30 of the bolt 18, when used in operative association with the washer 40, may be increased from conventional radii.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims :-

1. A washer for a bolted assembly, the washer comprising a body which defines a bore wherein the body comprises at least three lands projecting into the bore.

2. A washer for a bolted assembly as claimed in claim 1 wherein the body comprises a plurality of lands which form a generally castellated profile around the bore.

3. A washer as claimed in any one of claims 1-2 wherein the washer is annular.

4. A bolted assembly for securing at least two components together, the bolted assembly comprising a bolt, a nut and a washer, the washer comprising a body which defines a bore wherein the body comprises at least two lands projecting into the bore.

5. A bolted assembly as claimed in claim 4 wherein the body comprises a plurality of lands which form a generally castellated profile around the bore.

6. A bolted assembly as claimed in any one of claims 4 or 5 wherein the bolt comprises a shaft and a head, the shaft, in use, extends through a hole defined in each of the components and engages the nut to secure the components together, the washer disposed between the head and the components.

7. A bolted assembly as claimed in any one of claims 4-6 wherein the bolt further comprises a root radius between the shaft and the head, in use, the root radius engages and deforms the lands to enable the head to sit flush and generally coaxial with the washer.

8. A washer substantially as described in this specification and with reference to figures 2-3 of the accompanying drawings.