GB2277570A

GB2277570A - Lock washer

Info

Publication number: GB2277570A
Application number: GB9407821A
Authority: GB
Inventors: David John Hunt
Original assignee: Ror Rockwell Ltd; Rubery Owen Rockwell Ltd
Current assignee: Meritor Heavy Vehicle Systems Ltd; Rubery Owen Rockwell Ltd
Priority date: 1993-04-24
Filing date: 1994-04-20
Publication date: 1994-11-02
Also published as: GB9407821D0; GB9308557D0

Abstract

A lock washer 1 made of spring steel comprises a bore 2 into which extends an inner tab 4 for engaging a slot (not shown) in an externally screw threaded member to prevent relative rotation, and resilient outer tabs 5 having portions 7 inclined out of the plane of the lock washer 1, so that when a nut 8 is screwed onto the screw threaded member and against the lock washer 1, one or more inclined portions 7 are elastically deformed by, and engage against, the side surfaces of the nut to prevent unfastening. The lock washer 1 may be concave or convex. <IMAGE>

Description

LOCK WASHERS This invention relates to lock washers.

So called tab washers are used in many applications to ensure that a nut screwed on the end of a screw threaded member does not slacken off in use.

In one known design a tab washer has a lug or tab extending generally radially into its bore which engages in a slot on a screw threaded shaft to which it is fitted. A tab on the outer periphery of the washer is bent up to engage a flat on a nut when the latter has been tightened on the shaft. The internal and external tabs thus prevent relative movement between the shaft and the nut. In an alternative known design a washer has two external tabs, one of which is bent up to engage the nut and the other of which is bent down to engage with a surface, for example the side of a flange, when the nut has been tightened on a stud. The tabs prevent relative movement between the nut and a body in which the stud is secured.

This invention is concerned with providing an improved lock washer to replace the washers described above. Those washers are quite satisfactory provided they are used correctly. However, a problem can arise after dismantling, for example to replace a bearing on a shaft, if the fitter fails to bend up the external tab to engage the nut on re-assembly, or in trying to do so breaks the tab and does not replace the washer with a new one.

According to a first aspect, the present invention provides a lock washer adapted to be mounted on a member and retained on the member by fastening means, comprising a body provided with a bore, retaining means adapted to co-operate with the member to maintain the lock washer and the member in fixed angular relationship and resilient means adapted to be elastically deformed when the fastening means is secured to the member.

Part or all of the lock washer may be made of a spring material which may be spring steel.

The body of the lock washer may be planar; alternatively, the body may be concave, convex or of any other suitable shape.

The retaining means may comprise a tab extending substantially radially or axially from the body of the lock washer and adapted to co-operate with a slot or recess provided in the member to which the lock washer is adapted to be attached.

The resilient means may comprise one or more outer tabs positioned at the periphery of the body of the lock washer. The or each outer tab may extend generally tangentially to the body and may comprise a first portion which may be planar with the body and a second portion which may be inclined to the plane of the body. Such an inclination may be about an axis which is generally radially directed from the centre of the bore and lies in the plane of the body. Where inclined second portions are provided, they may be adapted to be deflected elastically towards or into the plane of the body of the lock washer when the fastening means is secured on the member. At least one inclined second portion may be adapted to co-operate with a side surface of the fastening means to restrain undesirable movement of the fastening means relative to the member.

The invention provides a lock washer that is re-usable and avoids the necessity of a separate operation of bending up of a tab when a fastening is made.

The lock washer of the present invention is particularly suited to securing vehicle axle assemblies although it will be understood that it has many other possible applications.

According to a second aspect, the present invention provides a vehicle axle assembly in which a hub and bearing assembly is secured to an axle by means of a member on which is mounted a lock washer in accordance with the first aspect of the invention retained to the member by fastening means.

According to a third aspect, the present invention comprises a fastener assembly comprising a member, a lock washer in accordance with the first aspect of the invention which mounts on the member, and fastening means by which the lock washer is retained on the member.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view of a lock washer with a plan view of the periphery of a hexagon nut superimposed; Figure 2 is a section on line A-A of Figure 1.

Referring to the drawings, a lock washer 1 comprises a flat body having an inner periphery or bore 2 and an outer periphery 3. Retaining means in the form of a tab 4 extends generally radially into the bore for the purpose of engaging in a slot in a male screw threaded member.

Outer tabs 5 forming resilient means, extend generally tangentially around the outer periphery.

Each outer tab 5 has a first portion 6 which lies in the same flat plane as the body and a second portion 7 which is inclined to the plane of the body. Each inclined portion 7 is separated from the body by a gap 8 as shown in Figure 1. The second portions 7 are inclined to the first portions 6 along radial lines extending from the centre of the ring. The outline of a hexagon nut is shown at 9.

The washer is made of a spring material, for example spring steel.

Figure 2 illustrates the inclination of a second portion 7 to the first portion 6 of an outer tab. The portions 7 are all equally inclined in the same direction.

In use, the lock washer 1 is applied to a male screw threaded member on or to which a component is to be secured, with the internal tab 4 engaged in a slot in the screw threaded member.

A nut is applied to the member and tightened.

The tightening action causes elastic deflection of the portions 7 of the outer tabs into the plane of the ring to make the fastening secure. The lock washer 1 retains a large bearing area and mechanical location on the threaded member which is not present with other forms of elastically deformable lock washers.

The provision of a plurality of outer tabs 5 and of a number of outer tabs which is different from the number of side faces of the nut 9 ensures that at least one of the inclined portions 7 in this embodiment, referenced 10 on Figure 1, is not deformed by the nut 9 in its secured position but projects above the plane of the body. This inclined portion 10 thus co-operates with a side face of the nut to restrain the nut against rotation which would tend to slacken the nut.

Claims

1. A lock washer adapted to be mounted on a member and retained on the member by fastening means, comprising a body provided with a bore, retaining means adapted to co-operate with the member to maintain the lock washer and the member in fixed angular relationship and resilient means adapted to be elastically deformed when the fastening means is secured to the member.

2. A lock washer in accordance with Claim 1 in which the retaining means comprises a tab extending from the body of the lock washer and adapted to co-operate with a slot or recess provided in the member.

3. A lock washer in accordance with Claim 2 in which the tab extends from the body of the lock washer into the bore.

4. A lock washer in accordance with any preceding claim in which the resilient means comprises one or more outer tabs positioned at the periphery of the body of the lock washer.

5. A lock washer in accordance with Claim 4 in which the body of the lock washer is substantially planar, and the resilient means comprise a plurality of generally tangentially extending outer tabs, each outer tab having a first portion which is planar with the body and a second portion extending therefrom which is inclined to the plane of the body.

6. A lock washer in accordance with Claim 5 in which the second portion of at least one outer tab is inclined about an axis passing substantially through the centre of the bore and lying in the plane of the body.

7. A lock washer in accordance with Claim 5 or Claim 6 in which the second portion of at least one outer tab is longer than the first portion of that outer tab.

8. A lock washer in accordance with any preceding claim in which the member to which the lock washer is adapted to be retained is a screw threaded shaft and the fastening means is a nut.

9. A lock washer in accordance with Claim 4, or any of Claims 5 to 8 as dependent from Claim 4, in which the outer tab, or at least one outer tab, is adapted to co-operate with a side surface of the fastening means to restrain undesirable movement of the fastening means.

10. A lock washer in accordance with Claim 9 as dependent from Claim 8 in which there is a plurality of the outer tabs and the number of outer tabs is different from the number of side faces of the nut.

11. A lock washer in accordance with any preceding claim made at least in part of a spring material.

12. A lock washer substantially as described herein with reference to the accompanying drawings.

13. A vehicle axle assembly in which a hub and bearing assembly is secured to an axle by means of a member on which is mounted a lock washer in accordance with any of the preceding claims retained to the member by fastening means.

14. A fastener assembly comprising a member, a lock washer in accordance with any one of the preceding claims which mounts on the member and fastening means by which the lock washer is retained on the member.