GB2287764A

GB2287764A - Lock nut

Info

Publication number: GB2287764A
Application number: GB9405735A
Authority: GB
Inventors: Keith Lyons
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-23
Filing date: 1994-03-23
Publication date: 1995-09-27
Also published as: GB9405735D0

Abstract

A resilient threaded lock washer 12 is retained in a recess in the bearing face of a nut 10, and is deformed from dished form to flat when the nut 10 is tightened against a workpiece 48, so that the lock washer 12 grips both the nut 10 and the screwthread 39 of the bolt 38. Recesses are provided in the periphery of the lock washer 12 to bite into the peripheral wall of the recess, and may project from the concave face of the lock washer 12. <IMAGE>

Description

DESCRIPTION LOCKING DEVICE The present invention relates to a locking device.

More particularly the present invention relates to a locking device for use in securing a workpiece or workpieces between the device and a bolt or like threaded member.

Locking nuts have previously been employed to lock onto bolts or like threaded members.

The most common type of locking nut has a screw thread formed in a central bore, a section of which bore contains a nylon unthreaded section. When a bolt or other like member is screwed therethrough the thread of the bolt or like member cuts a tight thread in the nylon (R.T.M.) so securing the nut on the threaded member.

However, nylon insert locking washers are unsuitable for applications where they could be exposed to adverse environmental conditions which could cause weakening or decomposition of the nylon (R.T.M.). Additionally, any movement of the nut relative to the threaded member will severely weaken the grip of the nut by shaving nylon from the insert.

Furthermore because the lock is achieved by the thread of the threaded member cutting into the nylon, this type of locking nut is not re-usable.

Locking washers, such as the type disclosed in U.K. Patent, Publication No: 1600015 have been utilised in co-operation with nuts to resist the unscrewing of the nut. They are, however, awkward to use.

It is an aim of the present invention to provide an improved locking device.

According to the present invention there is provided a locking device comprising a nut having a threaded bore extending axially therethrough between an upper surface and a bearing surface of the nut, a resiliently deformable threaded locking member being captively located in a recess in said bearing surface.

A locking device constructed according to the present invention has the advantage that it provides for a re-usable means of improved locking without the limitations of weakening and wear associated with prior art devices comprising a nylon (R.T.M.) insert.

It is also simpler to handle than devices comprising two or more loose i.e. separate pieces.

In a preferred embodiment of the present invention said deformable locking washer has a convex bearing surface which projects out from the nut's bearing surface. In use the locking washer is flattened into the recess so that it will press itself against a peripheral wall of said recess and the thread of the locking washer will press against the thread of a threaded member onto which the locking device is threaded.

Preferably the recess in the nut defines a peripheral wall which inclines inwardly as it approaches the bearing surface of the nut, this inclined peripheral wall captively retaining the locking washer in the said recess.

Further the said recess preferably has a face remote from the nut's bearing surface which lies parallel thereto, a guide section projecting from the face of the locking washer remote from its convex surface, engaging snugly in the bore in the nut as the washer is flattened.

The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of one embodiment of a locking device according to the present invention.

Fig. 2 is a side elevation of the locking washer of the locking device of Fig. 1.

Fig 3 is an axial cross section of the locking device of Fig. 1.

Fig. 4 is a plan view from below of the locking device of Fig. 1.

Fig. 5 is a side elevation of the locking device of Fig. 1 screwed onto a screw threaded member so that the convex face of the locking device is facing the workpiece against which the device is to be tensioned; Fig. 6 is an axial cross section of the locking device of Fig. 1 screwed further onto the threaded member so that the convex surface of the locking washer is touching the workpiece; Fig. 7 is an axial cross section of the locking device of Fig. 1 where the locking washer of the locking device is fully compressed into the nut recess and against the workpiece so that the thread of the locking washer is compressed against the thread of the threaded member thereby locking the nut against the workpiece; and Fig. 8 is an axial cross section of the locking device of Fig. 1 with the locking device screwed away from the workpiece after tensioning, the locking washer remaining fully compressed in the nut recess and still tensioned against the thread of the threaded member.

Referring to Fig. 1 of the accompanying drawings a preferred embodiment of a locking device 10 constructed according to the present invention is shown, which comprises a locking washer 12 and a nut 14. The nut, shown clearly in Fig. 3, has an upper surface 16 and a bearing surface 18 which has a recess 20 formed therein. Between the upper and bearing surfaces 16 and 18 runs a bore 22 on the wall of which is formed a thread 24. The recess 20 is substantially the shape of an inverted "T" in axial cross section, the invented T shape comprising a cross piece 28 and stem 36. To captively retain the locking washer 12 which is housed substantially within the recess 20 of the cross piece 28 the inverted T shape the recess has a peripheral wall 26 which is inclined inwardly towards the bearing surface 18.

The locking washer 12 is a substantially circular dish-shaped, resilient steel member having a convex outermost face 30 and a concave innermost face 32.

The innermost face 32 has projecting from the centre thereof, a guiding section 34 which snugly fits into the stem 36 or locking channel of the inverted "T" shape recess 20 assisting accurate location of the locking washer 12 within the nut 14. Passing through the centre of the locking washer 12 is a threaded bore 22', the thread formed thereon being denoted 24'. The thread 24' in the locking washer 12 and the thread 24 in the bore 22 in the nut 14 are coaxially aligned with each other and of the same pitch and depth, the respective threads being arranged so that a complimentarily threaded elongate member eg a bolt, can be secured through both the washer 12 and nut 14. To so align the threads mating projections/recesses (not shown) can be provided on the washer 12 and nut 14.

Formed around the periphery 40 of the locking washer 12 are a plurality of recesses 42 (Fig. 4) defined by two edges 44 and 46, one of which edges 44 passes substantially radially inwardly of the washer from the washer periphery 40. This edge 44 bites into the peripheral walls 26 of the nut recess 20 when the locking washer 12 is compressed ie deformed, within the nut recess 20.

The general principle of the use of the locking device 10 constructed according to the present invention will now be described with reference to Figs. 5 to 8 in which a workpiece 48 is secured to a surface 50 using an elongate threaded member 38 which projects form the surface 50.

Fig. 5 shows the locking device 10 screwed onto a thread 39 of the threaded member 38, so that the convex outermost face 30 of the locking washer 12 is facing the workpiece 48 against which the device 10 is to be compressed. From the position shown in Fig 5, the locking device 10 is screwed further onto the threaded member 38 and the threads 24, 24' on the nut and the locking washer 12 provide little resistance to and the locking washer 12 provide little resistance to the device 10 being screwed onto the threaded member 38 until the convex outermost face 30 of the locking washer 12 of the locking device 10 touches the workpiece 48 (Fig. 6).Once the locking device 10 has engaged the workpiece 48 with the workpiece engaging surface 50, further rotation of the device 10 on the threaded member 38 is resisted by the locking washer 12, since additional tongue must be applied to the device 10 to compress and deform ie flatten, the locking washer 12. As the locking washer 12 is flattened into the recess 20 (Fig. 7) the peripheral wall 26 of the recess 20 is contacted by the peripheral wall 40 of-the locking washer and the increased frictional forces produced by this further contact prevent movement of the locking washer 12 and nut 14 relative to each other so allowing for increased tightening of the locking device 10 against the workpiece 48.Additionally, the thread 24' of the locking washer 12 is by virtue of the movement of the thread 24' towards the thread 24 in the nut 14, compressed against the thread 39 of the threaded member 38 so locking the device 10 to the threaded member 38 and thus the workpiece 48. While this increased frictional contact is maintained it is extremely difficult to unscrew the locking device 10.

When an attempt is made to unscrew the locking device 10 the friction between the peripheral wall 40 of the locking washer 12 and the peripheral wall 26 of recess 20 and in particular the friction between the bite edge 44 into the peripheral wall 26 of the nut 14, prevent movement of the locking washer 16 relative to the nut 14 and thus the locking washer 16 is maintained flattened and compressed in the nut recess 20. As a result the thread 24' of the locking washer 12 remains in strong frictional contact with the thread 39 of the member 38 onto which it is screwed until the locking device 10 is actually unscrewed and clear of the threaded member 38.

Therefore, if the bolt is acted upon by a force, such as vibration, which could normally cause the bolt to unscrew from the member 38 the considerable friction between the threaded member 38 and the locking device 10 resists the unscrewing of the device not only for the first few turns but, for the full unscrewing of the locking device.

In the preferred embodiment of the present invention described hereabove the periphery 40 of the locking washer 12 (Fig. 4) has peripheral recesses 42 which recesses are defined by two edges 44 and 46 one of which edges 44 extends substantially radially inwards from the washer periphery 40. In use edge 44 will when the locking washer 12 is compressed into the nut recess 20, bite into the peripheral wall 26 of the nut recess 40 (Figs. 7 and 8). However, in other embodiments of the present invention there can be any number of peripheral recesses 42, including none. If peripheral recesses 42 are provided they can have any non-reflex angle between them including the case where any of the peripheral recesses lie substantially normal to each other. One edge of at least one peripheral recess 42 can project out of the concave surface 32 and/or the convex surface 30 of the washer 12.Said one edge 44 can also be chamfered. Further an edge 44, 46, projecting out of the convex surface 30, may be positioned~so as to bite into the workpiece 48 when an attempt is made to unscrew a locked device from the workpiece.

The outer periphery 40 of the locking washer in the above described preferred embodiment of the present invention, is substantially circular in lateral cross section. However, the periphery can alternatively be any other shape for example, triangular in lateral cross section whilst remaining dished so long as it is able to maintain the locking action. The nut recess 20 is thus usually correspondingly shaped to accommodate the locking washer. In the case of the outer periphery 40 being non-circular e.g. triangular the peripheral recesses may not be required.

The locking washer 12 and the nut 14 of the locking device of the present invention can be made of any suitable material. However the locking washer 12 must necessarily be resilient and when used in conjunction with a metal threaded member 38 is preferably made of spring steel.

The present invention thus provides a readily usable locking device for use on an elongate threaded member.

Claims

1. A locking device comprising a nut having a threaded bore extending axially therethrough between an upper surface and a bearing surface of the nut, and a resiliently deformable threaded locking member wherein the resiliently deformable threaded locking member is captively located in a recess in said bearing surface of said nut.

2. A locking device as claimed in claim 1, in which the resiliently deformable threaded locking member is a washer.

3. A locking device as claimed in claim 1 or 2, in which the threaded locking member is a substantially circular dish-shaped member.

4. A locking device as claimed in claim 3, in which the substantially circular dish-shaped resiliently deformable threaded locking member has a convex bearing surface which projects out from the bearing surface of the nut and a substantially concave innermost face which is housed within the recess of the nut.

5. A locking device as claimed in claim 4, in which the recess defines a peripheral wall which inclines inwardly as it approaches the bearing surface of the nut, thereby captively retaining the locking washer.

6. A locking device as claimed in claim 5, in which the recess is substantially the shape of an inverted "T" in axial cross section and the resiliently deformable threaded locking member has a guiding section which projects from the centre of the substantially concave inner most face, said guiding section extending into a stem of the inverted "T" shaped recess.

7. A locking device as claimed in any one of the preceding claims, in which about a periphery of the locking member is at least one peripheral recess defined by two edges one of which passes substantially radially inwardly from the periphery of the locking member and the other of which passes along a line such that said one edge is not faced by said other edge.

8. A locking device as claiemd in claim 7, in which the one edge of each peripheral recess is depressed slightly to project out of the concave surface of the locking member.

9. A method of securing a workpiece to a surface using a locking device as claimed in any one of the preceding claims comprising the steps of positioning the locking device against the workpiece so that the workpiece is sandwiched between the convex outermost face of the locking member and the surface, passing a threaded member through the surface and workpiece and tightening the locking device against the workpiece so that the convex outermost face of the locking member is flattened into the recess causing an edge formed thereon to bite into a peripheral wall formed in the nut thereby causing the locking member to lock against a peripheral wall of the nut.

10. A method as claimed in claim 9 in which the flattening of the convex intermost face of the locking member causes the thread of the locking member to lock against the thread of the threaded member onto which the locking device is threaded.

11. A locking device constructed and arranged substantially as hereinbefore described with reference to and as illustrated in any of Figs 1 to 8 of the accompanying drawings.

12. A method of securing a workpiece to a surface, substantially as hereinbefore described with reference to Figs. 3 and 5 to 8 of the accompanying drawings.