WO2011027164A1

WO2011027164A1 - Locking device for a nut such as a wheel nut

Info

Publication number: WO2011027164A1
Application number: PCT/GB2010/051457
Authority: WO
Inventors: John Sydney Lees
Original assignee: John Sydney Lees
Priority date: 2009-09-04
Filing date: 2010-09-03
Publication date: 2011-03-10

Abstract

A pair of locking devices (10) suitable for locking a pair of adjacent nuts or bolts in position, such as adjacent wheel nuts (20, 30) or bolts in position preventing the nuts or bolts from working loose. Each device comprises a body part (11) having a central opening (12) which allows the body part, in use, to be mated to a respective one of the nuts or bolts in such a manner that the body part can only rotate if the nut rotates about the axis of the respective stud; and an integral locking part (16) which extends from the body part of at least one locking device. In a position of use the locking part of the one of the locking devices co-operates with a part of the other locking device such as to substantially prevent relative movement between the devices in a direction that corresponds to loosening of the nuts or bolts. The locking part is placed under a substantial torsional load which acts to urge the nuts and bolts in a direction that would tend to tighten them in place.

Description

LOCKING DEVICE FOR A NUT SUCH AS A WHEEL NUT

This invention relates to a locking device. In particular it relates to a locking device for use in combination with a nut on a stud so that accidental loosening of the nut on the stud can be identified and which assists in preventing the nut from loosening. It has particular application to wheel nuts for vehicles, and may also be used to prevent nuts that secure railway track components in place from loosening. It also relates to locking devices for bolts .

It is well known to provide the adjacent wheel nuts or bolts of heavy goods vehicles with pointers . The nuts are tightened to the recommended torque value, and the pointers fitted to the nuts so the tips of the pointers of adjacent nuts are aligned. If the wheel nuts loosen this can be easily spotted because the tips of the pointers will no longer be in line. Although these pointers have proved popular they do not in any way help prevent the nuts working loose, merely allowing them to be inspected. All they do is point. It is also known to provide modified nuts, and even modified studs to which the nuts are secured, which can be locked to prevent the modified nut from loosening. Whilst these devices do offer a high degree of security, and so require less inspection, they are often complex to make. Because of this they can often be considered to be prohibitively expensive The applicant does not agree with this view, as the potential consequences of a failure of the fasteners can be significant, but nonetheless affordability is an issue in many cases .

According to a first aspect the invention provides a pair of locking devices suitable for locking a pair of adjacent nuts or bolts in position, each device comprising: a body part having a central opening which allows the body part, in use, to be mated to a respective one of the nuts or bolts in such a manner that the body part can only rotate if the nut rotates about the axis of the respective stud; and

an integral locking part which extends from the body part of at least one locking device, and in which:

in a position of use the locking part of the one of the locking devices cooperates with a part of the other locking device such as to substantially prevent relative movement between the devices in a direction that corresponds to loosening of the nuts or bolts.

The devices , when used to lock in place nuts on studs , or bolts in threaded holes, which includes a bolt head that can be considered essentially to be equivalent to a nut secured to a threaded stud lock together on installation to prevent the nuts or bolts working loose.

Both of the locking devices may include a locking part, with the locking part of each device engaging a corresponding locking part of another device. Most conveniently the locking part of one device may engage the body part of the other device. For instance, the or each of the locking devices may be provided with a set of teeth which may extend around a part of a circumference of the device to form an engagement region for the locking part of another device of the pair, the teeth helping ensue that the locking part securely engages the main body part of the other device to prevent the other device rotating.

They may be engaged such that the locking part is deflected relative to the main body part so the part is under a load, and to facilitate this the locking part may be resiliently deformable, or may be connected to the main body part through a resilient connecting part. This allows the parts to spring back to their unloaded form when the load is removed, and to maintain the load when in use.

The devices may be so constructed and arranged that they may be fitted to the nuts independently with the locking parts released and spaced from the other device, before being locked together with the locking part of each device being placed under a bending or torsional load which tends to act to cause the fasteners to move in a direction which would tighten the fasteners. By this we mean that when locked the locking devices apply a torsional tightening load to the nuts . The locking parts may press against one another under load, or against another part of a locking device.

An advantage of the devices being able to lock under such a load is that this helps secure the devices onto the nuts as the edges of the central opening may bite into the sides of the nut. This allows the device to be a relatively loose fit when not under load, allowing it to be fitted and removed from the nut easily with little force.

The locking devices may be so constructed that in use the locking parts permit a limited angular rotation of the nuts about their studs by the locking device sliding relative to the part of the corresponding device it engages. For example, when interlocked the locking part of the one device may be free to slide relative to the locking part of the other device as the load between them decreases.

By interlocked we mean that the two devices , for example the locking parts, are engaged in such as manner that they substantially prevent the two devices from rotating in a direction that would tend to lead to the respective fasteners from working loose. However, permitting a small amount of rotation due to the sliding between the locking parts so as to prevent the devices breaking if, for any reason, the fasteners were to loosen a small amount as may happen during use. A small amount of rotation between re-torquing is commonplace and acceptable. If such movement has occurred, then the torsion of the nuts should be checked, tightening as required, and one or both of the devices should ideally be repositioned on the nuts before relocking them to ensure they remain under load.

Each of the devices may comprise a pressed or stamped metal part. It may comprise a spring steel, perhaps a stainless steel.

Each device may preferably be formed as a single part, making it cheap to make and eliminating a need for any assembly of the device during manufacture. It may be formed from a flat sheet of metal or other material. It may, for example, comprise a plastic material or fibre reinforced material. Indeed any material could be used as long as it had some resilience allowing the locking part to deflect relative to the main body.

In a preferred arrangement, at least one of the devices comprises a generally planar main body with a generally planar locking part which lies in a plane substantially perpendicular to that of the main body, or at least 80 degrees or perhaps at least 60 degrees out of alignment with the plane of the main body. This can be achieved by providing a device in which the main body and locking part are unitary and formed from a single sheet of material which is twisted or folded, perhaps where the main body joins the locking part, or toward the end of the locking part. When the locking part engages a part of a corresponding device it may be under torsional load in direction parallel to the axis of the main body of the device and orthogonal to that plane. The locking part may include a notch which receives a portion of the corresponding locking device. This helps ensure that the devices cannot easily accidentally be released from one another if a force is applied to them that is parallel to the axis of the stud. The corresponding portion of the other locking device may comprise a row of teeth, most preferably saw teeth, the notch engaging between adjacent teeth.

Each of the devices may include a connecting part, such as a pointer, which projects from the main body part and carries or defines the locking part. The locking portion may be provided at or adjacent the free end of the pointer. The connecting part may taper from a first thickness where it joins the body portion to a second, smaller thickness towards its free end. It may taper uniformly in the manner of an arrow, or may be stepped. The pointer may also be bent or twisted as described above.

The connecting part may be arranged such that the locking portion can be resiliently displaced relative to the body portion around the axis of rotation of the fastener to which the device is fixed by an angle of between 1 and 5 degrees, or perhaps more than 5 degrees , under a torque of at least lONm or at least lOONMm whilst remaining elastic over a period in excess of 24 hours, or remaining substantially elastic, whilst permanently deformed in this manner. By this we may mean that when the load is removed the locking part will return back to , or substantially back to, its original position relative to the main body portion. To do this the pointer may be configured to function as a spring, and most preferably a simple leaf spring. To achieve the required degree of resilient deformation of the locking device relative to the body portion the connecting part may be reduced in width at some point between the body portion and the free end of the connecting part. It may, for instance, include a slit which projects inwards from an edge of the connecting part towards but not reaching an opposing edge of the connecting part. More than one slit may be provided.

The device may include a cut-out towards its free end of the tip into which a suitable tool may be inserted which allows the tip to be pulled or pushed around to move the locking devices together. This cut-out may align with a like cut-out on a like device when the devices are in the locked position, the alignment of the cut-outs providing a visual indication that the devices are correctly locked. In the event that the devices move in use the cut-outs will move out of alignment giving a visual warning that some movement has occurred.

In place of the cut-out into which a tool can be placed, an alternative cutout or perhaps a marking may be provided on the device which aligns with a like marker on a like device when in use.

The distance from the centre of the opening of the body portion to the tip of the locking device, for instance the tip of the pointer, may be greater than at least 2.5 inches, and preferably greater than 3 inches. This would make the device suitable for use with wheel nuts that are spaced apart from adjacent nuts by 4 inches (an industry standard) . Choosing these lengths ensures that the two devices overlap one another, and the locking portions should be located in the regions that overlap to permit them to interengage with one another. The length may be greater than 3 inches, or greater than 4 inches, or perhaps greater than 5 inches, which would make the device suitable for use also in the rail industry where a 5 inch spacing between adjacent nuts used to secure tracks is commonplace.

The central opening may have a corresponding shape to the nut when viewed along the axis of the stud. The shape may be that of a polygon, defining multiple sides to ensure that when fitted over a complimentary polygonal fastener it can not rotate. It may, for instance, have a hexagonal shape with 6 equal sides (to mate with a standard hexagonal fastener such as a wheel nut) but preferably has a dodecagon (12 sided) shape, or has 24 sides. This provides a good compromise between the desire to use fewer sides to give greater resistance to damage from shear forces , and a desire to use more sides to give finer alignment of the pointer.

The body portion may include a stand-off which protrudes orthogonally away from the central opening, which in use may extend over any washer or flange at the lower end of a nut or bolt received by the central opening. The stand-off may comprise an annular collar, skirt or lip which may be continuous or discontinuous and may be formed on the periphery of the body portion.

Alternatively, the body portion may have a non-flat cross section, and preferably a with a wave in the axial direction to provide a wavy cross section in the manner of a wavy washer. It may be formed from a flat thin sheet of material which is deformed into the wavy cross section. This achieves a similar effect to the stand-off in ensuring that the body portion cannot slip off the end of any fastener such as a nut or stud. The wavy cross section may provide an overall thickness to the body portion that is at least two times , or at least three times the thickness of the body portion at any point. Alternatively it may be frusto-conical in shape.

In an alternative arrangement, the central opening may receive an adapter which has an outer form that compliments the opening and an inner form that is shaped to compliment a nut to which the device is to be mated. The adapter once located in the opening is prevented from rotating relative to the body portion, and in turn when mated to the nut prevents the body portion rotating relative to the nut. Of course, there will perhaps be some limited rotation possible unless the device is a perfect fit to the nut, and this is acceptable within this invention as long as the rotation is limited.

The locking portions may comprise edge regions of the device at or close to the free end of the pointer.

The device may be brightly coloured on at least an upper face to allow the presence, or absence of the device on a fastener, to be easily determined. One of the pair of devices may include a male locking part, and the other a female locking part, the male part engaging with the female part. The female part may, for instance, comprises a slot in one edge of the pointer at or close to its free end, and the male part may comprise a portion of the edge of the pointer at or close to its free end which is received in the slot.

Each pointer may comprise both a male locking part and a female locking part. This is beneficial as it allows the two locking devices to be identical, reducing the tooling required to produce the locking devices . Where the female locking part is a slot in one edge, the male part may comprise a part of the opposing edge of the pointer.

Preferably the main body portion has a thickness that is less than the height of the fastener such that the fastener can be torqued using a suitable tool such as a torque wrench without removing the locking device. For example, a thickness of the main body portion of between 5mm and 10mm is preferable for use with wheel nuts .

According to a second aspect the invention provides a method preventing a pair of adjacent nuts or bolts from loosening, the nuts bolts being spaced apart by a distance, the method comprising: mating a first locking device having a main body and a central opening and a locking part extending away from the main body to a first of the nuts or bolts such that the nut or bolt is located within the central opening,

mating a second locking device having a main body and a central opening and a locking part extending away from the main body to a second of the nuts or bolts such that the nut or bolt is located within the central opening, the two devices being aligned such that the locking portions are spaced apart from one another,

applying a torsional force to at least one of the devices so as to bring the locking portion into engagement with a part of the other device, and releasing the at least one locking device to leave the two devices locked together and the at least one locking device under a torsional force. The locking portion of one device may engage the locking portion of the other device, or a different portion of the other device.

The step of applying a torsional force may comprise engaging a hooked tool with one of the locking devices close to its free end, and using the free end of the other device as a fulcrum levering the free ends of the one device around to bring the locking portion into engagement with the portion of the other device.

The step of applying a torsional force to the at least one device may comprise moving the locking part angularly about the axis of rotation of the nut to which it is mated in a direction that corresponds to tightening of the nut. In the case of a nut that is tightened by turning it clockwise, this will comprise moving the locking part clockwise relative to the body portion. This helps ensure that when the two locking devices are locked together the torsional load they are under tends to cause the nuts to tighten preventing, or at least resisting, the nuts working loose. The method may be applied repeatedly to secure pairs of devices to all adjacent pairs of nuts of a wheel, such as the wheel of a heavy goods vehicle.

According to a third aspect the invention provides a locking device which can be used with a further locking device to form a pair of devices according to the first aspect of the invention or to perform the method of the second aspect of the invention.

Whilst the invention is described above in terms of how the two locking parts engage when in the assembled position, the invention can be realised by providing an engagement between the locking part of one device and the main body of the other, the locking part of the other device being in turn optionally engaged with a part of a further device or perhaps even an adjacent nut. The locking part should still be positioned so that the device is under a load, with the locking part displaced relative to the main body part, which helps ensure the nut associated with the device does not loosen.

Therefore according to a fourth aspect the invention provides a locking device suitable for locking a first one of a pair of adjacent nuts in position on a respective stud comprising:

a body part having a central opening which allows the body part, in use, to be mated to the first one of the nuts in such a manner that the body part can only rotate if the nut rotates about the axis of the respective stud; and

an integral locking part which extends from the body part and which can be displaced relative to the main body part by resiliently deforming a part of the device, and in which: in a position of use the locking part of the locking devices is arranged to co-operate under load with a part of a corresponding locking device, or other fixed position object, such as to substantially prevent relative movement of the locking device in a direction that corresponds to loosening of the nut about its respective stud.

The body part and integral locking part may be integrally formed, each being generally planar and arranged substantially perpendicular to one another.

The device may include any of the features of the devices described in relation to the first aspect of the invention.

According to a fifth aspect the invention provides a combination of a pair of locking devices according to the first aspect of the invention and a pair of nuts or bolts, in which each locking device engages a corresponding one of the nuts or bolts , and in which the locking part of one device engages a part of the other device under a load to limit relative rotation of the two locking devices and accordingly limit rotation of the pair of nuts or bolts .

The locking part may be placed under a load of at least lONm and preferably at least 50Nm. The nuts or bolts may comprise wheel nuts or bolts securing a wheel to a vehicle. In practice, there may be as many locking devices as there are wheel nuts or bolts securing the wheel. They may engage in pairs of devices, or each device may engage an adjacent device, with that adjacent device optionally engaging a further adjacent device in the manner of a daisy chain. There will now be described, by way of example only, two embodiments of the present invention with reference to the accompanying drawings of which: Figure 1 is a view in plan from above of an embodiment of a locking device which forms part of a pair of locking devices according to the first aspect of the invention prior to use;

Figure 2 is a view in plan from the side of the locking device of Figure 1 ;

Figure 3 is a view in plan of two adjacent wheel nuts of a heavy goods vehicle wheel with a locking device of Figure 1 applied to the rightmost wheel nut;

Figure 4 is an identical view to figure 3 which also includes a locking device of Figure 1 applied to the leftmost wheel nut, the devices being aligned so that the free ends of the devices overlap with the locking portions spaced apart from one another;

Figure 5 shows the devices in the locked position;

Figure 6 illustrates in dotted line the deformation of the device in use with the exaggeration greatly exaggerated to make it easier to see;

Figure 7a shows the correct alignment between cut-outs of the two devices after installation, and 7b shows the misalignment of the slots that would arise if the nuts rotated and which provides a warning that movement has occurred; and

Figure 8 shows in side view a locking device mated to a wheel nut; Figure 9 is a view in plan from above of a further embodiment of a locking device which may be configured so as to form part of a pair of locking devices according to the first aspect of the invention prior to use;

Figure 10 is a view in plan from the side of the locking device of Figure 9;

Figure 11 is a view in plan of two adjacent wheel nuts of a heavy goods vehicle wheel with a locking device of Figure 1 applied to each wheel nut; and

Figure 12 is a view in plan of two adjacent wheel nuts of a heavy goods vehicle wheel with a locking device of Figure 9 applied to each wheel nut;

Figure 13 shows the use of multiple pairs of devices to secure a wheel to a wheel hub of a vehicle; Figure 14 is a plan view from above of two adjacent wheel nuts of a heavy goods vehicle wheel with a further alternative embodiment of a locking device according to the invention fitted to each nut;

Figure 15 is an isometric view of the two nuts and devices of Figure 14;

Figure 16 is an enlarged view of part of one device of Figure 14 and 15 showing the engagement between the locking part of one device and a set of teeth of the other device; and Figure 17 is a view in cross section of a still further embodiment of a locking device which may form one half of a pair of locking devices in accordance with the present invention.

The following embodiments of the invention will be described in relation to use in preventing the hexagonal wheel nuts of a wheel of a heavy goods vehicle from working loose. This is not intended to limit the invention, and whilst this is one preferred use the devices may be used to secure nuts in a wide range of other applications. One such application is the rail industry, where nuts are used in pairs to secure section of track to sleepers , or to secure parts of a point in position or to other parts of the points or track. It may also be used to lock in postion the heads of bolts , since outwardly the hexagonal head of a nut is generally the same as the hexagonal head of a bolt, and both are tightened by rotation. Figure 1 shows an exemplary locking device 10 prior to fitment to a wheel nut. When in position the locking device 10 provides a means for easily determining if the nut has worked loose, and also in this embodiment provides for a degree of locking of the nut through interaction with other similar devices secured to adjacent nuts .

The device 10 comprises a body portion 11 having a central opening 12 which allows the body part to be mated onto a wheel nut. The shape of the central opening 12 is polygonal when viewed along the axis of rotation of the nut to which it mates . As shown it has 12 sides . It is slightly larger than the nut to which it is to be mated so that when pushed onto the nut it is restricted from rotating about the axis of rotation of the nut unless the nut itself is rotating.

Extending from the body portion 11 is a connecting part or pointer 13 which extends around 3 inches from the central axis 14 of the central opening 12. This length has been chosen in this embodiment because the spacing between the wheel nuts it is to be used with is 4 inches and it is required that the pointer 13 extends far enough to overlap radially an identical device on the adjacent nut. Thus the device 10 will extend beyond the midway point between the axial centres of the adjacent nuts which it is to be used to lock.

Towards the free end 15 of the pointer 13 is a locking portion 16 defined by an edge portion of the pointer. This lies within the final 0.5 inches, i.e. in the free end 15 that radially overlaps an adjacent device when in use. This edge 16 of the free end of the pointer 13 is provided with a cutout 17 or recess.

Between the body portion 11 and the free end 15 the pointer 13 is reduced in width by a slit 18. This makes the pointer easier to deflect relative to the body portion 11. Figure 6 shows an undeformed device in solid line and overlaid in dashed line shows the deformation of the device when in use, in which the amount of deformation has been greatly exaggerated for clarity. Figure 2 shows the same device 10 viewed from the side. It can be seen that the body part 11 is relatively thin (compared with the width of the device viewed from above) . In this embodiment it is around 0.25 to 0.5inches thick. This thickness is chosen to ensure that the device can remain mated to a nut whilst leaving enough of the nut exposed for it to be retorqued.

To secure the wheel nut, the device should be used as one half of a pair of devices. The devices may be identical. Figures 3, 4 and 5 show the devices being applied to a pair of adjacent wheel nuts to lock them in place according to a method of the second aspect of the invention. The nuts are shown spaced apart by 4 inches between centres and threaded onto respective studs on a wheel carrier.

In a first step, shown in Figure 3 following tightening of the pair of wheel nuts 20, 30 to the required torque setting, a locking device 10 is mated to the right hand nut 30 by sliding the nut into the central opening of the device. The free end is generally pointed towards the adjacent nut 20 but is aligned slightly anti-clockwise of its final locked position. In a next step shown in Figure 4 an identical locking device 40 is mated to the left most nut 20. Again the free end of the device is generally pointed towards the adjacent nut 30 but is aligned slightly anti-clockwise of the final locked position. This means that the free ends of both devices are overlapped but the two devices are not interlocked. As shown, the left most one sits slightly over the top of the right most one.

In a final step, shown in Figure 5 an installation tool with a hooked end is inserted into the slot 17 in the edge locking portion 16 of the right most locking device, and using the corresponding locking edge of the left most device as a fulcrum a torque is applied to the two pointers until the locking portion of the rightmost device lies in the same plane as the locking edge portion of the left most device. The torque applied by the tool during this action is then released so the locking portions of the two devices snap together as shown in Figure 6. In this position the two devices are locked together. Because they remain slightly deformed they remain under a torsional load. This causes both devices to bite into the respective nuts, securely holding them in position.

Whilst only one pair is shown, it will be appreciated that for a wheel 70 secured with many nuts all of the nuts may be connected together in this manner by using several devices arranged in pairs spaced around the wheel. This is shown in Figure 13 for a wheel with 12 nuts, which are secured using 6 pairs of devices 71 ,72,73,74,75 and 76.

Figure 8 shows in side view one of the devices 40 when mated to a respective wheel nut 20.

Removal can be achieved by reversing the steps described above.

Once locked together with the locking portions pressing against each other, the cut-outs 17 one each device will be aligned as shown in Figure 7a to form a symmetrical slot. If the devices move for any reason, such as movement of one or both nuts, the two cut-outs will move relative to one another as the edges slide across each other. This will cause the slot to change form as shown in Figure 7b, providing a visual warning that movement has occurred. In that case the nuts will need to be checked and in most cases the devices will need to be unlocked, repositioned and relocked to align the cut-outs as described below.

If the nuts have moved, they should be retorqued using a torque wrench of other tool, the locking devices unlocked and one device rotated anticlockwise relative to its nut before locking the devices together. This repositioning ensures that the devices remain under load.

A second embodiment of the present invention is illustrated in Figures 9 to 12 of the accompanying drawings. In this embodiment a plurality of locking devices are provided, each of which may be identical, to secure the nuts of a wheel or other item. One device 50 is shown in plan from above in Figure 9 and in plan from the side in Figure 10. Each device 50,60 comprises a main body part 51 ,61 with a castellated central opening 53,63 and a locking part 52,62 connected to the main body part by a resiliently deformable connecting part. The device comprises a flat sheet of material, such as spring steel, that is twisted so as to provide a flat main body part 51 ,61 and a flat locking part 52,62 which lies in a plane that is generally perpendicular to the plain of the body part 51 ,61. As with the first embodiment the locking part can be resiliently deflected relative to the main body by applying a torsional load about the axis of the nut. The free end of the locking part 52,62 is provided with a recess 54,64 so that the end forms a two pronged fork shape.

Figure 11 shows the two devices in their position of use securing a pair of nuts 20,30 in place on respective studs. As can be seen when in this position the two devices are placed under a torsional load such that both locking parts 52,62 are deflected relative to their associated main body parts (the locking parts in their undeflected positions being shown in dotted line in Figure 11) . A circumferential edge portion of the main body part of each device is located within the recess 54,64 in the free end of the locking part 52,63 of the other device, which prevents them from readily springing apart. The two locking parts in this configuration may be configured so as to apply some load against each, or the load may be between the locking part and the edge portion of the main body of the other device.

Figure 12 shows an alternative position of use of the two devices, in which the locking part of one device is loaded by engagement with the main body only of the other device, rather than the locking part of the other device. Again the locking part is placed under a torsional load, with the unloaded device being shown by dashed line. This is especially useful where there are an odd number of nuts on a wheel and it would otherwise not be possible to arrange the devices in alternating pairs in the configuration shown in Figure 11. This arrangement could also be used for the devices shown in Figures 1 to 8 if required, although it is to be noted that the devices of those figures would need to be made longer (from axis of the hole in the main body part to the tip of the locking parts) to do that, or used with nuts that are closer together.

Figure 14 is a view of two nuts of a heavy goods vehicle wheel fitted with a pair of still further alternative locking devices . Each device 80, 90, as before, comprises a main body part 81 , 91 with a castellated central opening 83 , 93 and a locking part 82,92 connected to the main body part by a resiliently deformable connecting part. The device comprises a flat sheet of material, such as spring steel, that is twisted so as to provide a flat main body part 81 , 91 and a flat locking part 82, 92 which lies in a plane that is generally perpendicular to the plain of the body part 81 ,91. As with the first embodiment the locking part can be resiliently deflected relative to the main body by applying a torsional load about the axis of the nut. The free end of the locking part 82, 92 is provided with a recess 84 so that the end forms a two pronged fork shape. This fork engages with a set of radially extending teeth 95 arranged around a part of a circumference of the main body part of the adjacent locking device 90. The teeth 95 help ensure the fork does not slip relative to the main body, and the flank of the engaged tooth provides a surface against which the fork acts. Also notable is a collar 86, 96 of material which extends down from the top of the main body part to engage the surface of the vehicle wheel. This ensures that the castellated opening of the main body part is spaced from the end of the nut and cannot slip between the nut and the wheel, for instance if a washer is located between the nut and the wheel.

Figure 17 shows a still further embodiment of a locking device 100 which is identical to that shown in Figure 15 but in which the main body 110 does not include the collar or skirt and instead has a wavy cross section, to form a wavy washer. This can be formed by starting with a flat main body and then pressing it or otherwise deforming it to provide a non-flat main body. By providing a wavy main body at least part of the main body is kept away from the end of the nut and cannot slip between the nut and the wheel.

Claims

1. A pair of locking devices suitable for locking a pair of adjacent nuts or bolts in position, each device comprising:

a body part having a central opening which allows the body part, in use, to be mated to a respective one of the nuts or bolts in such a manner that the body part can only rotate if the nut or bolt rotates about the axis of a respective stud; and

2. A pair of locking devices according to claim 1 in which both of the locking devices include a locking part, with the locking part of each device engaging a corresponding locking part of another device.

3. A pair of locking devices according to claim 1 or claim 2 in which the devices are engaged such that the locking part of the one device is deflected relative to the main body part of that device so the part is under load, the locking part being resiliently deformable or connected to the main body part through a resilient connecting part.

4. A pair of locking devices according to any preceding claim in which the locking part of the at least one device include a notch which receives a portion of the corresponding locking device.

5. A pair of locking devices according to claim 4 in which the corresponding portion of the other locking device comprises a row of teeth, most preferably saw teeth, the notch engaging between adjacent teeth.

6. A pair of locking devices according to any preceding claim which are so constructed and arranged that they can be fitted to the nuts or bolts independently with the locking part of the one device released and spaced from the other device, before being locked together with the locking part of the one device being placed under a bending or torsional load.

7. A pair of locking devices according to any preceding claim in which each of the devices comprises a pressed or stamped metal part.

8. A pair of locking devices according to any preceding claim in which at least one of the devices comprises a generally planar main body with a generally planar locking part which lies in a plane substantially perpendicular to that of the main body, or at least 80 degrees or perhaps at least 60 degrees out of alignment with the plane of the main body, and in which the main body and locking part are of unitary construction and are formed from a single sheet of material which is twisted or folded, perhaps where the main body joins the locking part, or toward the end of the locking part.

9. A pair of locking devices according to any preceding claim in which the distance from the centre of the opening of the body portion to the tip of the locking device is greater than at least 2.5 inches, and preferably greater than 3 inches.

10. A pair of locking devices according to any preceding claim in which the central opening is polygonal.

11. A pair of locking devices according to any preceding claim in which the body portion includes a stand-off which protrudes orthogonally away from the central opening such as an annular collar, skirt or lip which may be continuous or discontinuous and may be formed on the periphery of the body portion.

12. A pair of locking devices according to any one of claims 1 to 10 in which the body portion has a non-flat cross section with a wave in the axial direction.

13. A method of preventing a pair of adjacent nuts or bolts secured to respective studs from loosening, the nuts or bolts being spaced apart by a distance, the method comprising:

mating a first locking device having a main body and a central opening and a locking part extending away from the main body to a first of the nuts or bolts such that the nut or bolt is located within the central opening,

applying a torsional force to at least one of the devices so as to bring the locking portion into engagement with a part of the other device, and releasing the at least one locking device to leave the two devices locked together and with the at least one locking device remaining under a torsional force.

14. A locking device which can be used with a further locking device to form a pair of devices according to any one of claims 1 to 12.

15. A combination of a pair of locking devices according to any one of claims 1 to 12 and a pair of nuts or bolts, in which each locking device engages a corresponding one of the nuts or bolts, and in which the locking part of one device engages a part of the other device under a load to limit relative rotation of the two locking devices and accordingly limit rotation of the pair of nuts or bolts.

16. A combination according to claim 15 in which the nuts or bolts comprise wheel nuts or bolts securing a wheel to a vehicle.