Wheel nut assembly

Details Wheel nut assembly Wheel nut assembly

1999-10-04

2001-07-24

Morano, S. Joseph (Department: 3617)

Land vehicles: wheels and axles

Wheel

Detachable wheel section

C411S431000

Reexamination Certificate

active

06264284

ABSTRACT:

This invention relates to improvements in a method and apparatus for mounting and retaining a wheel onto a hub, and in particular relates to fixings for vehicle wheels.
It is known to fix a wheel onto a vehicle hub using a plurality of wheel studs which are fixed to the hub and a plurality of wheel nuts with one nut provided for each stud. The studs have an external threaded portion which is adapted to co-operate with a corresponding internal threaded portion of the wheel nut. Such a wheel nut assembly will hereinafter be referred to as being of the kind set forth, and is illustrated in FIG.
6
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Modern vehicle wheels, especially those for use on commercial vehicles, comprise a rim portion and a nave or wheel disc. The nave joins the rim to the wheel centre, and is welded to the rim. Alternatively, one piece wheels are sometimes employed in which the rim and the nave are integral parts. To assemble the wheel to the vehicle hub, the wheel is first positioned so that the wheel is concentric with the hub and the wheel studs project through openings in the nave or disc. The wheel nuts are then tightened onto the studs. Because the nuts are of a larger diameter than the openings through which the studs are passed, the wheel is firmly clamped in place, by the nut against the hub.
Whilst the wheel nut assembly of the kind set forth is widely used to mount wheels on vehicles, there is a serious problem with the nuts working loose. In a worst case, if all the nuts work loose, the wheel can release itself from the hub with potentially catastrophic results. In practice, even if only one of the nuts retaining a wheel is loose, this will place extra loading on the adjacent nuts which causes them to start to work loose. It is not unknown for a whole wheel to work free within 20 minutes of a single nut starting to vibrate loose.
In accordance with a first aspect of the invention, we provide a wheel nut assembly of the kind set forth in which: the wheel stud comprises a first portion having a first external thread which is adapted to co-operate with an internal thread provided on the wheel nut, and a second threaded portion having a thread of the opposite hand to the first external thread which co-operates with a retaining member having a thread which is of the same hand as the second threaded portion.
Preferably, a locking means can be provided which is adapted to substantially prevent relative rotational movement between said wheel nut and said retaining member.
Thus, when the wheel is mounted onto the vehicle with the wheel nut screwed into position on the stud, the retaining member screwed into position on the stud and the locking means is fitted, any tendency for the wheel nut to rotate loose will cause the retaining member to tighten. Since the locking member prevents relative movement between the retaining member and the wheel nut, the nut cannot therefore work loose as it is prevented from doing so by the increasing resistance of the retaining member as it is tightened.
Preferably, the retaining member comprises a threaded bolt, for example a thrust bolt, and the stud is provided with an internal bore which defines the second threaded portion.
Most preferably, the retaining member has an external diameter greater than the internal diameter of the wheel nut. Thus, as the wheel nut starts to work loose, it is ultimately prevented from movement axially along the stud by the threaded bolt. The outer diameter of the wheel nut and the outer diameter of the head of the threaded bolt are preferably substantially the same.
The thread on the retaining member may have a pitch which is greater than the pitch of the first thread on the wheel nut.
The locking means may comprise a locking cap which may completely enclose the wheel nut and the retaining member. This helps prevent dirt and grime from entering the assembly, and can help to prevent rust forming on any exposed surfaces.
The locking means may be provided with a fastening means adapted to retain it onto either the stud and/or the wheel nut and/or the retaining member. This could prevent unauthorised removal of the wheel nuts as well as preventing the locking member from falling off accidentally. This may comprise a magnet which may be mounted into an inner face of the cap.
The shape of the wheel nut and the retaining member may be adapted so that the locking member can only be put in position once the nut and retaining member are tightened to substantially the correct torque.
In a preferred arrangement, an axial space is provided between the head of the nut and the head of the bolt when the assembly is put together. Thus, a portion of the wheel stud may extend beyond the head of the wheel nut. This space ensures that the bolt can tighten within its bore when it is rotated by the locking cap in response to loosening of the wheel nut.
Optionally, a pair of substantially orthogonal axial cuts can be made in the end of the stud distal from the wheel hub so as to define four segments. Thus, when the bolt is tightened, the stud will be caused to bulge slightly which helps to retain the wheel nut. This bulging can be further increased by manufacturing the bore and the bolt with a slight conical taper.
A second aspect of the invention lies in a method of converting a wheel stud for use in a wheel nut assembly of the first aspect of the invention.
Accordingly, it is within the envisaged scope of the invention to modify a set of wheel studs on a vehicle to accept the retaining member and/or locking means. For example, this could be done by drilling a bore into the end of the stud and tapping a suitable internal thread into the bore. Alternatively, the bore could be made by a spark erosion process.
It is also envisaged that the invention may comprise providing a kit of parts for converting the wheel nut assembly of a vehicle into a wheel nut assembly in accordance with the first aspect of the invention. The kit may comprise one or more of a stud, a locking means and a retaining member according to the first aspect of the invention.
According to a third aspect, the invention provides a lock assembly comprising a first locking portion having an internal bore adapted to receive one or more magnetic elements biased towards a first position substantially towards the axial centre of the bore by a resilient biasing means, and a second locking portion adapted to be received at least partially within the bore in said first portion and having a magnet receiving portion defined thereon into which said one or more magnets are biased to substantially prevent axial movement of the second portion relative to the first portion.
With the first portion and second portion interconnected in this way, the lock assembly is said to be “closed” or locked.
A lock releasing means may be provided which is adapted to apply a magnetic biasing force or field to the magnetic elements to retract at least some of the magnetic elements to a second position in which said second portion is free to move axially relative to the first portion. Thus, the lock can be “opened” using the lock releasing means.
The magnetic elements may be arranged in an annular groove provided around the inside of the bore, and the resilient biasing means may comprise one or more springs.
The magnetic elements may be arranged in the first portion so that an individual magnetic biasing force is required to release each magnetic element from the second portion. For example, the magnetic elements may be arranged so that one magnetic element needs to be attracted by a south pole placed against the first portion, whilst another may require a north pole. Thus, a lock combination can be built by varying the position and/or type of magnetic elements in the first portion. Only the correct arrangement of biasing force around the cap will therefore allow the first and second portions to be “opened”.
In a refinement, two or more annular arrays of magnetic elements may be provided in the first portion. This increases the number of possible combinations.
In another refinement, the second portion may have a hollow bore prov

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