Background to the Invention In US Patent Specification No. 5,279, 137 there is described a steering lock for a bicycle comprising:- a) a first tube member having means for rigid attachment to the bicycle handlebars, b) a second tube member having means for rigid attachment to the bicycle fork, c) the first and second tube members being disposed co- axially and arranged for relative rotation about the common axis, d) coupling means being provided for coupling the first and second members together so that steering movement of the handlebars can be transmitted to the bicycle fork, and e) lock-operated means for deactivating the coupling means so that steering movement of the handlebars is not transmitted to the bicycle fork, f) the lock-operated means comprising a cam that is movable between a first position in which the coupling means is activated and a second position in which the coupling means is deactivated, and the coupling means comprising rollers that are moved radially outwardly when the cam is moved from its second position to its first position.

Such a steering lock is hereinafter referred to as a steering lock of the kind specified.

In the particular arrangement shown in US Patent Specification No. 5,279, 137, the outer tubular member is formed with a plurality of recesses within which rollers are received when the cam is in its first position.

British Patent Specification No. 2 298 676 also discloses a steering lock of the kind specified, but in this case there is a cam assembly that comprises upper and lower cams and the outer tubular member is formed with axially extending grooves within which rollers are received when the cam assembly is in its first position.

When a steering lock of the kind specified is in its locked condition, the first and second tubular members are free to rotate relative to one another and forcing of the steering lock is, therefore, not possible.

When the lock is operated to move the cam into its first position, the rollers that couple the first and second tubular members together are moved radially outwardly into torque- transmitting relationship with the outer tubular member.

It is an object of the present invention to provide a steering lock of the kind specified that includes improved means for the transmission of torque between the first and second tubular members.

Summary of the Invention According to the present invention there is provided a steering lock as defined in Claim 1.

Further advantageous features of the invention are defined in the subsidiary claims.

Brief Description of the Drawings Figure 1 is an exploded perspective view of a steering lock for a bicycle, Figure 2 is a vertical sectional view of the bicycle steering lock, Figure 3 is a plan view of a bush, Figure 4 is a side view of the bush, Figure 5 is an underneath plan view of the bush, Figure 6 is an enlarged detail view of the bush, and Figure 7 is a side view of a steering support tube.

Description of the Preferred Embodiment The steering lock shown in Figures 1 and 2 is arranged to function in a manner similar to that described in US Patent Specification No. 5,279, 137, to which reference should be made, with important features of difference being high-lighted below.

The steering lock of the present invention includes a quill support tube 1 which is arranged vertically and is provided at its upper end with an outwardly directed flange. The lower end surface of the quill support tube 1 is inclined at an angle of 30° to the vertical so as to provide a wedge formation. A steering support tube 12, which has an external flange 12A that rests on the upper end of the quill support tube 1, is inserted into the upper end of the quill support tube 1 and there is a short stub axle at the lower end of the steering support tube 12. A pair of diametrically opposed vertical slots 12B are formed in the steering support tube 12 and the vertical slots 12B are arranged to receive roller formations 14, as described below.

A lock retainer bush 2 is secured to the upper part of the steering support tube 12 by means of threaded fasteners that enter tapped bores 12C at the upper end of the steering support tube 12.

Access to the fasteners can be obtained through openings in the lock retainer bush 2. A lock 5 having a cylindrical body is positioned within the interior of the retainer bush 2 and is fixed against rotation relative to the retainer bush 2 (and hence the steering support tube 12) by means of opposing threaded rod-type screws. A square cross-section bar 7 formed with tapped apertures is fixed to the cylindrical body of the lock 5 and extends downwardly therefrom.

A bush 3, shown in Figures 3 to 6, is positioned over the upper part of the steering support tube 12 and is arranged for rotation relative to the steering support tube 12. Plastic spacers 13 are disposed between the lower end of the bush 3 and the outwardly extending flange of the steering support tube 12. The plastic spacers 13 serve to position the bush 3 for rotation relative to the steering support tube 12 and prevent tilting of the bush 3 relative to its vertical axis.

The bush 3 is formed with two inwardly facing diametrically opposed vertically extending grooves 3A. Each groove 3A includes a main portion that is of substantially semi-circular form in horizontal cross-section and, at the base of the main portion of each groove 3A, there is a rebate 3B, that is of part-circular cross- section and has a radius of curvature that is less than the radius of the main portion of the groove 3A. The grooves 3A are arranged to receive roller formations 14, as described below.

An operating cam 8, formed of a suitable plastic material, has an upper section that is of tube-like form and has a square cross-section cavity to receive the square cross-section bar 7. The lower section of the operating cam 8 is of circular cross-section and is formed with opposed vertically extending grooves. The central section of the operating cam 8 forms about three quarters of the height of the operating cam and is of generally oval (or rounded rectangular) shape having a dimension in the cross- section shown in Figure 2 approximately twice that of the dimension at 90° to the section of Figure 2. There is thus, in the locked or resting condition of the steering lock, a pair of spaces on either side of the central section of the operating cam 8, to receive a substantial part of each of the roller formations 14, as described below.

A rotating sleeve 4 is fitted over the retaining bush 2 to prevent unauthorised access to the tapped holes in the bottom portion of the retaining bush 2. The sleeve 4 is formed with an aperture to enable access to be gained to the tapped holes in the upper portion of the retaining bush 2. A plastic cap 16 is fitted over the body of the lock 5 to restrict the ingress of foreign matter into the lock 5.

When a key 6 is inserted into the cylindrical body of the lock 5 and is rotated relative to the lock body, the operating cam 8 will rotate with the key 6 relative to the retaining bush 2 and thus relative to the steering support tube 12, as described in more detail below.

A sliding wedge 11 and a bolt 10 are used to fix the quill support tube 1 within the down-tube of the front forks (not shown) of the bicycle. The quill support tube 1 is prevented from rotating relative to the front forks by forcing the 30° angled wedge 11 to make surface contact with and slide against the 30° angled slope at the bottom of the quill support tube 1. The wedge 11 is assisted in forcing itself across the contacting surfaces by a threaded bolt revolving in a threaded bore in a member fixed to the wedge 11.

A fixing and support bracket 15, to which the bicycle handlebars (not shown) are connected, includes a cylindrical part that is lowered over the bush 3 and is firmly secured to the bush 3 in such manner that the cylindrical part of the bracket 15 rotates with the bush 3 about the axis of the bush 3.

There are two roller formations 14 and each comprises a tube 14A and a pair of balls 14B, one in contact with the open upper end of the tube 14A and the other in contact with the open lower end of the tube 14A. When the steering lock is in its locked condition, the roller formations 14 are partially contained in the vertical slots 12B in the steering support tube 12 and partially in the spaces within the steering support tube 12 on either side of the main portion of the cam 8. There is no significant projection of the roller formations 14 into the grooves 3A in the bush 3. When, therefore, the bicycle handlebars are turned to effect rotation of the bracket 15 and the bush 3 about the vertical axis of the bush 3, such rotational movement will not be transmitted to the steering support tube 12 and hence will not be transmitted to the bicycle forks. Steering of the bicycle will, therefore, not be possible.

When, however, the key 6 is inserted into the lock and is turned through 90°, the cam 8 will be turned through 90°, into the position shown in Figure 2, and the roller formations 14 will be caused to move radially outwardly, into the grooves 3A in the bush 3, the roller formations 14 will then act as torque transfer elements coupling the bush 3, i. e. an outer tubular member, to the steering support tube 12, i. e. an inner tubular member.

Each roller formation 14 comprises an open-ended tube 14A and a pair of balls 14B sitting against the ends of the tube 14A.

When the tubes 14A are forced radially outwardly by rotation of the plastic operating cam 8 and is caused to enter the associated groove 3A in the bush 3, each tube 14A is squashed into an egg- shape and moulds itself to the cross-section of the groove 3A, being located within the groove 3A but not having a single line contact with the base of the groove 3A as a result of the provision of the rebate 3B at the base of each groove 3A, as mentioned above. The increased area of contact between the roller formations 14 and the walls of the grooves 3A increases the mechanical stability of the roller formations 14 and ensures a better fit of the roller formations 14 in the grooves 3A, even with increasing wear of the sides of the grooves 3A.

When the tubes 14A are forced into the grooves 3A on rotation of the plastic cam 8, each tube 14A moulds itself to the shape of the associated groove 3A and its respective rebate creating a very close fit of each roller formation 14 in its respective groove 3A. When the pressure applied by the cam 8 is released at the end of turning movement of the operating cam 8 under the action of the key 6, each metal tube 14A recovers its original shape and reverts to its original cylindrical configuration.

The combination of two balls 14B and a tube 14A for each roller formation 14 also acts as an anti-tamper device in that unauthorised removal of the cam 8 would cause each column comprising two balls 14B and a tube 14A to collapse and fall inside the steering support tube 12. Rotation of the bracket 15 and the bush 3 would thus still not be transmitted to the steering support tube 12 and steering of the bicycle forks would still not be possible.

A complete, unvandalised steering lock is thus required to effect steering of the bicycle.

A steering lock for a motorcycle or scooter will be constructed as described above, except that the dimensions of the components of the lock will be increased to provide increased strength to accommodate the increased torque requirements.