FRONT WHEEL RETENTION IN A BICYCLE

The present invention relates to a bicycle and has particular reference to front wheel retention in a bicycle.

Bicycles conventionally include wheel-securing arrangements designed to facilitate removal of front wheels for puncture repair, tyre replacement, anti-theft protection and reduction in overall size of the bicycle for storage and other purposes, including transport in the case of folding bicycles. Such arrangements are generally based on provision in the bicycle front forks of aligned open-ended slots which receive stub axles of the front wheel hub. The stub axles can slide out of the slots following release of fastening means, normally a clamping system. For refitting the wheel, the stub axles are reinserted into the slots and the fastening means re-applied.

A risk arises with these arrangements, particularly those incorporating quick-release clamps in which a clamping force is applied by movement of clamping or locating members towards one another and relieved by movement of the members apart, that if the clamp is accidentally left untightened and the bicycle used in this state the stub axles can slide out of the fork slots and the wheel thus detach from the forks. This risk can be reduced by providing recesses, in which the members engage, in the forks so that the untightened members do not allow the slide axles to slide out of the slots unless the members are intentionally moved apart to escape from the recesses. This safety measure does not in itself inhibit movement apart of the members; this is exclusively the function, in the case of a common form of quick-release clamp design, of a spring or springs urging the members towards one another. There is no guarantee that the biassing force of the spring or springs cannot be overcome by abnormal loads acting on the loose wheel or that spring breakage or a pre-existing fault with a spring might not then allow the members to move apart.

It is therefore the principal object of the present invention to provide improved front wheel retention with enhanced security against the risk of detaching of a loose wheel.

Other objects and advantages of the invention will be apparent from the following description.

According to the present invention there is provided a bicycle including front forks provided with aligned open-ended slots and with recesses formed in the forks at mutually remote sides thereof and communicating with the slots, a front wheel removably mounted in the slots and wheel fastening means comprising a spindle extending through the slots and a hub of the wheel and respective locating members mounted on the spindle at the ends thereof to be received in the recesses with lateral play longitudinally of the slots, the locating members being tightenable relative to one another to fix the wheel in the forks and when not tightened being movable apart to exit the recesses and allow removal of the wheel from the forks and the recesses being formed with undercuts and the locating members with lips co-operable with the undercuts to prevent unintended movement apart of the untightened members in the event of displacement of the wheel causing movement of the members to the limits of their play longitudinally of the slots.

In the case of a bicycle embodying the present invention the co-operation of the lips on the locating members of the fastening means with the undercuts in the recesses provides a mechanically positive block against movement apart of the untightened members at the limits of the play of the members. Thus, if the members are left untightened and the bicycle ridden in this state the wheel hub can displace longitudinally of the fork slots only to the extent of interengagement of the lips and undercuts, i.e. at a limit of the provided play, at which point the locating members are retained in the recesses in the axial direction of the spindle by the mechanically positive block provided by the interengagement. The bicycle remains in an unsafe condition with the locating members loose, but the immediate risk of sudden departure of the front wheel from the bicycle is averted and the rider would normally become aware, from the behaviour of the bicycle, that the front wheel is loose and the fastening means requires attention.

For preference, the lip of each locating member and undercut of the associated recess are formed with surfaces of substantially complementary shape. If the lip and undercut are of complementary shape, albeit necessarily of different size so that the lip of the member is able to enter and exit the recess when required, the interengagement of lip and undercut can take place over at least a small area rather than at a point.

Various shapes of undercut are possible, for example, each undercut may be defined by at least a segment of a frusto-conical or part-spherical surface or by a groove of substantially

rectangular cross-section.

The recesses are preferably circular and the undercuts preferably extend entirely around the recesses. Although the zones of co-operation of the lips and undercuts may, depending on the design of the slots in the forks, be confined to regions in the vicinity of the open and closed ends of the slots, a circular recess and an undercut extending around the circumference allow simple manufacture by cutting or milling tools.

The fastening means preferably comprises a quick-release clamp, such clamps being simple to operate, but susceptible to improper use giving rise to wheel looseness and therefore able to benefit, to a particular degree, from the safety measure provided by the present invention. This benefit is particularly pronounced in the case of a form of quick- release clamp in which the locating members are movable apart against a resilient bias.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side view of the front end of a bicycle embodying the invention;

Fig. 2 is a schematic side view, to enlarged scale, of the lower end of front forks of the bicycle, showing details of the mounting of a front wheel therein; and

Fig. 3 is a schematic cross-section on the line IH-II of Fig. 2.

Referring now to the drawings there is shown in Fig. 1 the front end of a bicycle 10 of a conventional kind, although the invention is equally applicable to specialist forms of bicycle such as mountain bicycles, folding bicycles, etc. The bicycle 10 comprises a frame incorporating a crossbar 11 and down tube 12, which are coupled with a pivotable handlebar shaft 13 carrying front forks 14, only one of which is visible in Figs. 1 and 2. A front wheel 15 is removably mounted by a hub 16 thereof in the forks 17. For this purpose the forks have, as shown more clearly in Figs. 2 and 3, two aligned open-ended slots 17 which are oriented generally horizontally in this instance, but can equally well be aligned substantially vertically or at angle between horizontal and vertical. The slots 17 slidably receive stub axles 18 formed by protruding end portions of a tubular axle extending

through the hub 16. The hub 16 is normally rotatably mounted on the tubular axle by, for example, suitable bearings. The stub axles 18 are slidable in the slots 17 for removal and refitting of the wheel, for example to enable repair of a puncture or in connection with anti- theft measures or wheel-folding of a folding bicycle. The sliding movement of the stub axles 18 longitudinally of the slots 17 also facilitates alignment of the wheel, in particular to ensure that the vertical centre plane of symmetry of the wheel 15 is uniformly spaced from the two forks 14.

The wheel 15 is clamped in place between the forks 14 by fastening means 19 comprising a spindle 20 extending through and beyond the tubular axle, thus through the hub 15 and the slots 17 of the forks 18, and locating members 21 mounted on protruding end portions of the spindle and tightenable relative to one another to generate a clamping force acting on mutually remote sides of the forks. The fastening means 19 is preferably a quick- release clamp of a kind in which one of the locating members 21 is threadedly engaged on one spindle end portion and the other locating member 21 is slidably engaged on the other spindle end portion and resiliently urged by biassing spring means towards the threaded locating member. The clamping force is produced by, for example, an over-centre eccentric cam (not shown) rotatable in one direction by a lever and acting on the slidable locating member 21 to press it towards the threaded locating member 21 and thereby clamp the forks between the members 21 and hub 16. The clamping pressure is released by reverse rotation of the lever-operated cam, after which through movement apart of the members 21 , in particular sliding movement of the slidable member 21 , away from the threaded member 21 against the force of the biassing spring means the stub axles 18 can freely slide out of the slots 17.

As a safety feature the forks are provided at the mutually remote sides thereof with circular recesses 22 communicating with the respective slots 17, as evident from Figs. 2 and 3. The recesses 22 receive the locating members 21 with a radial play, i.e. the diameter of the recesses is greater than the diameter of the members 21. If the locating members 21 are not tightened relative to one another, for example through failure to operate the eccentric cam, the members 21 still remain in the respective recesses 22 as a consequence of the resilient biassing of the members towards one another. If the bicycle 10 is ridden in this condition the stub axles 18 may be able to move in the slots 17, but only to the extent of the provided radial play. Unless the members 21 are moved apart against the bias, they cannot exit the recesses 22 and the stub axles 18 consequently

cannot leave the slots 17 and allow the wheel 15 to detach from the forks. The radial play - effectively only play longitudinally of the slots, since play in other directions is precluded by the fit of the stub axles in the slots - permitted by the diametral difference between the members 1 and recesses 22 accommodates tolerances in fitting the wheel 15 and, especially, adjustments that may be needed to ensure correct wheel alignment or orientation.

In normal circumstances movement apart of the members 21 in an untightened state would require intentional displacement of the slidable one of the members against its resilient bias. However, if the bicycle is ridden in the described condition it is not impossible that that lateral loading of the wheel, jolting, twisting of the forks or other factors could create a risk of departure of either or each member 21 from its recess 22. In order to remove or at least reduce this risk, each recess is formed with an undercut 23 co- operable with the respective locating member 21 to prevent escape of the member from the recess when it has moved to the limit of its play in either direction longitudinally of the associated slot 17. This movement will arise when the members 21 are untightened and the stub axles 18 locating the wheel in the forks move to, in the usual case, the closed ends of the slots (upper ends for generally vertical slots and trailing ends for generally horizontal slots). Co-operation is achieved by providing each member 21 with a protruding lip 24 engaging in the undercut. The undercut and lip are preferably of substantially complementary shape, but different size, represented in the embodiment of Fig. 3 by frusto-conical surfaces of corresponding slope, but different diameter. The effective zones of the undercut and lip are formed by those segments of the surfaces disposed at the front and the back of the lip and the recess with respect to the slot longitudinal axis. Since the locating members 21 may or are intended to rotate in use, the frusto-conical surfaces are formed around the entire circumference thereof, although only the segments respectively positioned at the front and the back are effective to engage the frusto-conical surface of the recess. The recess is similarly formed with a frusto-conical surface entirely around its circumference, in this instance for manufacturing convenience and to provide some degree of tolerance for the rotational and sliding movement of the member 21.

As evident from Fig. 3, the maximum diameter of each locating member 21 , in particular at its lip 14, is slightly less than the minimum diameter of the associated recess 22, so that the member 21 can enter and exit the recess when centred relative thereto.

The complementary form of the undercut 23 and lip 24 can be achieved by other shapes, for example part-spherical surfaces or a groove and complementary lip of substantially rectangular cross-section.

The provision of a mechanically positive interengagement of the locating members 21 and forks 14 by way of the undercuts 23 and lips 24 at the limits of travel of the stub axles 18 in the slots 17 significantly reduces the risk of detaching of the wheel 15 from the forks 14, which could lead to an accident, if the bicycle is used without tightening the members 21. Although a quick-release clamp has been described as a preferred form of the fastening means 19, other forms of fastening means are possible, including locating members which are both threaded.