The present invention relates to a fork for the steering wheel of different forms of cycle, notably bicycles or motorised cycles. The fork has a new structure particularly chosen to allow moulding either in metal or in plastics material.
The structure of the fork according to the invention is also designed to allow mounting of the brake jaws in order to entirely suppress the flexing forces which appear, in braking, in the pivoted supports normally used for supporting the shoes or wear members cooperating with the rim of the wheel to be braked.
Various other characteristics will appear from the description below, given with reference to the attached drawings which show, by way of example, an embodiment of the invention.
FIG. 1 is an elevation view of a fork according to the invention, partly cut away;
FIG. 2 is a front view, half in section, taken on the line II--II in FIG. 1;
FIG. 3 is a section on the line III--III;
FIG. 4 is an elevation and a section of one of the elements comprising the fork; and
FIGS. 5 and 6 are views on the lines V--V and VI--VI.
FIG. 7 is a partial section of a second embodiment of one of the elements according to the invention.
According to the form of the invention shown in FIGS. 1 and 2, the fork is made entirely of an appropriate plastics material, for example polycarbonate, polyamide or polyester, reinforced with glass fibres. The fork has two arms 1, extending in slightly divergent directions from a common root 2 away from a stock 3. The latter is intended for the mounting and support of the handle bar and is itself mounted on the steering pivot 4 of a frame 5 represented in dot-dash lines in FIG. 1. The stock 3 takes the form of a bridge which defines, between the root 2 and a head 6, a recess 7 for receiving the steering pivot 4. The link between the stock 3 and the steering pivot 4 is made by a steering pin or shaft 8 centered within the pivot 4, the end parts being maintained in bearings 9 and 10 in the root 2 and the head 6. The particular structure of the stock 3 as described above is thus carefully designed for mounting of the fork on the steering pivot 4 by means of the steering pin or shaft 8. The latter is axially fixed after engagement in the bearings 9 and 10 by means, for example, of a shoulder at one end and a threaded end cap on the other end of the pin. Such a method of construction allows the threading of the threaded end cap to be used for varying the tension on the stock 3 and for regulating the axial play and the angular freedom between the fork and the steering pivot 4.
FIGS. 1 to 3 show that the bearings 9 and 10 are in the left hand part of the stock 3, considered in plan view. The right hand part of the stock beyond a connecting web 11 defines two parallel casings 12 of polygonal form extending between the head 6 and the root 2. The casings 12 are intended to receive a steering bracket 13, which according to the invention is also made entirely of a suitable plastics material, in particular polycarbonate, polyamide or polyester, reinforced with glass fibres. As seen in FIGS. 4 to 6, the bracket 13 has a half clamp 14 with two parallel extensions 15 of polygonal section complementary to that of the casings 12. The extensions 15 can be in the form of solid stems, or can be tubular, their length being different from or equal to the height or depth of the casings 12. The bracket 13 is held axially relative to the stock 3 in the position required or determined by means of a screwed member, such as a bolt extending freely through the part of the head 6 between the casings 12 and being threaded into an insert positioned in a hole 16 reserved for it. The hole 16 communicates with a passage 17 which crosses a slit or cut 18 in the upper frontal part of the head 6 which isolates a deformable portion thereof. This ensures that when the locking bolt is screwed up, the extensions 15 are locked axially in the interior of the casings 12.
The bracket 13 is completed by a top clamp 19, also manufactured in plastics material, which defines on one of its faces a semi-cylindrical seating 20 complementary to a seating 21 in the upper face of the clamp 14, which together receive the middle part of the cross piece of a handle bar (not shown in the drawings). FIG. 4 shows that the top clamp 19 is preferably formed in such a way that it can be mounted and demounted rapidly from the bracket 14. It is normally fixed in such a way as to hold the handle bar firmly, using a threaded member, or a cam or wedge-type locking member.
According to another characteristic of the invention, each arm 1 is formed by two U-profiles 22 and 23 extending in the same way from the root 2, at first being substantially parallel and connected by means of a wall 24. The profiles 22 and 23 are preferably of a U-type and are orientated with their ribs 22a and 23a directed outwardly of the arm. The profiles 22 and 23 are united by a moulding 25 which extends close to the bottom of a window 26 in the wall 24. Beyond the moulding 25, the profiles 22 and 23 take converging directions and then together form a curved part 27 in common, which ends in an open bearing 28 for the mounting of the axle of the hub of a wheel 29, such as is shown in dot-dash lines in FIG. 2.
The moulding 25, which extends substantially perpendicular to the longitudinal axis of the fork, is formed so as to provide a recess 30 of semi-circular shape for the mounting of a brake jaw 31. The latter is held by means of a pivot pin 31a, the ends of which are placed in bearings 33 provided in the moulding 25. The brake jaw 31 shown in dot-dash lines in FIG. 2 carries a friction pad 34 which is removable and which enters the window 26 so as to align with the rim of the wheel 29. The brake jaw 31 also forms a lever 32 on which is attached the end of a tension cable, the sheath of which, not shown in the drawings, bears on the fork of a guide finger 35 formed as a projection of the wall 11.
The brake jaws 31 are thus directly mounted for pivoting on independent axes disposed parallel to the plane of rotation of the wheel and receive no flexing loads during application of the brakes 34 on the rim of the wheel 29, as has been the case with pivoted supports for brake jaws of traditional construction. Such an arrangement leads to an extended life for the different linked parts of a front brake, but also and more importantly, leads to considerable improvement in the braking action of the pads 34.
As well as the different advantages mentioned above, it should be noted that the fork according to the invention and the support bracket for the handlebars are constructed in plastics material and thus have, for equal mechanical strength, a lower weight. Moreover, the use of an appropriate plastics material as a construction material allows the manufacture of the finished products which have a new and durable aesthetic appeal, for example, due to colouring in the material.
According to a further arrangement according to the invention, the forward and rearward surfaces of the arms 1 and the root 2 form two shouldered ledges 36 and 37 having channels of inverted U-shape. These can receive two half mud-guards 38 and 39, also in plastics material, which clip in position and which project in each direction from the fork in the plane of rotation of the wheel.
The invention can be applied to various forms of cycles, but has its preferred application in the construction of touring bicycles.
According to another characteristic of the invention shown by FIG. 7, each open bearing 28 is edged by a flange or projection 40 extending from the outer face of the arm 1 of the fork. The flange 40 forms an external partial bearing 41 in the shape of truncated cone which is concentric with the open bearing 28. The bearing 41 co-operates with a complementary seat 42 provided in a nut 43 screwed on the shaft 44 of a wheel. The bearing 41 and the seat 42 ensure together a locking against a disengagement of the shaft from the open bearing 28 in case of partial unscrewing of the nut 43. Preferably, the seat 42 is provided in a metallic piece such as a tubular threaded core over which the nut 43 is moulded.
The invention is not limited by the embodiments shown and described in detail, since many modifications can be made without departing from its scope. In particular, the fork can alternatively be made by moulding or casting of a metal alloy in place of a plastics material.
Moreover, in certain cases, the stock 3 can be replaced by a tubular stock of traditional type, one end of which is provided with an attached structure which constitutes a base upon which can be moulded the root 2 and in part the heads of the arms 1.