GB2501642A - Tube End Fitting - Google Patents

Abstract

An end fitting 14) suitable for a fork of a cycle frame comprises first and second plates 15,16 slotted together to form a cruciform sub-assembly and partially inserted into an open tube end 12 before fixing thereto. An aperture 19 on one of the plates serves as a mounting point or drop-out for a wheel axle. The cruciform shape provides lateral stiffness together with an orthogonal mounting surface for accessories and/or a reaction surface for a wheel hub. Additional apertures 21 may be provided for the connection of auxiliary components such as mudguard stays. A cross dowel may be inserted into an aperture 22 adjacent the main aperture 19 to form a secondary retention function.

Description

Tube End Fitting This invention relates to a tube end fitting, particularly though not exclusively for use in rclation to tubular framcs of cycles and like dcviccs.

tubular frames of cycles generally comprise very thin wall tubes joined together at nodes to form a rigid triangulated structure. Typically the tubes are of metal, and are connected by a metal fusion process such as welding or brazing; reinforcement may be provided at the nodes by means of tubular lugs or planar brackets.

Wheel attachments are generally provided by flat plates, termed drop-outs, fixed to an adjacent tube or tubes of the frame, and having an open slot to receive a wheel axle.

Drop-outs are typically stamped or cut from metal plate. Drop-outs are provided in pairs so as to support an axle at either end, and the axle is fixed in place by screw-threaded nuts, or by a through skewer and ovcr-ccntrc clamp. Thcse arrangcmcnts are conventional, and very well-known. The drop-outs are generally located in a slot formed in the end of the adjacent tube or tubes, and the tube itself is typically formed with a domed end to close off that part of the open end on either side of the drop-out.

Rear drop-outs generally link a tubular seat stay to a tubular chain stay, whilst front drop-outs are provided at the fork ends.

One disadvantagc of conventional drop-outs is that resistance to bending in the direction orthogonal to the plane thereof is low. On the other hand, the adjacent tubular frame member is relatively stiff in all planes. One solution to this problem is to cast or forge drop-outs with some stiffening webs in this perpendicular direction, but these processes are relatively costly and may be uneconomic where production volumes are low.

Other parts of cycle frames also require flat mounting surfaces for components such as suspension pivots, luggage carriers and mudguards. These attachment points may be associated with drop-outs, or may be provided at another point on the cycle frame.

What is required is a lower cost means of providing tube end fitting, such as a drop-out, which is relatively stiff in the orthogonal direction.

According to the invention there is provided a cruciform tube end fitting comprising connected first and second fiat plates, the second plate being fixed in a slot of the first plate, and both plates being adapted for close-fitting partial insertion into the end of an open tube, the first plate having an aperture in the region not adapted for insertion in the tube, and the second plate being spaced from said aperture to define an unobstructed perimeter thereto.

Such an end fitting is resistant to bending in the plane of the first plate, by virtue of the second plate, and can thus resist lateral bending forces which cannot be resisted by conventional drop-outs of flat plate.

In a cycle frame, the end fittings are inserted into the open end of tubular frame member, such as defined by a front or rear fork, and fixed in place by a conventional joining technique, such as by welding, brazing or by adhesive. The plates may be fixed together prior to insertion, for example by induction brazing of steel plates.

Plates for the cruciform tube end fitting can be inexpensively stamped or cut from metal plate. Moreover, the plate shape can be readily adapted to suit the intended purpose, and the degree of lateral stiffening required. For example an end fitting may or may not be provided with mudguard attachment holes. Furthermore, a change to a different grade or strength of material is easily facilitated. The invention is particularly suitable for small production volumes and/or where the design of end fitting is adapted to suit a bespoke frame design.

Tn a preferred embodiment, both plates are of the same material and thickness, and both define slots to permit mutual engagement. In one embodiment the plates are mutually co-extensive, but may taper somewhat towards the ends on the slot axis.

In one embodiment the end fitting provides an abutment for a tube end, by defining one or more shoulders at the periphery of one or more of said plates. The end fitting may be a sliding or push fit in the end of a tube, to facilitate correct positioning prior to fixing permanently.

The cruciform axis may or may not coincide with the tube axis, according to design and/or strength requirements. Furthermore the fitting of the invention is readily adaptable to tubes of non-circular section, for example oval or rectangular, without special measures.

A particular advantage of the invention is that the cruciform shape reduces the end opening in a tube, as compared with a conventional planar drop-out, and may thus act as a partial or substantially full closing plate for the open tube end. In such a construction the remaining tube end opening(s) may be sufficiently small to be filled with braze, weld or adhesive.

As will be further explained below, the second plate may act as a secondary mounting surface for cycle components, and/or as a torque reaction surface.

Other features of the invention will be apparent from the following description of a preferred embodiment of the invention in which: Fig. 1 illustrates an embodiment of the invention in exploded side view.

Fig. 2 illustrates the embodiment in assembled side view.

Fig. 3 illustrates a conventional cycle drop-out in side elevation.

Fig. 4 is a cross-section on line 4-4 of Fig. 3.

Fig. 5 is a cross-section equivalent to Fig. 4, but showing the effect of the invention.

With reference to the drawings, a tube 11 has an open orthogonal end 12. The tube may be part of a cycle frame, for example a seat stay, a chain stay or one leg of a front fork. Although shown of constant diameter and sectioll, it will be appreciated that the tube may taper to the end, and bc of non-circular section. Thc opposite end 13 of the tube is truncated for purposes of illustration, but in practice may be much longer.

Although the tube end is orthogonal in the illustration, it need not be.

A cruciform end fitting 14 comprises two flat plates 15, 16 stamped or cut from metal plate. As illustrated the plates are of identical thickness, but need not be. Each plate defines a straight parallel sided slot 17, 18 slightly wider than the plate thickness, so as to permit the plates to be inter-engaged as shown in Fig. 2.

Upon engagement the plates are substantially co-extensive, and each slot is about half the transverse dimension of the respective plate along the slot axis.

Thc platc 16 is somewhat largcr in area, and dcflncs an open sidcd aperture 19 in thc manner of a conventional cycle frame drop-out. As will be well understood, a pair of drop-outs provides for mounting of an axle of a cycle wheel by means of a circular fastener such as a threaded nut or cam device. Around the aperture 19 on both sides is provided an unobstructed planar perimeter sufficiently wide to be engaged by the circular fastener of a wheel, and accordingly the axis of the slot 17 is at one side of the plate 16.

The plate 16 also defines circular holes 21, 22 to illustrate the possibility of fixing other cycle components such as mudguard stays, and these also have an unobstructed perimeter for respective circular fasteners. The hole 22 may be used for a dowel pin that acts in usc as a secondary rctcntion device for a whccl.

The plate 16 defines shoulders 25 to engage the open end 12 of the tube, and this arrangemcnt both providcs for incrcascd strength and for precise rclativc positioning of the aperture 19. Similar shoulders may be provided, if desired, on the plate 15.

It will be observed that the cruciform axis 23 is not the same as the tube axis 24 (Fig. 2), and may be set according to the design requirements of the cycle, for example by changing the position of the shoulders 25.

The plates 15, 16 may be pre-assembled or may be fixed together at the same time as they are fixed to the tube 11. For example the plates maybe of steel and be induction brazed as a sub-assembly prior to forming the shoulders 25 in the desired orientation.

Tnsertion of the sub-asseimbly into a steel tube is followed by a secondary brazing operation.

Several advantages of the invention will be apparent. An expensive forged or cast end fitting is avoided, and the machining associated therewith. Slotting of the tube end for a single planar drop-out is avoided. The appearance of the tube and end fitting may be improved, since a slot is avoided, and the structural integrity may be greater.

The second plate provides capability for a mounting which is not in the plane of the first plate. Such an arrangement may provide for straight connection of a cycle accessory or frame component without manipulation to suit the plane of the first plate.

The second plate may also provide a reaction member or abutment to prevent unwanted rotation of a cycle wheel component, such as a hub. Such a reaction member may be desirable for a brake component or for the axle of an internal wheel hub gear.

A further advantage is illustrated in Figs. 3 and 4. Fig. 3 shows a conventional planar drop-out 31 inserted into a slot in the end of a tube 32. Fig. 4 shows a cross-section on line 4-4, and in particular the large areas of open tube 33 which are unfilled. It is desirable to close off these areas, for which purpose the tube end is generally somewhat domed, which is an awkward, time consuming and costly operation.

Tn the invention, as iflustrated in Fig. 5, these open areas are more completely fiHed by the cruciform component, and if at an angle (as shown in Fig. 2), the second plate 15 can be arranged to substantially close the tube end at one side 33 by contact with the inner surface thereof, at least sufficiently to permit final sealing by brazing, welding or adhesive.

The invention has been described in relation to a drop-out for a wheel of a cycle, but is also applicable to other cycle components such as pivot mountings for suspension components, luggage carrier attachments and mudguard attachments, which are not associated with the frame drop-outs. In place of metal fusion techniques, the cruciform fitting may be attached by adhesive, and thus permit the usc of dissimilar materials.

Claims (16)

1. Claims 1. A cruciform tube end fitting comprising connected first and second fiat plates, the second plate being fixed in a slot of the first plate, and both plates being adapted lbr close fitting partial insertion into the end of an open tube, the first plate having an aperture in the region not adapted for insertion in the tube, and the second plate being spaced from said aperture to define an unobstructed perimeter thereto.
2. 2. An end fitting according to claim 1, wherein said aperture is open at the side thcrcof.
3. 3. An end fitting according to claim I or claim 2, wherein the first plate fixed in a slot of thc second plate.
4. 4. An end fitting according to claim 3, wherein the plates are of substantially the same thickness, the slots being substantially straight and parallel sided.
5. 5. An end fitting according to claim 4, wherein each plate fits closely with the slot defined in the other plate.
6. 6. An end fitting according to any preceding claim, wherein the plates are of metal and connected by one of welding and brazing,
7. 7. An end fitting according to anypreceding claim, wherein the fitting defines an abutment!br an open tube end.
8. 8. An end fitting according to claim 7, wherein said abutment is defined at opposite sides of one of said plates.
9. 9. An end fitting according to claim 8, wherein said abutment is defined on both of said plates.
10. 10. An end fitting according to any preceding claim, and adapted to receive an axle in said aperture, said axle having a circular retainer engageable with said perimeter.
11. 11. A fbrk end ofa cycle, comprising a tube having affixed to an open end thereof a tube end fitting according to any ofclaims 1-10.
12. 12. A fork end according to claim 11, wherein the longitudinal axis of the tube in the vicinity of the tube end does not coincide with the cruciform axis of said end fitting.
13. 13. A fork end according to claim 12, wherein said second plate partially closes said tube end by contact with the inner surface thereof
14. 14. A cycle frame having a pair of fork ends according to any of claims 11-13, said fork ends being aligned to define a rotational axis of a wheel between respective apertures of the first plates thereot a said second plate defining a torque reaction member for a wheel rotatable on said axis.
15. 15. A cycle having drop-outs constituted by cruciform tube end fittings according to any of claims 1-10, a wheel being located in pairs of said apertures and secured by circular retainers engageable with respective pairs of said perimeters.
16. 16. A cruciform drop-out substantially as described herein with reference to Figs. 1 and 2 of the accompanying drawings.