WO1995015275A1

WO1995015275A1 - Bicycle suspension system

Info

Publication number: WO1995015275A1
Application number: PCT/GB1994/002655
Authority: WO
Inventors: Jonathan Hughes; Peter John Lamb; Michael Sefton
Original assignee: Bicycle Innovations Limited
Priority date: 1993-12-03
Filing date: 1994-12-02
Publication date: 1995-06-08
Also published as: GB9424448D0; AU1116695A; GB2284396A; GB9324841D0

Abstract

A bicycle is provided with a suspension assembly which is pivotally mounted on the dropout plate of the rear wheel or the dropout slot of the front wheel forks.

Description

BICYCLE SUSPENSION SYSTEM

The invention relates to a bicycle and in particular to a bicycle which is provided with a suspension assembly arranged to dampen or absorb the shocks caused especially when cycling over rough terrain. While the invention is applicable to all types of bicycles it is especially suitable for all terrain or mountain bikes and will be described with particular reference to such bikes.

The invention is based on the realisation that by pivotally mounting at least a part of the suspension assembly above the mounting for the axle of a wheel (rear or front or both) of the bicycle the suspension is especially simple in construction and efficient in use.

According to the invention in one aspect there is provided a bicycle frame including a top tube, a head tube, a down tube, a seat tube, seat stays and chain stays, rear wheel mounting means and front wheel mounting means characterised in that shock damping means are pivotally mounted on the frame above the rear wheel mounting means and/or the front wheel mounting means.

Typically the rear part of the frame forms a triangle as seen in side view defined by the seat tube, seat stays and chain stays. By mounting the damping means above the wheel mounting means, typically the drop out plate, and thus within or adjacent a corner of that triangle the distance of movement undergone by the suspension assembly is much reduced.

It is an especially preferred feature of the invention that the shock absorbing means is connected to a bridge for brake members of the respective wheel. Typically the brake mountings and pads are mounted in-board of the bridge. Most preferably the brake bridge is connected by a link to the adjacent frame member (the seat tube or stays in the case of the rear wheel), and the length of the link is selected to maintain the brake members adjacent the wheel rim.

Preferably the shock damping means is pivotally mounted on the drop out plates for the rear wheel. Preferably there are two pivots on the drop out plates, one connected to the brake bridge and the other to a shock dampening member. It is much preferred that the suspension assembly comprises a parallelogram including the shock dampening member which bridges the two pivots. However, the member may be located at another position on the frame, either instead of or in addition to the medium near the wheel mounting means.

It is a particularly advantageous feature of the invention that the suspension assembly may be installed on a bicycle when being manufactured or that the suspension assembly may be added as a retrofit to a pre-manufactured bicycle.

The shock dampening or absorbing member may take a wide variety of forms. In one class are elastomer systems including hard elastomers (which tend to shorten and bulge under load) and a microcellular elastomer (which contains pores and shortens but does not bulge). In another class are the coil spring or pressurised air systems with or without oil.

As indicated, the suspension assembly may be mounted on the front wheel as well as or instead of the rear wheel.

The frame may be made of any suitable material such as metal, e.g. steel, steel alloy, titanium or aluminium or of a composite, e.g. based on carbon or other fibre. In order that the invention may be well understood, it will now be described by way of example with reference to the accompanying drawings in which:-

Figure 1 is a side elevation of one mountain bike incorporating a suspension assembly of the invention;

Figure 2 is a side elevation drawn to an enlarged scale of the brake bridge and suspension assembly shown in Figure 1 ;

Figure 3 is a rear end view of the parts shown in Figure 2;

Figure 4 is a exploded side view of the major components of one embodiment of the suspension device in accordance with the invention showing the relative disposition of the parts;

Figure 5 is a side view of an assembled suspension device showing the connection to a bicycle frame;

Figure 6 is an exploded view of the connection between the upper and lower arms and the frame mounting means;

Figure 7 is an exploded view showing the connection between the upper and lower arms and the rear wheel axle support means; and

Figures 8, 9 and 10 show an alternative embodiment of the device in which the resilient bias means is differently located on the upper and lower arms. The mountain bike or all terrain bike shown in Figure 1 comprises a frame F, made of alloy, carbon fibre, or the like. The frame comprises a top tube F1 , a head tube F2, connected to forks F3, a down tube F4, a seat tube F5, from which depend two seat stays F6 on divergent axes and chain stays F7 which unite the lower end of the seat tube F5 and the seat stays F6. Dropout plates D are present where the seat stays F6 and the chain stays F7 meet to receive the axle A or spindle of the rear wheel WR and equivalent slots are present at the lower ends of the forks F3 to receive the axle A or spindle of the front wheel WF. The axles A are held in place by quick release fittings not shown, typical of a mountain bike but nuts may be used instead. The bike has the usual mountain bike handlebars H, saddle S, pedals P and chain C, and the gears G are typically of the derailleur type. Each wheel has brakes B associated therewith, the brakes being mounted in-board on a brake bridge BR for the rear wheel WR. The bridge is connected by a link L to seat tube F5, the link L being pivotally connected at each end to the respective part.

As best shown in Figures 2 and 3, the brake bridge BR is connected to the drop out plate D for the axle A of the rear wheel WR. The drop out plate is of generally trapezoidal form, having the usual blind slot to receive the axle A or spindle of the wheel.

Two pivot pillars P 1 and P2 are mounted on the drop out plate D, one above the other, each on the side remote from the drop out slot. An integral arm Q extends from the same side of each pivot pillar P1 and P2, the arms being parallel and each ends in a further pivot pillar P3 and P4 respectively, so that the overall shape is that of a parallelogram. A resilient shock dampening or absorbing member R, e.g. an elastomer, is located between an arm P5 integral with the pivot P 1 and an arm P6, integral with the pivot P4, diagonally across the parallelogram. A pivot pillar P7 is integrally formed above the pillar P2 and is connected to the brake bridge BR, the net effect being that when the wheel WR undergoes vibration or shock and the suspension assembly on the drop out plate moves vertically that movement will be transmitted to the brake bridge and to the link L which moves the same distance. As a result the brakes B are maintained in substantially constant alignment with the axle A. Because the components are located above the axle A they do not foul the gears G.

Referring to Figure 4, a frame mounting member 1 is formed by a body of generally triangular form having spaced holes 11 , 12 adjacent two of the vertices of the triangular body. A rear wheel axle support body 2 is formed of a generally lozenge- shaped plate having a first hole 21 proximate an acute-angled vertex and a second hole 22 adjacent an obtuse-angled vertex. Generally elongate upper and lower arms 3, 4 are pivotally connected by respective pivots, 31 , 21; 41 , 42 between the frame mounting member and the rear wheel axle support body. The upper arm 3 has a further pivot 33 offset from the axis defined by the pivots 31, 32 and the lower arm has a further pivot 43 on an extension of the longitudinal axis formed by the pivots 41 , 42, and a resilient bias member 5 has a density to suit particular rider weights and degree of suspension stiffness required, e.g. for bicycle use.

The frame mounting member 1 has a further hole 13 for engagement with the dropout slot of the bicycle frame. The rear wheel axle support body has a slotted cut-out 23 for supporting the rear wheel axle of the bicycle.

Referring to Figure 5, the suspension device is assembled to the bicycle frame with the hole 13 aligned with the rear wheel axle support slot 61 of frame 6 and the rear wheel axle may then be received in slot 23 such that the rear wheel is supported behind the normal rear wheel position on the frame. As will be seen from Figure 5, the spacing between the pivotal connections on the frame mounting member 1 is the same as the spacing between the pivotal connections on the rear wheel axle support member 2. Likewise, the spacing between the pivots on the lower arm 4. Thus, in the embodiment shown, the upper and lower arms 3, 4 are parallel, and will remain parallel regardless of rotation of the rear wheel axle support means with respect to the upper or lower arms.

Although it may be convenient for the upper and lower arms to remain parallel, this is not essential for the operation of the invention. For example the spacing between the pivots on the frame mounting means could be different to the spacing between the pivots on the rear wheel axle support member, or the spacing between the pivots on the upper arm could be different to the spacing between the pivots on the lower arm.

Referring now to Figure 6, there is shown the structure of the various pivots and the method of connection of the upper and lower arms to the frame mounting member 1. The upper arm 3 is connected to the frame mounting member 1 by a pivot joint which consists of an socket-headed screw 315 securing a pivot pin 314 to the frame mounting member 1. The socket-headed screw 315 passes through the hole 11 in the member 1 and engages with a screw thread within the pivot pin 314. The pivot pin 314 has a flanged portion 317 extending between the upper arm and the frame mounting member 1. A bush 313, of a low friction material such as nylon, is mounted on the pivot pin 314, the inner diameter of the bushing 313 conforming to the outer diameter of pivot pin 314. The bush has a flanged portion 317 for the flanged portion of the pivot pin 314. The outer diameter of bush 313 conforms to the inner diameter of a hole 316 in the upper arm 3 so that the upper arm 3 may be engaged over the bush 313. To retain the upper arm 3 engaged on bush 313 and pivot pin 314, a retaining cap 312 of aluminium material is attached to the pivot pin by a further socket-headed screw 311 which also engages in the threaded hole of the pivot pin 314. The diameter of the retaining cap 312 is larger than that of the hole 316 and abuts the end of brush 313 and pin 314, thus the upper arm 3 is maintained located on the assembly of the pivot pin 314 and bush 313.

The lower arm 4 is pivotally secured to the frame mounting body 1 by a similar pivot arrangement which consists of a socket-headed screw 415 passing through the frame mounting body hole 12 and engaging with the internal thread of a pivot pin 414 and the lower arm is located over the bush 413. A retaining cap 412 is secured to the pivot pin 414 by socket headed screw 411.

The further pivot 33 (see Figures 4 and 5) has a pivot pin 331 which is part of a mount for an elastomeric rod which constitutes resilient biasing member 5. This mount consists of a barrel-shaped member 331 having a first diametric hole 332. This hole 332 may be internally threaded to accept the end of the elastomeric rod 5. The barrel-shaped body has an axial extension 333 of reduced diameter which serves as a pivot pin and which has an axial hole which is internally threaded. A bush 334 which is generally similar to bushes 313 and 413 is assembled over the pivot extension pin extension 333 and the assembly is passed into hole 335 of the upper arm 3. A retaining cap 336 prevents the pivot 331 from escaping from the arm 3 and the retaining cap is secured by a socket-headed screw 337 which engages with the threaded hole in the pivot pin extension 333.

The frame mounting member 1 is secured to the frame by a mounting bolt 131 which has a head of reduced longitudinal extent. This prevents engagement with the rotating wheel, in use. The bolt 131 passes through the frame dropout slot 61 , through a threaded hole in the frame mounting body 1 and is locked by a locking nut 132. Referring to Figure 7, the pivotal connections between the upper and lower arms 3 and 4 and the rear wheel axle support body 2 and the pivotal connection between the resilient bias member and the lower arm are generally similar to those described with respect to figure 3. For the upper arm 3, a socket-headed screw 325 passes through the hole 21 in the rear wheel axle support member 2 and engages with pivot pin 324. Bush 323 is assembled over pivot pin 324 and upper arm 3 is located on bush 323, being secured by a socket-headed screw 321 and retaining cap 322. Likewise lower arm 4 is attached to the rear wheel axle support body 2 by a socket- headed screw 425, pivot pin 424, bushing 423, retaining cap 422 and alum screw 421. The resilient bias member 5 has a mounting which has a barrel-shaped body 431 with diametric hole 432 and axial extension 433. Bush 434 is located on pivot extension 433 and passes into arm 4, being secured by retaining cap 436 and socket-headed screw 435.

In operation the first member 1 is rigidly fixed to the frame 6 of the cycle and the rear wheel is mounted in the slot 23. A force upwardly directed on the rear wheel or downwardly directed on the frame causes the upper and lower arms 3, 4 to rotate clockwise about pivots 31, 41 which causes the spacing between pivots 33 and 43 to tend to decrease. However the action of the resilient means 5 resiliently inhibits such a decrease in spacing and the force exerted by resilient means 5 tends to restore the spacing towards the quiescent state. Thus the resilient rod 5 exerts a restoring force.

Referring to Figures 8 to 10, the modified upper 300 and lower 400 arms have the resilient bias means in the plane of the upper and lower arms. The lower arm 40 has a mounting 501 for the elastomeric rod 50 which is offset from longitudinal axis of arms 400. The rod 50 is secured by rigidly and/or rotary pins 502 and 503. The invention is not limited to the embodiment shown. The suspension assembly may be fitted to a brake bridge for the front wheel of a bike, by engagement with the spindle of the hub of the front wheel. The nature and shape of the particular shock absorbing means may be varied, and the means may be located at a different location on the frame remote from the axle, e.g. on the steerertube.

Claims

1. A bicycle frame including a top tube, a head tube, a down tube, a seat tube, seat stays and chain stays, rear wheel mounting means and front wheel mounting means characterised in that shock damping means are pivotally mounted on the frame above the rear wheel mounting means and/or the front wheel mounting means.

2. A frame according to Claim 1 , wherein the shock damping means is also connected to a bridge for brake members of the respective wheel.

3. A frame according to Claim 2, wherein the brake bridge is connected by a link to an adjacent frame member, and the length of the link is selected to maintain the brake members in substantially fixed relation relative to the wheel when the frame is undergoing shock.

4. A frame according to any preceding Claim, wherein the shock damping means is pivotally mounted on the drop out plates which are the mounting means for the rear wheel.

5. A frame according to Claim 2, 3 or 4, wherein two pivots are present on the drop out plates, one connected to the brake bridge and the other to a shock dampening member.

6. A frame according to Claim 5, wherein the shock dampening member bridges the two pivots.

7. A frame according to any of Claims 1 to 3, wherein the shock dampening means is at a location remote from the wheel axle.

8. A suspension assembly to be fitted to a bicycle the assembly comprising a drop out plate having pivots thereon for mounting of shock damping means.

9. An assembly according to Claim 8, including means to connect the plate to a brake bridge.

10. An assembly according to Claim 8 or 9, adapted to mount shock damping means at a location remote from the drop out plate.

11. An assembly according to Claim 8, adapted to be mounted on the rear wheel.

12. An assembly according to Claim 8, adapted to be mounted on the front wheel.