WO2002038437A1

WO2002038437A1 - Suspension system

Info

Publication number: WO2002038437A1
Application number: PCT/GB2001/004929
Authority: WO
Inventors: Peter Kendall-Torry; Steven Kendall-Torry
Original assignee: Kendall Torry Peter; Kendall Torry Steven
Priority date: 2000-11-09
Filing date: 2001-11-06
Publication date: 2002-05-16
Also published as: AU2002212516A1

Abstract

A suspension system for a bicycle, motorcycle or similar vehicle, includes a pair of forks 1, 2 with a bridge 3 rigidly connecting the upper ends of the forks to extend on opposite sides of a wheel 6. A pair of shock-absorbers 14 and 15 are mounted in front of the forks, having outer casings 16 located on opposite sides of the wheel and inner members 18 which are slidably guided within the casings and connected to the bridge 3 at their upper ends. A brace 22 rigidly connects the casings adjacent to their upper ends, and a pair of link members10, 11, one on each side of the wheel, have leading ends pivotally connected to respective casings and trailing ends pivotally connected to respective forks. The wheel spindle 7 is mounted adjacent to the leading ends of the link members. One of the shock absorbers 15 may be a gas spring and the characteristics of the suspension may be adjusted on the move by means of a pressurising pump 25 incorporating a pressure release valve. The other shock absorber 14 may be an oil damper with an adjustable recovery rate.

Description

SUSPENSION SYSTEM

TECHNICAL FIELD OF THE INVENTION

This invention relates to a suspension system for a vehicle.

BACKGROUND

Numerous suspension systems have been proposed for bicycles, motorcycles and similar vehicles going back many years, but few have successfully balanced the characteristics of providing a smooth ride without prejudicing other important handling characteristics of the vehicle. By way of example, wheel wobble can be a serious problem, and braking can often lead to a dangerous "dive" condition.

The present invention seeks to provide a new and inventive form of suspension system which can provides a smooth ride over a broad range of terrain conditions without prejudicing other important handling characteristics of the vehicle. SUMMARY OF THE INVENTION

The present invention proposes a vehicle which includes:

- a frame having front and rear ends;

- a pair of generally upright forks having upper and lower ends and being mounted from the frame;

- bridging means rigidly connecting said forks adjacent to their upper ends;

- a wheel located between said forks and provided with a wheel spindle;

- a pair of shock-absorbing elements mounted in a generally upright position in front of said forks, the shock absorbing elements having outer casings located on opposite sides of said wheel and inner members which are slidably guided within the casings and connected at their upper end to the forks;

- a brace member rigidly connecting said casings adjacent to their upper ends;

- a pair of link members, one on each side of the wheel, having leading ends which are pivotally connected to respective casings and trailing ends which are pivotally connected to respective forks; and

- a pair of spindle mounts for said wheel spindle located adjacent to said leading ends of said link members.

With such an arrangement stability of the wheel and of the vehicle is greatly improved even under conditions of moderate to severe braking.

The invention further provides a lightweight vehicle which includes:

- a frame including a pair of generally upright forks;

- a wheel located between said forks and provided with a mounting spindle; - a gas spring acting between the mounting spindle and the frame; and

- a control unit mounted remote from the gas spring and connected thereto by a gas conduit, the control unit being manually operable to increase the pressure of gas in the gas spring and incorporating a manually operable pressure-release valve for reducing the gas pressure within the gas spring.

The invention also provides a lightweight vehicle which includes:

- a frame including a pair of generally upright forks;

- a wheel located between said forks and provided with a mounting spindle;

- an oil damper acting between the mounting spindle and the frame, the oil damper including an oil cylinder, a piston rod carrying a piston which is movable within the cylinder, and a variable restriction for controlling the flow of oil past the piston; and

- a control unit mounted remote from the oil damper and being manually operable to vary the size of the restriction within the oil damper such as to vary the damping characteristics of the suspension.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings:

Figure 1 is a front view of a bicycle suspension system in accordance with the invention; Figure 2 is a side view of the suspension system;

Figure 3 is a detailed axial section through the gas spring of the suspension system;

Figure 4 is an axial section through the control valve used with the gas valve; and

Figure 5 is a detailed axial section through the oil damper of the suspension system.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Fig.s 1 and 2, a pair of upright forks 1 , 2 are rigidly joined at their upper ends by a bridge 3. The bridge may be fixed to the frame of a bicycle, tandem, tricycle, trailer or similar lightweight vehicle, but in this example the bridge is connected to a steering column 4 which, in use, is rotatably mounted in a head tube 5 forming part of the frame. A spoked front wheel 6 is mounted between the forks 1 , 2 by means of a spindle 7, opposite ends of which are held in spindle mounts 8 and 9 formed at the leading ends of a pair of links 10 and 11. The trailing ends of the links have independent pivotal connections 12 (Fig. 2) with the lower ends of the forks 1 and 2 such that the wheel can move up and down relative to the forks and the frame.

The leading ends of the links 10 and 11 are coupled to opposite ends of the bridge 3 via respective shock absorbers 14 and 15. Each shock absorber has an outer cylindrical casing 16, the lower end of which is pivotally connected to the respective link 10 or 11. Each casing 16 contains a compression spring which acts against an inner member 18 which is slidably guided within the respective casing. Each inner member projects from the upper end of the respective casing 16 and its upper end is non-slidably fixed to the bridge 3 via a forward-projecting collar 20. Rubber bushes may be interposed between each inner member and the respective collar to permit a small amount of angular movement of the shock absorbers whilst otherwise forming a rigid connection.

A horse shoe shaped brace 22 extends over the upper part of the wheel and is rigidly connected to the upper ends of the respective casings 16 on both sides of the wheel. A pair of brake pads (not shown) may be pivotally mounted from pins 23 and 24 fixed in suitable positions on the brace 22 to act against the opposing sides of the wheel 4 when operated by a brake cable in known manner. During normal movement of the bicycle over rough ground the shock absorbers allow the wheel to move up and down relative to the frame against their internal spring forces. The brace 22 stabilises the wheel to prevent the wheel from twisting and wobbling and ensures that the brake pads are always in the correct position relative to the wheel. The brace also transmits reaction forces between the brake pads and relieves the cylinders of braking forces which could cause distortion of the cylinders and adversely affect the suspension characteristics during heavy braking. The suspension arrangement is therefore very stable even under conditions of heavy braking. The arrangement also counters any tendency for the front of the bicycle to dive during braking. One of the shock-absorbers 15 forms a gas spring which is controllable by a pump unit 25 while the other shock-absorber 14 is an oil damper controllable by a thumb lever or screw 26.

Referring to Fig. 3, the outer casing 16 of the air spring shock absorber15 is closed at its lower end by a bottom end fitting 27. The fitting 27 is slotted to receive the link 11 with pivotal movement about connecting pin 28. A piston rod 29 extends upwardly from the fitting 27 to support a piston 30 within the casing 16. A gas spring cylinder forming the inner member 18 is slidably received within the top of the casing 16 to sealingly receive the piston 30 by virtue of the piston ring 34. A dirt seal 35 is inserted in the top of the casing 16 to slidably locate the cylinder 18, while the lower end of the gas cylinder contains a locating bush 36 which slidably guides the cylinder about the rod 29. The portion of the gas cylinder above the piston 20 forms a compression chamber which is sealed at the upper end by a top fitting 38. This fitting is fixed with the bridge 3 and hence the forks 1 and 2, and contains an axial passage 39 leading to a flexible pipe 40. It will thus be appreciated that the casing 16 and piston 30 are fixed with the wheel spindle so that when the wheel encounters a bump the piston will move upwardly within the gas cylinder 18 compressing the gas space above the piston. In addition, a compression spring 42 is located in the casing 16 acting between the bottom end fitting 27 and the bush 36 to absorb energy upon upward movement of the wheel. The combined energy stored within the spring 42 and the compressed gas within the cylinder 18 will thus tend to urge the piston and casing downwards to restore the wheel to its rest position. The opposite end of the pipe 40 is connected to the pump unit 25, shown in detail in Fig. 4, which is mounted in a position convenient for operation by a rider of the bicycle while the bicycle is moving. The pump unit includes a pump cylinder 48 with a cup-seal piston 49 movable within the cylinder by means of a rod 50 and operating knob 51. Thus, downward movement of the piston 49 forces air through a non-return valve 52 and along the pipe 40 to increase the gas pressure within the gas cylinder 18. Repeated pumping action causes the pressure in the gas cylinder to rise causing a progressive increase in the resistance to upward movement of the wheel and consequent hardening of the suspension. A pressure-release valve 54 mounted in the wall of the pump cylinder 38 is operable by a press-button 55 to release pressure from the cylinder 18 and thus cause a progressive softening of the suspension. Thus, the characteristics of the gas spring suspension can be adjusted by the rider while on the move.

Since the compression spring 42 will always be operable to counter upward movement of the wheel the spring defines a limiting suspension characteristic even if all the pressure is released from the gas cylinder 18.

The oil damper shock absorber 14 provides controlled damping of the spring characteristics of the suspension, principally during the recovery phase. As shown in Fig. 5, the casing 16 of the damper is again closed by a bottom end fitting 57. The fitting 57 is slotted to receive the second link 10 pivoting about a connecting pin 58. An oil cylinder 59 is connected with the fitting 57 sealed by ring 60. A tubular inner member 18 is slidably received within the top of the casing 16 with dirt seal 62 inserted in the top of the casing 16 to slidably locate the tube 18, while the lower end of the tube 18 carries a locating bush 63 which slidably guides the cylinder within casing 16. The upper end of the tube 18 has a top fitting 64 which is fixed with the bridge 3 and holds a hollow piston rod 66 rigid within the tube 16. The piston rod 66 slidably passes through a bush 67 inserted in the top of the oil cylinder 59, sealed by rings 68 and 69. Within the cylinder 59 the rod 66 carries an annular piston head 70 in slidable, but non-sealable contact with the inside of the cylinder 59. The tubular piston rod 66 extends on both sides of the piston head 70 and contains two sets of ports 71 and 72, on opposite sides of the piston. The ports thus provide a primary bypass route for hydraulic fluid, which can thereby flow past the piston through the tubular rod 66. It will therefore be appreciated that the casing 66 and oil cylinder 59 are fixed with the wheel spindle to move upwards with the wheel against a compression spring 73 which acts between the top fitting 64 and bush 67. In so doing, the inner tube 18 and piston rod 66 will remain fixed with the frame so that oil will flow past the piston in the manner described providing relatively free upward movement of the wheel.

The piston rod 66 contains a concentric valve element 74 with the upper end of the rod being sealed by an interposed sliding seal 75. The lower end of the valve element is formed with a tapered needle valve portion 76 which co-operates with a valve orifice formed at the lower end of the rod 66. Operation of the thumb lever 26 moves a cable within a cable sheath to move the valve element 74 axially within the hollow piston rod 66, thereby controlling the flow of fluid through the needle valve. Beneath the piston head 70 the rod 66 carries a sliding annular obturator ring 80, the movement of which is limited by the piston head 70 and an annular flange 81 on the rod 66. When the oil cylinder 59 moves upwards the pressure of oil within the lower part of the cylinder 59 causes the ring 80 to move against the piston head 70 so that oil can bypass the piston as described. However, on the return stroke the oil pressure acts in the opposite direction so that the ring moves over the lower ports 72. Thus, oil can only return from the upper part of the cylinder 59 by flowing through the needle valve, which thus limits the rate at which the wheel can return to the normal ride position assisted by spring 73. Operation of the thumb lever 26 will vary the restriction to oil flow provided by the needle valve and thus permit adjustment of the recovery rate.

Although the suspension system is described with specific reference to a bicycle a similar system could be applied to a motorbike or other vehicle. In a motorbike a variable gas spring can be used to advantage, but the adjustable oil damper may be omitted.

It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.

Claims

1. A vehicle which includes:

- a frame having front and rear ends;

- bridging means rigidly connecting said forks adjacent to their upper ends;

- a wheel located between said forks and provided with a wheel spindle;

- a brace member rigidly connecting said casings adjacent to their upper ends;

2. A vehicle according to Claim 1 , in which the brace member carries a brake assembly for applying a braking force to said wheel.

3. A vehicle according to Claim 1 , in which each casing contains a spring element acting against the inner member.

4. A vehicle according to Claim 1, in which at least one of said shock-absorbing elements includes a gas spring.

5. A vehicle according to Claim 4, including a control unit mounted remote from the gas spring and connected thereto by a gas conduit, the control unit being manually operable to increase the pressure of gas in the gas spring and incorporating a manually operable pressure- release valve for reducing the gas pressure within the gas spring.

6. A vehicle according to Claim 1 , in which at least one of said shock-absorbing elements includes an oil damper.

7. A vehicle according to Claim 6, in which the oil damper includes an oil cylinder, a piston rod carrying a piston which is movable within the cylinder, and a variable restriction for controlling the flow of oil past the piston; and a control unit mounted remote from the oil damper and being manually operable to vary the size of the restriction within the oil damper such as to vary the damping characteristics of the suspension.

8. A vehicle according to Claim 7, in which the variable restriction is formed within the piston rod and is controlled by axial movement of an operating member which is mounted within the piston rod.

9. A vehicle according to Claim 8, in which the operating member co-operates with a restriction fixed with the piston rod to form a needle valve.

10. A vehicle according to Claim 9, in which upward movement of the mounting spindle causes the piston to move against the action of a compression spring and return movement of the piston is controlled by the needle valve.

11. A vehicle according to Claim 10, in which, upon movement of the piston against spring pressure, the oil flows through a bypass orifice which is closed during the return movement.

12. A vehicle according to Claim 11 , in which the bypass orifice is formed in the wall of the piston rod and oil flow through the orifice is controlled by a ring element which slides on the piston rod.

13. A vehicle which includes:

- a frame including a pair of generally upright forks;

- a wheel located between said forks and provided with a mounting spindle;

- a gas spring acting between the mounting spindle and the frame; and

14. A vehicle which includes:

- a frame including a pair of generally upright forks;

- a wheel located between said forks and provided with a mounting spindle;