WO2005113324A1

WO2005113324A1 - A damper device for a spring suspension device for a bicycle wheel

Info

Publication number: WO2005113324A1
Application number: PCT/SE2005/000733
Authority: WO
Inventors: Ulf Johansson
Original assignee: Ulf Johansson
Priority date: 2004-05-24
Filing date: 2005-05-19
Publication date: 2005-12-01
Also published as: SE0401314D0; SE0401314L; SE527105C2

Abstract

A damper device for a spring suspension for a bicycle wheel comprises a fluid-cylinder unit, which is delimited into two chambers (91, 92) by a piston (94). A tubular valve body (31) is coaxially arranged inside a tubular longitudinal section (81) of the piston rod of the cylinder unit and is biased by a spring (35) in the direction upwards toward the piston (94) into an end position (33), wherein a valve cone (38) of the valve body closely screens off a wall opening (32) arranged in the piston rod and situated under the valve body, for the formation of an inertia-sensitive member (31, 35), which temporarily opens a fluid pipe (51) between the fluid chambers (91, 92) upon load from the wheel to the frame, but substantially blocks the fluid pipe in the opposite load direction.

Description

A damper device for a spring-suspension device for a bicycle wheel

The invention relates to a shoc -damper device of the kind that is seen in the preamble of claim 1.

In a bicycle having a spring-suspended wheel, in particular a spring-mounted and shock-dampened front wheel, it is well known that the pedal work exerted by the cyclist against the propulsion mechanism of the bicycle (the bicycle pedals) tends to entail that the wheel suspension is compressed, which means a loss of energy. It is also well known from, for instance, US 6105987, US 2003/0193163, US 2002/0149141 and US 2003/0042087, that it is possible to handle the mentioned the loss of energy by guaranteeing that the damper unit remains integral upon loads from above, but can be compressed during shock damping upon load from below against the wheel, in the direction upwards. This can be attained by arranging, between the cylinder chambers separated by the piston, a pipe that contains an inertia-sensitive valve, which only opens instantaneously upon shocks from below.

The previously known devices are complex and can, there- fore, not simply be sold on an industrial scale and at low costs in bicycles, for instance "mountain bikes".

Therefore, an object of the invention is to provide a damper device that has a simple design and can be manufac- tured as one unit and easily mounted in one forkleg of the front-wheel fork, wherein a suspension spring may be arranged in the other leg of the fork, between the two mutually linearly movable parts of the fork, which are mutually linearly guided and may be of a telescopic charac- ter. Thus, in a preferred embodiment, the damper unit may be in the form of a cylinder assembly, the cylinder part of which is connected to the part of the forkleg fixedly joined to the frame and the downward directed piston-rod end of which is connected to the wheel shaft.

In the following, the invention will be described by way of examples, reference being made to the appended drawing.

Fig. 1 shows schematically a partially cut spring-mounted and damping front fork of a bicycle.

Fig. 2 shows an explanatory outline of one forkleg of the fork including a damper unit positioned therein, in an unloaded state.

Fig. 3 shows schematically the damper unit during the compression stage.

Fig. 4 illustrates the piston of the damper unit including the appurtenant piston rod.

Fig. 5 shows an axial section through the object of fig. 4.

Fig. 6 shows an enlarged detail of the piston part in fig. 5.

Fig. 7 shows an enlarged detail of the inertia-controlled valve in the object of fig. 5.

Fig. 1 shows a front fork 1 of a mountain bicycle. The fork comprises a fork crown 2, which carries two parallel inner legs 4. Two outer legs 5 surround the respective inner leg and are inter-connected by a bridge 6. The front fork has two forklegs 3, between which a bicycle wheel 9 is introduced. In one of the forklegs 3, a spring 98 is positioned and connected between the inner leg and the outer leg. In the other forkleg 3, a hydraulic damper unit 7 is positioned. The damper unit comprises a cylinder, which is joined to the inner leg 4 and is shown to have a piston rod 8 extending through the cylinder, the piston-rod part 81 of which rod protruding downward is connected to the hub 10 of the wheel 9.

In fig. 2, it can be seen that the cylinder 9 contains a piston 94, which defines two chambers 91 and 92. Between the chambers 91, 92, there is a liquid pipe having a restriction and an inertia-controlled valve, whereby liquid from the chamber 91 can flow over under energy absorption upon an axial compression of the damper unit 7, while the valve is open.

The liquid pipe is formed by the fact that the piston rod 8 has a tubular longitudinal section that extends through the piston 94, the tubular section of the piston rod 8 having wall openings 74 above the piston 94 and openings 32 under the piston, as can be seen in figs. 6 and 7. A tubular valve cone is coaxially arranged in the piston-rod part 81 and is axially biased by a spring 35 in the direction of the piston 94, and has an upper end position defined by a stop 33. With the upper circumference part thereof, the tubular valve body 31 forms a valve cone 38, which in the end position closely screens off the openings 32. The valve body 31 has a through axial channel. The spring 35 is adjusted to the mass of the valve body 31 in order to guarantee that a shock from below of chosen size, via the wheel against the lower end of the piston-rod part 81, entails that the valve body 31 experiences a motion downward in relation to the piston rod 8 and exposes the openings 32, during a certain period of time, before the valve body 31 is brought back into the end position by the spring 35. While the valve device 31, 32, 33 is kept open, hydraulic fluid in the compressed chamber 91 can flow via the openings 74 and the hollow space in the piston rod 8, and out through the openings 32 of the chamber 92. Adjacent to the openings 74, a restriction cylinder 71 is shown, which is axially displaceable by a threaded joint between the body 71 and the inner wall of the piston rod 8 for the estab- lishment of a corresponding damping (shock-energy discharge) . The cylinder 71 has a driver 73 and may be adjusted into a selected axial position in order to partially screen off the openings 74, and in this way offer a limited restricted flowing through of hydraulic fluid. The body 71 is shown to have a driver 73, in which an adjusting tool can be inserted via the tubular piston-rod part 82. By the restriction adjacent to the opening 74, a shock damping is attained. Upon such a damping-liquid overflow into the chamber 92, the suspension spring is compressed. After the shock-damping operation, the damping spring is relieved and aims to bring back the damper unit to the state shown in fig. 2. For that sake, the piston 94 has a throughput channel 51, which is provided with a non-return valve 52, which at a selected pressure drop over the piston 94" opens and allows liquid overflow from the chamber 92 into the chamber

91. The non-return valve 52 is shown to be composed of a resiliently elastic plate 53, which screens off the channel 51 and is biased to the screening position by means of a support washer 54, which is loaded by a spring 55, which supports against a spring washer 60, which is axially displaceable by a screw 56, which is situated inside the piston-rod part 82 and co-operates with the interior wall thereof via a threaded joint 57. The body 56 is joined to a rod 58, which extends through the outer end of the piston- rod part 82 and which extends out of the cylinder 9, whereby the bias of the spring 55 simply may be adjusted.

A pressure-relief valve 63 is provided in connection with a channel 51 in order to, at high compression pressures in the chamber 91, allow an overflow through the non-return valve 63 into the chamber 92 at a pre-determined pressure difference over the piston 94. Once again, the non-return valve 63 contains a plate ring 62, which is biased to a sealing position by a support washer 64 in a biased spring 41, which is carried on the rod part 81 by means of a support washer 42.

The spring 41 generates the pressure difference by which the pressure-relief valve/the non-return valve 62 opens for the protection of seals between the cylinder and the piston rod/piston.

Reference being made to fig. 5, where it further can be seen that the tubular piston-rod part 81 has a sealing plug 38, which carries a support 36 for the spring 35. The plug 38 is connected to the piston-rod part 81, for instance by a threaded joint 37, in order to allow the plug and thereby the support 36 to be displaced away from the piston 94, so that the spring 35 is relieved and the valve piston 31 can be displaced away from the stop 33, whereby the adjustment of the non-return valve 52 is facilitated.

Claims

1. Damper device for a spring-suspension device for a bicycle wheel, the suspension device comprising two line- arly displaceable parts (45) , one of which carries the bicycle wheel (9) and the other is connected to the bicycle frame and a suspension spring (98) being connected between said mutually displaceable parts of the suspension device, and the damper device comprising a fluid-cylinder unit embracing a cylinder part (9) , which contains a piston (94) that in the cylinder part (9) defines two fluid chambers (91, 92) , and a piston rod (8) connected to the piston (94) , which rod extends out of the cylinder part (9) , the damper device being connected between the two mutually dis- placeable parts (4, 5) of the suspension device, the damper device comprising inertia-sensitive members (31-35) in order to substantially block the cylinder unit upon load from the bicycle frame in the direction of the wheel and in order to temporarily open a restricted fluid pipe (51) between the fluid chambers (91, 92) upon load from the wheel to the frame, the damper device being compressed and the suspension spring (98) being given an enhanced load and the damper device comprising members (52, 55) for controlled transfer of fluid between the chambers, for the expansion of the damper device under the impact of the load-relieving of the suspension spring (98) after shock load, characterized in that the piston rod (8) has a tubular longitudinal section (81) , which extends downward from the piston and which is sealed in the two ends thereof and which extends through the piston, that the tubular wall of the piston rod has through openings (74, 32) near the piston (94) , underneath the piston (94) , as well as above the piston, and that a tubular valve body (31) is coaxially arranged inside the tubular longitudinal section (81) of the piston rod and is spring-biased by a spring (35) in the direction upwards toward the piston (94) into an end position (33) , wherein a valve cone (38) of the valve body closely screens off the wall opening (32) of the piston rod located under the piston, in order to form the inertia-sensitive member.

2. Device according to claim 1, characterized in that the member (51, 52) for controlled transfer of fluid between the fluid chambers of the cylinder comprises a nonreturn valve (52) in a fluid channel (51) through the piston.

3. Device according to claim 2, characterized in that the non-return valve (52) is loaded in order to open in the flow-line direction at a pre-determined pressure difference over the non-return valve.

4. Device according to claim 3, characterized in that the spring bias (55) of the non-return valve is arranged adjustable by means of a set screw, that the piston rod (8) extends upwards from the piston (94) and out of the cylin- der (9) and has a coaxial shank (58) , which extends upwards through the piston rod (8) and is rotatable for the adjustment of the spring loading of the non-return valve by the rotation of the set screw (56) , which is connected to the piston rod (8) via a threaded joint (57) being coaxial therewith.

5. Device according to any one of claims 1-4, characterized in that a pressure-relief valve (62) is arranged in a fluid pipe (51) through the piston, for the limitation of the pressure in the cylinder upon a strong shock-like compression load of the damper unit.

6. Device according to claim 1, characterized in that the bias spring (35) of the valve body (31) is carried by a plug (38) that is displaceable in the direction away from the piston rod (8) , for the transfer of the valve body (31) into the open position.