GB2385568A

GB2385568A - Unitary slider for cycle suspension fork

Info

Publication number: GB2385568A
Application number: GB0204360A
Authority: GB
Inventors: Adrian John Carter
Original assignee: PACE CYCLES Ltd
Current assignee: PACE CYCLES Ltd
Priority date: 2002-02-26
Filing date: 2002-02-26
Publication date: 2003-08-27
Anticipated expiration: 2022-02-26
Also published as: GB0204360D0; GB2385568B

Abstract

The unitary slider 102, comprises a hollow cross brace 112 and hollow first and second legs or leg parts 114, 116. The legs can have integrally moulded on wheel axle dropouts 122, 124. The slider body can be of carbon fibre and optionally comprises an internal skeleton of aluminium, titanium or magnesium. The slider legs accept upper legs 106, 108 of the fork and house shock absorbing suspension elements, e.g. metal, pneumatic or eleastomer springs with hydraulic damping elements.

Description

Suspension Fork and Part The present invention relates to suspension forks and parts therefore, and in particular to a slider part of a suspension fork for cycles.

Suspension forks are provided for the front wheels of cycles (including bicycles and tricycles, and both pedal and motor powered) to provide improved comfort and handling for a rider over rough surfaces. A suspension fork must be sufficiently stiff and robust to be able to withstand a diverse range of loads during use. It is also advantageous if cycle components are of relatively light weight, particularly for use in racing. However, increased robustness tends to incur increased weight and vice versa.

Suspension forks have been provided with a lower slider assembly with a solid brace connecting a pair of lower slider legs. The slider is often die-cast or forged using magnesium or aluminium alloy as a single piece, but the brace is solid thereby adding to the unsprung weight of the slider and therefore suspension fork.

It would therefore be advantageous to be able to provide a light weight yet sufficiently robust suspension fork.

According to a first aspect of the present invention, there is provided a unitary hollow slider for a suspension fork, the slider comprising a brace, a first leg part and a second leg part.

A hollow brace and leg part renders the slider very light and the unitary construction of the brace and leg part provides the required strength.

The unitary construction also obviates the problems of using a hollow brace to which slider legs are attached which requires more parts, and so the slider is therefore heavier, more costly and difficult to manufacture and also the joints can suffer from fatigue or not be able to provide the structural stiffness required. Also the joints can lead to the ingress of dirt which can corrode and damage the slider assembly.

The first leg part can provide a first leg and the second leg part can provide a second leg. By extending the leg parts to provide the whole of the legs of the slider, a more simple slider can be provided which also addresses a number of the problems mentioned above.

Each leg can have an integral formation at a lower end for receiving an axle of a wheel. Moulding drop outs into the bottom part of the legs provides a complete slider part for a suspension fork without requiring any ancillary fixtures or fittings.

Preferably the slider is moulded. Providing the slider as a moulded item provides a simple way of manufacturing the unitary hollow construction of the slider.

Preferably, the inner diameter of the brace is less than the inner diameter of the leg parts. This helps to allow the geometry of the brace to fit within the constraints imposed by other parts of the suspension fork or cycle on which the slider is to be used.

The slider can be made of a non-metallic material.

Preferably the slider is made of carbon fibre and most preferably it is made entirely of carbon fibre.

The slider can include a first lower leg element attached to the first leg part to provide a first leg and a second lower leg element attached to the second leg part to provide a second leg. As the lower leg parts are not connected directly to the hollow bridge, the slider of the present invention can provide the necessary stiffness and strength.

The first and second lower leg elements can be made of metal or carbon fibre. The leg elements can be solid or hollow.

If solid, then suspension elements are located in the hollow slider leg parts.

The leg part of the slider can have a wall thickness greater than the thickness of the wall of a lower part of the leg.

By using lower leg parts with thinner walls, the weight of the slider is reduced while the slider still has sufficient strength.

The slider can include an internal supporting skeleton and a body. In this way the body can be reduced in mass compared to the case where no skeleton is present and the skeleton can provide both an inner mould for manufacture and provide structural support for the body. The skeleton can be of a different material to the body. The skeleton can be of a light weight, high strength metal such as aluminium, titanium or magnesium, or similar.

According to further aspects of the invention there is provided a suspension fork comprising a fork and a slider according to the first aspect of the invention and a cycle including such a suspension fork.

According to a further aspect of the invention, there is provided a method of manufacturing a unitary hollow slider body for a suspension fork comprising the step of moulding the slider body. Moulding provides a convenient way of

producing a unitary body which is also hollow in one step process.

Preferably slider body is moulded using carbon fibre, and more preferably using entirely carbon fibre. The method can include the step of arranging carbon fibres with an orientation selected to increase the strength and stiffness of the slider.

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows a front view of a suspension fork including a slider part both according to aspects of the invention; Figure 2 shows a side view of a front part of a bicycle including the suspension fork shown in Figure 1 and according to an aspect of the invention; Figure 3 shows a partially cut-away perspective view of the rear of the suspension fork of Figure 1 ; Figure 4 shows a partially cut-away side view of the suspension fork of Figure 1; Figure 5 shows a perspective view of an alternative slider part according to the invention; and Figure 6 shows a perspective view of another alternative slider part according to the invention.

Similar items in different Figures share common reference numerals unless indicated otherwise.

With reference to Figures 1 and 2, there is shown a suspension fork 100 and a front part 200 of a bicycle including such a suspension fork. The suspension fork is particularly suitable for mountain or off-road bicycles, but

can also be used on other types of cycles, including tricycles and pedal and motor powered cycles. The suspension fork has an upper fork part 101 and a lower slider part 102.

The upper fork 101 includes a steerer tube 103 connected to a crown 104 to which first 106 and second 108 upper legs are joined. The steerer tube 103 is a right circular aluminium tube. The crown 104 is an aluminium member that has been produced from a billet. Upper legs 106 and 108 are each right circular metal tubes having a low friction outer coating.

The slider part 102 includes a slider body 110. The slider body is a single, hollow, moulded carbon fibre part having a unitary construction and includes a brace element 112 connecting a first lower leg element 114 and a second lower leg element 116. Lower leg elements 114 and 116 have a right circular tubular shape over a lower portion and smoothly morph into the tubular brace element 112 which has a more complex geometry. First and second metal end cap elements 118 and 120 have a generally right circular cup like shape into which a free end of a respective lower slider leg is received. Each end cap has an integral dropout 122,124 downwardly depending therefrom and into which a part of an axle of a bicycle wheel can be received.

Figure 2 shows a front part of a bicycle 200 including a top tube 210 and a down tube 212 connected to a head tube 214.

Top and bottom bearings 216,218 of a headset surround the steerer tube which is received within the head tube 214. A stem 220 connects a handle bar 222 to the top end of the steerer tube attaching and securing the suspension fork 100 to the bicycle. A wheel 224 is mounted on a hub having an axle 226 passing there through. The wheel is received

between the legs 114,116 of the slider and the axle is attached to, and secured in, the drop outs at the bottom ends of the fork.

The suspension fork 100 is shown in more detail with cut away portions in Figures 3 and 4.

The slider 110 has an internal cavity which extends continuously along the entire length of the slider from the bottom of one leg, through the brace and to the bottom of the other leg.

Each leg of the suspension fork 100 is composite and comprises the upper leg and the lower slider leg. The upper legs 106,108 are received within the hollow lower slider legs 114,116. An upper end of each slider leg includes an aperture 130,130', 132,132'adapted to receive a respective upper leg. A top part of the slider leg wall 134 includes a recess into which an annular wiper seal 136 is located. Upper and lower annular bearings 138,138', 140, 140'are also provided through which the upper legs can slide. A connector element 142,142'is also provided in each leg and connects the upper legs and lower slider legs to prevent the upper legs and slider from separating.

The interior of slider legs also houses shock absorbing suspension elements, which are not shown for the sake of clarity. The shock absorbing element can include mechanical springs, e. g. metal or elastomer springs, and/or pneumatic springs in addition to hydraulic damping elements as are well known.

In use, the slider element slides over, and relative to, the upper legs in a direction parallel to the longitudinal axis of the suspension fork legs. The suspension elements

act to absorb shocks when the fork is compressed or to return the slider when the fork is extended, thereby providing shock absorption for a rider.

In use, loads of a complex and compound nature are applied to the slider. These loads may try to force lower fork legs 114,116 to deflect, distort or slide independently of each other, whereas the ideal response of the slider is for it to slide and travel as one integral unit with the minimum of independent leg movement. The brace 112 which connects the lower legs of the slider resists these loads and minimises their effect. The brace has a complex geometry determined by a number of factors. It should maintain as large a cross section as possible within the parameters created by other surrounding components such as the fork crown 104, bearing 218, any brake mountings, front wheel clearance 224 and down tube 212. The latter is relevant in an alternative embodiment in which the brace passes over the wheel to the other side of the upper legs compared to the side as shown in Figure 2.

The cavity 146 within the brace has a smaller internal diameter than the internal diameter of the cavity in the slider legs 114,116. The internal diameter of the lower legs is sufficient to accommodate the bearings, seal, suspension elements and the outer diameter of the upper fork legs.

The brace cavity can become partially or wholly sealed from the fork leg cavity during a suspension fork assembly process as elements of the upper legs, bearings or seals are added to the slider unit.

In a region 148,148'toward an upper end of each slider leg, the tube of the slider body bifurcates into the reduced

inner diameter brace part and into the top part of the slider leg resulting in the apertures 130,130'and 132, 132'for receiving the upper legs. As shown in Figure 4, an upper part of the lower leg has a wall 150 thicker than the wall of the lower part of the slider leg over a region so as to provide increased stiffness and strength in the region where the brace and the upper part of the slider legs meet.

Figures 5 and 6 show alternative sliders 160 and 180. The brace 162 of slider body 160 is similar to the brace of slider body 110. However the slider leg parts 164,166 are truncated compared to the slider legs 116,114 of slider 110. Leg parts 166 and 164 of slider 160 corresponds substantially to the bifurcation region 148 of slider 110.

The lower legs of the slider are completed by adding tubular lower leg sections or elements to the upper parts 166,164 of the lower legs. The thickness of the walls of the leg parts 166,164 is greater than the thickness of the lower leg sections so as to improve the strength of the area where the brace and legs meet.

The unitary construction and hollow brace of the slider body provide a light weight structure and sufficient stiffness for the total slider assembly. As the lower leg parts are not connected in a region directly adjacent the brace element, but rather to a leg part of the slider assembly, the stresses placed on the joints between the lower leg sections and the slider body are reduced and therefore a sufficiently robust and fatigue resistant slider can be provided.

Slider 180 is substantially similar to slider 110 and shares features of slider 110 and 160. Slider 180 also includes integral carbon fibre drop-outs 182, 182'for attaching a bicycle wheel.

Sliders 110,160, 180 are all made of carbon fibre by using a moulding manufacturing process. The slider bodies are manufactured using composite materials and techniques so that the slider body is formed as a single piece. An external mould provides for the external shape while accurate inner moulds create the inner cavity. The cavity can be produced through combining one or more techniques to support the inner wall during the manufacturing process.

The inner support mould may itself be tubular and become an integral part of the slider so that the slider has a composite structure comprising an inner skeleton provided by the support about which the carbon fibre body is disposed.

The composite carbon fibres of the structure are layered and oriented so as to add additional strength and stiffness to the tubular structure and the resin system which binds the fibres and thus the structure into a single unit also provides further mechanical strength and rigidity. When the external parts, and optionally the internal parts, of the mould are removed the slider body is released as a single piece which does not require the addition of supplementary structural parts.

It will be appreciated that the invention is not intended to be limited to the specific slider bodies shown in the Figures. Features described with respect to one of the specific sliders can be combined with features of another of the sliders as will be appreciated by a person of ordinary skill in this art. While the slider body has been described as a carbon fibre or carbon fibre composite item, it will be appreciated that the slider body can be made of any suitable advanced engineering material or composite material susceptible to manufacture by moulding or other forming processes, such as ceramic materials.

Claims

CLAIMS: 1. A unitary hollow slider for a suspension fork, the slider comprising a brace, a first leg part and a second leg part.
2. A slider as claimed in claim 1, in which the first leg part provides a first leg and the second leg part provides a second leg.
3. A slider as claimed in claim 1 or claim 2, in which the slider is moulded.
4. A slider as claimed in claim any preceding claim, in which the inner diameter of the brace is less than the inner diameter of the leg parts.
5. A slider as claimed in any preceding claim in which the slider is made of carbon fibre.
6. A slider as claimed in claim 1, in which the slider includes a first leg element attached to the first leg part to provide a first leg and a second leg element attached to the second leg part to provide a second leg.
7. A slider as claimed in claim 2 or 6, in which the leg part has a wall thickness greater than the thickness of the wall of a lower part of the leg.
8. A slider as claimed in claim 2, in which each leg has an integral formation at a lower end for receiving an axle of a wheel.
9. A slider as claimed in any preceding claim in which the slider comprises an internal skeleton and a body.

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10. A suspension fork comprising a fork and a slider as claimed in any preceding claim.
11. A cycle including a suspension fork as claimed in claim 10.
12. A method of manufacturing a unitary hollow slider body for a suspension fork comprising the step of moulding the body.
13. A method as claimed in claim 12, in which the slider body is moulded using carbon fibre and including the step of arranging carbon fibres with an orientation selected to increase the strength of the slider.
14. A unitary hollow slider substantially as hereinbefore described.
15. A method of manufacturing a unitary, hollow slider substantially as hereinbefore described.