Technical Field ^"

This invention relates to a multiple-speed cycle gear hub and to a cycle incorporating the same.

Background Art Multiple-speed gear mechanisms for use in transmission from the pedals to the rear wheel of a cycle fall broadly into two types, the encased gear hub and the Derailleur gear. The number of gear ratios obtainable with the former is relatively limited and in order to change gear it is necessary to reduce drive pressure temporarily while the gear selector mechanism is operated. A Derailleur gear can provide a greater number of available gear ratios and also makes it possible to change gear quickly without any substantial interruption in the pedalling. action- Thus, even though a Derailleur gear is not as quiet and as smooth as an encased gear hub it is usually preferred by racing cyclists and touring cyclists.

The touring cyclist particularly requires a wide overall range of gears with small changes of ratio between successive gears. A normal Derailleur gear system can provide either a wide range or close ratios, -yλTHEAy

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but not both. There is a practical maximum width of the gear and chain blocks, of about six gear sprockets, beyond which at extreme ends of the gear ranges the transmission chain is very far out of.alignment with 5 the sprocket and chain wheel teeth. This makes for adjustment difficulties and for rapid wear of the chain. If the sprockets on the gear block are bunched more closely together to try and minimise, the axial block width then difficulty in gear selection is introduced

10 as the chain tends either to bind against the next adjacent larger sprocket or to climb off onto the next adjacent smaller sprocket. Attempts have been made to overcome this problem and to multiply the number of speeds available from the Derailleur mechanism by

15 combining it with the traditional multiple-speed encased gear hub. However the traditional encased hub is relatively cumbersome and the axial width of the resulting combined hub and Derailleur block has been unacceptable in view of the fact that the rear

20 wheel must be very considerably dished in order to accommodate the mechanism and is potentially liable to failure under stress.

Disclosure Of Invention

According to the present invention a multiple-

25 speed cycle gear hub comprises a hub casing, a drive input member one end of which projects from the casing and is adapted to receive a multiple sprocket Derailleur gear block, a clutch member within the casing mounted to rotate with and be axially slidable relative to the

30 drive input member to at least first and second positions, in the first of which drive is transmitted from the clutch member to the hub casing without being transmitted through any internal gear train of the hub and in the second of which drive is transmitted from the

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clutch member throug an internal gear train to the hub casing.

Preferably, the hub itself is devoid of any freewheel ratchet mechanism, the Derailleur gear block incorporating any necessary freewheel mechanism."

With such a construction, the number .of speeds available, from the encased. gear hub will multiply the number of gears available from a Derailleur block fitted to the drive input member. If the encased hub incorporates no freewheel, ratchet mechanism it can be made much more compact radially than in traditional designs, and by restricting the gear hub to a small number of ratios, e.g. two, it may be made much more compact axially. The presence of the multiple-speed hub means that the Derailleur block does not need to accommodate the very large gap between top and bottom gear which would otherwise be necessary if that block alone were used and the sprockets on the block' can thus be made of closer ratio. The problem of chain misalignment may be overcome by restricting the number of sprockets to five or six and the disadvantages of a dished wheel are reduced or obviated by the.hub construction which allows even spoke tension to be obtained. . The combination provides the cyclist with the desired wide range of closely spaced but. properly usable gear ratios. It does not preclude the use of multiple chain wheels and with these added to the combination an even greater spread of gears is made available. The invention also extends to a cycle having a drive mechanism which comprises a wheel incorporating a multiple-speed gear hub as set forth above, a Derailleur gear block mounted on the drive input member to rotate therewith, pedals and a chain wheel and a chain for transmitting drive from the chain wheel to

the Derailleur gear block.

Brief Description Of Drawing

The sole Figure of the accompanying drawing is a schematic representation, partly sectioned, of a gear hub according to the invention.

Best Mode Of Carrying Out The Invention

The drawing shows, a hub that forms the central part of a cycle wheel, for example the wheel of a bicycle or a tricycle.. Neither.the cycle nor the wheel is shown in detail, but it will be seen from the drawing that spokes 1 radiate from the axially opposite flanges 2 and 3 of a hub casing 4. The spokes radiating from the flange 2 are longer than those radiating from the flange 3 and this compensates for the wheel being dished, i.e. having the rim offset axially from the hub mid-point to accommodate the width of the hub, allowing even spoke tension to be obtained. A hollow, tubular central axle 5 extends axially through the hub casing 4 and has externally threaded end regions 6 and 7 for securing the axle between the forks of the cycle frame in conventional manner. The axle supports bearing ■ elements 8 and 9 adjacent to opposite ends thereof, these elements being held in position by nuts- 10 and 11 engaging oppositely threaded sections of the axle. Ball-bearings 12 ride on the bearing element 8 and on a support member 13 screw threaded .into one end of the hub casing, the balls 12 thus supporting that end of the hub casing for rotation about the axle.

A further series of balls 14 run on the bearing element 9 and support an axial extension 15.of a drive input member shown generally as 16 so that the drive input member may rotate relative to the axle. The drive input member has an intermediate flange 17. The

axial extension 15 projects from this flange and has an externally threaded surface 18 to which.may be fitted a conventional multi-sprocket Derailleur block shown in broken outline as 19. It will be appreciated that any conventional block having any desired number of sprockets may be used and that methods of fitting the block to the axial extension 15 other than by way of screw threads may be employed.

On the opposite side of the flange 17 from the axial projection 15 the drive input member has a bearing section 20 which supports balls also running in contact with a support 22 screw threaded into the end of the hub casing 4 adjacent -to the flange 3. The hub casing is thus supported on the bearing section 16 in a manner allowing relative rotation between the two elements. At least two pins 23, 24 project from the bearing section 16 into the hub casing. These pins engage within grooves or holes formed in a clutch member shown generally as 25 which is formed with four diametrically opposed radially outwardly projecting dogs, two of which are shown in the drawing, 26 and 27. The clutch member is supported for rotation by a bearing 28 on a bush 29 surrounding /and axially slidable on the axle 5. A compression spring 31 bears on the bush 29 and urges the clutch 25 to the left as seen in the drawing. A pin 31 is secured to the bush 29 and extends through a slot 32 in the axle. The pin 31 is carried at the end of a rod 33 which is axially slidable within the hollow axle and connected in conventional manner by a cable to a lever under the control of the cyclist.

The hub houses a planetary gear train therein, comprising a sun wheel 34 secured to the fixed axle 5. Planet wheels 35 and 36 in mesh with the sun wheel are rotatably mounted by bearings on respective shafts 37

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and 38 extending from a carrier 39 rotatahle about the axis 5 and secured to the hub casing 4 -by screw threads 40. An annular gear.41 has internally formed sprockets in mesh with the planet wheels 35 and 36 and fits axially between the carrier 39 and the support 22. Adjacent to the support 22 the annular gear is formed with at least two radially inwardly projecting dogs 42 and 43 respectively. The internal gears within the hub are in constant mesh and, apart from slight axial tolerance on the annular gear 41, do not alter their relative radial or axial distances from one another at any time during the operation of the hub-

In the position shown in the Figure the clutch 25 has been moved to the right to compress the spring 30 by moving the rod 33 to the right under control of the cyclist. In this position the dogs 26 to 27 on the clutch engage against the dogs 42 and 43 on the annular gear 41. Drive to the Derailleur sprocket 19 is thus transmitted to the drive input member 16, to the clutch by virtue of the engagement-of the pins 24 in the grooves or holes of the clutch, to the annular gear 41 by virtue of the dog engagement, to the planet wheels 35 and 36 and thence to the carrier 39 to the hub casing 4 and wheel. Drive is thus through the fixed gear train, the gearing thereof being designed to give whatever transmission ratio is required. A particularly convenient ratio is a 2:1 reduction, to achieve which the annular gear 41 will be formed with twice as many teeth as the sun wheel 34. In the other condition of operation of the gear hub the rod 33 is released allowing the spring 30 to move the clutch 25 to the left as seen in the drawing, into a limit position wherein the pin 31 contacts the end of the slot 32. During this movement the dogs 26, 27 of the clutch move out of engagement with the. dogs 42, 43 of the

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annular gear and slide axially into a position where they engage the shafts 37, 38 carrying the planet wheels 35 and 36. In this position drive from the input member 16 is transmitted directly to the carrier 39, bypassing the gear train, and is .thus transmitted directly to the hub casing 4 and the wheel. The drive from the Derailleur gear sprocket to the wheel is thus in a 1:1 ratio. It will be particularly noted that the gear arrangement within the hub is devoid of any freewheel mechanism and is a siαnple two-speed gear selectable by axial movement of the clutch member 25. This simplicity enables the hub gear to be made extremely compact with a minimum of dishing of the cycle wheel. In either position of the clutch the position of the chain on the Derailleur sprocket may be changed at will by the cyclist.

It will be appreciated that many modifications can be made to the illustrated mechanism, which still fall within the scope of the invention. In particular, there are many ways in which the clutch arrangement could be modified and different types of gear train could be utilised.

Industrial Applicability

The invention is applicable to cycle hubs which can be used in the drive assembly of any type of bicycle or tricycle.