GB2207966A

GB2207966A - Epicyclic change-speed gear

Info

Publication number: GB2207966A
Application number: GB08813362A
Authority: GB
Inventors: Anthony William Hillyer
Original assignee: Sturmey Archer Ltd
Current assignee: Sturmey Archer Ltd
Priority date: 1987-06-05
Filing date: 1988-06-06
Publication date: 1989-02-15
Anticipated expiration: 2008-06-06
Also published as: GB2207966B; DE3819065C2; GB8813362D0; DE3819065A1; GB8713238D0

Description

1 EPICYCLIC CHANGE-SPEED GEAR 2 U 7 9 6 0' MECHANISM The invention

concerns epicyclic change-speed gear assemblies, and has more particular reference to such assemblies having a back-pedal brake arrangement incorporated therein.

Epicyclic change-speed gear assemblies for cycles are known in which the motion of a driver is selectively transmitted to a planet cage or to an annulus by means of a selector means, the motion of such planet cage or annulus being utilised to provide an output drive to a wheel hub.

In conventional change-speed gear hubs of the aforesaid kind the drive transmission path between the driver and hub may be interrupted during gear change, with attendant risk to the rider.

Conventional epicyclic change-speed gear hubs as aforesaid frequently incorporate a back-pedal brake arrangement, but is the effectiveness of the brake arrangement may not be constant.

For example, the braking action at any given instant is determined by the gear setting selected, being greater in normal and low gear setting than in high gear setting. A further disadvantage is that it is possible, in certain circumstances, for the assembly to be so adjusted, for instance when the gear selection mechanism is between high and normal gear setting, that no braking action results from applying a back pressure to the driving pedals.

The primary object of the invention is to provide a change-speed gear hub having a back-pedal brake arrangement which provides for uniformity of braking action in all situations and which is free from the inherent disadvantage of conventional such hubs as r is regards possible interruption of drive transmission during gear change or as a result of maladjustment.

In its broadest sense the present invention proposes a change-speed gear hub for a bicycle, tricycle or the like, said hub incorporating a back-pedal brake arrangement and comprising an epicyclic gear disposed within a hub shell, and drive input means manually adjustably connectable with said hub shell via a selected one of multiple drive transmission paths through an element or elements of said epicyclic gear for forward drive motion of the hub shell on movement of the drive input means in a first direction and connectable with the brake arrangement via a predetermined drive transmission path through the said epicyclic gear for braking action on movement of the drive input means in a second direction opposite to said first direction, characterised by a bi-directional paw[ and ratchet mechanism intermediate said drive input means and the annulus of the epicyclic gear, the said pawl and ratchet mechanism being capable of transmitting a motion between the drive input means and annulus on movement of the input means in said first direction and adapted to transmit a motion therebetween on movement of the input means in said second direction.

According to another aspect of the invention there is proposed an epicyclic change-speed gear hub for a bicycle, tricycle or the like comprising a hub shell, an epicyclic gear, including a sun gear, an annulus coaxial and radially aligned with the said sun gear, a planet cage likewise coaxial with the sun gear and a plurality of planet gears rotatably mounted in said planet cage and in mesh 3 - with said sun gear and with said annulus, disposed within said hub shell, respective unidirectional clutch means intermediate said hub shell and said annulus and planet cage, a driver adapted to receive an input drive, manually adjustable selector means drivingly connected with said driver and selectively drivingly engageable with said planet cage and said annulus, and further including a back-pedal brake arrangement operable through the epicyclic gear, characterised by a supplementary pawl and ratchet means interconnecting said driver and said annulus and drivingly connectable with said annulus to transmit a drive motion thereto in either direction thereof.

According to a preferred feature of the invention the said brake actuating mechanism includes a pawl and ratchet means and means whereby the pawl is adapted to be tripped whilst the assembly is in driving condition, at least in high gear, and by the provision of means adapted to ensure the selector sleeve is drivingly disengaged from the planet cage during braking, the said pawl and ratchet means being formed integrally with the supplementary pawl and ratchet means aforesaid.

The invention will now be described further, by way of example only, with reference to the accompanying drawings, illustrating one embodiment thereof and in which: - Fig. 1 is a longitudinal section through an epicyclic gear assembly according to the invention, the upper and lower halves of the drawing showing the assembly in high gear and low gear respectively; Figure 2 Figure 3 Figure 4 Figures 5 + 6 5.

Figure 7 is a section along line 11-11 of Figure 1; is a section taken along fine Ill-iif of Figure 1; is a section along line IV-IV of Figure 1; correspond to Figures 1 and 2, and show an alternative embodiment; and is an exploded perspective view showing various of the elements of the alternative embodiment.

Referring now to the drawings, and particularly to Figures 1 to 4 thereof, a change-speed gear assembly comprises a wheel hub 11 10. within which are disposed a driver 12 mounted for rotation about the axis of a fixed wheel spindle 13, a selector sleeve 14 mounted upon said spindle 13 and adapted to be actuated axially thereof by a control rod 15, a fixed sun gear 16 on said spindle 13, a multiplicity of planet gears 17 supported in a planet cage 18 and in engagement with 15. said sun gear 16, the said cage 18 being mounted for free rotational motion about the spindle 13, an annulus 19 disposed radially outwardly of the planet gears and having gear teeth at the inner radius thereof in engagement with the planet gears 17, a pawl and ratchet means 20 for high and normal gears between the annulus 19 and the wheel hub 20. 11, and a pawl and ratchet means 24 for low gear between a brake cone 21 in screw-threaded engagement with an axial extension to the planet cage 18 and the wheel hub 11. The brake cone is adapted, upon relative rotational motion between the brake cone 21 and the planet cage 18 in the appropriate direction, to cause a brake lining 22 to move into friction engagement with a brake drum 23 and brake actuating means 25 are provided within the hub 11 whereby the brake 1 P t' cone 21 may be caused so to move, by rotation of the'annulus 19 and planet cage 18, as to bring the lining into the said frictional engagement. The selector sleeve 14, whilst being in engagement with the driver 12 may not necessarily be in engagement with the planet cage 18 or the annulus 19.

The driver 12 has an axially directed through bore and such bore is provided with internal splines 26, and further includes pawls 27 pivotally mounted in respective pockets therein for engagement with internal ratchet teeth 28 provided on the annulus 19. The pawls 10. 27 are ordinarily loaded into engagement with ratchet teeth 28 in a manner to transmit a drive thereto in the forward direction thereof by spring means (not shown).

Planet pins 29 whereby the individual planet gears 17 are rotatably mounted in the planet cage 18 extend axially from such cage in a 15. direction towards the driver 12 and are engageable with internal dogs 30 formed at the innermost end of the selector sleeve 14, whilst the outermost end of the sleeve is provided with splines 31 to engage splines 26 formed on the driver.

A return spring 33 is disposed coaxially with the spindle 13 and 20. extends between the nose 34 of a fixed bearing cone 35 and a clutch key 36 in engagement with the selector sleeve.

The operation of the epicyclic gear assembly thus far described is as follows:- With the relative disposition of parts shown in the upper part of 25. the various Figures of the drawings, such disposition corresponding to the high gear condition of the assembly, rotation of a chain sprocket 6 - 37 connected with the driver 12 in a forward direction will cause the planet cage 18 to be rotated by virtue of the engagement of the selector sleeve 14 with, on the one hand, the driver 12 and, on the other hand, the ends of the planet pins 29 extending from the said cage 18, and thus the annulus 19 will rotate. Rotation of the annulus 19 will, through ratchet means 20, impart the desired motion to the hub and thus the drive is effected.

In the high gear condition of the hub the annulus 19 will be moving faster than the driver and thus ratchet teeth 28 will be 10. overrunning the pawls 27.

To engage normal or middle gear the selector sleeve 14 is withdrawn until the internal dogs 30 are disengaged from the ends of the planet pins, the drive then being from the driver 12 to annulus 19 via the supplementary pawl and ratchet means defined by pawls 27 and ratchet 15. teeth 28 and thence to the hub 11 through the pawl and ratchet means 20 as before.

For low gear the selector sleeve 14 is withdrawn further until the back of the dogs 30 at the said sleeve abut tails 38 of the pawls 39 of the pawl and ratchet means 20 and trip the said pawls out of 20. engagement with the respective ratchet 40. In this case the drive is taken from the driver 12 to the annulus 19 via pawls 27 and ratchet teeth 28, and thence to the planet gears 17. Rotation of the gears 17 about the fixed sun gear 16 causes the planet cage 18 to rotate and the brake cone 21 rotates therewith, transmitting motion to the hub 11 through the pawl and ratchet means 24.

When driving in high and normal gears the pawl and ratchet - 7 10.

means 24 has been overrunning.

The brake actuating means 25, see now particularly Figure 3, utilises the two pawls 27 supported by the driver 12 and positioned for engagement with the inwardly directed ratchet teeth 28 formed in 5.the annulus 19, the pawls and ratchet teeth 27, 28 being bi-directional.

In a forward direction of movement of the driver the nose 41 of each pawl 27 is positioned for engagement with a drive flank 42 of a ratchet tooth 28, being springloaded towards such position, but being overrun by the ratchet teeth 28 in the high gear condition of the assembly as has previously been indicated.

On reverse movement of the driver 12, splines 31 on selector sleeve 14 engage a camming face 43 of each pawl and pivot such pawl against the restraint of the spring means to bring the tail 44 thereof into a position for engagement with the braking flank 45 of a ratchet 15. tooth, there being a 'lost motion' between the co-operating splines 31 and 26 on the selector sleeve and driver respectively to permit of the necessary relative movement between the selector sleeve and driver.

It is necessary, if the brake is to be satisfactorily applied when high gear is selected, that either the internal dogs 30 be disengaged 20. from the planet pins 29 or that brake engagement be effected before any drive is transmitted to the planet in. the reverse direction through the selector sleeve, means for achieving either of these ends being known to one skilled in the art.

The operation of the back pedal brake is conventional in that 25. reverse motion of the driver will bring the tail 44 of each pawl 27 into cooperative engagement with the braking flank 45 of a respective - 8 ratchet tooth 28 and on continued such motion will apply a reverse motion to the annulus. Thus, motion will be transmitted to the planet cage, and reverse motion of such cage will effect an axial displacement of the brake cone and bring brake lining into friction engagement with the brake drum. since the drive transmission path, on braking, is invariably through the annulus to the planet cage constant braking efficiency is achieved.

By means of our invention we are able to avoid a 'no-drive' condition of the hub in that the adoption of a new drive-transmission 10. path is effectively instantaneous upon engagement or disengagement of the direct drive connection between the selector sleeve and planet cage.

Furthermore, uniformity of braking is assured, irrespective of the gear selection obtaining.

In an alternative embodiment, see now Figures 5 to 7, instead of providing bi-directional pawls on the driver for forward drive and for braking, separate pawls are provided for these different functions. Thus, referring now to Figures 5 to 7, four pawl pockets 51-54 are provided at 900 centres in the periphery of the driver 12 in a plane 20. in radial register with internal teeth 28 provided at the outer end of the annulus 19, diametrically opposed pairs of pockets being oppositely directed in the peripheral direction of the driver and respectively receiving individual ones of a pair of drive pawls 55 or braking pawls 56. An annular pawl actuator 57 is provided in angularly fixed position on the selector sleeve 14, the pawl actuator 57 being movable axially of such sleeve 14 and being spring-loaded towards the driver 12 by a 11; 9 clutch spring 58, the individual pawls 55, 56 being spring-loaded outwardly of the driver 12 and into engagement with internal teeth 28 20.

of annulus 19 by a pawl spring 59.

An axial lip 60 is provided at the outer periphery of and integrally with the annular pawl actuator, the lip 60 being cut away at two diametrically opposed locations to define windows 61 each of 900 arcuate extent through which pawls 55, 56 protrude, as can be seen in Figure 6. As is also apparent from the drawings, the driver 12 includes a radial protrusion 62 at each of two diametrically opposed positions 10. thereon and between adjacent inwardly-facing pawls 55, 56, the protrusion serving to ensure correct fitment of the pawl actuator 57 relative to the driver in that the diameter of the driver in the region of the protrusions 62 is in excess of the inside diameter of lip 60 and accordingly precludes incorrect fitment. In the position shown in Figure 6, the axial lip to the pawl actuator also serves to maintain proper location of the pawls in their respective pockets.

On relative angular movement between the driver 12 and selector sleeve 14 consistent with a change from drive mode to braking mode, the pawl actuator moves angularly relative to the driver and engages the backs of the braking pawls 56 and pivots such pawls out of engagement with ratchet teeth 28, such ratchet teeth moving back into engagement upon relative motion between the driver and selector sleeve in the reverse sense.

The operation of the modified structure is directly analogous to 25. that of the embodiment shown in Figures 1 to 4, and further description of such operation is thought unnecessary.

The invention is not restricted to the exact features of the embodiments hereinbefore described, since alternatives will readily present themselves to one skilled in the art. Thus, whilst we prefer to utilise the planet pins in providing a drive connection between the 5. selector sleeve and planet cage, it may be preferred, in some instances, to provide internal dogs on the planet cage to receive splines provided at the inner end of the selector sleeve.

I; 5.

Claims

1 A change-speed gear hub for a bicycle, tricycle or the like incorporating a back-pedal brake arrangement, the hub comprising an epicyclic gear disposed within a hub shell, and drive input means manually adjustably connectable with said hub shell via a selected one of multiple drive transmission paths through an element or elements of said epicyclic gear for forward drive motion of the hub shell on movement of the drive input means in a first direction and connectable with the brake arrangement via a predetermined drive transmission 10. path through the said epicyclic gear for braking action an movement of the drive input means in a second direction opposite to said first direction, characterised by a bi-directional pawl and ratchet mechanism intermediate said drive input means and the annulus of the epicyclic gear, the said pawl and ratchet mechanism being capable of transmitting a motion between the drive input means and annulus on movement of the input means in said first direction and adapted to transmit a motion therebetween on movement of the input means in said second direction.

2. A change-speed gear hub for a bicycle, tricycle or the like 20. comprising a hub shell, an epicyclic gear, including a sun gear, an annulus coaxial and radially aligned with the said sun gear, a planet cage likewise coaxial with the sun gear and a plurality of planet gears rotatably mounted in said planet cage and in mesh with said sun gear and with said annulus, disposed within said hub shell, respective unidirectional clutch means intermediate said hub shell and said annulus and planet cage, a driver adapted to receive an input drive, manually - 12 adjustable selector means drivingly connected with said driver and selectively drivingly engageable with said planet cage and said annulus, and further including a back-pedal brake arrangement operable through the epicyclic gear, characterised by a supplementary pawl and ratchet means interconnecting said driver and said annulus and drivingly connectable with said annulus to transmit a drive motion thereto in either direction thereof.

3. A change-speed gear hub as claimed in claim 2, wherein said brake actuating mechanism includes a pawl and ratchet means and 10. means whereby the pawl is adapted to be tripped whilst the assembly is in driving condition, at least in high gear, and by the provision of means adapted to ensure the selector sleeve is drivingly disengaged from the planet cage during braking, the said pawl and ratchet means being formed integrally with the supplementary pawl and ratchet means 15. aforesaid.

4. A change-speed gear hub as claimed in claim 1 or 2, wherein said bidirectional pawl and ratchet mechanism intermediate the drive input means and the annulus comprises oppositely directed drive and braking pawls resiliently loaded into engagement with respective ratchet 20. means, and a pawl actuator adapted to disengage the braking pawls in the forward drive condition of the hub.

5. A change-speed gear hub as claimed in claim 4, wherein said pawl actuator includes a windowed lip overlying the braking pawls and adjustable in the peripheral direction thereof between first and second positions respectively corresponding to engaged and disengaged conditions of said pawls, the lip being engageable with the pawls to 13 effect disengagement thereof from the opposed ratchet means.

6. A bicycle or like change-speed gear hub having a back-pedal brake arrangement therein, substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4 or Figures 5. 5 to 7 of the accompanying drawings.

Published 1986 at The Patent Off.,ce. State House. 66 77 1 High Holborn. London WC1R 4TP- Further. copies may De cl- f. r, T e ained c--- he Paten. Of-lie, Sales Branch. St Mary Cray. Orpingor. Kent BR5 3RD Printed by Multiplex techniques ltd. S: Ala-y Cray. Kent Con 1 87