GB2127123A - Actuating a back-pedalling brake in a bicycle driving assembly - Google Patents

Abstract

In a bicycle a rear wheel hub 1 is driven by a chain from a pedal shaft and includes a clutch-brake combination 3,4,5. The chain is shifted to various rear wheel sprockets 6 to change the transmission ratio. A chain tensioner compensates for the differences in diameter of the various sprockets. To avoid loosening of the upper chain strand and belated brake effect in response to backward pedaling, a separate brake- actuating transmission line is provided between the pedal shaft and a driver member 2 of the rear wheel hub. This transmission line comprises a free- wheel unit mounted onto the pedal shaft and a disengageable drive unit 8 adjacent the rear wheel hub. The units are interconnected by a transmission member 12 separate from the chain. The disengageable drive unit 8 may comprise a pinion 7 fixed to the driver member 2 and a rack 9 formed by a series of pins 10 engageable with the pinion 7 on displacement of the rack 9 in direction F. <IMAGE>

Description

SPECIFICATION A bicycle driving assembly The present invention is directed to a bicycle driving asembly including a rearwheel hub unit comprising a hub shaft having an axis, a hub shell mounted for rotation about said axis, a driver member mounted for rotation about said axis, a plurality of rear wheel chain sprockets of various diameters on said driver member, free wheel torque transmission means between said driver member and said hub shell permitting torque transmission from said driver member to said hub shell in a forward driving sense and permitting free rotation of said hub shell with respect to said driver member at least in said forward driving sense, hub shell braking means responsive to rotation of said driver member in a backward driving sense, a pedal shaft unit comprising a pedal shaft rotatable in said forward and said backward driving sense, at least one pedal shaft chain sprocket on said pedal shaft, a chain following a chain path and engaging said pedal shaft chain sprocket and one of said rear wheel chain sprockets, chain shifting means for selectively shifting said chain into engagement with various rear wheel chain sprockets, chain tensioning means compensating for variations of length of said chain path resulting from said chain being shifted into engagemenu with various rear wheel chain sprockets.

Difficulties occur if one tries to activate the hub shell braking means by backward pedalling through the chain, because the lower strand of the chain between the respective rear wheel chain sprocket and the respective pedal shaft chain sprocket is shortened against the action of the tensioning means while the upper strand of the chain between the respective rear wheel chain sprocket and the respective pedal shaft chain sprocket is loosened.

This loosening is undesirable. Moreover, the-brake becomes effective with delay only.

In a known construction as shown in German Offenlegungsschrift 3,032,504, one has tried to avoid this disadvantage as follows: The lower strand of the chain before arriving at the respective rear wheel sprocket runs over an intermediate sprocket. This intermediate sprocket is stationary with respect to the rear wheel hub unit. A chain thrower and tensionerwheel is provided between the intermediate sprocket and the respective rear wheel chain sprocket. The intermediate sprocket is connected to a coaxial gear. This coaxial gear is interconnected with an additional gear on the driver member by an auxiliary chain. The chain thrower and tensioner wheel is movable in a direction substantially parallel to the axis of the hub shaft in view of shifting the chain between various rear wheel chain sprockets.Moreover, the chain thrower and tensioner wheels transmit an elastic tension onto the chain. The chain thrower and tensioner wheels can be shifted only through a small path of movement, so that the chain can be shifted only between two rear wheel chain sprockets. When the pedal shaft is rotated in backward driving sense, a brake signal is transmitted from the pedal shaft chain sprocket to the intermediate sprocket by the chain and from the intermediate sprocket to the additional sprocket by the auxiliary chain. The upper strand of the chain remains substantially tensioned.

The chain shifting means and the chain tensioning means in this known construction are of a particular non-usual construction.

It is a main object of the present invention to provide a bicycle driving assembly of the abovedefined type, in which the brake signal transmission means allow the chain to be shifted between an increased number of rear wheel chain sprockets without substantial loosening of the upper chain strand and without substantial delay in brake activation.

It is a further object of this invention to provide a bicycle driving assembly as defined above, in which usual brake shifting and brake tensioning means can be used. Such usual brake shifting and brake tensioning means are known e. g. from German Offenlegungsschrift 3,037,394.

In view of at least one of the above objects the brake signal transmission means between the pedal shaft and the driver member comprise a free-wheel input member connected to the pedal shaft for common rotation therewith and a free-wheel output member being movable in response to rotation of said pedal shaft in backward driving sense. A clutch unit is provided adjacent the rearwheel hub unit.

This clutch unit comprises a clutch output member fixed to the driver member for common rotation therewith and a clutch input member connected to the free-wheel output member through a transmission member. The transmission member is separate from the chain. The clutch input member is lockable for common movement with the clutch output member in response to movement of the free-wheel output member, so as to rotate the driver member in said backward driving sense. On the other hand, the clutch input member is separable from the clutch output member in response to rotation of the driver member through the chain in the forward driving sense.

With the bicycle driving assembly of this invention the chain shifting means and the chain tensioning means and the actuating means for the chain shifting means can be maintained as usual in bicycle driving assemblies of the chain shifting type without brake means. The brake signal transmission means can be easily mounted and dismantled so that mounting and dismantling of the rear wheel can be easily performed.

A simple and reliable form of clutch unit comprises a pinion fastened to the driver member for common rotation therewith and a rack engagable and disengagable with the pinion, this rack being connected to or being apart from the transmission member.

In view of avoiding collision between the chain and the brake signal transmission means, the pinion of the clutch unit is provided on the inner side of the axial innermost sprocket.

The pinion can be used as a protection against the entrance of dust into the cavity defined by the hub shell.

In view of avoiding incorrect engagement of the rack and the pinion of the clutch unit, one can provide an idle movement unit in series with the transmission member between the free-wheel output member and the rack. This idle-movement unit is bridged by spring means which bias the rack towards its minimum distance from the free-wheel output member permitted by the idle-movement unit.

The invention is further directed to a bicycle comprising the above-defined bicycle driving assembly of the invention.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawing: Figure lisa longitudinal section of a rearwheel hub unit of this invention; Figure 2 is a partial sectional view along lines ll-ll of Figure 1 showing the clutch unit; Figure 3 is a view on the clutch unit of Figure 2 in the direction of arrow Ill of Figure 2; Figure 4 is a longitudinal section view of the pedal shaft unit with the free-wheel unit; Figure 5 is a side view of the pedal shaft unit of Figure 4 according to the arrow V of Figure 4 and Figure 6 is a side view of the chain shifting and tensioning means to be used in connection with the driving assembly of this invention.

Figures 1 and 2 show a back pedal brake hub unit of the rear wheel of a bicycle. The pedal pedal brake hub unit 1 is in part known from the prior art. It consists, inter alia, of a rotatably mounted hub shell 5 which is connected in known manner to the rim of a rear wheel through spokes. This hub shell 5 is directly or indirectly rotatably mounted on the hub shaft 32. In the hub shell 5 there is arranged, so as to be secured against rotation, a brake casing 4which can be brought into frictional contact with the hub shell 5 during back-pedalling view a double cone 3, which is arranged on a driver 2, for the initiation of the braking operation. By contrast, the double cone 3 is axially displaced during forward pedalling; it is then disengaged from the brake casing 4 and engages with the hub shell 5.There is thus established the rotary connection between the driver 2 and the rear wheel of the bicycle. The transmission of the rotary movement from the pedal shaft 23 of Figure 4 is effected in a conventional manner via a chain (see Figure 6) and a set of sprocket wheels 6 which is fixedly fastened on the driver 2 and comprises individual sprockets 6a, 6b, 6c and 6d, 6e of various diameters. There are provided chain shifting and tensioning means, such as are shown in Figure 6 and which allow the chain to be transferred to each of the sprocket wheels 6a and 6e of the set 6 along with the simultaneous compensation of the excessive length of the chain. In the exemplified embodiment under discussion, a pinion 7 is fixedly arranged, in addition to this set of sprocket wheels 6, on the side of the sprocket wheel 6a that is adjacent the hub shell 5.This pinion 7 has a cylindrical side wall 13 which defines a cup-shaped configuration together with a bottom member fixed to the driver 2.

The cylindrical side wall defines a labyrinth seal together with the hub shell 5 and closes the gap between the hub shell 5 and the driver 2. On the outer circumference of the cylindrical side wall 13 there is rotatably arranged a guide strap 14 with an angled tab 15. The arrangement and design of this guide strap 14 can also be seen in Figures 2 and 3. It serves for guiding a rack 9 which is kept by the strap 15 at a pre-set constant distance from the pinion 7, the rack 9 being displaceable in its longitudinal direction. The rack 9 comprises some pins 10, whose distance from one another corresponds to the spacing of the teeth 11 of the pinion 7. The rack 9 consists of two symmetrically drawn sheet-metal parts 9a as shown in Figure 3, the reciprocal connection of which is effected via the bottom walls 22a of the pot-shaped depressions 22.The distance of the rack 9 from the hub shaft 32 is ensured by the angled tab 15 of the guide strap 14. In the normal cycling condition, as shown in Figure 2, the pins 10 are disengaged from the teeth 11. This disengagement is obtained by the teeth 11 and the pins 10, when the pinion 7 rotates in counter-clockwise direction, as seen in Figure 2, and is completed when the stop 20 engages the edge 21 of the guide strap 14. The rack 9 is connected to a pull rod 12 which is connected to the pedal shaft unit 24, as seen in Figure 4. In series with the rack 9 and the pull rod 12 there is provided an idle-movement unit 16 which is constituted by a longitudinal slot 19 in the pull rod 12 and a stop 18 on the rack 9.This idle-movement unit is bridged by a spring 17 which urges the pull rod 12 and the rack 9 towards each other, the pull rod 12 being urged to the right in Figure 2 when the rack 9 is stationary in the position as shown in Figure 2. The rack 9 and the pinion 7 are regarded as a clutch 8 which is in a disengaged condition in Figure 2 and can be brought into an engaged condition by moving the rack 9 to the left in the direction of arrow F of Figure 2.

In Figures 4 and 5 one recognizes a pedal shaft 23, on which the pedal arms 28 are fixed as usually. The pedal shaft 23 is rotatably mounted within a tube 29 forming a part of a bicycle frame. Rotatable with the pedal shaft and with the pedal arms 28 is a wheel spider 31, on whose outer zone one or more pedal shaft sprocket wheels 30 are fixedly arranged.

Axially between the wheel spider 31 and the tube 29 there is provided a free-wheel unit 26 which consists of a free-wheel input member 25 and a free-wheel output member 26a. The free-wheel input member 25 is non-rotatably connected to the pedal shaft 23 and is provided with pawls 27. The pawls 27 engage an internal toothing of the free-wheel output member 26a, so that the free-wheel output member 26a is rotated through the pawls 27 only when the pedal shaft 23 is rotated in the usual backward driving sense. A radially extending arm 26b of the freewheel output member 26a is connected to the pull rod 12.

The mode of operation of the shown driving assembly with the back-pedalling brake is as follows: during cycling, the pedal shaft 23 is rotated by the pedal 28 in the forward direction, that is to say in the clockwise direction according to Figure 5. With the pedal shaft 23 there rotates also the free-wheel input member 25 of the free-wheel unit 26 including the spring-loaded pawls 27. In this direction of rotation, the pawls 27 cannot transmit a torque onto the free-wheel output member 26a of the free-wheel unit 26 so that this free-wheel output member 26a is at a standstill in the shown position. This also applied to the pull rod 12 acting as a transmission member and the rack 9. The rack 9 is in the position shown in Figure 2.The set of sprocket wheels 6 is driven by the revolving chain in the usual way, the double cone 3 ensuring a torque transmitting connection between the driver member 2 and the hub shell 5. The pinion 7 also revolves without any restriction with the set of sprocket wheels 6 since the pins 10 of the rack 9 are disengaged from the pinion 7. The guide strap 14 is prevented from co-rotating with the driver member 2 through the angled tab 15, which closely abuts the rack 9. This condition is maintained even if no pedalling is effected while the bicycle rolls.

For the initiation of a braking operation, the pedal shaft 23 is moved backwards with the chain in the backward driving sense, as is usual with back pedal brake hubs, that is to say in the anti-clockwise sense according to Figure 5. Consequently, torque can now be transmitted from the free-wheel input member 25 via the pawls 27 on the free-wheel member 26a of the free-wheel unit 26 since the radially sprin-loaded pawls 27 engage in the toothing of the free-wheel output member 26a. Consequently, the free-wheel output member moves together with the pedal pin in the backward driving sense, i. e. in the anti-clockwise sense in Figure 5. This movement is transmitted through the pull rod 12 and the spring 17 to the rack 9. The direction of movement of the pull rod 12 and the rack 9 is thus as per the arrow F in Figures 2 and 5.The back-pedalling simultaneously causes the set of rear wheel sprockets 6 and the pinion 7 to be also rotated in the backward driving sense. This rotation is transmitted to the driver member 2 and the torque transmitting connection between the double cone 3 and the shell 5 is separated. Now the double cone is capable of being axially displaced towards an expanding face on the brake casing 4. The torque necessary for generating the brake casing expanding force of the double cone 3 through the thread 3a is transmitted to the drive member 2 from the pedal shaft 23 via the free-wheel unit 26, the pull rod 12, the spring 17, the rack 9, the pins 10 and the teeth 11 of the pinion 7, which is also fixedly arranged on the driver 2.Due to an appropriate selection of the lever lengths of the radial extending arm 26b and the pinion 7, on the one hand, as well as the pedal shaft chain sprocket 30 and the rear wheel chain sprockets 6, on the other hand, it is possible to transmit the braking signal, without the upper strand of the chain starting to sag between the pedal shaft chain sprocket 30 and the respective rear wheel chain sprocket wheels 6a to 6e. Consequently, the driving torque transmission and the braking torque transmission are completely separate. The idlemovement unit 16 with the spring 17 and the longitudinal slot 19 substantially serve for preventing any jamming tendency if by chance a tooth of the pinion 7 is just about to run into a pin 10.

After the braking operation has been completed, when the pedal shaft 23 is again driven in the forward driving sense, the driver 2 is also moved in the forward driving sense via the chain; the double cone 3 is disengaged from the brake casing 4 and engages with the hub shell 5; simultaneously, the teeth 11 of the pinion 7 transport the pins 10 together with the rack 9 in the direction that is opposite to the arrow F in Figure 2 and thus out of engagement with the pins 10. This movement of the rack 9 is limited by the stop 20 and the edge 21 on the guide strap 14.

Figure 6 shows in a diagrammatic way the chain shifting means and the chain tensioning means. The clutch unit 8 of Figures 2 and 3 has been omitted for sake of clarity. It is, however, to be assumed that the clutch unit 8 is to be applied to the arrangement as shown in Figure 6. In Figure 6 one recognizes the hub shaft 32 and two of the rear wheel chain sprockets 6, namely 6d and 6e. The chain 40 runs around the rear wheel chain sprocket 6d and further around a chain shifting wheel 41 and a chain tensioning wheel 42. The wheels 41 and 42 are mounted on the double-armed lever 43 which is pivotally mounted by a pivot pin 44 on a bracket 45.

The bracket 45 is mounted on a movable joint head 46. The movable joint head 46 is connected to a stationary joint head 48 through a pair of levers 49 which define together with the joint heads 46 and 48 a parallelogram link. By this parallelogram link the joint head 46 is movable in a direction substantially perpendicular to the plane of Figure 6. By this movement the chain shifting wheel 41 can shift the chain 40 to various rear wheel sprockets 6a to 6d.

The double-armed lever 43 is biased in clockwise direction about the pivot pin 44 by a spring 50. This spring 50 creates a tension in the chain 40. The movement of the parallelogram link46,48,49 is caused by a Bowden cable 51 connected to a speed chain switch, not shown. The chain 40 runs over the pedal shaft spocket 30 as shown in Figure 4.

The above-discussed back-pedal braking system separates in an advantageous manner the driving transmission from the braking transmission completely. Furthermore, this braking system is basically independent of the type of derailleur system used since the two transmissions do not obstruct each other in their functions. The assembly and dismantling of the complete rear wheel is not obstructed by the clutch unit 8. All that has to be done when the rear wheel is re-installed is to thread the rack 9 between the pinion 7 and the guide strap 14. The brake application occurs at once without any harmful angle of rotation of the pedal shaft 23 and the chain from the pedal shaft chain sprocket 30 to the respective rear wheel sprocket 6 continues to be in a tensioned state.

While specific embodiments of the invention have been shown and described in detail to illustrate the applications of the inventive principle, it will be understood that the invention may be embodied otherwise without departing from such principles.

It is to be noted that the reference numbers used in the claims are only for the purpose of a better understanding, but are in no way limitative.

Claims (11)

1. In a bicycle driving assembly including a rear wheel hub unit (1) comprising a hub shaft (32) having an axis, a hub shell (5) mounted for rotation about said axis, a driver member (2) mounted for rotation about said axis, a plurality (6) of rear wheel chain sprockets (6a to 6e) of various diameters on said driver member (2), free wheel torque transmission means (3a, 3) between said driver member (2) and said hub shell (5) permitting torque transmission from said driver member (2) to said hub shell (5) in a forward driving sense and permitting free rotation of said hub shell (5) with respect to said driver member (2) at least in said forward driving sense, hub shell braking means (3a, 3,4) responsive to rotation of said driver member (2) in a backward driving sense, a pedal shaft unit (24) comprising a pedal shaft (23) rotatable in said forward and said backward driving sense, at least one pedal shaft chain sprocket (30) on said pedal shaft (23), a chain (40) following a chain path engaging said pedal shaft chain sprocket (30) and one of said rear wheel chain sprockets (6a, 6b, 6c, 6d, 6e), chain shifting means (41) for selectively shifting said chain (40) into engagement with various rear wheel chain sprockets (6a to 6e), chain tensioning means (43, 50,42) compensating for variations of length of said chain path resulting from said chain (40) being shifted into engagement with various rear wheel chain sprockets (6a to 6e), brake signal transmission means (2, 12, 16, 8) transmitting rotation of said pedal shaft (23) in said backward driving sense to said driver member (2), the improvement that said brake signal transmission means (26, 12, 16,8) comprise a free-wheel unit (26) mounted on said pedal shaft (23) and having a free-wheel input member (25) connected to said pedal shaft (23) for common rotation therewith and a free-wheel output member (26a) being movable in response to rotation of said pedal shaft (23) in said backward driving sense, a clutch unit (8) adjacent said rear wheel hub unit (1) having a clutch output member (7) fixed to said driver member (2) for common rotation therewith and a clutch input member (9) connected to said free-wheel output member (26) through at least one transmission member (12), said clutch input member (9) being lockable for common movement with said clutch output member (7) in response to movement of said free-wheel output member (26a) so as to rotate said driver member (2) in said backward driving sense and being separable from such common movement in response to rotation of said driver member (2) through said chain (40) in said forward driving sense.

2. A bicycle driving assembly as set forth in claim 1, said clutch output member comprising a pinion (7) fastened to said driver member (2) for common rotation therewith and said clutch input member comprising a rack (9), said rack (9) being brought into engagement with said pinion (7) in response to movement of said free-wheel output member (26a) in said backward driving sense and being releasable from such engagement in response to rotation of said pinion (7) with said driver member (2) in said forward driving sense.

3. A bicycle driving assembly as set forth in claim 2, comprising a rack retaining member (14) mounted on said driver member (2) for free rotation with respect thereto and maintaining said rack (9) in a predetermined radial distance from said axis.

4. A bicycle driving assembly as set forth in claim 2 or 3, said plurality of chain sprockets (6a to 6e) being provided adjacent one end of said hub shaft (32) and comprising an axially outermost sprocket (6e) adjacent said one end and an axially innermost sprocket (6a) mostly remote from said one end, said pinion (7) being provided on the side of said axially innermost sprocket (6a) remote from said one end.

5. A bicycle driving assembly as set forth in claim 4, said driver member (2) entering into one axial end of said hub shell (5), a gap being defined between said driver member (2) and said hub shell (5) at the entrance of said driver member (2) into said hub shell (5), said gap being substantially covered by said pinion (7).

6. A bicycle driving assembly as set forth in claim 5, said pinion (7) comprising a pot-shaped central portion, said pot-shaped central portion having a bottom fixed to said driver member (2) and a substantially cyclindrical side wall (13) overlapping said hub shell (5).

7. A bicycle driving assembly as set forth in claim 6, a rack retaining member (14) being mounted for free rotation on said substantially cylindrical side wall (13) for free rotation with respect thereto, said rack retaining member (14) maintaining said rack (9) in a predetermined radial distance from said axis.

8. A bicycle driving assembly as set forth in one of claims 2 to 7, an idle-movement unit (16) being provided in series with said transmission member (12) between said free-wheei output member (26a) and said rack (9), said idle-movement unit (16) being bridged by spring means (17) biasing said rack (9) towards the minimum distance from said free-wheel output member (26a) permitted by said idlemovement unit (16).

9. A bicycle driving assembly as set forth in one of claims 2 to 8, said rack (9) being defined by two strips (9a) of sheet material, both strips being provided with a linear sequence of pot-shaped depressions (11), respective depressions (22) of both strips (9a) having outer bottom faces (22a), the outer faces (22a) of respective pot-shaped depressions (22) being fastened to each other.

10. A bicycle comprising a bicycle driving assembly as claimed in one of claims 1 to 9.

11. A bicycle driving assembly substantially as herein described with reference to Figures 1 to 6 of the accompanying drawings.