WO1998030433A1

WO1998030433A1 - Improved bicycle braking system

Info

Publication number: WO1998030433A1
Application number: PCT/NZ1998/000001
Authority: WO
Inventors: Jonathan Phillips
Original assignee: Sarun Holdings Limited
Priority date: 1997-01-09
Filing date: 1998-01-09
Publication date: 1998-07-16
Also published as: AU5351098A

Abstract

An improved foot-actuated bicycle braking system is described. A first invention lies in a chain-side spider assembly adapted so that there is no lockup when a rider re-starts forward pedalling after braking via back pedalling. To this end, there is provided a degree of relative movement between the spider (or sprocket hub) (26) and the crank arm (25). The engagement mechanism comprises a limited movement dog clutch (51, 33) allowing limited rotational movement between spider and crank arm. The crank arm is biased by means of a spring mechanism which biases the crank arm against the hub or spider. The spring acts as a return spring and absorbs the shock when the cyclist begins forward pedalling. A second invention lies in a unidirectional roller bearing clutch mounted integrally with the axle end of the crank. The resulting component may be mounted upon a pre-existing bottom bracket axle and be connected to braking actuation means which operates front and/or rear brakes. A third invention lies in adjustable retention provided to the front and/or rear brakes by using a novel bias clamp. The bias clamp is constructed in the form of an integrated locking device having a labyrinth located therein in such a manner that, when a brake cable is threaded through the labyrinth, the brake cable biases against itself and the bias clamp thereby locks the brake cable in relation to itself. The bias clamp also provides a means of adjusting the front and rear braking forces to suit a user. The adjustment is effected by means of the specific location of the braking actuation means connection to the bias clamp. The present improved bicycle system may find application in virtually any chain-driven device, particularly off-road bicycles where hand-braking may be inadequate or uncomfortable.

Description

IMPROVED BICYCLE BRAKING SYSTEM

TECHNICAL FIELD

The present invention relates to an improved brake system for a bicycle or similar chain driven devices. Reference is made to PCT application No. PCT/NZ96/00020, the disclosure of which is herein incorporated by reference.

BACKGROUND TO THE INVENTION

PCT/NZ96/00020 describes an improved braking system which provides a means for augmenting the hand operated brakes on a bicycle. The system disclosed in that application transmits a component of a back pedal force to the brake calipers, via an axle mounted clutch and cable arm attachment. This enhances the braking effectiveness and control of conventional hand operated brakes. However, the known clutch and sprocket mounting constructions are of relatively complex construction and have not exhibited completely satisfactory durability.

Reference is also made to US Patent No. 5,337,861 (Romano). The foot augmented braking system described in this specification incorporates a coarse toothed one way ratchet system designed to mesh and lock when the rider back-pedals. A first part of the this meshing system is connected to a housing which is then linked to the cables by means of a balanced double cable connector clip. This system exhibits a number of disadvantages. For example, when a cyclist riding a bicycle implementing the Romano system back pedals, the clutch does not immediately engage. There is potentially some degree of play or slackness in the clutch before it takes up the backpedalling force and transmits it to the brake callipers. This is considered a significant disadvantage as, depending on the initial position of the pedals, foot braking may be ineffective if the pedals are at an upper or lower position when the slack is taken up. In this situation, the cyclist would need to reposition the pedals and re-apply the foot assisted braking force.

Further, when a braking force is applied using the Romano system, it is transmitted to the front and rear brake callipers by means of a double cable connection. This connection is symmetrical around the attachment point to the housing and therefore provides equal tensions to the front and rear brake cables and hence callipers. This results in equal braking of the front and rear bicycle wheels. As discussed in PCT/NZ96/00020 it is known that equal front and rear braking forces are not usually ideal for most cycling situations. Some degree of bias between the front and rear brakes is required to safely and effectively brake a bicycle. To this end, it would be an advantage if the forces were transmitted in an asymmetric manner wherein the amount of asymmetry could be readily adjusted.

Further problems have been encountered in sprocket/crank connections. Systems of this type require a degree of relative movement between the sprocket hub and driving boss or crank. This movement ensures that there is no lockup when a rider restarts forward pedalling after applying foot assisted braking. Previous designs have included mechanisms such as keyways and slots which, while performing their specified task, have proven to be lacking in durability under certain circumstances. Referring to applicants co-pending International Application PCT/NZ96/ 00020, a freewheel locking/unlocking mechanism is described. In implementing this functionality in the present system, a number of improvements were found to be necessary.

Referring again to durability, it has also been found that the bias cable clamp of PCT/NZ96/00020 can damage the cables which are inserted therethrough. Also, this component is subjected to relatively large forces which both increases the chance of damaging the cable at the point where it is secured within the labyrinth, as well as increasing the susceptibility of the bias clamp itself to damage when in contact with tensioned brake cables.

An object of the present invention is to provide an improved mechanism for progressive braking, and parts therefore, wherein conventional hand activated brake callipers are augmented by a force originating from the cyclist's legs, thereby reducing the need for hand strength and allowing the hands greater freedom of movement for steering control.

A further object of the present invention is therefore to provide an improved brake system which provides for a smooth continuously variable pedal activated braking force, adapted to augment conventional hand applied brakes, which is durable, strong, of simple construction and may be relatively easily retrofitted to preexisting brake systems on known bicycles.

A further object of this invention is to provide a consumer with the useful alternative choice. DISCLOSURE OF THE INVENTION

According to a first aspect of the invention there is provided a crank assembly for a chain driven mechanism, such as a bicycle, including;

- a journal located at one end of a crank arm, the journal adapted for engagement with an axle;

- a substantially cylindrical bearing surface located at the one end of the crank arm and oriented to be coaxial with the axle;

- a housing incorporating an extension which, in use, a brake activation means is or are attached, wherein the housing incorporates an aperture adapted to receive an integrated roller bearing device, the roller bearing device having a plurality of roller bearings facing inwards and oriented so that when the cylindrical bearing surface is inserted into the aperture, the roller bearings bear against with the cylindrical bearing surface, wherein the integrated roller bearing device, when interacting with the cylindrical bearing surface, operates as a unidirectional continuously variable clutch.

In an alternative embodiment the housing incorporates an annular insert adapted to accommodate therein the integrated roller bearing device in such a manner that when the integrated roller bearing device is inserted into the annular insert and the annular insert is then inserted into the housing, the integrated roller bearing device is secured and fixed in relation to the housing by a friction fit.

Alternatively, the roller bearing device can be secured in the housing by pins or similar means. The axle is preferably a standard bottom bracket axle of a bicycle.

Preferably a second end of the crank arm may have a connection adapted so that a pedal shaft or cycle pedal can be attached thereto.

Preferably the journal comprises a cylindrical protrusion extending from the first end of the crank arm at substantially 90° to the lengthwise axis of the crank arm, wherein the substantially cylindrical bearing surface corresponds to a sleeve which is pressed onto the journal and is secured in immovable relation thereto by means of a friction fit or the like.

The crank assembly may be frictionally engaged in a known manner to the bottom bracket axle of the bicycle.

In a preferred embodiment, the housing incorporates a slip-ring adapted to engage the cylindrical bearing surface, wherein the slip-ring is held in either fixed or movable relation to the housing thereby, when held in movable relation, allowing a user to backpedal without engaging the brakes.

Preferably the slip-ring is locked/unlocked by a locking means, the locking means being actuated by a user.

Preferably, the locking means comprises a locking pin, mounted in the housing, adapted to engage corresponding recesses located in an outer surface of the slip-ring. Preferably, the locking pin is oriented radially in relation to the rotational axis of the slip-ring with the pin biased so that its default position is to engage a corresponding recess to hold the slip-ring in fixed relation to the housing.

The present invention further provides a crank and sprocket attachment assembly incorporating:

- a spider for mounting one or more sprockets on a first end of a crank arm wherein:

- the first end of the crank arm and spider are attached by means of a limited movement dog clutch.

Preferably the limited movement dog clutch incorporates five protrusions located axially around a journal wherein the journal is located at the first end of the crank arm and wherein the spider incorporates corresponding recesses located axially around the perimeter of an aperture located coaxially with the spider hub so that the protrusion and recess configurations are adapted to locate snugly together.

The limited movement dog clutch may incorporate five protrusions and corresponding recesses wherein the width of the recesses allows angular movement of the crank with respect to the spider of approximately half the width of one of the protrusions.

Preferably the spider is rotationally biased against the journal by means of a semicircular spring, or the like, having one end attached to the spider and the other attached to a point adjacent the journal. Alternatively, the spider may be rotationally biased against the journal by means of a coil spring or similar having a first end biased against a protrusion of the dog clutch, and a second end biased against a wall of a recess in the dog clutch, the dog clutch omitting one or more pair of protrusions and recesses wherein the coil spring is adapted to be inserted in an annular channel formed by the omitted protrusion and recess.

The present invention further provides a cable bias clamp suitable for use in a bicycle brake system comprising:

- a locking member adapted to receive a continuous length of cable threaded therethrough wherein a cable entry aperture and a cable exit aperture are displaced with respect to one another and the locking member incorporates one or more attachment points adapted so that when a force is applied to at least one of the attachment points, an asymmetric tension is applied to the parts of the cable inserted into the entry and exit apertures, wherein the locking member has a shape adapted so that when the length of continuous cable is threaded therethrough, and tension applied thereto, portions of the cable bias against each other thereby preventing movement of the continuous cable through the locking member.

Preferably the locking member is formed from plate material of thickness sufficient to accommodate cable apertures drilled therethrough in the plane of the plate material, wherein the locking member is cut in the shape of a T, the T including a horizontal portion and an upright portion, said horizontal portion comprising a first and second arm, wherein the locking member incorporates first, second, third and fourth apertures oriented so that a cable can be threaded, in the plane of the flat plate, through the end of the first arm then through the intersection of the upright and horizontal portions through a second aperture whereupon it emerges proximate the junction of the second arm and the upright portion whereupon it is then threaded around an end of the upright portion and then threaded through the intersection of the upright portion and horizontal portion, entering the third aperture at a point proximate the junction of the first arm and the upright portion and emerging at a point proximate the entrance to the second aperture whereupon it is threaded through an end of the second arm.

Preferably the second and third apertures entrances are located at the same point on the horizontal portion whereby the junction of the second and third apertures are widened to accommodate the cable passing through the second aperture and returning through the third aperture in crossed over relation.

Preferably the first arm incorporates a protrusion over which the cable is passed after emerging from the first aperture and being inserted the second aperture and the second arm incorporates a protrusion which the cable passes over after emerging from the third aperture and being inserted into the fourth aperture.

Preferably the upright portion is in the form of a circular portion made from flat plate of thickness sufficient to accommodate the cable apertures therethrough in the plane of the flat plate.

Preferably the locking member is cut in such a way so that the edges of the flat plate are at right angles to the plane of the flat plate thereby providing a uniform surface against which the cable can bear when placed under tension at the first and fourth apertures.

In an alternative embodiment, the second and third apertures may be in the form of slots wherein the open portion of the slots oriented towards one face of the T-shaped member.

Further aspects of the invention will become apparent from the following description which is given by way of example only.

BRIEF DESCRIPTION OF DRAWINGS

Examples of this invention will now be described with reference to the accompanying drawings in which:

Figure 1 illustrates a side view of a housing and integrated roller bearing device prior to connection to a crank shaft; Figure 2 illustrates a section through the housing shown in figure 1 when attached to a first end of a crank shaft and the crank shaft is attached to an axle; Figure 3a illustrates a side view of a crank arm;

Figure 3b illustrates an end view of crank arm prior to engagement with the housing of figure 1 ; Figure 4 illustrates a side sectional view of the crank arm in figure 3b;

Figure 5 illustrates a section through the housing shown in figure 1 with the integrated clutch removed; Figure 6 illustrates a side view of the axle side of a spider and crank connection; Figure 7 illustrates a pedal side view of connection between a spider and a crank arm; Figure 8 illustrates a cross-section through a spider/crank arm connection; Figure 9 illustrates a side section through a crank arm/spider connection; Figure 10 illustrates a side view from the axle side of a spider;

Figure 1 1 illustrates a side view from the pedal side of a spider;

Figure 1 2 illustrates a side view of a cable bias locking clamp; and

Figure 1 3 illustrates a right hand end view of the cable bias clamp shown in figure 1 2. Figure 14 illustrates a side cutaway view of an alternative spider/journal biasing means; Figure 1 5 illustrates a side view of a spider adapted for use with the bias means of figure 14; Figure 1 6 illustrates a crank arm adapted for use with the bias means of figure 14; Figure 1 7a-d illustrates a backpedal locking/unlocking mechanism; and Figure 1 8 illustrates a detail of the slip-ring shown in figure 1 7c.

Referring to figures 1 and 2, a crank assembly for use in a foot operated bicycle braking system is shown. It is to be understood that this system may be used in other chain driven mechanisms. However, the following discussion will be in the context of its application to a bicycle.

Referring to figure 2, a crank arm 1 7 (shown in plan and side view in figures 3(a) and 3(b)) has, at a first end 23, a journal 22 which is adapted to receive an axle 21 . The axle 21 shown in the present example corresponds to that found in a conventional bicycle. The journal is formed from a cylindrical protrusion 1 8 extending from the first end 23 of the crank arm 1 7.

The crank arm first end 23 is shown in more detail in figure 4 as a cut away section. The dimensions of the cut away are such as to be compatible with standard axles.

Figure 1 illustrates a housing 10 (shown in cross section in Figure 5) having an extension 14 which, in use, is attached to the fore and aft brake cables by means of the bias clamp (see figure 1 2 and 1 3). In an alternative variation, the housing 10 may incorporate an annular insert 1 1 which is pressed into the aperture 1 3. Inside this insert is pressed an integrated roller bearing device 1 2. The roller bearings (not shown) are located around the inside surface 1 6 of the integrated bearing device. Such integrated roller bearing devices are available from a number of sources. Preferably, the annular insert is omitted and the integrated roller bearing device is pressed into the housing.

The combination of the integrated roller bearing 1 2, housing 10 and, where applicable, annular insert 1 1 form the actuating arm for a unidirectional clutch. In use, the device of figure 1 is threaded or pressed onto a cylindrical bearing surface 1 9 which is threaded or pressed onto the cylindrical protrusion 1 8. The cylindrical bearing surface is in the form of a sleeve 1 9. The cylindrical bearing surface 1 9 is pressed firmly onto the protrusion 1 8 and is fixed in relation thereto (by a friction fit) or the like. The bearing surface could possibly be aided in resisting rotation by means of a mechanical interlocking mechanism. When the device in figure 1 is inserted onto the cylindrical bearing surface 19, the roller bearings facing inwards, represented by the ring 1 2 in figure 1 , bear against the outer surface of the cylindrical bearing surface. The combination of the substantially cylindrical bearing surface 19 and the construction shown in figure 1 forms a smoothly acting unidirectional clutch which provides free rotational movement when the crank arm is rotated anticlockwise (when viewed from the pedal side) and provides a instantaneously engaging fixed lever arm when rotated clockwise (when viewed from the pedal side). There is no slack to be taken up and the rear- pedal braking action is effective immediately. The device of figure 1 is held in place by means of a circlip and washer 40 and 41 respectively. An 0 ring 42 seals the bearing. Details of the housing 10 are shown in figure 5 in section. Extension 14 is formed from two adjacent arms, each incorporating an aperture 15 for securing the bias cable clamp (see figures 12 and 13). The bias clamp may be retained by a pin (not shown). Figures 3a and 3b show a top and side view of a crank arm suitable for use with the present invention.

As noted in Applicants International Application PCT/NZ96/00020, it is desirable that a user be able to backpedal freely if required. To allow this, the crank 17 must be capable of backpedal movement without engaging the housing 10 via the unidirectional clutch. To allow backpedalling, a preferred embodiment of the present invention includes a slip-ring 170 (see figures 18a, b and 1 7d).

In the locked braking mode, the slip-ring 1 70 is locked in fixed relation to the housing 10 by a locking means 180 (see figures 17a-d). The locking means comprises a barrel 181 threaded into the housing 10. A locking pin 182 moves within the barrel 1 81 and is biased in a protruding position by a coil spring 183. The coil spring biases against a bearing face 185. The pin is moved within the barrel by a cable and lug 184 and 186 respectively. The locking pin 182 engages with recesses 171 a, b, c. When the user wishes to backpedal, the cable 184 is withdrawn. This disengages the locking pin 182 from recesses 171 a, b, c and allows the slip-ring 1 70 to rotate in the housing 18.

Referring to figures 6 and 7, the sprockets (not shown) are connected in a known manner to a spider 26 by means of holes 28 and bolts (not shown).. To ensure that there is no lockup when a rider restarts forward pedalling after braking via back pedalling, there is provided a degree of relative movement between the spider (or sprocket hub) 26 and the crank arm 25.

Referring to figure 9, the crank arm 25 incorporates, at a first end, a male part of a limited movement dog clutch represented by dashed lines 32. The male part of the limited movement dog clutch includes five protrusions 50. The male limited movement dog clutch incorporates a hub 51 and the hub and protrusions may be machined from a separate piece of metal and then attached by press fitting to the first end of the crank arm 25. The male part of the limited movement dog clutch has a limited degree of angular movement within a female parts cavity 29. The amount of movement is governed by the angular width of the corresponding female recesses and, in the present example, is shown as being approximately one half the width of the protrusions 50. By the present construction, the load is brought to bear against the female dog clutch cavity face 33 in five different locations at once, thus distributing the forces and reducing wear and tear on the protrusions and their corresponding bearing surfaces. Opposite angular movement bears against corresponding opposite dog clutch faces. A cross- section of the arrangement is shown in figure 8 whereby a cross-section of a protrusion 30 is shown at the junction of the outer edge of the female dog clutch cavity 31 . The limited movement dog clutch is sealed by means of 0 rings 52 and 53 and the spider or hub is located in place by means of a circlip 54 and washer and 55.

A side view from the pedal and axle side respectively of the spider incorporating the female part of the dog clutch are shown in figure 10 and 1 1 .

Figure 6 illustrates the biasing means 30 which biases the crank arm 25 against the hub or spider 26. A spring 30 acts as a return spring and absorbs the shock when the cyclist begins forward pedalling.

An alternative and preferred embodiment is shown in figures 14, 1 5 and 1 6. Here one of the dog clutch protrusions 50 is omitted (see figure 1 6). Also a corresponding recess and bearing surface 33 is removed from the spider leaving an annular channel. Into this channel segment is placed a coil spring 140 (see figure 14) having a first end 141 which bears against a protrusion 50 and a second end which bears against a bearing surface 33. An advantage of this construction is that the entire dog clutch and return bias may be sealed using O-rings or similar and thus be protected from dirt, moisture and the like.

It has been found that the present limited movement dog clutch construction is more durable than a single protrusion and recess construction as the angular load is spread more evenly around the circumference of the dog clutch boss.

Referring to figure 1 2, an example of a cable bias clamp is shown. In the applicant's previous international application, a bias clamp comprising a block having a labyrinth through which a continuous cable was threaded, was disclosed. This construction, while providing the required tension bias, proved problematic. When tensioning and/or securing the cable, by means of the screw oriented at right angles to an aperture through which the cable passes, the screw tended to crush and damage the cable in the labyrinth.

An improved cable bias clamp is shown in figures 1 2 and 1 3 which not only overcomes this problem, but is stronger and more easily adjusted with respect to the cable. The present novel clamp is also more easily adjusted with respect to the preset bias.

Referring to figure 1 2, a cable bias clamp locking member 45 is shown. This is in the shape of a "T" when figure 1 2 is rotated through 90° (anticlockwise). The horizontal portion of the T corresponds to the horizontal portion 70 (formed from a first and second arm 46 and 47 respectively) and the upright portion 71 . The horizontal portion 70 incorporates two protrusions 53 and 54 over which the cable passes prior to passing through the member. The upright portion is circular and filleted into the cross piece at their junction.

The locking member is formed from flat plate having square cut edges. These edges provide the surface over which the cable passes and bears against when tensioned. When threading a brake cable through the locking member 45, the path, indicated by A and B (arrowed), is followed. The cable is inserted into a first aperture 48 whereupon it is bent over a first protrusion 53 and inserted into a second aperture 51 . The cable is threaded through and passed around the upright portion 71 and inserted through the third aperture 50. The cable is then passed over the second protrusion 54 and threaded through the fourth aperture 49. Apertures 50 and 51 exit at a common point 52 which is of width sufficient so that the cables can be crossed one over the other. Therefore, when tension is applied between the two parts of the cable entering at A and exiting at B respectively and a pin passing locating any of apertures 60,61 or 62, the cable is locked off and cannot be moved from the labyrinth. The cable can be adjusted relatively easily by loosening the cable over the protrusions 53 and 54 and around the upright portion 71 . This loosens the cross over or bias point 52 thereby allowing adjustment. When the cable threaded through the device 45 is tightened, it is effectively secured.

A range of connection positions or attachment points 60, 61 and 62 are provided. These provide asymmetric braking between the fore and aft wheels of the bicycle. If the centre attachment point 62 is used to thread the pin 1 5 through the extension 14 (see Figure 2), the braking force is equal. Alternatively, threading the pin through the aperture 1 5 and through the cable clamps and hole 60 in the extension 14 causes an asymmetric braking action. The ratio of fore/aft braking is governed by the location of the holes 60 and 61 along the lengthwise axis of the cross-section arm 70. Three possible positions are shown in figure 1 2, however a larger number may be viable depending of the overall dimensions of the cable bias clamp. A right hand side view of the cable bias clamp shown in figure 1 2 is illustrated in figure 1 3. As can be seen from the apertures 50 and 51 , third and fourth apertures are open to the surface of the body. This can aid in locating the cable through the labyrinth. However, in an alternative and more preferred embodiment, the apertures 50 and 51 are fully enclosed and penetrate through the cable bias clamp block.

The cable is attached to the brake cable adjustment and connection means as described in PCT/NZ96/00020.

Thus it can be seen that the present invention provides for improvements in the handling characteristics of a foot operated hand brake augmentation system. The novel construction provides for a significantly more durable and long lasting device and, in the case of the cable bias clamp, provides a stronger, more easily adjustable cable biasing element.

The use of an integrated unidirectional variable clutch bearing against a stationary sleeve attached to the crank arm journal provides for significant improvements in the smoothness of application, simplicity in construction and durability.

Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth. Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/or improvements may be made without departing from the scope of the appended claims.

Claims

CLAIMS:

A crank assembly for a chain driven mechanism including;

- a housing incorporating an extension to which, in use, a brake activation means is or are attached, wherein the housing incorporates an aperture adapted to receive an integrated roller bearing device, the roller bearing device having a plurality of roller bearings facing inwards and oriented so that when the cylindrical bearing surface is inserted into the aperture, the roller bearings bear against the cylindrical bearing surface, wherein the integrated roller bearing device, when interacting with the cylindrical bearing surface, operates as a unidirectional continuously variable clutch.

A crank assembly for a chain driven mechanism as claimed in claim 1 wherein the housing incorporates an annular insert adapted to accommodate therein the integrated roller bearing device in such a manner that when the integrated roller bearing device is inserted into the annular insert and the annular insert is then inserted into the housing, the integrated roller bearing device is secured and fixed in relation to the housing by a friction fit.

3. A crank assembly for a chain driven mechanism as claimed in claim 2 wherein , the roller bearing device is secured in the housing by pins or similar means.

4. A crank assembly for a chain driven mechanism as claimed in any preceding claim wherein the axle is a standard bottom bracket axle of a bicycle.

5. A crank assembly for a chain driven mechanism as claimed in any preceding claim wherein a second end of the crank arm has a connection adapted so that a pedal shaft or cycle pedal can be attached thereto.

6. A crank assembly for a chain driven mechanism as claimed in any preceding claim wherein the journal comprises a cylindrical protrusion extending from the first end of the crank arm at substantially 90° to the lengthwise axis of the crank arm, wherein the substantially cylindrical bearing surface corresponds to a sleeve which is pressed onto the journal and is secured in immovable relation thereto by means of a friction fit or the like.

7. A crank assembly for a chain driven mechanism as claimed in any preceding claim wherein the crank assembly is frictionally engaged to the bottom bracket axle of the bicycle.

8. A crank assembly as claimed in any preceding claim wherein the housing incorporates a slip-ring located so as to engage the cylindrical bearing surface, wherein the slip-ring is held in fixed or movable relation to the housing thereby, when held in movable relation, allowing a user to backpedal without engaging the brakes.

9. A crank assembly for a chain driven mechanism as claimed in claim 8 wherein the slip-ring is locked/unlocked by a locking means, the locking means being actuated by a user.

10. A crank assembly for a chain driven mechanism as claimed in claim 9 wherein the locking means comprises a locking pin, mounted in the housing, the pin adapted to engage corresponding recesses located in an outer surface of the slip-ring.

1 1 . A crank assembly for a chain driven mechanism as claimed in claim 1 0 wherein the locking pin is oriented radially in relation to the rotational axis of the slip-ring with the pin biased so that the default position of the locking means is to engage a corresponding recess to hold the slip- ring in fixed relation to the housing.

1 2. A crank and sprocket attachment assembly incorporating:

1 3. A crank and sprocket assembly as claimed in claim 1 2 wherein the limited movement dog clutch incorporates five protrusions located axially around a journal wherein the journal is located at the first end of the crank arm and wherein the spider incorporates corresponding recesses located axially around the perimeter of an aperture located coaxially with the spider hub so that the protrusion and recess configurations are adapted to locate snugly together.

14. A crank and sprocket assembly as claimed in any one of claims 1 2 or

1 3 wherein the limited movement dog clutch incorporates five protrusions and corresponding recesses wherein the width of the recesses allows angular movement of the crank with respect to the spider of approximately half the width of one of the protrusions.

1 5. A crank and sprocket assembly as claimed in any one of claims 1 2 to

14 wherein the spider is rotationally biased against the journal by means of a semicircular spring, or the like, having one end attached to the spider and the other attached to a point adjacent the journal.

1 6. A crank and sprocket assembly as claimed in claim 1 2 wherein the spider is rotationally biased against the journal by means of a coil spring having a first end biased against a protrusion of the dog clutch, and a second end of the coil spring biased against a wall of a recess, the dog clutch omitting one or more pair of protrusions and recesses, and wherein the coil spring is adapted to be inserted in an annular channel formed by the omitted protrusion and recess.

1 7. A cable bias clamp suitable for use in a bicycle brake system comprising:

8. A bias clamp as claimed in claim 1 7 wherein the locking member is formed from plate material of thickness sufficient to accommodate cable apertures drilled therethrough in the plane of the plate material, wherein the locking member is cut in the shape of a T, the T including a horizontal portion and an upright portion, said horizontal portion comprising a first and second arm, wherein the locking member incorporates first, second, third and fourth apertures oriented so that a cable can be threaded, in the plane of the flat plate, through the end of the first arm then through the intersection of the upright and horizontal portions through a second aperture whereupon it emerges proximate the junction of the second arm and the upright portion whereupon it is then threaded around an end of the upright portion and then threaded through the intersection of the upright portion and horizontal portion, entering the third aperture at a point proximate the junction of the first arm and the upright portion and emerging at a point proximate the entrance to the second aperture whereupon it is threaded through an end of the second arm.

1 9. A bias clamp as claimed in claim 1 8 wherein the second and third apertures entrances are located at the same point on the horizontal portion whereby the junction of the second and third apertures are widened to accommodate the cable passing through the second aperture and returning through the third aperture in crossed over relation.

20. A bias clamp as claimed in any one of claims 1 8 to 1 9 wherein the first arm incorporates a protrusion over which the cable is passed after emerging from the first aperture and being inserted the second aperture and the second arm incorporates a protrusion which the cable passes over after emerging from the third aperture and being inserted into the fourth aperture.

21 . A bias clamp as claimed in any one of claims 18 to 20 wherein the upright portion is in the form of a circular portion made from flat plate of thickness sufficient to accommodate the cable apertures therethrough in the plane of the flat plate.

22. A bias clamp as claimed in any one of claims 1 8 to 21 wherein the locking member is cut in such a way so that the edges of the flat plate are at right angles to the plane of the flat plate thereby providing a uniform surface against which the cable can bear when placed under tension at the first and fourth apertures.

23. A bias clamp as claimed in any one of claims 18 to 22 wherein the second and third apertures are in the form of slots wherein the open portion of the slots oriented towards one face of the T-shaped member.

24. A crank assembly substantially as herein described and with reference to figures 1 to 6 and 17 and 18.

25. A crank and sprocket assembly substantially as herein described and with reference to figures 7 to 1 1 and 14 to 16.

26. A bias clamp substantially as herein described and with reference to figures 1 2 and 13.