GB2066179A - Bicycle with brake anti-locking device - Google Patents

Abstract

An anti-locking device for bicycles equipped with a back-pedal brake operated by the pedal crankshaft, comprises lost motion means in the drive to the driving wheel and a spring biasing the lost motion means so that rearward lost motion is taken up and sufficient lost motion is available on forward pedalling to release the brake. The lost motion may be provided by a spring biased pin and slot connection between the outer part of the chain wheel and the pedal arm or by lengthening the chain and using spring loaded idler wheels to transfer the slack to the upper run of the chain.

Description

SPECIFICATION Bicycle with brake anti-locking device This invention relates to pedal propelled vehicles such as bicycles and specifically to single speed, or multi-speed in-hub geared and multi-speed derailleur geared bicycles that are equipped with back pedalling brakes that are activated by a device or actuator associated with the pedal crankshaft.

Although the invention is also applicable to pedal propelled vehicles having more than two wheels, e.g. tricycles, it will for convenience hereinafter be explained and described in relation to bicycles which are by far the most common form of such vehicles.

Bicycle brakes are generally of two types, those that are hand operated and those that are foot operated. The most usual foot operated type is generally known as a "coaster" or back pedalling brake. The braking mechanism of the conventional type of coaster brake is contained in the hub of the rear wheel of the bicycle and the operating force is transmitted by the same chain that is used for propelling the bicycle. The means of operating such a coaster brake is by back pedalling, the reverse torque from the pedals being carried to the rear wheel via a tension force in the lower strand of the chain. The braking mechanism for a hand operated brake may be either a caliper arrangement which presses on the opposite flat sides of the rim of the wheel, a drum and shoe brake housed in the hub of the wheel, or a disc brake.Other and less satisfactory braking mechanisms have been used in the past for hand operated brakes, such as the simple "spoon" device that presses on the outside of the tire and the "stirrup" device that presses on the inside surface of the rim.

Both hand brakes and coaster brakes have disadvantages. The main disadvantage of the hand brake is the manual force required to apply it. This reduces the sensitivity of the hand for steering the bicycle, especially when one hand is removed from the handle bars.

The main disadvantage of the conventional coaster brake is that it becomes inoperative if the main drive chain accidentally breaks or slips off either the pedal, or rear wheel sprocket, whilst it cannot be applied to bicycles equipped with derailleur or similar change-speed gears in which the lower strand of the driving chain cannot be used to transmit any tension force.

It has many times been proposed, in order to overcome the problem, to associate a one way clutch mechanism with the pedal crankshaft, by means of which the back pedalling effort may be applied to a brake actuator lever and thence to a brake mechanism which may be of any of the types customarily operated by a hand brake lever.

One disadvantage of almost all such proposals and inventions to date is that the brake will lock the wheel when the bicycle has been brought to a halt while the rider is still exerting a back pedalling torque on the pedal crankshaft. Whilst riders can be taught to avoid this wheel locking by such a brake by reducing the back pedalling torque just prior to the bicycle coming to a halt, just as an automobile driver can avoid an uncomfortably abrupt stop by reducing the force exerted on the brake pedal just prior to the vehicle coming to a halt, this disadvantage of such a bicycle braking arrangement could be eliminated were there a device preventing brake lock-up.

The reason why the wheel of a bicycle that is equipped with a back pedalling brake that is actuated by the pedal crankshaft is locked by the brake when the bicycle is brought to a halt as described above is that the top strand of the bicycle chain is always either taut as in single, 3- and 6-speed bicycles or is kept taut by the spring loaded derailleur device of a 5-, 10- or 15-speed bicycle even when the rider is back pedalling to apply the brake. After such a halt, the brake is in the applied position. This prevents the bicycle wheel from rotating. Since the top strand of the chain is taut, the chain wheel and pedal crank are also prevented from rotating in the sense of direction that will release the brake actuator clutch on the pedal crankshaft and thereby release the brake. In short, the bicycle wheel is locked.This problem of lock-up in bicycles equipped with a crankshaft operated back pedal brake is considered in detail in U.S. Patent No. 4,134,481, issued on January 16, 1979 to Franklin J. Calderazzo. This patent also contains an extensive review of other prior art patents in this field, but is more pertinent than those other patents in that it not only recognizes the lock-up problem but also provides a means for releasing lock-up when it occurs. Unfortunately, this solution is not of general application to crankshaft operated back pedal brakes but depends upon use of a brake actuating mechanism of the type proposed by the inventor, which is considerably more complex than that proposed for example by the present inventor in his United States Patent Serial No.

4,199,046 which issued on April 22,1980. There therefore remains a need for means for preventing lock-up which will be of general application to bicycles with crankshaft operated brake actuators. A further problem with the Calderazzo device is that whilst it is effective in releasing lock-up when it occurs, it does not actually prevent it from happening. Thus if a bicycle equipped with the Calderazzo device is brought to a halt with its brakes applied, the brakes can only be released by withdrawing pawls from engagement with a ratchet wheel comprised by the actuator, resulting in an undesirable sudden abrupt release of the brakes as the pawls disengage before the actuator has returned to its brake releasing position, instead of the normal and expected gradual release.

The present invention provides lock-up prevention in bicycles equipped with crankshaft operated back pedal brake actuators of the normally proposed kind in which the brake actuator and crankshaft, once coupled at the commencement of a brake application, move conjointly from a brake releasing to a brake engaging position, and conjointly back to a brake releasing position at the end of a braking operation. Moreover, the invention can be implemented with the minimum of modifications to standard parts utilized in common types of bicycle.

According to the invention, in a bicycle or other pedal operated vehicle, having a pedal crankshaft operated back pedal brake actuator of the kind in which back pedalling couples the actuator to the crankshaft for movement of the actuator from the brake releasing position to a brake engaging position during application of the brake and said coupling is maintained until the actuator returns to said brake releasing position, lost motion means is introduced into the drive train between the crankshaft and a driving wheel of the vehicle whereby to permit sufficient initial forward angular movement of the crankshaft independent of the wheel to permit the brake actuator to move between its brake engaging and brake releasing positions conjointly with the crankshaft and with the wheel stationary.

This lost motion means may take several forms.

Thus an appropriate degree of relative angular movement may be permitted between a hub and rim portions of a chain wheel attached to the crankshaft.

Whilst the Calderazzo patent referred to above discloses a chain wheel structure in which a limited degree of relative movement occurs between hub and rim portions of the chain wheel, the purpose of the movement is either, depending on its direction, to establish or terminate conjoint movement of the crankshaft and the brake actuator, not to permit such conjoint movement between brake actuating and brake releasing positions to occur independently of movement of the driving wheel of the bicycle or other vehicle. It is apparent from the Calderazzo specification, and indeed claimed as an advantage, that the movement of the brake actuator required to operate the brake means may be quite large, certainly far larger than the small degree of lost motion available in the Calderazzo chain wheel.

An alternative approach is to provide the required lost motion by providing an appropriate length of slack in the drive chain connecting the chain wheel to the driving wheel and ensuring that this slack is available in the correct run of the chain to provide the desired lost motion. In a bicycle with derailleur type gearshift, a substantial amount of slack is available in the lower run of the chain to allow for movement of the jockey wheel which guides the chain into the appropriate rear wheel sprocket. A spring biased idler wheel may be utilized to transfer part of this slack to the upper run of the chain wheneverthe latter is not undertension, the desired lost motion being achieved by transfer of slack to and from the top run as tension is applied to the top chain run during forward pedalling or released during back pedalling.In bicycles without derailleur type gearshifts, a similar effect may be achieved by adding a second idler wheel taking up slack in the lower chain run in place of the jockey wheel, Conveniently, this second idler wheel is mechanicallylinkedtothefirstidlerwheel by being mounted on a common pivotal structure so that slack released by one idler wheel is automatically taken up by the other.

Transfer of slack by the above means provides a similar effect to providing float between the rim and hub of the chain wheel, and the actual method employed may depend both on the type of drive train employed in the bicycle and the type of back pedal operator employed. Thus in a bicycle with a hub-type gearshift or a fixed gear ratio, the doubleidler arrangement is preferred since it requires no modification of the existing drive components other than lengthening of the chain. In a bicycle, typically a five speed bicycle, with a derailleur type gearshift applied to the rear wheel hub, only a single idler is required.In a bicycle with ten or more speeds, and a chain wheel with multiple rims, there are complexities in applying an idler to the top run of the chain, and the provision of float in the chain wheel will generally be preferred, provided that sufficient lost motion can be introduced in this manner to permit the brake actuator to move between its brake actuating and brake releasing positions.

Since the arrangement of the invention permits normal and graded release of the brakes under all conditions, it acts to prevent lock-up occurring, rather than merely as a means to provide sudden and full release of the brake from a lock-up condition, as in the Calderazzo arrangement.

Further features of the invention will become apparent from the following description of the preferred embodiment of the invention with reference to the accompanying drawings.

In the drawings: Figure lisa vertical elevation of the chain wheel, pedal arm and spring assembly for a 5-speed bicycle made requiring minimal modification of conventional components and looking from the left side of the bicycle towards the right side; Figure2 is a section on line A-A in Figure 1; Figure 3 is an enlarged view of the hub portion of Figure 1; Figure 4 is a partial section on line B-B in Figure 3; Figure 5 is a vertical elevation of the chain wheel, pedal arm and spring assembly for a 10-speed bicycle looking from the left side of the bicycle towards the right side; Figure 6 is a section on line C-C in Figure 5; Figure 7 is a vertical elevation of the chain wheel, pedal arm and spring assembly for a 3-or 5-speed bicycle looking from the left side of the bicycle towards the right side;; Figure 8 is a section on line D-D in Figure 7; Figure 9 is a vertical side elevation of an antibraking-locking device that is suitable for single, 3and 6-speed bicycles with the centre lines of the chain, the pitch circles of the sprocket and chain wheel and a portion of the bicycle frame shown in light lines; Figure 10 is a view in the direction A-A in Figure 1; Figure 77 is a vertical side elevation of an antibrake-locking device that is suitable for a derailleur type 5-speed bicycle with the centre lines of the chain, the pitch circles of the sprockets and chain wheel, the rear derailleur idlers and a portion of the bicycle frame shown in light lines; Figure 12 is a view in the direction B-B in Figure 3; Figure 13 is an outline view of a bicycle showing the frame, brake actuator and rear brake.

The embodiments of the invention are described as applied to a bicycle equipped with a crankshaft operated back pedal brake actuator. Such a bicycle 50 is shown diagrammatically in Figure 13 with its drive train omitted, various possible forms of conventional drive train being illustrated in otherfigures. The bicycle has a crankshaft operated brake actuator 52 connected to a brake 54 acting on a rear wheel 58 by a cable 56, although other forms of brake can of course be used. The brake actuator is preferably but not necessarily of one of the forms described in my United States Patent No. 4,199,046 issued April 22,1980.

Referring now to Figures 1 to 4, a semi-floating chain wheel 1 has a hub 2 to which it is assembled by a press fit. The hub 2 is a running fit on a sleeve 3 which is a press fit in a pedal arm 4 to which a pedal 5 is attached. Sleeve 3 and pedal arm 4 are attached to pedal crankshaft 13 by the usual means. The chain wheel 1 and hub 2 are axially held on the shaft 3 by a retaining washer 6 which in turn is axially held on a reduced diameter extension of the shaft 3 by peening.

When a pedalling force is applied to the pedal 5, it is transmitted to the chain wheel 1 through a drive pin 7 bearing on a land 8 on chain wheel 1. The drive pin 7 is welded to the pedal arm 4 and located by a pin 9. When a braking force is applied to the pedal 5, a leaf spring 10, which is attached to the chain wheel 1 by a fastener 11, exerts forces on the pedal arm 4 and chain wheel 1 causing the chain wheel 1 to rotate "forwards" relative to pedal arm 4 until pin 7 bears against rubber stop 12. Thus, when forward pedalling is recommenced, there will be lost motion as the pedal arm 4 rotates "forward" with respect to the chain wheel 1 until the pin 7 engages the land 8.

It will also rotate pedal crankshaft 3 which will rotate with the brake actuator as described in my United States Patent No. 4,199,046 until the brake is released and the brake actuator clutch which bears on the centre portion of the crankshaft 3 then becomes disengaged. Thereafter the forward pedalling force will be transmitted to the chain wheel 1 through the pin 7 bearing on the land 8 driving the bicycle forward, since the bicycle brake, which is operated by the brake actuator, will have been released.

The important feature of this construction is the lost motion introduced by the freedom of the chain wheel to rotate through a limited arc relative to the pedals, pedal arms and pedal crankshaft and the spring loading of the chain wheel in such a way that this lost motion will enable sufficient motion of the pedals, pedal arms and pedal crankshaft assembly to release the brake actuator whenever forward pedalling is commenced.

An important detail of this embodiment of this invention is the centering of the chain wheel relative to the pedal arm and pedal crankshaft by the hub that is pressed into it. This hub also gives sufficient lateral stability to the chain wheel when the bicycle rider is coasting or braking. As soon as the rider commences to pedal forwards, pin 7 engages land 8 and the flanges on the pin 7 embrace the spring 10, the chain wheel 1 and a slotted plate 14 to which rubber stop 12 is integrally attached. By this means, the chain wheel 1 is firmly attached in a lateral sense to pedal arm 4.

Another embodiment of this invention is illustrated in Figures 5 and 6, which illustrate a pedal arm-chain wheel assembly for a 10-speed bicycle made from parts designed specifically for the purpose and arranged to have a minimum size of hub.

The larger of two chain wheel rims 1 a is attached to the smaller chain wheel rim 1 b by three suitable fasteners 15. The pedal arm 4a has two hub extensions 4b set at 120 degrees to the arm. Each has a drive pin 7a on a common pitch circle which engages one of three slots 16 to drive the chain wheel rims 1a and 1 band to hold them in lateral relationship with pedal arm 4a. The chain wheel rims 1a and 1 bare centred on the hub integral with pedal arm 4a by a running fit between the bore 17 of chain wheel rim 1a and the hub extension 18 of pedal arm 4a. A spring 1 0a performs the same function in this as in the previous embodiment as do the rubber stop 1 2a and the slotted plate 14a.

Athird embodiment of this invention is illustrated in Figures 7 and 8, which illustrate a pedal arm-chain wheel assembly which is suitable for use with either a 3- or a 5-speed bicycle.

The different features of this embodiment of this invention are that a spider 19 is integrally swaged onto an extension of the hub of the pedal arm 4b and that the three flanged drive pins 7b fitting in the slots 16b of the chain wheel rim 1c determine both the lateral and centering relationship of the pedal arm 4b with respect to the chain wheel rim 1 c. The leaf spring 10b performs the same function in this embodiment as the similar springs do in the previous embodiments as does rubber stop 12b. Three arcuate slots 20 at 120 degrees to each other are cut into chain wheel 1 c to allow it to be assembled over the pins 7b which are permanently fixed to the spider 19.

In all the above embodiments of this invention, the amount of "float" or permissible rotary motion of the chain wheel with respect to the pedal arm is about 15 degrees, but this may be altered according to the minimum angular movement of the crankshaft required to ensure release of the brakes.

Referring now to Figures 9 and 10, an anti-brakelocking device for single, and 6-speed bicycles comprises two idlers 21 and 22 which bear on the upper and lower strands of the bicycle chain 41 extending between a rear wheel drive sprocket 42 and a chain wheel 43. Idlers 21 and 22 are mounted in frame arms 23 and 24 which are joined together by a turnbuckle 25 to form a support pivotally mounted on the bicycle at the pedal crankshaft 26.

The spring 27, which is a combination cantilever-coil spring (or may be of the type subsequently described with reference to Figures 11 and 12) surrounds the pedal crankshaft housing 28, connects to the end of the frame arm 23 and loops over the bicycle frame member 29. The spring 27 is so made that it always exerts a downward force on the frame arm 23 which in turn and through the idler 21 exerts a downward force on the upper strand of the bicycle chain. The turnbuckle 25 is adjusted so that when the upper strand of the chain is straight, the slack in the lower run of the chain is taken up. Conversely, when the bicycle rider is coasting or back pedalling, the bicycle chain and idlers 21 and 22 will assume the positions shown in broken lines in Figure 9, with the idler 21 taking up the slack in the upper run of the chain.Therefore when the bicycle rider starts to pedal forwards the chain wheel and the pedal crankshaft 26 will rotate in the forward sense until the slack is transferred from the upper to the lower run and the upper run of the chain is once again straight before the chain will apply a force to the rear wheel sprocket causing it, and the rear wheel, to rotate in the forward sense of direction. This provides, by suitably adjusting the amount of slack in the chain, the required degree of lost motion to move the brake actuator to its released position.

Referring now to Figures 11 and 12, an anti-brakelocking device that is suitable for a derailleur type 5-speed bicycle having a rear wheel sprocket cluster 44, derailleur idlers 45 and 46, and a chain wheel 47 comprises one idler 31 which bears on the upper strand of the bicycle chain 48 and is mounted on the support member 32 which is pivotally mounted on the frame conveniently coaxially with the pedal crankshaft 33. A spring 34, which is a cantilever spring (or may be of the type previously described) passes underthe pedal crankshaft housing 35, connects to the end of the member 32 and is a sliding fit in a retainer 36 which surrounds the frame member 37. The spring 34 is so made that it always exerts a downward force on the member 32 which in turn and through the idler 31 exerts a downward force on the upper strand of the bicycle chain. The member 32 is equipped with a rubber padded stop 38 which bears on the bicycle frame member 39 thereby limiting the downward motion of the idler 31 and the member 32 to the position shown in broken lines. This is the position that idler 31 and member 32 assume when the rider is either coasting or back pedalling to apply the bicycle brake. The extra length of the upper strand of the chain under this condition is provided by overcoming the spring bias of the derailleur idler 46. When the bicycle rider commences to pedal forward, the pedal crankshaft and chain wheel rotate in the forward sense of direction until the upper strand of the chain is taut. This lost motion moves the brake actuator into its brake releasing position so that further forward pedalling by the rider rotates the rear sprocket and wheel and the bicycle thus proceeds forwards.

Claims (10)

1. In a bicycle having a pedal crankshaft, a chain drive connecting the crankshaft to the rear wheel, and a back pedal brake of the type operated by the pedal crankshaft, the improvement comprising incorporating bidirectional lost motion means into the chain drive, the degree of lost motion being such as to allow sufficient forward motion ofthecrankshaft independent of the rear wheel to permit release of said back pedal brake, together with means to bias said lost motion means to a condition in which the rearward lost motion is taken up and said forward lost motion is available.

2. A bicycle according to Claim 1, wherein the chain drive incorporates an endless chain, at least one chain wheel carried by the crankshaft and at least one drive sprocket carried by the rear wheel.

3. A bicycle according to Claim 2, wherein the lost motion means connects a hub portion and at least one rim portion together forming said at least one chain wheel.

4. A bicycle according to claim 3, wherein the lost motion means comprises at least one pin on one of said portions, a slot in the other portion engagingthe pin to form a pin and slot connection, and a spring connecting the portions so as to bias the at least one rim portion towards the most angularly advanced position relative to said hub means permitted by said pin and slot connection.

5. A bicycle according to Claim 2, wherein the lost motion means comprises two idler sprockets, engaging the upper and lower runs of the chain respectively, and means biasing said idler sprockets so as to take up slack in said chain runs, the length of the chain and the bias applied to the idler engaging the upper chain run being such as to enable said idlertotake up a length of chain such as will provide the required lost motion.

6. A bicycle according to Claim 5, wherein the idler sprocket engaging the lower chain run is a chain tensioning idler of a derailleur gear shift applied to the rearwheel of the bicycle.

7. A bicycle according to Claim 5, wherein the idlers are carried by a common support structure mounted for pivotal movement on the bicycle so that movement of the structure results in the transfer of slack in the chain between said upper and lower runs, and spring means act between the bicycle and said support structure to bias the latter to transfer slack in the chain to the upper run.

8. In a pedal operated wheeled vehicle, at least one of whose wheels has a drive sprocket connected therewith to provide forward propulsion of the vehicle and at least one of whose wheels has a brake engageable therewith to arrest the vehicle, said vehicle having a pedal crankshaft, a drive train connecting said crankshaft to said drive sprocket, and a brake train connecting said crankshaftto said brake, the drive train comprising a chain wheel connected to said crankshaft and an endless drive chain, and the brake train comprising a brake actuator connected to said brake and a releasable clutch engaged by reverse motion of said crankshaft for coupling said actuatorto said crankshaft for conjoint motion between brake releasing and brake engaging positions of said brake actuator, the improvement comprising lost motion means introduced in said drive train between the crankshaft and the drive sprocket, biased to permit sufficient angular movement of the crankshaft independently of the drive sprocket upon a change from back to forward pedalling to permit the brake actuator to move conjointly with the crankshaft from said brake engaging to said brake releasing positions.

9. A pedal operated vehicle having a pedal crankshaft, a crankshaft operated back pedal brake actuator of the kind wherein back pedalling couples the actuator to the crankshaftfor movement of the actuator from a brake releasing position to a brake applying position during application of the brake and said coupling is maintained until the actuator returns to said brake releasing position, wherein lost motion means is introduced into a drive train between the crankshaft and wheel of the vehicle driven by said crankshaft and biased to permit sufficient initial forward angular movement of the crankshaft to permit the brake actuator to move from its brake applying to its brake releasing position conjointly with the crankshaft and with the wheel stationary.

10. A bicycle according to Claim 4, wherein said pin is formed on a pedal crank extending radially adjacent said chain wheel.