GB2153460A - A bicycle braking system - Google Patents

Abstract

Operation of either of two brake levers 32,33 causes operation of both of the front and rear brakes of a bicycle: a number of embodiments are disclosed but the systems all include tension-transmitting members-cables or rods-and at least one brake is maintained operable in the event of one member breaking. In Figure 1 each lever has two cables 132,36 and 37, 133 respectively connected thereto-cables 132, 133 are connected to front brake 138-141 and cables 36,37 to rear brake-a triangular connector 145 prevents twisting and ensures operation of the front brake should a cable break. Figure 2 shows a ever utilising a movable pivot screw (78) whereby tension in cables can be adjusted. Figures 3,4 illustrate arrangements for connecting cables to ensure operation if a cable breaks. Figures 6,7 show an embodiment involving rods, 83,87 rather than cables. Differential braking with a smaller braking force at the rear wheel may be obtained e.g. utilizing tension spring(s) or by using front and rear brake blocks of different rim-contacting area, or by using calipers arms of different lengths. Rear brake may be actuated in advance of front brake. <IMAGE>

Description

SPECIFICATION A bicycle braking system The present invention relates to a braking system for a bicycle. It is usual for most bicycles intended for use by adults to be provided with brakes on their front and rear wheels, each operated by a separate manually operable brake-actuating lever mounted one on each side ofthe handlebars where the cyclist can reach them convenientlywhilst riding, with the levers being connected to the brakes either by cables or by rods.

In British PatentApplication No.83.01599 there is described an improved braking system for bicycles in which both brake levers operate both front and rear brakes with a braking-force differential between front and rear brakes as applied by one or both brake levers.

The present invention constitutes an improvement over the system described in that earlier Patent application, particularly to accommodate the possibility of a breakage in a rod or cable linking the brake levers with the brakes, so that fail-safe braking is still available even in the event of such a breakage.

The provision of brakes operated on both wheels from each of two levers stems from the realisation that one ofthe problems which cyclists face is that not only must they maintain the balance ofthe bicycle, but also they require to steerthe bicycle with one or both arms using the handlebars, and to slow down they have to operate one or both brake levers in orderto effect braking whilst, in addition, it is also sometimes necessaryto indicate intended movements to oncoming and following traffic by means of hand signals.

This requirementfor hand signals means that during certain critical periods the cyclist can only have one hand on the handlebars and there is no choice asto which one, so that if during this period it is necessary to use the brakes the cyclist has no choice over whetherto usethefront or rear brake; only the hand actually on the handlebars is available for braking.

It is of course well known that the front and rear brakes of a vehicle react differently to the brakeapplying force, and this is particularly important in the case of bicycles. In fact, due to the forward transfer of weight upon deceleration the adhesion between the road and the rearwheel reduces when the brakes are applied, causing the rearwheel to exhibit a tendency to lock or skid very much soonerthan the front wheel.

This situation is exacerbated in wet road conditions so that a cyclist indicating that he is turning right, and therefore having the right hand offthe handlebars has to exercise considerable caution in applying the rear brake which is usually actuated by means of the left hand brake lever.

Indeed, it is true to say that the application of the brake on either wheel, if applied alone, has significant disadvantages not only because the braking effect may be very considerably reduced (that is reduced by more than half in the case ofthe rearwheel brake being used alone since the contribution to the overall braking effect made by the frontwheel is greater than 50 per cent of the overall braking effect) but also because of the lack of stability when turning and braking at the same time and consequently the most effective braking can only be done in a staight line whilst no hand signals are being given, in which conditions the cyclist is free to apply both brakes using both brake levers. With a system in which both front and rear brakes are applied by either of the two levers, however, this disadvantage is overcome.

According to the present invention there is provided a bicycle braking system in which two brake levers are each independently operable to effect actuation of both front and rear brakes by applying a tension to tension-transmitting members linking the brake levers with the brakes themselves, in which the connections ofthetension members are so formed thatthe connection between at least one brake lever and both brakes is maintained operable in the event of breakage of one ofthetension-applying members.

In a preferred embodiment a respective tensionapplying member is connected to each lever and to each brake, and a connector assembly is provided to interconnectthetension-applying member and to accommodate loss oftension in any one such member due to breakage.

In orderto obtain "differential" braking,thatis braking with a smaller braking force applied to the rear wheel than to the front wheel to compensate forthe propensity ofthe rear wheel to skidding, the braking system ofthe present invention is preferably adapted in such a way that a greater braking force is applied to the front wheel than that applied to the rear wheel.

This can be effected in a number of ways, for example the cable leading to the rear brake may incorporate a tension spring connected in the section of cable between the actuator lever and the rear brake.

Alternatively, of course, both brakes may have tension springs incorporated in their respective actuating cables, the spring rates ofthe springs in the front brake cables being substantially greater than those of the springs in the rear brake cables. The required spring rates can be calculated in advancebyteststo determine the maximum admissible force which it is required thatthefront or rear brake caliper should apply, and then to correlate this with the average force which can be applied by a rider on the brake actuating lever. Likewise, both brake levers may be provided with springs acting to maintain a certain minimum tension on the associated cable so that no slack in the cable can occur even if the other brake leveris operated alone.

Forconvenienceitmaybearrangedthatthe rear wheel brake is actuated slightly in advance of the front wheel brake upon actuation of either lever so that the rear brake is applied before the front brake or, if the lever is only moved over a part of its travel the rear brake can be selectively applied withoutthefront brake in circumstances where only a gradual slowing ofthe bicycle is required. This can be achieved by means of suitable springs and/oradjustment ofthe rear brake calipers so that these contact the rim before the front brake.

The differential braking effect may also be obtained or enhanced by using front and rear brake blocks of different rim-contacting area, or of different materials having different coefficients of friction or by using caliper arms of different length.

In one embodimenttherefore, the connections at each brake caliper may include connections from two cables each of which is operated by a different brake actuating lever. The two cables at each brake will require a separate uni-directional connection which allows one cable to actuate the brake without being hindered bythe connection between the brake and the other cable. To avoid the need for special calipers a two-into-one cable connector may be provided close to the calipers so that no modification of these latter is required. In an alternative embodiment, in which a cable coupling is employed, only one cable is required to lead to each brake lever and to each brake caliper and no special connection ofthe cables will be required exceptforthetensioning spring referred to above.

The present invention also comprehends a bicycle having a braking system as hereinbefore defined.

Various embodiments of the present invention will now be more particularly described, byway of example, with referenceto the accompanying drawings, in which: Figure 1 is a perspective view of a front part of a bicycle equipped with a braking system according to the present invention; Figure 2 is a view, on an enlarged scale with respect to Figure 1, of a first embodiment of brake lever suitable for forming part of the braking system of the present invention; Figure 3 is a perspective schematic diagram illustrating a two-into-one cable connector which can be used with the braking system ofthe present invention; Figure 4 is a perspective view of an adapterto be fittedtoa cable brake system;; Figure 5 isa perspectiveviewofa braking system incorporating the adapter of Figure 9; Figure 6 is a perspective view of a part of a rod brake system formed as an embodiment ofthe invention; and Figure 7 is a front view seen from the arrowAfor FigureS.

Referringfirstto Figure 1 ofthedrawings,thefront fork and handlebars of a bicycle are shown, equipped with a front brake caliper ofthe centre-pull type and comprising two arms 138,139 each of which carries a respective brake block 140, 141. The two arms are pivoted together at 142 and cross over at the pivot point in a cruciform arrangementwiththetwo opposite ends, remote from the brake blocks, being connected to a yoke 143 passing over a hook 144 connected to a triangular coupling 145 to which two cables 132,133 are connected. The cabie 132 leads to a brake lever 32 and the cable 133 leads to a brake lever 33. Each of the two levers 32,33 also has a second cable connected thereto and identified as cables 34 and 35 respectively.

The advantage of the connection via the triangular connector 145 lies in the factthat no twisting force is applied to the centre-pull brake due to the necessary offsetting of the cables 132,133, necessary, that is, because there are two cables. lfthere were only one cable, of course, then this could be aligned with the pivot 142 between this and the fixed bracket 145.

Alternativelythetwo cables could both be directly clamped to the hook 144. However, the provision of coupling 145 allows variation in the tension to be accommodated when only one brake lever is operated, and more importantly, if a brake cable should break.

Referring now to Figure 2, the hand brake lever 35 is shown. The cable 33 from the front brake, as shown in Figure 1, is connected to the lever 35 together with the cable 37 leading to the rear brake.

Thetwo cables 37, 133 are connected to the brake lever35byspacedconnectors73,74which are different distances from a pivot 62 about which the brake lever 35 turns with respectto its fixed mounting.

The outer casing of the cable 133 is located art a position spaced furtherfrom the pivot 62 than the outer casing of the cable 37. The connectors 73,74 are linked by a rocker 76 which is pivoted at 77 to an adjustable pivot screw 78 mounted in a slot (not shown) in a fixed plate 75 carried by the brake lever 35.

The pivot screw can be slackened and moved along the slot in the plate 75 towards or away from the pivot 62 to varythe ratio ofthe leverarmsofthe rocker76.

Thus, as shown, for a given force exerted by the brake lever 35 when it is squeezed in a direction ofthe arrow Tof Figure 2 the cable 37 will experience a smaller tension than the cable 133.The rear brake, actuated by the cable 37, will thus be applied with less force than the front brake which is applied bythe cable 33.

Alternatively, the screw 78 may be adjusted in position with respect to the two couplings 73,74 so that the difference in the radial positions from the pivot 62 is compensated and the same tension applied to the cables 37, 133 by a given force applied to the brake lever 35. The close spacing of the rocker 76 and the plate 75 ensuresthat if one cable should break the otherwill nevertheless be tensioned upon actuation of the lever 34, force being transmitted by the contact of the said othercable withtheface ofthe plate 75.

Referring nowto Figure 3, a simple cable adapter useful for avoiding any twisting problems which might be encountered with an embodiment such as that illustrated in Figure 2 is shown. By using such a cable adapterthe caliper brake of Figure 2 could be replaced by a conventional single cable caliper brake of known type.The adapter illustrated in Figure 3 is shown attached to the two cables 36,37 by their conventional adjustersscrewed into afixed plate 161 of a base 162 having a longitudinal slot 163 in which slides a coupling body 164 having significant length parallel to the slot 163 and prevents the block 164 from turning about an axis perpendicularto the slot 163 and the plane ofthe base plate 1 62.The block 164 has three keyhole slots 166,167 and 168 for receiving the ends of the cables 36,37 and the end of a single cable 169 respectively. The cable 169 then leads to the caliper brake. A cover 170 closes the base 162 and keeps the whole mechanism dustfree. By filling the casing with a suitable grease or other lubricant it can be ensured that the block 164 slides freely along the slot 163 even when atension,which is laterallyoffsetfrom the block 163, is applied via one or other of the cables 36,37. Of course, if both brake levers are actuated then both cables 36 and 37 will be tensioned and no offsetforce will be applied to the block 164, but if only one brake lever is actuated then an offsetforce will be generated and is absorbed by the block 164 so that a straight tension on the cable 169 is generated.

In order to avoid the necessity for adapting both the brake levers and the brake calipers to accept two cable connections each, a cable connector may be employed, in which a coupling member interconnects all fourcablessothattensionon oneofthem is transmitted to two others. In the connector shown in Figure 4two cables 206,207 are shown leading from respective brake levers (not shown) and two cables 217,218 lead to respective brake calipers (not shown).

The brake levers and brake calipers can thus be entirely conventional. In the connector shown a fixed body 201 is intended to be mounted to a fixed part of the bicycle frame, for example as illustrated in Figure 10, andthetwo cables 206,207 are attached by their adjustable connectors to an upper or cover plate 203, whilsttheir connector nipples 208,209 at the ends of their respective inner cables, are connected to a plate 210 acting as the cable coupling member as will be described in greater detail below. Figure 4 is a schematic diagram and does not show in detail the practical arrangements necessaryfor attaching the nipples of the cables to the plate 210, northe necessary practical constructions for mounting the outer cable adjusters to the cover plate.

The outer casings of the cables 217,218 are connected to a base plate 204 by suitable adjusters, like those ofthe cables 206,207.

The coupling plate 210 hasfour lobes each of arcuate form centred on the connection pointwith the associated nipple 208, 209,211,21 2.The connections to the nipples 208,209 define a line which is perpendicularto that defined bythe nipples 211,212.

Now, if tension is applied to both cables 207,208 the whole ofthe plate 21 is lifted (as viewed in Figure 4) and both cables 217,218 are tensioned in the normal way. If only one cable, for example, the cable 207, is tensioned, whilstthe cable 208 remains untensioned, that is if one brake lever is operated whilethe other is not, then the resistance applied by the tension in the cables 217,218 will cause the plate 210 to turn about an axis defined by the line joining the nipples 211,212 until the lobe 220 around the nipple 208 contacts the bottom wall 204 after which the contact point between the lobe 220 and the bottom wall 204 acts as a fulcrum andthecables217,218aretensionedtoapplythe brakes.If one ofthe cables 217,218 should break, then the plate 210will no longerturn about an axis defined bythe line joining the nipples 211,212, but rather will rockaboutthe lobe 220 (orthe lobe222 if thecable208 is tensioned in place of the cable 207) until the adjacent lobe 223 or 221 contacts the bottom wall 204, and thereafter the plate 210 will turn about an axis defined bythetwo contact points between the lobes and the bottom wall 204. Asuitable location for the adaptor201 is illustrated in Figure 5.

The embodiment illustrated in Figures 6 and 7 is a modification ofthe known rod-brake system. As can be seen in Figure 6, two brake levers 90,190 are formed integrally at the ends of rods identified with the same reference numerals and carried on supports 71,72 and 171,172 respectively. These brake levers 90, 190 apply tension to two brake rods 83,87 via a connection mechanism generally indicated 80 which actstotension both rods from an actuation of either brake lever. Thismechanism comprises a generally U-shape bracket 88 the limbs of which are freely pivoted on the brake rod 90 and the brake rod 190.

Connection is made by introducing the ends ofthe brake rods 90,190 through aligned apertures in the limbs ofthe bracket 88 and screwing nuts 174, 175 to threaded ends thereof over cam-shape levers 191, 192 which are held by the nuts 174, 175 onto shoulder (not shown) on the ends ofthe rods 90, 190 so that the levers 191, turn with the rods as the brakes are squeezed. Springs 176,177 acting between the levers 191,192 and the bearers 72,172 biasthe rods 90,190 to the "brakes released" position.

As will be seen in Figure 7, the bracket 88 carries a pivot screw 178 the tip 89 of which contacts a transverse rocker member 85 to form a pivot about which the rocker 85 can turn. The rocker member 85 hastwo holes (not shown) one at each end,for allowing the two brake rods 83,87 to pass therethrough. These brake rods 83,87 have enlarged heads 180, 181 which contactthe respective lever arms ofthe rocker member 85, to form respective pivots 84,86.

The levers 191, 192 fixed to the respective brake rods 90,190 have lower portions (notvisible in Figure 6) which engage underthe bracket 88so that when either ofthe brake levers 90 or 190 is actuated the associated cam-shape levers 191 or 192 will engage under the bracket 88 which will rotate causing the pivot pin 178 to rise and applytension via the rocker member 85 to the two brake rods 87,83 in proportions depending on the length ofthe lever arms from the pivot 89to the two pivots 86 and 84 respectively. The screw 178 may be made laterally adjustable in order to vary the relative lengths of these two lever arms. If only one brake lever isturned the other is not disturbed by the movement ofthe bracket 88 due to the free mounting of this latter on the two brake lever rods 90, 190, whilst the same front/rear differential braking is achieved when either (or both) ofthe brake levers is squeezed.

Claims (15)

1. A bicycle braking system in which two brake levers are each independently operable to effect actuation of both front and rearr brakes by applying a tension to tension-transmitting members linking the brake levers with the brakes themselves, in which the connection ofthetension members are so formed that the inter-connection between at least one brake lever and both brakes, or between both brake levers and at least one brake is maintained operable in the event of breakage of one ofthe tension-transmitting members.

2. A bicycle braking system as claimed in Claim 1 in which a respective tension-transmitting member is connected to each lever and to each brake, and a connector assembly is provided to inter-connectthe tension-transmitting members and to accommodate loss of tension in any one such member due to breakage.

3. A braking systems as claimed in Claim 1 or Claim 2 adapted such that a greater braking force is applied to the front wheel than applied to the rear wheel upon actuation of either brake levers.

4. A braking system as Claimed in claim 3 in which the tension-transmitting members are cables, and the cable leading the rear brake incorporates a tensioner spring connected in the section of cable between the actuation lever and the rear brake.

5. A braking system as claimed in any preceding claim in which the rear wheel brake is actuated in advance ofthefrontwheel brake upon actuation of either lever so that the rear brake is applied before the front brake or, if the lever is only moved over a part of its travel, the rear brake can be selectively applied withoutthefront brake.

6. A braking system as claimed in any preceding claim, in which the tension-transmitting members are cables, and each pair of cables leading to a respective brake is connected to the brakevia a triangular link member having a cable secured to each oftwo apices and the brake fixed to the third.

7. A braking system as claimed in any of Claims 1 to 5, in which the tension-applying members are cables, and a connector assembly is provided having a casing within which is housed a connector element to which the two cables leading to each brake lever are connected at connection points joined by a first line, and the two cables leading to the two brakes are connected at points joined by a line extending substantially perpendicularly with respect to the said first line joining the fixing points to cables leading to the levers.

8. A braking system as claimed in any preceding Claim, wherein each of the said front and rear wheel brakes is a calliper brake having two brake-actuating cables connected thereto, each cable being connected to the caliper buy a respective couplings with both couplings being spaced from the caliper pivot bythe same distance.

9. A braking system as claimed in Claim 8, in which each said brake caliper includes two brake arms carrying respective brake blocks, and two lever arms connected to or integral with respective brake arms, the lever arms carrying dual cable couplings for attaching a respective brake-actuating cable thereto with one cable on each side of the lever arms.

10. A braking system as claimed in any preceding claim, in which a cable connecting device comprises a first plate fixableto the bicycle fixed frame and a rocker memberto which the ends of the four cables are connected in such a way as to turn with respect two the fixed plate when tension is applied to one of the cables by actuation of one or both brake levers.

11. A braking system as claimed in Claim 10, wherein the rocker member is supported solely by the connections thereto ofthe said cable.

12. A braking system as claimed in Claim 10, or Claim 11, in which the rocker member has a slot by means of which the position of at least one cable is adjustable with respect two the positions ofthe other cables,wherebyto adjusttheeffective length of the lever arms constituted by the rocker plate.

13. A braking system as claimed in any of Claims 1 to 4 in which the said tension-applying members comprises articulated rods leading from each ofthe frontwheelbrakeandtherearwheel brake, andthere are means inter-linking the said two brake actuating levers such that both sets of rods are actuated by operation of either lever.

14. Abraking system substantially as herein described with reference to, and as shown in, the accompanying drawings.

15. A bicycle having a braking system as claimed in any preceding claim.