GB2123501A - A braking system for a cycle, specifically a bicycle - Google Patents

Abstract

A cycle (pedal, motor or tri-) is provided with a braking system in which a single brake actuating member (34 or 35) is adapted to be connected to control the operation of brakes (30, 31) on both the front and rear wheels (29, 19) of the cycle. The member is shown as a manually operable lever - it could be a pedal. At least one wheel (19, 29) of the cycle is shown operatively connected to the levers (34, 35) and adapted to be actuated upon operation of either or both of the said levers via cables. The specification illustrates a number of embodiments of caliper brakes actuable by either of two cables connected respectively to levers (34, 35) (see Figures 2, 4) and various forms of lever are disclosed (see Figures 3, 5). It may be arranged that the rear brake is actuated in advance of the front brake; and that a smaller braking force is applied at the rear brake than at the front brake (see e.g. Figures 5, 6). Figure 7 illustrates an adaptor device for fitting in a conventional cable brake system to enable both brake levers to actuate both front and rear brakes. <IMAGE>

Description

SPECIFICATION A braking system for a bicycle The present invention relates to a braking system for a bicycle. Although the invention will be particularly described hereinafter with reference to pedal bicycles it is to be understood that it is equally applicable to motor bicycles and indeed, although they are rare, to tricycles as well, although various modifications to obtain balance between the rear wheels of a tricycle would be required.

Conventionally, bicycles are provided with brakes on their front and rear wheels, each operated by a separate manually operable actuating lever mounted on respective sides of the handlebars where the cyclist can reach them conveniently whilst riding. Usually the left hand brake lever actuates the rear brake and the right hand brake lever actuates the front brake. Known brake mechanisms either comprise a cable or rod operated rim brake, or else a hub brake. The latter are generally of the drum brake type but are not as common or popular as the former the most common type of which is operated via a cable and includes a caliper arrangement which spans the rim of the wheel and acts to press a pair of brake blocks of suitable material against the rim as the calipers are squeezed upon operation of the brake actuating lever.

Force from the brake actuating lever is transmitted in these known bicycle brakes via a cable comprising an inner, tension-applying cable and an outer compression casing. Sometimes, for lightness, a part of the outer compression casing is omitted and the inner tension cable extended between two fixed points on the bicycle frame.

Other known braking systems for bicycles include a stirrup-shape bracket which spans the rim of the wheel and carries two brake blocks which are moved radially into engagement with the rim as the "stirrup" is drawn radially away from the hub by operation of the brake level. Such brakes have the advantage of simplicity over the more widely used caliper brake, but since they cannot apply the same degree of force they are relatively less effective.

One of the problems which cyclists face is that not only must they maintain the balance of the vehicle, but also they require to steer the bicycle with one or both arms using the handlebars, and sometimes they have to operate one or both brake levers in order to effect braking whilst, in addition, it is also sometimes necessary, to indicate intended movements to oncoming and following traffic by means of hand signals. This requirement for hand signals means that during certain critical periods the pedal cyclist has only one hand on the handlebars and during this period it is frequently necessary to change speed, in particular to decelerate.This operation requires the use of the brakes and since the individual brakes are actuated by separate levers the pedal cyclist has no choice over whether to use the front or rear brake whilst at the same time giving a hand signal to other traffic because 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 brake-applying force, and this is particularly important in the case of bicycles and motorcycles.

In fact, due to the forward transfer of weight upon deceleration the adhesion between the road and the rear wheel reduces when the brakes are applied, causing the rear wheel to exhibit a tendency to lock or skid very much sooner than 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 off the handlebars has to exercise considerable caution in applying the brake by means of the left hand brake lever since this usually actuates the rear wheel brake.

Indeed, it is true to say that the application of the brake on either wheel, if applied alone, has significant disadvantages not only from the point of view that the braking effect is considerably reduced (that is reduced by more than half in the case of the rear wheel brake being used alone since the contribution to the overall braking effect made by the front wheel is greater than 50% of the overall braking effect) and consequently the most effective braking can only be done in a straight line whilst no hand signals are being given, in which conditions the cyclist is free to apply both brakes using both brake levers.

The present invention seeks to provide a braking system in which the disadvantages of the different braking effect of front and rear brakes is overcome whilst at the same time allowing a cyclist to give hand signals without detrimentally affecting the braking efficiency.

According to one aspect of the present invention there is provided a braking system for a bicycle, in which a single manually operable actuating lever is connected to control the operation of brakes on both front and rear wheels of the bicycle.

In a preferred embodiment of the invention the said manually operable actuating lever is connected by cable to the said front and rear brakes.

In order to obtain "differential" braking, that is braking with a smaller braking force applied to the rear wheel than to the front wheel to compensate for the propensity of the rear wheel to skidding, the braking system of the present invention is preferably adapted in such a way that the full braking force is applied to the front wheel whilst a smaller braking force is 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 of the 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 advance by tests to determine the maximum admissible force which it is required that the front or rear brake caliper should apply, and then correlate this with the average force which can be applied by a rider on the brake actuating lever.

For convenience it may be arranged that the rear brake is actuated slightly in advance of the front brake upon actuation of the common 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 without the front brake in circumstances where only a gradual slowing of the bicycle is required.

This can be achieved by fitting suitable springs in the rear brake cables and adjusting the rear brake calipers to contact the rim before the front brake.

A transient effect of this type may also be provided by means of an hydraulic bleed arrangement providing a transient pressure limiting effect determined by the size of a bleed orifice.

Conveniently a single cable interconnects the front brake and the rear brake and the brake operating lever, this cable passing over a pulley mounted on the operating lever. The pulley may be freely rotatable, in such a way as to compensate for difference in the brake actuating movements of the brakes when both brakes are applied, in which case the differential braking effect is obtained by using front and rear brake blocks of different rimcontacting area, or of different materials having different coefficients of friction or by using caliper arms of different length. Alternatively the pulley may be clamped so that the cable can experience different tensions on either side of it.

With wear, the brake calipers will gradually adopt different spacings from the wheel rim so that after a short time the displacement of the actuating cable required to apply a given brake force via the brake caliper will be different Toprevent the brake lever from becoming slack when this happens a further spring may be provided at the lever to take up any slack in the cable.

The common lever of the present invention for actuating both front and rear wheel brakes may, as in conventional brakes, be mounted on the handlebar to be easily reached by one or other of the riders hands, although alternatively it may be mounted on a fixed part of the frame so that either hand may be used.

In a preferred embodiment of the present invention, however, there are provided two manually operable levers both of which opera.te both front and rear brakes so that a rider can operate the brakes of both wheels using either hand thereby freeing the other hand for making road signals without detrimentally affecting the braking efficiency of the bicycle.

The connections at each brake caliper, therefore, or other brake device if brakes other than caliper brakes are employed, thus includes connections from two cables each of which is operated by a different brake actuating lever. The two cables at each brake therefore require a separate uni-directional connection which allows one cable to actuate the brake without being hindered by the connection between the brake and the other cable. This is achieved, in accordance with the principles of the present invention, by employing a common reaction bar with a recessed aperture housing each cable connector in such a way that relative movement between the cable connector and the common connector bar is prevented in one directional sense and permitted in the opposite directional sense.This will be described in more detail below with reference to the specific embodiment illustrated in the accompanying drawings.

The present invention also comprehends a bicycle, which may be a pedal bicycle or a motor bicycle, having a braking system as herein defined in which the brakes of both the front and rear wheels can be actuated from a common actuating member, preferably a manually operable lever although a foot pedal may be provided, in which case a common or respective cable would extend from it to respective brake calipers or other suitable brake devices.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view 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 caliper suitable for forming part of the braking system of the present invention; Figure 3 is an enlarged detail of a brake actuator lever suitable for use in the embodiment of Figure 2.

Figure 4 is a perspective view of a part of a brake caliper formed as a modification of that shown in Figure 2; Figure 5 is a schematic diagram illustrating the principle of operation of a brake lever adapted to provide a differential braking effect; Figure 6 is a schematic diagram illustrating the principle of operation of a differential rod brake; and Figure 7 is a perspective view of an adapter to be fitted to a cable brake system to achieve a similar effect to that achieved in the rod brake systems of Figure 6.

Referring now to the drawings, a bicycle of conventional type is generally indicated with the reference numeral 11, this bicycle comprising a frame 12 having a cross bar 13, a down tube 14 and a saddle column 1 5 carrying a saddle pillar 16 on which is carried a saddle 1 7. A rear fork 18 provides a mounting for a rear wheel 1 9 which is driven by a chain 20 via a chair wheel 21 and sprocket 22, the chain wheel 21 being turned by cranks 23, 24 having pedals 25, 26 respectively.

The junction between the cross bar 13 and down tube 14 is formed by a fork bearing 27 carrying, pivotally, a pair of front forks 28 supporting a front wheel 29. The front wheel 29 is braked by a caliper brake 30 and the rear wheel by a caliper brake 31. The front brake caliper 30 has two cables 32, 33 the first of which leads to a right hand brake lever 34 and the second of which leads to a left hand brake lever 35. The levers 34, 35 also are connected to respective cables 36, 37 both of which lead to the rear brake caliper 31.

The interconnections are such that the operation of either lever 34 or lever 35 (or both levers if desired) causes both brake calipers 30, 31 to close clamping the rims of the wheels 29, 19 respectively and effecting the required braking action in dependence on the pressure applied by the brake lever or levers.

As can be seen in Figure 2 a brake caliper, in this case a rear brake caliper, has two arms 38, 39 each of which carries a respective brake block 40, 41 and the two arms are pivoted together at 42.

The arm 39 has a subsidiary arm 43 extending laterally away from the pivot 42 and the arm 38 has an extension 44 beyond the pivot 42 diverging at an angle of about 200 with respect to the arm 43. Two parallel apertures 45, 46 allow two parallal cables 36, 37 to pass through the upper arm 44, these apertures being counter bored to accept adjustable connectors 49, 50 which receive the ends of the cables 36, 37 which latter are, conveniently, of the conventional "Bowden" cable type leaving an outer casing and an inner tension wire 47, 48 respectively. Each tension wire 47, 48 has an enlarged connector or nipple soldered to the end thereof, which is received in a respective counter bored aperture 51,52 in the lower arm 43, these apertures 51,52 being aligned with the counter bored apertures 45, 46 in the upper arm 44.The apertures 51, 52 are also slotted (in a manner not shown) to allow the cable tension wires 47, 48 to be inserted laterally before a tension applied to the cable draws the nipple at the free end of the cable into the respective cavity 51, 52. Two different examples of cable tensioner are illustrated in Figure 2. The cable 36 is fitted to an adjustable connector 49 which houses a tension spring 70 to which one end of the tension wire 47 is connected, a short length of wire 47a leading from the spring 47 to the lever 43. The alternative arrangement illustrated on cable 37 is a compression spring 71 located between retainer cups 72, 73 in a break in the outer casing 37. The effect of the tension spring 70 in the cable 47 and the compression spring 71 in the casing 37 is in practice the same.

As can be seen in Figure 3, one of the cables, for example the cable 47 and its associated outer casing 36 leads to the brake lever 61 illustrated in Figure 3. The cable 47 passes over a pulley 60 carried by the lever 61 and enters a second outer casing 66 which leads to the front brake 30 of the bicycle 11. The two outer casings 36, 66 are received at their ends in recesses 64, 65 carried by a brake lever support and reaction body 63 on which the brake lever 61 is pivotally mounted by means of a pivot 62. When the lever 61 is operated, therefore, the pulley 60 is drawn downwardly in a direction of the arrow F of Figure 3 to apply tension to the inner cable 47 thereby causing the brake caliper illustrated in Figure 2 to close and also the other brake caliper of the bicycle 11, namely the brake caliper 30 of the front wheel.As mentioned above, in order to obtain a differential braking effect with otherwise identical front and rear brake calipers the pulley 60 must be clamped and frictionally engage the cable.

With reference to Figure 2 it will be appreciated that a tension on the cable 47 causing the two arms 43, 44 to approach one another is permitted by the cable 48 the nipple of which simply emerges from the recess 52 as the two arms 43, 44 are drawn together. Alternatively, if the spring rates of the two springs 70, 71 are suitably chosen, they will retract or extend respectively to accommodate any slack in the unused cable. A biasing spring 75 holds the two arms 38, 39 of the caliper apart and thus maintains normal tension in the cables.

In an alternative embodiment, not illustrated, the ends of the outer casings 49, 50 are mounted in cup-like receiver elements which are biased by compression springs surrounding the cables between the ends of the outer casings 49, 50 and the arm 44 whereby to accommodate any variations in the tension applied by one or the other of the cables 47, 48.

Referring now to Figure 4 the caliper shown is a modification of a conventional caliper to make it similar in many respects to the caliper illustrated in Figure 2; consequently corresponding components will be identified with the same reference numerals. Like the arms 43, 44 of the embodiment of Figure 2, each of which have aligned apertures, the caliper of Figure 4 has two arms 53, 54 at the free ends of which are located respective elongate slots 55, 56. The upper slot 55 receives a transverse support or crosspiece 96 carrying two threaded adjusters 57, 58 having cup-like recesses in which respective outer cables 36, 37 are received in such a way that their inner cables 47, 48 respectively pass through the adjusters and the nipples 51, 52 at the ends of these fit into respective slotted counterbored apertures 67, 68 in a lower crosspiece 90.The transverse support 56 is formed in two parts and clamped on either side of the arm 54 by nuts 56a.

By having the crosspieces at the ends of the arms 53, 54 both cables 47, 48 exert the same force on the rear brake whereas in the embodiment of Figure 2 the innermost cable 47, that is the one close to the pivot 42, will exert less leverage on the arms 43, 44 than the cable 48 which is at a radially outer position thereby giving it a longer lever arm. The two cables 47, 48 lead to different brake levers at the handlebars so that the braking force applied by the rear brakes for a given force exerted on one handlebar brake lever will be different from that exerted from the other. This can be minimised by making the two adjusters close together, or as mentioned above, entirely eliminated by employing a side-by-side arrangement as illustrated in Figure 4.

Referring now to Figure 5 this principle is made use of in the hand brake lever 59 where the two cables 47 and 69 which lead respectively to a rear and a front brake are connected at the brake lever 59 at radially spaced connectors 73, 74 with respect to a pivot 62 of the brake lever 59.

Likewise, the outer cables 36, 75 of the respective tension cables 47, 69 are located at positions spaced from one another along a radial line with respect to the pivot 62 so that for a given force exerted by the brake lever 59 when it is squeezed in a direction of the arrow T of Figure 5 the cable 47 will experience a smaller tension than the cable 69. The rear brake, actuated by the cable 47, will thus be applied with less force than the front brake which is applied by the cable 69.

Should it be desired not to employ this differential braking effect the two couplings 73, 74 could be secured to a pivoted rocker bar such as that illustrated in broken outline and identified with the reference numeral 76 which is pivoted on the brake lever 59 by a pivot 77 which passes through a slot 91 in the bar 76 and acts as a fulcrum for the rocker bar 76. As shown in Figure 5 this fulcrum is asymmetrically positioned with respect to the two couplings 73, so that the difference in the radial positions from the pivot 62 is compensated and the same tension applied to the cables 47, 69 by a given force applied to the brake lever 59.This can be varied by moving either the pivot 77 radially with respect to the pivot 62 with the rocker bar in a given position, or by varying the radial position of the rocker bar 76 with respect to the pivot 62, the pivot 77 remaining fixed. These adjustments are possible because of the slot 91 in the rocker bar 76, which may be matched by similar slots (not shown) in the lever arm 55 itself.

In the embodiment illustrated in Figure 6 a stirrup-shape bracket 78 carries two brake blocks 79, 80 which are applied radially to a rim 81 of a wheel 82 when the bracket 78 is drawn in the direction of the arrow S of Figure 6 by a rod 83.

Differential braking is achieved by pivotally connecting the forward end of the rod 83 at a pivot 84 on a transverse connector bar 85 the other end of which is pivotally connected by a pivot 86 to a tension rod 87 leading to the rear brakes. Braking force is applied by a tension rod 88 pivotally connected by a pivot 89 to the transverse bar 85 and actuated, as schematically illustrated, by a brake lever 90 which is moved in the direction of the arrow U of Figure 6 about a pivot 91 upon brake actuation, The rod 83 leads to the front wheel brake whilst the rod 87 leads to the rear wheel brake and the pivot 89 is asymmetrically positioned with respect to the two pivots 84, 86 on the transverse bar 85 such that a major proportion of the braking force is applied to the rod 83 and a minor proportion of this force applied to the rod 87.

Although in the embodiments described the caliper brakes have been illustrated in the most common form with laterally offset operating arms such as the arms 53, 54, it is entirely possible for centrepull-type caliper brakes to be substituted in any of the arrangements described.

Referring now to Figure 7, there is shown an adapter device for fitting in a conventional cable brake system but which enables both brake levers to actuate both front and rear brakes. The device illustrated in Figure 7 comprises a body 101 formed as a generally C-shape metal bracket with a slot 102 in the base and two generally parallel arms 103, 104. The first of these, namely the arm 103, has openings for receiving couplings 105, 106 of two cables 107, 108 respectively. The cable 107 leads to the brake lever on the left hand handlebar and the cable 108 leads to the brake lever on the right hand handlebar although this connection is, in fact, arbitrary and the opposite connection could equally well be made.The couplings 105,106 are aligned on a centre line X-X of the arm 103 and the inner cables 107a, 1 07b in the outer sheaths of the cables 107,108 extend through the arm 103 and terminate in suitable connector nipples (not shown) connected to a cylindrical connector element 109 which passes through a rocker lever 110, the cables 1 07a, 1 07b, being connected to the member 109 on either side of the lever 110.

Also connected to the lever 110 are respective connector nipples 111, 112 of inner cables 113, 114 which pass through respective apertures 11 5, 116in the arm 104.Thecables 113, 114are housed within outer cable sheaths 11 7, 11 8 which lead, respectively, to a front brake caliper and a rear brake caliper of a bicycle.As can be seen in Figure 7 the two connector nipples 111, 11 2 are symmetrically positioned on the rocker lever 110 with respect to its length, but the connector member 109 is laterally offset towards the connector nipple 111 so that the ratio between the lever arms defined by the rocker, considering the connector member 109 as a fulcrum, have a length ratio of 40:60 so that the force applied to the rear brake cable 114 is less than that applied to the front brake cable 11 3 when a given force is applied by either or both of the brake lever cables 107a, 107b.

The slot 102 in the body 101 allows this body to be secured to a fixed part of the bicycle frame should this be desired, although since it is a lightweight component and the couplings are all securely made and not dependent on tension, this could in fact be a "flying" coupling located in the length of brake cable normally positioned.

somewhat forwardly of the handlebars of a bicycle.

Claims (19)

1. A braking system for a bicycle in which a single manually operable brake actuating lever is connected to control the operation of brakes on both front and rear wheels of the bicycle.

2. A braking system as claimed in Claim 1, in which the said manually operable brake actuating lever is connected by cable to the said front and rear brakes.

3. A braking system as claimed in Claim 1 or Claim 2, in which there are provided means for ensuring that a given operation of the said brake actuating lever applies a smaller braking force at the rear brake than at the front brake.

4. A braking system as claimed in any preceding Claim, in which the system is arranged so that upon actuation of the brake actuating lever the rear brake is applied before the front brake.

5. A braking system as claimed in any preceding Claim, in which a single cable interconnects both the front and rear brakes and the operating lever, this cable passing over a pulley mounted on the operating lever in such a way as to compensate differences in the brake actuating movement as both brakes are ap:ied.

6. A braking system as claimed in any of Claims 3, 4 or 5 in which the means for applying differential braking forces at the front and rear brakes from the common manually operable brake actuating lever, includes at least one spring connected in the section of cable between the actuator lever and the rear brake.

7. A braking system as claimed in Claim 6, in which both front and rear brakes have springs of different spring rates connected between the respective brake and the common brake actuating lever.

8. A braking system as claimed in any preceding Claim, in which there are provided two brake actuating levers both of which operate both front and rear brakes, there being provided means for accommodating brake actuating movement of each lever at the other.

9. A braking system as claimed in Claim 8, in which the means for accommodating brake actuating movement of the other lever includes resilient biassing means for maintaining a predetermined minimum tension in each brake cable.

10. A braking system as claimed in Claim 8 or Claim 9, in which each brake is a caliper brake having two brake-actuating cables connected thereto, each cable being connected to the caliper by a respective coupling with both couplings being spaced from the caliper pivot by the same distance.

11. A braking system as claimed in Claim 10, in which each 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 brakeactuating cable thereto with one cable on each side of the lever arm.

12. A braking system as claimed in any preceding Claim, in which the or each brake lever is connected to both brake cables by means of a coupling including a pivoted rocker lever having a central pivot and connection means on each side of the central pivot for respective cables.

13. A braking system as claimed in Claim 12, in which each of two brake-actuating levers is connected to the said coupling by a respective brake cable, and a single brake cable leads from the coupling to each said brake caliper.

14. A braking system as claimed in Claim 13, in which the rocker lever is supported solely by the connections thereto of the said cables.

1 5. A braking system as claimed in any of Claims 12, 13 or 14, in which the pivot of the said rocker lever is adjustable with respect to the brake lever.

1 6. A braking system as claimed in Caim 15, in which the rocker lever has a slot therein by means of which the rocker lever is adjustable with respect to its effective pivot whereby to adjust the relative lengths of the two arms of the rocker lever.

1 7. A braking system for a bicycle substantially as hereinbefore described with reference to the accompanying drawings.

18. A braking system for a bicycle in which a brake for at least one wheel is operatively connected to two separate brake actuating levers and adapted to be actuated upon operation of either or both of the said levers.

19. A bicycle having a braking system as claimed in any preceding Claim.