GB2027825A

GB2027825A - Disc brake wiper device

Info

Publication number: GB2027825A
Application number: GB7916024A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-15
Filing date: 1979-05-09
Publication date: 1980-02-27

Abstract

A disc brake wiper device for increasing the efficiency and performance of disc brakes (e.g. of motor cycles) under wet weather conditions comprises a pair of wiper blades (5) adapted to engage the sides of a brake disc (25) and means for moving the wiper blades into and out of engagement with the sides of the brake disc. Each wiper blade (5) is pivotally mounted on a respective arm (1, 2) and the two arms (1, 2) are pivotally mounted intermediate their ends on a bar (3). In one embodiment, the means for moving the wiper blades into engagement with the brake disc comprise a spring (7) located on projections (8) on the arms (1, 2). The means for moving the wiper blades out of engagement with the brake disc comprise a control lever connected by a cable (11) to the arms (1, 2) and operable to move said arms in a direction opposite to that in which they are urged by the spring (7) against the force of said spring. Other embodiments envisage the use of electro-magnetic means (Fig. 3) and hydraulic means (Fig. 4) for operating the wiper blades. <IMAGE>

Description

SPECIFICATION Disc brake wiper device This invention reiates to improvements in brakes for motor vehicles and is particularly concerned with a device for improving the braking performance of motorcycle disc brakes in wet weather conditions.

Motorcycle disc brakes performance can be substantially reduced in wet conditions and tests have shown that stopping distances can be more than doubled in wet as opposed to dry conditions. This detracts from the advantages of disc brakes which include good heat dissipation and stability of performance.

One previous attempt at overcoming this problem has been to provide a drilled or slotted brake disc. However, the wheel has to rotate several times, once the brake has been applied, before the water is forced through the holes or channelled down the slots thus causing a delay in brake response. The holes or slots also reduce the performance and efficiency of the brake under dry conditions. Further, any method which alters the brake disc itself after manufacture can cause problems of overheating and structural weakening.

The present invention aims to provide a device which reduces the effect of wet weather conditions on the performance of vehicle brakes and, in particular, on motorcycle brakes.

According to the invention, there is provided a device for increasing the efficiency and performance of disc brakes under wet weather conditions, said device comprising a pair of wiper blades adapted to engage the sides of a brake disc in advance of the brake pads and means for moving the wiper blades into and out of engagement with the sides of the brake disc.

Preferably, each wiper blade is pivotally mounted on a respective arm and the two arms are so mounted that they are capable of pivoting with respect to one another. The arms are desirably pivotally mounted on a bar or like member which is adapted to be mounted adjacent the brake disc in such a manner that the arms depend on either side of said brake disc.

Instead of relying on the brake pads to clear the disc surface of water under wet conditions, the wiper blades of the disc brake wiper device according to the invention are brought into engagement with the braking surfaces of the brake disc and these blades use the rotation of the disc itself to remove the layer of water from the braking surfaces just in front of the brake caliper thereby ensuring that, when the brake is applied, the brake pads instantly meet virtually dry braking surfaces.

According to one embodiment of the invention, the means for moving the wiper blades into engagement with the brake disc comprise a spring arranged to engage with the said arms. In this case, the means for moving the wiper blades out of engagement with the brake disc may comprise a control lever connected by a cable to the arms and operable to move said arms in a direction opposite to that in which they are urged by the spring against the force of said spring.

In another embodiment of the invention, each arm is provided with an inclined surface adjacent one end and a plunger is engageable with the inclined surfaces. In this case, the means for moving the wiper blades out of engagement with the brake disc may comprise a spring arranged to engage with said arms. A solenoid is desirably provided which is arranged, when activated, to force the plunger into engagement with inclined surfaces of the arms and to urge the wiper blades into engagement with the brake disc against the force of the spring.

According to a further embodiment of the invention, the means for moving the wiper blades into engagement with the brake disc may comprise a hydraulic slave cylinder having pistons which are engageable with the said arms. The hydraulic cylinder may be adapted to be connected to the hydraulic braking circuit of a vehicle fitted with the device.

The invention will now be further described, by way of example, with reference to the drawings, in which: Figure 1 is an exploded perspective view of one embodiment of a disc brake wiper device according to the invention; Figure 2 is a front elevation of the wiper blades of the device shown in Fig. 1 mounted for operation on a motorcycle brake disc; Figure 3 shows, diagrammatically, a second embodiment of a disc brake wiper device according to the invention; and Figure 4 shows, diagrammatically, a third embodiment of a disc brake wiper device according to the invention.

In the drawings, like parts are denoted by like reference numerals.

Reference will first to made to Figs. 1 and 2 of the drawings in which the device comprises a pair of arms 1 and 2 each of which is pivotally connected intermediate its ends to a bar 3 by means of a respective pivot pin 4. The pivot pins 4 may, if desired, take the form of bolts which are passed through suitable bores in the arms 1, 2 and bar 3 and secured in position by means of nuts (not shown). However, other suitable means can be employed for securing the pivot pins 4 4 in position as may be desired.

A wiper blade 5 is pivotally mounted by means of a respective pivot pin 6 on one end of each of the arms 1 and 2. Again, the pivot pins 6 may taken the form of bolts passing through bores in the wiper blades 5 and arms 1, 2 and secured in position by means of nuts (not shown) although other suitable means may be employed for securing the pivot pins in position. The wiper blades should be freely pivotable about a point substantially in the centre viewed in the longitudinal direction of the blades.

The wiper blades 5 are normally biased in a direction towards one another by a coil spring 7 which acts on the arms 1 and 2 to urge said arms away from each other. The spring is located by providing projections 8 on said arms adjacent the ends remote from the ends on which the wiper blades 5 are mounted whereby the wiper blade carrying ends of the arms 1 and 2, and hence the wiper blades 5 themselves, are urged towards one another. The ends of the spring 7 fit over the projections 8 on the arms 1 and 2 and thus the spring is positively located in position.

The end of each arm 1, 2 remote from the end carrying a wiper blade 5 is provided with a slot 9 leading to a bore 10. The width of each slot 9 is such that the inner core 11 of a Bowden cable can be passed through it to enter the associated bore 1 0. A nipple 1 2 at one end of the core 11 engages in the bore 10 in the arm 2 and the screw-threaded sleeve 14 of a cable adjuster 13, which is mounted on the cable core 11, engages in the bore 10 in the other arm 1.

The sleeve 14 is secured in position by means of nuts 1 5 engaging with the screw-thread of the sleeve in known manner. The inner core 11 is surrounded by an outer sheath 1 6 of the Bowden cable in known manner and its other end is mounted in a conventional control lever 1 7. The control lever 1 7 is adapted to be mounted on a motor cycle handle bar and is provided with a friction screw 1 8 which can be arranged to overcome the force of the spring 7 the purpose of which will become apparent from the following description.

A cranked arm 1 9 is secured to the bar 3 by means of a nut and bolt connection 20 and this cranked arm is provided with two bores 21 for the purpose of securing it to a bracket 22 by means of bolts 23 and nuts 24. The bracket 22 is shaped and adapted to be fitted to a motor cycle having a disc brake in such a manner that the wiper blades 5 are located on either side of the brake disc 25 as shown in Fig. 2.

It is known that the front brake of a motor cycle is more effective than the rear brake but, because the front wheel is more exposed to the elements, it is this brake which suffers most from adverse weather conditions in that, when the brake disc is wet, braking efficiency and performance are seriously adversely affected. The disc brake wiper device according to the invention is therefore primarily intended for use on the front wheel brake of a motor cycle. In order to fit the device, the front wheel should be removed and the mounting bracket 22 fitted to the mudguard stays. The shape of the bracket and the mounting holes provided therein may be so arranged that the bracket will fit most if not all motor cycles or, alternatively, a different bracket may be provided for each make or model of motor cycle.The wiper device is now fitted by securing the cranked arm 1 9 to the bracket 22 by means of the bolts 23 and nuts 24 and the cable is fitted to the arms 1 and 2 and operated to draw the slotted ends of the arms 1 and 2 towards one another against the force of the spring 7 to thus force the wiper blades 5 away from each other. The front wheel is now refitted, care being taken to ensure that the wiper blades 5 are located on either side of the brake disc 25.The control lever 1 7 can then be mounted at a suitable location on the motor cycle handlebar and the effective length of the cable adjusted by means of the adjuster 1 3 so that the wiper blades 5 can be urged by the spring 7 into engagement with the sides of the disc 25 and so that, when the control lever 1 7 is operated, the wiper blades 5 can be withdrawn from engagement with the sides of the brake disc. The friction screw 1 8 is adjusted so that the control lever 1 7 will remain in a position in which the wiper blades are inoperative against the force of the spring. A final check should be made to ensure that the wiper blades can be operated without touching any other part of the wheel after which the device is ready for use.A further cable adjuster 26 may also be provided if desired in order to increase the range of cable adjustment. The wiper blades 5 are so positioned that they are located just in front of the disc brake pads (not shown) as viewed in the direction of rotation of the brake disc when the motor cycle is moving in a forwards direction.

Under dry weather conditions, the disc brake wiper device is not required, so the control lever 1 7 is operated to withdraw the wiper blades 5 from engagement with the brake disc 25.

However, under wet conditions, the control lever 1 7 is moved to allow the spring 7 to urge the wiper blades 5 into engagement with the sides of the brake disc 25. The wiper blades have the effect of removing the layer of water from the braking surfaces of the disc just in front of the brake caliper so that the brake pads engage substantially dry surfaces and performance and efficiency of the brake is not impaired. The wiper blades also serve to wipe dirt and oil or grease from the braking surfaces thus protecting the braking surfaces of the disc from excessive wear and scoring and the brake pads from losing their efficiency.

The wiper blades 5 are preferably made from a plastics material such as polypropylene or nylon which, while being resistant to wear, is softer than the metal of the brake disc so that the blades will wear in time and will cause no adverse wear on the braking surfaces of the brake disc by virtue of their engagement. Wear of the wiper blades may be compensated by appropriate adjustment of the cable adjusters 1 3 and 26 and the blades may be readily replaced when fully worn. The arms 1 and 2, bar 3 and cranked arm 1 9 are preferably made of metal which may be chrome or zinc plates.

Tests conducted on a motorcycle having a disc brake fitted with a disc brake wiper device according to the present invention gave the following results:30 M.P.H. Dry Conditions Stopping Distance 47 ft.

Wet Disc Stopping Distance 63 ft.

Wet Disc with wiper on Stopping Distance 53 ft.

This shows that the braking distance under wet conditions was reduced from 1 6 ft to 6 ft.

50 M.P.H. Dry Conditions Stopping Distance 1 20 ft.

Wet Disc Stopping Distance 1 50 ft.

Wet Disc with wiper on Stopping Distance 1 28 ft.

This shows that the braking distance under wet conditions was reduced from 30 ft to 8 ft.

Figs. 1 and 2 show a disc brake wiper device which is mechanically operated but it should be noted that the invention is not restricted to this embodiment. Fig. 3 shows an embodiment in which the disc brake wiper device is controlled by electro-magnetic operation. In this embodiment, the ends of a coil spring 30 engage pegs 31 and 32 mounted respectively on the arms 1 and 2 to urge these ends of the arms towards one another. Thus, in this arrangement, the spring 30 normally urges the wiper blades 5 away from the braking surfaces of the brake disc 25.

Instead of the ends of the arms 1 and 2 remote from the wiper blades 5 being slotted, in this embodiment the arms are provided with inclined surfaces 33 which are engageable by the sides of a frusto-conical plunger 34. The plunger 34 is provided with a stem 35 of electro-magnetic material which is located in a solenoid 36. The solenoid is adapted to be earthed to the motor cycle frame (not shown) and is connected via a relay 37 to the motor cycle battery 38. The relay 37 is connected to a switch 39.

When the switch 39 is closed, it is effective to close the relay 37 so that electric current flows through the solenoid 36 which repels the plunger stem 35 and forcs the plunger 34 against the inclined surfaces 33 of the arms 1 and 2. These ends of the arms 1 and 2 are thus forced apart by the plunger, against the action of the spring 30 and the wiper blades 5 are forced into engagement with the braking surfaces of the brake disc 25. When the switch 39 is re-opened, the spring 30 pulls the upper ends of the arms 1 and 2 towards one another again so that the inclined surfaces push the plunger 34 back towards the solenoid 36 and the wiper blades 5 are again moved out of engagement with the brake disc 25. The relay 37 may, if desired, be omitted and the switch 39 connected directly between the solenoid 36 and the battery 38.

If a manual switch 39 is employed alone, it can be closed during wet weather conditions so that the disc brake wiper device is continuously in operation as with the embodiment shown in Figs. 1 and 2 of the drawings which operates independently of the motor cycle brakes.

However, in a modification of this device, the relay 37 is connected to the stop light circuit of the motorcycle. In this case, the disc brake wiper device will operate only when the brakes are applied. As a further alternative, the switch 39 may be connected to the motor cycle stop light circuit so that, under dry conditions, the disc brake wiper device is completely inoperative and, under wet conditions when the switch 39 is closed, the disc brake wiper device is operated only when the brakes are applied. This latter arrangement reduces wear of the wiper blades 5 to a minimum.

In the case of motor cycles fitted with hydraulic braking systems, it is possible to utilise the embodiment shown in Fig. 4 of the drawings. In this embodiment, a two-piston type slave cylinder 43 is located between the arms 1 and 2 of the disc brake wiper device. The pistons 44 and 45 of the cylinder are engageable in respective recesses 41 and 42 provided in the arms 1 and 2 adjacent the ends remote from the wiper blades 5. The cylinder 43 is connected by a hydraulic fluidine 46 to a T-piece 47 which is incorporated into the hydraulic braking system of the motor cycle (not shown). When the brakes are applied, the hydraulic line pressure forces the pistons 44, 45 away from each other and thus forces the adjacent ends of the arms 1 and 2 apart so that the wiper blades 5 are forced against the braking surfaces of the brake disc 25. A spring 30 or other suitable means (not shown) may be provided for urging the wiper blades 5 away from the brake disc 25 at the end of braking.

The invention is not restricted to the above described embodiments but modifications may be made without departing from the scope of the invention as defined by the appended claims. In particular, while coil springs are preferred, they are not essential and other spring means, for example leaf springs, may be utilised if desired. The device according to the invention may also be fitted to rear wheel disc brakes of motor cycles in addition to front wheel disc brakes. It should also be noted that the device according to the invention is not restricted to use on motor cycles but may be fitted to the disc brakes of any vehicles.

Claims

1. A device for increasing the efficiency and performance of disc brakes under wet weather conditions, said device comprising a pair of wiper blades adapted to engage the sides of a brake disc in advance of the brake pads and means for moving the wiper blades into and out of engagement with the sides of the brake disc.

2. A device according to claim 1, wherein each wiper blade is pivotally mounted on a respective arm and wherein the two arms are so mounted that they are capable of pivoting with respect to one another.

3. A device according to claim 2, wherein the arms are pivotally mounted on a bar or like member which is adapted to be mounted adjacent the brake disc in such a manner that the arms depend on either side of said brake disc.

4. A device according to claim 3, wherein the device further includes a bracket adapted to be connected to said bar or like member and further adapted to be mounted on a motor cycle in such a manner than the wiper blades are located on either side of a brake disc fitted to said motor cycle.

5. A device according to any one of claims 2 to 4, wherein the means for moving the wiper blades into engagement with the brake disc comprise a spring arranged to engage with said arms.

6. A device according to claim 5, wherein the means for moving the wiper blades out of engagement with the brake disc comprise a control lever connected by a cable to the arms and operable to move said arms in a direction opposite to that in which they are urged by the spring against the force of said spring.

7. A device according to any one of claims 2 to 4, wherein each arm is provided with an inclined surface adjacent one end and wherein a frusto-conical plunger is engageable with the inclined surfaces of the arms.

8. A device according to claim 7, wherein the means for moving the wiper blades out of engagement with the brake disc comprise a spring arranged to engage with said arms.

9. A device according to claim & wherein a solenoid is provided which is arranged, when activated, to force said plunger into engagement with the inclined surfaces of the arms and to urge the wiper blades into engagement with the brake disc against the force of the spring.

10. A device according to claim 9, wherein the solenoid is controlled by a manually operable switch.

11. A device according to claim 9 or claim 10, wherein the solenoid is arranged to be controlled by the stop light circuit of a vehicle fitted with said device.

12. A device according to claim 5 or claim 8, wherein the spring takes the form of a coil spring.

1 3. A device according to any one of claims 2 to 4, wherein the means for moving the wiper blades into engagement with the brake disc comprise a hydraulic slave cylinder having pistons which are engageable with said arms.

14. A device according to claim 13, wherein the hydraulic cylinder is adapted to be connected to the hydraulic braking circuit of a vehicle fitted with said device.

15. A device according to any preceding claim, wherein the wiper blades are made of polypropylene or nylon.

1 6. A disc brake wiper device substantially as described herein with reference to the drawings.