WO1989004790A1

WO1989004790A1 - Pneumatic system

Info

Publication number: WO1989004790A1
Application number: PCT/GB1988/001010
Authority: WO
Inventors: Howard Robert Philip Marshall
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-11-19
Filing date: 1988-11-17
Publication date: 1989-06-01
Anticipated expiration: 1990-05-19
Also published as: AU2787689A; GB8727123D0; ZA888668B

Abstract

A pneumatic braking system for a cycle or a wheelchair wherein the braking system is adapted to receive a bottle (12) pre-charged with compressed gas. The system comprises a gas pressure operated cylinder (2, 7) for connection to a brake of a wheel of the cycle or wheelchair and a control means (21, 33) to apply gas pressure to the cylinder or vent gas from the cylinder to apply the brakes. The system also has a pressure regulator (26) to regulate the pressure of gas emerging from the outlet. The source of compressed gas is a pre-charged bottle similar to those used to pressurise a domestic or industrial beer barrel. It can be charged to around 6900 kNm-2 and has been found to give a long-lasting supply of air. The gas pressure acts to release the brakes, and the cylinders have a spring (35, 36) to oppose this action and apply the brake. Thus a ''fail-safe'' mechanism is provided as the brakes are gradually applied when the gas pressure falls.

Description

PNEUMATIC SYSTEM The present invention relates to pneumatic systems. In connection with heavy goods vehicles, it is known to provide pneumatic braking systems, commonly called "air brakes", in which the brakes are operated from a source of compressed air. Such systems allow a powerful braking effect to be achieved but are relatively heavy and bulky and are only appropriate for large commercial vehicles. Thus, even other motor vehicles such as ordinary motor cars are not equipped with air brakes. It has now been found that it is possible and advantageous to provide a pneumatic braking system for a cycle or a wheelchair characterised in that the braking system is adapted to receive a bottle pre-charged with compressed gas. The term "pneumatic" is used to mean a system which is operated by compressed gas such as air or carbon dioxide. The term "cycle" is used herein to include motor cycles, tricycles, mopeds, pedal cycles assisted by motors and, especially, ordinary pedal bicycles which are propelled by the leg power of the user. By using the term "pre-charged" we mean that the bottle is charged with compressed gas before being fitted to the braking system.

Conveniently, the braking system comprises a gas pressure operated cylinder for connection to a brake for a wheel of the cycle or wheelchair and a control means to apply gas pressure to the cylinder or to vent gas from the cylinder in order to apply the brake. Suitably, the system comprises a pressure regulator to regulate the pressure of the gas emerging from the outlet. Preferably, the cycle is a bicycle having front and rear wheels and there is a respective said cylinder, brake and control means for each wheel. Suitably, at least one said control means is operated by a conventional brake lever mounted on the handlebars.

The pre-charged bottle is adapted to be charged with air from a conventional filling station air supply and/or from a handpump or footpump. Alternatively and preferably, the pre-charged bottle is similar to the kind which is used to pressurise a domestic or industrial beer barrel, and may be filled with any suitable gas such as air or carbon dioxide. Such a pre-charged bottle may be pressurised to a pressure of up to 250 Bar (3626 p.s.i.; 2.5 x 10⁴ kNm^-2 ) although a pressure of about 1000 p.s.i. (6900 kN ^-2) is preferred. Such pressures have been found to give a far longer lasting supply of air than a fixed reservoir which is re-charged by pumping in situ.

It may be advantageous for the bottle to comprise a non-return valve such that the bottle can be removed and replaced even though it is still under significant pressure. Thus, when the cyclist leaves the cycle in a public place, the cycle can effectively be disabled- by removing the compressed gas bottle. Alternatively, the braking system can comprise such a valve, which may be detached together with the bottle in such a situation.

It has been found that it is particularly convenient for the or each cylinder to comprise a spring acting to oppose the action of the gas pressure and to apply the brake to the wheel , the action of the gas pressure on the cylinder being to release the brake. Thus, the resting condition of the braking system is for the brakes to be applied to the wheels and the brakes are released only when the source of compressed gas is connected. Then, in use, the cyclist operates the brake levers in the usual way, the compressed gas in each cylinder is vented and the spring is then allowed to operate the brakes.

The cylinders may be conventional piston cylinders or, more preferably, may be diaphragm cylinders. The latter allow the system to operate at a lower gas pressure than would otherwise be the case, because the area of the diaphragm can be arranged to be significantly larger than the area of a piston, without creating an unwieldy overall unit.

It has been found to be convenient for the source of compressed air to be charged to at least 1380 kNm^-2 , preferably at least 2070, 3450 or 5520 kNm-² , and most preferably at least 6890 kNm^-2. A typical maximum pressure for readily obtainable components of the sort described below is 1500 p.s.i. (1 x 10⁴ kNm^-2 ) . Preferably, the pressure regulator delivers gas at 210 - 620 kNm^-2 , more preferably approximately 410 kNm^-2 , to the brake cylinders. It has been found that it is possible to have over 1000 braking operations, on both wheels, from one conveniently-sized bottle of compressed gas .

Cycles equipped with braking systems in accordance with the invention are particularly suitable for certain disabled cyclists who have insufficient muscle power in their hands to operate conventional braking systems safely.

Such a system can also be fitted to an invalid wheelchair. For easier operation of the brakes, the brake levers may be substituted with a twist grip applicator in the style of a motor cycle throttle control. This style of applicator may be used on a bicycle or a wheelchair. Such a braking system can be fitted to and operate conventional caliper style brakes on a pedal bicycle and the caliper style brakes can be fitted with the braking system to an invalid wheelchair. In preferred embodiments, no alteration to the caliper brake is needed, only the reconnection of the brake cables to the air braking system. Thus, the system can be fitted to a cycle which is already in use.

Specific embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a side view of a bicycle frame, showing some of the components of a first embodiment of a braking system in accordance with the invention in place;

Figure 2 is a pneumatic circuit diagram of the pneumatic parts of the braking system of Figure 1;

Figure 3 is a rear view of a piston air cylinder of the Figure 1 system connected to a conventional brake block assembly with caliper style brakes;

Figure 4 is a view corresponding to Figure 3 but showing a second embodiment where the piston air cylinder is replaced by a diaphragm air cylinder;

Figure 5 shows a third embodiment where the air cylinder and source of compressed air are mounted on an upright portion of the frame;

Figure 6 shows the main components of the system connected to a conventional caliper brake block assembly in isolation from the cycle;

Figure 7 shows the components of Figure 6 mounted to a wheelchair frame;

Figure 8 is an exploded longitudinal cross-section of the high pressure valve connection for the compressed air bottle and the pressure regulator; Figure 9 is a schematic view of the brake lever connection to the air valve via the brake cable; and

Figure 10 is a schematic view of the twist grip lever connection to the air valve via the brake cable.

Figure 11 shows a plan view of the twist grip applicator viewed along line A of Figure 10.

Referring first to Figure 1, a conventional bicycle frame 1 is equipped with a piston air cylinder 2 attached to the front upright portion 3 of the frame 1 by means of a bracket 4. The front cylinder 2 is connected to the conventional brake block assembly 5 via a cable 6. The brake block assembly 5 is illustrated schematically only. Similarly, a piston air cylinder 7 is attached to the rear brace 8 of the frame 1 by means of a bracket 9 and is connected to the rear brake block assembly 10 via a cable 11. A gas bottle 12 is slung below the horizontal member 13 of the frame 1 by means of brackets 14. In an alternative embodiment, a gas bottle 12a is fastened to a more or less conventional rear luggage rack 15 (shown in outline) . The gas bottle 12 is connected to the brake cylinders 2, 7 by means of pneumatic supply lines which are not shown.

Referring now to Figure 2, it can be seen that the front brake cylinder 2 is connected by a line 20 to a cylinder pressure regulator 21 which is in turn connected via a line 22 to a control valve 23 which is adapted and connected so as to be operated by the conventional front brake lever (not shown). The front brake control valve 23 is connected via lines 24, 25 to a main pressure regulator 26 which is in turn connected via a line 27 and a valve 28 to the compressed air bottle 12. A pressure display gauge 30, is fitted to line 27. It can be seen that the rear brake cylinder 7 is connected in an exactly analogous manner via the rear brake pressure regulator 33 and a rear brake control valve 34 to the line 25.

As is illustrated schematically in Figure 2, each brake cylinder 2 , 7 is equipped with a respective return spring 35, 36 which opposes the action of the air pressure. The respective piston rod 37, 38 of each brake cylinder 2, 7 is connected to the conventional cables 40 of the caliper brake block system 41 (Figure 3). Thus, with a low air pressure in the cylinders 2, 7, the spring acts to pull on the cable 40, thereby applying the brake blocks to the rim of the wheel (not shown). When compressed air is supplied to the cylinders 2, 7, the air pressure opposes the action of the spring 35, 36 and allows the brake blocks to be taken out of contact with the wheel rim by the conventional brake block assembly springs (not shown) .

In a further alternative embodiment (Figure 5) the piston air cylinders 2 and 7 are both attached to the central upright portion of the frame 1 by means of a bracket 45. The gas bottle 12b is also attached to the central upright portion of the frame 1 by means of a bracket (not shown) . Both brackets can be clipped onto the frame, so no drilling of the frame is required. This facilitates fitting the system to a cycle which is already in use and requires no specialised equipment. The bracket holding the source of compressed air takes the strain of the air source on itself so that no force is placed on the frame.

Figure 6 illustrates the connection of the piston air cylinder 7 to a conventional caliper brake block assembly 41. The piston air cylinder 2 is connected to the front brake block assembly in an analogous manner. To fit the system to a bicycle with conventional caliper brakes, the brake cables are detached from the brake fixings and the brake levers. New cables (not shown) are fitted from the brake levers to the operating valves 23 and 34 (Figure 2). A second set of cables 40a (Figure 6) is then fitted to the brake fixings and the piston rods 37 and 38 (Figure 2) of the air cylinders 2 and 7 (Figure 2 ) . The system now operates in the same manner as previously described.

To mount the braking system to an invalid wheelchair, the gas bottle, controls and brake actuating cylinders are mounted under the seat of the chair and fixed to the framework (Figure 7). The brake caliper 41 is fixed with a bracket 47 to the frame 46 of the wheelchair, so that it clamps the rim of the wheel 48 when operated. A caliper brake may be fitted in the same way to one or both wheels as required. A twist grip applicator or levers may be mounted onto the side rails of the wheelchair in an easily accessible position.

Figure 8 shows the non-return valve 28 (Figure 2) . The compressed gas bottle 12 has an outlet valve 28b which connects with the inlet valve 28a_ of the pressure regulator 27. The inlet valve 28a. screws into the outlet 28b of the compressed gas bottle, allowing gas out of the compressed bottle, but keeping the pressure seals enclosed from the atmosphere. The bottle can be removed whilst still under pressure by unscrewing 28b from 28a. The outlet 28b_ has an automatic shut-off which prevents gas escaping from the bottle while it is disconnected from the system.

The valve connection may be obtained from Brewicon Ltd., Batley, Yorkshire, England. Figure 9 shows the brake lever 60 on the handlebars 70 connected to the control air valve 23 via the brake cable 40 and return spring 35. The rear control valve 34 is connected to the brake lever in an analogous manner.

Figure 10 shows a twist grip applicator 75 with outer cover 76 connected to the control valve 23 via the brake cable 40 and return spring 35. The twist grip 75 may be similarly connected to control valve 24.

The components of the pneumatic system are generally conventional and easily obtainable. For example, the re- fillable compressed air bottle 12 may be obtained from Northern Cam Co. Ltd., Leeds, England, or Hambleton Bard Ltd., Sheffield, England. The brake operating valves 23, 34 and the adjustable one-way control valves forming part of the regulators 21, 33 may be obtained from Festo (U.K. ) Limited, Northampton, U.K. The single acting spring return air cylinders 2, 7 may be obtained from Schrader. The pressure regulator 26 may be obtained from Norgren, which is part of the IMI Group, Litchfield, Staffs., England.

The compressed air bottle 12 is initially filled with compressed air to a pressure of approximately 2.5 X 10⁴ kNm^-2. The pressure gauge 30 may be mounted adjacent the bottle or may be connected to line 27 by a suitable high pressure line so that it may be mounted on the handlebars for easy inspection by the cyclist while he is travelling along. The dial of the gauge may be marked with coloured zones or similar indications so that the cyclist is warned that the pressure is falling and that it is appropriate for him to replace the cylinder with a new pre-charged bottle. Th.e pressure regulator 26 is suitably set to supply air at approximately 410 kNm^-2 to the remainder of the system. The adjustable cylinder pressure regulators 21, 33 allow the braking characteristics of the system to be adjusted to suit different cycles, different cyclists and different conditions. Thus, a heavy cyclist will require a greater braking effect than a light cyclist. Similarly, the system can be adjusted so that the rear brakes are applied more firmly and/or sooner than the front brakes.

In an alternative embodiment, the piston brake cylinders are replaced by respective diaphragm cylinders, such as are obtainable from Mechman, Stockholm, Sweden. With such cylinders, the pressure delivered by the pressure regulator 26 may be as low as 20 to 25 p.s.i. and therefore more braking operations can be achieved from a given charge of air in the air bottle 29. A diaphragm cylinder 50 of this type is illustrated in Figure 4, connected via cable 40 to the rear brake block assembly 41. A diaphragm cylinder of this type may also be connected in an analogous manner to the front brake block assembly.

It will be appreciated that the system described above has a "fail safe" characteristic in that, when the air pressure in the system falls, the brakes are progressively applied. This means that the cyclist is never without a braking capacity. This characteristic would be particularly important for disabled users, whether on a bicycle or in a wheelchair, who may be less able to react quickly in an emergency.

Some users may perceive this arrangement as being unsatisfactory because, when there is insufficient air pressure, the bicycle cannot be ridden and, indeed, cannot easily be pushed along. Hence, in an alternative arrangement, the application of air pressure to the cylinders is used to apply the brakes and the spring is used to release the brakes. In such an arrangement, a manual linkage can be provided to override the pneumatic system in case of an emergency.

Claims

1. A pneumatic braking system for a cycle or wheelchair characterised in that the braking system is adapted to receive a gas bottle pre-charged with compressed gas .

2. A braking system according to Claim 1 comprising a gas pressure operated cylinder for connection to a brake for a wheel of the cycle or wheelchair and a control means to apply gas pressure to the cylinder or to vent gas from the cylinder in order to apply the brake.

3. A braking system according to Claim 2 wherein the cycle is a bicycle having front and rear wheels and there is a respective said cylinder, brake and control means for each wheel.

4. A braking system according to Claim 2 or 3 wherein at least one said control means is operated by a conventional brake lever mounted on the handlebars.

5. A braking system according to any one of Claims 2 to

4 wherein the or each cylinder comprises a spring acting to oppose the action of the gas pressure and to apply the brake to the wheel, the action of the gas pressure on the cylinder being to release the brake.

6. A braking system according to any one of Claims 2 to

5 wherein at least one said cylinder is a diaphragm cylinder. . A braking system according to any of the preceding claims wherein the pre-charged bottle is charged to a pressure of at least 6890 kNm^-2.

8. A braking system according to any one of the preceding claims and comprising a pressure regulator connected to the outlet of the gas bottle to moderate the pressure of the gas supplied to the remainder of the system.

9. A cycle comprising a pneumatic braking system according to any one of the preceding claims.

10. A wheelchair comprising a pneumatic braking system according to any one of the preceding claims .