Field of the Invention The invention relates to brake bleeding apparatus.

Brake fluid acts like a magnet to water to the extent it can actually draw moisture through flexible rubber brake hose. Unfortunately the presence of water in a brake fluid lowers the boiling point (vapour lock point) of the brake fluid, which can result in a slightly "spongy" brake pedal feel. The presence of moisture in brake fluid may even result in total brake failure. The heat generated by brake use can elevate the temperature of the brake fluid to a point at which vapour (steam) bubbles form, which will cause instant and total brake failure.

Moisture in a brake fluid may also lead to component corrosion to the extent the component may fail. This is both dangerous and potentially very expensive. Having a new ABS unit fitted can easily cost US$1,000.

It is desirable to be able to introduce new brake fluid into a brake system with minimum moisture ingress and to be able to replace the brake fluid in a brake system quickly and at low cost.

Summary of the Invention

The invention provides brake bleeding apparatus comprising a supply receptacle for brake fluid for supply to a braking system, ducting for connecting said supply receptacle with said braking system and a vacuum source connected with said supply receptacle for de-gassing brake fluid stored in said supply receptacle.

The invention also includes a self-winding supply reel system for an elongate member, said supply reel system comprising first and second reels mounted in spaced apart relation such that a distance between them reduces as said elongate member is drawn from said supply reel system and a resilient biasing device for increasing said distance to a place said reels in a rest condition in which said elongate member is substantially wound onto said supply reel system. The invention also includes bleeding apparatus comprising a supply receptacle for brake fluid to be supplied to a brake system, a receiving receptacle for receiving brake fluid from said brake system, a vacuum source communicable with said supply receptacle and a pump communicable with said supply receptacle, said brake bleeding apparatus being operable such that when said pump is operating to pump brake fluid from said supply receptacle to said brake system vacuum in said receiving receptacle draws brake fluid from said brake system.

The invention also includes a method of bleeding a braking system, said method comprising connecting a supply receptacle containing brake fluid to an inlet of a braking system and a receiving receptacle for receiving brake fluid to an outlet of said braking system, applying a positive pressure to brake fluid in said supply receptacle to drive said brake fluid into said braking system and a lower pressure to said supply receptacle such that brake as brake fluid from said supply receptacle is driven into said braking system brake fluid from said braking system is drawn into said receiving receptacle.

The invention also includes a method of operating a brake bleeding system that comprises a supply receptacle for brake fluid to be supplied to a braking system and a vacuum source for applying a vacuum to brake fluid in said supply receptacle, said method comprising operating said vacuum source to apply a vacuum to brake fluid to desgas said brake fluid and selectively isolating said supply receptacle for storing said degassed brake fluid in said supply receptacle under said vacuum.

Brief Description of the Drawings

In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the drawings in which:

Figure 1 is a perspective view from the front of a brake bleeding apparatus;

Figure 2 is a perspective view from the rear of the brake bleeding apparatus of Figure l; Figure 3 is a view similar to Figure 1 cutaway to show internal parts of the brake bleeding apparatus;

Figure 4 is a schematic illustration of the brake bleeding apparatus of Figure 1 connected to a braking system of an automobile;

Figure 5 is a schematic illustration of a self-winding reel supply system for ducting of the brake bleeding apparatus of Figure 1 showing the self-winding reel supply system in a condition in which the ducting is substantially fully wound in;

Figure 6 is a schematic illustration corresponding to Figure 5 showing the selfwinding reel supply system in a condition in which the ducting is substantially fully wound out;

Figure 7 shows a reel unit of the self-winding reel supply system of Figure 5 in an assembled condition;

Figure 8 shows the reel unit of Figure 7 in a disassembled condition;

Figure 9 shows a self-locking device for locking the ducting against the self-winding action of the self-winding reel supply apparatus of Figure 5; and

Figure 10 is a schematic illustration of another brake bleeding apparatus.

Detailed Description of the Illustrated Embodiments

Referring to Figures 1 to 3, a brake bleeding apparatus 10 comprises a wheeled cabinet 12. The cabinet 12 has two wheels 14 provided on an axle 16 (Figure 2). The axle 16 is fitted to respective rearward protrusions defined at the bottom rear of opposed side panels 18, 20 of the cabinet 12. The cabinet 12 has feet 22 provided generally opposite the wheels 14 at the bottom front of the side panels 18, 20. The feet 22 may be parts fitted to the side panels 18, 20. In the illustrated embodiment, the feet 22 are defined by forward protruding portions of the side panels 18, 20. A push handle 24 is provided at the top rear of the cabinet 12 generally above the wheels 14. The push handle 24 is a generally circular section rod that is fitted between respective rearwardly projecting ears defined by the side panels 18, 20. A user can readily move the brake bleeding apparatus 10 from place to place by standing to the rear of the cabinet 12, grabbing the push handle 24 and pivoting the cabinet rearwards in the direction indicated by the arrow 26 so that the feet 22 no longer contact the ground and the cabinet is supported only by the wheels 14. Once at a desired location, the cabinet 12 can be allowed to pivot about the pivot axis in the direction opposite that indicated by the arrow 26 to bring the feet 22 into contact with the ground so that the cabinet is supported by a combination of the wheels 14 and the feet.

As shown in Figure 3, the cabinet 12 houses a supply receptacle 28 for storing a supply of brake fluid to be supplied to a braking system, a vacuum storage receptacle (reservoir) 30 and a receiving receptacle 32 for receiving brake fluid from the braking system. The receptacles 28, 30, 32 each have pairs of connectors 34 for connecting with respective sight gauges 36, 37, 38. A front panel 40 (Figure 1) of the cabinet 12 is provided with apertures through which ends of the sight gauges 36, 37, 38 extend to connect with the connectors 34. Although not essential, in the illustrated embodiment the receptacles 28, 30, 32 are of common construction, each having a sealing filler cap 40 provided at its upper end. The receptacles 28, 30, 32 are disposed in generally parallel side-by-side relation and supported by a pair of generally parallel spaced apart support panels 42, 44 that extend between and are connected to the side panels 18, 20, for example, by riveting or welding.

The top panel 46 is supported by a hinge 48 (Figure 3) so that it can be lifted in the manner of a lid to permit access to the sealing filler caps 40.

As shown in Figure 4, the supply receptacle 28 and receiving receptacle 32 are each connected with the vacuum reservoir 30. A vacuum pump 46 that is housed in the cabinet 12 is connected between the supply receptacle 28 and the vacuum reservoir 30 for drawing down a vacuum in each receptacle.

Supply ducting 54 is connected to a lower end region of the supply receptacle 28. A supply pump 52 is fitted in the supply ducting 54 for pumping brake fluid from the supply receptacle through the supply ducting. At least downstream of the supply pump 52, the supply ducting 54 comprises flexible ducting. The flexible ducting is held on a self-winding reel supply system, which will be described in more detail below with reference to Figures 5 to 9. A quick release self-sealing hydraulic connector 56 is provided at the downstream end of the supply ducting 54 for snap- fitting to a self-sealing quick-release connector on a cap (not shown) that can be fitted to a brake master cylinder 58 of a motor vehicle brake system. Quick-release hydraulic connectors will be well known to those skilled in the art and so will not be described in detail herein.

Receiving ducting 60 is connected with a manifold 62 that is connected with a lower end of the receiving receptacle 32. The receiving ducting 60 comprises suitable flexible ducting that is held on a self-winding reel supply system in the same way as the supply ducting. In the illustrated embodiment, the receiving ducting comprises four separate receiving ducting hoses 60 that each has its own self-winding reel supply system.

Although not essential, the supply ducting 54 and receiving ducting hoses 60 may be made of a plastics material that can withstand brake fluid and are transparent or translucent. The ducting may, for example, be made of a translucent polyurethane. In one illustrative embodiment the ducting comprises 6mm diameter polyurethane tubing.

Respective connectors 64 are provided at the downstream end of the receiving ducting hoses 60 for connecting to the bleed valve 65 of a brake unit 66 of the motor vehicle brake system. The connectors 64 may be able to fit directly onto such a bleed valve or may be configured to be releasably connectable to a bleed valve connector so to allow different bleed valve connectors to be connected to the receiving ducting hoses 60. A manually operable valve 68 is provided in each receiving ducting hose 60 for closing the downstream end of the hose when not connected to a bleed valve. Although not essential, it is preferred that the manually operable valve 68 is disposed close to the downstream end of the receiving ducting hose 60. The connector 56 on the supply ducting 54 together with the connectors 64 and manually operable valves 68 on the receiving ducting hoses 60 have been omitted from Figures 1 to 3 purely for ease of representation.

A first connecting line 70 is provided between the supply receptacle 28 and the vacuum reservoir 30 and a second connecting line 72 is provided between the vacuum reservoir and the receiving receptacle 32. The first connecting line 70 is provided with a one-way check valve 74. The check valve 74 is arranged to open when the vacuum pump 46 is in operation and to close and maintain the vacuum in the supply receptacle 28 when the vacuum pump is not in operation. The second connecting line 72 is provided with a manually operable valve 76. The manually operable valve 76 can be used to isolate the receiving receptacle 32 from the vacuum reservoir 30 when the receiving receptacle is being drained.

Referring to Figures 3 and 5 to 9, the self-winding reel supply system 78 for the supply ducting 54 comprises a first reel unit 80 and a second reel unit 82. The first reel unit 80 is mounted on a cross-shaft 84. The cross-shaft 84 is fixed to the side panels 18, 20 to define a fixed axis of rotation for the first reel unit 80. The second reel unit 82 has a floating axis of rotation 86 that is disposed generally parallel to the cross-shaft 84 and can be moved from the rest position shown in Figure 5 to the position shown in Figure 6. The second reel unit 82 is biased to the rest position shown in Figure 6 by a resilient cable 88. The resilient cable 88 has a first end secured to a fixing point 90 located adjacent the hinge 48 at the top of the cabinet 12. The resilient cable 88 extends downwardly from the fixing point 90 to a position adjacent the bottom of the cabinet 12 where it is turned in an inward and then upward direction by guide reels 92, 94. The guide reels 92, 94 are mounted for rotation on respective guide reel cross-shafts 96, 98. The guide reel cross-shafts 96, 98 are disposed in parallel spaced relation and fixed to the side panels 18, 20 of the cabinet 12. The second end of the resilient cable 88 is fixed to the second reel unit 82. Although not shown in the drawings, the self-winding reel supply system 78 has a second resilient cable and guide reel set. The resilient cables 88 of the two sets are attached to opposite sides of the second reel unit 82 to apply a balanced biasing force to the reel unit. Referring to Figures 7 and 8, the first reel unit 80 comprises a spool 100 provided with an axially extending through-hole 102, which receives the cross-shaft 84. A plurality of slip rings 104 is mounted for rotation on the spool 100. For ease of representation only two slip rings 104 are shown in Figures 5, 7 and 8. However, a larger number may be used depending on the length of ducting that is to be held on the self-winding reel supply system 78. The slip rings 104 each have a circumferentially extending groove 106 sized to receive and guide the supply ducting 54. The slip rings 104 may be made from any suitable material, including a plastics material such as nylon, that has a relatively low coefficient of friction.

Each of the receiving ducting hoses 60 is provided with a separate self-winding reel supply system corresponding to the system 78.

Figure 9 shows self-locking devices 110 for preventing rewinding of the supply ducting 54 and receiving ducting 60 by their respective self-winding reel supply systems. The self-locking devices 110 are mounted on a cross-member 112 provided at the top of the cabinet 12 adjacent the cross-shaft 84. Each self-locking device 110 comprises a pusher member that comprises a shaft 114 and a knob 116. The free end of the shaft 114 is provided with a transverse through-hole 118 that is sized to receive the ducting 54, 60 with sufficient clearance to permit the ducting to be pulled through it when the device is in an open condition. The shaft 114 extends through an aperture defined by the cross-member 112 and a boss 120 provided on the underside of the cross-member such that the knob 116 is on one side of the cross-member and the through-hole 118 is on the opposite side. A compression spring 122 is mounted on the shaft 114 between the upper surface of the cross-member 112 and the underside of the knob 116. The compression spring 122 biases the knob 116 away from the cross- member 112 such that the through-hole 118 is drawn towards the underside of the cross-member and such as to trap the ducting 54, 60 between the wall of the through- hole 118 and the boss 120. The left-hand self-locking device 110 in Figure 9 is shown in an open, release, condition in which the supply ducting 54 can be drawn through the through-hole 118. The right-hand self-locking device 110 is shown in a locking condition in which the receiving ducting hose 60 is trapped between the wall defining the through-hole 118 and the boss 120. In use, if a user wishes to withdraw the supply ducting 54 or a receiving ducting hose 60 from the cabinet 12, he/she grips the end of the ducting and pulls on it while pressing the knob 116 of the respective self-locking device 110 downwardly towards the cross-member 112. As the ducting is withdrawn, the second reel unit 82 is progressively drawn upwardly towards the first reel unit 80 thereby decreasing the spacing between them. As the second reel unit 82 moves towards the first reel unit 80, the resilient cable 88 is stretched, thereby storing a restoring force for pulling the second reel unit back to the rest position shown in Figure 5. Once sufficient ducting has been withdrawn, the user releases the knob 116. This allows the spring 122 to drive the knob 116 away from the cross-member 112 so that the ducting is trapped between the wall defining the through-hole 118 and the boss 120 to prevent rewinding of the ducting under the influence of the restoring force stored in the resilient cable 88. It will be understood that the stiffness of the compression spring 122 and of the ducting 54, 60 is selected such that the self-locking device 110 can hold the ducting against rewinding without crushing the wall of the ducting. When the user wishes to rewind the ducting, he/she again depresses the knob 116 of the self-locking device 110 to release the ducting, which is then drawn back onto the first and second reel units 80, 82 under the influence of the restoring force stored in the resilient cable 88. When the ducting is fully rewound, the connector at its end and, in the case of the receiving ducting hoses 60 the respective manually operable valves 68, are stored in a tray 124 (Figures 2 and 3) provided on a rear wall 126 of the cabinet 12.

In use to bleed a braking system, the supply ducting 54 is withdrawn from the cabinet 12 and connected to the master cylinder 56 of the braking system. The receiving ducting hoses 60 are connected with the bleed valves 65 of the brake units 66 of the brake system. At this stage, the manually operable valves 68 on the receiving ducting hoses 60 are in a closed condition and the manually operable valve 76 is in an open condition. The vacuum pump 46 is started to draw down a vacuum in the supply receptacle 28 and receiving receptacle 32. The supply pump 52 is stalled. Initially the starting of the supply pump 52 has little effect as the manually operable valves 68 are closed. The manually operable valves 68 and respective bleed valves 65 are then opened one by one to successively bleed old brake fluid from each brake unit 66. Although not essential, it may be desirable to start the bleeding process at the bleed valve 65 located furthest from the master cylinder 56. As each bleed valve 65 is opened, old brake fluid is drawn into the receiving receptacle 32 under the influence of the vacuum in the receptacle and the supply pump 52 pumps new brake fluid from the supply receptacle into the braking system. Once the last brake unit 66 has been bled, all of the old brake fluid will have been removed from the brake system and replaced by new brake fluid from the supply receptacle. Once the bleeding process is complete, the vacuum pump 46 and supply pump 52 are turned off and the ducting is rewound into the cabinet 12 for storage.

The amount of fluid in the supply and receiving receptacles 28, 32 can be seen by inspecting the sight glasses 36, 38. If the supply receptacle 28 needs to be replenished, the sealing filler cap 40 is removed to allow fresh brake fluid to be poured into the receptacle. Once replenishment is complete, the sealing filler cap 40 is screwed back onto the receptacle and the vacuum pump 46 is started to draw down a vacuum in the supply receptacle 28 and degas the brake fluid. The degassing process may be deferred until the brake bleeding apparatus 10 is due to be used again.

However, it is believed preferable to store the brake fluid in the supply receptacle 28 under vacuum.

If the receiving receptacle 32 needs to be emptied, the manually operable valve 16 is closed to isolate the receptacle from the vacuum reservoir 30 and supply receptacle

28. The sealing filler cap 40 is then backed off to bring the pressure in the receptacle up to atmospheric pressure and the end of a receiving ducting hose 60 is placed in a vessel suitable for receiving the brake fluid. The manually operable valve 68 on the hose is then opened to allow the old brake fluid to drain out into the vessel. It may be desirable to elevate the receiving receptacle 32 relative to the vessel in order to allow the old brake fluid to clear from the receptacle. Once the draining process is complete the manually operable valve 68 is closed and the manually operable valve 76 is reopened. The vacuum pump 46 is then started to draw down the desired vacuum in the vacuum reservoir 30 and receiving receptacle 32.

If the brake bleeding apparatus 10 is used for the first time filling of an unused brake system with brake fluid, the apparatus is connected to the brake system as previously described. The bleed valves 65 on the brake units 66 are opened and the vacuum pump 46 is started to draw down a vacuum in the brake system and ensure that the brake fluid in the supply receptacle 28 is suitably degassed. The supply pump 52 is then started to pump new fluid into the brake system. Once the brake system has been filled, the supply pump 52 is turned off and the bleed valves 65 and manually operable valves 68 are closed prior to disconnecting the brake bleeding apparatus from the brake system. That the brake system has been completely filled can be verified by using the sight glass 36 to monitor the volume of brake fluid supplied or having translucent or transparent receiving ducting hoses 60 so that the new fluid flowing from the brake system can be seen.

Figure 10 illustrates features of another brake bleeding apparatus 210. The components of the brake bleeding apparatus 210 can be fitted in a wheeled cabinet similar to or the same as the cabinet 12 illustrated in Figures 1 to 3.

The brake bleeding apparatus 210 comprises a supply receptacle 212 for brake fluid to be supplied to a braking system and a receiving receptacle 214 for receiving brake fluid from such a braking system. Each receptacle 212, 214 has a pair of connection points 216 for connecting with respective sight glasses 218, 220. While not essential, the receptacles 212, 214 may be of identical construction, each having a sealing filler cap 222 provided at its upper end.

Supply ducting 224 is connected to a lower end region of the supply receptacle 212. A pump 226 is fitted in the supply ducting 224 for pumping brake fluid from the supply receptacle through the supply ducting. A pressure regulator valve 228 is provided downstream of the supply pump 226 for regulating the pressure of the brake fluid and a bypass duct 230 is provided for returning overpressure brake fluid to the supply receptacle 212. If the regulator valve 228 does not include a pressure gauge, a suitable gauge may be provided downstream of the valve.

At least downstream of the regulator valve 228, the supply ducting 224 comprises flexible ducting. The flexible ducting is held on a self-winding reel supply system 232 in the same way as the supply ducting illustrated in Figures 1 to 7. A quick release self sealing hydraulic connector 238 is provided at the downstream end of the supply ducting 224 for snap-fitting to a self-sealing quick-release connector on a cap (not shown) that can be fitted to a brake master cylinder as previously described in connection with the brake bleeding apparatus 10 illustrated in Figures 1 to 9.

Receiving ducting 242 is connected to a lower end of the receiving receptacle 214. The receiving ducting 242 comprises suitable flexible ducting that is held on a self winding reel supply system 244 in the same way as the receiving ducting of the brake bleeding apparatus 10 illustrated in Figures 1 to 9.

A connector 254 is provided at the downstream end of the receiving ducting 242 for connecting to the bleed valve (not shown) of a brake unit. The connector 254 may be one that can fit directly onto such a bleed valve or may be configured to be releasably connectable to a bleed valve connector so to allow different bleed valve connectors to be connected to the receiving ducting 242. A manually operable valve 256 is provided in the receiving ducting 242 for closing the downstream end of the receiving ducting when not connected to a bleed valve. Although not essential, it is preferred that the manually operable valve 256 is disposed close to the downstream end of the receiving ducting 242. Although not shown in Figure 10, the receiving ducting 242 comprises a plurality of separate hoses connected to a manifold, each hose being provided with a connector 254 and valve 256 so that the receiving ducting can be simultaneously connected with a plurality of bleed valves on multiple brake units of a brake system. For example, the receiving ducting 242 may have four such hoses for connecting with the respective bleed valves of four brake units of an automobile braking system.

The supply ducting 224 and each of the receiving ducting hoses 242 are provided with respective self-locking devices 258 corresponding to the self-locking devices 110 shown in Figure 9.

A connecting line 260 is provided between the supply receptacle 212 and receiving receptacle 214. The connecting line 260 comprises a duct 262 that extends from the receiving receptacle 214 into a first end 266 of a generally U-shaped duct 264. A suitable sealing arrangement is provided at the first end 266 to provide sealing between the duct 262 and U-shaped duct 264. The U-shaped duct 264 is of a larger diameter than the duct 262 so that the duct 262 can extend into the U-shaped duct with clearance. The U-shaped duct 264 acts as a trap for condensed vapour.

The connecting line 260 additionally comprises a duct 268 that extends from a second end 270 of the U-shaped duct 264. The end of the duct 268 remote from the second end 270 is connected with the supply receptacle 212. A pressurised air supply duct 272 extends from the duct 268. The upstream end of the air supply duct 272 is provided with a connector 274 for connecting to an outlet of a pressurised air supply 276. While the pressurised air supply may comprise an onboard compressor, it is envisaged that the brake bleed apparatus will typically be used in a workshop or similar such environment that is provided with an air line system. Therefore, for many applications it will be desirable to make the connector 274 a quick-release connector for connecting with an outlet of such an air line system. A manually operable valve 278 is provided in the air supply duct 272 to allow the connecting line 260 to be isolated from the air supply 276. Optionally, a regulator valve with pressure gauge (not shown) may be provided in the air supply duct 272 to allow the pressure of the air supplied to be regulated. The regulator valve may be provided instead of or in addition to the manually operable valve 278.

Optionally, the supply pump 226 is driven by pressurised air from the pressurised air supply 276. If this is the case, a pump supply duct 279 is branched from the air supply duct 272 from a position upstream of the manually operable valve 278. A manually operable valve 280 is provided in the pump supply duct 279 to allow the supply pump 226 to be isolated from the pressurised air supply 276.

A vacuum duct 282 extends from the duct 268 to a vacuum pump 284. The vacuum duct 282 connects with the duct 268 between the connection with the air supply duct 272 and the connection with the supply receptacle 212. A one-way check valve 286 is provided in the duct 268 between the connection with the vacuum duct 278 and supply receptacle 212. The check valve 286 may be a spring loaded self closing valve that opens when the vacuum pump 284 is in operation to allow drawing down of a vacuum in the supply receptacle 212 and closes when the pump ceases to operate to allow a vacuum to be maintained in the supply receptacle when the pump is not operating. The vacuum pump 284 is a venturi vacuum pump. The venturi vacuum pump 284 is supplied with pressurised air from the pressurised air supply 276 via a branch duct 288 that branches from the air supply duct 272 at a position upstream of the manually operable valve 278. A manually operable valve 290 is provided in the connecting duct 288 to allow the venturi vacuum pump 284 to be isolated from the pressurised air supply 276,

A manually operable valve 292 is provided in the duct 268 at a location between the connections with the air supply duct 272 and the vacuum duct 278. The manually operable valve 284 can be operated to isolate the vacuum duct 278 and supply receptacle 212 from the air supply duct 272 when pressurised air is being supplied into the duct 268 from the air supply 276.

In use to bleed a brake system, the user checks the sight glasses 218, 220 on the supply and receiving receptacles to ensure there is both enough new fluid in the supply receptacle and enough capacity to receive old fluid in the receiving receptacle. The area around the brake master cylinder is cleaned using dry lint free cloth to minimise the amount of moisture present. An appropriate master cylinder cap is fitted to the cylinder spout. The master cylinder cap may be fitted with a 6mm, or similar sized, down tube which extends into the master cylinder. If there is such a tube, it should be trimmed to the maximum fluid level of the master cylinder.

The knob of the self-locking device 258 associated with the self-winding reel supply 232 is then depressed and sufficient supply ducting 224 is withdrawn to allow the connector 238 to connect to the master cylinder cap. If the brake system is a vehicle brake system and the vehicle is going to be raised on a ramp during the bleeding operation, a sufficient length of supply ducting should be pulled from the cabinet 12 before the ramp is operated. This process is repeated with the respective receiving ducting hoses 242 to allow the connectors 254 to connect to the respective bleed valves of the brake system. If the brake bleeding process is to take place on a raised ramp, the connectors 254 can be conveniently fitted to the bleed valves once the ramp has been raised. The user should then check to ensure that all of the manually operable valves 256 on the receiving ducting hoses 242 and the manually operable valve 278 in the air supply duct 272 are closed and that the manually operable valve 292 is open to establish a connection between the venturi vacuum pump 284 and the receiving receptacle 214. The quick-release connector 274 is connected to the pressurised air supply 276 and the valves 280, 290 are opened to allow pressurised air to flow to the supply pump 226 and venturi vacuum pump 284. The supply pressure for the brake fluid is set by means of the regulator valve 228. The pressure should not be set too high as the higher the pressure the less efficient will be the brake bleed. This is because over pressuring the brake fluid compresses any air bubbles within the braking system making them smaller and harder to remove during the brake bleeding process. It is believed that 17 psi (approximately 117 kN/m ² ) is a good pressure to select for bleeding a motor vehicle braking system.

The bleed process is then commenced by opening the bleed valves and manually operable valves 256. Old brake fluid will be drawn from the brake system due to the vacuum present in the receiving receptacle 214 and degassed brake fluid from the supply receptacle 212 will be pumped into the brake system to take its place. It may be necessary to carry out the bleed process in a particular sequence or it may be preferable to start at the bleed valve furthest from the master cylinder, depending on the brake system and whether the bleeding process is being carried out simply to change the fluid or following a major repair of the brake system. By the time the last bleed valve is opened new fluid should be starting to flow into the respective receiving ducting hose (something that can be readily determined if transparent or translucent hose is used). The bleed valves should then be closed off in the same sequence in which they were opened (it is presently preferred that all bleed valves should be open together for at least ten seconds to avoid potential ABS control problems). Once the bleed valves are closed, the respective manually operable valves 256 can be closed and the connectors 254 removed from the bleed valves. Once the connectors 254 have been removed, the manually operable valves 256 may be briefly opened to drain the hose ends into a suitable vessel.

Finally, the quick-release connector 274 is disconnected from the pressurised air supply and the regulator valve 228 folly opened to allow the brake system to depressurise before removing the master cylinder cap from the brake master cylinder. The brake bleeding process is now complete so the supply ducting 224 and the receiving ducting hoses 242 can be rewound onto the reel units of their respective self-winding reel supply systems 232, 244.

Once the venturi vacuum pump 284 ceases to receive pressurised air from the pressurised air supply system 284, it ceases to draw down a vacuum and since the pump is open to atmosphere, the pressure in the receiving receptacle 214 slowly rises to atmospheric. A vacuum is maintained in the supply receptacle 212 due to the presence of the one-way check valve 286. Any brake fluid vapour present in the connecting line 260 will condense and collect in the U-shaped tube 264. As the pressure in the supply receptacle will initially be below atmospheric and will only rise very slowly due to the narrow diameter of the duct 262 the condensed fluid should be sucked into the supply receptacle 214.

If the supply receptacle 214 needs to be emptied, the manually operable valve 292 is closed to isolate the supply receptacle 212 from the air supply duct 272 and the connector 272 is connected to the pressurised air supply 276. The connector 254 on one of the receiving ducting hoses 242 is placed in a suitable vessel 300 and the respective manually operable valve 256 opened. The manually operable valve 278 in the air supply duct 272 is then opened to allow pressurised air to flow into the receiving receptacle via the U-shaped duct 264 and duct 262. The pressurised air pushes the old brake fluid from the receiving receptacle and into the vessel 300. Once the sight glass 220 indicates that the receiving receptacle has been sufficiently emptied, the quick-release connector 274 is disconnected from the pressurised air supply 276 and manually operable valves 256 and 278 are closed.

Although not shown in Figure 8, it will be appreciated that a pressure regulator valve may provided in addition to or as an alternative to the manually operable valve 278 and/or a pressure gauge may be provided to allow the user to set the air pressure used to drive the old brake fluid from the receiving receptacle. Similarly, a pressure regulator valve may be provided in the vacuum duct 272 or at a suitable position in the connecting line 260 to allow the vacuum in the supply and receiving receptacles 212, 214 to be set to a desired level. It will be appreciated that the embodiments provide a brake bleeding apparatus that allow a brake system to be quickly bled by drawing old brake fluid from the system by means of a low pressure in the receiving receptacle and pushing new brake fluid into the system by means of a pump.

It will be appreciated that by supplying the new brake fluid from a receptacle in which the brake fluid has been degassed by exposure to a vacuum it is possible to substantially reduce and/or eliminate the presence of air bubbles in the new fluid. This should result in less sponginess in the brake pedal operation, reduced likelihood of steam bubbles forming in use of the brake system and a reduced likelihood of corrosion of components of the brake system.

It will be appreciated that if the brake bleeding apparatus is operated so that the brake fluid in the supply receptacle is kept under vacuum, the possibility of contamination of the brake fluid is substantially reduced and/or eliminated.

It will be understood that while it is convenient to operate the supply pump and venturi vacuum pump with pressurised air from an air line system, this is not essential and electrically powered pumps could be used instead.

It will be appreciated that while for many applications it may be desirable to make the brake bleeding apparatus mobile, for example by housing components of the apparatus in a wheel cabinet or housing, this is not essential. The brake bleeding apparatus may be configured as a static apparatus to be mounted on, for example, a workbench or in a production line.

It will be understood that while it will often be convenient to have the supply and/or receiving ducting held on a self-winding reel supply system as in the illustrated embodiments, this is not essential. The ducting may be mounted on simple rotatable drums or simply connected to the respective receptacle without any form or storage apparatus. It will be understood that the brake bleeding system can be used for filling a new braking system for the first time as well as brake fluid replacement operations.

It will be appreciated that the self-winding reel supply system illustrated by Figures 5 to 8 could be used for elongate elements of various types that need to be drawn out and then rewound for storage. For example, the elongate member could be an airline.