FLUID SYSTEM BLEEDING APPARATUS

Abstract: Apparatus for use in the bleeding of fluid systems, especially the hydraulic brake system of a motor vehicle, comprises fluid pumping equipment (1) for pumping fluid to a main fluid reservoir (8) of the fluid system via a supply conduit (24). The pumping equipment (1) includes a fluid container (6), and an air pump (2) serving to discharge fluid from the container (6) into the supply conduit (24). The pump (2) is driven through electric circuit means (C1, C2) including fluid pressure control means (14) and a fluid level control (15A) of the container (6). The delivery end of the supply conduit (24) passes through an opening (26) of the reservoir (8) which opening (26) is sealed by an elastomeric plug (18) laterally expandable by compression means. The above apparatus considerably conveniences the bleeding of motor vehicle brake systems.

Description: "FLUIO SYSTEM BLEEDING APPARATUS' The present invention relates to apparatus for use in. the bleeding of fluid systems, and especially but not exclusively for use in the bleeding of hydraulic brakes in motor vehicles. In the hydraulic brake system of a motor vehicle, it is possible for air pockets to develop in the fluid line from the master cylinder or reservoi r to the fluid operable brake actuators at the brake shoes or pads, and this can adversely affect brake operation to a severe and even dangerous degree. Also, the quality of fluid in a fluid system can deteriorate through time so necessatating replacement of the fluid. In these situations it is necessary to bleed the fluid from the system and then pass replacement or fi lling fluid to the system, and in motor vehicles bleed valves are located at the brake actuators to enable bleeding of the fluid brake system. Up unti l now, fluid brake bleeding has been achieved by fitt ng a discharge pipe between the bleed valve and a collector vessel containing brake fluid, and with the bleed valve open, pumping the brake pedal to discharge fluid from the fluid line. The method s completed by closing the bleed valve and topping the system with brake fluid. However this method has not provect entirely satisfactory and it is possible for ai r pockets to remain in the system even after applications of the method. It is the principal subject of the present inventi.on to provide a fluid system bleeding apparatus enabling fluid bleeding in systems, especially of vehicle brakes, in a more efficient and convenient manner. According to the present invention there is provided apparatus for use in the bleeding of fluid systems comprising a fluid pumping means including a primary fluid reservoir, a conduit having an inner end fluidly connected to said primary reservoir and an outer end adapted to supply to a master reservoir of a fluid system to be bled, whereby fluid can be pumped from the primary reservoir to the master reservoir, an outer end portion of said conduit carrying sealing means enabling the conduit to be sealingly fitted into a fluid supply opening on said master reservoir. Preferably pressure control means are provided in the fluid pumping means to maintain the pressure of pumped fluid at a predetermined value. Preferably the pumping means comprises an air pump delivering pressurised air to said primary reservoir; the pressure control means preferably controls the pressure of the air delivery. Preferably a fluid level sensing means is provided operable to stop the pumping means when the fluid level in the primary reservoir falls to a predetermined level. In a preferred embod ment the sealing means comprises an elastomeric element and compression means actuabl.e to expand or deform the elastomeric element, whereby the element can seal said fluid supply opening. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing which shows schematically a fluid bleeding apparatus serving especially for the bleeding of motor vehicle brakes and in accordance with the present invention. Thus a fluid bleeding apparatus B includes a fluid pumping unit 1 comprisinp a base plate 1A carrying an air pump 2 and a primary fluid reservoir 6 receiving pressurised air from the pump 2 via a conduit 2A. Intercalated in the conduit 2A are an air .filter and moisture trap 3, an air pressure gauge 4, an air pressure control switch device 14 and a one way valve 17, whi le the inlet to the pump 2 is provided with an air filter 9. The pump 2 includes an electric drive motor 10 supplied with electric power via a circuit C1, w ich has a power source in the form of batteries 11 : as an alternative to the batteries 11 the circuit C1 could be plugged nto an external power source such as the vehicle battery. Circuit C2 is arranged in parallel with C1 and has a controlling role over C1 with respect to the fluid level in reservoir 6 and to the air pressure in conduit 2A. The circuit C2 is connected to C1 via a solenoid relay switch 13, and as can be seen circuit C2 include a switch 15 operable by a level sensing float 15A in the reservoir 6 w ile additionally the pressure control switch service 14 is connected into the circuit C2. Circuit C1 includes a master switch 16 and an appropriate fuse 12. A discharge conduit 6A extends close to the bottom of reservoir 6 and hence below the level of the brake fluid (liquid) in the reservoir 6 and serves for the delivery of brake fluid from reservoir 6 to the reservoir 8 of a brake master cylinder 25 w ich carries pipeline 25A supplying to a brake fluid actuator(not shown). The initial section of conduit 6A comprises a flexible tube 24 while the outer end of the conduit 6A is in the form of a sealing adaptor device 7 fitted to the tube 24 by a clip (jubilee) 30 and serving to sealingly secure the discharge end of conduit 6A to a fluid supply opening 26 in the master reservoir 8; the adaptor dev ce 7 comprising a threaded tube bend 23 carrying a sealing element of elastomeric material (e.g. rubber) in the form of a tapered bung 18 sandwiched between end flange plates 19, 20, and a compression device for deforming or expanding the bung 18 for sealingly fitting the adaptor 7 in the opening 26. The compression device comprises a nut 21 threaded on the bend 27 and secured to the plate 20 which has an abrasive surface for frictional engagement with the bung 18 so that the nut 21 is relatively fixed, and a collar 22 fixed to the threaded bend 23 and abutting the flange plate 19, the bend 23 including a large diameter neck portion 27. The adaptor device 7 is sealingly fitted into the opening 26 by screwing the pipe bend 23 into the nut 21 by turning in a clockwise direction (the bend 23 may be initially freed from the flexible tube 24 ) , the elbow of the bend enabling the application of a suitable turning movement, so that the collar 22 moves towards the fi ed nut 21 to expand the bung 18 laterally and to create the securing and sealing effect in the opening 26. The primary reservoir 6 includes a fluid supply inlet 5 provi ed with a closure cap 5A fitted with a filler/safety pressure release valve, and the various parts of the pump unit 1" can be covered by a casing. In operation of the apparatus to bleed an hydraulic brake in a motor vehicle, the bleed valve of the brakes fluid actuator is firstly connected to a fluid receiver by a short pipe section and then placed in the "open" condition. The adaptor 7 is sealing secured in the opening 26 of the master reservoir 8 with the outer end of the pipe bend 27 below the liquid level in the reservoir 8. With an appropriate liquid level in reservoir 6 the level switch 15 will be closed as will pressure switch 14 in circuit C2, and the pumping unit 1 is started by closing master switch 16 causing energisatio and closure of the solenoid switch 13 and thereby electric power supply to the pump motor 10. The operating pump 2 draws air through filter 9 and pumps the air through conduit 2A via the moisture trap 3 to the primary reservoir 6. The pump 2 continues to operate until the predetermined air pressure is attained at which stage pressure switch 14 opens to stop pump 2 through de-energ isation of the solenoid switch 13. The pressure s itch device 14 will control starting and stopping of the pump 2 to maintain the air pressure at the desired level. The apparatus is preferably set so that the switch 14 opens when a pressure of approximately 15 P.S.i . is present and preferably no more than about 20 P . S . i .; swi t ch 14 should be closed when the pressure has fallen to say about 11 P.S.i .- The float switch 15 will open if the liquid level L in reservoir 6 falls below the required level to stop pump 2 and closes automatically when the liquid level is increased. The one way valve 17 prevents air leaking back through the pump 2. The arrangement of unit 1 is such that the air pressure is kept virtually constant, and the pressurised air acting on the free surface of the liquid in the reservoir 6.causes the liquid to be delivered to the master reservoir 8 via conduit 6A resulting in fluid pressure build-up in the master cylinder 25 to discharge the liquid present in the line 25A via the bleed valve and to cause subsequent refilling of the line 25A with brake liquid. At an appropriate time, the pump unit 1 can be stopped, the bleed valve closed, and the vehicle brake system placed in readiness for further use with the bleed apparatus B removed. In comparison with the prior brake bleeding method, brake bleeding utilising the apparatus of the present invention does not require brake pedal pumping and consequently a more precise, accurate and convenient bleeding operation is possible. Whereas the above apparatus B was described in relation to the bleeding of a vehicle brake system, it will be appreciated that the apparatus can be readily used in the bleeding of other fluid systems. Modifications are of course possible: both the pump unit 1 and the adaptor device 7 could be of different form. For example the part 27 of the adaptor could comprise a nut threaded to the bend 23 so as to be axially movable towards the nut 21 thereby expanding the bung, and this would remove the need for the adaptor 7 to be freed from the tube 24 for lateral expansion of the bung 18.

Claims: C laims 1. Apparatus for use in the bleeding of fluid systems characterised in that the apparatus comprises a fluid pumping means (1) including a primary fluid reservoir (6), a conduit (24) ha ing an inner end fluidly connected to said primary reservoir (6) and an outer end adapted to supply to a master reservoir (8) of a fluid system to be bled, whereby fluid can be pumped from the pr ary reservoir (6) to the master reservoir (8) , an outer end portion of said conduit (24) carrying " sealing means (18) enabling the conduit (24) to be sealingly fitted into a fluid supply opening (26) on said master reservoir (8) . 2. Apparatus as claimed in claim 1, characterised in that pressure control means (14) are provided in the fluid pumping means (1A) to maintain the pressure of pumped fluid at a predetermined value. 3. Apparatus as claimed in claim 2, characterised in that the pumping means (1A) comprises an air pump (2) delivering pressurised air to said primary reservoir (6). 4. Apparatus as claimed in claim 3, characterised in that the pressure control means (14) controls the pressure of the air delivery. 5. Apparatus as claimed in any one of the preceding claims, characterised in that a fluid level sensing means ( 15A ) is provided operable to stop the pumping means ( 1A ) when the fluid level in the primary reservoir (6) falls to a predeterm ned level. 6. Apparatus as claimed in any one of the preceding claims, characterised in that the sealing means (18) comprises an elastomeric element and co press i on means (21, 27) actuable to expand or deform the elastomeric element, whereby the element can seal said fluid supply opening (26). 7. Apparatus as claimed in claim 6, characterised in that the elastomeric element comprises a tapering plug 8. Apparatus as claimed in claim 6 or 7, characterised in that said conduit (24) has an outlet portion (23) of metal tube form connected to a preceding conduit portion by fastener means (30), said elastomeric element being carried by said outlet portion (23) . 9. Apparatus as claimed in clai 2, characterised in that said fluid pumping means (1) includes electrical circuit means (C1, C2) serving to drive a pump (2) of the pumping means (1), said pressure control means (14 ) being connected into said electrical circuit means (C1, C2). 10. Apparatus as claimed in claims 5 and 9, wherein said fluid sensing means (15A) is additionally connected into said electrical circuit means (C1, C2).

Inventors: BRODIE JOHN, BUCHANAN NIGEL, BRODIE, JOHN, BUCHANAN, NIGEL
Applicants: BUCHANAN NIGEL, BUCHANAN, NIGEL
Application year: 1987
Main classification: B60T17
IPC codes: B60T17