GB2304840A

GB2304840A - Vacuum bleeding equipment

Info

Publication number: GB2304840A
Application number: GB9518120A
Authority: GB
Inventors: Michael Neil Basnett
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1995-09-06
Filing date: 1995-09-06
Publication date: 1997-03-26
Anticipated expiration: 2015-09-06
Also published as: GB9518120D0; GB2304840B

Abstract

Vacuum bleeding equipment for a hydraulic brake system of a vehicle, comprises a supply duct 18 through which hydraulic fluid can be supplied to a reservoir 12 of the system. Within the supply duct are located an on/off tap 20 and a flow restrictor 22. In vacuum bleeding the system, the tap 20 is initially closed so that the pressure within a working part of the system may be reduced. After the pressure has been reduced in the working part of the system, tap 20 is opened so that a limited flow of fluid is permitted to pass into the reservoir by the restrictor 22. The restrictor serves to ensure that reduced pressure in the system is maintained during bleeding.

Description

VACUUM BLEEDING EOUIPMENT In a hydraulic brake system for a vehicle provision has to be made for the system to be drained of hydraulic fluid (commonly referred to as being "bled") during servicing of the vehicle. Whilst such a system can usually be bled by gravity alone, it can be preferable to use a vacuum technique in which the fluid (and any entertained air) is drawn through the system by suction. Known equipment for this purpose comprises an air venturi which draws the fluid out through a bleed screw.

However, a fluid supplying arrangement for such a system, usually incorporating a reservoir, is normally not reliably sealed and furthermore the supply of fluid is effectively unrestricted. These factors reduce the degree of vacuum achievable in the system by means of vacuum bleeding equipment, and so reduce effectiveness in evacuating trapped air.

It is an object of the present invention to an improved performance of vacuum bleeding equipment applied to an hydraulic brake system.

The invention provides, in one of its aspects, vacuum bleeding equipment for use in bleeding an hydraulic brake system in a vehicle which system comprises means whereby hydraulic fluid can be introduced into a working part of the system and bleeding means whereby hydraulic fluid can be bled from the working part, the bleeding equipment comprising fluid flow controlling means which in a first condition seals the working part of the system to enable pressure within the working part to be reduced by means of vacuum bleeding equipment applied to the bleeding means, and which in a second condition permits a restricted flow of hydraulic fluid to be drawn into the working part whilst reduced pressure in the working part is maintained.

In a preferred construction, the flow controlling means is located within a supply duct leading to a reservoir, and may comprise a valve (e.g. in the form of an on/off tap) and a separate flow restrictor. The restrictor is preferably located upstream of the valve.

There now follows a detailed description, to be read with reference to the accompanying drawings, of an embodiment and its use which illustrates the invention by way of example.

In the accompanying drawings: Figure 1 is a diagrammatic illustration of a tap and restrictor applied to a reservoir of a hydraulic brake system; and Figures 2, 3 and 4 illustrate various conditions within the system in use of vacuum bleeding equipment.

In a hydraulic brake system in a vehicle, a supply of hydraulic fluid to a master cylinder 10 is ordinarily maintained within a reservoir 12. A lid 14 of vacuum bleeding equipment is sealed to the reservoir by sealing means 16 and a supply duct 18 extends through the lid to the reservoir.

Flow controlling means, of such fluid supplying means, located within the duct 18, comprises an on/off tap 20 which in a first (closed) condition seals a working part of the system between the tap and bleeding means (not shown) and in a second (open) condition permits hydraulic fluid to pass through the duct 18 to the reservoir. The flow of fluid through the duct is limited by a flow restrictor 22 positioned upstream of the tap 20.

Figures 2, 3 and 4 illustrate the presence of an air pocket 24 in the working part of the system, conduits 26 and 28 leading, respectively, to the pocket from the master cylinder 10 and from the pocket towards the system bleeding means.

Figure 2 shows the air pocket in ordinary conditions where the system has been filled, or gravity bled, under atmospheric conditions.

Figure 3 illustrates the effect on the pocket of applying suction to the bleeding means whilst the tap 20 remains closed. Owing to the reduction in pressure within the system, which may be brought as low as around 10 mbar, the air pocket 24 becomes enlarged in proportion to the pressure drop achieved.

Upon opening the tap 20, fluid becomes drawn through the system from a supply to the duct 18, the restrictor 22 ensuring that the degree of vacuum is substantially maintained. The fluid passing through the conduits 26 and 28 (Figure 4) displaces from the system the air which has expanded from the confines of the pocket 24.

As a result, upon restoring the system to atmospheric conditions, the volume of the air remaining trapped within the pocket 24 (and all such pockets within the system) will be only a small proportion (e.g. one hundredth) of the original volume and the performance of the braking system, in use, will be improved.

Claims

1. Vacuum bleeding equipment for use in bleeding a hydraulic brake system in a vehicle which system comprises means whereby hydraulic fluid can be introduced into a working part of the system and bleeding means whereby hydraulic fluid can be bled from the working part, the bleeding equipment comprising fluid flow controlling means which in a first condition seals the working part of the system to enable pressure within the working part to be reduced by means of vacuum bleeding equipment applied to the bleeding means, and which in a second condition permits a restricted flow of hydraulic fluid to be drawn into the working part whilst reduced pressure in the working part is maintained.

2. Vacuum bleeding equipment according to Claim 1 in which the flow controlling means is located within a supply duct leading to a reservoir.

3. Vacuum bleeding equipment according to either of Claims 1 and 2 in which the flow controlling means comprises a valve adjustable between open and closed conditions and a flow restrictor.

4. Vacuum bleeding equipment according to Claim 3 in which the restrictor is located upstream of the valve.

5. Vacuum bleeding equipment substantially as hereinbefore described with reference to the accompanying drawings.