GB1584728A

GB1584728A - Brake fluid reservoirs

Info

Publication number: GB1584728A
Application number: GB4425377A
Authority: GB
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1977-10-25
Filing date: 1977-10-25
Publication date: 1981-02-18
Also published as: IN148827B; FR2407103B1; FR2407103A1; DE2844494A1

Description

(54) BRAKE FLUID RESERVOIRS (71) We, AUTOMOTIVE PRODUCTS LIM)TED, a British Company of Tachbrook Road, Leamington Spa, Warwickshire, CV3 1 3ER do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to fluid reservoirs for hydraulic dual circuit braking systems.

In dual circuit braking systems it is common for the fluid reservoir to have a separate chamber for each circuit. It is usual for these chambers to be separated by a partition wall, and for the two chambers to be interconnected above a pedetermined level of brake fluid in the reservoir, so as to allow a continuous equalisation of air and fluid. Hence, it is typical for the reservoir to be constructed of a single plastic unit with a central partition forming a weir, which divides the unit into two chambers below the predetermined fluid level. This construction has the disadvantage that in the event of a fluid leak from one braking circuit and the emptying of its feed chamber in the reservoir, then as the vehicle moves over rough ground, accelerates, or brakes, the fluid in the other chamber will have sufficient inertia to splash over the weir into the empty chamber.Therefore, the still good circuit will be slowly deprived of fluid from its reservoir chamber.

The object of the present invention is to provide a dual circuit fluid reservoir that minimises the above problem.

According to this invention there is provided a fluid reservoir for a hydraulic dual circuit vehicle braking system and compns- ing two chambers changeable with fluid and interconnected for flow of fluid by a tube having ends which open one into each respective chamber as apertures located at a minimum required fluid level within the respective chamber and each aperture is located substantially midway along the longitudinal length of its associated chamber with respect to its attitude of mounting of the reservoir on a vehicle, and lies in a substantially vertical longitudinal plane through the reservoir, with respect to said attitude of mounting.

Preferably the tube and each of the two chambers share a common wall, constituted by a longitudinal sidewall of the reservoir.

Conveniently substantially the whole of the tube is external of the reservoir and the apertures are in the reservoir side wall.

Preferably the reservoir is formed from two portions, an upper portion and a lower portion respectively sealed together along a horizontal join line and the tube is also formed from two parts sealed together, an upper part integral with the upper portion of the reservoir and a lower part integral with the lower part of the reservoir.

It is preferable for the upper part of the tube to be an inverted 'u' shaped section channel along one side wall of the upper portions of the reservoir, and which is sealed to a flange normal to a corresponding side wall of the lower portion of the reservoir, said flange constituting the lower part of the tube, and the ends of the channel are sealed and the apertures are adjacent said sealed ends.

An advantage of this construction of the tube is that it enables tube and reservoir to be moulded and assembled simultaneously with no substantially extra tooling costs, and no handling of extra components during assembly of the reservoir.

An embodiment of the invention will now be decribed by way of example and with reference to the following drawings in which: Fig. 1 is a longitudinal vertical section through a fluid reservoir aceording to this invention; Fig. 2 is a view in the direction of arrow A of Fig. 1; and Fig. 3 is a section on the line III-III of Fig. 1.

With reference to Fig. 1 and Fig. 2 and Fig. 3, a brake fluid reservoir 11 for a dual circuit braking system has two chambers 12 and 13 for holding brake fluid. The chambers 12 and 13 communicate via outlets 14 and 15 with different braking circuits.

The two chambers 12 and 13, are separated by a partition wall 16, and each has a screwthreaded filler connection 17 and 18, respectively, which are normally each closed by a screw filler cap (not shown).

The reservoir comprises two moulded plastics portions, an upper portion 21 and a lower portion 22, the two portions being welded together along a horizontal longitudinal join line. The welding is facilitated by outwardly projecting mating flanges 19 which are on the outer periphery of the upper and lower portions, 21 and 22 respectively. The reservoir can be moulded out of high density polyethylene, or polypropylene materials.

The two chambers 12 and 13 are interconnected by a tube 23, and substantially the whole tube 23 is external to the reservoir 11. The tube 23 is formed from two parts 24 and 25, integral with the moulded upper and lower portions 21 and 22, respectively, of the reservoir. The upper part 24 is in the shape of an inverted 'u' shaped section channel which shares a common wall 26 with the reservoir, and has a outwardly projecting flange 27 on its other wall for welding with the other part 25 of the tube, which is constituted by a flange normal to the corresponding portion of side wall of the lower portion 22 of the reservoir. The ends of the 'u' section channel portion are blocked moulded-in end walls 29 and 30.

When the upper and lower portions of the reservoir are assembled together the upper and lower parts of the partition 16 abut each other and are welded together at the split line; and the common wall 26, end walls 29 and 30, and flange 27 all abut and are welded to the flange 25 to form the tube 23. The outer peripheral flanges 19 are also welded together so as to sealingly secure the upper and lower portion of the reservoir together. The tube communicates with the chambers 12 and 13 by means of apertures, 31 and 32, respectively, present in the common wall 26 adjacent the end walls 29 and 30, respectively.The apertures 31 and 32 are hence arranged so that they are orientated in a plane substantially parallel to a vertical longitudinal section through the reservoir, and are each located at the minimum required fluid level and at the approximate mid length of their respective chamber, side walls. When the reservoir is fitted into a vehicle, the longitudinal axis of the reservoir is substantially parallel with the longitudinal axis of the vehicle and the apertures 31 and 32 will lie midway along the longitudinal length of each respective chamber in relation to its longitudinal axis with respect to its attitude of mounting on the vehicle.

The floor of the tube 23, constituted by the flange 25 lies on the longitudinal split line between the upper and lower portions 21 and 22, and this line becoming the join line of the assembled reservoir and is located at the minimum desirable fluid level within the reservoir.

If the reservoir tilts about an axis parallel the wall 16 i.e. transverse to the vehicle, and the minimum fluid level pertains, then depending on the direction of the surge, or the direction of rotation of the tilting movement, one or other of the apertures 31 or 32 will tend to come clear of the fluid in that particular chamber and therefore the fluid flow between the two chambers will be prevented.

If for example the brake circuit connected to chamber 13 failed because of fluid loss, then the fluid in both chambers 12 and 13 would be lost until the fluid in chamber 12 reached the minimum level coinciding with the floor of the tube. Thereafter chamber 13 would empty, and if for example the reservoir tilted clockwise as when parking on a hill, the aperture 31 would lift clear of the fluid remaining in chamber 12 thus ensuring that it did not run downhill into chamber 13. Similarly if the reservoir tilted anticlockwise the tube 23 would be running uphill, and even if the aperture 31 dipped below the surface of the fluid, it would not run uphill into chamber 13.

However the major advantage of having the apertures located in the approximate centre of the side wall, is that when the reservoir is fitted to a vehicle such that its longitudinal axis is parallel to the longitudinal axis of the vehicle and one of the chambers has been emptied as previously described, then constant acceleration and deceleration, or travel over rough ground, will cause the remaining fluid to surge back and forth in the respective chamber. This surging gives rise to two effects and the positioning of the apertures 31 and 32 takes full advantage of these effects.

The constant surging causes the fluid to flow back and forth such that the fluid level (as shown in dotted lines in Fig. 1) tends to take on a 'u' shape for a longitudinal section through the tank. Taking chamber 12 for example, the fluid will tend to climb up the end wall 33 and the partition wall 16. This reduces the depth of fluid at the medial transverse line of the chamber and the aperture 31 will be above the fluid level and hence there will be no fluid flow between the two chambers. This picture is of course rather simple and there will be splashing and surface ripples in the reservoir, but the bulk of the fluid will behave as described.

The transverse section through the tank will show an substantially level fluid line.

The other advantage of having the openings of the tube constituted by apertures 31 and 32 orientated so that they are substantially parallel to a vertical longitudinal section, is that as the fluid moves back and forth in the chambers, either due to tilting or changes in momentum, then a "waterfall" type of effect is set up as the liquid moves over the openings. This has the effect of further reducing the loss of fluid into the tube 23, as the fluid rushes over the openings 31 and 32.

The two filler connections 17 and 18 allow the braking system to be rapidly charged as is required in the initial charging in the mass production of motor vehicles.

WHAT WE CLAIM IS:- 1. A fluid reservoir for a hydraulic dual circuit vehicle braking system and comprising two chambers chargeable with fluid and interconnected for flow of fluid by a tube having ends which open one into each respective chamber as apertures located at a minimum required fluid level within the respective chamber, and each aperture is located substantially midway along the longitudinal length of its associated chamber with respect to its attitude of mounting of the reservoir on a vehicle, and lies in a substantially vertical longitudinal plane through the reservoir, with respect to said attitude of mounting.

2. A fluid reservoir as claimed in Claim 1, wherein each of the two chambers and the tube share a common wall, constituted by a longitudinal side wall of the reservoir.

3. A fluid reservoir as claimed in Claim 2, wherein substantially the whole tube is external of the reservoir and the apertures are in the reservoir side wall.

4. A fluid reservoir as claimed in Claim 2 or Claim 3, wherein the reservoir is formed from two portions, an upper and lower portion respectively, sealed together along a horizontal join line and the tube is also formed from two parts sealed together, an upper part integral with the upper portion of the reservoir and a lower part integral with the lower part of the reservoir.

5. A fluid reservoir as claimed in Claim 6, wherein the upper part of the tube is an inverted 'u' shaped section channel integral with one side wall of the upper portion of the reservoir, and the lower part of the tube is a flange normal to a corresponding side wall of the lower portion of the reservoir, and the end walls of the channel are sealed and the apertures are adjacent said sealed ends.

6. A fluid reservoir substantially as described herein and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. will show an substantially level fluid line. The other advantage of having the openings of the tube constituted by apertures 31 and 32 orientated so that they are substantially parallel to a vertical longitudinal section, is that as the fluid moves back and forth in the chambers, either due to tilting or changes in momentum, then a "waterfall" type of effect is set up as the liquid moves over the openings. This has the effect of further reducing the loss of fluid into the tube 23, as the fluid rushes over the openings 31 and 32. The two filler connections 17 and 18 allow the braking system to be rapidly charged as is required in the initial charging in the mass production of motor vehicles. WHAT WE CLAIM IS:-

1. A fluid reservoir for a hydraulic dual circuit vehicle braking system and comprising two chambers chargeable with fluid and interconnected for flow of fluid by a tube having ends which open one into each respective chamber as apertures located at a minimum required fluid level within the respective chamber, and each aperture is located substantially midway along the longitudinal length of its associated chamber with respect to its attitude of mounting of the reservoir on a vehicle, and lies in a substantially vertical longitudinal plane through the reservoir, with respect to said attitude of mounting.