GB2230574A

GB2230574A - Coupling for linking two hydraulic systems

Info

Publication number: GB2230574A
Application number: GB8900488A
Authority: GB
Inventors: John Muirhead Druce; John M Druce
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-01-10
Filing date: 1989-01-10
Publication date: 1990-10-24
Also published as: GB8900488D0

Abstract

The coupling 1 comprises a master piston-cylinder device 2 adapted for fitting into a first hydraulic system, a slave piston-cylinder device 3 adapted to be fitted into a second hydraulic system, a cylindrical sleeve 4 for positioning said master and slave devices in operative relationship, and a bayonent connector for releasably coupling said slave device to the master piston-cylinder device, the arrangement being such that, in operation, outward movement of the piston 2A of the master device due to pressurising of the first hydraulic system causes movement of the piston 3A of the slave device to pressurise the second hydraulic system. <IMAGE>

Description

"APPARATUS FOR OPERATIVELY COUPLING TWO INDEPENDENT HYDRAULIC SYSTEMS": DESCRIPTION The present invention relates to apparatus for operatively coupling two independent hydraulic systems, and in particular to apparatus providing a mechanical interface between such systems.

In the automotive art, there exists the problem of providing suitable connection-means between the braking system of a towing motor vehicle and the braking system of a trailer e.g. caravan towed by the vehicle, such that uniform braking is present between the vehicle and the trailer while enabling the two braking systems to be joined and separated conveniently as desired. Motor vehicles utilise hydraulically operable braking systems and although for convenience of coupling it has been the practice to utilise a mechanical braking system for trailers, operable for example by relative movements between the vehicle and the trailer, it is now preferred that the trailer also uses an hydraulic braking system to provide increased braking efficiency.

It is the principal object of the present invention to provide apparatus which enables two independent hydraulic systems to be operatively coupled and separated conveniently as desired.

According to the present invention there is provided apparatus for operatively coupling two independent hydraulic systems, said apparatus comprising a master piston-cylinder device adapted for fitting into a first hydraulic system, a slave piston-cylinder device adapted to be fitted into a second hydraulic system, connecting means for positioning said master and slave devices in operative relationship, and coupling means for releasably coupling said slave device to the master piston-cylinder device, the arrangement being such that, in operation, outward movement of the piston of the master device due to pressurising of the first hydraulic system causes movement of the piston of the slave device to pressurise the second hydraulic system.

Preferably, in the operating condition, the pistons of the master and slave devices abut.

Preferably the connecting means comprises a connecting cylinder housing the cylinder of the slave device, said connecting cylinder being fittable onto the cylinder of the master device.

The coupling means preferably comprise a bayonet type connection.

In a preferred embodiment, the cylinder of the slave device includes lateral duct means, while the wall of the connecting cylinder includes a longitudinal slot through which said duct means extend to facilitate connection of the slave device to said second hydraulic system.

An adjuster/bleeder device is preferably provided for the slave piston-cylinder device, and conveniently this adjuster device can take the form of an adjusting spindle threaded to an end wall of the connecting cylinder and engaging the cylinder of the slave device.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Fig. 1 shows a sectional side elevation of apparatus for operatively coupling hydraulic systems, according to the present invention; Fig. 2 shows a side view of the connecting cylinder of the apparatus; Fig. 3 shows a sectional side view of the master cylinder of the apparatus, with Fig. 4 an end view; and Fig. 5 shows an end view of the slave cylinder of the apparatus.

Referring to the drawings, connecting apparatus 1 serves to couple by means of a mechanical interface two independent hydraulic systems, and in particular the independent hydraulic braking systems of a trailer and its towing vehicle. Thus the apparatus 1 comprises a master pistoncylinder device 2, a slave piston-cylinder device 3, and a connecting cylinder 4 connecting the two devices 2, 3 such that the pistons 2A, 3A of the devices 2, 3 are in facing relationship and capable of movement into abutting relationship, the cylinders 2B, 3B of the devices 2, 3 being a sliding fit in the cylinder 4. Suitable sealing rings 5 are provided on the pistons 2A, 3A to prevent fluid leakage from the respective cylinders 2B, 3B.Pistons 2A, 3A are in fact exactly similar and include an axial slot 6 which in the case of piston 2A receives a pin 7 extending through circular holes 8 of corresponding diameter in the cylinder 2B.

The slave piston-cylinder device 3 is fitted into the trailer hydraulic braking system and normally remains in the cylinder 4 so that the device 3 and the cylinder 4 in effect become part of the trailer braking arrangement and, when desired, the cylinder 4 is slid onto and coupled to the master piston-cylinder device 2 which is fitted into the hydraulic braking system of the towing vehicle. Coupling of the cylinder 4 to the device 2 is achieved by a bayonet connection 9 (Fig. 2), the pin 7 extending radially outwardly of the holes 8 so as to engage in the bayonet slots.

The cylinder 2B includes a port 10 in an inner end wall of the cylinder for flow of fluid to the inner end of the cylinder while an additional port 11 facilitates bleeding from the cylinder 2B. With the slave device 3 located in the cylinder 4, a lateral boss 12 is fixed to the cylinder 3B, the boss 12 extending through an elongate aperture 13 on the wall of cylinder 4, and the boss 12 contains a duct 14 whereby the inner end of cylinder 3B can be connected into the hydraulic brake system of the trailer while a further duct 15 serves for bleeding from cylinder 3B. A spindle 16 threaded in an end wall 4A of the cylinder 4 abuts against the cylinder 3B to provide for (a) fluid bleeding from the cylinder 3B and (b) operational positioning of the slave device 3. The port 11 and duct 15 will include appropriate bleed valves.

INSTALLATION: The master device 2 is suitably introduced into the vehicle brake circuit 17 via duct 10 by using for example a T-piece 18 etc, and the device 2 can be secured to the vehicle chassis by means of bolt holes 19 on the device 2. The vehicle brake fluid is bled and replenished. The trailer hydraulic brake system is then connected to the duct 14 of the slave device 3 by a flexible hose, and the trailer hydraulic system is filled and appropriately bled by means of adjuster 16 and bleed duct 15 so that a reservoir of fluid is present in the inner end of the cylinder 3B. The trailer brakes can be tested by pushing in the piston 3A.

IN-USE FITTING: The adjuster spindle 16 is firstly slackened off, and the cylinder 4 connected to the master device 2 by means of the bayonet connection 9.

The spindle 16 is then screwed in to bring the pistons 2A, 3A into abutment and until definite resistance is felt (the trailer brakes will come on hard) whereupon the spindle is screwed back appropriately e.g. one turn the trailer and vehicle hydraulic systems are now effectively coupled through the mechanical interface of the pistons 2A, 3A which operate in the manner of railway train buffers. Depression of the vehicle brake pedal causes piston 2A to push piston 3A whereby the trailer brakes function simultaneously with the vehicle brakes, and the piston combination 2A, 3A returns to its original position when the brakes are released. The pin/slot arrangement 6, 7 precludes the piston 2A from freeing from cylinder 3A, while suitable means e.g. a pin extending between opposed apertures 13 and slot 6 can be provided to hold piston 3A in position when master device 2 is freed.

As will be appreciated therefore, the connecting device 1 enables uniform braking between the hydraulic brakes of the trailer and towing vehicle which provides definite advantages as regards safety. Further the device 1 enables convenient and prompt coupling and uncoupling of the hydraulic circuits. Although the device 1 has been described with particular reference to hydraulic braking circuits of a trailer and a towing vehicle, the device 1 could be used for operatively coupling independent circuits of other hydraulic systems. Whereas in the above described embodiment the pistons 2A, 3A abut directly, it would be possible to have some intermediary device between the pistons.

INSTALLATION 1. Introduce operating cylinder into car brake circult by suitable tee piece etc 2. bleed car brakes 3. connect traller hydraulic brakes to slave cylinder 4. fill traller system and bleed using adjuster/bleeder and spare hole 5. jack up traller wheels to prove action METHOD OF USE 1. slacken adjuster bleeder screw 2. engage bayonet connection 3. tighten adjuster/bleeder until resistance is apparent or traler brakes come on hc 4. stacken back one turn.

Claims

1. Apparatus for operatively coupling two independent hydraulic systems, said apparatus comprising a master piston-cylinder device adapted for fitting into a first hydraulic system, a slave piston-cylinder device adapted to be fitted into a second hydraulic system, connecting means for positioning said master and slave devices in operative relationship, and coupling means for releasably coupling said slave device to the master piston-cylinder device, the arrangement being such that, in operation, outward movement of the piston of the master device due to pressurising of the first hydraulic system causes movement of the piston of the slave device to pressurise the second hydraulic system.

2. Apparatus as claimed in Claim 1, wherein the operating condition, the pistons of the master and slave devices abut.

3. Apparatus as claimed in claim 1 or claim 2, wherein the connecting means comprises a connecting cylinder housing the cylinder of the slave device, said connecting cylinder being fittable onto the cylinder of the master device.

4. Apparatus as claimed in any of the preceding claims wherein, the coupling means comprise a bayonet type connection.

5. Apparatus as claimed in any preceding claim, wherein the cylinder of the slave device includes lateral duct means, while the wall of the connecting cylinder includes a longitudinal slot through which said duct means extend to facilitate connection of the slave device to said second hydraulic system.

6. Apparatus as claimed in any preceding claim, wherein an adjuster/bleeper device is preferably provided for the slave piston-cylinder device, and conveniently this adjuster device can take the form of an adjusting spindle thread toLend wall of the connecting cylinder and engaging the cylinder of the slave device.

7. Apparatus for operatively coupling two independent hydraulic system, substantially as herein described with respect to the accompanying drawings.