GB1578147A

GB1578147A - Hydraulic coupling unit

Info

Publication number: GB1578147A
Application number: GB3798876A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-19
Filing date: 1977-05-19
Publication date: 1980-11-05

Description

(54) HYDRAULIC COUPLING UNIT (71) We, PETER THOMAS CAMP and DIANE CAMP, both British subjects, of 18, Townend Road, Paull, Hull, Yorkshire, 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 coupling arrangements and more particularly to a coupling for connecting two fluid pressure systems.

There are many fluid pressure applications wherein it is desirable for a first fluid pressure system, acting as a closed system, to affect a second, closed, fluid pressure system and in, for example, the vehicle field it is often desired to connect the fluid braking system for a towing vehicle to a fluid braking system for a towed vehicle whereby, application of the brakes on the towing vehicle results in application of the brakes on the towed vehicle. With such an arrangement the fluid pressure brake for the towing vehicle must be effective at all times but it is desirable for the towing vehicle braking system to be effective on the towing vehicle when the two vehicles are connected and the brake system for the towing vehicle is coupled with the brake system for the towed vehicle.

According to the present invention there is provided a coupling arrangement for connecting a first fluid pressure system to a second fluid pressure system and comprising a chamber of substantially uniform cross sections adapted to have a first region exposed to pressure fluid of said first fluid pressure system and a second region exposed to pressure fluid of said second fluid pressure system, a first displaceable member located in said chamber and arranged to present a surface exposed to pressure fluid in said first region and to abut a second displaceable member remote from said surface, said second displaceable member having a surface exposed to pressure fluid in said second region, said first and second displaceable members being arranged to seal pressure fluid in said first region from pressure fluid in said second region and being mutually displaceable within said chamber to maintain a balance between the fluid pressures in said first and second fluid pressure systems and said chamber being defined by a split casing, a first part of the casing including said first region, the second part of said casing including said second region and conveniently said casing parts mate in a plane normal to the axis of said chamber and substantially at the mid length region of said chamber.

Preferably said chamber comprises a bore and said first and second displaceable members are located in said bore.

Preferably the coupling includes means for retaining the first displaceable member in said first casing part and means for retaining the second displaceable member in said second casing part.

In a preferred embodiment in accordance with the invention the coupling arrangement comprises a first casing part, a second casing part, means for assembling and disconnecting said casing parts, a first bore region in said first casing part connectable to the first fluid pressure system, a second bore region in said second casing part connectable to the second fluid pressure system, said first and second bore regions being aligned to form a continuous bore with the ends connectable to the first and second fluid pressure systems at opposite ends thereof when the casing parts are assembled, the first displaceable member being located within said first bore region and the second displaceable member being located within said second bore region, said first and second displaceable members being in abutting relationship for mutual displacement when the casing is assembled.

In one embodiment in accordance with the invention said first displaceable member comprises a piston slidable in the bore of the first bore region, and means are provided for limiting the displacement of the piston away from the bore end connectable with the first fluid pressure system to retain said piston member in said bore region when the casing parts are separated. Conveniently second displaceable member may also comprise a piston slidable in said second bore region with means provided for limiting the displacement of said piston away from that end of said bore region connectable with the second fluid pressure system to retain said piston member in said bore region when the casing parts are separated.

When the first and second displaceable members comprise pistons one piston preferably includes an extension which engages in a recess in the other piston.

In an alternative arrangement said first displaceable member comprises a diaphragm. Conveniently the second displaceable member may also comprise a diaphragm, and with such an arrangement the displaceable mid-regions of the two diaphragms are in contacting relationship.

Preferably and when in combination with first and second fluid pressure systems the displaceable members are so arranged that, upon separation of the coupling, the first displaceable member seals the first pressure fluid system against loss of fluid therefrom and the second displaceable member seals the second fluid pressure system against loss of fluid therefrom.

In such a combination the first fluid pressure system may conveniently comprise the hydraulic brake system of a towing vehicle such as a car and the second fluid pressure system comprises the hydraulic braking system for a towed vehicle such as a trailer or caravan and whereby an increase in hydraulic pressure in the brake system of the car to apply brake thereto is transmitted by, displacement of the first and second displaceable members, to cause an increase in pressure in the hydraulic circuit of the trailer or caravan thereby to apply brake to the towed vehicle.

The invention will now be described further by way of example with reference to the accompanying drawings in which: Fig. 1 shows, diagrammatically and partially in cross section, a coupling arrangement in a vehicle braking system and Fig. 2 shows, in cross section, an alternative coupling arrangement.

In the embodiment illustrated in Fig. 1 a conventional four wheel vehicle hydraulic brake system, generally indicated by numeral 11, is connected to a two wheel vehicle hydraulic brake system, generally indicated by numeral 12, via a coupling arrangement, generally indicated by numeral 13. The system 11 includes a pedal-operated master cylinder 14 with four brake actuating piston and cylinder slave units 15, 16, 17 and 18 with a conduit 19, the bore of which opens to the pressure fluid in system 11. The system 12 includes two brake actuating piston and cylinder slave units 20 and 21 with a conduit 22 arranged with its bore open to the pressure fluid in system 12.

The conduit 19 opens to a bore 23 in a coupling part 24 fixed relative to the towing vehicle, the conduit 22 opens into a bore 25 of a coupling part 26 and which part 26 thereby associates with the towed vehicle and, conveniently, at least part of the conduit 22 is flexible to allow the coupling part 26 to be brought into coupling position relative to the coupling part 24.

The coupling part 26 presents, at its end remote from conduit 22, a radial flange 27 and the coupling part 24 presents, at its end remote from conduit 19, an externally threaded boss 28. The coupling part 26 is connected to coupling part 24 by a cup shaped member 29 which has a screw thread, engageable with the thread on boss 28 and a radial wall 30 which engages the flange 27. Thus, when the coupling parts 26 and 24 are in axial alignment and the flange 27 abuts boss 28 the cup shaped member 29 can be screwed onto boss 28 until the radial wall 30 engages and secures flange 27 against the radial face of boss 28. With the coupling parts 24 and 26 secured by the member 29 the bore 23 is axially aligned with the bore 25.

A displaceable piston member 31 is slidably disposed in bore 23 and presents, at that end remote from conduit 19, an elongate portion 32 of reduced cross section and, at the juncture of portion 32 with the main body of the member 31, the part 31 defines a radial abutment surface 33. An annular stop member 34 is located in bore 23 and serves to limit the displacement of coupling member 31 away from the end of bore 23 into which conduit 19 opens. The displaceable member 31 is therefore displaceable between the position shown in Fig. 1, and wherein the right hand side of the member 31 engages the blind end of bore 23, and an extreme left hand position (as viewed in Fig. 1) with abutment surface 33 in engagement with the stop member 34.

The bore 25 also has a displaceable piston member 35 slidably disposed therein, and the member 35 has a blind recess 36 in that radial wall remote from the connection with conduit 22. The free end of the reduced diameter portion 32 of member 31 engages in the recess 36 when the coupling is assembled.

An annular stop member 37, retained in bore 25 adjacent the open end thereof, is engageable by the displaceable piston member 35 to limit the displacement of member 35 outwardly of the bore 25.

A coiled compression spring 38 acts between the blind end of bore 25 and the adjacent radial end of the piston member 35 to urge piston member 35 towards the stop member 37. The piston member 31 has an annular seal 39, the piston member 35 includes an annular seal 40, and the radial face of flange 27 engageable with boss 28 also includes an annular seal 41 concentric with the axis of bores 23, 25. Bleeder valves 42 and 43 are provided adjacent that end of bore 23 adjacent the connection with conduit 19 and that end of bore 25 adjacent the connection with conduit 22 respectively.

The coupling arrangement described above operates as follows; With the coupling made and the foot operated master cylinder 14 in its released condition the hydraulic pressure in the circuit 11 is substantially at atmospheric pressure, the spring 38 extends to drive piston members S and 31 towards their extreme right hand positions as shown in Fig. 1 and whereby piston member 35 abuts stop member 37, and the pressure in circuit 12 is thereby reduced substantially to atmospheric pressure. In this condition the brakes of both the towing and towed vehicles are released.

When the foot-operated master cylinder 14 is operated the hydraulic pressure in the circuit 11 increases and the fluid pressure, acting on the right hand side of piston member 31, urges member 31 towards the left, as viewed in Fig. 1, displacement of member 31 causes simultaneous displacement of piston member 35 towards the left as viewed in Fig. 1 against the action of spring 38 and as member 35 moves towards the left the fluid pressure in system 12 increases. Thus, the system 12 experiences an increase in pressure in direct response to the rise in pressure in the system 11 and as the pressure in both circuits 11 and 12 increases the brakes of both vehicles are applied.

When the foot operated master cylinder 14 is again released, fluid pressure in system 11 falls and the pressure in system 12, in combination with the extension of spring 38, causes piston members 35 and 31 to be displaced towards the right as viewed in Fig. 1 to release the brakes of both vehicles.

When now the towing vehicle is to be detached from the towed vehicle it is only necessary to unscrew the cup shaped member 29 from threaded engagement with boss 28, the coupling parts 24 and 26 can then be separated, and the piston member 35 will be retained with coupling part 26 by the engagement with stop member 37, the piston member 31 will be retained with coupling part 24 by the engagement of member 31 with stop member 34, and the seals 39 and 40 on members 31 and 35 respectively prevent loss of fluid from the respective systems 11 and 12 respectively. The towing vehicle, defined by circuit 11, can then drive away with the circuit 11 operating normally.

Preferably the towing vehicle will include a cap or cover (not shown), engageable with the thread on boss 28 and arranged to retain the member 31 in its extreme right hand position when the coupling is disconnected, thus to avoid undue charging of system 11 from the conventional reservoir, should the brakes be applied and released with member 31 in its extreme left hand position as viewed in Fig. 1. Fig. 2 shows an alternative arrangement for the coupling and wherein coupling members 51 and 52 are connectable by a cup shaped member 53, in identical manner to the Fig. 1 embodiment, to axially align bores 54 and 55 in members 51 and 52 respectively. The bore 54 communicates with a conduit 56, identical with conduit 19, and bore 55 communicates with a conduit 57 in identical manner to conduit 22.

The first dis laceable member comprises a flexible, resilient diaphragm 58 peripherally retained to wholly close bore 54 and the second displaceable member comprises a flexible, resilient diaphragm 59 peripherally retained to wholly close bore 55.

The diaphragms 58 and 59 wholly close their respective bores 54 and 55 to prevent loss of fluid from their respective fluid pressure systems and, when the coupling is assembled, the diaphragms 58 and 59 are in contact whereby, when a pressure difference is generated between the two circuits the deflectable mid regions of the two diaphragms 58 and 59 move in unison to balance the pressures in the two systems.

Although the present invention has been described by way of example the invention is not limited to the specific examples and many modifications and variations will be apparent to persons skilled in the art.

WHAT WE CLAIM IS: 1. A coupling arrangement for connecting a first fluid pressure system to a second fluid pressure system and comprising a chamber of substantially uniform crosssection adapted to have a first region exposed to pressure fluid of said first fluid pressure system and a second region exposed to pressure fluid of said second fluid pressure system, a first displaceable member located in said chamber and arranged to present a surface exposed to pressure fluid in said first region and to abut a second displaceable member remote from said surface, said second displaceable member having a surface exposed to pressure fluid in said second region, said first

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. engageable by the displaceable piston member 35 to limit the displacement of member 35 outwardly of the bore 25. A coiled compression spring 38 acts between the blind end of bore 25 and the adjacent radial end of the piston member 35 to urge piston member 35 towards the stop member 37. The piston member 31 has an annular seal 39, the piston member 35 includes an annular seal 40, and the radial face of flange 27 engageable with boss 28 also includes an annular seal 41 concentric with the axis of bores 23, 25. Bleeder valves 42 and 43 are provided adjacent that end of bore 23 adjacent the connection with conduit 19 and that end of bore 25 adjacent the connection with conduit 22 respectively. The coupling arrangement described above operates as follows; With the coupling made and the foot operated master cylinder 14 in its released condition the hydraulic pressure in the circuit 11 is substantially at atmospheric pressure, the spring 38 extends to drive piston members S and 31 towards their extreme right hand positions as shown in Fig. 1 and whereby piston member 35 abuts stop member 37, and the pressure in circuit 12 is thereby reduced substantially to atmospheric pressure. In this condition the brakes of both the towing and towed vehicles are released. When the foot-operated master cylinder 14 is operated the hydraulic pressure in the circuit 11 increases and the fluid pressure, acting on the right hand side of piston member 31, urges member 31 towards the left, as viewed in Fig. 1, displacement of member 31 causes simultaneous displacement of piston member 35 towards the left as viewed in Fig. 1 against the action of spring 38 and as member 35 moves towards the left the fluid pressure in system 12 increases. Thus, the system 12 experiences an increase in pressure in direct response to the rise in pressure in the system 11 and as the pressure in both circuits 11 and 12 increases the brakes of both vehicles are applied. When the foot operated master cylinder 14 is again released, fluid pressure in system 11 falls and the pressure in system 12, in combination with the extension of spring 38, causes piston members 35 and 31 to be displaced towards the right as viewed in Fig. 1 to release the brakes of both vehicles. When now the towing vehicle is to be detached from the towed vehicle it is only necessary to unscrew the cup shaped member 29 from threaded engagement with boss 28, the coupling parts 24 and 26 can then be separated, and the piston member 35 will be retained with coupling part 26 by the engagement with stop member 37, the piston member 31 will be retained with coupling part 24 by the engagement of member 31 with stop member 34, and the seals 39 and 40 on members 31 and 35 respectively prevent loss of fluid from the respective systems 11 and 12 respectively. The towing vehicle, defined by circuit 11, can then drive away with the circuit 11 operating normally. Preferably the towing vehicle will include a cap or cover (not shown), engageable with the thread on boss 28 and arranged to retain the member 31 in its extreme right hand position when the coupling is disconnected, thus to avoid undue charging of system 11 from the conventional reservoir, should the brakes be applied and released with member 31 in its extreme left hand position as viewed in Fig. 1. Fig. 2 shows an alternative arrangement for the coupling and wherein coupling members 51 and 52 are connectable by a cup shaped member 53, in identical manner to the Fig. 1 embodiment, to axially align bores 54 and 55 in members 51 and 52 respectively. The bore 54 communicates with a conduit 56, identical with conduit 19, and bore 55 communicates with a conduit 57 in identical manner to conduit 22. The first dis laceable member comprises a flexible, resilient diaphragm 58 peripherally retained to wholly close bore 54 and the second displaceable member comprises a flexible, resilient diaphragm 59 peripherally retained to wholly close bore 55. The diaphragms 58 and 59 wholly close their respective bores 54 and 55 to prevent loss of fluid from their respective fluid pressure systems and, when the coupling is assembled, the diaphragms 58 and 59 are in contact whereby, when a pressure difference is generated between the two circuits the deflectable mid regions of the two diaphragms 58 and 59 move in unison to balance the pressures in the two systems. Although the present invention has been described by way of example the invention is not limited to the specific examples and many modifications and variations will be apparent to persons skilled in the art. WHAT WE CLAIM IS:

1. A coupling arrangement for connecting a first fluid pressure system to a second fluid pressure system and comprising a chamber of substantially uniform crosssection adapted to have a first region exposed to pressure fluid of said first fluid pressure system and a second region exposed to pressure fluid of said second fluid pressure system, a first displaceable member located in said chamber and arranged to present a surface exposed to pressure fluid in said first region and to abut a second displaceable member remote from said surface, said second displaceable member having a surface exposed to pressure fluid in said second region, said first

and second displaceable members being arranged to seal pressure fluid in said first region from pressure fluid in said second region and being mutually displaceable within said chamber to maintain a balance between the fluid pressures in said first and second fluid pressure systems and said chamber being defined by a split casing, a first part of the casing including said first region and the second part of said casing including said second region.

2. A coupling as claimed in claim 1 in which said chamber comprises a bore and said first and second displaceable members are located in said bore.

3. A coupling as claimed in claims 1 and 2 in which said casing parts mate to define said bore in a plane normal to the axis of said bore and substantially at the mid length region of said bore.

4. A coupling as claimed in claim 1, 2 or 3 including means for retaining the first displaceable member in said first casing part and means for retaining the second displaceable member in said second casing part.

5. A coupling arrangement as claimed in any preceding claim comprising a first casing part, a second casing part, means for assembling and disconnecting said casing parts, a first bore region in said first casing part connectable to the first fluid pressure system, a second bore region in said second casing part connectable to the second fluid pressure system, said first and second bore regions being aligned to form a continuous bore with the ends connectable to the first and second fluid pressure systems at opposite ends thereof when the casing parts are assembled, the first displaceable member being located within said first bore region and the second displaceable member being located within said second bore region, said first and second displaceable members being in abutting relationship for mutual displacement when the casing is assembled.

6. A coupling arrangement as claimed in claim 5 in which said first displaceable member comprises a piston slidable in the bore of the first bore region and means are provided for limiting the displacement of the piston away from the bore end connectable with the first fluid pressure system to retain said piston member in said bore region when the casing parts are separated.

7. A coupling arrangement as claimed in claim 5 or yin which said second displaceable member comprises a piston slidable in said second bore region and means are provided for limiting the displacement of said piston away from that end of said bore region connectable with the second fluid pressure system to retain said piston member in said bore region when the casing parts are separated.

8. A coupling arrangement as claimed in claims 6 and 7 in which one piston includes an extension which engages in a recess in the other piston.

9. A coupling arrangement as claimed in claims 1, 2, 3, 4, 5, or 7 in which said first displaceable member comprises a diaphragm. A

10. A coupling arrangement as claimed in claims 1, 2, 3, 4, 5, 6, or 7 in which said second displaceable member comprises a diaphragm.

11. A coupling arrangement as claimed in any preceding claim in combination with first and second fluid pressure systems and in which, upon separation of the coupling, the first displaceable member seals the first pressure fluid system against loss of fluid therefrom and the second displaceable member seals the second fluid pressure system against loss of fluid therefrom.

12. The combination set forth in claim 11 in which the first fluid pressure system comprises the hydraulic brake system of a towing vehicle and the second fluid pressure system comprises the hydraulic braking system for a towed vehicle, and whereby, an increase in hydraulic pressure in the brake system of the towing vehicle to apply brake to that vehicle is transmitted by displacement of the first and second displaceable members to cause an increase in pressure in the hydraulic circuit of the towed vehicle thereby to apply brake to the towed vehicle.

13. A coupling arrangement substantially as hereinbefore described with reference to the accompanying drawings.

14. A vehicle braking arrangement substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.