NZ217708A - Quick service valve for railway braking system - Google Patents

Description

2 17708 Priority Date(s): .. rr... i H Complete Specification Filed: ft Class: .. .?.T?S/^.4.a f:/k/£3i/3R'Z, p.O. Journal, No: . n.Z. PATENT OKFiCfc 26 SEP 1986 received PATENTS FORM NO: 5 PATENTS ACT 1953 COMPLETE SPECIFICATION "ACCELERATED APPLICATION VALVE" WE, BRAKE AND SIGNAL HOLDINGS PTY LTD a company incorporaed under che laws of Che State of New South Wales, Commonwealth of Australia of 27-29 George Street, Concord West, New South Wales, 2138, Australia, 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 21770 The present invention relates to braking systems such as are used to retard the motion of railway vehicles.

It is well known to use compressed air to effect the operation of a train's braking system. Each vehicle to which such a system is fitted is provided with an accumulator which is connected via a valve to a brake cylinder which is operably connected to a brake. A brake line runs from the locomotive along the length of the train and is connected to each of the valves. The locomotive is provided with a compressor and a control valve so that the flow of air and ultimately the pressure in the brake line can be controlled by the engine driver.

The valves, which are fitted to each car, are known as triple valves and are responsive to the pressure in the brake line. During normal running, the triple valves enable the flow of compressed air from the compressor to each of the accumulators. Upon operating the control valve the brake line is vented causing a reduction of the pressure therein. This reduction causes the triple valves to direct the compressed air stored in their respective accumulators into the respective brake cylinders, thereby to apply the brakes. Upon closing the control valve, the pressure in the brake line is restored and the triple valves direct the flow of compressed air from the brake line back into the accumulators. At the same time, the triple valves vent the brake cylinders, thereby releasing the brakes.

Such a system, whilst being suitable for use in 217708 trains having a small number of vehicles, is less suitable for trains having a large number.

It will be appreciated that in order to operate the brakes of every vehicle of the train, the pressure along the entire length of the brake line must be reduced.

Since the flow of compressed air from the brake line of such systems must be through the control valve, the reduction in pressure along the brake line is by no means instantaneous, and therefore the brakes of the vehicle close to the control valve are applied sooner than those of vehicles further away. This delayed brake actuation causes the later vehicles in the train to impact those in front during braking. This can result in damage to the train and in loss of operator comfort.

Hitherto, the abovementioned problem has been overcome by providing the triple valve with a further valve which is responsive to a reduction in pressure in the brake line relative to a reference pressure. Upon detecting such a reduction in pressure, the further valve is effective to vent the brake line at each carriage thereby to promote more nearly simultaneous operation of the brakes throughout the entire train. These further valves are known as "quick service valves".

The utilization of quick service valves represents a considerable improvement in the braking of trains.

However, such quick service valve must necessarily operate in unison with a triple valve and are formed integral therewith. 2 1770 The reference pressure used by the quick service valves is conveniently supplied by the high pressure in the accumulator. However, fluctuations in the accumulator pressure can affect the successful operation of the quick service valve.

It is an object of the present invention to provide an accelerated application valve which is responsive to a drop in the pressure in a brake line to vent that brake <L line without the need for reference to a separate pressure 10 source.

It will be appreciated that a significant difference between the accelerated application valve of the present invention and the quick service valve of the prior art is that the prior art device compares consecutive measurements of the pressure difference between the reference pressure and the pressure in the brake line. If the second difference is greater than the first difference then the valve is effective to vent the brake line. On the other hand, the device of the present invention 20 compares a first measurement of the pressure in the brake line directly to a second measurement of the pressure in the brake line. If the second measurement is less than i-j. the first, then the device is effective to vent the brake 'line.

The present invention consists in a valve for use in a brake control system, said valve having a single inlet O port adapted to be connected for gas flow communication with a brake line, and an outlet port, said valve being 217708 responsive to a reduction in the pressure in said inlet port to vent said brake line to said outlet port.

A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a railway vehicle braking system including a valve according to the present invention; and, <L- Figure 2 is a cross-sectional side elevation of the 10 valve of figure 1.

Referring firstly to figure 1, the railway vehicle braking system includes a compressor 1 which feeds compressed air to a control valve 2. The control valve 2 can selectively direct air from the compressor 1 to a brake line 4, or vent air from the brake line 4 to an exhaust pipe 3.

Each of the railway vehicles is provided with a brake cylinder 5 and a compressed air accumulator 6. A triple valve 7 is provided, selectively to connect the 20 accumulator 6 with the cylinder 5 for applying the brakes. The triple valve 7 is also connected with the brake line 4.

In normal non-braking operation, the control valve 2 •connects the compressor 1 with brake pipe 4 to increase or maintain the pressure therein. Upon detecting an increasing or constant pressure in the brake pipe 4, the 0 triple valves are responsive to direct a flow of compressed air from the brake pipe 4 to their respective 217708 accumulators 6. Triple valves 7 are simultaneously operative to vent compressed air in brake cylinders 5 to the atmosphere to ensure that the brakes are disengaged.

To engage the brakes, control valve 2 is operated to vent the brake pipe 4 to the atmosphere, thereby to reduce the pressure therein. Each of the triple valves 7 is responsive to such a drop in pressure to isolate the respective accumulators 6 from brake pipe 4 and to direct a flow of compressed air from the accumulators 6 to the brake cylinders 5 thereby to effect the engagement of the brakes.

According to the invention, each of the vehicles is additionally provided with an accelerated application valve 8, each of which is connected for gas flow communication with brake pipe 4.

The accelerated application valves 8 are responsive to a reduction in the pressure in the brake pipe 4 to vent the brake pipe 4 to an outlet port.

Referring to figure 2, the accelerated application valve 8 includes an inlet port 10 which communicates with the brake pipe 4. The inlet port 10 is in turn connected to an exhaust chamber 11 by a duct 12, restricted by a choke 13. Chamber 11 is closed by a valve closure 14 which is held in sealing engagement with a valve seat 15 by the action of a compression spring 16. An exhaust duct 17 is in gas flow communication with the atmosphere and provides a path downstream of valve closure 14 through which gas held in exhaust chamber 11 may pass when valve n .. t r^.,..-> «*.. ,. 217708 closure 14 is unseated. This then permits air to vent from the brake pipe, to atmosphere via the valve 14.

Inlet port 10 is also connected with a chamber 18 by a passage 19. Chamber 18 includes a diaphragm 20 to which is attached a valve closure 21. The valve closure 21 is held in upwardly directed sealing engagement with a valve seat 22 by a spring 23. Valve closure 21 thus closes a passage 24 which leads to a timing chamber 25 via a choke 26 from chamber 18a above diaphragm 20.

Chamber 18 is connected with chamber 27 via a choke 28 and thence to chamber 18a via passage 29.

Timing chamber 25 is closed by a valve closure 30 which forms part of a diaphragm assembly 31. A spring 32 acting on the diaphragm assembly 31 holds the valve closure 30 in engagement with a valve seat 33. The application of sufficient pressure in chamber 25 lifts the diaphragm assembly 31 to open the valve closure 30 and permits gas to flow through a passage 34 and thence to the atmosphere via a choke 35. A valve stem 36 extends from the diaphragm assembly 31 and serves to lift the valve closure 14 upon upward movement of the diaphragm assembly 31.

When a brake application is initiated by the operation of the control valve 2 the pressure in brake pipe 4 drops. This causes a fall in pressure in port 10 and chamber 18. However, choke 28 prevents pressure in chamber 27 from falling at the same rate. The resulting pressure difference across diaphragm 20 causes a downward 2 17708 force to be exerted on the diaphragm which overcomes the restoring force exerted by spring 23 thereby to unseat valve closure 21 from seat 22. This permits gas to flow from chamber 18 into timing chamber 25.

The pressure is thus able to rise in timing chamber 25 until the force exerted upon valve closure 30 is sufficient to overcome the force exerted by spring 32, at which time valve closure 30 lifts from seat 33 to expose the greater area of diaphragm assembly 31 to the pressure held in timing chamber 25. This causes the diaphragm assembly 31 and valve stem 36 to rise rapidly. Valve stem 36 is effective to lift valve closure 14 from seat 15 thereby to allow air in exhaust chamber 11 to exhaust to the atmosphere through passage 17.

Also when valve closure 30 lifts from valve seat 33, compressed air held in timing chamber 25 exhausts to atmosphere through passage 34 and choke 35. Spring 32 is then able to overcome the upward force exerted by the diminishing pressure in timing chamber 25 to reseat valve closure 30 on valve seat 33 against the force of spring 37. Simultaneously, spring 16 effects the resealing of valve closure 14 against seat 15 thereby to close chamber 11.

This cycle repeats continuously as long as compressed gas is able to flow into timing chamber 25 through choke 26. This is the case whenever the pressure at port 10 is reducing and the pressure difference across diaphragm 20 is thereby effective to unseat valve closure 21 from valve seat 22. 21770 It will be appreciated that the above described accelerated application valve releases gas from brake pipe 4 in a series of charges, of which the volume of each is determined by the volume of exhaust chamber 11.

It will also be appreciated that whereas the accelerated application valve of the present invention is effective to sequentially sample the pressure at an inlet port and to respond to a drop in that pressure to allow a quantity of compressed air to escape from a brake pipe to atmosphere, any valve which is responsive to a drop in inlet port pressure to open that valve will fall within the scope of the present invention. 217708

Claims (9)

WHAT WE CLAIM IS:-

1. A valve for use in a brake control system, said valve having a single inlet port adapted to be connected for gas flow communication with a brake line, and an outlet port, said valve being responsive to a reduction in pressure in said inlet port to vent said brake line to said outlet port.

2. A valve according to claim 1 including further valve means responsive to said reduction in inlet port pressure to control said valve so as to allow venting of said brake line to said outlet port.

3. A valve according to claim 2 wherein said further valve means comprises two chambers separated by a pressure responsive member, a first of said chambers being connected to said brake line and the other chamber being connected to said brake line via a restriction and a volume respectively, such that a reduction in pressure in said brake line causes a pressure difference to form between the said chambers resulting in displacement of said member and actuation of said valve means.

4. A valve according to claim 3 wherein said further valve means controls a pulsating device adapted to respectively open and close said valve.

5. An apparatus for operation in a fluid pressure operable vehicle braking system which operates to make brake applications in response to reductions of fluid pressure in a brake pipe, the — apparatus including an accelerated application'^valve having a single input port adapted to be connected for gas -10- 24NARI988 J;l. ✓ flow communication with said brake pipe and an outlet port connected to atmosphere, a pressure difference sensing device responsive to a reduction in pressure in said input port to open a further valve to apply fluid pressure from the brake pipe via at least a first restriction to a pulsating device, the pulsating device comprising a volume receiving fluid pressure from the brake pipe applied to the pulsating device, a pressure responsive member having a first side exposed continuously to atmospheric pressure 10 and a second side having a first area subject to the pressure in said volume and a second area connected via a second restriction to atmosphere, said member being displaceable in response to accumulated pressure in said volume applied to said first area to, on the one hand, open said accelerated application valve, and on the other hand, to connect said areas to permit reduction of pressure of said volume via said second restriction with resulting reclosure of the accelerated application valve and repetitive action during continued reduction of fluid 20 pressure in the brake pipe.

6. An appparatus according to claim 5 wherein a third restriction is provided between the brake pipe and said accelerated application valve.

7. An apparatus according to claim 6 wherein a further volume is provided between the third restriction and the accelerated application valve such that the reduction of brake pipe pressure resultant upon each pulsation is^ ( o rO determined by said further volume. t8 JAN*988 / -11- V- 2 17708

8. A valve as hereinbefore described with reference to Figure 2 of the accompanying drawings.

9. A vehicle braking system as herein before described with reference to the accompanying drawings. BRAKE AND SIGNAL HOLDINGS PTY LTD by their authorised agents P.L. BERRY & ASSOCIATES per: <-• c\ 26SfP/9g£ JH3CElVFr\ - 12 -