GB1583341A

GB1583341A - Fluidpressure operated anti-skid braking systems

Info

Publication number: GB1583341A
Application number: GB3119876A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1976-07-27
Filing date: 1976-07-27
Publication date: 1981-01-28
Also published as: FR2359736A1; FR2359736B1; DE2733883A1; CH624058A5; DE2733883C2; IT1081170B

Abstract

The brake system has two separate control valves (1, 2), which are connected to one another and are arranged in series in a pipeline between a pressure medium source and a brake. Each control valve (1, 2) contains a valve (13, 22) responding to the deceleration, for actuating the assigned control valve (1 or 2) independently of the other (2 or 1) or simultaneously with the other control valve (1, 2) as a function of the deceleration of the braked wheel. The rear valve (2) in the direction of flow is circumvented by a bypass arrangement (26), which makes a direct, throttled connection between the front valve (1) and the brake. In operation, after actuation of the brake, the fluid flow to the brake is regulated by the two control valves (1, 2). When the predetermined value for deceleration of the wheel is exceeded, the device with the two valves (13, 22) and the bypass arrangement (26) comes into operation in order to reduce the fluid pressure under conditions such that, whilst maintaining the same wheel adhesion, locking of the wheel is prevented. <IMAGE>

Description

(54) IMPROVEMENTS IN FLUID-PRESSURE OPERATED ANTI-SKID BRAKING SYSTEMS (71) We, GIRLING LIMITED, a British Company of Kings Road, Tyseley, Birmingham 11, 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 improvements in fluid-pressure operated anti-skid braking systems for rail or other vehicles of the kind in which the supply of operating fluid to a wheel brake is controlled by fluid-flow control valve means interposed in the line between the supply and the brake and means are incorporated for operating the valve means to relieve the pressure supplied to the brake when the deceleration of the wheel is excessive and exceeds a predetermined value.Hereinafter the pressure to be relieved under such conditions will be referred to as the "skid pressure".

In known braking systems of the kind set forth for vehicles the valve means comprises a single valve assembly which is operable by a deceleration responsive device to cut-off supply to the brake and subsequently reduce the skid pressure when the predetermined value of deceleration is exceeded. Subsequently the brake is re-applied automatically during the same braking sequence at the same rate at least up to the skid pressure which is undesirable since, for the same conditions of wheel adhesion, such a re-application will again cause the wheel deceleration to be excessive.

According to our invention in a fluid-pressure operated anti-skid braking system of the kind set forth for rail or other vehicles, the control valve means comprise two separate fluidflow control valves which are interconnected and are located in the line in series, and each valve is operable independently of, or simultaneously with, the other valve in accordance with the rate of deceleration of the braked wheel, a by-pass passage by-passing the downstream valve to provide direct restricted communication between the upstream valve and the brake.

Preferably the upstream valve comprise a dump valve and the other downstream valve comprises an on/off valve.

When the brake is applied, initially both valves are open so that full pressure is applied to the brake. When the wheel deceleration becomes excessive both valves close sequentially.

The upstream valve is first closed to isolate the inlet of that valve from the downstream valve and relieve the braking pressure through the downstream valve, which is still open. After a predetermined period of time the downstream valve then closes to isolate the outlet of that valve from the wheel brake. When the wheel deceleration is reduced to a predetermined value the brake is re-applied automatically in two stages in the first of which both valves are open to allow the pressure to rise at a normal rate to an intermediate value less than the full pressure at a changeover point at which the downstream valve closes, whereafter in the second stage the pressure continues to rise, but at a reduced rate due to the provision of the by-pass passage.

A two-stage re-application has the advantage that the brake can be re-applied relatively quickly and the reduced or more gradual rate of re-application operative in the second stage after the changeover point has been reached is less likely to cause excessive deceleration to occur. Should that happen of course the other upstream valve closes to reduce the brake applying pressure, where-after the sequence described above is repeated.

The two valves may be substantially identical in construction but with the upstream valve provided with an exhaust port for relieving the braking pressure when that valve is closed. That valve therefore comprises a double-acting valve with a valve member engageable alternatively with spaced seatings, and the other valve is single-acting having a valve member engageable with a single seating.

Preferably each valve is diaphragmoperated and controlled by a signal pressure acting on one side of the diaphragm, in combination with a solenoid-operated valve for controlling the application of the signal pressure to the diaphragm. In such a construction the pressure acting on the opposite side of the diaphragm of the valve provided with the exhaust port provides the signal pressure for the diaphragm of the other valve.

The by-pass passage may permit a restricted flow in both directions so that release of the brake can be controlled at a desired rate after the single acting downstream valve has closed, Alternatively the by-pass passage may include a pressure-operable valve member engageable with a seating to prevent flow in a direction from the outlet of the single-acting valve to the outlet of the double-acting valve, thereby providing a "hold" characteristic after closure of the downstream single-acting valve.

One embodiment of our invention is illustrated in the accompanying drawings in which: Figure 1 is an end elevation of valve means comprising a control valve-assembly for a fluid-pressure operated anti-skid braking system for a rail or other vehicle; Figure 2 is a plan of the same; Figure 3 is a longitudinal section through the valve assembly; Figure 4 is a fragmentary section on an enlarged scale of by-pass passage means of Figure 3; Figure 5 is a plan of a valve member for incorporation in the by-pass passage means; Figure 6 is a part section on the line 6-6 of Figure 2; Figure 7 is a part section on the line 7-7 of Figure 3; and Figure 8 is an inverted plan of the valve assembly.

The control valve means illustrated in the drawings comprises an assembly of first and second substantially identical valves 1 and 2 which are located in series in a common housing 3.

The valve 1 which comprises a double-beat diaphragm controlled valve of known construction will be described. In the valve 1 a valve member 4 in the housing 3 is engageable alternatively with spaced seatings 6 and 7 to control communication between an inlet port 8 connected to a supply part of a line from a source of operating pressure and an outlet passage 9 which, also comprise the inlet to the valve 2, and between the outlet passage 9 and an exhaust 10 to atmosphere.

Operation of the valve member 4 is controlled by a flexible diaphragm 11 which carries the valve member 4 and which is subjected on its upper face remote from the valve member 4 to a signal pressure through a passage 12 leading from the inlet port 8.

A solenoid-operated valve 13 located in the passage 12 is open to allow fluid-pressure to act on the diaphragm 11 when the solenoid is de-energised, and augment the closing force of a spring 14 which normally urges the valve member 4 into engagement with the seating 7 so that the inlet port 8 is in communication with the outlet passage 9 and the exhaust 10 is closed. In this position the solenoid operated valve 13 closes an exhaust port 15 which is opened when the solenoid is energised by a skid signal from means responsive to deceleration of the braked wheel to reduce the pressure acting on the diaphragm 11, energisation of the solenoid first closing the valve 13.Reduction in the pressure acting on the diaphragm 11 enables the higher pressure acting on its underside to urge the diaphragm and the valve member 4 upwardly into engagement with the seating 6 so that communication between the ports 8 and the passage 9 is cut-off and the pressure into the delivery part of the line is dumped to atmosphere through the exhaust 10.

The valve 2 comprises a single acting diaphragm controlled valve in which a valve member 16 carried by a diaphragm 17 is movable towards and away from a seating 18 to control communication between the passage 9 and an outlet port 19 for connection to an actuator of a wheel brake. The diaphragm 17 is subjected on its upper face through a passage 20 to the chamber 21 below the diaphragm 11.

A solenoid-operated valve 22 located in the passage 20 is open to allow fluid-pressure in the chamber 21 to act on the diaphragm 17 when the solenoid is de-energised and augment the force of a spring 23 which normally urges the valve member 16 away from the seating 18 and into engagement with a stop 24 so that the passage 9 is in communication with the outlet port 19. In this position the solenoid-operated valve again closes an exhaust port 25 which is opened when the solenoid of the valve 22 is also energised by a skid signal from the means responsive to the deceleration of the braked wheel.Reduction in the signal pressure acting on the diaphragm 17 through the passage 20 enables the higher pressure acting on its underside to urge the diaphragm 17 and the valve member 16 upwardly into engagement with the seating 18 to cut-off communication between the passage 9 and the port 19 of that valve, through the seating. The valve 2 therefore acts as an on/off valve.

A restricted by-pass passage means 26 which by-passes the valve 2 is located in the housing 3 between the passage 9 and a chamber 27 located between the seating 18 and the outlet port 19 and in which the valve member 16 is housed. The by-pass means 26 comprises an axial bore 27 parallel with the valves 1 and 2 and extending axially from the passage 9, an orifice 28 in a plate 29 located at the end of the bore 27 remote from the passage 9, a radially apertured resilient biassing disc 30 (Figure 5) carrying a valve member 31 for engagement with a seating 32 in the plate 29 which surrounds the orifice 28, and a passage 33 of reduced diameter which is located downstream of the disc 30 and which communicates with a passage 34 leading into the chamber 27, the passage 34 being of the same diameter as the bore 27. The valve member 31 permits flow from the bore 27 into the chamber 27 but engages with the seating 32 to prevent flow in the opposite direction.

When the brakes are applied the solenoids are de-energised and both valves 1 and 2 are in open positions so that the pressure fluid passes from the supply to the actuators through both valves 1 and 2, and the valve members 4 and 16 are both held away from the seatings 6 and 18 by the forces in the springs 14 and 23 which are augmented by the pressures acting on the diaphragms 11 and 17. Thus the inlet port 8 is in communication with the outlet port 19 through both the seating 18 of the valve 2 and the bypass passage means 26.

Should the deceleration of a braked wheel become excessive and exceed a predetermined value, the first solenoid is energised to close the solenoid valve 13 and exhaust the bias pressure to atmosphere. The valve member 4 then moves into engagement with the seating 6 to isolate the supply and exhaust the outlet port 19 to atmosphere through the valve 2, which is still open, the outlet passage 9, and the port 10, thereby relieving the braking force. After a predetermined period of time, the second solenoid is energised to operate the solenoid valve 22 and exhaust the bias pressure to atmosphere.

The valve member 16 then moves into engagement with the seating 18 to provide a hold characteristic because of the provision of the plate 30 and the valve member 31 which present further exhaustion of pressure through the by-pass passage means 26.

After the rate of wheel deceleration has dropped below the said value, the solenoids are de-energised and the valves 13 and'22 open to restore the bias pressure thereby opening the valves 1 and 2 again to close the exhaust port 10 and re-apply the brake. Initially the supply pressure is provided through both valves 1 and 2 until a changeover point is reached when the pressure in the delivery part of the line is less than the pressure which previously caused said value of deceleration. At the change over point the solenoid in the valve 22 is energised automatically to close the valve 2 itself. Thereafter the pressure applied to the brakes increases by flow through the by-pass passage means 26 only. This pressure increase is at a reduced rate determined by the size of the orifice 28.The pressure increase continues until the pressures of the supply and delivery parts of the line are equal or until deceleration of a braked wheel becomes excessive when the solenoid of the valve 13 will be energised to close the valve 1 and exhaust to atmosphere the pressure applied to the actuators, thereby again relieving the braking pressure.

In a modified construction the biassing disc 30 and the valve member 31 are omitted. This provides a flow through the. by-pass means 26 in the opposite direction to permit pressure fluid at the outlet port 19 to be relieved or "dumped" to atmosphere at a reduced rate determined by the size of the orifice 28, when the valve members 4 and 18 are in their respec tive closed positions in engagement with the seatings 6 and 18.

By subjecting the upper face of the diaphragm 17 to a biassing pressure from the chamber 21 below the diaphragm 11 ensures that the system cannot be completely exhausted in the event of failure, due to an electrical fault, of one of the solenoid-operated valves 13 or 22.

The construction above constitutes a fourphase system providing: 1. A fast pressure rise when both valves 13 and 22 are deenergised; 2. A fast pressure dump when the valve 13 is energised and the valve 22 is de-energised; 3. A slow dump or pressure hold when both valves are de-energised; and 4. A slow rise when the valve 13 is deenergised and the valve 22 is energised.

WHAT WE CLAIM IS: 1. A fluid-pressure operated anti-skid braking system of the kind set forth for rail or other vehicles, in which the control valve means comprise two separate fluid-flow control valve which are interconnected and are located in the line in series, and each valve is operable independently of, or simultaneously with, the other valve in accordance with the rate of deceleration of the braked wheel, a by-pass passage by-passing downstream valve to provide direct restricted communication between the upstream valve and the brake.

2. A braking system as claimed in claim 1, in which the upstream valve comprises a dump valve and the downstream valve comprises an on/off valve.

3. A braking system as claimed in claim 1, or claim 2, in which the by-pass passage permits a restricted flow in both directions.

4. A braking system as claimed in claim 1 or claim 2, in which the by-pass passage includes a pressure-operable valve member engageable with a seating to prevent now in a direction from the outlet of the downstream valve to the outlet of the upstream valve.

5. A braking system as claimed in any preceding claim, in which the two control valves are substantially identical in construction with the upstream valve provided with an exhaust port for relieving the braking pressure when that valve is closed.

6. A braking system as claimed in any preceding claim, in which the upstream valve comprises a double-acting valve with a valve member engageable alternatively with spaced seatings, and the downstream valve comprises a single-acting valve having a valve member engageable with a single seating.

7. A braking system as claimed in any preceding claim, in which each valve is diaphragmoperated and is controlled by a singal pressure acting on one side of the diaphragm, in combination with a solenoid-operated valve for controlling the application of the signal pressure to the diaphragm, the pressure acting on the op posite side of the diaphragm of the upstream valve providing the signal pressure for the dia phragm of the downstream valve.

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

Claims

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

open positions so that the pressure fluid passes from the supply to the actuators through both valves 1 and 2, and the valve members 4 and 16 are both held away from the seatings 6 and 18 by the forces in the springs 14 and 23 which are augmented by the pressures acting on the diaphragms 11 and 17. Thus the inlet port 8 is in communication with the outlet port 19 through both the seating 18 of the valve 2 and the bypass passage means 26.

Should the deceleration of a braked wheel become excessive and exceed a predetermined value, the first solenoid is energised to close the solenoid valve 13 and exhaust the bias pressure to atmosphere. The valve member 4 then moves into engagement with the seating 6 to isolate the supply and exhaust the outlet port 19 to atmosphere through the valve 2, which is still open, the outlet passage 9, and the port 10, thereby relieving the braking force. After a predetermined period of time, the second solenoid is energised to operate the solenoid valve 22 and exhaust the bias pressure to atmosphere.

The valve member 16 then moves into engagement with the seating 18 to provide a hold characteristic because of the provision of the plate 30 and the valve member 31 which present further exhaustion of pressure through the by-pass passage means 26.

After the rate of wheel deceleration has dropped below the said value, the solenoids are de-energised and the valves 13 and'22 open to restore the bias pressure thereby opening the valves 1 and 2 again to close the exhaust port

10 and re-apply the brake. Initially the supply pressure is provided through both valves 1 and 2 until a changeover point is reached when the pressure in the delivery part of the line is less than the pressure which previously caused said value of deceleration. At the change over point the solenoid in the valve 22 is energised automatically to close the valve 2 itself. Thereafter the pressure applied to the brakes increases by flow through the by-pass passage means 26 only. This pressure increase is at a reduced rate determined by the size of the orifice 28.The pressure increase continues until the pressures of the supply and delivery parts of the line are equal or until deceleration of a braked wheel becomes excessive when the solenoid of the valve 13 will be energised to close the valve 1 and exhaust to atmosphere the pressure applied to the actuators, thereby again relieving the braking pressure.

In a modified construction the biassing disc

30 and the valve member 31 are omitted. This provides a flow through the. by-pass means 26 in the opposite direction to permit pressure fluid at the outlet port 19 to be relieved or "dumped" to atmosphere at a reduced rate determined by the size of the orifice 28, when the valve members 4 and 18 are in their respec tive closed positions in engagement with the seatings 6 and 18.

By subjecting the upper face of the diaphragm 17 to a biassing pressure from the chamber 21 below the diaphragm 11 ensures that the system cannot be completely exhausted in the event of failure, due to an electrical fault, of one of the solenoid-operated valves 13 or 22.

The construction above constitutes a fourphase system providing: 1. A fast pressure rise when both valves 13 and 22 are deenergised; 2. A fast pressure dump when the valve 13 is energised and the valve 22 is de-energised; 3. A slow dump or pressure hold when both valves are de-energised; and 4. A slow rise when the valve 13 is deenergised and the valve 22 is energised.

WHAT WE CLAIM IS: 1. A fluid-pressure operated anti-skid braking system of the kind set forth for rail or other vehicles, in which the control valve means comprise two separate fluid-flow control valve which are interconnected and are located in the line in series, and each valve is operable independently of, or simultaneously with, the other valve in accordance with the rate of deceleration of the braked wheel, a by-pass passage by-passing downstream valve to provide direct restricted communication between the upstream valve and the brake.
2. A braking system as claimed in claim 1, in which the upstream valve comprises a dump valve and the downstream valve comprises an on/off valve.
3. A braking system as claimed in claim 1, or claim 2, in which the by-pass passage permits a restricted flow in both directions.
4. A braking system as claimed in claim 1 or claim 2, in which the by-pass passage includes a pressure-operable valve member engageable with a seating to prevent now in a direction from the outlet of the downstream valve to the outlet of the upstream valve.
5. A braking system as claimed in any preceding claim, in which the two control valves are substantially identical in construction with the upstream valve provided with an exhaust port for relieving the braking pressure when that valve is closed.
6. A braking system as claimed in any preceding claim, in which the upstream valve comprises a double-acting valve with a valve member engageable alternatively with spaced seatings, and the downstream valve comprises a single-acting valve having a valve member engageable with a single seating.
7. A braking system as claimed in any preceding claim, in which each valve is diaphragmoperated and is controlled by a singal pressure acting on one side of the diaphragm, in combination with a solenoid-operated valve for controlling the application of the signal pressure to the diaphragm, the pressure acting on the op posite side of the diaphragm of the upstream valve providing the signal pressure for the dia phragm of the downstream valve.
8. A fluid-pressure operated anti-skid brak

ing system for rail or other vehicles, substantially as described with reference to and as illustrated in the accompanying drawings.