GB2546254A

GB2546254A - Vehicle immobiliser system

Info

Publication number: GB2546254A
Application number: GB1600274.3A
Authority: GB
Inventors: Robert Mellings Carl
Original assignee: Haldex Brake Products AB
Current assignee: Haldex Brake Products AB
Priority date: 2016-01-07
Filing date: 2016-01-07
Publication date: 2017-07-19
Also published as: GB201600274D0

Abstract

A vehicle braking system has a control valve 10 connecting a spring brake actuator 58 to pressurised fluid or in a second position to exhaust 10c, the system including an electrically operated lock assembly 28 able to lock the control valve in the second position. The lock assembly can be part of the valve (e.g. figs 1 & 7) with a lock member (28c, fig 1) acting on a piston (26, fig 1), or by pressurising a lock chamber (62, fig 9). A lock valve or exhaust port of the control valve 10 can be connected to a service brake modulator 70, and there be a resilient biasing element to urge a valve member into a closed position by translational movement. The vehicle can be an air braked trailer and the system for immobilising.

Description

Title: Vehicle Immobiliser System Description of Invention

The present invention relates to a vehicle immobiliser system, in particular for a trailer vehicle.

Trailer vehicle are typically provided with a service braking system by means of which a braking force is applied to the trailer wheels as a result of the supply of pressurised fluid (generally compressed air) to a plurality of brake actuators, and a parking brake or spring brake system. The spring brake actuators are configured such that the supply of pressurised fluid (again, typically compressed air) maintains the spring brake in a release position, in which no braking force is applied to the trailer wheels, whilst release of pressurised fluid from the spring brake actuators causes these to move, under the action of a spring, to apply a braking force.

It is known to provide trailers with a security system for immobilising the trailer to prevent attempted theft of the trailer. Examples of such security systems are disclosed in W02009/046512, W02005/115810, US2005/0062344 and WO 01/94130. In the systems disclosed in US 2005/0062344 and WO 01/94130, the trailer is provided with a locking device which acts to prevent unauthorised movement or theft of the trailer by venting the compressed air that is used to release the parking brake. The locking device has a controller unit, a control valve and a power source mounted inside a housing. A control mechanism, such as a key pad or key lock system is located outside of the housing, preferably on a trailer wall. The inlet of the control valve connects to the brake line that delivers compressed air to the trailer’s parking brakes. In the locked condition, the control valve is set so compressed air vents out of the control valve’s outlet, preventing the release of the brakes. When the proper lock key code, key or other signal is received, the control valve closes the outlet to stop the venting and allow the brakes to be released.

The present invention relates to an alternative configuration of the vehicle immobiliser system.

According to a first aspect of the invention we provide a vehicle braking system comprising a spring brake control valve having an inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is adapted to be connected to a spring brake actuator, an exhaust port which is connected to a low pressure region, the spring brake control valve being movable between a first position in which the inlet of the spring brake control valve is connected to its outlet whilst the exhaust port is closed, and a second position in which the outlet of the spring brake control valve is connected to the exhaust port whilst the inlet is closed, characterised in the system further includes an electrically operated lock assembly which is operable to lock the spring brake control valve in its second position.

The spring brake control valve may comprise a valve member which is movable between a first position in which the inlet of the spring brake control valve is connected to its outlet whilst the valve member blocks the exhaust port, and a second position in which the outlet of the spring brake control valve is connected to the exhaust port whilst the valve member blocks the inlet, and a lock chamber which is pressurised in order to lock the valve member in its second position.

The lock chamber may be connected to a source of pressurised fluid via an electrically operable lock valve. Preferably the lock valve has an inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is connected to the lock chamber, and valve member which is movable between an open position in which the lock valve inlet is connected to the lock valve outlet, and a closed position in which the valve member closes the outlet.

The inlet of the lock valve maybe connected to a delivery outlet of a service braking modulator.

The lock valve may also include an electrically operated actuator which is configured to move the valve member to the open position when electrical power is supplied to the electrically operated actuator. The electrically operated actuator may comprise a solenoid.

The lock valve may also include a resilient biasing element which urges the valve member into the closed position. A lock piston may be mounted in the lock chamber, the lock piston being movable under the action of fluid pressure in the lock chamber to engage with the valve member and to urge the valve member into its second position.

Preferably the lock piston divides the lock chamber into two portions, the first portion being connected to a source of pressurised fluid and the second position venting to a low pressure region.

The lock piston is advantageously movable relative to the valve member.

The valve member may mounted in a main chamber formed in a housing, and the lock chamber is a portion of the main chamber.

The outlet of the lock valve may be connected to the lock chamber via a nonreturn check valve which is movable between a first position in which the flow of fluid from the lock valve to the lock chamber is substantially prevented whilst the lock chamber vents to a low pressure region, and a second position in which the lock valve is connected to the lock chamber whilst flow of fluid to the low pressure region is substantially prevented. The non-return check valve may include a resilient biasing means which biases it to its first position.

The spring brake control valve may have a control port, supply of pressurised fluid to the control port causing the valve member to move to its first position.

The spring brake control valve may have a resilient biasing element which acts on the valve member to urge the valve member into the second position. In this case, the spring brake control valve may have a control port and be configured such that when the fluid pressure at the control port exceeds a predetermined level, the valve member moves against the biasing force of the resilient biasing element from the second position to the first position.

Movement of the valve member between its first position and second position may comprise translational movement.

The vehicle braking system may further comprise a source of pressurised fluid which is connected to the inlet of the spring brake control valve. In this case, the source of pressurised fluid may comprise a pressurised fluid reservoir. Additionally or alternatively, the source of pressurised fluid may comprise a connector which is adapted to be connected to an external source of pressurised fluid. The vehicle may comprise a trailer, and the source of pressurised fluid may comprise a connector which is adapted, in use, to be connected to a pressurised fluid supply mounted on a tractor. In this case, where the spring brake control valve comprises a control port, the control port may also be connected to the connector.

The vehicle braking system may further comprise a spring brake actuator which has a spring brake chamber and which is configured to apply a braking force to a wheel of the vehicle the pressure in the spring brake chamber falls below a predetermined level, and to release the / not apply a braking force to the wheel of the vehicle when the pressure in the spring brake chamber is at or above the predetermined level, the outlet of the spring brake control valve being connected to the spring brake chamber. In this case, the spring brake actuator may further comprise a resilient biasing element by means of which the braking force is applied when the pressure in the spring brake chamber is below the predetermined level.

The exhaust port of the spring brake control valve may be connected to the low pressure region via a modulator valve assembly.

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, of which, FIGURE 1 shows a schematic illustration of a spring brake control valve suitable for use in a vehicle braking system according to a first aspect of the invention, the valve member of the spring brake control valve being in its first position with the lock assembly deactivated, FIGURE 2 shows a schematic illustration of the spring brake control valve shown in Figure 1, the valve member being in its second position with the lock assembly deactivated, FIGURE 3 shows a schematic illustration of the spring brake control valve shown in Figure 1 with the lock assembly in the process of being activated, FIGURE 4 shows a schematic illustration of the spring brake control valve shown in Figure 1 with the lock assembly activated to lock the valve member in its second position, FIGURE 5 shows a transverse cross-section through an example of spring brake control valve suitable for use in a braking system according to the first aspect of the invention, FIGURE 6 shows a schematic illustration of an example of a braking system according to the invention, FIGURE 7 shows a schematic illustration of an alternative embodiment of spring brake control valve suitable for use in a vehicle braking system according to a first aspect of the invention, the valve member of the spring brake control valve being in its first position with the lock assembly deactivated, FIGURE 8 shows a schematic illustration of the spring brake control valve shown in Figure 7, the valve member being in its second position with the lock assembly deactivated, FIGURE 9 shows a schematic illustration of the spring brake control valve shown in Figure 7 with the lock assembly in the process of being activated, and FIGURE 10 shows a schematic illustration of the spring brake control valve shown in Figure 7 with the lock assembly activated to lock the valve member in its second position.

Referring now to Figures 1 to 4, there is shown a spring brake control valve 10 comprises a housing 12 in which is provided an inlet 10a, an outlet 10b and an exhaust port 10c which vents to a low pressure region. The spring brake control valve 10 also comprises a movable valve member 14 which is movable between a first position in which the inlet 10a is connected to the outlet 10b whilst the valve member blocks the exhaust port 10c, and a second position in which the outlet 10b is connected to the exhaust port 10c whilst the valve member 14 blocks the inlet 10a. In this example, movement of the valve member 14 between its first position and second position comprises translational movement.

The spring brake control valve 10 also has a control port 10d, supply of pressurised fluid to the control port 10d causing the valve member 14 to move to its first position, and a resilient biasing element 16 which acts on the valve member 14 to urge the valve member 14 into the second position. In this example, the resilient biasing element 16 is a helical compression spring which extends between the valve member 14 and the housing 12. The spring brake control valve 10 is configured such that when the fluid pressure at the control port 10d exceeds a pre-determined level, the valve member 14 moves against the biasing force of the spring 16 from the second position to the first position.

Also illustrated is an electrically operated lock assembly which is operable to lock the spring brake control valve 10 in its second position. This includes a lock chamber 24 which may be pressurised in order to lock the valve member 14 in its second position.

In this embodiment of the invention, the lock assembly includes a lock piston 26 which is mounted in the lock chamber 24, the lock piston 26 being movable under the action of fluid pressure in the lock chamber 24 to engage with the valve member 14 and to urge the valve member 14 into its second position. In this embodiment, the lock piston 26 is movable relative to the valve member 14.

The lock piston 26 divides the lock chamber 24 into two portions, the first portion 24a being connected to a source of pressurised fluid and the second position 24b venting to a low pressure region. The first portion 24a of the lock chamber 24 is connected to a source of pressurised fluid via an electrically operable lock valve 28. The lock valve 28 has an inlet 28a which is adapted to be connected to the source of pressurised fluid, an outlet 28b which is connected to the lock chamber 24, and valve member 28c which is movable between an open position in which the lock valve inlet 28a is connected to the lock valve outlet 28b, and a closed position in which the valve member 28c closes the outlet 28b. In this exampler, the inlet 28a of the lock valve 28 is connected to the delivery outlet 70b of a modulator 70 of the trailer’s service braking system. The modulator will provide pressurised fluid to the inlet 28a of the lock valve 28 when the service brakes are applied, and an exhaust path (through the modulator exhaust) when the service brakes are released.

In this embodiment, the lock valve 28 also includes an electrically operated actuator 30, such as a solenoid, which is configured to move the valve member 28c to the open position when electrical power is supplied to the electrically operated actuator 30. The lock valve 28 also includes a resilient biasing element 32 which urges the valve member 28c into the closed position.

One embodiment of locking assembly and valve suitable for use as the spring brake control valve 10 is illustrated in Figure 5. In this embodiment, the housing 12 is generally tubular, having a longitudinal axis A, and a generally circular transverse cross-section. The housing 12 therefore comprises a housing wall which encloses a generally cylindrical space, and the inlet 10a and outlet 10b of the spring brake control valve 10 comprise apertures in this housing wall. The exhaust port 10c is provided at a first end 12a of the housing 12, whilst the control port 10d is provide at a second end 12b of the housing 12, opposite to the first end 12a. The outlet 10b is closest to the first end 12a of the housing 12, whilst the inlet 10a is closer to the second end 12b.

The valve member 14 is a generally cylindrical piston which lies on and moves along the longitudinal axis A of the housing 12. A plurality of seal assemblies are provided between the valve member 14 and the housing 12. A first seal assembly 18a is provided between the first end 12a of the housing, a second seal assembly 18b is provided between the inlet 10a and the outlet 10b, a third seal assembly 18c is provided between the second end 12b of the housing 12 and the outlet 10b, and a fourth seal assembly 18d is provided at the second 12b of the housing 12.

In this example, the first, second and third seal assemblies comprises an annular seal element such as an O-ring which is mounted in a seal element support which extends radially inwardly from the interior of the housing wall so that the seal element can enter into sealing engagement with a corresponding seal surface on the valve member 14 (depending on the position of the valve member 14) whilst allowing translational movement of the valve member 14 along the longitudinal axis A of the housing 12. In this example, the fourth seal assembly 18d comprises an annular seal such as an O-ring mounted in a groove around the second end 14b of the valve member 14 to engage with the interior of the housing wall at the second end 12b of the housing 12.

In this example, the second end 14b of the valve member 14 has a significantly larger outer diameter than the remainder of the valve member 14. The fourth seal assembly 18d therefore forms a sealed control chamber 20 at the second end 12b of the housing into which the control port 10d extends.

The valve member 14 also has two reduced outer diameter portions, 14c, 14d, the first reduced outer diameter portion 14c being at the first end 14a of the valve member 14, whist the second reduced outer diameter portion 14d is spaced from the first reduced outer diameter portion 14c by a first one of the seal surfaces.

The resilient biasing element in this example comprises a helical compression spring 16 which extends from a shoulder provided around the valve member 14 adjacent to the second end 14b thereof, and a spring support 22 which extends radially inwardly from the housing 12 between the second end 12a thereof and the third seal assembly 18c.

When the valve member 14 is in its first position, it is pushed by the spring 16 towards the second end 12b of the housing 12. The seal element of the first seal assembly 18a engages with the first seal surface, whilst the second seal surface, which extends from the second reduced diameter portion 14d to the larger outer diameter portion at the second end 14b of the valve member 14, engages with the seal element of the third seal assembly 18d. The second reduced diameter portion 14d then lies adjacent to the seal element of the second seal assembly 18b, and, as a result, the seal element of the second seal assembly 18b is spaced from the valve member 14. The first and third seal assemblies therefore enclose an annular chamber within the housing 12 into which both the inlet 10a and outlet 10b extend, and flow of fluid from the inlet 10a to the outlet 10b can occur, whilst the first seal assembly 18a prevents flow of fluid from either the inlet 10a or outlet 10b to the exhaust port 10c.

If pressurised fluid is directed to the control port 10d such that the pressure in the control chamber 20 builds up until it is sufficiently high to move the valve member 14 against the biasing force of the spring 16, the valve member 14 along the longitudinal axis A of the housing 12 towards the first end 12a of the housing to its second position. When the valve member 14 is in its second position (illustrated in Figure 5), the seal element of the second seal assembly 18b engages with first seal surface, and the seal element of the third seal assembly 18c engages with the second seal surface. The second and third seal assemblies 18b, 18c therefore form a closed annular chamber within the housing 12 into which the inlet 10a extends. In other words, the inlet 10a is effectively closed. The first reduced diameter portion 14c is adjacent to the first seal assembly 18a and, as a result it is the seal element of the first seal assembly 18a which is spaced from the valve member 14. Consequently, fluid can flow from the outlet 10b past the seal element of the first seal assembly 18a to the exhaust port 10c.

In this embodiment, the lock chamber 24 is formed by the housing 12 at the second end 12b thereof, and is cylindrical, having a cylinder axis which is parallel to (an in this example co-axial with) the longitudinal axis A of the housing 12. The lock chamber 24 has a smaller diameter than the housing 12, however, and the exhaust port 10c extends generally parallel to the longitudinal axis of the housing 12 between the housing wall and the lock chamber 24. The lock piston 26 comprises a piston disc 26a which has an annular seal element such as an O-ring mounted in a groove around its circumference, and a push rod 26b which extends from the centre of the piston disc 26a generally perpendicular thereto.

The piston 26 is mounted in the lock chamber 24 so that the push rod 26b lies along the longitudinal axis A of the housing 12, and the seal element engages with the portions of the housing 12 forming the curved wall of the lock chamber 24. The lock piston 26 therefore divides the lock chamber 24 into a first portion 24a which is located at the first end 12a of the housing 12, and a second portion 24b which is closer to the valve member 14. The push rod 26b extends into the second portion 24b of the lock chamber 24 through an aperture provided in the housing forming one of the two generally circular ends of the lock chamber 24, towards the valve member 14. When the valve member 14 is in its second position, the free end of the push rod 26b engages with the first end 14a of the valve member 14. In this example, the piston 26 is therefore completely separate from the valve member 14. A resilient biasing element (in this case a helical compression spring 24c) is, in this example, provided in the second portion 24b of the lock chamber 24, and extends between the housing 12 and the piston disc 26a. The spring 24c thus acts to push the lock piston 26 away from the valve member 14, i.e. downwardly towards the second end 12b of the housing 12. A conduit or pipe 34 is provided connecting first portion 24a of the lock chamber 24 to the outlet 28b of the lock valve 28.

The spring brake control valve 10 and locking assembly may be integrated into a vehicle braking system 36. An example of such a vehicle braking system 36 is disclosed in WO 2012/175927 and GB2492124, and is illustrated schematically in Figure 6. This is a braking system for a trailer vehicle and comprises a source of pressurised fluid 38 which is connected to the inlet 10a of the spring brake control valve 10. In this case, the source of pressurised fluid comprises a pressurised fluid reservoir 40 and a connector 42 which is adapted to be connected to pressurised fluid supply from a tractor or truck pulling the trailer, via corresponding connector mounted on the tractor.

The inlet 10a of the spring brake control valve 10 is connected to the connector 42 via a supply line 44 which extends from the connector 42 to a first inlet of a shunt valve 46, the outlet of the shunt valve 46 being connected to a junction between an emergency apply line 48 and a park line 50. The emergency apply line 48 extends to the inlet 10a of the spring brake control valve 10, whilst the park line 50 extends to the control port 10d of the spring brake control valve 10 via a manually operable park valve 52 and a electrically operable emergency braking override valve 54. A trailer reservoir supply line 56 extends from the emergency apply line 48 to a pressurised fluid reservoir 40 mounted on the trailer. An outlet from the trailer reservoir 40 is connected to a second inlet of the shunt valve 46.

The vehicle braking system 36 further comprises a conventional spring brake actuator 58 which has a spring brake chamber 58a and which is configured to apply a braking force to a wheel of the vehicle when the pressure in the spring brake chamber 58a falls below a predetermined level, and to release the / not apply a braking force to the wheel of the vehicle when the pressure in the spring brake chamber 58a is at or above the predetermined level. The outlet 10b of the spring brake control valve 10 is connected to the spring brake chamber 58a via a spring brake line 60. The brake actuator 58 further comprises a resilient biasing element by means of which the braking force is applied when the pressure in the spring brake chamber 58a is below the predetermined level. Such spring brake actuators are well known to those skilled in the art.

The brake actuator 58 also has a service brake chamber 58b which is connected to the delivery outlet 70b of a conventional EBS control valve assembly 70. The brake actuator 58 is configured such that the supply of pressurised fluid to the service brake chamber causes a braking force to be applied to the wheels of the vehicle

The EBS control valve assembly 70 typically comprises at least a modulator which has a control port 70a which is connected to a control line 72 for receipt of a fluid pressure braking demand signal, a supply port (not shown for clarity) which is connected to a source of pressurised fluid, the delivery port 70b which is connected to the service brake chamber 58b, and an exhaust port (not shown) which vents to a low pressure region. The delivery port 70b is also connected to the inlet 28a of the lock valve 28, as mentioned above.

The modulator 70 is operable to move between a build configuration in which the supply port is connected to the delivery port 70b whilst the exhaust port is closed, a hold configuration in which the exhaust port and the supply ports are closed and an exhaust configuration in which the delivery port 70b is connected to the exhaust port whilst the supply port is closed. Various configurations of modulator are well known to those skilled in the art. The EBS control valve assembly 70 is operable to provide anti-lock braking control.

The control line 72 is adapted to be coupled to a braking control line on a tractor to which the trailer is coupled, and carries a fluid pressure braking demand signal generated when a driver of the vehicle operates a brake pedal or the like to indicate a need for braking. The control line 72 is connected to a first inlet 74a of a brake apply valve 74, an outlet 74b of the brake apply valve 74 being connected the control inlet of the modulator 72 via a service brake line 76. A second inlet 74c of the brake apply valve 74 is connected to the trailer reservoir supply line 56.

The brake apply valve 74 is movable between a first position (illustrated in Figure 6) in which the first inlet 74a is connected to the outlet 74b, whilst the second inlet 74c is closed, and a second position in which the first inlet 74a is closed and the second inlet 74c is connected to the outlet 74b. The brake apply valve 74 is electrically operable, in this example, by means of a solenoid. Mechanical biasing means (in this example a spring) is provided to urge the brake apply valve 74 into the first position. Movement of the brake apply valve 74 from the first position to the second position is achieved by the supply of an electrical current to the solenoid 74d.

Full details of all the parts of this braking system 36, and its operation are described fully in WO2012/175927 and GB2492124, the entire contents of which are incorporated by reference herein.

Use of the inventive spring brake control valve 10 is not restricted to this particular configuration of trailer braking system, and could be used in any braking system which includes a 3/2 way valve that acts to deliver pressurised fluid to the spring brakes or to vent them to atmosphere. For example, the inventive spring brake control valve 10 could equally be used as the emergency apply valve in the trailer braking systems disclosed in our copending applications GB1511974.6 and GB1517354.5.

The spring brake control 10 according to invention operates as follows. Under normal driving conditions, the spring brakes are released so the spring brake control valve 10 is in the first configuration as illustrated in Figure 1. Pressurised fluid is supplied to the control port 10d of the spring brake control valve 10, and the resulting pressure in the control chamber 20 moves the valve member 14 downwardly in the housing 12 to its first position. The inlet 10a of the spring brake control valve 10 is thus connected to its outlet 10b, and so pressurised fluid from the source of pressurised fluid 38 is supplied to the spring brake chamber 58a of the brake actuator 58 to hold the spring brakes off. There is no supply of electrical power to the lock valve 28, and so the spring 30 holds the valve member 28c of the lock valve 28 in its closed position in which the outlet 28b is closed.

When the vehicle is parked, the spring brakes can be applied by the release of pressurised fluid from the control port 10d of the spring brake control valve 10. In the braking system shown in Figure 6, this can be achieved by manual movement of the park valve 52. It could alternatively be achieved by disconnecting the trailer from the tractor so that the connector 42 is disconnected from the external source of pressurised fluid and the supply line 44 thus exhausted to atmosphere. In the absence of pressurised fluid at the control port 10d of the spring brake control valve 10, the spring 16 pushes the valve member 14 upwardly into its second position, as illustrated in Figure 2. As a result, the inlet 10a is closed, and the outlet 10b is connected to the exhaust port 10c. The spring brake chamber 58a is thus vented to atmosphere via the exhaust port 10c, and the spring brake applied. Again, there is no supply of electrical power to the lock valve 28, and so the spring 30 holds the valve member 28c of the lock valve 28 in its closed position in which the outlet 28b is closed.

The spring brake may then be locked in its applied position by the supply of pressurised fluid to the first portion 24a of the lock chamber 24 via the lock valve 28. The inlet 28a of the lock valve 28 is, as mentioned above, connected to the delivery outlet 70b of the modulator 70, and so to provide the lock valve 28 with pressurised fluid, it is necessary to move the modulator 70 to its build position, in which the delivery outlet 70b is connected to its supply inlet. If the trailer is still connected to a tractor, this can be achieved by service braking, i.e. operation of the brake pedal to send a fluid pressure braking demand signal along the control line 72 to the control inlet 70a of the modulator 70. Alternatively, or if the trailer has been disconnected from a tractor, this can be achieved the the supply of electrical power to the solenoid 74d of the brake apply valve 72. This moves the brake apply valve 74 to its second position, whereby the control inlet 70a of the modulator 70 is connected to the reservoir 40.

The locking process is then completed by the supply of electrical power to the actuator of the lock valve 28. This moves the valve member 28c of the lock valve 28 to its open position in which its inlet 28a is connected to its outlet 28b so that pressurised fluid from the delivery outlet 70b of the modulator 70flows along the pipe 34 to the first portion 24a of the lock chamber 24. This pushes the lock piston 26 upwards so that its push rod 26b engages with the first end 14a of the valve member 14. This is illustrated in Figure 3.

To complete the locking process, the lock valve 28 is then deenergised so that it returns to its closed position. This may be achieved by disconnecting the electrical power supply to the entire vehicle or braking system. The biasing force of the spring 30 returns the valve member 28c to close the outlet 28b, thus retaining the pressure in the first portion 24a of the lock chamber 24, as illustrated in Figure 4. Service braking, or the supply of electrical power to the brake apply valve 74, can then cease, so the modulator 70 returns to its exhaust position. The fluid pressure in the first portion 24a of the lock chamber 24 prevents the piston 26 from moving, and therefore the piston 26 prevents the valve member 14 from moving downwardly to its first position. This cannot be overcome by the supply of pressurised fluid to the control port 10d, at least at the pressures normally applied to the control port 10d to release the spring brake. Consequently, the valve member 14 is locked in a position in which the spring brake chamber 58a is vented to atmosphere and therefore the spring brakes applied.

The locking of the brakes could be initiated in response to an input from the driver of the vehicle, for example by typing a pin into a keypad mounted on the trailer or in the cab of the tractor, by wireless transmission of a locking signal from a mobile telecommunications device such as a mobile phone, or by carrying out a specific locking sequence using the ignition key and service brake pedal.

Locking of the spring brakes may assist in preventing the theft or unauthorised movement of a parked trailer, as the spring brakes can no longer be released simply by connecting the connector 42 to a supply of pressurised fluid.

To unlock the brakes, the connector 42 must be connected to a supply of pressurised fluid, and the braking system 36 connected to a source of electrical power. In response to the input of an unlock signal from a user, for example, via the entry of a pin into a key, the generation of an unlock signal from a mobile telecommunications device such as a mobile phone, or the carrying out of a specific unlocking sequence using the ignition and service brake pedal, the actuator of the lock valve 28 is energised, and so the lock valve 28 moves to its open position to vent the first portion 24a of the lock chamber 24 at the exhaust port of the modulator via the lock valve 28The lock piston 26 can then move downwardly under the action of the spring 24c. This releases the valve member 14 so that, on the supply of pressurised fluid to the control port 10d, it is free to move downwardly in the housing 12 to its second position, whereby the inlet 10a is connected to the outlet 10b, and the spring brake chamber 58a pressurised.

Whilst in the embodiment of the invention described above, the lock chamber 24 is provided in a separate housing portion to the portion of the housing which encloses the valve member 14, this need not be the case. An alternative embodiment of spring brake control valve 10’ is illustrated in Figures 7-10.

This embodiment of spring brake control valve 10’ is exactly the same as the embodiment 10 described above and shown in Figures 1 - 5, with the exception of the following features. No separate lock piston is provided. The lock chamber 62 is the space around the valve member 14’ between the fourth seal assembly 18d’ at the second end Mb’ of the valve member 14’, and the third seal assembly 18c’ in which the spring 16’ and spring support 22’ is located. The conduit 34’ from the outlet 28b’ of the lock valve 28’ extends to the lock chamber 24’ via a non-return check valve 64. The check valve 64 has a first port 64a, a second port 64b, an exhaust port 64c, a valve member 64d and a spring 64e. The first port 64a is connected to the outlet 28b’ of the lock valve 28’ via a first portion 34a of the conduit 34’, the second port 64b is connected to the lock chamber 62 via a second portion 34b of the conduit 34’, and the exhaust port 64c is vented to atmosphere. The valve member 64d is movable between a first position in which it closes the first port 64a whilst the second port 64b is connected to the exhaust port 64c, and a second position in which it closes the exhaust port 64c whilst the first port 64a is connected to the second port 64b. The spring 64e biases the valve member 64c to its first position.

This embodiment of spring brake control valve 10’ is operated in exactly the same way as the first embodiment 10. Under normal driving conditions, the spring brakes are released so the spring brake control valve 10’ is in the first configuration as illustrated in Figure 7. Pressurised fluid is supplied to the control port 10d’ of the spring brake control valve 10’, and the resulting pressure in the control chamber 20’ moves the valve member 14’ downwardly in the housing 12’ to its first position. The inlet 10a’ of the spring brake control valve 10’ is thus connected to its outlet 10b’, and so pressurised fluid from the source of pressurised fluid 38 is supplied to the spring brake chamber 58a of the brake actuator 58 to hold the spring brakes off. There is no supply of electrical power to the lock valve 28’, and so the spring 30’ holds the valve member 28c’ of the lock valve 28’ in its closed position in which the outlet 28b’ is closed. The check valve 64 is maintained in its first position by the spring 64d, so the lock chamber 62 is vented to atmosphere.

When the vehicle is parked, the spring brakes can be applied by the release of pressurised fluid from the control port 10d’ of the spring brake control valve 10’. Again, in the braking system shown in Figure 6, this can be achieved by manual movement of the park valve 52. It could alternatively be achieved by disconnecting the trailer from the tractor so that the connector 42 is disconnected from the external source of pressurised fluid and the supply line 44 thus exhausted to atmosphere. In the absence of pressurised fluid at the control port 10d’ of the spring brake control valve 10’, the spring 16’ pushes the valve member 14’ upwardly into its second position, as illustrated in Figure 8. As a result, the inlet 10a’ is closed, and the outlet 10b’ is connected to the exhaust port 10c’. The spring brake chamber 58a is thus vented to atmosphere via the exhaust port 10c’, and the spring brake applied. Again, there is no supply of electrical power to the lock valve 28’, and so the spring 30’ holds the valve member 28c’ of the lock valve 28’ in its closed position in which the outlet 28b’ is closed, and he check valve 64 is maintained in its first position by the spring 64d, so the lock chamber 62 is vented to atmosphere.

The spring brake may then be locked in its applied position by the supply of pressurised fluid to the lock chamber 62 via the lock valve 28’. The inlet 28a’ of the lock valve 28’ is, as mentioned above, connected to the delivery outlet 70b of the modulator 70, and so to provide the lock chamber 62 with pressurised fluid, it is necessary to move the modulator 70 to its build position, in which the delivery outlet 70b is connected to its supply inlet. If the trailer is still connected to a tractor, this can be achieved by service braking, i.e. operation of the brake pedal to send a fluid pressure braking demand signal along the control line 72 to the control inlet 70a of the modulator 70. Alternatively, or if the trailer has been disconnected from a tractor, this can be achieved the the supply of electrical power to the solenoid 74d of the brake apply valve 72. This moves the brake apply valve 74 to its second position, whereby the control inlet 70a of the modulator 70 is connected to the reservoir 40.

The locking process is then completed by the supply of electrical power to the actuator of the lock valve 28’. This moves the valve member 28c’ of the lock valve 28’ to its open position in which its inlet 28a is connected to its outlet 28b so that pressurised fluid from the delivery outlet 70b of the modulator 70 flows along the conduit 34a to the first port 64a of the check valve 64. The fluid pressure at the first port 64a of the check valve 64 pushes its valve member 64d against the biasing force of spring 64e and moves the valve member 64 to its second position. The exhaust port 64c of the check valve 64 is therefore closed, and the fluid from the lock valve 28’ can pass into the lock chamber 62 via the second port 64c of the check valve 64 and the second portion of the conduit 34b. The resulting fluid pressure in the lock chamber 62 pushes the valve member 14’ upwardly to its second position. This is illustrated in Figure 9.

To complete the locking process, the lock valve 28’ is then deenergised so that it returns to its closed position. This may be achieved by disconnecting the electrical power supply to the entire vehicle or braking system. The biasing force of the spring 30’ returns the valve member 28c’ to close the outlet 28b’, but the fluid pressure in the check valve 64 maintains it in its second position, thus retaining the pressure in the lock chamber 62, as illustrated in Figure 10. Service braking, or the supply of electrical power to the brake apply valve 74, can then cease, so the modulator 70 returns to its exhaust position. The fluid pressure in the lock chamber 62 prevents the valve member 14’ from moving downwardly to its first position. This cannot be overcome by the supply of pressurised fluid to the control port 10d’, at least at the pressures normally applied to the control port 10d’ to release the spring brake. Consequently, the valve member 14’ is locked in a position in which the spring brake chamber 58a is vented to atmosphere and therefore the spring brakes applied.

To unlock the brakes, the connector 42 must be connected to a supply of pressurised fluid, and the braking system 36 connected to a source of electrical power. In response to the input of an unlock signal from a user, for example, via the entry of a pin into a key, the generation of an unlock signal from a mobile telecommunications device such as a mobile phone, or the carrying out of a specific unlocking sequence using the ignition and service brake pedal, the actuator of the lock valve 28’ is energised, and so the lock valve 28’ moves to its open position. The resulting loss of pressure at the inlet 64a of the non-return check valve 64 causes the valve member 64d to move under the action of spring 64e to its first position, and thus to vent the lock chamber 62 at the exhaust port of the modulator 70 via the lock valve 28’. The valve member 14 is therefore released, and, on the supply of pressurised fluid to the control port 10d, is free to move downwardly in the housing 12 to its second position, whereby the inlet 10a is connected to the outlet 10b, and the spring brake chamber 58a pressurised.

It should be appreciated that, whilst in the examples discussed above, the inlet 28a, 28a’ of the lock valve 28, 28’ is connected to the delivery port 70b of the modulator 70, this need not be the case. The inlet 28a, 28a’ of the lock valve 28, 28’ could, alternatively be connected directly to a supply of pressurised fluid, such as the reservoir 40. In this case, it would be necessary to provide a separate exhaust valve for venting the lock chamber 24a, 62 when unlocking the spring brake.

Moreover, in the examples discussed above, the exhaust port 10c of the spring brake control valve 10 is connected directly to the low pressure region (e.g. the atmosphere). This need not be the case, however, and the exhaust port 10c could be connected to a low pressure region via another valve assembly, provided that valve assembly operates to connect the exhaust port 10c to the low pressure region when application of the spring brake is required. For example, the exhaust port 10c could be connected to the delivery outlet 70b of the modulator 70 in the service brake system. As discussed above, the modulator 70 is configured to connect the delivery outlet 70b to a low pressure region when in its exhaust position (when no service braking is required). By virtue of connecting the exhaust port 10c of the spring brake control valve 10 to the delivery outlet 70b of the modulator 70, the spring brakes can only be applied when there is no service braking, and so there is no requirement for a separate anti-compounding valve to achieve this.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A vehicle braking system comprising a spring brake control valve having an inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is adapted to be connected to a spring brake actuator, an exhaust port which is connected to a low pressure region, the spring brake control valve being movable between a first position in which the inlet of the spring brake control valve is connected to its outlet whilst the exhaust port is closed, and a second position in which the outlet of the spring brake control valve is connected to the exhaust port whilst the inlet is closed, characterised in that the system further includes an electrically operated lock assembly which is operable to lock the spring brake control valve in its second position.

2. A vehicle braking system according to claim 1 wherein the spring brake control valve comprise a valve member which is movable between a first position in which the inlet of the spring brake control valve is connected to its outlet whilst the valve member blocks the exhaust port, and a second position in which the outlet of the spring brake control valve is connected to the exhaust port whilst the valve member blocks the inlet, and a lock chamber which is pressurised in order to lock the valve member in its second position.

3. A vehicle braking system according to claim 2 wherein the lock chamber is connected to a source of pressurised fluid via an electrically operable lock valve.

4. A vehicle braking system according to claim 3 wherein the lock valve has an inlet which is adapted to be connected to a source of pressurised fluid, an outlet which is connected to the lock chamber, and valve member which is movable between an open position in which the lock valve inlet is connected to the lock valve outlet, and a closed position in which the valve member closes the outlet.

5. A vehicle braking system according to claim 4 wherein the inlet of the lock valve is connected to a delivery outlet of a service braking modulator.

6. A vehicle braking system according to claim 4 or 5 wherein the lock valve also includes an electrically operated actuator which is configured to move the valve member to the open position when electrical power is supplied to the electrically operated actuator.

7. A vehicle braking system according to claim 4, 5 or 6 wherein the lock valve also includes a resilient biasing element which urges the valve member into the closed position.

8. A vehicle braking system according to any one of claims 2 to 7 wherein a lock piston is mounted in the lock chamber, the lock piston being movable under the action of fluid pressure in the lock chamber to engage with the valve member and to urge the valve member into its second position.

9. A vehicle braking system according to claim 8 wherein the lock piston divides the lock chamber into two portions, the first portion being connected to a source of pressurised fluid and the second position venting to a low pressure region.

10. A vehicle braking system according to claim 8 or 9 wherein the lock piston is movable relative to the valve member.

11. A vehicle braking system according to any one of claims 2 to 7 wherein the valve member is mounted in a main chamber formed in a housing, and the lock chamber is a portion of the main chamber.

12. A vehicle braking system according to claim 4 or claim 4 and any one of claims 5 to 11 wherein the outlet of the lock valve is connected to the lock chamber via a non-return check valve which is movable between a first position in which the flow of fluid from the lock valve to the lock chamber is substantially prevented whilst the lock chamber vents to a low pressure region, and a second position in which the lock valve is connected to the lock chamber whilst flow of fluid to the low pressure region is substantially prevented.

13. A vehicle braking system according to claim 12 wherein the non-return check valve includes a resilient biasing means which biases it to its first position.

14. A vehicle braking system according to any preceding claim wherein movement of the valve member between its first position and second position comprises translational movement.

15. A vehicle braking system according to any preceding claim wherein the spring brake control valve has a control port, supply of pressurised fluid to the control port causing the valve member to move to its first position.

16. A vehicle braking system according to any preceding claim wherein the spring brake control valve has a resilient biasing element which acts on the valve member to urge the valve member into the second position.

17. A vehicle braking system according to claim 16 wherein the spring brake control valve has a control port and be configured such that when the fluid pressure at the control port exceeds a pre-determined level, the valve member moves against the biasing force of the resilient biasing element from the second position to the first position.

18. A vehicle braking system according to any preceding claim further comprising a source of pressurised fluid which is connected to the inlet of the spring brake control valve.

19. A vehicle braking system according to claim 18 wherein the source of pressurised fluid comprises a pressurised fluid reservoir.

20. A vehicle braking system according to claim 18 or 19 wherein the source of pressurised fluid comprises a connector which is adapted to be connected to an external source of pressurised fluid.

21. A vehicle braking system according to claim 20 wherein the vehicle comprises a trailer, and the source of pressurised fluid comprises a connector which is adapted, in use, to be connected to a pressurised fluid supply mounted on a tractor.

22. A vehicle braking system according to claim 21 wherein, where the spring brake control valve comprises a control port, the control port is also connected to the connector.

23. A vehicle braking system according to any preceding claim wherein the vehicle braking system further comprises a spring brake actuator which has a spring brake chamber and which is configured to apply a braking force to a wheel of the vehicle the pressure in the spring brake chamber falls below a predetermined level, and to release the / not apply a braking force to the wheel of the vehicle when the pressure in the spring brake chamber is at or above the predetermined level, the outlet of the spring brake control valve being connected to the spring brake chamber.

24. A vehicle braking system according to claim 23 wherein the spring brake actuator further comprises a resilient biasing element by means of which the braking force is applied when the pressure in the spring brake chamber is below the predetermined level.

25. A vehicle braking system according to any preceding claim wherein the exhaust port of the spring brake control valve is connected to the low pressure region via a modulator valve assembly.

26. A vehicle braking system substantially as hereinbefore described with reference to and as shown in the accompanying drawings. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.