Abstract:
A valve comprising an inlet port, an outlet port, an exhaust port and a diaphragm disposed between the inlet and exhaust ports which is moveable, in response to air pressure within the valve, between a first position in which it seals the exhaust port and a second position in which the exhaust port is open, there being one or more projections associated with the exhaust port on which the diaphragm is able to rest in its first position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of pending International patent application PCT/GB2006/002989 filed on Aug. 10, 2006 which designates the United States and claims priority from the United Kingdom patent application 0516741.6 filed on Aug. 16, 2005, the content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a valve, particularly, though not exclusively, to a quick release valve for a vehicle braking system. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is known for large or heavy vehicles such as buses, coaches and heavy goods vehicles (HGVs) to be provided with brake actuators having a service brake for deceleration when the vehicle is in motion and a parking brake to hold the vehicle stationary. The service brake is usually pneumatically actuated, and the parking brake is usually spring-actuated, with a pneumatic system being provided to maintain the parking brake in an unactuated condition when it is not required. 
         [0004]    In some such vehicles, notably trailers for HGVs, the parking brake also acts as an emergency brake which can be used to decelerate and stop the vehicle automatically in the event of failure of the service brake, for example if the supply of compressed air to the service brake is interrupted or disconnected. In order to do this, a quick release valve (QRV) is provided which allows the rapid release of air from the parking brake system to actuate the parking brake. One such quick release valve is disclosed in the applicants&#39; co-pending UK patent application, no. 0415324.3, and includes a moveable disc or diaphragm with a resiliently deformable skirt disposed between an upper inlet port and a lower exhaust port, with an outlet port being provided to one side of and beneath the exhaust valve. When the parking brake is not required, compressed air is supplied through the inlet port of the QRV, creating pressure on the diaphragm such that it seals the exhaust port, whilst the skirt flexes to allow the compressed air to pass from the inlet port to the outlet port. When the parking brake is required, for example if the vehicle is parked, or if the supply of compressed air has been disconnected, the disc moves to seal the inlet port, allowing air to flow from the outlet port to the exhaust port, thus causing the parking brake to be actuated. 
         [0005]    The applicants have found that, whilst QRVs of this type are generally effective, there can be a delay, sometimes of up to fifteen seconds, between the supply of compressed air being disconnected from the inlet port and the parking brake being actuated, as the moveable disc and resiliently deformable skirt sometimes move in an unpredictable fashion, leaving the exhaust outlet of the QRV sealed. Although this is not a concern when the vehicle is stationary, in an emergency situation such a delay may be dangerous. 
         [0006]    Thus, it is an object of the present invention to provide a quick release valve which eliminates, or at least reduces, this delay. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with a first aspect of the present invention, there is provided a valve comprising an inlet port, an outlet port, an exhaust port and a diaphragm disposed between the inlet and exhaust ports which is moveable, in response to air pressure within the valve, between a first position in which it seals the exhaust port and a second position in which the exhaust port is open, there being one or more projections associated with the exhaust port on which the diaphragm is able to rest in its first position. 
         [0008]    The provision of the projections on which the diaphragm is able to rest enables the diaphragm to move between its first and second positions in response to a change in pressure within the valve substantially without any delay caused by a difference in pressure on one face of the diaphragm in relation to another face. 
         [0009]    The valve may comprise a body. The outlet port may be positioned on the periphery of the body. The projections may comprise ribs extending axially from the exhaust port. The projections may further comprise arc sections disposed at distal ends of the ribs. This ensures that the diaphragm is adequately supported in its first position. 
         [0010]    The exhaust port may be located generally opposite the inlet port. The exhaust port may be located above the inlet port. This ensures that when compressed air enters the valve through the inlet port, the exhaust port is sealed by the diaphragm. 
         [0011]    The diaphragm may be resiliency deformable. Alternatively, the diaphragm may comprise a generally rigid central portion with a resiliently deformable skirt. This ensures that, in its first position, the diaphragm forms an air-tight seal over the exhaust outlet. 
         [0012]    The diaphragm may be generally circular. 
         [0013]    The valve may comprise two parts, with the inlet port being provided on one part and the exhaust port being provided on the other part. 
         [0014]    According to a second aspect of the present invention, there is provided a braking system for a vehicle incorporating a valve according to the first aspect of the invention. 
         [0015]    The valve may be in accordance with any of the preceding paragraphs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Specific and non-limiting embodiments of the invention, in its various aspects, will now be described in greater detail, strictly by way of example only, by reference to the accompanying drawings, of which: 
           [0017]      FIG. 1  is a cutaway perspective view of a known quick release valve; 
           [0018]      FIG. 2  is a cutaway perspective view of a valve according to the present invention; and 
           [0019]      FIG. 3  is perspective view of an exhaust part of the valve of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Turning firstly to  FIG. 1 , a known quick release valve (QRV) for a pneumatic braking system for a vehicle is shown generally at  10 . The valve  10  comprises a body  12  cast or otherwise manufactured from steel or any other suitable material having an inlet port  14  through which compressed air is able to enter an inner chamber  16 , with outlet ports  18 , which are in fluid communication with the inner chamber  16 , being disposed around the periphery of the body  12 . A separate exhaust part  20 , having an exhaust port  22 , is received in air-tight engagement in an open part of the body  12 , with the exhaust port being located generally opposite and above the inlet port  14 , in fluid communication with the inner chamber  16 . A moveable diaphragm  24 , which may be resiliently deformable or may comprise a generally rigid central portion with a resiliently deformable skirt, is disposed within the inner chamber  16 , between the inlet port  14  and the exhaust port  22 . 
         [0021]    In use, the valve  10  forms part of a braking system for a vehicle such as a coach or HGV. The braking system includes brake actuators of known kind having a pneumatically-actuated service brake for deceleration when the vehicle is in motion and a spring-actuated parking brake to hold the vehicle stationary, or to halt the vehicle in the event of an emergency such as failure of the service brake. The parking brake uses a piston which is biased towards an actuated condition by a spring, and which is maintained in an unactuated condition by compressed air when the parking brake is not required. The quick release valve  10  is part of a pneumatic system to control the operation of the parking brake. The inlet port  14  is connected to a source of compressed air, which is controlled by a driver of the vehicle. The outlet ports  18  are connected to inlet ports on the brake actuators to control the operation of the parking brake piston. In normal operation, the parking brake is disengaged by supplying compressed air to the actuators through the quick release valve  10 . The compressed air enters the inner chamber  16  of the quick release valve  10  through the inlet port  14 , causing the diaphragm  24  to move and its edges to deform, creating an air-tight seal over and around the exhaust port  22 . This deformation of the diaphragm  24  around the exhaust port  22  leaves the outlet ports  18  free, allowing the air to escape into the brake actuators, thus causing the parking brake to become disengaged. 
         [0022]    When the parking brake is required, the supply of compressed air to the quick release valve  10  is halted. This causes the diaphragm  24  move to a position over the inlet port  14 , allowing air to pass from the outlet ports  18  and escape through the exhaust port  22 . As the air escapes from the quick release valve  10 , the air pressure within the brake actuators drops, causing the parking brake to be actuated. It will be appreciated that the supply of compressed air can be halted either deliberately by a driver of the vehicle, or in the event of an emergency, for example if the pneumatic system were to fail, leading to a loss in air pressure. In this instance, the quick release valve  10  would operate, causing the vehicle to come to a halt. 
         [0023]    Although this system is generally effective, the applicants have found that there can be a delay of up to fifteen seconds between the supply of compressed air being halted and the parking brake being actuated. This is because when the supply of compressed air entering the quick release valve  10  at the inlet port  14  is halted, the air escaping from the outlet ports  18  is directed over both a lower face  26  and an upper face  28  of the diaphragm  24 . As the diaphragm  24  is deformed, the lower face  26  has a greater surface area than the upper face. The pressure of the air passing over the lower face  26  of the diaphragm  24  urges the diaphragm towards the exhaust port  22 , thus preventing the escape of air through the exhaust port  22 . It is only when the pressure of the air passing over the upper face  28  of the diaphragm  24  is greater than that on the lower face  26 , which can take an unacceptably long period of time to occur, that the diaphragm  24  can move into a position where the inlet port  14  is obscured and the exhaust port  22  is free, allowing air to escape through the exhaust port. Thus, actuation of the parking brake may be delayed. 
         [0024]    Turning next to  FIG. 2 , a quick release valve according to the present invention is shown generally at  40 . The valve  40  is of a generally similar construction to the valve of  FIG. 1 , having a body  42  with an inlet port  44  leading to an inner chamber  46  and outlet ports  48  located around the periphery of the body  42  in fluid communication with the inner chamber  46 . A separate exhaust part  60  is provided, which is received in air-tight engagement in an open part of the body  42  and an exhaust port  62  with a plurality of exhaust apertures  63  located generally opposite (in this instance above) the inlet port  44  in fluid communication with the inner chamber  46 . Disposed around the exhaust port  62  are projections  64  (best illustrated in  FIG. 3 ), in the form of a series of ribs  66  which extend radially from the exhaust port  62 , some of which have peripheral arc sections  68  at their distal ends, which follow the curvature of the exhaust port. A moveable diaphragm  50 , which may be resiliently deformable or may comprise a generally rigid central portion with a resiliently deformable skirt, is disposed within the inner chamber  46  between the inlet port  42  and the exhaust port  62 . 
         [0025]    In use, the valve  40  is connected as described above, with the inlet port  42  being connected to a driver-controlled source of compressed air, and the outlet ports  48  being connected to brake actuators. The parking brake is disengaged by supplying compressed air to the actuators through the quick release valve  40 . The compressed air enters the inner chamber  46  of the valve  40  through the inlet port  44 . The pressure of the air causes the diaphragm  50  to move into a position in which it covers and seals the exhaust port  62 , where it is supported by the projections  64  on the exhaust part  60 . The movement of the diaphragm  50  allows fluid to escape through the outlet ports  48  into the brake actuators, thus to disengage the parking brake. 
         [0026]    When the parking brake is required, the supply of compressed air to the quick release valve  40  is halted. The pressure within the inner chamber  46  thus drops, allowing air to enter the inner chamber  46  through the outlet ports  48 . This air passes over both a lower face  52  and an upper face  54  of the diaphragm  50 . The pressure of the air passing over the lower face  52  of the diaphragm  50  urges the diaphragm  50  towards the exhaust port  62 . However, the air passing over the upper face  54  of the diaphragm  50  urges the diaphragm towards the inlet port  44 . When the air comes into contact with the projections on the exhaust part  60 , turbulence occurs, leading to increased pressure on the upper face  54  of the diaphragm  50 . When the pressure on the upper face  54  exceeds the pressure urging the diaphragm  50  towards the exhaust port  62 , the diaphragm  50  moves to a position in which it covers and seals the inlet port  44 , allowing air from the outlet ports  48  to escape through the exhaust port  62 , thus reducing the air pressure in the brake actuators, leading to actuation of the parking brake. The increased pressure on the upper face  54  of the diaphragm  50 , caused by the turbulence engendered by the projections  64 , leads to a reduction in the time taken for the diaphragm  50  to move from the position in which it seals the exhaust port  62  to the position in which it seals the inlet port  44 , thus reducing the delay between the supply of compressed air being halted and the actuation of the parking or emergency brake. 
         [0027]    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. 
         [0028]    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 utilized for realizing the invention in diverse forms thereof.