Fluid handling – Diverse fluid containing pressure systems – Fluid separating traps or vents
Patent
1999-08-18
2000-08-29
Michalsky, Gerald A.
Fluid handling
Diverse fluid containing pressure systems
Fluid separating traps or vents
137204, F16K 3112
Patent
active
061092894
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a drain valve, and particularly to a drain valve for use in an air braking system.
Efficient working of an air braking system requires exclusion of moisture which may be drawn in by the compressor (usually engine driven) or produced as a result of condensation.
Moisture can cause seizure of parts, and otherwise interfere with correct operation. It is thus usual to provide an air dryer to ensure that air delivered to the system is of a consistent quality. The air dryer usually comprises a replaceable canister of desiccant which is itself periodically regenerated by a volume of dry air. Such an arrangement is conventional.
It is desirable to hold air under pressure between the compressor and the air dryer when the compressor is off load; this arrangement ensures that oil is less likely to escape past the compressor piston rings under the influence of pressure in the engine crankcase, and thus contaminate the desiccant when the compressor is brought on load.
A valve is provided between the compressor and desiccant canister to hold the compressor outlet under pressure when the compressor is off load. This valve is conveniently located in the body to which the desiccant canister is attached, and is responsive to governor pressure to open and close communication between the compressor and the desiccant canister.
Typically this valve is under the desiccant canister and may accumulate excess moisture which drains down under gravity. If such moisture is not periodically expelled the valve may malfunction. The moisture is not able to escape to atmosphere through a simple vent because the valve must remain pressure tight in order for the air braking system to maintain its integrity. The present invention provides one means of eliminating such moisture.
According to the invention there is provided a drain valve comprising a housing defining a chamber, a flow inlet and a flow outlet opening into the chamber, a flow path defined in the chamber and providing fluid communication between the flow inlet and the flow outlet, a closure member arranged to move in use within the housing between a first position wherein the flow path is occluded and a second position wherein the flow path is unobstructed, the drain valve further comprising a signal port, and movement of the closure member being effected in use by the presence or absence of a signal pressure at said signal port, and a sump adapted to collect liquid in the drain valve, wherein the sump comprises discharge means adapted to discharge liquid collected in the sump to the exterior of the valve, the discharge means being activated in use by a predetermined variation in pressure at the signal port.
The chamber may be of uniform cross-section. Accordingly, the closure member may comprise a piston sealingly slidable in the housing. The flow inlet and flow outlet may be arranged to open into the chamber at one end of the housing.
The flow inlet and flow outlet may comprise concentric openings in one end of the housing; the closure member may define a sealing surface arranged to seal over the openings.
The signal port is preferably positioned in a sidewall of the housing. The signal port may be positioned in the sidewall so as to enter into the chamber on the opposite side of the piston from the flow inlet and flow outlet.
Preferably, the opposite side of the piston from the flow inlet and flow outlet is castellated. An abutment surface may be provided adjacent the signal port and parallel with the side of the piston opposite from the flow inlet and outlet, the abutment surface being arranged to abut, in use, against said side of the piston. The abutment surface may be defined by the discharge means.
The castellation of the piston ensures that the signal port is not obstructed at the extreme piston position.
The discharge means may comprise a valve member mounted in the housing across a discharge passage in fluid communication between the sump and the exterior of the housing, and an auxiliary sump, the valve member being movable between a fir
Firth Brian Frank
Thomas Barry David
Michalsky Gerald A.
WABCO Automotive (UK) Limited
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