Abstract: A pressure relief valve is disclosed. The pressure relief valve comprises a valve housing including fluid passageways, a poppet valve disposed within the housing, a piston disposed within the housing, and spring means disposed intermediate the piston and the poppet valve for biasly urging apart the piston and the poppet valve. The poppet valve has a valve seat which, together with a portion of the housing, defines a variable valve area. The piston has a piston area, relatively greater than the variable valve area, for modulating flow through, and pressure drop across, the poppet valve. The pressure relief valve preferably includes an orifice disposed within the housing for selectively controlling flow of hydraulic fluid through the housing passageways to the piston. The housing preferably includes an elongated cage within which the poppet valve is longitudinally slidable.

Abstract: A clutch pressure control valve for a hydraulically actuated friction clutch which includes a valve spool 5 disposed within a valve bore and having two control collars 6 and 7. The spool is acted upon at one end by a linear compression spring 8 and a speed dependent pressure signal, the spool serving to regulate the clutch pressure by regulating the free cross section at an outlet port disposed between its control collars. To avoid the second order variation of the clutch pressure with speed, the control collars 6 and 7 of the valve spool 5 have two different diameters and the spool 5 is disposed within a stepped bore 2, 3 and 4. The end of the linear compression spring 8, remote from the valve spool 5, abuts a reaction piston 9, which is disposed within the valve bore and is acted upon on one side by the speed dependent pressure signal and on the other side by a second, non-linear compression spring 11, which is compressed between the reaction 9 and a shoulder 12 in the valve bore.

Abstract: A check valve to be interposed between a source of pressure and a device to be moved by the application of the pressure. The valve has a passageway communicating with the source of pressure and a passageway communicating with the device. There is a valve seat formed between the two passageways and a valve member contacts the valve seat. A valve stem can move the valve member to rest on the valve seat to close the valve but the stem is separate from the valve. With lessening of pressure in the source of pressure beyond a desired level the check valve may be closed. Movement of the valve stem to a position away from the valve member ensures that the valve will open but only when the pressure on each side of the valve is about the same. A particular application is to protect the lip of a head box in a paper making machine but may applications are possible.

Abstract: A pressure regulating valve for controlling pressure in high pressure hydraulic circuits includes a closure member with an integral control piston and a conical seating surface cooperable with a complementary surface on a seat member. The valve closure member is biased in the closed position by an actuating mechanism including a pressure gas piston and cylinder arrangement utilizing a flexible diaphragm for sealing the actuator pressure chamber. The effective cross-sectional area of the control piston is large enough to minimize the differences in cross-sectional areas on the closure member exposed to pressure fluid between the valve closed and valve open positions whereby a minimum variation between the valve opening pressure and the control pressure is experienced.

Abstract: A fluid pressure actuated valve wherein a relatively low powered analog electrical signal accurately controls the position of the output member of a fluid pressure powered actuator which in turn can be used to exert mechanical forces or operate mechanical devices such as fluid pumps, motors or valves. Inlet and outlet passages communicate a pressure chamber to high and low pressures respectively. A control element totally within the chamber so as to have balanced pressure forces thereon and made of a magnetically sensitive material is moved to a fixed position in the chamber proportional to the strength of an externally generated magnetic field. At least one of the passages moves with the output member so as to be opened or closed by the control element relative to the other passage. The output member follows the control element automatically varying the pressure in the chamber to compensate for any variations in the external forces thereon.

Abstract: A safety valve for relief of overpressure from a relatively low pressure high temperature fluid system with which the valve is intended to be operative. System pressure is communicated via a body inlet leading to the underside of a displaceable closure disc that cooperates with an annular seat for opening and closing the valve to fluid flow. A predetermined loading force is applied against the topside of the disc urging it toward closed position in opposition to fluid pressure thereat. To minimize or eliminate adverse temperature effects on the disc loading force at the set point operation of the valve, the closure force imposed against the disc is divided between a coaxially supported mass of predetermined weight and a compressed coil spring operative in series relation therewith.

Abstract: An improved presettable, pressure-responsive retrievable fluid control valve contains a plurality of spring housing sections having individual springs disposed therein. Each of the springs is connected in mechanical parallel with each other spring. To select the preset pressure threshold at which the valve opens in response to a column of fluid in a tubing in which the valve is disposed, the number of springs and zero to two compression spacer members are chosen for each spring. The valve also includes a bypass section having an inner bypass mandrel connected by a frangible member to an outer bypass port member. Connected to the outer bypass port member is a sealing member for seating the valve in a seating nipple of a tubing. The bypass mandrel and the outer bypass port member are normally held by the frangible member in a fixed relationship so that ports through the bypass mandrel and the outer bypass port member are axially offset in a closed, or non-fluid conducting, position.

Abstract: A two-speed, pilot-operated selector valve which directs hydraulic fluid to two motor elements with a common output shaft to obtain a high-torque, low-speed mode, or to one motor element, while recirculating the second element in a loop, to obtain a low-torque, high-speed mode. The spool has a built-in logic mechanism which, while shifting from one position to the other, prevents any momentary condition where a motor discharge port is blocked or a fluid path exists that bypasses both motor elements.

Abstract: Apparatus for controlling the working stoke of the hydraulic props of a mine roof support unit is disclosed. The control apparatus comprises a control valve whose input side is connected to a hydraulic pressure line, and whose output side is connected to a working chamber of each of the props via a respective supply line. A sequence valve is provided in the supply line leading to one of the props. The sequence valve is such as to open the associated supply line when subjected to a predetermined hydraulic pressure, this predetermined hydraulic pressure being at least approximately equal to the hydraulic pressure necessary to overcome the resistance to the working stroke of another of the props. The sequence valve has a tubular valve body, a valve closure element mounted within the valve body, and a valve seat positioned within the valve body. A spring is provided for biassing the valve closure element towards the valve seat.

Abstract: A cartridge type directional control valve assembly includes an elongated housing having a bore and a plug threaded in the outer end of the housing adjacent the bore. A changeover, spring biased piston forming a load senser or pressure sensor is provided in the bore with a sealing O ring therebetween. A coil spring is interposed between the plug and the changeover piston. The plug has a vent passage for venting the chamber of the coil spring. A valve retaining screw located in the housing, is centrally apertured and loosely receives the shank of the cone or flow control valve. A coil spring is nested within the valve retaining screw and bears against the flow control valve which is normally seated with respect to a central aperture within the cone valve insert seat. A floating ball check valve is nested within the cartridge assembly and is axially aligned with and opposite from the flow control valve. The control valve and ball check valve control flow across their respective valve seats.

Abstract: A free-floating neutrally-bouyant, stemless, externally-guided, and abrasion-resistant valve for reciprocating pumps that quickly responds to pressure-gradient reversals across its sealing surfaces. The neutral buoyency is attained by means of a hollow air-tight or nitrogen pressurized valve shaft and lead ballast, whereas the valve is guided directly into its valve seat by means of radial guide fins affixed to the exterior of the valve shaft that centralize the free-floating valve within the valve throat downstream from the valve's sealing surfaces. The sealing surface at the valve is protected against erosion from abrasive fluids by a hardfaced fluid deflector just upstream from its sealing surface, whereas the valve seat is protected from erosion by a hardfaced fluid deflector just upstream from the valve seat.

Abstract: A safety valve designed for relieving pressure in a mine support jack. A washer and check valve are positioned in a counterbore located on the front surface of a resilient gasket member. A leg extends from the rear surface of the resilient gasket and extends through a rear chamber to support the check valve in a position sealing the outlet port. The rear chamber is filled with pressurized gas to form a gas cushion. The end of the leg is positioned to seal an inflation orifice.

Abstract: A mine roof support system including a relief valve communicable with the props of each roof support through respective control valve means, and a main return pipe for receiving liquid discharged, by way of the relief valve, from the props when liquid at high pressure is no longer supplied thereto and the roof support is being advanced. A movable element of the relief valve comprises at least two relatively-movable and connected parts and is so co-operable with its seating as to ensure that when the support is so advancing a substantially constant predetermined back-pressure is maintained in the props sufficient to maintain the support in contact with the mine roof. If the pressure in the main return pipe exceeds the pressure then subsisting in the control valve means, one of the parts of said element is caused automatically to close onto the seating.

Abstract: The invention relates to pressure relief valves which spring bias is controlled by a proportional magnet. The force applied by the proportional magnet is increased by an additional hydraulic pressure force which acts on the spring. There is the advantage of decreasing the size of the proportional magnet and/or increasing the flow capacity of the valve.

Abstract: The pressure response of a pressure control valve is adjusted by a solenoid valve of which the solenoid is connected to an electrical three point control device. A programmed signal and an actual signal derived from a transformer of the control pressure valve are fed to the input of the three point control device.

Abstract: Relief valve arrangement comprising a pressure limiting relief valve, the pressure setting thereof can be switched by an auxiliary piston between two or more ranges so that the control pressure, which is obtained by a pilot valve, can be within a region, which can be controlled accurately.

Abstract: A relief valve for relieving excessive fluid pressures in a fluid pressure system comprising: a valve body having a cavity therein and an inlet port and an outlet port in fluid communication with the cavity; and a plug assembly carried in the valve body for reciprocal movement between a closed position in which the plug assembly prevents flow of fluids through the inlet port and an open position, in which the plug assembly permits flow of fluids through the inlet port and into the cavity for exit through the outlet port.

Abstract: The present invention provides a pressure relief valve having a broad range of variable relief pressures. The valve has an inlet passage, an outlet passage, a valve seat interposed between said passages, a valving member mounted for movement into and out of sealing engagement with the valve seat, a valve stem assembly operably connected to said valving member, and two or more resilient compression springs of preferably variable length mounted relative to said valve stem to exert a progressively greater compressive force upon said valve stem upon compression of said valve springs, and an adjustable pressure plate assembly for pre-compressing of the compression springs so as to set the relief pressure at a desired pressure value. A preferred embodiment is directed to that comprising a valve stem assembly for preventing the valve spring from being compressed beyond a predetermined selected point of relief pressure.

Abstract: The valve, in the exemplary embodiment shown, comprises a gas inlet or intake valve for use with a gas compressor. It has a valve body with a gas inlet opening and a gas discharge opening, the latter for communication with the gas inlet of a compressor. A pair of concentrically-engaged pistons, relatively movable therebetween, cooperate to open, close, and throttle communication between the valve inlet and discharge openings. A first, compression spring, reactive from the valve body, urges the piston pair in a first closure disposition, to prevent gas flow through the valve body, and a second, compression spring, reactive from one of the pistons of the pair thereof, urges the other piston to a second, open disposition, to accommodate gas flow through the valve body.

Abstract: A fluid pressure device wherein a relatively low powered analog electrical signal accurately controls the position of the output member of a fluid pressure powered actuator which in turn can be used to exert mechanical forces or operate mechanical devices such as fluid pumps, motors or valves. Inlet and outlet passages communicate a control pressure chamber to high and low pressures respectively. A control element totally within the chamber so as to have balanced pressure forces thereon and made of a magnetically sensitive material is moved to a fixed position in the chamber proportional to the strength of an externally generated magnetic field. At least one of the passages moves with the output member so as to be opened or closed by the control element relative to the other passage. The output member follows the control element automatically varying the pressure in the chamber to compensate for any variations in the external forces thereon.

Abstract: The invention relates to a pressure limiting valve, mainly for hydraulic mine props, which has a working space with an inlet opening connected to a high-pressure space and an outlet opening connected to low-pressure space in the operative position of the valve, a displaceable first valve member engageable with a valve seat within this working space in the shut-off position of the valve, a spring pressing the first valve member to the valve seat and in a given case, a spring sustaining the valve seat, suitably a gas spring and in which according to the invention the first valve member has transfer passages ensuring communication between the inlet opening and the outlet opening in the open position of the valve, as well as second valve member provided with a frustoconical head facing the cover plate and having a stem loosely fitted in a guide bore formed in the first valve member which is formed with an annular axial flange surrounding the head of the second valve member which is concentrically arranged within

Abstract: A valve construction wherein a streamlined flow diverter is centered within a cylindrical valve body. A slidable annular seat ring is biased upstream to seal against a seating surface on the inwardly tapered downstream side of the flow diverter and is biased by fluid pressure so that the valve opens when line pressure exceeds the control pressure. The inner contour of the retractable seat ring and the tapered outer contour of the downstream side of the flow diverter are such that the minimum flow area between them occurs a short distance downstream of the seating surface and is thereafter maintained or slightly increased gradually to an abrupt termination of the tapered surface.

Abstract: Diverter valve for preventing blow-outs in oil wells during the early stages of drilling. The diverter valve has a simplified construction which reduces maintenance problems during use in the field.

Abstract: In order to correct non-linearities inherently existing in the relation between the value of a hydraulic fluid parameter controlled by a proportional valve and an operating signal controlling the valve, in an arrangement in which the setting of the valve is controlled by effecting a comparison between the operating signal and a feedback signal representing the valve movement, a memory is provided to modify one of those signals prior to comparison in a manner to compensate for such non-linearities.

Abstract: This drip preventing valve is adapted to be installed in a conduit between the discharge outlet of an oil burner pump and the nozzle. The valve responds to the pressure in that conduit and closes whenever the pump stops, thereby preventing leakage or dripping from the nozzle. This valve consists of a body of one or more closed, flexible-walled cells, filled with air at atmospheric pressure. When the valve body is subjected to a greater pressure, it is compressed, thereby opening the valve. When that greater pressure is relieved, the valve closes.

Abstract: An improved check valve for a backflow preventing valve of the type having an inlet passage, an intermediate chamber, and an outlet passage, includes a stationary valve port fluidly communicating with the intermediate chamber, a movable contoured valve seat for sealing the port, and a valve closing apparatus in rolling engagement with the valve seat and responsive to the pressure differential thereacross. The valve closing apparatus urges the valve seat to a valve closed position and includes a stationary shaft, a pair of rollers, and a spring. The spring biases the rollers against the contoured valve seat to thereby effect the closure of the seat member against the valve port. An improved exhaust valve is also provided and includes a balanced valve member providing a path between the intermediate chamber and the atmosphere when in a valve open position. The balanced valve member is resiliently biased between a valve seat and a moveable diaphragm.

Abstract: A spring-loaded safety valve has a housing with inlet and outlet, a valve member mobile between open and closed positions, a valve spring urging the valve member to the closed position and having a tendency to vibrate during the operation of the valve, and vibration-disturbing element for damping the vibrations of the valve spring during the operation of the valve. The vibration-disturbing element may be formed as a damping load or a damping spring which urges a valve spindle in direction of opening of the valve.

Abstract: An improved engine comprises a primary piston and primary cylinder in which air and fuel is precombusted. The piston is reciprocated in the cylinder by an external prime mover. The exhaust of the precombusted air/fuel mixture is controlled by a floating exhaust valve piston which seats against the exhaust port and has its other end pressurized at a set pressure preferably by an inert gas. The precombusted air/fuel mixtures are exhausted to secondary combustion chambers where additional air, fuel and prime mover exhaust gases are added to increase the velocity and pressure of the gas and provide for more complete combustion of the fuel.

Abstract: A pressure regulating device comprises a chamber (22) for receiving fluid under pressure and a valve (23) associated therewith, arranged to open at a preset fluid pressure in the chamber.In order to prevent any valve "chatter", the valve (23) comprises a valve disc (8), a bushing (9) on which the valve disc is freely mounted for sliding movement thereon, a valve seat (13) associated with the disc, and means (3) to bias the disc towards the seat against the fluid pressure, the disc and bushing being connected together by means of a flexible coupling (10) having resilient properties to accommodate the sliding movement of the disc.

Abstract: A self-monitoring hydraulic control valve unit has a main valve and a control valve for controlling supply of hydraulic fluid to a control duct of the main valve. A differential piston is connected in the control duct and has a longitudinal bore which forms part of the control duct, the piston acting at its smaller diameter end on the shutter of the main valve. An electrical monitoring switch such as a proximity switch monitors the position of the differential piston and, therefore, of the main valve.

Abstract: Pressure acting on the face of the poppet valve is opposed by a gas charge or a spring in the bellows. The valve controls evaporator pressure in an automotive air conditioning system. Destructive response to pressure pulses from the compressor is prevented by the static friction obtained by having a leaf spring bear on opposed sides of a self-lubricating plastic sleeve carried on a shaft fixed on the valve. The various modifications show ways of minimizing the effect of temperature change through the valve and minimizing the differential of the valve. One modification provides a temperature responsive charge in the bellows and the mean effective area of the bellows is greater than the mean effective area of the valve orifice to compensate the closing force and reduce the valve differential.

Abstract: A relief valve (10) having both spring biasing means (116) and air pressure biasing means (114). The spring biasing means (116) includes a plurality of spring washers (132) acting between the valve body (12) and a valve member (74). The air biasing means (116) includes an air cylinder defined by an intermediate portion (20) of the valve body (12), and a piston (118) disposed within the cylinder and acting on the valve member (74). An air inlet port (48) is provided above the piston (118) to permit the area above the piston (118) to be pressurized to add to the biasing force of the spring biasing means (116), and an air inlet port (52) is provided below the piston (118) to permit the area below the piston (118) to be pressurized to open the valve manually for testing and exercising. A "quiet" element (102) surrounds the valve member (74) to reduce the sound level of the fluid flowing through the valve when the valve opens.

Abstract: In a vehicle wherein road wheel travel is controlled by a hydraulic damper hose flow is controlled by a spring-urged metering valve, the improvement wherein the valve spring comprises a helical spring having a constant load-deflection curve and a plurality of coned spring disks having variable load-deflection curves. The preferred suspension for cross-country operation exhibits a relatively hard response to minor bumps, a soft floating response to major bumps, and a comparatively hard snubber-like response to abnormally large bumps. Movement in the rebound direction can be substantially unrestricted, controlled by conventional springs, or controlled by spring stacks similar to those described herein. Conversely, for operation on hard surfaced roads the major control functions could be reversed.

Abstract: In a valve wherein a flexible tube is stretched around a circular barrier between inlet and outlet slots and is conditioned to enable flow in an annular path around the barrier when upstream pressure overcomes pressure in a control jacket around the tube, the improvement comprising a second flow path directly through the barrier, which is normally closed off by a poppet valve engagable with a seat around the passage. A spring augmented by a control pressure biases the valve toward closed position and is preferably set so that, only after capacity of the flexible tube is reached or approached, does the poppet valve open to answer the need for high pressure demand downstream or for relief of a high pressure surge upstream.

Abstract: An exhalation valve for inhalation therapy includes a base member provided with an exhalation port encircled by a valve seat for a valve closure disc, the center of which is connected to the inner end of a pin extending outwardly away from the disc and slidably mounted in a sleeve spaced from the disc. The sleeve is held rigidly by a support connected with the base member. A number of Constant-Force Compression coil springs extend between the sleeve and disc and are bowed outwardly away from the pin. The ends of the springs are connected with the sleeve and closure disc to urge the disc toward the valve seat. The springs exert a substantially constant pressure against the disc as it is moved outwardly away from the valve seat by air flowing out through the valve port.

Abstract: An improved piston compression valve mechanism for a double acting shock absorber which includes an upwardly facing annular valve seat on the piston. A washer member is fixed to the piston above the valve seat. The exterior periphery of the piston between the valve seat and washer includes six annularly spaced radially outwardly facing arcuate surfaces. Six coil springs are mounted with their upper ends engaging the washer member and their inner exterior peripheries adjacent the arcuate surfaces. A lower spring support including an outer cylindrical peripheral wall is disposed in surrounding relation to the outer exterior peripheries of the coil springs. An inwardly projecting flange and six radially inwardly projecting portions extend toward and adjacent to the arcuate surfaces which are in supported relation to the lower ends of the coil springs.

Abstract: A combination pressure regulating and flow control valve having an upstream port and a downstream port interconnected by a flow passage. An adjustable pressure regulating valve is mounted in said flow passage for regulating the downstream pressure in said flow passage. The adjustable flow control valve is mounted in parallel with said pressure regulating valve in said flow passage for providing a meter out action on pressurized air flowing through said passage from said downstream port to said upstream port. The adjustable fluid flow control valve is shown in one embodiment as being provided with an adjustable quick exhaust valve structure for quickly dumping the exhausting air to reduce the pressure thereof to a reduced predetermined level, after which the meter out action follows.

Abstract: The invention comprises a novel oil distributing arrangement, employing a valve which has a plurality of responses, for use in a gas compressing system or the like. The valve has a plurality of ports for admitting oil thereinto from an oil pump via a cooler, and for discharging oil therefrom, to a gas compressor (or some such similar oil-using end item) or for by-passing oil directly back to the oil pump (or a pump-serving oil reservoir), or for by-passing the cooler, etc. A translating valving element opens and closes communication between different oil admittance and oil discharge ports in the valve, in response to discrete ranges of valve-operating fluid pressures addressed to the valving element, to effect the cited by-passing functions, and to maintain a fairly uniform pump output pressure level.

Abstract: A vacuum breaker for use on a moving tank for allowing atmospheric air to enter the tank to relieve a reduced pressure condition in the tank. The vacuum breaker has a light-weight closure assembly including a closure member of relatively large area. The closure assembly is normally held closed by permanent magnets. The magnets and the light-weight construction of the closure assembly substantially prevent the vacuum breaker from opening due to vibration of the moving tank. However, the vacuum breaker opens readily in response to a relatively slight reduced pressure in the tank because of the large area of the closure member. The permanent magnets are shielded from undesirable proximity of ferrous objects to prevent the magnets from being drained. The vacuum breaker may be opened manually to test for a positive pressure condition in the tank.

Abstract: A pressure relief mechanism seated within a wall of a pressure vessel features a novel flexible seal. The vessel pressure acts against both a spring and an internal valve pressure created by the flexible seal. The pressure relief mechanism can be designed to release over a wide range of critical vessel pressures due to the combination of the resistive spring force and the resistive internal pressure.

Abstract: A mine prop provided with an overpressure valve of large flow-through section which opens when excessive forces suddenly act on the prop to discharge pressure fluid from the interior of the prop. The overpressure valve comprises a hollow cylindrical housing forming at one end a valve seat communicating with the fluid-filled inner space of the prop and a valve member axially guided in the housing for movement between a closed position engaging the valve seat and an open position. The fluid-filled space of the prop communicates with channels leading to the outside of the prop. The valve member is normally maintained in the closed position by a gas pillow under high pretension confined in a pressure space delimited peripherally by the wall of the valve housing and at opposite ends respectively by the valve member and a plug fluid tightly mounted in and closing the other end of the housing.

Abstract: A temperature and pressure responsive fluid flow control valve, particularly useful for controlling the operation of a fluid fan drive. This valve regulates operation of the fluid fan drive by controlling the fluid flow from the fluid fan drive, in response to both engine coolant temperature and fluid pressure of the fan drive oil.

Abstract: A venting valve connected to the interior of the fuel tank has a sliding piston and a plurality of springs which hold the piston in different operative positions dependent upon the amount of pressure within the tank.

Abstract: An adjustable relief valve comprising a valve member and a valve seating one of which acts against the other under the pressure of a predetermined weight to close a valve port, and a removable weight which can be added to the predetermined weight to vary the closing pressure, said removable weight being of annular shape and being located by means of a bayonet type connection on a boss connected to the valve member or the valve seating.

Abstract: An improved backflow preventing valve having an inlet passage opening to an intermediate chamber via an improved inlet check valve with the intermediate chamber opening to an outlet passage via an improved outlet check valve. A diaphragm chamber communicates with the intermediate chamber having a diaphragm therein dividing the diaphragm chamber into an inlet pressure portion opening into the inlet passage and an intermediate pressure portion opening to the intermediate chamber. An exhaust passage opening to atmosphere communicates with the intermediate pressure portion whereby fluid normally flows from the inlet passage through the intermediate chamber to the outlet passage but upon attempted backflow of the fluid, the improved check valves close with a positive closing action to prevent such backflow and, upon failure of the outlet check valve, the diaphragm flexes to open to vent such backflowing fluid out the exhaust passage.

Abstract: A high efficiency water hammer type pump and more particularly, an improved construction for such a pump including a construction whereby water expelled from a waste valve is returned to the supply line of the pump.

Abstract: A valve for water pipes comprises a housing with an inlet opening and an outlet opening with a through-flow chamber arranged between both these openings, in which a spring loaded valve spindle provided with a sealing means is arranged to work in a direction to and from an engagement surface intended for the valve spindle sealing means in the chamber, for regulating the flow through the chamber in a direction from the one opening to the other.

Abstract: A non-return air flow system for supplying secondary air into the exhaust system of internal combustion engines by utilizing pulsating flow of exhaust gases in the exhaust system, wherein the critical valve opening pressure for a check valve incorporated in the non-return system is varied in accordance with intake air flow rate of the engine so that supply of secondary air is effected in proportion to air intake of the engine.

Abstract: A well service valve used primarily for the injection of closely controlled batches of well treating fluids into low pressure formations utilizes a biased one-way flow valve in a tubing string to hold the treating fluid in the column until the tubing is pressurized to open the valve and expose flow ports in the wall of the tubing to the formation. A partial pressure-balancing of the flow valve allows the use of a lower biasing force in the flow valve, thereby greatly increasing the reliability and useful life of the valve.

Abstract: A soil irrigating system includes a plurality of drip tubes communicating with a supply of pressurized water to dispense a substantially continuous flow of water to the soil. Flushing valves are connected to remote ends of the drip tubes to periodically flush the tubes clean. Each flushing valve comprises an inlet communicating with a drip tube, an outlet for discharging water from the drip tube, a pilot opening arranged to introduce pressurized pilot water to the valve, and a valve element of resiliently deformable material. The valve element has a recessed configuration suitable for enabling the valve element to extend longitudinally forwardly and radially outwardly into a sealing posture in response to urgings of pressurized pilot water at the pilot opening, to prevent discharge of water from the remote end of the associated drip tube.