Abstract: A pneumatically amplified conservation valve controls a flow of gas, such as oxygen, to a hospital patient. A sense tube monitors pressure variations as a result of exhalation by the user. The exhalation pressure variation deflects a diaphragm which closes a check valve that serves to vent gas through a bleed port. When the check valve closes the bleed gas is restricted in a chamber which deflects the diaphragm which in turn drives a connector that pushes a plunger to close a port that is connected to the source of gas through a supply tube. The gas is normally supplied through the supply tube and a normally open pneumatic valve to an output tube and then to the user. The pneumatically amplified conservation valve provides gas to the user except when the user is exhaling thereby substantially saving the amount of gas that must be provided to a user.

Abstract: A hydraulically unblockable non-return valve has a control piston (21), the control side of which can be connected with a control pressure medium source (35) and the other side of which can be connected with a supply container (33). In order to create a hydraulically unblockable non-return valve, in which the control side of the control piston does not need to be relieved of pressure, the other side of the control piston is perpetually connected with the supply container. Also provided is a throttle bore (27) which connects the two sides of the control piston with each other.

Abstract: A pneumatic control providing both a snap action mode and a throttling mode, action including a gas inlet connected to a source of gas pressure, a nozzle in communication with an exhaust port, a nozzle seat moveable to and away from the nozzle in response to a mechanically applied control action such as a liquid level float, a gas chamber in the flow passageway between the gas inlet and the nozzle port, a first passageway from the gas chamber to a control gas outlet, a diaphragm actuated valve in the first passageway, a second passageway from the gas chamber to the control gas outlet, a throttling screw serving to open or close the second passageway and a shut-off screw providing means of opening or closing the first passageway whereby the application of gas pressure to the control port in response to the closing of the nozzle is determined by the position of the throttling screw and the shut-off screw.

Abstract: An apparatus and system for filling containers with a required liquid to a predetermined level are disclosed. The apparatus includes a main valve means for controlling the flow of liquid through the apparatus and into the container; a fluid amplifier means for receiving at least a portion of the liquid from the main valve means and for generating a pressure signal until such time as the liquid within the container reaches the predetermined level; and pilot valve means for maintaining the main valve means open in the presence of the pressure signal from the fluid amplifier and for closing the main valve means in the absence of the pressure signal. The system includes the aforesaid apparatus together with liquid supply conduit and valve means.

Abstract: A control system for a valve actuator which is subject to oppositely directed displacement due to thermal expansion and spring forces has sensor switches which detect successively greater amounts of compression of a spring which compresses to accommodate thermal expansion of the valve, its stem and seat when the valve is seated in closed position. A position servomechanism which is responsive to the position of the stem and a control signal operates a motor for advancing and retracting the stem.

Abstract: An improved float actuated pilot valve is shown for use in an oil and gas separator. The pilot valve has a valve body with a gas inlet, a lower chamber communicating with the gas inlet, an upper chamber, a gas outlet, and a gas passage connecting the upper chamber, lower chamber, and gas outlet. An actuator piston is contained within the upper chamber and has a top stem contactable by the flapper arm of a displaceable float located within the separator. The actuator piston also has a bottom stem which is slidably received within a portion of the valve gas passage. A control piston is contained within the lower chamber and has an upper stem in contact with the actuator bottom stem and has a lower stem. The control piston has an upper sealing face which sealingly engages the opening of the gas passage into the lower chamber. A coil spring normally biases the control valve sealing face toward a closed position in contact with the gas passage opening to block the flow of gas from the gas outlet.

Abstract: A pinch sleeve valve having controllable opening positions regardless of internal sleeve pressure is disclosed. In the past it has not been possible to use a pinch sleeve valve as a control valve because a variation in pressure within the sleeve has affected the opening of the sleeve. The present valve comprises a flexible sleeve with a passageway therethrough, the sleeve having variable positions from a round cross section when fully open, to a collapsed cross section when closed. A rigid pressure sealed housing contains the sleeve and a sensing probe is connected to the sleeve which senses whether the sleeve is fully open, partially open or closed. A valve positioner is connected to the sensing probe and has a control system to set opening positions of the valve regardless of variations in the internal sleeve pressure, the valve positioner controls supply fluid to the housing at a pressure higher than the internal sleeve pressure and sufficiently high to close the sleeve to the desired opening position.

Abstract: A rising liquid level in a gas scrubber for an air compressor is sensed by a float in the scrubber which opens a normally closed pneumatic vent valve whereby a very small pneumatic signal is delivered through a pneumatic spool valve to the chamber of a large diaphragm liquid dump valve on the scrubber which is operated automatically to drain liquid from the scrubber to maintain a safe liquid level in the scrubber. The dump valve mounted on the scrubber side wall penetrates deeply into the scrubber to avoid freezing of the dump valve.

Abstract: The control mechanism is for pneumatic apparatus of the kind comprising a piston-and-cylinder motor coupled between two relatively-movable parts (such as door-leaves) for driving them, when energized, to a predetermined relative position. A pilot valve is actuated when required to switch the apparatus to an emergency mode by isolating the motor from its power source and discharging it into an emergency reservoir having a volume large compared with the maximum volume of gas in the motor. While the pilot valve is actuated, the relatively-movable parts are urged towards their predetermined relative positions by a force small compared with the normal operating force. The pilot valve may be arranged to operate operation of an emergency release bolt, on obstruction detected by a detector valve (in which case a timing reservoir provides time delay before full power is restored), on power failure, or as required.

Abstract: A surface controlled subsurface safety valve for deep well service. Communication of control fluid to the subsurface safety valve is controlled by a pilot valve at a subsurface location in close proximity to the safety valve. Responsiveness of the subsurface safety valve to decrease in control fluid pressure is thereby increased and the safety valve's closure speed is also increased. The pilot valve controllably communicates pressurized control fluid to open the safety valve and allows control fluid to be displaced into the flow path through the safety valve during valve closure.

Abstract: A device for remote control of actuator of a shut-off member comprises an autonomous source of energy and a distributor connected therewith. The autonomous source of energy is fashioned as two units, each unit containing at least two gas generators with igniter means, a pneumatic OR gate and a selector. The input of each unit is connected to a corresponding control channel while outputs are connected to respective input and control channels of the distributor. The present invention improves the reliability of control of the shut-off member and facilitates the maintenance of the device during operation.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to the actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator, and a pilot operated check valve operable for controlling flow from the meter-in valve means to one end of the actuator and for preventing flow out the end of said actuator, the pilot operated check valve being operable at a lower pilot pressure than the meter-out valve means and including time delay means such that the valve functions to prevent flow out of the actuator after a predetermined time delay from the time when pilot pressure to said meter-out valve means is interrupted, insuring relief valve protection.

Abstract: A liquid level valve for use in filling a liquid storage tank to control (in response to increased air pressure within the liquid level valve) the tank emergency loading valve which is held open by pressurized air.The liquid level valve has an air control cavity connected to the pressurized air and an actuating cavity which exhausts to the atmosphere and is disposed above the air control cavity and connected to it via an actuating passageway. An air control diaphragm divides the air control cavity into upper and lower portions and controls the flow of pressurized air into such lower portion which exhausts to the atmosphere. The air control diaphragm has a small air control passageway (of smaller diameter than the actuating passageway) allowing pressurized air into the air control cavity upper portion, thus permitting the pressurized air to act on both sides of the air control diaphragm.

Abstract: Control apparatus is disclosed for limiting overspeed in a steam turbine following a sudden loss in load. The apparatus includes at least one valve disposed in the steam conduit interconnecting higher and lower pressure sections of the turbine and an actuator for controlling operation of the valve between a fully open position and a pressure-relief position wherein the valve functions as a pressure relief valve. During normal operation, the valve is maintained in the fully open position. On receipt of a turbine overspeed signal, the valve is actuated to the pressure relief position and a volume of steam at a preselected pressure, necessary to open the valve, is held back within the turbine stages, crossovers, and so forth. This retained steam is thus prevented from adding energy to increase the speed of the turbine rotor.

Abstract: A back-flow prevention valve assembly is disclosed for use with a vacuum pump or the like and employs a valve element movable between positions opening or closing a passageway through the assembly. In the event of pump failure, a control valve, which is operated by fluid from the pressure side of the pump, vents ambient air behind the valve element to assist it in moving rapidly to the closed position to prevent backflow. After resumption of pumping, a controlled withdrawal of ambient air behind the valve element delays opening of the valve until the pump has created a sufficient vacuum to minimize influx of air upstream when the valve opens.

Abstract: A float operated valve for controlling the rate of flow of water from a pipe carrying water under pressure, to a vessel, comprises a pipe having an end opening of selected diameter and a flange of larger diameter surrounding the pipe. A flexible diaphragm is attached over the flange having a central closure pad adapted to cut off water flow when pressed against the pipe. A small orifice is drilled through the diaphragm so that when the flow is shut off, water can still flow through the orifice to the second side of the diaphragm. A second short pipe having a similar flange is bolted against the diaphragm to the first flange, to provide a water tight seal. There is a second small orifice in the second end of the second pipe, and a float mechanism is provided with a closure tip to close the second orifice when the water level is at a selected value. The closure tip provided can vary the size of the second orifice so that as soon as it is opened, the orifice size is a minimum.

Abstract: An actuator system is disclosed which modulates a linear output shaft associated with a working control valve or the like in response to a control signal input. The system includes a feedback control link, a pneumatic positioner, a pneumatically controlled hydraulic valving system and a hydraulic cylinder and piston assembly controlled by the hydraulic valving system. The hydraulic valving system includes a three-position, four-way valve actuated by pneumatic binary output signals from a signal conditioner which is in turn controlled by the positioner. Hydraulic flow to the three-position, four-way valve may also be controlled from the signal conditioner in response to positioner output for most effective actuation of the hydraulic cylinder and piston assembly. Failure modes are also disclosed with the present system. The resulting system exhibits extremely rapid response times and high accuracy with dynamic stability.

Abstract: An air pressure responsive liquid level valve used in filling a liquid storage tank to control the tank emergency loading valve which is held open by pressurized air.The liquid level valve has an air control cavity connected to the pressurized air and an actuating cavity exhausting to the atmosphere and is disposed above the air control cavity and connected to it via an actuating passageway. An air control diaphragm divides the air control cavity into upper and lower portions and controls the flow of pressurized air into such lower portion which exhausts to the atmosphere. The air control diaphragm has a small air control passageway (of smaller diameter than the actuating passageway) allowing pressurized air into the air control cavity upper portion, thus permitting the pressurized air to act on both sides of the air control diaphragm. An actuating diaphragm, responsive to increased pressure within the liquid level valve, controls the flow of pressurized air through the actuating passageway.

Abstract: An internal valve for the bottom loading of fuel tanks consists of a differential area piston acting within a chamber which is vented by a pair of pilot valves responsive to fluid level, to provide full open, throttled and closed positions of the valve automatically in response to inlet fluid pressure. Soft closure of the inlet valve which is formed of the piston head and a seat in the valve housing, is provided by metered fluid flow through an orifice between a sized aperture in the piston head and a restrictor sleeve carried on a tank vent actuator bar extending through the aperture and through the valve housing. A lost motion connection between the piston head and actuator bar allows limited relative movement for controlling the metering orifice and combined movement for coincident opening of the tank vent in response either to inlet fluid pressure or manual actuation.

Abstract: A vacuum operated valve mechanism for controlling transmission of fluid to servo means for emission control for an internal combustion engine or reducing emissions from the engine, including a single housing, a first and second diaphragm member, a first and second piston member, a pilot valve member and a working valve member.

Abstract: The invention relates to a security pneumatic control apparatus comprising an OR cell, an AND cell, a capacitor, connected to the OR cell by means of a debit regulator, and a priority cell connected to the capacitor and to the AND cell. The AND cell comprises a valve member, for engaging two seats, and a diaphragm, for moving the valve member onto one of the two seats. The cross-sections of the diaphragm and of the last mentioned seat of the AND cell are S'.sub.3 and S'.sub.2 respectively. The priority cell comprises a valve member, for engaging two seats, and a diaphragm, for moving the valve member onto one of the two seats. The cross-sections of the diaphragm and of the last mentioned seat of the prioritary cell are S.sub.3 and S.sub.1 respectively. In the invention,S'.sub.3 /S'.sub.2 <S.sub.3 /S.sub.1.When the supply pressures at the OR cell and AND cell are not equal, the security remains guaranteed for the control of dangerous machines.

Abstract: A safety valve is mounted on an underwater oil well and is remote-controlled from a central control station. The control station is connected to a receiving station, where the valve is disposed, via a single small-section hydraulic line which feeds, at a low rate of flow, a hydropneumatic accumulator for supplying an operating jack of the valve. A manostat switch at the receiving station controls a feed/bleed hydraulic relay of the jack in dependence on the pressures measured in the line at the receiving station. The invention finds application in oil valve safety operations.

Abstract: A pneumatic control for turbochargers includes an evaucated bellows-operated servo valve for controlling the pressure differential across a diaphragm, which in turn controls the position of a turbocharger wastegate valve. Discharge pressure from a turbocharger compressor is applied to both sides of the diaphragm. The bellows-operated servo valve is operable to vent one side of the diaphragm whenever the discharge pressure exceeds a predetermined magnitude resulting in a pressure differential across the diaphragm to control the position of the waste gate valve.

Abstract: A compound valve device comprises a body member, a first valve member being located in the body member and controlling the fluid communication between a first input port and a first output port, and a second valve member being located in the body member and controlling the fluid communication between a second input port and a second output port. The two valve members operate in sequence, without a significant difference in time in response to one signal pressure.

Abstract: A control valve has a body with an orifice open to an inlet port and to an outlet port. A valve sleeve is movable along an axis in the body to move a valve needle into and out of the orifice. A first bellows engages the body and valve sleeve to preclude leakage between them. An actuator housing on the body defines a first compartment and a second compartment spaced apart along the axis. There is a packing stem and an actuator stem secured to the valve sleeves and together extending through the first compartment into the second compartment. The stems carry devices to engage electrical circuit control mechanism in the first compartment. The end of the second compartment is closed by a mounting disc, and leakage between the actuator stem and the mounting disc is precluded by a packing. A recessed disc spans an end of the second compartment. There is a flexible diaphragm in the recessed disc partially spanning a chamber therein.

Abstract: An arrangement for regulating supercharger air pressure in a combustion engine operated with exhaust gas supercharge which equipped with an exhaust gas turbosupercharger, consisting of a supercharger and an exhaust gas turbine. The regulating device is a valve controlling an exhaust gas bypass to the exhaust gas turbine. The valve has a pressure unit divided by a diaphragm into two chambers. One side of the diaphragm is charged with supercharger air pressure, and the other side is loaded by a spring. The two chambers are connected by a calibrated opening in the diaphragm. Another valve connects the chamber holding the spring to the atmosphere and has the form of a nonreturn ball valve. The preloading of the spring of the nonreturn ball valve may be adjustable.

Abstract: A self-contained valve positioner having a single valve positioner housing including an actuator portion having a pneumatically operated actuator unit therein carrying a main valve member to position the main valve member relative to a main valve seat in a valve unit in relation to the magnitudes of first and second pneumatic signals directed to the valve positioner and one of which is being utilized as the fluid source therein for pneumatically operating the actuator unit, the single valve positioner housing including a pilot valve portion having a pilot valve relay disposed therein that initially receives the pneumatic signals and causes the one signal to operate the actuator unit in a manner to progressively open the valve member as the first signal being directed to the value positioner progressively increases from a first value to a second value and thereafter to progressively close the valve member as the first signal being directed to the valve positioner progressively increases from the second value t

Abstract: A pneumatic-hydraulic proportional valve actuator system is provided having a relatively simple and adjustable means of achieving two stroking speeds by the hydraulic actuator, high speed in normal operation and low speed for small position adjustments and for the final part of any large position adjustments. This prevents overshoot and instability of the actuator.

Abstract: The invention provides the functional reliability of an automatic device, constituted by the association of phase cells comprising, for each phase, a pneumatic AND gate and bistable memory, which is ensured by the interposition of a threshold relay between the feedback interrupter associated with a phase all and the control input of the memory.

Abstract: A self-contained valve positioner having a single valve positioner housing including an actuator portion and having a pneumatically operated actuator unit therein carrying a main valve member to position the main valve member relative to a main valve seat in a valve unit in relation to the magnitude of a single pneumatic signal directed to the valve positioner and being utilized as the fluid source therein for pneumatically operating the actuator unit, the housing including a pilot valve portion and the actuator unit having a pilot valve relay disposed in the pilot valve portion and that initially receives the pneumatic signal and causes the signal to operate the actuator unit to progressively open the valve member as the signal being directed to the valve positioner progressively increases from a first value to a second value and thereafter to progressively close the valve member as the signal being directed to the value positioner progressively increases from the second value to a third value.

Abstract: A valve actuator and a pilot assembly which may be utilized either alone or with the actuator is responsive to control fluid pressure for moving an operative means of a valve between open and closed positions. The actuator has a housing defining a cylindrical bore therethrough and a shaft is carried in the housing which is engageable with the operative means. A piston is carried by one of the shaft and the housing and is sealingly slidable along the other of the shaft and the housing and is longitudinally movable within the cylindrical bore.The pilot assembly comprises a cylindrical housing having pilot means within the housing, the pilot means having valve seat means thereon. Normally free traveling spherical members are provided immediate the pilot means and define valve head means selectively sealingly engageable on the pilot means to open and close the pilot means to control fluid flow therethrough.

Abstract: Disclosed is a surface controlled subsurface safety valve for deep well service. Communication of control fluid to the subsurface safety valve is controlled at a subsurface location in close proximity to the valve. Responsiveness of the subsurface safety valve to decreases in control pressure is thereby increased and the valve's closure speed is also increased. This abstract of the disclosure is neither intended to define the scope of the invention, which, of course, is measured by the claims, nor is it intended to limit the invention in any way.

Abstract: Variable differential pressure control apparatus is used in a hydraulic system including a pump, an accumulator for receiving hydraulic fluid under pressure from the pump and for discharging hydraulic fluid to a work device, and an unloading valve in the circuit between the pump and the accumulator for regulating pressure of the fluid to the accumulator. The control apparatus is connected with the unloading valve for opening and closing the latter and is adjustable (1) for selectively setting the maximum fluid pressure to the accumulator and (2) for selectively setting the variation between the maximum pressure to the accumulator, at which pressure the unloading valve will open, and the minimum pressure to the accumulator at which pressure the unloading valve will close for recharging the accumulator.

Abstract: A valve actuator and a pilot assembly responsive to control fluid pressure for moving an operative means of a valve. The actuator has a housing defining a cylindrical bore therethrough and a shaft is carried in the housing which is engagable with the operative means. A piston is carried by one of the shaft and the housing and is sealingly slidable along the other of the shaft and the housing and is longitudinally movable within the cylindrical bore. A plurality of piston chambers are companionly associated with the piston and is responsive to control of source fluid pressure within a pilot assembly to manipulate the piston.The pilot assembly comprises pilot means within the housing, having valve seat means thereon. Normally free traveling spherical members define valve head means selectively sealingly engagable on the pilot means to open and close the pilot means. A pilot spool permits selective movement of the spherical members to the immediate vicinity of the valve seat means of the pilot means.

Abstract: A plurality of gas actuated valves capable of high-speed action, great prure endurance and withstanding shock, vibration and a marine environment. A sliding member, closing the valves inlet ports, may be retained by a frangible flange. Electrically-initiated gas cartridges produce a rapid pressure rise causing the sliding member to be displaced thereby shearing the flange and allowing the sliding member to uncover the inlet ports for ambient fluid entry. A plurality of O-rings minimize functional sensitivity to external pressure and seal the valve against the entry of the ambient fluid.

Abstract: A pilot operated valve positioner having a pilot valve unit operated by a pneumatic signal to pneumatically operate an actuator unit carrying a main valve member to position the same relative to its main valve seat in a valve unit in relation to the magnitude of the pneumatic signal, the actuator unit having a range spring and a feedback spring for the pilot valve unit. The springs are coiled compression springs and are substantially concentrically mounted. The pilot valve unit has a feedback positioning diaphragm and part of its housing concentrically disposed in one end of the range spring to render the valve positioner relatively small and compact.

Abstract: An unloading valve spool with a tapered nose section is urged across a pair of unloading ports at a controlled rate eliminating violent upstream pressure generation. The unloading valve is subjected to equal system fluid pressure on each side of it as the spool is provided with a through passage that is dead headed on the back side of the unloading spool. A return spring urges the unloading spool to a normally closed position. An unloading piston prevents the unloading spool from closing too rapidly preventing the generation of a significant upstream pressure spike.

Abstract: A surface controlled subsurface safety valve having an operator and a pilot valve. The pilot valve controllably communicates pressurized control fluid to affect the operator and pressure balances the operator. This abstract is neither intended to define the scope of the invention, which, of course, is measured by the claims, nor is it intended to be limiting in any way.

Abstract: Disclosed is a safety valve and hydraulic actuator for the safety valve. The safety valve includes a valve body and a valve member. The hydraulic actuator is adapted to be attached to the valve body and includes a cylinder and piston. A pilot valve controls the pressurizing of the cylinder to affect movement of the piston. This abstract is neither intended to define the scope of the invention, which, of course, is measured by the claims nor is it intended to be limiting in any way.

Abstract: A fluid operated valve in which the fluid from the line in which the valve is placed is used to aid in the opening and closing of said valve. A shuttle valve communicating with both the inlet and outlet chambers of the valve is operable to permit one of said chambers containing fluid under pressure to communicate with an auxiliary chamber in the valve to provide a closing force for the valve.

Abstract: A fluid flow control valve has a bore within which a control member is slidable in response to variations in a servo pressure signal. The control member is also rotatable and includes a relieved portion which co-operates with a control orifice to regulate said servo pressure signal. It is arranged that in a number of discrete rotational positions of the control member the control orifice is shut off to prevent sliding movement, whereby flow through the valve can be set to predetermined levels by rotation of the control element to these positions. In one rotational position all flow is shut off, independent of the sliding position of the control element.

Abstract: A device for opening and closing a rotary valve by remote control comprising a cylinder having a main bore in which a movable unit is slidably mounted in fluid tight manner and which can be displaced in opposite directions by a pressurized fluid supplied by either of two pressurized fluid sources which can be remotely actuated in independent fashion. A sequencing mechanism is mounted in the cylinder for simultaneously applying the pressurized fluid from an activated source to a corresponding end face of the movable unit while connecting the other end face with the atmosphere. The movement of the slidable unit is transmitted to the rotary valve through a rack and pinion arrangement and a linkage composed of cranks and a connecting rod so arranged that when the valve is in either of its end positions it cannot produce movement of the linkage due to alignment of the axis of rotation of the pinion and the connection points of the rod to the cranks.

Abstract: A rapid shutoff extraction check valve has a movable valve body cooperating with a valve seat that divides a valve housing into an upstream housing chamber communicating with the valve inlet and a downstream housing chamber communicating with the valve outlet. The movable valve body is displaceably supported by an actuating piston which is slidably received in a guide cylinder enclosing a pressure chamber. The actuating piston has a radial face exposed to pressure in the downstream housing chamber. An auxiliary valve forming part of the rapid shutoff check valve has a first position in which communication is maintained between one housing chamber and the pressure chamber and a second position in which the pressure chamber is vented. In the first position of the auxiliary valve the actuating piston exerts a closing force on the movable valve body.

Abstract: A surface controlled, sub-surface well valve includes a main valve, a main valve actuator, and a control pressure responsive pilot valve to control application of control pressure to the actuator. The construction is such that the well valve is not affected by changes in pressure of the production flow, or excessive static control pressure in relation to production flow pressure, and irrespective of the depth at which the valve is installed in the well.

Abstract: A flow control valve for an exhaust gas purifying system which is divided into a first valve chamber into which the exhaust gases flow and a second valve chamber out of which the exhaust gases flow. A first valve means responsive to the exhaust gases controls the communication between the first and second valve chambers and a second valve means controls the operation of the first valve means in response to the negative pressure in an air intake system.

Abstract: A hydraulic servo valve assembly and a control system therefor employing a pneumatic sensor-actuator are disclosed. The servo valve assembly comprises a servo-operated power valve assembly including a differential piston, a solenoid operated override and hysteresis adjustment. The valve assembly is a "snap-action" device wherein the power valve differential piston is selectively positioned through use of the pneumatic sensor controlled servo valve to vent the pressure applied to the larger area reaction surface of the piston.

Abstract: Fluid control systems for controlling machine tool operations or other automated mechanical devices. An unlimited number of multiple function systems can be assembled from a basic simple function system employing two-way relay valves which, in their normally blocked state, have a "controlled leakage" venting feature effective to prevent any leakage to outlet and possible system malfunction. Fluid memory can also be built in the system. Simple relay valves, limit valves, pressure control relay valves, time delay relay valves and other variations in spool and slide form provide controlled leakage.

Abstract: This invention relates to pneumatic control systems, particularly to a timing device for the same, wherein a control device is maintained at a constant speed by means of a balance wheel or flywheel, whose kinetic energy furnishes a pneumatic signal and which mechanically shifts a valve to pass on the pneumatic signal. The shifting of the valve is adjustable.