Abstract: A pulse valve assembly including a main valve and a pilot valve that selectively actuates the main valve.

Abstract: A hydraulic system includes a hydraulic pump, a first hydraulic actuator, a second hydraulic actuator, a first control valve to control the first hydraulic actuator, a second control valve to control the second hydraulic actuator, a pressure increasing portion to increasing a pressure of the operation fluid, a first discharge fluid tube connected to any one of the first control valve and the second control valve and connected to the pressure increasing portion, a second discharge fluid tube connected to the first discharge fluid tube and configured to discharge the operation fluid, a float switching valve having an allowance position, a prevention position, and a float position, the allowance position blocking the second discharge fluid tube and allowing the operation fluid to flow to the pressure increasing portion, the prevention position unblocking the second discharge fluid tube and preventing the operation fluid from flowing to the pressure increasing portion.

Abstract: The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.

Abstract: An actuator system for an aircraft includes an actuator, and a control valve system operatively connected to the actuator. The control valve system includes a first direct drive valve (DDV) mechanically connected to a second DDV. A backup valve system is operatively connected to the actuator. The backup valve system includes one of an electro-hydraulic servovalve (EHSV) and a DDV.

Abstract: A hydraulic actuator includes a hydraulic cylinder; a piston within the hydraulic cylinder and movable in response to movement of hydraulic fluid in a hydraulic circuit coupled to the hydraulic cylinder; a synchronisation connection for receiving an input from a simultaneous transmission line; and a valve for controlling the flow of hydraulic fluid in the hydraulic circuit. The valve is a rotary valve comprising: a first valve section arranged to rotate in either a first rotational direction or a second rotational direction in response to input from the simultaneous transmission line in order to open a hydraulic flow path to the cylinder and urge the piston to move along the hydraulic cylinder in a corresponding first linear direction or second linear direction; and a second valve section arranged to rotate in either the first or second rotational direction.

Abstract: There is provided a die cushion device that includes a cushion pad, a hydraulic cylinder configured to lift the cushion pad, and a hydraulic closed circuit connected to a die cushion pressure creation chamber of the hydraulic cylinder. The hydraulic closed circuit includes a pilot drive type logic valve that is operable as a main relief valve at the time of the die cushion operation, and a pilot relief valve configured to create pilot pressure for controlling the logic valve. Hydraulic oil is filled in the hydraulic closed circuit, in a pressurized manner, and the hydraulic oil in the hydraulic closed circuit is pressurized by only die cushion force applied from the cushion pad through the hydraulic cylinder, in one cycle period of the cushion pad.

Abstract: The invention relates to a hydraulic system comprising a source of high pressure (A), a consumer (C) connectable to the source of high pressure (A) via a flow control valve (21), and a solenoid valve (22) arranged to control the flow control valve (21). The hydraulic system further comprises a hydraulic pilot valve (31) selectively controllable by the solenoid valve (22) to connect a control chamber (28) in the flow control valve (21) either to the source of high pressure (A) or to a low pressure side (T). When the solenoid valve (22) is actuated, the consumer (C) is pre-pressurized via a by-pass conduit prior to the opening of the flow control valve (21). At the same time, the source of high pressure (A) is arranged to act on a first and a second end (32, 33) of the hydraulic pilot valve (31) wherein a spring (36) is arranged to displace the hydraulic pilot valve (31) and connect the control chamber (28) to the low pressure side (T) to open the flow control valve (21).

Abstract: A control valve comprises a first spool 22, a second spool 24 encircling at least part of the first spool 22 and angularly moveable relative thereto, and a sleeve 32 encircling at least part of the second spool 24, the second spool 24 being angularly moveable relative to the sleeve 32, the first and second spools 22, 24 having first and second series of ports 28, 30 registrable with one another, depending upon the relative angular positions of the first and second spools 22, 24, to control communication between at least a pressure line 16, a return line 18 and a control line 50 provided in or connected to the sleeve 32, the second spool 24 and the sleeve 32 having third and fourth series of ports 66, 68, axially spaced from the first and second series of ports 28, 30 and registrable with one another, depending upon the relative angular positions of the second spool 24 and the sleeve 32, to control communication between at least the control line 50 and the return line 18, and latch means 56 operable to resist

Abstract: A control force transmission arrangement for an aircraft is provided. A transmission device has a first and a second force transmission point, and a coupling unit disposed between them. The coupling unit has a first and a second side element and a connecting element. The first and the second side elements are each connected to the first force transmission point and to the connecting element. At least the first side element has an element for altering the length of the side element. The second force transmission point is provided on the connecting element and is adjustable at least between a first and a second position.

Abstract: A floating piston actuator for use with multiple hydraulic systems includes a housing and a piston assembly. The piston assembly includes an elongate shaft or ram, at least one secured piston coupled to the ram, and a set of moveable pistons moveably disposed within the housing chamber on the ram such that the set of moveable pistons are translatable relative to a longitudinal axis of the ram. The set of moveable pistons form at least three hydraulically separate actuator cylinders where each of the three hydraulically separate actuator cylinders are disposed in fluid communication with a corresponding pressurized fluid source. The floating piston actuator allows hydraulic redundancy while maintaining a similar length compared to existing multi-system actuators. The floating pistons can be arranged in multiple configurations to allow operation with a hydraulic system failure without force fight or binding and with a higher output force than conventional multi-system actuators.

Abstract: A hydraulic cylinder system 1 is provided with a plurality of cylinders 3a and 3b, valves 4a and 4b provided at each of the cylinders 3a and 3b for adjusting amounts of operating fluid into and out of the cylinders 3a and 3b, driving systems 5a and 5b having motors 6a and 6b provided at each of the valves 4a and 4b for driving the valves 4a and 4b, and a connecting member 8 for connecting the motors 6a and 6b of the driving systems 5a and 5b in a manner capable of interlocking with each other.

Abstract: The present invention relates to a hydraulic distributor (2) of a servo-control (1) of an aircraft, the hydraulic distributor comprising main distributor member (10) and emergency distributor member (20) that are coaxial, said emergency distributor member (20) being caused to move by said main distributor member (10) in the event of said main distributor member (10) seizing, said hydraulic distributor being provided with a detector device (60) for detecting said seizing. The detector device (60) is provided with a reed switch (66) and with amplification means (62, 69, 68) for amplifying said movement of the emergency distributor member, said amplification means comprising a lever (62) having a magnetized free end (62?) that activates said reed switch (66) in the event of said emergency distributor member (20) moving.

Abstract: A hydraulic actuator is configured to provide redundant boost control to an aircraft within approximately the same space required by a single hydraulic cylinder. The hydraulic actuator includes a housing and a piston assembly disposed within the housing. The piston assembly includes a ram, a first piston secured to the ram, and second and third pistons disposed on the ram such that the second and third pistons are translatable relative to the longitudinal axis of the ram. The pistons form two hydraulically separate actuator cylinders within the space required by a single cylinder which results in a reduction in the weight and size of the hydraulic actuator.

Abstract: A hydraulic control apparatus includes two oil flow control valves (30, 32) each provided with a supply control portion (36, 38, 52, 54) for controlling an oil supply from a pressurized oil source, and a discharge control portion (40, 42, 56, 58) for controlling connection with a discharge passage. One of those oil flow control valves supplies/discharges oil to/from one of hydraulic chambers (22, 24) that are oppositely formed in a hydraulic servo mechanism. An operation direction of the hydraulic servo mechanism is performed by operating one of the oil flow control valves. The other operation direction of the hydraulic servo mechanism is performed by operating the other oil flow control valve.

Abstract: A hydraulic actuator is configured to provide redundant boost control to an aircraft within approximately the same space required by a single hydraulic cylinder. The hydraulic actuator includes a housing and a piston assembly disposed within the housing. The piston assembly includes a ram, a first piston secured to the ram, and second and third pistons disposed on the ram such that the second and third pistons are translatable relative to the longitudinal axis of the ram. The pistons form two hydraulically separate actuator cylinders within the space required by a single cylinder which results in a reduction in the weight and size of the hydraulic actuator.

Abstract: A hydraulic system includes a reservoir for a hydraulic fluid, a pump, a high-pressure line network, a low-pressure line network and operating cylinders each of which can be connected to the high-pressure line network or to the low-pressure line network via control units, each operating cylinder is associated with a local compensation volume element.

Abstract: The present invention relates to a hydraulic distributor (2) of a servo-control (1) of an aircraft, the hydraulic distributor comprising main distributor member (10) and emergency distributor member (20) that are coaxial, said emergency distributor member (20) being caused to move by said main distributor member (10) in the event of said main distributor member (10) seizing, said hydraulic distributor being provided with a detector device (60) for detecting said seizing. The detector device (60) is provided with a reed switch (66) and with amplification means (62, 69, 68) for amplifying said movement of the emergency distributor member, said amplification means comprising a lever (62) having a magnetized free end (621) that activates said reed switch (66) in the event of said emergency distributor member (20) moving.

Abstract: Two or more flow control valves may be used to provide redundant flow control for a hydraulic actuator or servoactuator. The flow control valves include a sleeve, a bypass control spool, and a primary control spool. Under normal operating conditions, each bypass control spool is stationary relative to the sleeve and the flow control valve functions as a four-way hydraulic flow control valve. Each flow control valve is connected to a bypass-shutoff valve including a bypass spool that is moveable from a shut-off position to a bypass position. Upon supply pressure failure to one flow control valve, the bypass spool moves to the bypass position, reducing pressure in the corresponding actuator piston chambers. When a primary control spool becomes jammed, the corresponding bypass control spool moves within its sleeve allowing a bypass groove to port control pressure to the return line, thereby reducing pressure in the corresponding actuator piston chambers.

Abstract: Methods and apparatuses for controlling aircraft devices with multiple actuators. An apparatus in accordance with one embodiment of the invention includes a first actuator coupled to a first power system having a first probability of failure, the first actuator being coupleable to at least one moveable component of an aircraft system. The apparatus can further include a second actuator coupled to a second power system having a second probability of failure less than the first. The second actuator can be operatively coupled to the first actuator and can be coupleable to the at least one moveable component, for example, to operate simultaneously with the first actuator. A second force applied by the second actuator can be less than a first force applied by the first actuator. Accordingly, the second power source can be reduced in size by virtue of the reduced probability of failure for the first power system.

Abstract: The invention concerns a hydraulic dual circuit steering system with first circuit having a first control unit and a first steering motor connected with the control unit via working connections, a second circuit having a second control unit and a second steering motor connected with the control unit via working connections, a changeover valve, which in a first position activates the first circuit and deactivates the second circuit and in a second position activates the second circuit and deactivates the first circuit. To improve the steering behaviour, in the first position of the changeover valve the working connections of the second circuit and in the second position of the changeover valve the working connections of the first circuit are connected with a pressure source.

Abstract: A switching system is described herein for an engine having redundant control components. The switching system generally includes an actuator, a control system, inlet and outlet lines, and a transfer valve. The actuator is operable to control an engine parameter. The control system includes a first electrohydraulic servo valve and a second electrohydraulic servo valve, the first and second servo valves being fluidically connected to the actuator for operating the actuator. The inlet line supplies pressurized fluid and the outlet line drains fluid. The transfer valve is positioned between the first and second servo valves and the inlet and outlet lines. The system may further include additional control systems with redundant EHSVs. This invention minimizes size and space requirements, and allows nearly simultaneous transfer of all control systems, while minimizing the transient disturbance to the control system(s).

Abstract: Provision of a fail-safe circuit which is capable of allowing a sub circuit to operate with reliability when a main circuit encounters abnormal conditions even in a system with only one supply source of pressure oil. A plurality of solenoid type control valves (3, 6) connected to an actuator (1) in parallel have centering springs respectively and are maintained at a neutral position in normal conditions. Each control valve is provided with a supply port, a return port and two actuator ports and is configured such that in the neutral position, the supply port and the return port are communicated with each other and interrupts communication with the actuator ports.

Abstract: A hydrostatic steering arrangement with two control systems, each of which has a control unit with an inner and an outer rotary slide and a steering motor, one steering handwheel being common for both control units, and the control units being arranged in series in the axial direction of the rotary slides. On a failure of one control unit it is desired that the steering can be continued with a relatively high accuracy. For this purpose, a common inner rotary slide is provided for both control units.

Abstract: An actuator for opening a poppet exhaust valve, which is closed by a spring and opens in normal operation against a relatively low pressure and which opens for compression braking against a relatively high pressure, is motivated in either event by the same hydraulic pressure. The actuator has a unitary central valve and piston element, which is coaxially directed toward the exhaust valve stem and has an area providing, when subjected to the pressure, a force sufficient to open the exhaust valve for normal operation but insufficient to open the exhaust valve during compression braking. The element extends through a relatively larger diameter annular piston which is slidably fitted about the element and within a bore receiving the annular piston. In normal operation, the element provides enough force to move from an unactuated position and open the exhaust valve, and initial movement of the element closes off passages in the element that admit the pressure to the piston which thus does not move.

Abstract: A high speed and high load operable hydraulic drive cylinder system comprises a principal cylinder (3) with a piston (3a)) defining an upper and a lower chamber (3c, 3d) and a piston rod (3b), and a subsidiary cylinder (2) smaller in pressure receiving area than the principal cylinder and a piston (2a) defining an upper and a lower chamber (2c, 2d) and a piston rod (2b) smaller in diameter than the piston rod (3b).

Abstract: This directional valve comprises a closing element (1) rotatively mounted in a fixed sleeve (5) disposed in a body (2) with interposition of an annular element (4) between the closing element and the sleeve. Means are provided for locking the annular element against rotation in normal use and for permitting the driving of the annular element by the closing element in the event of a seizing of the closing element in the annular element. These locking means comprise a device (12) having a push member (13) mounted laterally on the body at one end of the closing element (1) and extending in a direction perpendicular to the closing element (1), resilient means (15) being provided for biasing the push member against a rocker (30) inside the body, the thrust of which is applied to locking balls (21) which project from recesses (24) provided in an end of the annular element (4).

Abstract: A high speed safety circuit arrangement is provided for a hydraulic press which is driven by a hydraulic cylinder assembly constituted by a principal cylinder unit and a subsidiary cylinder unit. The circuit arrangement comprises a servo valve disposed in one of at least a pair of conduit lines for supplying a pressure fluid from a source thereof into the principal cylinder unit and the subsidiary cylinder unit, a first logic valve disposed in the other of the conduit lines and switched on and off and by the servo valve and a first electromagnetic valve for opening and closing that other conduit line, a second and a third logic valve of which each is switched on and off, and at least one is selectively actuatable, by a second electromagnetic valve to interconnect an upper and a lower chamber of the principal cylinder unit in a hydraulic circuit.

Abstract: The main control servo valve responsive to electrical input signals modulates a power piston to position a throttle valve that varies the flow of fluid during normal operation. A transfer servo valve responsive to the pressure in the servo system moves hard over upon sensing a low pressure signal that is normally lower than the system's pressure to cause the power piston to position the throttle valve closed. In the preferred embodiment the system throttles compressor air of a gas turbine engine to provide an anti-icing function and activates the transfer servo valve upon a hard over malfunction.

Abstract: A system and method for controllably positioning a hydraulic actuator which is operably connected to a control surface includes at least one main control valve for controlling the hydraulic pressure supplied to the actuator in response to a control signal indicative of a predetermined actuator position and at least one parallel control valve for supplying additional hydraulic pressure to the actuator in response to an error signal indicative of the difference between the position of the actuator and the predetermined actuator position to thereby correct for any differences indicated by the error signal. By correcting for any differences indicated by the error signal, the errors in positioning the control surface can be decreased and the stiffness of the control surface can be increased.

Abstract: A fluid-operated brake actuator having a hollow actuator rod between a spring chamber of a spring brake housing and a spring chamber of a service brake housing incorporates a valve within the actuator rod. The valve isolates the two spring chambers from each other in normal operation and releases a vacuum in the spring brake housing spring chamber when the spring brake is activated. A separate one-way check valve mounted in a well of the spring brake housing permits fluid to exhaust from the spring chamber to atmosphere and prevents contaminants in the atmosphere from entering the spring chamber.

Abstract: A system of modular electrohydraulic servovalves is centrally controlled may be used to control the operation of critical hydraulic actuators. A programmable controller operates a group of modular servovalves which each deliver a portion of the total actuator fluid requirements. The flow rate, valve position, and valve pressure of each servovalve is monitored by the controller and compared to expected values in memory to determine whether a servovalve malfunction exists. If so, the controller maintains the required flow rate to the actuator by closing the malfunctioning valve and either activating a spare or proportionally increasing the flow rates of the remaining servovalves to compensate for the loss.

Abstract: In a servo steering system for motor boats comprising a steering wheel which mechanically acts on the position of a hydraulic control valve, and a rubber cylinder connected to a hydraulic power unit by way of the control valve, the control valve comprises an additional adjustment unit which is connected to an autopilot unit and is controllable by this latter. In this way both normal servo-assisted hand-steering and autopilot steering are made possible in a simple manner.

Abstract: In a hydraulic system for roll stabilization of a vessel by motions of the rudder an arrangement for supplying a hydraulic fluid to the rudder engine comprises a constant delivery pump, a pressure accumulator, and a valve gear unit. While the valve is opened the hydraulic fluid is delivered by the pump and the accumulator, and when the valve is closed the pump fills up the accumulator to maximum working pressure. The valve gear unit comprises a proportional control valve for controlling period, direction and flow rate of the hydraulic fluid to the steering engine and a load compensation device for controlling the returning flow returning via the proportional control valve for compensating for irregular loads from the waves or the sea against the rudder.

Abstract: A monitoring system for detecting a fault condition in any one of multiple power control actuator units used for positioning an aircraft's control surface includes sensors for producing sense signals corresponding to the load on each actuator unit under a given control surface loading condition. The sense signals are compared with a reference level signal corresponding to a maximum allowable load. An indication is produced in response to the load on any actuator unit exceeding its allowed value.

Abstract: A dual hydraulic motor system where motor wobblers are mechanically linked and the motor outputs are torque summed, is controlled by a three position dual valve assembly. Each valve assembly is controlled by pilot pistons that are mechanically linked to provide three functions, one being normal operation, a second where one motor must be shut-off and its load on the system is minimized and the third where both motors are shut-off and significant drag is then provided. These functions are implemented by a separate spool in each valve which has three independent stable positions.

Abstract: Actuator control system includes two parallel connected orifices between a pair of fluid passages providing communication between an actuator and a flow control valve. Relief valves in series with the respective orifices block fluid flow through the orifices at low differential pressures between the fluid passages, thereby preserving the original high pressure gain of the control valve in a region about valve null. At higher differential pressures outside the valve null region, the relief valves open to permit restricted flow through the respective orifices to reduce the pressure gain of the control valve in a region outside the valve null region, which effectively reduces the stiffness of the control valve.

Abstract: A bidirectional flow communication passageway is provided by the present invention in a multiple-circuit fluid pressure responsive system on a motor vehicle to allow a gradual reduction of pressure in a parking brake circuit which is a part of such system. The passageway is restricted to limit such bidirectional flow to a predetermined level. The pressure reduction permitted is sufficient to activate a parking brake valve in such parking brake circuit when a defect occurs in an operating service brake circuit which is also a part of such system.

Abstract: An aircraft flight control system for use with a dual or tandem hydraulic actuator coupled to a flight control surface through an actuating rod. Each half of the tandem actuator is controlled by a respective electrohydraulic servovalve. Each electrohydraulic servovalve is controlled by signals applied to either of two actuating coils. Control signals are applied to the actuating coils from three controllers. The control signals are generated as a function of the difference between the flight control signal and a feedback signal indicative of the position of the actuating rod. Each electrohydraulic servovalve includes a pair of linear variable differential transformers generating feedback signals indicative of the position of the valve stem in each electrohydraulic servovalve. The valve feedback signals are compared to each other and to reference signals corresponding to the expected value of such feedback signals in order to detect and identify malfunctions in the flight control system.

Abstract: In one form of the present invention, a plurality of serovalves are connected to a common manifold. The manifold transmits fluid pressure from the servovalves to a modulator piston which controls the fluid pressure applied to a hydraulic actuator piston. The servovalves are designed such that, if the fluid pressure provided by any one of them to the manifold falls below a threshold, then the servovalve disconnects itself from the manifold, allowing control of the modulator piston to be assumed by the remaining, functioning servovalves. The present invention can be used in control surface actuators of short takeoff and landing (STOL) aircraft.

Abstract: Flight control system for aircraft of the type provided with ailerons, elevators, upper surface spoilers, and upper surface air-brakes, a rudder and horizontal stabilizers with variable angle of incidence, said system comprising an electric control, in some cases without any mechanical emergency control for said upper surface spoilers and air-brakes.According to the invention:the ailerons and elevators are electrically controlled without any mechanical aid,the rudder is mechanically controlled, andthe horizontal stabilizers with variable angle of incidence are electrically controlled with mechanical aid.the electrical flight controls are optimized.

Abstract: A servoactuator unit to operate flight-control mechanisms, in particular for control of the position of the oscillating plate which adjusts the cyclic pitch and collective pitch of helicopter rotors, in which two pairs of hydraulic actuators are used, connected together in parallel, arranged with their axes parallel and close together like the diagonals of a quadrilateral, their rods connected together at their end and acting on the said oscillating plate and the cylinders also being connected together at the back. Each pair of actuators is powered, through a servovalve, by an independent hydraulic circuit so as to enable operation even in the event of one of the pairs breaking down, with symmetrical stress being placed on the pair of actuators during operation.

Abstract: A fault detector for a triplexed mechanical or hydromechanical system which provides for improvement in cost, reliability and weight over previously known balance beam arrangements for achieving redundant two-channel operation to provide a fail-operating first failure mode for operation of aircraft components which require reliable operation for flight safety. The fault detector for a triplexed mechanical or hydromechanical system has a tripodal summing member which receives three mechanical position signals in three different channels with the tripodal summing member retaining a position perpendicular to the force transmitted by the tripodal summing member in response to the position signals and tipping when one of the input signals deviates significantly from the other two.

Abstract: Check device for a redundant flight control apparatus comprising at least two servo drive devices. Failure in supplying fluid and wedging of a control valve (20) can be simulated. Failure of the bypass valve (35) can be checked by reading and comparing the volume flows of the respective pumps as well as by evaluating the travelling rate of the servo drives (1, 2) by the pilot.

Abstract: A hydraulic fluid powered actuation system preferably for controlling the position of a control surface of an aircraft in response to a plurality of redundant control signals is disclosed. The system comprises an actuator adapted to be mounted in the aircraft, comprising a housing having first and second cylinders with a piston moveably mounted within each of the cylinders. A piston rod connects the pistons and is adapted to engage the control surface. Two rotary torque motors having a common drive shaft are provided which are adapted to receive the plurality of redundant controls signals. First and second rotary control valves, coupled to the drive shaft, and thus, adapted to be driven by the rotary torque motors, are used to control the emission and exhaust of hydraulic fluid from the first and second cylinders, respectively. Preferably, there are four control signals and the torque motors are DC, multiple-poled torque motors with each coil on each torque motor coupled to a different control signal.

Abstract: An actuator system for controlling the position of an aerodynamic control surface of an aircraft is disclosed. The actuator system (10) comprises a rotary actuator (12) rotatably mounted to the aircraft structure (20) with the actuator having an output member (22) adapted to be coupled to the control surface. A latch assembly (37) is provided which is mounted to the structure which releasably engages the actuator. Preferably, the latch assembly (37) comprises a grooved flange (38) mounted on the actuator (12) and a solenoid (47) mounted to the aircraft structure which is adapted to move a locking pin (44) from a first position in engagement with the grooved flange (38) to a second position out of engagement with the groove. In a second embodiment, a second rotary actuator (114) is mounted to the aircraft structure and is adapted to rotate the actuator (81) upon its failure and after the latch assembly is activated.

Abstract: An equalizer is arranged to continuously sense the control pressures of two valves. In the event of a differential between the control pressures, the equalizer operates to selectively adjust one valve so that the control pressures of both valves will thereafter be substantially equal.

Abstract: A fluid servo actuator control/damping mechanism and method which utilize and combine the functions of an electro-mechanically driven servo valve to achieve ram or actuator fluid flow and load control even after loss of fluid power as well as the main ram position control function under normal operating conditions.

Abstract: A redundant, dual-fail/operate fly-by-wire control system actuates a redundant tandem piston actuator (10) to provide a single composite output evidenced by movement of a piston rod (12). The basic fault-tolerate actuation system consists of dual hydraulic primary actuators, quadruplex electrical control loops (14-17), and control servo valves (22-25). A failure management system connects to the actuation system by means of lines (18-21) to control the servo valves (22-25). The four control loops (14-17) connect to a pilot controller that provides a pilot individual input signals to amplifiers (26-29) for each of the control loops. A tracking loop (450) includes switches (480, 482, 484) for connecting the four control loops (14-17) and providing isolation therebetween.

Abstract: The invention is directed to a multi-motor actuation system for a power drive unit. The system includes three independently hydraulically controlled motors adapted to be drivingly coupled to a power drive unit output. Two of the said motors are normally active at all times and the third motor acts as a back-up motor to provide redundancy for the two normally active motors. A hydraulic failure detection mechanism is controllingly coupled to the three independently hydraulically controlled motors. The hydraulic failure detection mechanism is responsive to any failure of one of the normally active hydraulically controlled motors to thereby cause the third motor to be coupled to the power drive unit. The failure detection mechanism is additionally responsive to a failure of both normally active hydraulically controlled motors to cause the third motor to take over the functions of both of the normally active hydraulically controlled motors.

Abstract: A fluid-operated brake actuator having a hollow actuator rod between a spring chamber of a spring brake housing and a spring chamber of a service brake housing incorporates a valve within the actuator rod. The valve isolates the two spring chambers from each other in normal operation and releases a vacuum in the spring brake housing spring chamber when the spring brake is activated. A separate one-way check valve mounted in a well of the spring brake housing permits fluid to exhaust from the spring chamber to atmosphere and prevents contaminants in the atmosphere from entering the spring chamber.