Abstract: A double-acting hydraulic jack, comprising a hollow piston reciprocable in a surrounding cylinder, includes a tubular shaft extending axially inside and carrying a nut of the circulating-ball type which coacts with a screw coaxially disposed in that shaft. The screw is rigid with the piston whereby an axial displacement of the latter is translated into a rotation of the shaft; a toothed wheel on the shaft, engaged by a spring-loaded detent, acts as a one-way brake enabling such rotation only in one direction and blocking it in the opposite direction unless the detent is withdrawn by a hydraulic servomotor which is pressurized concurrently with the admission of fluid to the cylinder tending to displace the piston in the normally blocked direction.

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 hydraulic cartridge suitable for releasing stores in aircraft relies on a ressurized piston rod which extends upon release of hydraulic pressure. The piston rod is enclosed in a cylinder and connected to a source of hydraulic fluid. Upon arming of the piston rod a hydraulic liquid is pumped into the piston rod and forces out a gas via an accumulation piston. Upon complete filling of the piston rod, a trigger is held in place by the pressurized fluid. Upon release of pressure, the pressure on the trigger becomes unbalanced and a spring releases the trigger from the piston rod permitting it to extend.

Abstract: This invention relates to a motor control unit and a feedback arrangement to minimize the effects of backlash in a rotary output system. The system includes a source of energy. The motor control has a directional control element moveable from a null position. The motor control unit is coupled to the source of energy and to a motor which in turn is coupled to the rotary output and to a second input of a differential harmonic drive that has first and second inputs and an output. The first input of the differential harmonic drive is coupled to a rotational command input unit and the differential harmonic drive output is drivingly coupled to the moveable direction control element. In response to a given rotational command input when the second input is in an initial static position, whereupon the motor is coupled to the source of energy through the motor control unit, the rotary output is driven a precise number of revolutions dependent upon the given rotational command input.

Abstract: Brake equipment for an underground mining machine, which in use traverses to and fro adjacent to a stationary rail extending along a longwall face and which includes a hydraulic haulage drive motor for hauling the machine along the longwall face, is activated to engage the stationary rail if other than a normal haulage condition of the drive motor is sensed, a control for the drive motor being moved into a neutral, machine non-traversing mode when the brake is applied.

Abstract: An improved brake valve for a hydraulically powered winch which has one flow path permitting the relatively unrestricted flow of hydraulic fluid through the valve when the winch is being used to raise a load and a second flow path in which the flow of fluid is controlled in response to the pressure of fluid at the motor inlet when the winch is being used to lower a load. Of particular significance are a fixed area orifice, an annular restrictive passageway and a variable area orifice which cooperate to distribute the pressure drop in the control circuit so as to reduce the sensitivity of the valve to pressure fluctuations in the hydraulic motor circuit. Also of significance are seals used on the spool and damper piston to retard the movement of the spool and to produce a desirable hysteresis effect in its response to pilot pressure.

Abstract: A grooved winch drum is driven by a reversible hydraulic motor. A pump supplies fluid to the motor through a system using an electrically controlled four-way, flow direction valve associated with a counterbalance valve and a manually adjustable flow control valve. The four-way valve controls the direction of drum rotation and the flow control valve regulates the drum rotational speed. The motor drives the drum through a planetary gearing which includes a ring gear normally held from rotation by a friction clutch band, spring biased into engaged position but releasable by the application of hydraulic pressure from a separate pump supplied through a second system that includes a second flow control valve. The flow control valves for the motor and clutch are each associated with a cam operator mounted on a shaft rotated by a lever which also carries a three position electrical switch to control the four-way valve.

Abstract: An improved hydraulic control circuit is disclosed for use in crawler type vehicles and the like in which relief valves as used in conventional circuits are eliminated. The resulting hydraulic circuit is not apt to be damaged by surge pressures and high pressures in the return passages, are simple in their design and more convenient to fabricate.

Abstract: Brake equipment for a mining machine which in use traverses to and fro adjacent to a stationary rail extending along a longwall face and which includes a haulage drive motor for hauling the mining machine along the longwall face, the brake equipment being activated to fixedly engage the stationary rail if other than a normal haulage condition of the drive motor is sensed.

Abstract: Disclosed is a mechanical locking device for locking a rod in a conventional hydraulic actuator, such as a hydraulic cylinder or a rotary actuator. The device comprises a radially contractible locking ring having a cylindrical inner surface for gripping the rod when the locking ring is contracted and an outer surface which is axially inclined, means for positively securing the locking ring around the rod in a position axially fixed in at least one direction with respect to the actuator housing, a ring-contracting member around the locking ring and having an inner surface which is axially inclined at the same angle as the outer surface of the locking ring for engaging that surface, and means for applying an axial force to the ring-contracting member in the direction of the inner surface axial inclination to cause the ring-contracting member to slide axially on the locking ring thereby causing the locking ring to contract and grip the rod.

Abstract: A parking brake for use primarily on railway vehicles of the mass transit type in conjunction with the service brake apparatus but operable independently thereof. A parking brake hydraulic cylinder is mechanically connected to the brake shoe hanger of the brake unit. After the vehicle has been brought to a stop, a parking brake application may be made by supplying pressure, by a handpump, to the hydraulic cylinder which also includes a lock-nut actuable by the pressure, in excess of a certain pressure for locking the parking brake hydraulic cylinder in its applied position. A relief valve is provided for relieving the hydraulic cylinder of hydraulic pressure when the application is to be released.

Abstract: The invention is a hydraulic control system for use in positioning and clamping a movable object on a support, which system is adapted to be connected to a source of pressurized hydraulic fluid, to a hydraulically operated piston-cylinder assembly connected to the movable object for moving the movable object and to a hydraulically operated clamp and which comprises a path for the supply of pressurized fluid to and from the hydraulically operated clamp, a check valve in the path which check valve normally prevents return of fluid from the hydraulically operated clamp, a hydraulically operated pilot piston movable between a non-actuating position and an actuating position in which it opens the check valve, a path for the supply of pressurized fluid to the piston-cylinder assembly, which path is connected on its high pressure side to the hydraulically operated pilot piston, and a switching valve for controlling the supply of pressurized fluid to the piston-cylinder assembly, the arrangement being such that when

Abstract: The invention relates to a servo assembly having a stationary part including a housing, a movable member and a servo motor. Of primary interest is the stopping mechanism which includes a stop unit on the movable member and two pressure operated, vertically reciprocal stop members mounted in the housing. Two hydraulic circuits are provided with a first circuit for the two stop members and the second circuit for the servo motor. Throttle valving for the first circuit is provided between the two stop members and the housing. Prior to reaching a stopping position the stop unit on the movable member actuates a switch which relieves the pressure in the first circuit and causes one of the stop members to descend to an intermediate position where throttling occurs and the other stop member to descend to a final position where throttling may or may not occur. The throttling causes substantial braking of the movable member during a short distance of travel just prior to the stopping position being reached.

Abstract: The motor grader drawbar assembly has a blade mounted on a circle gear and a drive unit operatively connected to the circle gear to selectively rotate it and the blade. A plurality of radially mounted pistons operate against an upright wall of the circle gear to provide a brake and/or locking mechanism. The pistons, and their accompanying cylinders, are mounted in members which also underlie and support the circle gear. Thus, the vertical position of the circle gear is not affected by the braking operation. A hydraulic circuit is provided to alternately operate the drive unit and the braking operation.

Abstract: A hydraulic system and latching mechanism for a cab tiltably mounted to the chassis of a vehicle. The cab is normally disposed over the engine of the vehicle and is pivotally attached to the chassis at its forward end for movement through 90.degree.. The cab is powered by an air-motor-actuated hydraulic pump which energizes lifting cylinders disposed between the chassis and cab. When the system is energized, a hydraulically actuated latch is released prior to commencement of the tilting movement of the cab. A direction-control valve is employed which, when in the neutral or closed position, utilizes the pressures generated in the hydraulic system by the weight of the tilted cab in certain positions to assist the valve in sealing the reservoir port in the valve against leakage thereby preventing the cab from creeping.