Abstract: A constant speed hydrostatic drive system is disclosed wherein a generator drive shaft is maintained at a constant speed by utilizing an electro-hydraulic controlled displacement pump responsive to a pressure transducer to control a hydraulic motor. A speed sensor is used to produce a direct current signal responsive to the drive shaft speed. The signal is converted into a series of voltage pulses also responsive to the shaft speed which are compared to a speed reference signal to provide a speed error signal. A loop gain control means is provided to utilize said speed error signal to adjust the shaft speed to coincide with said reference signal. A timing reference and digital trim control are also provided to compensate for long term drifting in the type speed control circuit described above.

Abstract: A mini arched bridge is provided with at leat two hollow pans having integral depending sides and ends forming a unitary structure, each side and end of the pans having comparable holes, a plurality of fasteners passing through the holes in adjacent ends of said at least two pans whereby said pans become a single arched member and placing the ends remote from the connection into the earth on opposite sides of the arc to be bridged.

Abstract: A method of manufacturing hemispherical tank heads is disclosed in which a pair of planar lune members having a generally football shape are cut from flat metal stock. The members are each then formed into a three dimensional lune section having a generally orange-peel sectional shape. Each section is placed onto a trim jig and a first edge of the sections are trimmed to leave some excess material beyond a desired trim line. A second edge of each section is then trimmed to a desired trim line. The two trimmed sections are placed on a joining jig with the second edges of the sections juxtaposed and joined to form a hemispherical member. Finally, the hemispherical member is placed onto the trim jig and the excess materials on the first edges is trimmed to form an accurate hemispherical tank head. Preferably, the trim jig is rotated relative to a stationary plasma torch during all trimming operations.

Abstract: A method and apparatus for tunnel lining is provided made up of arcuate liner segments having a formed body with two end walls and two substantially parallel sidewalls, at least two pins extending from one sidewall intermediate its length in the median plane of the body and transverse to said sidewall, a like number of openings in the other sidewall each adapted to receive one of said at least two pins from two adjacent interfitting segments and locking means in said opening permitting insertion of said at least two pins in said openings of adjacent segments and lockingly engaging the same against removal and urging said two adjacent fittings into tight end to end engagement.

Abstract: An impact relief valve and apparatus is disclosed which includes a hydraulic pump connected by two feed lines to a hydraulic cylinder. A first feed line provides fluid below a piston of the cylinder and the second feed line provides fluid above the piston providing a means to cause reciprocal motion of the piston within a cylinder housing. The piston is provided with at least one impact relief valve adapted to be opened upon impact of the piston with the housing at the top of the stroke of the piston whereby when fluid from the first feed line pushes the piston to the top of its stroke, the impact valve or valves are caused to open allowing any additional fluid pressure from the first line to pass through the second feed line to a suction side of the pump thereby reducing power requirements for the pump. An annular ridge on the cylinder head opens the impact relief valves.

Abstract: The present invention relates to a motor control circuit for a stepper motor which causes a motor shaft to oscillate between an incremental rotational position nearest above and nearest below a commanded average rotational position identified by an electrical command signal. A clock is provided for sending periodic clock signal pulses to the control circuit. An up/down counter is connected to the clock for counting clock pulses on each clock cycle and for providing an output signal in the form of a binary representation of total clock pulses. A comparing circuit electrically connected to the up/down counter is used to control an up/down direction of the up/down counter before each clock signal pulse so that the up/down counter causes the motor shaft to rotate to a position nearest beyond the commanded shaft position and to thereafter oscillate between an incremental count nearest above and an incremental count nearest below the commanded average rotational position.

Abstract: A fluid valve structure is provided having spaced first and second inlet sections connected to a source of pressure fluid and a plurality of side by side valve sections between said inlet sections, each having inlet, work and tank chambers intersected by a passage open at opposite ends to a control chamber and a tank chamber at a common pressure, a valve spool movable in said passage and having both ends at a common pressure and grooves adapted selectively to connect the work chamber to the inlet or tank chamber, a lever in the control chamber removably engaging one end of the spool and rotatable about a shaft transverse to the spool axis, and an external handle means operatively engaging the shaft to rotate the lever to move the spool axially in the passage, all of the spool, lever and shaft being fully enclosed with a valve housing in all operative positions.

Abstract: A magnetic detent joy stick and stack remote control valve is provided having a traction magnet detent in which a magnet plate activated by the detent is constantly urged against the coil housing to prevent dirt from getting between the coil plate and coil housing face when the power is cut off and/or the valve is in neutral.

Abstract: An axial piston pump is disclosed which includes a housing, a cylindrical bore in the housing, a piston barrel rotatable in the bore and spaced from the bore walls and an antifriction bearing structure surrounding the barrel between the barrel and the bore. A plurality of axial piston are provided in the barrel which are open at one end and have fluid passages through the barrel at the other end. A piston is provided in each such piston bore which extends out of the open end. A spring is provided between each piston and the other end of the piston bore. A fixed ramp swash plate is provided in the housing bore beneath the extending pistons and an antifriction thrust bearing is provided between the swash plate and pistons. An axial drive shaft is provided on the barrel which extends through an antifriction bearing in an opening in the housing opposite the bore for drivingly engaging on external drive structure.

Abstract: A fluid valve structure is provided having spaced first and second inlet sections connected to a source of pressure fluid and a plurality of side by side valve sections between said inlet sections, each having inlet, work and tank chambers intersected by a passage open at opposite ends to a control chamber and a tank chamber at a common pressure, a valve spool movable in said passage and having both ends at a common pressure and grooves adapted selectively to connect the work chamber to the inlet or tank chamber, a lever in the control chamber removably engaging one end of the spool and rotatable about a shaft transverse to the spool axis, and an external handle means operatively engaging the shaft to rotate the lever to move the spool axially in the passage, all of the spool, lever and shaft being fully enclosed with a valve housing in all operative positions.

Abstract: A gear pump and motor is provided having increased life and efficiency as a result of improved wiping action of the gear teeth on the inner periphery of the pump chamber. This is accomplished by providing a non-smooth surface layer of a dissimilar metal such as a carbide on the tip ends of the teeth.

Abstract: A hydraulic fluid seal, a pressure plate and gear pump are provided in which two spaced adjacent surfaces are sealed, one surface having a groove opening toward the other surface, a sealing member adapted to fit in said groove and a plastically deformable interference member in the sealing member having a section such that it will plastically deform before the seal surface of the sealing member.

Abstract: An air actuator device is provided for manually operable hydraulic valves having a valve spool moving in a bore in a valve housing in the form of an actuator housing adapted for attachment on the valve housing and having a bore carrying a piston coaxially engageable with the spool end, spaced openings in the actuator housing communicating with the bore therein to introduce air to act on opposite sides of the piston and resilient means on at least one side of the piston normally urging the piston and spool to a closed position.

Abstract: An inlet unloader valve is provided for insertion ahead of one or more open center valve work sections having a pressure beyond port, which unloader valve has a spring biased spool, normally closing communication from the inlet to exhaust and proportionally opened by signal pressure from the pressure beyond port and the inlet and exhaust chambers to control flow through the work sections.

Abstract: A remote valve positioning apparatus is provided in which a valve spool is resiliently loaded at each end to a normal position, hydraulic fluid is delivered selectively to one end or the other of the valve spool at a fixed flow and the valve is positioned by pressure drop caused by the fixed flow over an orifice proportional to the stroke of the valve spool.

Abstract: A crib member for forming underground cribbing is provided in the form of a concrete circle containing fibre reenforcing and preferably in the form of a donut shaped member. A plurality of such members is stacked one on top of another to form a cylindrical cribbing.

Abstract: A hydraulic valve is provided which can be modified to provide priority compensation, parallel pressure compensation, inlet check functions and a float function by changing a flow through inlet valve portion in the inlet chamber of the valve.

Abstract: A hydraulic valve is provided which can be modified to provide priority compensation, parallel pressure compensation, inlet check functions and a float function by changing a flow through inlet valve portion in the inlet chamber of the valve.

Abstract: A crib member for forming underground cribbing is provided in the form of a concrete annulus formed within at least one annular metal retaining member so as to form a donut shaped member. A plurality of such members is stacked one on top of another to form a cylindrical cribbing with a central hole.

Abstract: A gear pump structure is provided having a housing with a pump chamber, a suction chamber and a discharge chamber communicating with said pump chamber on opposite sides thereof, a suction port and a discharge port in said housing communicating respectively with the suction chamber and discharge chamber, each of said ports have spaced apart inlet and outlet means, said suction port being contoured to provide on introduction of fluid into the inlet end a point intermediate its inlet and outlet means having a pressure higher than the pressure at the inlet and outlet means, at least one pair of meshing gears mounted for rotation in said pump chamber and each having two axially spaced trunnions, a plurality of bearing means in said housing each having an axial bore mounting said trunnions for rotation in the pump chamber, drive means for rotating said gears so that liquid which is drawn through the suction port into the suction chamber is engaged by teeth on said gears and transferred to the discharge port under p