Abstract: An arrangement for supervising and controlling synchronous displacement of respective pistons of two cylinder-and-piston units, especially of an advancement and a roof cap displacement unit of a roof support assembly for use in underground mining, comprises first and second conduit systems each having two branches each connected with one of the piston and annular spaces of a different one of the units; a switching valve interposed between pressure and a return conduits and the first and second conduit systems; and first and second shut-off valves respectively interposed in those of the branches of the first and second conduit systems which lead to the piston spaces.

Abstract: In a combine header having a rotatable crop reel, a hydraulic cylinder is carried on each of the reel support arms for adjusting the fore and aft position of the reel. The cylinders are serially connected and comprise a phasing circuit wherein the cylinders have paired fluid inlets and flow-restricting orifices, and the piston is positionable between the inlet and orifice of a pair in either full-strode position. A check valve is operationally associated with each orifice to prevent loss of fluid acting on the piston when being moved from either full-stroke position.

Abstract: A hydraulic press having at least two cylinders adapted for providing relative displacement between the upper and lower platens of a hydraulic press, each cylinder being in fluid communication with only one chamber of a multiple chamber hydraulic system utilizing a common ram operating through all chambers, the ram portion in each chamber having a predetermined ratio of area of the ram in the direction of actuation to volume of hydraulic fluid within its chamber to provide equal find displacement in each chamber or movement of the ram.

Abstract: A hydraulic control arrangement for providing synchronism of a return cylinder between a face conveyor and a support, has a pushing cylinder which displaces the support transverse to a face, a control valve, a control cylinder influencing loading of the pushing cylinder via the control valve, and a control column provided between the return cylinder and the control cylinder and composed of a working fluid.

Abstract: A conveyor belt tensioning system having two fluid piston and cylinders units on each lateral side of the belt. The units are parallel to each other and are attached to a tensioning roll. A pair of cables are attached to both of the pistons and pass around pulleys in a manner as to compensate for any differences in force between the pistons such that the pistons move in the same direction the same amount.

Abstract: An apparatus for synchronizing a plurality of actuators, comprising a pressure fluid source 15 associated with a setting device 6, with transmitters 10 of the movements of the operating members 5, and also with multichamber adding elements 17 equal in number to the actuators 4 to be synchronized.

Abstract: A hydraulic system for synchronizing telescoping sections of a crane boom comprising a fixed section and second, third and fourth sections that can be extended and retracted, hydraulic cylinders between the sections for extending and retracting the adjacent sections relative to one another and a control valve for each cylinder. Cables are provided between the sections such that a non-uniformity in movement of the sections causes a change in displacement of the cables which is sensed by position sensing devices to provide a hydraulic pilot signal for modifying flow of hydraulic fluid to the cylinders.

Abstract: In a pivotally mounted rock drill boom and feed bar apparatus, the pivots of the boom and the feed bar positioner include angle sensors comprising cam actuated fluid pressure regulating valves. The pressure regulating valves are disposed in a control circuit which includes a pilot pressure fluid actuated control valve which senses an unbalanced pressure signal generated by the sensor connected to the boom pivot in response to movement of the boom about said pivot. The control valve responds to the unbalanced pressure condition by valving fluid to the feed bar positioner actuator to maintain the feed bar in a predetermined directional attitude. The angle sensor mounted on the boom pivot may be adjusted independent of movement of the boom to cause a change in the directional attitude of the feed bar as desired.

Abstract: Disclosed is a cabtilt system comprising conventional hydraulic tilting cylinders, a cock sensing member, and a synchronizing valve which causes one of the hydraulic tilting cylinders to slow or stop its motion until the other cylinder catches up with it if the cock sensing member senses that the cab is cocking as it tilts.

Abstract: In combination, a tractor having at its rear end an implement hitch and a lift system and an implement coupled at one end to the hitch and having at its other end a height adjusting system for controlling the working depth of the implement. The lift includes a first hydraulic cylinder and the height adjusting system includes a second or remote hydraulic cylinder. The tractor has a pump providing a source of fluid under pressure. An auxiliary services valve is in communication with the fluid source and a phasing valve, the two valves being selectively in communication with one another.The auxiliary services valve is operable to independently actuate the first hydraulic cylinder to raise the hitch or to coact with the phasing valve to serially couple the second hydraulic cylinder to the first hydraulic cylinder to provide synchronous actuation of both cylinders to raise both ends of the implement to a fully raised position.

Abstract: The invention relates to a method and apparatus for maintaining relative positional alignment between two spaced-apart points on a moveable member, such as a rotating axle on which is mounted a conveyor belt pulley. The invention comprises a hydraulic pump (80) which is operatively communicated to first and second hydraulic cylinders (21and 30, respectively). The first hydraulic cylinder (21) applies a reference hydraulic pressure to a first point (13) on the axle (11) and moves the axle (11) to maintain the pressure at a constant, pre-determined pressure level. The second hydraulic cylinder (30) is operatively connected to a second point (12) on the axle (11) spaced apart from the first point (13). A fork (77) and pin (42) mechanism senses relative movement between the first point (13) and the second point (12) on the axle (11).

Abstract: In a press with two parallel, spaced apart multiple-acting cylinders that have their respective pistons connected to end portions of a beam to which a bending or forming tool is secured, the cylinders are respectively fed from effectively separate pressure fluid sources providing equal pressures and flow rates. For synchronization of piston extension through an initial rapid advance, the chamber of each cylinder that is normally pressurized for retraction of its piston is connected in feedback relation to the pressure fluid source for the other cylinder, so that fluid expelled from a leading cylinder augments the fluid supply to the lagging one. The system further comprises a pair of sensors, one for each beam end, and a synchronizing bleed-off valve for each sensor.

Abstract: In a pivotally mounted rock drill boom and feed bar apparatus the boom and the feed bar positioner include angle sensors comprising cam actuated fluid pressure regulating valves. The pressure regulating valves are disposed in a control circuit which includes a pilot pressure fluid actuated control valve which senses an unbalanced pressure signal generated by one of the sensors in response to pivotal movement of the boom. The control valve responds to the unbalanced pressure condition by valving pressure fluid to the feed bar positioner actuator to maintain the feed bar in a predetermined directional attitude. The angle sensor responsive to pivotal movement of the boom may be adjusted independent of movement of the boom to cause a change in the directional attitude of the feed bar as desired.

Abstract: A control device is designed for center pivot irrigation units of the type having an elongate water carrying pipe with a plurality of support vehicles spaced therealong, and wherein each of the vehicles includes a double acting hydraulic cylinder mounted thereon for moving the vehicle and the water pipe over the ground. The irrigation unit includes a device for aligning the vehicles, a hydraulic pump with pressure and return lines, and power and retract manifolds respectively interconnecting power and retract sides of the cylinders. The control device includes a hydraulic valve with three positions which communicate the pressure line with the power manifold, the retract manifold, and the pump return line respectively.

Abstract: A parallel actuator pair force transmission system including a mechanical feedback apparatus capable of detecting differential movement between the actuator pair and providing a feedback signal to control valves phased in such a manner as to correct for and counteract the differential motion between the actuator pair.

Abstract: There is described a servo-control system incorporating a double-acting ram which is responsible for compensating electro-hydraulically for the imbalance in a servo-controlled load in order to achieve a high performance. To this end, a compensating loop is produced which slaves a balancing pressure P.sub.e to the variations in the imbalance. This pressure is exerted in one of the chambers of the ram, separately from the control pressure. It is governed by a pneumatic accumulator whose load is a function of the lack of balance between the pressure exerted by the imbalance and the balancing pressure.

Abstract: A power piston apparatus, comprising two or more double acting hydraulic piston drive means in which the cross-sectional areas of the pistons are identical and the cylinder spaces or chambers of which are hydraulically interconnected in crossed fashion above and below the pistons in the case of two cylinders, while being connected in series in the case of more than two cylinders having separately closed oil spaces of identical volumes, with each such oil space being connected to a positive-pressure oil supply through check valves for replenishing the leakage oil, and wherein said piston drive means have associated therewith metering cylinders with a coaxial and/or parallel direction of stroke, i.e. with mechanical connections between the ends of the piston rods.

Abstract: An improved master cylinder in which a pair of orifices extend through the cylinder wall and means is provided on the exterior of the cylinder to permit fluid communication therebetween. The orifices are located near the end of the cylinder to permit restricted flow around the piston in the master cylinder when it is near or at the end of its stroke to cause both the master and slave piston to complete their strokes and at substantially the same time. A similar pair of orifices and an exterior communication means at the other end of the cylinder provides for re-phasing during piston movement in the opposite direction.

Abstract: A hydraulic synchronizing system which comprises a double piston power source and a drain valve in fluid communication with the hydraulic lift cylinders of a vehicle mounted vibratory seismic energy source. The double piston power source supplies the hydraulic lift cylinders with substantially equal volumes of hydraulic fluid, and the drain valve adjusts the flow of hydraulic fluid out of the hydraulic lift cylinders. The system synchronizes the operation of the hydraulic lift cylinders and thus coordinates movement of the vibrator guide rods relative to the vehicle upon which the vibrator is mounted.

Abstract: Hydraulic mechanism controlling approach and separation of relatively movable platens of a press is provided to maintain them in parallel relation. If one of two columns of the press advances relative to the other, the advanced column is slowed by restricting fluid flow return from its cylinder. Diagonally opposite cylinders in a four-column press are thus controlled.

Abstract: A hydraulic positioning drive with a physically separated work cylinder which is connected via pressure oil lines, comprises a follow-up cylinder mounted at the positioning drive or in the immediate vicinity thereof, of the same type and the same volume as the work cylinder, which is hydraulically connected in series with the latter, so that its piston moves synchronously with that of the work cylinder. The piston position of the follow-up cylinder is sensed electrically and used as the positioner position. For synchronizing, both cylinders are connected in parallel from time to time and their pistons are run into the end positions.

Abstract: A mobile tree harvester includes a shear mounted at the base of a harvesting frame for shearing a tree trunk, a grip arm pivotably mounted to the frame above the shear for gripping the tree trunk, delimbers mounted above the grip arms for removing branches from the trunk, and an endless tract mounted on each grip arm for propelling the tree trunk along the forward frame. Lift arms pivotably couple the forward frame to a main body of a wheeled vehicle. A sway mechanism is coupled to both lift arms to provide for relative movement of one lift arm with respect to the other such that the harvesting frame can sway from the vertical position in a left or right direction. A tilt mechanism is coupled to the harvesting frame, lift arm, and main body to maintain the frame in its vertical ground position as the lift arms lift the frame off the ground. The tilt mechanism also tilts the frame about an axis transverse to the vehicle axis to a horizontal position such that the sheared end of the tree trunk faces rearwardly.

Abstract: The invention relates to hydraulically powered shears for metal sheets and plates and particularly to an improvement in the means for adjusting and controlling the rake angle or slope of the movable shear knife in such machines. In the present disclosure a rod member is pivoted at one end and normally is disposed along a line parallel to the direction of reciprocation of the ram of the shear. The upright member has a cable connection with a servo valve which controls the fluid circuitry of the shear to adjust the relative positions of the hydraulic motor means at opposite sides of the ram to change the inclination of the ram.When the rod member is in normal position the servo valve is blocked and the rake angle is maintained but when the rod member is adjusted angularly in either direction it operates through the cable means to adjust the servo valve in one direction or the other to change the relative vertical positions of the motor means.

Abstract: The invention is especially suitable when front and rear wheels are hydraulically steered, each set by its own hydraulic cylinder, the two cylinders being connected in hydraulic tandem so that the same angularity of steering will be imparted to both sets of wheels. The self-synchronizing of the present invention overcomes a serious prior fault that occasionally a nonsynchronous relationship would develop. The present invention opens a synchronizing valve on the occasion of each extreme swing of the wheels. A check valve then ensures a synchronized return swing.

Abstract: Synchronizer apparatus is provided in or for multi-section telescopic jibs comprising travel sensors each to be carried by a moveable jib section in at least one group of at least three sections, one of the sensors being adapted for interconnection with two travel sensors carried one by each of two other sections in the group for sensing disproportionate travel of one moveable section relative to travel of a further section with respect to another section, a signal device actuable by the sensors of each group and operative means for connecting the signal device to a power transmission valve associated with rams respectively operatively connected to the said one and said further moveable sections for controlling the travel of at least one of them to remove any disproportionate travel.

Abstract: A plurality of fluid-operated rams, e.g., for positioning the rolls of a sheet-metal bending machine, are each actuated by a respective servovalve and are each connected to a respective potentiometer whose output resistance varies in accordance with the position of the ram. The rams are grouped in pairs and one potentiometer of each pair is energized with positive voltage, the other with negative voltage so that a combined signal can be produced indicating the relative positions of the two rams of the pair. The combined signal representing the position deviation is fed to two separate amplifiers where it is combined with voltages of opposite polarity and then fed to the servovalves of the pair of rams. Thus the one servovalve is closed partially if its ram advances on the other ram. Similarly a plurality of such rams can be interconnected with all but at most two rams from two different pairs so that all ram positions will be equalized.

Abstract: A hydraulic control system for use for precise control of the height of the earth working blade on road graders, and in particular for use in combination with road graders that are automatically controlled. The control system is selectively operable, and when engaged will permit only simultaneous movement of the two cylinders used for controlling the depth of the earth working blade.

Abstract: Hydraulic control apparatus for automatic remote control of a hydraulic actuating ram. The apparatus has a double-acting slave cylinder connectable hydraulically to an actuating ram, and a double-acting master cylinder the piston of which is mechanically connected to the piston of the slave cylinder, the master cylinder being operable by hydraulic pressure supplied via a pilot-operated valve arranged automatically to reverse the stroke of the master ram at limits set according to the desired stroke of the actuating ram. The control apparatus may be used for controlling actuating rams which effect reciprocating pivotal movement about one or more axes of a water jet monitor.

Abstract: A rock drill having a control valve hydraulically operable to effect feed of oil from a bulk reservoir alternately to opposite ends of a power piston carrying a drill string to reciprocate the piston; having a motor for rotating the piston as the latter reciprocates; having a snubber for absorbing shocks in the event of piston override; and having carriage means automatically and hydraulically operable during reciprocation of the piston to feed the tool along a guide channel relative to the work.