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 connected to a downstream side of the first control valve and configured to control the second hydraulic actuator, a return fluid tube in which return fluid discharged from the first hydraulic actuator flows, the return fluid tube coupling the first control valve and the first hydraulic actuator, an internal fluid tube arranged in the first control valve and connected to the return fluid tube, an external fluid tube connected to the internal fluid tube, the external fluid tube coupling the first control valve and the second control valve, a branched fluid tube branched from the external fluid tube and connected to a discharge fluid tube, and a pressurizing portion provided to the discharge fluid tube.

Abstract: A hydraulic system of a construction machine includes: a pump that supplies hydraulic oil to a hydraulic actuator; a control valve on a center bypass line extending from the pump to a tank, the control valve including a bypass passage; an unloading valve on the center bypass line downstream of the control valve; and a controller that controls the unloading valve. The control valve is configured such that an opening area of the bypass passage is greater than an opening area of the unloading valve while an operation signal outputted from an operation device increases from a predetermined value to a first setting value, and such that the opening area of the bypass passage is less than or equal to ¼ of a maximum opening area of the bypass passage when the operation signal is greater than or equal to a second setting value greater than the first setting value.

Abstract: A hydraulic system includes a first hydraulic device, a second hydraulic device, a first control valve to control the first hydraulic device, a second control valve disposed on a downstream side of the first control valve and configured to control the second hydraulic device, a communication tube connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, a connection fluid tube disposed on the first control valve, the connection fluid tube connecting the communication tube to the supply fluid tube, a discharge fluid tube connected to the first control valve, a setting portion disposed on the discharge fluid tube and configured to increase a pressure in the discharge fluid tube, a branching fluid tube branched from the connection fluid tube and connected to the discharge fluid tube, and a throttle disposed on the branching fluid tube.

Abstract: A hydraulic system of a work machine includes a first hydraulic actuator, a first control valve, a first oil passage, a second hydraulic actuator, a second control valve, a second oil passage, and a bypass oil passage. The first control valve is connected to the first hydraulic actuator to control the first hydraulic actuator. The first oil passage is connected to the first control valve to supply hydraulic oil to the first control valve. The second control valve connected to the second hydraulic actuator to control the second hydraulic actuator. The second oil passage connects the second control valve and the first hydraulic actuator via the first control valve. Hydraulic oil returning from the first hydraulic actuator to the first control valve is to be supplied to the second control valve through the second oil passage. The bypass oil passage connects the first oil passage and the second oil passage.

Abstract: A fuel circulation system and methods are provided. The system includes a supply pump for providing an outlet flow of fuel. The system also includes at least a first and a second servo. The first servo is connected to an outlet of the supply pump. A flow regulation device is interposed between the first and second servos. At least a portion of the outlet flow from the supply pump is directed through the first servo, flow regulation device, and second servo and is returned to an inlet of the supply pump.

Abstract: A hydraulic arrangement for lifting and/or lowering at least one implement carrying arm on an agricultural machine. The arrangement comprises an inlet hydraulic line and an outlet hydraulic line connecting a fluid pump (18) and a fluid reservoir (26) respectively to a first valve means (12), said arrangement comprising at least one dual acting hydraulic cylinder (15) for lifting/and or lowering the implement carrying arm. The at least one cylinder is connected to the first valve means (12) allowing the cylinder (15) to be switched between a single acting mode wherein the arm can be lifted and a double acting mode wherein the arm can be lifted and lowered.

Abstract: The invention relates to a hydraulic manifold apparatus and system, connectable to a dual stage motor, for use in the topdrive of drilling operations. The hydraulic manifold is switchable between a low speed, high torque configuration and a high speed, low torque configuration. Valves within the manifold control the flow of working fluid through the manifold and into and out of the motor. Switching means are further provided to control the opening and closing of the valves. In the low speed, high torque configuration, working fluid enters each stage of the dual motor simultaneously, in parallel. In the high speed, low torque configuration, working fluid enters a first stage of the motor, returns to the hydraulic manifold, then enters a second stage of the motor, before returning again to the hydraulic manifold. Thus during high speed, low torque operation, working fluid enters each stage of the dual motor in series.

Abstract: A hydraulic strut assembly, for use in a semi-levered landing gear in an aircraft, comprising an actuator and a manifold associated with the actuator. The actuator comprises a housing, a first piston, a second piston, and a third piston. The first piston is positioned between outer and inner cylindrical structures of the housing. The outer and inner cylindrical structures and first piston form an outer chamber that receives a first fluid. The inner cylindrical structure, the first piston, and the second piston, which is nested within the first piston, form an inner chamber, which holds a second fluid comprising a gas. A volume of the inner chamber changes when at least one of the first and second pistons moves. The third piston is positioned between the outer cylindrical structure and the first piston. The first, second, and third pistons move in a direction parallel to an axis through the housing.

Abstract: An air pump comprises a main cylinder, a main piston, a piston rod, a linkage, and a pre-charger. The main piston is reciprocably movable within the main cylinder and defines a compression volume between the main piston and a first end of the main cylinder. The piston rod is connected to the main piston and extends along the main cylinder towards a second end. The linkage is configured to move the main piston and to generate pressure in the compression volume during a compression stroke, the linkage having ends pivotably connected to the main cylinder and to the piston rod. The pre-charger has a pre-charger piston movable within a pre-charger cylinder and is connected to the linkage to move within the pre-charger cylinder when the main piston moves within the main cylinder, the pre-charger generating pressure to augment operation of the main piston and main cylinder.

Abstract: A hydraulic drive system is mounted on a hydraulic excavator, and is provided with a directional control valve 23 for a boom, a directional control valve 24 for an arm, a boom control device 25 for selectively controlling the directional control valve 23 for the boom, and an arm control device 26 for selectively controlling the directional control valve 24 for the arm. The directional control valves 23, 24 control a boom cylinder 6 and an arm cylinder 7, respectively, which are driven by pressure oil delivered from a main hydraulic pump 21. The hydraulic drive system is provided with a communication control unit for communicating a rod chamber 6b of the boom cylinder 6 and a bottom chamber 7a of the arm cylinder 7 with each other when a stroke of the arm control device 26 has become a predetermined amount S or greater.

Abstract: Hydraulic actuating device comprising a first and a second hydraulic actuator, which actuators have a first and a second connection for the supply and discharge of hydraulic fluid, which connections are in communication with a first and a second chamber, respectively, by way of a first and a second opening, respectively, in the cylinder space. The first opening of the second hydraulic actuator is in communication with the first opening of the first hydraulic actuator. The second opening of the second hydraulic actuator is in communication with the second opening of the first hydraulic actuator via a third connection. The third connection is in communication with the cylinder space in the first hydraulic actuator via a third opening. Damping means are achieved by a restriction of the outflow of hydraulic fluid via the second opening before the piston/piston rod assembly reaches the second end position.

Abstract: The invention relates to a catapult drive for an object to be accelerated, preferably the car of a fairground ride, wherein the object is accelerated by means of a driving element. The movement of the driving element is produced by a flexible drive and a hydraulic cylinder via which all movements of the driving element can be controlled. The invention also relates to a control system for suitably controlling the inventive catapult drive.

Abstract: An actuator having two or more interconnected movement components, wherein the movement components are designed as linear actuators with substantially coaxial longitudinal axes or longitudinal axes that are parallel to each other and that are interconnected in longitudinal direction such that their linear movements are superimposed on one another, and such that at least one of the linear actuators can be stopped at one or several predetermined positions.

Abstract: A multistaged telescope boom, where a hydraulic unit, comprising a piston and a cylinder, is arranged between successive, telescopic arms, comprises a hydraulic system connecting to said hydraulic units for the operation thereof and which is designed to force the hydraulic units of at least the two innermost arms for filling a cylinder chamber of one of these cylinders (9, 10) at the time starting from that of the innermost arm and outwardly in the order of the arms when extending the boom and draining said cylinder chambers in the opposite order when retracting the boom. At least the hydraulic unit of said innermost arm is provided with an arrangement adapted to isolate the cylinder chamber of that first cylinder from communication with said hydraulic system when the cylinder is fully extended and re-establish said communication upon fully retraction of the cylinder next to said first cylinder.

Abstract: To permit using hold-side pressure oil in a first hydraulic cylinder for the acceleration of a second hydraulic cylinder upon performing a combined operation of the first and second hydraulic cylinders, a hydraulic drive system is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a directional control valve 23 for a boom and a directional control valve 24 for an arm, and a boom control device 25 and an arm control device 26. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamber 6b of the boom cylinder 6 to an upstream side of the directional control valve 24 for the arm when a bottom pressure of the arm cylinder 7 has increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valve 44 arranged in a reservoir line 42 which can communicate to the rod chamber 6b of the boom cylinder 6.

Abstract: A series hydraulic circuit for permitting motorized operation and independent control of a plurality of cutting decks of a mower. The circuit allows separate operation of one of the decks while enabling operation of one or more of the other decks associated with the mower to simultaneously occur.

Abstract: A hydraulic force control system is disclosed for controlling the clamping force applied to a load by the clamp arms of a clamping attachment of a load-lifting vehicle to prevent the arms from over- or under-clamping the load. The system includes a force control circuit interposed between the vehicle's conventional hydraulic circuit and clamp cylinders of the attachment that operate the arms. When a manual control valve in the conventional circuit is moved to operate the clamp arms, a load sense cylinder in the control circuit lifts a load carriage of the attachment, causing the pressure side of the sense cylinder to sense the weight on the load carriage. Carriage movement actuates a sequence valve in the control circuit to hydraulically connect the pressure sides of said sense and clamp cylinders so that clamping force applied to a load by the clamp arms is proportionate to the weight of the load.

Abstract: The invention relates to a hydraulic drive, especially for two-cylinder thick matter pumps. Said hydraulic drive comprises at least one main pump (10) embodied as a hydraulic variable displacement pump, and two hydraulically actuatable drive cylinders (20, 22) that are each connected to a connection line (16, 18) of the main pump (10) by means of pump connections mounted on one end thereof, forming a closed hydraulic circuit, and communicate with each other at the ends thereof opposing the pump connections (24, 26) by means of a swinging oil line (28). The hydraulic drive also comprises a feed pump (42), by which means pressurized oil is fed from an oil tank to the current low-pressure side into the hydraulic circuit, and a flushing branch (52), by which means a flushing oil flow is branched off from the current low-pressure side under a limited pressure into the oil tank (44).

Abstract: Apparatus and methods are provided for pumping concrete using a pumping apparatus including first and second drive cylinders, a valve, and a pump. Fluid is delivered into the cylinders from the pump to reciprocate pistons within the cylinders. Pressure within the cylinders is monitored, and a direction of flow of the fluid is switched based upon the pressure within the cylinders. For example, during rod-side operation, the valve is set to deliver fluid into a head side of the cylinders. When the pressure exceeds a predetermined threshold, the valve switches to head-side operation, and fluid is delivered into a rod side of the cylinders. If the pressure falls below the threshold, the valve switches the cylinders back to rod-side operation.

Abstract: The present invention relates to a hydraulic actuating device for a device having a first and a second hydraulically moveable component. This actuating device comprises a first and a second hydraulic actuator, respectively, for moving the first and second moveable components. The first and second actuators each have a housing in which there is a space in which a piston and piston rod assembly can move in a reciprocating manner, with a piston and a piston rod which is coupled to the piston and projects out of the housing. The piston delimits a first working chamber and a second working chamber in the housing. The housing is provided with a first and a second connection, which are respectively in communication with the first and second working chambers in order to supply and discharge hydraulic fluid in order to displace the piston and piston rod assembly.

Abstract: A description is provided of a volumetric operating system (10) for scissors-type vehicle lifts, comprising a plurality of cylinders (16, 18, 20, 22) for movement of the vehicle lifting runways (12, 14), of which the main cylinders (16, 22) receive the operating fluid directly from supply means (24, 28, 30), and the secondary cylinders (18, 20) receive the operating fluid from the outlet (32, 34) of a respective one of the main cylinders (16, 22), wherein with each runway (12, 14) there is associated at least one of the said main cylinders (16, 22), and at least one of the said secondary cylinders (18, 20). Preferably, the outlet of each main cylinder (16, 22) which is associated with one of the runways (12, 14) supplies a secondary cylinder (18, 20) which is associated with the other runway (12, 14).

Abstract: A hydraulic lift device for an attaching device of a tractor which has a hydraulic pressure supply device and a hydraulic tank, comprising for each of two lower steering arms, a double acting hydraulic cylinder having a cylinder housing, a piston rod, a piston with a piston-end piston area and a piston rod-end piston area, as well as a piston-end cylinder chamber and a piston rod-end cylinder chamber. The device further comprises a first switching valve, which has at least three switching positions and four ports. The first port represents a connection to the pressure supply device. The second port represents the connection to the hydraulic tank. The third port represents the connection to the piston-end cylinder chamber of the first hydraulic cylinder and the fourth port represents the connection to the piston rod-end cylinder chamber of the second hydraulic chamber.

Abstract: A fluid control system is disclosed that includes a reservoir, a pump in fluid communication with the reservoir, a first double-acting actuator having a first head end chamber and a first rod end chamber, a second double-acting actuator having a second head end chamber and a second rod end chamber. The first and second double-acting actuators are selectively fluidly connected via a conduit. A first independent metering valve is configured to selectively provide fluid flow to the first and second double-acting actuators, and a second independent metering valve is configured to selectively provide fluid flow to the first and second double-acting actuators. The fluid control system also includes a proportional valve attached to the conduit between the first double-acting actuator and the second double-acting actuator. The proportional valve is capable of operating the fluid control system in either an independent function mode or a regenerative function mode.

Abstract: A fluid control system is disclosed that includes a first double-acting actuator and a second double-acting actuator. A first independent metering valve has a first control port connected to the first double-acting actuator, a second control port connected to the second double-acting actuator, first and second independently operable valves disposed between the inlet port and the first and second control ports, and a first check control mechanism having a main check valve between the inlet port and the first and second independently operable valves. The first check control mechanism controls the main check valve to allow the first and second actuators to operate in either an independent function mode or a regenerative function mode.

Abstract: A wood splitting apparatus has a parting blade and a platen which undergo reciprocating motions in mutually opposite directions by means of a pair of hydraulic cylinders. After the parting blade splits off a portion of a sawn log horizontally, the portion which has been split off is dropped and then pushed by the platen into and through a cutting block provided with a plurality of knives so as to be cut into smaller pieces. The pair of hydraulic cylinders is directly connected by a pipe through which a hydraulic liquid can flow back and forth therebetween and is together controlled by a single valve for power economy. The floor of the cutting block is of an inverted V-shape and the knives are oriented such that the intervals therebetween increase on the downstream side so as to prevent jamming of the apparatus by the wood pieces.

Abstract: A high versatility can be obtained, the pipe laying can be configured easily and, by virtue of the fact that a pilot pressured oil is managed, a hydraulic apparatus can be compacted. A differential pressure &Dgr;P between a pressure of the pressured oil on an upstream side and a pressure of the pressured oil on a downward side of operation valves is set to a certain value by a front-to-rear differential pressure stabilizer. As a result, flow rates Q1, Q2 of the operation valves are determined univocally in accordance with opening surface areas (opening amounts) A1, A2 of the operation valves, irrespective of load fluctuations, that is to say, a fluctuation of &Dgr;P. When one of operation members are operated, the opening amount A2 of the other operation valve correspondent with the other operation member is changed in accordance with an operation amount S1 of that operation member, and the other hydraulic actuator correspondent with the other operation valve is driven.

Abstract: A series hydraulic circuit for permitting motorized operation and independent control of a plurality of cutting decks of a mower. The circuit allows separate operation of one of the decks while enabling operation of one or more of the other decks associated with the mower to simultaneously occur.

Abstract: There is provided a chuck having four radial jaw grooves, two pairs of opposed jaws movably provided in the grooves, a first rotary vane actuator for actuating one pair of the opposed jaws, and a second rotary actuator for actuating the other pair of the opposed jaws, an inlet for admitting fluid into chambers of the actuators, and an outlet for discharging fluid from the chambers. The first and second vane actuators are opearated by the fluid admitted from the one inlet such that the two pairs of opposed jaws are differentially actuated by said first and second rotary vane actuators. The first rotary vane actuator includes a first pressure chamber and the second rotary vane actuator includes a second pressure chamber, in which the first and second pressure chambers are in fluid communication via at least one fluid-conducting path.

Abstract: An actuator assembly that has a constant net pressure area telescoping piston. The actuator assembly has a cylindrical housing; nesting, telescoping pistons; a central plug; an outer cap; and a vent. The cylindrical housing has an interior surface and a base that terminates at an open end. The nesting, telescoping pistons are located in the housing and can extend past the housing open end. The telescoping pistons have an outer piston slidably sealed against the housing and an inner piston that is slidably sealed against the outer piston. The outer piston has a first end proximal to the housing base, and a second end distal to the housing base. The inner piston has an open end proximal to the housing base, and a closed end distal to the housing base. The central plug extends from the base and into the telescoping pistons. The central plug is in pressurized communication with the inner piston and is engagable with a pressurized fluid source. The outer cap has a first and a second member.

Abstract: An apparatus for felling and bunching trees is disclosed. The apparatus includes a front frame and a front axle supported by the front frame. The apparatus further includes a number of front wheels mounted on the front axle and a work tool supported by the front frame. The work tool has a blade for felling trees and a number of work arms which are movable to secure the trees within the work tool. The apparatus further includes a front hydraulic motor operable to rotate the front axle. The front hydraulic motor is supported by the front frame. The apparatus yet further includes a first hydraulic pump operable to supply pressurized hydraulic fluid to the front motor. The apparatus still further includes a rear frame which is pivotably coupled to the front frame, a rear axle supported by the rear frame, and a number of rear wheels mounted on the rear axle. The apparatus still further includes a rear hydraulic motor operable to rotate the rear axle. The rear hydraulic motor being supported by the rear frame.

Abstract: A power machine has a base, an operator support portion, and a hydraulic slew motor coupled to move the operator support portion relative to the base. A boom, an arm, and a tool are all coupled to one another and to the operator support portion and are powered by hydraulic actuators. A slew valve is coupled to receive hydraulic fluid under pressure from a hydraulic power circuit and is also coupled to the slew motor to provide hydraulic fluid to the slew motor and receive hydraulic fluid from the slew motor. A first power actuator valve is coupled to receive hydraulic fluid from the slew valve and is coupled to provide hydraulic fluid to one of the hydraulic boom actuator, the hydraulic arm actuator and the tool actuator. The slew valve is coupled in series with the power actuator valve.

Abstract: The telescoping system includes a first fluid motor and a second fluid motor. The first fluid motor includes a first extension chamber and a first retraction chamber, and the second fluid motor includes a second extension chamber and a second retraction chamber. A hydraulic control system in the telescoping system controls the supply of hydraulic fluid to the first fluid motor and between the first fluid motor and the second fluid motor such that the first and second fluid motors operate independently.

Abstract: A boom and drive train hydraulic system is described having a pressure source, preferably a pump operated by a motor, said pressure source providing hydraulic fluid at a high pressure to a first set of valves used to operate the drive train of the system. The first set of valves is equipped with a power beyond for allowing the hydraulic fluid to flow from the first set of valves to a second set of valves. At the second set of valves a pressure control is provided to reduce the pressure to a desired lower pressure. The second set of valves provides the hydraulic fluid at this reduced pressure to the boom portion of the system. The differential of the pressures is approximately 5,000 psi for the track system and approximately 2,500 psi for the boom system.

Abstract: Frame sections on an implement are supported above the ground by lift wheel assemblies having positive mechanical depth stops and series connected lift cylinders. A pressure responsive bypass valve is installed in series with an orifice between the ports of the series connected cylinders. The valve permits the corresponding cylinder to be retracted and positively held against the depth stop and allows bypass flow to the next cylinder in series for continued retraction of the next cylinder until it bottoms against the stop. The orifice protects the bypass valve poppet from damaging high flows and controls the rate of descent of the other frame sections onto the remaining stops. The system permits the cylinders to positively maintain the down-stopped positions of the sections without unwanted looseness typical with slotted or other lost motion types of connections. A restrictor valve may be added to limit the maximum pressure so that all the bypass valves cannot open at the same time.

Abstract: A hydraulic system for use in an automotive vehicle. A source of hydraulic pressure selectively operates in two modes. In one mode, it feeds a radiator cooling fan and a power steering system in parallel when a system pressure or flow exceeds a predetermined pressure rate. In another mode, it feeds the radiator cooling fan and the power steering system in series when the system pressure or flow is less than the predetermined pressure or flow.

Abstract: A fluid control system for powering vehicle accessories includes a pump for generating a supply flow of hydraulic fluid, and a supply line for receiving the supply flow of hydraulic fluid. The system further includes a fan control circuit in fluid communication with the supply line, wherein the fan control circuit includes (1) a hydraulic motor and a bypass valve, and (2) the hydraulic motor is positioned in parallel with the bypass valve. The system also includes a steering control circuit in fluid communication with the fan control circuit, wherein (1) the steering control circuit requires a first predetermined flow of hydraulic fluid from the fan control circuit for proper operation thereof, and (2) the bypass valve and the hydraulic motor cooperate so as to create a second predetermined flow of hydraulic fluid. Moreover, the system includes a sensor for detecting operational pressure within the fluid supply line and generating pressure status signals in response thereto.

Abstract: An aerial lift unit is truck mounted. The lift includes a lower boom pivoted to the truck and an upper boom pivotally connected to the outer end of the first boom. A lower boom cylinder unit is connected to pivot and thereby raise and lower the lower boom. A second tandem cylinder unit consists of first and second cylinders with the head end interconnected and having cylinder rods extending coaxially outwardly from the opposite rod ends. The one cylinder rod is connected to the lower boom and the second piston rod is connected to the base of a V-shaped coupling member having one arm pivotally connected to the lower boom and a second arm is pivotally connected to the upper boom. The second cylinder positions the upper boom in a preset orientation with respect to the lower boom. The first cylinder is connected in a hydraulic supply circuit with the lower boom cylinder and with the hydraulic fluid flow serially through the lift cylinder and second cylinder.

Abstract: A self-leveling system controlling a boom (13) and a bucket (15) by double acting cylinders (17, 19). The system includes a self leveling valve assembly (27) including a first valve section (27a) including a flow divider spool (41) whereby flow from the rod end of the boom cylinder (17) is divided, one portion flowing to the head end of the bucket cylinder (19). The valve assembly also includes a second valve section (27b) including a flow dividing spool (61), whereby flow from the head end of the boom cylinder (17) is divided, a portion flowing to the rod end of the bucket cylinder, as the boom (13) is lowered. The self leveling valve assembly (27) includes capability whereby, even when the bucket cylinder (19) is fully extended or fully retracted, it is still possible to operate the boom cylinder (17).

Abstract: A regenerative adaptive fluid motor position feedback control system integrating a load adaptive fluid motor position feedback control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary constant displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: The hydraulic circuit of the invention includes first and second directional control valves 13, 15, each shiftable between three positions. Hydraulic circuit extending from the second directional control valve 15 and a second cylinder 7 to a first cylinder 11 is so configured that, when the second directional control valve 15 is shifted to the first position, with the first directional control valve 13 being assigned to the N-position, hydraulic oil from the second cylinder 7 is directed to the first cylinder 11, so as to cause the attachment 9 to be tilted in the forward direction, and when the second directional control valve 15 is shifted to the second position, hydraulic oil expelled from the second cylinder 7 is directed to the first cylinder 11, so as to cause the attachment 9 to be tilted in the rearward direction.

Abstract: A pneumatic cylinder, especially for a spot-welding machine, has a sleeve valve mounted on the piston rod. The sleeve valve provides a venting valve for dumping pressure from a return chamber at the end of the forward stroke, and a progressive restrictor to close off a forward chamber and provide cushioning at the end of the return stroke.

Abstract: A tailgate locking apparatus for a refuse container comprises first and second locking cylinders for locking the tailgate in the closed position. The first and second locking cylinders are movable between a tailgate locked position and a tailgate unlocked position. Each of the first and second locking cylinders comprises a piston assembly disposed within its interior volume. The piston assembly comprises a piston and a piston rod extending from the piston through a central opening in an upper portion of the cylinder. The piston divides the interior volume into a lower chamber and an upper chamber. The upper chamber of the first locking cylinder is fluidly connected to the lower chamber of the second locking cylinder.

Abstract: A tilt angle control system has first and second sensors for sensing the position of the rod end portion of first and second lift jacks. A controller calculates an actual tilt angle of an implement connected to the rod end portions of the lift jacks based on a difference in the amount of extension relative to a baseline. A display device displays the actual and desired tilt angles. The controller compares the actual tilt angle to a desired tilt angle and actuates a fluid operated system to move one of the first and second jacks in response to a difference between the desired and actual tilt angles. An inclinometer sensed angle of the machine relative to a horizontal plane is added to the actual tilt angle to correct the actual tilt angle of the implement. The tilt angle control system is particularly suited for use on a bulldozer.

Abstract: A hydraulic system having a first bucket leveling circuit for controlling leveling of the bucket during raising of the boom and a second bucket leveling circuit for controlling leveling of the bucket during lowering of the boom. The second bucket leveling circuit includes a motor-type flow divider having first and second shaft connected motor sections. Controls are operative when the boom control valve supplies fluid under pressure to the rod end of the boom cylinder for passing fluid from the piston end of the boom cylinder to the inlet of the first and second sections of the motor-type flow divider, and for preventing passage of fluid from the piston end of the boom cylinder to the inlet of the first flow divider.

Abstract: A telescoping robot arm with singularity-free three degrees of motion freedom spherical joints is disclosed. The telescoping section and spherical joints are hydraulically operated to achieve a high power-to-weight ratio and use conventional seals of the type normally used on hydraulic pistons. The spherical joints of the instant invention are comprised of a generally spherical cavity containing a tiltable member with integral a retractable arcuate vanes interdigitized with retractable arcuate vanes in a non-tiltable member. A plurality of cavities is formed within the spaces between the interdigitized arcuate vanes of the instant invention, with the volume of these intervane cavities being controlled with an equal plurality of hydraulic valves. A plurality of spherical joints of the present invention may be interconnected with double acting telescoping sections of the present invention to form a robotic arm assembly.

Abstract: A device for raising and lowering a paper roll used in a printing press. This device is comprised of an inverted U-shaped frame made up of a horizontal member supported by two vertical members. Two hydraulic cylinders are supported by the horizontal member so that each extends substantially parallel to a vertical member of the frame. A hydraulic power unit is attached to the top of the horizontal member to actuate the hydraulic cylinders. A hydraulic directional control valve controls the direction of flow of hydraulic fluid in order to effectuate the extension and retraction of the hydraulic cylinders and thereby raise and lower the paper roll.

Abstract: The present invention includes a method for improving operating efficiency of a hydraulic actuator loop and an improved hydraulic actuator loop. The method includes transferring hydraulic fluid between a first and a second hydraulic actuator when the actuators are disengaged from a load and transferring hydraulic fluid from an energy source to each of the actuators separately when the actuators engage the load. The method also includes transferring fluid from the energy source to the first actuator when the actuators are approaching the load and transferring fluid from the first actuator to a drain when the actuators are retracting from the load.

Abstract: A hydraulic fluid Pressure-operated actuator comprises a first cylinder assembly having an output which operatively carries a second cylinder assembly such that an axial output force is effected from an output shaft of the second cylinder assembly, the output from the second cylinder assembly is a fast forward output stroke which is followed by a greatly increased high pressure force generated by the first cylinder assembly and effected through the output shaft of the second cylinder assembly.

Abstract: The combined pneumatic-hydraulic press with controlled stroke, includes a body inside which a substantially cylindrical main chamber is defined; the main chamber accommodates, so that it can slide along an axial direction, a working piston which protrudes from the body with its stem. The working piston delimits, in the main chamber, a first compartment which contains a liquid and is connected, through a passage, to a secondary chamber which is provided with elements for exerting pressure on the liquid contained in the secondary chamber in order to transfer at least part of the liquid from the secondary chamber to the first compartment in order to axially move the working piston.

Abstract: The combined pneumatic-hydraulic press head includes a body inside which a substantially cylindrical main chamber is defined; the chamber accommodates a main piston and a secondary piston so that they can slide along an axial direction. The main piston has a stem which protrudes from an axial end of the main chamber, and the secondary piston is spaced from the main piston on the side opposite to the stem. The two pistons sealingly divide the main chamber into three chambers: two end chambers, which can be connected to a source of compressed air or to the atmosphere in order to move the two pistons along the axis of the main chamber during the approach of the main stem or spacing motion with respect to the part to be treated, and an intermediate chamber which contains a liquid. An actuation stem is furthermore accommodated in the main chamber and sealingly passes through the secondary piston.