A hydraulic system includes: hydraulic actuators; a control valve for controlling the hydraulic actuators; a tank for storing a hydraulic operation fluid; a variable displacement pump for supplying the hydraulic operation fluid to the hydraulic actuators; a regulator for controlling the variable displacement pump; a pilot pump for discharging a hydraulic pilot fluid; a load sensing system for maintaining a differential pressure to be a constant pressure, the differential pressure being obtained by subtracting a second signal pressure from a first signal pressure that is the discharge pressure of the variable displacement pump, the second signal pressure being the maximum one of the load pressures generated in the hydraulic actuators; a signal tube for sending the second signal pressure to the regulator; a throttle provided on the signal tube; and a warm-up circuit for supplying the hydraulic pilot fluid to a downstream side of the throttle.

When hydraulic fluid discharged from a hydraulic actuator is to be recovered for driving a different hydraulic actuator, the recovery frequency is increased to achieve further energy saving. To this end, a pressure increasing circuit 36 is provided in which a communication pressure increasing valve 12 is disposed in a communication passage 26 that connects a bottom side line 23 of and a rod side line 24 a boom cylinder 4. A recovery control valve 11 is controlled such that, when a first operation unit 5 is operated in a boom lowering direction (own weight falling direction of the boom) and a second operation unit 6 is operated simultaneously, only if the pressure at the bottom side of the boom cylinder 4 is higher than the pressure at the arm cylinder side that is a recovery destination of hydraulic fluid, the recovery control valve 11 is opened to recover the flow rate discharged from the bottom side of the boom cylinder 4 to the arm cylinder side.

A device recovers energy in working machines with at least one power drive actuated to move a load mass back and forth and with an energy storage system (16) absorbing the energy released in the movement of the load mass in one direction and making it available for a subsequent movement in the other direction. The energy storage system includes an accumulator cylinder (16) mechanically coupled to the load mass and storing pneumatic pressure energy for movement in one direction. For movement in the other direction, the accumulator cylinder acts as an auxiliary working cylinder supporting the power drive and converting the stored pressure energy into driving force.

A hydraulic control device that reduces the loss of the power of a pump in combined operation of boom lowering and arm pushing. A controller performs single control of increasing capacity of a first pump in accordance with increase in an operation amount of a boom operation member, in a single operation of the boom lowering. On the other hand, the controller restricts the capacity of the first pump compared to capacity in the single control, during a restriction control period when the combined operation of boom lowering and arm pushing is detected, and the operation amount of the boom operation member is a prescribed operation amount or more.

Provided is a hydraulic shovel capable of moving a boom, an arm, and a bucket at respective adequate speeds even during complex operations thereof, without a significant pressure loss. This hydraulic shovel includes: a first pump (31) connected to a boom actuator (24) and a bucket actuator (28); a second pump (32) connected to an arm actuator (26) and the boom actuator (24); a third pump (33) connect to the arm actuator (26); a boom control valve (54) interposed between the first pump (31) and the boom actuator (24); an arm control valve (56) interposed between the second pump (32) and the arm actuator (26); a bucket control valve (58) interposed between the first pump (31) and the bucket actuator (28); a boom merging valve (55) for speed increase interposed between the second pump (32) and the boom actuator (24); and an arm merging valve (57) for speed increase interposed between the third pump (33) and the arm actuator (26).

A shovel includes a boom cylinder that drives a boom and an arm cylinder that drives an arm. A hydraulic pump supplies operating oil to the boom cylinder and the arm cylinder. An engine is connected to the hydraulic pump and equipped with a supercharger. The engine is controlled to maintain a revolution speed within a certain definite range. A controller controls a rotating speed of the supercharger. The controller performs a process of increasing the rotating speed of the supercharger so as to increase a supercharging pressure generated by the supercharger before a hydraulic load is applied to the engine.

A boom assembly includes a lower boom, an upper boom, and an actuator assembly. The lower boom has an upper end and a base end. The base end is configured to be pivotally coupled to a lift device. The upper boom has a lower end pivotally coupled to the upper end of the lower boom. The actuator assembly has (i) a first end coupled to at least one of the upper end of the lower boom and the lower end of the upper boom, and (ii) an opposing second end coupled to the upper boom. The actuator assembly includes a first actuator and a second actuator. The second actuator is rigidly joined to the first actuator at the first end of the actuator assembly and flexibly joined to the first actuator at the opposing second end of the actuator assembly.

A rope shovel has a boom and a hoist rope. The boom has a first end and a second end. The hoist rope extends over the second end of the boom. A digging assembly for the rope shovel includes a shaft, an elongated member supported for movement relative to the boom, an attachment, and a drive link. The shaft is positioned between the first end and the second end of the boom and transverse to the boom, and the shaft includes at least one pinion gear. The elongated member includes a first end and a second end. The attachment is coupled to the first end of the elongated member and is configured to be coupled to the hoist rope. The drive link includes a rack engaging the pinion gear of the transverse shaft such that rotation of the pinion gear moves the drive link and actuates the attachment.

A pin assembly for a piston block of a hydraulic cylinder includes a pin that is axially engaged with the piston block. The pin assembly also includes a floating bush that is spaced apart from the pin to receive a sleeve therebetween. The floating bush is also configured to exhibit axial and radial play in its movement relative to the sleeve. The axial and radial play in the movement of the floating bush allows the floating bush to align with a cap port of the cylinder housing prior to entering the cap port of the cylinder housing.

A drive control system for a work machine includes: a stabilization control calculation unit (60a) that calculates and outputs a gradual stoppage command and an operation speed limitation command; a stoppage characteristic modification unit (210) that includes a speed increasing unit and corrects a pilot pressure such that, upon a stoppage operation of a control lever, a drive actuator is stopped gradually; an operation speed limitation unit (240) that includes a speed reducing unit and corrects the pilot pressure such that an operation speed of the drive actuator is limited; and a speed increase interruption unit (330) that interrupts, when a failure of a speed increasing solenoid proportional valve of the speed increasing unit is detected, supply of the pilot hydraulic fluid to the speed increasing unit.