A piston lock system having first and second cylinders, first and second pistons telescopically connected to the cylinders, and first and second piston locks. The piston locks are movable in a transverse direction within a planar region between the cylinders, between unlocked positions in which the piston locks are not located between the free ends of the cylinders and the free ends of the piston, and locked positions in which the piston locks are located between the free cylinder ends and the free piston ends. A control link is operatively connected to the piston locks, and configured to simultaneously move the piston locks between the locked and unlocked positions.

The subject matter of this specification can be embodied in, among other things, a method that includes controlling, by a first fluid valve, a first fluid flow to a first fluid actuator, actuating, by the first fluid actuator, an output, controlling, by a second fluid valve, a second fluid flow to a second fluid actuator, and actuating, by the second fluid actuator, the output.

A robot includes elbows connecting forearms rotatably to upper arms with two rotational degrees of freedom. The elbow includes: an elbow joint connecting the forearm and the upper arm with two rotational degrees of freedom; an elbow drive main link; an elbow drive auxiliary link; a forearm-side main link attaching unit attached with one end of the elbow drive main link with two rotational degrees of freedom, and provided in the forearm; an elbow-drive-main-link-side auxiliary link attaching unit attached with one end of the elbow drive auxiliary link with two rotational degrees of freedom, and provided on the elbow drive main link; and two linear actuators for moving two upper-arm-side link attaching units each attached with the other end of either the elbow drive main link or the elbow drive auxiliary link with two rotational degrees of freedom, and provided so as to be movable along the upper arm.

The present invention provides a controller for a hydraulic apparatus. The controller is configured to determine (410) that a mode change criteria has been met for the hydraulic apparatus. In response to the determination, the controller is configured to control (420) a valve arrangement to change a first actuator chamber of a hydraulic actuator between being fluidly connected to a hydraulic machine and fluidly isolated from a second chamber of the hydraulic actuator, and being fluidly connected to both the second actuator chamber and the hydraulic machine. Further in response to the determination, the controller is configured to control (430) the hydraulic machine to change a flow rate of hydraulic fluid flowing through the hydraulic machine to regulate a movement of the hydraulic actuator during the control of the valve arrangement.

A hydraulic system includes a first and a second rotating hydraulic machine, the first and second hydraulic machine being arranged to provide a torque via a common output shaft; a first valve arrangement for providing a differential hydraulic pressure level over the first hydraulic machine by using two sources of hydraulic fluid having different hydraulic pressure levels, a second valve arrangement for providing a differential hydraulic pressure level over the second hydraulic machine by using two sources of hydraulic fluid having different hydraulic pressure levels; and a control unit configured to control the first valve arrangement and the second valve arrangement such that different discrete levels of torque are provided via the output shaft of the hydraulic system. A hydraulic system for providing different discrete levels of torque using one hydraulic machine and a plurality of differential pressure levels, and a method for controlling a hydraulic system, are also provided.

The invention concerns a device for the direct recovery of hydraulic energy in a machine, comprising at least one single-acting storage cylinder-piston device with a storage cylinder, a storage cylinder-piston and a storage cylinder chamber, with at least one differential cylinder-piston device with a differential cylinder comprising a separate rod side and base side, and with at least one hydraulic accumulator, which may be connected to the storage cylinder-piston device and/or the differential cylinder-piston device, wherein the potential energy of the storage cylinder-piston device, which retracts under a compressive load, may be at least partially stored in the hydraulic accumulator.

Device for recovering hydraulic energy in a machine comprising at least a first differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, at least a second differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, and at least one hydraulic accumulator that can be hydraulically connected to at least one of the differential cylinder-piston assemblies, wherein the differential cylinder-piston assemblies are mechanically coupled to one another, and wherein the potential energy of at least one of the differential cylinder-piston assemblies retracting under a compressive load can at least partially be stored in the hydraulic accumulator.

An apparatus for recuperating hydraulic energy in a working machine includes at least one first differential cylinder piston device with a differential cylinder and separate rod and bottom sides, and at least one hydraulic accumulator which is hydraulically connectable with the differential cylinder piston device. The potential energy of the differential cylinder piston device retracting under pressing load is at least partly storable in the hydraulic accumulator. The rod and bottom sides are connectable with each other via at least one brake valve for recirculating hydraulic fluid from the bottom side into the rod side.

A drive system with multiple hydraulic cylinders applying torque to the drive shaft of a machine. Each cylinder is attached at one end to the frame of the machine by a clevis that pivots and the other end is rotationally connected to a shaft fixed to a crank arm, fixed to the drive shaft. Each cylinder either pushes or pulls-the crank arm shaft producing torque on the drive shaft in the form of a moment about centerline. As the drive shaft rotates, each cylinder alternately pushes and pulls on the crank arm shaft, depending on the rotational position of the crank arm with respect to the cylinders. The direction of force applied by each hydraulic cylinder is determined by an electro/hydraulic direction control valve, driven by a programmable logic controller, using a signal from a sensor to detect the rotational position of the drive shaft.

A variable compression ratio internal combustion engine comprises a crankshaft and a connecting rod. The connecting rod comprises a connecting rod body, a first hydraulic cylinder, a first hydraulic piston, a second hydraulic cylinder, a second hydraulic piston, a linking member, a hydraulic oil path, and a spool between a first operating position permitting supply of hydraulic oil from the second hydraulic cylinder to the first hydraulic cylinder, and a second operating position permitting supply of hydraulic oil from the first hydraulic cylinder to the second hydraulic. The variable compression ratio internal combustion engine further comprises a biasing member arranged inside the crank pin and biasing the spool so as to selectively switch a position of the spool between the first operating position and the second operating position.