A pressure booster constituting a cylinder apparatus is provided with a first piston and a second piston that are coupled to each other by a rod. A connection member provided to the second piston is configured so as to be displaceable from a connection position to a blocking position as a result of the connection member making contact with a cylinder body when the second piston is displaced in a direction where a boosting chamber contracts, and so as to be displaceable from the blocking position to the connection position as a result of the connection member making contact with the cylinder body when the second piston is displaced in a direction where the boosting chamber expands.

An improved hydraulic control system for a lift truck attachment having opposed clamp arms that selectively grip and release a load. The improved hydraulic system utilizes a secondary hydraulic force control circuit that increases the gripping force on the load independently of inward movement of the clamp arms.

An improved hydraulic control system for a lift truck attachment having opposed clamp arms that selectively grip and release a load. The improved hydraulic system utilizes a secondary hydraulic force control circuit that increases the gripping force on the load independently of inward movement of the clamp arms.

A first position detection sensor and a second position detection sensor of a pressure booster detect the position of a first piston or a second piston. A fluid supply mechanism supplies a fluid to a first pressure-boosting chamber and/or a second pressure-boosting chamber. On the basis of the detection results of the first position detection sensor and the second position detection sensor, the fluid supply mechanism switches between performing an operation for supplying fluid to a first drive chamber and discharging fluid from a second drive chamber, and performing an operation for discharging fluid from the first drive chamber and supplying fluid to the second drive chamber.

A first position detection sensor and a second position detection sensor of a pressure booster detect the position of a first piston or a second piston. A fluid supply mechanism supplies a fluid to a first pressure-boosting chamber and/or a second pressure-boosting chamber. On the basis of the detection results of the first position detection sensor and the second position detection sensor, the fluid supply mechanism switches between performing an operation for supplying fluid to a first drive chamber and discharging fluid from a second drive chamber, and performing an operation for discharging fluid from the first drive chamber and supplying fluid to the second drive chamber.

A hydraulic actuator arrangement (1) is described comprising a hydraulic actuator having a pressure chamber (2), a cylinder (3) in a cylinder housing (4), and a piston (5) connected to a piston rod, a hydraulic pump (7) connected to the pressure chamber (2) and an electric motor (8) driving the hydraulic pump (7), wherein the pump (7) and the motor (8) are arranged within the actuator. Such an actuator arrangement should have many application possibilities. To this end, a hydraulic pressure amplifier (10) is arranged between the hydraulic pump (7) and the pressure chamber (2).

A hydraulic pressure amplifier arrangement (1) comprising a supply port (IN), a return port (R), a high pressure port (H1), and a pressure amplifier unit (2) having a low pressure inlet (3) connected to the supply port (IN) and a high pressure outlet (4) connected to the high pressure port (H1) is described, wherein the pressure amplifier unit (2) comprises an amplification factor. In such a hydraulic pressure amplifier arrangement it should be possible to allow simply releasing off pressure at the high pressure port while keeping small unnecessary energy consumption. To this end a control valve (8) is arranged in a connection between the high pressure port (H1) and the return port (R).

A hydraulic pressure amplifier arrangement (1) comprising a supply port (IN), a return port (R), a high pressure port (H1), and a pressure amplifier unit (2) having a low pressure inlet (3) connected to the supply port (IN) and a high pressure outlet (4) connected to the high pressure port (H1) is described, wherein the pressure amplifier unit (2) comprises an amplification factor. In such a hydraulic pressure amplifier arrangement it should be possible to allow simply releasing off pressure at the high pressure port while keeping small unnecessary energy consumption. To this end a control valve (8) is arranged in a connection between the high pressure port (H1) and the return port (R).

The invention relates to a device for supplying ports to a machine section (26) of a hydraulic machine arrangement (40), the device (10) comprising a low-pressure inlet port (12), a leakage inlet (16), a low-pressure chamber (18) having a low-pressure opening (22) for establishing fluid communication with the machine section (26), a high-pressure outlet port (14), and a high-pressure chamber (20) that is in fluid communication with the high-pressure outlet port (14), the high-pressure chamber (20) having a high-pressure opening (24) for establishing fluid communication with the machine section (26), wherein the low-pressure inlet port (12) is in fluid communication with the low-pressure chamber (18), wherein a leakage path (36) extends from the high-pressure chamber (20) through the machine section (26) to the leakage inlet (16), characterized in that the device (10) further comprises a control valve member (28) connecting the leakage inlet (16) to the low-pressure chamber (18), wherein the control valve member (28) transfers to an open state when a pressure in the leakage inlet (16) with respect to a pressure in the low-pressure chamber (18) is higher than a predefined control pressure threshold. The device (10) reduces cavitation in hydraulic machine arrangements (40).

The invention relates to a device for supplying ports to a machine section (26) of a hydraulic machine arrangement (40), the device (10) comprising a low-pressure inlet port (12), a leakage inlet (16), a low-pressure chamber (18) having a low-pressure opening (22) for establishing fluid communication with the machine section (26), a high-pressure outlet port (14), and a high-pressure chamber (20) that is in fluid communication with the high-pressure outlet port (14), the high-pressure chamber (20) having a high-pressure opening (24) for establishing fluid communication with the machine section (26), wherein the low-pressure inlet port (12) is in fluid communication with the low-pressure chamber (18), wherein a leakage path (36) extends from the high-pressure chamber (20) through the machine section (26) to the leakage inlet (16), characterized in that the device (10) further comprises a control valve member (28) connecting the leakage inlet (16) to the low-pressure chamber (18), wherein the control valve member (28) transfers to an open state when a pressure in the leakage inlet (16) with respect to a pressure in the low-pressure chamber (18) is higher than a predefined control pressure threshold. The device (10) reduces cavitation in hydraulic machine arrangements (40).