A hydrostatic drive system (1) has a hydrostatic pump (3) driven by a drive motor (2) and connected in a closed circuit with a hydrostatic motor (4). The hydrostatic motor (4) drives a consumer (5) and the closed circuit is formed by a first hydraulic connection (6a) and a second hydraulic connection (6b). A hydrostatic accumulator (30) can be connected with at least one of the two hydraulic connections (6a, 6b). A hydrostatic drive unit is located in an accumulator flow path (21) between one of the two hydraulic connections (6a, 6b) and the hydrostatic accumulator (30) and an additional hydrostatic drive unit is located in a tank flow path (22) between the other of the two hydraulic connections (6a, 6b) and a tank (17). The hydrostatic drive unit and the additional hydrostatic drive unit are a hydrostatic dual-flow double drive unit (20) provided in the accumulator flow path (21) and in the tank flow path (22).

Hydraulic circuit comprising a low-pressure circuit (6) fed by a booster pump (4) that draws from a very-low-pressure reservoir (2), characterized in that this very-low-pressure reservoir (2) is leaktight and has a device for placing the internal volume (12) under negative pressure with respect to atmospheric pressure.

A hydraulic engine system includes a first hydraulic pump-motor coupled to an engine and a second hydraulic pump-motor coupled to an electric machine. A hydraulic link fluidly connects the first and the second hydraulic pump-motors. During a cranking operation mode, the electric machine operates as a motor and transfers power via the second hydraulic pump-motor, the hydraulic link and the first hydraulic pump-motor to provide cranking torque to the engine. During a generator operation mode, the power generated by the engine is transferred via the first hydraulic pump-motor, the hydraulic link, and the second hydraulic pump-motor to the electric machine, operating as a generator, to generate electricity.

A hydraulic engine system includes a first hydraulic pump-motor coupled to an engine and a second hydraulic pump-motor coupled to an electric machine. A hydraulic link fluidly connects the first and the second hydraulic pump-motors. During a cranking operation mode, the electric machine operates as a motor and transfers power via the second hydraulic pump-motor, the hydraulic link and the first hydraulic pump-motor to provide cranking torque to the engine. During a generator operation mode, the power generated by the engine is transferred via the first hydraulic pump-motor, the hydraulic link, and the second hydraulic pump-motor to the electric machine, operating as a generator, to generate electricity.

A power system for a working machine includes a transmission for driving the working machine, the transmission including a continuously variable gear box having a gear unit and a hydraulic variator unit; a work hydraulic circuit for controlling at least one hydraulic actuator of the working machine; wherein the hydraulic variator unit is hydraulically connected to the work hydraulic circuit to hydraulically transfer energy from the hydraulic variator unit to the work hydraulic circuit.

A power system for a working machine includes a transmission for driving the working machine, the transmission including a continuously variable gear box having a gear unit and a hydraulic variator unit; a work hydraulic circuit for controlling at least one hydraulic actuator of the working machine; wherein the hydraulic variator unit is hydraulically connected to the work hydraulic circuit to hydraulically transfer energy from the hydraulic variator unit to the work hydraulic circuit.

A hydrostatic drive system (1) with a hydrostatic pump (3) driven by a drive motor (2) and connected in a closed circuit with a hydrostatic motor (4). The hydrostatic motor (4) is connected with a consumer (5). The closed circuit is formed by a first hydraulic connection (6a) and a second hydraulic connection (6b). A pressure accumulator device (30) can be connected with the two hydraulic connections (6a, 6b) for the storage of energy and the output of energy. The pressure accumulator device (30) is a double piston accumulator (31) having a high-pressure-side pressure chamber (32) and a low-pressure-side pressure chamber (33). The high-pressure-side pressure chamber (32) can be connected with one of the two hydraulic connections (6a, 6b) of the closed circuit and simultaneously the low-pressure-side pressure chamber (33) can be connected with the respective other hydraulic connection (6b, 6a) of the closed circuit.

A hydrostatic drive system (1) with a hydrostatic pump (3) driven by a drive motor (2) and connected in a closed circuit with a hydrostatic motor (4). The hydrostatic motor (4) is connected with a consumer (5). The closed circuit is formed by a first hydraulic connection (6a) and a second hydraulic connection (6b). A pressure accumulator device (30) can be connected with the two hydraulic connections (6a, 6b) for the storage of energy and the output of energy. The pressure accumulator device (30) is a double piston accumulator (31) having a high-pressure-side pressure chamber (32) and a low-pressure-side pressure chamber (33). The high-pressure-side pressure chamber (32) can be connected with one of the two hydraulic connections (6a, 6b) of the closed circuit and simultaneously the low-pressure-side pressure chamber (33) can be connected with the respective other hydraulic connection (6b, 6a) of the closed circuit.

Improvements to a hydro-mechanical transmission based on fixed displacement pump/motors rather than variable displacement pump/motors are disclosed. These include rpm-changing gears on the input and the output pump/motors which allow the pump/motors to be operated at their maximum rated rpm and facilitate compact packaging. A novel selectable clutch configuration is part of the packaging arrangement. The addition of a two-speed all mechanical transmission on the output extends the useful range of a mechanical bypass of the hydraulic transmission intended for cruising.

Improvements to a hydro-mechanical transmission based on fixed displacement pump/motors rather than variable displacement pump/motors are disclosed. These include rpm-changing gears on the input and the output pump/motors which allow the pump/motors to be operated at their maximum rated rpm and facilitate compact packaging. A novel selectable clutch configuration is part of the packaging arrangement. The addition of a two-speed all mechanical transmission on the output extends the useful range of a mechanical bypass of the hydraulic transmission intended for cruising.