Patent ID: 8869521

Claim:
A fluid working machine for actuating a piston-cylinder hydraulic actuator, said fluid working machine comprising: a housing with a first exterior port, a second exterior port, a third exterior port, and a plurality of cylinders, the plurality of cylinders divided into a first group and a second group; a plurality of pistons, each slideably received in a different cylinder of the plurality of cylinders; a plurality of first valve arrangements, each associated with one cylinder in the first group and selectively providing a first path for fluid to flow between the first exterior port and the one cylinder and selectively providing a second path for fluid to flow between the second exterior port and the one cylinder, each first valve arrangement having: (1) a first mode in which the first path is provided when pressure in the first exterior port is greater than pressure in the one cylinder and in which the second path is provided when pressure in the one cylinder is greater than pressure in the second exterior port, and (2) having a second mode in which the first path is provided when pressure in the one cylinder is greater than pressure in the first exterior port and in which the second path is provided when pressure in the second exterior port is greater than pressure in the one cylinder, and a plurality of second valve arrangements, each associated with a given cylinder in the second group and selectively providing a third path for fluid to flow between the first exterior port and the given cylinder and selectively providing a fourth path for fluid to flow between the third exterior port and the given cylinder, each second valve arrangement having: (3) a third mode in which the third path is provided when pressure in the first exterior port is greater than pressure in the given cylinder and in which the fourth path is provided when pressure in the given cylinder is greater than pressure in the third exterior port, and (4) having a fourth mode in which the third path is provided when pressure in the given cylinder is greater than pressure in the first exterior port and in which the fourth path is provided when pressure in the third exterior port is greater than pressure in the given cylinder.