Patent ID: 7243594

Claim:
A rotary actuator comprising: a. a lower housing comprising a central channel, a mounting surface and an outer wall; b. a first lower piston attached to, and extending above, the mounting surface; c. a second lower piston attached to, and extending above, the mounting surface diametrically opposite the first lower piston; d. a rotatable central shaft extending upward through the central channel; e. an upper housing attached to the shaft above the lower housing; f. a first upper piston attached to, and extending below, the upper housing at a location between the first and second lower pistons so as to define a first pressure cavity between the itself and the first lower piston, and to define a second pressure cavity between the itself and the second lower piston; g. a second upper piston attached to, and extending below, the upper housing at a location between the first and second lower pistons, diametrically opposite the first upper piston, so as to define a third pressure cavity between the itself and the first lower piston, and to define a fourth pressure cavity between the itself and the second lower piston; h. a first pressurization line extending through the outer wall to the side of the first lower piston adjacent the first pressure cavity, such that fluid can be injected into the first pressure cavity through the first pressurization line to cause the first upper piston to move away from the first lower piston; i. a second pressurization line extending through the outer wall to the side of the first lower piston adjacent the third pressure cavity, such that fluid can be injected into the third pressure cavity through the second pressurization line to cause the second upper piston to move away from the first lower piston; j. a third pressurization line extending through the outer wall to the side of the second lower piston adjacent the second pressure cavity, such that fluid can be injected into the second pressure cavity through the third pressurization line to cause the first upper piston to move away from the second lower piston; k. a fourth pressurization line extending through the outer wall to the side of the second lower piston adjacent the fourth pressure cavity, such that fluid can be injected into the fourth pressure cavity through the fourth pressurization line to cause the second upper piston to move away from the second lower piston; l. a bearing mounted to the shaft and the upper housing; m. an inner seal ring located radially inside the first and second lower pistons; and n. an outer seal ring located radially outside the first and second lower pistons.