Digitally controlled air-over-hydraulic actuator and method

An actuator comprising in combination:

• (a) a pneumatic cylinder with a penumatic piston thereon;
• (b) a hydraulic cylinder with a hydraulic piston therein;
• (c) means for connecting the pneumatic piston to the hydraulic piston so that movement of the pneumatic piston forces the hydraulic piston to move;
• (d) a first digital fluid valve including first and second fluid ports coupled in fluid communication with opposite end portions of the hydraulic cylinder, and first means for rapidly opening the first digital fluid valve and after a predetermined duration rapidly closing the first digital fluid valve in response to a control signal of the predetermined duration;
• (e) means for applying a predetermined pressure difference across the pneumatic piston to produce a first predetermined force on the connecting means and thereby produce a second predetermined force on the hydraulic piston;
• and
• (f) means for successively applying a predetermined number of the control signals in rapid succession to the first means to open and close the first fluid valve the predetermined number of times to thereby allow the hydraulic piston and the connecting means to move through a predetermined distance.

An actuator comprising in combination:

• (a) a first cylinder with a first piston thereon;
• (b) a hydraulic cylinder with a hydrauic piston therein;
• (c) means for connecting the first piston to the hydraulic piston so that movement of the first piston forces the hydraulic piston to move;
• (d) a first digital fluid valve including first and second fluid ports coupled in fluid communication with opposite end portions of the hydraulic cylinder, and first means for rapidly opening the first digital fluid valve and after a predetermined duration rapidly closing the first digital fluid valve in response to a control signal of the predetermined duration;
• (e) means for applying a predetermined pressure difference across the first piston to produce a first predetermined force on the connecting means and thereby produce a second predetermined force on the hydraulic piston;
• and
• (f) means for successively applying a predetermined number of the control signals in rapid succession to the first means to open and close the first fluid valve the predetermined number of times to thereby allow the hydraulic piston and the connecting means to move through a predetermined distance.