Patent ID: 6604451
Filing Date: 2003-08-12
Classification: F15B,F16F

Abstract:
A fluid actuator comprising:a single core having a plurality of discs protruding around an output shaft; a cylinder casing which has a body hollow configuration with an opening provided at its upper portion, and which receives the core in the hollow body in a state where not only an upper end of the output shaft is projected out of the opening but a lower portion of the core is set free, and which has an annular protrusion projecting into an air gap between the discs; at least one friction-less, annular small diaphragm interposed between a portion of the core located between the discs and the annular protrusion so as to allow their relative movement in upward and downward directions and so as to divide a space between the portion of the core and the annular protrusion into upper and lower portions; and a plurality of friction-less, annular large diaphragms each interposed between an inner peripheral surface of the cylinder casing and outer periphery portion of the disc so as to allow their relative movement in upward and downward directions and so as to allow their relative movement in upward and downward directions and so as to divide a space between the inner peripheral surface of the cylinder casing and the outer periphery portion of the disc into upper and lower portions; wherein a plurality of small cavities are each interposed between neighboring ones of the small diaphragm and the large diaphragms or between the lowest large diaphragm and a bottom portion of the cylinder casing so as to be arrayed in an axial direction of the core, a first group of the small cavities in even-numbered stages counted from the bottom communicate with the atmosphere and a second group of the cavities communicate with one another, at least one small-cavity of the second group communicates with a fluid flow passage for supplying and discharging pressurized fluid, and an effective pressure-receiving area on the large diaphragm side is larger than an effective pressure-receiving area on the small diaphragm side in each of the small cavities.