Fluid operated position selecting device

Claim 1

A device for selecting three different positions, comprising a hollow body of contoured internal section and having formed therein first and second bores selectively communicating with a source of pressurized fluid, said first bore being larger in cross section than said second bore, a first piston having a flange slidably fitted in said first bore and a hollow extension extending from said flange and slidably fitted in said second bore, a first piston ring provided between the outer peripheral edge of the flange of said first piston and the inner wall of said first bore, a second piston having a flange slidably fitted in said second bore and a hollow extension extending from said flange of said second piston and slidably fitted in the inner peripheral wall of said extension of said first piston, a second piston ring provided between the outer peripheral edge of the flange of said second piston and the inner wall of said second bore, a third piston ring mounted between said hollow extensions of said first and second pistons, said flange of said first piston having an aperture formed therein to provide communication between said first bore and the interior of said hollow extension of said second piston to cause the pressurized fluid admitted to said first bore to act on the inner wall surface of the flange of said second piston, a drain port communicating with a clearance between said hollow extensions of said first and second pistons to ensure smooth movement of said second piston relative to said first piston, and a piston rod rigidly connected to said flange of said second piston and extending through said second bore outwardly from said hollow body, said second piston being held in an intermediate position when both of said first and second bores communicate with said source of the pressurized fluid to cause both of the flanges of said first and second pistons to be subjected to a fluid pressure, said second piston being moved to an innermost position when the communication between said first bore and said source of the pressurized fluid is blocked to cause only the flange of of said second piston to be subjected to the fluid pressure and to an outermost position when the communication between said second bore and said source of the pressurized fluid is blocked to cause only the flange of said second piston to be subjected on its inner surface to the fluid pressure drawn from said first bore through said aperture, whereby said piston rod is moved to three different positions corresponding to said innermost, intermediate and outermost positions, of said second piston.

Claim 2

A device for selecting three different positions, comprising a hollow body of contoured internal section and having formed therein first and second bores selectively communicating with a source of pressurized fluid, said first bore being larger in cross section than said second bore, a first piston having a flange slidably fitted in said first bore and a hollow extension extending from said flange and slidably fitted in said second bore, a first piston ring provided between the outer peripheral edge of the flange of said first piston and the inner wall of said first bore, a second piston having a flange slidably fitted in said second bore and a hollow extension extending from said flange of said second piston and slidably fitted in the inner peripheral wall of said extension of said first piston, a second piston ring provided between the outer peripheral edge of the flange of said second piston and the inner wall of said second bore, a third piston ring mounted between said hollow extensions of said first and second pistons, said flange of said first piston having an aperture formed therein to provide communication between said first bore and the interior of said hollow extension of said second piston to cause the pressurized fluid admitted to said first bore to act on the inner wall surface of the flange of said second piston, a drain port communicating with a clearance between said hollow extensions of said first and second pistons to ensure smooth movement of said second piston relative to said first piston, and a piston rod rigidly connected to said flange of said second piston and extending through said second bore outwardly from said hollow body, said second piston being held in an intermediate position when both of said first and second bores communicate with said source of the pressurized fluid to cause both of the flanges of said first and second pistons to be subjected to a fluid pressure, said second piston being moved to an innermost position when the communication between said first bore and said source of the pressurized fluid is blocked to cause only the flange of of said second piston to be subjected to the fluid pressure and to an outermost position when the communication between said second bore and said source of the pressurized fluid is blocked to cause only the flange of said second piston to be subjected on its inner surface to the fluid pressure drawn from said first bore through said aperture, whereby said piston rod is moved to three different positions corresponding to said innermost, intermediate and outermost positions, of said second piston.