Abstract: The apparatus comprise a generally tubular outer element, a generally cylindrical inner element disposed therewithin and sized relative thereto to provide a generally annular operating space therebetween. An intermediate element is disposed in said operating space and is dimensioned relative thereto to create interference fits with said outer and inner elements and prevent relative movement therebetween. Means are provided to introduce pressurized fluid to the respective element interfaces to expand the outer element within the elastic limit thereof to an extent sufficient to release the interference fits and enable relative outer-inner element movement. Re-locking of the outer and inner elements occurs automatically upon depressurization of the fluid and attendant return of the outer element to its unexpanded configuration. Actuating means to effect relative outer and inner element movement upon apparatus unlocking are also provided, and include means to pressurize the fluid.

Abstract: The apparatus comprise a generally tubular outer element, a generally cylindrical inner element disposed therewithin and sized relative thereto to provide a generally annular operating space therebetween. An intermediate element is disposed in said operating space and is dimensioned relative thereto to create interference fits with said outer and inner elements and prevent relative movement therebetween. Means are provided to introduce pressurized fluid to the respective element interfaces to expand the outer element wherein the elastic limit thereof to an extent sufficient to release the interference fits and enable relative outer-inner element movement. Re-locking of the outer and inner elements occur automatically upon depressurization of the fluid and attendant return of the outer element to its unexpanded configuration. Actuating means to effect relative outer and inner element movement upon apparatus unlocking are also provided, and include means to pressurize the fluid.