Patent ID: 7963714

Claim:
A safety coupling apparatus which comprises: a first annular coupling part for torque attachment to an end of a first rotatable shaft, a second annular coupling part for attachment to an end of a second rotatable shaft which is coaxial with the first rotatable shaft, said second coupling part defining an axial groove which has an open end facing the first coupling part, a radially outwardly-extending collar located radially outwardly of the axial groove, and a radially outwardly-extending flange which is spaced from the collar to define a radially inwardly-extending recess therebetween, and said first coupling part defining an expandable hollow body which axially extends through said open end and into said axial groove of said second coupling part, said hollow body including a cavity which subdivides said hollow body into inner and outer cylindrical sections and which can be (1) filled with pressurized fluid to expand the inner and outer cylindrical sections relative to one another and cause external surfaces thereof to contact adjacent surfaces of said axial groove and thereby prevent relative rotation of the first and second coupling parts, or (2) emptied of pressurized fluid to contract the inner and outer cylindrical sections relative to one another and enable free rotation of the first and second coupling parts relative to the one another.