Coupling device

A coupling device comprising:

• a transmission member including a cylindrical rod with an axis, a rear end adapted to be coupled to a rotary drive unit so as to be rotated by the drive unit, a front end, and a circumferential outer surface extending between said front and rear ends, said transmission member further including a curved coupling flange which has a cross-section in the form of a circular sector and which extends circumferentially and co-axially along said outer surface of said cylindrical rod, said coupling flange being fixed to said outer surface of said cylindrical rod and projecting forwardly relative to said front end of said cylindrical rod, said coupling flange having a concave face confronting said axis of said cylindrical rod and formed with a plurality of engaging protrusions, and a convex face opposite to said concave face;
• and
• a work shaft including a main body which extends along said axis of said cylindrical rod of said transmission member and which has a spherical end, and a tubular sleeve sleeved on said spherical end and co-rotatable with said spherical end, said tubular sleeve cooperating with said spherical end to form a coupling end portion of said work shaft, said tubular sleeve being formed with a plurality of engaging grooves which are angularly displaced from one another with respect to said axis of said cylindrical rod of said transmission member, said coupling end portion being disposed on said concave face of said coupling flange so as to enable engagement between said engaging grooves and said engaging protrusions in order to permit transmission of rotation of said transmission member to said work shaft, wherein said transmission member further includes a plurality of transmission cylinders secured to said convex face of said coupling flange and projecting in radial directions relative to said convex face of said coupling flange, said transmission cylinders extending axially along said convex face of said coupling flange and being angularly displaced from one another, said coupling device further comprising an annular slide seat which has an inner wall surface that defines a central hole, said transmission member extending slidably into said central hole and being coupled with said slide seat such that said slide seat is slidable relative to said transmission member and is co-rotatable with said transmission member, said inner wall surface of said slide seat being formed with a plurality of angularly displaced and axially extending receiving grooves for receiving said transmission cylinders on said convex face of said coupling flange.