Coupling system

Coupling (1) for a shaft-end (2), substantially having a square cross-section, which at a distance (a) from its outer end is provided with a region with a transverse annular groove (3) having a circular or non-circular cross-section which is not greater over any angle than the smallest cross-section of the square shaft-end, the coupling comprising:

• a front plate (6), a locking plate (7) a bearing plate (12) and a rear plate (8) having a solid closed back surface, each of said plates being a flat planar plate, wherein the front plate and the locking plate both are provided with a continuous square opening (9 and 10 respectively) therethrough axially extending between front and rear surfaces thereof, and wherein the rear plate is provided with a non-continuous square opening (11) axially extending from a front surface thereof,
• wherein the front plate and the rear plate are fixedly interconnected in a position, in which the center lines of the openings in the front and rear plates are coaxially aligned and the orientation of the square openings correspond to each other,
• wherein the locking plate is rotatably mounted within a circular internal cavity of the bearing plate between the front plate and the rear plate such that the center line of the opening in the locking plate is coaxially aligned with the center lines of the openings in the front and rear plates, and such that the locking plate can be rotated back and forth between an unlocked position (I), in which the orientations of the square openings in the front plate and in the rear plate and the orientation of the square opening in the locking plate coincide with one another, and a locked position (II), in which the openings do not coincide, the coupling being arranged and sized such that in the unlocked position a square shaft-end can be inserted through the continuous square openings in the front plate and locking plate into the non-continuous square opening in the rear plate, after which the locking plate is rotated relative to the front plate and rear plate over a certain interlocking angle, by which the shaft-end is coupled with the assembly, which comprises the mutually interconnected front plate and rear plate and the interposed locking plate, so that the shaft-end cannot be pulled out without reversely rotating the locking plate into its unlocked position.