Mechanical coupling devices

A rotational and axial coupling arrangement between first and second elements, the elements being arranged for rotation about an axis, the first element comprising an elongate shaft, having a coupling portion arranged about an axial section of the shaft and said second element comprising a body having a bore defined therein, with a coupling portion about an axial section of the bore;

• said elements being coupled by way of a spheroidal member, the arrangement further comprising a resilient element operable to provide an axial force of separation when the coupling portions are axially aligned:
• wherein the coupling portion associated with one of the first and second elements comprises a surface defining two opposing linear ridges operable to provide first and second point contact points for abutment with the spheroidal coupling member in a coupling mode;
• wherein the coupling portion associated with the other of the first and second elements comprises a chamber operable to provide three point contact surfaces for abutment with the spheroidal coupling member in a coupling mode, the chamber being operable to retain the locking member in a non-coupling mode;
• the arrangement being such that, in a coupling mode, the spheroidal member is contacted by the respective contact points, the resilient forces causing forces from the respective contact points to act through the spherical member, preventing separation of the first and second elements, the contact surfaces thereby ensuring defined rotational and axial alignment between the first and second elements.