Shaft coupler

1. In a coupled shaft comprising a first and a second shaft segment which when coaxially assembled have a common central axis, said coupled shaft being transmissive of torque exerted by one of them, and resistive to axial separation in response to an axial separative force exerted on them, each said segment comprising a metal body having a terminal end, and adjacent to said terminal end a cylindrical peripheral wall coaxial with said central axis, an apparatus comprising:

a coupler sleeve comprising a metal body having an internal cylindrical wall forming a passage therethrough, said internal wall so proportioned and arranged as to embrace said cylindrical peripheral wall of both of said shaft segments, and a first and a second end, and a longitudinally extending slot in said internal cylindrical wall, opening on at least one end of said sleeve, said slot having a dimension of width;

an axially-extending groove in said peripheral wall of each shaft segment, said groove having a pair of axially extending, radially spaced apart side walls, spaced apart by a reference spacing and a dimension of depth;

a rigid key fitted in each of said grooves having opposite sides laterally spaced apart to closely fit in a respective said groove and also in said slot in said sleeve, and a thickness greater than said dimension of depth whereby to project radially beyond its respective peripheral side wall into said slot;

each said terminal end formed to complementarily engage the other terminal end to resist their axial separation from one another, each said terminal end including a transverse receiver recess and a tongue, said recess having a base wall extending across said central axis, a planar bearing wall which is neither parallel to or normal to the central axis, at an angle to said axis, a transition wall interconnecting said base wall and bearing wall as a smooth curve tangent to said bearing wall and base wall, said bearing walls being formed at the same said angle relative to the central axis, and which said angle is within the locking range of the material and its surfaces of which the bearing walls are made;

a tongue wall contiguous to said bearing wall and extending toward the end of the tongue;

whereby, when assembled together with the tongues in the recesses, the planar bearing walls can be brought together in sufficient surface contact, thereby resisting relative shear movement between them when an axial separative force is exerted on the completed shaft preventing axial separation of the segments, placement of the sleeve over the segments and keys preventing substantial relative rotation of the segments.

2. Apparatus according to claim 1 in which said tongue wall terminates in an end wall so disposed relative to its bearing wall that, when said segments are joined but pressed together, one of said end walls bears against one of said base walls to support said segments in axial compression.

3. Apparatus according to claim 2 in which said base wall and the terminal end of said end wall are planar and normal to said axis.

4. Apparatus according to claim 2 in which said end wall is tangent to said bearing wall.

5. Apparatus according to claim 1 in which a restraint is attached to one of said segments to limit the movement of the sleeve beyond a defined limit.

6. Apparatus according to claim 1 in which said slot is open at both ends of the sleeve.

7. Apparatus according to claim 1 in which said key has a lateral cross-section which is substantially rectangular.

8. Apparatus according to claim 1 in which a pair of said slots is formed in said internal cylindrical wall to receive a respective one of said keys, said slots being disposed 180 degrees apart.