Shaft coupling

An apparatus for coupling a pair of shafts, comprising:

• a pair of joint elements each having an internal cylindrical part with an inwardly tapered outer surface and an interior bore for receiving one of the shafts, each joint element further having an external cylindrical part which together with said internal parts defines an annular tapered recess;
• a pair of ring members receivable in said tapered recesses, respectively, each said ring member having at least one tapped bore defined therein and constructed so that when said ring member is not tightened, its outer surface is not in contact with the inner surface of said external cylindrical part:
• means for connecting each of said joint elements to the other;
• and
• means insertable into said tapped bores for urging said ring members into said tapered recesses, whereby the inner surfaces of said ring members radially press said internal cylindrical parts to cause said internal cylindrical parts to press inwardly and frictionally engage each of the shafts and at the same time the diameters of said ring members expand because of their elasticity to cause the outer surfaces of said ring members to press against the inner surfaces of said external cylindrical parts so that torque is transmitted from one shaft to the other through a first and second torque transmission routes, said first torque transmission route being from said shaft to said internal cylindrical part of joint element to said connecting means and said second torque transmission route being from said shaft to said internal cylindrical part of joint element to said ring member to said external cylindrical part of said joint element to said connecting means.