7.4.1 Flexible couplings
These are capable of absorbing small amounts of angular misalignment, as well as axial movement. Double flexible couplings can also accommodate eccentricity. Figure 1.116 shows some designs in common use. The claw coupling, which may be single or double, is robust and slides easily when transmitting light load; on heavy load, however, friction causes it to become axially rigid.
The Bibby coupling is satisfactory up to medium sizes and provides (in addition to the other features) torsional resilience, the torsional stiffness increasing with load.
The multitooth coupling transmits torque by internal and external gear teeth of involute form, which are curved to accommodate angular misalignment.
All these couplings require continuous lubrication, normally obtained from a jet of oil feeding into an annular recess, from which it is fed centrifugally to the coupling teeth through drilled passage-ways.