Universal joints (also called U-joints, universal couplings, Cardan joints, Hooke’s joints, or Hardy-Spicer joints) are used to transmit motion and rotational power, or torque, between two shafts that are offset at an angle.

Most universal joints consist of two yokes and a middle assembly; the hub end of each yoke attaches to a shaft while the yoke ears attach to and pivot around the middle assembly to accommodate shaft misalignment. The type of middle assembly determines its usage—pin and block joints are suitable for transmitting high torque, needle bearing joints are used to handle high rotational speeds, and ball and socket joints are used in applications requiring low backlash (play between moving parts).

The body of the universal joint may include a single joint to accommodate only angular misalignments between shafts, or two joints to accommodate both angular and parallel misalignments. Available in a variety of materials and configurations, universal joints are used in applications including motor vehicles, conveyors, medical and optical devices, forestry and mining equipment, robotics and space exploration, and aeronautics, among others.

Lovejoy manufactures flexible couplings, universal joints, variable speed drives, and other transmission and mechanical power products. The company, founded in 1900, is headquartered in Downers Grove, IL.