universal joint

A universal joint, (universal coupling, U-joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint) is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant velocity joint.