(Mech. & Engin.), a yielding joint or coupling for so
uniting parts of a machine or structure that expansion, as by heat, is prevented from causing injurious
strains; as: (a) A slide or set of rollers, at the end of bridge truss, to support it but allow end play.(b) A
telescopic joint in a steam pipe, to permit one part of the pipe to slide within the other.(c) A clamp for
holding a locomotive frame to the boiler while allowing lengthwise motion. —
Expansion valve
(Steam
Engine), a cut-off valve, to shut off steam from the cylinder before the end of each stroke.