Chapter Exody to Expansion of E by Webster's Dictionary (1913 Edition)

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Expansion joint, or Expansion coupling (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.