A gas cylinder of the present invention comprises a housing having a tube, a front head and an rear end cap defining a chamber. A pair of ports are provided to allow for the input and exhaust of gas in the chamber. A piston is received in the chamber for axial movement within the chamber and separates...http://www.google.com/patents/US6691607?utm_source=gb-gplus-sharePatent US6691607 - High and low temperature gas actuated cylinder
