Abstract: A piston for use with a rotary piston rod or so-called rotary piston can be constructed so as to utilize a solid sleeve-like piston body of a material selected from the group consisting of structural carbon and graphite. This piston body is utilized around an elongated, tubular center member which has openings extending to the interior of the piston body for the purpose of conveying hydraulic fluid so as to lubricate the piston body to facilitate relative rotation of the piston body relative to the sleeve. Appropriate grooves holding elastomeric fluorocarbon sealing rings are located in the piston body and holding structures are provided for holding the piston on the sleeve. The piston is particularly adapted for use in machines for use for cleaning tubes and pipes.

Abstract: The safety of a machine for cleaning tubes and pipes constructed so as to include an elongated cylinder, a piston located within the cylinder, a non-round piston rod attached to the piston so as to extend out of one end of the cylinder and hydraulic components for introducing a high pressure fluid into and out of the ends of the cylinder can be improved by providing a second cylinder which is located concentrically around the first cylinder. A discharge structure is attached to the second cylinder so as to be capable of venting or dissipating any fluid which may enter the second cylinder as a result of rupture of the first to the ambient surroundings. Preferably the discharge structure includes a pressure reducer such as an orifice and preferably the discharge structure is located so that any fluid discharged from it cannot cause damage.