Patent ID: 8328831

Claim:
A water jet apparatus for severing a biological structure with a jet of severing liquid comprising water, the water jet apparatus comprising a storage container for the severing liquid, a piston-cylinder unit comprising a generally cylindrical opening formed in a casing having a wall and a bottom, a piston received in the cylindrical opening for reciprocal motion of the piston in the cylindrical opening with space remaining adjacent to the bottom of the cylindrical opening, the space functioning as a pressure space upon downstroke of the piston and as a suction space upon upstroke of the piston, opposite the bottom formed by the cylindrical opening, the cylindrical opening takes on a conical portion, an annular membrane extending between an inner periphery and an outer periphery, the outer periphery is attached to the conical portion of the generally cylindrical inner wall at a position in an upper zone of the piston-cylinder unit and the inner periphery is attached to the piston at a position in the upper zone of the piston-cylinder unit, the upper zone being defined by an annular space above the suction-pressured space, the membrane sealing interior of the piston-cylinder unit below the membrane from exposure to the ambient outside the piston-cylinder unit and the membrane being dimensioned so as to allow reciprocation of the cylinder and the annular space being dimensioned so as to allow movement of the membrane therein as the piston reciprocates and to accommodate the membrane when the piston is at rest at the end of downstroke, a manipulable operating device including an internal pressure tubule terminating in the jet, a suction line for conducting the severing liquid from the storage container to the suction-pressure space in the cylinder, a pressure line for conducting the severing liquid from the suction-pressure space in the cylinder to the operating device, a coupling for attaching an eccentric drive to and detaching the eccentric drive from the piston, the piston-cylinder unit together with the suction line, the pressure line and the operating device constituting a sub-assembly, wherein the suction line is attachable to and detachable from the storage container and the cylinder casing by means of a first and a second coupling and the pressure line is attachable and detachable from the manipulable operating device by a third coupling, a first opening through the cylinder casing, the first opening effecting communication of the pressure line with the suction-pressure space, a second opening through the cylinder casing, the second opening effecting communication of the suction line with the suction-pressure space the first and second openings being radially oriented and diametrically opposed and a check valve, opening in the suction direction, is inserted in the suction line.