Cryogenic expander with collar bumper for reduced noise and vibration characteristics

A cryogenic expander having a pneumatically driven reciprocating piston in a cylinder comprising:

• a cylinder;
• a pneumatically driven reciprocating piston in the cylinder, the piston having a warm piston end and a cold piston end, the piston reciprocating between a warm cylinder end and a cold cylinder end, a distance of travel of the piston in the cylinder between the warm cylinder end and a cold cylinder end being defined as a stroke;
• a piston seal at the warm piston end between the piston and said cylinder;
• a bumper in the cylinder;
• a collar comprising a lip on a top of the collar, the collar being disposed at the warm piston end, the collar having a length, between the seal and the lip, that is at least as long as the stroke, the collar having an inside diameter that is at least 90% of the outside diameter;
• wherein the warm cylinder end comprises a cylinder head with a neck that extends inside the collar, the neck having a neck seal between the neck and the inside of the collar,
• wherein the lip engages the bumper that prevents the piston from touching the cold cylinder end to reduce noise and vibration characteristics.

A cryogenic expander with reduced noise and vibration characteristics, the cryogenic expander comprising:

• a cylinder;
• a pneumatically driven reciprocating piston in the cylinder, the piston having a warm piston end and a cold piston end, the piston reciprocating between a warm cylinder end and a cold cylinder end, a distance of travel of the piston in the cylinder between the warm cylinder end and a cold cylinder end being defined as a stroke;
• a seal at the warm piston end between the piston and said cylinder;
• a bumper in the cylinder;
• a collar comprising a lip on a top of the collar, the collar being disposed at the warm piston end, the collar having a length, between the seal and the lip, that is at least as long as the stroke, the collar having an outside diameter that is less than a diameter of the piston, the collar having a cross sectional area that is less than 20% the cross section area of the piston;
• wherein the lip engages the bumper that prevents the piston from touching the cold cylinder end to reduce noise and vibration characteristics.