Balanced compressor

Claim 1

In a closed cryogenic cooling system comprising an electric motor driving a compressor which feeds a regenerator through a conduit, the system containing a low molecular weight gas at a minimum pressure orders of magnitude greater than atmospheric pressure; the improvement wherein said compressor comprises: a crankshaft having at least first and second cylindrical sections with axes parallel to but displaced a short distance in opposite directions from the axis of rotation in said crankshaft; a piston and a first rod connected between said piston and said first cylindrical section to provide a displacement thereof equal to twice said short distance associated with said first section; a hollow cylinder closed at one end snugly and coaxially fitted around said piston to provide a compression chamber therebetween, and at least a second rod connected to said cylinder and said second cylindrical section to produce a displacement of said cylinder which is opposite to that of said piston the weights and displacements of said piston and cylinder being balanced to produce minimum crankshaft vibration; a housing surrounding said motor crankshaft, piston and cylinder, the walls of said housing being charged with said gas at said minimum pressure and having inward projections providing bearing supports for said crankshaft and a first guide recess to slideably engage the outer surface of said cylinder, thereby restricting it to axial translation only; and said conduit being sealed through the wall of said housing into said recess and having a telescoping section within said housing communicating with said compression chamber, whereby said gas at high ambient pressure within said housing leaks into said chamber and is forced into said conduit at even higher pressure by the relative motion of said piston and cylinder and any gas leaking through said telescoping section into said recess passes freely back into said housing.