SCREW COMPRESSOR BEARING ARRANGEMENT WITH POSITIVE STOP ACCOMMODATE THRUST REVERSE

Title SCREW COMPRESSOR BEARING ARRANGEMENT WITH POSITIVE STOP TO ACCOMODATE THRUST REVERSAL Inventor Randy E. Dewhirst A first shim mounted on the shaft extending from the high pressure end face of a screw rotor in a screw compressor establishes the operating clearance between the high pressure end face of the rotor and the high pressure end wall of the compressor's working chamber by fixing the axial position of a bearing group which is likewise mounted on the rotor shaft. A second shim, disposed between the bearing group and a spring biased spacer element, is determinative of the distance the spacer element, and therefore the rotor, can travel in a direction toward the high pressure end of the compressor under the impetus of reverse axial thrust. Contact of the rotor with the high pressure end wall of the working chamber is positively precluded because movement of the spacer element, under the influence of rotor movement toward the high pressure end of the compressor, collapses the biasing spring which causes the spacer element to contact a fixed surface of the compressor. The spacer element contacts the fixed compressor surface and the reverse axial thrust is taken up by a roller bearing before the rotor can migrate sufficiently within the working chamber to contact the end wall of the working chamber. The biasing spring is selected to have sufficient strength to both preload the bearing set and to provide a limited amount of resistance, of itself, to reverse axial thrust while not being so strong as to cause significant frictional losses in the compressor or degradation of bearing life.