Vacuum scroll pump having pressure-balanced orbiting plate scroll

摘要

A vacuum scroll pump has a frame, a stationary plate scroll fixed to the frame, an orbiting plate scroll, an eccentric drive mechanism for driving the orbiting plate scroll, and counterbalancing features by which axial loads produced on the eccentric drive mechanism are offset. Scroll blades of the stationary and orbiting plate scrolls are nested to define pockets which constitute a compression stage between opposing front sides of plates of the stationary and orbiting plate scrolls. The counterbalancing features include an axial counterbalancing chamber defined at a back side of the plate of the orbiting plate scroll, i.e., opposite the side at which the compression stage is provided, and a mechanism by which an intermediate one of the pockets can be placed in communication with the counterbalancing chamber through the plate of the orbiting plate scroll.

主权项

1. A vacuum scroll pump, comprising:
an inlet portion having a pump inlet, and an exhaust portion having a pump outlet; a frame; a stationary plate scroll fixed to the frame and comprising a stationary plate comprising a central portion, a back side, a front side, and a stationary scroll blade projecting from the front side, wherein the stationary scroll blade has the form of a spiral comprising a plurality of successive wraps emanating from the central portion of the stationary plate; an orbiting plate scroll comprising an orbiting plate comprising a central portion, a back side, a front side that faces the front side of the stationary plate, and an orbiting scroll blade projecting axially from the front side of the orbiting plate toward the front side of the stationary plate, wherein the orbiting scroll blade has the form of a spiral comprising a plurality of successive wraps emanating from the central portion of the orbiting plate, and wherein the stationary scroll blade and the orbiting scroll blade are nested such that pockets are delimited by and between the stationary scroll blade and the orbiting scroll blade, the pockets being disposed in series between the pump inlet and the pump outlet and collectively constituting a compression stage of the vacuum scroll pump; an eccentric drive mechanism supported by the frame and operatively connected to the orbiting plate scroll so as to cause the orbiting plate scroll to orbit about a longitudinal axis of the vacuum scroll pump, and the orbiting plate scroll being supported by the eccentric drive mechanism so as to be rotatable about a second axis parallel to the longitudinal axis; and a tubular bellows comprising a first end connected to the orbiting plate at the back side thereof and a second end connected to the frame, wherein an axial counterbalancing chamber is defined within the frame at least in part by the tubular bellows, and is aligned in the direction of the longitudinal axis with part of the back side of the orbiting plate, and the orbiting plate has a gas bypass passage connecting the counterbalancing chamber and an intermediate one of said series of pockets that constitute the compression stage; and axial gas force control means for selectively placing said intermediate one of the pockets in open communication with the counterbalancing chamber and for closing off communication between said intermediate one of the pockets and the counterbalancing chamber, via the gas bypass passage.