Patent ID: 6439864
Filing Date: 2002-08-27
Classification: F04C

Abstract:
A scroll vacuum pump having:a first stage including a first stage fixed plate having a spiral involute, a first stage orbiting plate having a spiral involute wrap, a first stage inlet, and a first stage outlet; said spiral involute wraps meshing with each other to define chambers, said chambers increasing in size from said first stage inlet to said first stage outlet; and a second stage including a second stage fixed plate having a spiral involute wrap, a second stage orbiting plate having a spiral involute, a second stage inlet in fluid communication with said first stage outlet, and a second stage outlet; said second stage spiral involute wraps meshing with each other to define chambers, said chambers decreasing in size from said second stage inlet to said second stage outlet; said first stage having an expansion ratio greater than or equal to one and said second stage having a compression ratio greater than or equal to one; and the displacement of the first stage is greater than the displacement of the second stage so that the interstage pressure will be at a value between the first stage inlet and the second stage outlet.