Scroll-type liquid pump

Abstract From the Canadian patent

Scroll apparatus for pumping liquids wherein recessed liquid transfer passage means are provided in the end plates of the scroll members. The transfer passage means may be inner passages within the scroll involutes, outer passages outside the scroll involutes or a combination of inner and outer passages. These passages are located and configured to be opened substantially immediately after the orbiting involute wrap has reached that point in its orbiting cycle to define three essentially completely sealed-off liquid zones. These passages remain open at least until the liquid passages between the wraps are sufficiently large to prevent any substantial pressure pulsations within the scroll …