Abstract: A scroll compressor is provided with a two groups of commmunication ports formed in and extending through an end plate of a stationary scroll member. Each group includes two or more communication ports. A lead valve is associated with each of the two groups of communication ports and is operable by a pressure differential in between an associated compression chamber and the discharge chamber to communicate the communication ports of the group to the discharge chamber to prevent the occurrence of over-compression in the compression chamber.

Abstract: A scroll compressor comprises an orbiting scroll and a fixed scroll, each of which includes a spiral wrap. These orbiting and fixed scrolls define between their wraps a plurality of close spaces at symmetrical positions. These closed spaces are moved toward the center of the scrolls by means of orbital motion of the orbiting scroll relative to the fixed scroll for reducing their capacities to compress fluid confined therein. Upon starting the compressor, some of the spaces which are in mid course of compressing and the other closed spaces which locate at the downstream side just before the communication with a discharge port, are communicated with each other through valves which open when pressure in the closed spaces at the upstream side is higher than that in the closed spaces at the downstream side, whereby a loading torque upon starting is decreased.