PURPOSE: To increase the capacity of a compressor by decreasing the flow resistance through an enlarged flow channel in a structure where the whole body is cast- moulded including a suction channel with a L-shaped section, the coupling part between a circular groove and a side hole of the flow channel is moulded in a curved shape, and the surface of the channel is hardened as cast.

CONSTITUTION: A valve seat 1 is cast-moulded as one unit. The properly shaped core must give roundings to an opening edge 7 of a circular groove 4, a bottom-side corner 8 and an opening edge 9 of a side hole 5, thereby reducing the suction flow resistance against the refrigerant gas. The increased hardness of the surface of a suction channel 6, due to being hardened as cast, enables the thinning of both sides 10 between the upper-lower sides and the side hole 5, whose diameter can be thus enlarged compared to the thickness of the valve seat 1, thereby decreasing the flow resistance