The compressor comprises an oil spray and a drive disc (26) which is arranged in a crank chamber (21) and mounted on a drive shaft (16). A piston (20) works with the drive disc in a cylinder bore (19). The disc turns the shaft with a reciprocating piston movement in the cylinder bore. The piston compresses the gas in the bore which leaves via an outlet chamber (33) and an outlet passage (34). An oil separator mechanism (41) is situated half way into the outlet passage to separate the oil from the flowing gas. A storage chamber (48) in the lower section of the mechanism stores the separated oil. The oil can be directed from the storage chamber to the crank chamber via a feed passage (49). A feed valve (51) arranged half way into the feed passage opens to let the oil pass from the storage chamber to the crank chamber if the compressor stops.
