Capacity controllable compressor apparatus

A capacity controllable compressor apparatus comprising:

• a plurality of high-pressure chamber compressors which are connected in parallel to a common refrigerant suction pipe and a common refrigerant discharge pipe having an oil separator, one of said compressors being operated with its chamber kept at a higher internal pressure than the other compressors;
• means for returning lubricating oil separated from discharged refrigerant, by said oil separator to a suction side of that one of said compressors operated with its chamber kept at the higher internal pressure;
• oil equalizing pipes through which oil sumps of said plurality of compressors communicate with each other;
• first control means disposed in said oil equalizing pipes so as to prevent the lubricating oil from flowing, through respective ones of said oil equalizing pipes, from a compressor which is in operation into one which is being made inoperative in accordance with effecting control of the capacity of the compressor apparatus;
• and
• valve means disposed in a discharge pipe of said inoperative compressor so as to prevent refrigerant, discharged by one or more compressors which are in operation, from flowing into said inoperative compressor.