Compressor for single or multi-stage operation

Compressor means having a crankcase, a suction inlet adapted to be connected to an evaporator and a discharge adapted to be connected to a condenser comprising:

• three banks;
• a first and a second one of said three banks being normally connected to said suction inlet;
• a third one of said plurality of banks being normally connected to said crankcase and said discharge;
• means for selectively connecting said first and second banks to either said crankcase or said discharge;
• means for fluidly connecting said crankcase to said suction inlet when said first and second banks are connected to discharge;
• whereby when said first and second banks are connected to said crankcase they act as a first stage and said third bank acts as a second stage and when said first and second banks are connected to discharge they act as a single stage and said third bank acts as a single stage in parallel with said first and second banks.

Refrigeration means for cooling a zone including a closed circuit serially including compressor means, condenser means, expansion means and evaporator means:

• said compressor having three banks, a crankcase, a suction inlet connected to said evaporator and a discharge connected to said condenser;
• a first and a second one of said three banks being normally connected to said suction inlet;
• a third one of said three banks being normally connected to said crankcase and said discharge;
• means for selectively connecting said first and second banks to either said crankcase or said discharge;
• means for fluidly connecting said crankcase to said suction inlet when said first and second banks are connected to discharge;
• whereby when said first and second banks are connected to said crankcase they act as a first stage and said third bank acts as a second stage and when said first and second banks are connected to discharge they act as a single stage and said third bank acts as a single stage in parallel with said first and second banks.

A method for operating a compressor having three banks, a crankcase, a suction inlet adapted to be connected to an evaporator and a discharge adapted to be connected to a condenser comprising the steps of:

• supplying gas from said suction inlet to a first and second bank of said three banks;
• supplying gas from said crankcase to a third bank of said three banks;
• delivering compressed gas from said third bank to said discharge;
• selectively connecting said first and second banks to either said crankcase or said discharge whereby when said first and second banks are connected to said crankcase they act as a first stage and said third bank acts as a second stage and when said first and second banks are connected to discharge they act as a single stage and said third bank acts as a single stage in parallel with said first and second banks.