Multistage compressors for pet bottle blowing processes

A multistage reciprocating piston air compressor for compressing atmospheric pressure air to an elevated pressure level, the air compressor comprising:

• a first reciprocating piston stage comprising a first cylinder, a second reciprocating piston stage comprising a second cylinder, and a third reciprocating piston stage comprising a third cylinder, wherein
• the first reciprocating piston stage comprises:
• at least one first atmospheric air inlet;
• at least one first inlet valve operable to control air flow from the at least one first atmospheric air inlet to the first cylinder;
• and
• at least one first discharge valve from the first cylinder,
• the second reciprocating piston stage comprises:
• a second inlet valve operable to control air flow from the at least one first discharge valve to the second cylinder;
• and
• a second discharge valve from the second cylinder, and
• the third reciprocating piston stage comprising:
• a third inlet valve operable to control air flow from the second discharge valve to the third cylinder;
• and
• a third discharge valve from the third cylinder;
• a first solenoid operable in response to a sensed discharge pressure level from a discharge of the first reciprocating piston stage to mechanically hold open the at least one first inlet valve of the first reciprocating piston stage;
• a second solenoid operable in response to a sensed discharge pressure level from a discharge of the second reciprocating piston stage to mechanically hold open the second inlet valve of the second reciprocating piston stage;
• a third solenoid operable in response to a sensed discharge pressure level from the third reciprocating piston stage to mechanically hold open the third inlet valve of the third reciprocating piston stage;
• a first pressurized air discharge at the elevated pressure level from the third reciprocating piston stage;
• and
• at least one selected from (i) a first intermediate pressure air discharge line configured to selectably extract first lower pressure compressed air from a first interstage region between the first and second reciprocating piston stages for first lower pressure uses and (ii) a second intermediate pressure air discharge line configured to selectably extract second lower pressure compressed air from a second interstage region between the second and third reciprocating piston stages for second lower pressure uses.