Below is a list of Reciprocating Compressors manufacturers from Milford, Connecticut. Reciprocating compressors, also known as piston compressors, are positive displacement air compressors that use a piston in a cylinder as the mechanism for compressing air. Usually an electric motor provides power for a crankshaft to push the piston up and down; to reciprocate. When the crankshaft pushes the piston up, the air is pushed into a tank with a one-way check valve that does not permit it back into the cylinder. As more air enters the tank, the pressure increases. When the piston is pulled down, new air enters and the process begins again.