A two stage reciprocating piston oil free air compressor having an improved
service interval. In a first stage, a first wobble piston is reciprocated
in a first cylinder to compress ambient air to an intermediate pressure.
In a second stage a second wobble piston is reciprocated in a second
cylinder to compress the intermediate pressure air to a desired high
pressure. Each wobble piston is provided with a seal which seals to the
adjacent cylinder walls as the piston reciprocates and rocks. The stroke
of the higher pressure second stage piston is less than the stroke of the
lower pressure first stage piston to increase the operating life of the
second seal, preferably to substantially the same operating life as the
first seal.
