A pneumatic motor having a motor body having a main piston chamber with
opposed first and second chamber ends, at least two spool chambers in
fluid communication with the main piston chamber, an inlet for flowing a
pressurized fluid into each of the at least two spool chambers, and an
outlet provided in the housing for exhausting the pressurized fluid from
the main piston chamber and each of the spool chambers. At least two spool
members are in the two spool chambers, with each spool member adapted to
be movable in a first direction to permit pressurized fluid to be supplied
to the main piston chamber and also in a second direction to permit the
pressurized fluid to be exhausted from the main piston chamber. A piston
member is movable in a reciprocating manner in the main piston chamber in
response to movement by the spool members. The piston has first and second
piston ends and an annular piston chamber located between and in fluid
communication with the first and second chamber ends, the first and second
piston ends defining, with the first and second chamber ends, a first
chamber and a second chamber, respectively, in the main piston chamber
during reciprocation of the piston. First and second seals between the
piston ends and the annular piston chamber are provided such that while
the piston reciprocates within the main piston chamber, the first and
second seals alternately exhaust the first and second chambers into the
annular piston chamber.