Penn’s 1996 design describes an inner and outer stator
that acts as the cam surfaces as shown in Figure 7 [30].
A cylindrical concentric rotor is placed between the two
stators. Vanes translate through the rotor between the
inner and outer cam surfaces; each set of vanes creates
chambers between the inner cam and rotor and between
the rotor and outer cam. A roller is used at the vane tip
at the outer cam surface to carry the vane load. A set of
vane tip seals is placed for sealing between adjacent
chambers and to account for the changing curvature of
the cam surface. Rollers are used in the rotor to guide
the vane. Seals are also used between the rotor and
vane to minimize leakage into the rotor or from the inner
to outer chambers. There are means to communicate
the working fluid between the inner and outer chambers,
tailoring the cycle.