Toothed-gear rotary engine designs are not as common
as the vane and oscillatory designs are. The contact
areas between the rotating elements involve at least two
independent rotating elements and provides for a more
complex geometry to seal. These mechanisms have
found more success in the compressor and pump
industries.
Two early designs, Kryszat 1896 design and Burlich
1906 design, illustrate external combustion toothed gear
mechanisms. Kryszat’s design is shown in Figure 10.
These designs consist of round rotors and stators
concentrically located. Multiple teeth and receptors are
used. The later of these designs has means for
reversing the rotor direction