Animation of the crankless rotors


A new efficient mechanical transmission


Animation of the crankless compressor operation

The crankless compressor is a positive displacement type of compressor.

It is a reciprocating compressor, in the sense that it uses pistons that increase and then decrease the size of a working chamber to deliver gases at high pressure. The intake gas enters the suction manifold, then flows into the working chamber where it gets compressed by two rotating pistons driven in a reciprocating motion via the crankless drive, and is then discharged. There is no need for valves, and no pressure loss at the intake or outlet.

It is also a rotary compressor, as the working chambers rotate in a toroid, and the pistons are mounted on rotating rings.

Pneumatic motor

Animation of the crankless gas expander or pneumatic motor operation

Alternatively, the crankless drive can also be used as gas expander or pneumatic motor. In this case, mechanical work is extracted from the expanding high pressure gas. A special type is the compressed air engine.

The compressed gas is fed into working chamber of the engine, where its pressure starts the motion of the rings. The crankless drive transforms the motion of the rings into a powered rotation of the machine axle (see crankless drive technology). At the end of the expansion, the expanded gas is release in the exhaust. There is no need for valves, and no pressure loss over the intake or outlet of the crankless pneumatic motor.


The main advantages of the crankless compressor or pneumatic motor compared to the classic reciprocating design are:

Better technology Tangible advantages
More efficient geometry, with better use of working chamber volume (both sides of the piston are used)
  • Lower weight
  • Smaller size
Much less moving parts (no valves, no valve opening / closing mechanism)
  • Lower production cost
  • Simplified serviceability
  • Lower maintenance cost
  • Quiet
  • Low vibration
No pressure loss over the intake or discharge, as there are no valves
  • Increased efficiency
No back and forth linear movements of pistons
  • Quiet
  • Low vibration
Higher revolution speeds possible as all components are rotating
  • Scalable
  • Flexible
Possibility to adapt the compressions ratio, by adapting the angle of the machine axle
  • Scalable
  • Flexible


Possible applications include:

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