Animation of the crankless rotors


A new efficient mechanical transmission


Animation of the crankless liquid pump operation

The crankless pump is a rotary positive displacement type pump.

Positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.

In the crankless pump, the cavity is the working chamber between to rotating pistons. Therefore, the crankless pump benefits from having 4 working chambers or cavities operating simultaneously. Additionally, there is no need for valves, so the crankless pump is also a valveless pump.

Hydraulic motor

Animation of the crankless hydraulic motor operation

The hydraulic motor is the conceptual opposite of the pump.

When the direction of the flow is reversed, the hydraulic motor performs the opposite function of the pump. It becomes a mechanical actuator that converts hydraulic pressure and flow into mechanical work: torque and angular displacement (rotation) of the machine axle.

The pressure of the liquid at the intake pushes the working chamber to expand up to its maximum volume, delivering work to the machine axle. The liquid is then discharged at low pressure by the contracting working chamber.


The main advantages of the crankless pump or hydraulic motor compared to the classic reciprocating piston 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 back and forth linear movements of pistons
  • Quiet
  • Low vibration


Possible applications include:

Typical liquids include:

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