Rotary piston and cylinder device with flared curved rotor surface

A rotary piston and cylinder device comprising:

• a rotor, having a rotor surface,
• a stator,
• a rotatable shutter disc, the rotatable shutter disc provided with a slot,
• a piston which extends from the rotor surface, said slot of the rotatable shutter disc arranged to allow the piston to pass therethrough during operation of the device,
• the rotor surface and the stator together defining an annular chamber, and the piston arranged to rotate through the annular chamber,
• and the rotor surface faces away from, or outwardly of, an axis of rotation of the rotor,
• and the rotor surface is of a curved flared profile when viewed in axial cross-section,
• and said curved flared profile extends between a first rotor surface end region and a second rotor surface end region, and the first rotor surface end region being spaced along the axis of rotation of the rotor with respect to the second rotor surface end region, and one of the rotor surface end regions having a greater radial extent than the other rotor surface end region,
• and the rotary piston and cylinder device further comprising a transmission assembly having a toothed gear, the transmission assembly configured to maintain timing of the rotatable shutter disc in synchrony with the rotor.