A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4) and a rotatable shutter (3), the rotor comprising a piston (5) which extends from the rotor into a working chamber, the rotor and the stator together defining a working chamber, the shutter arranged to extend through the working chamber and forming a partition therein, and the shutter comprising a slot which allows passage of the piston therethrough, a bearing (20) which mounts the rotor relative to the stator, the rotor comprising a formation (12; 30) which extends substantially axially away from the chamber, and the formation being radially outward of the bearing and extending around the axis of rotation, and the formation comprising a surface which at least in part defines a space between the rotor and the stator, and at least part of that space and/or the formation overlaps in an axial direction with the bearing.

A rotary piston and cylinder device comprising a rotor (2), comprising a rotor surface (2a), a stator (4), a rotatable shutter (3), a piston (5) which extends from the rotor surface, 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 being orientated at an incline to a plane (P-P) substantially perpendicular to the axis of rotation (A-A) of the rotor and the rotor surface faces generally away from, or outwardly of, the axis of rotation of the rotor.

A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4), a rotatable shutter (3), the rotor and the stator comprising surface portions which define a chamber, wherein the rotor comprises a first surface portion (2A) and the stator comprises substantially two surface portions (4a; 4b′), and the two surface portions of the stator neighbour each other.

A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4) and a rotatable shutter (3), a rotary piston and cylinder device comprising a rotor, a rotatable shutter, the rotor comprising a piston (5), the piston comprising a first side (5b) and a second side (5a), the first side (5b) arranged to seal with a slot of the shutter, and comprises a working face, the second side being a substantially oppositely directed side to the first side, and the second side (5a) comprising a sealing portion arranged to seal with the shutter slot and/or stator and a non-sealing portion arranged not to seal with the shutter slot.

In a rotary piston and cylinder device (1) having a stator and a rotor, in which the stator at least partially defines an annular cylinder space and the rotor includes at least one piston that extends from the rotor into the cylinder space, and in which, during use, the piston moves through the annular cylinder space on rotation of the rotor relative to the stator, wherein at least part of an outer surface (30) of the rotor (22) is a substantially frusto-conical shaped surface.

A rotary piston and cylinder device (1) comprising a rotor (2), a stator and a shutter disc (3), the rotor comprising a piston (5) which extends from the rotor into the cylinder space, the rotor and the stator together defining the cylinder space, the shutter disc passing through the cylinder space and forming a partition therein, and the disc comprising a slot (3a) which allows passage of the piston therethrough, the slot provided between two surface portions which receive the piston therethrough,at least one of the surfaces defines a close-running region with the piston to provide a fluid seal, and for at least part of the period during which the piston passes through the slot, the close-running region is offset from a mid-plane which extends through the disc and is co-planar with the disc.

A rotary piston and cylinder device (1) comprising: a rotor (2), comprising a rotor surface (2a), a piston (5) which extends from the rotor surface, a stator (4), a rotatable shutter (3), the rotor surface and the stator together defining an annular chamber, and the piston arranged to rotate, through the annular chamber, wherein when the chamber is viewed in axial cross-section, substantially a single surface of the stator in part defines the chamber (100).

A toroidal combustion engine is provided. The toroidal combustion engine includes a first and a second toroidal cylinder which share a single common intersection to define a combustion chamber. The first toroidal cylinder carries a first piston set, while the second toroidal cylinder carries a second piston set. The first and second piston sets are each rotatable about circular paths which are disposed in planes that are perpendicular to one another.

A transmission assembly for a rotary piston and cylinder device, comprising a rotor including a piston, a stator, a shutter including a slot to receive the piston, and a first gear and a gear sub-assembly, the first gear connectable to a rotatably mounted shutter of the device, and the first gear extending from a side of the shutter, and the first gear connected to the gear sub-assembly which converts rotation to an axis of rotation different to that of the shutter.

A rotary piston and cylinder device (1) comprising a rotor (2), a stator and a shutter disc (3), the rotor comprising a piston (5) which extends from the rotor into the cylinder space, the rotor and the stator together defining the cylinder space, the shutter disc passing through the cylinder space and forming a partition therein, and the disc comprising a slot (3a) which allows passage of the piston therethrough, and a surface of the rotor and a surface of the stator opposing each other forming a close-running surface pair, and at least one of the surfaces comprising an abradable coating (10) which is provided with a plurality of recess formations, and the recess formations are discontinuous from each other.