Abstract: A piston for an internal combustion engine, said piston having a combustion chamber formed in its head, the combustion chamber having an inlet orifice in the top surface of the head, a flat bottom wall, and a side wall which includes a plurality of concave recesses which intersect to define cusps directed towards a central zone of the combustion chamber, said cusps including concavely curved portions which extend upwardly from the flat bottom wall and inclined portions which extend between the curved portions and the top surface of the head along the surface of an imaginary cone having its apex above said top surface.

Abstract: A liquid sealing device, for inhibiting passage of liquid between a rotatably mounted shaft and an aperture through which the shaft extends with working clearance, including an annular shoulder projecting from the shaft, means adjacent the shaft formed with a cylindrical bore in which the shoulder is rotatable with working clearance, a helical groove extending around the periphery of the annular shoulder, and closure means for the bore adjacent one end of said annular shoulder, said closure means defining said aperture through which the shaft extends with working clearance, whereby rotation of the shaft in a given direction will cause the helical groove to resist the passage of liquid between the annular shoulder and the bore, and will enable the annular shoulder and closure means to co-operate and thereby inhibit passage through the clearance between the shaft and the aperture of any residual liquid which overcomes the resistance of the helical groove.