with coaxially-mounted members having continuously-changing circumferential spacing between them

Rotary-piston machines or engines > of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents > with coaxially-mounted members having continuously-changing circumferential spacing between them

Rotary-piston machines or engines (with axes of co-operating members non parallel F01C3/00; with the working-chamber walls at least partly resiliently deformable F01C5/00; with fluid ring or the like F01C7/00; rotary-piston machines or engines in which the working fluid is exclusively displaced by, or exclusively displaces, one or more reciprocating pistons F01B13/00) > of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents > with coaxially-mounted members having continuously-changing circumferential spacing between them