Geometrical aspects of novel internally geared screw machine.

Cylindrical helical gearing can be used in a positive displacement machine where an externally lobed inner gear rotates inside an internally lobed outer gear while maintaining continuous lines of contact between the gears. This creates a series of separate working chambers between the rotors. In this type of machine the rotors have parallel axes of rotation, and both rotors can be free to rotate about their own axes. Fixed end plates are proposed as a method of controlling the period during which fluid is allowed to enter or leave the working chambers of the internally geared screw machine. As with conventional screw machines, these internally geared rotors can then be used to achieve compression or expansion of a trapped mass of fluid. This paper describes the geometrical analysis of some simple rotor profiles and explores the effect on rotor forces for particular applications of this novel screw configuration.