Structural specialities of the GL-spirals are compounded by the cubicparabola, line, circle, parabola and designed with unequal spiral distances.

This paper introduces a new and simple design of variable pitch screw, this method makes use of manufactural method of curve which is invariable acceleration and brings out the operation rang of the method.

According to analysis the math theory of variable pitch screw, we found the parameterized mathematical model.

New thread profile of rotors for dry double-screw vacuum pump:single thread with varying pitch;

A discussion on the critical speed of the upright cylinder helix ditching machine of the variable pitch;

It is on the principle of numerically-controlled process simulating and automaically create the 3-D soid model of pitch-varying spiral with the method of parameterized design .

This paper expounded some key problems of design for part carrying spiral of the high speed filling machine, and researched the some effective method of analying and designing to the changing pitch spiral, and introduced the controlling factors of the can in realizing high speed and steady movement.

In this article, a roller profile of single thread and changing pitch screw for dry twin screw vacuum pump is introduced, and the profile equations, the formula of pump speed and the explanation of parameter determination principles are given.