GB1001336A - Helical gear pump - Google Patents

Abstract

1,001,336. Helical gear pumps. MONO PUMPS Ltd. July 14, 1964 [July 25, 1963], No. 29000/64. Heading F1F. A helical gear pump of the Moineau type includes inner and outer members of equal pitch with the inner member having one more start on its external thread than the outer member has on its internal thread and the teeth shaped in transverse cross-section to give continuous sealing contact between the members. As shown in Fig. 1, the inner member or rotor 10 is of elliptical form and the outer member or stator 11 similar to that of a cardiod. As the rotor 10 rotates its own centre describes a circle 12 whose radius is equal to E, i.e., twice the difference between the semimajor axis a and the semi-minor axis b of the ellipse. The number of points of contact equals the sum of the starts of the two members, i.e., in the present case two plus one, except in that position in which the small end of the rotor passes the nodal point on the stator. In another embodiment, Fig. 5, a substantially triangular, three-start rotor 20 rotates in a bi-arcuate, two-start stator 22. The inner member is preferably made of metal and the outer member of natural or synthetic rubber, but this arrangement may be reversed. It is usual to drive the inner member through a flexible drive such as a universal joint or Cardan shaft with the outer member remaining stationary but since the members are symmetrical about their respective axes, the outer member may be driven with the inner member freely rotating therein. The speed of the inner member with respect to the outer member then being in the inverse ratio to the number of starts on the two members. The flexible drive is then omitted.