Rotary expansible chamber devices – Interengaging rotating members – Helical or herringbone
Patent
1988-11-01
1991-03-26
Vrablik, John J.
Rotary expansible chamber devices
Interengaging rotating members
Helical or herringbone
F04C 1816
Patent
active
050024728
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to rotary machines comprising a stator housing two rotors, respectively male and female, driven in opposite rotations in either controlled or non-controlled manner. The object of the invention relates to the technical field of machines of the aforesaid type of which the rotors have complementary helical teeth creating, by their intermeshing, cells of variable volume, which, by developing along a direction parallel to the rotors rotation axis, set up a flow of gaseous fluid between an admission or induction orifice and an expelling orifice.
The object of the invention concerns machines of the aforesaid type working as compressors or vacuum-pumps.
PRIOR ART TECHNIQUE
In the machines of the aforesaid type, the rotation of the rotors inside their housings, when it is caused by the controlled rotation of one rotor driving the other in rotation, is performed with interposition of a liquid, generally oil, then achieving sealing between the teeth of the rotors and the housings of the stator, lubrication between rotor and stator, and cooling of the compressed gaseous fluid.
The screw-type rotors, known from application GB-A-1 342 287, have tooth tips in wedge form. With this particular construction, the presence of the sealing, lubricating and cooling liquid causes an important loss of power, due to the phenomenon whereby the liquid molecules are wedged between the tip of the teeth of the male and female rotors and the housings of the stator containing them. Said wedging phenomenon generates high pressures exerting radial forces which are harmful to the rotors and to the bearings supporting them. Said radial forces are amplified, on the one hand, by the centrifuging of the liquid in concentration near the top of the teeth, due to the high rotation of the rotors, and on the other hand, by the flowing of said liquid from the delivery plane toward the induction plane, caused by the difference of pressure between said two planes.
It is to be noted that a similar phenomenon occurs also in cases where the rotors are driven in gear-synchronized controlled rotations. In such cases, there is no lubricant fluid provided. The formation is however noted, for each tip of the teeth, of a wedge of high pressure air which is responsible for overheating and loss of power.
It is the object of the invention to propose new profiles for male and female rotors, seeking to reduce, altogether, the importance and extent of phenomenon of wedging of the molecules either of the sealing, lubricating or cooling liquid of the gaseous fluid, or of said gaseous fluid.
SUMMARY OF THE INVENTION
In order to reach the aforesaid object, the invention proposes cutting profiles, characterized in that they involve, at least for the teeth of the male rotor, an apex: between, on the one hand, a tangent to the apex, perpendicular to a straight line joining said apex to the center of rotation of the male rotor and, on the other hand, a straight line tangent to the apex and perpendicular to a straight line joining said apex to the instantaneous center of rotation.
Various other characteristics will emerge from the following description with reference to the accompanying drawings which show, by way of example and non-restrictively, embodiments of the object of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section of a rotary machine according to the invention.
FIG. 2 is an elevational view of an axial section taken substantially along line II--II of FIG. 1.
FIG. 3 is a cross-section showing, on a larger scale, the embodiment of the profiles according to the invention.
FIGS. 4 to 10 are diagrammatical views, similar to FIG. 1, illustrating various characteristic phases of operation of the object of the invention.
FIGS. 11 and 12 are cross-sections showing two variants of embodiment of one of the means of the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
FIGS. 1 and 2 show a rotary machine 1 comprising a body or stator 2 defining two bores 3 and 4 which have parallel and secant axes.
REFERENCES:
patent: 3166238 (1965-01-01), White et al.
Traite Theorique et Pratique des Engrenages, par G. Henriot, 6'edition, pp. 11 and 12.
Baudrier Patrick
Helliot Bernard R. A. G.
Societe Anonyme: Baudot-Hardoll S.A.
Vrablik John J.
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