US3387539A - Radial seals of rotary engines - Google Patents

Description

June 1968 G. DE COYE DE CASTELET 3,387,539

RADIAL SEALS OF ROTARY ENGINES Filed NOV. 7, 1966 United States Patent 3,387,539 RADIAL SEALS 0F ROTARY ENGINES Gatan de Coye dc Castelet, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt,

France Filed Nov. 7, 1966, Ser. No. 592,436 Claims priority, application France, Nov. 25, 1965, 39,841, Patent 1,464,875 3 Claims. (Cl. 91-56) This invention relates to rotary engines of the type comprising a rotor having 2N lobes, an epicycloidal contour, and revolving eccentricallly in a stator of conjugate contour having (2N +1) lobes.

This type of engine comprises (2N+1) variable volume working chambers formed between the inner contour of the stator on the one hand and the outer contour of the rotor on the other hand.

The necessary fluid-tightness between two adjacent working chambers is obtained by means of radial sealing strips fitted in grooves formed in the stator along the apex lines whereat two adjacent lobes merge into each other, these sealing strips resiliently engaging the epicycloidal contour of the rotor along a generatrix thereof.

These sealing strips have mostly a rectangular crosssectional contour and are urged against the rotor both by the springs usually associated with these strips and by the gas pressure exerted on the edges of these strips which are opposite to their bearing surfaces.

However, the operation of these sealing strips is not always satisfactory for their possibility of movement in their guide grooves is attended by substantial variations and is sometimes inadequate to keep them in sealing contact with the rotor.

Radial sealing strips are also known which operate by pivoting instead of sliding and are therefore free of the above-mentioned inconveniences.

This invention is concerned with pivoting sealing strips of the type broadly set forth hereinabove, which have a cross-sectional contour such that the frictional force developed by its contact with the rotor revolving in its normal direction of rotation cannot cause the strips to jam since on the contrary it tends to unwedge them.

This invention is also remarkable in that the gas pressure exerted on these sealing strips urges these strips against their cylindrical recess, the rotational torque exerted by the gas pressure being null or negligible.

In order to afford a clearer understanding of this in vention and of the manner in which the same may be carried out in practice, reference will now be made to the accompanying drawing illustrating diagrammatically by way of example a typical form of embodiment of a radial sealing strip constructed according to the teachings of this invention. In the drawing:

FIGURE 1 is a diagrammatic cross-sectional view of a rotary engine of the type referred to herein;

FIGURE 2 is a cross-sectional view showing on a larger scale a radial sealing strip according to this invention, and

FIGURE 3 is a detail view of the strip contour.

Referring first to FIGURE 1, a rotary engine is shown diagrammatically therein which comprises a five-lobed stator 1 having mounted therein for eccentric rotation a four-lobed rotor 2. The necessary fluid-tightness between adjacent working chambers such as 1 and 2 is obtained by means of radial sealing strips 3 fitted in guide grooves formed in the stator along the apex lines separating adjacent lobes, these sealing strips resiliently engaging the epicycloidal contour of the rotor 2 along a generatrix thereof.

3,387,539 Patented June 11, 1968 FIGURE 2 illustrates on a considerably enlarged scale one of these radial sealing strips, the reference numerals 1 and 2 designating the engine stator and rotor, respectively, the rotor revolving in the direction of the arrow and being adapted during its eccentric rotation to assume the two endmost positions shown by the lines 2 and 2 respectively with respect to the stator.

The radial sealing strip 3 according to the present invention is of substantially cylindrical configuration and mounted with a very small clearance in a cylindrical recess 4 having a diameter d and its center axis 0 is parallel to the apex line whereat two adjacent lobes 1 and 1 of the stator (denoted by the point P) but somewhat offset in relation to this point F in a direction opposite to the direction of rotation of the rotor. v

The strip portion providing the desired fluid-tightness by engaging the rotor contour, as already known per se, is a portion AB of a circle centered at P and having a radius R, this radius R being the one selected for tracing the epicycloidal contour of the rotor which is tangent to the points A and B in the endmost positions 2 and 2 of the rotor, said arc AB, according to a specific feature of this invention being disposed on either side of the circle centered at 0 whereby both points A and B are as close as possible to this center as shown in detail in FIGURE 3, under these conditions the rotational torque exerted by the gas pressure on the sealing strip is of zero or negligible value.

The aforesaid arc AB extnds on either side to points A and B to take due account of plays and thermal expansion.

The relative positions of centers P and 0 must be such that an extension of radius B P will always be on the right-hand side of center 0, in the case illustrated in the figure.

Thus, the frictional force produced at the point of contact between the rotor and the sealing strip, in a direction inclined to the normal at this point and in the direction of motion by a certain angle corresponding to the coeflicient of friction will always be directed to the right of center 0 and will therefore tend to rotate the strip in the direction to unwedge same.

The cross-sectional contour of the sealing strip 3 further comprises on the left-hand side of the figure a backed-off surface A C this point C being selected to permit the pivoting of strip 3 about the center axis 0 without causing this point C to interfere with the rotor 2 in the endmost position 2 thereof.

Similarly, on the right-hand side the strip 3 has a backed-01f face B 'DE to avoid any contact thereof with the stator 1 during its rotation.

The sealing strip 3 is urged against the rotor 2 by a spring 5 engaging a recessed flat face MN of the strip through the medium of a cup 6 having a domed stripengaging face.

Each strip 3 comprises a plurality of springs 5 (not shown) received in holes 7 formed in the stator 1, the axis xy of each hole being offset as much as possible to the right with respect to the axis C, whereby the springs 5 will tend to rotate the strip about the axis 0 in a direction opposite to that in which the rotor normally tends to rotate this strip.

The sealing strip 3 is made of self-lubricating material and if desired lubricating oil may be fed thereto through an oil duct 8 opening into its lower portion of groove 4.

As already known in the art the sealing strip 3 is divided into sections of adequate length in the longitudinal direction of the guide groove 4.

This radial sealing strip operates as follows:

During its rotational motion the rotor 2 is constantly 3 tangent to the strip 3 at a point normally lying between A and B.

Theoretically, if all the engine components were geometrically perfect, and if no distortion or wear occurred during the engine operation, the strip would be relatively motionless.

Actually a certain degree of distortion and play cannot be avoided and the strip is oscillated about the center axis 0. If the rotor departs somewhat away from its theoretical position the sealing strip is caused to move angularly in the counter-clockwise direction in the case illustrated, and if the rotor moves towards the strip the latter pivots in the opposite direction whereby the contact with the rotor is constantly maintained to the benefit of a highly reliable fluid-tightness between the two adjacent Working chambers.

Of course, various modifications can be made both in the strip structure and in the instrumentalities and mounting means used therefor, and it is contemplated in the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

Iclaim:

1. Radial sealing strips for rotary engines of the type comprising a rotor having N lobes of epicycloidal contour revolving eccentrically in a stator of conjugate contour with (ZN-H) lobes, said strips being pivotally mounted in grooves of substantially circular cross-sectional configuration which are formed in the stator parallel to and in close vicinity of the apex lines along which two adjacent lobes merge into each other, said strips being resiliently urged against the epicycloidal contour of the rotor along a generatrix thereof and characterised by their novel shape defined as follows:

said strips comprise a portion bearing on the stator which comprise a first circular are having substantially the same radius as the groove, and another portion bearing against the rotor which has the shape of a second circular arc having its center ottset in relation to the center of said first circular arc by a distance such that all the extensions of the radiuses of said second circular arc lie on one side of the center of said second circular arc with respect to the center of said first circular are, said second circular are being so positioned that its endmost points are as close as possible to, and on either side of, said first circular arc.

2. Sealing strip according to claim 1, wherein said second circular arc extends on either side of its theoretically endmost points to take due account of clearances and thermal expansions, said strip contour comprising on either side between the two circular arcs backed-off portions enabling the strip to oscillate without interfering with the rotor on the one hand and the stator on the other hand.

3. The sealing strip according to claim 1 further comprises on the first circular are a clearance engageable by a spring, said spring acting along an axis as remote as possible from the first circular arc and being so positioned that its action constantly tends to counteract the rotation of said strip by said rotor.

References Cited UNITED STATES PATENTS 12/1965 Toyoda et al 230- 11/1966 Linder 230-145

Claims (1)

1. RADIAL SEALING STRIPS FOR ROTARY ENGINES OF THE TYPE COMPRISING A ROTOR HAVING N LOBES OF EPICYCLOIDAL CONTOUR REVOLVING ECCENTRICALLY IN A STATOR OF CONJUGATE CONTOUR WITH (2N+1) LOBES, SAID STRIPS BEING PIVOTALLY MOUNTED IN GROOVES OF SUBSTANTIALLY CIRCULAR CROSS-SECTIONAL CONFIGURATION WHICH ARE FORMED IN THE STATOR PARALLEL TO AND IN CLOSE VICINITY OF THE APEX LINES ALONG WHICH TWO ADJACENT LOBES MERGE INTO EACH OTHER, SAID STRIPS BEING RESILIENTLY URGED AGAINST THE EPICYCLOIDAL CONTOUR OF THE ROTOR ALONG A GENERATRIX THEREOF AND CHARACTERISED BY THEIR NOVEL SHAPE DEFINED AS FOLLOWS: SAID STRIPS COMPRISE A PORTION BEARING ON THE STATOR WHICH COMPRISES A FIRST CIRCULAR ARC HAVING SUBSTANTIALLY THE SAME RADIUS AS THE GROOVE, AND ANOTHER

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