US3894820A

US3894820A - Sealing devices for rotors of rotary piston engines

Info

Publication number: US3894820A
Application number: US401606A
Authority: US
Inventors: Michel Durin
Original assignee: Automobiles Citroen SA
Current assignee: Automobiles Citroen SA
Priority date: 1972-10-02
Filing date: 1973-09-28
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: FR2201718A5; JPS504408A; ES418430A1; IT997247B; GB1438850A; DE2349471B2; DE2349471A1

Abstract

The sealing device comprises a central bar and two angular segments mounted end to end in a groove situated along each crest of the rotor. Each groove is formed in the rotor at the level of the bar and in a drum sliding at the level of each segment. A spring exerts a centrifugal radial force on the segments, the bar and each segment are in contact through oblique support surfaces and stop surfaces are provided between each segment and each drum to transmit to the latter the axial component, due to the said oblique surfaces, of the total radial force of the spring.

Description

United States Patent Durin July 15, 1975 FOREIGN PATENTS OR APPLlCATIONS 1,223,612 8/1966 Germany 418/120 Primary Examiner.lohn .1. Vrablik Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher 5 7] ABSTRACT The sealing device comprises a central bar and two angular segments mounted end to end in a groove situated along each crest of the rotor. Each groove is formed in the rotor at the level of the bar and in a drum sliding at the level of each segment. A spring exerts a centrifugal radial force on the segments, the bar and each segment are in contact through oblique support surfaces and stop surfaces are provided between each segment and each drum to transmit to the latter the axial component, due to the said oblique surfaces, of the total radial force of the spring.

9 Claims, 6 Drawing Figures SEALING DEVICES FOR ROTORS OF ROTARY PISTON ENGINES The invention relates to scaling devices for prismatic rotors of rotary piston engines, which are constituted by a central bar and by two angular segments mounted end to end in a groove situated along each crest of the rotor, this groove being formed in the rotor or in part rigidly fixed to the rotor at the level of the central bar, and in a drum at the level of each angular segment, each drum being guided, in a housing formed in the rotor, so as to be slidable without rotating parallel to the crest of the rotor, and elastic means being provided to urge, on one hand, the central bar, and the angular segments radially outward, and, on the other hand, each of the drums axially in the direction which spaces it from the middle transverse plane of the rotor.

In general, prismatic rotors have, in profile, the shape of a curvilinear polygon, and more particularly ofa cur vilinear triangle, and the generators of the rotors which pass through the apices of this polygon are called crests." Also, the drum and their housings have generally, for reasons of machining, a cylindrical shape, but this shape can also be prismatic.

As is known, such a rotor is intended to be mounted in an envelope whose transverse inner surface has a tro choidal profile and it limits, with this inner surface, combustion chambers of variable volume, which must remain separated from one another by the above said sealing devices, whatever the degree of wear of the latter. ln being urged radially outwrads, not only by the abovesaid elastic means but also by centrifugal force and possibly by the pressure existing in the combustion chambers, the central bar and the crest segments mounted along each crest are held in contact with the transverse inner surface of the envelope, along a continuous line. In being urged axially, the drums are held in contact by flat surfaces with the lateral inner surfaces of the envelope (surfaces perpendicular to the axis of the motor shaft or output shaft), which completes laterally the radial sealing action of the bar and of the angular segments which flank it.

Usually, there coexists, at the level of each crest, two types of elastic means. The elastic means of the first type have the effect of radially urging the central bar and the angular segments. The elastic means of the second type have the effect of axially urging each bar and are generally constituted by a spring having the shape of a flat yoke of small thickness about 0.2 mm surrounding the crest segment, the spring being placed between the surface of each drum opposite that which cooperates with the lateral surface of the envelope and the bottom of the housing wherein this drum is guided.

By reason ofthe slight thickness and the high tempcratures that it withstands, this spring breaks more or less rapidly. The drum no longer being then applied to the lateral surface of the envelope, a sealing fault is produced between neighbouring combustion chambers and there is immediately noticed a loss of power. Moreover, there rapidly ensues a degradation of the housing of the drum and of the portion of the above said drum which is formed in this drum and finally of the drum itself, the latter finally breaking, which places the engine out of operating condition.

It is an object of the invention to overcome the abovementioned drawbacks, by eliminating the usual elastic means of the second type.

To this end, the sealing device defined above according to the invention comprises elastic means arranged to exert a centrifugal radial force on the angular segments, the central bar and its angular segment being in mutual contact through oblique support surfaces such that the abovesaid centrifugal radial force is manifested on the angular segment concerned, by an axial component tending to space it from the abovesaid middle transverse plane, and is characterized by the fact that stop surfaces are provided between this angular segment and the drum associated therewith to transmit to the latter said axial component.

Thus, the wear of each angular segment, on its surface bearing on the lateral surface of the envelope, is manifested by a movement of this segment towards said surface, hence by a constant thrust of the stop surfaces on the corresponding drum, of which the wear is thus automatically compensated. On initial assembly, the simultaneous contact of the lateral surface of the envelope with, on the one hand, the outer surface in the axial direction of the drum, and, on the other hand, the corresponding surface of the angular segment, is ensured, when the stop surfaces of these two latter elements touch, by machining previously these two surfaces at the same time, after having assembled for this operation the drum and the angular segment in a mutual contact position identical with that of their opera tion.

In a first embodiment, the abovementioned stop surfaces are constituted by shoulders which form a body with each angular segment, thereby projecting into the housing of the drum on both sides of the middle radial plane of said segment, and through one surface of the drum opposite through which it enters into sealing contact with the lateral surface of the envelope.

In a second embodiment, the stop surfaces concerned are constituted by the cross-section of the angular segment and by the bottom of the groove which is formed radially in a surface of the drum which is opposite that through which it enters into sealing contact with the lateral surface of the envelope.

The invention will, in any case, be better understood with the aid of the supplementary description which follows and of the accompanying drawings, which supplement and drawings relate to preferred embodi ments, without being in any way limiting.

FIGS. 1 and 2, of these drawings, show partially a sealing device according to a first embodiment of the invention, respectively in section through a plane passing approximately through the axis of the drive shaft and in section through a plane perpendicular to the foregoing one.

FIG. 3 shows separately in perspective the central bar and the two angular segments of the sealing device FIGS. 1 and 2.

FIG. 4 shows in perspective, on a larger scale, one of the two angular segments belonging to a sealing device according to a second embodiment of the invention.

FIGS. 5 and 6 show separately in perspective, on a larger scale still, one of the two angular segments and the corresponding drum which belong respectively to two sealing devices according to a third and to a fourth embodiment of the invention.

According to the embodiment shown partly in FIGS. 1 and 2, the prismatic rotor I, ofa rotary piston engine, is housed inside an envelope 2 bounded internally by a transverse surface 3 of troehoidal profile and by two lateral surfaces 4. The transverse surface 3 is defined by generators parallel to the axis of the outward shaft not shown of the engine. The lateral surfaces 4 are flat and perpendicular to this outward shaft and are generally borne respectively by attached flanges.

The rotor 1 comprises sealing devices which are each constituted by a central bar 5 and by two angular segments 6 mounted end to end in a groove 7 situated along each crest of the rotor l. Groove 7 is formed in the rotor l or in the part rigidly fixed to the latter at the level of the central bar 5 and in the drum 8 at the level of each angular segment 6. Each drum is guided, in a housing 9 formed in the rotor 1, so as to be slidable without rotating parallel to the crest of the rotor. Elastic means, which will be more explicitly disucssed below, are provided to urge, on one hand, the central bar 5 and the crest segments 6 radially outwardly, that is to say towards the surface 3, and on the other hand, each of the drums 8 axially in the direction which spaces it from the middle transverse plane of the rotor plane not shown, situated to the right of FIGS. I and 2), that is to say in the direction which tends to apply its terminal flat surface 10 against the neighbouring lateral surface 4 of the envelope 2.

This being the case, in each sealing device constructed according to the invention, the abovesaid elastic means are arranged to exert a centrifugal radial force on the angular segments 6, the central bar 5 and each angular segment 6 are in mutual contact through oblique support surfaces 50 and 60 such that the abovesaid centrifugal radial force is manifested on the angular segment concerned 6 by an axial component tending to space it from the abovesaid middle transverse plane that is to say to push it towards the left in FIGS. 1 and 2) and stop surfaces are provided between this angular segment 6 and the drum 8 associated with to transmit to the latter the said axial component. As is seen in the Figures, the oblique support surfaces 5a of the

central bar

5 and 6a of the angular segments 6 are flat and each pair of support surfaces is situated in a plane inclined in such a way that by approaching the axis (towards the bottom of FIG 1), it also approaches the abovesaid middle transverse plane towards the right of FIG. 1).

Preferably, the abovesaid elastic means are constituted by a spring strip 1 I incurved so as to be supported in its central portion, on the portion of the groove 7 formed in the rotor l and, at its two ends, on the respective inner surfaces in the radial direction of the angular segment 6. In this case, each angular segment can comprise a projection 6b adapted to prevent the spring strip 11 from being moved axially in the groove 7, the shape of the latter being such that it prevents this strip from pivoting on an axis parallel to the crest of the rotor I.

In the embodiment of FIGS. I to 3, as well as in that of FIG. 4, the above mentioned stop surfaces are constituted by shoulders 12, which form a body with each angular segment 6 thereby projecting to the housing 9 of the drum, on each side of the middle radial plane of said segment (plane of FIG. I), and by a surface 13 of the drum 8 opposite to the surface 10 trough which it comes into sealing contact with the neighbouring lateral surface 4 of the envelope. More accurately, each shoulder 12 possesses the support surface 14 which cooperates by abutment with the surface 13 of the drum 8. In the embodiment of FIGS. 1 to 3 each shoulder has a triangular profile limited by an oblique surface 15 which is situated in the same plane as the above mentioned oblique support surfaces 6a. The embodiment of FIG. 4 only differs from the foregoing one by the rectangular profile of the shoulders, the oblique surface 15 being replaced by surface 15a parallel to the support surface 14.

The two embodiments have the common feature that the bottom of the groove 7 is situated approximately at the same level on the rotor l and on the drum 8 (as is seen on FIG. 1) and that this groove opens on the sealing surface 10 of each drum 8. On the lateral surface 4 of the envelope are supported not only this sealing surface l0 but also a coplanar surface 16 belonging to the neighbouring angular segment 6.

In the embodiments of FIGS. 5 and 6, the above mentioned stop surfaces are constituted by the crosssectional surfaces 6c or 6d of the angular segments 6, and by the bottom 17a ofa groove 17 which is formed radially in one surface of the drum 8 which is opposite its sealing surface 10.

The two latter embodiments only differ between themselves by the fact that, in FIG. 5, the bottom 17a of the radial groove 17 extends over the whole of the radial dimension of the drum 8 whilst, in FIG. 6, the bottom 17a is interrupted by intersection with an axial groove I8 that is to say parallel to the axis of the engine), formed on the portion of the drum furthest away from the axis of the drive shaft. In the first case, the above mentioned support 16 is placed at the end of an appendage 19 which bears internally on the periphery of the drum. In the second case, the support surface 16 is placed at the end of an appendage 20, which is engaged in the radial groove I8 and which, for this reason, is higher (in the radial direction) and, consequently, more robust than in the foregoing case. In the two cases, a strip spring, similar to that which is denoted by 11 in FIG. 1, acts through its ends, on the lower surface 21 in FIGS. 5 and 6) of the angular segments 6, these ends being, preferably, curved and ending close to the bottom 17a of the radial groove 17.

There are thus obtained sealing devices which can be adjusted and which operate in the following manner.

To adjust each drum/angular segment pair, they are placed in the mutual position that they must occupy on the rotor, that is to say by placing their stop surfaces I3, 14 or 60 (6d), 17a, in contact, then their

sealing surfaces

10, 16 are simultaneously machined with the corresponding lateral surface 4 of the envelope.

Once the sealing device has been placed in position on the rotor, the spring I] urges radially outwardly the angular segments 5 by direct action and the central bar 5 by the play of the oblique support surfaces 5a, 6a. The wear of each angular segment 6, on its sealing surface 16, causes its radial displacement under the effect of spring I I. By the play of the oblique surfaces 5a, 6a, the radial force exerted by the spring is manifested by an axial thrust applied directly on the angular segment 6 and, through stop surfaces l3, 14 or 60 (6d), 170, on the drum 8 whose wear is thus automatically compensated.

I claim:

I. In a multi-lobed rotor ofa rotary piston engine, the improvement comprising:

means defining a housing in each end of an apex of the rotor,

a drum positioned in each housing so as to be slidable axially of but not rotatable relative to the apex of the rotor. each drum having an aubtment surface,

means defining a longitudinally extending groove along the apex of the rotor and the drums,

an elongated central bar, each end of said central bar being bevelled.

a pair of end bars, one end of each of said end bars being bevelled, each end bar having an abutment surface which abuts the abutment surface of a respective one of the drums,

said central bar and said end bars being positioned in said groove with one bevelled end of the central bar lying in facing abutment with the bevelled end of one of the end bars and the other bevelled end of the central bar lying in facing abutment with the bevelled end of the other one of the end bars,

elastic means for biasing the central bar and end bars radially outwardly and for biasing each of the drums axially outwardly in a direction from the central bar to the respective drum, said elastic means exerting a radially outward force on the end bars which is transmitted to the central bar through the facing abutment of the ends of the central bar with the end of end bars and is transmitted to each drum through the abutment of the abutment surface of each end bar with the abutment surface of its respective drum.

2. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, wherein:

the abutment surface of each end bar is a surface on each one of a pair of shoulders thereof which project transversely from each side of the bar at a radially inner portion thereof, and

the abutment surface of each drum is opposite to that through which the drum is adapted to sealingly contact a lateral surface of an envelope of the engine.

3. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, wherein:

said elastic means comprises an incurved spring strip the central portion of which contacts the central portion of the groove in the rotor and each end of which contacts the radially inner surface of a respective one of the end bars.

4. In a multi-lobed rotor of a rotary piston engine as claimed in claim 3, wherein:

each end bar comprises a radially inwardly extending projection adapted to prevent the spring strip from moving axially in the groove, said projection being shaped so as to prevent the spring strip from pivoting about an axis parallel to the apex of the rotor. 5. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, further comprising:

means defining a radially extending groove in the surface of each drum which is opposite to the surface thereof through which the drum is adapted to sealingly contact a lateral surface of the envelope of the engine, the bottom of the groove in each drum defining its said abutment surface, and the abutment surface of each end bar is a crosssectional surface adjacent an end thereof which is opposite said one end thereof. 6. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, wherein:

the bottom of the radially extending groove in each drum extends throughout the entire radial dimension thereof, and each of said end bars comprises an appendage which extends axially away from the central bar, the end surface of each appendage is adapted to contact a respective one of the lateral surfaces of the envelope of the engine, and the radially inner surface of each appendage bears radially inwardly against the periphery of its respective drum. 7. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, further comprising:

means defining an axially extending groove in the radially outer portion of each drum which intersects the radially extending groove therein, and each of said end bars comprises an appendage which extends axially away from the central bar, and each of said appendages is positioned in the axially extending groove of a respective one of the drums, and the end surface of each appendage is adapted to contact a respective one of the lateral surfaces of the envelope of the engine. 8. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, wherein:

the ends of the spring strip are positioned close to the radially inner most portion of the radially extending grooves of the drums. 9. In a multi-lobed rotor of a rotary piston engine as claimed in claim 8, wherein:

the ends of said spring strip are curved,

Claims

1. In a multi-lobed rotor of a rotary piston engine, the improvement comprising: means defining a housing in each end of an apex of the rotor, a drum positioned in each housing so as to be slidable axially of but not rotatable relative to the apex of the rotor, each drum having an aubtment surface, means defining a longitudinally extending groove along the apex of the rotor and the drums, an elongated central bar, each end of said central bar being bevelled, a pair of end bars, one end of each of said end bars being bevelled, each end bar having an abutment surface which abuts the abutment surface of a respective one of the drums, said central bar and said end bars being positioned in said groove with one bevelled end of the central bar lying in facing abutment with the bevelled end of one of the end bars and the other bevelled end of the central bar lying in facing abutment with the bevelled end of the other one of the end bars, elastic means for biasing the central bar and end bars radially outwardly and for biasing each of the drums axially outwardly in a direction from the central bar to the respective drum, said elaStic means exerting a radially outward force on the end bars which is transmitted to the central bar through the facing abutment of the ends of the central bar with the end of end bars and is transmitted to each drum through the abutment of the abutment surface of each end bar with the abutment surface of its respective drum.

2. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, wherein: the abutment surface of each end bar is a surface on each one of a pair of shoulders thereof which project transversely from each side of the bar at a radially inner portion thereof, and the abutment surface of each drum is opposite to that through which the drum is adapted to sealingly contact a lateral surface of an envelope of the engine.

3. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, wherein: said elastic means comprises an incurved spring strip the central portion of which contacts the central portion of the groove in the rotor and each end of which contacts the radially inner surface of a respective one of the end bars.

4. In a multi-lobed rotor of a rotary piston engine as claimed in claim 3, wherein: each end bar comprises a radially inwardly extending projection adapted to prevent the spring strip from moving axially in the groove, said projection being shaped so as to prevent the spring strip from pivoting about an axis parallel to the apex of the rotor.

5. In a multi-lobed rotor of a rotary piston engine as claimed in claim 1, further comprising: means defining a radially extending groove in the surface of each drum which is opposite to the surface thereof through which the drum is adapted to sealingly contact a lateral surface of the envelope of the engine, the bottom of the groove in each drum defining its said abutment surface, and the abutment surface of each end bar is a cross-sectional surface adjacent an end thereof which is opposite said one end thereof.

6. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, wherein: the bottom of the radially extending groove in each drum extends throughout the entire radial dimension thereof, and each of said end bars comprises an appendage which extends axially away from the central bar, the end surface of each appendage is adapted to contact a respective one of the lateral surfaces of the envelope of the engine, and the radially inner surface of each appendage bears radially inwardly against the periphery of its respective drum.

7. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, further comprising: means defining an axially extending groove in the radially outer portion of each drum which intersects the radially extending groove therein, and each of said end bars comprises an appendage which extends axially away from the central bar, and each of said appendages is positioned in the axially extending groove of a respective one of the drums, and the end surface of each appendage is adapted to contact a respective one of the lateral surfaces of the envelope of the engine.

8. In a multi-lobed rotor of a rotary piston engine as claimed in claim 5, wherein: the ends of the spring strip are positioned close to the radially inner most portion of the radially extending grooves of the drums.

9. In a multi-lobed rotor of a rotary piston engine as claimed in claim 8, wherein: the ends of said spring strip are curved.