US3400691A

US3400691A - Seal construction for rotary combustion engines

Info

Publication number: US3400691A
Application number: US575481A
Authority: US
Inventors: Jones Charles
Original assignee: Curtiss Wright Corp
Current assignee: John Deere Technologies International Inc
Priority date: 1966-07-21
Filing date: 1966-07-21
Publication date: 1968-09-10
Anticipated expiration: 1985-09-10

Description

Sept. 10, 1968 QJONr-:s 3,400,691

SEAL CONSTRUCTI R BUSTION u ATT URNEY Sept. 10, 1968 C. JONES 3,400,691v

SEAL CONSTRUCTION FOR ROTARY COMBUSTION ENGINES Filed July 21, 1966 a Sheets-Sheet 2 66 INVENTOR 7 /Q/ EHAFQLEE INEI ATTRNEY Sept' 10, 1968 c. JONES 3,400,691

SEAL CONSTRUCTION FOR ROTARY COMBUSTION ENGINES Filed July 2l, 1966 5 Sheets-Sheet 5 INVENTOR. LHARLEE .JDNEE ATTORNEY United States Patent O 3,400,691 SEAL CONSTRUCTIN FOR ROTARY COMBUSTION ENGINES Charles Jones, Paramus, NJ., assigner to Curtiss-Wright Corporation, a corporation of Delaware Continuation-impart of application Ser. No. 384,056,

July 21, 1964. This application July 21, 1966, Ser.

9 Claims. (Cl. 12S-8) ABSTRACT F THE DISCLQSURE Rotor apex seal construction for rotary combustion engines, comprising at least a main seal piece and an end seal piece with cooperating inclined faces at the juncture of the main and end pieces, and a spring biasing the end piece substantially radially outwardly of the rotor.

This invention relates to rotary combustion engines and in particular is directed to a seal construction for such engines. This application is a continuation in part of applicants prior application, Ser. No. 384,056 file-d July 21, 1964, now abandoned.

The invention is specifically directed to a novel construction of an apex seal member which provides irnproved sealing eiciency for the working chambers of a rotary combustion engine. In engines of this type combustion takes place in the same region of the Outer body which results in variations in the heat input around the lperiphery of said outer body. These variations in the heat input cause changes in the distance between the end walls of the rotary combustion engine around its periphery which therefore results in variations in the width of the working chambers. In order to effectively seal the Working chambers of the rotary combustion engine, a seal means must be provided which can change its dimensions to compensate for the variations in the dimensions in the associated working chamber caused by the temperature differences in the outer body.

While many seal constructions perform satisfactorily during high speed operation, it has been found that during slow speed operation, such as in the idling speed range, or upon starting the engine, particularly when the engine is cold, most of the prior type seal constructions for rotary combustion engines are relatively inefficient and operation of the engine during starting and idling is not always satisfactory. The present invention provides a seal construction which functions to provide more eficient sealing of the working chambers particularly during starting and slow speed operation,

The sealing means of the invention generally comprises a multi-piece apex seal means including a main seal piece having at least one end face inclined from its base toward an associated rotor end face and an end seal piece at the end of the apex seal piece having the inclined end face which end seal piece has an inclined face for mating engagement with the inclined'end face of the main seal piece. One form of the invention comprises a three-piece apex seal means in which the main apex seal piece has an inclined end -face at each end thereof with a mating end seal piece in sliding engagement therewith. A single-lobed spring means is provided which bears against the bottom groove wall of the rotor which receives the apex seal means and bears against the end seal pieces so that a substantially equal spring force is provided through each end Vseal piece which force is transmitted through said end pieces to the main seal piece for urging said main seal piece into sealing engagement with the inner surface of the peripheral wall of the outer body. At the same time, the spring force also urges the ice end pieces to slide along the planes including the inclined end faces of the main seal piece for urging said end seal pieces into sealing engagement with the inner faces of the end walls of the outer body. As will be explained hereina-fter, the relationship between the inclined faces of the end seal pieces and the main seal piece as well as the application of the spring force is important for insuring sealing contact between the main seal piece with the inner surface of the peripheral wall and the end seal pieces with the end 'faces of the end Walls as well as insuring sealing contact between the main and end seal pieces, even when the heat input to the housing causes the distance between the end walls to vary. In other words, the seal means of the invention comprises an apex seal construction which is variable in axial width so that the seal means compensates for variations in the dimensions of the workingchamber to provide an effective seal means therefor even during starting and low spec-d operation when compression leakage in the working chambers must be kept to a minimum. It has also been Ifound that the engagement between the main seal piece and the end seal piece serves as a friction damping means for preventing excessive radial movement of the main seal piece and thus aids in reducing seal chatter.

In lieu of the aforesaid three-piece apex seal means, a two-piece apex seal means is now preferred in which only one end of the main apex seal piece has an inclined face for sliding sealing engagement with an end seal piece. As compared to the three-piece apex seal means, such a two-piece apex seal means has numerous advantages. Thus the two-piece apex seal results in less leakage, is more rugged and therefore is less susceptible to breakage, is less expensive and is easier to assemble. What is more significant however is that the two-piece seal appears to have improved dynamic characteristics probably because of the greater frictional resistance to movement of the main seal piece as compared to the frictional resistance to movement of the relatively small end piece. These advantages of the two-piece arrangement have proved to be sufficiently great that it is utilized in all current engine designs of the assignee of this application.

Accordingly, it is one object of the invention to provide a novel and improved multi-piece seal construction for a rotary combustion engine.

Another object of the invention is to Iprovide a novel and improved variable dimension apex seal means for the rotor of a rotary combustion engine.

It is an additional object of the invention to provide a seal means for the working chambers of a rotary combustion engine which seal means provides eiiicient sealing for the working chambers of the rotary combustion engine for all speed ranges of operation of said rotary combustion engine.

It is still another object of the invention to provide a novel and improved seal means for the working chambers of a rotary combustion engine which seal means is of a multi-part construction and which is capable of varying its axial dimensions to provide effective sealing even -for variations in the width of the working chambers of said rotary combustion engine.

It is a further object of the invention to provide a novel and improved multi-piece apex seal construction for a rotary combustion engine wherein the coaction between the elements of said multi-piece seal construction provides efficient sealing of the Working chambers of said engine and also provides a friction damping for preventing excessive radial movement of said apex seal construction to minimize seal chattering.

It is still a further object of the invention to provide a novel and improved seal means wherein a spring force is provided for urging the seal means into sealing engagement with the inner surface of the peripheral wall of the housing of said rotary combustion engine and for urging said seal means into sealing engagement with the end faces of the end walls of said housing and wherein said seal means comprises ra multi-piece construction which pieces have an angular relationship which serves to control the distribution of the spring force between the pieces of said multi-piece construction.

Other objects and advantages of the invention will become apparent upon reading the following detailed description with the accompanying drawings in which:

FIG. 1 is an axial-sectional view of a rotary combustion engine embodying the invention;

FIG. 2 is a sectional view taken along line 2 2 of FIG. 1; r

FIG. 3 is an exploded view of the multi-piece seal construction of the invention and illustrating the forces acting between the pieces of said multi-unit construction;

FIG. 4 is a partial sectional view of a rotary combustion engine showing the multi-piece seal construction with the end pieces in one of its variable positions during operation of the rotary combustion engine;

FIG. 5 is a partial sectional view showing the multipiece seal construction in another of its variable positions during operation of said rotary combustion engine;

FIG. 6 is a perspective view of a portion of a seal construction illustrating another embodiment of the invention; and

FIG. 7 is a view similar to FIG. 3 illustrating a preferred embodiment of the invention.

Referring to the drawings, a rotary internal combustion engine is generally indicated by reference numeral 10. The engine 10 comprises an outer body 12 having

axiallyspaced end walls

14 and 16 and a peripheral wall 18 interconnected to form therebetween a cavity 20. As viewed in FIG. 2, the cavity has a shape which is preferably a multi-lobed shape which may be defined as being basically an epitrochoid. In the specific embodiment illustrated, the cavity has two lobes although the engine is not limited to this specific number.

An inner body or rotor 24 is disposed within the cavity of the outer body 12 with said rotor 24 having axiallyspaced end faces 26 and 28 disposed adjacent to the outer

body end walls

14 and 16. The rotor 24 is further provided with a plurality of circumferentially-spaced apex portions 30 which are one more in number than the number of lobes of said cavity 20. As illustrated, the rotor 24 has three apex portions 30 and the periphery of the rotor has a generally triangular profile. The apex portions 30 are in sealing engagement with the inner surface of the peripheral wall 18 to form -a plurality of working chambers 32 between the inner rotor 24 and the outer body 12, there being three such working chambers 32 illustrated. Each working chamber 32 includes a working face 31 formed between the apex portions 30 of the rotor 24 with each said face forming a substantial part of the combustion space during combustion in said chamber. As further illustrated, the axis 34 of the rotor 24 is offset from and disposed parallel to the axis 22 of the outer body.

In the engine 10 illustrated, the outer body 12 is stationary while the inner rotor 24 is journaled on an eccentric portion 36 of the shaft 38, said shaft being coaxial with that of the cavity 20 of said outer body. Upon rotation of the inner rotor 24 relative to the outer body 12 the working chambers 32 vary in volume. An intake port 40 is provided in one or both

end walls

14 and 16 or in the peripheral wall 18 for admitting air and fuel into the working chambers, a spark plug 42 is provided for igniting the combustible mixture and an exhaust port 44 is provided in the peripheral wall for discharge of the exhaust gases from the working chambers 32. During engine operation the working chambers 32 have a cycle of operation including the four phases of intake, compression, expansion and exhaust, said phases being similar to the strokes in a reciprocating-type internal combustion engine having a four-stroke cycle. In order to maintain the relative motion of the rotor 24 relative to the stationary outer body an internal gear 46 is, as illustrated, coaxially secured to the rotor 24 and is disposed in mesh with a fixed gear 48 secured to the outer body, said fixed gear being co-axial with the shaft 38. It should be understood however, that the outer body 12 as well as the inner body 24 may rotate instead of, as in the embodiment illustrated, only one of said bodies rotating.

As generally explained above, combustion always takes place adjacent one region of the outer body so that this region has a substantially high heat input compared to, for example, the region adjacent the intake port 40. It will be apparent therefore, that the heat input varies around the periphery of the engine so that there will be a differentiation in the expansion of the engine outer body around its periphery. For this reason, the distance between the end walls, which defines a portion of the working chambers 32, will vary during engine operation. It is desirable in this case to provide a seal means which may vary its dimensions so that for differences in the dimensions of the working chambers during operation effective sealing will always be provided. This is particularly true during engine staiting and at idling or low speed conditions since loss of compression at these times will cause diiculty in starting or roughness in idling. At high speed operation, it has been found that the effectiveness of the sealing between the working chambers 32 is not as critical since the rotor is rotating at substantially higher speeds and therefore there will only be a slight loss of compression during this time due to the time element of the working chambers passing through the cycles 0f operation. It is during starting of the engine and at loW speed operation that other seal means, such as a one piece seal construction, do not provide satisfactory operation because they are not variable in dimension for compensating for the differences in workin g chamber dimensions during operation. The leakage past the seals is more significant at low speed operation because there is more time, relative to any given phase of the cycle of operation, for the gas, which is being compressed, to leak through a given sized opening. Any such losses during compression result in a loss of available energy. During the compression phase of the working cycle such losses lower the effective compression ratio and volumetric efficiency. During the power or expansion phase these losses reduce the pressure level and thus reduce output work and, in addition, by leaking back into the succeeding compression chamber, the charge in said chamber is diluted with products of combustion which adversely affects engine economy and operation. Tests have indicated that a substantial amount of work of turning the engine over at low speeds is due to the lost work caused by seal leakage. The structure of the present invention minimizes leakage between the working chambers and thus minimizes losses in available energy so that starting at lower cranking speeds is possible and low speed operation is substantially improved.

In the construction of the present invention, the working chambers 32 are sealed by providing a novel apex seal construction, which will be explained in greater detail hereinafter, in a groove 50 formed in each apex portion 30 of the rotor 24 with said apex seal means running from one end face 26 to the other end face 28 of the rotor in a direction parallel to the rotor axis. The apex seal means in each apex portion 30 of the rotor seals the working chambers in the circumferential direction between the respective apex portions 30 and cooperates with an intermediate seal means 52 and side face seal means 54 to complete the sealing of each working chamber 32 between the inner surface of the peripheral wall and the end walls of the outer body. No invention is alleged in the particular construction of the intermediate seal structures 52 and the side face seal means 54 and their related cooperation with the apex seal means and reference may be made, for example, to U.S. Patent 3,033,180 issued to Max Bentele on May 8, 1962, for a more detailed description of the intermediate and side face seal means.

The apex seal means, to which the present invention is directed, comprises a main seal piece 56 which extends from one end face of one end wall of the outer body 12 to the end face of the opposite end wall at the narrowest spacing between said end walls and is disposed so as to be in sealing engagement with the inner surface of the peripheral wall 18. As illustrated in FIGS. 3-5, the main seal piece preferably has inclined end faces 58, which as shown in particular in FIG. 3, are inclined to the engine axis in a direction toward an associated rotor end face and which pass substantially through each radially outward corner of the main seal piece 56. In order not to have sharp edges at the seal corners of the main seal piece 56 and to increase the structural strength of the seal construction the angular end faces 58 pass slightly below the radially outward corners of the main seal piece 56 so that the end faces are slightly squared off, as shown in FIGS. 3, 4 and 5. It should be understood however, that this feature has been exaggerated in said figures for ease and clarity of illustration and that the faces 58 preferably pass as close to the corners as possible while still providing a surface which will not have unduly poor wearing qualities. A pair of

end seal pieces

60 and 62 are disposed in the seal grooves 50 for sealing engagement with the main seal piece 56 and the end faces of the

end walls

14 and 16. The

end seal pieces

60 and 62 have inclined faces 64 which are cut so as to mate with the inclined end faces 58 and 64 of the main seal piece so that the

end seal pieces

60 and 62 may slide along said inclined end faces 58 in order to vary the width of the apex seal means. As can be seen in FIGS. 4 and 5, the main seal piece 56 and the

end seal pieces

60 and 62 have a substantial portion extending radially outwardly beyond the rotor 24 or in other words these seal pieces project radially outwardly beyond the seal groove 50. It is therefore necessary to insure that sealing contact is maintained between the main seal piece 56 and the

end seal pieces

60 and 62 as well as between the seal pieces and the outer body since a portion of the mating surfaces of the respective seal pieces also projects beyond the seal groove 50. It will be apparent that, if these seal pieces are not maintained in sealing engagement, a substantial amount of leakage at the mating surfaces will occur.

A single-lobed curved leaf spring 66 is provided which spring is disposed so as to provide aspring force against the bottom or radially inward side of each of the

end pieces

60 and 62, respectively, with the bottom portion thereof bearing against the bottom of the groove 50. It is important to the invention that the major force provided by the spring means passes through the

end pieces

60 and 62 and not also directly through the main seal piece 56 so that the greatest radial spring force provided for the main seal piece 56 must pass through said

end seal pieces

60 and 62. This insures that there will be sealing engagement between the inclined end faces 58 of the main seal piece 56 and the inclined faces 64 of the

end seal pieces

60 and 62 even during relative movement between said pieces.

In order to maintain substantially equal linear intensity of sealing pressure on both the end lwalls and inner surface of the peripheral wall and to provide for relative movement between the `main seal piece 56 and the end seal pieces -60 and 62, the slope angle of the plane including the mating surfaces 58 and 64 of the seal pieces must be controlled in order to insure proper distribution of the spring force between the main and side seal pieces. Referring to FIG. 3, there is shown therein the forces acting on the respective seal pieces and the relationship of the slope of the plane including the mating surfaces 64 and 58. It should be understood however, that other forces are also present which act -on the seal pieces, such as for example the friction force between the spring 66 and the

seal pieces

60 and 62, and the friction force between the inner faces of the

end walls

14 and 16 and the associated side faces of the

seal pieces

60 and 62. Also, due to varying housing widths and radial motion caused by bearing clearances, thermal distortions, machining tolerances, etc. the seal movement will at .times reverse which will cause a reversal of some of the forces illustrated in FIG. 3. The forces and their respective directions of action illustrated in FIG. 3 are shown only for purposes of explaining the determination of the slope angle of the plane including the mating surfaces 58 and 64-and the forces affecting the linear intensity of sealing pressure at v the sealing surfaces between the seal elements and the housing. As illustrated in FIG. 3, it will be seen that the spring force provides a substantially radial force Fs at the base of the

side seal pieces

60 and 62 which is transferred to the main seal piece 56 substantiallyas a normal force Fn at the mating surfaces 58 and 64. Resisting the relative movement of the main seal piece 56 and the side seal piece 69 and 62 is a friction force Ff with the resultant movement of the individual seal pieces being shown as a force Fr. With the specific seal configuration illustrated, in order to determine the proper slope angle of the plane including the mating surfaces 58 and 64 for insuring equal linear intensity of sealing pressure, it has been found that for materials having a maximum coeficient of friction of 0.15 the slope angle will vary from the horizontal, that is from the base of the seal piece 56 between the angles of substantially 16 to 45. Preferably however, the materials are chosen so that the coefcient of friction ranges from 0.09 to 0.135 which therefore dictates a slope angle ranging between 30 and 40 and more specifically it is preferred to choose materials having an average coefficient of friction of 0.125 with a slope angle -of 37. By using the above values, it has been found that the sealing pressure expressed in pounds! inch o-f seal length lis substantially equal at the sealing surfaces including those between the main seal piece and the inner surface of the peripheral wall and the end faces of the end walls and the

side pieces

60 and 62. Since the singlelobed spring -66 bears solely against the

side seal pieces

60 and 62, the main seal piece 56 will be urged into sealing engagement with the inner surface of the peripheral wall with a force which is directed through said side seal pieces and sealing engagement between said

side seal pieces

60 and 62 at the mating surfaces 58 and 64 will always be maintained. Due to the cooperation `of the single-lobed spring with the multipiece construction of the invention, it is not necessary to use filling pieces or inserts between the mating surfaces of the seal pieces, such as that required in the multi-piece seal construction shown in U.S. Patent 3,064,880.

In FIG. 4 there is shown a partial sectional view of a rotary combustion engine embodying the seal construction of the invention with the seal construction being illustrated as passing through a heated portion of the outer housing. As can be seen therein, the main seal piece 56, which is constructed so as to be wide enough for l mating engagement with the inner faces of the

end walls

14 and 16 at the narrowest spacing therebetween, does not extend entirely across the width of said end walls at the heated portion of the outer housing. As explained above, this is due to the fact that the heat input in this region causes the rot-or housing -width to vary during engine operation. It will therefore be apparent that, if a one-piece seal construction were used in this situation, there would be a substantial loss of compression between the one-piece seal and the

end walls

14 and 16 due to the increase in axial width of the housing relative to the apex seal. However, due to the fact that the present seal construction allows for a variation in the dimensions of the seal construction, there will be very little leakage between the working chambers. During rotation of the rotor, as the apex portion 30 of the rotor reaches a portion of the housing which is acted upon by a relatively high heat input, the spring 66 acting on the

seal pieces

60 and 62 causes said

seal pieces

60 and 62 to slide along the mating surfaces 58 and 64 to move said seal pieces axially outwardly to compensate for the increase in axial width of the spacing between said end -

walls

14 and 16. At the same time, the spring 66 maintains the

seal pieces

60 and 62 in tight mating engagement at the

surfaces

58 and 64 so that no leakage will be present between the main seal piece 56 and the

end seal pieces

60 and 62. As also explained above, the spring force exerted through said

seal pieces

60 and 62 passes through said

seal pieces

60 and 62 to urge the main seal piece 56 into sealing engagement with the inner surface of the peripheral wall 18. Thus, during starting of the engine, particularly when the engine is cold, or during low-speed operation, there will be little loss of compression between the working chambers.

In FIG. 5, which is a view similar to FIG. 4 but showing the rotor in a position with respect to the housing wherein the housing is relatively cool, it will be seen that the

end seal pieces

60 and 62 have moved inwardly or toward each other along the mating surfaces 58 and 64 since in this position the width between the

end walls

14 and 16 has not substantially increased due to the relatively low heat input in this area ofthe outer body. Since the mating plane between the

seal pieces

56, 60 and 62 passes substantially through the corners of the main seal piece 56, which main seal piece 56 will now be in sealing engagement with the inner faces of the

end walls

14 and 16, there will be little, if any, blowby or loss of compression between the yworking chambers. Thus, it will be apparent that the seal construction of the invention will provide etiicient sealing between the working chambers 32 of the rotary combustion engine of the invention and there will be little loss of compression or blowby between the working chambers because of ,the relative movement of the

seal pieces

56, 60 and 62 even during substantial relative axial movement of the

end seal pieces

60 and 62. It will be apparent that this would not be the case, if the mating plane did not pass substantially through the corners of the main seal piece 56 or if the axial width of the main seal piece S6 were not chosen as described. For example, if the mating planes pass substantially below lthe corners of the main seal piece 56 or through the side faces below the corners, when the

end seal pieces

60 and 62 were caused to move to compensate for increased axial ywidth of the working chambers there would be substantial spacing between the main seal piece and the end faces of the

end walls

14 and 16 which would increase the l-oss of compression between the working chambers and would not serve to carry out the purpose of the invention.

With the construction of the present invention the cranking speed required for starting the engine has been substantially reduced and a substantial reduction in idling speeds has also been possible without accompanying roughness in engine performance at reduced speeds. It should also be noted, as stated above, that effective sealing is provided by the seal construction of the present invention without the use of additional shims or other construction for insuring that no leakage is present between the

pieces

56, 60 and 62 at their

mating surfaces

58 and 64 which constructions were required in some other multipiece seal embodiments. The combination shown by the present invention of the main seal piece 56, the

end seal pieces

60 and 62 and the arrangement of the single-lobed spring 66 serves to provide a seal construction where effective sealing is always maintained at the inner surface of the peripheral wall 18 and the end faces of the

end walls

14 and 16 as well as at the seal piece mating surfaces 58 and 64. With the values of the coeflcient of friction and the slope angles of the mating plane chosen as described above, it has also been found that the end seal pieces may be moved relatively freely for compensating for variations in the dimensions of the combustion chamber while at the same time maintaining effective sealing.

In FIG. 6 there is shown another embodiment of the invention which operates in the same manner as the embodiment described above. In the embodiment of FIG. 6 the main apex seal member 68 is provided with a cutout portion 70 which portion 70 is cut so as to have an inclined face 71 which is substantially identical to the inclined face 58 in the above described embodiment. An end seal piece 72 is provided with said end seal piece 72 being substantially identical to one of the

end seal pieces

60 or 62 of the prior embodiment, which end seal piece 72 has an inclined face 74 for sliding engagement with the inclined face of the main seal piece 68. It will be apparent that the inclined seal face 74 is constructed so it has to tit into the groove 70 in the main seal piece 68 with the inclined face 74 thereof being in sliding, mating engagement with the inclined end face 71 of said main seal piece 63. With this construction, the main seal piece 68 provides a sheath-like cover over the end seal piece 72 which makes the composite structure more durable since the mating surfaces of the respective seal pieces are not as exposed, as in the previous embodiment, so that there will be less likelihood of breakage particularly at the corners and mating surfaces of their respective seal pieces. Thus, the structure of the embodiment in FIG. 6 may be used for more heavy duty applications and where increased structural strength of the seal structure is desired. It will be understood that the seal construction and embodiment of FIG. 6 operates in the same manner as the prior described embodiment.

FIG. 7 discloses a further embodiment of the invention in which a two-piece apex seal means replaces the threepiece apex seal means of the embodiments of FIGS. l-5 and 6 in each rotor apex groove 50. FIG. 7 is similar to FIG. 3 except that in FIG. 7 the apex seal means has only one end seal piece, the other end seal piece in effect being integral with the main seal piece.

With the arrangement of FIG. 7, each apex seal means has a two-piece construction comprising a main seal piece (corresponding to the main seal piece 56 of FIG. 3) and only a single end seal piece 82 (corresponding to end

seal piece

60 or 62 of FIG. 3). One end face 84 of the main seal piece 80 is disposed at right angles to the outer seal edge 86 of said main seal piece for sealing engagement with the

adjacent end wall

14 or 16 and the other end of said main seal piece as an inclined face 88` which makes an acute angle with said outer edge 86. The single end seal piece 82 of each said two-piece apex seal means has a shape which is generally that of a right triangle with its long face 90 slidingly and sealingly engaging the inclined face 88 of the associated main seal piece 80. A second face 92 of said end seal piece 82 is disposed at right angles to the outer edge 86 of the main seal piece for sealing engagement with the

other end wall

14 or 16. A spring 94 (corresponding to the spring 66 of FIG. 3) is disposed under each two-piece apex seal means and comprises a single-lobed curved leaf-type spring having only its two ends contacting the apex seal means so that one end contacts and exerts a radially outward force on the single end seal piece 82 and the other end contacts and exerts a radially outward force on the end of the main seal piece 80 remote from the end seal piece 82, the mid portion of the spring 94 `bearing against the bottom of the rotor groove receiving said apex seal means.

Compared to the previously described three-piece apex seal construction, the two-piece apex seal means 80 and 82 obviously is simpler and therefore less expensive. Also, elimination of the acute corner at one end of each main apex seal piece 80 makes this piece more rugged and therefore less likely to break than the main apex seal 56 of FIG. 3. Furthermore, by in effect making one of the end seal pieces 60 to 62 integral with o-ne end of the main seal piece, leakage across that end of each main seal piece, during engine operation, is reduced. What is even more important is that the two-piece apex seal means appears to have improved dynamic stability probably because of the greater frictional resistance to movement of the main seal piece 80 compared to the frictional resistance to movement of the relatively small end seal piece which is eliminated by the two-piece seal construction. Because of its advantages said two-piece apex seal means has replaced the three-piece seal arrangement in current rotary combustion engine designs of applicants assignee.

While I have described my invention in detail in its preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. For example, the invention is not intended to be limited to a three-piece seal construction and the invention may be embodied in a two-piece construction with the main seal piece having only one sloping end face and only one end seal piece being provided. In such an embodiment it would of course be understood that the spring means would include means for insuring sufcient spring force to maintain the one end seal piece and the main seal piece in sealing engagement with each other. I aim in the appended claims to cover all such modifications.

l claim as my invention:

1. A sealing arrangement for the working chambers of a rotary combustion engine comprising an outer body having axially-spaced end Walls interconnected with a peripheral wall to form a cavity therebetween; a rotor received within said cavity and having axially-spaced end faces adjacent to said end walls and a plurality of circumferentially-spaced apex portions for sealing engagement with the inner surface of said peripheral wall to form a plurality of Working chambers between said rotor and said peripheral wall which upon relative rotation between said rotor and said outer body vary in volume; and means for igniting a combustible mixture in said working chambers adjacent one region of said outer body so that the heat input in said region causes variations in the size of said working chambers; said sealing arrangement comprising a multipiece seal construction disposed in a groove in each apex portion of said rotor, said multi-piece seal construction including a main seal piece extending from one end face of said rotor to the other end face of said rotor and disposed in said rotor apex portion for sealing engagement with the inner surface of said peripheral wall, said main seal piece having an inclined face at each end thereof with each said inclined face inclining from the base of said main seal piece in a direction toward an associated rotor end face and passing substantially through its radially outward corner radially outwardly of the rotor, and said multi-piece seal construction further including an end piece disposed at each end of said main seal piece for sealing engagement with said end walls, and each said end piece having an inclined face disposed for sliding sealing engagement with the inclined end face of said main seal piece so that each said end piece is movable relative to said main seal piece along their engaged inclined faces; and spring means in engagement solely with said rotor and said end pieces for exerting a radial outward force against said main seal piece through said end pieces and for urging said end pieces to slide along said inclined faces relative to said main seal piece such that said multipiece seal construction may increase its axial dimension with increases in the axial dimension of said working chambers.

2. A sealing arrangement as recited in claim 1 wherein said spring means comprises a single-lobed curved leaf spring disposed in each rotor apex groove with the lobe portion thereof bearing against the base of said groove and the ends thereof bearing against the base portion of each said end piece so that said single-lobed spring exerts a direct spring force only on the end pieces of said multipiece seal construction.

3. A sealing arrangement as recited in claim 1 wherein thereof lies within a groove in said main seal piece.

4. A sealing arrangement for the working chambers of a rotary combustion engine comprising an outer body having axially-spaced parallel end walls interconnected with a peripheral wall to form a cavity therebetween; a rotor received within said cavity and having axially-spaced end faces adjacent to said end walls and a plurality of circumferentially-spaced apex portions for engagement with the inner surface of said peripheral wall to form a plurality of working chambers between said rotor and said peripheral wall which upon relative rotation between said rotor and said outer body vary in volume; intake means in one region of said outer body for supplying air to said working chambers for combustion adjacent a second region of said outer body so that the heat input to said outer body varies between said first and second outer body regions and produces differences in the axial distance between said end walls; said sealing arrangement comprising a multi-piece seal construction including a first seal piece disposed in a groove in each apex portion of said rotor with at least the outer edge of said first seal piece extending substantially from one end face of the rotor to the other and at least one end of said first seal piece having an end face inclined to the outer edge of the first seal piece such that the width of the first seal piece between the radially inner portion of said end faces is less than that of said outer edge; at least one second seal piece also being disposed in a groove in each apex portion of said rotor for sealing engagement with an outer body end wall with said second seal piece having an inclined face disposed in sliding mating engagement with the inclined face of said first seal piece for permitting relative movement between said first and second seal pieces and said mating inclined surfaces of said seal pieces including a line which passes substantially through a radially outward corner of said radial rst seal piece adjacent said one axial end thereof and radially outwardly of the rotor; and a single-lobed curved leaf-spring means for each said multi-piece seal construction and disposed so as to engage only the ends of said multi-piece seal construction so that one end thereof exerts a radially outward spring force through said second seal piece for urging said first and second seal pieces in a radial direction and for producing relative movement therebetween such that said multi-piece seal construction may vary its axial dimensions for differences in the axial distance between said outer body end walls while maintaining sealing contact between said first and second seal pieces of said multi-piece seal construction.

5. A sealing arrangement as recited in claim 4 wherein said main seal piece and said end seal pieces are composed of materials having a maxim-um coefficient of friction of 0.15 and said inclined end face has a slope substantially between the angles of 16 to 45 6. A sealing arrangement as recited in claim S wherein the coefficient of friction of said materials preferably averages 0.125 and said slope angle is 37.

7, A sealing arrangement as recited in claim 4 wherein said first seal piece includes a groove formed in one end thereof with said one inclined face comprising one wall of said groove and said second seal piece being substantially disposed Within said first seal piece groove so that said rst seal piece forms a sheath around a substantial portion of said second seal piece.

8. A sealing arrangement for the working chambers of a rotary combustion engine comprising an outer body having axially-spaced parallel end walls interconnected with a peripheral wall to form a cavity therebetween; a rotor received within said cavity and having axially-spaced end faces adjacent to said end walls and a plurality of circumferentially-spaced apex portions for engagement with the inner surface of said peripheral wall to form a plurality of working chambers between said rotor and said peripheral wall which upon relative rotation between said rotor and said outer body vary in volume; intake means in one region of said outerbody for supplying air to said working chambers for combustion adjacent a second region of said outer body so that the heat input to said outer body varies between said rst and second outer body regions and produces differences in the axial distance between said end walls; said sealing arrangement comprising a two-piece seal means for each rotor apex portion with each two-piece apex seal means disposed in a rotor apex portion groove running from one rotor end face to the other, each said two-piece apex seal means comprising a main seal piece and a single end seal piece, each said main piece having an outer seal edge extending substantially from one outer body end wall to the other for sealing engagement with the outer body peripheral wall and having an end face at one end disposed at right angles to said outer seal edge for sealing engagement with the adjacent end wall of the outer body and also having an inclined end face at the other end, making an acute angle with said outer edge, the single end seal piece of each two-piece seal means having a generally triangular shape with one face disposed in sliding engagement with the inclined end face of the associated main seal piece and with a second face disposed at right angles to the outer edge of said main seal piece for sealing engagement with the adjacent end wall of said outer body, and a singlelobed curved leaf spring for each two-piece sealmeans disposed in the rotor groove for said seal means between said seal means and bottom of said groove with the ends only of the leaf spring contacting the apex seal means such that one end contacts and exerts a radially outward force on said end seal piece and the other end contacts and exerts a radially outward force on the end of the main seal piece remote from said end seal piece.

9. A sealing arrangement as recited in claim 8 wherein the end seal piece of each two-piece apex seal means extends radially outwardly beyond the rotor.

References Cited UNITED STATES PATENTS RALPH D. BLAKESLEE, Primary Examiner.