US3926538A

US3926538A - Apex seal

Info

Publication number: US3926538A
Application number: US351873A
Authority: US
Inventors: Dennis Welt
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-04-17
Filing date: 1973-04-17
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: DE2319475A1; CA958647A

Abstract

In a rotary piston mechanism, an apex seal and an inertia counterbalancing means mounted within an apex slot of the rotary piston so that the centrifugal forces generated by the rotation of the counterbalancing means substantially balances that of the apex seal for all rotational speed of the piston.

Description

' United States Patent [191 Welt [ Dec. 16, 1975 APEX SEAL [76] Inventor: Dennis Welt, PO. Box 314,

Kitimat, BC, Canada [22] Filed: Apr. 17, 1973 [21] Appl. No.1 351,873

[30] Foreign Application Priority Data Apr. 17, 1972 Canada 139780 [52] US. Cl. 418/115 [51] Int. Cl. FOlC 19/02 [58] Field of Search 418/113, 114, 115

[56] References Cited UNITED STATES PATENTS 3,547,451 12/1970 Milot 418/115 X FOREIGN PATENTS OR APPLICATIONS 1,925,125 ll/l970 Germany 418/115 Primary Examiner-C. J. Husar Assistant Examiner-Leonard E. Smith Attorney, Agent, or Firm-Feth.erstonhaugh & Co.

[5 7 ABSTRACT In a rotary piston mechanism, an apex seal and an inertia counterbalancing means mounted within an apex slot of the rotary piston so that the centrifugal forces generated by the rotation of the counterbalancing means substantially balances that of the apex seal for all rotational speed of the piston.

1 Claim, 21 Drawing Figures US. Patsnt Dec.16,1975 Sheet10f3 3,926,538

US. Patent Dec. 16, 1975 Sheet 3 0f 3 3,926,538

APEX SEAL FIELD OF INVENTION This invention relates to apex seals for rotary combustion engines, rotary pumps, rotary compressors and the like. In particular this invention relates to an apex seal which is effectively counterbalanced to prevent excessive wear in use.

PRIOR ART The efficiency of operation of a rotary internal combustion engine pump or compressor is effected by the frictional losses and heat generated as a result of the centrifugal forces applied to the apex seals during rotation of the rotor. Attempts have been made to reduce the effect of the centrifugal force by the use of counterbalances, however, none of the proposed counterbalancing devices are capable of operating effectively over a wide range of rotational speeds. Typical known devices are described in U.S. Pat. No. 3,456,626, July 22, 1969, C. Jones; U.S. Pat. No. 3,456,625, July 22, 1969, C. Jones, U.S. Pat. No. 3,482,551, Dec. 9, 1969, C. Jones and U.S. Pat. 3,496,916, Feb. 24, 1970, C. Jones. All of these structures employ devices for reducing the centrifugal force at the seal which are largely disposed radially inwardly from the apex slots within which the seals are located. As a result, the counterbalancing weights cannot effectively counterbalance the weight of the apex seals for all rotational speeds of the rotor. Because of the fact that rotary engines have considerably fewer moving parts than the conventional reciprocating engines, it is possible to operate a rotary engine at much higher speeds than the rotational speeds of conventional engines. So far the limitation on the rotational speed of a rotary engine compressor or the like has been the wear and heat generated by the friction of the seals bearing against the outer wall of the combustion chamber.

SUMMARY OF INVENTION The present invention overcomes the difficulties of the prior art described above by relating an apex seal which is effectively counterbalanced for all rotational speeds of the rotor. This construction permits the designer to preselect the frictional force to be applied by the apex seal at any rotational speed. The construction of the present invention also permits the seals to be mounted and removed from the apex slots without difficulty.

According to an embodiment of the present invention, a rotary internal combustion engine has an apex seal and an inertia counterbalancing means mounted within the apex slots in communication with one another whereby upon rotation of the rotor the centrifugal forces generated by rotation of the counterbalancing means substantially balances that of the apex seals for all rotational speeds of the rotor.

PREFERRED EMBODIMENT The invention will be more clearly understood after reference to the following detailed specification read in conjunction with the drawings.

FIG. 1 is a diagrammatic illustration of a conventional apex seal construction.

FIG. 2 is an end view of a counterbalanced apex seal in accordance with the embodiments of the present invention.

FIGS. 3 to 10 are views similar to FIG. 2 illustrating alternative seal and counterbalance arrangements.

FIG. 11 is a side view of a combined counterbalance apex seal according to the embodiment of the present invention.

FIG. 12 is a sectional view taken along the line 2-2 of FIG. 17.

FIG. 13 is a plan view of a counterbalancing weight of FIG. 11.

FIG. 14 is a sectional view taken along the line l1 of FIG. 11.

FIG. 15 is a plan view of the support bracket for supporting the apex seal and counterbalance weight of FIG. 11.

FIG. 16 is a plan view of a pivot pin used in association with the support bracket of FIG. 15.

FIG. 17 is an end view of the toothed wheel device of FIG. 12.

FIG. 18 is a partial side view illustrating one form of end seal slot for sealing the combustion chamber at the ends of the apex seals.

FIG. 19 is an end view similar to FIG. 18 showing an alternative form of end seal passage.

FIG. 20 is a partial front view of an end seal mounted on an apex seal for use in the slot illustrated in FIG. 18. FIG. 21 is a partial front view of an end seal mounted on an apex seal for use in the slot illustrated in FIG. 19.

With reference to FIG. 1 of the drawings, the reference numeral 10 refers generally to a rotor of the type described in my copending application Ser. No. 134,1l0 now abandoned. The rotor 10 consists of a pair of oppositely disposed end walls 12 (only one shown) and a generally triangular shaped main body portion 14. A slot 16 is located at each apex of the main body portion and extends transversely between the oppositely disposed end walls 12. The slots 16 have extensions 18 which extend through the end walls 12. The extensions 18 which extend through the end walls 12 are of a greater height than the slots 16 so as to receive end seals as will be described hereinafter. An apex seal assembly 20 constructed in accordance with the embodiments of the invention illustrated in FIGS. 2 to 21 inclusive is located in each slot 16 so as to be directed outwardly into sealing engagement with the inner wall of a combustion chamber in use.

The structure of an apex seal assembly suitable for use in the present invention is illustrated in FIG. 2 of the drawings wherein it will be seen that the apex seal assembly 20 consists of a sealing member 22 and a counterweight member 24 which are connected to one another by means of a flexible connection 26 which extends around a pulley 28. The pulley 28 is mounted for rotation in at least two support members 30. The lower ends 32 of the support members 30 are mounted in slots 34 formed in the base of the slots 26. An important feature of the present invention is that the center of gravity 36 is the apex sealing member 22 is disposed close to the center of gravity 38 of the counterweight member 24 in the radial direction. In the embodiment illustrated in FIG. 2, the center of gravity 36 is located at a radius R, and the center of gravity of the counterweight 24 is located at a radius R from the center of rotation.

The centrifugal force generated by the rotation of the apex seal assembly may be determined by the formula;

wherein C the centrifugal force,

M the mass of apex seal or counterweight R the radius of gyration w angular velocity In order to eliminate the centrifugal force applied to the wall of the cylinder resulting from the rotation of the apex seal assembly, the centrifugal force C generated as a result of rotation of the apex seal member must equal the centrifugal force C generated by the rotation of the counterweight member. It will be obvious that this condition can best be achieved when the radius R is equal to or substantially equal to the radius R and when the mass M is equal to or substantially equal to the mass M In the embodiments of the invention illustrated in FIGS. 2 to inclusive, like numerals have been applied to like parts as they appear in FIG. 2 of the drawmgs.

The embodiment illustrated in FIG. 3 of the drawings differs from that illustrated in FIG. 2 in that the counterweight 38 is in the form of two

counterweight members

38a and 38b disposed on opposite sides of the apex seal 22. Again, the

counterweights

38a and 38b are connected to the apex seal 22 by means of flexible connector 26 and pulleys 28. In this embodiment, the center of gravity of the

counterweights

38a and 38b are disposed at a radius R and R respectively which, for clarity of illustration, is not shown as coincident in FIG. 3 but which would, in fact, be coincident or substantially coincident. Similarly the mass of the

counterweights

38a and 38b would preferably be substantially identical.

In use, the mass M of the counterweight will equal mg, m In an embodiment where a multiplicity of counterweights are employed, the mass of the counterweight may be determined by the formula m m 1. m o+. m n.

In the embodiment illustrated in FIG. 4 of the drawings, two

weights

38a and 38b are connected by means of a flexible connector 26 about pulley 28. An apex sealing strip 40 is located between seal member 22 and counterweight 38 and a pin 41 projects from strip 40 into a wedge shaped groove 43 on the inner face of the seal 22. This permits limited movement of the sealing strip relative to the seal 22. Radial outward movement of the strip 40 causes the seal 22 and weight 38 to be forced into contact with the side walls of the slot 16 thereby preventing further radial outward movement of either weight and substantially eliminating the effect of the centrifugal force.

FIG. 5 of the drawings illustrates a seal constructed substantially in accordance with FIG. 2 of the drawings with the introduction of a leaf spring 46 disposed between the upper face of the counterweight 38 and an inwardly directed face of the seal 22. Again the counterweight 38 is connected to the seal 22 by means of a flexible connector 26, pulley 28, support arms 30. The leaf spring 46 provides the static pressure necessary to ensure that the seal 22 will be urged towards the combustion chamber wall to form an effective seal.

It will be understood that the flexible connector 26 is preferably in the form of a semi-rigid wire or strap having sufficient rigidity to retain the seal member 22 and the counterweight members 38 in a position spaced outwardly from the base of the slots 16; that is to say, the flexible member 16 is not so flexible that the seals and counterweights will drop into the slots when the rotor is stationary with the slots opening upwardly.

FIG. 6 of the drawings illustrates an embodiment of the invention wherein the flexible connector 26 is replaced by a lever arm 50 which is pivotally mounted in the upper end of a support rod 30 and pivotally connected at opposite ends to the seal 22 and counterweight 24. In use, the balanced condition prevailing in the embodiment of the invention illustrated in FIG. 2 is maintained by ensuring that the mass and center of gravity of the counterweight 24 and seal 22 are such that moments taken about the fulcrum pin 52 resulting from the centrifugal forces generated by the rotation of the rotor are substantially balanced. A compression spring 46a reacts between the bottom face of the slot 16 and the underside of the seal 22 so as to provide a static pressure forcing the seal against the wall of the combustion chamber.

FIG. 7 illustrates an embodiment of the invention similar to FIG. 6 and differs only in that the arm 50 is located within V-shaped notches 54 formed in the seal 22 and counterweight 24.

A further structure for connecting the counterbalance 24 to the seal 22 is illustrated in FIG. 8 of the drawings wherein the connection is achieved by means of a gear wheel 56 and by providing a gear tooth rack 58 on an inwardly directed face of the seal 22 and the gear tooth rack 60 on an inwardly directed face of the counterbalance 24. Again, a balance is achieved by reason of the fact that the moments taken about the fulcrum pin 52 are substantially balanced.

A further form of connection between the seal 22 and counterweight 24 is obtained by forming the seal member 22 with a chamber 64 and the counterweight member 24 with a chamber 66 within which pistons 68 and 70 are connected to the upper ends of rods 30 are free to reciprocate. A damping effect is achieved by filling the portions of the

chambers

64 and 66 which are disposed below the pistons 68 and 70 with a fluid and providing passages 72 to permit the fluid to pass to and fro between the

chamber

64 and 66.

A further form of connection between the sealing member 22 and counterweight 24 is illustrated in FIG. 10 of the drawings wherein bellows 74 and 76 are connected to the cross-bar member 78 which is rigidly connected to the support column 30. The bellows 74 and 76 are connected to the seal member 22 and counterweight member 24 by means of

support brackets

80 and 82 respectively.

FIGS. 1 1 to 17 of the drawings illustrate a further embodiment of the invention which includes a base member 84 which has two pairs of upstanding lugs 30a which are disposed at opposite ends of the base and two gear members 86 which are mounted for rotation on the base 80 by means of pivot pins 88 which extend through the passages provided in the lugs 30a. The counterweight 24 is formed with gear teeth 90 at opposite ends thereof adapted to engage the gear teeth of the gear members 86. The counterweight 24 is disposed between the gear members 86 as shown in FIG. 1 1. The seal 22 has a pair of downwardly projecting lugs 92, each of which are formed with rack gear teeth 94 which are adapted to engage the gear teeth of the gear wheels 86 and the seal is mounted in a position with the lugs 92 disposed outwardly from the gear members 86 so that the gear teeth 94 engage the teeth of the gear members 86. Passages 96 open upwardly from the underside of the lugs 96 and a spring member 98 is mounted in each passageway. In use, the assembly illustrated in FIG. 11 is located within the apex slot 16 of the rotor and the base member 84 is secured to the base of the slot. When the rotor rotates, the centrifugal force generated by the rotation of the counterweight applies a turning moment about the pivot pins 86 in an opposite direc tion to the direction of the moment applied by the centrifugal force generated by the rotation of the seal 22. By a careful selection of the mass of the counterweight 24, it is again possible to minimize the influence of the centrifugal force set up by rotation of the rotor. The spring 96 serves to urge the seal 22 into a minimum sealing engagement with the wall of the combustion chamber.

As shown in FIG. 14 of the drawings, the base member 84 is preferably formed with a pair of diverging lips 100 adjacent the lower edge thereof. FIG. 18 of the drawings illustrates a form of apex slot similar to that shown in FIG. 1 of the drawings wherein a recess 102 is formed in the base to receive the lips 100 of a seal assembly of the type illustrated in FIG. 11.

FIG. 19 illustrates an apex groove 16 formed in a rotor 106 of the type commonly used in the Wankel engine. This rotor is different from the rotor of my prior application in that the side walls of the combustion chamber are not formed integrally with the rotor and, as a result, the rotor must be sealed by means of seals 108 against the stationary side walls of the combustion chamber. Again this apex groove is formed with a recess 102 so as to receive the apex seal assembly of the type illustrated in FIG. 11 of the drawings. An additional end seal 112 (FIG. 21) is located within the circular recess 110 so as to seal the ends of the apex seals with respect to the side walls of the combustion chamber.

FIG. of the drawings illustrates an end seal 114 suitable for use in association with the apex seal 22 when used in an

apex slot

16, 18 of the type described in FIGS. 1 and 18 of the drawings.

It will be apparent that the apex seal of the present invention may be employed in rotor compressor, pumps and the like to equal advantage. The invention is not limited to use in association with the conventional Wankel engine, or the engine illustrated in my copending application. The apex seal construction of the present invention may be employed in rotary engine having piston of the common triangular piston or general square section piston or any other form of piston used in a rotary engine, pump, compressor or the like.

From the foregoing it will be apparent that when the apex seal assembly of the present invention is used, the centrifugal forces produced by rotation of the seal 22 and counterweight 24 about the axis of rotation of the rotor are substantially equal regardless of the rotational speed of the rotor and are, therefore, balanced one against the other so that the friction at the point of contact of the apex seal does not increase significantly with increased rotational speed. This permits a rotary engine compressor or the like equipped with the seals of the present invention to operate at very high speeds.

What I claim as my invention is:

1. In a mechanism having a rotary piston mounted for rotation in a chamber about a central axis of the chamber, the piston having a plurality of apexes for dividing the chamber into a plurality of compartments, each apex being disposed on a radial axis generated from said central axis, the piston being formed to provide U- shaped slots having a bottom wall and a pair of oppositely disposed side walls, said side walls being uniformly spaced on opposite sides of one of said radial axes, the improvement of, an apex seal assembly mounted in each slot comprising;

a. an apex seal member having a pair of oppositely disposed side walls, an upper face having an apex ridge extending longitudinally thereof, a lower face and a pair of oppositely disposed end faces, said apex seal member being proportioned to fit within said apex slot such that said oppositely disposed side walls of said seal member fit in a close fitting sliding relationship within said side walls of said slot, said apex ridge being disposed on said radial axis of said apex groove, the lower face of said apex seal member being notched to provide a recess extending upwardly upwardly into said apex seal member and extending longitudinally thereof,

an inertia counterbalancing weight member mounted within said slot and proportioned to project into said notch of said apex seal member, to underly a portion of said apex seal member, said inertia counterbalancing weight member being slidable within said slot in the direction of said radial axis,

0. a base member fixedly secured with respect to said bottom wall of said Ushaped slot,

d. connector means mounted on said base member for angular movement about a centre of rotation disposed within said U-shaped slot, and directly underlying said apex seal member, said connector means having opposite ends disposed within said U-shaped slot on opposite sides of said centre of rotation, one end of said connector means being connected to said apex seal member and the other end of said connector means being connected to said counterbalancing weight whereby upon rotation of said piston the centrifugal forces generated by the movement applied by said inertia counterbalancing weight member substantially balances the movement generated by said apex seal member.

Claims

1. In a mechanism having a rotary piston mounted for rotation in a chamber about a central axis of the chamber, the piston having a plurality of apexes for dividing the chamber into a plurality of compartments, each apex being disposed on a radial axis generated from said central axis, the piston being formed to provide U-shaped slots having a bottom wall and a pair of oppositely disposed side walls, said side walls being uniformly spaced on opposite sides of one of said radial axes, the improvement of, an apex seal assembly mounted in each slot comprising; a. an apex seal member having a pair of oppositely disposed side walls, an upper face having an apex ridge extending longitudinally thereof, a lower face and a pair of oppositely disposed end faces, said apex seal member being proportioned to fit within said apex slot such that said oppositely disposed side walls of said seal member fit in a close fitting sliding relationship within said side walls of said slot, said apex ridge being disposed on said radial axis of said apex groove, the lower face of said apex seal member being notched to provide a recess extending upwardly upwardly into said apex seal member and extending longitudinally thereof, b. an inertia counterbalancing weight member mounted within said slot and proportioned to project into said notch of said apex seal member, to underly a portion of said apex seal member, said inertia counterbalancing weight member being slidable within said slot in the direction of said radial axis, c. a base member fixedly secured with respect to said bottom wall of said U-shaped slot, d. connector means mounted on said base member for angular movement about a centre of rotation disposed within said Ushaped slot, and directly underlying said apex seal member, said connector means having opposite ends disposed within said U-shaped slot on opposite sides of said centre of rotation, one end of said connector means being connected to said apex seal member and the other end of said connector means being connected to said counterbalancing weight whereby upon rotation of said piston the centrifugal forces generated by the movement applied by said inertia counterbalancing weight member substantially balances the movement generated by said apex seal member.