US3796527A

US3796527A - Sealing device for rotary mechanisms

Info

Publication number: US3796527A
Application number: US00346638A
Authority: US
Inventors: G Woodier; W Pratt
Original assignee: Curtiss Wright Corp
Current assignee: John Deere Technologies International Inc
Priority date: 1973-03-30
Filing date: 1973-03-30
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12
Also published as: CA1001080A

Abstract

In a rotary mechanism of the Wankel type, a sealing device for each of the apex portions of the rotor which sealing device comprises a seal blade disposed for reciprocation toward and away from the trochoidal surface of the mechanism housing and a pressurized fluid actuating means responsive to the angular velocity of the rotor and coacting with the seal blade to hold the latter out of engagement with the trochoidal surface at a predetermined rotor angular velocity.

Description

United States Patent 1 Woodier et al.

[451 Mar. 12,1974

1 1 SEALING DEVICE FOR ROTARY MECHANISMS [75] Inventors: George H. Woodier, Ringwood;

4 Winthrop B. Pratt, North l-laledon,

both of NJ.

[73] Assignee: Curtiss-Wright Corporation,

Wood-Ridge, NJ.

22 Filed: Mar. 30, 1973 211 App1lNo.:346,638'

[52] US. Cl 418/115,4l8/123,4l8/l24, V 277/28 [51] Int. Cl. F01c 19/02, F04c 15/00, F040 27/00 [58] Field ofSearch 418/84,93, 113, 115, 418/122-121, 277/28 [56] References Cited UNITED STATES PATENTS 3,229,673 1/1966 Ehrhardt 418/123 Jones et a1. 418/115 3,456,626 7/1969 418/115 3,482,551 7 12/1969 418/115 3,496,916 2/1970 418/1 15 3,721,510 3/1973 Gilbert 418/115 Primary Examiner-Carlton R. Croyle Assistant Examiner.lohn J. Vrablik Attorney, Agent, or Firm-Arthur Frederick [5 7 ABSTRACT In a rotary mechanism of the Wankel type, a sealing device for each of the apex portions of the rotor which sealing device comprises a seal blade disposed for reciprocation toward and away from the trochoidal surface of the mechanism housing and a pressurized fluid actuating means responsive to the angular velocity of the rotor and coacting with the seal'blade to hold the latter out of engagement with the trochoidal surface at a predetermined rotor angular velocity.

16 Claims, 4 Drawing Figures SEALING DEVICE FOR ROTARY DISCLOSURE This invention relates to sealing devices for rotary mechanisms and, more specifically, pertains to sealing devices disposed at the apex portions of the rotors of rotary mechanisms of the Wankel type such as disclosed in the U.S.'Pat. to Wankel et al., No. 2,988,065.

BACKGROUND or THE- INVENTION It is well-known in rotary mechanisms that it is desirable to minimize friction between the rotor and housing within which the rotor rotates and that diminution of friction can be accomplished at relatively high angular velocities of the rotor without a material penalty in efficiency by retraction of the seals away from the station- I ary housing wall surface. Such sealing devices which automatically adjust the position of the sealing devices in accordance with the angular speed of the rotor are exemplified in the following 'U.S. Pat. Nos.:

1,158,733 Shepard et a1.; 2.041,]21 Fareso, Sr.; 3,229,673 Ebrha'rdt; 3,444,843 Sabet; 3,456,625 Jones et al.; 3,456,626 Jones; 3,482,551 Jones; 3,496,9l6-Jones; 3,707,340 Brille. I

In rotary mechanisms of the Wankel type in which a rotor rotates within a housing cavity defined by end walls and an inner trochoidal wall surface, the trochoiweighls are employed to retract a'seal blade in a direction away from the trochoidal surface by overcoming the centripedal acceleration forces acting on the seal blade, it is necessary to provide in the interconnection between the flyweights and seal blade a lost motion to prevent the seal blade from re-engaging the trochoidal surface due to the change in direction of the centripedal acceleration forces acting on the flyweights. Thus, in such sealing devices the lost motion results in clatter and possible excessive wear of the seal blade components.

It is therefore an object of this invention to provide in a rotary mechanism of the Wankel type a sealing device carried by a rotor which sealing device automatically holds the seal blade out of engagement with the trochoidal sealing surface at a predetermined angular speed of the rotor and retains the seal blade out of engagement for the entire length of the trochoidal sealing surface until the angular speed of the rotor falls below the predetermined value.

Another object of the present invention is to provide in a rotary mechanism of the Wankel type a sealing'device carried by a rotor which sealing device is capable of holding the seal away from the trochoidal sealing surface without the use of relatively complex pivotal linkages and flyweights.

A further object of this invention is to provide in a rotary mechanism of the Wankel type a sealing device carried by a rotor, which sealing device responds to a fluid pressure, the magnitude of which is a function of the angular velocity of the rotor. I

SUMMARY OF THE INVENTION In a rotary mechanism of the Wankel type, a rotor is eccentrically mounted on a crankshaft for rotation in a cavity formed by the mechanism housing. The rotor has a plurality of apex portions. The flank portions of the rotor and the trochoidal shaped peripheral wall surface of the housing cavity, taken together, define a plurality of working chambers which successively increase and decrease in volumetric size as the rotor rotates. The rotor. has, at each apex portion, an apex sealing device according to this invention which includes a seal blade means sealingly sweeping the peripheral wall surface and radially movable relative to the rotor for maintaining sealing engagement with the peripheral wall surface. The apex sealing device also includes a pressurized fluid actuating means responsive to a predetermined rotor angular velocity and coacting with the seal blade means to remove the contact pressure of the seal blade means against the peripheral wall surface and hold the seal blade means away from the peripheral wall surface as rotor speed increases beyond the predetermined angular velocity. This source of pressurized fluid may be the bearing lubricant fluid which may be circulated by means of a positive displacement pump such as a gear pump, driven by the crankshaft as disclosed in the US. Pat. to Jones et :al., No. 3,359,952, or some other suitable means providing a fluid pressure which varies as a functionof rotor speed such as the change in fluid pressure due to centrifugal force acting on the column of lubricating oil in passageways extending radially in the shaft eccentric and rotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a view in cross-section taken substantially along line 22 of FIG. 1 on an-enlarged scale;

FIG. 3 is a cross-sectional view taken substantially along line 33 of FIG. 2; and

FIG. 4 is an isometric view of the collar forming part of the sealing device of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawings and more particularly to FIG. 1, the. reference number 10 generally designates a rotary mechanism ,of the Wankel type which has a rotor 12, the apices 14 of which carry sealing devices 16 according to this invention. The rotary mechanism 10 for illustration purposes only is shown as an internal combustion rotary engine and it is therefore to be understood that the invention is not limited thereto. The rotary mechanism without departure from the scope and spirit of the invention may be applicable to other rotary mechanisms, such as compressors, pumps and expansion engines.

As shown in FIG. 1, rotary mechanism 10 comprises, in addition to rotor 12, a housing 18 defining a cavity which has a peripheral wall surface 20 of epitrochoidal on a crankshaft 22 to effect rotation of the latter through an eccentric portion 24 of the crankshaft. The housing cavity has two lobes while rotor 12 hasthree peripheral surfaces or flanks 26 which define with housing 18 three working chambers 28. The working chambers 28 successively increase and decrease in volumetric size as rotor 12 eccentrically rotates within the housing cavity. A fluid intake port 30 is provided to pass combustible gaseous fluid into the working chamber during a suction or intake phase of operation. After the compression phase of operation, the gaseous fluid is ignited by an ignition means, such as spark plug 32. An exhaust port 34 is provided so that on the exhaust phase of operation the products of combustion can be expelled, from the working chambers. To maintain working chambers 28 out of communication with each other, rotor 12 carries, in addition to sealing devices 16, a plurality of seal strips 36. The seal strips 36 are located in each of the side faces 38 of rotor 12 and function to seal thespace between the side faces and the adjacent end wall 37 of housing 18. The sealing devices 16 serve to seal the space between each rotor apex portion 14 and trochoidal surface of housing 18.

As best shown in FIGS. 2 to 4, each of the sealing devices 16 comprises a seal blade means 40 mounted for reciprocative movement in a slot 42 in the apex portion 14 of rotor 12 and fluid pressurized actuating means 44 coacting with the seal blade means.

The blade means 40 is preferably, as shown, a single blade element which has two spaced leg portions or tabs 46. Each of the tabs 46 is disposed inwardly of and adjacent to the apex seal pin 48 and extend radially from the inner edge of blade means 40 through a radially extending slot 50. The slot 50 communicates, at one end,'with slot 42 and at the opposite end, with an axially extending bore 52 in the apex portion of rotor 12. A biasing means, such as a flat spring 54, is disposed between the bottom of slot 42 and the inner edge of blade means 40 to urge the blade means toward trochoidalsurface 20. While blade means 40 is shown as a single blade element, the blade means may be a multiblade assembly, such as disclosed in the US. Pat. to Jones, No. 3,400,691, without departure from the scope andspirit of this invention.

The fluid pressurized actuating means 44 comprises two pistons 56, each of which is disposed for reciprocation in a counterbored portion or piston-cylinder 58 of bore 52. Each piston 56 has an axially extending arm 60 which is bifurcated at its distal end to embrace an associated tab 46. Each arm 60 has camming edges 62 which are inclined radially outward in a direction toward distal end and engages a pin 64 carried in tab 46 of blade means 40. Each of the pistons 56 is biased inwardly away from the rotor side faces 38 by a helical spring 66. One end of the spring bears against the piston and the other end against a collar 68 which is disposed in bore 52. The collar 68 is secured in bore 52 by a split ring 70 which bears against a disc-shaped cover element 72. The cover element 72 fits against collar 68 in a fluid tight manner to prevent passage of gas or liquid from bore 52.

As best shown in, FIG. 4, collar 68 is cylindrical and has a diametral dimension so that it is snugly receivable in bore 52. A longitudinally extending diametral slot 74 is provided in collar 68. The slot 74 is of such width as to receive therein the bifurcate distal end portion of piston arm 60' (see FIG. 2) and pin 64. A second diametral'slot 76 is provided in collar 68 which slot 76 communicates with slot 74 through the bottom wall 75 of slot 74. The slot 76 is substantially narrower in width than slot 74 and, when the collar is properly positioned in bore52, it is in register with slot 50 so that tab 46 of blade means 40 can project from slot 50 into slot 74. The slot 76 together with slot 50 serve to guide tab 46 in its slidable movement relative to rotor 12. v

The pistons 56 are subject to fluid pressure in a pressure chamber 78 which is defined between the pistons 56 and another counterbored portion 80 of bore 52. To seal the interstices between the pistons and piston cylinders 58, each piston is provided with O-ring seals 79 or other suitable sealing means. The pressure chamber 78 is in communication with a suitable source of pressurized fluid through a supply passageway 82. As

. shown, such source of pressurized fluid may be bearing I rotor speed and, therefore, if the pressurized fluid is lubricating oil, the oil pump (not shown) may be driven by the crankshaft as is disclosed in the-US. Pat. to-

Jones et al., No. 3,359,952. However, it is within the purview of the present invention to employ any suitable source of pressurized fluid, the pressure of which varies with rotor rpm. For example, the change in oil pressure in

passageways

82 and 84 due to the centrifugal force acting thereon as rotor 12 rotates, may be utilized to provide a pressure in chamber 78 which varies as a function of rotor speed.

In operation of rotary mechanism 10, each of the sealing devices 16 according to this invention are subjected to inwardly and outwardly'directed centripedal acceleration forces as is fully explained in the US. Pat. to Jones, No. 3,456,625. Thus, in the area of minor axis of the housing or lobe junction 90 each blade means 40 is subjected to a negative acceleration force or inwardly directed centrifugal forceQAt relatively low angular velocities of rotor 12, the pressure of fluid in pressure chamber 78 acting upon pistons 56 'in a direction toward rotor end faces 38 exerts a force on each piston which is insufficient to overcome the counteracting force exerted by spring 66. The effect of the force of spring 54 on pistons 56 is negligible because of the shallowness of inclined edges 62. Thus, until a predetermined high rpm of rotor 12 is reached, pistons 56 are unable to retract and disengage blade means 40 from trochoidal surface 20. As the rotor rpm increases the pressure of fluid in pressure chamber 78 increases. Also, as rotor rpm increases, the centrifugal force acting inwardly upon blade means 40 increases. When a predetermined rotor rpm is reached, the fluid pressure in pressure chamber 78 is of such magnitude that the force exerted on each of the pistons 56 is sufficient to overcome the force of spring 66 so that, when blade means 40 is moved inwardly in the area of lobe juncture 90 under the inwardly directed centrifugal force, pistons 56 are moved toward rotor end faces 38 and arms 60 are wedged between the pin 64 and the bottom wall of slot 74. This wedging action holds the blade means 40 in a retracted position as rotor rpm increases above the predetermined value, thus reducing friction at the higher rpm when sealing contact is less necessurface in spite of the varying direction of centrifugal force acting upon the blade means. The fluid pressurized actuating means 44.0t" each sealing device 16, will hold the associated blade means 40 captive until rotor rpm and, hence, fluid pressure in pressure chamber 78 falls below the predetermined values and the force of springs 66 is sufticient to overcome theforce exerted on pistons 56 by the fluid pressure. Under the urging of springs 66, each piston is moved away from the rotor side face 38, thus releasing tabs 46 for movement toward trochoidal surface 20 under the centrifugal force exerted thereon in the area of lobe junction 90.

reto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by 'those skilled in the art.

. What is claimed is: l

1. In a rotary mechanism of the type comprising a housing having an inner peripheral wall of trochoidal shape and end walls defining a cavity therebetween and a rotor supported for eccentric rotation within the cavity and defining with said housing walls a plurality of working chambers which successively expand and contract in volumetric size as the rotor rotates, the rotor having apex portions and sealing devices carried in the apex portions, each sealing device comprising:

a. a blade means disposed for reciprocative move ment in a groove in an associated apex portion of the rotor;

b. biasing means for urging said blade means into en gagement with the peripheral wall, and

c. a pressurized fluid actuating means responsive to the angular velocity of the rotor and coacting with the seal blade to achieve disengagement of the seal blade with theperipheral wall at a rotor angular velocity above a predetermined value.

2. The apparatus of claim 1 wherein the pressurized fluid actuating means includes a linear motor means connected to a source of pressurized fluid, the pressure of which varies in direct proportion to the variation in the angular velocity of the rotor.

3. The apparatus of claim 2 wherein said motor means is two piston and cylinder mechanisms. 4. The apparatus of claim 1 wherein said pressurized fluid actuating means includes lubricating pump means.

5. The apparatus of claim 1 wherein the pressurized fluid actuating means includes two pistons disposed for reciprocative movement in cylindrical bores extending it is believed now readily apparent that the present in the rotor parallel to the axis of rotor rotation, and wherein said blade means includes spaced radially extending projections each of which is engageable by a piston to maintain the blade means out of engagement with the housing peripheral wall at rotor angular velocity above a predetermined value.

6. In a rotary mechanism of the type comprising a housing having an inner peripheral wall of trochoidal shape and end walls defining a cavity therebetween and a rotor supported for eccentric rotation within the cavity and defining with said housing walls a plurality of.

working chambers which successively expand and contract in volumetric size as the rotor rotates, the rotor having apex portions and sealing devices carried in the apex portions, each sealing device comprising:

a. a blade means disposed for reciprocative movement in a groove in an associated apex portion of the rotor; v

b. biasing means for urging said blade means into contact with said peripheral wall;

c. a piston and cylinder motor means in said rotor disposed so that the piston is engageable with said blade means;

d. a source of pressurized fluid, the pressure of which varies as .a function of the angular velocity of the rotor;

e. passageway means communicating said source of pressurized fluid with said piston and cylinder means to effect actuation of the piston into engage ized fluid exerts a force on each piston tending to move the piston outwardly from the centerline of the rotor extending normal to the rotor axis of rotation.

9. The apparatus of claim 6 whereinthe said. piston and cylinder means includes a wedging means coacting with said blade means to prevent radial outwardly directed movement of the blade means when said. predetermined fluid pressure is attained.

10. The apparatus of claim 9 wherein said blade means includes inwardly extending tab means engageable by said wedging means.

11. The apparatus of claim 10 wherein said tab means comprises an elongated arm and stop element carried in said arm to be engaged by said wedging means.

12. The apparatus of claim 6 wherein said piston and cylinder motor means comprises two pistons disposed in a cylindrical bore in the rotor and arranged in juxt-. aposed position for reciprocative movement, each piston carries an axially extending wedging means coacting with said blade means to prevent radial outwardly directed movement of the blade. means when said predetermined fluid pressure is attained.

13. The apparatus of claim 12 wherein said blade means includes two axially spaced radially extending tabs each of which has a stop element adapted to be en inner side of the arm has an inclined surface which extends in a direction radially outward of the associated piston relative to the apex portion of the rotor.

l6.'The apparatus of claim 12 wherein each piston is spring biased in a direction away from coaction with said blade means, said spring being selected to permit piston movement upon said predetermined pressurized fluid pressure.

Claims

1. In a rotary mechanism of the type comprising a housing having an inner peripheral wall of trochoidal shape and end walls defining a cavity therebetween and a rotor supported for eccentric rotation within the cavity and defining with said housing walls a plurality of working chambers which successively expand and contract in volumetric size as the rotor rotates, the rotor having apex portions and sealing devices carried in the apex portions, each sealing device comprising: a. a blade means disposed for reciprocative movement in a groove in an associated apex portion of the rotor; b. biasing means for urging said blade means into engagement with the peripheral wall, and c. a pressurized fluid actuating means responsive to the angular velocity of the rotor and coacting with the seal blade to achieve disengagement of the seal blade with the peripheral wall at a rotor angular velocity above a predetermined value.

3. The apparatus of claim 2 wherein said motor means is two piston and cylinder mechanisms.

4. The apparatus of claim 1 wherein said pressurized fluid actuating means includes lubricating pump means.

5. The apparatus of claim 1 wherein the pressurized fluid actuating means includes two pistons disposed for reciprocative movement in cylindrical bores extending in the rotor parallel to the axis of rotor rotation, and wherein said blade means includes spaced radially extending projections each of which is engageable by a piston to maintain the blade means out of engagement with the housing peripheral wall at rotor angular velocity above a predetermined value.

6. In a rotary mechanism of the type comprising a housing having an inner peripheral wall of trochoidal shape and end walls defining a cavity therebetween and a rotor supported for eccentric rotation within the cavity and defining with said housing walls a plurality of working chambers which successively expand and contract in volumetric size as the rotor rotates, the rotor having apex portions and sealing devices carried in the apex portions, each sealing device comprising: a. a blade means disposed for reciprocative movement in a groove in an associated apex portion of the rotor; b. biasing means for urging said blade means into contact with said peripheral wall; c. a piston and cylinder motor means in said rotor disposed so that the piston is engageable with said blade means; d. a source of pressurized fluid, the pressure of which varies as a function of the angular velocity of the rotor; e. passageway means communicating said source of pressurized fluid with said piston and cylinder means to effect actuation of the piston into engagement with said blade means to hold the latter from contact with the inner peripheral wall upon a predetermined fluid pressure which is a function of rotor rpm.

7. The apparatus of claim 6 wherein said source of pressurized fluid is a lubrication pump drivably connected to the rotor.

8. The apparatus of claim 6 wherein said piston and cylinder motor means comprises two pistons disposed in a bore in the rotor extending parallel to the rotor axis and wherein both pistons are Exposed to pressurized fluid in a common pressure chamber so that pressurized fluid exerts a force on each piston tending to move the piston outwardly from the centerline of the rotor extending normal to the rotor axis of rotation.

9. The apparatus of claim 6 wherein the said piston and cylinder means includes a wedging means coacting with said blade means to prevent radial outwardly directed movement of the blade means when said predetermined fluid pressure is attained.

12. The apparatus of claim 6 wherein said piston and cylinder motor means comprises two pistons disposed in a cylindrical bore in the rotor and arranged in juxtaposed position for reciprocative movement, each piston carries an axially extending wedging means coacting with said blade means to prevent radial outwardly directed movement of the blade means when said predetermined fluid pressure is attained.

13. The apparatus of claim 12 wherein said blade means includes two axially spaced radially extending tabs each of which has a stop element adapted to be engaged by a wedging means of a piston to prevent radial outwardly directed movement of the blade means when said predetermined fluid pressure is attained.

14. The apparatus of claim 13 wherein said wedging means comprises an arm axially projecting from each of the pistons and bifurcated to embrace a tab of said blade means so that the stop element engages the radially inner side of the arm.

15. The apparatus of claim 14 wherein said radially inner side of the arm has an inclined surface which extends in a direction radially outward of the associated piston relative to the apex portion of the rotor.

16. The apparatus of claim 12 wherein each piston is spring biased in a direction away from coaction with said blade means, said spring being selected to permit piston movement upon said predetermined pressurized fluid pressure.