SPLIT RING SEAL ASSEMBLY

Technical Field

This invention relates to seals.

More particularly, the present invention relates to annular seals of the type especially adapted for use in connection with linear or reciprocal movement. In a further and more specific aspect, the present invention concerns a seal assembly having improved means for retarding flow of fluids past the seal.

Background Art Various mechanical apparatus includes first and second members which are substantially coaxial and disposed for relative reciprocal movement. Exemplary are internal combustion engines, positive displacement pumps, pneumatic motors and other mechanical devices incorporating a piston and cylinder assembly. Other examples will readily occur to those skilled in the art.

Commonly, the cylinder is defined by a bore having a cylindrical sidewall. The piston, a generally cylindrical member, includes a sidewall and a top. An endwall or head, opposing the top of the piston, closes one end of the bore. A chamber of variable capacity is defined within the bore between the head and the top of the piston.

Pressurized fluid functions within the chamber. In an internal combustion engine, the fluid is the expanding gases of combustion which serve to propel the piston downwardly or away from the head. The upwardly driven piston in a pump pressurizes the fluid. Pressurized fluid from an external source is introduced into the chamber of a pneumatic motor to force movement of the piston.

In order to provide for relative movement between the members, it is necessary that the diameter of the

piston be of lesser dimension than the diameter of the bore. Frequently, additional clearance is required. For example, it is well known that a piston is more sensitive to thermal expansion than is a cylinder. Accordingly, where heat is a factor, such as in an internal combustion engine, additional space must be provided between the sidewall of the bore and the sidewall of the piston to accommodate thermal expansion of the piston. The space, commonly referred to as sidewall clearance, is generally in the range of fifteen ten-thousandths of an inch to five one-thousandths of an inch, or greater.

For reasons which are immediately apparent to those having an appreciation for the art, it is necessary that the piston be sealed to the cylinder. Conventionally, this is accomplished by a device commonly referred to as a piston ring, an annular seal usually fabricated of metal such as cast iron and having a generally rectangular cross-section. The ring is received within a mating annular ring groove formed into the sidewall of the piston. To facilitate expansion during installation, and for other reasons, the ring is radially severed.

The spacing between the opposed ends of the severed ring, known as the end gap, serves various functions after installation. Having an inherent tendency to expand, the ring maintains tension for attendant sealing against the sidewall of the cylinder as the bore increases in diameter as a result of wear. The end gap also allows for thermal expansion of the ring resulting from heat generated by friction, compression of fluid, combustion of fuel and other sources.

Although necessary and even beneficial, the end gap is also the source of considerable concernment. Normal end gap clearance in a newly installed ring ranges from approximately ten one-thousandths of an inch to approximately forty one-thousandths of an inch. The end gap defines a path for leakage of fluids between the sidewall of the piston and the sidewall of the bore. Throughout the life of the device, the piston ring

continuously expands as normal compensation for wear. Resultingly, the end gap ever increases with corresponding increase in leakage, usually referred to as a blow-by.

Efficiency, economy and service life of the apparatus is directly related to blow-by. In general, less than optimum output of the apparatus results from loss of pressure or compression of the fluid. Other deleterious effects are unique to the particular apparatus. In an internal combustion engine, for example, contaminating by-products of combustion suspended in the blow-by gases are carried into the lubricating system which in turn harms components throughout the engine. in recognition of the desirability of enhancing the seal between the piston and the cylinder, the prior art has proposed various seals which purportedly reduce or eliminate blow by. Several prior art proposals are direct attempts to eliminate the end gap in the conventional piston ring. In general, the proposals include an insert which spans the end gap and is received in a notch formed into the ring on either side of the end gap.

Numerous proposals include the use of a relatively thin steel member, alternately named a ribbon member or a gap seal member, having a substantially rectangular cross-section. In one particular configuration, there is provided a helix of juxtaposed coils having a height corresponding to the width of the ring groove. The use of a lesser number of coils which are angularly arranged has also been advanced. Also advanced is a plurality of severed annular members, installed in stacked arrangement with staggered end gaps.

The prior art has also advocated the use of thin steel members, colloquially dubbed rails, in combination with ring members having a general resemblance to conventional piston rings. Being of substantially heavier construction than a rail and usually fabricated

of malleable material, such as cast iron, the ring member is variously referred to as a packing member or a sealing ring. The ring member in combination with the rail member comprise a seal assembly of which various embodiments are known.

In accordance with one known arrangement the rail resides within an annular groove formed into the inner circular wall of the seal member and exerts outwardly directed radial pressure to hold the seal member in contact with the sidewall of the bore. In another configuration, the rail occupies a space between the top of the seal member and the upper radial surface of the containing ring groove. Still other formations orient the radial axis of the rail at an angle. For various reasons, annular seals of the foregoing character are not perceived as being entirely satisfactory. For example, in an assembly wherein the rail resides within the seal member and exerts an expansive force, excessive friction is generated against the sidewall of the bore. Where only the rail contacts the sidewall, seating or breaking-in of the seal is substantially retarded or even prohibited. An angled rail is subject to vibration, commonly known as ring flutter, when used in connection with a rapidly reciprocating piston. A thin steel member exposed to extreme heat, such as when utilized as the top compression ring in an internal combustion engine, will be become distorted.

Seal assemblies of the above character where devised mainly during the time period ranging from approximately the middle nineteen thirties to early nineteen fifties. During the early nineteen seventies, there was developed a seal assembly which substantially remedied the foregoing deficiencies inherent in the prior art. Distributed by POWERFORMANCE INTERNATIONAL CORPORATION under the trademark TOTAL SEAL*, the seal assembly has achieved commercial success, especially for use in connection with four-cycle internal combustion engines.

Briefly, the Total Seal ^® device, referred to as a ring set, includes a sealing ring member and a rail member. The sealing ring member, a severed annular member preferably fabricated of malleable metal such as cast iron, has thickness and radial dimensions to be received within a conventional piston ring groove in accordance with standard tolerances. Extending inwardly from the outer cylindrical surface along the underside of the sealing ring member is an annular notch in which is received the rail member. The intricacies and advantages of the ring are described in U.S. Patent No. 3,811,690 and are well known to those having regard for the art.

Notwithstanding continuing success in the trade, the Total Seal* ring set has proven to be less than optimum. As installed, the respective end gaps of the sealing ring member and of the gap seal member are diametrically opposed. The elastic expansiveness or outward radial force of a severed annular seal under tension is gradiently distributed throughout. Therefore, while the set as an assembly is free to move or work within the ring groove, theoretically movement between the members should be prohibited as the result of the relative forces therebetween.

Extensive use in testing has shown that occasionally relative movement will occur between the members. The ultimate relative movement is capable of aligning the respective end gaps. While the other advantages of the set remain, leakage can occur.

Considerable research and development has been directed to devising a ring set which will retain the numerous benefits of the present Total Seal* ring set and yet provide additional benefits and resolve other problems of longstanding in the art. Substantial attention has been directed to an assembly in which the end gap in the sealing ring member is positively sealed. Additional benefits were directed to ameliorating the advantages of the ring set in such areas as reducing generated heat and increasing ring stability. Further

consideration has been given to extending the utility of the assembly for use in additional applications, including internal combustion engines having sleeve or port valves and making practical a piston having a single compression ring.

It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.

Summary Of The Invention

The present invention provides a seal assembly especially adapted for use in combination with an apparatus which includes a first member having a bore and a second member which is reciprocally movable along a linear axis within the bore of the first member. The seal assembly is held in an annular groove formed in one of the members and sealingly engages sidewall of the other of the members. In accordance with a preferred embodiment of the invention there is first provided an annular primary member sized to be received within the groove and having top and bottom surfaces for residing in juxtaposition with the upper and lower, respectively, surfaces of the groove. The primary member further includes a sealing surface for contacting the sidewall of the other of the members of the apparatus. A notch formed into the bottom of the surface of the primary member is defined by a radial surface extending from the sealing surface and an axial surface spaced from the sealing surface. An end gap severs the primary member and defines a pair of spaced apart ends.

Next provided is an annular secondary member which is carried within the notch for extending across the end gap and including an upper surface for residing in juxtaposition with the radial surface of the notch and a lower surface for residing in juxtaposition with the lower surface of the groove. Further included is a contact edge for contacting the sidewall of the other of said members of the apparatus. The secondary member terminates with first and second spaced apart ends.

In a more specific embodiment, the secondary member is generally in the form of a helix having an angle of rotation greater than a full turn with the upper surface, the lower surface and the contact edge extending continuously between the ends. Preferably, the helix includes first and second contiguous coils terminating with respective ones of the ends. More specifically, the coils are planar and parallel and are joined by a

contiguous transition element which is angularly disposed intermediate the ends.

In yet a further embodiment of the invention, the primary member exerts a force in a direction toward the sidewall to be sealed which is greater than the force exerted by the secondary member. Further, the primary member includes a relieved terminal portion extending from each of the ends along the sealing surface and, similarly, the secondary member includes a relieved terminal portion extending from each of the ends along the contact surface. Preferably, each of the relieved terminal portions is inturned with respect to the respective edge.

Disclosure Of The Invention

Accordingly, it is an object of the present invention to provide improved means for sealing between a pair of coaxial components having relative reciprocal movement therebetween.

Another object of the invention is the provision of improved sealing means especially adapted for use in connection with internal combustion engines, positive displacement pumps, linear fluid actuated motors and other apparatus having a bore housing a piston or other reciprocally movable component.

And another object of this invention is to provide an improved annular seal of the normally severed type as exemplified by the conventional piston ring. Still another object of the invention is the provision of a seal assembly having positive means for materially reducing leakage between the bore and the reciprocally movable member.

Yet another object of the immediate invention is to provide a seal assembly having rapid seating or break-in characteristics.

And yet another object of the invention is the provision of a seal assembly which will provide excellent sealing while substantially reducing cylinder wall friction.

And a further object of the instant invention is to provide a seal assembly having an extended service life.

Still a further object of this invention is the provision of a seal assembly having inherent stability within the ring groove.

Yet a further object of the invention is to provide a seal assembly which is suitable for use as a primary compression ring in an internal combustion engine.

And still a further object of the invention is the provision of a seal assembly according to the foregoing which is adapted for use in mechanisms having an opening in the sidewall of the bore.

Brief Description of Drawings

The foregoing and other objects, features and advantages of the instant invention will be readily apparent from the following detailed description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be affected without departing from the spirit and scope of the novel concepts of the disclosure and in which:

Fig. 1 is a perspective view of a seal assembly embodying the principles of the instant invention;

Fig. 2 is an elevation view of the gap seal member of the seal assembly of Fig. 1;

Fig. 3 is a fragmentary perspective view of the seal assembly of Fig. 1 as it would appear when installed in the ring groove of a piston encased in a cylinder;

Fig. 4 is a vertical sectional view taken along the line 4-4 of Fig. 3;

Fig. 5 is a partial perspective view of an alternate embodiment of the seal assembly of the instant invention;

Fig. 6 is a top plan view of the seal assembly of

Fig. 5 as it would appear after being installed, the illustration being a fragmentary plan view partially in section; and

Fig. 7 is a vertical sectional view of yet another embodiment of the invention as it would appear in combination with a mechanical apparatus viewed in fragmentary sectional illustration.

Best Modes For Carrying out The Invention

Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is first directed to Fig. 1 which illustrates a seal assembly of the instant invention comprising a primary member and a secondary member generally designated by the reference characters 20 and 22, respectively. The co-functioning of the members to achieve the desired objects of the instant invention will become readily apparent to those skilled in the art in the ensuing detailed description.

Primary member 20, a severed annular sealing ring member having an analogy to the conventional device known as a piston ring, includes outer cylindrical surface 23, inner cylindrical surface 24, top surface 25 and bottom surface 27. The terms top and bottom, used for purposes of spatial orientation and reference, are not intended to be limiting upon the scope of the invention. In accordance with conventional practice and for well recognized reasons, primary member 20 is radially severed by end gap 28 which results in opposed ends 29 and 30. Annular notch 32, of which further description will be made presently, extends inwardly from outer cylindrical surface 23 along the underside of member 20. Secondary member 22, as seen with further reference to Fig. 2, is generally in the form of a helix having upper and lower contiguous coils 33 and 34, respectively, with continuous outer edge 35 and continuous inner edge 37. Upper surface 38 and bottom surface 39 are also continuous throughout. Member 22 terminates with ends 40 and 42 which function as the free ends of upper coil 33 and lower coil 34, respectively.

The coils 33 and 34 are arranged each to lie in one of a pair of parallel planes. Transition element 43, residing intermediate ends 40 and 42, extends angularly between the fixed ends of the coils. It is understood that the edges 35 and 37 and surfaces 38 and 39 are continuous throughout transition element 43.

Notch 32 within primary member 20 is sized and shaped to receive secondary member 22. The assembly is sized and shaped to be received within a conventional ring groove. For purposes of orientation and reference ^D there is seen in Fig. 3 an apparatus of the type in which the seal assembly of the instant invention is intended to be used. Typically representative of internal combustion engines, positive displacement pumps, linear fluid actuated motors and similar mechanisms, the apparatus 0 includes a cylinder 50 having bore 52 with cylindrical sidewall 53. A movable member 54, such as a piston, having cylindrical sidewall 55 and top 57 is disposed within bore 52 for reciprocal movement along a linear axis as represented by double arrowed line A. A variable 5 volume chamber 58 for pressurized fluid is defined within bore 52 adjacent to top 57 of movable member 54. An annular groove 59, commonly referred to as a ring groove, is formed into the sidewall of the movable member for purposes of holding a seal such as the conventional 0 piston ring. The seal assembly of the instant invention is seen as it would appear when residing within the groove 59.

Annular groove 59, illustrated in greater detail in Fig. 4, includes upper surface 60, lower surface 62 and 5 inner surface 63. Surfaces 60 and 62, colloquially referred to as the sides of the ring groove, lie in parallel respective planes which are generally radial to the axis of movement of the movable member. Surface 63, commonly referred to as the bottom of the groove, is 0 generally cylindrical and coaxial with the axis of movement. Notch 32 is defined by radial surface 64 and inner surface 65, the latter being generally cylindrical and concentric with the inner and outer cylindrical surfaces 23 and 24, respectively, of primary member 20. r For optimum operation of the invention, certain relationships are preferred between the primary member and the secondary member and between the seal assembly and the apparatus within which it is installed,

especially the containing annular groove. For exemplary purposes not to be considered as imposing limitations upon the scope of the invention, a preferred embodiment of the invention will now be described in specific detail. Chosen for environmental purposes is an apparatus in the form of an internal combustion engine wherein movable member 54 is a piston driven downwardly in response to the expanding gases of combustion generated in chamber 58. Typically, sidewall clearance,

10 the distance between surface 53 of bore 52 and surface 55 of piston 54, is approximately fifteen ten-thousandths of an inch. In the area between the ring groove 59 and the top 57 of the piston, the clearance may be somewhat increased to approximately ten one-thousandths of an

15 inch. The axial dimension or width of the ring groove is nominally sixty-four one-thousandths of an inch, although variations from fifty-nine one-thousandths to ninety-four one-thousandths are characteristic.

Primary member 20 is generally L-shaped in cross-

20 section and sized to be closely received within groove 59. In accordance with conventional practice the axial dimension, distances between surfaces 25 and 27, is approximately one one thousandths to two one thousandths of an inch narrower than groove 59. This clearance 5 allows the ring assembly to move or work within the groove. In the embodiment chosen for purposes of illustration, the cross-sectional radial measurement, distance between surfaces 23 and 24, is approximately one hundred and forty one-thousandths of an inch, which is 0 approximately six one-thousandths less than the distance between sidewall 53 of bore 52 and the inner surface 63 of groove 59.

Preferably, the cross-sectional dimensions of groove 32 are slightly larger than the cross-sectional

> dimensions of the secondary member 22. Continuing with the above example, the radial dimension of secondary member 22, the distance between outer edge 35 and inner edge 37, is approximately one hundred and five one-

thousandths of an inch. Each coil 33 and 34 has an axial dimension of fifteen one-thousandths of an inch. Since the lower surface 39 of the upper coil 33 is in contact with the upper surface 38 of the lower coil 38, the inclusive axial dimension is thirty one-thousandths of an inch. The corresponding axial and radial dimensions of groove 32 range between five ten-thousandths and one one- thousandths greater than the dimensions of secondary member 2-2. in accordance with the immediately preferred embodiment of the invention, the elastic expansiveness or outwardly directed radial force of each of the members, as indicated by the arrowed line B, is significant. Continuing the foregoing example, primary member 20 exerts a total outward force of approximately ten pounds. The outwardly directed force of secondary member 22 is zero. That is, secondary member 22 is neutral and is in the relaxed state when installed. The fabrication of annular seals having prescribed elastic expansiveness will be readily apparent to those skilled in the art.

Seating of the assembly, mating with the cylindrical sidewall of the bore, is an important consideration in the art. As initially installed, the seal assembly of the instant invention appears as illustrated in Fig. 4. it is noted that outer cylindrical surface 23 of primary member 20 and outer edge 35 of secondary member 22 are in contact with sidewall 53 of bore 52. Accordingly, a space of approximately five ten-thousandths to one one- thousandths of an inch exist between inner edge 37 of secondary member 22 and the inner or axially 65 of groove 32. Primary member 20 fabricated of a material which is relatively softer than the material of construction of secondary member 22. Preferably, primary member 20 is fabricated of a malleable material such as cast iron nodular iron. Surface 23 may be coated with molybdenum or other facings conventional in the art. A preferred material for secondary member 22 is steel. Further, it is recommended that outer edge 35 be rounded in cross-

section and coated with a friction reducing material such as chromium. Typically, the chrome plating may range between two one-thousandths and three one-thousandths of an inch.

~ Due to the inherent characteristics of primary member 20, relatively soft material and tendency to expand, outer cylindrical surface 23 is quickly worn away against surface 53 of bore 52 during initial operation.

Accordingly, rapid wear-in or seating of the seal is accomplished. The seating phase continues until sufficient material is removed from surface 23 to allow inner surface 65 of notch 32 to abut the inner edge 37 of secondary member 22. The outwardly directed force of primary 20 is then transferred to secondary member 22. While surface 23 remains in contact with surface 53, the force against surface 53 is borne by outer edge 35 of secondary member 22. As a result of the arcuate shape of edge 35, the load bearing contact between the seal assembly and the bore is in the form of two spaced apart parallel lines. Accordingly, friction against surface 53 is vastly reduced as is wear of surface 53. To further reduce friction, it is suggested that edge 35 be chrome plated in accordance with conventional techniques to a thickness of approximately two one-thousandths of an inch to three one-thousandths of an inch.

Over the operating life of the apparatus considered from initial operation to normal time for rebuild, the diameter of bore 52 will enlarge by several one- thousandths of an inch and the seal assembly will decrease in diameter by a few one-thousandths of an inch. However, no loss in effectiveness of the seal assembly nor leakage between the movable member 54 and the bore 53 will occur. As material is worn away, primary member 20 will continue to expand to maintain the desired seal. Concurrent with the expansion of primary member 20, end gap 28 will increase. Secondary member 22, however, will continue to function as an end gap seal member. It is noted that since only a small portion of secondary member

22 is exposed to the super-heated gases of combustion, no warpage or distortion will occur.

Attention is now directed to Fig. 5 wherein there is seen an alternate embodiment of the instant invention, which in general similarity to the previously described embodiment, includes primary member 70 and secondary member 72. In further similarity, primary member 70 includes outer cylindrical surface 73, notch 74 and end gap 75 laying between ends 77 and 78. Also, secondary member 72 includes upper coil 79 and lower coil 80 terminating with free ends 82 and 83, respectively. The coils are joined by transition element 84 and includes continuous outer edge 85. In all other aspects not specifically noted, primary member 70 and secondary member 72 are analogous to previously described primary member 20 and secondary member 22, respectively.

The immediate embodiment is especially devised for use in combination with mechanisms in which the cylinder is provided with a sleeve valve. For reference, there is seen in Fig. 6 such a mechanism, as for example a two- cycle engine, including cylinder 90 and bore 92 having cylindrical sidewall 93. Movable member or piston 94 having ring groove 95 is reciprocally disposed within bore 92. Primary member 70 and secondary member 72, functioning as a seal assembly, reside within ring groove 95.

Sleeve valve 97, an open port extending through cylinder 90 communicates with bore 92. As will be appreciated by those skilled in the art, port 97 is alternately opened and closed in response to movement of piston 94. During the movement of piston 94, the seal assembly periodically passes over the opening in cylindrical sidewall 93. To accommodate port 97, the terminal portions of edge 73 adjacent ends 77 and 78 of primary member 70 are relieved. Reference is made to the inwardly turned terminal portions laying within the brackets designated C in Fig. 6. For purposes of illustration, the amount of inturn is exaggerated. In

actuality, the inturn, measured at the ends 77 and 78, need only be three one-thousandths to four one- thousandths of an inch, slightly greater than the anticipated wear of surface 73 during the service life of the seal assembly. Also, the terminal portions of outer edge 85 adjacent ends 82 and 83 are similarly relieved. While the relieved terminal portions are shown as being arcuate, other inturned geometric configurations will readily occur to those skilled in the art. Each of the foregoing embodiments of the invention were especially devised to be carried by the movable member for sealing against the bore of the cylinder. It is also contemplated by the instant invention to provide a seal assembly to be carried by the housing member and seal against the movable member. Reference is now made to Fig. 7 wherein there is seen a housing 100 having bore 102 in which is disposed movable member 103 having outer cylindrical surface 104. Movable member .. 103 is reciprocally movable along a linear axis as suggested by the double arrowed line D. Exemplary of such an apparatus is the operating shaft extending from a linear hydraulic motor.

An annular ring groove 105 is formed into housing 100 from bore 102. The immediate embodiment of the seal assembly of the instant invention carried in ring groove 105 includes primary member 107 and secondary member 108. Although not specifically described in detail, it is to be understood that the members 107 and 108 are analogous to the previously described members 20 and 22 except that the notch extends outwardly from the inner cylindrical surface of the primary member and that the sealing function is accomplished by the inner cylindrical surface of the primary member and the inner edge of the secondary member. To complement the sealing function, the force generated by the primary member is also reversed. That is, primary member 107 is elastically contractive to display an inwardly directed radial force as represented by the arrowed line E. For a further understanding of

the instant embodiment where not specifically described, reference is made to the embodiment described in connection with the illustrations of Figs. 1 through 4.

Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. For purposes of illustration, the invention has been described in connection with an internal combustion engine with attenuate excessive heat and loading. Accordingly, it has been suggested that the elements be made of metal, especially cast iron or nodular iron for the primary member and mild steal for the secondary member. Consistent with the requirements of other apparatus, the seal assembly may be readily fabricated of softer metals such as copper or aluminum alloys or synthetics such as plastic or resinous materials. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.

The above description is given by way of example only. Changes in form and details may be made by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Industrial Applicability

The instant invention provides an ameliorated seal which is usable in internal combustion engines, positive displacement pumps, linear nu adic motors and other mechanical devices incorporating a piston and cylinder assembly. The inventive seal assembly can, for example, be manufactured in various physical sizes to be utilized in original equipment manufacture of the exemplary mechanical devices or as an after-market replacement item. The seal assembly is readily fabricated of known materials using skills and equipment of the trade as will be appreciated by those skilled in the art.