More particularly, this invention relates to annular seals of the type for use in connection with a mechanism having linearly or reciprocally movable members.

In a further and more specific aspect, the instant invention relates to a seal apparatus having improved means for minimizing fluid leakage between the members and through the seal.

BACKGROUND ART Various mechanical apparatus include 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 a cylinder assembly. Further 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 end wall 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. Pressurized fluid from an external source is introduced into the chamber of a pneumatic motor to force movement of the piston. In a

pump, which is companion to the engine and to the pneumatic motor, fluid is compressed and pressurized within the chamber.

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, substantial 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 concern. 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 compensation for normal wear. As a result, 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 at attempts to eliminate the end gap in the conventional piston ring. Various 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.

Other 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. 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 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 gap seal 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 gap seal 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 long-standing in the art. Substantial attention has been directed to an assembly in which the possibility of leakage is minimized. Additional efforts 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 to making practical a piston having a single compression ring.

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

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 present 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 encircling a piston, shaft or other reciprocally movable component.

And another object of the present 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 present invention is the provision of a seal assembly having ameliorating means for materially reducing the possibility of leakage between the bore and the reciprocally movable member.

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

Yet still another object of the instant invention is the provision of a seal assembly which will provide excellent sealing while substantially reducing friction.

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

Still a further object of the present invention is the provision of a seal assembly which is easily installed.

Yet a further object of the invention is to provide a seal assembly which is readily produced in accordance with known manufacturing techniques.

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.

And yet still a further object of the invention is the provision of a new and improved method of sealing a one of a pair of reciprocally movable members to another of the pair reciprocally movable members.

Briefly, to achieve the desired objects of the instant invention in accordance with a preferred embodiment thereof, there is provided a first annular member and a second annular member comprising a seal assembly to be received within an annular groove having opposed radial surfaces and carried by one of a pair of reciprocally movable members for sealing engagement with the sidewall of the other of the pair of reciprocally movable members. The first annular member includes a first radial surface to reside adjacent one of the radial surfaces of the annular groove, a second radial surface to reside adjacent another of the radial surfaces of the annular groove, an outer surface to reside adjacent and spaced from the sidewall, an annular groove adjacent the outer surface and extending inwardly therefrom and having a first inner radial surface, a second inner radial surface and terminating with an inner axial surface. An end gap severs the first annular member and defines space-apart ends.

The second annular member is removably receivable within the annular groove of the first annular member and includes a first radial surface to reside adjacent the first inner radial surface of the first annular member, a second radial surface to reside adjacent the second inner

radial surface of the first annular member, an inner axial surface to reside adjacent the inner axial surface of the first annular member, and a contact surface to sealingly engage the sidewall. An end gap severs the second annular member and defines space-apart ends. The end gaps of the first and second annular members are offset relative one another, and the first annular ring is biased to exert a force in a direction toward the sidewall for facilitating the sealing engagement of the contact surface of the second annular member to the sidewall.

It is contemplated by the instant invention that the end gap in at least one of the members be effectively eliminated. In accordance with an embodiment thereof, each annular member serves to seal or close the end gap of the other member.

The instant invention may also include a stop means interacting between the first annular member and the second annular member for retarding relative rotation between the first annular member and the second annular member. The stop means may include one or more protuberances or nodes extending from the first annular member and/or the second annular member to reside proximate either or both of the end gaps.

The present invention also provides a method for sealing a one of a pair of reciprocally movable members having an annular groove with opposed radial surfaces to the sidewall of the other of the pair of reciprocally movable members. The method is comprised of the steps of providing a seal assembly having a first annular member removably engaged to a second annular member having a contact surface and placing the seal assembly into the annular groove of the one of the pair of reciprocally movable members to sealingly engage the contact surface of the second annular member to the sidewall.

The method may further include the step of replacing the second annular member after a predetermined period of use or wear of the contact surface of the second annular member and/or the sidewall. The step of replacing the second annular member may further include the steps of removing the seal assembly from the annular groove of the one of the pair of reciprocally movable members, removing the second annular member from the annular groove of the first annular member, installing a new second annular member into the annular groove of the first annular member to form a new seal assembly, and reinstalling the new seal assembly into the annular groove of the one of the pair of reciprocally movable members.

In accordance with a preferred method, the step of providing a seal may further include the steps of providing the first annular member having an end gap severing the first annular member, forming an annular groove into the first annular member adjacent an outer surface and extending radially inwardly therefrom, providing a second annular member having a contact surface and an end gap severing the second annular member and placing the second annular member into the annular groove of the first annular member to form the seal assembly, the contact surface extending radially outwardly therefrom the outer surface of the first annular member.

The method may further include the step of imparting a bias to the first annular member to exert a force in a direction toward the sidewall for facilitating the sealing engagement of the contact surface of the second annular member to the sidewall. Additionally, the step of placing the second annular member into the annular groove of the first annular member may further include the step of aligning the end gap of the first annular

member in a generally offset relation relative the end gap of the second annular member.

In accordance with a preferred method, further included is the step of providing a stop means for retarding relative rotation between the first annular member and the second annular member. The step of providing the stop means includes providing one or more protuberances or nodes extending from the first annular member and/or the second annular member to reside proximate either or both of the end gaps.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of preferred embodiments thereof taken in conjunction with the drawings in which: Fig. 1 illustrates a fragmentary horizontal sectional view taken along the ring groove of a typical reciprocating mechanism and especially showing a commercially successful prior art seal assembly installed therein; Fig. 2 illustrates a plan view of a seal assembly constructed in accordance with a preferred embodiment of the present invention; Fig. 3 illustrates a fragmentary vertical sectional view of the mechanism of Fig. 1 having the seal assembly of Fig. 2 installed therein; Fig. 4 illustrates a perspective view of the seal assembly of Fig. 2 as it may appear prior to assembly; Fig. 5 is a fragmentary perspective view of the seal assembly of Fig. 2 and showing a portion thereof as it would appear assembled;

Fig. 6 is a view generally corresponding to the view of Fig. 5; Fig. 7 is a fragmentary perspective view of the seal assembly of Fig. 2 and showing a portion thereof as it would appear assembled; Fig. 8 is a view generally corresponding to the view of Fig. 7; Fig. 9 is a fragmentary perspective view of one of a pair of annular members comprising the seal assembly of Fig. 2; and Fig. 10 is an enlarged fragmented perspective view of the seal assembly of Fig. 2 and shown as it would appear assembled.

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 mechanism including a first member, generally designated by the reference character 20 and a second member, generally designated by the reference character 22, which are disposed for relative reciprocal movement along a linear axis which is substantially perpendicular to the plane of the illustration. The mechanism is typically representative of internal combustion engines, positive displacement pumps, linear fluid actuated motors and similar apparatus in which first member 20 is generally referred to as the cylinder and second member 22 is usually referred to as the piston. First member 20 includes inner cylindrical sidewall 23 which is coaxial with and spaced from outer cylindrical sidewall 24 of second member 22. The space, commonly termed sidewall clearance and herein exaggerated for purposes of illustration, is necessary to ensure

relative movement between the members. To retard leakage, the second member 22 is provided with an annular groove 25, commonly known in the art as a ring groove, for the purpose of carrying sealing means. The traditional sealing means is the conventional piston ring.

Chosen for purposes of illustration is the sealing means set forth in United States Patent No. 3,811,690 and commercially distributed by POWERFORMANCE INTERNATIONAL CORPORATION under the trademark TOTAL SEAL@. The Total Seal@ device, actually an assembly, includes a sealing ring member and a gap seal member generally designated by the reference characters 27 and 28, respectively.

Sealing ring member 27, preferably fabricated of malleable metal such as cast iron, has thickness and radial dimensions to be received within groove 25 in accordance with standard tolerances. Analogous to the conventional piston ring, sealing ring member 27 is severed by end gap 29 and has a sealing surface 30 which engages cylindrical sidewall 23. Gap seal member 28, preferably fabricated of steel, is dimensioned to be received within a notch (not specifically shown) formed in the underside of sealing ring member 27. Gap seal member 28, similar to sealing ring member 27, is severed by end gap 32 and has sealing surface 33 which also engages sidewall 23.

The intricacies and advantages of the above described seal assembly are well known to those having regard to the art. Therefore, it will be appreciated that while the assembly is free to move or work within the ring groove, movement between the members should be theoretically prohibited as the result of the relative forces therebetween. Concern has been expressed, however, that it is possible for the end gap to align,

substantially as illustrated in Fig. 1, and allow leakage of pressurized fluids through the seal.

The foregoing is set forth for purposes of orientation and understanding in connection with the ensuing description of a preferred embodiment of the present invention. Aspects not fully described will be readily apparent and appreciated by those skilled in the art.

The present invention provides improvements to the above described seal assembly, and to similar sealing means, whereby the possibility of leakage is minimized.

In accordance with a preferred embodiment of the present invention as illustrated in Fig. 2, there is provided a seal assembly including a first annular member generally designated by the reference character 40 and a second annular member generally designated by the reference character 42. The seal assembly is dimensioned to be received within the conventional ring groove 25 as illustrated in Fig. 3 and in accordance with standard tolerances. For additional reference, it is noted that annular groove 25, which is generally rectangular in cross-section, includes a first radial surface 35, a second radial surface 37, and an axial surface 38. The relative movement between members 20 and 22 occurs in linear directions represented by the double arrowed line A which is parallel to sidewall 23.

First annular member 40, which is preferably constructed of a malleable material such as cast iron, steel, aluminum or other similarly ductile material, includes a first radial surface 43, a second radial surface 44, an outer surface 45 having a generally arcuate shape and an inner axial surface 46. First annular member 40 further includes an annular groove 50 formed therein adjacent outer surface 45 and extending inwardly therefrom. Annular groove 50 is substantially

centrally located within first annular member 40 intermediate first radial surface 43 and second radial surface 44 and includes a generally rectangular cross- section as defined by a first-inner radial surface 51, a second inner radial surface 52 and an inner axial surface 53. End gap 55 severs first annular member 40 and defines spaced apart ends 56 and 57.

Second annular member 42, in general analogy to first annular member 40, includes a first radial surface 60, a second radial surface 61, an inner axial surface 62 and an outer surface 63 having a generally rounded or arcuate shape. Preferably constructed of carbon steel, second annular member 42 is dimensioned to be removably received within annular groove 50 of first annular member 40 with first radial surface 60 adjacent first radial surface 43, second radial surface 61 adjacent second radial surface 44, inner axial surface 62 adjacent inner axial surface 46 and outer surface 63 extending outwardly from annular groove 50 adjacent outer surface 45. Outer surface 63 functions as a contact surface to sealingly engage with sidewall 23 of first member 20. Outer surface 63 may be heat treated and/or may be coated with chrome or other protective anti-wear or anti-friction coating for the purposes of wear and reduction of friction. With respect to a preferred embodiment, it is recommended that outer surface 63 be rounded or arcuate in cross-section. Typically, the chrome plating may range between two one-thousands and three one-thousandths of an inch. End gap 65 severs second annular member 42 and defines spaced apart ends 66 and 67. With momentary reference to Fig. 10, outer surface 63 leading toward ends 66 and 67 of second annular member 42 may be beveled inwardly at 68 and 69, respectively, for reasons presently to appear.

First annular member 40 and second annular member 42 are coupled as an assembly and installed in groove 25 with the members orientated substantially as seen in Fig.

2 and Fig. 4. It is noted that end gap 55, and thus ends 56 and 57, lie in an offset relation relative end gap 65, and thus ends 66 and 67, respectively. First annular member 40 and second annular member 42 are elastically expansive or biased to exert an outward force toward or against sidewall 23. The outwardly biased forces urge outer surface 63 of second annular member 42 toward sidewall 23 to sealingly engage outer surface 63 to sidewall 23. In accordance with a preferred embodiment, the outwardly biased force of first annular member 40 is greater than the outwardly biased force of second annular member 42 so that as outer surface 63 wears, first annular member 40 will operate to maintain outer surface 63 in sealing engagement with sidewall 23. In the desired orientation, each annular member serves to seal or close the end gap of the other member thereby eliminating the fluid leakage path inherent in conventional prior art piston rings.

In accordance with the phenomenon well established in connection with the prior art assembly specifically described in Fig. 1, the outwardly biased forces act to prohibit relative movement between the annular members of the seal assembly. However, it has been noticed that relative rotation normally does occur which results in fluid leakage past the seal assembly. To retard relative rotational movement, one or both of the annular members may be constructed having one or more protuberances or nodes positioned proximate the respective end gaps when the seal assembly is assembled. As shown in Fig. 5 and Fig. 6, a node 70 is shown having been stamped or otherwise formed or imparted to second annular member 42 to reside within end gap 55 intermediate ends 56 and 57

of first annular member 40 and extending from second annular surface 61. Relative rotational movement of first annular member 40 and second annular member 42 is thus retarded as node 70 is constructed to have a size of such a dimension as to be denied receipt into annular groove 50 past either end 56 or 57. It will be readily understood that the node may extend from first radial surface 60 and that one or more may be provided.

As shown in Fig. 7 and Fig. 8, a node 71 is shown having been stamped or otherwise formed or imparted to first annular member 40 to reside within end gap 65 intermediate ends 66 and 67 of second annular member 42 and extending inward from first inner radial surface 51.

Relative rotational movement of first annular member 40 and second annular member 42 is thus retarded as node 71 is constructed to have a size of such a dimension as to be denied receipt into annular groove 50 past either end 66 or 67. It will be readily understood that the node may extend from second inner radial surface 52 and that one or more may be provided. As shown in Fig. 9, first annular member 40 may be formed having a pair of diametrically opposed and corresponding notches 80 and 81 carried by ends 56 and 57, respectively, for receiving node 71 when ends 56 and 57 are brought together in the direction indicated by arrowed line C, although this is not essential.

First annular member 40 is sized to be removably received within groove 25. In accordance with conventional practice the axial dimension, the distance between surfaces 43 and 44, is approximately four one- thousandths to six one-thousandths of an inch narrower than groove 25. This clearance allows the seal assembly to move or work within groove 25, and further allowing it to be easily installed and removed. In the embodiment chosen for purposes of illustration, the cross-sectional

radial measurement, the distance between surfaces 45 and 46, is generally equal to the distance between surfaces 38 and 24.

Preferably, the cross--sectional dimensions of annular groove 50 are slightly larger than the cross- sectional dimensions of second annular member 42. As a result, second annular member 42 may be readily installed within and removed from annular groove 50. Continuing with the above example, the distance between surfaces 62 and 63 is somewhat greater than the distance between surfaces 45 and 53. In this manner, when housed within annular groove 50, surface 63 of second annular member 42 extends beyond surface 45 for sealing engagement to sidewall 23. Furthermore, the axial dimension of second annular member 42 is somewhat smaller that the distance between surfaces 51 and 52 of annular groove 50.

In accordance with the immediately preferred embodiment of the invention, the elastic expansiveness or outwardly directed radial force of each of the annular members, as indicated by the arrowed line B in Fig. 3, is significant. Continuing the foregoing example, first annular member 40 exerts a total outward force of between three to twelve pounds, depending on the needs of the user and the specific application. The outwardly directed force of second annular member 42 is generally negligible. In other words, second annular member 42 is substantially neutral and is in a relatively 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 seal assembly, mating with the cylindrical sidewall of the bore, is an important consideration in the art. As initially installed, the seal assembly of the present invention appears as illustrated in Fig. 3. It is noted that outer surface 45

of first annular member 40 is spaced-apart from sidewall 23 of member 20, outer surface 63 of second annular member 40 is in contact with sidewall 23 and inner axial surface 62 is in contact with inner axial surface 53 of first annular member 40 defining, in part, annular groove 50. First annular member 40 is fabricated of a material which is relatively softer than the material of construction of second annular member 42.

Consistent with the foregoing, due to the inherent characteristics of second annular member 42, outer surface 63 is not easily worn away against sidewall 23 during initial and prolonged operation. Accordingly, seating of the seal assembly is accomplished upon installation and no appreciable wear-in is required. The outwardly directed force of first annular member 40 facilitates the sealing engagement of outer surface 63 to sidewall 23, the force against sidewall 23 being borne by inner axial surface 53. As a result of the rounded or arcuate shape of outer surface 63, the load bearing contact between the seal assembly and the bore is born solely by outer surface 63 in the form of a parallel line. Accordingly, friction against sidewall 23 is vastly reduced, with no wear occurring to outer surface 45 of first annular member 40. Furthermore, and in accordance with Fig. 10, the beveled nature of ends 66 and 67 of second annular member 42 prevent ends 66 and 67 from clipping irregularities present upon inner cylindrical sidewall 23 of first member 20 as second member 22 reciprocates. The various irregularities that may be present upon inner cylindrical sidewall 23 may be superficial surface irregularities, irregularities present in and around apertures formed through inner cylindrical sidewall 23 for permitting the communication of combustible or combusted gases, or the like.

Specifically, ports formed in the sidewalls of 2-stroke

engines often cause"clipping"if a conventional seal ring rotates so that the gap aligns with the port. The outwardly directed bias of the ring causes corners at the gap to be clipped off as the-ring reciprocates past the port. This is conventionally avoided by pinning the ring, a time consuming and expensive operation. First annular member 40 and second annular member 42 each prevent the other from extending a corner which could be clipped. To further insure that clipping is avoided, the beveled ends of Fig. 10 can be employed.

Over the operating life of the apparatus considered from initial operation to normal time for replacement or rebuild, the diameter of sidewall 23 will somewhat enlarge and the diameter of the seal assembly will somewhat decrease. However, no loss in effectiveness of the seal assembly or leakage between the first annular member 20 and the second annular member 22 will occur.

As sidewall 23 material and second annular member 42 material wears away, first member 40 will continue to expand to maintain the desired seal of outer surface 63 of second annular member 42 to sidewall 23 without coming in contact with sidewall 23. Concurrent with the expansion of first annular member 40, end gap 55 will increase. Second member 42, however, will continue to function as an end gap seal member. It is noted that because only a small portion of second annular member 42 is exposed to heat from the gases of combustion, no warpage or distortion will occur.

Over an extended period of operation, outer surface 63 of second annular member 42 will wear down to such a degree such that outer surface 45 of first annular member 40 will come very close to contacting sidewall 23. At this point in operation, the seal assembly may be removed from annular groove 25, second annular member 42 removed from annular groove 50 of first annular member 40,

replaced with a new annular member to form a new seal assembly to be then reinstalled into annular groove 25 to resume operation. Second annular member 42 is relatively inexpensive, while first annular member 40 is considerably expensive. As a result, replacement of second annular member 42 is relatively expensive as compared to replacing the entire seal assembly which is customary in prior art apparatus. In a further respect, second annular member 42 can be periodically and inexpensively replaced and the more expensive first annular member 40 reused without having to be replaced.

The foregoing embodiment of the invention is especially adapted to be carried by the inner one of a pair of coaxial reciprocally movable members for sealing against the cylindrical sidewall of the outer of the two members. Exemplary is the seal assembly held in the ring groove of a piston for sealing engagement with the sidewall of a cylinder in an internal combustion engine.

Although not herein specifically disclosed, it is contemplated by the instant invention to provide a seal assembly to be carried by the outer member and sealingly engage the inner coaxial member.

Various changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. 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.

Industrial Applicability The present invention is capable of being exploited in any situation where a seal ring is needed for use in sealing reciprocating elements. The present invention is particularly appropriate for use in the automotive industry.