SEAL ASSEMBLY HAVING A CONE SPRING ENCAPSULATED IN A LOAD RING

Abstract: A seal assembly (10) having a Belleville spring completely encapsulated within a load ring (30) supporting a seal member provides a bias force to a resilient seal portion of the seal member (28) to assure positive contact with an opposed face of an adjacently disposed member (12, 14) of a joint assembly. The seal assembly (10) requires minimal counterbore depth in the member in which the seal assembly (10) is mounted, and no modifications are required in the Belleville spring (50) or in the base of the counterbore.

Description: Description SEAL ASSEMBLY HAVING A CONE SPRING ENCAPSULATED IN A LOAD RING Technical Field This invention relates generally to a seal assembly, and more particularly to a seal assembly having a cone spring encapsulated within a load ring component of the seal assembly. Background Art Various seals have been developed for use in sealing a variable space between two relatively ratable members. A joint in which movement of this type occurs is that found in the track structure of a track-type vehicle such as a tractor or the like. For example, US Patent 4,392,657, issued 12 July 1983 to Robert D. Roley, titled Belleville Spring Loaded Seal and assigned to the assignee of the present invention, describes a seal structure having a Belleville spring which urges the sealing component of the structure into sealing engagement with an opposed face of the joint assembly. In the Roley seal structure, the Belleville spring is disposed within the actual sealing element of the assembly and is modified by a plurality of annularly arranged openings extending through the spring itself. The sealing element, containing the Belleville spring, is attached to one end of a support spring which has an opposite end pressed into an annular groove formed in the radial wall of a counterbore in which the seal assembly is positioned. The seal assembly described by Roley requires a relatively deep counterbore to support the sealing element with a cantilevered spring supported Belleville spring, in addition to requiring a deep groove machined into the flat radial face of the counterbore to support one end of the cantilevered spring. The present invention is directed to overcoming the problems set forth above. It is desirable to have a seal assembly in which a Belleville spring advantageously provides improved sealing performance as a result of being encased in a load ring that applies a consistent load to the sealing component of the seal assembly. It is also desirable to have a seal assembly which only requires a relatively shallow counterbore thereby allowing more engagement area between the member in which the counterbore is formed and a pin pressed into the counterbored member. It is also desirable to have such a seal assembly that does not require an annular cantilevered spring retained within a groove in the base of the counterbore. DISCLOSURE OF THE INVENTION In accordance with one aspect of the present invention, a seal assembly for sealing a joint between two coaxially mounted members mounted on a pin or elongated cylindrical member (16) , in which the two members are rotatably movable with respect to each other about the longitudinal axis of the pin and have a variable space extending axially between opposed radial faces of the two members, includes a seal member and a load ring. The seal assembly is mountable in a counterbore provided in a preselected one of the two members. The counterbore is defined by a cylindrical circumferential wall and a recessed radial wall extending radially inwardly from the cylindrical circumferential wall . The seal member component of the seal assembly has a support portion and a resilient seal portion. The resilient seal portion is adapted to be disposed in contacting relationship with an opposed radial face of the non-preselected one of the two members. The support portion of the seal member has a face adapted to support the resilient seal portion and a mounting surface that is spaced from the face. The load ring component of the seal assembly has a frustoconical Belleville spring completely encapsulated within a plastic annular housing. The annular housing has an outer cylindrical wall adapted to be forcedly received within the cylindrical circumferential wall of the counterbore formed in the radial face of the preselected member. The load ring also includes a seal member support surface spaced from the outer circumferential wall that is adapted to forcedly abut the mounting surface of the support portion of the seal member and retain the seal member in fixed relationship with the load ring. At least a central portion of the encapsulated frustoconical Belleville spring is disposed between the mounting surface of the support section of the seal member and the recessed radial wall of the counterbore. The encapsulated Belleville spring thereby urges the seal member in a direction away from the recessed radial wall of the counterbore and the resilient seal portion of the seal member into biased contact with the opposed radial face when the joint is assembled. Other features of the seal assembly embodying the present invention include the support section of the seal member being an annular ring and the mounting surface of the support section having a compound curved surface comprising a radially disposed wall portion, a circumferentially disposed wall portion, and a concave curved portion extending between the radially disposed wall portion and the circumferentially disposed wall portion. Also, the mating seal member support surface of the annular ring of the load ring has a compound curved surface comprising a radially disposed wall portion, a circumferentially disposed wall portion, and a convex curved portion extending between the radially disposed wall portion and the circumferentially disposed wall portion. Still other features of the seal assembly embodying the present invention include the support section of the seal member being formed of a plastic material such as an inj ection-moldable polycarbonate. Yet another feature of the seal assembly includes the resilient seal portion of the seal member being formed of polyurethane material having a Shore D hardness from about 40 to about 50. Yet another feature of the seal assembly embodying the present invention includes the plastic annular housing in which the Belleville spring is embedded being formed of an inj ection-moldable polyurethane material having a Shore D hardness from about 40 to about 50. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the structure and operation of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a fragmentary diametric section of a track pin joint having the seal assembly embodying the present invention disposed therein; Fig. 2 is a fragmentary enlarged section of the seal assembly embodying the present invention; and Fig. 3 is a fragmentary three-dimensional view of the load ring component of the seal assembly embodying the present invention showing the load ring in its free state prior to assembly in a joint. BEST MODE FOR CARRYING OUT THE INVENTION An illustrated embodiment of a seal assembly embodying the present invention is generally designated by the reference numeral 10 in Figs. 1 and 2 of the drawings. The seal assembly 10 is advantageously used to seal the variable space between a first joint member 12 and a second joint member 14, which have relative movement toward and from each other so as to have variable spacing therebetween during operation. In the illustrated embodiment, the first joint member 12 comprises a portion of a first track link, and the second joint member 14 comprises a bushing that is rotatably mounted on a track pin 16 and is received in a portion of a second track link 18. The track pin 16 is pressed into a bore 22 of the first track link 12, thereby prohibiting relative movement between the first track link 12 and the track pin 16. The first joint member 12 further has a counterbore defined by a cylindrical circumferential wall 24 and a recessed radial wall 26 extending radially inwardly from the cylindrical circumferential wall 24. Movement of the first joint member 12 and the second joint member 14 toward each other is limited by a thrust ring 20. The seal assembly 10 includes a seal member 28 and a load ring 30. The seal member 28 has a support portion 32 and a resilient seal, or lip, portion 34. The resilient seal portion 34 is adapted to be disposed in contacting relationship with the opposed radial face of the second joint member 14 when the joint is assembled. The support portion 32 of the seal member 28 has a face 36 adapted to support the resilient seal portion 34, and a mounting surface 38 spaced from the face 36. Advantageously, the resilient seal, or lip, portion 34 is formed of a relatively soft, compliant material such as polyurethane, having a Shore D hardness of from about 40 to about 50. The support portion 32 of the seal member 27 is formed of a relatively harder material, such as an inj ection- moldable polycarbonate. The resilient seal portion 34 may be preformed and insert molded into the support section 32, or injection molded in a two-stage mold with the support portion 32. The seal member 28, as best illustrated in Fig. 2, generally has an annular ring shape with the face 36 disposed on one radial face of the ring and the mounting surface 38 generally disposed on rear radial surfaces of the ring. The mounting surface 38 is generally defined by a compound curved surface having a radially disposed wall portion 40, a circumferentially disposed wall portion 42, and a concave curved portion 44 extending between the radially disposed wall portion 40 and the circumferentially disposed wall portion 42. Importantly, the load ring 30 has a frustoconical Belleville spring 50 completely encapsulated within a plastic annular housing, or ring, 52. Belleville springs, often called dish, conical springs, or washers, occupy a very small space and are stressed in a manner such that they provide unusually high spring rates. The Belleville spring 50 provides a bias force that is transmitted through the load ring 30 to the seal member 30 and thence to the resilient seal portion 34 to maintain the resilient seal portion 34 in biased contact with the opposed face of the second joint member 14. When in its free state, the load ring 30 with the Belleville spring 50 encapsulated therein, is displaced outwardly at its center such that when it is assembled in the joint assembly, the center portion is compressed toward the recessed radial wall 26 of the counterbore. As a result, the compression provides a bias force urging the seal member 34 into contact with the radial face of the second joint member 14. The annular plastic housing 52, encapsulating the Belleville spring 50, is preferably formed of an inj ection-moldable polyurethane material having a Shore D hardness from about 40 to about 50. Desirably, the Belleville spring is encapsulated, in its free state, within the plastic housing 52 by insert molding. The annular plastic ring 52 has an outer cylindrical wall 54 having a diameter slightly greater than the diameter of the cylindrical circumferential wall 24 of the counterbore so that the respective circumferential walls 24, 54, forcedly abut each other as a result of an interference fit between the respective walls. In an illustrative example of an interference fit in a typical track joint, the cylindrical circumferential wall 24 of the counterbore has a diameter of 92.3mm and the outer circumferential wall 54 of the load ring 30 has a diameter of 93.8mm, resulting in an interference of about 0.75mm between the outer cylindrical wall 54 of the load ring 30 and the cylindrical circumferential wall 24 of the counterbore. This assures tight retention of the seal assembly 10 within the counterbore of the first joint member 12. The load ring 30 further comprises a seal member support surface 56 that is shaped to mate with the mounting surface 38 of the seal member 28. More specifically, the seal member support surface 26 is spaced from the outer cylindrical wall 54 of the load ring 30 and is adapted to not only mate with, but to forcibly abut the mounting surface 56 of the support section 32 of the seal member 28. The seal member support surface 56 of the load ring 30 has a compound curve shape comprising a radially disposed wall portion 58, a circumferentially disposed wall portion 60, and a convex curved portion 62 extending between the radially disposed wall portion 58 and the circumferentially disposed wall portion 60. The seal member support surface 56 is adapted to forcedly abut the mounting surface 38 of the support portion 32 of the seal member 28. In an illustrative embodiment of the above- described typical track joint, the forced abutment between the respective surfaces 56, 38, is provided by an interference fit between the circumferentially disposed wall portion 42 of the support portion 32 of the seal member 28 and the circumferentially disposed wall portion 60 of the plastic housing 52 of the load ring 30. In the illustrative example, the outer diameter of the circumferentially disposed wall portion 42 of the mounting surface 38 has a diameter of about 92.3mm, and the diameter of the circumferentially disposed wall portion 60 of the seal member support surface 56 has a diameter of about 93.8mm, thereby providing an interference of about 0.75mm between the two members. Thus, the seal member 28 is retained in fixed rotational relationship with respect to the load ring 30, but is urged axially outwardly away from the counterbore by the Belleville spring 50 disposed within the load ring 30. INDUSTRIAL APPLICABILITY The seal assembly 10 embodying the present invention provides an improved seal for variably spaced joint members, such as found in track joints. The Belleville spring 50, encapsulated within a plastic housing 52, provides a load ring 30 that urges the seal member 28 axially outwardly from the counterbore of the first joint member 12 into biased contact with the radial face of the second joint member 14, thereby assuring positive, continuously biased, abutment of the resilient seal portion 34 with the opposed face of the second joint member 14. The seal member 10 provides improved sealing performance due to the consistent load provided by the Belleville spring 50. Also, pin retention capability of the link assembly is improved due to the reduced requirement for a deep counterbore in the joint member that nonrotatably receives the common mounting pin. Thus, pin retention capability of the first joint member 12 is improved due to the requirement for the reduced counterbore depth. Advantageously, the reduction in counterbore depth allows more pin engagement surface area with the link 12. Although the present invention is described in terms of an illustrated exemplary embodiment, with specific illustrative constructions related to a track pin joint, those skilled in the art will recognize that application of the seal member embodying the present invention in other joint arrangements and constructions may be made without departing from the spirit of the invention. Such changes are intended to fall within the scope of the following claims. Other aspects, features, and advantages of the present invention may be obtained from the study of this disclosure and the drawings, along with the appended claims.

Claims: Claims 1. A seal assembly (10) for sealing a joint between first and second members (12,14) coaxially mounted on an elongated cylindrical member (16) having a longitudinal axis, said first and second members (12,14) being rotatably movable with respect to each other about said longitudinal axis and having a variable space between axially opposed radial faces of said first and said second members, a radial face of a preselected one of said first and second members (12,14) having a counterbore defined therein by a cylindrical circumferential wall (24) and a recessed radial wall (26) extending radially inwardly from said cylindrical circumferential wall (24), said seal assembly (10) being mountable in said counterbore and comprising: a seal member (28) having a support portion (32) and a resilient seal portion (34) , said resilient seal portion (34) being adapted to be disposed in contacting relationship with the opposed radial face of the non-preselected one of the first and second members (12,14), and said support portion (32) having a face (36) adapted to support said resilient seal portion (34) and a mounting surface (38) spaced from said face (36) , and a load ring (30) comprising a frustoconical Belleville spring (50) completely encapsulated within a plastic annular ring (52), said annular ring (52) having an outer cylindrical wall (54) adapted to be forcedly received within the cylindrical circumferential wall (24) of the counterbore of said radial face of the preselected member (12,14), and a seal member support surface (56) spaced from the outer cylindrical wall (54) and adapted to forcedly abut the mounting surface (38) of the support portion (32) of the seal member (28) and retain said seal member (28) in fixed relationship with said load ring (30) , at least a portion of said encapsulated frustoconical Belleville spring (50) being disposed between said mounting surface (38) of the support portion (32) and the recessed radial wall (26) of the counterbore when said seal assembly (10) is disposed in said counterbore (22) thereby urging the seal member (28) in a direction away from the recessed radial wall (26) and the resilient seal portion (34) of the seal member (28) into biased contact with said opposed radial face of the non-preselected member (12,14) when the joint is assembled. 2. The seal assembly (10), as set forth in Claim 1, wherein said support portion (32) of the seal member (28) is an annular ring and said mounting surface (38) of the support portion (32) has a compound curved surface comprising a radially disposed wall portion (40) , a circumferentially disposed wall portion (42), and a concave curved portion (44) extending between the radially disposed wall portion (40) and the circumferentially disposed wall portion (42) . 3. The seal assembly (10), as set forth in Claim 1, wherein said seal member support surface (56) of the annular ring (52) of the load ring (30) has a compound curved surface comprising a radially disposed wall portion (58) , a circumferentially disposed wall portion (60), and a convex curved portion (62) extending between the radially disposed wall portion (58) and the circumferentially disposed wall portion (60) . 4. The seal assembly, as set forth in Claim 1, wherein the said support portion (32) of the seal member is formed is an inj ection-moldable polycarbonate material . 5. The seal assembly (10) , as set forth in Claim 1, wherein said resilient seal portion (34) of the seal member (28) is formed of a material having a Shore D hardness of from about 40 to about 50. 6. The seal assembly (10) , as set forth in Claim 6, wherein said material of which the seal member (34) is formed is polyurethane. 7. The seal assembly (10), as set forth in Claim 1, wherein said plastic annular ring (52) in which the Belleville spring (50) is embedded is formed of a plastic material having a Shore D hardness of from about 40 to about 50. 8. The seal assembly (10), as set forth in Claim 8, wherein said material of which said plastic annular ring (52) is formed is an inj ection-moldable polyurethane material .

Inventors: KUPPER DAVID G, KUPPER, DAVID, G.
Applicants: CATERPILLAR INC, CATERPILLAR INC.
Application year: 2000
Main classification: F16J15
IPC codes: F16F1, F16J15