GB1593757A

GB1593757A - End face seal assembly

Info

Publication number: GB1593757A
Application number: GB19898/78A
Authority: GB
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1977-10-27
Filing date: 1978-05-16
Publication date: 1981-07-22
Also published as: FR2407404B1; AU3929478A; IT7828551A0; IT1099277B; AU521163B2; GB1593759A; MX149200A; FR2407404A1; GB1593758A; BR7807015A; DE2846896A1; DE2846896C2

Description

(54) END FACE SEAL ASSEMBLY (71) We, CATERPILLAR TRACTOR CO., a corporation organized and existing under the laws of the State of California, United States of America, of 100 N.E. Adams Street, Peoria, Illinois 61629, United States of America do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates generally to end face sealing ring assemblies, that is to say assemblies for forming a seal between an axially directed end face and a member which is rotatable about the axis relative to the end face. It relates particularly to a compact end face sealing ring assembly having improved service life and load deflection characteristics for use in a severe service environment such as a joint between two links of an endless track for a tracked vehicle.

Extensive development work has been directed toward improving end face sealing rings for protecting the pin joints of endless track chains. Such track chains operate in extremely abrasive environments under all types of weather conditions. Consequently, the axial face load of the sealing rings must be maintained at a substantial level, for example above about 100 pounds (445 N), while the sealing rings experience a considerable amount of axial motion between the track joint members. This imposes substantial demands upon the materials that are utilised in the sealing ring, since the sealing ring must not only be sufficiently resilient to follow rapid movements of the joint members over a considerable temperature range, but must also exhibit a substantial wear life in order to retain lubricant within the joint and to exclude dirt.

For the most part, prior art sealing rings have proven only partially satisfactory towards solving the aforementioned problems. One ring includes an elastomeric load ring in combination with an abrasion-resistant annular sealing element. The load ring is seated within a counterbore in the track link and applies a substantially axial load upon the sealing element to press it against the end face of the associated bushing. In such a location space is at a premium, so that the radial and axial dimensions of the chamber in which the seal is received impose restrictive limitations upon the geometric construction of the seal. As a result of these limitations the sealing ring either does not perform in a desirably effective manner throughout the deflection range or exhibits a less than desirable service life.

Still another problem with the prior art sealing rings is that many present one or more exterior grooves in which mud and ice can collect so that the operation and responsiveness of the sealing rings is less than desirable. Still other seals have sharp grooves or notches in the elastomeric material which results in strain discontinuties and a less than desirable fatigue life in the elastomeric material.

The aim of the present invention is to provide a.simple and compact end face sealing ring assembly having long life expectancy and operational effectiveness over a wide range of deflection in the severe service environment of a track joint, and which sealing ring assembly will overcome some at least of the problems associated with the prior art.

According to this invention, an end face sealing ring assembly comprises a sealing ring of a first material, which is elastomeric, and having an axially facing annular sealing lip for forming a seal against an end face, a support ring of generally L-shaped radial section and of a second material supporting said sealing ring, and a load ring of a third material, which is elastomeric, for sealingly engaging the support ring and, when compressed, exerting an axial pressure thereon, the three rings being concentric and said first material having a higher durometer scale hardness than, and being chemically different from said third material, and said second material having greater rigidity than said first and third materials.

Advantageously, the load ring and the support ring have a precise geometric relationship to each other and to the joint member in which, in use, they are received. For example, the cross-section of the load ring has precisely defined interior and exterior surfaces to allow desirable deformability under compression.

Two examples of an end face sealing ring assembly and one example of an articulated joint incorporating one example of the sealing ring assembly will now be described with reference to the accompanying drawings, in which: Figure I is a diagrammatic, fragmentary sectional plan view showing details of construction of one end of a track joint incorporating one example of the sealing ring assembly; Figure 2 is a diagrammatic and greatly enlarged fragmentary view of the sealing ring assembly and associated members shown in Figure 1 to show details of construction thereof; Figure 3 is a simplified diagrammatic cross-sectional view of the sealing ring assembly and associated members shown in Figure 1, but showing the sealing ring assembly in a first relatively free or unloaded position; Figure 4 is a view similar to Figure 3 but showing the sealing ring assembly in a second fully loaded or compressed position; Figure 5 is a graph illustrating the relationship between the face load on the sealing ring assembly of Figures 1 - 4 and the axial deflection thereof; and Figure 6 is a diagrammatic and fragmentary view of another example of the sealing ring assembly.

The first example of the end face sealing ring assembly 10 is shown in Figure 1 in the environment of a articulated track joint 12 such as is utilised in the endless track chain of a track-type vehicle. In a conventional manner, each of the plurality of track joints utilized in the track chain includes a first link member 14 and a pin 16 secured thereto, a second link member 18 and a cylindrical bushing 20 secured thereto, and a metallic spacer ring 22. In operation, the first link member and the pin rotate on a central axis 24 as a unit with respect to the second link and the bushing.

As shown in greater detail in Figure 2, a counterbore or seat 26 is formed in the first link member 14 and is defined by an axially outwardly-facing end face 28, a cylidrical surface 30 and an arcuate corner portion 32. Moreover, the bushing 20 provides an axially inwardly-facing end face 34. The spacer ring 22 is loosely received on the pin 16 and is adapted to abut both the faces 28 and 34 and limit the minimum axial distance therebetween as is known in the art. In this regard, cross reference is made to U.S. Patent No. 3,841,718 issued to H. L. Reinsma on October 15, 1974, for further reference to the construction of the track chain itself.

The end face seal assembly 10 is disposed within the counterbore 26 and axially seals against the end face 34 of the bushing 20 to retain lubricant within the track joint 12 and to prevent the entry of dirt or deleterious matter into the area between the pin 16 and the bushing. For this purpose the illustrated embodiment end face seal assembly has a seal ring means 35 including a resilient seal ring 36 for dynamic primary sealing engagement with the end face 34 and a relatively rigid support ring 38 for holding the seal ring. The seal assembly further includes a resilient load ring 40 for solely supporting the support ring 38 and for static secondary sealing engagement with both the support ring 38 and the counter bore 26 of the first link member 14. Advantageously, the seal ring 36, the support ring 38, and the load ring 40 are serially arranged in the counterbore 26 and have a construction such that all are disposed generally concentrically of the axis 24.

More specifically, the seal ring 36 has a generally triangular cross section having an annular sealing lip or axial outward face 42 that extends axially therefrom to engage the bushing end face 34. The seal ring 36 also has an annular base 44 which may be securely bonded or otherwise connected to the support ring 38. The seal ring 36 is of a first elastomeric material having a durometer "D" scale hardness magnitude of at least 30 and preferably in the range of 40 to 50 on this scale. Preferably further, the elastomer is a nonrigid thermoplastic polyester based urethane rubber having a tensile modulus magnitude (Youngs modulus) of approximately 21 MPa (3,000 psi) minimum.

As is clearly shown in Figure 2, the support ring 38 has a generally L-shaped cross sectional configuration having a cylindrical portion 46 and an integrally connected radial portion 38. The cylindrical portion 4 defines a cylindrical surface 50 and an axially inner end 52, and the radial portion defines an axially inwardly-facing end face 54, a radially outwardly-inclined peripheral surface 56 extending from the end face, a radially outer peripheral edge 58, and an axially outwardly-facing end face or seat 60. Moreover, an arcuate corner portion 62 connects the surface 50 and the end face 54 to define a seat which is indicated overall by the reference numeral 64.

The support ring 38 is constructed of a relatively rigid second material for retaining concentricity with respect to the axis 24 and for maintaining a proper support and force transmitting relationship with respect to the seal ring 36. Preferably, the second material is an organic plastics material rather than metal for economy, anti-corrosion properties, and ease of connection to the seal ring. Preferably further, the plastics material is polycarbonate 40% glass reinforced to increase its impact strength. This material also has excellent thermal stability and a tensile modulus magnitude (Youngs modulus) of approximately 7000 MPa (1,000,000 psi) minimum.

The load ring 40 is preferably constructed of a third resilient material having a durometer "A" scale hardness magnitude in a range of about 40 to 70 and a relatively low tensile modulus magnitude (Youngs modulus) of approximately 3 MPa (500 psi). Preferably further, the third material is an elastomer, for example nonrigid epichlorohydrin copolymer rubber, to provide a relatively rapid rate of resiliently yielding, deflecting and returning. In this regard, and as used herein, the terms "rigid" and "nonrigid" have a precise meaning such as is set forth in ASTM Designation D883-75a pertaining to standard definitions of terms relating to organic plastics. Particularly, "rigid" refers to a modulus of elasticity in tension of a magnitude greater than 700 MPa (100,000 psi) and "nonrigid" refers to a similar modulus of a magnitude not over 70 MPa (10,000 psi). With these definitions in mind the load ring 40 may be referred to as a non-rigid plastics material the support 38 as a rigid plastics material, and the seal ring 36 as a non-rigid plastics material.

Referring now to the construction of the load ring 40, best illustrated in Figure 3 in a substantially unloaded first position, the free cross section thereof may be noted to have a cooperating outer peripheral surface 66 and an axially inner end face 68, an opposite cooperating inner peripheral surface 70 and an axially outer end face 72, a radially inclined exterior surface 74 connected between the outer peripheral surface and the outer end face, and an interior surface 76 connected to the inner end face 68 at a first edge 78 and connected to the inner peripheral surface 70 at a second edge 80.

Preferably, the outer peripheral surface 66 of the load ring 40 is cylindrical so that an interference fit is defined between that surface and the cylindrical surface 30 of the counterbore 26. Also, the inner peripheral surface 70 is cylindrical so that an interference fit is defined between that surface and the cylindrical surface 50 of the support ring 38. The load ring is solely connected to the counterbore and support ring by these interference fits, in other words without use of a binding agent, which fits are preferably defined in a range of about 0.5% to 2.0% of the diameters of the cylindrical surfaces 38 and 50 respectively.

A preferred construction parameter of the load ring 40 resides in the preselected geometry of the interior surface 76 when it is in a free or unloaded state. Such interior surface is predominantly characterized by a shallow arcuate recess extending between the first edge 78 and the second edge 80 as shown in Figure 3. The shallow arcuate recess is formed by a revolved radius RR as indicated on the drawing having a length about equal to the least distance between the inner end face 68 and the inner peripheral surface 70, that is to say, about equal to the distance between the first and second edges 78 and 80. If the radius RR is too small, the load ring will buckle under substantial compression; if the radius RR is too large or if the surface is part-conical or convex as seen in radial section, the axial face load upon the seal ring 36 will increase undesirably fast because the remaining space is filled too rapidly. Consequently, the radius RR should preferably be from 0.9 to 1.25 times the aforementioned distance between the first and second edges 78 and 80.

Another preferred construction parameter of the load ring 40 exists in the preselected geometry of the inclined exterior surface 74. Particularly, such exterior surface is a truncated right circular conical surface. It is of substantial significance to note that the inclined exterior surface 74 of the load ring 40 and the inclined peripheral surface 56 of the support ring 38 both define a preselected angle "A" with a plane 82 disposed transverse the central axis 24 and on opposed sides of the plane as is illustrated in Figure 3. Specifically, the angle "A" is preferably defined within a range of about 28 to 38 degrees from the plane.

If the angle "A" is below such value excessive deformation and strain is observed at the surface 74 under high load. On the other hand, if the angle "A" is above such range the surface 74 will not close against the surface 56 of the support ring and contaminants can get trapped therebetween.

Another preferred construction parameter of the load ring 40 exists in the preselected geometry of both the inner end face 68 and the outer end face 72 of the load ring 40.

Preferably, the cross sectional contact length L2 of the outer face as axially projected and radially measured is about 1 1/2 to 2 times the corresponding contact length L1 of the inner end face as is indicated in Figure 3 and such contact lengths are radially offset to provide the desired shear loading and static sealing thereat.

Lastly, as shown in Figure 4, a first chamber 84 having an axial width (W) and a radial height (H) is defined between the link member 14, the bushing 20 and the spacer ring 22 when the seal assembly 10 is in a fully compressed second position. In such position the link member 14 and the support ring 38 face each other in such a way that a second compact chamber 86 having an axial width CW and a radial height CH is defined within the first chamber between the load ring seats 26 and 64 respectively formed therein.

As the end face seal assembly 10 is axially compressed a preselected deflection distance D by relative axial movement of the first and second link members 14 and 18 from a first substantially unloaded position as shown in Figure 3 to a second fully compressed position as shown in Figure 4, the load ring 40 substantially fills the second chamber 86 thereby making maximum use of available space. Specific parameters of the instant example seal assembly, including the size of the chambers, are as follows: Examlule Radius of Counterbore (RC) = 46.2 mm (1.817") Radial Height of Chamber (CH) = 6.78 mm it,267") Radial Height (H) = 9.85 mm (0.388") Comprcssed Axial Width (W) = 11.10 mm (0.437") Deflcction (D) = 3.91 mm (0.154") Axial Width of Chamber (CW) = 8.66 mm (0.341") Radius of Recess (RR) = 9.00 mm (0.354") The compact nature of the embodiment of the seal assembly 10 just described, is indicated by a preselected ratio of the axial deflection distance D between the aforementioned first and second positions to the radial height H of the first chamber 84 of at least 1:4. in the embodiment shown the ratio is about 4:10. This contrasts to corresponding prior art ratios of about 1.10. In other words, the total deflection distance D for the instant invention is in the range of about three times that of prior art while the radial height H is believed to be less than the prior art by about 30% or more.

in operation, the end face seal assembly 10 provides a gradually increasing axial face load on the sealing lip 42 as the load ring 40 is loaded in shear between the seats 26 and 64 and compressed between the first and second positions illustrated in Figures 3 and 4. The relationship is bcst illustrated by the graph in Figure 5. Importantly, the face load is maintained at a minimum value of at least 100 pounds (445 N) upon the initial installation of the seal assembly in the track joint 12 in order to assure positive retention of lubricant in the region between the pin 16 and bushing 20 and to exclude the entry of foreign material. Note that the load/deflection rate is substantially a straight line up to a maximum value of about 440 pounds (1,957 N) as is limited by the axial width W of the spacer ring 22.

Attention is now directed to the contour change of the exterior surface 74 of the load ring 40 as the seal assembly 10 is compressed. Note that the exterior surface 74 is deformed in such a way that the truncated conical surface becomes convex in radial section as may be appreciated by joint reference to Figures 3 and 4. As the load ring is compressed the exterior surface engages the surface 30, the end face 54 and the inclined peripheral surface 56 with a desirable rolling motion that controls the gradually increasing internal strain rate and that function to extrude dirt. Moreover, in the Figure 4 position, note that the external surface of the load ring is desirably supported by the peripheral surface 56 of the support ring 38 without any sharp increase in strain. Note further that the external surface, the peripheral edge 58 of the support ring and the external surface of the seal ring 36, all lie adjacent the smooth arc 88 in cross section as indicated in phantom in Figure 4. There is thus a minimal region of accessibility for outside contaminates.

Simultancously, as the load ring 40 is compressed the interior surface 76 rollingly engages the end face 28 of the link member 14 and also allows a controlled increase of the internal strain rate of the load ring. As shown in Figure 4, the second chamber 86 is desirably substantially filled by the load ring. Specifically, the second chamber is at least 90 percent filled by the load ring in the position of maximum compression. This advantageously maximizes the use of minimal space and avoids weakening of the first link member 14 as would be the case with a counterbore 26 of larger dimensions.

An alternate embodiment end face seal assembly is shown in Figure 6, which differs from the seal assembly previously described solely by the seating and support construction of the resilient seal ring 36' on the support ring 38'. Specifically, the support ring is modified to incorporate an annular retaining lip 88 and the seal ring is modified to incorporate a contoured exterior surface 90. The cooperating relationship between the axially extending retaining lip 88 and the entrapped contoured exterior surface 90 is such as to provide increased containment of the radially outer peripheral portion of the seal ring 36. This increased support reduces the tendency for separation between the seal ring and the support ring under heavy loading.

It is thus apparent that the present invention provides an effective and extremely compact end face seal assembly for a severe service environment such as is found in a rotary track joint, but which seal assembly would be useful in a variety of other applications as well. It is simple and reliable in construction, and upon being compressed includes a load ring that controllably distorts to minimize internal stress therein while providing a gradually increasing face load on the sealing lip. Such distortion is controlled by precise geometric relationships between the juxtaposed and conforming elements, and also the use of three different materials for the seal ring 36, the support ring 38 and the load ring 40. By using three materials having preselected physical characteristics, each portion of the seal can be constructed to be most effective. For example, the relatively high tensile modulus or high rigidity level of the reinforced polycarbonate plastics material of the support ring serves to prevent any rotational movement of the support ring in cross section so that the sealing lip 42 will continually contact the end face 34 in an axial direction. Moreover, the material of the seal ring 36 is importantly maintained at a higher durometer hardness than the load ring 40 to maintain maximum wear life. Still further, the material of the load ring has a rate of resiliently yielding, deflecting and returning that is greater or faster than the corresponding rate of the material of the seal ring and a lower durometer hardness scale reading than that of the seal ring to maximize the responsiveness of the seal assembly.

Other aspects of the disclosure of this specification are disclosed and claimed in our co-pending Applications Nos. 15607/79 and 15612/79 (Serial No's 1593758 and 1593759) WHAT WE CLAIM IS: 1. An end face sealing ring assembly comprising a sealing ring of a first material, which is elastomeric, and having an axially facing annular sealing lip for forming a seal against an end face, a support ring of generally L-shaped radial section and of a second material supporting said sealing ring, and a load ring of a third material, which is elastomeric, for sealingly engaging the support ring and, when compressed, exerting an axial pressure thereon, the three rings being concentric and said first material having a higher durometer scale hardness than, and being chemically different from, said third material, and said second material having greater rigidity than said first and third materials.

2. An assembly according to Claim 1, wherein said support ring is solely resiliently supported by the load ring when the sealing ring is unloaded.

3. An assembly according to Claim 2, in which the sealing ring, the support ring and the load ring are disposed generally concentrically.

4. An assembly as according to any one of the preceding Claims, wherein said first material is urethane rubber.

5. An assembly according to any one of the preceding Claims, wherein said first material has a hardness of at least 30 on the durometer "D" scale.

6. An assembly according to Claim 5, in which the hardness is of from 40 to 50 on the durometer "D" scale.

7. An assembly according to any one of the preceding Claims, wherein said second material is an organic plastics material.

8. An assembly according to Claim 7, wherein said plastics material is a reinforced polycarbonate.

9. An assembly according to any one of the preceding Claims, wherein said third material is epichlorohydrin copolymer rubber.

10. An assembly according to Claim 9, wherein said third material has a hardness of from 40 to 70 on the durometer "A" scale.

11. An assembly according to any one of the preceding Claims, in which the support ring comprises a cylindrical portion and a radial portion which has a radially inclined peripheral surface supporting the load ring.

12. An assembly according to any one of the preceding Claims, in which the load ring has a outer peripheral surface for co-operation with an axially extending cylindrical surface on a first of two members between which a seal is to be formed by the assembly, and an axially inner end face, an inner peripheral surface co-operating with the support ring and an axially outer end face, an exterior surface extending between said outer peripheral surface and said outer end face, and an interior surface extending between said inner end face and said inner peripheral surface.

13. An assembly according to Claim 12, wherein said interior surface of said load ring includes a shallow arcuate recess defined by a revolved radius having a length substantially equal to the least distance between said inner end face and said inner peripheral surface.

14. An assembly according to Claim 12 or Claim 13, wherein said exterior surface is a truncated conical surface, which is co-axial with the rings.

15. An assembly according to any one of the preceding Claims, in which the support ring has first and second seats on the axially opposed sides thereof, the sealing ring being connected to said first seat of the support ring and the load ring being releasably connected

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. It is thus apparent that the present invention provides an effective and extremely compact end face seal assembly for a severe service environment such as is found in a rotary track joint, but which seal assembly would be useful in a variety of other applications as well. It is simple and reliable in construction, and upon being compressed includes a load ring that controllably distorts to minimize internal stress therein while providing a gradually increasing face load on the sealing lip. Such distortion is controlled by precise geometric relationships between the juxtaposed and conforming elements, and also the use of three different materials for the seal ring 36, the support ring 38 and the load ring 40. By using three materials having preselected physical characteristics, each portion of the seal can be constructed to be most effective. For example, the relatively high tensile modulus or high rigidity level of the reinforced polycarbonate plastics material of the support ring serves to prevent any rotational movement of the support ring in cross section so that the sealing lip 42 will continually contact the end face 34 in an axial direction. Moreover, the material of the seal ring 36 is importantly maintained at a higher durometer hardness than the load ring 40 to maintain maximum wear life. Still further, the material of the load ring has a rate of resiliently yielding, deflecting and returning that is greater or faster than the corresponding rate of the material of the seal ring and a lower durometer hardness scale reading than that of the seal ring to maximize the responsiveness of the seal assembly. Other aspects of the disclosure of this specification are disclosed and claimed in our co-pending Applications Nos. 15607/79 and 15612/79 (Serial No's 1593758 and 1593759) WHAT WE CLAIM IS:

1. An end face sealing ring assembly comprising a sealing ring of a first material, which is elastomeric, and having an axially facing annular sealing lip for forming a seal against an end face, a support ring of generally L-shaped radial section and of a second material supporting said sealing ring, and a load ring of a third material, which is elastomeric, for sealingly engaging the support ring and, when compressed, exerting an axial pressure thereon, the three rings being concentric and said first material having a higher durometer scale hardness than, and being chemically different from, said third material, and said second material having greater rigidity than said first and third materials.

to said second seat which is cylindrical.

16. An assembly according to Claim 15, wherein said support ring and said load ring are connected by being an interference fit in a range of from 0.5% to 2.0% of the diameter of said second seat.

17. The combination comprising a first member having an annular seat, comprising an axially extending portion and a radially extending portion, a second member having an end face facing towards said radially extending portion and a sealing ring assembly in accordance with any one of the preceding Claims, the sealing ring of the assembly engaging said end face and the load ring of the assembly being located on said annular seat.

18. The combination according to Claim 17, wherein said first member is a track link and said second member is a track bushing.

19. The combination according to Claim 17 or Claim 18, wherein said load ring is an interference fit in said axially extending portion of said seat in a range of from 0.5% to 2.0% of the diameter of said counterbore.

20. An assembly according to Claim 1, substantially as described with reference to Figures 1 to 5, or Figure 6, of the accompanying drawings.

21. The combination according to Claim 17, substantially as described with reference to Figures 1 to 5, or Figure 6, of the accompanying drawings.