Radial lip seal.

DESCRIPTION

This invention relates to a radial lip seal for sealing with a relatively rotating cylindrical element. The invention is of particular utility in the automobile and heavy equipment industry for crankshaft seals, transmission seals and wheel bearing seals.

The radial, hydrodynamic lip seals have been developed to improve the performance and durability of the rotational contact seals.

The radial lip seals used in relatively rotary applications are inherently hydrodynamic to a limited extent. Hydrodynamic activity can be increased by incorporating special hydrodynamic aids such as grooves, channels, ribs or threads adjacent to the sealing lip. As the lips of the joint rotate, provided with hydrodynamic aids, said aids act as small hydrodynamic pumps that direct fluid in contact with the lip of the joint towards the fluid side of the lip. Hydrodynamic elements must be carefully formed and properly installed to be effective.

Hydrodynamic joints are sensitive to the eccentricity of the tree or cuff. If the joint is eccentric, with respect to the element against which it performs the sealing function, the hydrodynamic activity can be substantially reduced.

The use of polytetrafluoroethylene (PTFE) as a joint material has been proposed for rotational contact joints. Although hydrodynamic elements can be molded or punched into a lip of the PTFE joint, frictional wear tends to quickly neutralize the effect of hydrodynamic aids.

Likewise, PTFE wafers have been used as sealing elements due to deformation of the wafers to a coonic configuration. In the conical configuration, the PTFE wafer is retained, with a substantial tightening adjustment, against the relatively rotating machine element. PTFE gaskets that have a conical configuration must be carefully installed to avoid scratching the PTFE wafer.

An advantage of PTFE gaskets is that imperfections on the surface in contact with the sealing element can be filled by the deposition of PTFE in grooves or indentations. This smooths the sealed surface and tends to improve the service life of the joint.

Although hydrodynamic joints have improved service life and performance characteristics when properly manufactured and installed, the need for a simple and effective hydrodynamic joint, which is easy to manufacture and install, has been created for a long time to allow use. of hydrodynamic joints in conventional and innovative sealing applications.

An object of the present invention is to provide an improved bidirectional hydrodynamic joint that is easily manufactured and installed.

Another object is to provide a durable hydrodynamic joint that features a lip that provides the advantages of using a fluorinated elastomer or PTFE material, in alternating arrangement with a second material having different phosphoric characteristics.

The rotational contact seal of the present invention comprises a sealing annular crown having a sealing lip that comes into contact with a relatively rotating shaft or sleeve. From here on, references to the machine element that comes into contact with the lip of the joint will be simplified by referring to the machine element in the sense of an tree. However, it was understood that the gasket of the present invention can be used as an inner or outer diameter gasket. The sealing lip of the joint was formed of a first material and a second material that have different fossil characteristics. The first material and the second material form a continuous contact band, which extend circumferentially, and having a first alternating region and a second region formed in the first material and second material, respectively.

The first material and the second material can be differentiated in terms of the fossil characteristics related to their hardness, coefficient of friction or elastic modulus. Preferably, the first material is PTFE. The second material is preferably an elastomer such as silicone, fluorinated elastomer, nitrile, acrylic ethylene or polyacrylate.

The confines or flanges of the first region between the first and second regions, on the lip of the joint, extend in an angle with respect to the circumferentially extending contact band. In the preferred embodiment, the boundaries of the first regions between the first and second regions converge radially inwardly from a point on the air side of the contact band to the contact band and diverge radially inwardly from a point on the fluid or oil side of the contact band to the contact band.

The shaft oil seals of the present invention preferably include a rigid annular receptacle attached to an annular sealing ring of elastomer material. The sealing annular crown has a sealing lip with a smaller diameter than the internal diameter of the receptacle. An annular wafer used to form part of the sealing lip includes spaced portions between which the elastomeric material of the sealing annular crown is deposited. The sealing lip is preferably formed by circumferential roughing of the annular wafer in the recesses that provide a continuous sealing lip formed of elastomeric material and PTFE alternately.

The method of the present invention comprises forming an annular wafer of a first material. The annular wafer has an undulating circumferential flange that has radially recessed spaced portions or radially spaced spaced portions. The wafer is placed in a mold to form a joint with a ring of a second material. The wafer and the ring are then molded to the gasket configuration of 2

012 124 sea. During the molding operation, the ring of elastomeric material flows into the recessed portions or between the radial wafer extension portions, as the latter and the elastomotic material join together. The joint is laminated by circumferential grinding of a sealing lip by alternative cutting of the molded wafer and the portion of the second material contained in the recesses or between the radial extension portions of the wafer.

The first material is preferably a PTFE or similar material and the second material is preferably an elastomer. When a PTFE wafer is used, it is generally necessary to include the additional stages of biting the wafer surface and applying an adhesive coating to the wafer before performing the molding operation.

The wafer and the ring are placed inside the mode by placing the wafer and the ring in position adjacent to a cylindrical wall of the mold, which retains the wafer and the ring concentrically in the mold.

The method may also include in the step of placing an annular receptacle inside the mold when the mold is loaded with the wafer and the ring. The ring joins the annular receptacle during the molding phase.

The molding phase may also include in the stage of forming one or more auxiliary lips in the joint separated from the sealing lip. The auxiliary lip is preferably molded integrally from the second material.

The objects, features and advantages of the present invention will be readily apparent from the following detailed description of the best embodiment of the invention, in connection with the attached drawings.

Figure 1 is a perspective view of a radial lip seal formed in accordance with the present invention.

Figure 2 is a perspective view of a radial lip seal formed in accordance with the present invention.

Figure 3 is a cross-sectional view taken on line 3-3 of Figure 2.

Figure 4 is a cross-sectional view taken on line 4-4 of Figure 2.

Figures 5 to 10 are plan views of annular wafers used in the formation of radial lip seals in accordance with the present invention.

Figure 11 is a perspective view of a radial lip seal formed in accordance with the present invention.

Figure 12 is a fragmented perspective view of a portion of the sealing lip of a raial lip seal produced in accordance with the present invention.

Figure 13 is a semi-sectional view of a joint mold loaded with an annular wafer, a ring of elastomer material and a receptacle.

Figure 14 is a fragmented cross-sectional view of the joint mold of Figure 13 in the initial phase of the molding operation.

Figure 15 is a fragmented cross-sectional view of the joint mold of Figure 13 as the ring of elastomer material forms around the annular wafer.

Figure 16 is a fragmented cross-sectional view of the joint mold of Figure 13, showing the fully molded joint.

Figure 17 is a cross-sectional view of a joint with a schematically illustrated blade, showing the stage of deburring of the sealing lip.

With reference now to Figures 1 and 2, there are shown two different modalities of the radial lip seal 10 of the present invention. The gasket 10 includes a receptacle 12 which is preferably a metalic annular element used to support and install the gasket. An elastomeric annular crown 14 was attached to the receptacle 12. A sealing lip 16 includes a first region and a second region 20, 22 formed of a first material and a second material, respectively, which have different fossil characteristics. The sealing lip 16 facing a fluid reservoir to which the gasket was intended to prevent fluid leakage thereof. The air side 26 is that side of the sealing lip 16 from which the fluid retained by the gasket is excluded. A trim ring 28, which is roughed out of the joint 10 after molding, is illustrated in Figures 1 and 2 to show how the seal is roughed to provide a seal having a sealing lip 16 formed of a first region and a second region 20, 22, alternatives.

Referring now to Figures 3 and 4, two cross sections of the joint 10 are shown in the same to illustrate the structure of the sealing lip 16 as it changes around the inner circumference of the joint. In Figure 3, the sealing lip 16 is formed of the elastomeric material that forms the second region 22. In Figure 4, the sealing lip 16 was formed of the material that forms the first region 20. In Figure 3, the first region 20 does not form part of the sealing lip 16, neither on the fluid side 24 nor on the air side 26 of the sealing lip 16. In Figure 4, the first region 20 forms both the side of fluid 24 as the air side 26 of the sealing lip 16.

A toroidal spring groove 30, radially separated outwardly from the sealing lip 16, is shown in FIGS. 3 and 4. A toroidal spring, not shown, can be installed in the toroidal spring groove 30 to provide an inwardly applied force. on the sealing lip 16, as is well known in the art.

With reference now to Figures 5 to 10, different alternative configurations of the wafer used in the joint formation of the present invention are illustrated therein. The wafer includes an undulating edge that can form the inside or outside diameter of the wafer. The circular edge 35 of the wafer was adapted to be guided on a cylindrical surface of the mold used to form the joint. In each of Figures 5 to 10, a roughing line T is shown, in hidden lines, to indicate the approximate area of ​​the wafer that would have to be roughed up after molding.

012 124

Figure 5 shows a wafer ring having an undulating edge of inner diameter 34 comprising 3 recesses 36.

Figure 6 shows a wafer ring 32 having an undulating edge of inner diameter 34 comprising 12 recesses 36. The recesses 36 are different and separate recesses of semi-moon configuration, separated by protrusions 38 comprising a series of arcuate segments defining an inner diameter, circular, notched. Figure 2 illustrates a joint made with a similarly configured wafer.

Figure 7 shows an alternative form of the wafer ring 32 having an undulating edge of inner diameter 34. Eight recesses 36 will be separated by 8 protrusions 38. The protrusions 38 of the illustrated embodiment comprise sections of a circular inner diameter. The recesses 36 define sections of an outer diameter of the wafer ring 32. The ramp surfaces 39 interconnect the recesses 36 and the projections 38.

Figure 8 shows a wafer ring 32 having an outer diameter defined by an undulating edge 34. The recesses 36 are formed by straight-line segments that intersect in oblique angle between adjacent projections 38.

Figure 9 shows an alternative embodiment of the wafer ring 32 having an undulating edge of outer diameter 34. The undulating edge 34 will be formed by 12 recesses 36 that have a half-moon configuration. The recesses 36 are separated around the circumference of the wafer ring by protrusions 38. The joint illustrated in Figure 1 is representative of a joint made with a similarly configured wafer ring

32 The first regions 20 of Figure 1 are roughing projections 38 of the wafer ring 32.

Referring now to Figure 10, there is illustrated an integrally formed wafer ring 32 having an undulating edge of outer diameter 34 and which is especially contoured in irregular configuration, as substantially illustrated. The undulating edge 34 will be formed by 5 projections 38. The grooves 40 converge on opposite sides of the projections 38 to separate the recesses 36 from the projections. As illustrated, this type of wafer ring 32 is incorporated into a joint, figures 11 and 12. The wafer ring is roughed outwardly from the recessed portions 34 so that the protrusions 38 are separated from the ring. The protrusions 38 are left as separate regions 20 in the finished joint, which have specially oriented ends as described below. This design of the wafer has given rise, in the tests carried out, to the best hydrodynamic behavior.

With reference now to Figures 11 and 12, the sealing lip 16 of a molded joint 10 is shown in greater detail in accordance with the present invention. The sealing lip 16 includes a first region and a second region 20, 22 that are separated by a different channel 42. The channel 42 is believed to improve the hydrodynamic effect achieved by the joint 10 without the use of grooves or other hydrodynamic aids. The sealing lip 16 is a continuous lip that has no conventional hydrodynamic elements that can be separated by wear. Rotation of the sealing lip 16 with respect to a shaft or shaft creates the desired hydrodynamic effect.

As best illustrated in Figure 12, the confines 42 of the first region 20 converge on an angle A with respect to a radial line from the air side 26 of the joint to the sealing lip

16. On the fluid side 24 of the sealing lip 16, the confines 42 of the first region 20 diverge in an angle B with respect to a radial line.

It is believed that conflan 42, even though formed as a continuous surface, acts as a blade that can create a fluid pressure difference to pump fluid back to the fluid side of the joint. The difference in the physical characteristics of the materials that form the first region and the second region, apparently improves the hydrodynamic behavior of the joint.

The material of the first region 20 may have a lower coefficient of friction, a greater hardness or a smaller elastic modulus than the second region 22. The difference in hardness or coefficient of friction between the material that forms the first region 20 and the second Regioán 22 can create a difference of presioán from one side to another of the confán.

It has been determined, on some occasions, that the grade of the quadrone 42 is angled with respect to the sealing lip, can improve or reduce the hydrodynamic effect.

With reference now to Figures 13-17, the method of forming a joint 10 will be described in detail in accordance with the present invention. In figure 13, a mold 44 with a receptacle 12, wafer ring 32 and prep ring 45 located in the lower half of the mold 44 is shown. The prep ring 45 is formed of substantially uncured elastommeric material, such as a silicone, polyacrylate, fluorinated elastomer, acrylic ethylene or fluorinated elastomer, acrylic ethylene or nitric elastomer. Wafer ring 32 is preferably formed of PTFE, but may also be formed of another fluorinated elastomer or natural rubber. It is important that the physical characteristics of the wafer 32 and the prep ring 45 differ from each other. As illustrated in Figure 13, the upper half 48 of the mold will be disengaged from the lower half 46 to proceed with loading.

Referring now to Figure 14, the molding operation is initiated by moving the upper half 48 of the mold towards the lower half 46. The prep ring 45 and the wafer ring 32 are located concentrically on a cylindrical surface 52 in the lower half 46 of the mold 44. The cylindrical surface 52 keeps the wafer ring 32 and the prep ring 45 located concentrically within the moldd during the entire molding operation. As the upper half 48 moves towards the lower half 46, the prep ring 45 is connected by the upper half 48 of the mold 44. The mold 44 is heated to melt and cure the prep ring 45.

With reference now to Figure 15, the prep ring 45 is deformed to fill the mold cavity formed by the upper and lower halves 48, 46. The elastomeric material of the prep ring

012 124 flows into the recesses 36 of the wafer and throughout the mold cavity.

Referring now to Figure 16, the molding operation is completed when the elastomeric material of the prep ring 45 completely fills the cavity between the upper and lower halves 44 and the elastomeric material is substantially cured. As the mold is closed, preferably, a flange 54 of the receptacle 12 is formed on the inner edge of the receptacle

12. The elastomeric material of the prep ring 45 flows around the flange 54 of the receptacle 12 and joins said flange. The outer portion of the wafer ring 32 is forced downwards by the flow of the elastomeric material of the prep ring 45 and configured to a trunk-chunk shape. One of the sides of the frustocogenic portion of the wafer ring 32 may form the air side 26 of the sealing lip 16.

Referring now to Figure 17, the roughing phase is schematically illustrated by a knife that roughs the joint through the elastomeric material of the wafer ring recesses and through the wafer ring 32. By roughing the operation it forms a continuous sealing lip 16. The sealing lip 16 includes a first region and a second region 20, 22 follow a sequentially alternative model. The circular band of the wafer ring 32 may be roughened with the trim ring 28 as illustrated in Figure 1, or it may be included as part of the air side 26 of the sealing lip 16 as illustrated in Figure 2.

Although the best embodiment of the invention has been described in detail, those skilled in the art could recognize other alternative ways of putting the invention into practice as defined by the following claims.

Describing sufficiently the nature of the invention, as well as the manner of carrying it out in practice, it should be noted that the provisions indicated above and represented in the attached drawings are susceptible to modifications of detail as long as they do not alter its fundamental principle.

012 124