US20110024989A1 - Dynamic Seal - Google Patents

Abstract

A dynamic shaft seal assembly is provided including a dynamic seal for engaging a rotary shaft. The dynamic seal includes a base portion that is mounted within a casing and has an axially extending barrel portion extending from a radially inner end of the base portion. The axially extending barrel portion terminates in a radially extending leg portion which extends inwardly from an end of the axially extending portion. A generally conically shaped seal portion extends from an end of the radially extending portion and the seal portion includes a radially inner face engaging the shaft and a radially outer face having a stiffening bead integrally formed thereon. The stiffening bead reduces the seal's propensity for “bell mouthing” while the axially extending barrel portion provides improved shaft followability for the dynamic seal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 11/285,652, filed Nov. 22, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 11/065,023, filed on Feb. 24, 2005, the disclosures of which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
• The present invention relates to “lay-down” dynamic shaft seals, and more particularly, to a dynamic shaft seal design to reduce the seal's torque, propensity for bell mouthing, and for providing improved shaft followability and improved ability to withstand internal excessive pressure or vacuum. The “lay-down” seal for their function rely on hydrodynamic pumping features as opposed to “standard” or “point-contact” seals that rely primarily on the intrinsic ability of some elastomers to pump in properly designed seals.
BACKGROUND AND SUMMARY OF THE INVENTION
• Rotary shaft seals have been utilized in machinery, the automobile industry, as well as other industries. Three major problems associated with seals designed to have substantial contact areas between the shaft and the lip of the seal are “bell mouth,” the shaft followability at low temperatures, and oil carbonization in the pumping grooves due to local temperature rise causing increased torque. “Bell mouth” is a phenomenon associated with the lift of the edge of the lip from the shaft. The problem is extenuated for highly incompressible materials, like rubber and PTFE. The ability of the seal to follow the shaft when the shaft either wobbles or is misaligned is also important to a seal design.
• The present invention is designed to reduce seal torque, the propensity for “bell mouthing” and also provides for improved shaft followability at low temperatures. The dynamic seal includes an annular mounting portion which is capable of being mounted to a casing which surrounds a rotary shaft. The seal includes an axially extending portion extending from the radially inner end of the mounting portion, with a radially extending portion extending inwardly from an end of the axially extending portion. A generally conically shaped seal portion extends from an end of the radially extending portion with the seal portion including a radially inner face provided with a plurality of grooves or ribs and a radially outer face having a special bead defining a region of increased thickness. The bead acts as an integral spring to control the gap between the essentially conical portion of the seal and the shaft as well as a means for counteracting the “bell mouthing” propensity of the seal portion. The bead can have different shapes including a triangular-cross section or a rounded bead, as well as other configurations which are deemed to be appropriate. The bead is positioned slightly away from the edge of the lip to provide a sufficient lip “lay-down” to properly engage the hydrodynamic pumping features, which would normally be located on the lip contact are between the edge of the seal and the bead. The flexibility of the axially extending portion of the seal provides an improvement in the shaft followability due to the generally cylindrical shape of the axially extending portion having lower bending stiffness. Therefore, if the material of the seal does not have sufficient intrinsic elasticity, making the axially extending portion of the seal in a generally cylindrical shape improves the overall shaft followability. The length and the wall thickness of the cylindrical portion allow one to control the degree of flexibility to match the application requirements.
• Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
• FIG. 1 is a detailed cross-sectional view of the dynamic seal according to the principles of the present invention;
• FIG. 2 is a cross-sectional view of the dynamic seal disposed against a shaft according to the principles of the present invention;
• FIG. 3 is a perspective view of the dynamic seal according to the principles of the present invention;
• FIG. 4 is a cross-sectional view of second embodiment of the dynamic seal according to the principles of the present invention;
• FIG. 5 is a cross-sectional view of the seal ofFIG. 4 shown under internal pressure;
• FIG. 6 is a cross-sectional view of the seal ofFIG. 4 shown under vacuum;
• FIG. 7 is a cross-sectional view of a dynamic seal according to the principles of the present invention, incorporating a deflection limiting retainer;
• FIG. 8 is a cross-sectional view of a dynamic seal according to the principles of the present invention including an interior shaft ring;
• FIG. 9 is a cross-sectional view of a dynamic seal according to the principles of the present invention including a dust lip integrally formed therewith;
• FIG. 10 is a cross-sectional view of a dynamic seal according to the principles of the present invention, including a support ring and casing;
• FIG. 11 is a detailed cross-sectional view of the dynamic seal according to the principles of the present invention with a support ring disposed therein; and
• FIG. 12 is a cross-sectional view of the dynamic seal disposed against a shaft according to the principles of the present invention with a support ring disposed therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
• With reference toFIGS. 1-3, thedynamic seal10, according to the principles of the present invention, will now be described. Thedynamic seal10 is mounted to acasing12 which is disposed in a fixed housing16 (best shown inFIG. 2) in a manner which is well known in the art. Thedynamic seal10 engages arotary shaft14 so that thedynamic seal10 provides a sealed relationship between therotary shaft14 and thehousing16 in which thecasing12 is disposed. With reference toFIG. 1, thedynamic seal10 includes amounting portion20 which is designed to be engaged between first and second portions12A,12B ofcasing12. It should be noted that themounting portion20 can take on many shapes and forms and is not considered to be particularly relevant to the present invention. Themounting portion20 is mounted to thecasing12 which can be made of plastic or metal and themounting portion20 can be clamped or bonded thereto according to well known mounting techniques.
• Thedynamic seal10 includes an axially extendingbarrel portion22 extending from a radially inner end20A of themounting portion20. The axially extendingbarrel portion22 is preferably generally cylindrical in shape although other shapes, such as conical or a convoluted curve shape, can also be utilized. Thedynamic seal10 includes a radially extendingportion24 extending inwardly from a distal end22B of the axially extendingbarrel portion22. A generally conicallyshaped seal portion26 extends from a radially innermost end24A of the radially extendingportion24. Theseal portion26 includes a radiallyinner face28 which may be provided with a plurality ofgrooves30. Thegrooves30 can be helical in shape or can take other known forms. Thegrooves30 provided in the radiallyinner surface28 of theseal portion26 are capable of retaining oil therein in order to provide lubrication between thedynamic shaft seal10 androtary shaft14 and also can provide a pumping function for returning leaked oil to the oil side of the seal. A radiallyouter face32 of the conicallyshaped seal portion26 is provided with astiffening bead34 defining a region of increased thickness. Thestiffening bead34 can have different shapes, including a triangular shape, as shown, or can have rounded or other shape configurations. Thestiffening bead34 is positioned slightly away from the end edge26A of thelip26 to allow a proper contact area to develop. Thebead34 serves as an integrally formed spring for biasing thesealing lip26 against therotary shaft14 for counteracting bell mouthing of the sealinglip26. Normally, the seal lip-free edge faces the oil side. However, reverse mounting is also possible. In that case, the design of the spiral grooves have to be accommodated appropriately to pump in the direction of the oil sump.
• The improvement in the shaft followability of thedynamic seal10 is provided by the axially extendingbarrel portion22. The generally cylindrical shape of thebarrel portion22 has a lower bending stiffness than other structures; therefore, the axially extendingbarrel portion22 is able to readily account for a wobbling shaft or a shaft that is out of center relative to thehousing16.
• It should be noted that if desired or advantageous in a particular application, thedynamic shaft seal10 of the present invention can optionally include one or more axial or radial dirtprotective lips38 as are known in the art, one of which is shown, for example, inFIG. 2. The optional dirtprotective lip38 can be formed integrally with the dynamic shaft seal, or can be formed separately therefrom and attached thereto, and can have any of a number of shapes or configurations, as is also known in the art. In addition, thelip38 can protrude transversely from the dynamic shaft seal in any of a number of directions, including, but not limited to, the exemplary angular relationship protruding generally radially away and axially away from the shaft-engaging sealing components, as shown, for example, inFIG. 2.
• The radially extendingleg portion24 can be straight, as shown, or alternatively, can be provided with a convoluted shape. The outer diameter of the shaft is specifically designed to have a larger diameter than the inner diameter of the radially inwardly extendingleg portion24. As illustrated inFIG. 2, the generally conically shapedseal portion26 is designed to take on a generally cylindrical form when deformed by therotary shaft14 and theleg24 is designed to apply pressure to theheel portion36 of theseal portion26. Theleg portion24 acts radially on the end22A of thebarrel portion22 which has a length sufficient to allow thebarrel portion22 to flex radially inwardly and outwardly to accommodate for shaft wobble or shaft misalignment. The length of the leg portion is derivative from the length of the seal portion, the amount of the seal-to-shaft interference, and the distance between the casing and the shaft.
• Thedynamic shaft seal10 of the present invention can be utilized for isolating an oil environment from an air environment disposed on either side of thedynamic seal10. In order to optimize the seal design, the length of theseal portion26 and the stiffness of the bead34 (geometry, thickness, material, etc.) are specifically chosen for particular applications. Furthermore, the thickness of the radially extendingleg portion24 is also specifically designed to provide sufficient pressure on theheel36 of theseal portion26. The thickness and length of thebarrel portion22 should also be specifically designed to accommodate the requisite flexibility of a particular application. The seal material composition for the dynamic seal can include plastic, rubber, or any of a wide variety of known elastomers, such as PTFE, TPE (thermoplastic elastomers), TPV (thermoplastic vulcanizates), and Flouroprene™ material, a composition described in U.S. Pat. No. 6,806,306. An additional embedded spring in the bead may be utilized in order to extend the life of the seal due to the fact that creep can occur in thermoplastic or elastomeric materials which prevents the material from regaining its original properties. The spring would then provide an additional radial load on the seal surface that the thermoplastic material is incapable of maintaining over a long life. The spring can also improve the robustness of the seal required in contaminated environments. Instead of imbedding, the spring can be placed in a specially designed and manufactured spring groove after completion of the molding operation (as is normal with other radial lip seals).
• With reference toFIGS. 4-6, a dynamic seal according to a second embodiment of the present invention will now be described. Thedynamic seal100 includes a mountingportion102 which is designed to be engaged between first and second portions of a casing. It should be noted that the mountingportion102 can take on many shapes and forms and is not considered to be particularly relevant to the present invention. The mountingportion102 is mounted to a casing which can be made of plastic or metal and the mountingportion102 can be clamped, bonded or otherwise secured thereto according to well-known mounting techniques.
• Thedynamic seal100 includes an axially extendingbarrel portion104 extending from a radially inner end102A of the mountingportion102. The axially extendingbarrel portion104 is preferably generally cylinder shaped although other shapes, such as conical or a convoluted curve shape, can also be utilized. Thedynamic seal100 includes aradially extending portion106 extending inwardly from a distal end104A of the axially extendingbarrel portion104. A generally conically shapedseal portion108 extends from a radially innermost end106A of theradially extending portion106.
• The axially extendingbarrel portion104 extends in a first axial direction from mountingportion102, while the generally conically shapedseal portion108 extends from the radially innermost end106A of radially extendingportion106 in an axial direction opposite to the first axial direction.
• Theseal portion108 includes a radiallyinner face110 which may be provided with at least one groove or a plurality of grooves. The grooves can be helical in shape or can take other known forms. The grooves provided in the radiallyinner surface110 of theseal portion108 are capable of retaining oil therein in order to provide lubrication between thedynamic shaft seal100 androtary shaft14 and also can provide a pumping function for returning leaked oil to the oil side of the seal.
• A radiallyouter face112 of the conically shapedseal portion108 is provided with a stiffeningbead114 defining a region of increased thickness. The stiffeningbead114 can have different shapes, including a triangular shape as shown, or can have rounded or other shaped configurations. The stiffeningbead114 is positioned slightly away from the end edge108A of thelip108 to allow a proper contact area to develop. Thebead114 serves as an integrally formed spring for biasing the sealinglip108 against therotary shaft114 for counteracting bell mounting of the sealinglip108. The location and shape of thebead114 is dependent upon the specific application and the desired spring force.
• Normally, the seal lip-free edge108A faces the oil side. However, reverse mounting is also possible. In that case, the design of the spiral grooves has to be accommodated appropriately to pump in the direction of the oil side.
• With the design of the present invention, thedynamic seal100 is capable of withstanding excessive internal pressure or vacuum.FIG. 5 illustrates a cross-sectional view of thedynamic seal100 disposed against ashaft14 and under a pressure of 170 MBAR.FIG. 6 illustrates thedynamic seal100 disposed against ashaft14 and exposed to a vacuum pressure of −50 MBAR. In the case of excessive internal pressure being applied to thedynamic seal100, the axially extendingbarrel portion22 which radially overlaps theseal portion108 provides a radial spring acting upon theradially extending portion106 to limit the deformation in theseal portion108.
• In the case of an excessive vacuum being applied, the axially extendingbarrel portion104 limits the axial movement of radially extendingportion106, thus limiting the axial movement of theseal portion108.
• The improvement in the shaft followability of thedynamic seal100 is provided by the axially extendingbarrel portion104. The generally cylindrical shape of thebarrel portion104 has a lower bending stiffness than other structures. Therefore, the axially extendingbarrel portion104 is able to readily account for a wobbling shaft or a shaft that is out of center relative to the housing.
• It should be noted that if desired or advantageous in a particular application, thedynamic seal shaft100 of the present invention can optionally include one or more axial or radial dirtprotective lips120 as illustrated inFIG. 9. The optional dirtprotective lip120 can be formed integrally with the dynamic shaft seal, or it can be formed separately therefrom and attached thereto and can have any of a number of shapes or configurations, as is also known in the art. The radially extendingleg portion106 can be straight, as shown, or alternatively, can be provided with an angled or convoluted shape. As illustrated inFIGS. 5 and 6, the generally conically shapedseal portion108 is designed to take on a generally cylindrical form when deformed by therotary shaft14 and theleg106 is designed to apply pressure to the heel portion of theseal portion108. Theleg portion106 acts radially on the end104A of thebarrel portion104 which has a length sufficient to allow thebarrel portion104 to flex radially inwardly and outwardly to accommodate for shaft wobble or shaft misalignment. The length of theleg portion106 is derivative from the length of theseal portion108, the amount of the seal-to-shaft interference, and the distance between the casing and the shaft.
• Thedynamic shaft seal100 can be utilized for isolating an oil environment from an air environment disposed on either side of thedynamic seal100. In order to optimize the seal design, the length of theseal portion108 and the stiffness of the bead114 (geometry, thickness, material, etc.) are specifically chosen for particular applications. Furthermore, the thickness of the radially extendingleg portion106 is also specifically designed to provide sufficient pressure on the heel of theseal portion108. The thickness and length of thebarrel portion104 should also be specifically designed to accommodate the requisite flexibility of a particular application. The seal material composition for the dynamic seal can include plastic, rubber, or any of a variety of known elastomers, such as PTFE, TPE (thermoplastic elastomers), TPV (thermoplastic vulcanizates) and Flouroprene™ material.
• With reference toFIG. 7, thedynamic seal100 according to the principles of the present invention is shown mounted to aretainer ring130. Theretainer ring130 is designed to be press fit within a bore of a housing and includes an axially extending portion130A, a first radially extending mounting portion130B to which thedynamic seal100 is mounted, and a retaining flange130C disposed at an opposite end of the axially extending portion130A. Asupport ring132 includes an axially extending arm portion132A and a radially inwardly extending arm portion132B. The axially extending arm portion132A is designed to be retained by theretainer130 and can include an inwardly angledexterior surface134 which facilitates thesupport ring132 to being press fit within retaining flange130C. The radially inwardly extending arm portion132B is disposed adjacent to theradially extending portion106 ofdynamic seal100 with an axial gap extending therebetween. Thegap136 permits axial movement of theradially extending portion106, but limits the axial movement thereof relative to the mountingportion102.
• With reference toFIG. 8, adynamic seal100, according to the principles of the present invention is shown utilized in a cassette-type seal including a runningsleeve150 adapted to be mounted to a shaft and to be rotated therewith. The runningsleeve150 includes a finishedexterior surface152 that is engaged by theseal portion108 ofdynamic seal100. The runningsleeve150 also includes a radial wall portion150A extending adjacent to theradially extending portion106 of thedynamic seal100. The radial wall portion150A limits the axial movement of theradially extending portion106 ofdynamic seal100 in the rightward direction as illustrated inFIG. 8. Theradially extending portion106 of thedynamic seal100 may also include a protrudingportion154 that can come in contact with the radially extending wall portion150A of runningsleeve150. The protrudingportion154 limits the contact surface that engages the radial wall portion150A so as to limit the friction contact between thedynamic seal100 and runningsleeve150.
• The runningsleeve150 also includes a radial flange portion150B provided at a second end thereof that provides a barrier for limiting axial movement of theseal portion108 in the leftward direction as illustrated inFIG. 8. Thus, the retaining flange150B prevents theseal portion108 from being dislodged from the exterior finishedsurface152 of runningsleeve150. The runningsleeve150 can be connected to theretainer130 so that the seal assembly can be assembled as a cassette-type seal or can be separate, as shown.
• With reference toFIG. 10, adynamic seal200, according to the principles of the present invention, is shown. Thedynamic seal200 is mounted to ametal casing202 and is also provided with asupport ring204 which can be made from plastic, metal, or other materials. Thedynamic seal200 is mounted to thecasing202 which is adapted to be disposed in a fixed housing in a manner which is well known in the art. Thedynamic seal200 engages a rotary shaft or other member so that thedynamic seal200 provides a sealed relationship between the rotary member and the housing in which thecasing202 is disposed. Thedynamic seal200 includes a mounting portion206A,206B with the portion206B of the mounting portion overlapping themetal casing202 on at least one face thereof. A mounting portion206B defines abead portion208 extending radially outward away fromcasing202. The mounting portion206B can also extend radially beyondmetal casing202 so as to provide a friction engagement with the housing in which the seal assembly is inserted. The mounting portion206A,206B can take on many shapes and forms. Thedynamic seal200 includes an axially extendingbarrel portion212 extending from a radially inner end of the mounting portion206A,206B, the axially extendingbarrel portion212 is preferably general cylindrical in shape, although other shapes, such as conical or a convoluted curve shape, can also be utilized. Thedynamic seal200 includes aradially extending portion214 extending inwardly from a distal end212B of the axially extendingbarrel portion212. A generally conically shapedseal portion216 extends from a radially innermost end214A of theradially extending portion214. Theseal portion216 includes a radiallyinner face218 which may be provided with a plurality ofgrooves220. Thegrooves220 can be helical in shape or can take other known forms. Thegrooves220 provided in the radiallyinner surface218 of theseal portion216 are capable of retaining oil therein in order to provide lubrication between thedynamic shaft seal200 and a rotary member, and also can provide a pumping function for returning leaked oil to the oil side of the seal. A radiallyouter face222 of the conically shapedseal portion216 is provided with a stiffeningbead224 defining a region of increased thickness. The stiffeningbead224 can have different shapes, including a triangular shape, as shown, or can have rounded or other shaped configurations. The stiffening bead of224 is provided to allow a proper contact area to develop on the sealinglip216. Thebead224 serves as an integrally formed spring for biasing the sealinglip216 against the rotary shaft for counteracting bell mouthing of the sealinglip216. Normally, the seal lip-free edge faces the oil side. However, reverse mounting is also possible. A dirtprotective lip226 extends from the end portion214A of radially extendingleg portion214.
• Thesupport ring204 includes an outer ring portion204A which engages thebead208 of mounting portion206B in order to provide an axial restrain on thesupport ring204. A radially extending portion204B extends radially inward from the outer ring portion204A and a second inner ring portion204C extends axially from an innermost end portion of radial portion204B. The inner ring204C extends axially and parallel to the axially extendingbarrel portion212 ofdynamic seal200. The inner ring204C limits the radial movement of the axially extendingbarrel portion212. The inner ring portion204C includes a radially inwardly extending leg portion204D which is generally parallel to theradially extending portion214 of thedynamic seal200. The radially extending leg portion204D limits the axial movement of theradially extending portion214 of the dynamic seal.
• Thecasing202 includes an outer ring portion202A adapted to be received in a bore of a housing. A first radially inward step portion202B extends radially inward from the outer ring portion202A. A intermediate ring portion202C extends axially from the radially inwardly extending portion202B. A mounting arm202D extends radially inward from the intermediate axial portion202C. Thedynamic seal200 is mounted to the radially inwardly extending arm202D.
• With reference toFIG. 11, a free floatingsupport ring300 is shown for use with thedynamic seal10 which is shown inFIG. 1. Thesupport ring300 can be formed from plastic, metal, or other materials. Thesupport ring300 extends axially and parallel to the axially extendingbarrel portion22 of thedynamic seal10 and limits the radial movement of the axially extendingbarrel portion22. Thesupport ring300 includes a radially extendingend surface300awhich is generally parallel to theradially extending portion24 of thedynamic seal10. The radially extendingend surface300alimits the axial movement of theradially extending portion24 of the dynamic seal. Thesupport ring300 is restrained from axial movement by radially extendingportion24 and by theexterior housing302, or can be otherwise restrained by other members such as adust lip38, as shown inFIG. 12, or by other means either attached to or separate from the seal assembly.
• The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims (6)

1. A dynamic seal, comprising:

an annular mounting portion;

an axially extending portion extending in a first axial direction from said mounting portion toward an air side of the dynamic seal and terminating in a first end;

a radially extending portion extending radially inwardly from said first end of said axially extending portion and being displaceable in a radially outward direction; and

a generally conically shaped seal portion extending from an end of said radially extending portion in a direction opposite said first axial direction toward an oil side of the dynamic seal, said seal portion being adapted to take on a generally cylindrical form when engaged with a rotary member and thereby including a radially inner face adapted to engage the rotary member along a substantial axial length thereof, wherein said radially inner face of said seal portion is provided with at least one groove for retaining oil therein for providing a lubricated interface between the seal portion and the rotary member and providing a pumping function for returning leaked oil to the oil side of the dynamic seal.

2. The dynamic seal according toclaim 1, wherein said seal is made from an elastomeric material.

3. The dynamic seal according toclaim 1, wherein said seal is made from a plastic material.

4. The dynamic seal according toclaim 1, further comprising a dirt lip extending from said radially extending portion.

5. The dynamic seal according toclaim 4, wherein said dirt lip is integrally formed with said radially extending portion.

6. The dynamic seal according toclaim 1, wherein the composition of said dynamic seal includes one of PTFE, thermoplastic elastomer, and thermoplastic vulcanizates.

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