WO2015148956A1

WO2015148956A1 - Lip seal including a base portion and a lip portion

Info

Publication number: WO2015148956A1
Application number: PCT/US2015/023051
Authority: WO
Inventors: Jon LENHERT; Julien NALLET; Roland Lucotte
Original assignee: Saint-Gobain Performance Plastics Corporation
Priority date: 2014-03-28
Filing date: 2015-03-27
Publication date: 2015-10-01

Abstract

A lip seal has a seal main body including a base portion and a lip portion. The base portion and the lip portion can form a single monolithic seal main body. The seal main body can comprise a material including a polymer and a filler. A method for forming a lip seal can include transfer molding a polymer material to form a seal main body.

Description

LIP SEAL INCLUDING A BASE PORTION AND A LIP PORTION

FIELD OF THE DISCLOSURE

The present disclosure relates to a lip seal, and more particularly to, a lip seal including a base portion and a lip portion.

RELATED ART

A rotary or reciprocating machine can feature an enclosed internal mechanism that drives a shaft that will, in some cases, pass through the housing of the machine on one or both ends. In such cases, a lip seal can be disposed near an exit point to retain a lubricating fluid, such as oil or grease, in the housing as well as keep out contaminants, such as moisture and dust. The lip seal can have an outer diameter that provides a seal against the housing, and a sealing lip that provides a seal against the shaft. The sealing lip should exert a radial load on the shaft that provides sufficient sealing properties without excessive friction losses or wear. There exists a need for a lip seal having improved sealing properties. There also exists a need to simplify the process of manufacturing of a lip seal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and are not limited in the accompanying figures.

FIG. 1 illustrates a side view of an embodiment of a seal main body having a base portion and a lip portion;

FIG. 2 illustrates a top view of the seal main body illustrated in FIG. 1 ;

FIG. 3 illustrates a top view of another embodiment of a seal main body;

FIGs. 4 and 5 illustrate cross-sectional views of the seal main body illustrated in FIG. 1, respectively with and without a shaft;

FIGs. 6 and 7 illustrate side views of embodiments of a seal main body with enhancements on the lip portion;

FIG. 8 illustrates a side view of an embodiment of a seal main body with an embedded support substrate; and

FIG. 9 illustrates a side view of an embodiment of a seal main body with a band disposed on an inner surface and an outer surface of the base portion.

Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention. DETAILED DESCRIPTION

The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings. However, other embodiments can be used based on the teachings as disclosed in this application.

As used herein, "substantially parallel" refers to a condition where two planes are within 10° of parallel and includes parallel; "substantially perpendicular" refers to a condition where two planes are within 10° of perpendicular and includes perpendicular; "substantially uniform throughout" refers to a condition where a property exists throughout at least 80% of the entire volume and includes 100% uniform throughout; "substantially the same value" refers to a condition where one value is within 10% of another value and includes the same value.

The terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the use of "a" or "an" is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one, at least one, or the singular as also including the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and may be found in textbooks and other sources within the sealing art.

The lip seal can have a seal main body that includes a base portion and a lip portion. The seal main body can be a single monolithic piece that includes both the base portion and the lip portion. A lip seal typically requires a two-part construction, namely a rigid outer member that is coupled with the housing, and a flexible inner portion that can accommodate the moving shaft. Reducing the seal main body to a one-piece construction can simplify the manufacturing process.

The method can include molding a polymer to form a monolithic seal main body. The molding can include a transfer molding process that can improve the quality of the lip seal.

As described in more detail below, if an injection molding process is used, the seal main body can develop an outer skin layer. The outer skin layer can degrade the sealing properties of the lip seal, especially in a dynamic environment. Thus, a seal main body in accordance with an embodiment can be free of an outer skin layer, provide an improved leakage rate, provide an improved wear rate, or any combination thereof.

The concepts are better understood in view of the embodiments described below that illustrate and do not limit the scope of the present invention.

FIG. 1 illustrates an embodiment of the lip seal having a seal main body 10 that includes a base portion 20 and a lip portion 30. As illustrated, the seal main body 10 can be a single monolithic piece that includes both the base portion 20 and the lip portion 30.

However, the base portion may be separate from the lip portion.

The seal main body can include a material including a polymer. The base portion and the lip portion can include the same material or different materials. In an embodiment, the base portion and the lip portion include the same material. In a particular embodiment, the base portion and the lip portion together can be a single monolithic seal main body including the same material.

The polymer in the material can include a moldable polymer, such as a transfer- moldable polymer. In an embodiment, the polymer can include a fluoropolymer. The fluoropolymer can include a perfluoroalkoxy polymer (PFA), an ethylene tetrafluoroethylene polymer (ETFE), a polychlorotrifluoroethene (PCTFE), a modified polytetrafluoroethylene (TFM), or any combination thereof. In another embodiment, the polymer can include a polyolefin. The polyolefin can include a high density polyethylene (HDPE), a fluorinated polyethylene (FLPE), a high density crosslinked polyethylene (XLPE), polymethylpentene (PMP), fluorinated polypropylene (FLPP), and any combination thereof. In yet another embodiment, the polymer can include a nitrogen-containing polymer, such as a nylon. The nylon can include a high performance nylon such as Zytel™ brand nylon from E. I. du Pont de Nemours and Company, Wilmington, Delaware.

The polymer in the material can include a polymer having a high enough Young's modulus that it contributes to the rigidity of the seal main body. In a particular embodiment, the polymer present in the material has a Young's modulus of at least 200 MPa, at least 400 MPa, at least 500 MPa, or at least 550 MPa. In another embodiment, the sealing properties of the lip seal depend on some stretching of the inner diameter of the lip portion. If the Young's modulus is too high, the force that is developed with the stretching will be so high as to create excessive frictional losses or wear and may not be able to return to its original size. For example, the polymer present in the material may have a Young's modulus of no greater than 4,700 MPa, no greater than 3,700 MPa, or even no greater than 2,700 MPa. Moreover, in yet another embodiment, the polymer present in the material has a Young's modulus in a range of any of the minimum and maximum values described above, such as in a range of 200 to 4,700 MPa, 400 MPa to 3,700 MPa, or even 550 to 2,700 MPa.

The polymer can be present in the material in an amount that provides a reasonable wear rate under mild conditions, such as a low pressure difference across the lip seal. In an embodiment, the amount of polymer in the material can be reduced to accommodate a filler, which can improve, for example, the lubrication and wear rate of the seal main body under more extreme conditions. For example, the polymer may be present in the material in an amount of no greater than 98 wt%, no greater than 95 wt%, or even no greater than 92 wt%. In a further embodiment, the polymer can be present in the material in an amount sufficient to maintain the structural integrity of the seal main body. For example, the polymer can be present in the material in an amount of at least 80 wt%, at least 85 wt%, or even at least 88 wt%. Moreover, the polymer can be present in the material in an amount in a range of any of the maximum and minimum values described above, such as in the range of 80 to 98 wt%, 85 to 95 wt%, or even 88 to 92 wt%. The above values are based on the total weight of the seal main body.

As previously stated, the filler can help improve lubrication and wear rate. In a particular embodiment, the filler can be present in the material in an amount of at least 2 wt%, at least 5 wt%, or at least 8 wt%. Too much filler may adversely affect the sealing properties, such as by making the material too stiff. Since lip seals depend on the material to stretch and be resilient, the fillers may be present in an amount of no greater than 40 wt%, no greater than 30 wt%, no greater than 25 wt%, or no greater than 15 wt%. Moreover, in yet another embodiment, the filler can be present in the material in an amount in a range of any of the maximum and minimum values described above, such as from 2 wt% to 30 wt%, 5 wt% to 25 wt%, or even from 8 wt% to 15 wt%. The above values are based on the total weight of the seal main body.

In an embodiment, the filler can include a metallic filler, a glass fiber, a polymer powder, a ceramic, an aramid, a carbon, a molybdenum disulfide, or any combination thereof. Examples of the filler include a wallonstonite, a mica, a barium sulfate, a tungsten disulfide, a nickel powder, a polyphenyl sulfide (PPS), a crosslinked polytetrafluoroethylene, a polyimide (PI), a polyether ether ketone (PEEK), a bronze, a silicon carbide, a boron nitride, a carbon fiber, a powder coated with various metallic coatings, a polybenzimidazole (PBI), or any combination thereof. The material can include additives in addition to the filler and the polymer. Alternatively, in a more particular embodiment, the filler can make up a portion of the material and the polymer can make up the remainder of the material.

The molecular chains in the material can be at least partially aligned such that the material of the seal main body can be a crystalline material. The degree of crystallinity refers to the fraction of the molecular chains that are aligned. When a portion of the molecular chains are aligned and the degree of crystallinity is less than 100%, the material can be referred to as a semi-crystalline material. A higher degree of crystallinity, such as greater than 45%, may provide an improved wear rate. In a particular embodiment, the material of the seal main body can have a degree of crystallinity that is at least 45%, at least 55%, or even at least 65%. A degree of crystallinity that is too high, such as greater than 90%, may cause frictional losses. In another embodiment, the material of the seal main body may have a degree of crystallinity that is no greater than 90%, no greater than 85%, or no greater than 80%. Moreover, in yet another embodiment, the material of the seal main body can have a degree of crystallinity that is in a range of any of the maximum and minimum values described above, such as in a range of from 45% to 90%, 55% to 85%, or even 65% to 80%.

In an embodiment, the material of the seal main body has a degree of crystallinity that is substantially uniform throughout the entire volume of the seal main body. A more uniform degree of crystallinity can provide a more consistent wear rate and improve sealing performance. For example, the uniformity of the degree of crystallinity throughout the entire volume of the seal main body can be at least 85%, at least 90%, at least 95%, at least 99%, or even 100% uniform.

The seal main body can have a tensile strength sufficient to withstand extreme dynamic environments. For example, the seal main body can have a tensile strength of at least 30 MPa, at least 35 MPa, at least 40 MPa, at least 45 MPa, or at least 50 MPa. As the tensile strength of the seal main body increases, the seal main body may become too stiff and its sealing properties may begin to degrade. In further embodiments, the seal main body may have a tensile strength of no greater than 500 MPa, no greater than 400 MPa, no greater than 300 MPa, no greater than 200 MPa, or no greater than 100 MPa. Moreover, the seal main body has a tensile strength in a range of any of the minimum or maximum values described above, such as from 35 MPa to 500 MPa, 40 MPa to 300 MPa, or 50 MPa to 100 MPa.

In an embodiment, the seal main body can be free or substantially free of an outer skin layer. As used herein, the term "free of an outer skin layer" refers to the absence of a layer disposed on an outer surface of the seal main body that is structurally distinct from the core of the seal main body. For example, an outer surface of an embodiment of the seal main body may be free of an outer skin layer while having an outer surface that is of a different texture (for example, glossy) than the core of the seal main body. As used herein, the term "substantially free of an outer skin layer" refers to the absence of any outer skin layer that is greater than 50 μιη.

Polymeric articles formed using an injection molding process may develop an outer skin layer that has different structural properties than the underlying core of the polymeric article. When such an article is used as a sealing device in a dynamic environment, displacement of the outer skin layer is common and can degrade sealing performance. For example, a fluid can leak through the lip seal between the core and the skin layer.

Additionally, portions of the skin can be introduced into the fluid if it breaks away from the core. In an embodiment of the lip seal found in accordance with the concepts herein, the seal main body can be manufactured according to a process that does not produce an outer skin layer on the seal main body. As described in more detail below, such a process can include transfer molding. In another embodiment, the process does not include injection molding.

The shape and size of the seal main body can vary based on the desired application, such as based on the shape and size of the housing and the shaft. For example, the base portion can be adapted to fit a particular housing, and the lip portion can be adapted to fit a particular shaft, such as a radial shaft. With reference to FIGs. 1-6, the base and lip portions of the seal main body are described in more detail below.

As illustrated in FIG. 1, the base portion 20 has a first major surface 15 and an opposing second major surface 25. The first major surface 15 can lie along a first plane 13, and the second major surface 25 can lie along a second plane 23. The first and second planes 13 and 23 can be non-parallel to each other or, as illustrated in FIG. 2, substantially parallel, within 10° of parallel, within 5° of parallel, within 1° of parallel, or even parallel to each other.

Further, the base portion 20 can have a distal surface 35 and an opposing proximal surface 45. The distal surface 35 can lie along a distal plane 33, and the proximal surface 45 can lie along a proximal plane 43. The distal and proximal planes 33 and 43 can be non- parallel to each other or, as illustrated in FIG. 1, substantially parallel, within 10° of parallel, within 5° of parallel, within 1° of parallel, or even parallel, to each other.

Moreover, first and second planes 13 and 23 can be non-perpendicular, or as illustrated in FIG. 1, substantially perpendicular to distal and proximal planes 33 and 43, such as within 10° of perpendicular, within 5° of perpendicular, within 1° of perpendicular, or even perpendicular planes 33 and 43.

The perimeter of the base portion 20 can be defined by distal surface 35. The perimeter of the base portion 20 is not limited to particular shape; its shape can depend on the desired application, such as the shape of the housing for the lip seal. The shape of the perimeter of the base portion 20 can advantageously prevent or limit the rotational movement of the lip seal when in use in radial shaft applications.

FIG. 2 illustrates a top view of the seal main body illustrated in FIG. 1, the perimeter of the base portion 20 having a circular shape, such as a complete circle. The proximal surface 45 can define the perimeter of a space 60 extending radially inwardly from the proximal surface 45. The perimeter of the space 60 can have a circular shape, though the shape of the perimeter of the space can be adapted to a particular application.

In an alternative embodiment, as illustrated in FIG. 3, a seal main body 110 can have a base portion 120 and a lip portion 130. The perimeter of the base portion 120, defined by distal surface 135, has a polygonal shape such as a rectangle shape. The rectangle shape can include a square. Other polygonal shapes are also envisioned, such as a triangle, a pentagon, a hexagon, a heptagon, or an octagon. The proximal surface 145 can define the perimeter of a space 160 extending radially inwardly from the proximal surface 145. The perimeter of the space 160 can have a circular shape, though the shape of the perimeter of the space can be adapted to a particular application.

Further, the perimeter of the base portion defined by the distal surface can have an elliptical shape or an irregular shape (not illustrated).

Referring to FIG. 1, the lip portion 30 can have a first major surface 65 and a second major surface 75. The lip portion can have a thickness defined by the distance between the first and second major surfaces 65 and 75 of the lip portion. The lip portion 30 can extend radially inwardly from a point along the proximal surface 45 of the base portion 20, such as a point near the second major surface 25 of the base portion. Initially, the lip portion 30 can extend from the base portion 20 in a direction that is substantially perpendicular to proximal plane 43 to an end 55. In an embodiment, the lip portion 30 can curve toward an end 55 (from a side view) as illustrated in FIG. 2, or the lip portion can extend toward an end without curving (not illustrated).

When the lip portion 30 curves to the end 55, at least part of the first major surface 75, such as the part nearest the end 55, can define a space 73 for receiving a shaft. Alternatively, the end 55 can define the space 73 for receiving the shaft. The space 73 defined by the lip portion 30 can have an annular shape, such as for receiving a radial shaft. FIG. 4 illustrates a cross section of the seal main body 10 illustrated in FIG. 1 before receiving a shaft and FIG. 5 illustrates a cross section of the seal main body 10 illustrated in FIG. 1 after receiving a shaft 5.

FIGs. 6 and 7 illustrate additional embodiments of a seal main body that include enhancements 201, such as indents, protrusions, ribs, or any combination thereof, on the lip portion 230. The enhancements can be adapted to retain lubricant, such as adapted to collect small amounts of leakage that pass the initial seal and entrain it such that it can be fed back into the sealing area. The enhancements can be manufactured by making a spiral cut along the surface of the lip portion that will be facing the shaft. The spiral cut can form a thread along the shaft-facing surface that pumps the oil away from the lip. Alternatively, the enhancements can be manufactured by embossing the shaft-facing. FIG. 6 illustrates a seal main body 210 having a base portion 220 and a lip portion 230 similar to other base and lip portions described herein except for the enhancements 201. The enhancements 201 on the surface 275 of the lip portion include protrusions. FIG. 7 illustrates a seal main body 310 having a base portion 320 and a lip portion 330 similar to other base and lip portions described herein except for the enhancements 301. The enhancements 301 on the surface 375 of the lip portion include indents, instead of protrusions.

The seal main body can have a reasonable structural strength to withstand particular operating conditions without an embedded support substrate. Thus, in a particular embodiment, the seal main body can be free of an embedded support substrate, such as free of an embedded metal support substrate, free of an embedded plastic support substrate, free of any embedded support substrate. Further, in more extreme conditions, a support substrate may be desired or needed. FIG. 8 illustrates an embodiment of a seal main body 410 having a base portion 420 and a lip portion 430, where the base portion 420 includes an embedded support substrate 402. The shape and size of the embedded support substrate 402 can be adapted as desired or needed. In addition, the seal main body 410 can include one or more embedded support substrates.

A separate component can be disposed on the seal main body. For example, a band can be disposed on the distal surface of the base portion, on the proximal surface of the base portion, or on both the distal and proximal surfaces of the base portion. FIG. 9 illustrates an embodiment of a seal main body 510 having a base portion 520 and a lip portion 530. The distal surface 533 includes a band 580, and the proximal surface 543 includes a band 590. When there is more than one band disposed on the seal main body, as illustrated in FIG. 9, the bands can include different materials or the same material. For example, the bands can include a metal or an elastomer, such as an elastomer o-ring. In FIG. 9, the band 580 is an elastomer o-ring, and the band 590 is an annular metal ring. To minimize the effect of extreme temperatures on the lip seal, the material of the band, such as the material of the annular metal ring 590, can be selected to have a thermal expansion coefficient that is greater than the thermal expansion coefficient of the base portion. Further, in an embodiment, the band can have a thermal expansion coefficient that matches the thermal expansion coefficient of the seal housing.

The lip seal can be described in terms of its leakage rate. As used herein, leakage rate is a measure of the amount of a fluid that passes through the lip seal over a predetermined amount of time per unit of shaft circumference, for example ml/hr/mm, tested at a predetermined pressure and shaft surface velocity.

When tested at a shaft surface velocity of 8.7 meters per second (m/s) and a pressure difference across the lip seal of 70 kPa, the lip seal may have a leakage rate of no greater than 0.1 mL/hr/mm, no greater than 0.09 mL/hr/mm, no greater than 0.08 mL/hr/mm, no greater than 0.07 mL/hr/mm, no greater than 0.06 mL/hr/mm, no greater than 0.05 mL/hr/mm, no greater than 0.04 mL/hr/mm, no greater than 0.03 mL/hr/mm, no greater than 0.02 mL/hr/mm, or no greater than 0.01 mL/hr/mm. Although it may be desirable to have no leakage at all, a small amount of leakage may occur, such as at a rate of at least 0.0001 mL/hr/mm, at least 0.001 mL/hr/mm, at least 0.002 mL/hr/mm, at least 0.003 mL/hr/mm, at least 0.004 mL/hr/mm, or at least 0.005 mL/hr/mm. Moreover, if the lip seal has some leakage, the lip seal can have a leakage rate in a range of any of the minimum and maximum values described above, such as from 0.0001 to 0.1 mL/hr/mm, from 0.001 to 0.05 mL/hr/mm, or at least 0.005 to 0.01 mL/hr/mm. The lip seal can be described in terms of its wear rate. As used herein, wear rate is a measure of the decrease in a thickness of the lip portion per unit time, such as mm/hr, tested at a predetermined shaft surface velocity and contact pressure. The thickness of the lip portion is measured as described above, and the decrease in thickness is the difference between the thickness before the testing period and the thickness after the testing period.

When tested at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa, the lip seal may have a wear rate of no greater than 0.1 mm/hr, no greater than 0.09 mm/hr, no greater than 0.08 mm/hr, no greater than 0.07 mm/hr, no greater than 0.06 mm/hr, or no greater than 0.05 mm/hr. Although it may be desirable to have no wear at all, a small amount of wear may occur, such as at a rate of at least 0.0001 mm/hr, at least 0.0002 mm/hr, at least 0.0003 mm/hr, at least 0.0004 mm/hr, or at least 0.0005 mm/hr. Moreover, if the lip seal has some wear, the lip seal can have a wear rate in a range of the minimum and maximum values described above, such as from 0.0001 mm/hr to 0.09 mm/hr, from 0.0002 mm/hr to 0.08 mm/hr, or from 0.0003 mm/hr to 0.07 mm/hr.

A method for manufacturing the lip seal can include providing a moldable material including a polymer and transfer molding the material to form seal main body. The moldable material can include the material of the seal main body described above.

As discussed above, an embodiment of the method does not include injection molding. Injection molding can include feeding granular plastic from a hopper into a heated barrel. The plastic can be heated to lower its viscosity and a plunger can advance the heated plastic through a nozzle into the mold. Generally, the mold remains cold so the plastic solidifies almost as soon as it comes in contact with the mold, which can produce an outer skin layer on the article.

The transfer molding can include preheating the material and loading the preheated material into a chamber. The chamber can be directly adjacent to a mold. Pressure can be applied to the chamber, such as by a plunger, to force the material from the chamber into the mold, such as through a channel in a wall of the mold. The mold walls can be heated to a predetermined temperature, such as a temperature above the plastic point of the material or a temperature above the melting point of the material. Heating the walls of the mold can increase the rate of the flow of the material in the mold and avoid producing an outer skin layer on the seal main body. Thus, compared to injection molding, transfer molding allows for a smoother material flow during transfer, can produce a seal main body having a more homogeneous material at the molecular scale, and can produce a seal main body being substantially free of an outer skin layer. The method can form a monolithic seal main body that is ready for use without any further machining. The further machining referred to herein does not include insignificant machining, such as trimming along a seam. Instead, the further machining refers to more significant machining such as forming the lip portion or the base portion. Thus, in an embodiment, the method includes forming a seal main body that is not machined after transfer molding. Such a method can simplify the manufacturing process by reducing the amount of machinery necessary to manufacture the lip seal and producing less waste. The seal main body formed according to embodiments of the method can have one or more of the properties discussed above with respect to embodiments of the lip seal.

An embodiment of the lip seal can provide one or more of the following benefits. For example, an embodiment of the lip seal can include a seal main body that can be of a one-part construction, such as a monolithic seal main body that does not require an embedded support substrate. Further, an embodiment of the lip seal can include a seal main body that does not have an outer skin layer, can provide an improved wear rate, can provide an improved leakage rate, or any combination thereof. Moreover, embodiments of the lip seal can include a seal main body that does not require further machining. One or more of these

characteristics can improve sealing properties of the lip seal or simplify the manufacturing process of the lip seal.

Many different aspects and embodiments are possible. Some of those aspects and embodiments are described below. After reading this specification, skilled artisans will appreciate that those aspects and embodiments are only illustrative and do not limit the scope of the present invention. Embodiments may be in accordance with any one or more of the items as listed below.

Item 1. A lip seal comprising:

a seal main body having a base portion and a lip portion extending from the base portion, wherein the base portion and the lip portion comprise a same material comprising a moldable polymer and a filler, and the seal main body is free of an outer skin layer.

Item 2. The lip seal of item 1, wherein the base portion and the lip portion together are a single monolithic piece.

Item 3. A lip seal comprising:

a monolithic seal main body having a base portion and a lip portion extending from the base portion,

wherein the lip seal has a leakage rate of no greater than 0.1 mL/hr/mm, the leakage rate being a measure of the amount of a fluid that passes through the lip seal when tested at a a shaft surface velocity of 8.7 meters per second (m/s) and a pressure difference across the lip seal of 70 kPa.

Item 4. A lip seal comprising:

wherein the lip seal has a wear rate of no greater than 0.1 mm/hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 5. The lip seal of items 3 or 4, wherein the seal main body comprises a material comprising a moldable polymer and a filler.

Item 6. A method of manufacturing a lip seal comprising:

providing a material comprising a moldable polymer and a filler; and

transfer molding the material to form a monolithic seal main body having a base portion and a lip portion extending from the base portion.

Item 7. The lip seal or method of any one of items 3-6, wherein the seal main body is free of an outer skin layer.

Item 8. The lip seal or method of any one items 1-7, wherein the seal main body comprises a transfer-moldable polymer.

Item 9. The lip seal or method of any one items 1, 2, and 5-8, wherein the moldable polymer comprises a fluoropolymer.

Item 10. The lip seal or method of any one items 1, 2, and 5-9, wherein the moldable polymer comprises a perfluoroalkoxy polymer (PFA), an ethylene tetrafluoroethylene polymer (ETFE), a polychlorotrifluoroethene (PCTFE), a modified polytetrafluoroethylene (TFM), or any combination thereof.

Item 11. The lip seal or method of any one items 1, 2, and 5-8, wherein the moldable polymer comprises a high density polyethylene (HDPE), a fluorinated polyethylene (FLPE), a high density crosslinked polyethylene (XLPE), polymethylpentene (PMP), fluorinated polypropylene (FLPP), and any combination thereof.

Item 12. The lip seal or method of any one items 1, 2, and 5-8, wherein the moldable polymer comprises a nitrogen-containing polymer.

Item 13. The lip seal or method of any one of items 1, 2, and 5-12, wherein the filler comprises a metallic filler, a glass fiber, a polymer powder, a ceramic, an aramid, a carbon, a molybdenum disulfide, or any combination thereof. Item 14. The lip seal or method of any one of items 1, 2, and 5-13, wherein the filler is present in an amount of no greater than 40 wt%, no greater than 30 wt%, no greater than 25 wt%, or no greater than 15 wt%, based on a total weight of the seal main body.

Item 15. The lip seal or method of any one of items 1, 2, and 5-14, wherein the filler is present in an amount of at least 2 wt%, at least 5 wt%, or at least 8 wt%, based on a total weight of the seal main body.

Item 16. The lip seal or method of any one of items 1, 2, and 5-15, wherein the filler is present in an amount in a range of 2 wt% to 30 wt%, 5 wt% to 25 wt%, or 8 wt% to 15 wt%, based on a total weight of the seal main body.

Item 17. The lip seal or method of any one of items 1, 2, and 5-13, wherein the material has a Young's modulus of at least 200 MPa, at least 400 MPa, at least 500 MPa, or at least 550 MPa.

Item 18. The lip seal or method of any one of items 1, 2, and 5-14, wherein the material has a Young's modulus of no greater than 4,700 MPa, no greater than 3,700 MPa, or even no greater than 2,700 MPa.

Item 19. The lip seal or method of any one of items 1, 2, and 5-15, wherein the material has a Young's modulus in a range of from 200 to 4,700 MPa, 400 MPa to

3,700 MPa, or even 550 to 2,700 MPa.

Item 20. The lip seal or method of any one of the preceding items, wherein the seal main body has a degree of crystallinity that is substantially uniform throughout a volume of the seal main body.

Item 21. The lip seal or method of any one of the preceding items, wherein the base portion has a distal surface and an opposing substantially parallel proximal surface.

Item 22. The lip seal or method of item 21, wherein the lip portion extends radially inwardly from the proximal surface of the base portion.

Item 23. The lip seal or method of item 22, wherein, from a side view, the lip portion curves to an end.

Item 24. The lip seal or method of any one of the preceding items, wherein the base portion has a first major surface and an opposing second major surface.

Item 25. The lip seal or method of item 24, wherein the first major surface of the base portion is substantially parallel to the second major surface of the base portion.

Item 26. The lip seal or method of any of the preceding items, wherein a band is disposed on the seal main body. Item 27. The lip seal or method of item 26, wherein the band is an annular ring comprising a metal or an elastomer.

Item 28. The lip seal or method of items 26 or 27, wherein the band is has a thermal expansion coefficient that is greater than a thermal expansion coefficient of the seal main body.

Item 29. The lip seal or method of any one of the preceding items, wherein the seal main body has a tensile strength of at least 30 MPa, at least 35 MPa, at least 40 MPa, at least 45 MPa, or at least 50 MPa.

Item 30. The lip seal or method of any one of the preceding items, wherein the seal main body has a tensile strength of no greater than 500 MPa, no greater than 400 MPa, no greater than 300 MPa, no greater than 200 MPa, or no greater than 100 MPa.

Item 31. The lip seal or method of any one of the preceding items, wherein the seal main body has a tensile strength in a range of 35 MPa to 500 MPa, 40 MPa to 300 MPa, or 50 MPa to 100 MPa.

Item 32. The lip seal or method of any of the preceding items, wherein the seal main body is free of an embedded support substrate.

Item 33. The lip seal or method of any one of the preceding items, wherein lip seal has a leakage rate of no greater than 0.09 mL/hr/mm, no greater than 0.08 mL/hr/mm, no greater than 0.07 mL/hr/mm, no greater than 0.06 mL/hr/mm, no greater than 0.05 mL/hr/mm, no greater than 0.04 mL/hr/mm, no greater than 0.03 mL/hr/mm, no greater than 0.02 mL/hr/mm, or no greater than 0.01 mL/hr/mm, the leakage rate being a measure of the amount of a fluid that passes through the lip seal when tested at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 34. The lip seal or method of any one of the preceding items, wherein the lip seal has a leakage rate of at least 0.0001 mL/hr/mm, at least 0.001 mL/hr/mm, at least 0.002 mL/hr/mm, at least 0.003 mL/hr/mm, at least 0.004 mL/hr/mm, or at least 0.005 mL/hr/mm, the leakage rate being a measure of the amount of a fluid that passes through the lip seal when tested at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 35. The lip seal or method of any one of the preceding items, wherein the lip seal has a leakage rate is in a range of from 0.0001 to 0.1 mL/hr/mm, from 0.001 to 0.05 mL/hr/mm, or at least 0.005 to 0.01 mL/hr/mm, the leakage rate being a measure of the amount of a fluid that passes through the lip seal when tested at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa. Item 36. The lip seal or method of any one of the preceding items, wherein the lip seal has a wear rate of no greater than 0.09 mm/hr, no greater than 0.08 mm hr, no greater than 0.07 mm/hr, no greater than 0.06 mm/hr, or no greater than 0.05 mm/hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 37. The lip seal or method of any one of the preceding items, wherein the lip seal has a wear rate of at least 0.0001 mm/hr, at least 0.0002 mm/hr, at least 0.0003 mm/hr, at least 0.0004 mm/hr, or at least 0.0005 mm/hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 38. The lip seal or method of any one of the preceding items, wherein the lip seal has a wear rate in a range of 0.0001 to 0.09 mm/hr, 0.0002 to 0.08 mm/hr, or 0.0003 mm/hr to 0.07 mm/hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

Item 39. The method of any one of the preceding items, wherein the seal main body is not machined after transfer molding.

EXAMPLES

The concepts described herein will be further described in the following examples, which do not limit the scope of the invention described in the claims. Some of the parameters below have been approximated for convenience.

Each of the following Examples describes the leakage rate of sample lip seals. Unless indicated otherwise, the sample lip seals were prepared by transfer molding about 20 grams of a PFA material at the following parameters: an oven temperature of about 390°C; an oven time of at least 90 minutes; a piston strength of at least 390 daN; a piston speed of at least 1 mm/s; a pressure time of about 10 minutes; and either a progressive cooling or a shock cooling.

The testing in each Example included a preliminary sequence and two principal sequences, wherein different lip seals were used for each of the sequences. The preliminary sequence ran for about 2 hours at 5,000 rpm without a pressure difference across the lip seal. The first and second sequences ran for about 8 hours each at 5,000 rpm at a pressure difference across the lip seal of 70 kPa. As discussed below, in Comparative Example 1 , the sample lip seals were not able to complete the first sequence, and the second sequence was not attempted. For each sequence, a pair of sample lip seals was mounted in a test chamber on a radial wear sleeve having a circumference of approximately 104 mm. The test chamber includes oil, spray nozzles, and electric heaters and is regulated with ambient air or nitrogen. Any leakage through the seal is collected directly or within a weighted absorbent material, and then post-test quantified by volume or weight gain.

Example 1

Example 1 tested monolithic lip seals made by transfer molding a filled PFA material including a blend of PFA450HP™ brand polymer from E.I. du Pont de Nemours and Company, Wilmington, Delaware, 8% carbon, and 2% graphite. After transfer molding, the lip seals were cooled according to a progressive cooling method.

The sequence details and results are listed in Table 1. There was no measurable or visible leakage after any of the sequences. After each sequence, the pair of sample lip seals appeared to have only very minor wear (approximately 0.025 mm wear loss) on the lip portion.

Table 1

Example 2

Example 2 tested monolithic lip seals made by transfer molding the same filled PFA blend used in Example 1. After transfer molding, the lip seals were cooled according to a shock cooling method.

The sequence details and results are listed in Table 2. There was no measurable or visible leakage after any of the sequences. After each sequence, the pair of sample lip seals appeared to have only very minor wear on the lip portion. Table 2

Comparative Example 1

Comparative Example 1 tested monolithic lip seals made by injection molding an unfilled PFA material including PFA450HP™ brand polymer from E.I. du Pont de Nemours and Company, Wilmington, Delaware.

The sequence details and results are listed in Table 3. The unfilled PFA lip seals were able to complete the preliminary sequence without a pressure difference across the lip seals. However, the first sequence was stopped after one hour because the sample lip seals were torn, resulting in excessive leakage. A second sequence was not attempted.

Table 3

Based on the results in Tables 1-3, the filled PFA monolithic lip seals exhibited superior leakage and wear performance as compared to unfilled PFA monolithic lip seals. The filled PFA samples were able to complete all sequences without noticeable leakage, whereas the unfilled PFA lip seals were not able to complete a sequence under a pressure of 70 kPa because of tearing and excessive leakage.

Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Separate embodiments may also be provided in combination in a single embodiment, and conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.

Claims

WHAT IS CLAIMED IS:

1. A lip seal comprising:

a seal main body having a base portion and a lip portion extending from the base portion,

wherein the base portion and the lip portion comprise a same material comprising a moldable polymer and a filler, and the seal main body is free of an outer skin layer.

2. The lip seal of claim 1, wherein the base portion and the lip portion together are a single monolithic piece.

3. A lip seal comprising:

4. A lip seal comprising:

wherein the lip seal has a wear rate of no greater than 0.1 mm hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

5. The lip seal of claims 3 or 4, wherein the seal main body comprises a material comprising a moldable polymer and a filler.

6. A method of manufacturing a lip seal comprising:

providing a material comprising a moldable polymer and a filler; and

7. The lip seal or method of any one of claims 3-6, wherein the seal main body is free of an outer skin layer.

8. The lip seal or method of any one claims 1-7, wherein the seal main body comprises a transfer-moldable polymer.

9. The lip seal or method of any one claims 1, 2, and 5-8, wherein the moldable polymer comprises a perfluoroalkoxy polymer (PFA), an ethylene tetrafluoroethylene polymer (ETFE), a polychlorotrifluoroethene (PCTFE), a modified polytetrafluoroethylene (TFM), or any combination thereof.

10. The lip seal or method of any one claims 1, 2, and 5-8, wherein the moldable polymer comprises a high density polyethylene (HDPE), a fluorinated polyethylene (FLPE), a high density crosslinked polyethylene (XLPE), polymethylpentene (PMP), fluorinated polypropylene (FLPP), and any combination thereof.

11. The lip seal or method of any one claims 1, 2, and 5-8, wherein the moldable polymer comprises a nitrogen-containing polymer.

12. The lip seal or method of any one of the preceding claims, wherein the seal main body has a degree of crystallinity that is substantially uniform throughout a volume of the seal main body.

13. The lip seal or method of any of the preceding claims, wherein the seal main body is free of an embedded support substrate.

14. The lip seal or method of any one of the preceding claims, wherein lip seal has a leakage rate of no greater than 0.09 mL/hr/mm, no greater than 0.08 mL/hr/mm, no greater than 0.07 mL/hr/mm, no greater than 0.06 mL/hr/mm, no greater than 0.05 mL/hr/mm, no greater than 0.04 mL/hr/mm, no greater than 0.03 mL/hr/mm, no greater than 0.02 mL/hr/mm, or no greater than 0.01 mL/hr/mm, the leakage rate being a measure of the amount of a fluid that passes through the lip seal when tested at a shaft surface velocity of 8.7 m/s and a pressure difference across the lip seal of 70 kPa.

15. The lip seal or method of any one of the preceding claims, wherein the lip seal has a wear rate of no greater than 0.09 mm hr, no greater than 0.08 mm/hr, no greater than 0.07 mm/hr, no greater than 0.06 mm hr, or no greater than 0.05 mm hr, the wear rate being a measure of a decrease in a thickness of the lip portion at a shaft surface velocity of 8.7 m s and a pressure difference across the lip seal of 70 kPa.