Patent Application
20080280040
This disclosure relates to gaskets and more particularly to gaskets formed with pervious screen-like base sheets and to gaskets with applied patterned beads and to methods of making such gaskets.
The present invention generally relates to gaskets for sealing an interface between two components.
Gaskets have long been used to seal interfaces between components in a wide variety of machines, particularly in gasoline and diesel engines. For example, head gaskets are used to create a seal between the heads of an engine and an engine block; oil pan gaskets are used to create a seal between an oil pan and an engine block; and water pump gaskets are used to create a seal around the ports of a water pump. Most gaskets are designed specifically for their particular intended use. For example, head gaskets are designed to seal against high temperatures and pressures and the generally caustic environment within the cylinders of an engine. As another example, water pump gaskets are designed to prevent the leakage of coolant, which may consist of a mixture of water and anti-freeze that is heated and under pressure.
Two performance characteristics required of most compressible gaskets are compression resistance and sealability. Compression resistance refers to the ability of a gasket to withstand high compression forces when clamped between two flange surfaces without crushing, deforming, or yielding to the point that the mechanical properties of the gasket material and ultimately the seal provided by the gasket are compromised. Sealability refers to the ability of a gasket to resist or prevent leakage of fluid both between the gasket faces and the flanges between which the gasket is clamped (referred to as “interfacial leakage”) and the ability to resist or prevent leakage of fluid through the gasket material itself (referred to as “interstitial leakage” or “bulk seal” properties).
Many different materials have been used to form gaskets. Metal gaskets traditionally have been favored because they generally have higher heat resistance, but are prone to failure in some applications due to a high level of precision needed to obtain a tight seal. In contrast, polymeric gaskets are able to conform to the surfaces more readily, but often fail over time due to chemical or physical changes in the polymer. Additionally, even prior to failure, polymeric gaskets often are perceived as failing due to oozing or creep from the sealed surfaces resulting from extrusion under pressure of the gasket. As used herein, “extrusion under pressure” refers to the radial or planar expansion or spreading of a gasket material when subject to a compression force normal to the plane of the gasket. Extrusion under pressure typically results in an undesirable permanent deformation or even destruction of the material. Thus, there is a need for an improved gasket with improved performance characteristics and sealing properties.
In one aspect, the invention is generally directed to a gasket having an upper face and a lower face. The gasket comprises a base sheet. The base sheet comprises a pervious material having interstitial spaces therein. The gasket further comprises a permeating material at least partially covering the base sheet and at least partially filling the interstitial spaces. The permeating material comprises a polymer material and has an upper patterned surface on the upper face of the gasket and a lower patterned surface on the lower face of the gasket.
In another aspect, the invention is generally directed to a gasket having an upper face and a lower face. The gasket comprises a base sheet and a primary sealing material for providing a bulk seal of the gasket. The primary sealing material at least partially covers the base sheet. A secondary sealing material at least partially covers the primary sealing material for providing an interfacial seal of the gasket.
In another aspect, the invention is generally directed to a method of forming a gasket having an upper face and a lower face. The method comprises providing a base sheet having interstitial spaces. The method further comprises at least partially covering the base sheet with a permeating material and at least partially filling the interstitial spaces. The method further comprises forming an upper patterned surface on the upper face of the gasket and forming a lower patterned surface on the lower face of the gasket.
In another aspect, the invention is generally directed to a method of forming a gasket having an opening, an upper face, and a lower face. The method comprises providing a base sheet and at least partially covering the base sheet with a primary sealing material. The primary sealing material is for providing a bulk seal of the gasket. The method further comprising at least partially covering the primary sealing material with a secondary sealing material. The secondary sealing material is for providing an interfacial seal of the gasket.
In another aspect, the invention is generally directed to a gasket comprising a base sheet formed of a mesh material and a coating of polymeric material on the based sheet. The coating is configured in a pattern defined by raised portions and lowered portions.
In another aspect, the invention is generally directed to a gasket comprising a wire mesh base sheet having first and second faces. A coating of polymeric material is on the base sheet. The coating being formed into a predetermined pattern on at least one face of the base sheet.
In yet another aspect, the invention includes a method of making a gasket having a surface coating of polymeric material formed in a predetermined pattern characterized by raised and lowered portions, which may take the form of beads. The polymeric material may be dispensed or applied to the surface of the gasket through a technique known as jetting. More specifically, the polymeric material is dispensed onto the gasket using a jetting machine having a jetting head from which the polymeric material is ejected or jetted in a highly controllable manner. Motion of the jetting head is also controllable to move precisely in a predetermined pattern across the surface of the gasket. As a result, a polymeric coating can be applied to the gasket surface in a precisely determined pattern and custom gaskets with custom coatings and patterns can be designed and manufactured quickly and efficiently.
In an additional aspect, the invention includes a method of making a gasket having patterned raised and lowered portions or beads applied to the surface with a computer controlled dispenser having a pneumatic syringe-like head that dispenses polymer to the gasket surface in a controlled manner as the head moves in a precise pattern over the gasket. As with jetting techniques, custom designed beaded gaskets can be formed with this method quickly and easily without the need to produce special masks, presses, and other equipment.
Those skilled in the art will appreciate the above stated advantages and other advantages and benefits of various additional embodiments reading the following detailed description of the embodiments with reference to the below-listed drawing figures.
According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate the embodiments of the invention.
a is a photograph showing the results of a Fujifilm pressure test for a gasket such as that of
b is a photograph showing the results of a Fujifilm pressure test for a gasket such as that of
c is a photograph showing the results of a Fujifilm pressure test for a coated mesh screen base sheet gasket with no sealing beads illustrating variations in pressure throughout a clamped-together joint.
a-23d illustrate the process of collecting calibration data for use in applying custom engineered sealing beads to gasket base sheets according to the invention.
a and 24b illustrate use of the calibration data to engineer a sealing bead for a gasket with custom and changing sealing characteristics throughout its length. Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
The present invention generally relates to a device for creating a seal between two surfaces and, more particularly, relates to various gaskets that may have beneficial and/or improved performance characteristics (e.g., extrusion under pressure, compression resistance, heat resistance, and sealability, etc.). In one embodiment, the gasket generally includes a pervious base sheet with a penetrating material coated, deposited, applied, or otherwise integrated or incorporated into (sometimes collectively “applied to” and/or “incorporated into”) the base sheet. The base sheet and permeating material are selected to obtain the desired heat resistance, compression resistance, and sealing robustness and durability of the resulting gasket. Additionally, the gasket may result in reduced extrusion under pressure and, therefore, improved aesthetics and performance.
The various gaskets of the present invention may be used for numerous applications including, but not limited to, intake manifold gaskets for internal combustion engines, oil pan gaskets, valve cover gaskets, fuel pump gaskets, differential cover gaskets, transmission cover gaskets, water pump gaskets, air conditioning compressor gaskets, gas meter gaskets, and a variety of coupling flange gaskets for industrial pipelines, steam conduits, and other plumbing connections.
Any suitable base sheet may be used to form a gasket according to the present invention. It will be understood that the particular material selected will depend on the intended application for the gasket and the particular performance requirements for the application. In one particular embodiment, the base sheet may be selected from materials described herein that are sometimes referred to as being formed from “fibers”, “wires”, “strands”, or “elements” with “interstitial spaces”, “interstices”, or “void volume” therebetween, collectively and generally referred to as a screen material. However, it will be understood that such terms are not intended to restrict the type of material used to form the base sheet. For example, the base sheet may be formed of materials that are pervious without being fibrous, for example, foams, and that such materials may have what is commonly termed “pores” or “openings”, even though the term “interstices” is used.
In other embodiments, the base sheet may be a compressible or substantially rigid material that is not a pervious material and is substantially contiguous. A substantially contiguous base sheet would comprise a material that is uninterrupted across its flange width, that is, the base sheet would be substantially free from pores or interstitial spaces. The base sheet can comprise a fibrous gasket material of a predetermined thickness, or a material suitable for use as a rigid carrier (e.g., metal) of controlled compression rubber gaskets. The term “base sheet” when used alone without being identified as a base sheet of gasket material is intended to include rigid carriers and all other suitable base sheet materials.
In one embodiment, the base sheet is formed from a woven material, for example, a metal (wire-type) mesh or screen, a polymeric mesh, or any combination thereof. As used herein, the term “woven” refers to a fabric or material made or constructed by interlacing wires, threads, strips, fibers, or strands (collectively “strands”) of material or other elements into a whole. Numerous variations of such materials are contemplated for use with the present invention. It will be understood that the number of strands per unit area, the strand diameter, and the percent open area may be varied depending on the requirements of the particular application.
The number of strands per unit area and the opening size may vary for a particular application. For example, where the base sheet is a wire mesh or screen, the screen may have any suitable mesh (number of openings per lineal inch), for example, from 5 mesh to 100 mesh. Specific examples include, but are not limited to, 5 mesh, 6 mesh, 8 mesh, 10 mesh, 12 mesh, 14 mesh, 16 mesh, 18 mesh, 20 mesh, 24 mesh, 30 mesh, 36 mesh, 40 mesh, 50 mesh, 60 mesh, 80 mesh, and 100 mesh.
Alternately, the base sheet may be formed from a nonwoven material (also referred to as a nonwoven “web” or “fabric”). As used herein, the term “nonwoven” material or fabric or web refers to a web having a structure of individual fibers or threads that are interlaid, but not in an identifiable manner as in a woven fabric. Nonwoven fabrics or webs have been formed from many processes including, but not limited to spunbonding processes, meltblowing processes, bonded carded web processes, felting processes, and needlepunching processes.
As used herein the term “spunbond fibers” refers to small diameter fibers of molecularly oriented polymer formed from a spunbonding process. Spunbond fibers are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced.
As used herein the term “meltblown fibers” refers to fine fibers of unoriented polymer formed from a meltblowing process. Meltblown fibers are often formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and deposited on a collecting surface to form a web of randomly disbursed meltblown fibers. Meltblown fibers may be continuous or discontinuous, and are generally smaller than 10 microns in average diameter. In one embodiment, meltblown fibers include fiberglass, or any other suitable material.
As used herein, “bonded carded web” refers to webs made from staple fibers that are sent through a combing or carding unit, which breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. Such fibers usually are purchased in bales that are placed in a picker that separates the fibers prior to the carding unit. Once the web is formed, it then is bonded by one or more of several known bonding methods. One such bonding method is powder bonding, wherein a powdered adhesive is distributed through the web and then activated, usually by heating the web and adhesive with hot air. Another suitable bonding method is pattern bonding, wherein heated calendar rolls or ultrasonic bonding equipment are used to bond the fibers together, usually in a localized bond pattern, though the web can be bonded across its entire surface if so desired. Another suitable bonding method is through-air bonding. In one embodiment, a bonded carded web includes aramid fibers or any other suitable material.
As used herein, a “felt” refers to a matted nonwoven material formed from natural and/or synthetic fibers, made by a combination of mechanical and chemical action, pressure, moisture, and heat.
As used herein, “needlepunching” refers to a process of converting batts of loose staple or continuous fibers, or a combination of staple fibers and continuous fibers, into a coherent nonwoven fabric in which barbed needles are punched through the batt, thereby entangling the fibers.
Any suitable material may be used to form a nonwoven material for use with the present invention. For example, the base sheet may be formed from glass fibers (fiberglass), carbon fibers, a polymeric material, or any combination thereof. As used herein the term “polymer” or “polymeric material” includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random, and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the molecule. These configurations include, but are not limited to isotactic, syndiotactic, and random symmetries. Typical thermoplastic and thermoset polymers that may be suitable for use with the present invention include, but are not limited to, polyolefins, e.g. polyethylene, polypropylene, polybutylene, and copolymers thereof; polytetrafluoroethylene; polyesters, e.g. polyethylene terephthalate; vinyl polymers, e.g., polyvinyl chloride, polyvinyl alcohol, polyvinylidene chloride, polyvinyl acetate, polyvinyl chloride acetate, polyvinyl butyral; acrylic resins, e.g. polyacrylate, polymethylacrylate, and polymethylmethacrylate; polyamides, e.g., nylon 6,6; polystyrenes; polyurethanes; cellulosic resins, e.g., cellulosic nitrate, cellulosic acetate, cellulosic acetate butyrate, ethyl cellulose; copolymers of any of the above materials; or any blend or combination thereof.
Alternatively still, any combination of synthetic or natural woven, nonwoven, and other materials, for example, papers or foams, may be used as the base sheet. Such materials may be layered and joined to form a composite or laminate or may be assembled or combined in any other suitable manner.
According to various aspects of the invention, a material (e.g., a permeating material), is applied to or incorporated into the base sheet. Any suitable permeating material may be used to form the gasket, and is selected generally to engage, conform to the shape of, and adhere to the mating surfaces to provide the desired compression resistance and sealability for a particular application. In one aspect, the permeating material and base sheet are selected so that the permeating material penetrates a minimal amount of the thickness of the base sheet. In this aspect, the layer of permeating material sometimes may be referred to herein as a “face coating”. In another aspect, the permeating material and base sheet are selected so that the permeating material penetrates only a portion of the thickness of the base sheet. In yet another aspect, the permeating material and base sheet are selected so that the permeating material penetrates substantially all of the thickness of the base sheet.
In each aspect, the permeating material is selected so that, upon compression, the permeating material and base sheet operate in concert to prevent interfacial and interstitial leakage, thereby creating an exceptional, sometimes perfect seal, even under non-ideal conditions. The various mechanisms by which the seal is achieved will be understood by those of skill in the art and described only briefly herein. When the gasket is compressed between two flange surfaces, the face coating (where present) or the permeating material proximate the flange surface tends to fill any imperfections such as scratches or roughness in the mating surfaces that otherwise might result in leakage. Further, the face coating or the permeating material proximate the flange surface tends to conform to any waviness or deviations from flatness in the mating surfaces that might occur, for example, with slightly warped flanges or with thin flanges that can deflect significantly between bolt holes.
The permeating material further is selected to be impervious to and substantially chemically non-reactive with the particular fluid that must be sealed. Any of the polymers or polymeric materials described above may be used in accordance with the present invention. Some particular examples of materials that may be suitable include, but are not limited to, elastomeric materials such as polyacrylates (ACM), ethylene-acrylic copolymers (AEM) such as VAMAC polymer available from E. I. du Pont de Nemours and Company, silicon rubber, acrylic, acrylonitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and styrene butadiene rubber (SBR), acrylic-acrylonitrile copolymers, carboxylated acrylonitrile polymer, carboxylated styrene butadiene polymer, polyvinylidene chloride, chloroprene rubber polymer, ethylene/vinyl acetate polymer, epoxy, fluorosilicones, and polyurethane. Any of the above materials may be UV curable, heat curable, or room temperature curable, or may require combinations of curing techniques. Any of the polymeric materials may include a variety of fillers such as, for example, silica, carbon black, or clay to provide material properties adapted to a particular fluid or condition to be sealed. Any of such materials also may include one or more additives as needed to attain the viscosity, color, flexibility, chemical resistance, UV resistance, and so forth.
The hardness of the permeating material may vary for a particular application, and for example, may range from approximately 20 to approximately 95 in Shore A hardness. In one aspect, the Shore A hardness of the permeating material may be from about 40 to about 80, from about 50 to 70, from about 50 to 60, from about 60 to about 70, for example, about 65. The permeating material also may exhibit some degree of tackiness.
The permeating material may be applied to or incorporated into the selected base sheet in any suitable amount as needed to minimize extrusion under pressure and achieve the desired compression resistance and sealability of the resulting gasket. At a particular point on the base sheet, the permeating material generally may be from 0 to about 99.9% of the total weight of the coated base sheet. In one aspect, the permeating material is from 0 to about 10 wt % of the coated base sheet. In another aspect, the permeating material is from about 10 to about 20 wt % of the coated base sheet. In yet another aspect, the permeating material is from about 20 to about 30 wt % of the coated base sheet. In another aspect, the permeating material is from about 30 to about 35 wt % of the coated base sheet. In yet another aspect, the permeating material is from about 35 to about 40 wt % of the coated base sheet. In a further aspect, the permeating material is from about 40 to about 50 wt % of the coated base sheet. In another aspect, the permeating material is from about 50 to about 60 wt % of the coated base sheet. In yet another aspect, the permeating material is from about 60 to about 70 wt % of the coated base sheet. In still another aspect, the permeating material is from about 70 to about 80 wt % of the coated base sheet. In a further aspect, the permeating material is from about 80 to about 90 wt % of the coated base sheet. In a still further aspect, the permeating material is from about 90 to about 99.9 wt % of the coated base sheet.
The permeating material may be incorporated into or selectively applied to the facial area of the base sheet in any suitable amount and in any pattern needed or desired for a particular application. For example, the permeating material may be applied in a ring, grid, stripe, or any other configuration. In one aspect, the permeating material is applied to or incorporated into greater than 0 to about 10% of the facial area of the base sheet. In another aspect, the permeating material is applied to or incorporated into from about 10 to about 20% of the facial area of the base sheet. In yet another aspect, the permeating material is applied to or incorporated into from about 20 to about 30% of the facial area of the base sheet. In another aspect, the permeating material is applied to or incorporated into from about 30 to about 40% of the facial area of the base sheet. In still another aspect, the permeating material is applied to or incorporated into from about 40 to about 50% of the facial area of the base sheet. In another aspect, the permeating material is applied to or incorporated into from about 50 to about 60% of the facial area of the base sheet. In yet another aspect, the permeating material is applied to or incorporated into from about 60 to about 70% of the facial area of the base sheet. In another aspect, the permeating material is applied to or incorporated into from about 70 to about 80% of the facial area of the base sheet. In still another aspect, the permeating material is applied to or incorporated into from about 80 to about 90% of the facial area of the base sheet. In still a further aspect, the permeating material is applied to or incorporated into from about 90 to about 100% of the facial area of the base sheet.
Depending on the amount of permeating material incorporated into the base sheet, the porosity or open area of the base sheet, the viscosity of the permeating material, and numerous other factors, the gasket may have a thickness that is from about 100% to about 105% of the thickness of the base sheet, from about 105% to about 110% of the thickness of the base sheet, from about 110% to about 115% of the thickness of the base sheet, from about 115% to about 120% of the thickness of the base sheet, from about 120% to about 125% of the thickness of the base sheet, from about 125% to about 130% of the thickness of the base sheet, from about 130% to about 135% of the thickness of the base sheet, from about 135% to about 140% of the thickness of the base sheet, from about 140% to about 145% of the thickness of the base sheet, from about 145% to about 150% of the thickness of the base sheet, from about 150% to about 155% of the thickness of the base sheet, from about 155% to about 160% of the thickness of the base sheet, or any other thickness.
While various ranges are set forth herein, it will be understood that numerous other values and ranges are contemplated hereby. Additionally, it will be understood that portions of the base sheet may have a greater or lesser percentage coating by weight, either by design or as a result of the inherent variations in the particular materials and processes used to apply the permeating material to the base sheet.
The permeating material may be applied to or incorporated into the pervious base sheet in any suitable form or manner needed to achieve the desired coating weight and pattern, for example, as a fusible powder, solid-filled polymer, a 100% solids fluid, a latex, or any combination thereof. It will be understood that permeating material may be applied as a composition including one or more additives that provide the desired viscosity, surface wetting, and other coating or extrusion properties that provide the desired film forming characteristics. For example, the permeating material may be applied as a composition having a viscosity of from about 100 to about 100,000 centipoise (cP), for example, from about 1000 to about 50,000 cP, for example, from about 2000 to about 25,000 cP. In one particular example, the composition has a viscosity of about 2500 cP. In another particular example, the composition has a viscosity of about 21,000 cP.
In some embodiments of the invention, the gasket may comprise a primary sealing material at least partially covering the base sheet and a secondary sealing material at least partially covering the primary sealing material. The primary sealing material provides a bulk seal and the secondary sealing material provides and/or enhances the interfacial seal of the gasket. The primary sealing material has strong bonding characteristics to the base sheet and provides structural strength to the gasket. The secondary sealing material comprises the upper and lower faces or contact surfaces and provides the interfacial seal of the gasket by providing the seal between the gasket faces and the flanges or sealing surfaces between which the gasket is clamped. Both the primary and secondary sealing materials have good thermal, chemical, and fluid permeation resistance against the fluid to be sealed. The secondary sealing material may be applied in the form of beads in predetermined patterns on the surface of the primary sealing material or on the surface of a gasket base sheet.
In one particular embodiment, the primary sealing material is a polymeric coating and the secondary sealing material is a polymeric coating. The polymer coating of the primary sealing material and secondary sealing material can include the same or different material class without departing from the invention. In one embodiment, a suitable primary sealing material includes a polymer that is strong, well cross-linked, and is capable of adhering strongly to the base sheet. Suitable polymers for the primary sealing material include polymers with relatively high glass transition temperatures (Tg) and low to zero filler loading, and polymers with low Tg and relatively high filler loadings (e.g., for strength reinforcement and/or cost reduction). In one embodiment, the primary sealing material includes a polymer with a Tg in the range of approximately 20° C. to approximately 40° C. In another embodiment, the sealing material includes a polymer with a Tg of approximately −50° C. and a substantial amount of filler loading. Also, the primary sealing material may be relatively hard, with a Shore A hardness ranging from approximately 40 to approximately 95, preferably in the range of approximately 60 to approximately 85.
In one embodiment, a suitable secondary sealing material includes a polymer that is relatively soft compared to the primary sealing material and has good conformability so that the secondary sealing material conforms well to the flanges or sealing surfaces. Suitable polymers for the secondary sealing material include polymers having a low Tg and/or minimal or zero filler loading. In one embodiment, suitable secondary sealing materials include polymers having a Tg no higher than approximately −10° C. and a Shore A hardness in the range of approximately 5 to approximately 75, preferably between approximately 15 and approximately 60.
It is understood that the primary sealing material and secondary sealing material may comprise any suitable “polymer” and “polymeric materials” or type of polymer generally noted above for the permeating material, or the primary and secondary sealing materials may comprises any other suitable material. In one exemplary embodiment, the primary sealing material includes a fluoroelastomer polymer, such as TECNOFLON TN latex that is commercially available from Solvay Solexis, Inc. of Thorofare N.J., and other additives with the primary sealing material being formulated and cured such that the primary sealing material exhibits a Tg of approximately −14° C., a Shore A hardness of approximately 82 and a tensile strength of approximately 1550 psi. In another exemplary embodiment, the primary sealing material includes an acrylic latex, such as HYSTRETCH V-29 acrylic latex that is commercially available from the Noveon, Inc. of Cleveland Ohio, and other additives with the material being formulated and cured such that the primary sealing material exhibits a Tg of approximately −29° C., a Shore A hardness of approximately 65, and a tensile strength of approximately 850 psi. In another embodiment, the primary sealing material includes a styrene butadiene rubber, such as BUTOFAN NS-432 SBR latex that is commercially available from BASF Corporation of Germany, and other additives with the material being formulated and cured such that the primary sealing material exhibits a Tg of approximately −25° C., a Shore A hardness of approximately 76, and a tensile strength of approximately 1000 psi.
In one exemplary embodiment, the secondary sealing material includes a fluoroelastomer polymer, such as TECNOFLON TN latex that is commercially available from Solvay Solexis, Inc. of Thorofare NJ, and other additives with the secondary sealing material being formulate and cured such that the primary sealing material exhibits a Tg of approximately −14° C., a Shore A hardness of approximately 65 and a tensile strength of approximately 650 psi. In another exemplary embodiment, the secondary sealing material includes a solvent-based fluroelastomer and other additives with the material being formulated and cured such that the primary sealing material exhibits a Tg of approximately −30° C., a Shore A hardness of approximately 54, and a tensile strength of approximately 800 psi. In another embodiment, the secondary sealing material includes an acrylic polymer, such as HYSTRETCH V-29 acrylic latex that is commercially available from the Noveon, Inc. of Cleveland Ohio, and other additives with the material being formulated and cured such that the secondary sealing material exhibits a Tg of approximately −29° C., a Shore A hardness of approximately 22, and a tensile strength of approximately 510 psi. In another embodiment, the secondary sealing material includes an acrylic polymer, such as HYSTRETCH V-43 acrylic latex that is commercially available from the Noveon, Inc. of Cleveland Ohio, and other additives with the material being formulated and cured such that the secondary sealing material exhibits a Tg of approximately −43° C., a Shore A hardness of approximately 18, and a tensile strength of approximately 500 psi.
The exemplary primary and secondary sealing materials listed herein are intended to illustrate suitable materials for certain embodiments of the invention, but the listing of exemplary materials is not intended to limit the scope of the invention. Further, the primary and secondary sealing materials may be other suitable materials than the specific materials described herein without departing from the scope of the invention.
If desired, a gasket according to the invention may include a release coating to reduce undesired adhesion to mating surfaces and to make a spent gasket easier to remove after use. Release coatings typically are very thin, usually having a coating thickness of less than approximately 0.001 inch (0.025 mm), and are designed to be surface coatings that do not penetrate the base sheet of the gasket. Accordingly, release coatings typically do not detrimentally affect the compression resistance of the gasket material. One example of a commonly used release coating is a mica or vermiculite dispersion.
Numerous processes may be used to form the various gaskets described herein. For example, where the base sheet is provided as a rolled material, the base sheet may be unrolled and subjected to one or more dipping, coating, spraying, printing, extrusion, lamination, or other processes to incorporate the permeating material and/or the primary sealing material and secondary sealing material. Where the permeating material (and/or primary sealing material and secondary sealing material) is applied or incorporated to only a portion or portions of the base material, the permeating material may be applied selectively to the base material. Alternatively, a removable mask may be used to shield the base sheet in the areas not intended to be coated with the permeating material and/or primary sealing material and secondary sealing material. In yet another alternative, the permeating material and/or primary sealing material and secondary sealing material may be applied to the base sheet and selectively removed as desired to form the gasket. In one embodiment, the primary sealing material and particularly the secondary sealing material may be “printed” onto the base sheet in a process known as “jetting,” a process that is reminiscent of the operation of an ink jet printer. This process may result, for example, in beads applied to the surfaces of a gasket in predetermine patterns to enhance sealing characteristics. In another embodiment, such patterned beads or other gasket surface features may be applied with computer controlled fluid dispensing robots that move a syringe-like dispenser over the surface of a gasket while dispensing sealing material in a controlled manner through the dispenser. While examples of processes are provided herein, it will be understood that various other processes may be used to make a gasket according to the present invention.
Further, it is understood that gaskets of the type having a base sheet, a primary sealing material, and a secondary sealing material, as noted above, can be formed from any of the exemplary processes described herein, or may be formed from various other suitable processes.
Various aspects of the invention may be illustrated further by referring to the figures. For purposes of simplicity, like numerals may be used to describe like features. It will be understood that where a plurality of similar features are depicted, not all of such features are necessarily labeled on each figure. While various exemplary embodiments are shown and described in detail herein, it also will be understood that any of the features may be used in any combination, and that such combinations are contemplated hereby.
In the illustrated embodiment, the gasket 100 includes a permeating material 129 covering the base sheet and filling the interstitial spaces 123. In the illustrated embodiment, the permeating material 129 covers substantially all of the base sheet and comprises substantially all of the surface area of the upper face 104 and substantially all of the surface area of the lower face 106. In other embodiments, the permeating material 129 may be otherwise arranged so as only to cover selected portions of the base sheet 115 and/or only fill the interstitial spaces 123 partially.
In the embodiment of
As shown in
A permeating material 330 is incorporated throughout the spaces 323 of the pervious base sheet 309. In the illustrated embodiment, the permeating material 330 fills the void volume of the interstitial spaces 323 of the base sheet 309. The permeating material 330 may be configured by embossing, printing, or otherwise to form a patterned surface of the upper face 303 of the gasket 300 having multiple recesses 335 arranged in a grid or other suitable arrangement. In the illustrated embodiment, the permeating material 330 also forms a patterned surface of the lower face 305 of the gasket 300 that has multiple recesses 337 and is similarly shaped and arranged as the patterned surface of the upper face 303. In the illustrated embodiment, the permeating material 330 is located in adjacent interstitial spaces 323 (as viewed in the cross-sectional view of
As shown in
In the illustrated embodiment, the upper and lower surfaces 315, 319 of the first elements 311 of the base sheet 309 are at least partially free from coverage with the permeating material 330 at locations corresponding to the upper and lower recesses 335, 337. Alternatively, one or both of the upper and lower surfaces 315, 319 of the first and second elements may be at least partially covered with permeating material 330 at locations corresponding to the upper and lower recesses 335, 337 without departing from the scope of this invention. Although only the first elements 311 are shown in the cross-section of
In the illustrated embodiment, the upper and lower patterned surfaces 303, 305 of the gasket 300 each include at least one complete recess 335, 337 that is located between the edge 361 of the gasket adjacent the aperture 102 and each of the bolt holes 110. That is, the upper projections 339, 347 on the upper face 303 should be arranged so that at least one recess 335 is completely enclosed on all four sides by permeating material 330 between the edge 361 and the bolt hole 110 to inhibit the flow of fluid at the upper face between the aperture 102 and the bolt hole. Similarly, the lower projections 341, 351 on the lower face 305 should be arranged so that at least one recess 337 is completely enclosed on all four sides by permeating material 330 between the edge 361 and the bolt hole 110 to inhibit flow of fluid at the lower face of the gasket from the aperture 102 to the bolt hole. The recesses 335, 337 may be alternatively shaped (e.g., having other than four sides), but the gasket 300 should include at least one fully enclosed recess between the edge 361 and the bolt hole 110 to improve sealability of the gasket.
The gasket 300 may have first elements 311 and/or second elements, or other parts or components, being otherwise shaped and/or arranged. For example,
Similarly,
The gasket 300, 400, 500 with corresponding patterned surfaces may be made by any suitable process or technique. One method for forming the gasket includes coating a continuous roll of mesh base sheet material with liquid polymer permeating material and allowing the permeating material to dry. The base sheet material may be immersed in a container of polymeric fluoroelastomer coating. The coated base sheet material may be removed from the coating and allowed to dry. Next, the coated base sheet material may be heated in an oven to allow at least partial curing of the permeating material. At this stage, the coated base sheet material may be cut into appropriate shapes corresponding to the desired shape of the gasket by a cutting die. The cut part may be placed between a press to flatten any curled edges from the die cutting process. Next, the cut part may be pressed between two heated plates each having a machined surface for forming the respective upper and lower patterned surface of the gasket. After forming the patterned upper and lower surfaces, the gasket 300, 400, 500 may be further heated to complete the cure cycle of the fluoroelastomer polymer. This technique of formed a patterned polymer surface gasket may be referred to as an embossing technique.
Various alternative methods and steps may be used in forming the gasket 300, 400, 500. For example, calendared rolls may be used to maintain the uniformity of the grid patterns. Further, heated embossing rolls may be used instead of a flat press. In another alternative method, the mesh base sheet material is coated with liquid polymer permeating material and dried and then the projections forming the grid, bead, or other patterns on the upper and lower faces of the gasket are applied by suitable printing, depositing, or dispensing techniques (e.g., screen printing, gravure printing, flexographic printing, lithographic printing, jetting, syringe dispensing, other automatic dispensing methods, etc.). Jetting and dispensing methods of creating patterned polymer projections and beads on the surface of a gasket will be discussed in greater detail below. In a further alternative method, a thin film of permeating material may be applied to the base sheet material by various suitable lamination techniques and then a heated embossing roll used to form the permeating material into the grid patterns of the gasket.
It is understood that the above methods and techniques for forming the gasket 300, 400. 500 are illustrative are not intended to be limiting. Further, the methods and techniques may include other processes or steps not discussed in detail herein without departing from the scope of this invention. For example, any of the above techniques and methods for forming the gasket may utilize either a continuous roll of base sheet material or a precut sheet of base sheet material. Furthermore, any of the above techniques and method may utilize only a partial coating of the base sheet material with permeating material rather than a complete coating.
The edge sealing projection 711 concentrates the compression load at the edge margin of the gasket 701 so as to reduce the total amount of secondary sealing material 709 that is needed to provide a fluid-tight interface between the gasket and the two sealing surfaces.
The edge sealing projection 711 may be applied to the primary sealing material 705 in a variety of methods including screen printing the secondary sealing material onto the base sheet 707 that has been previously coated with primary sealing material, injection molding the edge sealing member onto the base sheet coated with primary sealing material, spraying the secondary sealing material onto the base sheet coated with primary sealing material, or any other suitable application method.
It will be understood that with this exemplary construction and others contemplated hereby, the base sheet, permeating material, and/or primary and secondary sealing materials may be selected to provide a particular minimum gap or, conversely, a maximum compression between flanges. In doing so, the need for rigid spacers or other devices commonly used to maintain a gap between the flange surfaces may be eliminated. By way of example, and not by limitation, consider a metal or other semi-rigid mesh used as the pervious base sheet. Where the wires or strands of the mesh intersect, there is a total base sheet thickness approximately equal to the sum of the two strand diameters that restricts the ability of a flange to approach an opposed flange pressed against the opposite surface of the gasket. Thus, by selecting the base sheet to have a particular wire or strand diameter, the minimum gap between the flange surfaces can be controlled. Additionally, it is understood that many permeating materials and/or primary and secondary sealing materials, for example, polymers, are susceptible to stress relaxation, thereby resulting in extrusion from the flange area. By providing a minimum gap and, therefore, maximum compression, the polymer may be subject to less compressive force and, therefore, less extrusion under pressure. Alternatively, where it is desired to use a particular polymer, the base sheet can be selected to minimize stress relaxation and, therefore, extrusion under pressure. It will be understood that since the pervious base sheet and the permeating and/or primary and secondary sealing materials material work in concert, numerous combinations thereof may be selected to provide the desired properties of the resulting gasket.
Polymeric coatings, and particularly polymeric coatings applied to a gasket in a predetermined pattern as described above, can also be created through a relatively new technology known as “jetting.” Jetting refers generally to the application or dispensing of high viscosity fluids in the form of millions of small highly controlled microdots. In some aspects, jetting of high viscosity fluids bears similarities to ink jet printing, wherein small microdots of a low viscosity fluid, ink, are applied through a printer head to paper in a controlled way to create text, images, and photographs. High viscosity fluid jetting technology has been developed by various companies such as, for example, Asymtek, Inc. of Carlsbad, Calif., U.S.A. and has been used, for instance, in the electronics industry to apply coatings to circuit boards and other components. The technology also has been used to apply adhesives and sealants to joints of various components before there are assembled together. To the knowledge of the inventors, jetting technology has not been used to apply patterned coatings of high viscosity polymeric sealants and/or coatings to the surfaces of gaskets. The technology offers promise for creating highly customized gasket coatings because of its precision and versatility. For instance, custom designed gaskets with intricate and easily changeable patterns of sealants on their surfaces such as, for example, specially patterned beads designed to maximize sealability, are possible and can be created virtually overnight for testing or production. This has not been possible with prior art techniques such as those described above, including embossing, screen printing, and molding, which all require laborious and time consuming construction of molds, screens, and the like to produce even one gasket.
As can be seen from
Another technology that has been found useful in applying custom patterned beads and/or surface features to gaskets quickly and efficiently is robotic liquid dispensing technology. This technology differs from jetting technology primarily in the way in which liquid polymer is dispensed onto a gasket. In jetting technology, the polymer is dispensed in tiny and controllable microdots as described above. This allows for variations in, for example, the width, thickness, slope, and other characteristics of an applied bead of polymer by controlling the pattern, number, and volume of dispensed microdots. In dispensing technology, liquid polymer is dispensed from a dispensing head that functions as a pneumatic syringe. The syringe has a tip designed for dispensing a bead of polymer having a desired characteristic and the dispensing rate can be carefully controlled by controlling the pneumatic pressure that expels polymer from the tip. The dispensing head is carried on the arm of an industrial robot and a gasket base sheet, which may be a pervious or non-pervious base sheet with or without a primary or permeating polymer coating, is secured to a base. A controller coupled to the robot and dispensing head is pre-programmed to move the tip of the dispensing head over the surface of the gasket in a predetermined pattern and simultaneously to control the dispensing of polymer. In this way, a gasket with specially patterned beads is created in short order. Further, since the dispensing rate is controllable, the beads themselves can have varying characteristics along their lengths being, for example, wider or thicker at specified locations on the gasket than at others. Highly customized gaskets for specific sealing applications can thus be designed and produced in very short order for testing or use.
A supplier of dispensing heads that have been found to be useful in dispensing patterned sealing beads on gaskets is EFD, Inc. located at 977 Waterman Avenue, East Providence, R.I., USA. EFD, Inc. also is a source of computer controlled robots for use with their dispensing heads suitable for applying dispensed beads of polymer in predetermined patterns to the surfaces of gaskets. Another supplier of a suitable industrial robot for carrying out the patterned gasket bead dispensing methodology of the present invention is Janome, Inc. located at 1822 Brummel Avenue, Elk Grove Village, Ill.
A desired pattern of polymeric beads is engineered for the gasket using a CAD or other appropriate design software package. The pattern generally is designed to provide the most effective seal given, for example, the shape and size of the flanges to be sealed, their bolt patterns, and the like. For instance, for flanges with relatively large spans between bolt holes, thicker beads or multiple beads may be desired in the mid spans where clamping pressures are lower whereas thinner beads may be appropriate near and around the bolt holes where clamping pressures are higher. Many other and much more complex patterns are possible to accommodate even the most complicated flange configurations and applications. With the bead pattern engineered, instructions for controlling the robot and dispensing head are generated and uploaded to the controller of the dispensing apparatus 830 and dispensing head. The gasket is then secured to the table and the apparatus engaged. The controller controls the carriage 832 and the arms 833 and 834 to move the tip of the dispensing head over the surface of the gasket 838 in the pre-engineered pattern. Simultaneously, the controller controls the dispensing head to dispense polymer at predetermined and varying rates to create beads of varying (or non-varying) characteristics such as, for instance, varying widths, thicknesses, and the like. As a result, the pre-engineered bead pattern is applied to the surface of the gasket precisely, repeatably, and quickly without the need to construct ancillary equipment such as molds, screens, and the like.
a is an image of the results of a Fujifilm pressure analysis (known as a “Fujifilm Test”) performed on the gasket of
b is a photograph of a Fujifilm gasket test for a gasket where the bead applied with the dispensing methodologies of this invention was customized. Specifically, the bead was engineered to be higher in regions where less pressure is expected (i.e. in the mid-spans between bolt holes) and lower in regions of more pressure (in the vicinities of the bolt holes). From this test, it can be seen that the custom engineered patterned bead provides significantly more uniform sealing properties around the aperture of the gasket than the uniform bead used in the Fujifilm test of
c is a photo of a Fujifilm test on a polymer impregnated screen mesh gasket base sheet with no applied beads. The pattern of the screening on the base sheet is seen to produce a fine pressure matrix. Moreover, the reduced pressure in the mid-spans of the gasket between the bolt holes is clearly visible from this Fujifilm test.
a-24b illustrate in more detail the process for custom engineering and applying custom configured sealing beads to a gasket substrate according to the present invention. An initial step in the methodology is to create calibration data for a particular combination of variables in order to determine how the dimensions and particularly the height of a bead dispensed on a gasket substrate varies with, for instance, substrate characteristics, dispenser tip size, dispenser pressure, and speed of the dispenser tip over the gasket substrate surface. These calibration data can then be used to engineer a custom configured bead to a gasket substrate to meet a particular clamping requirement.
With these variables set for each base sheet configuration, the dispenser tip was moved over the surface of the gasket base sheet at various speeds and the width of the resulting bead was measured. Under the “speed” columns in
a and 24b illustrate the use of the calibration data to design custom engineered gasket bead configuration on a gasket base sheet.
It can be seen from the forgoing that it now is possible to custom engineer and produce quickly and easily a gasket having a highly complex sealing bead shape and configuration not possible with prior art techniques for applying beads to gasket surfaces. Further, immediate tests of a gasket can be made using, for instance, Fujifilm sheets, and fine adjustments to the shape and configuration of the bead can be made in very short order. In this way, virtually real time production of custom engineered gaskets is now possible for tailoring gaskets to optimize sealing under very specific conditions.
Although certain embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. Any directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are used only for identification purposes to aid the reader's understanding of the various embodiments of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the claims. Joinder references (e.g., joined, attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily imply that two elements are connected directly and in fixed relation to each other.
While the present invention is described herein in detail in relation to specific aspects, it is to be understood that this detailed description is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the present invention. It will be recognized by those skilled in the art, that various elements discussed with reference to the various embodiments may be interchanged to create entirely new embodiments coming within the scope of the present invention. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention. The detailed description set forth herein is not intended nor is to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications, and equivalent arrangements of the present invention.
The foregoing description of the invention illustrates and describes various embodiments of the present invention. As various changes could be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Furthermore, the scope of the present invention covers various modifications, combinations, alterations, etc., of the above-described embodiments that are within the scope of the claims. Additionally, the disclosure shows and describes only selected embodiments of the invention, but the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings, and/or within the skill or knowledge of the relevant art. Furthermore, certain features and characteristics of each embodiment may be selectively interchanged and applied to other illustrated and non-illustrated embodiments of the invention without departing from the scope of the invention.
This is a continuation-in-part of U.S. patent application Ser. No. 11/692,573 filed on Mar. 28, 2007 and claims priority to the filing date of U.S. provisional patent application Ser. No. 60/926,853 filed on Apr. 30, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60926853 | Apr 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11692573 | Mar 2007 | US |
| Child | 12112434 | US |
