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Liquid sealing gasket sheet materials
Patents pressure on the oil-sealing lip is prevented because the elastic dia;whrs$eheflded by the ptc--
Valve stem seal
assembly
According to the advantageous feature of the invention, the pressurestable zone is formed by a radial& inwardly extending flange of the housing which penetrates into the elastomer body. As a result, the housing and the flange function as a stiffening member so that the oMeAi.ng lip is shielded from the gas pressure.To make possible a removal of oil from the space between the oil-sealing lip and the gas=W3 hp, the g;rs-seallaghp angle that opens towards the oil-sealinglip is smaller than the gas-sealinglip angle that opens in the direction away from the oil-sealing lip. The set-up of these angles means that the pressure forces the gas seahng lip strongly onto the valve stem and the gas-sealing lip may not flip over in the space between the oil-sealing lip and the gas-sealing lip. For the purpose of obtaining a permanent gas sell, the inner diameter of the gas-sealing is smaller than the diameter of the valve stem so that the gas-sealing lip engages the valve stem with an overlap.
Patent number: US 5237971 (g-ted) Publication date: 24 August 1993 Inventoi: Clifford R Worsley Applicant: Goetze AG Thisinventionrelates to a valve stem seal assembly for valves of internal combustion engines where high pressures prevaiJ in the intake and/or outlet ports. The seal assembly (1) includes a rigid housing (2) in which an elastomer sealing body (3) is arranged that has at least two sealing lips engaging the valve stem and being effective in opposite directions. One of the sealing lips, which is closer to the combustion chamber served by the valve, functions as a gassealing lip (9); the other sealing lip which is more remote from the combustion chamber functions as a oil-sealinglip (5). The elastomer sealing body has an adhering portion insertable on a valve guide sleeve and an elastic diaphragm which permits radial displacments and which is connected with the oilsealing lip. The main objective of the invention is to provide an improved shaft stem seal assembly in which the oilsealing lip remains in contact with the shaft stem even in case of significant pressure fluctuations. The valve stem assembly for installation about a valve stem surrounded by a valve guide includes a sleeve-like elastomer body with: 0 an annular, outer, oil-sealing lip for surrounding the valve stem in the installed state of the seal assembly 0 an annular, inner gas-sealing lip for surrounding the valve stem in the installed state of the seal assembly l a diaphragm situated axially between the oil-sealing lip and the gas-sealing lip and being connected to the oil-sealing lip 0 a generally cylindrical mounting part (12) for surrounding and engaging the valve guide in the installed state of the seal assembly. The gas-sealing lip is directly connected with the mounting part externally of a region of the diaphragm. Sealing Technology
No. 5
Figure 1. the valve stem seal aasembly
The seal asembly also has a rigid housing surrounding and contacting the mounting part; and a pressure stable zone between the gas-sealing lip and the diaphragm for separating the oil-sealinglip from the gas-sealing lip with respect to vibrations. By virtue of the particular arrangement and the isolation of the gas-sealing lip from the oil-sealing lip with regards to vibrations, upon pressure increase the gas-sealinglip is presed with a greater force against the valve stem. An effect of the
Liquid sealing gasket sheet materials Patent number: WO 94/02760 (4W-aon) Publication da* 3 February 1994 Inventor: Nowaf Halout, Alexandra M Kavoulakis, Ellen R Roman0 Applicant: Armstrong World Industries This invention relates to gaskets designed to seal against liquids, in particular polar liquids.This particular type of gasket is found in engines and can seal against all ftuids, espedally polar liquids such as mhttures containing water or coolant. Engine gasket facings have, in the past, been prepared from mMures of f&es, t3ller-sand binders. The gasket material relies on soft binders to achieve a sufficient sealing ability in
II
Patents
the gasket sheet. The layered silicates and clays can Binders allow compression of the be obtained commercially. The filler sheet and obtain a sealing of internal in these gasketing sheets can include pores. Traditionally, gasketing materi- a non-gelling type of filler. This type of filler can be inorganic or orgac. als require high binder levels which Most preferably, it is mineraL A nonseal out the polar liquids. However, higher binder levels are more costly, gelling filler can be selected from the and result in lower torque retention, group consisting of: calcium silicate, mica, pyrophyllite, exfoliated vermian increased creep relaxation, and culite, talc, calcium carbonate, maghave a lower temperature stability. This invention provides gasketing nesium hydroxide, diatomaceous earth, phlogopite, silica, kaolinite, materials which have lower binder graphite, flake graphite, and cork. levels without a drop in sealabllity Clays (such as kaolinite) are preferred against polar liquids. In fact, these fillers. The most preferable non-gelmaterials can give good to excellent ling filler can be selected from the seals against polar liquids. group consisting of: talc, mica, kaolin, The term "polar liquid" includes and diatomaceous earth. liquids which are slightly polar and have less than complete miscibility in The non-gel forming filler included in the present gasketing is preferred to water (for example, alcohols like have at least about 75% by weight of butyl or isobutyl alcohol). particles less than 2 microns in The term "gel-forming mineral filler" indicates a mineral fiUer which diameter. If the filler cannot be characteristically swells and/or forms commercially obtained in this particle size, the particle size of the filler can a gel when it contacts water (or, for be reduced by such methods as example, alcohol). The present gasket materials will grinding. If a gasketing sheet is made by also seal other fluids such as isocompounding, the gel-forming filler is octane, and even gases. The seal mixed with a sufficient amount of a against such non-polar liquids and liquid (such as water, alcohol, etc.) to gases, however, is comparable with the sealability given by gasketing that form the gel. For this preparation method at least about 5% TDW binder does not contain the gel-forming will be needed. The mixed ingredifiller. ents are then spread (or laid) out in a Gasketing which does not have sheet or layer, and dried. Preferably the gel-forming filler cannot match the binder is water miscible. the high sealing ability (sealabUity) against polar liquids. The filler can be Preferably, the instant liquid sealing a gel-forming mineral filler or it can be gaskets are made by wet-laying. The gaskets obtained by this method have a mixture which includes both the better sealability than the gaskets of gel-former and a non-gelling filler. In order to reduce the binder level the same formulation which have with no loss in the sealability against been made by compounding. Using polar liquids, however, the filler must the wet-laying process, the ingredients (fiber, filler, and an optional include the gel-forming filler. A suitable gel.forming filler can be binder) are flocculated out of an selected from the group consisting of: aqueous suspension. Additives such as papermaker's alum are added in sepiolite, attapulgite, palygorskite, smectite, montmoriilonite, bentonite, amounts effective to achieve fiocculation (generafiy from about .02 to hectorite, hydrobiotite, chemically about 6% by weight). delaminated vermiculite and chemiAfter the binder has precipitated out cally delaminated mica A preferred gel-forming filler can be selected from of the suspension in floccuiation, the ingredients are dewatered by wetthe group consisting of: sepiolite, laying the flocculated solids (ingrehectorite, and bentonite. An even more preferred gel-forming filler can dients) into a substantially homogebe selected from the group consisting neous sheet materiaL Wet-laying can of: sepiolite and hectorite, particularly be done with or without pressing. where the binder is used at an amount The gasket sheet material is then dried. Usually a sheet-forming (paof about 5% TDW or less in the permaking) apparatus is used. As a gasketin~ sheet. The most preferred general rule, at least about 90% of the gel-forming filler(s) is sepiolite.
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solids are retained, recovery normally being in the range of from about 90 to about 9996. A good (and obtainable) solids recovery is about 99% or more solids retention. In preferred embodiments for preparing gaskets having improved sealability against polar liquids, the fiber and filler are combined in an aqueous suspension. In preparing the suspension, an amount of water is used which is sufficient to put the solids level suitably at from about 0.5 to about 3% or more preferably at from about .5 to about 2%. Agitation can be used to saturate the solid ingredients and achieve a uniformly mixed suspension of the solids. Agitation is also preferably applied while retying the ingredients in the suspension, and/or during the addition of the fiocculant, and/or during fiocculation. The binder (when used) can be added either before or after the flocculant. Binders can be mixed in the suspension with the filler and fiber, but the preferred embodiments call for adding the binder to the flocculation bath after the fiocculant is added and before wet-laying is begun. A "flocculant" is any additive or agent (including ncoagulantsn) which brings the binder, fiber, and filler out of the aqueous suspension for dewatertn8. Both fiocculants and coagulants can be used for this. Floccuiants and/or coagulants are well known in papermaking. One or more may be used. Suitable flocculants indude polyelectrolytes and/or soluble salts. The soluble salts are preferred. Preferred soluble salt flocculants can be selected from the group consisting oF. alumi~lum salts, ferric Salts, and stannic salts. Polyelectrolytes are low molecular weisht polymers which reverse the charge on particle surfaces. Preferred polyelectrolytes have molecular weights ranging from about 10,000 up to about 1,000,000 and charge densities ranging from 3 to 8 milliequivalents/gram. Suitable poly. electrolytes include polyethyleneimines, polyamines, substituted polyamines, etc. A preferred polyelectrolyte is
po~dmyidimethylammonium)
chloride whose molecular weight is between I00,000 and 400,000 and whose charge density is 6.2 milltequivalents/gram. In preferred embodiments, after the
Sealing Technology Na 5
Patents latex has precipitated (during flocculation), additives such as drainage aids and retention aids are added (with or without continued agitation). These additives can be similar to the polyelectrolyte-flocculant, and range from 100,000 up to 10,000,000 in molecu. lar weight. Some of these additives are charged and have charge densities ranging from about 3 down to 0.1 milliequivalents/gram in charge densities. They may be cationic, anionic, or nonionic and Include polyacrylamides, copolymers of acrylamide with substituted acrylates, polyethyleneimides, etc. The water is then drained from the slurry through a screen or on a typical Fourdrinier paper line to produce a sheet. At this time the sheet can also be pressed if desired. The gasketing sheet material is then dried. Preferably the sheet material is drum dried and then calendered. Ad~tional ingredients which are commonly used in gaskets can also be included in the present gasketing. Such materials, for example, include curing agents, pigments, and antioxidants. This also includes the additives which are included as processing aids during the preparation of the gasketing. Such additives can include dispersing agents, retention aids, and drainage aids as well as chemicals to adjust the pH. Adjustments to the pH are preferably made by adding a base. A pH in the range of from about 6 to about 9 is preferred. Any base capable of adjusting the water to the desired pH can be used. Alkali metal and alkalineearth metal hydroxides are preferred. A preferred base can also be selected from sodium aluminate, sodium carbonate, and sodium hydroxide. Suitably the base can be added to the water than preparing the suspension or at any other time before dewatering. For preferred embodiments, it is added either directly before or after the flocculant. The instant gasketing sheet materials can provide sealabilty of all fluids. Good seals against non-polar fluids (such as iso-octane) can be obtained. For non-polar fluids, however, it is preferred that the binder be in the range of from about 5 to about 18% by weight. The instant gasket materials which have at least about 5% TDW of binder have good sealability against
Sealing Technology No. 5
the non-polar liquids (this has been noted using ASTM method F-38); and at any given filler concentration, more gel-forming filler can be included (and less non-gelling filler) to have a gasket with an even better sealability against polar liquids. Since binder levels are lower, creep relaxation is lower for these gasketing sheets. They also have a high torque retention. With these qualities and characteristics, the present gasketing sheets are excellent engine gaskets. Polar-liquid sealing gaskets are gaskets which contain the instant gelforming filler so that they can provide a seal against and/or provide a seal in the presence of polar liquids such as water, ethylene glycol and other coolants. These gaskets, therefore, are particularly good for sealing water, coolant, water/oR mixtures, and water/coolant mixtures; the gaskets, furthermore, can be used as a sealing gasket for any fluid type. The instant gasketing sheets can be made into gasket facings, for example, such as cylinder head facings for the cylinder head gasket. Facing sheets can be saturated with binder-types of ingredients and given coatings. This can be done after the sheet is prepared and/or after it is put onto the supporting gasket core. Added saturation steps (such as impregnation, coating, and immersion) for facing materials fill internal pores and enable the sheet to give the performance required of a cylinder head gasket. The level of sealability which is needed in a gasket will depend on the particular application of the gasket. Thus, a more preferred (excellent) sealer is needed where the gasket is needed for 1) a low flange pressure, 2) a high internal pressure of the polar liquid against the gasket seal, or 3) an uneven flange surface. For a more preferred (excellent) level of sealability, the particular type (or formulation) of gasketing sheet material should give a coolant leakage rating of about 40 or more at 1500 PSI (flange pressure) in the coolant leakage rating test which is described in the examples which follow. The most preferred gasketing sheet materials will have a coolant leakage rating of 60 (very excellent) at 1500 PSI flange pressure; an acceptable (suitable) coolant leakage rating is down
to 10 at 1500 PSI flange pressure (for good sealabllRy). A preferred polar Hquid sealing gasket material (for a very good sealability) has a rating down to about 20 at 1500 PSI flange pressure when it is tested on the
Coolant Leakage Sating Rig. Gaskets with good (acceptable) sealing ability can easily be used for 1) higher flange pressures, 2) on smoother and/or more even flange surfaces, or 3) in locations having low internal pressures (20 PSI or less) of the fluid against the seal of the gasket. Gaskets with better sealing ability, however, are more preferred over the good sealers which have a rating of only I0 at 1500 PSI on the Coolant Liquid Sating Rig. To get the preferred, more preferred, and most preferred polar liquid sealability levels in the gasketin8 sheet materials, the amount of gel-forming filler is increased. An acceptable seating ability can be achieved in gasketing which is about 3% (TDW) or more in the gel-formin~ filler. At least about 12% by weight of the gel-forming mineral filler can be used to obtain a very good and even very excellent sealability against polar liquids. At least about 1696 by weight of the gel-forming filler is preferred to obtain a gasket with a higher sealability; the more preferred and most preferred sealability r a t i t ~ can be achieved. A preferred rat~ge is from about 16 to about 5596 of the gelforming filler in the gasket. Sealability does increase with an increased
concentration of gel.forming filler in the total amount of filler, although the most preferred sealability level can be achieved with mixtures of gel-forming and non-gel forming fillers. There is more than one important characteristic and requirements which is considered in prepartn8 and formulating gaskets. Preferred embodiments of the gasket sheet materials have filler which is from about 7 to about 5596 TDW of the gel-forming filler. Casketing which has a nongelling filler and a gel-forming filler is preferred for ease of processing, handling and having better handlin8 properties than a gasket where the filler is only the gel-formin8 filler. In addition to this, preparation is more dimcult when the filler consists only of the gel-former because drainage becomes Increasingly more difficult as
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Patents the concentration of the gel-forming filler increases over about 50% (by weight) of the total amount of filler. Preferred embodiments in the wetlaid processes, therefore, will have the gel-forming mineral filler being included in an amount less than about 50% by weight of the total amount of filler.
Bidirectional gasket with water energizing pockets Patent n u m b e r : US 5217 237 (granted) Publication date: 8 J u n e 1993 Inventor: J a m e s A Kelly, J a m e s A Westhoff Applicant: Poly-Tec P r o d u c t s Inc
12 12c
12c
,=
24a
Figure 2. A sectional view o f a gasket installed o n a pipe
The present invention relates to a novel bidirectional gasket (10) having self-energtsin8 water pockets which enhance the water-tisht seal provided shaped portion to form a pair of water by the gasket. The sealing pressure pockets, one of which becomes active increases with increasing water presdependent upon the direction in sure and the gasket design is capable which the gasket is deflected, to of accepting pipe diameters over a provide a water-tight seal which wider tolerance than conventional increases an effectiveness with the gaskets. increasing water pressure imposed on The gasket of the present inventhe gasket. The legs also provide tion is characterised by comprising a significantly greater body contact T-shaped anchoring portion and an Abetween the gasket and the pipe, shaped (12) or pear-shaped pipe further enhancing the water-tight engaging portion similar to those seal. found in conventional gaskets. The flexibility and compresibility As a departure from the conventional design, the A-shaped portion is of the gasket are increased through the use of nvoids in the head portion provided with a recess near its wide end which defines a pair of legs that of the gasket. The gasket material has a durometer comparable with conextend away from the head portion ventional gaskets; the durometer of and act as water seal flaps. The wide the gasket also contributes to the end of the A.shaped is joined to the effectiveness of the water pocket. anchoring portion by an integral The bendability, flexibility and connecting web (18) having a thickcompressibility of the gasket, in hess which is significantly reduced addition to providing a good water relative to the thickness of the tight seal also permit the gasket to adjacent anchorin8 portion; the connectin8 web greatly facilitating bend- accomodate a wider tolerance range ing of the connecting web and hence of pipe diameters. The weight of the gasket is further the gasket. reduced and the compressibility is The cotmectin8 web cooperates enhanced by the continous openings with the legs and recess in the A-
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21
or voids extending around the gasket and arransed within the A.shaped portion of the gasket, which voids are capable of being filled with a suitable liquid, in situations requiring reduced compresibility. A coupling web increases the gasket flexibiliW to such an extent that the gasket, in addition to providing a wider tolerance range for pipe diameter, provides a water-tight seal for pipes whose longitudinal axes are offset for desired alignment by an offset angle of as much as 15 ° as compared with a m~Ytmum offset angle of 10° obtainable when employing conventional gaskets of similar design. In addition, integral tapered projections provided near the narrow tip of the A-shaped portion serve as wipers which wipe lubricant applied to the external periphery of the pipe to facilitate coupling with the pipe, the wiping action further enhances the pipe/connector seal. The projection performing the wipin8 action is ultimately compressed against the surface of the pipe.
Sealing Technology Na 5
Valve stem seal
assembly
According to the advantageous feature of the invention, the pressurestable zone is formed by a radial& inwardly extending flange of the housing which penetrates into the elastomer body. As a result, the housing and the flange function as a stiffening member so that the oMeAi.ng lip is shielded from the gas pressure.To make possible a removal of oil from the space between the oil-sealing lip and the gas=W3 hp, the g;rs-seallaghp angle that opens towards the oil-sealinglip is smaller than the gas-sealinglip angle that opens in the direction away from the oil-sealing lip. The set-up of these angles means that the pressure forces the gas seahng lip strongly onto the valve stem and the gas-sealing lip may not flip over in the space between the oil-sealing lip and the gas-sealing lip. For the purpose of obtaining a permanent gas sell, the inner diameter of the gas-sealing is smaller than the diameter of the valve stem so that the gas-sealing lip engages the valve stem with an overlap.
Patent number: US 5237971 (g-ted) Publication date: 24 August 1993 Inventoi: Clifford R Worsley Applicant: Goetze AG Thisinventionrelates to a valve stem seal assembly for valves of internal combustion engines where high pressures prevaiJ in the intake and/or outlet ports. The seal assembly (1) includes a rigid housing (2) in which an elastomer sealing body (3) is arranged that has at least two sealing lips engaging the valve stem and being effective in opposite directions. One of the sealing lips, which is closer to the combustion chamber served by the valve, functions as a gassealing lip (9); the other sealing lip which is more remote from the combustion chamber functions as a oil-sealinglip (5). The elastomer sealing body has an adhering portion insertable on a valve guide sleeve and an elastic diaphragm which permits radial displacments and which is connected with the oilsealing lip. The main objective of the invention is to provide an improved shaft stem seal assembly in which the oilsealing lip remains in contact with the shaft stem even in case of significant pressure fluctuations. The valve stem assembly for installation about a valve stem surrounded by a valve guide includes a sleeve-like elastomer body with: 0 an annular, outer, oil-sealing lip for surrounding the valve stem in the installed state of the seal assembly 0 an annular, inner gas-sealing lip for surrounding the valve stem in the installed state of the seal assembly l a diaphragm situated axially between the oil-sealing lip and the gas-sealing lip and being connected to the oil-sealing lip 0 a generally cylindrical mounting part (12) for surrounding and engaging the valve guide in the installed state of the seal assembly. The gas-sealing lip is directly connected with the mounting part externally of a region of the diaphragm. Sealing Technology
No. 5
Figure 1. the valve stem seal aasembly
The seal asembly also has a rigid housing surrounding and contacting the mounting part; and a pressure stable zone between the gas-sealing lip and the diaphragm for separating the oil-sealinglip from the gas-sealing lip with respect to vibrations. By virtue of the particular arrangement and the isolation of the gas-sealing lip from the oil-sealing lip with regards to vibrations, upon pressure increase the gas-sealinglip is presed with a greater force against the valve stem. An effect of the
Liquid sealing gasket sheet materials Patent number: WO 94/02760 (4W-aon) Publication da* 3 February 1994 Inventor: Nowaf Halout, Alexandra M Kavoulakis, Ellen R Roman0 Applicant: Armstrong World Industries This invention relates to gaskets designed to seal against liquids, in particular polar liquids.This particular type of gasket is found in engines and can seal against all ftuids, espedally polar liquids such as mhttures containing water or coolant. Engine gasket facings have, in the past, been prepared from mMures of f&es, t3ller-sand binders. The gasket material relies on soft binders to achieve a sufficient sealing ability in
II
Patents
the gasket sheet. The layered silicates and clays can Binders allow compression of the be obtained commercially. The filler sheet and obtain a sealing of internal in these gasketing sheets can include pores. Traditionally, gasketing materi- a non-gelling type of filler. This type of filler can be inorganic or orgac. als require high binder levels which Most preferably, it is mineraL A nonseal out the polar liquids. However, higher binder levels are more costly, gelling filler can be selected from the and result in lower torque retention, group consisting of: calcium silicate, mica, pyrophyllite, exfoliated vermian increased creep relaxation, and culite, talc, calcium carbonate, maghave a lower temperature stability. This invention provides gasketing nesium hydroxide, diatomaceous earth, phlogopite, silica, kaolinite, materials which have lower binder graphite, flake graphite, and cork. levels without a drop in sealabllity Clays (such as kaolinite) are preferred against polar liquids. In fact, these fillers. The most preferable non-gelmaterials can give good to excellent ling filler can be selected from the seals against polar liquids. group consisting of: talc, mica, kaolin, The term "polar liquid" includes and diatomaceous earth. liquids which are slightly polar and have less than complete miscibility in The non-gel forming filler included in the present gasketing is preferred to water (for example, alcohols like have at least about 75% by weight of butyl or isobutyl alcohol). particles less than 2 microns in The term "gel-forming mineral filler" indicates a mineral fiUer which diameter. If the filler cannot be characteristically swells and/or forms commercially obtained in this particle size, the particle size of the filler can a gel when it contacts water (or, for be reduced by such methods as example, alcohol). The present gasket materials will grinding. If a gasketing sheet is made by also seal other fluids such as isocompounding, the gel-forming filler is octane, and even gases. The seal mixed with a sufficient amount of a against such non-polar liquids and liquid (such as water, alcohol, etc.) to gases, however, is comparable with the sealability given by gasketing that form the gel. For this preparation method at least about 5% TDW binder does not contain the gel-forming will be needed. The mixed ingredifiller. ents are then spread (or laid) out in a Gasketing which does not have sheet or layer, and dried. Preferably the gel-forming filler cannot match the binder is water miscible. the high sealing ability (sealabUity) against polar liquids. The filler can be Preferably, the instant liquid sealing a gel-forming mineral filler or it can be gaskets are made by wet-laying. The gaskets obtained by this method have a mixture which includes both the better sealability than the gaskets of gel-former and a non-gelling filler. In order to reduce the binder level the same formulation which have with no loss in the sealability against been made by compounding. Using polar liquids, however, the filler must the wet-laying process, the ingredients (fiber, filler, and an optional include the gel-forming filler. A suitable gel.forming filler can be binder) are flocculated out of an selected from the group consisting of: aqueous suspension. Additives such as papermaker's alum are added in sepiolite, attapulgite, palygorskite, smectite, montmoriilonite, bentonite, amounts effective to achieve fiocculation (generafiy from about .02 to hectorite, hydrobiotite, chemically about 6% by weight). delaminated vermiculite and chemiAfter the binder has precipitated out cally delaminated mica A preferred gel-forming filler can be selected from of the suspension in floccuiation, the ingredients are dewatered by wetthe group consisting of: sepiolite, laying the flocculated solids (ingrehectorite, and bentonite. An even more preferred gel-forming filler can dients) into a substantially homogebe selected from the group consisting neous sheet materiaL Wet-laying can of: sepiolite and hectorite, particularly be done with or without pressing. where the binder is used at an amount The gasket sheet material is then dried. Usually a sheet-forming (paof about 5% TDW or less in the permaking) apparatus is used. As a gasketin~ sheet. The most preferred general rule, at least about 90% of the gel-forming filler(s) is sepiolite.
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solids are retained, recovery normally being in the range of from about 90 to about 9996. A good (and obtainable) solids recovery is about 99% or more solids retention. In preferred embodiments for preparing gaskets having improved sealability against polar liquids, the fiber and filler are combined in an aqueous suspension. In preparing the suspension, an amount of water is used which is sufficient to put the solids level suitably at from about 0.5 to about 3% or more preferably at from about .5 to about 2%. Agitation can be used to saturate the solid ingredients and achieve a uniformly mixed suspension of the solids. Agitation is also preferably applied while retying the ingredients in the suspension, and/or during the addition of the fiocculant, and/or during fiocculation. The binder (when used) can be added either before or after the flocculant. Binders can be mixed in the suspension with the filler and fiber, but the preferred embodiments call for adding the binder to the flocculation bath after the fiocculant is added and before wet-laying is begun. A "flocculant" is any additive or agent (including ncoagulantsn) which brings the binder, fiber, and filler out of the aqueous suspension for dewatertn8. Both fiocculants and coagulants can be used for this. Floccuiants and/or coagulants are well known in papermaking. One or more may be used. Suitable flocculants indude polyelectrolytes and/or soluble salts. The soluble salts are preferred. Preferred soluble salt flocculants can be selected from the group consisting oF. alumi~lum salts, ferric Salts, and stannic salts. Polyelectrolytes are low molecular weisht polymers which reverse the charge on particle surfaces. Preferred polyelectrolytes have molecular weights ranging from about 10,000 up to about 1,000,000 and charge densities ranging from 3 to 8 milliequivalents/gram. Suitable poly. electrolytes include polyethyleneimines, polyamines, substituted polyamines, etc. A preferred polyelectrolyte is
po~dmyidimethylammonium)
chloride whose molecular weight is between I00,000 and 400,000 and whose charge density is 6.2 milltequivalents/gram. In preferred embodiments, after the
Sealing Technology Na 5
Patents latex has precipitated (during flocculation), additives such as drainage aids and retention aids are added (with or without continued agitation). These additives can be similar to the polyelectrolyte-flocculant, and range from 100,000 up to 10,000,000 in molecu. lar weight. Some of these additives are charged and have charge densities ranging from about 3 down to 0.1 milliequivalents/gram in charge densities. They may be cationic, anionic, or nonionic and Include polyacrylamides, copolymers of acrylamide with substituted acrylates, polyethyleneimides, etc. The water is then drained from the slurry through a screen or on a typical Fourdrinier paper line to produce a sheet. At this time the sheet can also be pressed if desired. The gasketing sheet material is then dried. Preferably the sheet material is drum dried and then calendered. Ad~tional ingredients which are commonly used in gaskets can also be included in the present gasketing. Such materials, for example, include curing agents, pigments, and antioxidants. This also includes the additives which are included as processing aids during the preparation of the gasketing. Such additives can include dispersing agents, retention aids, and drainage aids as well as chemicals to adjust the pH. Adjustments to the pH are preferably made by adding a base. A pH in the range of from about 6 to about 9 is preferred. Any base capable of adjusting the water to the desired pH can be used. Alkali metal and alkalineearth metal hydroxides are preferred. A preferred base can also be selected from sodium aluminate, sodium carbonate, and sodium hydroxide. Suitably the base can be added to the water than preparing the suspension or at any other time before dewatering. For preferred embodiments, it is added either directly before or after the flocculant. The instant gasketing sheet materials can provide sealabilty of all fluids. Good seals against non-polar fluids (such as iso-octane) can be obtained. For non-polar fluids, however, it is preferred that the binder be in the range of from about 5 to about 18% by weight. The instant gasket materials which have at least about 5% TDW of binder have good sealability against
Sealing Technology No. 5
the non-polar liquids (this has been noted using ASTM method F-38); and at any given filler concentration, more gel-forming filler can be included (and less non-gelling filler) to have a gasket with an even better sealability against polar liquids. Since binder levels are lower, creep relaxation is lower for these gasketing sheets. They also have a high torque retention. With these qualities and characteristics, the present gasketing sheets are excellent engine gaskets. Polar-liquid sealing gaskets are gaskets which contain the instant gelforming filler so that they can provide a seal against and/or provide a seal in the presence of polar liquids such as water, ethylene glycol and other coolants. These gaskets, therefore, are particularly good for sealing water, coolant, water/oR mixtures, and water/coolant mixtures; the gaskets, furthermore, can be used as a sealing gasket for any fluid type. The instant gasketing sheets can be made into gasket facings, for example, such as cylinder head facings for the cylinder head gasket. Facing sheets can be saturated with binder-types of ingredients and given coatings. This can be done after the sheet is prepared and/or after it is put onto the supporting gasket core. Added saturation steps (such as impregnation, coating, and immersion) for facing materials fill internal pores and enable the sheet to give the performance required of a cylinder head gasket. The level of sealability which is needed in a gasket will depend on the particular application of the gasket. Thus, a more preferred (excellent) sealer is needed where the gasket is needed for 1) a low flange pressure, 2) a high internal pressure of the polar liquid against the gasket seal, or 3) an uneven flange surface. For a more preferred (excellent) level of sealability, the particular type (or formulation) of gasketing sheet material should give a coolant leakage rating of about 40 or more at 1500 PSI (flange pressure) in the coolant leakage rating test which is described in the examples which follow. The most preferred gasketing sheet materials will have a coolant leakage rating of 60 (very excellent) at 1500 PSI flange pressure; an acceptable (suitable) coolant leakage rating is down
to 10 at 1500 PSI flange pressure (for good sealabllRy). A preferred polar Hquid sealing gasket material (for a very good sealability) has a rating down to about 20 at 1500 PSI flange pressure when it is tested on the
Coolant Leakage Sating Rig. Gaskets with good (acceptable) sealing ability can easily be used for 1) higher flange pressures, 2) on smoother and/or more even flange surfaces, or 3) in locations having low internal pressures (20 PSI or less) of the fluid against the seal of the gasket. Gaskets with better sealing ability, however, are more preferred over the good sealers which have a rating of only I0 at 1500 PSI on the Coolant Liquid Sating Rig. To get the preferred, more preferred, and most preferred polar liquid sealability levels in the gasketin8 sheet materials, the amount of gel-forming filler is increased. An acceptable seating ability can be achieved in gasketing which is about 3% (TDW) or more in the gel-formin~ filler. At least about 12% by weight of the gel-forming mineral filler can be used to obtain a very good and even very excellent sealability against polar liquids. At least about 1696 by weight of the gel-forming filler is preferred to obtain a gasket with a higher sealability; the more preferred and most preferred sealability r a t i t ~ can be achieved. A preferred rat~ge is from about 16 to about 5596 of the gelforming filler in the gasket. Sealability does increase with an increased
concentration of gel.forming filler in the total amount of filler, although the most preferred sealability level can be achieved with mixtures of gel-forming and non-gel forming fillers. There is more than one important characteristic and requirements which is considered in prepartn8 and formulating gaskets. Preferred embodiments of the gasket sheet materials have filler which is from about 7 to about 5596 TDW of the gel-forming filler. Casketing which has a nongelling filler and a gel-forming filler is preferred for ease of processing, handling and having better handlin8 properties than a gasket where the filler is only the gel-formin8 filler. In addition to this, preparation is more dimcult when the filler consists only of the gel-former because drainage becomes Increasingly more difficult as
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Patents the concentration of the gel-forming filler increases over about 50% (by weight) of the total amount of filler. Preferred embodiments in the wetlaid processes, therefore, will have the gel-forming mineral filler being included in an amount less than about 50% by weight of the total amount of filler.
Bidirectional gasket with water energizing pockets Patent n u m b e r : US 5217 237 (granted) Publication date: 8 J u n e 1993 Inventor: J a m e s A Kelly, J a m e s A Westhoff Applicant: Poly-Tec P r o d u c t s Inc
12 12c
12c
,=
24a
Figure 2. A sectional view o f a gasket installed o n a pipe
The present invention relates to a novel bidirectional gasket (10) having self-energtsin8 water pockets which enhance the water-tisht seal provided shaped portion to form a pair of water by the gasket. The sealing pressure pockets, one of which becomes active increases with increasing water presdependent upon the direction in sure and the gasket design is capable which the gasket is deflected, to of accepting pipe diameters over a provide a water-tight seal which wider tolerance than conventional increases an effectiveness with the gaskets. increasing water pressure imposed on The gasket of the present inventhe gasket. The legs also provide tion is characterised by comprising a significantly greater body contact T-shaped anchoring portion and an Abetween the gasket and the pipe, shaped (12) or pear-shaped pipe further enhancing the water-tight engaging portion similar to those seal. found in conventional gaskets. The flexibility and compresibility As a departure from the conventional design, the A-shaped portion is of the gasket are increased through the use of nvoids in the head portion provided with a recess near its wide end which defines a pair of legs that of the gasket. The gasket material has a durometer comparable with conextend away from the head portion ventional gaskets; the durometer of and act as water seal flaps. The wide the gasket also contributes to the end of the A.shaped is joined to the effectiveness of the water pocket. anchoring portion by an integral The bendability, flexibility and connecting web (18) having a thickcompressibility of the gasket, in hess which is significantly reduced addition to providing a good water relative to the thickness of the tight seal also permit the gasket to adjacent anchorin8 portion; the connectin8 web greatly facilitating bend- accomodate a wider tolerance range ing of the connecting web and hence of pipe diameters. The weight of the gasket is further the gasket. reduced and the compressibility is The cotmectin8 web cooperates enhanced by the continous openings with the legs and recess in the A-
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or voids extending around the gasket and arransed within the A.shaped portion of the gasket, which voids are capable of being filled with a suitable liquid, in situations requiring reduced compresibility. A coupling web increases the gasket flexibiliW to such an extent that the gasket, in addition to providing a wider tolerance range for pipe diameter, provides a water-tight seal for pipes whose longitudinal axes are offset for desired alignment by an offset angle of as much as 15 ° as compared with a m~Ytmum offset angle of 10° obtainable when employing conventional gaskets of similar design. In addition, integral tapered projections provided near the narrow tip of the A-shaped portion serve as wipers which wipe lubricant applied to the external periphery of the pipe to facilitate coupling with the pipe, the wiping action further enhances the pipe/connector seal. The projection performing the wipin8 action is ultimately compressed against the surface of the pipe.
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