CA2026727A1 - Method of forming a laminate and the product thereof - Google Patents
Method of forming a laminate and the product thereofInfo
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- CA2026727A1 CA2026727A1 CA 2026727 CA2026727A CA2026727A1 CA 2026727 A1 CA2026727 A1 CA 2026727A1 CA 2026727 CA2026727 CA 2026727 CA 2026727 A CA2026727 A CA 2026727A CA 2026727 A1 CA2026727 A1 CA 2026727A1
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- sheets
- bonding agent
- liquid bonding
- along
- laminate
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Abstract
ABSTRACT OF THE DISCLOSURE
Method for forming a laminate and a product formed therefrom. A thin layer of oil is applied to a facing surface of at least one of a plurality of adjacent sheets and a wax is applied along the longitudinal edges of a facing surface of at least one of the sheets. The sheets are combined into a laminate by being passed between a pair of rollers which apply sufficient pressure to remove excess oil from between the facing surfaces and to spread the wax thereby forming a continuous seal along the longitudinal edges of the laminate. Air between the facing surfaces is displaced by the oil and the wax forms the seal to prevent reentry of the air and seepage of the oil along the longitudinal edges of the laminate. The laminate is tightly held together to permit handling or fabrication without delamination.
Method for forming a laminate and a product formed therefrom. A thin layer of oil is applied to a facing surface of at least one of a plurality of adjacent sheets and a wax is applied along the longitudinal edges of a facing surface of at least one of the sheets. The sheets are combined into a laminate by being passed between a pair of rollers which apply sufficient pressure to remove excess oil from between the facing surfaces and to spread the wax thereby forming a continuous seal along the longitudinal edges of the laminate. Air between the facing surfaces is displaced by the oil and the wax forms the seal to prevent reentry of the air and seepage of the oil along the longitudinal edges of the laminate. The laminate is tightly held together to permit handling or fabrication without delamination.
Description
METHOD OF FORMING A LAMINATE
AND THE PRODUCT THEREOF
BACKGROUND OF THE INVENTION
This invention relates to a method of forming an improved laminate and a lamillated cors formed therefrom. More particularly, the invention relates to applying a liquid bonding agent and a sealing agent to the facing surfaces of 10 sheets and applying sufficient pressurs to the sheets to remove excsss liquidbonding agent to displace air from between the facins surfaces of the sheets while spreading the sealing agent to prevent reentry of the air and to prevent seepage of the liquid bonding agent along the edges of the sheets.
There are several applications such as electric powar transformsrs, 1 S motors, electronics and catalytic converters employing thin gauge sheets. Thin gauge electrical steel sheets or amorphous metal sheets for electrical applications reduce magnetically induced eddy currents by reducing the cross-sectional area through which those currents may flow. Grain oriented steel sheets have a thickness iess than .5 mm, typically in the ran~e of .18 to .35 mm.
AND THE PRODUCT THEREOF
BACKGROUND OF THE INVENTION
This invention relates to a method of forming an improved laminate and a lamillated cors formed therefrom. More particularly, the invention relates to applying a liquid bonding agent and a sealing agent to the facing surfaces of 10 sheets and applying sufficient pressurs to the sheets to remove excsss liquidbonding agent to displace air from between the facins surfaces of the sheets while spreading the sealing agent to prevent reentry of the air and to prevent seepage of the liquid bonding agent along the edges of the sheets.
There are several applications such as electric powar transformsrs, 1 S motors, electronics and catalytic converters employing thin gauge sheets. Thin gauge electrical steel sheets or amorphous metal sheets for electrical applications reduce magnetically induced eddy currents by reducing the cross-sectional area through which those currents may flow. Grain oriented steel sheets have a thickness iess than .5 mm, typically in the ran~e of .18 to .35 mm.
2 0 Amorphous metal sheets typically have a thickness of about .02 to .05 mm.
It is well known the above type electrical devic~s are more afficient when the thickness of the sheet is decreased with the lower limit for the sheat thicknesses determined by manufacturin~ considerations. However, reducing the sheet thickness has undesirable effects on handling and fabrication 2 S productivity. Handling tissue-like thin sheets is a problem because the sheets are fragila and prone to damage during handling. The very thinness of the sheets reduces the productivity during processing and fabrication, making the pr~duct more labor intensive to utilize.
f ~
The prior a t discloses adhesiv0s, varnishes, oxides or mixtures thereof which may be applied to the surfaces of sheets so that several of the sheets canbe bonded (or laminated) together for simultaneous processing. Processing such a laminate greatly increases productivity and diminishes handling 5 problems since the laminate is thicker and more rigid than a single sheet.
Nevertheless, ~here are several disadvantages when using adhesives, varnish0s or oxides to bond sheets which are discussed at langth in pendin U.S. patent application serial no. 07/043077, filed April 27, 1987, having a common assignee and incorporated herein by reference. For axample, to 10 develop a good bond between sheets requires the bonding agent to be applied as a relatively thick layer creatins space between adjacent sheets. This is undesirable for bonded laminates used in electrical applications which are wound or stacked because the increased spacing between the sheets decreases the space factor. Even a thinly applied adhesive is undesirable 1 5 because it tends to shrink when cured. Such a shrinkage, particularly for thin metal sheets, may strain or induce stress into the sheets. A further disadvantage when using chemical bonding is that an elevated temperature may be required to cure the bonding agent. Such an slevated temperature may dirninish the effects of domain refinement treatments for electrical steel sheets. Another 2 0 disadvantage when using chemical bonding is that ths sheets become rigidly connected. Winding a rigidly formed electrical steel lamlnate into a coil may induce stress thereby increasing core losses of the laminate. A further disadvantage with chemical or ceramic bonding is that the bonding layers tend to be brittie. Cutting, punching or corrugating may fracture a brittle bonded layer 2 ~ causing the sheets to delaminate.
~ . . ! f , ,:
My pending patent application 07/043077 discloses a larninate can be formed ~hat will resist separation indefinitely by applying a liquid of an appropriate viscosity to tha facing surfaces of sheets and applying sufficient pressure tn the shee~s to rsmove excess liquid and to displace air from between 5 the facin~ surfaces of ~he sheets. The liquid remaining between the facing surfaces forms a seal preventing reentry of the air which enables the laminate to rasist separation during subsequent prscessing and fabrication. The laminate formed has no increase in the space between its sheets and no induced stress in its sheets. Unfortunately, some of the liquid remaining between the sheets 10 seeps out from between the sheets along the sheet edgss. Such ss~page may cause a number of physical problems during subsequent processing of a laminate when punchin~ to form stacked laminates. In the case where transformer oil was used as the bondin~ liquid to forrn laminated elsctrical steel sheets, oil buildup on a punch prsss caused the laminate to slip in the driv~
15 system, making it difficult to ob~ain precisely mitred cuts such as are needed to build a transformer core from electrical steel sheets. Saepage also may result in the bondin~ llquid transferring onto the exterior surfaces of the larninated sheets so that stacked cut laminatad sheets become stuck together makin~ it difficult to align properly in a core stack. Delamination may even occw when 2 0 handling the laminated sheets or punchings.
Accordingly, there remains a naed for an improved technique for forming a laminate using a liquid bonding agent wherein seepage of the liquid bonding agent from between the facing surfaces of the formed iaminate is minimized or prevented.
"'~ rJ ~
BRIEF SUMMARY OF THE INVENTION
This invention relates to a method of forming an improvad laminate and a laminated core formed therefrom. A liquid bonding agent and a sealin~ agent 5 are applied to a facing surface of at least one of a plurality of sheets. Pressure is applied to the sheets to remove excess liquid bonding agent and to displace air from between the facing surfaces of the sheets and to spread the sealing agent to form a continuous barrier along each longitudinal edge of the formed Iaminate to minirnize seepage of the liquid bonding agent along the longitudinal10 edges of the laminate Principal objects of my invention are to form a laminate using a liquid bonding agent wherein the laminate resists separation, has no decrease in its space factor, and can be fabricated without delamination.
A feature of my invention is to form a laminate from two or more sheets 15 using a liquid bonding agent and a sealing agent.
Another feature of my invention is to form a laminate using a liquid bonding agent by applying a sealing agent along longitudinal ed~es of at least one facing surface of a plurality of sheets to form a continuous barrier to prevent seepage of the liquid bonding agent along the longitudinal ed~es of the formed 2 0 laminate.
Another feature of my invention is to form a laminate using a liquid bonding agent by applying a sealing agent along longitudinal edges and at a position intermediate the longitudinal edges to at least one facin~ surface of aplurality of sheets to form continuous barriers along the longitudinal edges and2 5 at the intermediate position, slitting the laminate along the intarmadiats position into narrower width iaminates, whereby the sealing agent prevents seepage of the liquid bonding agent along the longitudinal edges of the forrned laminates.
Another featur~ of my invention is to form a laminate using a low viscosity liquid bonding agent and a high viscosity sealing agent to preYent seepage of S the bonding asent along longitudinal edges of the formed laminate.
Another feature of my invcntion is to form a larninate using a liquid bondin~ a~ent havin~ a viscosity no ~reater than about 80 cP at 24C and a sealing agent having a viscosity no greater than about 2500 cP at 24C.
Another feature of my invention is to form a laminate by providing at l~ast 10 two sheets each having a facing surface, applying a liquid bonding agent to one of the facing surfaces of the sheets, applying a sealing agent along the longitudinal ed~es sf one of the facin~ surfacos, appiying pressure to the sheets to removc excess liquid bonding agent from between the surfaces and forming a continuous` barrier by sprcading the sealing agent between the surfaces as 15 the surfaces are brought into contact with each other, whereby air between the surfaces is displaced by the liquid bonding agent and the sealing agant prevents reentry of the air and minimizss seepaye of the liquid bonding agent along the edges of the formed laminate.
Another foatur~ of my invention is to form a laminate from a plurality of 2 0 grain orisnted steel sheets each having a facing surface and a thickness l~ss than about .5 mm, passing the sheets along a feedpath at a prode~ermined speed, applying a liquicl bonding agent having a viscosity no ~r~atar than about80 cP at 24C to one of the facing surfaces, applying a sealing agent having a viscosity no greater than than 2500 cP at 24C along the longitudinal edges of 25 one of the facing surfaces, passing the sheQts between a pair of rollers, .J
applying pressure to the sheets by the rollers to remove excess liquid bonding ag0nt from betwesn the surfaces and forming a continuous barrier by the sealing agent betwesn the facing surfaces as the facing surfaces ara brought into contact with each other, whereby air between the surfaces is displaced by 5 the liquid bonding agent and the sealing a~snt prevents reentry of the air an minimizes seepage of ths liquid bonding agent along the edgss of the formed laminate.
Advantages of my invention include reduction in manufacturing costs of a laminate which can be siit, cut or punched with little or no seepa~e of the 10 liquid bonding agent and production of fabricated cores using the laminates whose sheets are free from strain and induced stress.
The above and other objects, features and advantagss of my invention will become apparent upon consideration of the detailed description and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic showing two sheets moving along a feedpath being laminated ~oge~har by a pair of sealing rollers and the laminate being wound 2 0 into a coil, FIG. 2 is a cross-section view along line 2-~ of FIG. lt FIG. 3 shows an enlarged fragmentary cross-seotion view of laminated sheets of my invention, FIG. 4 shows an enlarged longitudinal section view of two sheets being 2 5 pressed together according to my invention.
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DETAILED DE!;CRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fl(i. 1, reference numeral 12 denotes a sheet being uncoiled from a coil 10 and fed at a predetermined speed along a feedpath 13 while 5 passing over a wax applicator 17. Anether sheat 16 is fed at the sam~ speed from a coii 14 under an oiling roller 18. Sheet 16 is brought together with sheet 12 by a change of direction roller 20.
For my invention, it will be understood a sheet is meant to include continuous strip, foil, ribbon and the like as well as strip cut into individual10 lengths. Preferably, the sheet will include cold reduced or cast steel and amorphous base metals having a thickness of less than about .5 mm. A more preferred sheet includes grain oriented steel having a glass insulativs coating on both sides of the sheet with a total thickness of the sheet and coating layers less than about .35 mm. U.S. Patent 3,948,786 - Evans, incorporated herein by 15 reference, discloses grain oriented steei having Mg-PO4 glass insulative coatings.
Wa~ applicator 17 can b~ any conventional mechanical devic~ such as a sprayer, a capillary-action applicator, a wipin~-type roller, an extnuder, and the like. For exampls, wax applicator 17 may include a heater 19, a faQd tube 21, 20 and a plurality of nozzles 23 for applying a sealing agent 34 along each longitudinal edge of the facing surface of sheet 12. Oiling roller 18 applies a thin coating of a liquid bonding agent to the facing surface of sheet 16. Sheets 12 and 16 pass between a pair of s~aling or consolidation rollers 22 and 24 which apply sufficient pressure to sheats 12 and 16 so that the adjacent (facing~
2 5 surfacss of sheets 12 and 16 are brought into intimate contact with each other.
~ ~ J r~ S~ ~' Continuous films of liquid bonding agent and sealing agent substantially displace all air between the facing surfaces to form a laminate 26. Laminate 26 is wound around a mandrsl 28 forming a coil 30.
The clearance between rollers 22 and 24 preferably should not be less 5 than the combined thicknesses of sheets 12 and 16. For grain oriented sheets, rollers 22 and 24 must apply sufficient pressure to remove excess liquid bonding agent to displace air and to spread the sealing agent to form a continuous barrier or seal along both longitudinal edges oS the formed laminate without inducing stress into sheets 12 and 16.
1 0 FIG. 1 illustrates how a sealing agent is applied by wa~ applicator 17 to the bottom (facing) surface of sheet 12 and a liquid bondin~ agent is applied byroller 18 to ~he top (facin~) surface of sheet 16. Wax applicator 17 also could be used to apply the sealing agent to the top (facing) surface of sheet 16 and roller 18 could be used to apply the liquid bonding agent to the bottom (facing)15 surface of sheet 12. Alternatively, the bonding agent and the sealing agent could be applied to both of the facing surfaces of sheets 12 and 16. I~ will be understood the sealing agent can be applied to a facing surfacs of a sheet in a number of patterns such as a continuous line, parallel lines, squares, cross-hatched lines, sinusoidal lines, an extruded bead, and the like so long as a 20 continuous barrier is formed along the longitudinal edges when laminating thasheets. The liquid bonding agant can be applisd as a roller coating or sprayed as a fine mist. Depending on the equiprnent available, the number of sheets simultaneously fed along feedpath 13 and the type of material being laminated, it may be advantageous to apply ~he liquid bonding agent and the sealing agent 2 5 to a sheet during a previous processing operation. In any event, the liquid ? ;~
bonding a~ent and sealing agent are applied only to sheet surfaces which are facing surfaces when the sheets are combined into a laminate.
FIG. 2 illustrates a cross-section of sheets 12 and 16 taken along line 2-2 of FIG. 1 before sheets 12 and 16 are combined by rollers 22 and 24 into 5 laminate 26. Small beads of sealing agent 34 are placed along each of the longitudinal adges 36 and 38 on facing surface 32 of sheet 12. A thin film 42 ofthe liquid bonding agent is placed on facing surface 40 of sheet 16. If laminate26 is to be slit into narrower widths, additional sea3ing agent would be appliedlongitudinally along facing surface 32 at those positions whsre the laminate is 10 to be slit. For an electrical steel laminate that is to be slit and mitred into core punchings at an angle of 45 degrees, the additional sealing agent applied at those positions to be slit preferably would be in a pattern such as square, cross-hatched, or sinusoidal to insure the sealing agent extends continuously along the longitudinal and transverse edges of the slit and cut laminates.
FIG. 3 illustrates an enlarged fragmentary cross-section view of a portion of laminate 26 formed from sheets 12 and 16 illustrated in FIG. 1. The planar surfaces of metallic sheets normally are not perfectly flat and are somewhat roughened. This rnsans facing surface 32 of sheet 12 will no~ ba in continuous contact with an adjacent facing surface 40 of sheet 16. Facing surfaces 32 and 2 0 40 engage each other at point contacts 44. As sheets 12 and 16 are brought into contact with each other by rollers 22 and 24, void areas 46 representing non-contact points between surfaces 32 and 40 are filled with liquid bonding ag~nt 42. Sealing agent 34 is spread to form thin continuous barriers or dams along the longitudinal edges of laminate 26. FIG. 3 illustrates a thin barrier 34a 25 form6d by rollers ~2 and 24 by spreading sealing agent 34 along longitudinal 7 2 ~
edge 38. The separation between sul~aces 32 and 40 at non-contact points, i.e.
void areas 46, will be Isss than about .005 mm. Air is displaced as excess liquid bonding agent is squeezed from betwa~n surfacas 32 and 40. A
continuous film of sealing agent 34a formed along lon~itudinat edges 36 and S 38 betwaen surfaces 32 and 40 of sheets 12 and 16 pravsnts reentry of the air and prevents seepage of liquid bonding agent 42 from between facing surfaces 32 and 40 alon~ the longitudinal edges of larninate 26. Accordingly, sheets 12 and 16 are tenaciously held together. Without barri~rs 34a along the longitudinal edges, liquid bonding agent 42 could saep out from betw~en the sheet facing sur~aces as illustrated by seepage 42a.
FIG. 2 illustrates beads 34 of sealing agent being applied along longitudinal edges 36 and 3~ of sheets 12 and 16. If laminate 26 illustrated in FIG. 3 is slit longitudinally into two or more narrower width laminates, liquid bonding agent 42 could seep from between facing surfaces 32,40 along the newly cut longitudinal edges of the narrower laminates. In this situation, it isdesirable to apply additional sealing agent 34 along the facing surface of the sheet at those positions corresponding to where the she0t would be slit so that both longitudinal edges of each laminate include a continuous sealin~ barrier 34a. For a laminate to be slit into two laminates of equal width, sealiny agent 34 woulct be applied to the facing surface approximately midway b0tween opposing edges 36,3a.
Not being bound by theory, it is believed the laminate is tightly held together by a pressure differential existing between voids 46 filled with the iiquid bonding agent and/or sealing agent and the ambient atmospheric pressure surrounding taminate 26. In other words, sheets 12 and 16 resist 1~
tJ
delamination since the interlaminar pressure upon separation would decrease below ambient atmospheric pressur~ pushing against the outside surfaces of laminate 26 as illustràted by arrows 48 in FIG. 4. Facing surfaces 32 and 40 of sheets 12 and 16 respectively include a bead of sealing agent 34 and a thin 5 layer of liquid bonding agent 42. Sheets 12 and 16 ars being fed from left to right ~hrough the bite of rollers 22 and 24. As rollers 22 and 24 brin~ surfacas32 and 40 into intimate contact with each other, a meniscus 50 is formed and displaces air 52 as sealing agent 34 and axcess liquid bonding agsnt 42 are displaced from between facing surfaces 32 and 40.
The liquid bonding agent can be any low viscosity liquid preferably having a viscosity no greatar than about 80 cP at 24C when applied lo the sheets. Using a bonding agent having a higher viscosity makes it difficult to obtain a good space factor and to avoid shifting of the laminated sheets.
Acceptable bondiny agents include water, alcohol, oil and the like. For hi~her viscosity bonding agents, it may be desirable to heat the bonding agent to a ternperaturs above arnbient for application to the sheet. For cut electrical steel sheets, the bonding agent is formed into a continuous film to provide for continuous interlaminar insulation to preserve magnetic quality. A natural or synthetic transformer oil is preferred for this purpose. The important 2 0 considerations are that the bonding agent adequately wets the surfaces of the shests, is compatible with the environment in which the laminate will be used, and has the necessary viscosity.
For a sealing agent, a relatively high viscosity iiquid or a solid such as wax can be used having a viscosity preferably greater than about 25û cP at 2 5 24C. Waxes having a viscosity greater than about 2500 cP at 245 are difficult ~ ~"j f~ ,? 7 to extrude. The added force necess,ary to extrude thick resin-like waxes could produce microplas~ic strain to the sheets which would harm the core loss of electrical steel. A sealing agent which is solid at ambient t~mperature, such ashard beeswax, would induce coil set and harm tha stress condition of slectrical 5 steel. As in the case of the liquid bonding agent, it may be desirable to heathigher viscosity sealing agents to a temperature above ambient for application to sheets. The important considerations for the sealing agent are the same as that for the liquid bonding agent and additionally to have sufficient viscosity to retard or prevsnt seepage of the li~uid bonding a~snt through the conUnuous 10 barriers formed alon~ the longitudinal edges of the laminate.
Viscosity is a measurement of a liquid's resistancs to flow due to the attraction between moiecules. The greater the attractive force, the slower the liquid is to flow. Ths viscosity of the liquid bondins agent and the sealing agent used is important because it effects the flow rate of meniscus 50 between facing15 surfaces 32 and 40 when joined together by rollers 22 and 24 as illustrated in FIG. 4.
As disclosad in pending patent application 07/043077, I have determined experimentally that a variaty of low viscosity liquids perform well as a bondin~agent. Cores used as transformers in electric power transmission frequQntly are 2 0 permanently immersed in and cooled by a transformer oil. Using this oil as the bonding liquid is particularly advantageous in that it is compatible with the transformer oil. For some applications. the formed core may receive a 7inal heattreatment before its end use. For those heat treated cores where carbon in a hydrocarbon based liquid bonding agent could contaminate the sheet base metal, i.a. ~rain oriented steel, a synthetic non-carbonaceous oil could be usedas the bonding agent.
By way of example, conventional grain oriented elec~rical steel sheets 7.65 crn wide, 30.5 cm iong and .18 mm thick were coatsd with a 5-6 gm/m2 insulativ~ coating applied over a mill glass coatin~. In tests 1-3, only a liquid bonding agent was applied to the sheets. A silicone type transformer oil having a nominal viscosity of 40 cP at 24C was appiied by brushing oil onto one facing surface of eaoh pair of the steel sheets. Two sheets wsre laminated by passing the sh~ets through a pair of 76 mm diametcr neopren~ roliers and appiying sufficient pressure to r~move excass transformer oil and to displace air from between the facing surfaces. In tests 4-6, only a sealing agent was used.
An organic wax having a viscosity of 500 cP at 24C was applied by contact wiping onto one facing sheet surface as a series of parallel lines aach having awidth of about 10 mm and spaced at about 25 mm int~rvals alon~ the longitudinal (rolling) direction of the sheets. The wax sealing agsnt was spreadinto a thin film between the facing surfacas of the sheets by applying sufficient pressure to the axterior surfaces of ths sheets. All the tests were evaluated immadiately after laminating and after subjected to metal cuttin3. Tssts 1-3 2 O resuited in good quality laminates and preserved the intrinsic rnagnetic quality of the ~rain oriented eleotrical st0el. Avsrage cor~ loss at 15 kG and 17 kG wasincreas~d by .8% and .9% respectively. However, seepage of ths transformer oil from between the sheets along ~he edges was evident during consolidation of the sheats and during shearing of the laminates. As was expected for ~es~s 4-6, saepage did not occur since only a high viscosity sealin~ agent was used.
However, the laminates produced were of poor quality which experienced considerable deterioration in their magnetic quality when sheared. Average core loss at 15 kG and 17 kG increased 5.1% and 5.2% respectiv~ly. Tests 4-6 demonstrate that the use of a sealing agent alona without a llquid bonding S agent to form a continuous film between the sheet facing surfaces will not prevent deterioration of ma~netic quality. Metal-to-metal contact, i.e.
interlaminar "shorting~, occurs when continuous interlaminar insulation is lacking and produces circuiating or eddy currents during AC magnetization.
This shorting is ~he result of loss of the insulative coating from the sheet 10 surfaces if the formed laminats is cut when making cores. When a continuous film of the liquid bonding agent is present, the insulativo coating still flakes off when cutting the metal sheets but the bonding agent apparently holds the powdered insulative coating at the point of cuttin~ keepin~ ths sheets from coming into contact with each other.
1 5 i~pl~ 2 High permeability oriented electrical steei sheets 7.65 cm wide, 30.5 cm long and .23 mm thick were coated with a 9-10 gm/m2 insulativs coating applied ov~r a milJ glass coating. In tests 7-10l the same liquid bonding agent was applied in a similar manner to that for tests 1-3 above. The same sealing 2 0 agent and a similar method of application to that for tests 4-6 was used for tests 11-14 sxcept the s0aling agent was applied in a series of parallel bands with each band having a width of about 10 mm and spacsd at abeut 30 mm intervals. All the tests again were evaiuated immediately after laminating and aRer subjectcd to metal cutting. The rosults for the laminates produced from 25 tests 7-14 were substantially the same as reported above for tests 1-6.
Magnetic quality for laminates made from tests 7-10 using only a liquid bonding agent was good but seepage of the bondin~ agent occurred during consolidation of the shsets and after shearing of the laminates. Average core loss at 15 kG and 17 kG increased -0.3% and 0.8% respectively. The laminates produced from tests 11-14 were of poor quality and the average core loss at 15 kG and 17 kG increased 2.4% and 4.3% respectively.
Example ~
Additional laminates were prepared according to the invention from shaets identical to those for Example 2. Sheets for tests 15-17 had the sam~
liquid bonding agent and manner of application as described for tests 1-3 in Exampl~ 1. After applying the liquid bondin~ agent to the sheets, the sealing agent described for tests 4-6 in Example 1 was applied also to tests 15-17 in the form of a 10 mm wide bead aiong the longitudinal and transverse edges of the sheets. The sheets were then consoliciated into laminatee in the same manner 1 5 as that described ~r tests 4-6 in Example 1. No seepage of lhe bonding agent along any of the ed~es of the laminates occurred after consolidation of the sheets or after shearing of the laminates. The ma~netic quality of ~he laminateswas excellent both before and after shearing. The average cora ioss for 15 kG
and 17 kG was well within the ran~e of the test resuits r~ported above when 2 0 only liquid bonding agent was used for tests 1-3 for Exampla 1 or tests 7-10 for Example 2. During consolidation of the sheets, it was demonstrated the sealing agent was spread into a thin continuous film along the edges of th0 formed laminates which retained the liquid bonding agent betwsen the facing surfaces of the sheets forming the laminates.
2 5 Results of the trials discussed above are summarized in Tabls 1.
:~ble ~
T~ ~ Laminate Quality After Sh~a~ing $eepa~ ~ftec She,,~r~n~ ?
good yes 2 good yes 3 good yes 4 poor no poor no 6 poor no 7 ~ood yes 8 good yes 9 good yss good yes 11 poor no 12 poor no 15 1 3 poor no 14 poor no 15 (invontion) good no 16 (invention) good no 17 (invention) good no While only one embodiment of my invention has been described, it will be understood various modifications rnay be made to it without deparling from the spirit and scope of it. For example, various liquid bonding agents and sealing a~ents may be used so long as they are compa~ible with the 2 5 environment within which the laminats is to be used and hava ~he necessary if ~ f. ~ I ~/`s ,~;
viscosity to form a seal when formed into very thin layers. Two or more sheets may be lan~inated simultaneously usin~ various maans to apply tha liquid bonding agent and sealin~ agent to the facing surfaces of at least one of the sheets. One or both surfaces of the sheets may have previously appliad 5 coatings such as metallic or glass insulative coatings. The laminate may be wound into a core, forrned into a stacked core of cut laminates or otherwise fabricated. Thsrefore, the limits of my invention should be determined from the appended claims.
It is well known the above type electrical devic~s are more afficient when the thickness of the sheet is decreased with the lower limit for the sheat thicknesses determined by manufacturin~ considerations. However, reducing the sheet thickness has undesirable effects on handling and fabrication 2 S productivity. Handling tissue-like thin sheets is a problem because the sheets are fragila and prone to damage during handling. The very thinness of the sheets reduces the productivity during processing and fabrication, making the pr~duct more labor intensive to utilize.
f ~
The prior a t discloses adhesiv0s, varnishes, oxides or mixtures thereof which may be applied to the surfaces of sheets so that several of the sheets canbe bonded (or laminated) together for simultaneous processing. Processing such a laminate greatly increases productivity and diminishes handling 5 problems since the laminate is thicker and more rigid than a single sheet.
Nevertheless, ~here are several disadvantages when using adhesives, varnish0s or oxides to bond sheets which are discussed at langth in pendin U.S. patent application serial no. 07/043077, filed April 27, 1987, having a common assignee and incorporated herein by reference. For axample, to 10 develop a good bond between sheets requires the bonding agent to be applied as a relatively thick layer creatins space between adjacent sheets. This is undesirable for bonded laminates used in electrical applications which are wound or stacked because the increased spacing between the sheets decreases the space factor. Even a thinly applied adhesive is undesirable 1 5 because it tends to shrink when cured. Such a shrinkage, particularly for thin metal sheets, may strain or induce stress into the sheets. A further disadvantage when using chemical bonding is that an elevated temperature may be required to cure the bonding agent. Such an slevated temperature may dirninish the effects of domain refinement treatments for electrical steel sheets. Another 2 0 disadvantage when using chemical bonding is that ths sheets become rigidly connected. Winding a rigidly formed electrical steel lamlnate into a coil may induce stress thereby increasing core losses of the laminate. A further disadvantage with chemical or ceramic bonding is that the bonding layers tend to be brittie. Cutting, punching or corrugating may fracture a brittle bonded layer 2 ~ causing the sheets to delaminate.
~ . . ! f , ,:
My pending patent application 07/043077 discloses a larninate can be formed ~hat will resist separation indefinitely by applying a liquid of an appropriate viscosity to tha facing surfaces of sheets and applying sufficient pressure tn the shee~s to rsmove excess liquid and to displace air from between 5 the facin~ surfaces of ~he sheets. The liquid remaining between the facing surfaces forms a seal preventing reentry of the air which enables the laminate to rasist separation during subsequent prscessing and fabrication. The laminate formed has no increase in the space between its sheets and no induced stress in its sheets. Unfortunately, some of the liquid remaining between the sheets 10 seeps out from between the sheets along the sheet edgss. Such ss~page may cause a number of physical problems during subsequent processing of a laminate when punchin~ to form stacked laminates. In the case where transformer oil was used as the bondin~ liquid to forrn laminated elsctrical steel sheets, oil buildup on a punch prsss caused the laminate to slip in the driv~
15 system, making it difficult to ob~ain precisely mitred cuts such as are needed to build a transformer core from electrical steel sheets. Saepage also may result in the bondin~ llquid transferring onto the exterior surfaces of the larninated sheets so that stacked cut laminatad sheets become stuck together makin~ it difficult to align properly in a core stack. Delamination may even occw when 2 0 handling the laminated sheets or punchings.
Accordingly, there remains a naed for an improved technique for forming a laminate using a liquid bonding agent wherein seepage of the liquid bonding agent from between the facing surfaces of the formed iaminate is minimized or prevented.
"'~ rJ ~
BRIEF SUMMARY OF THE INVENTION
This invention relates to a method of forming an improvad laminate and a laminated core formed therefrom. A liquid bonding agent and a sealin~ agent 5 are applied to a facing surface of at least one of a plurality of sheets. Pressure is applied to the sheets to remove excess liquid bonding agent and to displace air from between the facing surfaces of the sheets and to spread the sealing agent to form a continuous barrier along each longitudinal edge of the formed Iaminate to minirnize seepage of the liquid bonding agent along the longitudinal10 edges of the laminate Principal objects of my invention are to form a laminate using a liquid bonding agent wherein the laminate resists separation, has no decrease in its space factor, and can be fabricated without delamination.
A feature of my invention is to form a laminate from two or more sheets 15 using a liquid bonding agent and a sealing agent.
Another feature of my invention is to form a laminate using a liquid bonding agent by applying a sealing agent along longitudinal ed~es of at least one facing surface of a plurality of sheets to form a continuous barrier to prevent seepage of the liquid bonding agent along the longitudinal ed~es of the formed 2 0 laminate.
Another feature of my invention is to form a laminate using a liquid bonding agent by applying a sealing agent along longitudinal edges and at a position intermediate the longitudinal edges to at least one facin~ surface of aplurality of sheets to form continuous barriers along the longitudinal edges and2 5 at the intermediate position, slitting the laminate along the intarmadiats position into narrower width iaminates, whereby the sealing agent prevents seepage of the liquid bonding agent along the longitudinal edges of the forrned laminates.
Another featur~ of my invention is to form a laminate using a low viscosity liquid bonding agent and a high viscosity sealing agent to preYent seepage of S the bonding asent along longitudinal edges of the formed laminate.
Another feature of my invcntion is to form a larninate using a liquid bondin~ a~ent havin~ a viscosity no ~reater than about 80 cP at 24C and a sealing agent having a viscosity no greater than about 2500 cP at 24C.
Another feature of my invention is to form a laminate by providing at l~ast 10 two sheets each having a facing surface, applying a liquid bonding agent to one of the facing surfaces of the sheets, applying a sealing agent along the longitudinal ed~es sf one of the facin~ surfacos, appiying pressure to the sheets to removc excess liquid bonding agent from between the surfaces and forming a continuous` barrier by sprcading the sealing agent between the surfaces as 15 the surfaces are brought into contact with each other, whereby air between the surfaces is displaced by the liquid bonding agent and the sealing agant prevents reentry of the air and minimizss seepaye of the liquid bonding agent along the edges of the formed laminate.
Another foatur~ of my invention is to form a laminate from a plurality of 2 0 grain orisnted steel sheets each having a facing surface and a thickness l~ss than about .5 mm, passing the sheets along a feedpath at a prode~ermined speed, applying a liquicl bonding agent having a viscosity no ~r~atar than about80 cP at 24C to one of the facing surfaces, applying a sealing agent having a viscosity no greater than than 2500 cP at 24C along the longitudinal edges of 25 one of the facing surfaces, passing the sheQts between a pair of rollers, .J
applying pressure to the sheets by the rollers to remove excess liquid bonding ag0nt from betwesn the surfaces and forming a continuous barrier by the sealing agent betwesn the facing surfaces as the facing surfaces ara brought into contact with each other, whereby air between the surfaces is displaced by 5 the liquid bonding agent and the sealing a~snt prevents reentry of the air an minimizes seepage of ths liquid bonding agent along the edgss of the formed laminate.
Advantages of my invention include reduction in manufacturing costs of a laminate which can be siit, cut or punched with little or no seepa~e of the 10 liquid bonding agent and production of fabricated cores using the laminates whose sheets are free from strain and induced stress.
The above and other objects, features and advantagss of my invention will become apparent upon consideration of the detailed description and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic showing two sheets moving along a feedpath being laminated ~oge~har by a pair of sealing rollers and the laminate being wound 2 0 into a coil, FIG. 2 is a cross-section view along line 2-~ of FIG. lt FIG. 3 shows an enlarged fragmentary cross-seotion view of laminated sheets of my invention, FIG. 4 shows an enlarged longitudinal section view of two sheets being 2 5 pressed together according to my invention.
r ` -~` ?: '~ i' ~
DETAILED DE!;CRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fl(i. 1, reference numeral 12 denotes a sheet being uncoiled from a coil 10 and fed at a predetermined speed along a feedpath 13 while 5 passing over a wax applicator 17. Anether sheat 16 is fed at the sam~ speed from a coii 14 under an oiling roller 18. Sheet 16 is brought together with sheet 12 by a change of direction roller 20.
For my invention, it will be understood a sheet is meant to include continuous strip, foil, ribbon and the like as well as strip cut into individual10 lengths. Preferably, the sheet will include cold reduced or cast steel and amorphous base metals having a thickness of less than about .5 mm. A more preferred sheet includes grain oriented steel having a glass insulativs coating on both sides of the sheet with a total thickness of the sheet and coating layers less than about .35 mm. U.S. Patent 3,948,786 - Evans, incorporated herein by 15 reference, discloses grain oriented steei having Mg-PO4 glass insulative coatings.
Wa~ applicator 17 can b~ any conventional mechanical devic~ such as a sprayer, a capillary-action applicator, a wipin~-type roller, an extnuder, and the like. For exampls, wax applicator 17 may include a heater 19, a faQd tube 21, 20 and a plurality of nozzles 23 for applying a sealing agent 34 along each longitudinal edge of the facing surface of sheet 12. Oiling roller 18 applies a thin coating of a liquid bonding agent to the facing surface of sheet 16. Sheets 12 and 16 pass between a pair of s~aling or consolidation rollers 22 and 24 which apply sufficient pressure to sheats 12 and 16 so that the adjacent (facing~
2 5 surfacss of sheets 12 and 16 are brought into intimate contact with each other.
~ ~ J r~ S~ ~' Continuous films of liquid bonding agent and sealing agent substantially displace all air between the facing surfaces to form a laminate 26. Laminate 26 is wound around a mandrsl 28 forming a coil 30.
The clearance between rollers 22 and 24 preferably should not be less 5 than the combined thicknesses of sheets 12 and 16. For grain oriented sheets, rollers 22 and 24 must apply sufficient pressure to remove excess liquid bonding agent to displace air and to spread the sealing agent to form a continuous barrier or seal along both longitudinal edges oS the formed laminate without inducing stress into sheets 12 and 16.
1 0 FIG. 1 illustrates how a sealing agent is applied by wa~ applicator 17 to the bottom (facing) surface of sheet 12 and a liquid bondin~ agent is applied byroller 18 to ~he top (facin~) surface of sheet 16. Wax applicator 17 also could be used to apply the sealing agent to the top (facing) surface of sheet 16 and roller 18 could be used to apply the liquid bonding agent to the bottom (facing)15 surface of sheet 12. Alternatively, the bonding agent and the sealing agent could be applied to both of the facing surfaces of sheets 12 and 16. I~ will be understood the sealing agent can be applied to a facing surfacs of a sheet in a number of patterns such as a continuous line, parallel lines, squares, cross-hatched lines, sinusoidal lines, an extruded bead, and the like so long as a 20 continuous barrier is formed along the longitudinal edges when laminating thasheets. The liquid bonding agant can be applisd as a roller coating or sprayed as a fine mist. Depending on the equiprnent available, the number of sheets simultaneously fed along feedpath 13 and the type of material being laminated, it may be advantageous to apply ~he liquid bonding agent and the sealing agent 2 5 to a sheet during a previous processing operation. In any event, the liquid ? ;~
bonding a~ent and sealing agent are applied only to sheet surfaces which are facing surfaces when the sheets are combined into a laminate.
FIG. 2 illustrates a cross-section of sheets 12 and 16 taken along line 2-2 of FIG. 1 before sheets 12 and 16 are combined by rollers 22 and 24 into 5 laminate 26. Small beads of sealing agent 34 are placed along each of the longitudinal adges 36 and 38 on facing surface 32 of sheet 12. A thin film 42 ofthe liquid bonding agent is placed on facing surface 40 of sheet 16. If laminate26 is to be slit into narrower widths, additional sea3ing agent would be appliedlongitudinally along facing surface 32 at those positions whsre the laminate is 10 to be slit. For an electrical steel laminate that is to be slit and mitred into core punchings at an angle of 45 degrees, the additional sealing agent applied at those positions to be slit preferably would be in a pattern such as square, cross-hatched, or sinusoidal to insure the sealing agent extends continuously along the longitudinal and transverse edges of the slit and cut laminates.
FIG. 3 illustrates an enlarged fragmentary cross-section view of a portion of laminate 26 formed from sheets 12 and 16 illustrated in FIG. 1. The planar surfaces of metallic sheets normally are not perfectly flat and are somewhat roughened. This rnsans facing surface 32 of sheet 12 will no~ ba in continuous contact with an adjacent facing surface 40 of sheet 16. Facing surfaces 32 and 2 0 40 engage each other at point contacts 44. As sheets 12 and 16 are brought into contact with each other by rollers 22 and 24, void areas 46 representing non-contact points between surfaces 32 and 40 are filled with liquid bonding ag~nt 42. Sealing agent 34 is spread to form thin continuous barriers or dams along the longitudinal edges of laminate 26. FIG. 3 illustrates a thin barrier 34a 25 form6d by rollers ~2 and 24 by spreading sealing agent 34 along longitudinal 7 2 ~
edge 38. The separation between sul~aces 32 and 40 at non-contact points, i.e.
void areas 46, will be Isss than about .005 mm. Air is displaced as excess liquid bonding agent is squeezed from betwa~n surfacas 32 and 40. A
continuous film of sealing agent 34a formed along lon~itudinat edges 36 and S 38 betwaen surfaces 32 and 40 of sheets 12 and 16 pravsnts reentry of the air and prevents seepage of liquid bonding agent 42 from between facing surfaces 32 and 40 alon~ the longitudinal edges of larninate 26. Accordingly, sheets 12 and 16 are tenaciously held together. Without barri~rs 34a along the longitudinal edges, liquid bonding agent 42 could saep out from betw~en the sheet facing sur~aces as illustrated by seepage 42a.
FIG. 2 illustrates beads 34 of sealing agent being applied along longitudinal edges 36 and 3~ of sheets 12 and 16. If laminate 26 illustrated in FIG. 3 is slit longitudinally into two or more narrower width laminates, liquid bonding agent 42 could seep from between facing surfaces 32,40 along the newly cut longitudinal edges of the narrower laminates. In this situation, it isdesirable to apply additional sealing agent 34 along the facing surface of the sheet at those positions corresponding to where the she0t would be slit so that both longitudinal edges of each laminate include a continuous sealin~ barrier 34a. For a laminate to be slit into two laminates of equal width, sealiny agent 34 woulct be applied to the facing surface approximately midway b0tween opposing edges 36,3a.
Not being bound by theory, it is believed the laminate is tightly held together by a pressure differential existing between voids 46 filled with the iiquid bonding agent and/or sealing agent and the ambient atmospheric pressure surrounding taminate 26. In other words, sheets 12 and 16 resist 1~
tJ
delamination since the interlaminar pressure upon separation would decrease below ambient atmospheric pressur~ pushing against the outside surfaces of laminate 26 as illustràted by arrows 48 in FIG. 4. Facing surfaces 32 and 40 of sheets 12 and 16 respectively include a bead of sealing agent 34 and a thin 5 layer of liquid bonding agent 42. Sheets 12 and 16 ars being fed from left to right ~hrough the bite of rollers 22 and 24. As rollers 22 and 24 brin~ surfacas32 and 40 into intimate contact with each other, a meniscus 50 is formed and displaces air 52 as sealing agent 34 and axcess liquid bonding agsnt 42 are displaced from between facing surfaces 32 and 40.
The liquid bonding agent can be any low viscosity liquid preferably having a viscosity no greatar than about 80 cP at 24C when applied lo the sheets. Using a bonding agent having a higher viscosity makes it difficult to obtain a good space factor and to avoid shifting of the laminated sheets.
Acceptable bondiny agents include water, alcohol, oil and the like. For hi~her viscosity bonding agents, it may be desirable to heat the bonding agent to a ternperaturs above arnbient for application to the sheet. For cut electrical steel sheets, the bonding agent is formed into a continuous film to provide for continuous interlaminar insulation to preserve magnetic quality. A natural or synthetic transformer oil is preferred for this purpose. The important 2 0 considerations are that the bonding agent adequately wets the surfaces of the shests, is compatible with the environment in which the laminate will be used, and has the necessary viscosity.
For a sealing agent, a relatively high viscosity iiquid or a solid such as wax can be used having a viscosity preferably greater than about 25û cP at 2 5 24C. Waxes having a viscosity greater than about 2500 cP at 245 are difficult ~ ~"j f~ ,? 7 to extrude. The added force necess,ary to extrude thick resin-like waxes could produce microplas~ic strain to the sheets which would harm the core loss of electrical steel. A sealing agent which is solid at ambient t~mperature, such ashard beeswax, would induce coil set and harm tha stress condition of slectrical 5 steel. As in the case of the liquid bonding agent, it may be desirable to heathigher viscosity sealing agents to a temperature above ambient for application to sheets. The important considerations for the sealing agent are the same as that for the liquid bonding agent and additionally to have sufficient viscosity to retard or prevsnt seepage of the li~uid bonding a~snt through the conUnuous 10 barriers formed alon~ the longitudinal edges of the laminate.
Viscosity is a measurement of a liquid's resistancs to flow due to the attraction between moiecules. The greater the attractive force, the slower the liquid is to flow. Ths viscosity of the liquid bondins agent and the sealing agent used is important because it effects the flow rate of meniscus 50 between facing15 surfaces 32 and 40 when joined together by rollers 22 and 24 as illustrated in FIG. 4.
As disclosad in pending patent application 07/043077, I have determined experimentally that a variaty of low viscosity liquids perform well as a bondin~agent. Cores used as transformers in electric power transmission frequQntly are 2 0 permanently immersed in and cooled by a transformer oil. Using this oil as the bonding liquid is particularly advantageous in that it is compatible with the transformer oil. For some applications. the formed core may receive a 7inal heattreatment before its end use. For those heat treated cores where carbon in a hydrocarbon based liquid bonding agent could contaminate the sheet base metal, i.a. ~rain oriented steel, a synthetic non-carbonaceous oil could be usedas the bonding agent.
By way of example, conventional grain oriented elec~rical steel sheets 7.65 crn wide, 30.5 cm iong and .18 mm thick were coatsd with a 5-6 gm/m2 insulativ~ coating applied over a mill glass coatin~. In tests 1-3, only a liquid bonding agent was applied to the sheets. A silicone type transformer oil having a nominal viscosity of 40 cP at 24C was appiied by brushing oil onto one facing surface of eaoh pair of the steel sheets. Two sheets wsre laminated by passing the sh~ets through a pair of 76 mm diametcr neopren~ roliers and appiying sufficient pressure to r~move excass transformer oil and to displace air from between the facing surfaces. In tests 4-6, only a sealing agent was used.
An organic wax having a viscosity of 500 cP at 24C was applied by contact wiping onto one facing sheet surface as a series of parallel lines aach having awidth of about 10 mm and spaced at about 25 mm int~rvals alon~ the longitudinal (rolling) direction of the sheets. The wax sealing agsnt was spreadinto a thin film between the facing surfacas of the sheets by applying sufficient pressure to the axterior surfaces of ths sheets. All the tests were evaluated immadiately after laminating and after subjected to metal cuttin3. Tssts 1-3 2 O resuited in good quality laminates and preserved the intrinsic rnagnetic quality of the ~rain oriented eleotrical st0el. Avsrage cor~ loss at 15 kG and 17 kG wasincreas~d by .8% and .9% respectively. However, seepage of ths transformer oil from between the sheets along ~he edges was evident during consolidation of the sheats and during shearing of the laminates. As was expected for ~es~s 4-6, saepage did not occur since only a high viscosity sealin~ agent was used.
However, the laminates produced were of poor quality which experienced considerable deterioration in their magnetic quality when sheared. Average core loss at 15 kG and 17 kG increased 5.1% and 5.2% respectiv~ly. Tests 4-6 demonstrate that the use of a sealing agent alona without a llquid bonding S agent to form a continuous film between the sheet facing surfaces will not prevent deterioration of ma~netic quality. Metal-to-metal contact, i.e.
interlaminar "shorting~, occurs when continuous interlaminar insulation is lacking and produces circuiating or eddy currents during AC magnetization.
This shorting is ~he result of loss of the insulative coating from the sheet 10 surfaces if the formed laminats is cut when making cores. When a continuous film of the liquid bonding agent is present, the insulativo coating still flakes off when cutting the metal sheets but the bonding agent apparently holds the powdered insulative coating at the point of cuttin~ keepin~ ths sheets from coming into contact with each other.
1 5 i~pl~ 2 High permeability oriented electrical steei sheets 7.65 cm wide, 30.5 cm long and .23 mm thick were coated with a 9-10 gm/m2 insulativs coating applied ov~r a milJ glass coating. In tests 7-10l the same liquid bonding agent was applied in a similar manner to that for tests 1-3 above. The same sealing 2 0 agent and a similar method of application to that for tests 4-6 was used for tests 11-14 sxcept the s0aling agent was applied in a series of parallel bands with each band having a width of about 10 mm and spacsd at abeut 30 mm intervals. All the tests again were evaiuated immediately after laminating and aRer subjectcd to metal cutting. The rosults for the laminates produced from 25 tests 7-14 were substantially the same as reported above for tests 1-6.
Magnetic quality for laminates made from tests 7-10 using only a liquid bonding agent was good but seepage of the bondin~ agent occurred during consolidation of the shsets and after shearing of the laminates. Average core loss at 15 kG and 17 kG increased -0.3% and 0.8% respectively. The laminates produced from tests 11-14 were of poor quality and the average core loss at 15 kG and 17 kG increased 2.4% and 4.3% respectively.
Example ~
Additional laminates were prepared according to the invention from shaets identical to those for Example 2. Sheets for tests 15-17 had the sam~
liquid bonding agent and manner of application as described for tests 1-3 in Exampl~ 1. After applying the liquid bondin~ agent to the sheets, the sealing agent described for tests 4-6 in Example 1 was applied also to tests 15-17 in the form of a 10 mm wide bead aiong the longitudinal and transverse edges of the sheets. The sheets were then consoliciated into laminatee in the same manner 1 5 as that described ~r tests 4-6 in Example 1. No seepage of lhe bonding agent along any of the ed~es of the laminates occurred after consolidation of the sheets or after shearing of the laminates. The ma~netic quality of ~he laminateswas excellent both before and after shearing. The average cora ioss for 15 kG
and 17 kG was well within the ran~e of the test resuits r~ported above when 2 0 only liquid bonding agent was used for tests 1-3 for Exampla 1 or tests 7-10 for Example 2. During consolidation of the sheets, it was demonstrated the sealing agent was spread into a thin continuous film along the edges of th0 formed laminates which retained the liquid bonding agent betwsen the facing surfaces of the sheets forming the laminates.
2 5 Results of the trials discussed above are summarized in Tabls 1.
:~ble ~
T~ ~ Laminate Quality After Sh~a~ing $eepa~ ~ftec She,,~r~n~ ?
good yes 2 good yes 3 good yes 4 poor no poor no 6 poor no 7 ~ood yes 8 good yes 9 good yss good yes 11 poor no 12 poor no 15 1 3 poor no 14 poor no 15 (invontion) good no 16 (invention) good no 17 (invention) good no While only one embodiment of my invention has been described, it will be understood various modifications rnay be made to it without deparling from the spirit and scope of it. For example, various liquid bonding agents and sealing a~ents may be used so long as they are compa~ible with the 2 5 environment within which the laminats is to be used and hava ~he necessary if ~ f. ~ I ~/`s ,~;
viscosity to form a seal when formed into very thin layers. Two or more sheets may be lan~inated simultaneously usin~ various maans to apply tha liquid bonding agent and sealin~ agent to the facing surfaces of at least one of the sheets. One or both surfaces of the sheets may have previously appliad 5 coatings such as metallic or glass insulative coatings. The laminate may be wound into a core, forrned into a stacked core of cut laminates or otherwise fabricated. Thsrefore, the limits of my invention should be determined from the appended claims.
Claims (22)
1. A method of forming a laminate, comprising the steps of:
providing at least two sheets each having a facing surface, applying a liquid bonding agent to one of said surfaces, applying a sealing agent along the longitudinal edges to one of said surfaces, applying pressure to said sheets to remove excess liquid bonding agent from between said surfaces and forming a continuous barrier along said edges as said surfaces are brought into contact with each other, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges.
providing at least two sheets each having a facing surface, applying a liquid bonding agent to one of said surfaces, applying a sealing agent along the longitudinal edges to one of said surfaces, applying pressure to said sheets to remove excess liquid bonding agent from between said surfaces and forming a continuous barrier along said edges as said surfaces are brought into contact with each other, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges.
2. The method as set forth in claim 1 wherein said liquid bonding agent is an oil and said sealing agent is a wax.
3. The method as set forth in claim 2 wherein each of said sheets is grain oriented steel having a thickness less than about .5 mm, said surfaces of said sheets being coated with a glass insulating film impervious to said oil and said wax.
4. The method as set forth in claim 1 wherein the separation between said surfaces is less than about .005 mm after said pressure is applied.
5. The method as said forth in claim 1 including the additional steps of:
passing at a predetermined speed one of said sheets along a feedpath, passing at said speed another of said sheets along said feedpath.
passing at a predetermined speed one of said sheets along a feedpath, passing at said speed another of said sheets along said feedpath.
6. The method as set forth in claim 5 wherein said pressure is applied by passing said sheets between a pair of spaced rollers, the clearance between said rollers being no less than the combined thicknesses of said sheets.
7. The method as set forth in claim 6 wherein said sealing agent is applied to said surface of one of said sheets and said liquid bonding agent is applied to said surface of another of said sheets as said sheets are passing along said feedpath.
8. The method as set forth in claim 3 wherein each of said sheets has a thickness of less than about .5 mm and including the additional step of winding said laminate into an electrical transformer core.
9. The method as set forth in claim 3 wherein each of said sheets has a thickness of less than about .5 mm and including the additional steps of:
cutting said laminate without delamination, stacking a plurality of said cut laminates into an electrical transformer core.
cutting said laminate without delamination, stacking a plurality of said cut laminates into an electrical transformer core.
10. The method as set forth in claim 1 wherein said liquid bonding agent has a viscosity of no greater than about 80 cP at 24°C and said sealing agent has a viscosity of no greater than than 2500 cP at 24°C.
11. A method as set forth in claim 1 wherein the temperature of said liquid bonding agent and said sealing agent is greater than ambient when said liquid bonding agent and said sealing agent are applied to said surface.
12. The method as set forth in claim 1 wherein said sealing agent is applied as a pattern from the group consisting of a continuous line, parallel lines, cross-hatched lines, sinusoidal lines, squares, and an extruded bead.
13. A method of forming a laminate, comprising the steps of:
providing at least two sheets each having a facing surface, applying a liquid bonding agent to one of said facing surfaces, applying a sealing agent along the longitudinal edges and at a position intermediate to said edges to one of said surfaces, applying pressure to said sheets to remove excess liquid bonding agent from between said surfaces and to form a continuous barrier along said edges and along said intermediate position as said surfaces are brought into contact with each other, slitting said laminate along said intermediate position thereby forming a continuous barrier along each of the slit edges between said sheets of the laminates, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges of said laminates.
providing at least two sheets each having a facing surface, applying a liquid bonding agent to one of said facing surfaces, applying a sealing agent along the longitudinal edges and at a position intermediate to said edges to one of said surfaces, applying pressure to said sheets to remove excess liquid bonding agent from between said surfaces and to form a continuous barrier along said edges and along said intermediate position as said surfaces are brought into contact with each other, slitting said laminate along said intermediate position thereby forming a continuous barrier along each of the slit edges between said sheets of the laminates, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges of said laminates.
14. A method of forming a laminate from a plurality of grain oriented steel sheets each having a facing surface, each of the sheets having a thickness less than about .5 mm, comprising the steps of:
passing at a predetermined speed one of said sheets along a feedpath, passing at said speed another of said sheets along said feedpath, applying a liquid bonding agent having a viscosity no greater than about 80 cP at 24°C to one of said surfaces, applying a sealing agent having a viscosity no greater than 2500 cP at 24°C along the longitudinal edges of one of said surfaces, passing said sheets between a pair of rollers, applying pressure to said sheets by said rollers to remove excess liquid bonding agent from between said surfaces and forming a continuous barrier by said sealing agent between said surfaces as said surfaces are brought into contact with each other, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges.
passing at a predetermined speed one of said sheets along a feedpath, passing at said speed another of said sheets along said feedpath, applying a liquid bonding agent having a viscosity no greater than about 80 cP at 24°C to one of said surfaces, applying a sealing agent having a viscosity no greater than 2500 cP at 24°C along the longitudinal edges of one of said surfaces, passing said sheets between a pair of rollers, applying pressure to said sheets by said rollers to remove excess liquid bonding agent from between said surfaces and forming a continuous barrier by said sealing agent between said surfaces as said surfaces are brought into contact with each other, whereby air between said surfaces is displaced by said liquid bonding agent and said sealing agent prevents reentry of said air and minimizes seepage of said liquid bonding agent along said edges.
15. The method as set forth in claim 14 wherein said liquid bonding agent is applied to said one of said sheets and said sealing agent is applied to said another of said sheets as said sheets are passed along said feedpath.
16. A laminate, comprising:
at least two sheets each having a facing surface, said surfaces in contact with each other, a sealing agent along the longitudinal edges on said surfaces and a liquid bonding agent between said sealing agent on said surfaces, air between said surfaces being displaced by said liquid bonding agent and said sealing agent, said sealing agent forming a continuous barrier to prevent reentry of said air and minimizing seepage of said liquid bonding agent along said edges whereby said laminate can be handled without delamination.
at least two sheets each having a facing surface, said surfaces in contact with each other, a sealing agent along the longitudinal edges on said surfaces and a liquid bonding agent between said sealing agent on said surfaces, air between said surfaces being displaced by said liquid bonding agent and said sealing agent, said sealing agent forming a continuous barrier to prevent reentry of said air and minimizing seepage of said liquid bonding agent along said edges whereby said laminate can be handled without delamination.
17. The laminate as set forth in claim 16 wherein said liquid bonding agent is an oil and said sealing agent is a wax.
18. The laminate as set forth in claim 16 wherein said surfaces include a glass insulating coating inpervious to said liquid bonding agent and said sealing agent, each of said sheets being grain oriented steel having a thickness less than about .5 mm.
19. The laminate as set forth in claim 16 wherein said liquid bonding agent has a viscosity no greater than about 80 cP at 24°C and said sealing agent has a viscosity of no greater than than 2500 cP at 24°C.
20. A metallic core, comprising:
at least one laminate, said laminate including at least two sheets each having a facing surface, said sheets having a thickness of less than about .5 mm, said surfaces in contact with each other, a sealing agent along the longitudinal edges on said surfaces and a liquid bonding agent between said sealing agent on said surfaces, air between said surfaces being displaced by said liquid bonding agent and said sealing agent, said sealing agent forming a continuous barrier to prevent reentry of said air and minimizing seepage of said liquid bonding agent along said edges, whereby said core can be handled without delamination of said laminate.
at least one laminate, said laminate including at least two sheets each having a facing surface, said sheets having a thickness of less than about .5 mm, said surfaces in contact with each other, a sealing agent along the longitudinal edges on said surfaces and a liquid bonding agent between said sealing agent on said surfaces, air between said surfaces being displaced by said liquid bonding agent and said sealing agent, said sealing agent forming a continuous barrier to prevent reentry of said air and minimizing seepage of said liquid bonding agent along said edges, whereby said core can be handled without delamination of said laminate.
21. The core as set forth in claim 20 wherein said core is a wound electrical transformer.
22. The core as set forth in claim 20 wherein said liquid bonding agent has a viscosity of no greater than about 80 cP at 24°C and said sealing agent has a viscosity of no greater than than 2500 cP at 24°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2026727 CA2026727A1 (en) | 1990-10-02 | 1990-10-02 | Method of forming a laminate and the product thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2026727 CA2026727A1 (en) | 1990-10-02 | 1990-10-02 | Method of forming a laminate and the product thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026727A1 true CA2026727A1 (en) | 1992-04-03 |
Family
ID=4146083
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2026727 Abandoned CA2026727A1 (en) | 1990-10-02 | 1990-10-02 | Method of forming a laminate and the product thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2026727A1 (en) |
-
1990
- 1990-10-02 CA CA 2026727 patent/CA2026727A1/en not_active Abandoned
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