US2462474A - Coating apparatus for wires, filaments, and the like - Google Patents

Description

- Feb. 22, 1949. DELA-NO 2,462,474

COATING APPARATUS FOR WIRES, FILAMENTS AND THE LIKE Filed March 18, 1947 2 Sheets-Sheet 1 INVENTOR ATTO EY J. K. DELANO Feb. 22, 1949.

COATING APPARATUS FOR WIRES, FILAMENTS AND THE LIKE Filed Marchl8, 1947' 2 Sheets-Sheet 2 l II lll INVENTOR 1f. BY

ATTORN l I l I l I I I l l I f Patented Feb. 22, 1949 COATING APPARATUS FOR wmEs,

FILAMENTS, AND THE LIKE James K. Delano, Rye, N. Y.

Application March 18, 1947, Serial No. 735,384

2 Claims.

This invention relates to the art of providing continuous filaments with coatings, especially the art of providing filaments as, for example, wire with suitable insulating coatings.

Various lacquers, varnishes and other insulating materials in dissolved or liquid forms may be applied to electrically conducting filaments, e. g. copper wire, to provide a liquid coating which may then be solidified or hardened by processes such as solvent removal or solvent removal plus oxidation or polymerization of the residue.

The problem is not to provide any sort of coating but one which is perfectly concentric in shape and uniform in thickness and to accomplish that result While the wire is'traveling at as high a speed as possible to obtain a correspondingly high output.

The natural tendency of a liquid coating applied to wire is to distribute itself in a manner which results in much lack of uniformity. Since in many instances the requirements are so rigid that the coating must be perfectly concentric throughout the entire length of the wire with a maximum variation of about 0.0002 inch in thickness, serious difficulties have been encountered and much coated wire has been rejected.

One object of the invention is to provide wires, filaments,'etc,'with a coating which is uniform in shape and thickness.

Another object is to accomplish that result at a high rate of output.

Other objects and advantages will appear from the following description and the appended drawings showing apparatus suitable for practicing the invention and in which:

Fig. 1 is a plan view with cover portions removed to show the rolls and driving mechanism and other parts;

Fig. 2 is a view, partly in section, on line 2-2 of Fig. 1;

Fig. 3 is a transverse elevational view, partly in section, on line 3-3 of Fig. 1; I

Fig. 4 is a vertical sectional view online 4-! of Fig. 1;

Fig. 5 is a vertical sectional view on line 5-5 of, Fig. 1; and

.2 wire and the operation is so conducted that the thickness of the liquid coating does not vary beyond the required close tolerances. After-the coating operation, the coated filament continues its travel and the coating is solidified or hardened by any desired operation, depending on the particular composition of the liquid coating, such operations being illustrated by evaporation of a solvent and, if necessary, further hardening of the coating by chemical action, such as oxidation, polymerization, etc. To effect the removal of excess coating liquid, there is established and maintained a continuously moving surface and on that surface there is produced and maintaineda thin film of coating liquid suflicient only to maintain that moving surface in a slightly wet or dampened condition. A linear movement is imparted to the film, that is, a movement in the dirction of the filament axis and the filament or wire having such movement and carrying an excess of coating liquid is contacted with said damp surface. The rate of movement or speed of travel of the damp surface is different from that of the filament (preferably greater) and it has been found that under such conditions the excess liquid on the filament is effectively drained away or blotted by the moving surface. Any desired number of contacts can be made between the filament and the said moving surface or surfaces so as to effect any desired degree of drainage or blotting. One way of providing the moving surface with the above-mentioned thin film or dampness is to apply coating liquid to said moving surface at one area thereof and then as said surface continues to advance'in its movement beyond the point of application, to apply a brush or wiper to said surface so as to remove therefrom all except the thin film mentioned and to produce the slightly damp condition described. From the apparatus point of view, one way of carrying out that process is to provide a cylindrical roll which rotates at a desired speed, applycoating liquid to said roll at the lower part thereof and then as the roll surface continues to advance beyond the point of application to employ a blade or brush to remove all of the coating liquid from. the said cylindrical surface except just enough to mak it damp. Such removal can be effected at a point intermediate between the top of the roll and the point of application of the coating liquid so that the roll area at the top thereof is in the desired slightly dampened condition. Then a filament having a longitudinal or linear movement and carrying an excess of coating liquid can be contacted with said roll near the top thereof tangentially whereby the damp surface effectively serves to drain oil or blot the desired proportion of excess coating liquid from the filament, particularly where there is a difference in the rate of movement of the said moving surface andfilament respectively. Such procedure and apparatus are satisfactory up to a certain point, that is, where the linear rate of movement of the filament does not exceed values of 370 to 390'feet per minute. Thereby, of course, a limit is placed on the output of the process and apparatus. The reason for that limit is that it has been found that when such speeds are substantially exceeded then the corresponding and preferably differential speed of the moving surface makes it difllcult or impossible to effectively remove therefrom the excess coating liquid which has been applied thereto and thus makes it difficut or impossible to obtain and maintain the desired slightly damp condition above described.

In accordance with the present invention, that difllculty is overcome by suitably limiting the amount of coating liquid which is applied to said moving surface and this is preferably done by confining that liquid under pressure between that moving surface at one area thereof and a stationary surface, opposite to and in closely spaced relation to said area. Then after that area of the moving surface has advanced beyond and away from the stationary surface, all excess coating liquid is wiped or scraped from said sur- -.face except just enough to produce the abovementioned slightly damp condition. By so limiting and confining the amount of coating liquid applied to said moving surface and then following that step with the wiping step, the present invention makes it possible to greatly speed up the rate at which said moving drainage or blotting surface travels and also to greatly speed up the linear movement of the coated filament which carries an excess of coating from which said excess is drained or blotted by the high speed slightly damp moving surface. Thus the output of the process and apparatus is greatly increased; indeed, the increase may be several-fold as compared to the process and apparatus where the amount of coating liquid applied to the blotting surface is not limited as above described.

One kind of apparatus or machine provided in accordance with the invention includes an applicator roll for applying an excess of liquid coating to the filament or wire and at least one blotting roll to remove that excess. Those rolls are rotatably mounted in a container or tank provided with a body of coating liquid at the bottom thereof, the rolls being arranged to rotate about their horizontal axes. The applicator roll and also the blotting roll or rolls are arranged to have coating liquid applied thereto, as, for example, by having the lower part of said roll dip into the coating liquid and carried up said liquid on the surface thereof. From the applicator roll liquid may be applied in excess to a filament to which linear movement has been imparted and which filament has a tangential contact with the applicator roll, then the filament carrying said excess liquid comes into tangential contact with one or more blotting rolls. In connection with the blotting roll, structure is provided which cooperates with the surface of the blotting roll to limit the amount of coating liquid on that roll to a thin film. Where the speed of travel of the coated filament and the corresponding differential speed of the cylindrical surface of the blotting roll are relatively low, such cooperating 4 structure may be asuitable brush or blade hearing against the surface of said roll between the area where the roll receives the coating liquid and the area or point of tangential contact of said surface with the filament carrying its excess of coating liquid. However, where it is desired to secure effective action at high speeds and thereby greatly increase the output of the method and apparatus such blade or brush is ineffective to reduce the amount of coating liquid .on-the blotting surface to the desired thin film which is necessary for effective drainage and blotting purposes and in accordance with the present invention means are provided to limit the amount of coating liquid carried by a blotting roll from the lower toward the upper part thereof so that said means in cooperation with a suitable blade or wiper will effectively maintain the blotting roll at the point of tangential contact thereof with the coated filament to the slightly damp condition. Said means comprises a shield structure which may surround the lower part of the blotting roll, that structure having an inner surface concentric with and in closely spaced relation to the adjacent surface of the blotting roll, and an outer part arranged to be in contact with the coating liquid and also including orifice means to admit coating liquid from the outer part of said shield to the inner surface thereof. Coating liquid can come into contact with the .lateral cylindrical surface of the blotting roll only through said orifice and that liquid then becomes confined under pressure between the inner surface of the shield and the opposed cylindrical surface of the blotting roll in a manner similar to that in which lubricating oil is confined between a shaft and its bearing. Not only is the amount of coating liquid thus limited but it is effectively spread under pressure over the lateral 40 surface of the blotting roll; then, as the said lateral surface continues to rotate away from and beyond the terminal edge of the "shield, the amount of liquid on the blotting roll cylindrical surface is so limited by the action of the shield that the subsequent action of suitable wiping or blade means can readily produce the thickness of film on the blotting roll so that the slightly damp condition above-mentioned is attained at the point ofv tangential contact between said blotting roll and the wire or filament traveling longitudinally. This point or area may, for example, be at the top of the blotting roll and the wiping or blade means may be interposed to bear against the blotting roll surface at a position intermediate between the terminal or trailing edge of the shield and the top of the roll.

Further in accordance with the invention, the applicator roll preferably has suitable means such as at least one annular groove therein to receive and carry coating liquid and that roll is preferably so arranged that the filament or wire receives its excess coating of liquid by contact with said applicator roll in said groove. It is also preferred to have a shield cooperating with the applicator roll and that shield may have substantially the same structure which is provided for the blotting roll. The relation of the shield to the applicator roll is also quite similar to the relation of the shield to the blotting roll. Moreover, there is also preferably provided a blade or wiping means for the applicator roll similar to that used on the blotting roll. It will thus be seen that the combination of shield and wiping means in association with the applicator roll 75. serves to limit the amount of coating liquid carried by the applicator roll to that amount which is found in the groove or grooves thereon, even when the applicator roll operates at rather high speed, it being noted that the applicator roll does not need to rotate at as high a speed as the blotting roll since the applicator roll may rotate at such a speed that the movement of the cylindrical surface thereof may be about one-third the speed of the cylindrical surface of a blottin roll.

In addition to the function above described I for the shield in combination with the applicator roll, it has another and important function in accordance with the present invention. Wires, filaments, ribbon. etc., as produced by the usual drawing or extrusion processes are contaminated by metallic or other particles on the surface and it is of course undesirable for such particles to appear on the finished product. Indeed, in many cases such a condition might well result in the rejection of the product. In accordance with the present invention, the liquid in the tank is recirculated and subjected to purification in the path of. recirculation; for example, it may be filtered or centrifuged to remove all sediment, then the filtrate or purified liquid is conveyed back to the container. It is, however, delivered only to the shield interposed between the applicator roll and the bath of liquid in the tank and then in the space between the applicator roll and said shield. Thereby the applicator roll receives only liquid purified from all particles and the traveling filament receives a coating only of purified liquid.

It will be understood that numerous modifications may be made within the scope of the principles herein described and with this understanding attention is directed to the drawings which show for purposes of illustration an apparatus or machine which may be used in the practice of the invention. A container or tank I has a bottom portion 2, end walls 3, side walls 4 and top 5 which may be hinged on the pivot 6 to provide a swingable cover. The tank or container I contains a suitable insulating coating material I in liquid form. Integral with the container thus provided there is a housing I having a top II which may conveniently be made removable, a bottom portion HA and vertical side walls I. The housing contains spiral gears I2, I3 and I4 each of which is keyed to shaft I! by keys I6, one

of which keys is specifically shown in Fig. 3. The shaft I5 is rotatably mounted in bearings I1 and I3 carried by end walls 9 of the housing. The bearings I1 and I8 are shown diagrammatically, it being understood that roller bearings may desirably be provided. The spiral gears I2, I3 and I4 mesh, respectively, with spiral gears 2|. 22 and 23. Gear 2I is keyed to shaft 24, gear 22 is keyed to shaft 25 and gear 23 is keyed to shaft 28 by means of keys, one of which, I9, is specifically shown in Fig. 3. Shaft 24 is rotatably mounted in bearings 21, 21A, and shaft 25 is likewise in bearings 28, 28A, and shaft 26 in bearings 23, 29A. The said bearings are mounted in side walls of the housing I0 and are diagrammatically shown, it being understood that the bearings are preferably roller bearings provided with suitable raceways to facilitate friction reduction and smooth operation when the shafts 24, 25 and 2C rotate at relatively high speeds. Packing gland 30 is provided to effect a proper seal and prevent leakage of the liquid from the container I.

- Each of the shafts 24, 25 and 26 extends from the housing II into the container or tank I and on the extensions of said shafts and secured 6 thereto are mounted the rolls ll, 34 and 31, 3| being an applicator roll and 3| and 31 being blotting rolls. The construction of the apparatus is such that the said rolls may very easily be removed from the container I and that construction will be clear from the description immediately following. The shafts 24. 25 and 28 have at the ends thereof adjacent side wall 4 of the container I keyed portions II, 33 and 4., respectively. The said keys are fitted, respectively, in corresponding plates 4|, 42 and 43 and the said plates are secured to rolls 3!, 34 and 31, respectively, by means of screws 44," and 43. Opposite the said plates, the side wall 4 of the container is equipped with removable insets 52, I3 and i4, removably secured to the side wall 4 of the container by bolts 55, 56 and 51, respectively.

' By removing the insets 52, 53 and 54 and the 'of the arrows shown in Fig. 2 at higher R. P. M.

than roll 35. In practicing the invention, it is preferred to have the peripheral speed of the lateral cylindrical surfaces of blotting rolls 38 and 31 move at a speed somewhat greater than the rate of linear movement of the filaments'or wires I03. whereas the peripheral speed of the lateral cylindrical surface of the applicatorroll 38 is less and may be, of the same order of magnitude of the speed of linear movement of the filaments or wires I03.

The rolls 3!, 36 and 31 have associated therewith shields GI, 62 and 63. respectively. The said shields may be solid or hollow. In any event, each shield has an inner surface 64 concentric with and in spaced relation tothe opposed cylindrical surface of the roll. The spacing may be adjusted to any desired degree of closeness. In the case of the blotting rolls 36 and 31, the spacing may be no more than inch. Each shield has an outer surface 65 in contact with the coating liquid I. Each shield is fitted tightly to the sides 4 of the container (see, for example, Figs. 3 and 5) and such tight fit is sufficient to support the shields in container I although any suitable additional support means may be employed. Because of the construction mentioned, coating liquid can be admitted or applied to the rolls only after first passing through ports or orifices in the shields and therefore the amount of coating liquid which is applied to each roll, that is, to the moving surface illustrated by the lateral cylindrical surfaces of the rolls, is limited to the amount admitted through said ports or orifices and to the film which isconfined between said moving surface and the opposed stafor the applicator roll the liquid is shown as admitted through a single orifice or port 09A communicating with a manifold 68. The port A connected to'pipe 09 which passes through end wall 3 of the container I and continues into pipe or conduit." (valve 10 being provided), the pipe II being connected to pump 12 operated by motor 13. Pump 12 is connected by pipe 14 to a liquid purifying apparatus illustrated by filter 15 containing filtering material I8. The container I is'provided with overflow pipe "having valve 18 and being diagrammatically shown Y as connected to the filter I5. Thus it will be seen that coating liquid can be recirculated, that is, withdrawn from the container I through pipe 11, filtered in filter IS-and then return to the container I through pipe 1 I, it being noted, how ever, that the liquid so returned is not mixed with the main body of liquid 1 in container I but is delivered only through pipe 60, port 59A and manifold 68 to applicator roll 35. Insteadof the filter 15, any suitable purifying apparatus, as, for example, a centrifuge, could be used, the significant feature being that the coating liquid may be continuously purified andseparated from impurities, including metallic or other particles eroded from the wire or filament I03 and that the applicator roll 35 may be supplied only'with liquid so'purified. The container I is also preferably provided with sump 19 and drawoif pipe 80 having valve 8|.

As the'blotting rolls 36 and 31 rotate they exert a pumping action and the coating liquid is drawn in through the ports 66. The liquid is then spread out and confined under pressure as a film between the moving surface, which is the rapidly rotating lateral cylindrical surface of a blotting roll, and the opposed concentric stationary surface 64 of the shield. Thus the coating liquid is confined under pressure between said moving surface at one area thereof and an opposed stationary surface in closely spaced relation to that area. As the rolls continue to rotate, the area to which the coating liquid has been applied advances beyond and away from the stationary surface. In the drawings the terminal or trailing edges of the shields are shown edges, it is then possible to wipe from the lateral surface of the rolls all coating liquid'except Just enough to maintain the surface of the roll in a slightly damp condition at the point at which it is desired to effect contact between said roll and the moving filaments or wires I03 so as to drain excess liquid from the latter, and said wiping means may be interposed at a position intermediate between the terminal or trailing edge of a shield and the said point of contact of theroll with the traveling wires or filaments. The drawing shows the filaments I03 as having tangential contact with each roll at the top thereof and it will be understood that suitable means are provided for imparting to the wires or filaments a desired linear rate of movement and for efiecting said tangential contact.

In the drawings the wiping means are shown as blades or brushes 9|, 92 and 93 secured to and supported onsuitable brackets. Each bracket has upright legs 88, a horizontal portion 89 to which the blade of the bracket is secured by means of screws 94. The upright legs 88 are pivoted on bosses and are provided with springs 08 to bias the blades 9|, 02 and 03 agalmtv their respective rolls.

The applicator roll 35 has one or more annu-' lar grooves I00 which serve not only to receive a wire or filament I03 having a linear movement and a tangential contact with each of the rolls, but also to carry a body of coating liquid to apply an excess thereof to said wire or filament.- The shield 0| also carries a series of fingers IOI secured to theshield by screws I02, the said fingers IOI being received in the grooves I00 and facilitating return of the coating fluid from the grooves in the upper portion of the applicator roll to the space between said roll and shield BI.

It is possible to omit the shields. In that case, however, one depends on the brushes or blades BI, 92 and 03'. In the case of the applicator roll 35, the purpose is to confine the coating liquid carried upwardly by the roll to an amount not exceeding that-carried by the grooves, that is, Just enough to apply an excess of coating liquid to, the filament or wire. In the case of the blotting rolls 38 and 31, the purpose is to have at the point of tangential contact of the wire and the roll only that very slight amount of film of coating liquid or dampness which will serve to effectively withdraw excess coating liquid from the filament or wire. If dependency isplaced on the brushes or blades 9|, 92 and 03 to effectuate' those purposes, the output of the method and apparatus is limited because there is a critical maximum peripheral speed of the lateral cylindrical surface of the'blotting roll and if that speed is exceeded then the brushes or blades are ineffective because the rolls carry up more liquid than the blades can cope with. The blotting rolls then cease to function as such because, due to the pumping action of the rolls too much liquid is carried up to the blotting area or because sometimes air pockets develop between the roll and liquid which deprive the roll of the necessary damp blotting surface. The above effects are also accompanied by spattering or throwing of liquid.

The above-mentioned critical maximum speed is about 400 feet per minute and since the linear velocity of the filament or wire in tangential contact with said blotting surface should not be greater than that value (and preferably less, e. g. 2.5 to 7.5 per cent less, so as to enhance the draining or blotting effect produced by the blotting surface) the rate of linear movement of the filament or wire and therefore the output of coated filament or wire is distinctly limited. However, by limiting the amount of coating liquid applied to the rolls and confining it in the manner described, it then becomes possible for the brushes or blades to effectively accomplish their purpose, even when the blotting surface is moving at high speed. Speeds as high as 1600 feet per minute of the blotting surfaces (and linear velocities of the filament or wire of the same order of magnitude) can be achieved and the out-' 9 liquid insulating material, an applicator roll to apply an excess of coating material to the wire and at least one blotting roll to remove said excess, each of said rolls being mounted to rotate within said container, a shield structure surrounding the lower part of each of said applicator and blotting rolls, said shield structure having a lower outer portion arranged for contact with said coating liquid and an upper portion extending above the level of liquid in said container and an inner portion having a surface concentric with and in closely spaced relation to the adjacent roll surface, and orifice means in said lower portion to admit'coating liquid to the concentric space between said roll and the adjacent shield surface, and each of said shields limiting the liquid contained in the con- I centric space between the inner portion of the shield and the adjacent roll surface to the amount of liquid delivered through said orifice means and confined in said concentric space; a doctor blade bearing against each of said rolls at a point intermediate between the top of'said roll and the upper portion of said shield, meansdelivered to the top 01' the blotting roll to be limited to a thin blotting film even at blotting roll peripheral speeds as high as 1600 feet per minute.

2. Apparatus according to claim 1 in which the orifice means in the shield for the applicator roll communicates with a pipe extending through a wall of the container, and the orifice means in the shield for said blotting roll is arranged to communicate with the liquid in said container, said apparatus having a conduit to withdraw liquid from said container, means to separate solid material from said withdrawn liquid and thereby purify said liquid and means to return said purified liquid to the container only through the above-mentioned pipecommunlcating with the orifice means in the shield for the applicator roll.

JAMES K, DELANO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Reevely Aug. 31, 1943

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