US3589332A

US3589332A - Apparatus for insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic materials

Info

Publication number: US3589332A
Application number: US745763A
Authority: US
Inventors: Bernhard Dinse
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-07-18
Filing date: 1968-07-18
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29

Abstract

Apparatus for insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic material includes a tank for containing a thixotropic dispersion of the synthetic material, a coating roller mounted outside the tank and provided with a pair of spaced surfaces between which the conductor is to be passed in a vertical direction, and means for supplying the dispersion from the tank to the coating roller in an amount adequate for coating the electric conductor therewith, the coating roller being rotatable in a direction opposite to the direction in which the conductor is to be passed.

Description

United States Patent [72] Inventor Bernhard Dinse 894,592 7/1908 Callan 1l8/DIG. 20 Schwekertdam 322, 1 Berlin 13,Germany 1,031,620 7/1912 callan 118/6 [211 App]. No. 745,763 2,269,150 1/1942 Flynn 118/234 X [22] Filed July 18,1968 2,649,758 8/1953 Cowgill 118/259 X [45] Patcnted June 29, 1971 v rmary Exammer-John P. McIntosh [731 Ass'gnee if??? f Berh" and Attorneys-Curt M. Avery. Arthur E. Wilfond. Herbert L.

. umc ,erman Lerner and Daniel J. Tick [54] APPARATUS FOR INSULATING THIN ELECTRIC CONDUCTORS, PARTICULARLY EXTREMELY THIN COPPER CONDUCTORS, WITI-I RM PL STI YN BE AT A I 0 A c? T Em LS ABSTRACT: Apparatus for insulating thin electric conduc- 1 Claim, 4 Drawing Figs.

tors, particularly extremely thm copper conductors, with ther- [52] US. Cl 118/67, moplastic synthetic material includes a tank f containing a 1 l8/23 4, l 8/ thixotropic dispersion of the synthetic material, a coating It. Q roller mounted ouside the tank and provided a pair of of Search l spaced urfaces between the conducor is to be DIG v 259, in a vertical direction, and means for supplying the dispersion R f cgted from the tank to the coating roller in an amount adequate for l 1 e erences coating the electric conductor therewith, the coating roller UNITED STATES PATENTS being rotatable in a direction opposite to the direction in 246,728 9/1881 Crich et a1. 1 18/234 X which the conductor is to be passed.

PATENTEH JUN29 19?:

SHEET 1 OF 2 APPARATUS FOR INSULATING THIN ELECTRIC CONDUCTORS, PARTICULARLY EXTREMELY THIN COPPER CONDUCTORS, WITH THERMOPLASTIC SYNTHETIC MATERIALS My invention relates to apparatus for insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic materials.

In the copending application Ser. No. 392,775 of H. Gerland et al., filed Aug. 28, 1964, now U.S. Pat. No. 3,47 l ,327, and assigned to the assignee of the instant application, there is described a method of insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic materials, preferably with polyolefins, such as polyethylene especially. The viscosity of the polyolefin is mechanically reduced at the locality where the conductor emerges from the dispersion. Thereafter, the dispersioncovered conductor is passed through one or more heated furnace zones wherein the dispersion medium is evaporated and the pulverulent polyolefin remaining on the conductor is sintcred to form a homogeneous coherent coating.

This method is employed primarily when the insulating layer to be applied to the conductor is thin but must nevertheless be centered about the conductor. By the method of the aforementioned copending application, insulating walls are able to be applied to thin conductors such as copper conductors having a diameter of 0.3 mm. for example. Conventional extrusion presses are able to produce such thin walls for centered copper conductors only with great difficulty and at great cost.

In the aforementioned copending application, apparatus has already been described for carrying out the method disclosed therein, by means of which the viscosity of the thixotropic dispersion is reduced by a coating roller having two opposed surfaces or flats between which the conductor being insulated is vertically traversed. In the embodiment of the apparatus disclosed in the aforementioned copending application, this coating roller is located within the tank containing the thixotropic dispersion. For this purpose, the tank is open at the top so that the relatively large surface of the thixotropic dispersion is in contact with the air and, consequently, evaporation of the dispersion medium occurs which, in turn, causes an undesired change in the viscosity of the dispersion.

It is accordingly an object of my invention to provide apparatus for insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic materials, which avoids the aforementioned disadvantages and difficulties of the aforementioned copending application.

With the foregoing and other objects in view, in accordance with my invention, I provide a coating roller that is located outside of the supply tank proper of thixotropic dispersion and provide the roller with a pair of spaced surfaces between which the conductor is to be passed in a substantially vertical direction, and means for supplying an amount of the dispersion adequate for coating the conductor therewith from the tank to a location of the coating roller substantially diametri cally opposite the location thereof along which the conductor is to be passed, the coating roller being rotatable in a direction opposite to the direction in which the conductor is to be passed. Assurance is thereby provided that only a small part of the dispersion will come into contact with air whereas the larger part of the dispersion will be enclosed in the tank proper which is completely covered, so that undesired evaporation of the dispersion medium is prevented. Since the viscosity of the thixotropic dispersion is reduced only at location where shearing forces occur, there forms on the traversing conductor a thin, centered or coaxial coating having a thickness that can be determined in essence by the rotary speed of the coating roller.

It is an important feature of my invention that the conductor to be insulated does not have to first traverse the entire supply tank of thixotropic dispersion but rather only the portion of the dispersion wherein the viscosity of the thixotropic dispersion has been reduced by shearing forces or shear stresses. Directly after the conductor leaves the vicinity of the coating rollers, or directly after the conductor has passed out of the dispersion supplied thereto by the coating roller, the dispersion surrounds the conductor homogeneously and concentrically or coaxially due to the thixotropic characteristics thereof.

In accordance with yet another feature of my invention, I provide a pump for pumping thixotropic dispersion from the supply tank to the coating roller.

In accordance with a further feature of my invention, I pro vide wiper means adjacent the coating roller for adjusting the amount of dispersion supplied to the coating roller and accordingly to the conductor that is being coated with insulation.

In accordance with a concomitant feature of the invention and in order to adjust the thickness of the coating to be applied to the conductor with accuracy, the coating roller is mounted so that it is adjustable in a direction substantially perpendicular to the substantially vertical direction in which the conductor traverses the space between the opposing surfaces of the coating roller in a manner corresponding to that described in the Austrian Pat. No. 259,048, in the name of the assignee of the instant application.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in apparatus for insulating thin electric conductors, particularly extremely thin copper conductors, with thermoplastic synthetic materials, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range ofequivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. I is a diagrammatic view of apparatus for coating an electric conductor wire with thixotropic dispersion in accordance with my invention;

FIGS. 2 and 3 are enlarged schematic side and front elevational views, respectively, of part of the apparatus of FIG. 1 showing an embodiment of a coating roller located outside of the dispersion supply tank proper;

FIG. 4 is a view corresponding to that of FIG. 2 showing a modification of the embodiment thereof.

Referring now to the drawings and first, particularly, to FIG. I thereof, there is shown a coating roller 18" which is rotatable so that the viscosity of a thixotropic dispersion being applied to a wire 2 is reduced. The coating roller 18" is located outside of a supply tank 6 for thixotropic dispersion and is rotatably mounted in common with the supply tank 6' on the shaft of a guide roller 8, as shown more clearly in FIGS. 2 to 4, and described more fully hereinafter. The apparatus of FIG. 1 includes a vertical arrangement of tubular furnaces traversed by a copper wire after the latter has been coated with thixotropic dispersion. A copper wire, having a diameter of 0.3 mm., for example, is supplied from a reel 1 and travels first through a cleaning bath 3 and subsequently through an annealing device 4 having an internal temperature of 500 C. and a reducing or inert atmosphere. The annealing device 4 serves to soften the copper material of the wire. The wire, thus cleaned and softened, then passes over succeeding

guide rollers

5 and 8 which direct it finally in a substantially vertical direction passing through a space between opposed surfaces, such as on end plates, of the coating roller 6' and thence through a vertical arrangement I I of furnaces which comprise three heating zones a, b and c of respectively different temperatures. The dispersion medium which is supplied to the coating roller 6, in a manner hereinafter more fully described with regard to FIGS. 2 to 4, and applied by the roller 6' to the copper wire 2, evaporates in the first heating zone a so that the wire 2, when entering the heating zone I), possesses a uniform and centered or concentric covering of dry powder of thermoplastic synthetic material such as polyethylene. This powder sinters together in the heating zone I) and fuses in the heating zone so as to form a coherent and smooth coating of the thermoplastic material.

The wire 2, when issuing from the vertical furnace II, is deflected downwardly by a guide roller 12 and pulled off by a pulling device 13 to be wound upon a takeup drum 14.

For a pulling speed of m./min., there is required a length of about 60 m. for the furnace 11 with the following temperature distribution:

zonea 2l0C.

zone b 240 C.

zone c 260 C.

Several wires are preferably simultaneously run through one and the same furnace. In order to keep the number of wires as large as feasible, it is advisable to provide the vertical furnace 11 with a longitudinal heating chamber having a cross section of annular shape, and to uniformly distribute the wires circumferentially over the annular heating space of the furnace.

While the wires to be insulated travel substantially vertically to the furnace 11, an appreciable draft of air is caused to pass through the furnace. In order to prevent oxidation of the thermoplastic material such as polyethylene by the oxygen supplied in the air draft, the furnace is preferably rinsed with inert gas in counterflow to the travel direction of the wire. For example, hydrogen may be passed from above through the furnace and along the wire.

In contrast to the embodiment shown and described in the aforementioned copending application, the coating roller 18" of the instant application, due to the rotation of which the viscosity of the thixotropic dispersion is reduced, is mounted outside the supply tank 6' proper. A pump 24 is located within the supply tank 6 and by the aid thereof the thixotropic dispersion is supplied through a tube 25 to a side of the coating roller 18" which is located substantially diametrically opposite the side thereof along which the wire 2 passes in a vertical direction. At the location 26, a supply of thixotropic dispersion is formed which penetrates in part onto the spaced surfaces of the coating roller 18" between which the conductor wire 2 passes, the greater portion of the thixotropic dispersion being held back in the supply tank 6', however, by suitable wiper 27. The excess of the dispersion accordingly flows downwardly over a wiper 28 back into the supply tank 6. The supply tank 6' is completely closed, except for the opening required due to the arrangement of the coating roller 18", the tube 25 and the

wipers

27 and 28, so that evaporation of the dispersion medium is reduced to a minimum. Furthermore, due to the aforedescribed circulation of the dispersion medium, the formation of dead ends or stagnation pockets is avoided. The quantity of the dispersion supplied to the coating roller 18" is determined both by the power of the pump 24 and also by the adjustment of the

wipers

27 and 28. The coat ing roller 18" which is driven by a nonillustrated electrical motor, for example, rotates in a direction opposite to the direction in which the wire 2 advances vertically. The thickness of the applied insulating coating depends approximately upon the rotary speed of the coating roller 18",the value of which determines also the reduction of viscosity of the dispersion supplied to the wire 2 and depends also upon the spacing of the opposing surfaces and of the core of the coating roller 18" from the wire 2. In order to permit fine adjustment of thickness of the applied coating, the roller 18" is mounted so that it is adjustable in a direction perpendicular to the vertical direction in which the conductor is advanced.

The apparatus constructed in accordance with the invention of the instant application has a further advantage over the embodiment disclosed in the aforementioned copending application in that the reversing guide roller 8 is also located outside the dispersion. Consequently, if desired, the reversing guide 8 can be utilized simultaneously for imprinting, if the wire 2 which may have been previously provided with a coating is to be suitably identified or marked.

As aforementioned, the apparatus of my invention is suited particularly for coating a conductor with an insulating layer of polyethylene. In such a case it is recommended that the composition of the polyethylene dispersion of thixotropic structure be selected in such a manner as that given in the aforementioned copending application. The following composition of the dispersion, for example, has proven to be particularly advantageous:

40 percent polyethylene powder (stabilized) having a median grain size of 20 p.

36.5 percent water 15 percent methyl alcohol I percent nonylphenolpolyglycol ether 2.5 percent hydrate cellulose 5 percent isopropyl alcohol As aforementioned, for practical realization of apparatus according to the invention, it is recommended to permit several wires to pass through the apparatus simultaneously. In this manner the capacity of the apparatus is greatly increased.

As a further feature of my invention, it can be provided that the coating roller 18'', pivotable about a pivot point, be pressed by mechanical forces in a direction toward the conductor which is passed in the vertical direction between the opposing surfaces of the coating roller 18", whereby the spacing of the coating roller 18" from the conductors to be insulated is determined by an adjustable abutment or detent. In this manner assurance is provided that the spacing between the opposing surfaces of the coating roller 18" and the conductors that are being insulated is also maintained during shaking and vibrations occurring in the course of the operation of the apparatus. For this purpose, the coating roller 18" can be pressed by a spindle provided with a worm thread, which acts upon a gear connected with the coating roller 18", against the abutment or detent determining the spacing thereof from the conductors being insulated.

An example of such a construction of a coating roller located outside of the dispersion supply tank proper is shown schematically in FIGS. 2 and 3. As can be seen in FIGS. 2 and- 3, the coating roller 18'', due to the rotation of which the viscosity of thixotropic dispersion is reduced when applied to the wire 2, is located outside of the supply tank 6 proper and is rotatably mounted in common with the latter on the shaft of the reversing roller 8. Additionally mounted on the shaft of the reversing roller 8 is a gear 29 in the teeth of which a worm thread of a spindle 30 meshes. By rotating the handwheel 31 the shaft of the reversing roller 8 and therewith the position of the coating roller 18 can be twisted with respect to the vertically traversing wires 2. The size of this rotary motion is limited by the fact that a plate 32 secured to the coating roller 18" abuts against a stop pin 33 at the lower end of the plate 32, as shown in FIG. 2, for example. Due to the mechanical force which is exerted through the spindle 30 and the gear 29 on the coating roller 18'', assurance is afforded that the relative position of the coating roller 18" and the vertically traversing wires 2 are maintained even during the shaking and vibrations occurring in the course of operation of the apparatus. The amount of spacing between the opposing surfaces of the coating roller 18" and the wires 2 passing through the space therebetween is accordingly adjustable by the stop pin 33 which can be suitably screwed into the and out of the thread holder 34 thereof. It is also possible, however, to press the coating roller 18 against the abutment or stop member, which determines the spacing between the coating roller and the conductors to be insulated, by means of a lever provided with a weight. An embodiment of such apparatus is shown schematically in FIG. 4.

The embodiment of FIG. 4 differs from that of FIGS. 2 and 3 in that the rotary motion of the coating roller 18", which is mounted on the shaft of the reversing roller 8, is effected by a lever 35 provided with a weight at the free end thereof. Due to the action of this lever 35, the lower end of the plate 32 connected to the coating roller 18" is pressed against the adjustable stop pin 33 in the same manner as in the embodiment shown in FIGS. 2 and 3.

With the aid of this lever 35 the adjustment of the spacing between the opposing surfaces of the coating roller 18" and the wires 2 which are being insulated and which are traversing therebetween is effected more rapidly than is possible with the spindle of the embodiment shown in FIGS. 2 and 3.

lclaim:

1. Apparatus for insulating thin copper wires and other thin electric conductors with a coating of a polyolefin, comprising a tank for containing an aqueous dispersion of thixotropic structure, a coating roller mounted outside said tank and provided with a pair of spaced surfaces between which an electric conductor is traversable in a substantially vertical direction, said coating roller being rotatable in a direction opposite to the direction in which the electric conductor is traversable, said coating roller being pivotally mounted in a direction perpendicular to the substantially vertical direction in which the electric conductor is traversable between said spaced surfaces of said coating roller for adjusting the distance between said coating roller and the electric conductors being insulated, means for supplying the dispersion from said tank to said coating roller in an amount adequate for coating the electric conductor therewith, mechanical force-applying means for pressing the coating roller in a direction toward the electric conductors vertically travcrsable through the space between said surfaces of said coating roller, adjustable abutment means for limiting the distance between said coating roller and the electric conductors being insulated, and furnace means located upstream of said coating roller and traversable by the dispersion coated electric conductor for heating the same to vaporize the dispersion medium and sinter the remaining pulverulent polyolefin on the conductor to form a homogeneous coherent coating, and a gear connected to a plate on which said coating roller is rotatably mounted, and a spindle formed with a worm thread meshing with the teeth of said gear and coacting therewith for pressing said plate in direction against said abutment means.