US2291720A - Die suspension - Google Patents

Description

ug 4, 1942.v

R. M. HUKL DIE SUSPENSION Filed Dec. 27, 1939 ATTORN EYS Patented Aug. 4, 1942 ori-'ics DIE SUSPENSION Roy M. Hukle, Muskegon, Mich., assigner to' Anaconda Wire & Cable Company, a corporation of Delaware Appucano December 27, ms, servo. '311,123

(o1. sai-53) 8 Claims.

strong 'to prevent withdrawal-'lof thedie there-` from by forces normally acting on the'die. In

a preferred embodiment of the invention, a die chamber is formed within the eld of an electromagnet. 'A' die of magnetizable material is positioned within the die chamber in such manner as to be free to move to a limited extent in ail coating material adhering to the wire is baked' on.l AThe finished product is drawn from the oven and wound on a suitablereel. This method is satisfactory so long as the coating material is ot such non-viscous character that a thin coating of uniform thickness adheres to the wire as a result of its being drawn through the bath of coating material. However, in an effort to .provide improved coatingv materials, thick, heavy varnishes, such as polyvinyl acetal varnishes,.

have been developed. These are of such viscous character that it is not possible -to obtain a thin coating ,of uniform thickness simply by passing the wire through thecoating material, for such materials adhere to the wire in the form of heavy coats of irregular thickness. In orderv to form a thin uniform coating, it has been proposed to draw the Wire, after passage in contact with the viscous coating material, through a die to remove excess coating material and produce a. lm of uniform thickness about the wire. This proposal has been diicult to carry out successfully because of the diculty of keeping the wire centered in the die. There is a tendency for the Wire to whip somewhat as it passes rapidly through the die, and the irregular lateral movement resulting from this Whip makes it virtually impossible to keep the wire properly centered in the die. Unless the wire is properly centered, the coating produced is not of uniform thickness, for if the wire whips to the side, too much coat- 'ing material is taken oi that side and not enough o the other.

The present invention overcomes this diiiiculty by providing an improvedapparatus in which the die` is suspended or "floated so that it may be free to move to a limited extent in all directions. The die thus is enabled to center itself about the wire, with the result that a coating of uniform thickness is formed on the wire.

In accordance with the invention, a die comprising magnetizable material is disposed within amagnetic eld in such manner that the die is free to move to a limited extent in al1 directions within the eld, but the field is made sumciently ing to .pull the die downwards.

directions. -Means are provided for drawing a wire through the die, and other means are vprovided for` energizing the'electromagnet suii'iciently to create a strong enough magnetic field to.

prevent withdrawal of the die from the die chamber either by the force of gravity or by forces acting on the die as wire is drawn therethrough.

The apparatus of the invention may be arranged to permit wire to be drawn either vertically or horizontally through the die. In the former case, the die may be positioned within a simple annular electromagnet coil or solenoid. In the latter case, it is preferredto employ upper and lower electromagnet coils with the die chamlber and die located in the field between them, provision being made to energize the upper electromagnet coil with a greater number of ampereturns so as to Ibalance the force of gravity tend- The invention will -be better understood Afrom the following description, consideredin conjunction with the accompanying drawing, in which Fig. 1 is a schematic elevation of a. 'wire coating apparatus including the apparatus of the invention;

Fig. 2 is a cross-section through the magnetic die suspension apparatus shown in Fig. l; and

Fig. 3 is an elevation of modified die suspension apparatus especially adapted for drawing Wire horizontally. y

' The apparatus shown in the drawing (Fig. l)

Y comprises a supply yreel lo from which wire la to becoated is drawn. The wire passes over a guide sheave i2 through a gland i3 in a vessel it containing a viscous varnish, such as a solution of polyvinyl formal or other polyvinyl acetal composition. The wire passing through the vessel id acquires a heavy, irregular coat of the viscousvarnish. In order to remove excess varnish adhering to the wire and to produce a uniform varnish iilm thereabout, the coated wire from the varnish vessel is passed through a die'l comprising magnetizable material disposed in a die chamber within the field of an annular electromagnet or solenoid coil i6. The electromagnet coil is energized suiciently by a generator G to produce a field sufficiently strong to prevent withdrawal of the die from the die chamberby the force otgravty or by the force exerted on the die by the wire beingdrawn therethrough. 'I'he die, however, is free to move to a limited extent in all directions within the die chamber, and so is able to accommodate irregular lateral motion of the wire and remain centered at all times about the rwire. Consequently the varnish iilm` about the wire emerging from the die is substantially uniform in thickness around the circumference of the iwire.

The Ielectrcmag'net coil I6 shown in the drawings is of conventional solenoid construction. It comprises a large number of turns of wire of suitf able size wound on a cylindrical form 24, which The wire emerging from the die passes through an oven II of conventionakdesign, in which the varnish is baked on the wire at temperatures suitable for the particular coating composition employed, and thence over a guide sheave I8 to terial, is :dared outwardly to form a bell-shaped mouth, thus providing for smooth admission of the wire to the die aperture. AThe bell-shaped entrance 22 also allows the excess varnish being `scraped from the wire to build up enough pressure to aid in keeping the die centered about the wire.

The die i5 comprises a large proportion of iron or other magnetizable material, and is positioned within a die chamber 23 dened by the cylindrical opening through an electromagnet coil or solenoid I6. The wire passes substantially centrally throughthis die chamber. The die, which advantageousiy is generally sphericalin shape (it may be made, for example, from a steel ball bearing), is considerably smaller in ldiameter than the die chamber 23, and so is free to move to a limited extent (determined by the bounds of the die chamber) iuanydirection.

The electromagnet coil I6 is composed of a suriicient number of turns of wire, and is energized suihciently from a suitable source of current, to create a magnetic iield in and about the die chamber and the -de therein which is strong enough to prevent withdrawal of the die from the die chamber either by the force of gravity 4or by the force exerted on the die by the wire being drawn therethrough. So long as the die remains within the die chamber, it is free to move in any direction, but asssoon as the die begins to emerge from the chamber, the magnetic forces developed by the energized coil resist further withdrawal, Hence the die is enabled to move with sufdcient freedom in any direction to accommodate irregular lateral movement of the wire being drawn therethrough, and yet is held by magnetic forces within the confines of the die chamber.

The die I5 is shown in Fig. 2 substantially-as it appears when a wire is being drawn therethrough with the electromagnet coil properly energired. Ihe drag of the wire has drawn the die to the upper limit of the die chamber, but

form denes the boundaries of the die chamber 23. Annular end plates 25 serve to retain the coil on the cylindrical form. The form 24 should be of brass, copper, plastic composition, or other suitable non-magnetic material so as not to shortcircuit the magnetic flux path through the die chamber. The annular end plates 25, however, may be of iron, and the cylindrical outer surface of the coil may be surrounded with iron or other suitable magnetic material so as to improve the ilux path throughout this portion of the magnetic circuit, and thus increase the 'magnetic eiiiciency of the structure. 1 The terminals 26 of the coil are connected to a suitable source of current for energizing purposes. Any of the usual sources of either alternating or direct current may be employed. The voltage impressed across the terminals 26 of the coil I6 depends at least in part upon the electrical design of the coil, and any alternating or direct current source capable of supplying this voltage, such, for example, as alternating or direct current generators, or batteries may be used: The particular construction and shape of the electromagnet structure 'described above and shown in Fig. 2 is generallyrsatisfactory, but the invention is not limited to any particular form or shape of electromagnet structure. For exam-F ple, in some cases it may be preferred to form "the die chamber, and correspondingly the form this force tending u withdraw the wire from the die chamber is more than balanced by the magnetic forces developed by the electromagnet coil. Ihe die, therefore, is prevented from being wholly withdrawn from the die chamber, but it is free to move laterally to a.' limited extent to accomn 1o+ date irregular lateral motion ofthe wire.

on which-the electromagnet coil is wound, with a central portion of reduced diameter and ends of greater diameter, thus providing a form in the shape of the well-known hour glass. `Instead of circular forms on which the coil is wound, square or rectangular forms may be employed if desired.

It is even possible to employ permanent magnets instead of electromagnets about the form to provide the magnetic iield'required to hold the die within the die chamber. A

The electromagnet structure described above is particularly suitable `for use in cases where a wire is drawn vertically, or at an inclination approaching the vertical, through the die. In cases where it is desired to draw'a wire through the die horizontally or at an inclination approaching the horizontal, a modiiled form of 'electromagnet structure generally is preferred. Such a structure is shown in Fig. 3. In this modiiied apparatus a spherical die 3U, preferably constructed similarly to the die I5 described above, isi mounted so as to be free to move to a limited extent in any direction within the connes of a die chamber 3l. The die chamber 3l is deiined by a pair of form members 32 of substantially semicylindrical shape. Arcuate sections 33 are cut from the edges of the form members 32 near the central portion thereof. Upper and lower electromagnets coils 3l and 35 are wound on the forms 32 above and below the arcuate cut-out portions Il, and the terminals 3i and`31 of these coils are connected to a suitable source of alternating or .direct current.

In order to compensate for the eil'ect of gravity tending to pull the magnetizable die downwardly, provision is made for energizing the upper magnet coil 3l to a sulciently greater extent than the lower coil 35 to balance magnetically This may be greater number of ampere-turns than the lower coil. The upper coil S thus may be wound with ture is substantially the same as that described above in connection with the apparatus shown in Fig. 2. Wire to which a relatively heavy irregular coat of varnish has been applied is drawn substantially horizontally, or inclined somewhat with respect to 'the horizontal; through the die. The force exerted on the die by the wire passing therethrough and tending to withdraw the die lateral movement of the die as the wire is drawn therethrough.

4. Apparatus for coating wire withl a plastic composition comprising means for applying said composition to a wire, and means'for removing excess compositionl from the wire and forming a uniform nlm thereof about the wire comprising a magnet, aldie of magnetizable material having a die opening extendingtherethrough positioned in the eld of said magnet, said eld being sutliciently strong to prevent withdrawal of the die therefrom by forces normally acting on the die, means for drawing the compositioncoated wire through the die opening, the entrance portion of said die opening being ared in a manner to maintain the die at all times centered about the wire, and the die being free to prising a die chamber, a die of magnetizable material positioned within said chamber so as to be thereof, means for drawing a wire horizontally through said chamber and through the die, electromagnet coils mounted above and below the die chamber in magnetic relation with the die therein, and means for energizing said coils suiiiciently to create a magnetic iield in and about said move to a limited extent in all directions within the magnetic iield to accommodate irregular lateral movement of the die as the wire is vdrawn therethrough.

5. Apparatus ofthe character described comprising an electromagnet, a die chamber arranged within the eld oi said electromagnet, a die of magnetizable material having a die opening 'extending therethrough positioned within said die chamber, means for drawing a wire having coating composition thereon through the die opening, the entrance portion of said die opening being dared in a manner to maintain a die at all times` centered about the wire,l and means for energizing the electromagnet sufficiently to prevent withdrawal of the die from the chamber by the forces exerted on the die as the wire is drawn therethrough, the 'die being free to move to a j limited extent in all directions within the die chamber to accommodate irregular lateral movedie chamber of suiiicient strengthwto prevent rst electromagnet coil mounted above said die chamber in magnetic relation with the die therein, a second electromagnet coil mounted below said die chamber in magnetic-relation with the -die.therein, and means for energizing said coils suiiiciently to create a magnetic neld in and about said die chamber of suicient strength to prevent withdrawal of the die from thechamber by the forces acting on the die as wire is drawn therethrough, said rst electromagnet coil being energized with a sufficiently greater number oi ampere-turns than said second electromagnet prising means for creating a magnetic eld, a

die of magnetlzable material having-adie opening extending therethrough positioned in said magnetic neld, said magnetic eld being sumciently strong to prevent withdrawal of the die therefrom by forcesV normally acting on the die, means for drawing a wire having coating composition thereon through the die opening, the entrance portion of said die opening being ared in .a manner to maintain the die at all times =ment of the die as the Wire is drawn therethrough.

6. Apparatus Aof the character described comtending therethrough positioned within said coil,

means for drawing a wire having coating composition thereon vertically through said coil and through the opening of the die therein, the entrance portion of said die opening being ared in a manner to maintain the die at all times centered about the wire, and means for energizing the coil suiiiciently to-create a magnetic iield of suicient strength. toprevent withdrawal of the die from its position in the-coil by the force of gravity or by the force exerted on the die as the wire is drawn therethrough, the die being free to move to a limited extent in all directions within the electromagnet coil to accomodate irregular lateral movement of the die as wire is drawn therethrough;

7. Apparatus of the character described comprising a'dle chamber, a die of magnetizable material having a die opening extending therethrough positioned in said die chamber, means for drawing a wire having coating composition thereon 'horizontally through said chamber and through'the opening .of the die therein, the enthroughfelectromagnet coils mounted,above and below the die chamber in magnetic relation with f thedie therein, and means for energizing said and about said die chamber to' prevent withdrawal of the die from the chamber by the forces exertedon the die as wire is drawn therethrough.

8. The method of coating a wire with a film of uniform thickness of a viscous liquid which comprises applying a relatively thick coating of the liquid to a wire,y passing the thus-coated wire through a die of magnetizable material, whereby excess liquid is removed from the Wire, and creat-`l ing a magnetic eld about the die in such manv10 ner as to establish about the die a magnetic eld substantially balanced radially about the wire thus permitting the die to move freely to a limited extent in any direction radially about the wire, said balanced field being of sumcient strength to prevent withdrawal of the die o ut of said balanced magnetic neld by the forces acting longitudinally of the Wire as the wire is drawn through the die.

r ROY M. HUKLE.

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