US3117887A

US3117887A - Apparatus and procedure for evaporating metal in vacuum metalizing

Info

Publication number: US3117887A
Application number: US151661A
Authority: US
Inventors: George A Shepard; Jr Carl F Brooker
Original assignee: Republic Steel Corp
Current assignee: Republic Steel Corp
Priority date: 1961-11-13
Filing date: 1961-11-13
Publication date: 1964-01-14
Anticipated expiration: 1981-01-14
Also published as: NL285351A; BE624470A; FR1337659A; DE1293516B; LU42655A1; NL125589C; GB964461A

Description

Jan. 14, 1964 s. A. SHEPARD ETAL 3,117,887

APPARATUS AND PROCEDURE FOR EVAPORATING METAL IN VACUUM METALIZING 2 Sheets-Sheet 1 Filed Nov, 13. 1961 /m/enf0r5 6602616 A Shepard Car/ .Brooker, L/r

By 1b. 44

Afro/n y 1 Jan. 14, 1964 .A. SHEPARD APPARATUS AND PROCEDURE FOR EVAPORATING v METAL IN VACUUM METALIZING Filed Nov. 115, 1961 2 Sheets-Sheet 2 0 "3 m \k n "x Q "3 {Q g \I Q & "3 N N a R i l l 1 p l II 1 i e o I i L] 5 //7 ven/ers George A. Shepard United States Patent 3,1173%7 APPARATUS AND PRGCEDURE FER EVAPORAT- ING METAL IN VAQUUM METAMZING George A. Shepard, Parma, and (Jarl F. Brooker, In,

(Garfield Heights, Cuhio, assignors to Republic Steel Corporation, Cleveland, ()hio, a corporation of New Jersey Filed Nov. 13, 196i, Ser. No. 151,661 Claims. (Cl. Ill-4597.1)

This invention relates to vacuum metalizing, i.e., meth- Oils and apparatus for generating and depositing metal vapor in a vacuum, to produce metal coatings on various articles. In particular, the invention is concerned with improved means and methods of vaporizing metal for plating such metal on desired substrates, especially strip materials such as thin steel strip.

In the art of vapor deposition of aluminum, with which the invention is concerned in important, specific aspects, considerable problem has arisen in achieving continuing conversison of the supplied aluminum metal to vapor, over relatively long periods of time, and in relatively large quantity, for example as is necessary to obtain an economical operation for plating steel strip with aluminum. One form of apparatus commonly proposed or used for this purpose has involved an elongated, horizontal member of suitable electrical resistance material arranged to contain a shallow pool of molten aluminum in its upper face and connected to a suitable source of electric current for generation of heat by passage of said current through the member and the aluminum pool. Such members have sometimes been called boats, by reason of their configuration, including the upwardly facing, elongated cavity. The supplied heat not only keeps the aluminum molten and melts further supplies of the metal, but converts such metal into vapor which travels to a passing work surface above the boat, where the vapor condenses or deposits as an adherent, solid film. As will be understood, the apparatus is enclosed in a suitable chamber or vessel, with appropriate connection to vacuum pumping means so that a relatively high vacuum, of the order of microns or fractions of a micron of mercury, is maintained at all times.

While a variety of materials have been proposed for the composition of the so-called boat, including graphite or carbon and particularly including materials more resistant to chemical attack or other deterioration, such as various borides, nitrides and carbides, apparatus of this character has often been unsatisfactory where the service requirement has been to produce relatively considerable volumes of vapor over extended periods and in an economical manner. Even those materials which seem best from the standpoint of resistance to attack or other deterioration and which have suitable characteristics of electrical resistance, tend to Wear out rapidly, either by eroding or corroding action of the aluminum metal, or by cracking under the high temperatures involved, such cracking being the result of localized overheating which is diflicult to avoid. I11 consequence, the described horizontal boats have failed to provide the desired results, especially in that they must be frequently replaced, necessisting correspondingly costly shut-down of the equipment. While as explained below, yet other arrangements have been suggested for establishing a continuing supply of molten aluminum and converting such metal to vapor, such proposals have involved objectionable features or have not been adapted for many conditions of services, such as in plating steel strip with the stated metal. Accordingly, important objects of the invention are to provide new methods and apparatus of the character described, especially for overcoming the disadvantages of prior devices and for the provision of aluminum vapor generation in relatively considerable quantities and over relatively long periods of time, i.e., without interruption.

To these and other ends, important features of the invention comprise the provision of a metal heating and vaporizing member of plate or block-like configuration, arranged in a vertical position and havingoppositely facing surfaces of relatively considerable area. i This heating and vaporizing member is composedof appropriately durable material, resistant to attack under the conditions of use and having electrical properties appropriate for generation of heat at the desired rate. Examples of suitable material are given hereinbelow; indeed :a variety of substances known as appropriate for conventional boats or similar structures of the prior art, can be employed for the present device. For brevity, the material of the metalcarrying and evaporating element will sometimes be identified herein simply as electrical resistance material, it being understood that such term is employed to designate compositions of the type just described, and it being further understood that reference-s to an elementcomposed of the defined material will in general include combinations of substances, e.g., as in the use of a core of one material, having superior electrical properties, with an outer sheath of sufficient thickness) having superior resistance to deterioration.

The invention further embraces the combination of means engaging the plate-like member at its top and bottom ends for holding it in a vertical position, preferably under spring pressure, together with elements, which may cooperate in constituting the supporting means, for conducting electric current to the ends of the plate, i.e., for passage of such current through the latter and through the coatings of molten metal hereon. Means are further provided for supplying aluminum continuously to both faces of the heating member, a special feature residing in arrangements for feeding aluminum wire .or equivalent body of aluminum to each of the faces at an uppermost region thereof. In this fashion, the wire or like members continuously urged against the respective faces of the vaporizing block, are continuously melted, causing the molten aluminum to spread, as a coating, across and indeed all over each face of the block, including the entire area below the locality of impingement of the wire and any small area above it. As will be apparent, the material composing the heating element is selected to be wetted by molten aluminum, at least at the operating temperatures, whereby the desired spread of molten metal over each entire face is readily achieved.

As will now be appreciated, this arrangement, when brought to temperature and established with a descending coating of aluminum on each side, functions to cause evaporation of the metal under the vacuum conditions whereby the vapor is projected outwardly and in a preponderantly lateral direction. As will also now be seen, the method of the invention embraces the generation and outward projection of metal vapor from descending coatings of the molten metal on oppositely facing surfaces of a plate-like structure, supply of metal to such surfaces being effected by feed of aluminum wire or equivalent into abutment with an upper part of each surface. An important mode of arrangement involves the disposition of the described vapor source between vertical paths traversed by the work structure to be coated, the work being sometimes described, in this art, as the substrate upon which the metal of the vapor is deposited. In a specifically advantageous use or embodiment of the invention, i.e., where it is desired to plate vaporized aluminum on a continuously passing strip of steel, the operation is such that the strip travels upward past one face of the source, and then after traversing an appropriately shielded roller, moves back downward in spaced and appropriately close 3 relation to the opposite face. In this fashion two coats or films of the transmitted metal are applied to the same surface of the strip, thus building up a particularly satisfactory coating.

In an operation designed to treat both surfaces of the strip, the latter would then be turned vertically upward again, while maintaining a second vapor source, of identical construction with the first, in the U-shaped loop so provided. Whether used for both sides or only one, of the passing sheet material, the vapor-producing device and method is unusually convenient and reliable and provides an abundant supply of condensable metal vapor. Coatings of desirable thickness are thus readily and economically obtained, even at relatively high speeds of strip travel. While some proposals have heretofore been made for the use of an upright rod as a heating and vaporizing element, such methods have generally involved attempts to disposed molten metal on the rod by its creeping upward from a pool into which the rod dips. Alternatively, there has been some suggestion of arranging transfer of molten metal from a liquid supply pool, to or along the rod. The requirement has generally involved a rise of such metal by its wetting action, or has included other complex or uneconomical expedients, for example as by causing the metal first to rise from such pool by the wettin g effect, to a downward turn of the rod, whence gravity cooperates in carrying the metal further down the rod, it being apparently necessary that the rod have only a sloping position rather than a truly vertical one. In the present device,

there is no separate melting or low-temperature heating section, nor is reliance placed on any significant extent of upward path to be traversed by molten metal under Wetting action alone. A simpler and more readily controllable operation is realized in the present invention, which at the same time affords a substantially larger out put of aluminum vapor so as to achieve results that have not been heretofore obtained. One such result is the accomplishment of a vapor-deposited aluminum coating on steel strip in a sumciently economical way to yield aluminum plated strip under conditions that are commercially feasible. In other words, the present invention contributes materially to enable the production of such strip for use in the manufacture of cans and like containers.

The foregoing aspects of the invention, together with further features of specific improvement, are illustrated in the accompanying drawings, wherein:

FIG. 1 is a perspective view of the vapor source of the invention, with certain necessary elements related to the source, all arranged to illustrate the disposition of this and another similar source to coat both sides of a passing strip;

FIG. 2 is a vertical view, generally in elevation, of the arrangement of the invention in a vacuum chamber, some parts being shown in vertical cross-section; and

FIG. 3 is a side elevation of the aluminum-holding part of the combination shown in FIG. 2, with illustration of the spring-supporting means also shown in FIG. 1.

As indicated in FIG. 1, the invention is illustrated in connection with vacuum deposition of aluminum on steel strip 10, which is continuously fed lengthwise into the evacuated region from a suitable coil (not shown) to a roller 11 about which the strip is turned upward, at right angles, to travel vertically as indicated at Illa. At an upper locality the strip traverses another roller 12, turning through 180 and thence descending, as at 1012 to a further roller 13 below. A vapor source assembly 14 is disposed between the vertical portions 10a, lilb of the traveling strip, for applying two successive layers or films of aluminum upon the surface of the strip which faces the source. If the opposite side of the strip is also to be coated, the strip may turn upwardly again as at 100, from the roller 13, so as eventually to be delivered over the roller 15 and out of the evacuated space to a take-up reel or coil, not shown. It will be understood that the chamber or vessel in which the apparatus is disposed and which is subjected to vacuum is of any conventional or suitable nature and is therefore not shown in FIG. 1, although such vessel is indicated by simplified representation of its top and bottom walls 17, 18 in FIG. 2.

Referring also to FIGS. 2 and 3, the vapor source comprises a plate-like body or block 20 of electrical resistance material, for example, a monolithic element consisting of a compacted, homogeneous mixture of boron nitride and titanium diboride. Although other shapes may be used, the element 2% is advantageously elongated in a vertical direction, with

wide faces

21, 22 extending vertically and disposed respectively opposite the near faces of the traveling strip portions 10a and lilb. The upper and lower ends of the plate 249 (which has sometimes been designated as a boat, because of its similarity of function rather than of appearance to the horizontal evaporating boats previously used) are engaged by

respective connector elements

23, 24.

These elements, made of copper for electrical conductivity and likewise for thermal conductivity to insure that they are suitably cooled, may have a variety of shapes, the chief requirement being for electrical contact, as by tight abutment with the boat over a considerable area, rather than point contacts which tend to cause hot spots in the boat. For example, each is shown as having a tapered cavity, as at 26 in the element 23, into which a correspondingly tapered or truncated wedge-like portion of the member 2t will fit. That is to say, the

elements

23, 24 are identical and suitably engage the ends of the member 26? in good electrical contact, the wedgeshaped arrangement of the latter being merely illustrated as one of various suitable modes of achieving such contact. Each of these connector members is also interiorly hollowed or drilled, as at 27 in the member 23, to accommodate a circulating, liquid coolant, supplied through proper connecting tubes, as the

tubes

28, 29 for the member 23 and the tubes 3t), 31 for the member 24%. The

copper tubes

23, 29 and 3t 31 are carried to the outside of the vacuum chamber, for example through insulating fittings as shown for purposes of illustration at 32, 33 in the walls 18, 17 of FIG. 2. This copper tubing also functions as electrical conductor, whereby one side of an adjustable current source 35 is connected to the

tubes

28, 29 and thus to the upper end of the plate 20, while the other side of the source 35 extends to the

other tubes

30, 31 and hence to the lower end of the plate. Water or other suitable coolant is circulated through the tubing, for corresponding removal of heat from the

copper connectors

23, 24.

Means, preferably of a spring-clamping nature, are provided to hold the assembly of the source plate and connectors in desired position. For example, a pair of heavy spring steel strips 36, 37 (FIG. 3) are supported, as by a wall (not shown) of the chamber, with the aid of suitable means, diagrammatically illustrated as

bracket arms

38, 39, the arrangement being such that the outer ends 36a, 37a of the strips tend to be sprung apart by a substantially greater distance than the vertical height of the vapor source assembly. These ends 36a, 370 are brought into engagement with the assembly, specifically with intervening electrical insulation blocks it), 41, respectively abutting the top and bottom faces of the

electrical con ductors

23, 24, all in such fashion as to hold the assembly firmly together and in place. Specifically, a screwdown device consisting of a rod 42 having its threaded ends passed through holes in the

arms

36, 37 and retained by corresponding nuts 43, 44, brings the arms together so that their free ends 36a, 37a engage the vapor source assembly with considerable spring pressure. The nuts 43, 44 are suitably screwed down so that the stiff resilience of the

arms

36, 37 over the regions between the screw-down rod 42 and the source assembly 14 provides substantial spring loading in the engagement of the arm portions 36a, 37a with the insulator blocks 40, 41 and in holding the

connectors

23, 24 firmly against d the ends of the plate 20. The resilient support of the source assembly not only holds it in the vertical position, with good contact of the electrical connectors, but also allows freedom for expansion, e.g., during heat up.

Supply of aluminum metal in solid form to the

faces

21, 22 of the plate or boat is achieved by feeding aluminum wire, or such metal in equivalent, elongated pieces, against uppermost areas of the surfaces. Thus

aluminum wires

46, 47, entering the chamber from suitable supplies (not shown), are advanced continuously lengthwise by appropriate means as indicated at 4-8, 49 so that the leading end of each wire continuously abuts the corresponding face of the plate 20, and melts off to furnish the desired coating, for evaporation.

in operation, the described arrangement has been found to function effectively in achieving delivery of aluminum vapor in a lateral direction from the

faces

21, 22. In starting up, the element 2%) is gradually heated by passing current through it, ie, by resistance heating. When its temperature has reached a point sufficiently high to start the evaporation process, some wire is fed to the surfaces, i.e., by advancing the

wires

46, 47 against the faces, where it promptly melts and spreads over each surface, providing a coating of descending molten metal. The current supply is maintained, continuing the heating action, so that evaporation of aluminum commences and thereafter continues indefinitely. In such operation, the heating current actually travels both through the plate or block 2t) and the layer of aluminum on its surfaces, although the major development of heat is occasioned by the path through the plate, which is composed of material having substantially higher electrical resistance than aluminum metal.

Control of the operation is relatively simple, the chief requirement being to maintain a balance between the rate of metal feed, with the wire 46, 4'7, and the current supply to the assembly. If the metal feed rate is too high, the resistance becomes low, so that not enough heat is generated for desired conversion or the desired rate of conversion of the aluminum to vapor form. That is to say, an over-supply of metal provides an overly thick layer or coating of aluminum in molten form, increasing the low resistance path and reducing the heating effect. On the other hand, if the metal feed rate is unduly low, the element 20 becomes too hot, with a resultant tendency to crack and deteriorate. It has been found quite easy, however, to maintain a balance so that abundant vapor is generated and the plate 20 nevertheless does not get too hot. As necessary, the control factors of feed rate and current flow may be adjusted from time to time to preserve balance of conditions, it being understood that unavoidable attack on the material of the structure 20 by the molten aluminum may alter the electrical profile of the structure, i.e., its resistance and thus its heat-producing ability, at various localized regions.

By way of example, a plate 8 inches tall, 2 inches wide and 1 inch thick, thus providing two

faces

22, 21, each having dimensions 2 inches by v8 inches, has been found to be efficient in producing and delivering aluminum vapor at rates selectable in the range of a few grams per minute up to or grams per minute. At the higher rates of aluminum feed, the life of the structure 20 tends to be shorter, an optimum value for feed rate being about 20 grams per minute with the element dimensioned as above. Higher feed and delivery rates are indicated to be obtainable with structures 20 of larger cross-section than the given example, with no undue shortening of the life of the element.

As aluminum vapor is evolved, the work structure or other substrate to be coated is advanced and passed along both sides of the vapor source, in appropriately spaced relation (as will be understood in the art) for deposition of the desired aluminum coating by condensation from the impinging vapor. The vapor travels outward from 6 the faces of the source, e.g., along straight line paths, ranging generally from the perpendicular to some useful angle, whereby efficient deposit of aluminum is achieved on the passing work, such as the steel strip indicated at 10a, 1%.

It will also be understood that the described control of the operation is readily effected through inspection of the coated surfaces of the passing strip, as likewise on the surfaces of the member 20* (through an appropriate sight glass, not shown), the further observable factor being the amount of current flow from the source 35, as indicated by a meter (not shown). In general, adjustment is chiefly necessary of the rate of wire feed, in that if adequate coating is being obtained on the structures 10a, 10b, and the surfaces of the element 20 are Well coated with the metal, proper functioning is generally assured. By way of example, when wire was fed at a rate of about 20 grams per minute to a representative block 20 as specifically described above, it was found that a current of 3,000 amperes, at an impressed potential of 8.5 volts, across the terminals of the block, afforded satisfactory results for plating a steel strip 6 inches wide and spaced (as at 10a, 10b) 9 inches from the

faces

22, 21, the voltage and current values being averages over the life of the boat, with the total power being fairly constant.

With a suitable material as the composition of the plate 29, relatively long life is achieved, for instance in that 40 hours or more of service can be had without deterioration of the plate (exhibited by erratic results, cracking or breakage of the plate body) such as to require replacement. The cooling arrangements for the

copper connecting elements

23, 24 prevent damage to these parts, so that insertion of a new piece 29- is all that is required from time to time. A particular advantage of the described wapor source is that no supplemental or feed pools of molten metal are required, nor any separate melting area. The aluminum is directly fed to the evaporating surface in solid form, while the structure serves both to melt and evaporate the metal, and the wetting of the surface with molten metal is greately assisted, to the point of maintaining an ample supply thereon at all times and at relatively high feed rates, by the aid of gravity in causing continuing downward flow. Evaporation can nevertheless be adequately controlled to prevent loss of molten metal at the foot of the plate; essentially all of the supplied aluminum is converted to vapor.

Thus as shown in FIG. 1, where a steel strip is to be coated, the passage of the strip 10 through. the vertical path sections 10a and 10b deposits two successive layers :of aluminum in satisfactory manner. If the other side of the strip is to be similarly coated, a like vapor source '50 (e.g., identical with the device 14 and its appurten- :ances) mounted vertically between the strip paths 1th) and We will deliver vapor to the opposite side of the strip, again applying two sucessive layers so that the strip continuously discharged from the chamber over the roll 15 is completely plated with aluminum.

As indicated above, a presently preferred composition for the plate or block 20 is a mixture of borin nitride and a boride, such as zirconium or titanium boride, intimately and homogeneously compacted to form a block which is machined to the desired shape and dimensions. Such material, sometimes known as a cermet, has good resistance to molten aluminum and also appropriate electrical resistance, the former quality being imparted by the boron nitride and the relatively poor thermal and electrical conductivity of such compound being counterbalian-ced by the superior qualities of the boride, preferably titanium =diboride, whereby a composition of thedesired durability is provided, having electrical resistance .(e. g., in the range of 5 00' to =0=micro ohm centimeters) which provides heating effect that is adequate for a good rate of evaporation yet is not excessive to the point of premature cracking or destruction of the element. With electrical resistance material of the specific composition mentioned above, e.g., so-called conductive boron nitride, the metal-melting and evaporating elements afford long periods of use, to the extent that more than 100 pounds of aluminum and indeed up to 150 pounds or more, may be evaporated at a satisfactorily rapid rate, before the condition of the element deteriorates to a point where it should be replaced for the sake of efficiency or other reasons.

It will be understood that other materials may be used, examples being various nitrides, borides and carbides, and combinations of them, likewise even carbonaceous material such as graphite or the harder forms of carbon, but in a number of instances, the life of the element so composed may be shorter than with the presently preferred substances. Alternatively, the plate 20 may be a structure of composite nature, as in having a core of rather highly conductive material, encased by a layer or sheath of material specially resistant to corrosion or erosion but of relatively high electrical resistance. In all instances, many of the advantages of the invention, particularly in affording an arrangement for both melting and evaporating the aluminum while providing such evaporation over extended areas and at a relatively high rate, will be substantially achieved. Indeed in general, any material having the requisite electrical properties, durability, and resistance to attack, as outlined hereinabove, may be employed for the body of the source element, being selected to suit the desired conditions and the metal to be evaporated, as will now be readily understood.

In the specific source mounting design shown in the drawings, the insulating

elements

40, 41, effective in permitting the spring loaded grasp of the source assembly by the

members

36 and 37, are blocks of appropriate insulating material. Thus these members may be composed of refractory substances such as ceramic-type insulators, or alternatively, if cooling of the

copper connector members

23 and 24 is sufliciently effective, other conventional insulating substances such as bakelite, hard rubber, or various other synthetic resins, may be employed.

Ordinarily, when the metalizing apparatus is first put in operation or when the equipment is restarted with a new plate 20, care is preferably taken to avoid adverse effects of unduly rapid heating-up. With the cooling water traversing the

connectors

23, 24 to keep them cool, the system is first pumped down to the metalizing pressure, for example one-half micron, and direct current is then passed through the plate or boat 20. By progressive adjustment of the current, the heating is achieved gradually so that the material is not subject to unduly large thermal shock. When the material has reached a temperature suflicient to evaporate aluminum, e.g., 1260 C. (as estimated by optical view of the color of the heated source element, through a sight glass), small amounts of wire are fed until the surfaces, particularly the opposed faces 21 and 22, are entirely wet with the molten metal. The feed rate of the wire is then increased and adjusted, with appropriate adjustment of the current supply, until the rate of evaporation is equal to the feed rate, both preferably at a suitable value for optimum life of the vapor source element as explained above. Within obvious limits of convenience, the size of the aluminum Wire supply is not critical, good results being readily obtained with wire of 0.062 to 0.375 inch diameter, for example 0.093 inch; larger wires are also contemplated, as for larger boats.

While in a specific aspect the invention is concerned with the evaporation of aluminum for vacuum metalizing, especially to plate steel or other ferrous metal strip for use in the manufacture of cans to be employed as food containers or the like, the described methods and apparatus are adaptable to vacuum deposition of other metals, particularly those with which vacuum evaporation and plating have been achieved. Hence any of a Wide variety of metals may be used, providing appropriate material for the source element is selected, to have the properties outline above, and suitable vacuum conditions are chosen; among others, some examples of such metals are gold, silver, cadmium and tin. In each case the selected metal may be fed in wire or other suitable solid form to the faces of an element 20 of appropriate composition, while the latter is electrically heated to provide full wetting of the surfaces with downwardly traveling molten metal, and to achieve continuous evaporation of such metal. In the light of the explanation of the invention as set forth above, it will be apparent that conditions can be readily selected to achieve good rates of evaporation at the temperatures required for these alternatively usable metals.

It is to be understood that the invention is not limited to the specific structures and operations herein shown and described, but may be carried out in other ways without departure from its spirit.

We claim:

1. In vacuum metalizing apparatus, a metal vapor source comprising an upright plate-like structure of electrical resistance material having opposite vertical faces, means for feeding solid metal to the respective faces at upper portions thereof, to be melted against said faces, and to form a descending coating of molten metal on the faces, and current supplying means electrically connected to said structure at its top and bottom ends to generate heat by passage of electric current, for melting the supplied solid metal on the faces of the structure to establish the aforesaid coating and for evaporating metal from the aforesaid coating to deliver metal vapor laterally from said faces.

2. In vacuum metalizing apparatus, a metal vapor source comprising an upright plate of electrical resistance material having opposite vertical faces, means for feeding elongated members of solid metal against the respective faces at upper portions thereof, to be melted against said faces, and to form a coating of molten metal on the faces, and current supplying means electrically connected to said plate at its top and bottom ends to generate heat by passage of electric current, for melting the supplied solid metal on the faces of the structure to establish the aforesaid coating and for evaporating metal from the aforesaid coating to deliver metal vapor laterally from said faces.

3. In vacuum metalizing apparatus, a metal vapor source comprising an upright plate of electrical resistance material having opposite vertical faces, means for holding said plate at its top and bottom ends to support it in vertical position, current supplying means electrically connected to said ends to generate heat by passage of electric current through the plate and through the descending molten metal on the faces thereof, for vaporizing said metal, and means for feeding solid metal against the faces of the plate at an upper region thereof, for coating said faces with a layer of descending molten metal, for evaporation.

4. In vacuum metalizing apparatus, a metal vapor source comprising an upright plate of electrical resistance material having opposite vertical faces, means, including resilient structure, for holding said plate at its top and bottom ends, under spring pressure vertically exerted against the plate, to support it in vertical position, current supplying means electrically connected to said ends to generate heat by passage of electric current through the descending plate and through molten metal on the faces thereof, for vaporizing said molten metal, said current supplying means including connecting members respectively engaging the plate at said ends and held in place against the plate by said plate-holding means, and means for feeding solid metal against the faces of the plate at an upper region thereof, for coating said faces with a y r f es nding molten metal, for evaporation.

5. In vacuum metaliziug apparatus, a metal vapor source comprising an upright structure of electrical resistance material having opposite vertical faces, means for feeding solid metal to the respective faces at upper portions thereof, to be melted against said faces, and to form a coating of descending molten metal on the faces, current supplying means, including connector members engaging said structure in electrical contact respectively at its top and bottom ends to generate heat by passage of electric current, for melting the supplied solid metal on the faces of the structure to establish the aforesaid coating and for evaporating metal from the aforesaid coating to evolve metal vapor laterally from said faces, and spring means engaging said connector members under resilient pressure to hold the members against said structure and to support the structure in vertical position.

6. Apparatus as defined in claim 5, in which each of the connector members includes cooling means therefor.

7. Apparatus as defined in claim 5, which includes insulator members respectively between the connector members and the spring means, said spring means comprising a pair of spring arms respectively engaging the insulator members and holding the latter against the connector members and the upright structure.

8. In vacuum metalizing apparatus, in combination, metal vapor source means comprising an upright structure of electrical resistance material having opposite, vertical, substantially plane faces which are spaced by the thickness of the structure and which have vertical and horizontal dimensions both substantially greater than the thickness of the structure, means connected to said structure at its top and bottom ends, for supplying electric current to heat the plate and to evaporate molten metal from said faces, and means for feeding continuing elongated pieces of solid metal to the respective faces at upper portions thereof, to melt solid metal against the faces and to form a coating of descending molten metal to be evaporated, and means for advancing strip material to be coated through regions respectively parallel to and spaced from said opposite faces, for receiving metal delivered from the faces by evaporation.

9. In vacuum metalizing apparatus, in combination, metal vapor source means comprising an upright plate of electrical resistance material having opposite vertical faces, means connected to said plate at its top and bottom ends, for supplying electric current to heat the plate and to evaporate molten aluminum from said faces, and means for feeding solid aluminum to the respective faces at upper portions thereof, to melt said aluminum against the faces and to form a descending coating of molten aluminum to be evaporated, and means for advancing work structures to be coated through regions respectively parallel to and spaced from said opposite faces, for receiving aluminum delivered from the faces by evaporation.

10. Apparatus as defined in claim 9, wherein the advancing means comprises roller means arranged to guide a continuous strip, as the work structure, first in one vertieal direction through one of the regions and then in the opposite vertical direction through the other region.

11. In vacuum metalizing procedure, the method of generating metal vapor which comprises supplying solid metal to upper portions of opposite vertical faces of an upright plate-like structure of electrical resistance ma terial, melting said supplied solid metal to form a coating of descending molten metal on said faces, and evaporating metal from said coating to deliver metal vapor laterally from the faces, said melting and evaporating operations being effected by conducting electric current between the top and bottom of the structure, to generate sufficient heat for said melting and evaporation of the metal.

12. In vacuum metalizing procedure, the method of generating aluminum vapor which comprises supplying aluminum to a vertical, substantially plane surface of an electrical resistance body, by feeding aluminum wire to an upper portion of said surface, melting said supplied aluminum to form a coating of descending molten aluminum on said surface, and evaporating aluminum from said coating to deliver aluminum vapor laterally from the surface, said melting and evaporating operations being effected by conducting electric current between the top and bottom of the body, to generate sufiicient heat for said melting and evaporation of the aluminum.

13. In vacuum metalizing procedure, the steps of advancin g work structures to be metalized along mutually spaced, parallel, vertical paths while generating and directing aluminum vapor against said work structures from a pair of oppositely exposed surfaces disposed between said paths and respectively facing the paths, supplying metal to said surfaces by feeding solid metal to upper portions of said surfaces to melt and to provide coatings of downwardly flowing molten metal, and electrically supplying heat to said surfaces for melting the supplied metal and for vaporizing metal from the aforesaid coatings.

14. In a method of vacuum metalizing a continuing strip of sheet material, the steps of advancing said strip through successive, laterally spaced, vertical paths while generating and directing aluminum vapor against said strip \frorn substantially plane surfaces disposed between said paths and respectively facing the paths, supplying aluminum metal to said surfaces by feeding solid aluminum to upper portions of said surfaces to melt and to provide coatings of downwardly flowing molten aluminum, and electrically supplying heat to said surfaces for melting the supplied aluminum and for vaporizing aluminum from the aforesaid coatings.

15. In vacuum metalizing procedure, the steps of advancing Work structures to be metalized along mutually spaced, parallel, vertical paths while generating aluminum vapor from molten aluminum on opposite surfaces, respectively facing said paths, of a vertical plate of electrical resistance material disposed between said paths, said vapor generation including supplying electric current to travel through said structure and the molten aluminum thereon, and continuously feeding aluminum wire to said opposite surfaces at upper localities thereof, to melt said wire and provide a coating of descending molten aluminum over said faces for conversion to vapor.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,476 Guellich iune 19, 1945 2,622,041 Godley Dec. 16, 1952 2,909,149 Gerow Oct. 20, 1959 2,969,448 Alexander Jan. 24, 1961 3,020,177 Alexander Feb. 6, 1962 UNITED STATES RATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3,, 117 887 January 14 1964 George AD Shepard et alu It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1,, lines 61 and 62 for "neoessisting" read necessitating -=-g line 6'1 for "services" read we service column 2 line 24 before "of" insert an opening parenthesis; column S line 18 for "disposed" read dispose column 8 line 4 for "outline" read outlined line 68 strike out "descending"; same line 68 after "through" insert the descending n Signed and sealed this 16th day of June 1964:.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W; SWIDER Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE F COR EUHUN Patent Noe 3 ,ll7 887, January l4 1964 George A Shepard et ale It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l lines 61 and 62 for "neoessisting read necessitating line 67 for "services" read service column 2 line 24 before "of" insert an opening parenthesis; column 3 line l8 for "disposed" read ea dispose column 8, line 4 for "outline" read as outlined line 680 strike out "descending"; same line 68 after "through" insert the descending "-"O Signed and sealed this 16th day of June 1964c.

(SEAL) Attest:

ERNEST W; SWIDER EDWARD J@ BRENNER attesting ()fiieer Commissioner of Patents

Claims

13. IN VACUUM METALIZING PROCEDURE, THE STEPS OF ADVANCING WORK STRUCTURES TO BE METALIZED ALONG MUTUALLY SPACED, PARALLEL, VERTICAL PATHS WHILE GENERATING AND DIRECTING ALUMINUM VAPOR AGAINST SAID WORK STRUCTURES FROM A PAIR OF OPPOSITELY EXPOSED SURFACES DISPOSED BETWEEN SAID PATHS AND RESPECTIVELY FACING THE PATHS, SUPPLYING METAL TO SAID SURFACES BY FEEDING SOLID METAL TO UPPER PORTIONS OF SAID SURFACES TO MELT AND TO PROVIDE COATINGS OF DOWNWARDLY FLOWING MOLTEN METAL, AND ELECTRICALLY SUPPLYING HEAT TO SAID SURFACES FOR MELTING THE SUPPLIED METAL AND FOR VAPORIZING METAL FROM THE AFORESAID COATINGS.