US3852095A

US3852095A - Method and apparatus for applying wax to can lid rims

Info

Publication number: US3852095A
Application number: US00076167A
Authority: US
Inventors: E Hogstrom
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1970-09-28
Filing date: 1970-09-28
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

A method and apparatus for applying a film of wax to the rim of a can end before that end is assembled onto the body of a can. The wax is applied by melting a 100 percent solids wax and forcing it as a liquid without the addition of a solvent through an airless spray nozzle under conditions which result in a thin film of 100 percent solids wax being applied as a narrow annular ring around the rim of the can end.

Description

a States atent 1 Hogstrom [451 Dec. 3, 1974 4] METHOD AND APPARATUS FOR APPLYING WAX TO CAN L111) RIMS [75] Inventor: Edwin F. Hogstrom, Sheffield Lake,

Ohio

[73] Assignee: Nordson Corporation, Amherst,

Ohio

[22] Filed: Sept. 28, 1970 [21] Appl. No.: 76,167

[52] US. Cl 1117/43, 117/104, 1l7/105.4,

117/168 [51] Int. Cl. B05c l/16, B05b 13/02 [58] Field of Search 117/43, 104 R, 105.4, 168

[56] References Cited UNITED STATES PATENTS 2,313,750 3/1943 Hothersall 117/43 2,906,640 9/1959 Bartlett ll7/43 2,944,510 7/1960 Jeremiah 117/43 Primary Examiner Mayer Weinblatt Assistant ExaminerM. F. Esposito Attorney, Agent, or Firm--Wood, Herron and Evans [5 7] ABSTRACT A method and apparatus for applying a film of wax to the rim of a can end before that end is assembled onto the body of a can. The wax is applied by melting a 100 percent solids wax and forcing it as a liquid without the addition of a solvent through an airless spray nozzle under conditions which result in a thin film of 100 percent solids wax being applied as a narrow annular ring around the rim of the can end.

10 Claims, 9 Drawing Figures PATENTEL B53 319% SHEET 1 [1F 3 PAIENIEL B59 SHEH 2 OF 3 Pmmmm 3W 2.852095 sum a nr 3% I N V ENTOR.

' METHOD AND APPARATUS FOR APPLYING WAX TO CAN LID RIMS This invention relates to the manufacture of metal cans, and more particularly to the coating of the interior of the cans to prevent the interior metal surface of the cans from contacting and contaminating the contents of the cans.

Metal cans are made by either one of two processes. One process, the two-piece can process, involves forming a drawn cup from a cylindrical slug of metal and then deep drawing the cup to a can configuration. The other process, the three-piece process, involves forming a cylindrical can body from a sheet of metal and then attaching two lids or ends to the opposite ends of the body. The invention of this application is applicable to cans made by both processes. I

Metal cans, and particularly steel cans, are made from precoated sheet material which is coated with protective material, as, for example, vinyl lacquer, while the steel is still in its sheet form. After the can bodies and ends are completely configurated and assembled, the interior surfaces are coated with a second protective coating, generally vinyl lacquer, although numerous other materials, as, for example, resins, lacquers, waxes and paints are applied for this same purpose, i..e., to afford protection of the contents of the can against contamination by the metal. Particularly beer, beverage and foods must be protected against metal contamination by the application of a tasteless and odorless protective coating material to the interior of the can.

This protective material on the interior of the can must be continuousand uniform throughout the entire interior surface. The continuity requirements are abso lute. There can be no pinholes, scratches or imperfections of any kind in this surface coating since any such minor imperfection will, during the shelf life of the can, result in deterioration of the can contents.

The precoated can ends and bodies are assembled and crimped together on automatic machinery. The assembly generally occurs at the rate of between 300 and 600 cans per minute on a single can line. At this speed the ends are literally slapped into place on the can bodies. The ends of the bodies and the lids are so configurated that the ends are cammed into position on the body even if the two are slightly misaligned. Often, though, in the process of slapping the two together, this high speed camming action results in a scratch of the protectivecoatingoneither the can lid or the can body at the interface between the two. This scratch is an imvent so that the mix is diluted to 50 percent or less wax solids. This wax-solvent mix is then extruded at approximately 180F. as a bead onto the rim of the can end while the can end is rotating so that the low viscosity bead flows outwardly and forms an annular ring around the interior peripheral surface of the rim. The end is then passed through an oven wherethe solvent is driven off or out of the wax-solvent mix. A lid with the a cured wax applied around the rim of the lid or end may any defects which may have occurred in the course of forming or shaping the can end. If there are any scratches or voids in the lacquer at the point of union of the body and the end the wax covers those voids and protects the contents of the can from contamination-by metal which would otherwise be exposed.

The can manufacturing industry has several objections to its present commercial practice for applying wax to the rim of can lids. The primary objection is inconsistency of the wax applied as well as, of course, cost. Present practice is to try to apply approximately 6 to 10 milligrams of wax to each beer or beverage can end or lid. This is the desired weight of the wax layer after the lid is force dried and the wax solvent driven off. When multiplied by the millions and billions of cans made by a single can manufacturer each year the cost of solvent is very appreciable.

Can manufacturers also object to the mess created around the area of application of the wax to the can end. Using conventional extrusion procedures, some wax bounces off or is thrown off of the target and over a period of time builds up in the general area of application of the wax to the can ends. Periodically the line must be stopped to clean the wax from the equipment in that area.

- Another objection which has only recently received a great deal of attention is the atmospheric contamination which results from the solvent being driven off of the wax. The gases and solvents driven off from the wax inthe ovens must be exhausted into the atmosphere withthe result that they add to the general pollution problem.

It has therefore been a primary objective of this invention to provide a new method and apparatus for applying wax to can ends which overcomes or substantially reduces these problems and objections of the can industry. Specifically, it has been a primary objective of this invention to provide a method and apparatus for applying a consistently even and thin film of wax around the rim of a can end under high speed production conditions. It has also been an objective to provide a method and apparatus forapplying wax to can ends with a minimum of contamination of the general area in which the wax is applied to the lids.

Still another principal objective of this invention has been to eliminate the use of solvents in the wax and reduce the cost of applying the wax to the rim of can ends. I

These objectives are accomplished and one aspect of this invention is predicated upon the concept of spraying meltedwax without the addition of any solvents onto the rim of a can end. The can end, therefore, does not need to be baked to cure the wax and drive the solvent from it. Because there is no solvent used in this application, the cost which results from its use is eliminated. Additionally, the atmospheric contamination or pollution is avoided.

Another aspect of this invention is predicated upon the determination that an airless spray gun and nozzle may be utilized to apply a narrow band, uniform thickness 100 percent solids wax in the form of an annular ring around the periphery of a can end. Airless spray is a well known spraying technique which is distinct and different from conventional air spray. It involves forcing a liquid material through a generally elliptical shaped orifice at high pressures, i.e., generally on the order of from 50 psi to 500 psi with the result that the spray fans out after emerging from the orifice and breaks up into an atomized spray without the impingement of any air against it. The conventional air spray on the other hand involves extruding a low pressure stream of liquid material from a nozzle at a pressure of from -l-50 psi and impacting that extruded stream with a high pressure stream of air (on the order of 35-100 psi) to atomize it and convert it into a spray. The use of this airless spray technique in the application of the wax results in a more uniform and consistently thin film of wax being applied than is possible using conventional extruding techniques. Additionally, there is little or no overspray and resulting mess in the area in which the wax is applied to the can ends or lids.

Still another aspect of this invention is predicated upon the empirical determination of conditions under which an airless spray tehnique may be utilized to apply a wax film consisting of 100 percent melted wax solids to the rim of a can end. Specifically, it has been determined that if the wax is heated substantially above its melting temperature so as to lower its viscosity and is forced through a very small spray orifice at relatively low pressure, and if the substrate or can end is located very close to the nozzle orifice, a film of 100 percent solids wax may be applied to the rim of a can in a manner to satisfy all requirements of the can industry. Spe* cifically, the resulting film will be consistently thin and uniform and will use very little material,'i.e., approximately half that now being utilized using the conventional (air spray) extruded bead technique. Additionally, the resulting narrow band of wax, usually about /8 inch to A inch in width covers the area in which the protection is required. To achieve this narrow band, the substrate or can end is located very close to the nozzle orifice so that the fan shaped spray of wax emerging from the nozzle orifice contacts the can lid before it can travel far enough to break up into droplets of material. Consequently, the fan shaped spray contacts the can as a solid extruded curtain of wax rather than as an atomized spray of wax.

Still another aspect of this invention is predicated upon the discovery that a more even or uniform airless spray wax film may be applied to can ends if a restrictor plate is located between a spray nozzle orifice and a check valve which controls the flow of wax through the nozzle orifice. Specifically, it has been determined that a minimal size orifice in a restrictor plate which extends from the check valve to the nozzle orifice minimizes or eliminates spitting and sputtering of the wax. Consequently, the use of this restrictor plate results in a more uniform film of wax being applied to can ends.

The application of wax by the technique which forms the subject matter of this invention has numerous advantages over present commercial practice. Specifically and most importantly, it substantially reduces the cost of material utilized to provide a thin film of wax around the rim of can ends. Because it results in a more uniform even layer of wax it may be applied in a much thinner film to afford the same degree of protection provided by a heavier layer of wax laid down by the air spray technique.

Another primary advantage of this invention is that it eliminates the use of solvent in the wax. This has sev eral inherent advantages. Principally it reduces cost by eliminating the need for solvent and all expenses incurred for that material. It also eliminates the pollution problem which results from exhausting that solvent to atmosphere when it is driven off of the wax during the wax curing cycle.

The elimination of the solvent from the system has other advantages as well. When solvent is used, the entire area in which the solvent and wax are applied is required to be explosion proofed. This requirement is eliminated by the practice of this invention.

Another problem which results from the use of a solvent in the wax is that the material after melting is required to be agitated to maintain the melted wax and solvent in a homogeneous solution. With the elimination of the solvent the agitation problem is eliminated. With the elimination of the solvent there is also no need in the system for ovens to heat the wax and drive off the solvents. Consequently, the cost of the ovens as well as the cost of heating the ovens to drive off the solvent is eliminated.

Another advantage which results from the practice of this invention is the elimination of wax transfer from the inside of one lid to the outside of a lid against which it is placed when the lids are stacked prior to assembly onto can bodies. By eliminating the solvent, the wax hardens immediately upon application and the lids are never stacked while solvent is present in the wax or while the wax is soft.

Another advantage which results from the elimination of the solvent from the wax is the elimination of the problem of wax attacking compound on the can end. Quite often, in fact generally, the can ends to which the wax is applied have a previously applied ring of resilient latex-like compound surrounding the area of application of the wax. This compound acts as a seal between the can end and the can body when the two are subsequently assembled. On this type of end the film of wax abuts the edge of the annular ring of compound. Quite often the solvent in the wax attacks the compound and destroys its resiliency, thereby creating subsequent problems. By eliminating the solvent from the wax, the problem of the solvent attacking the compound is thereby eliminated.

The primary advantage of this invention though results from the consistency with which it enables a wax film to be applied to can ends. Present commercial practice of extruding a bead of wax-solvent mix onto a can end while the end is rotating and allowing that bead to spread and form a film produces very inconsistent results, particularly over long production runs. Any change in the percentage of wax-solvent ratio, or any viscosity changes in the mix, or any temperature or pressure changes very materially affect the consistency with which the extruded film is applied. All of these variables are materially reduced in effect or eliminated by the practice of this invention and, consequently, the film applied by the practice of this invention is more consistent and uniform than has ever heretofore been possible.

These and other objects and advantages of this invention will be more readily apparent from the following description of the drawings in which: I

FIG. 1 is a diagrammatic illustration of an indexing table and a system for applying wax to the rim of can ends incorporating the invention of this application;

FIG. 2 is a cross-sectional view of the nozzle and of the can end to which-wax is applied showing the relationship between the nozzle and the can end;

FIG. 3 is a cross-sectional view similar to FIG. 2 but viewing the end and nozzle from a different angle;

FIG. 4 is a cross-sectional view through the nozzle of the gun of FIG. 1;

FIG. 5 is an enlarged cross-sectional view of a portion of the can rim of FIG. 3;

FIG. 6 is a cross-sectional view through a can body and a can lid after assembly of the lid to the body but before the two are crimped together;

FIG. 7 isa view similar to FIG. 6 but illustrating the can body and the can end crimped together;

FIG. 8 is a side elevational view of a spray pattern as it emerges from an airless spray nozzle; and

FIG. 9 is a perspective view of a can end or lid looking down upon the inside of the lid.

Referring first to FIG. 1 there is diagrammatically illustrated an airless spray system for applying wax to can lid rims incorporating the invention of this application. The system includes an indexable table '10 upon which there are mounted multiple individually rotatable heads ll. The heads rotate at a speed of approximately 3,200 rpm when the heads 11 are located at a wax application station 12. At this station, wax is sprayed from a nozzle 13 onto the rim of the can end or lid as the lid rotates through slightly more than one full revolution. This requires approximately 20 milliseconds.

The individual heads on the indexing table are mounted on shafts 15 supported in bearings 16. The

hold-down mechanism has not been illustrated since it forms no part of the invention of this application.

belts, electric motors or air motors mounted beneath the table. In actuality,1all three systems are used on tables manufactured by different manufacturers. These tables are commercially available and are well known in the can manufacturing industry. One such machine is manufactured by Dewey Almey Company and is identified as their Can End Repair Machine. Another commercially available machine is Crown Cork and Seal Companys Can End Repair Machine; Since these machines are commercially available and are well known, the details of the machine have not been illustrated. Specifically, the mechanism for feeding can ends 5 onto the top surface of the individual heads 11 and the mechanism for removing the lids from the heads has not been illustrated since it forms no part of the invention of this application. Nor has the mechanism been illustrated for holding the individual lids on the top of the heads during rotation. The commercially available Dewey Almey Company machine utilizes a vacuum hold-down. Crown Cork and Seal Companys Can End Repair Machine on the other hand uses an upper chuck vertically movable into engagement with the top surface of the canends when they are supported on the table 10 to hold the lidsdown on the head during rotation. Asin the case of the mechanism for rotating the heads and the mechanism for feeding lids or'ends onto and off of the indexing table, the lid A typical can end of the type withwhich this invention is concerned is illustrated in FIGS. 6, 7 and 9. In FIG. 6, the end 5 is depicted prior to completion of the assembly onto a can body 18. In FIG. 7, the end is depicted after completion of the assembly and after crimping onto the outwardly flared end 19 of the can body 18.

The can end 5 comprises a generally planar circular section 20 around the periphery of which there is a When the flange 22 and flared rim 19 are subsequently crimped together as depicted in FIG. 7, the two together form the chime 24 of the assembled can.

The groove or rim 21 of the. can lid fits within the interior of the can body 18 and is located in juxtaposition to the inside wall of the body. Functionally, it reinforces the can end as well as the end of the assembled can. It also serves the secondary function of locating the can end on the can body during assembly of the two. It isusually tapered so that it serves as a cam to center the can end of the body if the two are slightly off-center or misaligned during assembly.

Referring now to FIG. 5, there is illustrated an exploded view of the can end rim 21 and can end flange 22. In this view, the end is inverted or turned upside down from the position depicted in FIGS. 6 and 7. This is the position of the end when a sealing compound 25 is applied to the recess formed by the flange and when a thin film of wax 26 is applied to the rim 21. The compound 25 serves as a seal for the can chime 24 when the end 5 and body 18 are assembled. Generally this compound is a rubber or latex based material.

The film of wax 26 extends from the inside edge 27 of the compound 25 over the rim 21. Functionally, this wax film serves to protect and repair a protective coating 28 which extends over the complete interior surface of the can end as well as the complete interior surface of the can body. The protective coating 28 is applied to the metal or steel while it is still in sheet form as a very thin film. In the case of beer and beverage cans, it is absolutely critical that the protective coating 28, generally a vinyl lacquer, completely cover the interior surface of the can. Any imperfections whether they be pin holes, cracks or just uncovered areas render the can unsuitable as a food or beverage container.

One of the areas in which cans most commonly fail because of a breakdown of this protective layer 28 is at the point of intersection 30 of the can body with the can end. Principally, failure at this point is attributable to cracks and breaks which occur during the stamping and forming of the can ends and bodies. Additionally, though, when the two are assembled at the conventional commercial speed of 300 cans per minute, the two inside surfaces rub and scratch each other and thereby create faults in otherwise perfectly coated surfaces. The application of the wax 26 to the interior rim of the can provides an additional layer of protection at the intersection 30 and additionally provides a lubricant between the can end and the can body when the two are assembled together. If the two are slightly misaligned, the wax precludes damage to the vinyl lacquer or protective coating 27 located beneath the wax.

In order to apply the wax as a thin film to the interior rim of a can end or lid, the wax is sprayed as a film from the nozzle 13 of a spray gun 35. In the practice of a pre ferred embodiment of this invention, this gun 35 is a pneumatically operated airless spray gun in which the pneumatic pressure functions under the control of a solenoid valve 37 to open and close a check valve 38 of the gun. Liquid pressure alone forces this liquid wax through the gun and causes it to emerge as a fan shaped spray.

The wax which is applied by the gun 35 is a 100 percent solids wax. The significance of the 100 percent solids is that the wax is completely solid at room temperature. Heretofore it has been the practice to heat the wax and mix it with at least 50 percent by weight of solvent, usually a liquid acetone or hexane solvent, before applying it onto can ends via an extrusion process. By the practice of this invention, the wax is simply heated and sprayed as a 100 percent solids without the addition of any solvent. This is accomplished by heating the wax in a reservoir 40 to a temperature of approximately 350F. The melted wax is then pumped via a pump 41 through a heated hose 42 into the spray gun 35. The gun is of the so-called circulating flow type because it has a return line 43 through which wax is returned to the reservoir 40. There is a continuous flow of heated wax through the gun so that the wax cannot solidify or harden in the gun when the line is temporarily shutdown. The gun, other than the nozzle, forms no part of the invention of this application and therefore has not been described in detail. A complete description may be found in an application of E. F. Hogstrom et al. which has not yet been accorded a serial number but which was filed in the Patent Office on July 20, 1970, is entitled Method and Apparatus for Striping Inside Seams of Cans, and is assigned to the assignee of this application.

Air pressure from a source 36 is supplied via a pneumatic line 44 under the control of the solenoid valve 37 to control opening and closing of the check valve 38 interiorly of the gun 35. The solenoid 46 of the valve is controlled by a conventional electric control and timer circuit. It is operable to open the check valve 38 for slightly more than one full revolution of a lid on the rotatable table 11 [f the lid is rotating at 3,200 rpm, the timer control circuit is operableto open the check valve 38 for approximately milliseconds to apply wax to each lid.

The nozzle 13 comprises an externally threaded nose piece 48 of the gun, an internally threaded nozzle cap 49, a restrictor plate 50 and a nozzle plate 51. The cap 49 is threaded over the nose piece 48 and has a flange 62 which secures the restrictor plate 50 and nozzle plate 51 onto the end of the nose 48.

The nose piece 48 has a stepped axial bore 53, the larger diameter inner end of which serves as a chamber 54 for molten wax. The axially slidable closure 55 of the check valve 38 is slidable within this chamber 54 and is engageable with a shoulder 56 of the nose piece to close the check valve. The shoulder 56 thus serves found that the restrictor plate 50 with its small axial orifice 58 extending from the end of the check valve up to the nozzle approach passage 59 has the effect of minimizing spitting and sputtering of wax as it emerges from the nozzle. Apparently, this elimination of spitting by the use of the restrictor plate derives from minimization of material contained between the check valve seat and the nozzle orifice.

The nozzle tip 60 is generally hemispherical in configuration. It has a hub portion which extends rearwardly from the hemispherical end and is brazed in the plate 51. The approach passage 59 extends from the rear of the nozzle tip up to the nozzle orifice 61.

The nozzle orifice 61 is generally elliptical in configuration when viewed in a direction parallel to the axis of the nozzle. It is made by making a cut into a generally hollow hemispherical shaped nozzle of substantially uniform wall thickness. The cut is made by a grinding wheel which has a tapered edge.

Referring now to FlG. 8 there is depicted a typical spray pattern as it emerges from the elliptically shaped orifice 61 of an airless spray gun. Upon emerging from the nozzle, generally at a pressure of from 200l,000 psi but sometimes at a lesser pressure, the spray spreads out or fans out to form a generally fan shaped solid curtain of liquid material. As the solid curtain moves away from the nozzle, ripples or waves form in it as indicated by the numeral 71. The ripples then break up into longitudinal ligaments indicated by the numeral 72. These ligaments subsequently break up as they move away from the nozzle into droplets 73 which then atomize into a fine spray 74. As viewed in crosssection, the pattern of atomized-spray is elliptical in configuration. The distance at which the atomization occurs from the nozzle depends on such variables as the viscosity of the liquid, the size of the orifice and the pressure of the liquid in the gun.

Referring now to FIGS. 2, 3 and 5,-there is illustrated the position of the nozzle 13 with respect to the orientation of the can end. As may be seen in these figures, the nozzle is positioned very close to the rim of the can end, generally from 1/16 to /z inch. At this distance D, the wax emerging from the nozzle orifice is still a solid extruded curtain of wax as indicated by the line AA of FIGS. 2 and 8. The wax may show signs of ripple at this distance but it does not have a chance to break up into ligaments or droplets.

As may be seen in FIG. 2, the nozzle axis 75 is angulated at an angle of 23 to the vertical in a radial plane of the can end 5. When viewed in that radial plane, it is also angulated at 10 to the vertical plane. The 23 angulation is provided in order for the spray to contact the nearly vertical surface 76 of the can end rim 21. The l0 angulation is aimed into the direction of rotation of the can lid. It has been found that the wax or any liquid sprayed onto a rotating substrate bends in the direction of rotation of the substrate. Consequently, by angulating the nozzle slightly and aiming it into the direction of rotation the spray pattern contacts the rotating substrate at an angle of approximately Throughout this application, the material being sprayed from the nozzle onto the can end rim has been described as a percent solids wax. The formation of this wax varies from manufacturer to manufacturer as do the characteristics of the wax. Some waxes are formulated with resins so as to melt at a slightly higher temperature than other waxes. Some are harder than others. Generally, the higher temperature melting waxes are used on beer cans in which the beer is pasteurized in the can. The term wax therefore is intended in this application to describe and encompass all wax and wax-like materials used on the rims of can ends to protect the can contents against metal contamination. The wax may be the old fashioned paraffin wax used for home canning or it may be a more complex wax formulated for particular properties. Examples of I such waxes, all of which have been tested and sprayed onto can end rims under the conditions set forth in this application are: Cerafilm wax sold by American Can Company; Mobile Oil Company wax No. 67-658; Standard Oil of Ohio wax No. 66-2242-6; National Wax Company wax No. 6396 LY; and National Can Company wax No. 6396 LX. Additionally, conventional paraffin as well as DuPonts Elvax have been sprayed onto can ends under the conditions set forth herein.

The specific conditions under which one particular I wax, American Can Companys Cerafilm, has been applied to beer and beverage size cans are depicted in the following chart. Additionally depicted in the chart are the range of conditions under which other waxes have been or may be applied to this size can.

By way of explanation of this chart, the width W refers to the width of the spray pattern of wax applied to the rim of the can end. In the example of Column 1, this pattern was A inch in width. It may vary as shown in Column 2, though, from Va to inch. The distance D of the nozzle orifice from the can was Vs inch in the example of Column 1. It may vary as shown in Column 2 from 1/16 to /2 inch. In the example of Column 1 the wax temperature was 350F. 1 25F. At this temperature the wax in the-example of Column 1 reaches its minimum viscosity so that any further heating serves no useful purpose. Other waxes have been heated and applied at temperatures ranging from their melting temperature approximately 140F., through 350F. The nozzle orifice in the example of Column 1 has a flow rate of 0.015 gallons per minute of water at 500 psi gauge. This is the smallest size at which airless spray nozzles are commercially available. Special nozzles, though, can be made slightly smaller. The permissible range of nozzle size varies from 0.0075 gallons per minute to 0.04 gallons per minute water at 500 psi. The diameter of the restrictor plate in the example of Column 1 was 0.007 inch. It may vary, though, from 0.006 inch through 0.020 inch. The pressure employed to eject-liquid wax from the nozzle in the example of Column 1 was 50-75 psi gauge. Other waxes have been applied from 25-250 psi gauge pressure; In the example of Column l the wax was applied for approximately one revolutionof the can end while the end was rotating at 3,200 rpm. It may be applied from 1-4 revolutions depending upon the speed of the can end. In the example of Column '1, 8 milligrams of wax was applied per can end i 2 milligrams. Using other waxes under other conditions the wax will vary from 4-16 milligrams i 2 milligrams.

In general, the practice of wax application to the rim of can ends according to the practice of this invention results in the application of a more consistent and uniform film of wax over the can end rims than has heretofore been possible under production conditions over prolonged production runs. It also results in a thinner film of material, yet one which provides the same or a greater degree of protection to the contents of the can.

Probably the greatest advantage which accrues from the practice of this invention is the elimination of the necessity to add a wax solvent, as, for example, an acetone or hexane solvent, to the mix. With the elimination of the solvent, there is no need for an oven to drive the solvent from the wax after it is applied to the can lid or end, there is no need to heat the can, there is. no need to protect the atmosphere from pollution when the solvent is baked from the wax, and there is no need to explosion proof the area in which the wax is applied. Additionally, the practice of this invention enables the wax to be applied in a thinner film with less overspray and clean-up problems. Additionally, the film weights may be more closely and consistently controlled with the result that approximately one-half the material is used in the practice of the process as is now used commercially using conventional extrusion techniques to apply a wax-solvent material. I

While I have only described a single preferred embodiment of this invention, those persons skilled in the arts to which it pertains will readily appreciate numerous modifications and changes which may be made without departing from the spirit of my invention. Therefore, I do not intend to be limited except by the scope of the appended claims.

Having described my invention, I claim: 1. The method of applying a percent solids protective layer of wax in the configuration of an annular ring to the rim of a can end without the addition of any solvent so that the end need not be baked to drive off solvent from the wax, which method comprises:

rotating the end relative to the orifice of a nozzle of a spray gun,

melting a 100 percent solids wax and supplying it in the as melted condition to the nozzle of said spray gun without the addition of any solvent,

ejecting said melted wax in the form of a fan-shaped sheet of liquid from said nozzle orifice and'directing it onto the rotating end, said end being located sufficiently close to the nozzle orifice that said wax film is applied to the end as an unatomized curtain sheet of wax.

2. The method of claim 1 wherein said rim of said end to which said film of wax is applied is located less than one-half inch from said nozzle orifice. 4

3. The method of claim 1 wherein said wax is heated to a temperature of approximately 350F. before it is supplied to the nozzle of said spray gun.

4. The method of claim 1 wherein said wax is supplied to said nozzle of said spray gun at a pressure in excess of 25 psi but less than 250 psi.

5. The method of claim 1 wherein said wax is sup-- 8. The method of claim 2 wherein said wax is heated to a temperature of approximately 350 F. before it is supplied to the nozzle of said spray gun.

9. The method of claim 8 wherein said wax is supplied to said nozzle of said spray gun at a pressure of approximately 50 psi.

10. The method of claim 9 wherein said wax is ejected from a spray nozzle which has a flow rate of approximately 0.015 gallons per minute water at 500 psi. 4:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,852,095 Dated Dec', 3, 4

Inventor(s Edwin F. Hogstrom v It is certified that error appears in-the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 7 line 56 "larger" shnul d b e 1arge Col. 8 like 63 -"forma tion" shduld be ---fo rm ulationsi ned] and sealed this llth day of February 1975.

(SEAL) Attest':

r r C. MARSHALL DANN igi g i gg g Commissioner 0i Patents 8 and Trademarks.

FORM PC4050 (069)

Claims

1. THE METHOD OF APPLYING A 100 PERCENT SOLIDS PROTECTIVE LAYER OF WAX IN THE CONFIGURATIONN OF AN ANNULAR RING TO THE RIM OF A CAN END WITHOUT THE ADDITION OF ANY SOLVENT SO THAT THE END NEED NOT BE BAKED TO DRIVE OFF SOLVENT FROM THE WAX, WHICH METHOD COMPRISES: ROTATING THE END RELATIVE TO THE ORIFICE OF A NOZZLE OF A SPRAY GUN, MELTING A 100 PERCENT SOLIDS WAX AND SUPPLYING IT IN THE AS MELTED CONDITION TO THE NOZZLE OF SAID SPRAY GUN WITHOUT THE ADDITION OF ANY SOLVENT,

2. The method of claim 1 wherein said rim of said end to which said film of wax is applied is located less than onE-half inch from said nozzle orifice.

3. The method of claim 1 wherein said wax is heated to a temperature of approximately 350*F. before it is supplied to the nozzle of said spray gun.

5. The method of claim 1 wherein said wax is supplied to said nozzle of said spray gun at a pressure of approximately 50 psi.

6. The method of claim 1 wherein said wax is ejected from a spray nozzle which has a flow rate of less than 0.040 gallons per minute water at 500 psi but more than 0.0075 gallons per minute water at 500 psi.

7. The method of claim 1 wherein said wax is ejected from a spray nozzle which has a flow rate of approximately 0.015 gallons per minute water at 500 psi.

8. The method of claim 2 wherein said wax is heated to a temperature of approximately 350* F. before it is supplied to the nozzle of said spray gun.

10. The method of claim 9 wherein said wax is ejected from a spray nozzle which has a flow rate of approximately 0.015 gallons per minute water at 500 psi.