US3442742A

US3442742A - Processes for applying printing to metal substrates

Info

Publication number: US3442742A
Application number: US276051A
Authority: US
Inventors: Donald E Jorgensen
Original assignee: DONALD E JORGENSEN
Current assignee: DONALD E JORGENSEN
Priority date: 1963-04-26
Filing date: 1963-04-26
Publication date: 1969-05-06
Anticipated expiration: 1986-05-06

Description

3,442,742 PROCESSES FOR APPLYING *PRINTING TO METAL SUBSTRATES Filed April 26, 196s Sheet May 6, 1969 D. E. JoRGENs'EN May 6, 1969 n. E. JORGENSEN 3,442,742

PROCESSES FOR APPLYING PRINTING TO METAL SUBSTRATES Filed April 26, 196s i Sheet Z of4 DE LAMINATING STAGE. MYLAR &PLASTIC STEEL PLASTIC SOLMINATING STAGE METALLIZEB ADH vSVE ROLLS D. E. JORGENSEN May 6, 1969 PROCESSES FOR APPLYING PRINTING To METAL sUBsTRATE's Sheet Filed April 26, 1963 dwars LINEN?" vm. www

INVENTOR. DGN/:Lo E, Jo/QGE/vssf/ WM j yu? May 6, 1969 D. E. JoRGENsEN 3,442,742

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INVENTOR.

3 00A/HL@ 5 .JQeGA/rfm 9 Trae-11(5)?" United States Patent Office 3,442,742 PROCESSES FOR APPLYING PRINTING TO METAL SUBSTRATES Donald E. Jorgensen, 4730 Center Ave., Oakland, Pittsburgh, Pa. 15213 Filedv Apr. 26, 1963, Ser. No. 276,051 Int. Cl. B29c 27/14; B44d 1/09 U.S. Cl. 156-244 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to processes for applying printing to metal substrates which are intended for fabrication into containers, caps, tubes or the like. More specifically, the invention relates to the application of printing to a metal substrate by an indirect printing process wherein the characters, letters or other indicia are applied to a flexible film of suitable material which is itself applied to the metal substrate rather than direct printing on the metal substrate.

It has been proposed, in various packaging arts, to improve the method of applying printing to metal substrates, which do not lend themselves to direct printing because of the inflexibility of the metal which cannot readily be passed through printing rolls and printed the same as a roll of paper or other material which is flexible and can therefore be readily printed on. To meet this problem of printing on metal substrates, the art has extensively used `printed paper which is formed with adhesive surfaces whichfare affixed to the outer surface of the container. The presently used methods are not only costly, but are inherently slow and tend to reduce packaging speeds and methods of constructing containers.

In the present invention, processes are proposed for greatly increasing the speed of printing for metal substrates, by novel processing steps in which the printing is applied first to a flexible film and the film then secured to sheet metal rolls which are thereafter fabricated into containers of a desired size and shape. By substantially increasing the rate of speed at which the printing can be effected on the lamination, it is possible to print at a speed which is substantially greater than comparable speeds heretofore obtained and which therefore permit the application of printed material onto steel rolls or other substrates in applications wherein production volumes are substantial and where it is necessary, from time to time, to vary the printed material,

It is one of the important objects of the present invention to provide a new and improved method for applying printing to metal surfaces which do not readily lend themselves to direct printing and to accomplish this by means of an intermediate printed surface which initially receives the printed information, indicia, figures or the like, and which is thereafter applied to the metal subsurface.

A further object of the invention is to substantially increase the rate at which printing can be produced on a flexible transparent material by printing on such material while it is located on each side of a flexible carrier and in this manner greatly increase the rate of producing print- 3,442,742, Patented May 6, 1969 ed material for attachment to the surface ofthe metallic substrate. The printing can be reverse or non-reverse and can be applied to the surface or viewed at the subsurface through the transparent plastic film or lamination.

A further object of the present invention is to provide a process wherein a lamination of plastic or other suitable material can be secured to opposite sides of a web and thereafter receive printing in one of a plurality of different ways', and which can then be followed by delaminating to provide rolls of printed film material thereafter adapted for securement with a metal substrate or other composition substrate which is not readily adaptable itself to direct printing.

A further object of the invention is to provide a process in which two laminations are provided, one on each side of a web and are then printed and thereafter directly applied to a metal substrate.

Other objects and features of the present invention will become apparent from a consideration of the following description, which proceeds with reference to the accompanying drawings, wherein:

FIGURE 1 is an enlarged sectional view illustrating the web and transparent laminations secured to the opposite sides of the web and adapted to receive printed material thereon;

FIGURE 2 is a schematic view of the processing steps in which the product of FIGURE 1 is obtained by spray coating the laminations at the opposite sides of the web and are thereafter printed in any one of several suitable manners indicated, then subjected to metallizing operation, if desired, and then delaminated for winding up and subsequent securement to a metal substrate;

FIGURE 2A illustrates the process of FIGURE 2 in which the printed laminations are directly applied to the metal substrate;

FIGURE 3 is a modification of the process illustrated in FIGURE 2 wherein the lamination is secured to the web by extruding rather than spray coating;

FIGURE 3A is a further modification of the process for producing the plastic laminations on opposite sides of the web;

FIGURE 3B is an enlarged detail view of the discharge portion of the laminator in FIGURE 3A;

FIGURES 4, 5, 6, 7 and 8 illustrate schematically the different methods of printing on the surfaces of the larninations;

FIGURE 9 illustrates the structure for effecting metallizing of the printed laminations;

FIGURE 10 shows the structure for applying the printed lamination on the metal substrate by joining the two together and heating them within a chamber, the substrate then being formed into containers or other structures;

FIGURE 1l illustrates the method of applying the printed material onto fully constructed containers; and,

FIGURE 12 illustrates the finished product having the plastic material affixed over its outer surface.

Referring now to the drawings, the web or carrier designated generally by reference numeral 10 (FIGS. 1 and 2) in the form of a roll supported on a trunnion mounting 12 and receives from a spray nozzle 14 a spray of plastic material such as polyvinyl chloride, or the like, forming a first lamination of 16 at the one side of the web 10 and a second spray from a nozzle 18 which forms a second lamination or coating 20 on the opposite side of the web. The article is then passed back and forth over the first and second series of rollers 13 and 17 as it passes upwardly through the tower and exits from the laminating tower 22.

The terms coating and lamination are used interchangeably hereafter.. These terms include and are meant to include either the usage of a'solid phase laminae which is secured to the web or liquid phase coating which is formed on the web by kiss-coating or immersing the web with a liquid phase resin. The invention also encompasses a release coating which forms a part of the web, prior to the additional applications of resin coatings and is heat treatable to obtain release from the web.

The operation of FIGURES l, 2 takes place within a coating or laminating tower 22, the exact construction of which is not a part of the present invention. For details of a suitable spray coating laminator of the type referred to, reference may be made to the Waldron Microjet coater and Ross Tower Drier, Ross/Waldron Division of Midland-Ross Corporation.

Subsequently to receiving the coatings or laminations 16, which either adhere by their own cohesiveness or are adhesively joined at web 10 by an adhesive layer at the interface, the coated web then follows the course indicated by arrows 23 and is channeled into one or the other of the

printing apparatus

24, 26, 28, or 32 representing printing by rotogravure, flexographic, offset (dry or wet) letter press, or web screen. By means of any of these printing procedures, suitable impressions are made on the coatings or

laminations

16, 20 at the opposite sides of the web.

The printing can be either reverse printing or nonreverse, depending upon whether or not the printing is viewed through the transparent lamination. The various printing procedures are illustrated schematically in FIG- URES 4-8.

Referring to FIGURE 4, in the web rotogravure process, each coating or

lamination

16, 20 is separately printed, and then the web is turned by a suitable turn bar (not shown) and the opposite surface printed. In the web rotogravure process (FIGURE 4), the web 10 and its

laminations

16, 20 are passed over an impression roll 34 and the printing occurs by means of a printing cylinder 36 which rotates partially within a well 38 having ink 40. After being printed on one lamination, the web is turned and then the opposite lamination is printed.

In the flexographic printing process shown in FIGURE 5, the web 10 is passed between an impression roll 44 and a printing plate cylinder 46 which receives ink from a combination of an ink roller 48 rotatable within well 50 having ink 52 and an ink transfer roller 54 which transfers ink onto the surface of the printing cylinder 46.

Referring next to FIGURE 6, offset printing (dry or wet process printing) is obtained by passing web 10 together with the

laminations

16, 20 between an impression roller 58 and a blanket roller 60 which transfers the design onto the lamination of the web, the blanket roller 60 having received the impression from a printing plate cylinder 62 and ink roller 64.

Referring next to the letter press method of printing shown in FIGURE 7, the web 10 and its laminations is passed between an impression roller and a printing plate cylinder 72 which receives an impression from ink transfer roller 74.

Referring next to FIGURE 8, which illustrates schematically the web screen method of printing, the web 10 and its coatings or laminations is passed rst through a pair of rollers 76, 78 and then through an impression roller 80 and screen printing roller 82.

For further details of these printing procedures, reference should be made to Modern Packaging Encyclopedia for 1963, p. 655, Printing Arts for Packagers by C. K. Billeb, volume 36, No. 3A, published by C. A. Breskin.

In each of the illustrated printing methods shown schematically in FIGURES 4-8, the surface of iirst one

lamination

16 or 20 is printed, and then the web is turned over and the

other lamination

16 or 20 is printed. Depending upon the method of afxing the lamination to the container, the printing may differ. For example, if the printing is to be viewed through the thickness of the lamination,

then the printing is reverse printed, that is, it appears the same as surface printing would appear through a transparent page. The particular details of the printing, and method of printing, do not form an essential part of the present invention and the description of the various printing steps is intended to illustrate the wide scope by which the present invention can be applied.

If the printing on the casting or lamination at the time it is aflixed to the container is not viewed through the lamination, the printing is generally protected by a lacquer to provide some means of protection.

i Following the printing, if it is desired, the printed surface can next be metallized, that is, a thin coating of opaque metallic material can be applied over the printed surface so that it will form a bright background against which the printing appears. Prior to being metallized, which step is indicated by reference numeral 84, the web laminations and printing is lirst dried as indicated by reference numeral 86.

Referring to FIGURE 9, the metallizing is accomplished by passing a roll 88 of the printed material back and forth over a series of rollers 90 and which are located within a vacuum chamber 92. First one lamination is coated with a spray of linely atomized metallic particles, the spray being indicated by reference numeral 94. The fine spray is directed or evaporated on one of the

laminations

16 or 20 at a time and it makes a uniform coating over the surface of the printed lamination.

The spray 94 is obtained from a nozzle 96 which subdivides the metallic material and projects it onto the surface of the lamination. A turn bar 98 is then used to turn the web side-over-side and the web then continues to travel over rollers 98 and past a second spray 100 of nely divided metallic material which is then deposited on the printed surface of the

other lamination

16 or 20. The metallized material is then passed to a wind-up roll 102. The operation of the metallizer is intermittent, that is, periodically a fresh roll of unmetallized material is started at the left-hand side of FIGURE 9 and the metallized roll at the right-hand side of FIGURE 9 is removed.

Referring next to FIGURES 2, l0, the printed coatings or laminations are next removed from the web at a station indicated by reference numeral 104 in FIGURE 2, this being obtained by passing the web and coatings or laminations over heated rollers 105 which, by virtue of the different compositions for the web and release coating laminations respectively, cause the

laminations

16,20 to separate from the web 10 and the laminations 16,1 20 are then separately wound on wind-up

rollers

120 and 122, respectively. The web 10 which is freed of the laminations is wound onto a wind-up roller 124 is then returned to the trunnion 12 for reuse. The printed laminations are then either applied onto sheet metal stock which is later formed into the size and shape of the container or directly applied to the container in the manner shown in FIGURE l1.

Referring rst, however, to the method shown in FIGURE 10, a roll of the plastic material which is wound onto

rollers

120, 122 is transferred to a mounting standard 126 (FIGURE 10) and is then passed over

rollers

128, 130 moving in the direction of the arrows 132. The lamination is then heated by suitable heating elements 134, then passed over additional-

rollers

136, 138 and the lamination is met with a roll of sheet metal stock 140 which is supported on a mounting standard 142, the metal being passed over

rollers

146, 148 and then, for some applications, the metal can receive a skim coating of adhesive from an applicator 150 prior to meeting the printed lamination at roller 138. The two materials, that is the metal substrate and the printed lamination are then passed through a heater chamber 152 a linal lacquer coating can be applied by applicator 154 and the material is next passed over cooling rollers 156 and then a nal wind-up roll 158. The metal stock which has the printed lamination secured thereto can next be formed into the containers of the suitable size and container shape according to consumer preference.

Alternatively, the sheet metal stock can be rst formed into containers of the desired shape and size as ndicated in FIGURE. 11. In this embodiment, the sheet metal stock has already been formed into cylindrical containers 160 and the containers move in the direction of the arrow 162 into position to receive a printed lamination from supply roll 164. The finished container is then separated from the flow of material and is indicated by reference numeral 166. The container 166 appears to have the printing directly applied to its surface rather than a lamination of printed material.

The described process, providing printed laminations for containers, has a substantial advantage over previous processes in that it is possible to provide the printed material at substantial rates of speed which are at least coequal with the capacities for `handling the metal containers or sheet metal stock and it is possible to effect the printing lamination either at the rolling mill where the metal stock is obtained or to ship the printed laminations to the point of use of the container. Both of these applications are within the scope of the present invention.

A further advantage of the present invention, is that the printing is inherently protected by disposing it below the thickness of the lamination in the case that reverse printing is followed, i.e., in the case that the printing is viewed through the thickness of the lamination.

In the event that the printing is surface viewed and is not viewed through the thickness of the lamination, it is the practice to provide a protective lacquer finish over the coating which is itself transparent but which prevents picking of the surface print off of the lamination, this lacquering being obtained at 154, FIGURE 10.

The lamination of material can be applied to the web or carrier in any one of several different manners. Instead of spray coating as illustrated in FIGURE 2, it is possible to extrude the lamination and then apply it to the web of material which is composed of Mylar or other suitable web material. The requisite properties of the web are that it be relatively inert, heat resistant and separable from the lamination on which the printing is effected without injuring the lamination.

According to the embodiment shown in FIGURE 3, there is provided an extruder 170 which forms the lamination is then sized in a casting-and-drafting station 172 and thereafter successively heated at 174, stretched at 176 to obtain a suitable orientation then annealed at station 178. There is concurrently formed two

such laminations

16 and 20 which then meet with a web 10 of Mylar or the like and are squeezed between

pressure rollers

180, 182 which urge the two

laminations

16, 20 against opposite sides of the Mylar or other suitable web material from roll to provide the article shown in FIGURE 1. The article is next printed by any one of the processes previously described in the embodiment of FIGURE 2. The apparatus for extruding, casting, drafting, etc., prior to securement of the roll 10, does not form a part of the present invention in its exact details. Apparatus, however, which is found suitable for the present invention, is one manufactured by National Rubber Machinery Co., for the production of biaxially oriented plastic films. The extruder is a standard NRM Pacemaker extruder and the film is passed through a standard NRM casting-anddrafting unit and a tentering unit which includes the heating, stretching and annealing steps in a unit of the type supplied by a Winsor and Ierauld tentering unit through a Proctor and Schwartz tentering unit. The stretching is effected to as high as a 10 to 1 ratio depending on the particular resin with a ratio of 3 or 4 to l being more nearly typical. The apparatus is constructed by National Rubber Machine Company and its construction details are not a part of the present invention.

Following attachment of film at

rollers

180, 182 to the web roll 10, processing as to printing and steps 6 thereafter is the same as described in the embodiment of FIGURE 2.

It has been found, where it is desired to eliminate wrinkles in the printed plastic material, that instead of winding up the printed plastic rolls in

separate rollers

120, 122 as described in FIGURES 1, 2, the printed plastic laminations 16, 20 (FIGURE 2A) can be immediately joined to the metal, which is supplied from two supply rolls 190, 192 which are heated by heaters 194:1, 196, and 196a. The film as it is separated from the web is joined to continuously traveling metal rolls. The coated metal rolls 198, 200 correspond with the finished product 158, FIGURE 10. The roll of web material 124 (FIGURE 2A) is then returned to the support 12 at the laminating tower or the extruder depending upon the particular process selected.

In each of the described processes, the printed lamination can, prior to securing with the metal substrate, be embossed to provide a desired surface finish. The embossing is with rollers (not shown) and can be used or not as desired.

In addition to extruding the plastic lamination, which may consist of polyvinyl chloride, polyvinyl alcohol, polyethylene or the like, it is also possible to apply the plastic material either by immersion coating or kiss-roller type application, depending upon the characteristics of the resin material. See Modern `Packaging Encyclopedia for 1963 (supra.) pp. 623-630.

In operation, it is possible to produce the product at substantial speeds, in the order of 600 to 3000 lineal feet per minute. The securement of the printed film to the metal substrate can be either direct or indirect, that S, some of the plastic coatings or lamination materials provide their own adhesivity and bind themselves to the metal substrate whereas in other applications, it is necessary to apply an adhesive between the metal substrate and the plastic coating or lamination having the printing.

In operation, my invention is adapted for use with the light weight metal substrates which have been developed and about .055 to .005 inch in thickness. These materials are generally formed in coils but are not readily adapted for direct printing. It has also been found unfeasible to print rolls of metal because of the substantial thickness or surface which occurs 0n the leader section of metal which is fed through the printing apparatus. This waste is totally eliminated in the present invention since the plastic film which I apply to the metal substrate is not as expensive as the metal and therefore its waste is not as important.

In operation, the plastic, printed lamination is sealed to the metal substrate and t-he roll coil is then shipped to the container or can manufacturer in printed form or the printed lamination can be applied to the metal substrate at the place where the container is manufactured.

The lamination which I utilize is typically about 2%. mils in thickness and the carrier web which is Mylar is about 5 mil thickness. The printing can occur at a speed of about 300 feet per minute but because of the turn bar which is used in the center of the press for printing both sides of the web, each side having a lamination, I effectively produce printed laminations at the rate of 600 feet per minute.

The printed plastic lamination can be applied either to back lacquered or non-backed lacquered metals and its use is proposed for oil containers, food or juice containers as well as other applications. Food content containers which require a clean open area have a seam weld to lock under pressure, is readily usable by the present invention because of the removability of the plastic laminate at the seam area following application of the lamination to the metal.

In operation, I utilize each of the opposite sides of the web carrier 10 for receiving a

plastic lamination

16, 20 and on which is effected printing by any one of suitable printing processes. This can be followed by metallizing, if

desired, and then the plastic laminations are delaminated and either directly applied t a container or wound into coils and then applied to containers. The plastic material can be embossed at the surface in which only the plastic becomes embossed and none of the web is embossed. This latter is known as a superficial emboss. If it is desired, embossing rollers can be provided which will effect a total embossment including the web as well as the plastic. The term embossing includes and is meant to include the process of debossing as well. It will be appreciated that many different printing effects are obtainable and these effects are generally obtainable in the present invention.

During metallizing, as described hereinbefore, the metal material is obtained by evaporating the metal under heat and vacuum, the metal heated being reduced to a molten state, generally by electrical energy. The molten metal is then transferred in finely divided form and deposited as an even coating which completely covers the lamination. Satisfactory adhesion of the metal coating is generally obtainable on the plastic materials described. For additional details of metallizing, reference may be made to Paper Trade Journal, Oct. 3, 1960, p. 46, High Quality Metallized Paper by Fred B. Shaw.

The Mylar tape or other web material prior to being used following the delamination is preferably treated with a release agent which will facilitate the delaminating step. This is generally accomplished by passing the web, following delamination, through a release material which typically consists of Elvax or with a material of like properties, the emboss being obtained from E. I. Du Pont Company. These release agents are commonly known in the trade and are applied to the web before receiving the lamination or coating in one of the processes previously described.

The web can receive its lamination or laminations by a spray coating procedure, extruding, dipping or kiss-roller operation,

All of these ramifications of the invention incorporate the essential quality of a high rate of production for the printing material which adapts itself to a versatile combination of printing and other processing procedures, followed by application of the printed film to the metal substrate.

Referring next to the embodiment in FIGURE 3A, a roll of Mylar or other suitable web 210 is mounted on a turret on winding apparatus 212, there generally being two rolls which are joined together to provide for continuous running. The roll 210 being on one station and a roll 214 on the other station. The Mylar tape is fed through a float roll 216 by passing over idler rollers 218, the web traveling in the direction of the arrow 220. From the fioat roll the web is passed through a preheater 222 over heater rollers 224 and then into a laminator designated generally by reference numeral 226 where it receives a first coating on one side from a laminating device 228 which contains a quantity of the laminating material within a storage 230 and feeds it through a metering device 232 into a triangle cross section discharge 234 having outlet orifices 236. At the bottom of the discharge end is an applicator surface 238 which smooths out the flow of lplastic material from the orifices 236 to provide a lamination. The plastic coated web is then turned over by turn bar 240 and the opposite side of the web is coated by a second applicator 242 in the same manner as previously described. The web which is now coated or laminated on both sides is passed over idler rolls 244 and then to a turret winder 246 which includes

rolls

248 and 250 in two different stations on the stanchion 252. In this way, a fully wound roll is always available for removal and one roll is in the process of being formed. The laminating proceeds at substantial speeds in the order of 2500 feet per minute. For additional reference to apparatus of the type described, reference may be made to the Frank W. Egan and Company, Somerville, New Jersey, which is the manufacturer of the extrusion coating process described.

From the turret winder, the roll of material is next printed and is treated in the same manner described for the previous application.

Although the present invention has been illustrated and described in connection with a single example embodiment, it will be understood that this is illustrative of the invention and is by no means restrictive thereof. It is reasonably to be expected that those skilled in this art can make numerous revisions and adaptations of the invention to suit individual design preferences and it is intended that such revisions and variations which incorporate the herein disclosed principles, will be included within the scope of the following claims as equivalents of the invention.

I claim:

1. A process for applying printed material on relatively hard surfaces such as metal containers, intended for packaging foods, petroleum and beverages, comprising the steps of (a) continuously passing a roll of flexible web backing material through a chamber having a plurality of spray elements located one on each side of said web backing;

(b) depositing by spray application a plastic coating or lamination on each of the opposite surfaces of said backing as it moves through said chamber;

(c) printing indicia on each of the surfaces of the two laminations while the plastic laminations are backed by said web and are in fixed relation therewith;

(d) thereafter continuously removing the printed coatings or laminations from said web which is thereafter adapted for recoating by repeating the steps of a, b, and c;

(e) and applying the printed plastic films to a metal surface, which permanently receives the plastic film and displays the printed surface over the exterior of said containers.

2. A process for applying printed material on relatively hard surfaces such as metal containers for food, beverages, petroleum and other products comprising the steps of:

(a) continuously passing a continuous roll of flexible web backing material through a chamber having a plurality of spray elements located one on each side of said web backing;

(b) depositing by spray application a plastic lamination on each of the opposite surfaces of said backing as it moves through said chamber whereby said plastic lamination is received on the surface of the web, and is in fixed relation therewith and which is treated to facilitate release of the plastic lamination;

(c) printing indicia on the surfaces of the laminations at the opposite sides of the web while the plastic material is backed by said web and is carried by said web;

(d) applying an opaque deposit or spray over the printed surfaces of the plastic material at the opposite sides of said web as it is carried;

(e) thereafter removing the printed laminations from said web which is then adapted for recoating as provided in steps a, b, c, and d;

(f) and applying the printed plastic films to a metal surface of said containers, which receives and displays the printing on the plastic film.

3. A process for printing on relatively hard surfaces such as metal containers for food, beverages, petroleum, and other such products comprising the steps of (a) forming laminations of flexible material in sheet form, casting, and drafting the sheets following their forming;

(b) applying the laminations to opposite sides of a continuously movable web or backing member;

(c) thereafter printing selected indicia on the surfaces of the extruded laminations affixed to said web while said laminations are in fixed relation to said web and are carried thereby;

(d) applying over each of the printed surfaces of the exible plastic material a metallized lamination which forms an `opaque surface visible through the transparent plastic material and which provides a background for the printed material when it is mounted;

(e) heating the web and printed plastic material subsequently to rnetallizing to release the adhesion between said plastic laminations and the opposite sides of said web;

(f) and thereafter applying the removed printed plastic coating to a metal substrate suitable for forming into said lcontainers to provide labelling thereto.

4. A process for printing on relatively hard surfaces such as metal containers, comprising the steps of:

(a) extruding laminations of flexible material in sheet form;

(b) applying the extruded laminations of the material to opposite sides of a continuously movable web or backing member;

(c) thereafter printing selected indicia on the surfaces of the extruded laminations axed to said web while said extruded laminations are in xed relation to said web;

(d) applying over the printed surface of the exible plastic material a metallized lamination 'which forms 2 an opaque surface visible through the transparent plastic material and which provides a background for the printed material;

References Cited UNITED STATES PATENTS Little et al 156-231 Mitchell 117-12 Prindle et al. 161-214 Hahn 161-214 Hansen 117-71 Palmquist et al 161-214 Scharf 117-71 EARL M. BERGERT, Primary Examiner.

5 T. R. SAVOIE, Assistant Examiner.

U.S. Cl. X.R.