US 3887414 A
A hot melt coating on a window patch is softened and adhered in place on a blank window for a a windowed container such as a window or the like using one or more hot rolls nipped against a cooled vacuum roll which holds the window and blank in place relative to each other. This system can also be applied to patching webs from which window envelopes can be cut.
Description (OCR text may contain errors)
I United States Patent 1191 1111 3,887,414 Cohn June 3, 1975  ENVELOPE WINDOW PATCHING 2,257,829 10/1941 Winkler et al. 93/61 A 2,794,485 6/1957 Ashton et al. 156/282  Invent: 00h", Mllbrae Cahf- 3,416,414 12/1968 Smithe 156/521  I Assignee: Champion International Corporanon, Hamllton Primary Examiner-Daniel .l. Fritsch 2 Filed; Man 2 1973 Atgorieyl, Agent, or FirmGardiner, Sixbey, Bradford an ar son ] Appl. No.: 345,165
[52 US. Cl. 156/108; 93/61 A; 156/256; ABSTRACT  i g 156/498; 156/514; 15 1 63; A hot' melt coating on a window patch is softened and 58] i 2 6 4 282 adhered in place on a blank window for a a windowed 152/498 62 container such as a window or the like using one or 63 more hot rolls nipped against a cooled vacuum roll which holds the window and blank in place relative to each other. This system canalso be applied to patch-  :Z" ing webs from which window envelopes can be cut.
2,072,875 3/1937 Gray 93/61 A 7 Claims, 5 Drawing Figures ENVELOPE WINDOW PATCHING.
BACKGROUND AND SUMMARY'OF'THE l INVENTION 1 This invention relates to improvements in a method and apparatus for applying a window patch to a blank or web from which can be made a windowed container such as a window envelope. One aspect of the invention is to use a vacuum to hold the patch and web or container blank in position relative to each other. An aspect of the invention is to use all rotary means such as a vacuum drum and a rotary heated roll in combination, in connection with which the same will be described for applying a patch to an envelope blank by way of example, it being understood that other applications of the invention such as to webs from which blanks for forming into containers of various types are to be cut are contemplated and embraced herein. Thus the invention is limited only to the extent that the container stock or blanks must be flexible enough to respond readily to the various manipulative acts or steps comprising the hereinafter described method.
The prior art knows to use vacuum rolls or drums as a means to feed envelope blanks or the like through equipment for gumming and forming them into a finished envelope. Vacuum has also been employed in connection with the manufacture of window envelopes. There are special problems in making window envelopes because if the adhesive for holding the patch over the window runs out and down the front of the window it will tend to stick to the adjacent envelope and at least look unsightly. If the adhesive runs out from under the patch inside the envelope then the front and back panels of same are stuck together which is unsatisfactory.
The 1937 US. Pat. No. 2,072,875 to Gray teaches using a source of vacuum to hold an envelope and a window patch therefor in relative position while applying heat sufficient to melt a hot melt adhesive coated on the patch to the adhering point. Reciprocating members are taught by Gray. Moreover, this patent teaches using a concave surface to support the blankpatch combination (the window portion of the patch is supported in said concavity out of conductive heat contact with the heating surface), during the application of heat and thereby requires precise placement of his work pieces relative to the concavity. At the same time the Gray apparatus utilizes reciprocating members with all of the disadvantages of the slow vibrating type of operation realized with reciprocating members.
The present invention provides an advance over Gray in that a completely rotary system is provided whereby smoother and faster running is achieved. Moreover, a cylindrical vacuum drum is used to hold the blank and patch in register with each other during the time heat is applied. The convex surface of the drum acts as a support for the blank-patch assembly.
Although the blank and patch are placed carefully relative to each other, it is unnecessary to precisely place the blank and patch relative to the drum, as with Gray and his concavesupport. However, the patch is pulled into the window of the blank to thus be spaced away from the heat source and to avoid sticking to the vacuum roll.
. Y The present invention has consistently produced windowed containers where the windows are adhered right up to the edge of the hole in the envelope blank on the outside and are adhered right up to the edge of the patch on the inside of the container. Such a resulting other envelopes, machine elements) on the outside or of hooking inserts on the envelope inside, respectively, if the patch is not adhered to the edges of the window or of the patch to leave loose, free marginal edges which can hook such other objects.
Additional features and advantages will become apparent from the following description when read in connection with the drawings wherein:
FIG. 1 is a schematic side view of a patch applying machine showing the rotating elements of the invention;
FIG. 2 is a view of an envelope blank and window patch as seen from the inside of the envelope;
FIG. 3 is an isometric view of an assembled envelope with a window patch in place;
FIG. 4 is a schematic axial view along 4 4 of FIG. 1; and
FIG. 5 schematically shows details of one embodiment of a patch feeding means and cooled vacuum roll as used with and/or in the FIG. 1 assembly.
As seen in FIGS. 2 and 3, the well-known window envelope used as an example of one product to which the invention pertains, comprises basically three elements an envelope blank 1 folded in an appropriate fashion, a window patch 2 and adhesive 3 to hold the patch on the blank. The patch obviously is secured in place in register and over the window 4 on the envelope. Although some window envelopes are made without a patch, they are not germane to this invention.
In the present invention, the window patch 2 has for an adhesive 3 a coating of hot melted adhesive, preferably formed from Elvax either alone or extended by various waxes, microcrystalline waxes, and similar dilutants. Elvax is the trademark for a vinyl resin copolymer made by E. I. duPont de Neumours and Company which broadly speaking is a copolymer of ethylene and vinyl acetate. A preferred hot melt formulation consists in 30 percent by weight of either of the grades of Elvax mixed thoroughly with about 70 percent by weight of paraffin wax. Alternative hot melt mixtures can be formulated in any of the known manners. A thorough discussion of the 30/70 formulation, other formulae, and uses for Elvax is found in the July, 1961 Modern Packaging, pages 134 et seq.
Alternative mixtures may include other waxes and polymers, anti-oxidant, anti-scorching or clarity preservers, or release agents.
The preferred hot melt adhesive has a softening point in the range from about 250 to about 300 F. and is applied to the window patch material by conventional equipment prior to the instant patching operation.
The window patch for such an envelope by way of example is of a material that is selected from the group comprising or consisting of transparent and translucent adherable films and webs capable of withstanding the,
high temperature of about 425 F. to which it is subjected momentarily. For many years glassine has been preferred for windows despite its tendency to be translucent and it is still preferred because it can withstand the high temperature (about 425 F.) which it is subjected to with the Elvax heat. Most plastic films such as polystyrene, cellulose, and the like will soften, wrinkle, or even stick to the equipment if subjected to such temperatures. However, Mylar (polyethylene terephthalate) film can also be used at these temperatures with the Elvax hot melt adhesive and also is preferred material especially where transparency is desired as a prime consideration. The envelope blank is made of ordinary envelope paper which is a sized uncoated grade of quality paper and which is of such basis weight as to be flexible enough to permit of the manipulative steps of the method, as must be any base stock or blank employed in the operations to be subsequently described in greater detail.
The apparatus according to the present invention (FIGS. 1,4) comprises a water cooled vacuum drum 5 which is supported on a frame 6 (that is between the side frames 6) to rotate substantially adjacent to a heated roll 8 which is also supported on the frame 6.
Vacuum drums and their construction are old and well known in the envelope making art. Vacuum drum 5 is a hollow cylindrical shellvAs best seen in FIG. 5 the drum comprises a cylindrical shell having a plurality of radially extending vacuum ports 9 arranged around its face. Shell 10 is preferably of aluminum. Formed within the wall of the shell are a plurality of vacuum passages 11 each of which is connected to a number of the ports 9. The drum is, as is conventional, connected by suitable means such as a rotary coupling or shaft seal to a suitable vacuum source such as a vacuum pump, steam jet ejector, or the like. The vacuum established through ports 9 are employed to hold the blank and the patch on the drum in register with each other from the time of depositing the patch in register over the window within the nip between vacuum roll 5 and the vacuum transfer roll 12. In some cases it may be necessary to provide additional Heating and/or auxiliary cooling, This may readily be accomplished as by providing a supplemental heating or cooling roll 15. However, on most occasions, the roll 15 will not be needed and for this reason is shown in dotted lines on FIG. 5.
The interior of the drum 5 is connected by appropriate means such as tubing, a hollow shaft, and rotary coupling or shaft seal to a source of cooling fluid, preferably cooling water. By use of this cooling system, the convex surface of the drum is kept cool enough so that the adhesive on the window of the envelope wont stick to the surface, scorching of the blank is prevented, clouding or blooming of the window patch and/or its coating is reduced, and cooling is accelerated once the hot melt has been activated by the heat from roll 8.
The blank feeding means illustrated in FIG. 5 is the preferred embodiment although various other types of patch feeders could be employed. Basically, this involves a system for unwinding a web of patch material, such as glassine or Mylar, directing it against a knife or other cutting means where individual patches are severed, and then using the vacuum transfer roll 12 to feed the patch to the envelope blank. The system is coordinated with the feeding of the individual blanks or a web containing a series of blanks so that the patch arrives means of a pair of draw rolls 17. The draw rolls form a nip or turning couple and are pressed against each other hard enough that they firmly engagethe patch material 2A, unwinding it from the roll or reel 2A, and feeding it to a rotary knife 18 which cooperates with a stationary knife 19 to sever individual window patches from the web. Each patch 2 is severed at the time enough of it has fed past the rotaryknife I8, 19 to form a window at which time it engages the vacuum transfer roll 12 which is an ordinary vacuum roll of the sort well known in the envelope machine industry.
The vacuum rolls 5 and 12 are of conventional construction so far as the vacuum portions are concerned. They use rotary shaft seals and couplings as already mentioned for the feeding of air through the vacuum passages to a vacuum pump or the like. The various vacuum ports 9 in both rolls are turned on and shut off in a predetermined timed sequence controlled by valve plates or some other conventional timing device which need not be belabored further at this point.
For example, parts A in the vacuum drum 5 (FIG. 5) are turned on as they reach the position A which is where the envelope blank is first fed to the drum. These ports stay on, pulling a vacuum through them and thereby retaining the blank thereon until after all the operations of affixing the window have been completed. The envelope blank with window is, after completing such operations, removed from the drum 5 at a position E where the ports 9 are turned off to free the windowed blank for such as are required subsequent operations complete the gumming, flap folding, etc.
The vacuum transfer roll 12 has its ports turned on at approximately position F so that a severed window patch can be received from the knife 18, 19, retained on the blank for a time sufficient to seat it or transfer it down to the position B where it is brought into the nip between the two vacuum rolls 5, l2 and placed in register on the envelope window. At the position B the vacuum through the ports of the vacuum transfer roll 12, is shut off since this roll has completed its function of transferring the window patch. Release of the patch by the drum 12 and its retention by the vacuum existing through ports 9 on the water cooled drum surface 10 is thus affected. The vacuum remains turned off on the ports of the vacuum roll 12 for the time it takes to travel (rotate) from position B to position F and then is on for the rotation from F to B.
As indicated previously, the construction of vacuum drums and their control means is well known in the art. Typical vacuum passage manifolding and control means comprising a valving disc are taught in U.S. Pat. No. 3,457,696 and the references cited therein to that effect such as Skow U.S. Pat. Nos. 2,853,296 and 2,635,538. Inasmuch as the details of these constructions are well known in the art, it is not deemed necessary at this time to repeat them.
Returning to the description of the valve timing for vacuum roll 5, vacuum is turned on as the ports 9 reach point A, remains on at the nip B where the patch is received and continues on until the point C at which time heat is applied from the heated roll 8. If supplemental heating or cooling is needed, of course, the vacuum stays on during those functions whether it is prior to or after the heated roll 8. For example, if additional cooling or heating is required by a supplemental roll 15, the vacuum through ports 9 is kept on at least while the ports pass the position D and until the ports have reached the position E where the vacuum, by a suitable control means such as the valve plates mentioned in the abovementioned references, is turned off and the envelope with its now affixed patch is released for manipulation through the remainder of the. envelope manufacturing functions.
It will, therefore, be observed that the process for applying a window patch 3 to an envelope or web blank having a window cut out comprises the steps of feeding a strip 2A of hot melt coated transparent or translucent window patch material; severing a patch 2 from said strip by cutting off a predetermined length of it with a rotary knife 18; meanwhile feeding the envelope blank 1 to the rotating cooled vacuum drum 5 and securing same on the surface thereof by vacuum means; depositing at position B the patch 2 over the window 4 in the blank and holding it in place there by the vacuum drawn through the ports 9 in the vacuum roll, thereby pulling the patch down into the window opening (e.g. FIG. 1); and then moving the blank with the patch on it on the drum surface (where it is held immovably) through at nip at position C formed by rotating the drum 5 against a rotating heated roll 8 whereby the hot melt coating 3 is softened sufficiently to adhere the patch to the blank. Similarly where a web is used instead of an individual envelope blank.
In the present invention, it is important that the patch be on the outside or top of the envelope window as shown in FIGS. 2 and 3 because the vacuum roll 5 is thereby enabled to suck the patch down into the window 4 and actually out of contact with the heated roll 8 except for the border of the patch which overlies the areas immediately adjacent the marginal edges of the window to which the patch is ultimately adhered. This feature thereby reduces the amount of heat transferred between the heated roll 8 and the window portion of the patch while at the same time, due in part to the increased thickness of the patch where it overlies the envelope blank around the window, heat is applied directly to the patch and to the envelope thereby achieving the requisite adhesion by means of melting the hot melt adhesive.
It is important that cooling take place on the nonadhering surfaces (i.e. against the drum face 10), not only during, but immediately after the activation at C of the hot melt adhesive and any other heating step. First, scorching and other discoloration of both the envelope and the blank are thereby minimized and in most instances eliminated. Secondly, quick cooling assures that the adhesion process is rapidly completed and reduces or eliminates the opportunity for the patch to be moved out of register with the window or the like.
The heated roll 8 is preferably electrically heated and has an outer cylindrical surface made of aluminum. However, a heated ceramic roll may on some occasions be selected as conditions may dictate.
Thepressure with which the heated roll 8 is urged against the vacuum roll is also extremely important. A heavy pressure is desired. Where the heated roll is merely swung freely on arms or brackets 22, there ordinarily would not be enough pressure along the line of contact in the nip C to achieve the desired amount of heat transfer and adhesion. Therefore, some sort of positive pressure inducing means such as a counterweight 23 on the mounting arm 22A should be used if the weight of the roll itself will not produce the desired pressure. Too, as is obvious. various other pressure applying means, such as springs, air cylinders, etc., may readily be employed to produce the desired results.
Artificial cooling of the drum 5 to lower the temperaturevof surface 10 is preferred. However, where operating temperatures are low it is possible on some occasions to cool the drum surface 10 with either or both internal and/or external streams of air (e.g. compressed air) and in some instances to eliminate artificial cooling altogether.
By the term artificial cooling is meant intentionally supplying a cooling medium in addition to that resulting from natural forces such as conduction, convection, and/or radiation resulting from conditions of operation (e.g. rotational speed, surface temperature) and ambient conditions (eg room temperature).
The above machinery may be driven by an electrical motor which is connected by a suitable transmission to the various drums and rollers. Belt or chain drives are preferred as the most uncomplicated drive means because one motor can be connected to drive and set up and keep the various timed relationships between the moving elements with relative ease.
The invention claimed is:
1. A process of applying a window patch to a container blank such as an envelope or web for formation into a window container and having a window cut out comprising the steps of A. Feeding a strip of hot melt coated transparent or translucent window patch material;
B. Severing a patch from said strip by cutting off a predetermined length of it; I
C. Feeding said blank or web material to a rotating cooled vacuum drum with a cylindrical outer surface and securing it uniformly over its entire surface area by vacuum to said cylindrical surface of said drum;
D. Depositing said patch over the window cut out area in said blank or web and holding it in place uniformly over its entire surface area within the marginal confines of said window cut out by vacuum thereby pulling the patch down in its free area into the window opening; while leaving the marginal edges of the patch overlying the marginal edge areas circumscribing the window cutout area; and
E. Moving said blank or web with the patch on it on said drum convex surface through a nip formed by rotating said drum against a rotating heated roll so that the heated roll contacts only the overlapped marginal edges of said patch and said blank or web circumscribing said window cut out whereby the hot melt adhesive is softened sufficiently to adhere said patch to said blank only in said overlapped areas.
2. A process of applying a window patch according to claim 1 wherein the step of feeding comprises the feeding of a strip of hot melt coated transparent polyethylene terephlhalate film to subsequently define a window patch applied to said blank or web.
3. A process of applying a window patch according to claim 1 wherein said step of feeding further comprises the feeding of a strip of hot melt coated transparent glassine to subsequently define a window patch applied to said blank or web.
4. A process according to claim 1 including the further step of artificially cooling the vacuum drum.
5. A process according to claim 4 wherein said step of cooling includes supplying cooling water to the drum interior.
6. Apparatus for applying by heat sealing a window patch to a stock material having a window cut out area therein, such as an envelope blank or the like comprisa rotatable, cylindrical, hollow drum having a plurality of suction holes dispersed uniformly throughout at least a portion of its cylindrical surface to hold the windowed web or blank stock material in position on the drum surface throughout its entire area; means to cool the drum by a cooling fluid passing through the interior of said drum, and
means to create a vacuum through said suction holes;
rotary means to feed a window patch to and deposit it on the windowed web or blank material in register with the window cut out therein, said patch being held in position throughout its entire surface area within the marginal confines of said window cut out by vacuum drawn through said suction holes, and with its marginal edges overlying the marginal areas of said stock material circumscribing said out out; and
a heated cylindrical roll rotatably supported with its cylindrical surface adjacent the cylindrical surface of said drum which carries said blank and said patch, so that the heated roll contacts only the overlapped marginal edge areas of said patch and said stock material circumscribing said window cut out.
7. Apparatus for applying a window patch to a stock material all as defined in Claim 6, wherein said rotary means to feed a window patch includes rotary means to withdraw a web of patch material from a roll source thereof and means to sever individual patches from said web prior to positioning of said individual patches against the stock material.