US3062432A - Self-sealing metallic overwrap - Google Patents

Description

Nov. 6, 1962 R. E. JACKE SELF-SEALING METALLIC OVERWRAP 2 Sheets-Sheet 1 Filed Jan. '7, 1958 E M J 6 D N o M M R ATTORNEY Nov. 6, 1962 R. E. JACKE SELF-SEALING METALLIC OVERWRAP 2 Sheets-Sheet 2 Filed Jan. '7, 1958 RAYMOND I /A/(E ATTORNEY ired States T ice 3,062,432 SELF-SEALING METALLIC OVERWRAP Raymond E. .lacke, Louisville, Ky., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed Jan. 7, 1958, Ser. No. 707,490 8 Claims. (Cl. 22987) This invention relates generally to an improved laminated sheet having a metallic surface and more particularly to such a sheet for use in overwraps or lners and in which the sheet may be self-sealed, in enveloping relation to the material to be enclosed, by application of heat to its metallic surface. In addition, the invention further relates to an improved method and apparatus for producing the improved sheet.

Laminated sheet of this general type which includes layers of metallic foil, adhesive and paper is well known and has been employed in many specialized wrapping and lining usages. More specifically, this invent'on relates to providing such a sheet with apertures in the metallic foil layer so that when heat is applied to the metallic layer, the adhesive may readily flow through the apertures and spread upon the metallic layer surface thereby to provide a medium for bonding the metallic layer to itself by a self-sealing action in regions where such layer is in contact with itself. Difiiculty is experienced in providing apertures which enable this purpose to be accompl shed without, at the same time, unduly weakening the sheet; unduly limiting the spread of adhesive which, of course, would weaken the self-sealing action; or unduly interfering with rapid production of a clean sheet due to flaking of the metallic surface, accumulation of adhesive on the aperture-forming means or inability to maintain accurate depths of apertures Over a period of time.

It is these and similar problems in the manufacture of, and in broadening the capabilities of, laminated sheet comprising metallic, adhesive and paper layers, which my invention overcomes. For simplicity of description, such sheet will hereinafter be referred to generally as overwrap although it will be understood that the invention comprehends the use of such sheet for lining of containers or in other ways in which the sheet envelops a material or object and wherein its self-sealing function is employed. As an illustrative example of one use of the invention, an overwrap suitable for efficiently enwrapping a conventional loaf of bread will be disclosed.

An object of the invention is to provide an improved self-sealing metallic type overwrap which contains a plurality of perforations adapted to dIr-ect sufiicient adhesive to the metallic surface to insure a secure metallic to metallic sealing of the overwrap.

Another object is to provide an improved self-sealing metallic type overwrap which contains a plurality of'perforation arranged to avoid any tendencythereof to act as tear strips during normal usage of the overwrap.

Another object is to provide an improved method for rapidly perforating an imperforate web of laminated metallic type overwrap material.

A further object is to provide an improvedapparatus for rapidly perforating an imperforate web of laminated metallic type overwrap material under an exacting control with respect to depth of perforation.

Still a further object is to provide an improved overwrap for a loaf of bread.

In carrying out my invention, I provide a spooling machine to which a rapidly travelling imperforate Web of overwrap is supplied under tension furnished by that machine, and on which the web may be spooled after being perforated. Cooperating with the spooljng ma.- chine i an improved perforating means comprising a plurality of rotatable toothed blades which are driven by contact with the moving web and which are adjusted by a biasing means to effect a closely controlled depth of penetration of the web. A resilient and rotatable back ng roll is disposed on the paper side of the travelling web and serves as a backing against which the pressure of the blade biasing means is expended as the blade cuts through the metallic side of that web. Each blade includes a number of spaced cutting teeth on its periphery, such teeth having a configuration which not only minimizes the flaking or detach'ng of particles of the metallic layer from that layer, but also minimizes the tendency of the exposed adhesive to build up on the blade. Following the perforating step, the perforated web as an intermediate article of manufacture may be stored for later use or may be directed immediately into packaging mach'nery in which it is cut transversely to form the improved overwrap as a separate article.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operat on, may be best understood by reference to the following description, taken in conjunction with the accompanying drawing in which:

FIG. 1 is diagrammatic side elevation view showing the path of travel of the web under treatment;

FIG. 2 is a transverse view along line 22 of FIG. 1, showing the relation of the backing roll and perforating blades;

FIG. 3 is a view partly in section taken on line 3-3 of FIG. 2;

FIG. 4 is a plan view partly in section taken on line 44 of FIG. 2;

FIG. 5 is a side elevation view of a typical perforating blade, only a portion of the teeth being shown;

FIG. 6 is a plan view of a'finished overwrap;

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6, and to a greatly exaggeratedscale; and

FIG. 8 is a perspective view of a loaf of bread enwrapped with the overwrap of FIG. -6.

Referring first to FIGS. 6 and 7, a typical overwrap article made in accordance with the invention may comprise a rectangular sheet having parallel side edges 10 and 11 and parallel end edges 12 and 13. The sheet is of a laminated construction comprising a relatively thin metallic layer .14 .on .a first side and a relatively thick paper layer 15 on a second side. Intermediate these layers is a layer of thermoplastic adhesive such as a heat sealable wax 16 having a thickness commensurate with the degree of sealing required when the sheet is employed for its intended purposes. Along each of the side edges of the overwrap, a band of laterally spaced rows of perforations is provided for the purpose of directing the adhesive to the outer surface of the metallic layer during the sealing operation, these bands being shown generally at 17 and 18 and comprising five such rows of perforations in each band. As will later appear, the number of such rows of perforations is not critical and may be more or less than the five rows as shown without departing from the invention. The overall dimensions of the overwrap are, of course, chosen with respect to the article to be enwrapped, as, for example, the loaf of bread indicated by the dotted outline 20 near the center of FIG. 6.

'Consideringnow FIG. 1, as conventional spooling machine may include-a frame portion 21 for rotatably supporting a driven shaft 22 to which is detachably connected a take-up spool 23. A suitably controlled motor 24 may drive shaft 22 by any conventional means such as a belt 25. Guiderolls 26, 27 may be mounted upon the spooler frame to direct the incoming perforated web toward the take-up spool after a generally horizontal passage from the supply roll 28. Similar guide rolls 29, 30 may be mounted upon any suitable support to direct the imperforate web toward the perforating apparatus.

The perforating apparatus may be mounted upon a stationary portion 31 of the spooler frame intermediate the pairs of guide rolls as be means of spaced, fiat mounting plates 32 and 33 suitably affixed to the sides of the frame by bolts 34 (FIG. 1). As seen in FIG. 1, these mounting plates project forwardly of the frame in the direction of the incoming web. Adjacent an upper projecting edge of the frame, inclined recesses 35 and 36 are provided with an open end facing in the direction of the incoming web and into which the stub shaft ends 37 and 38 of a backing roll 39 are adapted to rest. This roll may include a cylindrical hollow tube of metal to which the stub shaft ends are aifixed. As an important feature of the invention, the metallic roll has a resilient covering 40 thereon into which the final biasing energy of the perforating blades, later to be described, is expended. As will be understood, the roll is driven by contact of its covering with the paper layer of the travelling web. I have found that a covering of rubber having a durometer reading of ninety and a thickness of about inch is suitable for use with the perforating apparatus now to be described and when manufacturing an overwrap as described in the example hereinafter disclosed.

As another feature of the invention, an adjustable shaft 41 serving the dual function of providing an initial positioning of the perforating blades supported thereby and of forming a support with respect to which those blades may be carefully adjusted for variation of depth of web penetration, is also provided.

This shaft extends parallel to roll 39 and may conveniently be mounted at one end in a pillow block 42 which may be adjustably clamped as by means of bolts 43 to a forwardly extending portion of plate 33 (FIG. 2). At its other end, the shaft is supported between complementary upper and lower bearing boxes 44 and 45. These bearing boxes may contain threaded holes for receiving bolts 46, 47 adjustably clamping the lower bearing box to plate 32 and for receiving bolts 48, 49 for clamping the upper bearing box to the lower bearing box. At the end adjacent these bearing boxes, the shaft has rigidly affixed thereto a handle 50.

Depending upon the width of the web to be perforated, a number of perforating assemblies, here shown as four, at 51, 52, 53 and 54, are mounted upon shaft 41 for support thereby. Considering now FIGS. 3 and 4, each of the perforating assemblies includes a yoke member having spaced arms 60 and 61 joined at a rear end by a cylindrical spacer 62 having an aperture therethrough for reception of shaft 41 with a close but freely movable fit. Suitably attached to the spacer as by welding, is a tangentially extending plate 63 projecting above and rearwardly of shaft 41. A threaded aperture is provided in this plate adjacent its rearmost end and engaging in the aperture is a selectively adjustable screw 64 having an abutment 65 engaging at all times with a compression spring 66.

Laterally disposed with respect to the yoke member is an L-shaped spring backboard member having a spring backing plate portion 67 and a shaft engaging portion 68. This latter port'on includes a generally semi-circular recess, which recess fits against the under surface of shaft 41, as best seen in FIG. 3. Cooperating with that latter portion is a cap member 69 adapted for clamping to the spring backboard member as by bolts 70 and 71 on each side of shaft 41. Compression spring 66 of course, bears at all times against the backing plate portion 67.

By means of the construction as thus far described, the shaft may be initially set into prescribed angular relation with respect to the mounting plates on the sides of the frame merely by rocking it with handle 58 whereupon it may be locked into stationary position by adjustment of bolts 48 and 49 bringing the bearing boxes 44 and 45 into tight engagement with that shaft. If desired, a conventional rapid adjusting handle 59 may be employed for this purpose. Since the spring backboard members are securely clamped to the shaft by means of the caps bolted therewith, rocking movement of the shaft during this initial adjustment also rocks the spring backboard members. Moreover, due to the presence of the compression springs the adjustment of the spring backboard members causes the yokes to pivot downwardly toward the web as seen in FIG. 1.

Carried between the arms of each yoke is one or more, preferably identical, perforating blades, five being shown in FIG. 4 at 74, 75, 76, 77 and 78. These blades are mounted for rotation independently of each other upon a pin 79 extending between the sides of the yoke and are provided with a conventional friction reducing bearing, such as a ball bearing, permitting the blade to move easily. Since these blades serve the purpose of perforating the metallic layer of the overwrap to enable adhesive to be directed outwardly upon that metallic layer and are not for the purpose of providing an overwrap weakening or tear-strip function, the construction, as well as the actuation of those blades is significant. I have found that the length of the perforation formed by the blade, as well as the spacings between adjacent perforations within the same row, is in general more important than the width between adjacent rows of perforations or the number of such rows of perforations. Accordingly, I provide each of the perforating blades, one being shown at FIG. 5, with a series of peripheral sharp bevelled teeth so, each of which is about & inch in length and which are spaced from each other bv an undercut 81 which likewise is about inch in length.

Accordin ly, it will be seen that the perforations in each row of the bands 17. and 18 (FIG. 6) are equal in length and are equally spaced within a given row, but that the perforations of one row are randomly spaced as regards the perforations in an adjacent row due to the independent rotation of the several perforating blades. The pattern of perforations thus obtained may be designated as a sk p-score pattern in which the ends of adiacent perforations in a given row are separated by a brid e of metal helping to preserve the tensile strength of the web.

Having in mind the type of overwrap to be produced and the above-described apparatus, mv method may be practiced as follows by reference to FIGS. 1 and 2. Operation of motor 24 rotates roll 23 at a desired speed wh ch imposes a tension on the web coming from supnlv roll 28 and guided across backing roll 39 bv the several guide rolls. Frictional en agement of the paper side 15 of the web with the resilient covering 40 of the backing roll causes that roll to rotate. By means of ap ropriate adjus ments. the shaft 41 occupies a position above the metallic surface of the moving web. which causes the vokes supported b that shaft to hold the rotatable blades in enga ement with the metallic surface of that web. The blades accordin ly are driven b their contact with the web and cut into the thin metallic layer. The selected adin t nent of s rews 64 determi es the value of the biasin z spring pressure which is to be expended by the blade upon the web, the heavier such pressure. the deeper the cut for a given web. and the lighter such pressure the shallower the cut. Upon penetratin the metallic laver 14 (F G. 7) the blade encounters little or no resistance from the adhesive 16 and if the spring biasing is sufficient to cause the blade to cut throu h the former. the blade extends its cut to the upper surface of the paper layer as seen at 82. As will further be seen, the more the yoke pivots about the shaft 41, the less will be the residual biasing pressure since the spring is diminishing its applied energy as it elongates. Therefore, when the blaoe touches the metallic layer, the entire web is pressed firmly against the covering of the backing roll which is sufficiently resilient to assist in reducing the tendency of the blade to bite too deeply into the web. The residual energy of the biasing sprmg thus is opposed and absorbed by the rubber covered backing roll. Should the blade tips scratch the upper surface of the paper layer, however, no appreciable weakening of the web occurs, since in general the thickness of that paper layer is several times the thickness of the metallic layer and, at the same time, the compression spring is substantially fully extended by the time the blade tips reach the paper layer. Thus, it will be seen that in carrying out the method, a gross or approximate setting of the blades is first provided by the setting of shaft 41, followed by a refine-:1 setting of the blade by application of a spring biasing pressure, followed by expanding of any surplus biasing energy upon the blade by absorbing that energy in the resilient backing roll. As the web moves through the perforating stage it is thus perforated in parallel bands the number of which depends upon the number of perforating assemblies employed. If wrinkles or discontinuities are present in the incoming web, the separate perforating blades are unaffected since they rotate independently. No flaking or abrasion of the metallic layer occurs and no build-up of adhesive occurs on the blades since centrifugal force tends to keep the blades clean.

Overwrap made in accordance with the above process may be used for various purposes and for all such purposes possesses the self-sealing characteristic. As seen in FIG. 7, the several perforations 82 expose the adhesive layer 16 so that when heat is applied to the metallic layer 14, such adhesive may bleed outward upon that metallic surface. Also, as is well known in the art, the adhesive will bleed or strike-through the pores of the paper layer upon heat application. When enwrappinng a loaf of bread for example, as seen in FIG.8, this bleeding is employed to fashion a longitudinal seam 19. In general, the

.most difficult seal and the one which heretofore has caused the greatest problem, is the seal at the ends of that loaf. When the loaf is enwrapped by conventional wrapping apparatus which forms and tucks in the wrapper, these tucks include metallic surfaces face-to-face and since the loaf of bread is readily compressible, it is essentially that the overwrap be self-sealing upon application of a'heating means with relatively little pressure. The present invention satisfies these requirements since the band 17 of perforations permits ample adhesive to bleed through the perforations into an area near the ends of those tuck portions and to spread upon the metallic surfaces. Since aluminum is an excellent conductor of heat, merely touching a heating means to the tucks near the ends of the loaf effects a rapid self-sealing which when the adhesive sets, will afford a substantially air-tight seal.

The tensile strength retainedby the overwrap following its perforating is of significance as regards the enwrapping since many conventional wrapping machines hold the overwrap which is furnished as a roll, under tension at one or more stages of operation. By reason of the present invention, the perforated self-sealing, overwrap may be used upon such conventional machines since it does not tear along the perforated lines.

The advantageous features of the above described apparatus and method of the invention may be further seen by reference to the following specific example of the particular overwrap article used for a standard size and shape of a loaf of bread.

Example The width of the overwrap was 15% inches and the length was 18%. inches. The outermost row of perforations of each bank was /8 inch from the side edge of the overwrap and the five rows were each 4 inch apart. Th perforations within each row were inch long and were spaced from each other by 7 inch bridges of aluminum. The metallic layer comprised dry annealed aluminum foil, 0 temper and 0.00035 inch in thickness. The paper layer comprised fully bleached sulphite 20 pound bond paper having a thicknes of about 0.002. inch (depending upon the density of the paper). The wax layer comprised microcrystalline wax amounting to 16 pounds of wax per ream of paper. A ream consists of 480 sheets 24 inches by 36 inches. Following perforation, the described sheet retained a tensile strength of 17.8 pounds per inch when subjected to stress in the direction of the axis of the rows of perforations; of 3.54 pounds per inch when subjected to stress in a direction normal to the axis of those rows; and of 7.65 pounds per inch when subjected to stress at 45 diagonally of those rows. When sealed by lightly passing a heat sealing means into contact with the folded ends of the overwrap enclosing a loaf of bread and after heat sealing the longitudinal seam 19, the overwrap provided a substantially hermetic seal for the article enclosed thereby. During the enwrapping and sealing operation on high-speed packaging operation no tearing of the overwrap along the rows of perforationsoceurred.

In accordance with the patent statutes, I have described what at present is considered to be the preferred embodiment of my invention, but it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the true spirit and scope of the invention and I aim, therefore, to cover, in the appended claims, all such equivalent variations and modifications.

What I claim is:

1. In a laminated heat-scalable overwrap having a layer of metallic foil on a first side, a layer of paper on a second side, said paper layer being thicker than said metallic layer, and a layer of adhesive intermediate said metallic and paper layers, the improvement comprising, two bands of perforations formed in said metallic layer for directing said layer of adhesive to the outer surface of said metallic layer during the sealing thereof, said bands extending continuously along each of two parallel side edges of said overwrap, each band comprising a plurality of laterally spaced rows of elongated perforations having each perforation in each row spaced longitudinally of its adjacent perforation in the same row and extending in the same direction, each band being of a size suflicient to provide within the confines of said bands a substantial area of metal-to-metal contact upon folding of each of said side edges upon itself, each perforation having a depth sufficient to fully penetrate said metallic layer and insufficient to penetrate said paper layer to a substantial weakening extent while penetrating at least part of said layer of adhesive, said overwrap containing said perforations having a greater tensile strength in the axes of said bands of perforations than in the direction transversely thereof, the lateral spacing between adjacent rows of each band and the longitudinal spacing between perforations within each row being sufficiently great to overcome the tendency of said perforations to act as tear-strips during normal enwrapping and sealing operations employing said overwrap.

2. An overwrap as defined in claim 1 wherein the length of each perforation within a row is substantially equal to the spacing between adiacent perforations in the same row.

3. An overwrap as defined in claim 1 wherein the perforations within each row have a predetermined spacing rela* tive to each other and a random spacing relative to the nearest perforation in adiacent rows.

4. An overwrap as defined in claim 1 wherein the length of each perforation is about inch.

5. A product hermetically sealed by a laminated heatsealable overwrap comprising: a product to be sealed; a heat-sealable overwrap enveloping said product; said heatsealable overwrap consisting of a layer of metallic foil on a first side, a layer of paper on a second side, a layer of adhesive intermediate said foil and paper layers, said layer of foil having two bands of elongated perforations extending continuously along each of two parallel side edges of said erwrap, each band comprising a plurality of laterally spaced rows of perforations having each perforation in each row spaced longitudinally from its adjacent perforation in the same row; the perforations in each row being randomly spaced relative to the perforations in adjacent rows, said laminated overwrap having each band of perforations folded about opposite ends of said product to form at least some areas of foil to foil contact; and said foil to foil contact areas being sealed to each other by the migration of said layer of adhesive through the perforations in said foil layer upon the application of heat and pressure to the ends of said product.

6. A product hermetically sealed by a laminated heatsealable overwrap comprising: a product to be sealed; a heat-scalable overwrap enveloping said product; said heatsealable overwrap consisting of a layer of metallic foil on first side, a layer of paper on a second side, a layer of adhesive intermediate said foil and paper layers, said layer of foil having two bands of perforations extending continuously along each of two parallel side edges of said overwrap, each band comprising a plurality of laterally spaced rows of perforations having each perforation in each row spaced longitudinally from its adjacent perforation in the same row; said laminated overwrap having eac band of perforations folded about opposite ends of said product to form at least some areas of foil to coil contact and other areas of paper to foil contact; said foil to foil contact areas being heat-sealed to each other by the migration of said layer of adhesive through the perforations in said foil layer and said areas of paper to foil contact being heat sealed by the migration of said layer of adhesive through the paper layer to the foil layer.

7. A product hermetically sealed by a laminated heatsealable overwrap comprising: a product to be sealed; a heat-sealable overwrap; said heat-scalable overwrap consisting of a layer of metallic foil on a first side, a layer of paper on a second side, a layer of adhesive intermediate said foil and paper layers, said layer of foil having two bands of perforations extending continuously along each of two parallel side edges of said overwrap, each band comprising a plurality of laterally spaced rows of perforations having each perforation in each row spaced longitudinally from its adjacent perforation in the same row; said laminated overwrap enveloping said product with its bands of perforations being normal to the longitudinal axis of said product and with its ends being overlapped forming a longitudinal seam parallel to the longitudinal axis of said product; said longitudinal seam being scaled by migration of said layer of adhesive through the paper layer to the foil layer upon the application of heat and pressure to said seam; said laminated overwrap having each band of perforations folded about opposite ends of said product to form at least some areas of foil to foil contact; and said foil to foil contact areas being sealed to each other by the migration of said layer of adhesive through the perforations in said foil layer upon the application of heat and pressure to the ends of said product.

8. A production hermetically sealed by a laminated heat-sealable overwrap comprising: a product to be sealed; a heat-scalable overwrap enveloping said product; said heat-sealable overwrap consisting of a layer of metallic foil on a first side, a layer of paper on a second side, a layer of adhesive intermediate said foil and paper layers, said layer of foil having two bands of perforations extending continuously along each of two parallel side edges of said overwrap, each band comprising a plurality of laterally spaced rows of perforations having each perforation in each row spaced longitudinally from its adjacent perforation in the same row; said laminated overwrap enveloping said product with its hands of perforations being normal to the longitudinal axis of said product and with its ends being overlaped forming a longitudinal seam parallel to the longitudinal axrs or said product; said longitudinal seam being sealed by migration of said layer of adhesive through the paper layer to the foil layer upon the application of heat and pressure to said seam; said laminated overwrap having each band of perforations folded about opposite ends of said product to form at least some areas of foil to foil contact and other areas of paper to foil contact, said foil to foil contact areas being heat-sealed to each other by the migration of said layer of adhesive through the perforations in said foil layer and said areas of paper to foil contact being heat-sealed by the migration of said layer of adhesive through the paper layer to the foil layer.

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