US3832821A

US3832821A - Use of corrugated paperboard for skin packaging substrates

Info

Publication number: US3832821A
Application number: US00382075A
Authority: US
Inventors: R Walus
Original assignee: Possis Corp
Current assignee: Possis Corp
Priority date: 1973-07-23
Filing date: 1973-07-23
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03

Abstract

Corrugated paperboard substrate is moved through a skin packaging machine with its corrugations oriented transversely to direction of advance. Lengthwise extending marginal edge portions of the substrate are maintained compressed, at least all along that portion of the substrate that is over the suction nozzle, thereby preventing air from leaking into the corrugations.

Description

United States Patent Walus 1 Sept. 3, 1974 USE OF CORRUGATED PAPERBOARD FOR SKIN PACKAGING SUBSTRATES Richard L. Walus, Minneapolis, Minn.

Assignee: Possis Corporation, Minneapolis,

Minn.

Filed: July 23, 1973 Appl. No.: 382,075

Inventor:

U.S. Cl 53/22 A, 53/112 A, 53/140 Int. Cl 1365b 33/02 Field of Search 53/22 A, 112 A, 140

References Cited UNITED STATES PATENTS Goodman 53/22 A 3,468,099 9/1969 Vogt 53/140 Primary Examiner-Travis S. McGehee Attorney, Agent, or Firm-Ira Milton Jones [5 7 1 ABSTRACT Corrugated paperboard substrate is moved through a skin packaging machine with its corrugations oriented transversely to direction of advance. Lengthwise extending marginal edge portions of the substrate are maintained compressed, at least all along that portion of the substrate that is over the suction nozzle, thereby preventing air from leaking into the corrugations.

6 Claims, 4 Drawing Figures or-mole 5 PATENTED I974 V 3.832.821

SNEEI 30? 3,

USE OF CORRUGATED PAPERBOARD FOR SKIN PAQKAQLNQ SUBSTRATES This invention relates to so-called skin packaging in which an article mounted on a substrate of paperboard or the like is protected and secured to the substrate by a film of thermoplastic material that covers the article and its adjacent face portions of the substrate; and the invention is more particularly concerned with a method and means for enabling corrugated paperboard to be used as a skin packaging substrate.

Two general types of skin packaging are practiced. In one, a thermoplastic sheet that has been heated to soften it is draped over a substrate and an article or articles thereon. In the other, fluid thermoplastic material is debouched downwardly from a nozzle or die to form a film that covers the substrate and articles.

In both cases satisfactory skin packaging requires that the space between the substrate and the film be substantially completely evacuated of air before the thermoplastic cools to hardness, to insure that the film will not have wrinkles, blisters or bubbles. To this end the substrate is moved through the skin packaging machine directly from the station at which film is applied to a vacuum table or a suction nozzle by which suction is applied to its underside. The substrate is either an inherently porous material or one that has been provided with numerous very small perforations, to permit air to be drawn downwardly through it from beneath the film.

Obviously the complete evacuation of the space heneath the film requires that air should not be permitted to enter the vacuum chamber or suction nozzle except from that space. Because of this requirement, it has heretofore been considered impracticable to use corru-- gated paperboard as a substrate for skin packaging.

Such material, as is well known, comprises two laminations of paper that are held in flatwise spacedapart relationship by an intervening layer of corrugated paper. If suction is applied to the undersurface of the lower lamination, no air would normally be drawn through the upper one because of the leakage along the corrugations, which, in effect, define a series of open tubes along which air can flow freely.

In all other respects, however, corrugated paperboard is an ideal material for skin packaging substrate. It is strong, rigid, light in weight, andaffords a degree of cushioning and impact protection that is often of value for the packaging of fragile articles.

With these considerations in mind, it is the general object of the present invention to provide a method and means for enabling corrugated paperboard to be use as a skin packaging substrate.

More specifically it is an object of this invention to provide a simple method of sealing the ends of the open tubes that are defined by the corrugations of corrugated paperboard, so that when suction is applied to one surface of the paperboard air is prevented from leaking into those tubes and is instead constrined to flow transversely through the paperboard from its other surface.

It is also a specific object of this invention to provide inexpensive apparatus for the practice of that method that can be readily installed on conventional skin packaging machines.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the precise method of practicing the invention and in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of an embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a more or less diagrammatic perspective view of a portion of a skin packaging machine that embodies the principles of the present invention;

FIG. 2 is a view in side elevation of the portion of the machine shown in FIG. 1, FIG. 2 also being somewhat diagrammatic;

FIG. 3 is a view in cross section, taken on the plane of the line 3-3 in FIG. 2; and

FIG. 4 is a view in longitudinal section, on an enlarged scale, taken on the plane of the line 4-4 in FIG. 3.

Referring now more particularly to the accompanying drawings, the numeral 5 designates generally a skin packaging machine of the type disclosed in US. Pat. No. 3,596,432, to MJ. Straub et a], to which reference may be made for a more detailed description of such a machine. As is conventional, the machine 5 comprises means 6 for moving a substrate 7 in one direction along a horizontal path. In this case the substrate is carried along on a conveyor which comprises a flat belt 8 trained around rollers 9 that are spaced apart in the direction of conveyor travel.

The substrate 7 is conventional corrugated paperboard which, as best seen in FIG. 4, comprises two laminations 10 and 11 of kraft paper held in flatwise spaced apart relationship by an intervening layer of corrugated paper 12.

In the present case the substrate is in the form of a continuous strip or web, drawn from a roll or other supply source .which is not shown but which will be understood to be located to the right of the portion of the machine depicted in FIGS. 1 and 2. To the left of the illustrated portion of the machine there can be a flying guillotine (not shown), as described in the above mentioned patent, for cutting the substrate into individual packaging lengths. Of course the machine 5 can be used with substrate that has been precut into panels.

Irrespective of whether the substrate is a continuous strip or in discrete lengths, it has its corrugations oriented transversely to the length of the conveyor for the purposes of this invention.

In the present case articles 13 to be packaged are illustrated as bar-like items, and it will be understood that these have been placed on the substrate, at regular intervals along its length, by means of known apparatus not illustrated.

Although the present invention is entirely suitable for skin packaging methods and apparatus wherein a heat softened sheet of thermoplastic material is draped over an article and a substrate, the machine here illustrated is of the type that comprises a die or nozzle 15 which is mounted above the conveyor. As the conveyor advances at a steady rate, liquid plastic issues downwardly from the nozzle 15 in a curtain-like stream and forms a continuous coating or film 26 over the articles and the substrate.

Immediately after passing beneath the nozzle 15, the substrate is carried over a suction nozzle 16 that applies suction to its underside to evacuate the space between the substrate and the plastic film. As shown, the suction nozzle extends a substantial distance lengthwise along the conveyor and nearly completely across it, being in the form of a shallow pan that opens to the underside of the top stretch of the conveyor belt 8. Numerous holes 17 through the belt 8, at intervals all along its length and across most of that part of its width that is overlain by the substrate, allow air to be drawn through it from the substrate into the suction nozzle. The top stretch of the belt 8 rides on a coplanar rim or top edge 18 of the suction nozzle to form a sliding seal around its mouth as well as to be locally supported by it.

it will be understood that the laminations 10 and 11 of the substrate, and also the corrugated layer 12 thereof, are either porous or are provided with numerous tiny perforations, so that air can readily pass through the substrate from one of its surfaces to the other.

To prevent leakage of air into the space between the laminations l0 and 11 of the substrate, the present invention contemplates that the lengthwise extending marginal edge portions 19 of the substrate shall be maintained under firm compression all along at least that portion of the substrate that overlies the suction nozzle 16. Such compression of course seals the ends of the tubes that are defined by the corrugations.

The means for effecting such sealing compression comprises two sets of rollers 20, one set over each side edge portion of the conveyor. The axes of. the rollers extend horizontally and traversely to the direction of conveyor travel, and all of the rollers in each set are radially aligned with one another to have a belt 22 trained around them. The belt 22 serves to distribute the compressive force due to the rollers fairly evenly along that portion of the substrate margin that the rollers overlie.

The rollers 20 are of course freely rotatable so that they and the belt 22 are driven by the conveyor belt 8 through the substrate. Preferably, as indicated in FIG. 2, the rollers 20 are so mounted as to be capable of limited bodily up and down motion independently of one another, and each is urged downwardly with a fairly strong biasing force. Such mounting of the rollers enables them to accommodate themselves automatically to corrugated paperboard substrates of different weights and also to variations in thickness along the length of a particular substrate.

Obviously the plastic film material should not be applied to the marginal zones 19 of the substrate that are engaged by the compressing belts 22, since the plastic is still in a fluid or tacky state as the substrate moves across the suction nozzle 16 and would stick to those belts. Preferably the compressed and uncoated marginal edge portions of the substrate are cut off and discarded after the substrate has passed the suction nozzle.

The corrugated layer of the substrate is of course relatively resistant to compression, but once broken down it can be rather easily recompressed and maintained in compressed condition. Preferably the roller sets 20 and their cooperating belts 22 merely maintain compression of the marginal portions of the substrate, and the initial breaking down of the corrugated layer is effected by a pair of single rollers 24, one mounted at each side of the conveyor, at a zone upstream from the suction nozzle. As shown, the rollers 24 are located to engage the substrate just before it is carried under the die from which the thermoplastic film material issues. Like the roller sets 20, the single rollers 24 are freely rotatable, are mounted for bodily up and down motion, and are yieldingly biased downwardly. inasmuch as they engage only small areas of the substrate, they can exert high compressive forces upon it to flatten the corrugated layer.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides a simple method and inexpensive means for enabling the use of corrugated paperboard substrates for skin packaging.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

I claim 1. In the packaging process in which articles to be packaged are placed upon substrate and the substrate is moved-horizontally in one direction along a defined path, a thermoplastic film is applied over the articles and the substrate, and suction is thereafter applied to the underside of the substrate in one zone of said path to draw air through the substrate and thus suck the film down into intimate engagement with it and the articles thereon, the improvement which enables use for substrate of corrugated paperboard comprising two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which allow air to flow edgewise between the laminations, said improvement residing in the steps of:

A. orienting the substrate with the corrugations extending transversely to said direction; and

B. maintaining 'sufficient compressive force upon each of the marginal edge portions of the substrate that extends in said direction, all along at least that portion of the same that extends through said zone, to seal the paper laminations to one another and thus prevent edgewise flow of air between them.

2. The process of claim 1, further characterized by:

C. prior to entry of the substrate into said zone, ap-

plying a localized compressing force to each of said marginal edge portions of the substrate as the substrate moves in said direction, to break down the corrugations of said intervening layer at said marginal edge portions thereof and thus facilitate maintenance of sealing compression at said zone.

3. A packaging machine comprising means for effecting lengthwise motion along a defined path of an elongated horizontal substrate carrying articles at spaced intervals therealong, means for applying a thermoplastic film over the substrate and the articles, and means at a zone along said path for drawing air through the substrate and thus sucking film down into intimate engagement with the substrate and the articles thereon, said machine being characterized by means that enable it to operate successfully with corrugated paperboard substrate that comprises two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which extend transversely to said path and which allow air to flow edgewise between the laminations, the last mentioned means comprising:

means positioned to engage and collapse the longitudinal marginal edge portions of the substrate as it approaches said zone, and thereby seal the ends of the transversely extending corrugations.

4. A packaging machine comprising means for effecting lengthwise motion along a defined path of an elongated horizontal substrate carrying articles at spaced intervals therealong, means for applying a thermoplastic film over the substrate and the articles, and means at a zone along said path for drawing air through the substrate and thus sucking film down into intimate engagement with the substrate and the articles thereon, said machine being characterized by means that enable it to operate successfully with corrugated paperboard substrate that comprises two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which extend transversely to said path and which allow air to flow edgewise between the laminations, the last mentioned means comprising:

means extending lengthwise along each longitudinal marginal edge portion of the substrate through at ginal edge portions of the substrate as itmoves through said zone;

B. two sets of rollers at said zone, one set at each side of said path,

1. all of said rollers being rotatable on axes that extend transversely to said path,

2. the rollers of each set being radially aligned with one another and spaced in said direction at intervals along said zone, and

3. each of said rollers being mounted for limited independent bodily up and down motion and being yieldingly urged downwardly; and

C. a belt trained around each set of rollers and through which the compressive force of the rollers of the set is imposed upon and distributed along a marginal edge portion of the substrate.

6. The packaging machine of claim 5, wherein all of said rollers are mounted for free rotation, further characterized by:

D. an additional pair of freely rotatable rollers, one at each side of said path, at a location in advance of said zone relative to the direction of substrate motion, each of the rollers of said additional pair being freely rotatable on a horizontal axis transverse to said path and being mounted for limited bodily up and down motion and biased downwardly with sufficient force to break down the corrugations of said intervening layer of the substrate along said marginal edge portions thereof.

Claims

1. In the packaging process in which articles to be packaged are placed upon substrate and the substrate is moved horizontaLly in one direction along a defined path, a thermoplastic film is applied over the articles and the substrate, and suction is thereafter applied to the underside of the substrate in one zone of said path to draw air through the substrate and thus suck the film down into intimate engagement with it and the articles thereon, the improvement which enables use for substrate of corrugated paperboard comprising two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which allow air to flow edgewise between the laminations, said improvement residing in the steps of: A. orienting the substrate with the corrugations extending transversely to said direction; and B. maintaining sufficient compressive force upon each of the marginal edge portions of the substrate that extends in said direction, all along at least that portion of the same that extends through said zone, to seal the paper laminations to one another and thus prevent edgewise flow of air between them.

2. The process of claim 1, further characterized by: C. prior to entry of the substrate into said zone, applying a localized compressing force to each of said marginal edge portions of the substrate as the substrate moves in said direction, to break down the corrugations of said intervening layer at said marginal edge portions thereof and thus facilitate maintenance of sealing compression at said zone.

3. each of said rollers being mounted for limited independent bodily up and down motion and being yieldingly urged downwardly; and C. a belt trained around each set of rollers and through which the compressive force of the rollers of the set is imposed upon and distributed along a marginal edge portion of the substrate.

3. A packaging machine comprising means for effecting lengthwise motion along a defined path of an elongated horizontal substrate carrying articles at spaced intervals therealong, means for applying a thermoplastic film over the substrate and the articles, and means at a zone along said path for drawing air through the substrate and thus sucking film down into intimate engagement with the substrate and the articles thereon, said machine being characterized by means that enable it to operate successfully with corrugated paperboard substrate that comprises two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which extend transversely to said path and which allow air to flow edgewise between the laminations, the last mentioned means comprising: means positioned to engage and collapse the longitudinal marginal edge portions of the substrate as it approaches said zone, and thereby seal the ends of the transversely extending corrugations.

4. A packaging machine comprising means for effecting lengthwise motion along a defined path of an elongated horizontal substrate carrying articles at spaced intervals therealong, means for applying a thermoplastic film over the substrate and the articles, and means at a zone along said path for drawing air through the substrate and thus sucking film down into intimate engagement with the substrate and the articles thereon, said machine being characterized by means that enable it to operate successfully with corrugated paperboard substrate that comprises two paper laminations held in flatwise spaced relation by an intervening layer of paper having parallel corrugations which extend transversely to said path and which allow air to flow edgewise between the laminations, the last mentioned means comprising: means extending lengthwise along each longitudinal marginal edge portion of the substrate through at least said zone for imposing sufficient compressive force upon said marginal edge portions to maintain a seal between the two laminations thereof.

5. The packaging machine of claim 4, wherein said means for imposing compressive force upon the marginal edge portions of the substrate comprises: A. means for supporting at least the longitudinal marginal edge portions of the substrate as it moves through said zone; B. two sets of rollers at said zone, one set at each side of said path,

6. The packaging machine of claim 5, wherein all of said rollers are mounted for free rotation, further characterized by: D. an additional pair of freely rotatable rollers, one at each side of said path, at a location in advance of said zone relative to the direction of substrate motion, each of the rollers of said additional pair being freely rotatable on a horizontal axis transverse to said path and being mounted for limited bodily up and down motion and biased downwardly with sufficient force to break down the corrugations of said intervening layer of the substrate along said marginal edge portions thereof.