US 3554435 A
Description (OCR text may contain errors)
United States Patent Inventor Harvey F. Martinez Milwaukee, Wis.
App]. No. 791,625
Filed Jan. 16, 1969 Patented Jan. 12, 1971 Assignee Muprint, Inc.
Milwaukee, Wis. a corporation of Delaware POUCH WITH REINFORCED EDGE 4 Claims, 4 Drawing Figs.
11.5. CI 229/55, 229/62, 229/63 Int. Cl 86511 33/02 Field of Search 229/55, 62, 66, 86, 63
 References Cited UNITED STATES PATENTS 2,971,874 2/1961 Canno 229/55X 3 ,426,959 2/1969 Lemelson 229/62X Primary ExaminerDavid M. Bockenek Attorneys-Donald G. Casser and Adrian L. Bateman, .11.
ABSTRACT: A pouch of heat sealable packaging film having a string impregnated or coated with a heat scalable composition arranged between opposed pouch walls along an edge of the pouch, wherein the string is heat sealed to the walls to thereby reinforce said edge of the pouch.
PATENTEU JAN 1 2 I97! HARVEY F MARTINEZ BY ATTORNE POUCH WITH REINFORCED EDGE BACKGROUND OF THE INVENTION 1. Field This invention relates to pouches of the type having at least one edge strengthened by the addition of a reinforcing member between the walls of the pouch, the walls being of thin packaging film material.
2. Prior Art Pouches of the general class to which this invention pertains are commonly formed of superimposed thin sheets of packaging film heat sealed along their marginal edges to define a container enclosure for the packaging of food and nonfood commodities.
In many instances, it is desired to display the filled pouches by hanging them on a suitable fixture, .typically a metal hanger on a pegboard holder. The common practice is to form a hole, slot or other aperture near one edge of the pouch by which it can be hung on the fixture. An aperture of this type weakens the pouch and it thereby becomes subject to rupture or tearing as it is displayed or handled by prospective purchasers.
Package designers have devised .several constructions to reinforce the edge of the pouch near which the aperture for hanging the pouch is formed to reduce the danger of tearing the pouch when it is displayed. One prior art solution is to form a substantial heat sealed area surrounding the aperture along the edge of the pouch. Another is to form the hole somewhat further from the edge of the panel pouch to provide extra material above the aperture. A third prior art solution is to add a strip of heat sealable material between the pouch walls and the edge near which the aperture is formed, and either heat sealing the edges of the reinforcing strip along the side seams of the pouch or heat sealing each side of the reinforcing strip to an abutting wall panel; in either case, this gives three layers of material along the edge by which .the pouch is to be hung. U.S. Pat. Nos. 2,878,849, 2,971,874 (now Re. 26,075), 3,024,062, and 3,096,0l3 are representative of prior art teachings in this particular field.
None of the foregoing pouch constructions, however, have completely solved the problem, in that the several edge reinforcement systems exhibit a generally low order of increased toughness, say on the order of only one to two times, relative to the toughness of the pouch without reinforcement.
SUMMARY OF THE INVENTION The present invention as distinguished from the prior art discussed above provides a pouch with an edge reinforced by the addition of a string impregnated or coated with a heat sealable composition arranged between the pouch walls along the edge which is to be reinforced. The string extends across the entire width of the pouch but does not project beyond its sides. The string is heat sealed to each pouch wall, and if an aperture is to be placed in the pouch it is formed interiorly of the string in relation to the edge of the pouch.
It has been found that a pouch with a reinforced edge according to this invention is markedly stronger than pouches reinforced according to prior art constructions, as will be demonstrated in the comparative examples included in the following description.
DESCRIPTION OF THE DRAWINGS The ensuing description fully sets forth the present invention in sufficient detail to enable those skilled in the art to practice the same and discloses several presently preferred examples which are included for the purposes of illustration and not of limitation, it being expected that those skilled in the art can vary the examples and still remain within the true spirit and scope of the present invention. The description makes reference to the accompanying drawings, wherein:
FIG. 1 is a plan view, with a portion broken away, of a pouch according to this invention;
FIG. 2 is a sectional view of the pouch of FIG. 1; and
FIGS. 3 and 4 are fragmentary sectional views of prior art pouches shown here for comparison purposes.
DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrating pouch 1 according to this invention having a front wall 2 and rear wall 3 formed of superimposed sheets of packaging material joined along side heat seal seams 4 and 5 and top heat seal seam 6 to define a container enclosure 7 in which articles are to be packaged. The top heat seal seam 6 is desirably of a relatively large area to add stiffness to the top of the pouch. As indicated by the fold line 8 at the top of the pouch, a single large sheet of film can be folded as at fold tine 8 to provide the walls 2 and 3, thereby enabling formation of the pouch I from a single sheet of material. A hole 9 is formed near the edge defined by the fold line 8 to be used for hanging the pouch from a suitable fixture, or for lifting the pouch with a fork, for example, if it is used for boil-in food applications. The hole can be round as shown, oblong, or any other desired shape and is formed within the top heat seal seam 6 if it is desired to form an air tight package from the pouch.
At the bottom 10 of the pouch, the walls are left unsealed to provide an access opening through which commodities can be inserted and one wall can be longer than the other as shown in the drawings in order to facilitate opening the bag for filling. After articles are inserted in the pouch, it is sealed across its bottom to close the container.
The pouch 1 as described to this point is of conventional construction and may be formed of any suitable flexible packaging material selected with due regard to the end use to which it is to be put. Heat sealable materials are useful for manufacture of the pouch and can be either a thermoplastic material that is inherently heat sealable without modification, such as low density polyethylene, or a nonheat sealable material which has a functional heat seal coating applied to at least one of its surfaces, such as heat seal coated cellophane. The pouch material can be single-layer monofilms, multiple layer laminated films of two or more similar or dissimilar layers, or coated films such as those hoving functional heat seal coatings. Synthetic plastic films such as polyethylene, polypropylene, vinyl polymers and copolymers, polyester films, and cellophane and other cellulosic ester films may be used. For normal packaging uses of consumer goods, such as food, hardware items, etc. the pouch walls 2 and 3 may be in the range of one-half to 10 mils thick, or thicker, if so desired.
The term heat seal as used herein is meant to refer to the process or property of softening or fusing to form a bond between contacting portions of material upon momentary application of heat and pressure. Temperatures employed are above the softening temperature of the material being heat sealed when the material is inherently thermoplastic or above the softening temperature of the heat seal coating in the case of a coated material. Pressures generallyvary between less than 1 pound to 50 pounds per square inch or more, and the dwell time during which the contacting material is subjected to the applied heat and pressure is normally from a frac tion of a second to several seconds. While other forms of seams may be utilized in the pouches of this invention, heat seals are preferred because of their relative ease of formation and for reasons of economy.
The gist of the present invention resides in the addition of a string 15 along one edge of the pouch, shown herein as along the fold line 8 at the top of the pouch. The string 15 extends from side to side of the pouch but does not protrude beyond the sides of the walls 2 and 3. The hole 9 is positioned on the opposite side of the string 15 from the fold line 8, i.e. the hole is located interiorly of the string in relation to the pouch edge along which the string is positioned.
The string 15 is to be impregnated or coated with a heat sealable composition so that it will become heat sealed to the interior of the pouch walls 2 and 3 when the top seam 6 is formed. The string 15 is made of twisted threads of material such as rayon, nylon, cotton, etc. so as to provide a large surface area and irregular surface configuration to thereby improve the strength of the edge reinforced by the string. The string may include any suitable heat sealable composition, de-
pending upon the materials from which pouch walls are made. particularly such as those applied as hot melt coatings, for example, ethylene/vinyl acetate copolymer blended with wax, a coating of ethylene/vinyl acetate copolymer by itself, a coating of polyethylene, etc. The pouch 1 can be manufactured in various ways, both manually and mechanically with suitable apparatus. A satisfactory method has been to fold a web of film material from which the sidewalls are to be made about a fold line 8, add the string 15 along the fold line, and then forming the top heat seal 6 across the pouch. Next, a U-shaped sealer is used to apply pressure on both sides of the pouch walls around the fold line 8 after the string has been inserted so that the string will become well heat sealed to both pouch walls. The side heat seals 4 and were then formed to extend between the top and bottom of the pouch in order to provide a positive seal at the ends of the string. Following formation of the side seams, individual pouches can be severed from the formed web along the side seams in the usual manner.
The following examples will further clarify the present invention and compare pouch structures according to its teachings with those made according to the prior art.
EXAMPLE 1 A pouch l as shown in FIGS. 1 and 2 was manufactured from packaging film comprising a 0.0006 inch thick film of biaxially oriented polypropylene with a 250 K cellophane adhesively laminated to one of its surfaces and with 1.5 mil thick layer of heat sealable polyethylene applied to its other surface. Rayon string comprising a No. 6 spun fine twine, four ply, having a l6-pound tensile strength and with a heat scalable coating of ethylene/vinyl acetate copolymer and wax, was used to provide a string in the pouches.
The string had a weight of 4,800 feet per pound. The
pouches made from the film were 4% inches wide by 1 1 inches long, the side seams 4 and 5 were approximately one-fourth inch wide and the top heat seal seam 6 was about ZA-inch wide. The hole 9 comprised a one-fourth inch diameter hole with its upper edge spaced one-fourth inch from the top edge of the pouch.
The toughness of the pouch reinforced with the string 15 according to this invention was measured utilizing a modified ASTM procedure. A one-eighth inch steel peg was rigidly clamped in the upper or fixed jaw of an Instron tensile tester, and pouch samples were placed on the peg (which was inserted through the hole in the pouch) with the bottom of the pouch clamped in the lower or movable jaw of the tensile testing machine. The lower jaw was then moved at a rate of 10 inches per minute until the hole was pulled out of the top of the pouch, and a stress versus strain curve was recorded on the continuously moving chart associated with the machine. Toughness was calculated by measuring the area under the stress-strain curve with a polar planimeter and converting the values thus obtained to units of gram inches. The average toughness of a number of samples tested in this fashion was 3,435 gram inches.
EXAMPLE 2 FIG. 3 illustrates a typical prior part pouch of the same general type as the pouch l of this invention but wherein the sidewalls 21 and 22 are heat sealed together along a top seam 23 extending between the top edge of the pouch and position 230 in the drawing. Pouches 20 were made of this construction using the same film as the pouch in example 1, of the same size, and wherein the top heat seal seam 23 was the same size as the top heat seal seam 6 used with the pouches 1. A hole 24 was formed in the pouches 20 of the same size and in the same position as the hole 6 with the pouch 1.
When pouches 20 were tested for toughness with the procedure described above under example 1, they were found to have an average toughness of 298 gram inches. Thus the pouch 1 according to this invention exhibited a toughness of over I 1 times that of the prior art pouch 20.
EXAMPLE 3 FIG. 4 exhibits another prior art pouch of the same general type. The pouch 25 of FIG. 4 includes sidewalls 26 and 27 with a header strip 28 interposed between them along the top edge of the pouch. The header strip 28 is heat sealed to both sidewalls 26 and 27 and is intended to provide reinforcement of the top edge of the pouch. A hole 29 is formed near the top in the same manner as the holes 9 and 24.
A number of samples of pouches 25 were made with the same film of pouch l of example 1, in the same size, and with the hole 29 of the same diameter and in the same position as the hole 9 in pouch l. The header strip 28 of the pouches 25 had the same width as the top heat seal seam 6 utilized in the pouches l and was a 4-mil thick strip of polyethylene film.
The pouches 25 were tested for toughness and maximum yield stress according to the procedure set forth in example 1, and it was found that they exhibited an average toughness of 761 gram inches.
The data of Examples 1-3 are summarized in the following table:
TABLE I Toughness (gram Pouch: inches) Example 1 c 3, 435 Example 2 (prior art) 298 Example 3 (prior art) 761 The foregoing examples demonstrate that the pouch reinforced with a string along one edge in accordance with the present invention exhibits a toughness of over I 1 times that of the prior art pouch of example 2 and more than 4.5 times that of the prior art pouch of example 3.
There has thus been described a pouch having an edge reinforced with a string containing a heat sealable composition wherein the string is heat sealed to opposed abutting portions of the sidewalls of the pouch and which demonstrates a surprising and dramatic increase in the toughness of the pouch as related to comparable prior art pouches. The pouches of this invention have found use in the packaging of meat, such as cold meat slices, wherein the filled pouches were hung on a metal hanger attached to a peg board. Further, the present pouches are adapted for boil-in pouches for the packaging of cooked or partially cooked products which are to be heated by immersion in hot water. In this instance, the hole formed along the top edge of the pouch can be oblong in shape so that the pouch may be removed from the water, which is often boiling, by inserting a fork in the hole. The unusual toughness of the present pouches enables them to be retrieved from the boiling water in this fashion without tearing, thereby eliminating the necessity to grasp the pouch from the hot water by ones finger tips. The pouches of the present invention exhibit advantageous properties in comparison to known pouches of the same general type and such properties enhance their utility in diverse packaging applications.
I claim: v
1. In a pouch of the type having opposed pouch walls of flexible heat sealable packaging film joined together along at least some of their edge portions to define a container enclosure, and having an aperture extending through the pouch walls near one edge portion of the pouch, the improvement wherein said edge portion of the pouch is reinforced by (l) a string positioned between the pouch walls and extending thereacross to lie closely adjacent to said one edge portion between said one edge portion and said aperture, (2) said string including a heat scalable composition and being heat sealed to contacting portions of the opposed pouch walls to thereby reinforce said one edge of the pouch.
2. A pouch according to claim 1, wherein the pouch is formed of a single sheet of packaging film folded over along a fold line to define a pair of opposed pouch walls, the pouch walls are heat sealed along their side edge portions at an angle 4. A pouch according to claim 2 wherein the pouch walls are heat sealed together along their contacting portions alongside the string.