US3607521A

US3607521A - Plastic bag or the like with handle

Info

Publication number: US3607521A
Application number: US823322A
Authority: US
Inventors: Heikki S Suominen; Viljo J Makinen; Aarno S Lindstrom
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-05-09
Filing date: 1969-05-09
Publication date: 1971-09-21
Anticipated expiration: 1988-09-21

Abstract

A method of manufacture of plastic bags with handles formed from a tube of thin film plastic material and with the handles formed from the same material as the bag walls. Portions of the sidewalls of the tube of plastic material are cut away to form the handles, and in order to provide handles of sufficient strength to carry the load and to properly distribute the resulting stresses over the entire sidewalls of the bag, the tubular thin film of plastic is extruded so as to have portions thereof formed of a thicker material than the rest of the bag walls, and the handles are located so as to include portions of the thicker material.

Description

United States Patent Inventors Heikki S. Suominen;

Vilio J. Makinen; Aarno S. Lindstrom, all of Tampere, Finland Appl. No. 823,322

Filed May 9, 1969 Division of Ser. No. 699,988, Jan. 8, 1968, Pat. No. 3,482,761.

Patented Sept. 21, 1971 Assignee said Suominen, by said Makinen and Lindstrom PLASTIC BAG OR THE LIKE WITH HANDLE 1 Claim, 2 Drawlng Figs.

Int. Cl B3lf l/00 Field of Search 156/244,

Primary Examiner-Samuel W. Engle Att0rney-Hall, Pollock & Vande Sande ABSTRACT: A method of manufacture of plastic bags with handles formed from a tube of thin film plastic material and with the handles formed from the same material as the bag walls. Portions of the sidewalls of the tube of plastic material are cut away to form the handles, and in order to provide handles of sufficient strength to carry the load and to properly distribute the resulting stresses over the entire sidewalls of the bag, the tubular thin film of plastic is extruded so as to have portions thereof formed of a thicker material than the rest of the bag walls, and the handles are located so as to include portions of the thicker material.

This application is a division of our copending application 5 Ser. No. 699,988, now U.S. Pat. No. 3,482,761, filed Jan. 8, 1968.

BACKGROUND OF THE INVENTION It is well known in the art to provide plastic bags which are formed from a continuous tube or extruded plastic material. Successive bags are cut from the tubular material with the length of the bag lying along the axis of the tube. The bottom of each cutout portion is heat sealed to form the closed bottom of the bag, and additional portions of the tube are cut away at the other or top end of the bag to form spaced carrying handles which are heat-sealed at their topmost edges to form continuous carrying loops extending between the front and rear bag walls.

It is also old in the art to provide bags of this general type in which the carrying means for the bag does not comprise space loops but instead is formed of registering hand holes or apertures cut out of the front and back walls and with the mouth of the bag open. With both types of the aforesaid constructions, one of the problems which arises is that when an appreciable load is carried in the bags, there is a high concentration of forces adjacent to the handle or carrying means. Thus, where the spaced loops are provided by cutouts at the top of the bag, there is a high concentration of tensile forces along the loop forming the handle and also at the point of juncture of each handle or loop with the front and rear bag walls. Similarly, with they type of construction using the registering apertures in the front and back bag walls, there is a high concentration of forces in the material of the front and back walls immediately adjacent the aperture. One way to overcome this problem is to construct the bag of sufiiciently thick therrnoplastic film to ensure that the resultant forces can readily be borne without rupturing the material of which the bag is formed for the expected size of load carried in the bag. This, however, results in a product which is not commercially competitive because of the excessive amount of material used in the manufacture of each bag. Another solution which has been devised is to laminate extra strips or bands of thermoplastic material to the bags and/or to the handles of the bag in such a manner that the forces resulting from the carrying of a heavy load in the bag are distributed along the thus reinforced portions. This attempted solution is also not entirely satisfactory because of the difficulties inherent in the lamination process which not only involves extra material costs but also reduces the speed of manufacture.

It is proposed, according to the present invention, to overcome the aforesaid difiiculties in bag manufacture by extruding the thermoplastic tube of material with thickened walls over selected portions thereof in such manner that the thickened portions are so disposed as to absorb the stresses resulting from the carrying of a heavy load in the bag. In the illustrated embodiment, which is particularly concerned with a type of bag construction providing for two spaced carrying handles formed by suitable cutouts formed at the top of the bag, thickened extruded portions are provided about the periphery of the tube at four different locations so that, in the resulting bags, there will be two spaced reinforced portions on both the front and rear bag walls with each pair on one of the bag walls being spaced so as to be longitudinally aligned with the carrying handles or straps.

Referring to the drawings:

FIG. 1 illustrates the manner of construction of a bag of the present invention from a continuous tube of extruded thermoplastic material; and

FIG. 2 is a cross-sectional illustration of the extruded tube from which the bag of the present invention is made, particularly illustrating the thickened extruded portions.

The bag of the present invention is made from a tubular sheath 1 of a thermoplastic, heat-sealable film. As shown in FIG. 1, crosswise seams 3 are formed in the tubular material at spaced intervals corresponding to the desired longitudinal length of each bag. Such crosswise seams may be formed by heat welding together in a known manner the front and rear walls of the tubular sheath 1.

Spaced portions

5, 6, and 7 are cut out of the tubular seam as shown in FIG. 1, and the portions cut out extend upwardly into the crosswise sheath 3 so that the subsequent cutting operation through the seams 3 at 9, Le, along the midpoint of the seam 3, will intersect the

cutout portions

5, 6, and 7 and thereby leave an open mouth for the bag other than for the carrying straps 8. It will be noted that the front and rear carrying straps of each pair are joined together at the top by the crosswise seam 3.

It can be appreciated that a bag formed with spaced carrying handles in the manner illustrated in FIG. 1 will, when heavily loaded, produce a high degree of stress of the thin film material along those portions of the front and rear side walls which are longitudinally aligned with the carrying straps or handles 8 and that this will tend to rupture the material. For this reason, the bag of this invention is provided with reinforced portions 2 comprising longitudinally extending webs of thickened material which are formed in the extrusion of the material from the extruder die. In FIG. 2, the thickened portions are shown as comprising relatively narrow bands, but it will be apparent to one skilled in the art that the thickened extruded portions can be much wider than shown in FIGS. 1 and 2 and may, if desired, extend at least as wide as the width of each of the carrying straps 8.

It will also be apparent to one skilled in the art that a single thickened extruded band may be provided on both sides of the tubular sheath, but extending generally down the midsection thereof. In such an embodiment (not shown) the handles for the bags may be formed by punching out a finger grip lying in the thickened extruded portion so that the stresses of carrying the loaded bag are borne by the thicker weighted material running along the center of the front and rear bag walls.

It is, of course, also within the scope of the invention to make the reinforced or thickened zones of extruded material of a different color than the rest of the material of the bags by extruding the thickened zones from different nozzles. Also, instead of providing merely one thickened longitudinal zone in each of the handles 8, it is, of course, possible to provide two or more such thickened portions in each handle member 8.

What I claim is:

l. A method for making a thermoplastic bag having at least one integrally formed handle comprising the steps of extruding tubular sheath of thermoplastic film having four laterally spaced longitudinally extending band portions thereof which are of greater film thickness than the remainder of said sheath so as to form a plurality of reinforcing zones,

flattening said sheath to form a flattened tube having front and rear panels and with said band portions of greater thickness overlying each other in pairs with each pair of said thicker band portions lying inwardly the same predetermined amount from the side edges of the flattened sheath,

heat-sealing together said front and rear panels at spaced intervals substantially corresponding to the length of each bag to from transverse seams,

cutting out three portions of the juxtaposed front and rear walls adjacent one of said transverse seams in each space between a pair of said seams to form two bag handles for each bag adjacent the top of said bag,

a first of said cutout portions lying between said two pairs of reinforcing zones and the other two said cutout portions each extending inwardly from a respective edge of the sheath to a point short of the respective longitudinally extending reinforcing zone to thereby form two spaced handle loops each of which is longitudinally aligned with one of said reinforcing zones,

and cutting said flattened tube along each transverse seam to separate each bag from the next.