US3170619A

US3170619A - Tear strip packaging

Info

Publication number: US3170619A
Application number: US143203A
Authority: US
Inventors: John P Repko
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1961-10-05
Filing date: 1961-10-05
Publication date: 1965-02-23
Anticipated expiration: 1982-02-23
Also published as: GB973297A

Description

Feb. 23, 1965 J. P. REPKO 3,170,619

TEAR STRIP PACKAGING Filed OGbv. 5. 1961 INVENTOR.

JOHN P. REPKO 52.0 PMM@ ATTORNEYS Fig. 6

United States Patent() 3,170,619 TEAR STRIP PACKAGING John P. Repko, Parma, Ohio, assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan Filed oct. s, l1961, ser. No. 143,203 11 claims. (c1. 22a-s2) This invention relates to packaging and sealed packages, ie., packaging enclosing packaged contents. More particularly, this invention solves the problem of providing such sealed packages with convenient opening means when the packaging therefor is comprised in whole (except for the opening means) or in part of a film of a class hereinafter referred to as stretchable packaging films.

The stretchable packaging films to which this invention is directed are relatively tough, grainless, non-fibrous organic films characterized by a tendency to stretch and take a permanent deformation before rupture .under direct tensile and tearing loads. Herefore, unless'a film of theclass in question were first weakened by a line of perforation or heavy scoring, the vareas and location of yield under such rupturing loads would not progress uniformly. As a consequence, tears in such film generally fail to follow a predictable line and, due to such deformation, the torn edges are characteristically randomly ruffled. Many films suitable for packaging kexhibit the above characteristics; polyethylene films are currently by farthe most widely used films of this nature; others are, for example, other polyolefin films, rubber hydrohalide lms, and certain plasticized vinyls, sarans, and the like.

An objection of' long standing to a sealed package employing practically any organic film is the difficulty of opening the package unless some opening means is provided on the package. When the packaging film is one of the various cellulosic films, or other film having no pronounced tendency to stretch before rupture, the most convenient opening means has long been a tear strip, tape, or string, often adhered to the film. Especially when 'such film is provided with starting nicks adjacent the opening means, the package is readily opened by pulling on such lengths of tear strip or tape. Unfortunately such now practically' conventional opening means have not been Satisfactory for use with the stretchable packaging films. Whereas the opening tear in non-stretchable film will follow and be controlled by the tear tape, in stretchable film an opening tear will not normally ltend to follow'such tape.` Such uncontrolled tearing is not particularly objectionable in some overwraps of stretchable film, except that the obvious uselessness Vof the tear tape adds to the consumers irritation at packaging which is not readily torn .,open. In sealed packaging such as bags and pouches, this uncontrolled tearing of the stretchable film willoften destroy the bag or pouch as a container and,

thus, is an actual detriment when the bag, for example, should still be a usable container after opening.

Accordingly, -it is a principal object and advantage of this invention to provide a tear tapeor flap which permits a package of scale/i stretchable film' to be readily opened ,with a controlled tear. Another object and advantage of the invention is that the tear tape may be applied as the'package is sealed in conventional heat-sealing equipment, thereby permitting the tape to be applied without elaborate production equipment ormanufacturing or assembling operations. A still further advantageisthat,

althoughtheopening tear is easilyvstarted,-the package is Y not appreciably weakened along the predictable line of opening, as was the case where opening tears were atl tempted to be controlled by heavy scoring,perforations,

or the like. Other objects and attendant advantages o f the invention ICC will become apparent when considered in connection with the followingdetailed description and the accompanying drawings wherein: y

FIGURE 1 is an elevation of a bagstretchable film provided with a tear strip according to this invention.

FIGURE 2 is an enlarged detail of the bag shown in FIGURE 1.

FIGURE 3 is a cross-section taken along the line 3-3 of FIGURE 2.

. FIGURE 4 is a perspective of the rear of the bag shown in FIGURE 1.

FIGURE 5 is a detailed elevation showingy one modication of this invention; the elevation in FIGURE 5 is of the reverse side of the bag and tape as shown in FIG- URE 3.

FIGURE 6 is a cross-section taken along the line 6-6 of FIGURE 5.

In general and broadly, the invention is based on the discovery that if a stretchable film is sealed to a tape of relatively heavier or stiffer material along a line of juncture which tends to corrugate the film and the edge of the seal, then by pulling the tape away from the film, the film will tear at the line of juncture and follow it as a controlled tear. Why the tear should follow this line of juncture which undulates as a consequence of the corrugation is not fully understood. It is suspected that the effect of the corrugation of the film and heavy tape at the lline of juncture tends to keep the film stretched at least slightly along theundulating line, as is evident when the tape is corrugated and the sealing of the film to it tends to pucker the film at the edges of the seal. Thus, as the stretchable film is ruptured, the stretching prior to rupture follows where the film is already stretched by the corrugated( line of juncture to the stiffer tape, rather than to extend into the unstretched film. Consequently, rupture follows the controlled line of stretch.

Illustrating the invention as specifically applied to a conventional polyethylene bag, FIGURE 1 shows a conventional bag It) of polyethylene film extruded as a tube and sealed at one end by a transverse heat seal 11, the upper end of the bag being cut as a bag length from the tube to provide the mouth 13 through which the bag is filled. After the bag is filled, a length of embossed tape I2 is laid across theV fiattened mouth of the bag, whereupon the bag is sealed by heat-seal bars to provide the closingseal I4 sealing the plies of the film in the bag mouth to each other and to the tape I2. In this particular embodiment, the tape IZ is preferably a tape of polyethylene having a gauge somewhat greater than twice the gauge of the film in the bag It) (see FIGURE 3)., A satisfactory pattern of embossing is a wafe patternof diamond-'shaped displacements from the plane of the tape (see FIGURE 2). The depth of the diamond is preferably about equal to the gauge of one thickness of film (see FIGURE 3). When the heat seal bar seals the plies of film constituting the mouth of the bag 10 andthe tape 12 together, the resultant seal I4 effectively embosses the following thisline of juncture't i As will b'enot'ed inFIG- URE 4,Y the torn edges Y16 of the plies of the bag are not v the linvention to demonstrate that akey consideration ofr straightbutare slightly serrated or undulating as the tear follows the puckeringof the `film caused by thetseal 14. FIGURES 5 and 6 are to illustrate amodification of i r, the invention is to have the plies of the bag puckered by corrugation in the tape and the line of juncture of the seal and the free plies ofthe bag enclosing the contents thereof.V Thus, instead of laying a strip of corrugated tape across the mouth of the bag, a strip of unembossed tape 112 is laid across ythe mouth of the bag ll. The bag isthen sealed` by a heat seal closing v,the'mouth ofthe bag and joining the tape 112 thereto by a seal 114 which (seamed ,or seamless and forms lengthwise corrugations 117 in the sealed pliesand were described as bags in which the transverse tapes were appliedafter the bags were filled and ready'to be-closed by the heat sealer of conventional bag closing machinery. It isV to be understood, of course, that to eliminate the operation of applying the tape at that stage, the tape may be applied across the bottom of the bags at the time of making them in a bag machine. Or the tape may be sealed or otherwise carried by one ply at vthe mouth of the unsealed bag; after filling, the sealing of the mouth of the bag can thus re-seal the tape and all pliestogether to provide a requisite line of juncture that will be followed when the bag is opened. If the tape is to be applied tol a wrap or overwrap, rather than a bag, it may obviously be applied to the web of packaging film which becomes the wrap either before the wrapping operation or during it. Also, in the embodiment described, the tear `tape is of a heavier gauge but of the same heat-scalable material as the packaging film. Provided that the tape maybe securely sealed together with the film -so as to provide corrugations extending transversely to lines of juncture and is of sufficient strength to permit the film to be ruptured by pulling on the tape, materialsV other than that of the heat-scalable stretchable film may be used.l Likewise, the .tape is preferably colored so as to make it readily apparent on thev sealed package; it may also be printed with-instructions for opening the package and carry advertising matter or such printed matter may be carried on paper or film attached to the tape. In the specific illustrative k,embodiments shown,v the tape extends belowl the seal to provide a flap which convenient-l of vsuch a flap by the extension of the tape below the seal is often a `matter of choice. Also, the tape is shown as sealed toY only one ply of' film at the seal. If desired, in

the case of bags to which the tape is `sealed* at one end, 'a wider tape may be folded over the top of the bag and sealed tothe other ply. Y

J Accordingly, it is tobe understood that this invention is not limited to the embodiments shown but Vonly by the appended claims. As used in the claims, the term pack- :age.; or package of stretchable'filmV is to be understood Vto be, packaging comprised at least in part of such lm and enclosing packaged contents. The term packaging (as a noun) or Vpackaging'material is to be understood with y or withoutk rer-entrant pleats), said attened tube being closed by one or more seams or seals except for afmouth portion whichmay be opened to permit filling. 1 What is claimed is: f

1. A package of sealed stretchable filmand a tear'tape j therefor, said tape being sealed to said vfilm andfhaving a greater resistance to tearing than the lm sealed thereto, said tape having corrugations formed therein,y said corlrugations having k,at least av component extendingrtransversely at least up to the line of juncture-of the unsealed film with the seal topucker the film at said line of juncture, whereby, when said film is ruptured by a 4pullV at the location'of the tape, the rupture vfollows the said line of juncture.'

2. A package as defined in claim 1 in whichsaid tape is embossed to provide such corrugations. j

3. A package as defined in Vclaim 2 in which said package is a bag enclosingcon'tents sealed therein,.thel tape is located at the mouth of the bag, and the seal closes said bag by. joining opposite plies vof film together'` rat the mouth and one of said plies to said tape extending along thetape being greater than the plies yof film sealed together are to it, andthe seal Ais a heat-seal deforming said taperand plies.

' 5. Packaging for enclosing contents in a sealed package comprising a stretchable film, a tape having .greater resistance to tear than said film, said tape being sealed to said film and corrugated at least-upto the line of juncture between sealed and unsealed portions of said film,- and the film is thereby vpuckered at said line of juncture, whereby, when said film is ruptured by pulling on said film vand tape in directions having opposite vcomponents to start a rupture at said line of juncture, the rupture Will vfollow said line. j

6. Packaging material as defined in claim 5 inV which said packaging is a bag formed from a flat tube of said film, said tape extending across one face of said bag and the seal securing said tape to the bag lforms an end closure joining the tape and opposite plies of film together.

' 7.; Packaging materialas defined iti-claim Y,6 in which the. stretchable -film and the -tape are polyethylene, the

tape being of heavier gauge than the nlm.

8. Packaging material `as defined in claim 5 in-Which said packaging isa bag lin the form of a flattened tube of said nlm, having a closed end and arl-open end and said tape is carried on one face of said bag ladjacent Vthe open end, whereby, upon sealing the'open' end of the bag afterV filling `so that `a seal extends across said tape,vsaid line of juncture will be formed fora tear: toffollowwhen the sealed bag is opened by pulling ,on saidtape.

9.-Pacl aging materialas defined in claim 8 in which ythe stretchable film andthe-tape are polyethylene, the tape being ofheavier gauge thanthe film.

l0. The Vmethod, of 'providing' packaging employing stretchableV film with Yan opening Vtear `tape comprising the and tubes Y(seamedA or seamless)"which are either` cut to v 'Y lengthorarein the form of sheets or roll stock intended foriuseas wraps or forsubsequent conversion Vto various steps Yof sealing -a length of tear tape to fthe surface of stretchable film by means of a seal extendingl along the Y length of the tape, said tape having a greater resistance to tearing than said film, and providing the tape with corrugations having atleasty a component extending at least up 6.5' tothe line of juncture between the unsealed and sealedV kto encompass containers, such as bags, aswell Vas Vsheetsportions ofthe film to pucker thev filmat such'line of juncture, whereby, upon lstarting tofrupture said Ifilm at Vsaid line of; juncture, the Vrupture will followy saidl line.

` V1l. Themethod as vdefined *in clai'mplOin .which said is .embossed on .its surface adjae'entrtothe surface of fthe film to whichjit is to be ,sealedto provide said corrugation's. f

`12.` The mined as deemed in' Claimy 1i in which 'the film and tape lare' ofa heat s'ealablepthermoplastic resin,

i' the tape beingofa heavier gauge than. the `film,"an`d the sealforming-,the puckered lineofjuncture is aheat seal L gti.. J.

formed under heat and pressure Vto deform the tape and lrn as it is thereby Sealed together.

13. The method as defined in claim 10 in which the corrugations are formed in said tape at the time of sealing the same to the film.

14. The method as defined in claim 13 in which the film and tape are of a heat sealable thermoplastic resin, the tape being of a heavier gauge than the film and the seal forming the puckered line of juncture is a heat seal formed under heat and pressure to deforrn the tape and film as it is thereby sealed together.

15. The method of packaging comprising the steps of filling a bag of polyethylene film with contents to be packaged, ilattening the bag to bring opposite plies of the lm togethery and close the bag, applying a tape, having a greater resistance to tearing than said film, to the outside of one of the contacting plies and heat-sealing said tape and film together along the length of said tape, said tape being corrugated up to the line of juncture between sealed portions of said lm and unsealed portions, such corrugations extending in a direction having a component transverse to said line, and the film being puckeredk by said sealing at said line of juncture. f

16. The vmethod as claimed in claim 15 in which said tape is thermoplastic and corrugatedfon the surface in Contact with said lrn prior to heat-sealing, whereby the heat sealing deforrn-s said tape and said film to form the puckering at said line of juncture.

17. The method as defined in claim 15 in which said tape is thermoplastic and corrugated by the heat-sealing to deform said tape and iilm and form the puckering in 'said film at the said line of juncture.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A PACKAGE OF SEALED STRETCHABLE FILM AND A TEAR TAPE THEREFOR, SAID TAPE BEING SEALED TO SAID FILM AND HAVING A GREATER RESISTANCE TO TEARING THAN THE FILM SEALED THERETO, SAID TAPE HAVING CORRUGATIONS FORMED THEREIN, SAID CORRUGATIONS HAVING AT LEAST A COMPONENT EXTENDING TRANSVERSELY AT LEAST UP TO LINE OF JUNCTURE OF THE UNSEALED FILM WITH THE SEAL TO THE PUCKER THE FILM AT SAID LINE OF JUNCTURE, WHEREBY, WHEN SAID FILM IS RUPTURED BY A PULL AT THE LOCATION OF THE TAPE, THE RUPTURE FOLLOWS THE SAID LINE OF JUNCTURE.