US 3565329 A
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Description (OCR text may contain errors)
. United States Patent Inventors Victor K. Wagner, Jr.
Charles E. Palmer, Somers, Conn. 790,543
Jan. 13, 1969 Feb. 23, 1971 Springfield Wire, Inc. Springfield, Mass.
Appl. No. Filed Patented Assignee TEAR STRAND FOR PACKAGES 51 s 206/(Rip Spring); 57/146, 144
References Cited Primary ExaminerLeonard Summer AttorneyChapin, Neal and Dempsey ABSTRACT: Package formed of sheet material and a flexible cutting strand disposed on the package for cutting through the sheet material, said strand having a soft or compactible core with a cutting filament or wire wound helically around the core.
1 TEAR STRAND ron PACKAGES BACKGROUND years, with the advent of heavy gauge bag and pouch-type packages of plastic or paper, difficulties have been encountered in providing efficient and economical means by which 1 such packages can be easily and cleanly opened.
The other objects and advantages of this invention will be more readily apparent from the following description of the accompanying drawings, in which:
FIG. 1 is a view showing a cutting strand embodying this invention;
FIG. 2 is an elevational view showing the cutting strand encapsulated in a carrier strip;
FIG. 3 is a perspective view showing a package provided with a cutting strand embodying this invention; and
FIG. 4 is a partial perspective view, on an enlarged scale, showing structural detailof the package of FIG. 3.
A tear strand embodying this invention is shown on a greatly enlarged scale at 8 in FIG. 1. The strand is composed of a flexible core 10 with a fine cutting wire or strip 12 wound helically and unidirectionally around the core. The core may be formed of any suitable material by which the turns of cutting wire will be held against longitudinal sliding movement along the core.
gitudinal displacement of the turns even when the strand is used for cutting through a sheet mate rial as will hereafter be described. Of course, it will be appreciated that a relatively nonyielding core material could also be used, and such may be surfaced with an adhesive or other suitaole coating to hold the cutting wire in place on the core.
It is also important that the core material have sufficient tensile strength to enable the cutting strand to be pulled Iongitudinally with the force required in cutting through heavy gauge materials. I
The cutting wire 12 may be of any suitable material which will retain its helical disposition on the core. The metal should be corrosion resistant, particularly when used in food packages, and may have any suitable cross-sectional configuration, including round, oval or polygonal. The wire diameter may be relatively small, on the order of .003 inches-.008
inches for maximum cutting efficiency, economy, and so that the composite strand does not become too rigid. In addition,
' tends outwardly of the core whereby the composite strand has an irregular or corrugated surface for enhanced cutting action and for firmly interlocking in a carrier sheet. The turns of the wire should be relatively closely spaced with finer wire spaced more closely than a larger diameter wire. It has been found that for .008-inch wire there should be at least 21 turns per inch.
Preferably, the cutting wire is formed of a stainless steel, or other noncorrosive alloy, since in many cases, the cutting strand would be used in packages containing food products. Of course, the selection of any particular material depends upon the end use of the packages to which the tear strand is to be applied. It should also be appreciated that the use of a nonmetallic cutting wire is not'beyond the scope of this invention The selection of various parameters, suchas core diameter, wire diameter, and configuration, winding pitch and the number of turns per inch may be varied depending upon the type of material to be severed by the tear strand.
The tear strand may be applied to a package in any convenient manner. Thus, for example, it may be coated, laminated encapsulated in a carrier strip, as shown at 14 in FIGS. 2-4. The strip comprises the composite tear strand 8 and the encapsulating material 16, which may be foil, paper or a thermoplastic extrusion capable of being heat sealed to a plastic bag or package formed of any other suitable material which has been surfaced with a heat sealable coating. Where paper or foil tape is used, it may be applied to the packaging material by using any suitable adhesive or by heat sealing to a plastic coated package. The tear strand may be disposed at any convenient location in the carrier strip as, for example, it may be located centrally or along one edge as shown in FIG. 2. The location of the tear strand within the carrier strip depends upon the type of package to which the strip is to be applied.
In FIGS. 3 and 4 is shown a plastic bag 20 to which a thermoplastic tear strip 14 has been applied by heat sealing. The composite carrier and tear element provide closure means for the package as well as the means by which it can be readily opened. The bag may be formed by using a web of plastic to which along one edge, the strip heat sealed. The bag, with the seal strip in place may be formed in any suitable machine, such as a Transwrap" machine. After filling the opposed open end portions of the bag and tear strip 14 are sealed together outwardly of the cutting strand 8. Alternately, a separate strip 14 may be inserted in the open end of a bag after the filling operation and the bag sealed as shown in FIG. 4. For
a finished appearance a cover strip 22 may be applied over the end of the bag 20. In order toopen the bag, the strand 8 is pulled through the package wall in either direction forming a slit 31 which provides access to the bag. The bag I may be opened using the tear strand 8 by grasping a pull tab 30, pulling it outwardly and in the direction of the cut. As previously mentioned, when the tear strand is pulled in the manner described, a slit in the wall 20 provides access to the contents of the bag. In the embodiment shown, the pull tab 30 is provided by punching a cutout through a sealed corner portion 32 of the bag. Because of its irregular, or. corrugated surface, the cutting strand as best seen in FIG. 1, is firmly anchored, or interlocked, in the carrier strip and also the pull tab 30 so that it will out clearly through the package material and not be pulled longitudinally from the material. In addition to this interlock feature, the irregular surface contour of the strand enhances its cutting action which is somewhat similar tr the cutting action of a sawtooth.
1. Package formed, at least in part, of a sheet material, a flexible cutting strand disposed within and bonded to the sheet material and comprising a core with -a cutting filament wound helically around said core, and with the turns thereof spacedapart longitudinally of the core.
2. Package as set forth in claim 1 in which said cutting strand comprises a soft, compactible core with a metallic filament wound helically around the core.
, 3. Package as set forth in claim l-in which said cutting filament is helically wound unidirectionally about said core throughout its length.
4. Package as set forth in claim 1 in which said cutting strand is carried in a strip of metal material bonded to the sheet material of said package.
5. Package as set forth in claim 4 in which said sheet material of the said package is a thermoplastic material and in which said cutting strand is carried by a. thermoplastic strip heat sealed to said sheet material of the package.
6. Package as set forth in claim 5 in which the core of the said cutting strand is a fibrous thread and in which said cutting filament is a malleable metallic wire.
7. Package as set forth in claim 5 in which said cutting filament has at least 21 turns per inch about said core.
8. Package of thermoplastic sheet material in the form of a bag, a flexible closure and cutting strip sealed within said bag between opposed edge portions, said strip comprising a soft core, a cutting filament disposed helically about the core and a thermoplastic web carrier for said core and filament, said strip being laminated between said opposed edge portions and a pull tab cut out of the laminated sealed portion of said package adjacent the end of said cutting strip, said core and cutting filament being interlocked in the thermoplastic cutout portion of the tab.
9. Package closure and opening strip comprising a web of sheet material, a cutting strand carried by said web, said cutting strand comprising a soft, flexible core, a metallic cutting wire wound helically around the core and extending outwardly of the surface thereof, the corrugations formed by the turns of said wire providing'a sawtooth cutting surface and means for interlocking the cutting strand against longitudinal displacement relative to said web.
10. Package closure as set forth in claim 9 in which said web is a thermoplastic material, said core is a fibrous thread and said cutting wire is a stainless steel wire wound about the thread at least 21 turns per inch of thread.
@ 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF- CORRECTION Patent No. 3, 565, 329 Dated February 23, 1971 Inventor(s) Victor K. Wagner, Jr. and Charles E. Palmer It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:
Column 2, line 63, "metal" should read "sheet"- Signed and sealed this 8th day of June 1971.
EDWARD M.FI.ETCHER,JR. WILLIAM E. SGHUYLER, J1 Attesting Officer commissioner of Patent