Method for Manufacturing Draw String Bags
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(19) & (11) EP 2 275 356 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 19.01.2011 Bulletin 2011/03 B65D 33/28 (2006.01) B31B 19/90 (2006.01) (21) Application number: 09165531.6 (22) Date of filing: 15.07.2009 (84) Designated Contracting States: (72) Inventor: Knudsen, Hans Erik AT BE BG CH CY CZ DE DK EE ES FI FR GB GR DK-4350, Ugerløse (DK) HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR (74) Representative: Trier, Mikkel Roed et al Designated Extension States: Awapatent A/S AL BA RS Rigensgade 11 1316 Copenhagen K (DK) (71) Applicant: Ulfoss Company Group A/S 4300 Holbaek (DK) (54) Method for manufacturing draw string bags (57) Method for manufacturing draw string bags comprising the steps of providing a plastic material, ex- truding the plastic material to a longitudinal tubular foil (2), cutting (104) longitudinally at least two strips (10, 11) from said tubular foil, thereby providing a U-profiled foil (3) having two legs with an inner side (16), an outer side (17) and a free cut edge (18), leading (106) the at least two strips on either outer side of said legs adjacent the free cut edge, folding (108) the foil adjacent the free cut edges over said strips to form hems (8) and sealing the hems (8) to form tubular channels (19) in which the strips extend, thus forming draw strings (9), and sealing (110) transversely the U-profiled foil to provide a plurality of bags. EP 2 275 356 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 2 275 356 A1 2 Description by cutting said strips with a sealing knife, whereby the cutting and the sealing of the strips may be performed [0001] The present invention relates to a method for simultaneously. manufacturing draw string bags, particularly draw string [0009] According to a further particularly preferred em- garbage bags, comprising the steps of providing a plastic 5 bodiment of the invention the method further comprises material, extruding the plastic material to a longitudinal the step of twisting saidstrips to form twisted draw strings, tubular foil and cutting longitudinally at least two strips whereby the draw strings are provided with further from said tubular foil, thereby providing a U-profiled foil strength. having two legs with an inner side, an outer side and a [0010] According to another preferred embodiment of free cut edge. 10 the invention the method further comprises the step of [0002] Such a method is known from US 3,196,757 in providing the strips with one or more substantially longi- which hems with draw string access means are formed tudinal welds to provide for strengthening of the draw at bag mouth forming margins, the hems being sealed strings, whereby the draw strings are provided with fur- to the body of the bag to form tubular channels enclosing ther strength. continuous draw strings, generally in the form of ribbons 15 [0011] According to another preferred embodiment of of a suitable material. In one particular embodiment ac- the invention the method further comprises the step of cording to US 3,196,757 the draw strings may be formed punching at least one hole or at least one perforation in by cutting thin ribbons of the web material from the bag the material of said foil, to provide for pulling said draw mouth. In this embodiment a tubular foil with a W-shaped string when closinga bag, which providesfor easy access pleat is slit to form a folded web with a hem at each edge 20 to the draw string when it is desired to close a bag. by cutting away a bottom portion of the W- shaped pleat, [0012] According to a preferred embodiment of the and a draw string with a U- shaped profile is formed from method said plastic material is a polyolefin, such as a said bottom portion. polypropylene or a polyethylene, this material being par- [0003] The known method is, however, disadvanta- ticularly convenient and easy to manipulate in a method geous in that the process used to form said draw string 25 according to the invention. is very complicated to implement, particularly in a con- [0013] According to a particularly preferred embodi- tinuous process. ment of the method according to the invention a contin- [0004] Thus, the object of the present invention is to uous line of draw string bags are produced, each two provide a method for manufacturing draw string bags bags being separated by a weakened line, thereby pro- which method is considerably easier to implement in a 30 viding a method resulting in a row of bags that may be continuous bag manufacturing process. rolled up to form rolls of bags each containing a desired [0005] This object is according to the invention number of bags and being ready for shipping. achieved by a method of the abovementionedtype, which [0014] According to another particularly preferred em- method comprises the further steps of leading the at least bodiment of the invention the method is performed as an two strips to either outer side of said legs adjacent the 35 in-line method, thereby providing a particularly conven- free cut edge, folding the foil adjacent the free cut edges ient and time saving method for producing draw string over said strips to form hems and sealing the hems to bags. form tubular channels in which the strips extend, thus [0015] Furthermore, according to the invention a draw forming draw strings, and sealing transversely the U-pro- string bag comprising a U-shaped plastic foil providing a filed foil to provide a plurality of bags. 40 closed bottom, an open end and two sealed sides, a hem [0006] Such a method provides for considerably easier formed by folding and sealing the foil at said open end implementation in that performing the operations neces- onto itself, and a draw string placed in said hem, wherein sary to form a hem and a draw string on the outside of said hem is placed externally on said U-shaped plastic the legs of the U-shaped foil provides for considerably foil, and wherein said draw string is formed by at least more space for manoeuvring folding and cutting tools as 45 two strips of the material of said U-shaped plastic foil is compared to the prior art, in which the hem and draw provided. string forming operations necessarily must be performed [0016] Thereby a draw string bag is provided in which in the space delimited within the foil, which in present hem and draw string may be formed in a considerably manufacturing facilities would at best be highly compli- simpler way as forming hem and draw string on the out- cated. 50 side of the legs of the U-shaped foil provides for consid- [0007] According to a particularly preferred embodi- erably more space for performing the necessary folding ment of the invention the method further comprises the and cutting operations as compared to the prior known step of sealing said strips to form tubular draw strings, art. whereby the draw strings thus formed are provided with [0017] According to a particularly preferred embodi- additional strength, and thus perform better when closing 55 ment the draw string is a tubular draw string, whereby a bag. the draw string is provided with additional strength, and [0008] According to another embodiment of the inven- thus perform better when closing the bag. tion the method said sealing of said strips is performed [0018] According to another particularly preferred em- 2 3 EP 2 275 356 A1 4 bodiment the draw string is twisted, whereby the draw 104, cf. fig. 2B, at least two strips 10, 11 are cut longitu- string is provided with further strength. dinally, i.e. parallel with the direction of feed indicated by [0019] According to another particularly preferred em- arrow 15 in fig. 1 of the foil, from the tubular foil 2, whereby bodiment the draw string comprises one or more sub- a U-profiled foil 3 having two legs each comprising an stantially ongitudinal welds, whereby the draw string is 5 inner side 16 an outer side 17 and a free cut edge 18 is provided with further strength. provided - cf. fig. 2C. [0020] According to a preferred embodiment the bag [0025] The cutting process of step 104 is preferably further comprises at least one hole or at least one perfo- performed using a sealing knife, such as for instance a ration in the material of said foil, said hole or said perfo- so called slit sealer, which is a knife that may be heated ration being adapted for pulling said draw string when 10 on one or both sides to perform simultaneous cutting and closing a bag, thereby providing a bag with easy access sealing of a plastic foil. Referring to fig. 2B two sealing to the draw string when it is desired to close it, the bag knifes are used in the preferred embodiment of the in- thus being more convenient to use for the end user. ventive method. The sealing knifes are represented by [0021] According to another preferred embodiment the lines indicating a first 20 and a second 21 sealing knife tubular plastic foil is a polyolefin, such as a polypropylene 15 respectively. In the embodiment indicated in figs. 2A - 2E or a polyethylene, this material providing for particularly the first sealing knife 20 is insulated on the side facing well functioning bags. towards strip 11 and heated on the side facing towards [0022] The invention will now be described in further strip 10, while the second sealing knife 21 is insulated detail based on a non-limiting exemplary embodiment, on both sides (hence the second sealing knife 21 might and with reference to the schematic drawings.