Refuse bags with integral ties and method of manufacture

A roll of plastic refuse bags comprises a fully gussetted, tubular form folded longitudinally to form a star seal configuration. The individual bags are separated by separation lines which form the open ends of the bags and welds which form the closed ends of the bags. A tie cut-out region is formed in each bag along one of the longitudinal edges beneath the separation line so that when an individual bag is separated from the roll and opened, four ties are formed which can be used to tie the bag closed.

This invention relates to plastic bags and, more specifically, to plastic
 bags which are intended to be used as refuse bags.
 BACKGROUND OF THE INVENTION
 Plastic bags are commonly used for holding refuse and other material. Such
 bags come in various forms. One common bag is manufactured from an
 extruded tube of plastic, typically polyethylene, which includes a
 multiplicity of heat sealed welds and perforated separation lines
 separating the individual bags. The tube of plastic is gussetted, folded,
 and wound into a roll so that individual bags can be dispensed one at a
 time by tearing the leading bag from the roll at a perforated separation
 line.
 In the case of a refuse bag, it is often desirable to secure the contents
 by tying the bag after it has been filled. Separate ties or straps may be
 provided for this purpose but this is not optimal since the ties can be
 misplaced and it is often cumbersome to hold a full bag while attempting
 to apply the tie.
 A number of attempts have been made to provide a plastic refuse bag which
 is formed in such a way that the bag itself includes integral flaps or
 ties which can be used to tie the bag closed. Representative examples of
 such constructions are shown in Gim U.S. Pat. No. 4,345,712 and
 Greyvenstein U.S. Pat. No. 5,246,110.
 The present invention provides a roll of plastic bags which are easily
 dispensed and opened, and which include integrally formed portions at
 their open ends which can be used to tie the bag after it has been filled.
 SUMMARY OF THE INVENTION
 A roll of plastic bags comprises a tubular web having a series of seals
 which form the bottoms of a series of bags, and adjacent separation lines
 which form the open ends of the bags. Each bag includes a tie cut-out
 region extending from the separation line along at least one edge of the
 web so that when the individual bags are dispensed, the upper portions of
 the bag form flaps or ties which can be used to tie the bags closed.
 The method of making the bags comprises extruding a tubular form, fully
 gussetting the form, and, optionally, folding the fully gussetted web to
 form a star seal configuration. The web is sealed at predetermined
 intervals and separation lines are cut into the web adjacent the seal so
 that individual bags can be separated from the web. In accordance with the
 invention, a tie cut-out region is formed in each bag immediately beneath
 each separation line so that when a bag is separated from the web, the
 open end of the bag will include two or more ties which can be used to
 close the bag after it has been filled.

DETAILED DESCRIPTION
 The refuse bag of this invention is structurally similar to the produce
 bags illustrated in U.S. Pat. No. 5,558,262 which is hereby incorporated
 by reference into this specification.
 FIGS. 1A and 1B show diagrammatically the steps in the manufacture of
 refuse bags in accordance with the preferred embodiment of the invention;
 FIGS. 2A, 2B and FIGS. 3A, 3B and 3C show the form of the plastic web at
 each stage in the process.
 Referring to these figures, an extrusion machine 10 produces a hollow
 tubular plastic form 12A. In the case of a refuse bag, high density
 polyethylene film may be extruded to a thickness of about 10 to 25
 microns; however, the selection of materials and dimensions form no part
 of this invention.
 The hollow tubular form 12A from the extrusion machine is then passed
 through a gussetting station 14 in which it is fully gussetted as shown at
 12B, forming two inner folds 16 and four outer folds 18 (FIG. 3B).
 The fully gussetted tube 12B is then fed to a folding station 20 where it
 is folded in half to form an eight-ply web 12C with one longitudinal edge
 22 formed by the fold in the web and the other longitudinal edge 24
 defined by the four outer folds 18 formed in the gussetting step.
 After the fully gussetted web has been longitudinally folded, the eight
 layer web 12C is fed to a conventional sealing or welding station 26 to
 form linear welds or seals 28 which bond all eight layers together and
 which serve as the bottoms of the bags. Perforated separation lines 30 are
 then cut into the web with slot 30A in the center of each separation line
 at a perforation and tie-cutting station 32. As explained in U.S. Pat. No.
 5,558,262, the slot in the perforation line is intended to be engaged by a
 tongue in a dispenser so that individual bags can be dispensed one at a
 time. Bags formed in this fashion are known as "star seal" bags.
 In accordance with the invention, a small elongated tie cut-out region 34
 is cut into each of the individual bags in the region immediately beneath
 the perforated separation line 30 at the perforation and tie-cutting
 station 32. The tie cut-out region 34 can be formed in either edge of the
 bag, i.e. either the longitudinal fold 22 or the four fold edge 24. It is
 preferred that the cut-out region 34 be formed in the four fold edge 24
 because it is easier to cut accurately on that edge. This is because the
 distance between the inside fold 16 and the edge 22 after the web is
 folded may be variable, whereas the folds 18 are relatively closely
 aligned after folding. Consequently, a narrower cut can be made in the
 four fold edge 24 than in the longitudinal fold 22. Each region includes a
 short edge 34A coincident with a separation line 30, a longitudinal edge
 34B and a bottom edge 34C in the form of an arc.
 After the bags have been formed with the tie cut-out regions 34, the web is
 rolled on a core 36 to form a roll of bags 38. Core 36 is slightly longer
 than the width of the plastic web so that the core can be supported in a
 dispensing device to facilitate the dispensing of the bags, one by one.
 A roll may contain one hundred (for example) plastic bags. After the
 requisite number of bags has been wound on a core 36, the web is cut, the
 roll 38 removed and the moving web wound on another core 36. The entire
 process is continuous; that is the tube is gussetted, folded, sealed,
 perforated, die cut and rolled as the web moves continuously from the
 extrusion machine through the various stations shown in FIGS. 1A and 1B.
 The bags are preferably dispensed with the perforation lines 30 behind the
 seals 28 so that as each bag is dispensed, the bag which becomes the
 leading bag has its open end in front. The bags can be dispensed by any
 device which includes a tongue capable of engaging the slots 30A in the
 separation lines. For example, the device shown in U.S. design Pat. No.
 409,027 may be used.
 FIG. 4 illustrates a bag in accordance with the invention after it has been
 separated from the roll 38 and opened. Because of the cut-out regions 34
 (shown in phantom in FIG. 4), four flaps or ties 40 are formed at the top
 of the bag. The length and width of the ties 40 will, of course, depend on
 the dimensions of the cut-out regions 34. The ties 40 are separated by
 adjacent cut-out regions 34. After the bag has been filled, the ties 40
 can be tied together to secure the contents of the bag.
 The arc 34C is important for two reasons. First, it avoids a sharp corner
 at its junction with the longitudinal edge 34B which would be more likely
 to tear if subject to stress. Secondly, because of the shape of the arc,
 the presence of a "valley" in the cut-out region when it is opened (as
 explained below) is avoided. With the shape shown in FIG. 4, a slight peak
 42 is formed in the open bag but that does not enhance the likelihood of
 tearing. On the other hand, a valley, i.e. a V-shaped region, would be
 more likely to tear at the apex or point of the "V".
 There are a number of ways in which the tie cut-out regions can be formed.
 In a preferred embodiment, a die 44 (FIGS. 5 and 6) is attached to the
 perforation blade 46 which is used to form the separation lines 30.
 Perforation blade 46 includes teeth 48 which form the perforations, and
 elongated teeth 50 and 52 which form the slot 30A and the upper edge 34A
 of cut-out region 34, respectively. The cutting edge 44A of die 44 is
 shaped to form the longitudinal edge 34B and the arc 34C of the cut-out
 region 34.
 As shown in FIG. 6, the blade 46 and die 44 are moved vertically just after
 a seal 28 in the moving web has passed the blade. The mechanism for
 actuating and moving the blade is conventional and, therefore, is not
 described in detail.
 It is also contemplated that the cut-out region 34 may be die cut after the
 perforation line 30 has been formed. For example, if the perforation line
 is formed by a rotary perforation blade, a male punch 54 may cooperate
 with a fixed female die 58 (FIGS. 7, 8 and 9). The timing of the die
 cutting operation can be based on a sensing device 60 which optically
 detects the perforation line. If a rotary perforation blade is used, the
 timing and functioning of the male die may be actuated directly by the
 blade itself.
 A pressurized water jet 62 (FIG. 10) may also be used to remove the tie
 cut-out area. In this case, the water jet nozzle 62 is moveable
 longitudinally on a first rail 64. The entire assembly is moveable
 laterally on a second transverse rail 66. The apparatus for moving the
 nozzle may be conventional. The movement of the nozzle both longitudinally
 and laterally is synchronized with the device which cuts the perforation
 line to cause the nozzle 62 to trace a line which defines the cut-out
 region 34. The nozzle must be capable of moving longitudinally at a speed
 greater than the speed of the web so that it can cut the arc 34C at the
 bottom of the cut-out region.
 Obviously, the size and shape of the cut-out region can vary depending on
 circumstances. In the case of refuse bags made of high density
 polyethylene, the individual bags may be thirty inches long and the star
 seal web six inches wide. The cut-out region 34 may be 1/4 to 1/2 inch
 wide and four to five inches long. In the illustrated embodiment, the
 cut-out regions are literally cut-out prior to rolling the web, but
 instead of physically removing the tie cut-out regions, they may be
 separated from the bag by means of a perforated separation line, in which
 case the user would have the option of removing the cut-out region prior
 to use. If the cut-out regions are not removed, the capacity of the bag is
 enhanced although the problem with closure is not satisfied.
 In the preferred embodiment a star seal configuration is used, but the
 principles of the invention can be applied to other types of bags. For
 example, if a bag is fully gussetted (but not folded to form a star seal
 configuration), cut-out regions formed in one or both longitudinal edges
 would provide a useful result. If a flattened tube alone were used, it
 would be necessary to form tie cut-out regions in both edges. Although the
 provision of integral means for tying a bag is of particular utility in
 the case of a refuse bag, the invention is not limited to refuse bags and
 would have utility in any situation where it may be desirable to provide a
 means for tying a bag after it has been filled.