DE102004022845A1 - Method of making drawstring bags with stretchable drawstring - Google Patents

Abstract

The invention relates to a machine for producing draw tape bags (1) from a thermoplastic film (16) with a welding device (45) containing a welding drum (46), the welding drum (46) being provided with at least one over the length of the welding drum (46). extending welding bar (47) is equipped. The invention further relates to a generic machine with a feed device (20) for a drawstring (10, 11), which is equipped with a device for influencing the feed tension of the drawstring (10, 11), wherein the means for influencing the feed voltage with a pendulum swing (32) is provided.

Description

The The invention relates to a machine for producing drawstring bags from a thermoplastic plastic film with a welding drum including welding device, the welding drum with at least one about the Length of welding drum extending welding bar Is provided. The invention particularly relates to a generic machine with a feeder for a Tieback, wherein the feeder equipped with a device for influencing the feeding tension of the drawstring is.

bag The type mentioned here are in the bag opening with an elastic drawstring elastic around the circumference of the bag to design. With this configuration, a possibility be created, the bag to a container, such as a Trash or a trash can to fix. Such bags have the advantage that if the inside of the container filled The bag is not placed in the container falls into it. This is after the insertion of the bag into the interior of the container, the provided with the drawstring upper portion of the bag to the outside over the container edge beaten. The elastic drawstring comes on the outside of the container under tension to concern.

A generic bag is in the EP 1 364 892 A1 disclosed. The bag described herein comprising a bag body having an opening and an elastic band extending along a peripheral portion of the bag body in the area of the opening, which is shorter than the peripheral area in a relaxed state and thus leaving a compensation area at the peripheral portion of the bag body is attached, that the tape does not curl the bag body. The tape is also referred to as loose, that is, the tape is longer than the mother foil and does not pull the bag together in the relaxed state. In particular, this loose introduction of a drawstring in the Kunststoffolienbahn during the production of the bag is always a problem because the Kunststoffolienbahn would curl when contraction of the drawstring.

To adjust the feed tension of the drawstring is out of DE 38 21 905 C1 a device for feeding the drawstrings has become known. This device also has a tension and control function for the supplied drawstring. The drawstring is coming from a spool guided over pulleys, which are mounted on the one hand in the machine frame and on the other hand mounted in a swing frame. Here, the drawstring is guided meandering around the pulleys. In a described embodiment, this frame has two rollers over which the drawstring is guided and in its central region an adjustable weight. By means of this weight, the tension and controlled feeding of the tension band can be adjusted by adjusting the frame and the weight. There is thus a continuous tension on the tension band available. With this tensile stress superimposed tension of the drawstring of plastic web is fed. However, feeding a tension band under tension has a disadvantageous effect on the weld.

A welding device for producing a bag is known from DE 39 13 099 C1 known. It describes how, on the one hand, the cyclical conveying of the plastic film web takes place and, on the other hand, how a stress-free welding in the area of the plastic film web can be produced. By means of a blowing tube arranged in the region of the welding station, air is applied to the plastic film web. As a result, a loose is achieved in the film web and a tensionless welding is possible. By blowing on the air, the web tension of the film web can be safely maintained.

Another generic drawstring bag is from the DE 101 51 843 A1 known. Described is a bag made of thermoplastic film with a front and a rear wall, which is connected to form a filling opening by side welds together and each formed double-layered in the region of the filling opening. Pull bands extend over the entire bag width, one of which is inserted between the two layers of the front wall and the rear wall. The drawstrings are welded together at their two ends, wherein the drawstring is exposed by a introduced in the plastic film track grip hole.

A The object of the invention is to develop a welding device, with a more efficient, constructive and simple design cheaper welding allows becomes.

These The object is achieved by the characterizing part of the claim 1 solved.

A further object of the invention is to develop a drawstring bag manufacturing machine with a device for feeding the drawstring, in which an extensible drawstring is fed without tension on the one hand to the plastic foil web and subsequently to the welding device. The object of the invention is achieved in that the device for influencing the feed voltage is provided with a pendulum swing arm. The inventive use of a pendulum rocker, in the means for supplying the drawstring, now the possibility is created to influence the tension between the means for influencing the feed tension and the actual feeding of the drawstring to the plastic film web. With the pendulum rocker according to the invention thus the tensile stress between the feed unit and the actual loading area can be influenced in the Kunststoffolienbahn.

This Influence on the supply voltage in the drawstring can be adjusted by means of the pendulum swing attached to one arm of the pendulum swing a variable, adjustable weight is. The pendulum swing arm acts only by gravity on the drawstring. An even more precise influence on the tensile stress can then be made when to the central axis of the pendulum swing a rotary encoder is arranged. With the rotary encoder acts in Zugbandlaufrichtung Pull roller arranged in front of the pendulum rocker together. The drawstring wraps around the tension roller and is conveyed by means of the tension roller. there The rotary encoder forms on the pendulum swing arm with the drive motor the draw roller a control loop. Will now the pendulum swing, the is wrapped in s-shaped at their arms of the drawstring, strong deflected, so receives the drive motor for the tension roller a corresponding signal and is braked in this case, since in this case too much tension band of the plastic film web is supplied.

Around the tensionless feeding to allow the provided with the drawstring plastic film web is proposed according to the invention behind the merger for the Drawstring and the plastic film web to arrange a deflection roller, from which the to be welded Film web to the welding device arrives. Inventions possesses in accordance with this pulley in the region of the drawstring a larger diameter. Through this change the diameter in the region of the drawstring in the plastic film web will this area, that is the drawstring, stronger accelerated and relaxed behind the guide roller. The larger peripheral speed on the guide roller causes a pull in front of the guide roller and a To press the tension band behind the guide roller. The drawstring is thus the welding equipment supplied loose. Loose in this context means that on the elastic drawstring no tensile stresses act or the tensile stresses in operation are almost zero.

following The invention will be explained in more detail with reference to an embodiment.

It demonstrate

1 a bag with elastic drawstring,

2 a drawstring bag according to the section II-II from the 1 .

3 a first part of a Zugbandbeutelherstellmaschine in side view,

4 a detailed view according to the section IV-IV on a device for tension relief on the tension band,

5 another part of the Zugbandbeutelherstellmaschine in side view,

6 a detailed view of a welding device for welding the drawstring in section VI-VI and

7 a side view of welding device for continuously welding a Zugbandbeutels.

The 1 shows a drawstring bag made of a thermoplastic resin film 1 , The drawstring bag 1 consists of a front wall 2 and a back wall 3 by side welds 4 . 5 are connected together at their edges. The floor 6 of the drawstring bag 1 is by folding the drawstring bag 1 produced plastic film web. At least in the area of the filling opening 7 are both the front wall 2 as well as the back wall 3 double-layered, as in particular in 2 shown. To create a double-layered area, either in the area of the filling opening 7 made by turning the respective web edges a hem or the drawstring bag 1 is made up of four superimposed webs so that the front wall 2 and the back wall 3 are each designed as an entire double-layered. The double-layered area of the filling opening 7 is made by longitudinal welds 8th . 9 limited, each of the two layers of the front wall 2 and the back wall 3 connect with each other. At the edge of the filling opening 7 are the two layers of the front wall 2 and the back wall 3 each closed to each other. This is achieved by the fact that the front wall 2 and the back wall 3 in the area of the filling opening 7 be transhipped. It is also possible the two layers of the front wall 2 and the back wall 3 at the edge of the filling opening 7 with a welded longitudinal weld not welded together.

In the folded area of the filling opening 7 is between the layers of the front wall 2 and the back wall 3 one drawstring each 10 . 11 inserted. The drawstrings 10 . 11 extend over the entire bag width and are at their ends by means of the transverse welds 4 . 5 welded to the plastic film web. Before inserting the drawstrings 10 . 11 in the area of the filling opening 7 are punched in the plastic film web 12 . 13 been introduced. Additional transverse welds 14 . 15 limit the filling area 7 of the drawstring bag 1 ,

In the 3 is an example of a machine for the production of drawstring bags 1 in the side view in the region of the supply of drawstrings 10 . 11 shown. The plastic film web 16 that also mother foil 16 is called, is supplied in the direction of arrow P of the machine. Here, the unwinding device for the plastic film web 16 also be part of the machine. The plastic film web 16 passes through a storage roller system 17 to a first punching station 18 , In this first punching station 18 Vent holes can be introduced into the plastic film web. In the following punching station 19 Be the punching 12 . 13 in the plastic film web 16 in the area of the filling opening 7 brought in. In the following step, the Kunststoffolienbahn, which is present as a folded web is opened and the edges of the Zugbandbeutels 1 turned over and the drawstring 10 . 11 fed. This feeder for the drawstring 10 . 11 is with 20 designated. After feeding 20 of the drawstring 10 . 11 becomes the folded plastic film web 16 merged again and over a pulley 21 fed to a subsequent welding device.

In the lower part of the machine in 3 are two coils 22 . 23 with drawstrings 10 . 11 shown. By way of example, the tension-free feeding of the drawstring should now be used here 10 to be discribed. For the drawstring 11 The same voltage-free feed to the feed unit applies 20 , The drawstring 10 is via a pulley 24 a storage roller system 25 with a swingarm 26 fed. With the rocker is a acted upon by a tensile compressive cylinder 27 connected. By in the cylinder 27 Adjustable tension can be the tension in the drawstring 10 be set. About another pulley 28 becomes the tieback 10 a further device for influencing the supply voltage supplied.

In the 4 is a view according to the view IV-IV 3 shown. In the 4 is again shown the arrow P, the web running direction of the drawstring 10 . 11 reproduces. In the 4 is a drive motor 29 , a draw roller 30 , a pressure roller 31 , a swingarm 32 that with a rotary encoder 33 equipped as well as various unspecified pulleys reproduced. From the pulley 28 the train band will come 10 in the direction of arrow P on the draw roller 30 diverted. Here is the draw roller 30 a pressure roller 31 assigned over which the drawstring 10 to the draw roller 30 is pressed. By this draw roller, the tensile stress of the drawstring 10 from the storage roller system 25 in combination with the pendulum swingarm 32 be almost eliminated. The swingarm 32 acts on the drawstring 10 only by its own weight. Here are the thighs 34 . 35 of equal length and weight. The setting of the variable weight of a swivel 34 the swingarm 32 via a leg 34 fixed weight 36 , The drawstring 10 wraps around the ends of the thighs 34 . 35 almost s-shaped. The deflection at the ends of the legs 34 . 35 takes place via cylindrical rollers or cylindrical pins. The edition of the drawstring 10 at the cylindrical ends 37 . 38 is identical, so that always the same wrap angle of the tension band around the cylinder 37 . 38 given is. Will now be too fast promotion of the drawstring 10 the pendulum swing 32 strongly deflected, leaving the swingarm 32 is in the position A, A 'so receives the on the pendulum swing 32 located rotary encoder 33 a corresponding signal directly to the control for the drive motor 29 is forwarded. In this control loop is now a readjustment of the engine, which slows down the draw roller something. The drawstring 10 is thus stretched again and there is no overhang on drawstring 10 in the plastic film web 16 , By this inventive integration of a tension roller 30 with downstream pendulum swing 32 and control loop 33 . 29 consisting of drive motor 29 and rotary encoder 33 the solution according to the invention of the object is met and the drawstring 10 becomes tension-free of the plastic film web 16 in the feeder for the drawstring 20 fed. Another erfindungsge moderate advantage is that with relatively simple design means the tension of the tension band 10 after unwinding from the spool 22 . 23 is realized.

Like in the 5 is shown provided with the drawstring plastic film web 16 a welding unit 39 fed. It should be noted that between the feeder 20 and the welding unit 39 an unillustrated system can be inserted, in which the plastic film web 16 from a continuous to a discontinuous promotion is feasible. In the following description, the discontinuous promotion is needed. In a first welding process, the side welds become 4 . 5 by means of two welding beads ken 40 . 41 over a bag width L in the plastic film web 16 brought in. In this welding station in the side welds 4 . 5 are introduced, also the drawstrings 10 . 11 with welded, see 1 , A significant advantage of the invention is that of the drawstring bag 1 can be welded without tension. Would a tension on the drawstring 10 . 11 abut, so could on the one hand by the tension of the drawstring 10 . 11 during welding or on the other hand after welding by the contraction of the drawstring 10 . 11 the bag width L by curling the plastic film web 16 reduce. Since in the subsequent cycles the Zugbandschweißungen must be made but the bag width L remain identical to a reproducible welding result and useful drawstring bag 1 to be able to produce.

By the inventive use of the pendulum swing 32 The tension band is now lying loosely between the welding bars 40 . 41 and can easily handle the Muttefolie 16 be welded.

In addition, the invention proposes the pulley 21 to vary in diameter. By changing the diameter of the pulley 21 in the area of the drawstring 10 . 11 results in the promotion in relation to the other roll diameter higher speed. Due to the higher speed, will be on the side of the feeder 20 for the drawstring 10 . 11 on the drawstring 10 . 11 pulled and the drawstring 10 . 11 in the direction of the welding station 39 pressed. This gives the drawstring 10 . 11 one to the parent foil 16 light forward, leaving the elastic drawstring 10 . 11 between the welding bars 40 . 41 is loosely placed, where against the parent foil 16 under a certain to promote the parent foil 16 necessary voltage to promote. The change in diameter in the region of the tension band is only slight. A change in diameter of only 0.5 mm already results in a noticeable increase in the transport of the drawstring area of the drawstring bag 1 , With a diameter change of 0.5 mm over a width of about 30 mm results in a feed of about 1.5 mm.

After the side welds 40 . 41 be by means of the welding equipment 42 . 43 the welds 14 . 15 carried out in Zugbandbereich. Two bags are always welded at the same time.

The 6 displays the view VI-VI 5 again.

To different tieback bag 1 The machine has sleds 44 on which the welding equipment 42 . 43 are arranged adjustable for the drawstrings. About the sled 44 are the welding equipment 42 . 43 adjustable for the drawstrings in the direction of arrow D.

Behind the feeder 20 can according to the invention also a welding device 45 for continuous welding of the plastic film web 16 be arranged. In this case, the feeder would 20 for the drawstring 10 . 11 directly in front of the welding device 45 be arranged and the plastic film web 16 becomes the welding device 45 directly over the pulley 21 fed. The welding device 45 consists of a welding drum 46 and across the width of the welding drum 46 extending sealing strips 47 at the periphery of the welding drum 46 are arranged at a distance L. Between the welding bars 47 in each case the distance L is present, which is the width of a tension-bag to be welded 1 and the transverse welds to be produced 4 . 5 equivalent. With the welding drum 46 the sweatband works 48 together. This is the sweatband 48 over deflection and / or drive rollers 49 to the welding drum 46 introduced. The sweatband 48 wraps around the welding drum 46 in this embodiment about 180 °.

According to the invention it is now proposed, in addition to the welding strips 47 short welding bars 50 in the area of the drawstring 10 . 11 to arrange. The welding bars extend here 50 in length just as far in the welding drum 46 into it, that the Zugbandschweißungen 14 . 15 can be performed. According to the invention, the welding bars 50 on the circumference of the welding drum 46 arranged changeable who the. Here are the welding bars 50 be adjusted in the direction of the arrow E, as diverse drawstring bag 1 to be able to produce. It is also conceivable, not just a welding bar 50 next to the welding bars 47 but it can also be two or more welding bars 50 on each side of the welding bar 47 be arranged.

The plastic film web 16 is in the direction of arrow P of the welding device 45 fed. About a first deflection or drive roller 49 becomes the plastic film web 16 on the sweatband 48 guided and thus passes between the welding drum 46 and the sweatband 48 , During the passage of the plastic film web 16 through the welding device 45 Now takes place a continuous welding process. Starting from the point 51 , which defines the welding start, there is a continuous welding of the plastic film web 16 with the drawstring 10 . 11 and a simultaneous welding of the drawstrings 10 . 11 in the area of the openings 12 . 13 , with the additional transverse welds 14 . 15 through the welding bars 50 be performed. Starting from the welding start 51 the welding drum moves in the direction of the arrow F, so that the plastic film web 16 during a rotation angle of about 180 ° in this embodiment is welded. It goes without saying that by changing the rotational speed of the welding drum 46 and the conveying speed for the plastic film web 16 the welding time is changeable. In this embodiment of the invention are continuously two Zugbandbeutel 1 welded. At the point 52 the welding drum is released 46 again from the sweatband 48 and the plastic film web 16 and in the point 53 the plastic film web is further promoted for further processing.

By the use according to the invention of the welding bars 50 in the field of welding strips 47 can now look for more welding equipment behind the welding drum 46 be waived. Due to the adjustability of the welding bars and the arrangement of several welding bars 50 on the circumference of the welding drum 46 are also any drawstring bag 1 produced. The embodiment according to the 7 shows a welding drum 46 and a sweatband 48 , But it is also conceivable to work with counterpressure bars. Will a different width L of drawstring bags 1 needed, so is the welding drum 46 in the welding device 45 changed in diameter or with a corresponding number of welding bar, with any number: 1, 2, 3, 4, 5, etc. which are switched on or off, drove. The same applies to narrower bags and corresponding matched to the width L diameter of the welding drum 46 , Welding takes place via the welding strip 47 and the welding bars 50 , including the welding bars 50 Welding strips are both 47 . 50 can be equipped with a glow band. About the sweatband 48 gets on the welding bars 47 . 50 the corresponding counter-pressure required for welding is generated.

Claims (11)

Machine for producing drawstring bags ( 1 ) made of a thermoplastic plastic film ( 16 ) with a welding drum ( 46 ) welding device ( 45 ), wherein the welding drum ( 46 ) with at least one over the length of the welding drum ( 46 ) extending welding strip ( 47 ), characterized in that the welding drum ( 46 ) in the region of the drawstrings ( 10 . 11 ) with at least one additional welding bar ( 50 ) Is provided. Machine according to claim 1, characterized in that the welding bar ( 50 ) over the circumference of the welding drum ( 46 ) is arranged displaceably (E). Machine according to one of claims 1 and 2, characterized in that on each side of the welding strips ( 47 ) at least one welding bar ( 50 ) is arranged displaceably. Machine for producing drawstring bags ( 1 ) made of a thermoplastic plastic film ( 16 ), in particular according to one of claims 1 to 3, with a feed device ( 20 ) for a drawstring ( 10 . 11 ) equipped with means for influencing the supply voltage ( 25 ) of the drawstring ( 10 . 11 ), characterized in that the means for influencing the supply voltage ( 25 ) with a pendulum swing arm ( 32 ) is provided. Machine according to any one of claims 1 to 4, characterized in that the weight ( 36 ) of the pendulum swing arm ( 32 ) is adjustable. Machine in particular according to one of claims 1 to 5, characterized in that on the pendulum rocker ( 32 ) a rotary encoder ( 35 ) arranged with a draw roller ( 29 ) of the drawstring ( 10 . 11 ) is in electrical contact. Machine in particular according to one of claims 1 to 6, characterized in that the draw roller ( 29 ) with a pressure roller ( 31 ) for the drawstring ( 10 . 11 ) and that the draw roller ( 29 ) in front of the swingarm ( 32 ) is arranged. Machine according to one or more of the preceding claims, characterized in that behind the feeder ( 20 ) for the drawstring ( 10 . 11 ) and in front of a welding device ( 39 . 45 ) a deflection roller ( 21 ) arranged in the region of the drawstring ( 10 . 11 ) has a larger diameter. Machine in particular according to one of claims 1 to 8, characterized in that the pendulum rocker ( 32 ) immediately behind one with a rocker ( 26 ) provided memory roll system ( 25 ) is arranged Machine in particular according to one of claims 1 to 9, characterized in that an elastic drawstring ( 10 . 11 ) is supplied. Machine in particular according to one of claims 1 to 10, characterized in that at least two pendulum swing ( 32 ) for at least two drawstrings ( 10 . 11 ) are arranged in the machine. Method for feeding a drawstring ( 10 . 11 ) for producing a drawstring bag ( 1 ) comprising the steps of: - unwinding a drawstring ( 10 . 11 ) from a coil ( 22 . 23 ) - feeding the drawstring ( 10 . 11 ) into a storage roll system ( 25 ), wherein the storage roll system ( 25 ) via a with a pneumatic cylinder ( 27 ) movable rocker ( 26 ) and - feeding and inserting the drawstring ( 10 . 11 ) to and into a plastic film web ( 16 ), characterized in that - the drawstring ( 10 . 11 ) behind the storage roller system ( 25 ) first via a draw roller ( 29 ) and then via a pendulum swing arm ( 23 ) of the plastic film web ( 16 ) is supplied.