Patent Application
20060255201
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(1) Field of the Invention
The present invention relates to a method for unrolling web material in a packaging machine operating intermittently in a cycle and to a packaging machine.
(2) Description of Related Art Including Information Disclosed Under 37 CFR §§1.97 and 1.98
Packaging machines are known which are constructed as schematically shown in
In the packaging machine shown in
Such packaging machines work in an intermittent way in a cycle wherein in a step with active (closed) working station processing of the web material is effected and in another step with inactive (opened) working station supply of web material to be processed from the supply roll to the working station and removal of processed web material from the working station are effected.
In the known packaging machines the working station remains inoperative in the inactive opened state for a long time since, on the one hand, unrolling of the web material from the supply roll has to be performed very carefully because plastic films having a thickness of only 25 μm are used as web material, for example, and, on the other hand, the supply roll weighs up to 100 kg such that large mass accelerations are necessary for unrolling. During winding-up of the processed web material large mass accelerations are necessary as well.
To ensure an efficient utilization, a working station must be available for its actual functions for at least 75-90% of the time and be inactive in the opened state only for 10% to a maximum of 25% of the time. The inoperativeness of the working station in the inactive state due to the web transport means that no processing can be effected during this time so that the processing speed is limited by the supply of the web material.
Further, with the known packaging machines the problem occurs that the necessary mass accelerations are not constant over the duration of processing of many packages but rather the mass of the supply roll decreases due to unrolling and the mass of the removal roll increases due to winding-up of the residual material. Thus, it is difficult to control the method in the packaging machine such that, on the one hand, the web material is transported into the working station and out of the working station fast and that, on the other hand, the web material is tautly held and yet is not subjected to stresses large enough to cause to rupture of the web material. Additionally, due to the frame or grid structure with the web material to be removed the problem arises that it easily gets caught on components of the machine and that it disrupts more easily than the unprocessed material.
It is known to realize the advance of web material with transport chains which laterally grip the web material and convey it for a distance. However, such transport chains do not allow using different widths of web without complex refitting measures.
From DE 195 35 535 A1 a packaging machine is known which operates intermittently in a cycle and comprises a printer for printing on a web of film as well as several working stations such as a sealing station. In the device containing the printer two rolls form linear storages arranged upstream and downstream of the printer, respectively, which serve to forward a region of the web of film in the printer device portion by portion in a faster cycle while the web of film outside the printer device stands still in a main cycle. In the disclosed packaging machine the web of film is unrolled from a supply roll in the main machine cycle with inactive (i.e. inoperative) printer and with inoperative sealing station. During this, the working stations remain inoperative for the time of unrolling the web of film.
In GB 1 089 792 a packaging machine is disclosed in which respective linear storages for accommodating a portion of a web material are provided upstream and downstream of a station for marking or punching which operates in a cycle and wherein the two storages are coupled. In the disclosed packaging machine a continuous movement of the web material is transformed into a cyclical movement upstream of the working station and back into a continuous movement downstream of the working station. However, the packaging machine has the disadvantage that adjustment of the length of a portion of the web to be moved on in a cycle can only be attained by means of the transport speed of the continuous web supply and removal and of the processing speed of the working station which moreover have to be coordinated. Further, this document does not show unrolling of web material from a reservoir roll or supply roll.
From U.S. Pat. No. 4,753,059 a packaging machine is known in which two linear storages, upstream and downstream of a printing roll, are used. These are controlled such that passage of the web of film through the print device is effected at constant speed to achieve good printing. The packaging machine has the disadvantage that unrolling of web material from a supply roll must be effected carefully when the working station is inoperative.
It is the object of the present invention to provide a method and a packaging machine which decrease the inactive operating times of a working station and are thus faster but at the same time ensure secure unrolling of web material even for different widths of web.
The object is attained by a method for unrolling web material in a packaging machine operating intermittently in a clocked way with web material, comprising the steps: unrolling a predetermined length of web material to be processed (6) from a supply roll (1) and receiving it in a first storage (2) arranged upstream of a working station (3) in the processing direction as well as transporting processed web material (6′) away from a second storage (4) arranged downstream of the working station (3) in the processing direction, when the working station (3) is operative; and supplying web material to be processed (6) from the first storage (2) to the working station (3) and simultaneously transporting processed web material (6′) away from the working station (3) and receiving it in the second storage (4), when the working station (3) is inoperative.
The object is also attained by a packaging machine, which is constructed for intermittent clocked transport of web material, comprising:
Further developments of the invention are methods including one or more of the following features:
a. transporting away from the second storage (4) the processed web material (6′) is supplied to a removal device (5) and wound-up thereon;
b. wherein cutting-out of portions of the web material (6) is performed in the working station when the working station (3) is operative;
c. wherein the processed web material (6′) which is transported away is a remaining frame of waste web material;
d. wherein the web tension is substantially maintained constant during the entire method;
e. wherein fixation of the web material (6) at the input side of the working station (3) is effected when the working station (3) is operative;
f. wherein steps requiring mass acceleration of the supply roll (1) and of the removal device (5) are only performed when the working station (3) is operative; and
g. adjusting the length of web to be transported before processing web material (6).
Further developments of the invention also packaging machines including one or more of the following features:
1. wherein the removal device (5) is a roll for winding-up processed web material (6′);
2. wherein the working station (3) is a sealing and cutting station.
3. wherein the first storage device (2) and the second storage device (4) are mechanically coupled to each other;
4. wherein the first storage device (2) and the second storage device (4) are adjustable to receive a predetermined length of web material (6, 6′);
5. wherein the first and second storage devices (2, 4) each store the web material (6, 6′) in form of a loop;
6. wherein the coupling of the first and second storage devices is realized by a strand of chain (7) or a belt;
7. formed such that the strand of chain (7) or belt is moved in one direction (73) for filling the first storage device (2) and for emptying the second storage device (4) when the working station (3) is operative and such that the strand of chain (7) or belt is moved in the opposite direction (72) for supplying web material to be processed (6) to the working station (3) and for removing processed web material (6′) from the working station (3) when the working station (3) is inoperative;
8. wherein the first and second storage devices (2, 4) are each formed by two fixed rolls (20, 21; 40, 41) and a shiftable roll (22; 42) movable relative thereto; and
9. wherein the supply roll (1) and the removal device (5) each comprise a drive mechanism (10, 50) rotationally driving them.
With the method according to the invention and the device according to the invention, unrolling of web material from the supply roll and winding-up of processed web material are decoupled from the web transport into a working station and out of the same. This allows the web transport into the working station and out of the same to be performed very fast since no large mass accelerations are necessary to move the web material from the first storage into the working station and from the working station into the second storage. Time consuming unrolling of the web material and winding-up of processed web material which require large mass accelerations are performed in the time during which the working station is closed and operates.
Furthermore, it is made possible that the supply of web material to be processed to the working station and the removal of processed web material from the working station can be coupled in a simple way and thus the web tension can be substantially maintained constant during this fast transport.
According to the present invention further a simple changeover to different widths of web is ensured and unrolling of web material to be processed from the supply roll and winding-up of the processed web material onto the removal roll can take place independently from each other in the time during which the working station is closed. For this reason, the decreasing mass of the supply roll and the increasing mass of the removal roll during unrolling and winding-up can be taken into account.
Further features and advantages of the invention will become apparent from the description of embodiments with reference to the enclosed drawings. The figures show:
An embodiment of the present invention is described in the following with reference to FIGS. 1 to 4.
As illustrated in
A large amount of the web material to be processed 6 is provided in stock on the supply roll 1 in wound-up form and the removal device 5 is also formed as a roll onto which the processed web material 6′ is wound.
The first storage device is formed by three rolls arranged in parallel to each other wherein two rolls 20 and 21 are fixedly mounted on a machine frame and one variable roll 22 is arranged to be shiftable in the vertical direction. Coming from the supply roll 1, the web material to be processed 6 runs over the first fixed roll 20, over the variable roll 22 to form a loop, and then over the second fixed roll 21. Downstream of the second fixed roll 21 the web material to be processed 6 runs to the working station 3 via a fixed guide roll 30 arranged on the input side of the working station 3. The processed web material 6′ runs from the working station 3 to the second storage device 4 via a fixed guide roll 31 arranged on the output side of the working station 3.
The second storage device 4 is formed similar to the first storage device 3 by three rolls arranged in parallel wherein two rolls 40 and 41 are fixedly mounted on a machine frame and a variable roll 42 is provided below the two fixed rolls 40 and 41 to be shiftable in the vertical direction. The processed web material 6′ runs from the fixed roll 31 of the working station 3 over the fixed roll 40, over the variable roll 42 to form a loop and, thereafter, over the fixed roll 41. From the fixed roll 41 the processed web material 6′ runs to the removal device 5.
The variable roll 22 of the first storage device 2 and the variable roll 42 of the second storage device 4 are mechanically coupled by a strand of chain 7 mounted on the machine frame. In the embodiment shown in FIGS. 1 to 4, the strand of chain 7 passes over four pulleys 70, 70a of which the pulley 70a can be rotationally driven via a drive mechanism 71. The variable roll 22 and the variable roll 42 are fixed to the strand of chain 7 and guided in elongated recesses 23 and 43, respectively, in the rear wall of the machine frame.
By means of this coupling, as shown in
Inversely, as shown in
In FIGS. 1 to 4 the supply roll 1 is further illustrated to be provided with a drive mechanism 10 capable of rotationally driving it and the removal roll 5 is provided with a drive mechanism 50 capable of rotationally driving the latter.
Further, on the input side of the working station 3 a brake which is not shown in the drawings is provided which can prevent movement of web material 6 into the working station.
Either the working station 3 is in an opened state/inoperative state shown in
In the following the operation of the illustrated embodiment is described with reference to FIGS. 1 to 4.
In
In a step shown in
Due to the coupled movement of the variable roll 22 and the variable roll 42, a predetermined length of web material to be processed 6 is transported from the first storage device 2 to the working station 3 in the direction of arrow 25, simultaneously processed web material 6′ is removed from the working station 3 in the direction of arrow 32, and processed web material 6′ is transported into the second storage device 4 in the direction of arrow 45. Since the supply roll 1 and the removal device 5 are inoperative during this transport no large mass accelerations are required and the transport can be effected at high speed.
The transport illustrated in
By setting the distance between the upper end position of the variable roll 22 and the lower end position of the variable roll 22 the length of web material 6 to be transported during the step described with reference to
Immediately after the start of processing by the working station 3 the strand of chain 7 is moved counter-clockwise in the direction of arrow 73 by the drive mechanism 71, as shown in
This step takes place when the working station 3 is operative such that a long period of time is available. The required large mass accelerations for unrolling web material to be processed 6 and for winding-up processed web material 6′ can be effected carefully and a coupling between the movement of the variable rolls 22 and 42 and the drive mechanisms 10 and 50 can be realized which takes the decreasing/increasing mass of the supply roll 1 and the removal device 5 into account. In doing so, the regulation of the web tension can be separately controlled for unrolling and for winding-up when the working station 3 is operative. How the control of the web tension can be performed is described in U.S. Pat. No. 4,753,059, for example.
At the end of the step illustrated in
Compared to the known prior art this packaging machine has the advantage that the material transport into the working station 3 and out of the working station 3 is decoupled from unrolling of web material to be processed 6 and from winding-up of processed web material 6′ since these steps are effected in different time periods of the working cycle. For this reason, a fast transport of the web material 6, 6′ with opened working station 3 is allowed and no variations in tension occur during supply of the web material since only a negligible mass acceleration occurs during supply. The weight of the supply roll and of the removal roll is only relevant in those steps of the method which are performed when the working station is operative and for which much time is available. With this construction the tension of the web material can be kept substantially constant during the entire process.
Further, the packaging machine allows an easy adjustability of the length of web material to be transported by adjustment of the two end positions of the variable roll of the first storage device.
In the embodiment described with reference to FIGS. 1 to 4 coupling of the first storage device with the second storage device is realized by a strand of chain, however, this coupling can also be mechanically realized with a lever, electronically with a synchro-tie or with another appropriate coupling.
Driving of the fast web transport when the working station 3 is inoperative can also be realized with friction rollers arranged on both sides of the working station 3. A realization with chains laterally gripping the web of film is also possible but in this case the use of web material with different width is not possible without further adaptations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 018 111.2 | Apr 2005 | DE | national |
