The present patent document claims the benefit of priority to European Patent Application No. EP 09156125.8, filed Mar. 25, 2009, and entitled “DEVICE FOR AUTOMATICALLY CONTROLLING THE EDGES OF A WEB OF SHEETING,” the entire contents of each of which are incorporated herein by reference.
The invention relates to a device for automatically controlling the edges of a web of sheeting, especially when guiding the sheeting through blister machines of the pharmaceutical industry.
Devices of this type for automatically controlling the edges of webs of sheeting in blister machines have been known for a long time. In the production of blister packs, a forming sheet and a cover sheet are sealed together in a blister machine, wherein pockets, which are filled with the pharmaceutical products, are formed beforehand in the forming sheet. To guide the sheets, i.e., the forming sheet and the cover sheet, a web edge control system is required, because, as the sheets are being transported through the machine, they have the tendency to move transversely to the main travel direction. This tendency is caused by deviations in the parallelism of the deflecting rollers and guide rollers and also by inaccuracies in the cutting of the rolls of forming sheet or cover sheet.
To control this movement of the sheets, the forming sheet has up to now been guided transversely to the travel direction by two guide plates located at the last deflecting roller before the forming station.
When a sensor provided for this purpose sends a signal that the forming sheet threatens to leave the tolerance range, a motor pushes the guide plates transversely to the sheeting travel direction to correct the direction in which the sheeting is traveling.
Especially in the case of sheetings of aluminum foil, the use of lateral guide plates to shift the sheeting can lead to a situation in which the sheeting does not follow the movement of the guide plates. Instead, the edges of the sheeting climb up the guide plates and fall back on themselves.
This problem does not exist to the same degree in the case of sheets of PVC because of their greater stiffness, but fine dust abraded from the PVC does accumulate on the guide plates.
It is an object of the present invention to provide a device for automatically controlling the edges of a web of sheeting by means of which, in a small space and in a simple, reliable, and nondamaging manner, the edges of webs of any type of sheeting can be automatically controlled.
According to one aspect of the invention, the device for automatically controlling the edges of a web of sheeting comprises
With the use of this design, it becomes possible to control reliably the edges of webs of any desired type of sheeting, wherein positively-acting guide elements which suffer from the disadvantages described above do not have to be used. As a result, it is possible to control the edges of the web continuously and yet in a manner which is extremely protective of the sheetings.
In a first embodiment, the deflecting rollers are arranged next to each other in the axial direction in such a way that the sheeting moves widthwise over at least one section of each of the two deflecting rollers. As a result of this two-part division of the contact surface for the sheeting, it becomes easy to influence the friction between the sheeting and each of the deflecting rollers.
The deflecting rollers are preferably supported on the same shaft, which comprises a first thread in the area of the first deflecting roller and a second thread in the area of the second deflecting roller, wherein the first thread and the second thread turn in opposite directions, and wherein the drive for shifting the deflecting rollers in axially opposite directions drives the shaft. As a result of this design, it is especially easy to control the shifting of the deflecting rollers in axially opposite directions by means of a single drive.
To influence the friction between the sheeting and each deflecting roller, the means for changing the ratio between the friction of the sheeting on the first deflecting roller and the friction of the sheeting on the second deflecting roller comprises two pressure rolls, the first of which is assigned to the first deflecting roller, the second of which to the second deflecting roller.
Each pressure roll can preferably be shifted in the axial direction simultaneously with the associated deflecting roller. In this way, the sheeting can be shifted laterally by the combination of the pressure which the pressure roll exerts against the sheeting and thus against the associated deflecting roller and the simultaneous lateral displacement of the deflecting roller and the pressure roll.
Each pressure roll is preferably connected to the associated deflecting roller in such a way that the drive for shifting the deflecting rollers in axially opposite direction can shift each of the pressure rolls simultaneously with the associated deflecting roller. Thus, in a simple manner, the synchronicity of the movement of the deflecting roller and the associated pressure roll is ensured.
In a second embodiment, the deflecting rollers are arranged next to each other in the radial direction in such a way that the sheeting passes over only one deflecting roller, wherein each deflecting roller comprises its own shaft. With this design, it is possible to process sheetings which have a relatively high retraction force.
In this case, the two shafts preferably comprise oppositely-directed threads, and the drive for shifting the deflecting rollers in axially opposite direction drives both shafts simultaneously. Alternatively, a drive can be provided for each shaft.
The means for changing the ratio between the friction of the sheeting on the first deflecting roller and the friction of the sheeting on the second deflecting roller preferably comprises a bearing for the shafts which is designed with freedom to pivot. As a result, it is possible in a simple manner to change over from the case in which the sheeting is traveling over one shaft to the case in which the sheeting is traveling over the other shaft.
Although there are many possible designs, it is preferable for the first deflecting roller to be slightly farther away from the pivot axis than the second deflecting roller is. In particular, if the bearing is now free at the same time to pivot around an angular distance of between 92° and 105°, and preferably between 93° and 98°, the bearing can be easily pivoted between two positions in which there is a connection between only one deflecting roller and the sheeting.
In all of the embodiments, it is advantageous to provide at least one sensor to detect the end positions of the travel of each deflecting roller, wherein the sensor is connected to the automatic control device. Thus the rotational direction of the drive for shifting the deflecting rollers in opposite axial directions can always be changed at the correct time.
Additional features and advantages of the present invention can be derived from the following description, which refers to the drawings.
The device for automatically controlling the edges of a web of sheeting 2 comprises a housing 4, in which a first deflecting roller 6 and a second deflecting roller 8 are arranged parallel to each other. In the first embodiment shown in
A sensor 10 (
The two deflecting rollers 6, 8 can rotate independently of each other and can be moved in opposite axial directions, either toward or away from each other, by a certain amount such as by about 10 mm. A motorized drive 14 is preferably used to shift the deflecting rollers 6, 8 in opposite axial directions. It is also possible to provide two separate drives 14 to shift the deflecting rollers 6, 8 in the axial direction.
In the example in
The device comprises a means for changing the ratio between the friction of the sheeting 2 on the first deflecting roller 6 and the friction of the sheeting 2 on the second deflecting roller 8. In the case of
To illustrate the control principle, let the sheeting 2 be shifted by an exaggerated distance to the right, that is, in the transverse direction. The visual field 12 of the sensor 10 (
For this purpose, the left pressure roll 20 is laid with light pressure against the left deflecting roller 6, and it thus generates a frictional force between the deflecting roller 6 and the sheeting 2 which is slightly higher than the frictional force between the other deflecting roller 8 and the sheeting 2.
Because the sensor 18 has also recognized that the deflecting rollers 6, 8 are as close as possible to each other in the axial direction, the automatic control device for the drive 14 will select a rotational direction such that the deflecting rollers 6, 8 move away from each other in the direction of the arrows B (
In the example given here, the sheeting 2 always has the tendency to move toward the right. Because the axial movement of the deflecting rollers 6, 8 toward the outside is limited, at a certain point the ability to transport the sheeting 2 to the left by moving the deflecting rollers 6, 8 apart will be used up. This is shown in
Because, on the other hand, the sheeting 2 should continue to be pushed toward the left, the right pressure roll 22 is now pressed lightly against the right deflecting roller 8, whereas the left pressure roll 20 lifts off and remains free. The drive 14 changes its direction of rotation and thus has the effect that the deflecting rollers 6, 8 start to move toward each other again in the axial direction (
By the use of this principle, therefore, the control system can correct the transverse travel of the sheeting 2 in endless fashion without any loss of time and without the need to use positively-engaging guide elements.
It is also conceivable that the pressure rolls 20, 22 could be omitted in cases where the friction between the deflecting rollers 6, 8 and the sheeting 2 is relatively high. Using the pressure rolls 20, 22, is preferable, however. In the example shown here, each of the pressure rolls 20, 22 is arranged in the axially inner area of the deflecting rollers 6, 8, but they could also be located farther out in the axial direction. The lateral surface of the pressure rolls 20, 22 will usually consist of an elastic material such as rubber.
Especially for sheeting 2 with relatively high retraction force, a second embodiment of web edge control is suitable; it is shown schematically in
As the means for changing the ratio between the friction of the sheeting 2 on the first deflecting roller 6 and the friction of the sheeting 2 on the second deflecting roller 8, a pivotable bearing 24 is used here, in which the shafts 16 of the deflecting rollers 6, 8 are supported. All of the sheeting 2 always travels over only one of the deflecting rollers 6, 8, whereas the sheeting 2 does not touch the other deflecting roller 6, 8 at all.
In
If the adjusting distance of the deflecting roller 6 has been used up but it is still necessary to continue pushing the sheeting 2 in the same direction, the bearing 24 can execute a pivoting movement (
In the case of this embodiment as well, it would be possible to use a pressure roll to increase the friction between the deflecting roller 8, 9 and the sheeting 2.
Overall, therefore, a device for controlling the edges of a web is provided, by means of which irregularities in sheeting guidance can be corrected in a simple, reliable, and nondamaging way.
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09156125 | Mar 2009 | EP | regional |
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Number | Date | Country | |
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