Device and process for transferring a material web

Abstract

A device for transferring a material web includes a transfer zone to which vacuum can be applied and at least one sealing mechanism with sealing lips. The sealing mechanism limits or divides the transfer zone, where suction can be applied to a space between the sealing lips.

Description

BACKGROUND

This invention relates to a device for transferring a material web, particularly a web made of paper, board, tissue, or other pulp, from a first supporting surface, for example a drying cylinder, to a subsequent supporting surface, for example a suction roll.

The device comprises a transfer zone to which vacuum can be applied and at least one sealing mechanism with sealing lips. This invention also relates to a process for transferring a material web performed with the device according to the invention.

Devices of this kind for web transfer are used in the dryer section of paper machines, for example. These dryer sections usually consist of a number of drying cylinders and suction rolls, each of which are arranged in a row. The web to be dried, usually supported in a meandering path by an air-permeable supporting belt, runs from a first drying cylinder to a suction roll and on to a further drying cylinder. Here, the web is guided round the suction roll with the aid of vacuum. The web must be transferred in the areas between the drying cylinders and the suction rolls. This transfer is effected using special web transfer devices.

Patent application EP 1 788 153 A2, for example, describes a web transfer box with a transfer zone that is divided into a pick-up zone and a stabilizing zone. In the pick-up zone, the material web and the supporting belt are lifted off the drying cylinder with the aid of vacuum, and in the stabilizing zone that immediately follows, the material web and supporting belt are stabilized by means of vacuum. Here, the pick-up zone is sealed off towards the atmosphere and the stabilizing zone by means of seals. The two vacua in the pick-up zone and the stabilizing zone can be set and adjusted separately in this process, with the vacuum in the pick-up zone generally being higher than in the stabilizing zone in practice.

Ever increasing machine speeds require higher and higher vacua in the transfer zone, particularly in the pick-up zone, however conventional seals cannot always guarantee adequate sealing. Particularly in transfer devices with a high vacuum, conventional seals are not sufficient to perform this function satisfactorily.

SUMMARY

The problem thus addressed by the present invention is to create a web transfer device and a transfer process that provides good sealing of the vacuum in the transfer zone, even at high machine speeds.

This problem is solved by a device in which the transfer zone is limited or divided by the sealing mechanism and where suction can be applied through an opening to a space between the sealing lips of the sealing mechanism.

By applying suction to the sealing mechanism, a higher vacuum can be set in the transfer zone and, due to the reduced leakage of air through the sealing mechanism and into the transfer zone, a lower performance suction unit can be used, which results in energy savings.

Applying suction between the individual sealing lips also leads to improved closure of the seal on the material web to be transferred or on a supporting belt because the individual sealing lips adhere to the web by suction.

In a preferred embodiment the material web is supported in the transfer zone on a supporting belt, which should preferably be air-permeable. The supporting belt provides additional purchase for the material web.

It is an advantage if the sealing lips of the sealing mechanism form a labyrinth seal. If the individual sealing lips are mounted in a labyrinth arrangement, the sealing effect can be improved substantially.

In a favourable embodiment the transferzone comprises a pick-up zone and a subsequent stabilizing zone. The vacua in these two zones can then be selected such that the material web is lifted off the first supporting surface as close as possible to the tangent point and such as to provide optimum guiding and stabilizing of the web in the stabilizing zone.

Here it is useful if the sealing mechanism to which suction can be applied forms the limit of the pick-up zone, in which case it can also be located between the pick-up zone and the stabilizing zone. During operation, the pick-up zone is normally placed under a higher vacuum than the stabilizing zone, which is why it is particularly desirable to have a good seal in the pick-up zone.

It is an advantage if the sealing mechanism is swivel-mounted. With a swivel-mounted sealing mechanism, it is easy to perform maintenance work or change a supporting belt.

The invention also relates to a corresponding process for transfer of a material web, where suction is applied to a sealing mechanism in the transfer zone.

By applying suction to the sealing mechanism, a certain level of vacuum can be maintained in the transfer zone throughout the entire production process.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which:

FIG. 1 is a schematic side view of a web transfer device according to the invention;

FIG. 2 is an enlarged section of the schematic side view in FIG. 1;

FIG. 3 is a side view of a further web transfer device according to the invention; and

FIG. 4 is a schematic detail of the web transfer device according to the invention with swivel-mounted sealing mechanisms.

DETAILED DESCRIPTION

The web transfer device 5 according to the invention is shown in FIG. 1. During operation, a material web 1, coming from the right, is supported on a supporting belt 2 and guided over a first supporting surface 3. In the present example, this first supporting surface 3 is a rotating and heated drying cylinder. Then the material web 1 and the supporting belt 2 are lifted off the first supporting surface 3 by the web transfer device 5 and transferred to the subsequent supporting surface 4. For this purpose, a vacuum is applied to the web transfer device 5, causing the material web 1 and the supporting belt 2 to be lifted off the first supporting surface 3 by suction and stabilized until they are transferred to the subsequent supporting surface 4. On one side the transfer zone 6 is sealed over the entire machine width by means of the sealing mechanism 10, to which suction is applied. In the present example, the subsequent supporting surface 4 is a rotating suction roll around which the material web 1 and the supporting belt 2 are guided with the aid of vacuum. After the suction roll the material web 1 and the supporting belt 2 are transferred to a further drying cylinder. The direction of rotation of the two drying cylinders and of the suction roll is indicated by arrows.

FIG. 2 shows a detailed view of the sealing mechanism 10 to which suction is applied, as illustrated in FIG. 1, where the reference numerals used in all figures refer to the same items. The sealing mechanism 10 consists of several sealing lips 11. These can have a blade-like shape and can form a labyrinth seal. The sealing lips can be made of silicone, Teflon, or another synthetic material.

A space 12 is formed between the sealing lips 11. According to the invention, the air in this space 12 is extracted by suction through the opening 7 in the sealing lip mounting. The direction of flow 13 of the air extracted is indicated here by arrows. The vacuum prevailing between the sealing lips 11 ensures that the sealing lips 12 close evenly on the supporting belt 2 because the sealing mechanism 10 adheres to the supporting belt by suction. Leakage air flowing in is also removed through the opening 7 by suction. In the transfer zone 6 there is also a vacuum, and the vacuum flow direction is indicated by the two arrows 8. The vacuum inside the sealing mechanism 10 and the vacuum in the transfer zone 6 can be generated by the same vacuum blower. It would also be possible, however, to generate the two vacua using separate systems. It is also conceivable that the vacuum in the space 12 is adjustable and regulated separately and independently of the vacuum in the transfer zone 6. The sealing mechanism 10 can also have several openings 7, located at regular intervals across the machine running direction, for example. The opening 7 can also be connected directly to the transfer zone 6, where the leakage air in the space 12 is sucked through the opening 7 into the transfer zone 6. A reducing damper can also be installed in the connecting duct between the opening 7 and the transfer zone 6 in order to set a lower vacuum in the space 12 than in the transfer zone 6.

FIG. 3 shows a further variant of the invention. Here, the web transfer device 5 has two sealing mechanisms 10 and 10′. In this case, the transfer zone 6 is divided into a pick-up zone 6′ and a stabilizing zone 6″. These two zones (6′, 6″) are separated by the sealing mechanism 10′. As an option, a further seal 14 may also be provided, in which case there is an additional zone between the sealing mechanism 10′ and the seal 14 that may have a different pressure to the pick-up zone 6′ and the stabilizing zone 6″. It is also conceivable that the pressure in this further zone can be set, by means of a gate damper for example. In the pick-up zone 6′, the material web 1 and the supporting belt 2 are lifted off the first supporting surface 3 by vacuum. In the stabilizing zone 6″, the material web 1 and the supporting belt 2 are stabilized with the aid of vacuum. The vacuum in the pick-up zone 6′ is preferably higher than the vacuum in the stabilizing zone 6″. Preferably, it should be possible to set and adjust the pressure ratios in the pick-up zone 6′ and the stabilizing zone 6″ separately. Both sealing mechanisms 10 and 10′ are subject to suction in FIG. 3, however it is conceivable that suction is applied to only one of the two suction mechanisms 10, 10′. It is also conceivable that suction is applied to the seal 14.

FIG. 4 shows the sealing mechanisms 10 and 10′ from FIG. 3 in detail. It clearly shows that suction can be applied to the space 12 between the sealing lips 11 through the opening 7. Here, the sealing mechanism 10′ is connected to a vacuum system via the flow duct 9. The two sealing mechanisms 10 and 10′ can be connected to the vacuum system for the pick-up zone, but it is also possible that both or one sealing mechanism 10 and/or 10′ is connected to a separate vacuum system or to the vacuum system for the stabilizing zone 6″. The vacuum in the stabilizing zone 6″ can also be generated via the vacuum system for the suction roll.

The sealing mechanisms 10 and 10′ can be swivelled round an articulated joint 15 and 15′. The dot-dash lines here show the sealing mechanisms 10 and 10′ swung into position outwards. This swing movement of the sealing mechanism 10, 10′ facilitates maintenance work and changing of the supporting belt 2. It is also possible to swing the sealing mechanisms into position downwards (not shown). As a result, the sealing mechanism 10, 10′ can yield if the paper wraps right round the cylinder or round the first supporting surface 3, and can thus prevent damage to the sealing lips 11 and the supporting belt 2. The sealing mechanism 10, 10′ can also be pre-stressed by means of a spring and motor, or by a pneumatic cylinder, which swing it back into the sealing position if it is moved. If a motor or a pneumatic cylinder is used, the sealing mechanism 10, 10′ can also be swung out of position for maintenance work.

The embodiments in the drawings only show one preferred embodiment of the invention. The invention also relates to other embodiments in which, for example, the sealing mechanism 10, 10′ limits the stabilizing zone 6″. It is also conceivable that the web transfer device 5 is used to transfer a material web 1 at a converting or winding unit of a paper machine.

The web transfer device 5 according to the invention can be used in all processes in which a material web 1 is transferred with the aid of vacuum from a first supporting surface 3, which can also be a plane, to a subsequent supporting surface 4, to which suction need not be applied.

It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

1. A device for transferring a material web from a first supporting surface to a subsequent supporting surface, the device comprising a transfer zone to which vacuum can be applied and at least one sealing mechanism having a plurality of sealing lips, the sealing mechanism limiting or dividing the transfer zone, at least two of the sealing lips defining a space therebetween to which suction can be applied through an opening.

2. The device of claim 1, further comprising a supporting belt adapted to support the material web in the transfer zone.

3. The device of claim 1, wherein the sealing lips of the sealing mechanism form a labyrinth seal.

4. The device of claim 1, wherein the transfer zone comprises a pick-up zone and a stabilizing zone.

5. The device of claim 4, wherein the sealing mechanism defines the limit of the pick-up zone.

6. The device of claim 5, wherein the sealing mechanism is disposed intermediate the pick-up zone and the stabilizing zone.

7. The device of claim 1, wherein the sealing mechanism is swivel-mounted.

8. A process for transferring a material web from a first supporting surface to a subsequent supporting surface, the process comprising

applying a vacuum in a transfer zone to transfer the material web from the first supporting surface to the subsequent supporting surface; and

applying a suction to a sealing mechanism in the transfer zone.