Shunt for a web divided into several sectional webs

Abstract

A shunt for a web, in particular a web of corrugated board, which is to be divided into several sectional webs in the conveying direction, comprises several shunting elements which are disposed side by side below the web of corrugated board and which are individually movable at least into a top position and a bottom position. Several compressed-air nozzles are provided, which are disposed above the shunting elements and directed towards the shunting elements and which are individually actuated by compressed air.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a shunt for a web, in particular a web of corrugated board, which is to be divided into several sectional webs in the conveying direction.

2. Background Art

Shunts, i.e. switches, of the generic type comprise several shunting elements crosswise of the conveying direction; these shunting elements are arranged side by side below the web and are individually movable into at least one top and bottom position of shunt. Adjusting drives are provided for these motions to be carried out; they move the individual shunting elements from one position of shunt into another. Shunts, or switches, of the generic type are provided in machines for treating, in particular dividing, webs, in particular webs of corrugated board; the sectional webs, mostly in the number of two, are fed to a cross cutter where the sectional webs are cut into individual sheets, so-called blanks, and deposited. The individual cross cutters of such a cross-cutter arrangement are disposed one on top of the other. During continuous conveyance of the sectional webs, the shunting elements that are allocated to a top sectional web are in their top position of shunt, whereas the shunting elements that are allocated to a bottom sectional web are in their bottom position of shunt. Upon change of format i.e., a change in the width of the sectional webs, the entire web is being cut through crosswise and the leading sectional webs are run at a higher speed, producing a gap between the leading sectional webs and the lagging sectional webs. When the gap between these sectional webs is in the vicinity of the shunt, the shunting elements are set for correct allocation in width to the lagging sectional webs. For the sectional webs to be kept on the shunting elements, it has been known, over the total width of the web, to provide a pipe with a plurality of downward outlets, compressed air being blown through this pipe. Strong swirls of air occur in particular when the lagging sectional webs enter the shunt, which may result in the sectional webs not being led accurately on their way to the cross cutters of the cross-cutter arrangement. Experience has in particular shown that an air jet is reflected by the bottom sectional web, lifting the top sectional web off the shunting elements so that it rises. The higher the velocity of the web, the more grows this problem. These web velocities can be higher than 300 m/min.

SUMMARY OF THE INVENTION

It is an object of the invention to embody a shunt of the generic type in such a way that reliable guidance of the lagging sectional webs is ensured upon change of format.

According to the invention, this object is attained in a shunt, comprising a plurality of shunting elements, which are disposed side by side below the web of corrugated board, and which are individually movable at least into a top position and a bottom position; an adjusting drive which acts on each shunting element, moving each shunting element between the positions; and several compressed-air nozzles which are disposed above the shunting elements and directed towards the shunting elements, the nozzles being individually actuatable by compressed air. The gist of the invention resides in that several compressed-air nozzles are provided over the width of a web; they can be triggered individually so that the sectional webs are kept reliably on the shunting elements that lead them, in particular directly after a change of format. Triggering the compressed-air nozzles can be handled appropriately: it is for example conceivable not to actuate the compressed-air nozzles that directly adjoin the longitudinal cut between the lagging sectional webs so that compressed-air swirls are precluded. The object according to the invention can be attained by special advantage in keeping with an embodiment wherein the compressed-air nozzles are individually actuatable by compressed air from a valve unit which is triggered by a control unit. Another advantage is offered when one or several compressed-air nozzles are provided above each shunting element.

Further advantageous embodiments consist in each compressed-air nozzle being disposed centrally above a shunting element; and in each compressed-air nozzle being disposed closely above a shunting element in the top position thereof.

Use can be made of the solution according to the invention not only when a web is cut through entirely upon a change of format with the leading sectional webs running at a higher speed, but by advantage even in case of so-called gapless changes of format with only partial cross cuts being made.

Further features, advantages and details of the invention will become apparent from the ensuing description of an exemplary embodiment, taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side view of part of a corrugating machine, including a shunt according to the invention;

FIG. 2 is a plan view of the machine according to FIG. 1; and

FIG. 3 is a view of details of FIG. 1 on an enlarged scale.

DESCRIPTION OF A PREFERRED EMBODIMENT

Seen in the conveying direction 1 of a web of corrugated board 2, the part of a corrugating machine illustrated in the drawing successively comprises a short cross cutter 3, a corrugating unit 4, a longitudinal cutter 5, a shunt 6 and a duplex cross cutter 7. A transfer table 8 is provided between the longitudinal cutter 5 and the shunt 6. Two tables, one on top of the other, are provided between the shunt 6 and the duplex cross cutter 7, a top table 9 of which leading to the top cross cutter 10 of the duplex cross cutter 7 and a bottom table 11 leading to the bottom cross cutter 12 of the duplex cross cutter 7. The shunt 6 includes shunting elements 13 of the type of so-called blades. These blades 13 are comprised of parallel, side by side bars of a width of for instance approximately 10 cm crosswise of the conveying direction 1, which are pivoted about a joint pivoting axis 14 that is located in vicinity to the table 8. By means of a linear drive, for example a pneumatically actuated piston-cylinder drive 15, each shunting element 13 is pivoted between a bottom and top position, which is roughly outlined in FIGS. 1 and 3. In the shunted top position, the shunting elements 13, when pivoted upwards, align with the top table 9, whereas the corresponding shunting elements 13 align with the bottom table 11 in the shunted bottom position.

As far as described, this part of the machine is known and general practice.

A compressed-air nozzle 16 is disposed above each shunting element 13; it is directed substantially vertically from above towards the shunting element 13. Related to a direction crosswise of the conveying direction 1, the nozzles 16 are disposed centrally above the shunting elements 13. They are located in proximity to the free ends 17, turned towards the tables 9, 11, of the shunting elements 13.

Compressed air is admitted to each nozzle 16 by a valve unit 19 via a supply line 18 allocated to each nozzle. This valve unit 19 is supplied with compressed air by a central source 20 of compressed air and a compressed-air storage unit 21 that provides for constant air pressure. The valve unit 19 is triggered by a central control unit 22 that also serves for triggering the drives 15. A central valve unit 23 is disposed upstream of the drives 15, which is fed by the compressed-air source 20.

The mode of operation is as follows:

A web 2a advances in the conveying direction 1 on the top table 9, approaching the top cross cutter 10 where it is divided into individual sheets and led to a deposit (not shown). Another sectional web 2b is located on the bottom table 111 and approaches the bottom cross cutter 12 of the duplex cross cutter 7 where it is likewise cut into sheets and deposited. The two sectional webs 2a and 2b had previously been produced from the web 2 by a longitudinal cut in the longitudinal cutter 5.

Upon the change of format that is roughly outlined in the drawing, the web has been cut crosswise by a cross cut referenced 24. The leading sectional webs 2a and 2b are accelerated in the duplex cross cutter 7 so that a gap 25 forms between the leading sectional webs 2a and 2b and the lagging sectional webs 2c and 2d. The webs 2c and 2d are divided by a longitudinal cut 26 which is displaced from the cut 24 of the two sectional webs 2a and 2b, which is the norm for a change of format.

When the gap 25 between the sectional webs 2a, 2b on the one hand and 2c and 2d on the other is located above the shunt 6, the shunting elements 13 are pivoted by corresponding actuation of the drives 15 so that the shunting elements 13 are pivoted upwards over the width of the sectional web 2c which is thus piloted on to the top table 9, whereas the shunting elements 13, which reach over the width of the sectional web 2d, are in their bottom position so that the sectional web 2d is led on to the bottom table 11. With compressed air being admitted, in particular during this change of format, to the nozzles 16 which are allocated to the sectional web 2d that must be piloted on to the bottom table 11, this sectional web 2d is reliably kept on the shunting elements 13 in their downwards pivoted position and led on to the bottom table 11 through the gap 27 between the top table 9 and the bottom table 11. In like manner, during this change of format, compressed air can be admitted to the compressed-air nozzles 16 that are allocated to the top sectional web 2c, this reliably preventing the sectional web 2c, which is to be led to the top table 9, from lifting off the shunting elements 13. It is also possible to leave one or two nozzles 16 unaffected in the vicinity of the longitudinal cut 26, thus avoiding any swirls of air along this boundary between the two sectional webs 2c, 2d.

Claims

1. A shunt (6) for a web (2) of corrugated board, which is to be divided into several sectional webs (2a, 2b, 2c, 2d) in the conveying direction (1), comprising

a plurality of shunting elements (13), which are disposed side by side below the web (2) of corrugated board, and which are individually movable at least into a top position and a bottom position;

an adjusting drive (15) which acts on each shunting element (13), moving each shunting element (13) between the positions; and

several compressed-air nozzles (16) which are disposed above the shunting elements (13) and directed towards the shunting elements (13), the nozzles (16) being individually actuatable by compressed air.

2. A shunt (6) according to claim 1, wherein the compressed-air nozzles (16) are individually actuatable by compressed air from a valve unit (19) which is triggered by a control unit (22).

3. A shunt (6) according to claim 1, wherein at least one compressed-air nozzle (16) is disposed above each shunting element (13).

4. A shunt (6) according to claim 1, wherein each compressed-air nozzle (16) is disposed centrally above a shunting element (13).

5. A shunt (6) according to claim 1, wherein each compressed-air nozzle (16) is disposed closely above a shunting element (13) in the top position thereof.