EP0065179A2 - Apparatus for cutting a hole in a paper web - Google Patents

Abstract

A device for punching a hole in a paper web, in particular for the production of liquid packs, has a movable punch with a circular knife at its tip, which can be pressed against a counterplate. To enable the desired hole to be punched into the desired layer depth of the packaging material with simple means, the invention provides that the punch has a rotatably driven cutting head. Due to the rotary movement of the punch or the edge forming the knife at the tip of the stamp, the knife is no longer pressed into the paper web as in previously known punching devices, but according to the invention it is rotated perpendicular to this printing movement, and there is a cutting effect such as when using a knife.

Description

The invention relates to a device for punching a hole in a paper web, in particular for the production of liquid packs, with a movable punch with circular pressure which can be guided against a counterplate. the knife at its tip.

Various types of packs with punch holes are known, in particular packs for liquid beverages made of paper coated with plastic. The punched holes in the paper web of such packs are used to pierce a straw. The aim of the manufacturer of such packs is to pre-punch the hole in the paper web in such a way that, on the one hand, the pack is or remains tight and, on the other hand, the user can easily pierce it using the straw.

Various machines have been developed for producing such a punch hole. In a known machine, two punch rolls rotatable about axes arranged parallel to one another are provided, between which the as yet uncoated paper web is passed in register. A projection located on the punching roller hits the recess in the opposing counter-pressure roller while punching through the paper web. The paper web thus provided with the perforation is then passed between a further pair of rollers, namely a pressure roller and a cooling roller for coating the paper web on both sides with plastic. In this punching method or this known machine, the paper web is completely punched out, and the punched-out piece of paper or cardboard, also called the middle part, is completely removed from the paper web. The resulting leakage is in turn compensated for by the plastic skin applied to both surfaces of the paper web.

It is a complex process or an expensive machine. The heavy rollers are expensive to manufacture, they have to work with high precision and at high running speeds, and there is a need for register control. Such machines are therefore only acceptable for very large quantities of packaging.

In addition, there is a risk that when coating the paper web between the above-described cooling and pressure roller of the plastic, in most cases polyethylene, sticks to the roller at precisely the places where the middle part is removed from the cardboard or the hole is provided, because the adhesion to the paper carrier is missing. It is actually observed that some punched holes are not properly sealed as a result.

To make this known machine cheaper, attempts have also already been made to introduce the holes into the paper web by means of an oscillating punch instead of using a pair of rollers. Although these known devices are cheaper to manufacture and easier to operate, they do not allow the punching knife to penetrate precisely into the exact depth of the paper web.

Instead of the subsequent coating of the completely punched-out paper web, attempts have been made to use the stamping dies on paper webs that have already been coated on both sides. If you go e.g. from a paper thickness of 0.4mm, including the plastic coatings; then the thickness of the outward facing plastic coating is e.g. 0.01 mm, while the plastic layer to be placed inside has a thickness of 0.04 mm. The punching knife should completely punch through the outer thin layer and the paper layer arranged between the two plastic layers, while the plastic coating on the inside should remain intact so that the tightness is not endangered. In the example mentioned above, this means that the punching knife has to be pressed so deep into the coated paper web that the punching depth is 0.35 mm.

However, this exact punch depth cannot be achieved with the disadvantage. Rather, it is often observed that the punch knife is pressed deeper or less deeply into the coated paper web. If the punch is too deep, the tightness of the liquid pack is at risk. Is the If the punching is not deep enough, then piercing the paper web of the finished, filled package with the help of the straw causes considerable difficulties. This known device is particularly dependent on the sharpness of the punching knife. As soon as this becomes dull, there are problems. It has been shown that so far there has been no possibility of setting the pressure with sufficient precision so that the paper web is always punched in at the correct depth.

With knowledge of this difficulty, attempts have already been made to punch the paper web coated on both sides completely and to subsequently seal it again with a plastic film in the area of the hole. However, this effort is too high and such machines are often prone to failure.

The object of the invention is therefore to provide a device of the type mentioned at the outset, which enables the desired hole to be punched into the desired depth with simple means.

The object is achieved in that the punch has a rotatably driven cutting head. The basic idea of the invention lies in the movement of the punch or the edge forming the knife at its tip, so that it is not only pressed into the paper web as in the previously usual pure punching process, but is moved perpendicular to this direction of movement, thereby creating a cutting effect like when using a knife. With this measure, the desired hole is cut, and it is even possible with advantage to insert holes of larger diameter in paper webs in exact cutting depth and over the entire circumference of the same punching or cutting depth. Even if a position on the knife edge protrudes higher than another from the cutting head towards the tip during rough operation of the machine, the rotation around the longitudinal axis of the cutting head, which is perpendicular to the Pa to be punched out, still results pierbahn stands, a cut of uniform depth, because the protruding point of the knife is guided around by the rotation along the entire circumference.

Due to the rotary movement of the cutting head, considerably lower compressive forces are sufficient to insert the cutting head into the paper web to be punched. The consequence of this in turn is the possibility of designing the punching device according to the invention to be smaller and lighter, so that it can be attached in a particularly advantageous manner at appropriate points in the packaging machine. E.g. Suitable carrier beams can be selected, preferably those at the embossing station, so that additional control devices are omitted, which cause increases in price and susceptibility to faults in the known devices.

It is also advantageous according to the invention if the cutting head is held in an outer carrier and can be adjusted and locked relative to this by means of an adjusting nut in the axial direction. In this way you can achieve an exact cutting depth and vary it in the desired way. The adjusting nut is therefore rigidly connected to the cutting head, e.g. by a screw connection, and is supported with its end face against the outer support, which holds the cutting head. This support takes place via a friction clamping surface, which is preferably located on the outer carrier mentioned and against which the adjusting nut can be firmly locked by suitable means, preferably clamping screws.

It is also expedient according to the invention if the cutting head is detachably attached to a drive shaft. The cutting head carrying the knife is therefore advantageously exchangeable as a wearing part and is held by its fastening means in the drive shaft, for example a correspondingly secured screw connection, so that the cutting head is carried along by the drive shaft. The drive shaft in turn is connected to a motor that intermittently or continuously rotates them during the punching process.

The possibility of adjusting the variable but exact cutting depth is further facilitated in that the hollow drive shaft, which is preferably held in an adjustable bearing cylinder via ball bearings, is kept free of play in the direction of its axis. This can be achieved, for example, by a nut with a lock nut placed above it.

In an advantageous further embodiment of the invention, the cutting head and the drive shaft are hollow, the cavities are flush with one another, and the drive shaft is provided with at least one radial bore at its rear end facing away from the cutting head tip. Should, contrary to expectations, the cut forming the middle part in the paper web result in tearing out this middle part from the non-perforated plastic coating, then this piece of cardboard can move backwards through the cavities, which are preferably designed as bores, in the cutting head and further back in the drive shaft and through one or several radial holes (holes) are discharged to the outside.

So that this loosening of the middle part of the paper does not happen in the punched hole area, the circular knife at the tip of the cutting head is preferably designed such that, according to the invention, a circular edge is formed, which is defined by the cutting line between the cylinder of the central bore forming the cavity of the cutting head and one of the cone extends backwards. One surface behind the circular knife edge is therefore a cylindrical surface which surrounds the central bore, and the other surface behind the circular knife edge is a truncated cone surface, the truncated cone moving backwards from the tip of the cutting head, ie from the Paper web continued, expanded. This configuration of the cutting head tip causes friction to be applied to the correct surface parts: the greatest friction occurs with such a cutting head knife on the truncated cone surface described. Here, the greater the pressure, the greater the radius of the truncated cone surface. The lowest friction, however, results in this knife according to the invention in the area of the cylindrical surface, ie on the circumference of the central bore. In this way, the paper middle part can be least torn off from the point of adhesion, preferably from the opposite plastic, by the penetration of the knife with the central bore. The round middle section remains in the paper web.

An exact cutting depth can be provided in a particularly favorable manner in that, according to the invention, the outer carrier holding the cutting head can be pressed against a resiliently mounted plate of large surface area. The counterplate mentioned at the beginning, against which the punch or cutting head is pressed, rests on at least one compression spring which acts in the direction of the lifting movement of the punch (for performing the punching or the cut) and thus in the direction of the longitudinal axis of the hollow drive shaft and Longitudinal axis of the cutting head is compressible.

In a particularly preferred embodiment of the invention, the punching device is arranged on the support bar of an embossing station or the resiliently mounted plate is provided on the opposite part of the bar. In this way, two functions take place simultaneously with the same stroke, embossing the necessary line in the paper web on the one hand and punching holes on the other. If two --- functions are performed simultaneously by parts that can be moved against each other, one function must necessarily be carried out before the other. The resilient mounting of the counter plate gives the punching device the option of performing the punching before the stamping. It is also advantageously achieved by the invention that the distance between the spring-loaded plate and the outer carrier, ie those two surfaces which lie opposite one another in the punching device and between which the paper web to be punched is passed and clamped, determines the depth of penetration of the knife into the paper web. The paper web is clamped between the outer support or its front-side contact surface and the spring-loaded plate (single-layer or double-layer, depending on the requirements) as the one or more springs allow.

The area of the spring-loaded plate is chosen to be large in relation to the hole to be punched, because it eliminates fluctuations in paper thickness.

A scale can also be expediently attached to the adjusting nut, which cooperates with a pointer attached to the outer carrier for the cutting head and drive shaft. In this way you get a simple indication of the cutting depth because the scale can be calibrated in cutting depth.

• Fig. 1 die Querschnittsansicht einer Stanzvorrichtung gemäß der Erfindung von der Seite,
• Fig. 2 eine Draufsicht auf die Stanzvorrichtung der Fig. 1 und
• Fig. 3 abgebrochen und schematisch in vergrößertem Maßstab das kreisrunde Messer an der Spitze des Schneidkopfes in der gewünschten Eindringtiefe in der Papierbahn.

Further advantages, features and possible uses of the present invention result from the following description of a preferred embodiment in conjunction with the drawings. Show it:

• 1 is a cross-sectional side view of a punching device according to the invention,
• Fig. 2 is a plan view of the punching device of Fig. 1 and
• Fig. 3 broken off and schematically on an enlarged scale the circular knife at the tip of the cutting head in the desired depth of penetration in the paper web.

FIGS. 1 and 2 show a punching device with a punch bar on the punch punch side, which is arranged in the area of the stamping station indicated in FIG. 1 and generally designated 1 with the two stamping plates 2 and 3 (on the right in FIGS. 1 and 2) and a support bar 5 on the counter plate side (on the left in FIGS. 1 and 2). On the support beam 4, the outer support 6 is fastened with its end-face contact surface 7, while on the opposite support beam 5, the support bracket 8 for the spring-loaded plate 9 is attached. As already mentioned, the embossing plates 3 and 2 are also fastened to the support beams 4 and 5. These are provided with embossing devices (bulge and channel) at the locations marked with 10.

The spring-mounted counter plate 9 is guided by two screws 11 and supported against the compression spring 12. As a result, it has the possibility of moving in the direction of the double arrow 13 shown in FIG. 2, although the support bar 4 or 5 or both also has the possibility of moving in the direction of the double arrows 14 shown. It can be seen that at least in one direction (perpendicular to the paper plane in Fig. 1 and from top to bottom in Fig. 2 in the paper plane) the spring-mounted plate 9 has a large surface area, in particular in relation to that in the Paper web 15 hole to be punched.

On the support beam 4, the outer support 6 is fastened, which is open on one side towards the rear, forms the contact surface 7 on the front on the front side and is provided in the middle with a further opening through which the cutting head 16 can protrude in front of the contact surface 7. In the cylindrical cavity 17 of this outer carrier 6, an adjustable bearing cylinder 18 is arranged displaceably in the direction of the longitudinal axis 19 of the entire arrangement. The adjustable bearing cylinder 18 is also hollow on the inside and holds the ball bearings 20, which are arranged at a distance from one another in the axial direction 19, for the concentrically arranged and supported hollow drive shaft 21, in the front end of which the cutting head 16 is screwed in, and the rear end of which via the coupling 22 is attached to the drive shaft of the motor 23. In addition, there are two radial bores 24 at this rear end over the frustoconical surface 25 in free Connection to the outside air.

It can be seen in particular from FIG. 1 that the two cylindrical cavities 26 and 27 which are arranged coaxially in the cutting head 16 and are in alignment with one another are in alignment with the cylindrical cavity 28 and are therefore in connection therewith, which as a central bore along the axis 19 in the drive shaft 21 is arranged. Furthermore, the radial bores 24 are connected to the cylindrical cavity 28, so that in operation, pieces of paper punched out of the paper web 15, which should, contrary to expectations, be torn off every now and then, can reach the outside in the manner just described of the interconnected cavities .

The motor 23 is fastened to an elongated motor mounting plate 31 via screws 29 and sleeves 30.

On the adjustable bearing cylinder 18, this motor mounting plate 31 is firmly attached, so that when moving along the axes 19 to the front (in FIGS. 1 and 2 on the left) or to the rear (in FIGS. 1 and 2 to the right), motor 23 with Sleeves 30, motor support plate 31, bearing cylinder 18, drive shaft 21 and cutting head 16 can be moved. So that this displacement in the direction of the axis 19 can be carried out properly and precisely, the adjustable bearing cylinder 18 is clamped absolutely free of play against a movement in the direction of the axis 19 via the ball bearings 20, a spacer 32 and two nuts 33 placed one behind the other.

The adjustment itself is carried out with the aid of the adjusting nut 34, on which a scale 35 shown in FIG. 2 is provided for the interaction with a pointer 36 on the outer carrier 6. By turning the adjusting nut 34, the above-described unit consisting of motor 23, adjustable bearing cylinder 18, drive shaft 21 and cutting head 16 is moved forwards or backwards in the direction of the axis 19 (left or right in the drawings). The adjusting nut 34 acts the friction clamping surface 37 on the outer carrier 6 and is clamped on the other hand via the locking screws 38. In this way, the tip 40 of the cutting head 16 can be adjusted to protrude the desired distance beyond the contact surface 7 of the outer carrier 6.

In Figure 3, the tip 40 of the cutting head 16, which e.g. rotates in the direction of arrow 39 and is pressed into the paper web 15 with the outer plastic layer 41, the carrier material made of paper 42 and the inner plastic layer 43 while cutting. The circular knife at this tip 40 is formed by the circular edge 44, which is formed by a cutting line which results when the cylinder of the central bore forming the front cavity 26 of the cutting head 16 is cut with a cone which extends from the tip 40 extended backwards (upwards in FIG. 3) so that the truncated cone surface 45 results.

The greatest pressure is transferred to the paper web 15 in the areas in front of the truncated cone surface 45 on the outer plastic 41. `Towards the tip 40, this pressure slowly decreases. In the cylindrical cavity 26, the central part 46 is cut out of the paper web 15 by the knife edge 44, which has approximately the shape of a cylinder. The friction between the cylinder jacket and the cylindrical cavity 26 or its surface is towards zero and comparatively less than at the truncated cone surface 45.

In operation, the support beams 4 and 5 move apart, the paper web 15 is conveyed from top to bottom and inserted between the dies 2 and 3 and the contact surface 7 and the surface of the spring-mounted plate 9 opposite this. If the support beams 4 and 5 are now moved towards one another, the single-layer or two-layer paper web 15 initially comes into contact with the resilient surface of the resilient surface, pushed against the contact surface 7 of the outer carrier 6 mounted plate 9, which evades the compression of the spring 12 in FIGS. 1 and 2 to the left. The motor 23 sets the drive shaft 21 with the cutting head 16 in rotation according to arrow 39 in FIG. 3 and in doing so carries out the cut to the desired depth, as shown in FIG. 3. It can be seen from FIG. 3 that the inner plastic layer 43 remains uninjured, so that the tightness is not endangered. The adhesion between the middle piece 46 and the plastic layer 43 is sufficient, or is less than the friction towards the cutting head 16, so that the cylindrical middle part 46 remains stuck even when the cutting head 16 is withdrawn again.

After the punching-cutting process, the cutting head 16 moves out of the position shown in FIG. 3 by moving the support bars 4 and 5 apart again.

The tip 40 of the cutting head 16 protrudes just as far in front of the contact surface 7 of the outer carrier 6 as is to be made in the operation mentioned above, i.e. e.g. by 0; 35 mm if the example mentioned at the beginning is used. The depth of cut is determined by the distance between the resilient plate 9 and the outer support 6 or its front contact surface 7. At this distance, the knife edge 44 can penetrate the paper web 15.

Claims (6)

1. Device for punching a hole in a paper web, in particular for the production of liquid packs, with a movable punch with a circular knife at its tip, which can be guided with pressure against a counterplate, characterized in that the punch (16, 21) is a rotatably driven one Has cutting head (16). 2. Device according to claim 1, characterized in that the cutting head (16) is held in an outer carrier (6) and can be adjusted and locked in relation to this by means of an adjusting nut (34) in the axial direction (19). 3. Apparatus according to claim 1 or 2, characterized in that the cutting head (16) on a drive shaft (21) is releasably attached. 4. Device according to one of claims 1 to 3, characterized in that the cutting head (16) and the drive shaft (21) are hollow, the cavities (26, 27, 28) are in alignment with one another and the drive shaft (21) on it the rear end facing away from the cutting head tip (40) is provided with at least one radial bore (24). 5. Device according to one of claims 1 to 4, characterized in that the circular knife at the tip (40) of the cutting head (16) is formed by a circular edge (44) which by the line of intersection between the cylinder - the Cavity (26) of the cutting head (16) forming central bore and a cone (45) widening backwards from the tip (40). 6. Device according to one of claims 1 to 5, characterized in that the cutting head (16) holding outer support (6) can be pressed against a spring-loaded plate (9) with a large surface.

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