EP0065179B1 - Apparatus for cutting a hole in a paper web - Google Patents

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 a circular knife at its tip, which can be pressed against a counterplate, the punch having a rotatably driven cutting head.

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 punching hole, in which the paper web is completely punched out and the punched-out piece of paper or cardboard is completely removed from the paper web. The resulting leakage must in turn be compensated for by a 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 justifiable for very large quantities of packaging.

In addition, there is a risk that when the paper web is coated between the cooling and pressure roller, the plastic, in most cases polyethylene, will stick to the roller at precisely the points where the middle part is detached from the cardboard or the hole is provided because there is no liability towards the paper backing. It is actually observed that some punched holes are not sealed properly.

A punching device of the type mentioned is shown and described in GB-A-1 150 785. This device is used to punch thick pieces of paper. The entire machine housing with motor and drill are movably arranged in relation to a stationary paper platen. The waste chips punched out with the cutting knife are transported upwards by a hollow shaft. The well-known drilling and piercing device can be used for office use, but a hole cannot be punched into this depth to a desired depth.

The situation is similar for the device according to US Pat. No. 3,066,554, in which a web is also completely punched through, so that a web provided with holes is created after the punching process. The punched round plates are also removed in this device, only that they are thrown outwards in an area not far from the cutting knife through an opening. With all devices known to date, it was not possible to ensure the precise penetration of a punching knife into the exact depth of a paper web.

Instead of a subsequent coating of a completely punched-out paper web, attempts have already been made to use the stamping dies on paper webs already coated on both sides. If you go e.g. from a paper thickness of 0.4 mm, including the plastic coatings, then the thickness of the outward-facing plastic coating is z. B. 0.01 mm, while the inward-facing plastic layer receives 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 lying on the inside should remain intact so that the tightness is not endangered. In the example given 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 frequently 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. If the punch 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 print with sufficient precision, so that the paper web is always punched in at the correct depth.

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 according to the invention in that the cutting head is held in an outer carrier and can be adjusted and locked in relation to this by means of an adjusting nut in the axial direction, that the outer carrier can be pressed against a spring-mounted plate with a large surface area, and that the circular knife on the Tip of the cutting head is formed by a circular edge. The basic idea of the invention lies in the movement of the punch or the edge forming the knife at its tip, so that there is a cutting effect, even holes of larger diameter in paper webs in exact cutting depth and over the entire circumference of the same punching or cutting deep can be introduced. Even if one place 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 paper web to be punched out, results in a cut of uniform depth.

By holding the outer carrier and its adjustability in the axial direction, an exact cutting depth can be achieved and this can be varied as desired. 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 carrier, 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.

The exact cutting depth is ensured in a particularly favorable manner by the fact that the outer carrier holding the cutting head can be pressed against the 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 an advantageous 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 performed before the other. The resilient mounting of the counter plate gives the punching device the possibility 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, i. H. those two surfaces, which are opposite each other 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 carrier 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 this eliminates fluctuations in paper thickness.

It is also expedient according to the invention if the cutting head is releasably attached to a drive shaft. The cutting head carrying the knife is therefore advantageously exchangeable as a wearing part and is fastened by its fastening means in the drive shaft, for. B. a correspondingly secured screw connection, held so that the cutting head is carried by the drive shaft. The drive shaft in turn is connected to a motor that intermittently or continuously rotates it 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 led outwards.

So that this loosening of the paper middle part does not happen in the punch hole area, the circular edge is preferably formed by the cutting line between the cylinder of the central bore forming the cavity of the cutting head and a cone which widens backwards from the tip. One surface behind the circular knife edge is therefore a cylindrical surface that surrounds the central bore, and the other surface behind the circular knife edge is a truncated cone surface, the truncated cone expanding backwards from the tip of the cutting head, that is, away from the paper web. 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 least by the penetration of the knife with the central bore from the point of adhesion, preferably from the counter overlying plastic. The round middle section remains in the paper web.

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 shows the cross-sectional view of a punching device according to the invention from the side,
• 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.

1 and 2 show a stamping device arranged in the area of the stamping station indicated in FIG. 1 and generally designated 1 with the two stamping plates 2 and 3, with a carrier bar 4 on the punch stamp side (on the right in FIGS. 1 and 2) and a carrier bar 5 on the counter plate side (left in Figs. 1 and 2). On the support beam 4, the outer support 6 is attached with its end face 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 movement 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 the paper plane in FIG. 2), 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 bar 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 via the truncated cone 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 pieces of paper punched out of the paper web 15 during operation, which should be torn off from time to time unexpectedly, can escape to the outside in the same way as 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 to the left) or to the rear (in FIGS. 1 and 2 to the right), the motor 23 also 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 correctly and exactly, 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 on the outer carrier 6 via the friction clamping surface 37 and, on the other hand, is clamped 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.

3 shows schematically and broken off the tip 40 of the cutting head 16, which rotates, for example, 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 created by an intersecting line results if the cylinder of the central bore forming the front cavity 26 of the cutting head 16 is cut with a cone which widens backwards (in FIG. 3 upwards) from the tip 40, 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. This pressure slowly decreases towards the tip 40. 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 carrier beams 4 and 5 are now moved towards each other, the single-layer or two-layer paper web 15 initially comes into contact with the surface of the spring-mounted plate 9, which is pushed against the contact surface 7 and is pushed against the contact surface 7 of the outer carrier 6 and which is pressed together Spring 12 in FIGS. 1 and 2 evades 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 in that the carrier bars 4 and 5 are moved 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 the incision is to be made in the aforementioned operation, i. H. e.g. B. by 0.35 mm if the example mentioned above 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 (4)

1. Apparatus for punching a hole in a web of paper, in particular for the production of liquid packs, comprising a movable punch which can be moved under pressure towards a counter-plate and which has a circular blade at its tip, wherein the punch (16, 21) has a rotatably driven cutting head (16) characterised in that the cutting head (16) is held in an outer carrier (6) and can be adjusted and arrested relative to the carrier in the axial direction (19) by means of an adjusting nut (34), that the outer carrier (6) can be pressed against a resiliently mounted plate (9) of large surface area, and that the circular blade at the tip (40) of the cutting head (16) is formed by a circular edge (44).

2. Apparatus according to claim 1 characterised in that the cutting head (16) is releasably fixed to a drive shaft (21).

3. Apparatus according to claim 1 or claim 2 characterised in that the cutting head (16) an the drive shaft (21) are hollow, the hollow spaces (26, 27) are in alignment with each other and the drive shaft (21) is provided with at least one radial bore (24) at its rearward end which is remote from the tip (40) of the cutting head.

4. Apparatus according to one of claims 1 to 3 characterised in that the circular edge (44) is provided by the line of intersection between the cylinder of the central bore forming the hollow space (26) in the cutting head (16), and a conical portion (45) which increases in size in a rearward direction from the tip (40).

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