Apparatus for the cross-perforation or cross-cutting of continuous material webs

In a cylindrical knife holder rotatable about its longitudinal axis, at least one groove is present. The groove extends in the direction of the longitudinal axis of the knife holder. Inserted exchangeably in this groove is a perforating knife, the perforating edge of which protrudes over the peripheral surface of the knife holder. The perforating knife, which can be clamped in the groove by a releasable clamping device, is supported, at its end lying opposite the perforating edge, on a stop element disposed in the groove. The stop element rests on supporting elements distributed over the length of the groove, which are adjustable in directions running transversely to the longitudinal extent of the groove. The supporting elements define the once set radial position of the perforating knife.

TECHNICAL FIELD

The present invention relates to an apparatus for the cross-perforation or cross-cutting of continuous material webs.

BACKGROUND

An apparatus of this type is known from DE-A-39 26 640 (FIGS. 1-3) and has a cylindrical knife holder in which two diametrically opposing cutting blades are inserted, which cutting blades protrude with their cutting edge over the peripheral surface of the knife holder. For the reception of the cutting blades, the knife holder is provided with radial grooves, which extend in the direction of the longitudinal axis of the knife holder and which are open towards the peripheral surface of the knife holder. Inserted in these grooves are holding bars, into which are screwed adjusting screws, which are supported by their front ends on the bottom of the grooves. Each holding bar has a projection, on which the associated cutting blade is supported by its end lying opposite the cutting edge. For the clamping of the cutting blades, clamping screws screwed into the knife holder are present, which engage on the holding bars on that side thereof which lies opposite the cutting blades.

For the radial adjustment of a newly inserted cutting blade, the adjusting screws, once the clamping screws are loosened, are screwed individually. Following completion of the adjusting operation, the clamping screws are tightened. The setting of the cutting blades is then checked on the basis of sample cuts. If need be, this adjusting operation has to be repeated one or more times until the correct setting is found. It is clear that this adjusting operation is very time-consuming. To enable the holding bars to receive the adjusting screws, which, for reasons of strength, must have a certain minimum diameter, they must be relatively wide. The effect of this is that the grooves, too, must be made correspondingly wide.

SUMMARY

The object of the present invention is now to provide an apparatus for cross-perforation or cross-cutting of the type stated in the introduction, in which a simple adjustment of a newly inserted perforating or cutting knife is possible, in conjunction with a space-saving construction.

This object is achieved according to the invention with an apparatus having the features of the present application.

Owing to the resilient supporting of the stop element, once the clamping device is loosened, the stop element, together with the perforating or cutting knife, is pushed out of the groove in the radial direction. This facilitates the adjustment of the perforating or cutting knife with respect to a counterpressure cylinder which lies opposite the knife holder and cooperates therewith, since, by rotation of the knife holder, the perforating or cutting knife is brought into contact with the counterpressure cylinder, whereby the perforating or cutting knife is forced back. As soon as the perforating or cutting blade is in the correct position, it is clamped by means of the clamping device.

Preferably, the stop element is supported on a supporting device, which is adjustable in a direction running transversely to the longitudinal extent of the groove. This supporting device serves to store the adjustment position of a perforating or cutting knife, so that, when a knife is changed, the position thereof has no longer to be readjusted. This supporting device further serves to absorb the forces which act on the perforating or cutting blade, and the stop element, in the perforating or cutting operation.

Other preferred refinements of the apparatus according to the invention are defined herein.

DETAILED DESCRIPTION

InFIG. 1an apparatus1for the cross-perforation of continuous material webs is shown, which apparatus has a cylindrical knife holder (knife cylinder)2, which is represented in greater detail inFIG. 2and which cooperates with a counterpressure cylinder3. The knife holder2and the counterpressure cylinder3are driven about their longitudinal axis2′ and3′ in the direction of the arrows A and B, respectively. The continuously moved material web (not represented) to be perforated runs between the knife holder2and the counterpressure cylinder3.

The knife holder2has four grooves4which are open towards its peripheral surface2a, which grooves extend in the direction of the longitudinal axis2′ of the knife holder2and lie diametrically opposite one another in pairs. As shown inFIG. 2, two mutually opposing grooves4perforating knives5are inserted, whilst in the other pair of mutually opposing grooves4filling elements6are inserted. The design of the mounting for the perforating knives5and the filling elements6in the grooves4is explained below with reference toFIGS. 2 to 9.

Self-evidently, at variance with the shown embodiment ofFIG. 2, only one perforating knife5and three filling elements6as shown inFIG. 1, or else four perforating knives5, can be inserted into the grooves4. Under some circumstances, the insertion of filling elements6into grooves4devoid of a perforating knife5can be dispensed with.

As represented schematically inFIG. 2, the perforating knives5and the filling elements6are held in the grooves4by means of a releasable clamping device7. The structure of this clamping device7will be further described with reference toFIGS. 5,8and9.

As shown byFIGS. 3,5,6and7, the perforating edge5aof the perforating knives5protrudes over the peripheral surface2aof the knife holder2. Each perforating knife5is supported at its end lying opposite the perforating edge5aon a stop element8disposed in the groove4, which stop element is provided with a stop member8aon which the perforating knife5rests. The perforating knife5is clamped between this stop element8and a clamping bar9inserted in the groove4. The clamping bar9is provided with a travel-limiting arrangement10configured as a stop, which travel-limiting arrangement cooperates with the stop member8aand limits a movement of the stop element8radially outwards. As shown, in particular, byFIG. 4, a spring arrangement11disposed in the groove4acts on the stop element8, which spring arrangement has at least one, preferably a plurality of pressure springs12acting on the stop element8. These pressure springs12are supported against the bottom4aof the groove. This spring arrangement11or the pressure springs12, once the clamping device7is loosened, force the stop element8radially outwards, the travel-limiting arrangement10, as already mentioned, preventing the stop element8, once the clamping bar9is inserted, from being pushed fully out of the groove4.

AsFIGS. 3,6and7show, the stop element8is supported on a supporting element14of a supporting arrangement13. The latter has a number of such supporting elements14, which are distributed over the length of the groove4. Each supporting element14is adjustable in directions C, D running transversely to the longitudinal extent of the groove4. Each supporting element14has a support surface14a, which is inclined in the direction of displacement C of the supporting element14. The stop element8rests on this support surface14awith a counterface8b, which is inclined in accordance with the support surface14a. Each supporting element is connected to an adjusting arrangement15, with which the supporting element14can be adjusted in the direction of the arrow C or in the opposite direction in the direction of the arrow D. The adjusting arrangement15has a transmission element16, which is disposed in a transverse bore17in the knife holder2. The transmission element16is surrounded by a pressure spring18, which is supported at one end against a flange16aof the transmission element16and at the other end against a shoulder17aof the transverse bore17. At that end of the transmission element16which lies opposite the stop element14, the transmission element bears against an adjusting member19, which is mounted rotatably in the knife holder2by means of a thread20(not represented in detail). In a bore21in the knife holder2, which bore runs transversely to the transverse bore17, there is disposed a plastics pressure body22, which bears with an end face against the adjusting member19and, at the opposite end face, is in contact with a fixing threaded locating pin23, which is screwed into the bore21. By means of the threaded locating pin23, the adjusting member19, via the pressure body22, can be secured in its respective rotational position. The working method of the supporting arrangement13and of the adjusting arrangement15will be explained later with reference toFIGS. 6 and 7.

Below, the structure of the clamping device7is described with reference toFIGS. 5,8and9.

The clamping device7has a number of clamping elements24distributed over the length of the groove4, which are respectively disposed in a transverse bore25in the knife holder2(FIG. 5). Each clamping element24has a clamping member26, which is designed to be pushed against the clamping bar9by means of a spring arrangement27. This spring arrangement27is formed by a cup spring assembly or a cup spring column28. The working direction E of the spring arrangement27runs transversely to the longitudinal extent of the groove4. The spring arrangement27is supported at one end against the clamping member26and bears at the other end against a tensioning element29, which is mounted rotatably in the knife holder2by means of a thread30(not represented in detail). A retaining bolt31passes through the spring arrangement27and engages at one end in an opening32in the clamping bar9. This retaining bolt31prevents the clamping bar9from falling out once the clamping device7is loosened. In the transverse bore25there is disposed a travel-limiting screw33, which is screwed into the knife holder2. This travel-limiting screw33limits the path of movement of the tensioning element29and prevents the tensioning element29from being unscrewed too far out of the knife holder2.

Below, the working method of the clamping device7and of the clamping elements24is explained with reference toFIGS. 8 and 9respectively.

InFIG. 8, the clamping device7, that is to say one of its clamping elements24, is shown in the clamping position in which the tensioning element29is screwed far enough into the knife holder2that the cup spring assembly or cup spring column28is compressed. The generated force acting in the working direction E is transmitted via the clamping member26to the clamping bar9. The perforating knife5is thereby clamped between the stop element8and the clamping bar9.

FIG. 9shows the clamping element in the loosened state. The tensioning element29is unscrewed to the point where the cup spring assembly or cup spring column28is slackened. In this loosened state, too, the retaining bolt31engages in the opening32in the clamping bar9and prevents the clamping bar9from falling out of the groove4.

The shown and described embodiment of the clamping elements24has the advantage that the rotary movement of the tensioning element29is not transmitted to the clamping member26, and nor, therefore, to the clamping bar9. The relatively high clamping force generated by the cup spring assembly or cup spring column28is transmitted by frictional contact to the clamping bar9.

InFIGS. 6 and 7, the adjusting device15is shown in a first, rear end position (FIG. 6) and in a second, front end position (FIG. 7). In both end positions, the stop element8rests with its counterface8bon the support surface14aof the supporting element14. Between the supporting element14and the stop element8, a positive connection exists. A positive connection of this kind also exists between the stop element8and the perforating knife5resting on the stop member8aof the stop element8.

In order to obtain this positive connection between the supporting element14and the stop element8, and thus between the perforating knife5and the supporting element14in respect of each radial adjustment position of the perforating knife5, the supporting element14can be displaced out of the rear adjustment position shown inFIG. 6, in the direction of the arrow C, towards the front adjustment position shown inFIG. 7. All intermediate positions are here continuously adjustable. The supporting element14is fixed in the respectively set adjustment position by tightening of the threaded locating pin23.

The pressure spring18ensures that, when the adjusting member19is unscrewed, the supporting element14is automatically forced back in the direction of the arrow D.

The supporting elements14absorb the forces which in the perforating operation act on the perforating knife5and the stop element8.

The supporting elements14fixed in a specific adjustment position fix the adjustment position of the perforating knife5. This means that, when the perforating knife5is changed, the new perforating knife can be inserted into the groove4without the need for a new adjusting operation. In the event of a knife change, the new perforating knife5, once the clamping elements24are loosened, is inserted between the stop element8and the clamping bar9and, together with the stop element8, is forced back to the point where the stop element8butts against the supporting elements14. The clamping elements14are then brought into the clamping position shown inFIG. 8.

When a perforating knife5is inserted for the first time, its working position must naturally be set. For this, the clamping elements24are totally released (seeFIG. 9) and the supporting elements14are moved into their rear end setting (seeFIG. 6). Then a perforating knife5is pushed between the clamping bar9and the stop element8, which is pushed radially outwards by means of the pressure springs12. Through rotation of the knife holder2, the perforating knife5is guided past the counterpressure cylinder3and, together with the stop element8, is hereupon forced back. In the adjustment position which has thus been fixed, the clamping elements24are tightened to the point where the perforating knife5is secured between the clamping bar9and the stop element8. The supporting elements14are now advanced in the direction of the arrow C, until their support surface14abears against the counterface8bof the stop element8. The clamping elements24are then brought into their clamping setting (seeFIG. 8) by rotation of the tensioning elements29.

If, in place of the perforating knives5with perforating edge5a, cutting knives provided with a cutting edge are inserted into the grooves4, then the apparatus described with reference toFIGS. 1 to 9can be used for the cross-cutting of continuous material webs.