DE20022182U1 - Narrow knife holder for a device for slitting material webs - Google Patents

Description

Designation: Narrow knife holder for a device for slitting material webs

Description
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Knife holders are used to cut material webs lengthwise. These are attached to a knife bar that is aligned transversely to the direction of travel of the material web and are each equipped with a rotatably mounted circular knife that interacts with the cutting edge of a rotating counter knife or cutting ring, so that the material web that is running through is cut lengthwise into longitudinal strips in accordance with the number of knife holders used, like a scissor cut. The width of the longitudinal strips is determined by the distance between the knife holders. This means that the smallest possible width of the longitudinal strips is also determined by the width of the knife holders.

Such a knife holder has a base body which is designed in such a way that it can be detachably attached to the knife bar. The base body is designed on the side facing away from the circular knife as a piston-cylinder unit which can be pressurized with compressed air and whose piston is rigidly connected to a holding arm on which the circular knife is mounted. The bearing of the circular knife is provided with a further, usually pneumatic actuator for generating the transverse movement. With the help of the pneumatic piston-cylinder unit, the circular knife is first fed in the direction of the counter knife and after reaching a predeterminable immersion depth, i.e. a predeterminable overlap of the cutting edge of the circular knife with the cutting edge of the counter knife, the second actuator is controlled and the circular knife is brought into contact with the cutting edge of the counter knife with a predeterminable drive force. Such a narrow knife holder is known, for example, from WO99/16594.

The invention is based on the object of creating a knife holder of the type described above, with which an even smaller overall width can be achieved.

This object is achieved by a knife holder for a device for slitting a material web lengthwise, with a flat base body that can be attached to a knife bar, in which a holding arm provided with a rotatable circular knife is arranged so that it can be moved longitudinally and transversely to the sliding direction and which is connected on the one hand to a piston of a pneumatic actuator via at least one hard spring element and on the other hand is supported on the base body via at least one soft spring element, wherein an actuating element connected to the piston is provided, which acts on the holding arm to generate the transverse movement. The advantage of the knife holder designed according to the invention is that the piston of the pneumatic actuator is decoupled from the actuating element with respect to the holding arm with the circular knife and is only connected to one another in the closing-0 actuating direction via the hard spring element. As a result of the support via the soft spring element on the base body, when pressure is applied to the pneumatic actuator, the piston is advanced together with the actuating element while the soft spring element is compressed. As soon as an end position is reached, which can conveniently be specified by an adjustable stop on the base body, the piston with the actuating element is pushed further forward relative to the holding arm when further pressure is applied, whereby the hard spring element is then compressed and at the same time the transverse movement of the holding arm and thus the transverse movement of the circular knife is generated via the actuating element connected to the piston.

Since the base body, which is preferably designed like a housing, can be included for the guidance and support of the individual moving parts, a knife holder can be created which, despite its narrow design, has high

rigidity. All parts required for the movements are conveniently arranged within the housing-like base body and are thus protected. It is particularly useful if the actuating element connected to the piston on the one hand and the holding arm guided in the base body on the other hand are arranged parallel to one another. This makes it possible, despite the narrow design, to provide relatively large material cross-sections for both the holding arm and the actuating element, so that correspondingly large forces can be transmitted. A further advantage of a housing-like design of the base body is that the walls of the housing enclosing the actuating element and the holding arm can be used for support at the same time, so that even with a relatively flat actuating element, no problems can arise due to the actuating element buckling. This also makes it possible to make the holding arm relatively thick and thus rigid, so that the cutting forces are reliably absorbed, and to provide a correspondingly smaller thickness for the actuating element.

A knife holder is known from DE-C-24 25 201, which has a cylinder with a circular cross-section as its base body, in which a corresponding piston is guided on a piston rod. An adjusting rod is guided longitudinally in the piston rod, which is provided with a longitudinal bore and a transverse window, and is pushed forward by a spring in the direction of the circular knife connected to the piston rod. A stop element is arranged on the adjusting rod, which extends 0 through the transverse window. When pressure is applied to the piston, the piston rod is lowered together with the circular knife. As soon as the stop element comes into contact with a counter stop fixed to the housing, the circular knife, which is pivotably mounted on the piston rod, is pivoted via a pressure head on the fixed adjusting rod via the piston rod, which continues to lower 5 relative to the now fixed adjusting rod, and thus against the cutting edge of the knife.

This well-known knife holder is very wide, whereby essential functional parts, namely the adjustment mechanism for the pivoting movement, are exposed and can thus become dirty. The holding arm can be guided directly in the base body. However, according to one design, it is advisable to arrange a sliding body in the base body on which the holding arm is mounted so that it can move transversely. This achieves decoupling. The sliding body largely absorbs the forces in the sliding direction, so that it is practically only acted upon by the forces required for the transverse movement and the cutting forces.

The circular knife for the knife holder according to the invention is expediently designed as a so-called spring-loaded knife, so that the required spring-loaded contact of the cutting edge of the circular knife with the cutting edge of the counter knife is brought about directly by the spring-loaded properties of the circular knife itself and accordingly the holding arm can be pressed against an end stop in its transverse movement via the adjusting element.

In an advantageous embodiment of the invention, it is provided that the holding arm is connected to the sliding body with respect to its transverse movement via at least one return spring element. This arrangement has the advantage that when pressure is applied to the pneumatic actuator, the actuating element acting on the holding arm initially moves it into its working position against the force of the return spring element, so that the circular knife rests against the counter knife. When the pressure is released, the return spring moves the cutting edge of the circular knife away from the cutting edge of the counter knife before the holding arm is raised to its starting position.

In an embodiment of the invention, it is provided that at least one pressure body is arranged on the actuating element or on the holding arm to generate the transverse movement, and correspondingly at least one pressure body is arranged on the holding arm or on the actuating element for sliding

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counter pressure surface inclined in the direction. This makes it possible to generate the required transverse movement as soon as the holding arm or the sliding body rests against its end stop when pressure is applied to the pneumatic actuator and then, under the influence of the pressure force, the piston with the actuating element is pushed further in the sliding direction past the holding arm. The pressure body runs onto the pressure surface designed as an inclined plane and thus causes the transverse movement of the holding arm relative to the base body and thus the contact of the circular knife with the counter knife.

The support of the holding arm on the sliding body to generate the transverse movement can be carried out in different ways. In one embodiment of the invention, the holding arm is supported on guide pins on the sliding body that are aligned transversely to the sliding direction. In another embodiment, the holding arm is pivotably connected to the sliding body via a joint with its axis aligned transversely to the sliding direction. In both embodiments, the arrangement is such that at least one return spring element is provided for the holding arm.

Depending on the design of the return spring element, it is also possible to use the return spring element to create the necessary guidance of the holding arm for the transverse movement.

The invention is explained in more detail using schematic drawings of embodiments of a knife holder designed according to the invention, from which further features of the invention can be seen. They show:

Fig. 1 a vertical section through a

knife holder,
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Fig. 2 is a partial section along line II in Fig. 1,

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Fig. 3 in a section corresponding to Fig. 2 a modification of the embodiment according to Fig. 1,

Fig. 4 an embodiment with hinged

holding arm,

Fig. 5 in a section corresponding to Fig. 2 a further modification of the embodiment according to Fig. 1.

Fig. 6 in a front view the arrangement

a version with reinforced pneumatic actuator, 15

Fig. 7 shows a partial section according to VII in Fig.

by a first knife holder of the arrangement,

0 Fig. 8 a partial section according to VIII in Fig.

for a second knife holder of the arrangement .

The knife holder shown in the working position in Fig. 1 consists essentially of a base body 1 which can be fastened to a knife bar 3 of a device for slitting material webs lengthwise via holding means 2 which are only shown schematically here. The base body 1 is essentially designed as a flat box and has a frame part 0 which is covered on both sides by two thin, preferably dimensionally stable plates 1.2 (Fig. 2). At its upper end there is a cylinder chamber 4 which can be supplied with compressed air via a supply line. A piston 5 is arranged in the cylinder chamber 4 and is guided so as to be displaceable in the direction 5 of the double arrow S in the base body 1 via guide pins 6.

In the base body 1, a sliding body 7 is also slidably guided, which is supported on the base body 1 via soft spring elements 8 and which is connected to the piston 5 via hard spring elements 9. The sliding body 7 has a nose 10, to which an adjustable stop 11 is assigned on the base body 1, which is formed, for example, by a spindle that can be actuated from the outside.

A holding arm 12 is connected to the sliding body 7. The connection between the holding arm 12 and the sliding body 7 is explained in more detail below for the different embodiments. A circular blade 13 is mounted so that it can rotate freely at the free end of the holding arm. In the embodiment shown here, the circular blade is designed as a so-called spring-loaded circular blade. For this purpose, notches 14 are provided on the hub side of the circular blade 13, which limit corresponding spring tongues so that the circular blade has a corresponding elastic flexibility perpendicular to the plane of the drawing.
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The circular knife 13 is assigned a counter knife G with a cutting edge Gl, on which the cutting edge 13.1 of the circular knife 13 lies with corresponding contact pressure.

5 The holding arm 12 is divided in this embodiment into an arm part 12.1 connected to the sliding body 7 and an arm part 12.2 supporting the bearing of the circular knife. The two arm parts 12.1 and 12.2 can be firmly connected to one another via a lockable plug or screw connection 15. This arrangement allows a damaged circular knife to be replaced by loosening the holding arm part 12.2 without having to detach the knife holder from the knife bar 3. This means that a predetermined distance setting of the knife holder to the neighboring knife holders remains unchanged even when replacing a damaged or blunt circular knife.

The holding arm 12 is mounted on the sliding body 7 so that it can move transversely (arrow Q) to the sliding direction (arrow S) (Fig. 2). In the sliding direction, however, the holding arm 12 is immovably connected to the sliding body 7 so that when the sliding body 7 moves in the direction of arrow S, the circular knife can be moved in a defined manner against the counter knife G or lifted off again.

In the embodiment shown in Fig. 1, the holding arm 12 or the arm part 12.1 is mounted on guides 16 so that it can be moved against the force of return springs 17. Depending on the design of the return springs 17, for example when using disc springs, these can also guide the holding arm 12, so that separate guides can be omitted. 15

When the pneumatic actuator is depressurized, the soft spring elements 8 and the hard spring elements 9 are relieved, so that the piston is initially in an upper basic position. If the cylinder 4 is subjected to pressure, the piston 5 slides over the hard spring elements

the sliding body 7 downwards against the force of the soft spring elements 8 until the projection 10 comes to rest against the stop 11. The hard spring elements are not compressed in this case.
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To generate the transverse movement, a tongue-like actuating element 18 is firmly connected to the piston 5 and is provided with one or more, for example wedge-shaped, pressure bodies 19 which act on corresponding counter-pressure surfaces 20 on the holding arm 12, as can be seen from the section in Fig. 2.

However, as soon as the sliding body 7 rests against the stop 11, the piston 5 with its adjusting element 18 moves further in the sliding direction S relative to the holding arm 12, so that the wedge-shaped pressure body 19 runs onto the counter-pressure surface 20 acting as an inclined plane and thereby counteracts the force of the

Return spring elements 17 move the holding arm 12 transversely (arrow Q) so that the cutting edge 13.1 of the circular knife 13 comes into contact with the cutting edge G.l of the counter knife G, as shown in Fig. 1. The adjusting element is supported on the plate 1.2 so that deformation is excluded despite the small thickness.

If the cylinder 4 is depressurized, the hard spring elements 9 initially push the piston 5 together with the actuating element 18 into an intermediate position relative to the sliding body 7, so that the soft spring elements 8 can then return the sliding body 7 with the holding arm 12 and together with the piston 5 into the basic position.

Instead of arranging guide pins 16 with spring elements 17, it is also possible, as the section according to Fig. 3 shows, to attach the holding arm 12 to the sliding body 7 via an elastomer spring body 21. If the pneumatic actuator is subjected to pressure, the sliding body 7 with the holding arm 12 is pushed forward to the stop 11 and then the actuating element 18 is pushed further relative to the holding arm 12, the elastomer body 21 is compressed and the transverse movement is brought about.

Fig. 4 shows a modification of the embodiment according to Fig. 1. Components that correspond to the embodiment according to Fig. 1 are provided with the same reference numerals, so that reference can be made to the preceding description.

The difference from the embodiment according to Fig. 4 is that the arm 12 is pivotably mounted on the sliding body 7 via a joint 22. The pivot axis of the joint 22 is aligned perpendicular to the sliding direction (arrow S).

5 In relation to the joint 22, the holding arm 12 is designed as a two-armed lever. The lever part facing the piston 5 is in turn supported by return spring elements 17 relative to the

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Sliding body 7 is supported. As soon as the tongue-like actuating element 18 is pushed forward in the direction of the circular blade 13 with further pressure being applied to the cylinder 4 after the sliding body 7 has rested on the stop 11, the pivoting movement is brought about by the action of a corresponding pressure body 19 on the counter-pressure surface 20 on the holding arm 12 and the cutting edge of the circular blade is brought into contact with the cutting edge of the counter blade.

In Fig. 5, a modification of the embodiment according to Fig. 1 in conjunction with Fig. 2 is shown in the basic position with the pressure-relieved cylinder 4 in a section corresponding to Fig. 1.

In this embodiment, the piston 5 is firmly connected to an actuating element 18 designed as a flat slide, which is supported directly in the lower area of the base body 1 via the soft spring element 8. Instead of a sliding body 7, in this embodiment the holding arm 12.3 0 is connected directly to the actuating element 18 via the hard spring element 9. The holding arm 12.3 is provided with elongated holes 22 through which guide pins 23 are inserted, which are firmly connected to the actuating element 18. On the side facing away from the actuating element 18, return springs 17, 5, for example disc springs, are provided, which press the holding arm 12.3 against the actuating element 18 in the basic position shown here. At the lower end of the base body 1, a stop 11.1 is also provided here, which can be designed to be adjustable. However, it is also possible, as shown in Fig. 10, to provide the holding arm 12, similar to the sliding body 7 in the embodiment according to Fig. 1, with a nose 10 which can come into contact with a correspondingly designed adjustable stop 11.

5 If cylinder 4 is now pressurized with air, then

First, the adjusting element 18 compresses the soft spring element, whereby the holding arm 12.3 ....... ......... ....... .: ....... : : .:

is moved downwards in the sliding direction S until the nose-shaped projection 10 comes to rest on the stop 11.1. When further pressure is applied, the hard spring element 9 is then also compressed so that the actuating element 18 can move further in the sliding direction S relative to the holding arm 12.3 until the pressure body 19, which is for example wedge-shaped, runs onto the corresponding counter surface 20 acting as an inclined plane and, during further movement in the sliding direction S, moves the holding arm 12.3 against the force of the return springs 17 in the transverse direction (arrow Q), and thus brings the circular knife connected to the holding arm 12.3 to rest on the cutting edge of the counter knife.

With very narrow knife holders of the type according to the invention, it can happen that the piston surface of the pneumatic actuator is no longer sufficient to generate sufficient actuating forces at the pressures available. This problem can be solved with the embodiment described below with reference to Figs. 6, 7 and 8. The structure and function essentially correspond to the embodiments described above, so that the same components are provided with the same reference numerals.

The solution is achieved by providing two different knife holder types A and B, which are constructed in two parts and have a base body part I which is connected to a separate piston-cylinder part II. This makes it possible to design type A as described for example for the embodiment according to Fig. 1. Type B has a narrow bridge part III between the base body part I and the piston-cylinder part II. The piston-cylinder parts II can therefore be made wider than the base body parts I. The arrangement of the bridge part III in each type B means that the knife holders can be positioned "close together" with their parts II offset higher up on the knife bar 3 despite the wide piston-cylinder parts II.

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Like the partial section according to Fig. 7, type A corresponds in construction to the design according to Fig. 1, for example. Only part II containing the cylinder chamber 4 is detachably attached to part I for manufacturing reasons.
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The partial section according to Fig. 8 for type B shows that the
Part I and Part II over a bridge-shaped section
III, which consists of two bridge webs 25. The sliding body 7 has corresponding extensions 7.1, which are connected to the

Piston 5 are connected. The tongue-like actuating element 18.1 connected to the piston 5 is correspondingly longer, but is otherwise identical in structure and function to the previously described embodiments.

Arrangement, design and function of the sliding body
connected holding arm 12 also corresponding to the previously described embodiments.

0 Another possible solution is to use a

Base body I two piston-cylinder parts with the same width
like the basic body I, one above the other, in order to
to achieve a double active piston area. Both pistons
are connected to each other via a connecting element at least in the pressure direction 5, so that when pressure is applied
both pistons have a higher actuating force despite the small width
becomes effective.

Claims (8)

1. Knife holder for a device for longitudinally dividing a material web, with a flat base body (I) which can be fastened to a knife bar ( 3 ), in which a holding arm ( 12 ) provided with a rotatable circular knife ( 13 ) is arranged so as to be longitudinally displaceable and movable transversely to the sliding direction (S) and which is connected on the one hand via at least one hard spring element ( 9 ) to at least one piston ( 5 ) of a pneumatic actuator and on the other hand is supported on the base body (I) via at least one soft spring element ( 8 ), wherein an actuating element ( 18 ) connected to the piston ( 5 ) is provided, which acts on the holding arm ( 12 ) to generate the transverse movement (Q). 2. Knife holder according to claim 1, characterized in that the holding arm ( 12 ) is arranged to be transversely displaceable in a sliding body ( 7 ) which is supported on the base body by at least one soft spring element ( 8 ) and which is connected to the piston ( 5 ) and the actuating element ( 18 ) via at least one hard spring element ( 9 ), which acts on the holding arm ( 12 ) to generate the transverse movement. 3. Knife holder according to claim 1 or 2, characterized in that the holding arm ( 12 ) is connected to the sliding body ( 7 ) with respect to its transverse movement via at least one return spring element ( 17 ). 4. Knife holder according to one of claims 1 to 3, characterized in that at least one pressure body ( 19 ) is arranged on the adjusting element ( 18 ) or on the holding arm ( 12 ) to generate the transverse movement, to which at least one counterpressure surface ( 20 ) inclined with respect to the sliding direction (S) is assigned on the holding arm ( 12 ) or on the adjusting element ( 18 ). 5. Knife holder according to one of claims 1 to 4, characterized in that the holding arm ( 12 ) is mounted on the sliding body ( 7 ) on guide pins ( 16 ; 23 ) aligned transversely to the sliding direction (S). 6. Knife holder according to one of claims 1 to 4, characterized in that the holding arm ( 12 ) is pivotally connected to the sliding body ( 7 ) via a joint ( 20 ) with its axis aligned transversely to the sliding direction (S). 7. Knife holder according to one of claims 1 to 6, characterized in that an adjustable stop ( 11 ) for limiting the sliding path of the sliding body ( 7 ) is arranged on the base body (I). 8. Knife holder according to one of claims 1 to 7, characterized in that a base body part (I) is provided which can be connected to a separate piston-cylinder part (II) and that the base body part (I) can be connected to the piston-cylinder part (II) either directly or via a bridge part (III).