EP0513576A1 - Apparatus for cutting foil webs - Google Patents

Abstract

A cutting device for webs of film by means of intrinsically elastic circular knives which are mounted on a knife-driving shaft and which are axially offset against keyway? cutter bars which are also circular and which are mounted on a keyway cutter bar driving shaft, is described. The circular knives are clamped in intermediate rings (13) which have a circular cylindrical recess (5) on one side, into which a spring element (14) is inserted, which presses the circular knife (1) against the following intermediate ring (13), the point of action of the spring element on the circular knife lying inside the radial diameter of the intermediate ring and the spring effect being so powerful that it does not give way even when there is an axial setting of the keyway cutter bar driving shaft and deformation of the circular knife (1') as a result, resulting in a rigid clamping of the circular knife. <IMAGE>

Description

The invention relates to a device for cutting film webs with inherently elastic circular cutting knives which are interchangeably received in a hub flange of a knife shaft and which are axially adjusted against likewise circular slot knives which are clamped on a slot knife shaft.

• 1. Das Scheibenmesser wird durch eine Feder an das Nutmesser angedrückt.
  Das Prinzip dieser Anordnung zeigt die Figur 1. Entsprechende Vorrichtungen sind bekannt aus den deutschen Patenten 305 586 sowie 24 05 849. Bei dieser bekannten Anordnung sitzt das Scheibenmesser (1) auf Zwischenringen (3) der Scheibenmesserwelle und wird durch eine Feder (4), beispielsweise eine Tellerfeder, zunächst an die Seitenfläche des benachbarten Zwischenrings angepreßt. Da die Feder (4) das Scheibenmesser (2) bei einem Durchmesser beaufschlagt, der größer als der Durchmesser der Anlagefläche des Scheibenmessers am Zwischenring ist, wird das meist dünne Scheibenmesser (z. B. 0,5 mm dick) von der Feder verformt (1' - in Figur 1). Diese Anordnung hat folgende Nachteile
  • Inhomogenitäten in der Umfangsrichtung der Tellerfedern verursachen einen Taumelschlag bei den Scheibenmessern
  • Die Scheibenmesser werden durch eine axiale Verschiebung in Kontakt mit den Nutmessern gebracht, wobei die Feder (4) die Anpreßkraft zwischen Scheiben- und Nutmesser erzeugen soll. Durch die von der Feder verursachte Verformung des Scheibenmessers "zum Nutmesser hin" entsteht eine unerwünschte Berührung der Scheiben- und der Nutmesserkanten. Dadurch entsteht ein erhöhter Messerverschleiß und als Folge davon eine schlechte Schnittqualität
  • Ein weiterer Nachteil ergibt sich daraus, daß üblicherweise eine große Anzahl von Scheibenmessern und eine entsprechende Anzahl von Nutmessern auf Wellen angebracht werden, um breite Bahnen in schmale Streifen zu zerschneiden. Da die Tellerfedern normalerweise in ihrer Steifigkeit gewisse Toleranzen aufweisen, ist diese unerwünschte Verformung der Scheibenmesser unterschiedlich groß, was wiederum Abweichungen im Teilungsmaß der Scheibenmesserwelle, das heißt, Abstand von Messer zu Messer, bewirkt. An sich hat die Dicke der Scheibenmesser keinen Einfluß auf die Wellentoleranzen; die Teilungsgenauigkeit der Scheibenmesserwelle sowie der Summenfehler der Messerwelle (Gesamtlänge) wird zunächst nur durch die Dicke der Zwischenringe festgelegt. Durch die Verformung der Scheibenmesser aufgrund der Federkraft treten jedoch wieder Abweichungen von der theoretischen Wellenteilung auf.
    Vorteilhaft ist bei dieser Anordnung, daß die Scheibenmesser einfach von der Welle demontierbar sind und somit als Paket verspannt nachgeschliffen werden. Dadurch können kurze Schleifzeiten und gute Schleifqualitäten erreicht werden.
  
  In der DE 36 42 005 wird eine Scheibenmesseranordnung beschrieben, bei der durch eine entsprechende Gestaltung der Zwischenringe oder durch die Kraft der Tellerfedern die Scheibenmesser kegelstumpfförmig "zum Nutmesser hin" verformt werden. Dadurch soll eine günstige Berührung zwischen Scheiben- und Nutmesser erfolgen. Nach den Untersuchungen der Anmelderin kommt es hierbei jedoch zu einer Berührung der Messerkanten, wie auch aus Figur 1 erkennbar ist.
  In der DE 968 269 ist ein Kreismesser beschrieben, das aus einer dünnen Ringscheibe besteht, die auf einem ringförmigen Trageglied gehalten wird. Das Kreismesser ist schwach konisch verformt. Die Anpressung des Kreismessers an das Gegenmesser erfolgt federnd durch eine Schraubenfeder. Durch die zusätzliche Verwendung eines Tragrings ist das beschriebene Messersystem im Aufbau sehr kompliziert.
• 2. Die Scheibenmesser sind starr zwischen Distanzringen eingespannt.
  Das Prinzip dieser Anordnung zeigt die Figur 2. Diese Anordnung ist bekannt aus den US-Patenten 4 330 092 und 4 428 265. Bei diesen Anordnungen sind die Scheibenmesser (1) zwischen Distanzringen (9) fest eingespannt und dienen selbst als federndes Element. Da die Scheibenmesser mit engen Toleranzen hergestellt werden und aus hochwertigen Materialien, beispielsweise Hartmetall, bestehen, sind die einzelnen "Federn" sehr gleichmäßig. Eine Verformung der Scheibenmesser erfolgt bei dieser Anordnung, wie die Figur 2 zeigt, so, daß die Kante der Scheibenmesser die Nutmesserkante nicht berührt, wodurch eine Beschädigung der Scheibenmesserkante vermieden wird was günstig für die Schnittqualität ist. Nachteilig an dieser Anordnung ist
  • gegenüber der Anordnung nach Figur 1 werden die Toleranzen von doppelt so viel Teilen beeinflußt (Distanzringe und Scheibenmesser), wodurch ein erhöhter Montage- und Anpassungsaufwand entsteht. Außerdem muß die Dicke der Scheibenmesser mit einer Toleranz von cirka 1 µm gewählt werden, wodurch die Scheibenmesser sehr teuer werden.
  • Erfolgt der Nachschliff der Scheibenmesser auf der Scheibenmesserwelle, entsteht dabei ein hoher Schleifzeitbedarf und Probleme mit der Schleifqualität, da die dünnen Scheibenmesser beim Schleifen federn können. Erfolgt dagegen der Nachschliff im demontierten Zustand als Paket, so entsteht dabei ein großer Montageaufwand wegen der hohen Genauigkeitsanforderung.

The following basic forms are known from the prior art for the construction of the disc knife shaft

• 1. The disc knife is pressed against the slot knife by a spring.
  The principle of this arrangement is shown in FIG. 1. Corresponding devices are known from German patents 305 586 and 24 05 849. In this known arrangement, the disc knife (1) sits on intermediate rings (3) of the disc knife shaft and is supported by a spring (4), For example, a plate spring, first pressed against the side surface of the adjacent intermediate ring. Since the spring (4) acts on the disc knife (2) at a diameter that is larger than the diameter of the contact surface of the disc knife on the intermediate ring, the mostly thin disc knife (e.g. 0.5 mm thick) is deformed by the spring ( 1 '- in Figure 1). This arrangement has the following disadvantages
  • Inhomogeneities in the circumferential direction of the disc springs cause the disc knives to wobble
  • The disc knives are brought into contact with the slot knives by means of an axial displacement, the spring (4) being intended to generate the contact force between the disk and slot knives. Due to the deformation of the disk knife caused by the spring "towards the slot knife" there is an undesirable contact of the disk and slot knife edges. This results in increased knife wear and, as a result, poor cutting quality
  • Another disadvantage arises from the fact that usually a large number of disc knives and a corresponding number of slot knives are mounted on shafts in order to cut wide webs into narrow strips. Since the disc springs normally have certain tolerances in terms of their stiffness, this undesired deformation of the disk knives is of different sizes, which in turn causes deviations in the pitch of the disk knife shaft, that is to say the distance from knife to knife. As such, the thickness of the disc knives has no influence on the shaft tolerances; the division accuracy of the disc knife shaft and the total error of the knife shaft (total length) is initially only determined by the thickness of the intermediate rings. Due to the deformation of the disc knives due to the spring force, deviations from the theoretical shaft pitch occur again.
    It is advantageous with this arrangement that the disc knives can be easily removed from the shaft and thus re-sharpened as a package. This enables short grinding times and good grinding qualities to be achieved.
  
  DE 36 42 005 describes a disc knife arrangement in which the by an appropriate design of the intermediate rings or by the force of the plate springs Disk knives are frustoconically shaped "towards the slot knife". This should result in a favorable contact between the disc and slot knife. According to the investigations of the applicant, however, the knife edges come into contact, as can also be seen from FIG. 1.
  In DE 968 269 a circular knife is described, which consists of a thin washer, which is held on an annular support member. The circular knife is slightly conical. The circular knife is pressed resiliently by a helical spring. Due to the additional use of a support ring, the knife system described is very complicated in structure.
• 2. The disc knives are rigidly clamped between spacer rings.
  The principle of this arrangement is shown in FIG. 2. This arrangement is known from US Pat. Nos. 4,330,092 and 4,428,265. In these arrangements, the disc knives (1) are firmly clamped between spacer rings (9) and serve themselves as a resilient element. Since the disc knives are manufactured with tight tolerances and consist of high-quality materials, such as hard metal, the individual "springs" are very even. The disc knives are deformed in this arrangement, as shown in FIG. 2, so that the edge of the disc knives does not touch the groove knife edge, thereby avoiding damage to the disc knife edge, which is favorable for the cutting quality. This arrangement is disadvantageous
  • Compared to the arrangement according to FIG. 1, the tolerances are influenced by twice as many parts (spacer rings and disc knives), which results in increased assembly and adjustment effort. In addition, the thickness of the disc knives must be selected with a tolerance of approximately 1 µm, which makes the disc knives very expensive.
  • If the disc knives are reground on the disc knife shaft, this results in a high grinding time requirement and problems with the grinding quality, since the thin disc knives can spring during grinding. If, on the other hand, regrinding is carried out as a package in the disassembled state, this results in a large assembly effort due to the high accuracy requirement.

• eine für den Messerverschleiß ungünstige Verformung der Scheibenmesser "zum Nutmesser hin" vermieden wird
• die Scheibenmesser exakt und schwingungsarm fixiert werden
• möglichst wenig genauigkeitsbestimmende Teile vorhanden sind
• eine einfache Montage sowie Demontage der Scheibenmesserwelle möglich ist und somit ein Nachschliff der Scheibenmesser im demontierten Zustand erfolgen kann.

Therefore, the task was to find a cutting device of the generic type mentioned in the

• an unfavorable deformation of the disk knives "towards the slot knife" is avoided for the knife wear
• the disc knives are fixed precisely and with little vibration
• there are as few accuracy-determining parts as possible
• simple assembly and disassembly of the disc knife shaft is possible and regrinding of the disc knives can thus be carried out in the dismantled state.

Figuren 1 und 2

bekannte Schneidevorrichtungen

Figur 3

einen Axialschnitt durch eine prinzipielle Anordnung der erfindungsgemäßen Schneidevorrichtung

Figuren 4 bis 7

spezielle Ausführungsformen der vorliegenden Erfindung.

The object was achieved with a cutting device as described in the characterizing part of claim 1 and shown in principle in FIG. 3. more details the invention emerge from the subclaims, the further figures and the description. The invention is explained in more detail below, namely represent

Figures 1 and 2

known cutting devices

Figure 3

an axial section through a basic arrangement of the cutting device according to the invention

Figures 4 to 7

specific embodiments of the present invention.

As FIG. 3 shows, the disc knives (1) are held on the intermediate rings (13) in such a way that they lie completely flat in the installed state and are not deformed. Each of the intermediate rings (13) has on its one cylindrical side a shoulder or a recess (5) in which one or more spring elements (14) sit, which press the disc knife (1) against the next intermediate ring. Disc knives and intermediate rings sit on a knife shaft (6). If the slot knife shaft is now pressed axially against the disk knife when assembling the disk knife and slot knife shaft to form the entire cutting arrangement, only the disk knife is deformed by the slot knife (2) (1 '). However, the spring force of the spring (14) is so great that it does not give way when the disk knife comes into contact with the slot knife, as a result of which the disk knife is clamped rigidly. As a result, it is also possible that the grooving knife can optionally be applied to the disk knife with its two cutting flanks, so that both knife flanks can be used without dismantling the knife shafts and without regrinding, so that the arrangement has a double service life.

Some preferred arrangements of the cutting device according to the invention are described below, without the invention being restricted thereto.

Figure 4 shows in its left or right part two arrangements, which have in common that the disc spring (4, 4 ') presses the disc knife (1) on the intermediate ring (13) so that the point of attack takes place in the area in which the Disc knife lies axially on the intermediate ring. Either the outside diameter of the plate spring (4) can press against the disc knife (arrangement a) or, conversely, the outside diameter of the plate spring (4 ') can be supported on the radially extending surface (15) of the intermediate ring (13) during the drilling adjacent part of the plate spring presses the disc knife onto the next intermediate ring (arrangement b). In order to achieve the quasi-rigid clamping of the disc knife, the disc spring must have a sufficiently high spring stiffness. In any case, the point of force of the disc spring on the disc knife takes place with a diameter that is radially further inside than the diameter of the intermediate ring.

5 shows, with the same design of the intermediate ring (13), three different designs of spring washers (24, 25, 26), which the arrangement shown in FIG. 4 has in common that their force application point also takes place within the diameter of the intermediate ring (13). The spring ring (24) can have the cross-sectional shape of a U-shaped yoke with two ends projecting in the axial direction, or the cross-sectional shape of an open (isosceles) triangle (25), the two ends of which are supported on the disk knife and the third edge of which is on the intermediate ring supports. The third possibility for the spring ring is a so-called O-ring (26). Metals, plastic or rubber are suitable for the spring washers, the spring washer being able to be designed such that it produces a sufficiently large spring force for this cutting device with a very small spring travel. Due to the described spring washers, a narrow construction of the entire knife shaft is possible, which is particularly important if a wide one Material web is cut into narrow strips, for example in 3.81 mm wide magnetic tape strips for audio tapes.

FIG. 6 shows a further embodiment of the invention. The intermediate ring (23) is provided with bores (7) in the axial direction and has the shape shown in FIGS. 3 to 5. The helical springs (14) distributed around the circumference are supported at one end on the bottom of the bore and at the other end on the disc knife (1). In addition, a ball thrust piece (8) can be inserted between the spring end and the disk knife, as shown in the left part of FIG. 6. If the springs (14) or the ball thrust piece (8) are captively connected to the intermediate ring (23), spring elements that are to be handled separately are avoided in this embodiment, which gives advantages in handling the disassembly and assembly of the disk knife shaft.

Another preferred form can be seen from FIG. 7. The intermediate ring (33) has a radially circumferential groove (21) adjacent to its one side surface, the depth of which in the radial direction extends approximately to the inner bore of the disk knife (1). In this way, a thin elastic spring ring (18) is formed, the outer open end of which is bent and with its side surface (19) presses the disc knife (1) against the next intermediate ring (33), the outside of the open end of the spring ring with the radius of the intermediate ring (33) is flush. To improve the elastic effect, the spring ring has a recess (20) between the outer and inner end on its side facing the disc knife. This device has the same advantages as the one shown in FIG. 6, namely narrow construction, avoidance of variety of parts and is also suitable for cutting narrow strips.

Of course, other embodiments are also possible, for example, according to FIGS. 4 and 5, the disk knife can be pressed in between the radial surfaces (15, 16, 17) of the intermediate rings (13) and the springs (4, 24, 25, 26).

Claims (8)

Device for cutting film webs with inherently elastic circular cutting knives, which are interchangeably received in the hub flange of a knife shaft and are axially adjusted against likewise circular slot knives which are clamped on a slot knife shaft, characterized in that the disk knives (1) are provided by means of intermediate rings ( 13) are clamped on the disc knife shaft, in which each of the cylindrical intermediate rings has on one of its outer surfaces a radial circular cylindrical groove (5) in which one or more spring elements (14) are inserted, one end of which rests on the radial surface of the intermediate ring (13 ) is supported and the other end of which is supported on the circular knife (1) so that the point of application of the spring elements lies within the radial diameter of the intermediate ring (13), so that the disk knife lies completely flat when the disk knife shaft is clamped (1) and only at axial adjustment by the slot measuring he (2) is deformed axially (1 '- Figure 3). Apparatus according to claim 1, characterized in that the spring force of the spring elements (14) is so great that when the grooving knife (2) is turned axially, the disc knife (1) does not deform within the region in which it rests on the intermediate ring (13) becomes. Device according to claims 1 and 2, characterized in that the spring element is a plate spring (4), the outer diameter of which is located either on the disc knife (1) or on the radial surface (15) of the intermediate ring (13) slightly below the outer cylindrical circumference of the intermediate ring supports (Figure 4). Apparatus according to claims 1 and 2, characterized in that the spring element is a deformable ring (24, 25, 26) which has either the cross-sectional area of a U-shaped upwardly open yoke (24), the two open ends of which are on the intermediate ring or supported on the disc knife, or the shape of an open triangle (25), the two open ends of which are supported on the disc knife and the third edge of which is supported on the intermediate ring, or the shape of an O-ring (26) which is pressed in between the intermediate ring and the disc knife ( Figure 5). Device according to Claims 1 and 2, characterized in that the intermediate ring (23) has axially extending bores (7) distributed in the circumference, in which are inserted coil springs (14), one end of which is supported on the bottom of the bore (7) and the other Press the disc knife (1) onto the next intermediate ring (Figure 6). Device according to claim 5, characterized in that a ball thrust piece (8) is inserted between one end of the helical spring (14) and the disk knife. Device according to claims 5 or 6, characterized in that the intermediate ring (23), spring (14) and ball thrust piece (8) are a captive unit. Apparatus according to claims 1 and 2, characterized in that each intermediate ring (33) spanned on the disc knife shaft (6) has a radially extending groove (21) adjacent to its one cylindrical outer surface, the depth of which in the radial direction approximately up to the inner one Bore of the disc knife (1) is sufficient and that the outer open end of the thin spring ring (18) thus formed is bent in the direction of the next intermediate ring (33) and with its side surface (19) presses the disc knife onto the next intermediate ring and that the spring ring comes on has a recess (20) on its side facing the disc knife between the outer and inner ends (FIG. 7).

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