FR2672837A1 - CUTTING DEVICE, IN PARTICULAR FOR REFINING PLASTIC FILMS. - Google Patents

Abstract

The cutting device for slitting a plastic film, which moves continuously between two transfer rolls rotating about horizontal axes and which is maintained under mechanical tension between the two rolls, comprises a knife with a circular edge. The circular-edged knife 6 consists of a thin disc with a sharp edge which is driven in slow rotation about an axis substantially parallel to that of the transfer rollers 3 and 4, and which, in the cutting position, intersects from below by penetrating through a circular segment 6a the oblique plane 5, inclined substantially at 45 degrees relative to the horizontal, formed by the film 2 between said cylinders, and the direction of rotation F of the disc is such that the tangential displacement of its edge of cutting 6b in the zone which intersects the film is carried out in the direction opposite to the displacement of the film 2. Application to the cutting of the edges of a thin plastic film.

Description

CUTTING DEVICE, IN PARTICULAR FOR REFINING

FILMS OF PLASTIC MATERIAL

  The present invention relates to a cutting device, intended in particular for slitting or cutting in banks a plastic film which moves continuously between a first and a second rotating transfer cylinder

  around horizontal axes and is kept under mechanical tension

  between said first and second cylinders, this arrangement

  tif comprising a circular cutting knife mounted on a support arm Such a device meets in particular

  in an installation for the continuous production of

  these or films of plastic material, in particular when it comes to eliminating the irregular edges of these films or films, as they may result from a transverse stretching

of the material.

  Until now, we used for this division of

  a razor blade attached to a support.

  this use is that the razor blade is only used for a part of its length and that its irregular wear is rapid, which

  frequent changes of the cutting blade and natural night-

productivity.

  An object of the present invention is, therefore,

  to propose a cutting device which has a resistance

  high wear rate of the sharp edge of the knife and allows cutting a long film length before

  must exchange or regrind his knife.

  Another object of the invention is to provide a cutting device which regularly distributes the wear of the cutting edge of the knife over a long length thus ensuring a long life at this cutting edge and which allows to benefit from a cut as good, faithful and

  regular than conventional razor blades.

  Another object of the invention is to propose

  a cutting device whose straightness of cut is improved to such an extent that it

  the eye the successive layers of film on a reel of

  bearing and which allows to accurately slit the

  coil in elements of smaller width.

  According to another object of the invention, there is provided a cutting device for a plastic film which

  makes it possible to discharge the electronic charges more safely

  static that could wear the plastic film.

  Another subject of the invention relates to a cutting device for plastic films which is less sensitive to dirt and wear by dust and

debris from the cut.

  Still another object of the present invention is to provide a cutting device which allows a collection

  easy debris and cutting waste.

  Still another object of the invention relates to an

  for the cutting of plastic films which allows sharp and sharp cutting of the film banks after transverse drawing, said banks often having a serrated edge and a thickness different from that of the body of the

  film subjected to transverse and longitudinal stretching.

  According to the invention, the knife consists of a thin disc with a sharp circular edge, which is driven in slow rotation about an axis substantially parallel to that of the

  transfer cylinders and which, in the cutting position,

  sect from below, penetrating by a circular segment, an oblique plane inclined substantially at 450 with respect to the horizontal formed by the film between said first and second cylinders, the direction of rotation of the disk is such that the tangential displacement of its cutting edge in the area that intersects the film is in the opposite direction to the displacement of the film and the sharp edge of the knife that

  through the film runs, in use, near said first

first transfer cylinder.

  Thanks to the rotation of the knife, the wear of the cutting edge or

  the knife is regularly distributed over the entire

  of the latter and the penetration of the knife

  below through the film in a circular segment, until close to the first cylinder or cylinder upstream relative to the displacement of the film, ensures a very good cut while protecting the cutting edge of the cutting debris. According to another embodiment of the invention, the knife is removably mounted on a shaft which is journalled at the end of the fixed support arm, and on which is mounted a driven pulley driven in rotation, via

  of a belt, by a driving pulley of a drive motor.

  ment. Preferably, the support arm has a concave recess substantially following, in cutting position, the contour

  of the first transfer cylinder so that the knife

  at a distance of about one millimeter from the first

transfer cylinder.

  Advantageously, the cutting edge of the knife is sharpened at an angle of about 450. The knife can be

  sharpened at an angle of about 45 by grinding or machining

  of an annular grinding face on both sides of the

knife disk.

  The present invention also relates to the installations

  for cutting or slitting films or films, in particular continuously moving plastic films, which

  comprise a device of the type described.

  Other goals, features and benefits will appear

  upon reading the description of embodiments

  of the invention, given by way of nonlimiting example and with reference to the appended drawing, in which:

  FIG. 1 is a side view of an embodiment of

  cutting device in accordance with the

vention;

  FIG. 2 is a fragmentary view, in cross section,

  versale along the line II-II of Figure 1, a first embodiment of the knife itself;

  FIG. 3 is a fragmentary view, in cross section,

  versale along line II-II of the

  re 1, a second embodiment of the knife. In the embodiment shown in FIG. 1, the cutting device according to the invention, designated by the

  general reference 1, is intended to split a film of

  plastic film 2, circulating in the cutting region between two transfer rolls 3 and 4, from the upper cylinder to the lower cylinder, as indicated by the arrows f The film or film 2 may have, for certain plastics, a relatively large thickness a few tenths of a millimeter, and for others, a very small thickness of the order of a few micrometers Between the two cylinders 3

  and 4, the film 2 moves, at high speed, which can reach

  dre several meters per second, in an oblique plane 5

  inclined substantially at 450 relative to the horizontal.

  The cutting device 1 comprises a cutting knife

  circular edge 6, having the shape of a thin disc sharpened at 450 on its periphery and made of a suitable material,

  for example hard steel suitably hardened.

  The knife 6 is mounted on an axial shaft 7, horizontal

  and parallel to the plane 5 of the film 2, journalled in the

  mite 8 of a support arm 9 secured to a fixed frame not shown On the same shaft 7, is fixed rigidly, at least in rotation and preferably on the side of the end 8 opposite the knife 6 (see Figure 3 ), a toothed driven pulley 10 on which is engaged an endless belt

  The belt 11 is driven by a pulley me-

  nante 12 mounted on a shaft 13 of axis parallel to that of

  the shaft 7 and rotated by a powertrain

14.

  According to a first embodiment (see FIG.

  re 2), the arm 9 can be formed by two sheet metal plates

  parallel 8 a, 8 b superimposed via

  toises not shown and which keep the two plates apart by an interval i substantially equal to the thickness of the blade of the knife 6 The shaft 7 is thus supported on either side of the blade of the knife in a respective plain bearing 16 17 The endless belt 11 is preferably notched, but may be a thin, flat belt retained in a flat groove, as shown in FIG.

  shown in Figure 2, or one can use a

  llb with a circular section and high elasticity, as

  shown in Figure 3 The pulley and belt systems

  Figures 2 and 3 are completely interchangeable.

  In order to make it possible to block the toothed belt 11, the former

  8 arm tremité comprises, fixed by all appropriate means,

  in particular by means of screws 20 on an eccentric not shown

  felt, a belt lock support 21 housed between the two

  strands of the belt 11 and which is provided with a protruding notch.

  After displacement of the eccentric, the notch is engaged between two teeth of the belt 11 to immobilize this

  last axially and thus block in rotation the shaft 7.

  The direction of rotation of the geared motor unit 14 is such

  that the knife 6 rotates in the direction of the arrow F, that is

  that is, the tangential displacement of the cutting edge 6b of the knife is in the opposite direction to the movement of the film 2 In use, the linear speed of rotation of the knife's circular cutting edge is small compared to the speed of movement of the film The bearings of the tree 7 which

  may be prestressed radial rolling bearings

  (including deep groove ball bearings) pre-

  feel a minimum clearance compatible with the rotation of the knife disk and a very low resistance to rotation and

  retain these qualities thanks to the speed of rotation

  and, where appropriate, to a high-performance, single-stage lubrication system (eg grease)

  (see Figure 3) or bearings (Figure 2).

  The arm 9 has a generally tapered shape so that the knife 6 is arranged, in cutting position, between the two cylinders 3 and 4, its cutting edge 6 b being

  extremely close (at the distance e in Figure 1) from the first

  The distance e can be, for example, of the order of a millimeter. For such a comparison to be possible, the upper contour of the arm 9

  has a recess of concave shape 15.

  During its displacement, the film 2 meets in its plane 5, the cutting edge or cutting edge 6b of the knife 6 which is inclined relative to the plane 5 (which reduces the angle of cut) and which cuts the film As as can be seen in FIG. 1, the knife 6 is arranged in such a way that its cutting edge 6b intersects from below the plane 5 of the film 2 along the cutting line by penetrating through a circular segment 6a through the film 2 The line joining the axes of the driven and driving pulleys 10 and 12 is slightly inclined (from 10 to 30) with respect to the horizontal, which makes it possible to better use the angular space at 450 left free underneath plan 5 of the film to house the end 8

of the arm 9.

  It is important to keep the film 2 moving under mechanical tension between the two cylinders 3 and 4, for

  prevent the film from coming into contact with the knife.

  The radial and axial guidance of the bearing or bearings of the shaft 7 ensures precise positioning at the cutting edge 6 b.

  where it is necessary to provide two clean and straight edges

  On the film in production, it is naturally expected that two cutting devices such as 1, neighbors each of one of the edges A similar device can be used each time

  that it is planned to split the film.

  As shown in FIG. 2, the cutting edge 6b of the

  knife 6 makes an angle x close to 45 Of course, from

  very different cutting angles are possible to take into account the nature of the material to be cut. Moreover, several sharpening modes are possible.

  embodiment of FIG. 2, it is possible to form, by grinding

  gentiel, a single annular sharpening face 6c which makes a

  angle x with the flat face 18 of the knife 6.

  According to the embodiment shown in FIG. 3, two annular sharpening faces 6d and 6e that form

  a respective angle y and z with the cutting plane 19 of the neck

  water 6, that is to say a plane passing through the entire circular cutting edge 6b of the knife when the cutting edge has no warping In other words, the cutting plane 19, extended in outline mixed in Figure 3, is a

  plane parallel to the two parallel faces 18 and 18b of the neck.

  6 and passing through the cutting edge or wire 6b (edge

  The angles y and z are usually

  substantially identical and equal to half the year

  gle x, that is to say 22,50, which restores the sharpening 450 razor blades It is obvious that the angles y and z may be different depending on the material to cut or slit and that their sum may differ from 450 for

same reasons.

  According to an embodiment shown in FIG. 1, the end 8 of the arm 9 carries a brush or a scraper 26 to scrape and permanently clean the cutting edge 6b and the annular grinding faces 6c or 6d-6e. and drop adherent debris from the cut This debris 27 fall on a plate 28 of protection of the cylinder 4 and are removed without the risk of disturbing the cut and being driven on the film 2 on the move A self-sharpening member (grinding wheel or other) can also be provided on the arm 9 to sharpen

  edge 6b is either permanently or at regular intervals

  During the service or during stops of the film 2 the cutting device according to the invention has proved to be suitable for

  ensure between two sharpening times impressing cutting lengths

  over a thousand kilometers, which justifies

  the sharpening in the workshop after removal of the knife 6 or the

entire arm 9.

  In the embodiment shown in Figure 3 and which has been experimented in detail, the shaft 7 is permanently mounted in the end portion 8 of the arm 9 by means of a rolling bearing 22 with high rigidity axial and radial (for example a deep-groove ball bearing or a roller bearing) and with sealed lubrication In order to allow the shaft 7 to be cantilevered in the bearing 22 and on one side of the arm 9 , the circular knife 6, bearing laterally on an annular rim 23 at the outlet of the shaft 7, is provided with an annular fixing ring 25, integral with it and traversed by at least one screw 24 clamping on the 7 To remove the knife 6, in order to change or refit it, it suffices first of all to press the locking support 21 against the

  toothed belt hl in order to lock in position the

  11 and to immobilize in rotation the shaft 7 The screw 24 can then be unscrewed to extract laterally the annular ring 25 and the knife 6 which is secured thereto. The precise positioning of the knife 6 is carried out by threading on the shaft 7 to the end of the face 18 of the knife 6 on the annular flange 23 Then simply tighten the screw 24

  on the shaft 7 which remains in a rotating position on its roll-

rigid 22.

  As already indicated, the cutting time without regrinding is considerably improved by

  the duration of use of a conventional razor blade

  In the embodiment of FIG. 2, the knife change 6, in particular for regrinding of this

  last, can be performed after removal of the support arm 9.

  The removal of the knife 6 and its axial shaft 7 is achieved

  after removal of the driven pulley 10 and after

  One of the plates 8a or 8b for reasons of productivity of the plastic film winding installation associated with the cutting device according to the invention, it is possible to very quickly deposit the support arm 9 after having disconnected the group power supply

  geared motor 14 so as to remove the entire

  cutting device and replace it with another

  new or revised cutter The removed cutting device is

  completely revised in the workshop both with respect to the knife 6 (which is removed or resharpened) than the belt, the bearings and the gear motor 14, the assembly being

  completely cleaned, checked and greased if necessary.

  By using the cutting device according to the invention, the cut film edges obtained are particularly

  free of tears or cracks In case of slowing down

  or stop the scrolling of the film 2, the rotation of the

  6 ensures the cutting of the film throughout the area in contact

  with the sharpness of the knife while cutting becomes irre-

  gulière with a classic razor blade.

  Of course, the present invention is not limited to the embodiments described and shown but it is capable of numerous variants accessible to the man of

  art without departing from the spirit of the invention.

Claims (6)

  1. Cutting device, intended in particular to slit or cut in banks a plastic film which moves continuously between a first and a second transfer cylinder rotating about horizontal axes and is kept under mechanical tension between said first and   second cylinder, comprising a circular cutting knife   wheel mounted on a support arm, characterized in that the knife (6) consists of a thin disk with a sharp circular edge, which is driven in slow rotation about an axis substantially parallel to that of the transfer cylinders (3 and 4 ) and which, in the cutting position, intersects from below,   penetrating through a circular segment (6 a), a plane   that (5), inclined substantially to 450 with respect to the horizon   tale, that forms the film (2) between said first and second cylinders, in that the direction of rotation (F) of the disk is such that the tangential displacement of its cutting edge (6 b)   in the area that intersects the film is in the direction   opposite to the displacement of the film (2) and in that the cutting edge (6b) of the cutter (6) passing through the film (2) rotates, in use, close to said first roll of transfer (3).   2. Device according to claim 1, characterized in that the knife (6) is removably mounted on a shaft (7) which is journalled at the end (8) of the fixed support arm (9), and on which is mounted a driven pulley (10) driven in rotation, by means of a belt (11), by a   drive pulley (12) of a drive motor.   3. Device according to claim 1 or 2, characterized   characterized in that the support arm (9) has a concave recess (15) substantially in the cutting position, the contour of the first transfer cylinder (3) so that the   knife (6) approaches at a distance of about   meter of said first transfer cylinder.   4 Device according to any one of the claims   1 to 3, characterized in that the cutting edge (6b) of   knife (6) is sharpened at an angle (x, y-z) of about 45   ron. he 5. Device according to claim 4, characterized in that the knife (6) is sharpened at an angle of about 450 by grinding or tangential machining, on both sides (18, 18 b) of the knife disc, a annular grinding face (6d, 6e). 6. Installation for cutting or slitting films or films, in particular continuously moving plastic films, characterized in that it comprises at least one   cutting device (1) according to one of claims 1 to 5.