The invention relates to a cutter arrangement, in particular for trimming sealed packaging-tube ends.

Cutting tools for such trimming are used in tube filling machines where the tubes are processed in an in-line procedure, i.e. empty tubes provided with a closure are set into a holder in the machine, the tubes are indexed to a filling station where the tubes are filled with product via their open ends and then closed in order to be finally fed out in the form of filled tubes.

Apart from the mentioned process steps, there are normally also additional steps in the form of checking operations, marking stations and trimming (i.e. clean-cutting) of the seal which provides the closed end after filling.

Present machines operate at a high production speed, which requires precision in the various processing stations.

It has shown itself to be the case that certain tube materials, typically in laminate form, comprise layers which cause a great deal of wear on the cutting tools or the cutting edges. This wear is possibly due to the presence of silicon oxide in the material.

The problem underlying the invention is to allow self- adjustment of the cutting tool whilst maintaining precision, as well as allowing re-adjustment as soon as the self-adjustment is no longer sufficient.

The invention thus provides a cutter arrangement, preferably for trimming sealed packaging-tube ends, comprising means for producing a forward and return movement for at least one pair of cooperating cutting

blades in a machine support, as well as a holder for said cutting blades, whereby the holder and said movement- producing means are arranged so that the cutting edges of the cutting blades meet in a parallel movement.

The cutter arrangement is notable in that at least one of said cutting blades is supported by a sprung holder.

In order to achieve said re-adjustment, means are arranged for adjusting the holder in a direction which is at right angles to the plane of parallel movement.

In a preferred embodiment, the holder defines a sub-zone between a pair of material-weakening channels on either side of a central plane through the cutting blade, and the cutting blade is supported entirely within said sub-zone.

Each channel suitably comprises two part-channels which are open on respective sides of the holder plate and which extend over the whole width of the plate as seen in the direction of parallel movement, and between said sides, and which between them define material bridges for forming elongation zones.

In order to achieve a re-adjustment, an adjustment screw is arranged with means for displacing the material bridges and the sub-zone in said adjustment direction.

The adjustment screw is suitably conical and is positioned in a plane parallel to the plane of parallel movement in one of said part-channels.

The channels in the holder plate are produced by means of spark-machining the holder plate.

DESCRIPTION OF THE FIGURES:

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 schematically shows a cutter arrangement according to the invention, intended to be mounted in a tube filling machine,

Fig. 2 shows, in schematic cross-section, the sprung cutter arrangement or the cutting blade according to the invention,

Fig. 3 shows, on an enlarged scale, the encircled area in Fig. 2,

Fig. 4 shows the principle of parallel movement of the opposed cutting edges,

Fig. 5 shows a packaging-tube end trimmed with the cutter arrangement of Fig. 2,

Fig. 6 is a cross-section along line VI-VI in Fig. 2 which shows the extent of the cutter holder plate in the direction of parallel movement.

In Fig. 1, reference numeral 10 denotes a support part intended to be mounted on the tube filling machine in the trimming station. A linear control 11 is arranged in conjunction with part 10, and moving supports (carriages) 13, 14 are mounted on the linear control 11 via linkage arms 15, 16. The link arms are manoeuvred via additional links 17, 18 for rotation around shafts 19, 20, and at the ends of the link arms 15, 16 these engage with dogs 21, 22

on the moving supports 13, 14. The moving supports are carried on a track 12.

On the moving support 13, there is a holder 26 for a counter-blade 23 which, in the present embodiment, is removably supported but not sprung in the holder 26.

A cutting blade 24 is supported in the holder 25 and, as can be seen in Fig. 4, the two cutting blades 23, 24 perform a parallel movement with opposing cutting edges.

Figure 2 shows schematically in cross-section how a pair of cutting blades 24 are supported by a holder plate 25 of the moving support 14. The cutter arrangement in figure 2 is intended to achieve a trimming (clean cut) of two tube ends in the trimming station, said tube ends having been fed forwards with the aid of indexable pairs of tube holders of the tube filling machine.

The cutter holder plate 25 comprises, seen in accordance with Fig. 2, three vertically-extending webs, one of which is centrally placed and the remaining two being at respective ends of the plate. The pair of cutting blades 24 is fixed to the plate 25 by means of bolts applied through holes extending in a central plane through respective cutting blades 24.

The horizontal part of the holder plate 25 in figure 2 presents four sets of material-weakening channels 27, 27' placed at the outer ends of the cutting blades in the lateral direction in Fig. 2, so that the cutting blades lie completely within respective pairs of channels which are open on the cutting blade side of the holder plate.

In this way a pair of sub-zones 25', 26' are formed, each of which carries one cutting blade 24.

Figure 3 shows more clearly how the channels 27, 27' are arranged. The channel 27 is open at the upper side 29 of the holder plate 25 and extends over the whole width of the holder plate as seen in a plane parallel to the plane of parallel movement.

The other channel 27' is open at the opposite side 30 of the holder plate and also has the same dimension as seen in a plane parallel to the plane of parallel movement.

The channels 27, 27' in figure 3 have horizontally and vertically extending parts, these being positioned so that narrow material bridges are formed between the channels 27, 27' and between the upper side 29 and the underside 30 of the holder plate, so as to form elongation zones ("stretching" zones) .

In one of the channels, channel 27 in this embodiment, there is an eccentric screw 28 for re-adjustment of the position of the cutting blade holder plate's cutting blade supporting surface 29.

, The preliminary adjustment of the opposed cutting edges (Fig. 4) is made so that a spring effect from the material bridges between the channels 27, 27' will occur, i.e. a certain upwardly-directed force is exerted from the sprung, material-weakened parts provided with channels in the part of the movement when the cutting blades or cutting edges meet in accordance with Fig. 4. By applying this force, the blades will come into contact with each other correctly even after a certain amount of wear.

When however the wear has reached such proportions that the available upwardly-directed extent of movement from the parts 25', 26' of the holder plate is no longer sufficient, a re-adjustment is necessary.

Such adjustment is performed with the adjustment screws 28 which, in the shown embodiment, are conical and provide lift to the surface 29 to a new self-adjusting level within certain limits.

The channels 27, 27' are suitably constructed with the aid of spark-machining and can thereby be given complicated dimensions in order to provide the best possible elongation characteristics and self-adjustment characteristics respectively.

Although only one specific embodiment of the invention has been described, it should be understood that modifications and alternatives are possible within the scope of the appended claims.