The invention relates to a cutting device for preforms for plastic containers which are intended to hold a medium. These preforms are preforms for containers, for example bottles or other types of containers, which during production are moulded with a superfluous part which needs to be cut off.

Cutting devices of this type are known, for example, for automatically cutting off a superfluous top part which has formed during blow-moulding of a preform for a container, in order to make the container suitable for further use, for example for the container to be filled with a liquid medium and then a lid, cap, cover or the like to be fitted to the container. In this context, both cutting devices in which a blade with a cutting action is pressed onto a preform for a container which is held clamped in place and is moved around the preform, as well as in which during cutting the preform is pressed onto a stationary blade and the preform itself is rotated, are known. To position the blade with respect to the predetermined location on the preform where it is desired to make the cut, the known cutting devices comprise positioning means which during cutting bear against the preform.

A cutting device according to the preamble of claim 1 is known from US 2003/0188620. In this document, the device comprises a plurality of centring fingers connected to a stator and a blade which is provided at one end of a pivot arm and is connected to a rotor. The centring fingers are provided around an opening which can be lowered over a top part, which is to be cut off, of a preform for a plastic bottle which has been formed by blow- moulding. To enable the top part to pass through during the lowering operation, the centring fingers are designed such that they can move in the radial direction. Furthermore, the centring fingers are positioned above the blade, in order in this way to be able to engage on the superfluous top part which is to be cut off and to position the blade with respect to an intended cutting line on the preform. During cutting, the blade is moved

around the circumference of the preform as a result of the rotor being driven.

Drawbacks of this arrangement are that the cutting device is of relatively complex construction and that the cut obtained after the top part has been cut off leaves something to be desired with regard to position, shape and quality. The latter problem partly arises on account of the fact that the centring fingers engage on the superfluous top part, the shape of which is not always constant on account of blow-moulding. To limit this disadvantageous effect, the preforms for the bottles are produced with a relatively large superfluous top part by blow- moulding, so that at least the part beneath this top part has a relatively accurate constant shape on which positioning can be effected. In addition, during cutting the top part is increasingly detached from the remainder of the preform, making the positioning unstable to some extent. Furthermore, the cutting device is difficult to clean and consequently has problems being used under conditioned circumstances.

It is .an object of the present invention to at least partially overcome the abovementioned drawbacks and/or to create a usable alternative. In particular, it is an object of the invention to provide a cutting device of simple design, with which a top part of a preform for a container can be cut off quickly, efficiently and highly accurately.

According to the invention, this object is achieved by a cutting device according to claim 1. This advantageously enables very accurate positioning of the cutting member with respect to the cutting groove throughout the entire cutting operation. The accuracy and quality of the cut are in this case determined in particular by the accuracy of the cutting groove. The design of the cutting device can be kept simple since few components are required. This is of benefit to cleanability of the cutting device and its use under conditioned atmospheres. It is also possible to save material, on account of the fact that the top part that is to be cut off can be kept small. The shape of the top part has no negative effect on the accuracy and quality of

the cut .

In a preferred embodiment, the positioning means comprise two guides located opposite one another with guiding surfaces. In a starting position, the guides are arranged at a fixed distance from one another. The guiding surfaces are in this case at substantially the same height as the cutting member and are at a distance from one another which substantially corresponds to the diameter of the encircling cutting groove. This advantageously makes it possible for the cutting groove of the preform to be moved laterally between the guides, after which cutting can commence. There is advantageously no need to provide a mechanism for moving the guides towards and away from one another in order for the cutting groove of the preform to be positioned between them. However, it is possible to provide a mechanism for temporarily moving the guiding surfaces away from one another, for example to enable a preform to be moved towards a cutting device lying behind without being impeded.

In particular, the guiding surfaces extend at least partially parallel to one another in a passage direction for the preform. In this way, the preform with its cutting groove can be accurately slid through between the guides in order to search out its optimum position automatically and then to be held in this position.

In a further embodiment, the guiding surfaces comprise converging and/or diverging entry and exit parts. As a result, the feeding and discharging of a container can take place flexibly and quickly.

In one. particular embodiment, the cutting device comprises a stator and a rotor, in which both the positioning means and the cutting member are connected to the rotor. During the cutting operation, the positioning means then move through the cutting groove, with the advantage that the positioning means are always located as close as possible to the cutting member without them having to extend around the entire circumference of the preform.

Further preferred embodiments are defined in the subclaims .

The invention also relates to a method according to claim 17.

The invention will be explained in more detail below with reference to the accompanying drawings, in which:

Fig. 1 shows a diagrammatic front view of a preferred embodiment of a cutting device according to the invention; Fig. 2 shows a view from below on line II-II in Fig. 1; Figs. 3 - 6 show views corresponding to Fig. 1, showing successive steps of positioning and cutting;

Fig. 7 shows a diagrammatic perspective view of an assembly of a plurality of cutting devices as shown in Fig. 1; and Fig. 8 shows a cross-sectional view on line VIII-VIII in Fig. 1; and

Fig. 9 shows a cross-sectional view on line IX -IX in Fig. 1.

In Fig. 1, the cutting device is denoted overall by reference numeral 1. The device 1 comprises positioning means 2 which are composed of two guides 3 with guiding surfaces 4 which face one another and in this case form side edges of the guides 3 (cf . Fig. 2) . Parts 4a of the guiding surfaces 4 extend parallel to one another in a direction which is identical to an intended passage direction 6 for a preform for a container that is to be treated through the cutting device 1. In addition, the guiding surfaces 4 are provided with a converging entry part 4b and a diverging exit part 4c.

At the end of one of the parallel guiding surface parts 4a there is a sharply pointed cutting member which is fixedly connected to the associated guide 3 and is in this case formed by a blade 8 which projects inwards. The blade 8 is at the same height as the guiding surfaces 4 of the guides 3.

The cutting device 1 is intended to cut a top part of a preform for a container. Fig. 3 shows a possible embodiment of a preform 15 of this type, comprising a container 15a and a superfluous top part 16 which is to be cut off the container 15a. Between the container 15a and the top part 16 is a cutting groove 17

which encircles the preform 15 in a substantially cylindrical circumferential wall part. The preform 15, including the top part 16, can be formed, for example, by blow-moulding, in which case the superfluous top part 16 is a result of this production method and is used, for example, to temporarily close off the preform 15 in an airtight manner at the top side in order to keep the container 15a clean from the inside. At a desired time, for example just before the time of filling, the superfluous top part 16 can then be cut off and removed.

The distance between the parallel guiding surface parts 4a substantially corresponds to the diameter of the encircling cutting groove 17. As a result, the blade 8 which projects from the guiding surface part 4a will automatically make an initial cut in the cutting groove 17. The blade 8 has a cutting surface length which is only slightly greater than the wall thickness of the preform 15 that is to be cut through at the location of the cutting groove 17.

On the underside, the guides 3 are provided with delimiting wall parts 20 which are intended to bear against a part of the circumferential wall of the preform 15 which is located directly beneath the cutting groove 17. This effects additional positioning of the blade 8 with respect to the cutting groove 17, which can play a role in particular when a substantial part of the cut has already been made by the blade 8. As an alternative to two delimiting wall parts, it is also possible to make do with just one delimiting wall part, which is provided on the guide on the opposite side from the cutting member.

Each guide 3 is suspended from a frame 22 which is connected to a rotatable rotor part 24 by means of a pivot spindle 23. The pivot spindles 23 are positioned eccentrically with respect to the centre axis of the rotor part 24. The guides 3 and the blade 8 as a result advantageously have the freedom to move to a certain extent when the cutting groove 17 of the preform 15 is being pushed between the guides 3. This is advantageous both when the cutting groove 17 of the preform 15 is being pushed between the guides 3 and during the cutting operation itself. As

a result, the cutting surface of the blade 8 can in each case correctly coincide with the intended cutting plane which extends through the cutting groove 17, with the result that the cutting force required is minimized and an accurate cut can be achieved at the intended position.

In the rotor part 24 there is a stator part 25 which can be moved up and down with respect to the rotor part 24 and which furthermore is arranged non-rotatably . The rotor part 24 can be rotated with respect to the stator part 25 in order to enable the assembly of guides 3 and blade 8 to move around the preform 15, with the guides 3 engaging in the cutting groove 17 while the blade 8 is cutting through the wall of the preform 15 at the location of the cutting groove 17.

The stator part 25 is provided with clamping means, in this case formed by a diaphragm 26, for in the first instance retaining the top part 16 during the cutting operation and then removing the top part 16 after it has been cut off. Further removal of the top part 16 which has been cut off can be effected by suction via the stator part 25. It is also possible for the stator part 25 to be moved upwards to such an extent that the top part 16 which has been cut off can be pressed out, for example above a separate discharge. The diaphragm may, for example, comprise an elastically deformable rosette. In a variant, it is also possible for the top parts 16 which have been cut off to be discharged by the stator part 25 being moved to above a new top part 16 of a preform 15 that is to be cut off, with in each case the top parts 16 which have been cut off in previous cycles automatically being pressed further upwards in the direction of a discharge. It is also possible to provide other retaining means for preventing undesirable rotation of the container with respect to the cutting member during cutting. In that case, the stator part may also be rotatable with respect to the rotor part.

One possible cutting-off method will now be described with reference to Figs. 3 - 6. Fig. 3 shows the situation in which the cutting groove 17 of the preform 15 has just been pushed

between the guides 3 until it bears against the blade 8. The stator part 25 is in this case in a raised position in order to enable the top part 16 of the preform 15 to pass through. Then, the stator part 25 is moved downwards, as shown in Fig. 4, in order to enclose the top part 16 and retain it using the clamping means to prevent any rotation of the preform 15. Then, the rotor part 24 is driven in rotation over an angle of at least 360 degrees by drive means 27, in this case formed by a gear wheel/toothed belt pulley. As a result, the blade 8 cuts the entire top part 16 off the remainder of the preform 15. In a subsequent step as shown in Fig. 5, the stator part 25 is moved upwards together with the top part 16 which has been cut off and is clamped securely therein, after which the container 15a as shown in Fig. 6 can be advanced past the guides 3, for example to a filling and/or closing station for filling and closing the container 15a. In a variant, cutting members are provided on both the opposite guides, with the result that a rotation of the cutting device of 180 degrees with respect to the preform can suffice .

Fig. 7 shows an assembly of a plurality of cutting devices 1 as shown and described above. The cutting devices 1 are in this case positioned in adjacent pairs. Accordingly, containers 15 are supplied in pairs. To prevent the front preforms 15 which are intended for the rear cutting devices Ib from already being partly cut into by the front cutting devices Ia, the cutting devices Ia can be designed in such a manner that they can be completely or partially moved upwards, so that in any event the cutting members are temporarily not blocking the way of the passage of the preforms. In a variant, the guides 3, which are arranged rotatably about the pivot spindles 23, can be moved away from one another in the radial direction with the aid of a suitable cam mechanism or other type of drive. In this case too, a preform can pass through the cutting device without being cut into.

Furthermore, Fig. 7 shows part of a top plate 30 through which the cutting devices 1 can fit in a sealing manner. To enable the rotor part 24 to rotate, dynamic seals are provided between the

rotor part 24 and the top plate 30. It is in this way possible for the space beneath the top plate 30 to be conditioned, for example by providing gas feed means which are designed to emit conditioned gases, such as substantially sterile air or hydrogen peroxide vapour or air which contains hydrogen peroxide. On account of the simple structure of the cutting devices and the relatively small number of moving parts, it is consequently reliably possible to maintain substantially aseptic conditions around the cutting devices. This is advantageous in particular when cutting preforms which have been blow-moulded under sterile conditions, since the sterility is then maintained even after the top part has been cut off and removed. In a variant to having the cutting device operate in a substantially sterile environment, or in addition to this, it is possible for the preform to be decontaminated on the outer side before being fed to the cutting device. As an alternative to using conditioned gases in order to achieve the substantially sterile conditions, it is also possible to use UV light, steam, etc. Figure 7 also shows that the rotor parts 24 are formed by a plurality of connecting rods 35 which extend from the top downwards and to which a lower ring 36 is secured. This has the advantage of making it easy to decontaminate the cutting device.

In addition to the embodiment shown, numerous variants are possible. For example, it is possible to use other types of positioning means or other types of cutting members, such as a circular blade, a hot wire or a heated blade. In the case of two guides, it is possible to provide either one or two cutting members. The blade may be disposed so as to be fixed or rotatable. The cutting member extends only part way into the passage space for the container, and as a result is designed in particular to cut through the cutting groove by moving circumferentially along the cutting groove. In addition, the device is suitable for cutting all types and sizes of preforms for containers, both preforms with a closed top part that is to be cut off and preforms with an open superfluous part that is to be cut off.

The cutting device according to the invention can be used both

in an arrangement in which the preforms are moved in steps along a conveying path and in an arrangement in which the preforms are conveyed continuously along a conveying path. In the case of the latter option, the cutting device will move along the conveying path with the preform as it is cutting, whereas in the former option the cutting device is held in place during the cutting operation. The conveying path may, for example, be linear or circular. The guiding surfaces are preferably of a shape which is complementary to the shape of the cutting groove and/or may be shaped in such a manner that they can move as deep as possible into the cutting groove. Furthermore, it is possible for the assembly of guides and blades to be arranged such that it can to some extent be moved freely in the vertical direction, for example by an amount of approx. 1 mm, so that the guides have the freedom to search out a cutting groove at a slightly different height. As an alternative to two guides, it is also possible to use just one guide, for example a spring-loaded guide .

During the cutting operation, the preform can be held in place by retaining means. These retaining means can then be designed to lock the preform preventing it from rotating with respect to the conveyor means during the cutting operation. The retaining means can then also be used to move the preform towards the cutting device together with the conveying means. The retaining means are preferably designed to retain an upper neck part of the preform, but may also be designed to retain the container body or to support the container base.

Thus, the invention provides a cutting device which is of simple design, is inexpensive to produce and is eminently suitable for use under conditioned environments and for reliably and accurately cutting a superfluous part off a preform for a container which is intended in particular for the food industry.