BLOW MOULDING MACHINE WITH ARRANGEMENT FOR CLEANING THE BLOW MOULD

An apparatus for transforming plastic preforms into containers, includes at least one blow mould which forms a cavity, inside which the plastic preforms can be transformed into containers. The apparatus includes an opening and closing mechanism for opening and closing the blow mould, and a cleaning device for cleaning regions of the blow mould. The cleaning device includes at least a first cleaning element for cleaning an inner wall of the blow mould, which cleaning element is arranged at least at times outside the blow mould.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows an apparatus for transforming plastic preforms (not shown) into plastic containers (not shown). This apparatus comprises a main carrier11, on which a blow mould2is arranged in a blow mould carrier3(in each case shown only partially).

Formed inside the blow mould2is a cavity4, inside which the plastic preforms are expanded through the application of compressed air to form plastic containers. Furthermore, the apparatus comprises a stretching rod12, which is movable here in the longitudinal direction L in order to stretch the plastic preforms. Reference22denotes a first blow mould half and reference24denotes a second blow mould half. In addition, the blow mould also has a bottom or a bottom part which closes the cavity4in the downward direction during operation. Reference14denotes a pressure application device or blowing nozzle which applies compressed air to the plastic preforms.

FIG. 2shows a schematic view to illustrate a cleaning procedure. This shows in detail a machine in a preferably special cleaning mode. More specifically, this is an automatic cleaning process which nevertheless can be incorporated on machines that are already in development and on mould changing machines that have already been developed by the applicant. This mould changing device already has the ability to open the mould carrier automatically and also to loosen appropriate fixing screws and tighten these again. This arrangement also already allows an automatic closing of the mould carrier.

For use as a cleaning device, in particular the fixing functions are replaced by the cleaning function. In this case, the mould is unlocked and opened in a first stage or the region denoted by reference A. A spray head16applies a cleaning agent to the inner wall of the open blow mould2. For this purpose, this spray head10may be moved (arrow P1) by means of a transport or displacement device into the inner region of the blow mould2, which is now open, or else can be guided over the inner surface8of the blow mould by means of a special device, such as a robotic arm for example, and can spray said surface.

It would also be possible that a plurality of such spray heads are provided. For example, use could be made of spray heads which are set in rotation by the cleaning medium passing through, and which thus dispense the cleaning agent in the full circumferential direction. A plurality of such spray heads could also be arranged one above the other in the longitudinal direction L of the blow moulds2shown inFIG. 1.

In the region denoted by reference B, the cleaning agent acts on the inner surface8of the blow mould2(cf.FIG. 1). It would also be possible to close the blow mould again in this region, but in the embodiment shown inFIG. 2the blow mould2remains open in this state. In the section denoted by reference C, a second cleaning element18is used which mechanically cleans the sprayed inner surface. This may be for example a rotating polishing head which cleans the inner surface. At the same time as this polishing process, the rinsing liquid, such as distilled water for example, may also be applied to the inner surface. However, this application of distilled water could also take place at the end of the region B, or after the polishing process.

The cleaning element18is also moved into the inner region of the open blow mould2for cleaning purposes. However, it would also be possible that a corresponding cleaning element is moved into the blow mould from above or from below. Depending on the geometric dimensions, two polishing elements in the form of two parallel brushes would also be conceivable, which mechanically clean the inner wall8.

After the region C, the blow mould is closed again. Reference15denotes the rotating carrier (arrow P2) on which the blow moulds2are arranged, and reference10denotes the cleaning device in its entirety. In addition, the apparatus may have cams (not shown) which bring about the opening and closing of the blow moulds2. Cams which move the cleaning elements16and18into the open blow mould and out of the latter may additionally also be provided. However, these movements may also be brought about by electric motors and in particular by servo motors.

By virtue of the mould cleaning according to the invention, there is no need for manual cleaning which is very complicated in the prior art. For example, the moulds must at present be placed into a cleaning fluid during storage in a mould changing carriage. Furthermore, there is the advantage that this automatic mould cleaning can be carried out even while the blow moulds are still very hot in parts, which is not possible in the case of manual cleaning due to the risk of injury to the user. However, these increased temperatures, particularly of the inner surfaces8, offer the advantage of a possible greater efficiency of the cleaning agent and of the cleaning process per se. Preferably, the apparatus according to the invention has a special cleaning mode, which may be provided for example as an interval circuit. Furthermore, removal or opening of the blow moulds by the user is no longer necessary, and the safety risk is reduced since the protection circuit of the machine remains closed even during the cleaning.

Furthermore, as mentioned above, an increased temperature of the blow mould can be maintained even during the cleaning, or the blow mould may also be temperature-controlled or cooled during the cleaning. This ensures a quicker restart after the cleaning process.

It is pointed out that the cleaning arrangement according to the invention can also be retrofitted on already existing installations. As shown inFIG. 2, both the cleaning element16or the spray head16and the cleaning element18are arranged in a stationary manner relative to the direction of rotation of the carrier15. However, it would also be possible to arrange these elements16,18in a movable manner, for example on the carrier15. In a cleaning mode, the individual blow moulds2can be moved (preferably in cycles), so that for example a specific blow mould remains in a correct position and then the cleaning processes are carried out.

All of the features disclosed in the application documents are claimed as essential to the invention in so far as they are novel individually or in combination with respect to the prior art.

LIST OF REFERENCES