APPARATUS AND METHOD FOR FORMING PLASTIC PREFORMS INTO PLASTIC CONTAINERS WITH VARIABLE PRESSURE STORAGE

Abstract

Apparatus for forming plastic preforms into plastic containers, having at least one forming station configured to form the plastic preforms into the plastic containers by the application of a flowable and, in particular, gaseous medium, wherein the forming station has an application device configured to apply on the plastic preforms with the flowable medium, and at least one first pressure reservoir configured to store the flowable medium at a predetermined pressure, wherein the apparatus has a pressure fluctuation reducing device which is configured for reducing pressure fluctuations in the first pressure reservoir.

Claims

1. An apparatus for forming plastic preforms into plastic containers, having at least one forming station configured to form the plastic preforms into the plastic containers by applying a flowable medium, wherein the forming station has an application device configured to apply the plastic preforms with the flowable medium, and at least one first pressure reservoir configured to store the flowable medium at a predetermined pressure, wherein the apparatus has a pressure fluctuation reducing device which is configured for reducing pressure fluctuations in the first pressure reservoir.

2. The apparatus according to claim 1, wherein the apparatus comprises at least a second pressure reservoir configured to store the flowable medium under a second predetermined pressure.

3. The apparatus according to claim 1, wherein the apparatus has a valve unit configured for the plastic preforms to be applied with different pressure stages of the flowable medium.

4. The apparatus according to claim 1, wherein an intake volume of the first pressure reservoir is variable.

5. The apparatus according to claim 1, wherein the apparatus comprises volume changing device configured to change the intake volume of the first pressure reservoir.

6. The apparatus according to claim 5, wherein the volume changing device comprises a membrane or a movable piston element.

7. The apparatus according to claim 5, wherein the volume changing device comprises a movement generating device.

8. The apparatus according to claim 1, wherein the apparatus comprises a sensor device configured to detect pressures within the reservoir.

9. The apparatus according to claim 8, wherein the apparatus comprises a control device which controls the volume dependence in dependence on the pressure values detected by the sensor means.

10. A method of forming plastic preforms into plastic containers, wherein the plastic preforms are formed into the plastic containers by the application of a flowable medium with at least one forming station using the apparatus having a forming station, a pressure reservoir and a pressure fluctuation reducing device as claimed in claim 1, the steps of: applying the plastic preforms with the flowable medium and at least one first pressure reservoir which stores the flowable medium under a predetermined pressure, and reducing pressure fluctuation using the reducing device to reduce pressure fluctuations in the first pressure reservoir.

11. The method according to claim 10, wherein the pressure fluctuations in the first pressure reservoir are reduced by volume changes of the first pressure reservoir.

12. The method according to claim 10, wherein including the step of determining pressures within the reservoir using a sensor device.

13. The method according to claim 10, wherein the volume of the reservoir is changed periodically at least at times.

14. The method according to claim 12, wherein the intake volume is changed in dependence on the pressures detected by the sensor device.

15. The method according to claim 13, wherein the intake volume is changed in dependence on the pressures detected by the sensor device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further advantages and embodiments can be seen in the attached drawings:

[0042] In the drawings:

[0043] FIG. 1 shows a representation of an apparatus according to the invention for forming plastic preforms into plastic containers;

[0044] FIG. 2 shows a representation of pressure fluctuations in a reservoir;

[0045] FIG. 3 shows a first schematic representation of a pressure fluctuation reduction device;

[0046] FIG. 4 shows a second illustration of a pressure fluctuation reducing device; and

[0047] FIG. 5 shows a further illustration of a pressure fluctuation reduction device.

DETAILED DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 shows an apparatus 1 for forming plastic preforms 10 into plastic containers 15. This apparatus has a rotatable carrier 12 on which a plurality of forming stations 20 are arranged. These individual forming stations each have blow moulds 82 which form a cavity 84 in their interior for expanding the plastic preforms. The reference sign 88 indicates a stretching bar which serves to stretch the plastic preforms in their longitudinal direction. Preferably, all the forming stations comprise such blow moulds 82 and stretching bars 88. Preferably, the number of these forming stations is between 2 and 100, preferably between 4 and 60, preferably between 6 and 40.

[0049] The plastic preforms 10 are fed to the apparatus via a first transport device 32, such as in particular but not exclusively a transport starwheel. The plastic containers 15 are transported away via a second transport device 34.

[0050] The reference sign 7 indicates a pressure supply device such as a compressor or also a compressed air connection. The compressed air is conveyed via a connection line 72 to a rotary distributor 74 and from there via a further line 76 to the reservoir 2a, which in this case is an annular channel.

[0051] In addition to this ring channel 2a shown, further ring channels are preferably provided, but in the illustration shown in FIG. 1 they are covered by the ring channel 2a, for example they are located below it. The reference sign 98 indicates a connection line which delivers the compressed air to a forming station 20. Preferably, each of the ring channels is connected to all forming stations via corresponding connecting lines.

[0052] FIG. 2 shows the pressure fluctuations in the reservoir 2a, i.e. the annular channel 2a over time. You can see periodic pressure fluctuations that occur here in a time span of 12 seconds. These pressure fluctuations have a negative effect especially at low pressures such as the P1 pressure.

[0053] FIG. 3 shows a first illustration of a pressure fluctuation reduction device 4. Here, the reference sign 2a again refers to the reservoir or the annular channel. The reference sign 48 indicates a sensor device which is used to record pressure fluctuations and, in particular, to record them with a time dependency.

[0054] The reference sign 46 indicates a permanent magnet and the reference sign 48 indicates a coil. This is mechanically coupled to a vibrating part such as a diaphragm 1. By moving this diaphragm in the horizontal direction H, the volume of the reservoir 2a can be changed and can also be changed periodically, for example. In this way, pressure fluctuations inside the reservoir 2a can be compensated.

[0055] FIG. 4 shows a further design of a pressure fluctuation reduction device. Again, a permanent magnet 46 and a coil 48 are provided. The reference sign 54 here also indicates a vibrating element, such as a plate. Also by moving this plate in the horizontal direction H, the size of the reservoir 2a is changed and in this way pressure fluctuations can be counteracted.

[0056] FIG. 5 shows a further embodiment of a pressure fluctuation reducing device 4. In this embodiment, the motor drive such as linear motor 62 is provided, to which in turn a plate 64 is attached, which is movable in the horizontal direction H to change the volume of the reservoir 2a.

[0057] Overall, pressure fluctuations within the reservoir can be compensated for in the way described.

[0058] The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided that they are individually or in combination new compared to the prior art. It is further pointed out that the individual figures also describe features which may be advantageous in themselves. The skilled person immediately recognises that a certain feature described in a Fig. can also be advantageous without adopting further features from this Fig. Furthermore, the skilled person recognises that advantages can also result from a combination of several features shown in individual figures or in different figures.