METHOD AND DEVICE FOR PRODUCING CONTAINERS FROM PREFORMS

Abstract

A method and a device for producing containers formed by pneumatic or hydraulic pressure (i.e. blowing pressure or the pressure of a fluid to be filled) from preforms with a blow mold are provided. The blow mold has a bottom mold with an axially displaceable bottom die, wherein for exerting a counterforce on the bottom die is configured to bias the bottom die into an extended position being arranged in the interior of the blow mold and being extended from the bottom mold, wherein the stretching rod is configured to displace the bottom die against the counterforce into a retracted position substantially being arranged in the bottom mold. The counterforce clamps the preform stretched by the stretching rod between the tip of the stretching rod and the bottom die so that the container being formed is always kept centered.

Claims

1. A method for producing a container formed by pneumatic or hydraulic pressure, comprising: providing a preform; arranging the preform in a blow mold; stretching the preform towards an axially displaceable bottom die with a stretching rod; biasing, by a counterforce, the bottom die into an extended position in an interior of the blow mold extended from a bottom mold of the blow mold; and displacing, during stretching with the stretching rod, the bottom die against the counterforce into a retracted position substantially being arranged in the bottom mold.

2. The method according to claim 1, wherein the counterforce is generated by one or more of a spring, a pressurized fluid, a permanent magnet, and an electromagnet.

3. The method according to claim 1, further comprising cooling an area of the preform adjacent to the bottom die during stretching by cooling the bottom die.

4. The method according to claim 1, wherein the bottom die releasably engages in the retracted position when the latter is reached, wherein the engagement is released by removing a formed container from the blow mold or by closing the blow mold, wherein after releasing the engagement the counterforce pushes the bottom die into the extended position.

5. A device for producing containers formed by pneumatic or hydraulic pressure from preforms, comprising: a blow mold; and a stretching rod for stretching the preforms, wherein the blow mold comprises a bottom mold with an axially displaceable bottom die, and a pusher for exerting a counterforce on the bottom die, wherein the pusher is configured to bias the bottom die into an extended position being arranged in an interior of the blow mold and being extended from the bottom mold, and wherein the stretching rod is configured to displace the bottom die against the counterforce into a retracted position substantially being arranged in the bottom mold.

6. The device according to claim 5, wherein the pusher for exerting the counterforce comprises a spring, a pressurized fluid, a permanent magnet, or an electromagnet.

7. The device according to claim 5, wherein the bottom die comprises a plurality of coolant channels.

8. The device according to claim 5, wherein an adjustable stop is configured to adjust a distance between the extended position and the retracted position of the bottom die.

9. The device according to claim 5, wherein the bottom die releasably engages in the retracted position.

10. The device according to claim 9, wherein the engagement is released after removing a molded container or after closing the blow mold, and wherein the pusher is configured to push the bottom die to the extended position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a first phase (initial state) of a blow molding method;

[0019] FIG. 2 shows a second phase (initial state) of blow molding;

[0020] FIG. 3 shows a third phase (clamping and cooling) of blow molding;

[0021] FIG. 4 shows a fourth phase (stretching) of blow molding;

[0022] FIG. 5 shows a fifth phase (springing back) of blow molding;

[0023] FIG. 6 shows a sixth phase (initial state) of blow molding; and

[0024] FIG. 7 shows an alternative exemplary embodiment of the disclosure.

DETAILED DESCRIPTION

[0025] FIGS. 1 to 6 show a preferred first exemplary embodiment. Those figures show a blow mold 10 with a bottom mold 11. A bottom die 12 is integrated into the bottom mold 11, which is movably guided in the axial direction of the blow mold 10. The blow mold 10 further comprises a stretching rod 13, which is also movably guided in the axial direction of the blow mold 10. Preferably, the bottom die 12 and stretching rod 13 are centered in the blow mold 10.

[0026] The stretching rod 13 is moved axially into and out of the blow mold 10 in the known manner by a drive (not shown).

[0027] Furthermore, a pusher 15 is provided which serves to exert a counterforce on the bottom die 12 and prestresses it axially in the direction of the interior of the blow mold 10, i.e. into an extended position being inside the blow mold 10 and extended from the bottom mold 11 of the blow mold 10. The pusher is realized in the form of a spring 15 according to FIGS. 1 to 7. As already mentioned, the counterforce can also be generated pneumatically or hydraulically by a pressurized fluid (gas or liquid) and/or magnetically by a permanent magnet or electromagnet.

[0028] The extended position of the bottom die 12 is preferably a stop position at which the axial movement towards the inside of the blow mold 10 ends by a mechanical stop acting on the bottom die 12. Such a mechanical stop is usually provided, for example, as part of an axial guide for the bottom die 12 and therefore does not need to be explained further.

[0029] This stop can preferably be adjusted in such a way that the distance between the extended position in the base mold 11 and a retracted position of the bottom die 12 essentially is adjustable.

[0030] The bottom die 12 has one or more channels 14 inside, through which a coolant (for example water) can be passed to cool the bottom die 12. Inlets and outlets for the coolant as well as corresponding pumping devices are realized in the usual manner and are therefore not shown.

[0031] FIGS. 1 to 6 show successive phases during a method for producing containers formed from preforms by pneumatic or hydraulic pressure (i.e. blowing pressure or the pressure of a fluid to be filled).

[0032] FIG. 1 shows a first phase in which the blow mold 10 is in an initial state. During this phase, the spring 15 presses the bottom die 12 into the extended position, i.e. an upper stop position (initial position) in which the bottom die 12 projects into the blow mold 10. The stretching rod 13 (not shown) is in an upper position outside the blow mold 10.

[0033] FIG. 2 shows a second phase (stretching) in which a preform P is placed in the (locked) blow mold 10 and is stretched by the stretching rod 13 guided in this mold. For this purpose, the stretching rod 13 is moved into the blow mold 10 in the known manner. In the state shown in FIG. 2, the distance between the top of the preform P and the opposite face of the bottom die 12 is still about 10 mm.

[0034] In the third phase shown in FIG. 3, the stretching rod 13 and thus also the top of the preform P has reached the bottom die 12 and is thus clamped between the tip of the stretching rod 13 and the opposite face of the bottom die 12 according to the counterforce exerted by the spring 15. At the same time, the coolant is passed through the channels 14 of the bottom die 12 so that the preform P and in particular its tip touching the bottom die 12 (or its end face) is cooled.

[0035] After the preform P has been stretched by the stretching rod 13 and has been expanded against the inner wall of the blow mold 10 by the medium introduced under pressure into the preform P, the fourth phase shown in FIG. 4 is reached, in which the stretching rod 13 presses the bottom die 12 against the counterforce exerted by the spring 15 into its retracted position, essentially in the bottom mold 11, in which the bottom die 12 engages with a releasable lock. The preform P is now pressure-molded into a container.

[0036] By appropriately selecting the distance between the bottom die 12 in its extended position and the retracted position (i.e. by adjusting the stop as explained above), the duration for cooling the preform P or the container formed from the preform by the bottom die 12 can be determined.

[0037] After reaching the fourth phase according to FIG. 4, the stretching rod 13 may be retracted, the blow mold 10 may be opened, the container may be removed from the blow mold 10 and the blow mold 10 may be closed again. Preferably, when the container is removed or the blow mold 10 is closed, the locking mechanism of the bottom die 12 is also released so that the bottom die 12 is then pushed back into its extended position (upper stop position) by the counterforce of the spring 15 according to the fifth phase shown in FIG. 5 and, according to FIG. 6, the blow mold 10 is returned to its initial state shown in FIG. 1. The sequence can then be repeated with the next preform P fed in.

[0038] FIG. 7 shows a simplified embodiment of the invention. This embodiment differs from the preferred embodiment shown in FIGS. 1 to 6 in that the bottom die 12 has no channels 14 and is therefore not cooled. However, the sequences described above for forming and stretching the preform P remain unchanged, so that also in this embodiment, the preform P is clamped with its tip between the tip of the stretching rod 13 and the bottom die 12 (or its end face) in accordance with the counterforce of the spring 15 and the container being formed is always kept centered.

[0039] While the present invention has been described with reference to exemplary embodiments, it will be readily apparent to those skilled in the art that the invention is not limited to the disclosed or illustrated embodiments but, on the contrary, is intended to cover numerous other modifications, substitutions, variations and broad equivalent arrangements that are included within the spirit and scope of the following claims.