DE102013103543A1 - Apparatus and method for forming plastic preforms into plastic containers - Google Patents

Abstract

A method for reshaping plastic preforms (10) into plastic containers (20) with the steps: - introducing a plastic preform (10) into a blow mold (2); - Applying a flowable medium to the plastic preform (10) arranged in the blow mold (2) in order to expand it; - Stretching the plastic preform (10) by means of a rod-like body (16) which is inserted through an opening of the plastic preform (10) therein by means of a movement in a first direction of movement; - Returning the rod-like body (16) by means of a movement of the rod-like body (16) in a second direction of movement, which is opposite to the first direction of movement. According to the invention, the plastic preform (10) is subjected to different pressures of the gaseous medium during its expansion, and the rod-like body (16) is returned at least partially by an overpressure present in the plastic container (20), with one supply of pressure to the plastic container (20) predetermined time is interrupted, and this time is before the completion of the return movement of the rod-like body (16) in the second direction of movement.

Description

The present invention relates to an apparatus and a method for forming plastic preforms into plastic containers. Such devices and methods have been known for a long time from the prior art. Usually first plastic preforms are heated and then, in particular as part of a stretch blow molding process, expanded to plastic containers, such as plastic bottles. As part of this process, the plastic preforms are usually passed to a plurality of forming stations and expanded in these by applying compressed air to the plastic containers. Usually also so-called stretch rods are used in the prior art, which stretch the plastic preforms in the longitudinal direction during the expansion process. Such devices and methods therefore require a lot of resources, in particular compressed air and electric power in electrically driven stretch rods. In the prior art, there is always an effort to develop ways to reduce such resource consumption.

It is also known to carry out the deformation of the plastic preforms with different pressure levels, for example a Vorblasdruck and a Fertigblasdruck.

The present invention has for its object to further improve the resource efficiency of such devices in the process. This is achieved according to the invention by the subject matters of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

In a method according to the invention for forming plastic preforms into plastic containers, plastic preforms are introduced into a blow mold or a multiplicity of blow molding stations. Furthermore, the plastic preforms arranged in the blow mold are acted upon by means of a flowable and in particular a gaseous medium so as to be expanded. Furthermore, the plastic preforms are stretched by means of a rod-shaped body, said rod-shaped body is inserted through an opening of the plastic preform in this, wherein for this movement in a first direction of movement of the rod-like body relative to the plastic preform. Furthermore, the rod-like body is returned again by means of a movement of this rod-like body in a second direction of movement, which is opposite to the first direction of movement. The time of the first compressed air supply may be before or after the insertion of the rod-like body.

According to the invention, the plastic preform is acted upon during its expansion with different pressures of the gaseous medium, and a return of the rod-like body is at least partially by an existing in the container pressure, further a pressure supply to the plastic container is interrupted at a predetermined time and this time in time the conclusion of the return movement of the rod-like body in the second direction of movement is.

It is therefore proposed in the context of the invention that the recirculation of the rod-like body of existing in the container overpressure, in particular the overpressure, which is constructed towards the end of the expansion process is used.

Furthermore, however, it has also been found that in order to achieve this return movement, it is not necessary for the container to be further pressurized, but it may be sufficient if the pressure supply is already switched off before or during the return of the rod-like body. For this purpose, it is possible, for example, that a high-pressure valve, which supplies the plastic preform or the plastic container with a pressure, is closed.

By the time after the time in the blow mold existing (highest possible) pressure, it is possible to exert a (high) force on the lower end of the rod-like body, at the same time the volume of the rod-like body by closing the compressed air supply is not filled with new compressed air must become.

In a preferred method, the plastic preforms or plastic containers are moved along a circular path during their expansion.

To drive the rod-like body, an electric drive and in particular an electric motor and in particular a linear motor is preferably used. In addition, however, it would also be possible to provide a threaded spindle drive for the movement of the rod-like body. Advantageously, the plastic preform is at least temporarily stretched both in its longitudinal direction and expanded by compressed air, so that at least temporarily, a stretching of the material of the plastic preform takes place biaxially.

In a further preferred method, it is also possible that this electric motor by means of a force compensating a through the Internal pressure of the gas generated in the container and acting on the engine force at least partially and preferably at least temporarily compensated.

In a further preferred method, energy can also be generated by the aforementioned backward movement of the rod-like body, for example by a corresponding drive acting as a generator here.

In a further preferred method, however, it would also be possible for such regenerative operation of an electric motor to be deliberately prevented or prevented. In a further preferred method, a spring element can be provided, which counteracts a return of the rod-like body. Thus, it is possible that a force compensation, as mentioned above, is performed by means of a spring element.

It would also be possible that an internal pressure within the container is used for the said force compensation.

In a further advantageous method, the plastic preforms are initially subjected to a first pressure level during their expansion and subsequently to a second pressure level, which is higher than the first pressure level. Thus, for example, the first pressure level may be in a range between 5 and 15 bar and, for example, the second pressure level in a range between 20 bar and 40 bar.

In a further advantageous method, the above-mentioned time at which the pressure supply is interrupted in the container, before or at the beginning of the backward movement of the rod-like body. As mentioned above, it has been found that it may also be sufficient for the return of the rod-like body when its full backward movement is supported or attained by the pressure in the container without further pressure being applied to the container. In this way, a high energy saving is possible.

In a further advantageous method, the return movement of the rod-like body takes place against gravity. It has even been found that the internal pressure in the container may even be sufficient to carry out the rod-like body against its own gravity and possibly against the force of gravity of other elements, such as a guide carriage. In this preferred method, the plastic preforms are preferably expanded while the mouth is at the top.

In a further preferred method, the plastic preform is subjected during its expansion to a third pressure level, which differs from the first pressure level and the second pressure level. Thus, it would be possible, for example, for the pre-blowing of the plastic preforms to take place first, followed by application of an intermediate blowing pressure and, finally, by means of an even higher blow-molding pressure to complete the molding of the plastic containers.

In a further advantageous method, at least a portion of the flowable medium used for the expansion of the plastic containers is supplied to a reservoir after this use in order to be used for a further expansion process of at least one further plastic container. It is possible that the above-mentioned different pressure levels are provided via a plurality of gas reservoirs, which may be formed, for example, as a ring channels. It is possible that when releasing the container, a certain proportion of the gas is returned to a reservoir, which has a lower pressure.

In a further advantageous method, after the return of the rod-like body, the expanded plastic container is pressure-relieved. After this pressure relief, the plastic container can be preferably removed from its blow mold.

The discharge may also take place at a time when the rod-like body is not yet completely returned from the blow mold, especially at about 10-95% of the (simple) way of the rod-like body to be covered in the blow mold.

In a further advantageous embodiment, the forming process of the plastic containers takes place within a clean room. This means that the plastic containers are preferably conveyed through a clean room during their expansion.

In a further preferred method, a loading device for applying the gaseous medium to the plastic preforms is also moved in a longitudinal direction of the container relative to the container, and at least temporarily coupled a movement of the loading device with the movement of the rod-like body. It is possible that the loading device, such as a blowing nozzle, is delivered to the plastic preform.

By this simultaneous movement, a further energy saving can be achieved. Furthermore, it is possible in this embodiment to save special guide curves for the loading device, which is in particular a blowing nozzle.

In this case, for example, at times and in particular during the return of the rod-shaped body, the said coupling with the movement of the loading device consist. A driver of the rod-like body for returning the loading device comes in particular with this for lifting this first in contact when more than 70%, preferably more than 85% and more preferably more than 95% of the (simple) path of the bar-like body to be covered in the blow mold was covered. In this way, a force acting on the rod-like body by the blowing pressure for a longer time, because a lifting of the loading device away from its sealing position on the hollow body draws a vent by itself.

The present invention is further directed to an apparatus for forming plastic preforms into plastic containers. This device has a movable support on which a plurality of forming stations is arranged, wherein each of these forming stations comprises a blow molding device which forms a cavity within which the plastic preforms are deformable by applying a flowable and in particular gaseous medium to the plastic containers. In this case, each of these forming stations on a loading device, which is movable relative to the plastic preforms or plastic containers in the longitudinal direction, to pressurize the plastic preforms or plastic containers with the flowable medium. Furthermore, each of these forming stations has a rod-like body which can be inserted into the plastic preforms or plastic containers and which is movable in the longitudinal direction of the plastic preforms or plastic containers in order to stretch these plastic preforms or plastic containers in their longitudinal direction. Furthermore, the device has a control device in order to control the supply of the gaseous medium to the containers with at least two different pressure levels, this control device having at least one valve device (or controls) to interrupt a supply of the flowable medium at a predetermined time ,

According to the invention, the device has a movement device for introducing the rod-like body into the plastic preforms or plastic containers by means of a movement in a first predetermined direction of movement, wherein a return of the rod-like body in a second movement direction opposite to the first movement direction is effected by means of a pressure built up in the plastic container flowable medium is possible and wherein the control device is designed such that a pressure supply to the plastic container is interrupted at a predetermined time and this time is prior to the completion of the return movement of the rod-like body in the second direction of movement.

Therefore, a combination is proposed on the device side in that, on the one hand, the return of the rod-like body is carried out or at least promoted by an internal pressure in the container and, on the other hand, a gas supply into the container is interrupted before completion of the return movement in order to save pressure in this way.

Advantageously, the device has at least two further valves in order to control the supply of the gaseous medium into the plastic containers. Preferably, at least three and preferably at least four such valves are provided. These valves may in particular be 2/2-way valves.

In a further advantageous embodiment, the device has at least one reservoir for storing the gaseous medium, wherein this reservoir is designed in particular as an annular channel, which can supply the individual transformation stations with compressed air. Advantageously, a plurality of such reservoirs are provided for the gaseous medium, so that the gaseous medium can be supplied to the plastic containers under different pressures.

Advantageously, the individual valves described above are arranged on or in a valve block. In this case, this valve block can be movable relative to the container to be expanded.

In a further advantageous embodiment, the device or in particular each transformation station also has at least one valve, which allows a release of air from the expanded container. It is possible that at least temporarily discharge of this gaseous medium takes place in one of the above-mentioned reservoirs.

In a further advantageous embodiment, the device has a coupling device, which is a movement of the rod-like body relative to the plastic container at least temporarily coupled with a movement of the loading device relative to the plastic container. This may in particular be a mechanical coupling device, which couples at least a portion of the movement, for example a feed movement or a return movement of the rod-like body with the movement of the loading device.

In a further advantageous embodiment, the rod-like body is designed as a stretching rod, which mechanically stretches the plastic container. It is also possible that the rod-like body has a cavity or a conduit, so that the container compressed air can be supplied through the rod-like body through or compressed air can be removed from the container.

In a further advantageous embodiment, the control device controls the supply of compressed air to the containers as a function of a rotational position of the arranged on the carrier forming station. Advantageously, the carrier mentioned above, to which the forming stations are arranged, is a carrier rotatable about a predetermined axis of rotation and in particular a so-called blowing wheel.

Further advantages and embodiments will be apparent from the attached drawings, in which:

1 A schematic representation of an arrangement for producing plastic containers;

2 a schematic representation of a valve assembly for a blowing station;

3 a sectional view of in 2 shown valve assembly;

4 a representation of the course of the individual valve positions; and

5a - 5d four further possible variations of the valve positions.

1 shows a schematic plan view of a plant 100 for the manufacture of plastic containers. In this case, this machine is a stretch blow molding machine and more particularly a continuous stretch blow molding machine. These are plastic preforms 10 initially via a sawtooth star shown only schematically 140 a heating device 150 fed. This may, for example, be an infrared oven, but it would also be conceivable to use a microwave oven. In the course of this warming become the plastic preforms 10 led to a variety of Heizdornen, which in mouths of the plastic preforms 10 are introduced, these heating mandrels are again guided on a revolving chain. However, instead of the oven shown here, a rotary machine could be used for heating, on which a plurality of heating stations is provided.

After tempering, the plastic preforms 10 of holding elements or gripping elements 131 transported further. The reference number 130 indicates an inlet star, which is used to transfer the plastic preforms 10 to the actual blow molding machine or its (only partially shown) forming stations 8th serves.

After the forming process, the now manufactured containers 20 from a sampling star 120 dissipated. Furthermore, the containers can 20 to other stations, such as a labeling machine, a filling machine or a capper, promoted. The transport routes of the plastic preforms 10 and the bottles 20 are indicated here by arrows.

The individual blowing stations 8th be here by means of a compressor 160 that has a variety of compressor levels 161 has, supplied with a gaseous medium, in particular with compressed air. For example, in the first stage of the compressor shown on the right 160 Air to be compressed to a pressure of, for example, 5 bar. In the subsequent stage, for example, 10 bar can be compressed, etc.

Subsequently, the air is supplied via a supply line 162 a rotary distributor 165 fed, which here with a stationary part of the machine 100 with a rotatable part, namely the blowing wheel 170 combines. After passing through the rotary distributor, the high-pressure blowing air is advantageously guided to a plurality of pressure reducers, not shown, which are connected to the compressor 160 reduce the pressure to different pressure levels. For this purpose are on the blowing wheel 170 , on which also the transformation stations 8th are arranged a plurality of annular channels S1-S4 arranged, which also represent the above-mentioned compressed air reservoirs. Thus, these ring lines serve as a pressure distributor for the individual blow molding stations 8th on the blowing wheel 170 , With a larger design, they can also be used as storage. Thus, for example, a pre-blowing pressure of, for example, 10 bar is provided in the ring line or the reservoir S3. In the ring line S2, an intermediate blow pressure of, for example, 20 bar is provided and in the loop S1 a Fertigblasdruck of, for example, 35 bar.

Advantageously, each individual blowing station also has a valve unit or a valve block 5 on, which is connected to the individual ring lines S1-S4. To this valve block, as will be explained in more detail below, a plurality of valves are arranged, which control the individual pressures. This unit connects this valve unit 5 the individual ring lines S1-S4 optionally with the plastic preform to be inflated.

After sealing the plastic preform 10 by means of a blowing nozzle 12 (see. 3 ) This is connected successively and in a predetermined order with the individual ring channels. First, a pre-blowing by a connection with the annular channel S3, then an intermediate bubbles by connection to the annular channel S2 (wherein preferably the connection to the annular channel S3 is closed again) and finally a finished blowing by connection to the annular channel S1, in which case again preferably the compounds closed to the first two ring channels.

After the finished expansion, the air is removed from the container 20 (Which is preferably still below the Fertigblasdruck), preferably first returned back into the annular channel S2 and advantageously so long until the pressure in the container has reached approximately the pressure in this annular channel S2. Subsequently, the air is in the container 20 (which is now approximately under the pressure of the annular channel S2) preferably still fed to the channel S3.

However, it would also be possible for the pre-blow channel S3 to be used initially for recirculating the air, in particular if it is to be ensured that a minimum pressure is always to be provided therein. In addition, it would also be conceivable to regulate the return time via the pressure in one of the channels S2, S3, S4 by means of a pressure sensor, not shown.

It would also be conceivable to dispense with the pressure reducers, which provide the pressure for the channels S2 and S3, during production, if enough air can be recycled. However, for starting the blow molding machine, these pressure reducers are advantageous.

Instead of allowing the remaining air to escape through an outlet into the atmosphere, it is also conceivable that the blown air is then fed back into the channel S4 again to a level of about 3 to 5 bar. Since the pre-blowing from the channel S3 under a certain pressure of 10 bar here must represent the first step in the production of the hollow body, this fourth annular channel S4 is due to its lower pressure level in the embodiment shown in particular and preferably exclusively collecting, but especially the (Intermediate) storage, of recirculated air from the container 20 and not for blowing. From there, the air can either still on the blowing wheel 170 For example, pilot valves or other drives of the individual blow molding stations 8th (For example, a drive for stretching bars) are provided. In addition, it would also be conceivable that this air over another line and through the rotary distributor 165 back to the stationary part of the machine, for example via a pipe 163 , is transferred. From there, for example, the air can enter an intermediate stage of the compressor 161 be fed back or turn over a line 164 a Hallluftluftnetz or other uses such as a bottle bottom post-cooling or a labeling or filling machine are supplied.

It would also be possible that the ring lines S1-S4 shown are only partially annular. For example, such an annular channel could also be formed by two semicircular halves. The reference number 14 (shown here only very schematically) denotes a drive unit for moving a stretch rod 16 ,

As mentioned above, it is proposed in the context of the invention that the supply of high pressure air, that is the connection to the annular channel S3, is interrupted before or while the stretch rod is being returned from the containers. The reference number 40 Roughly schematically indicates a control device which controls the supply of the gaseous medium into the plastic preforms. This control device can in particular control the supply of compressed air under the different pressures as well as the timing of the opening and closing of the individual valves, which supply the plastic preform air or remove air from this. It can also be arranged at each blowing station control.

2 shows a more detailed representation of a blowing station or its valve assembly 5 , Here is also the stretch rod 16 shown, which moves to stretch the plastic preforms perpendicular to the plane of the figure. Furthermore, the individual valves 22 . 24 . 26 . 28 and 32 shown. These individual valves each have pilot valves 22a . 24a . 26a and 28a on, which ultimately serve to control the actual valve body. The valve is used 26 for pre-blowing and is therefore in fluid communication with the loop S3. The reference number 24 indicates a valve for inter-bubbles, and this valve is therefore connected to the ring line S2 in 1 in fluid communication. The reference numeral 22 indicates the valve for final blowing, and this valve is therefore in fluid communication with the loop S1. The connection holes in the valve block 5 to the ring lines are not shown in this sectional view - these are perpendicular to the plane of the figure at the points between the piston shown and their sealing surfaces in the direction stretching bar 16 ,

The reference number 32 indicates an exhaust valve, which, as mentioned above, the compressed air can recirculate, for example in one of the other loops. The reference number 28 indicates a further outlet valve, which can also lead compressed air to the ring lines or can also lead to a further use. The reference number 44 indicates a carrier to which the valve assembly 5 is arranged.

3 shows a sectional view of in 2 shown valve assembly. Here one recognizes that over the connecting lines 26b and 32b each connection to reservoirs can be made. For example, is the connection line 26b in flow communication with the channel S3.

Also here is the stretch rod again 16 which can be moved, indicated here by the arrow P1 in a vertical direction. Also schematically is partially the plastic preform to be expanded 10 shown.

The reference number 12 indicates an impingement device such as a blowing nozzle, here by means of sealing means 54 opposite a support ring 10a the plastic preform can be sealed. The reference number 56 indicates a circulation body which surrounds the mouth region of the plastic preform during the expansion process.

Also the admission device 12 is here in the direction of the arrow P1 movable so as to be delivered to the plastic preform. As mentioned above, in a preferred embodiment, this movement of the plastic preform is at least temporarily due to movement of the stretching rod 16 coupled. The admission device 12 can firmly with the valve block 5 be connected, or arranged to be movable to this. In the second case, the valve block 5 immovably arranged at the blowing station.

As mentioned above, prevails during the Fertigblasens the container 10 a comparatively high internal pressure in the container. This pressure can be used to stretch the bar 16 again from the plastic container 10 push out. The reference number 58 indicates sealing devices which prevent air from the side of the stretch rod 16 pass by.

Such a coupling between the stretching rod movement and the movement of the loading device 12 could here, for example mechanically, be designed so that a return or even an insertion of the stretch rod is temporarily coupled with the movement of the loading device. Here would then be the stretch rod 16 and the applying device 12 at least temporarily moving in the same direction at the same speed.

4 shows a representation to illustrate the individual pressure gradients. In each case, the opening and closing positions of the individual valves 26 . 24 . 22 and 28 shown, wherein the horizontal higher beam each illustrates an open position and the lower beam a closed position. It can be seen that first the Vorblasventil 26 is opened for a predetermined period, then this is closed and the intermediate blow valve 24 is opened. Then also the intermediate blow valve 24 closed again and Fertigblasventil 22 open. It can be seen that at this moment the stretch rod (see the bottom line) is returned again (compare area A4). In this position all air supply valves are closed, so that the volume of the stretch rod does not have to be filled. On the intermediate bubbles and the authoritative valve could also be dispensed with.

Preferably, the rod-like body 26 around a hollow body, that is, it can also be fed through this rod through air. However, since there is still pressure in the container, the stretch rod is pushed out of the container, since at least in the region of the return movement A4 and the exhaust valves are also still closed. The outlet valve 28 is opened, as seen here, only when the stretch rod is completely out of the container out, but it could also open sooner to gain process time - this depends, inter alia, very much on the bottle.

By not shown sensors, the valve circuit via the controller 40 also controllable, so that can be determined when entering total output and quality of the operating mode in which an optimal energy consumption exists. The quality is determined by means of a wall thickness measurement or weight distribution measurement. In addition, the performance of the compressor and, if necessary, the electrical power of the drives (stretch rod, main drive) is measured.

The 5a - 5d show further possible embodiments of such a valve circuit. During the actual expansion process, the course is similar to the embodiment in FIG 1 , That is to say in a sequence valves 26 . 24 and 22 open. After returning the stretch rod in the area A4, however, the intermediate blow valve again 24 opened so as to allow the air to escape from the container in the associated channel S2. Subsequently, this valve 24 closed again and still the valve 26 opened to recycle also in the ring channel S3. Only at the end of the process is the exhaust valve 28 open. Also in this embodiment, the stretch rod or the rod-like body is pushed up by the highest pressure, which is particularly suitable, for example, if power is to be generated in this area with a generator operation of an electric drive device. With regard to the air consumption, better solutions are conceivable, since the volume of the stretch rod within the blow mold must still be filled up by the pressure P2.

Possibly. In order to recycle the air, it is also possible to use channels or reservoirs to which only air is returned. In this case, a check valve between the reservoir and the hollow body can be arranged, which excludes exactly the effect of refilling. From this reservoir could be a return of the air to the reservoirs, which in turn serve to inflate, for example via a pressure reducer.

5b shows a further embodiment of the valve circuit, wherein, in contrast to the in 5a shown embodiment, first an air recycling in the two channels S2 and S3 is performed and only then the stretch rod is returned and finally the exhaust valve 28 is open. This embodiment is particularly suitable for minimizing air consumption, since the high pressure level can be used to fill up the other channels.

At the in 5c The procedure shown is similar, as in the in 5b shown method, only with the difference that the stretch rod movement is used while the valve 26 is closed and while the exhaust valve 28 is opened. This method is particularly suitable for gaining process time. The individual figures are not shown to scale. Both 4 to 5c can also be dispensed with the intermediate bubbles. If it is used, the air can also be routed in the return flow first in the Vorblaskanal and only then in the Zwischenblaskanal. It could also be completely dispensed with a return, if required by the required process time.

At the in 5d As shown, a recycling valve is also opened during the stretching rod movement. Thus, the travel of the stretch rod is divided into a first portion in which the full force acts on the stretch rod (caused by the pressure in the container) and a subsequent section in which the force on the stretch rod or an electric motor driving them is lower (the pressure reduction due to the withdrawn volume of the stretch rod is not counted). In this embodiment, an additional recycling channel may be provided which is connected, for example via a check valve with the container or the blow mold. Compressed air can be supplied again via this further recycling channel, for example the P1 channel or other consumers.

As mentioned above, the rod body or stretching rod is preferably hollow. In this way you can the container, as mentioned, also by the stretch rod through (against the atmosphere or another annular channel) to flush. This can be interesting, for example, for a so-called heatset process.

However, it would also be possible for the stretch rod to be raised while such a rinse phase is still taking place.

The Applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are novel individually or in combination with respect to the prior art.

LIST OF REFERENCE NUMBERS

LIST OF REFERENCE NUMBERS

5

manifold

8th

blowing stations

10

The plastic preforms

10a

support ring

12

Blast nozzle / application device

14

drive unit

16

stretching rod

20

Containers / bottles

22, 24, 26, 28

valves

22a, 24a, 26a, 28a

pilot valves

26b, 32b

interconnectors

32

outlet valve

44

carrier

54

seal means

56

recirculating

58

sealing means

100

investment

120

removal star

130

feed star

131

gripping element

140

Sägezahnstern

150

heater

160

compressor

161

compressor stages

162-164

supply lines

165

rotary distributor

170

blow wheel

S1-S4

annular channels

P1

vertical direction of movement of the stretch rod / valve

A4

Range of return movement

Claims (15)

Method for shaping plastic preforms ( 10 ) to plastic containers ( 20 ) comprising the steps of: - introducing a plastic preform ( 10 ) in a blow mold ( 2 ); - stretching the plastic preform ( 10 ) by means of a rod-like body ( 16 ) passing through an orifice of the plastic preform ( 10 ) is introduced in these by means of a loading movement in a first direction of movement; - loading in the blow mold ( 2 ) arranged plastic preform ( 10 ) with a flowable medium to expand it; - return of the rod-like body ( 16 ) by means of a movement of the rod-like body ( 16 ) in a second direction of movement, which is opposite to the first direction of movement; characterized in that the plastic preform ( 10 ) is acted upon during its expansion with different pressures of the gaseous medium and that a return of the rod-like body ( 16 ) at least partially by a in the plastic container ( 20 ) existing pressure is carried out while a pressure feed into the plastic container ( 20 ) is interrupted at a predetermined time, and this time in time before the completion of the return movement of the rod-like body ( 16 ) lies in the second direction of movement. A method according to claim 1, characterized in that a (to the rod-like body 16 ) cooperating drive in the return movement is operated as a generator. A method according to claim 1 or 2, characterized in that a venting of the finished molded hollow body against the atmosphere is carried out only after at least 50% of the distance to be traveled by the rod-shaped body within the blow mold. Method according to claim 1 or 2 or 3, characterized in that the plastic preform ( 10 ) is first acted upon during its expansion with a first pressure level and then with a second pressure level, which is higher than the first pressure level. A method according to claim 1, characterized in that the predetermined time before or at the beginning of the backward movement of the rod-like body ( 16 ) lies. Method according to at least one of the preceding claims, characterized in that the return movement of the rod-like body ( 16 ) takes place against gravity. Method according to claim 2, characterized in that the plastic preform ( 10 ) is acted upon during its expansion with a third pressure level, which differs from the first pressure level and the second pressure level. Method according to at least one of the preceding claims, characterized in that at least a portion of the flowable medium used for the expansion of the plastic containers after this use a reservoir (S1, S2, S3) is supplied to at least one further plastic container used for a further expansion process become. Method according to at least one of the preceding claims, characterized in that after the return of the rod-like body ( 16 ) the expanded plastic container ( 20 ) is depressurized. Method according to at least one of the preceding claims, characterized in that an admission device ( 12 ) for applying the plastic preforms ( 10 ) is moved with the gaseous medium in a longitudinal direction of the plastic preform relative to the plastic preform and at least temporarily movement of the loading device ( 12 ) with the movement of the rod-like body ( 12 ) is coupled. Method according to at least one of the preceding claims, characterized in that the valve of the second pressure stage when inflating the container is opened only when the stretching rod has covered at least 50%, in particular 95% of the way within the blow mold, in particular only when the stretch rod below rests on Blasformboden. Method according to at least one of the preceding claims, characterized in that the rod-like body from the time of connection of the preform with a second pressure accumulator until the predetermined time in contact with the bottom of the hollow body in contact, that as little force in the direction of withdrawal on the rod-like body acts. Contraption ( 100 ) for forming plastic preforms ( 10 ) to plastic containers ( 20 ) with a movable support ( 2 ), where a large number of transformation stations ( 8th ), each of these transformation stations ( 8th ) comprises a blow molding device which forms a cavity within which the plastic preforms ( 10 ) by applying a flowable medium to the plastic containers ( 20 ) are convertible, and wherein each of these transformation stations ( 8th ) an admission device ( 12 ), which opposite the plastic preforms ( 10 ) is movable in the longitudinal direction of the plastic preforms ( 10 ) to be supplied with the flowable medium, and wherein each of these transformation stations ( 8th ) one in the plastic containers ( 10 ) insertable rod-like body ( 16 ), which in the longitudinal direction of the plastic preforms ( 10 ) is movable in relation thereto in order to stretch these plastic preforms in their longitudinal direction, wherein the device further comprises a control device ( 40 ) to control the supply of the gaseous medium to the containers with at least two different pressure levels and this control device ( 20 ) a valve device ( 22 ) in order to interrupt a supply of the flowable medium at a predetermined time, characterized in that the device ( 1 ) a movement device ( 14 ) to the rod-like body ( 16 ) with a movement in a first predetermined direction of movement in the plastic preforms ( 10 ), wherein a return of the rod-like body ( 16 ) in a direction of movement opposite to the second direction of movement by means of a in the plastic container ( 20 ) is established, and the control device ( 40 ) is designed such that a pressure supply into the plastic container ( 20 ) is interrupted at a predetermined time, and this time in time before the completion of the return movement of the rod-like body ( 16 ) lies in the second direction of movement. Contraption ( 1 ) according to claim 9, characterized in that the device comprises at least two further valves ( 24 . 26 ) to control the supply of the gaseous medium in the plastic containers. Contraption ( 1 ) according to claim 9, characterized in that the device comprises a coupling device, which movement of the rod-like body ( 16 ) relative to the plastic container at least temporarily with a movement of the loading device ( 12 ) coupled to the plastic container.

Images