DE102005045942A1 - Method and apparatus for blow molding containers - Google Patents

Abstract

The method and the device are used for blow molding containers. After thermal conditioning, a preform made of a thermoplastic material is stretched by a stretching rod inside a blow mold and shaped into the container by the action of blowing pressure. The positioning of the stretching rod is specified using a cam control. At least one pickup coupled to the stretching rod is only guided along a curved path on both sides along a partial area of a lifting movement of the stretching rod.

Description

The The invention relates to a method for the blow molding of containers, in a preform made of a thermoplastic material after a thermal conditioning within a blow mold from a stretch rod is stretched and transformed by blowing pressure into the container.

The Invention relates to this In addition, a device for blow molding containers made of a thermoplastic Material containing at least one blowing station provided with a blow mold and which is provided with a stretching device, in whose Area a stretch rod for applying one in the blow mold usable preform is arranged and in which the stretch rod with a lift control for the implementation a motion coordination of the stretch rod is coupled.

at a container molding by blowing pressure are preforms of a thermoplastic Material, for example preforms made of PET (polyethylene terephthalate), within a blow molding machine different processing stations fed. Typically, such a blow molding machine has a heating device and a blowing device, in the region of which previously tempered Preform expanded by biaxial orientation to a container becomes. The expansion takes place with the help of compressed air, which in the is initiated to expanding preform. The procedural Sequence in such an expansion of the preform is in the DE-OS 43 40 291 explained. The introductory mentioned Introduction of the pressurized gas also includes the introduction of compressed gas in the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process.

Of the fundamental Construction of a blowing station for container molding is described in DE-OS 42 12 583. Possibilities for tempering The preforms are described in DE-OS 23 52 926.

Within the blow molding apparatus, the preforms and the blown containers transported by means of different handling devices become. proven In particular, the use of transport thorns, to which the preforms are attached. But the preforms can be handled with other support devices. The usage grippers for handling preforms and use of expanding mandrels for mounting in a mouth region of the preform insertable are, belong also available Constructions.

A Handling of containers using transfer wheels For example, in DE-OS 199 06 438 in an arrangement of the transfer wheel between a blowing wheel and an output path.

The already explained Handling of the preforms takes place on the one hand in the so-called two-stage process, where the preforms initially in an injection molding process produced, then stored and later conditioned in temperature and inflated to a container become. On the other hand, an application in the so-called one-step process, in which the preforms immediately after their injection molding Manufacture and sufficient solidification suitable tempered and subsequently be inflated.

in the With regard to the blowing stations used are different embodiments known. At blow stations, which are arranged on rotating transport wheels are, a book-like Aufklappbarkeit the mold carriers are frequently encountered. But it is also possible to use relatively displaceable or differently guided mold carriers. at fixed blow molding stations, which are particularly suitable for multiple cavities for container molding are typically arranged parallel to each other Plates as mold carriers used.

The execution The motion coordination of the stretch rod can be based on different principles respectively. It is known, for example, the stretch rod using of cam rollers to position along curved paths guided are. A particularly high accuracy and reproducibility of the Stretching process can be realize in such curve controls when the cam rollers guided on two sides and thereby follow a precisely defined path. such However, cam controls have the disadvantage that heavy and spatially large dimensioned Curved tracks must be used which usually must be used from curved tracks, the usually made of steel. A conversion of the stretching system to perform modified stretching movements causes a lot of effort.

There are also curve controls are known in which the cam rollers are guided only on one side and are pressed using pneumatic cylinders against the one-sided guideway. Although there is a simplified and therefore cheaper and lighter construction before, depending on the stretching forces occurring the cam roller but can stand against the loading pneumatic clamping force of the cam track and the stretching process thus leaves the specified process characteristic. This results in a deteriorated quality of blown containers.

Very exact stretching systems can be provided using linear electric motors. However, linear motors of the required power are currently still very expensive and claim it In addition, a large space.

All Previously known systems for coordinating the execution of a stretching process thus have a number of advantages and disadvantages, an optimal fulfillment the requirements with a minimization of the remaining However, disadvantages have not yet been achieved.

task It is therefore an object of the present invention to provide a method of the invention specify such a way that an easily adaptable, inexpensive and at the same time provided lightweight control device for the stretching system becomes.

These Task is inventively characterized solved, that one Specification of the positioning of the stretch rod using a Curve control performed in which a cam roller coupled to the stretch rod is merely along a portion of a carrying out a lifting movement of Stretching rod is guided on both sides along a curved path.

Further Object of the present invention is to provide a device of initially mentioned type to make that a compact and easy adaptable stretch bar control is provided.

These Task is inventively characterized solved, that the Drawbar coupled with a curve control, which is a with the stretch rod has connected cam roller, the only along a partial area of a control path on both sides along a curved path guided is.

By the only partially two-sided leadership of the cam roller is the construction weight of the cam control significantly reduced. The curve control can over it also made cheaper and faster assembled and disassembled become. The local Localization of the two-sided leadership the cam follower takes place along the intended control path in such a way that in the Area especially large expected stretching forces or in the area of large expected changes the stretching forces the mutual obsession ensured the cam roller is.

A particularly critical phase of the execution of the stretching process is controlled by the fact that the Customer after a contact of the stretch rod with a bottom of the preform guided on both sides becomes.

In As a rule, it proves to be sufficient that the customer after a contact the stretch rod with the bottom of the preform maximum along 80 Percent of the ensuing Reckweges guided on both sides becomes.

The Dimensioning of the cams can be reduced by that the Customer after contact of the stretch rod with the bottom of the preform maximum along 50 percent of the subsequent stretching path on both sides guided becomes.

A extremely compact cam control is provided by the fact that the customer after contact of the stretch rod with the bottom of the preform maximum along 30 percent of the subsequent stretching path on both sides guided becomes.

According to one another embodiment is provided that the Customer after contact of the stretch rod with the bottom of the preform maximum along 20 mm of the subsequent stretching path on both sides guided becomes.

Low sized cams can also be provided by the customer after a contact the stretch rod with the bottom of the preform maximally along 10 mm of the subsequent Reckweges is performed on both sides.

A defined leadership in the inlet region of the customer in the curved path is supported by the fact that the adapter before contact of the stretch rod with the bottom of the preform is guided on both sides along a flow area.

to Adaptation to different length preforms is proposed that the for the two-sided leadership Ab Abnehmers provided section along the cam track slidably is arranged.

A Combination of different drive systems takes place in that the stretching rod in addition to Positioning is positioned pneumatically by the customer.

According to one Another variant is it also possible that the Stretch rod in addition to Positioning is electrically positioned by the customer.

In addition, it is also thought that the stretching bar is hydraulically positioned in addition to positioning by the taker.

A simple mechanical realization can be done by the customer is guided by at least one cam roller along the curved path.

One compact device construction is supported by the fact that the customer by a direct contact between the cam roller and the cam track guided becomes.

According to one Another variant is it also possible that the Customer by an indirect roller guide along the curved path is positioned.

to Avoiding reversals of rotation by alternating Contact of the cam follower with two guideways is proposed that the Pickup of at least two cam rollers along the curved path is positioned.

One compact and easy-to-install fixture construction is thereby achieved that the customer by at least two on top of each other arranged cam rollers along the curved path is positioned.

to further increase the operational safety is provided that an additional non-mechanical positioning for the Reckstange is designed to be switched off.

In The drawings are exemplary embodiments of the invention shown schematically. Show it:

1 A perspective view of a blowing station for the production of containers from preforms,

2 a longitudinal section through a blow mold, in which a preform is stretched and expanded,

3 a sketch to illustrate a basic structure of a device for blow molding containers,

4 a modified heating section with increased heating capacity,

5 a side view of a blowing station, in which a stretch rod is positioned by a stretch rod carrier,

6 a side view of a stretching system with partially guided on two sides cam rollers

7 a side view according to the viewing direction VII in 6 .

8th a side view according to viewing direction VIII in 6 .

9 a longitudinal section along section line IX-IX in 6 .

10 a top view according to the viewing direction X in 6 and

11 a cross section along section line XI-XI in 6 ,

The basic structure of a device for forming preforms ( 1 ) in containers ( 2 ) is in 1 and in 2 shown.

The device for forming the container ( 2 ) consists essentially of a blowing station ( 3 ), which are blown ( 4 ) into which a preform ( 1 ) can be used. The preform ( 1 ) may be an injection-molded part of polyethylene terephthalate. To enable insertion of the preform ( 1 ) in the blow mold ( 4 ) and to allow removal of the finished container ( 2 ) the blow mold ( 4 ) from mold halves ( 5 . 6 ) and a bottom part ( 7 ), which by a lifting device ( 8th ) is positionable. The preform ( 1 ) in the area of the blowing station ( 3 ) of a transport mandrel ( 9 ), which together with the preform ( 1 ) passes through a plurality of treatment stations within the device. But it is also possible to use the preform ( 1 ), for example via pliers or other handling means directly into the blow mold ( 4 ).

To enable a compressed air supply line is below the transport mandrel ( 9 ) a connecting piston ( 10 ) disposed of the preform ( 1 ) Supplies compressed air and at the same time a seal relative to the transport mandrel ( 9 ). In a modified construction, it is basically also conceivable to use solid compressed air supply lines.

A stretching of the preform ( 1 ) takes place in this embodiment by means of a stretch rod ( 11 ), by a cylinder ( 12 ) is positioned. According to another embodiment, a mechanical positioning of the stretch rod ( 11 ) carried out over curve segments which are acted upon by Abgriff. The use of curve segments is particularly useful when a plurality of blow molding stations ( 3 ) are arranged on a rotating blowing wheel

At the in 1 illustrated embodiment, the stretching system is designed such that a tandem arrangement of two cylinders ( 12 ). From a primary cylinder ( 13 ), the stretch rod ( 11 ) first before the beginning of the actual stretching process into the area of a soil ( 14 ) of the preform ( 1 ) hazards. During the actual stretching process, the primary cylinder ( 13 ) with extended stretch rod together with a primary cylinder ( 13 ) carrying carriages ( 15 ) from a secondary cylinder ( 16 ) or via a cam control. In particular, the secondary cylinder ( 16 ) such a cam-controlled use that of a leadership role ( 17 ), which slides along a curved path during the execution of the stretching process, a current stretching position is specified. The leadership role ( 17 ) is from the secondary cylinder ( 16 ) pressed against the guideway. The sled ( 15 ) slides along two guide elements ( 18 ).

After closing in the range of girders ( 19 . 20 ) arranged mold halves ( 5 . 6 ) there is a locking of the carrier ( 19 . 20 ) relative to each other by means of a locking device ( 20 ).

For adaptation to different shapes of a mouth section ( 21 ) of the preform ( 1 ) is according to 2 the use of separate thread inserts ( 22 ) in the area of the blow mold ( 4 ) intended.

2 shows in addition to the blown container ( 2 ) also shown in dashed lines the preform ( 1 ) and schematically a developing container bubble ( 23 ).

3 shows the basic structure of a blow molding machine with a heating line ( 24 ) and a rotating blowing wheel ( 25 ) is provided. Starting from a preform input ( 26 ), the preforms ( 1 ) of transfer wheels ( 27 . 28 . 29 ) in the area of the heating section ( 24 ). Along the heating route ( 24 ) are radiant heaters ( 30 ) as well as blowers ( 31 ) arranged to the preforms ( 1 ) to temper. After a sufficient temperature of the preforms ( 1 ) these are to the blowing wheel ( 25 ), in whose area the blowing stations ( 3 ) are arranged. The finished blown containers ( 2 ) are provided by further transfer wheels of a delivery line ( 32 ).

To get a preform ( 1 ) into a container ( 2 ) that the container ( 2 ) Has material properties which have a long useful life from inside the container ( 2 ), in particular beverages, special process steps in the heating and orientation of the preforms ( 1 ) be respected. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

When thermoplastic material can different plastics are used. Can be used for example PET, PEN or PP.

The expansion of the preform ( 1 ) during the orientation process is carried out by compressed air supply. The compressed air supply is in a Vorblasphase in which gas, for example, compressed air, is supplied at a low pressure level and divided into a subsequent Hauptblasphase in which gas is supplied at a higher pressure level. During the pre-blowing phase, compressed air is typically used at a pressure in the interval of 10 bar to 25 bar and during the main blowing phase compressed air is supplied at a pressure in the interval of 25 bar to 40 bar.

Out 3 is also apparent that in the illustrated embodiment, the heating section ( 24 ) from a plurality of circulating transport elements ( 33 ) is formed, the chain-like strung together and along deflection wheels ( 34 ) are guided. In particular, it is envisaged to open a substantially rectangular basic contour by the chain-like arrangement. In the illustrated embodiment, in the region of the transfer wheel ( 29 ) and an input wheel ( 35 ) facing the extent of the heating section ( 24 ) a single relatively large-sized deflection ( 34 ) and in the region of adjacent deflections two comparatively smaller dimensioned deflection wheels ( 36 ) used. In principle, however, any other guides are conceivable.

To enable a dense arrangement of the transfer wheel ( 29 ) and the input wheel ( 35 ) relative to each other, the arrangement shown to be particularly useful, since in the region of the corresponding extent of the heating section ( 24 ) three deflection wheels ( 34 . 36 ), in each case the smaller deflection wheels ( 36 ) in the area of the transition to the linear curves of the heating section ( 24 ) and the larger deflection wheel ( 34 ) in the immediate transfer area to the transfer wheel ( 29 ) and to the input wheel ( 35 ). Alternatively to the use of chain-like transport elements ( 33 For example, it is also possible to use a rotating heating wheel.

After a finished blowing of the container ( 2 ), these are picked up by a picking wheel ( 37 ) from the field of blowing stations ( 3 ) and via the transfer wheel ( 28 ) and an output wheel ( 38 ) to the output section ( 32 ).

In the in 4 illustrated modified Heating section ( 24 ) can by the larger number of radiant heaters ( 30 ) a larger amount of preforms ( 1 ) are tempered per unit time. The blowers ( 31 ) direct cooling air into the area of cooling air ducts ( 39 ), which the associated radiant heaters ( 30 ) in each case opposite and deliver the cooling air via outflow openings. Due to the arrangement of the outflow directions, a flow direction for the cooling air is substantially transverse to a transport direction of the preforms ( 1 ) realized. The cooling air channels ( 39 ) in the area of the radiant heaters ( 30 ) opposite surfaces provide reflectors for the heating radiation, it is also possible on the discharged cooling air and a cooling of the radiant heater ( 30 ) to realize.

5 shows one opposite the representation in 1 modified representation of the blowing station ( 3 ) in a line of sight from the front. In particular, it can be seen from this illustration that the stretch rod ( 11 ) of a stretch rod carrier ( 41 ), which consists of a support base ( 40 ) and one via a coupling element ( 42 ) with the support base ( 40 ) connected roller carriers ( 43 ) is trained. The roller carrier ( 43 ) holds the leadership role ( 17 ), which serves to position the stretching system. The leadership role ( 17 ) is guided along a curved path, not shown. It is realized here a mechanical control of the stretching process.

This in 5 illustrated coupling element ( 42 ) can also in the embodiment according to 1 to allow complete mechanical decoupling of the cylinders ( 12 ) from each other or from a support element for the guide roller ( 17 ) are used.

5 illustrates a locked state of the coupling element ( 42 ), in which the support base ( 40 ) and the roller carrier ( 43 ) with each other through the coupling element ( 42 ) are connected. This results in a rigid mechanical coupling, which leads to a positioning of the guide roller ( 17 ) directly and directly into a positioning of the stretch rod ( 11 ) is implemented. It lies thereby in each movement state of the blowing wheel ( 25 ) a precisely predetermined positioning of the stretch rod ( 11 ) and the positioning of the stretch rod ( 11 ) is at a plurality of on the blowing wheel ( 25 ) arranged blow molding stations ( 3 ) at each blow station ( 3 ) exactly reproduced. This exact mechanical specification of the positioning of the stretch rod ( 11 ) contributes to a high product quality and to a high uniformity of the produced containers ( 2 ) at.

5 also shows the arrangement of a pneumatic block ( 46 ) to the blowing pressure supply of the blowing station ( 3 ). The pneumatic block ( 46 ) is equipped with high pressure valves ( 47 ) equipped with connectors ( 48 ) can be connected to one or more pressure supplies. After blow-molding of the containers ( 2 ) blowing air to be discharged into an environment is transmitted via the pneumatic block ( 46 ) first a silencer ( 49 ).

A typical implementation of the blowing process can be most easily based on 2 be illustrated. After inserting the preform ( 1 ) in the blow mold ( 4 ) and a locking of the blowing station ( 3 ) is first a retraction of the stretch rod ( 11 ) in the preform ( 1 ) with simultaneous blowing pressure support such that the preform ( 1 ) by the axial stretching not on the stretch rod ( 11 ) shrinks radially.

After the in 2 shown complete implementation of the stretching process, the complete expansion of the container bubble ( 23 ) in the final contour of the container ( 2 ) and the maximum internal pressure is maintained until the container ( 2 ) has reached a sufficient dimensional stability by cooling. After reaching this dimensional stability, the blowing pressure supply is switched off and the stretching rod ( 11 ) is again from the blow mold ( 4 ) and thus from the blown container ( 2 ) withdrawn.

6 shows a side view of one with the stretch rod ( 11 ) provided stretching device ( 50 ). The stretching device ( 50 ) is as part of a blowing station, not shown ( 3 ), which together with a blowing wheel ( 25 ) rotates. The stretching rod ( 11 ) is with a curve control ( 51 ), which has a primary curve ( 52 ) extending along the extent of a stretching path. At a distance to the primary curve ( 52 ) is a secondary curve ( 53 ), which extends only along a portion of the stretching path. Between the curves ( 52 . 53 ) is a customer ( 54 ) guided in the illustrated embodiment, two cam rollers ( 55 . 56 ) having. The cam rollers ( 55 . 56 ) are in the direction of a longitudinal axis ( 57 ) of the stretch rod ( 11 ) arranged one behind the other.

The stretching rod ( 11 ) is in the direction of the longitudinal axis ( 57 ) with a positioning rod ( 58 ), the customer ( 54 ) wearing. The positioning rod ( 58 ) is also equipped with a pressure device ( 59 ), which is realized in the illustrated embodiment as a pneumatic cylinder. The pressure device ( 59 ) performs the cam follower ( 55 ) along the primary curve ( 52 ).

According to the embodiment 6 is the secondary curve ( 53 ) with a positioning device ( 60 ), which provides a controlled increase in distance between the primary curve ( 52 ) and the Secondary curve ( 53 ) and thereby can prevent otherwise predetermined by the curve control forced execution of the stretching process. The positioning device ( 60 ) consists of a pneumatic cylinder ( 61 ) and a carriage guide ( 62 ) with the secondary curve ( 53 ) is coupled. The carriage guide ( 62 ) consists of two guide rods ( 63 . 64 ), on which displaceable sockets ( 65 . 66 ) are guided. The sockets ( 65 . 66 ) are via a cross-beam ( 67 ) with each other and with the pneumatic cylinder ( 61 ) and the secondary curve ( 63 ) connected. As an alternative to carrying out the above-described translation process, it is also possible that the positioning device ( 60 ) the secondary curve ( 53 ) pivoted so that the customer ( 54 ) no longer through the secondary curve ( 53 ) is forced.

A piston rod ( 68 ) of the pneumatic cylinder ( 71 ) is on a main crossbar ( 69 ), in addition the two guide rods ( 63 . 64 ) connects to each other.

To support an adaptability of the stretching path to be traversed to different geometries of preforms ( 1 ) is in the illustrated embodiment, the secondary curve ( 53 ) along one of the primary curve ( 52 ) defined curved path ( 70 ) arranged displaceably. This allows the section of the mechanical mutual positive guidance of the customer ( 54 ) to be changed.

To support a further adaptability of the curve control to respective application requirements, it is provided that the primary curve ( 52 ) into a stationary element ( 71 ) and an adapter ( 72 ), which is adjustable and limits the effective stretching height.

According to the embodiment in 6 a stretching of the preforms takes place ( 1 ) with the mouth sections ( 21 ) oriented in the vertical direction upwards. The main crossbeam ( 69 ) and the guide rods ( 63 . 64 ) are together with the piston rod ( 68 ) immovable with the other components of the blowing station ( 3 ) connected. In a control of the pneumatic cylinder ( 61 ), the pneumatic cylinder ( 61 ) together with the sockets ( 65 . 66 ) along the guide rods ( 63 . 64 ) postponed. The sockets ( 65 . 66 ) are rigid with the secondary curve ( 53 ) and thereby cause the height positioning of the secondary curve ( 53 ) by.

Alternatively, it is also possible to use the pneumatic cylinder ( 61 ) rigidly with the main crossbar ( 69 ) and the piston rod ( 68 ) with the crossbeam ( 67 ) or another fixed abutment.

7 shows the arrangement in 6 in the direction of vision VII. It is particularly illustrated that the primary curve ( 52 ) of a support element ( 73 ) is held, which also the pressing device ( 59 ) and the main crossbar ( 69 ), on which the guide rods ( 63 . 64 ) are attached. Clearly recognizable is the guidance of the superimposed cam rollers ( 55 . 56 ) between the primary curve ( 52 ) and the secondary curve ( 53 ).

Out 7 It can also be seen that together with the cam roller ( 55 ) along the primary curve ( 52 ), another cam follower ( 74 ) next to the cam roller ( 55 ) which is for guiding along the adapter ( 72 ) is provided which provides a damping curve.

8th shows the arrangement in 6 according to viewing direction VIII and thus from a respect 7 opposite viewing direction. From this view, in particular, once again the course of the guideway for the cam rollers ( 55 . 56 ) to be recognized by the curves ( 52 . 53 ) is stretched.

9 shows a longitudinal section along section line IX-IX in 6 , In particular, the assignment of the curves ( 52 . 53 ) and the cam rollers ( 55 . 56 . 74 ) and the structure of the pneumatic cylinder ( 61 ).

10 illustrates in a plan view the arrangement of the curves ( 52 . 53 ) relative to each other and the extension of the primary curve ( 52 ) through the adapter ( 72 ). From the cross section in 11 is the assignment of the pneumatic cylinder ( 61 ) to the guide rods ( 63 . 64 ), in addition, the arrangement of the adapter ( 72 ) to be recognized as a damping curve. The primary curve ( 62 ) serves as a stretching curve and the secondary curve ( 53 ) as Anreckkurve. A basic element ( 75 ) serves for holding and guiding the secondary curve ( 53 ). The assignment of the cam roller ( 55 ) to the primary curve ( 52 ) and the cam roller ( 74 ) to the adapter ( 72 ) as a damping curve.

10 and 11 illustrate, moreover, that the support element ( 73 ) of base elements ( 76 . 77 ) and vertical bars ( 78 . 79 ) is formed, which the base elements ( 76 . 77 ) connect with each other.

Claims (36)

A method of blow molding containers in which a preform made of a thermoplastic material after thermal conditioning within a blow mold is stretched by a stretching rod and re-circulated into the container by blowing pressure is formed, characterized in that a specification of the positioning of the stretch rod ( 11 ) is performed using a cam control in which at least one with the stretch rod ( 11 ) coupled customer ( 54 ) only along a portion of a carrying out a lifting movement of the stretch rod ( 11 ) is guided on both sides along a curved path. Method according to claim 1, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with a bottom of the preform ( 1 ) is guided on both sides. Method according to claim 2, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along 80 percent of the subsequent stretching path. Method according to claim 2, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along a maximum of 50 percent of the subsequent stretching path. Method according to claim 2, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along a maximum of 30 percent of the subsequent stretching path. Method according to claim 2, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along a maximum of 20 mm of the subsequent stretching path. Method according to claim 2, characterized in that the customer ( 54 ) after contact of the stretching rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along a maximum of 10 mm of the subsequent stretching path. Method according to one of claims 1 to 7, characterized in that the adapter ( 54 ) before contact of the stretch rod ( 11 ) with the bottom of the preform ( 1 ) is guided on both sides along a lead region. Method according to one of claims 1 to 8, characterized in that for the two-sided guidance of the customer ( 54 ) provided portion is slidably disposed along the curved path. Method according to one of claims 1 to 9, characterized in that the stretch rod ( 11 ) in addition to the positioning by the customer ( 54 ) is pneumatically positioned. Method according to one of claims 1 to 9, characterized in that the stretch rod ( 11 ) in addition to the positioning by the customer ( 54 ) is electrically positioned. Method according to one of claims 1 to 9, characterized in that the stretch rod ( 11 ) in addition to the positioning by the customer ( 54 ) is hydraulically positioned. Method according to one of claims 1 to 12, characterized in that the customer ( 54 ) by at least one cam roller ( 55 . 56 ) is guided along the curved path. Method according to one of claims 1 to 13, characterized in that the customer ( 54 ) by a direct contact between the cam roller ( 55 . 56 ) and the curved path is guided. Method according to one of claims 1 to 13, characterized in that the customer ( 54 ) is positioned along the cam track by an indirect roller guide. Method according to one of claims 1 to 15, characterized in that the customer ( 54 ) of at least two cam rollers ( 55 . 56 ) is positioned along the curved path. Method according to claim 16, characterized in that the customer ( 54 ) by at least two superimposed cam rollers ( 55 . 56 ) is positioned along the curved path. Method according to one of claims 1 to 17, characterized in that an additional non-mechanical positioning device for the stretch rod ( 11 ) is designed to be switched off. Apparatus for blow-molding containers of a thermoplastic material having at least one blowing station provided with a blow molding device, in the region of which a stretching rod is arranged for loading a preform which can be inserted into the blow mold and in which the stretching rod is provided with a lifting control coupled for carrying out a movement coordination of the stretch rod, characterized in that the stretch rod ( 11 ) is coupled to a cam control, the at least one with the stretch rod ( 11 ) associated customers ( 54 ), which is guided along both sides along a curved path only along a partial region of a control path. Apparatus according to claim 19, characterized in that the mutual guidance of the pickup ( 54 ) is arranged following a position of the cam track, by a first contact the stretch rod with a bottom of the preform ( 1 ) is defined. Apparatus according to claim 20, characterized in that the area of the two-sided guide of the pickup ( 54 ) extends along a maximum of 80 percent of the stretching path. Apparatus according to claim 20, characterized in that the area of the two-sided guide of the pickup ( 54 ) extends along a maximum of 50 percent of the stretching path. Apparatus according to claim 20, characterized in that the area of the two-sided guide of the pickup ( 54 ) extends along a maximum of 30 percent of the stretching path. Apparatus according to claim 20, characterized in that the area of the two-sided guide of the pickup ( 54 ) extends along a maximum of 20 mm of the stretching path. Apparatus according to claim 20, characterized in that the area of the two-sided guide of the pickup ( 54 ) extends along a maximum of 10 mm of the stretching path. Device according to one of claims 19 to 25, characterized in that in front of the first contact of the stretch rod ( 11 ) defined with the bottom of the preform position of the cam track a flow area with a two-sided leadership of the customer ( 54 ). Device according to one of Claims 19 to 26, characterized in that at least one curve ( 52 . 53 ) to guide the customer ( 54 ) is positioned along the curved path. Device according to one of claims 19 to 27, characterized in that the stretching rod ( 11 ) has a pneumatic drive in addition to the provided by the cam control mechanical drive. Device according to one of claims 19 to 27, characterized in that the stretching rod ( 11 ) has an electric drive in addition to the provided by the cam control mechanical drive. Device according to one of claims 19 to 27, characterized in that the stretching rod ( 11 ) has a hydraulic drive in addition to the mechanical drive provided by the cam control. Device according to one of claims 19 to 30, characterized in that the consumer ( 54 ) at least one cam roller ( 55 . 56 ) having. Device according to one of claims 19 to 31, characterized in that the cam roller ( 55 . 56 ) directly along the curve ( 52 . 53 ) is guided. Device according to one of claims 19 to 31, characterized in that the cam roller ( 55 . 56 ) indirectly along the curve ( 52 . 53 ) is guided. Device according to one of claims 19 to 33, characterized in that the consumer ( 54 ) at least two cam rollers ( 55 . 56 ) having. Apparatus according to claim 34, characterized in that the cam rollers ( 55 . 56 ) are arranged substantially one above the other. Device according to one of claims 19 to 35, characterized in that the additional drive of the stretch rod ( 11 ) is designed to be switched off.