WO2006108382A1 - Method and device for blow molding containers while using a displaceably guided valve support - Google Patents

Abstract

The method and device serves to blow-mold containers. A parison (1) is shaped into the container after a thermal conditioning inside a blow mold (4) due to the action of blowing pressure. Blowing gas is introduced into an inner space of the parison via a connecting element (50). The blowing gas is supplied via at least one valve (63, 64, 65, 66), which is held by a valve support (52) that can be displaceably guided relative to the blow mold.

Description

METHOD AND DEVICE FOR BLOWING CONTAINERS USING A MOVING VALVE CARRIER

The invention relates to a method for blow molding containers in which a preform is converted into the container after thermal conditioning within a blow mold by blowing pressure and in which a blowing gas is introduced through a connecting element into an interior space of the preform.

The invention further relates to an apparatus for blow molding containers having at least one blow station with a blower, and in which a flow path for a blown gas for blow molding the container through a connecting member extends therethrough.

In the case of container molding by means of blowing pressure, preforms made of a thermoplastic material, for example preforms made of PET (polyethylene terephthalate), are fed to different processing stations within a blow molding machine. typical Typically, a blow molding machine of this type has a heating device and a blowing device, in the region of which the previously tempered preform is expanded by biaxial orientation to form a container. The expansion takes place by means of compressed air, which is introduced into the preform to be expanded. The procedural sequence in such an expansion of the preform is explained in DE-OS 43 40 291. The introductory mentioned introduction of the pressurized gas also includes the introduction of compressed gas into the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process.

The basic structure of a blowing station for container forming is described in DE-OS 42 12 583. Possibilities for tempering the preforms are explained in DE-OS 23 52 926.

Within the blow molding apparatus, the preforms as well as the blown containers can be transported by means of different handling devices. In particular, the use of transport thorns, onto which the preforms are attached, has proven to be useful. The preforms can also be handled with other support devices. The use of gripping tongs for handling preforms and the use of spreaders which can be inserted into an opening area of the preform for mounting are likewise among the available constructions.

Handling of containers using transfer wheels, for example, in DE-QS 199 06 438 described in an arrangement of the ϋbergaberades between a blowing wheel and a discharge path.

The already described handling of the preforms takes place firstly in the so-called two-stage process, in which the preforms are first produced in an injection molding process, then temporarily stored and later conditioned in terms of their temperature and inflated to a container. On the other hand, there is an application in the so-called one-step process, in which the preforms are suitably tempered immediately after their injection-molding production and sufficient solidification and then inflated. ^<

With regard to the blowing stations used, different embodiments are known. In blow stations, which are arranged on rotating transport wheels, a book-like Aufklappbarkeit the mold carrier is often-meet. But it is also possible to use relative to each other ver-displaceable or differently guided mold carriers. In fixed blowing stations, which are particularly suitable for receiving a plurality of cavities for container molding, typically plates arranged parallel to one another are used as mold carriers.

A detailed description of a stretching system of a blowing station with associated stretching rod is provided in DE-OS 101 45 579. The stretching rod is designed here as a solid rod and the blowing air is supplied to the blow mold through a connecting piston which has a larger internal diameter than the outer diameter of the stretch rod is. As a result, between the stretch rod and an inner surface of the an annular gap provided. through which the pressurized gas can flow.

The use of a hollow stretch rod is known for example from DE-OS 28 14 952. A connection for the pressurized gas takes place here via an end of the tube-shaped stretching rod facing away from a stretching rod tip. A compressed gas supply via the end of a hollow stretch rod is also described in DE 34 08 740 C2. i

In all known BlasgasZuführungen valves are used to control the Blasgaszufuhr. In particular, the use of electromagnetically controllable valves is widespread. Inputs of the valves are connected via connecting lines with compressed gas supplies. After opening the valves, both a flow path extending from the valve to the preform or to the container and the interior of the preform or the container are subjected to the compressed gas. This means that in order to achieve a desired pressure level within the preform or the container, so much compressed gas must flow through the valve that both the region of the flow path and the corresponding interior of the preform or container is filled with a sufficient amount of compressed gas. The volume of the flow path thus results in a delay of the desired pressure build-up in the preform or in the container, since ^{■ in} addition to the actually required amount of compressed gas, the amount of compressed gas required to fill the flow path through the valve must flow through. In addition to the corresponding Prozeßverzδgerung resulting from this increased consumption of compressed gas with correspondingly increased operating costs. Object of the present invention is therefore a method of the initially mentioned. To improve the type such that both occurring delay times and the consumption of blowing gas are reduced.

This object is achieved erfindύngsgemäß in that the blowing gas is supplied by at least one of a fixed relative to Blasforπi movably guided valve carrier valve. ^■

A further object of the present invention is to design a device of the aforementioned type in such a way that dead space volumes are reduced in the area of the blown gas feed.

This object is achieved in that the connecting element has a relative to the blow mold immovably arranged base member and a movable relative to the base member guided valve carrier and that, the valve carrier at least one blow valve hal- tert.

The arrangement of the blow valve directly on the movably guided valve carrier, it is possible to position the blow valve with extremely short spatial distance to the blow mold and the container to be produced. ¹ Very short flow paths are thereby provided, which lead to a reduction in the consumption of blowing gas and to a reduction in delay times. In addition, the blowing process is more precisely controlled. A compact embodiment is particularly supported by the fact that the blowing gas is supplied from a laterally positioned on the valve carrier valve.

Particularly short flow paths and short delay times can be achieved in that the valve carrier is at least partially positioned between a stationary relative to the blow mold base part of the connecting element and the blow mold.

To support a mobility of the valve carrier, it is proposed that the blowing gas is supplied to the valve through a flexible hose.

A simple controllability is supported by the fact that the Blasgaszufuhr is supplied by at least one electromagnetically controllable valve.

An exactly reproducible implementation of positioning movements of the valve carrier is achieved in that the valve carrier is positioned by a cam control. , ^• ,

It contributes to a simplified embodiment that only one direction of movement of the valve carrier is predetermined by the cam control.

In particular, it is envisaged that the valve carrier is returned by at least one spring in a basic positioning. ,

A further reduction in weight in the region of the valve carrier can be achieved in that at least one of the valves is connected to a pilot valve. According to one embodiment it is provided that the valve carrier is moved in the vertical direction from below relative to the preform.

It is also contemplated that the valve carrier is moved in a vertical direction from above relative to the preform.

To _. Prevention of pressure losses is proposed that the valve carrier is sealed relative to the preform.

It also proves to be expedient that the stretch rod is sealed relative to the valve carrier.

A relatively independent specification of movements can take place in that the stretching rod is guided displaceably within the valve carrier.

A compact and mechanically heavy-duty arrangement while providing a high. Reliability is achieved by positioning the valve carrier in an axial direction of the stretch rod.

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

1 is a perspective view of a blow molding station for the production of containers from preforms,

2 shows a longitudinal section through a blow mold, in which a preform is stretched and expanded, 3 shows a sketch to illustrate a basic structure of a device for blow-molding containers,

4 shows a modified heating section with increased heating capacity,

Fig. 5 is a side view of a blowing station, in which a stretch rod is posi-tioned by a Reckstangenträger and

6 shows a longitudinal section through a connecting piston for the supply of blowing gas, in which the blow valves are arranged in the region of a movable part of the connecting element as well as in the immediate vicinity of the blow molds.

The basic structure of a device for forming preforms (1) in container (2) is shown in FIG. 1 and in FIG. 2. , ',

The device for forming the container (2) consists essentially of a blowing station (3) which is provided with a blow-mold (4) into which a preform (1) can be inserted. The preform (1) may be an injection-molded part of polyethylene terephthalate. To allow insertion of the preform (1) into the blow mold (4). and to allow removal of the finished container (2), the blow mold (4) consists of mold halves (5, 6) and a bottom part (7) which can be positioned by a lifting device (8). The preform (1) may be maintained in the range of the blowing station (3) by a transport mandrel (9), ^"passes through, together with the preform (1) stations, a plurality of treatment within the device. It is but also possible to use the preform (1) example, via pliers or other handling means directly into the blow mold (4).

For your convenience. a compressed air supply line below the transport mandrel (9) a connecting piston (10) is arranged, which feeds the preform (1) compressed air and at the same time makes 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 stretching rod (11), which is positioned by a cylinder (12). According to another embodiment, a mechanical positioning of the stretching rod (11) is carried out via curve segments, which are acted upon by Abgriffrollen. The use of Kurvensegmeήten is particularly useful when a plurality of blowing stations (3) are arranged on a rotating blowing wheel

In the embodiment shown in Fig. 1, the stretching system is designed such that a tandem arrangement of two cylinders (12) is provided. From a primary cylinder (13), the stretching rod (11) is first moved into the region of a bottom (14) of the preform (1) before the beginning of the actual stretching process. During the actual stretching process, the primary cylinder (13) with extended stretching rod together with a carriage (15) carrying the primary cylinder (13) is posi-tioned by a secondary cylinder (16) or via a cam control. In particular, it is envisaged to use the secondary cylinder (16) in such a way that it is controlled by a guide roller. Ie (17), which slides along a curved path during the execution of the stretching process, a current stretching position is specified. The guide roller (17) is pressed against the guideway by the secondary cylinder (16). The carriage (15) slides along two guide elements (18).

After closing the mold halves (5, 6) arranged in the region of carriers (19, 20), the carriers (19, 20) ^'are locked relative to one another by means of a locking device (20).

In order to adapt to different shapes of a mouth section (21) of the preform (1), the use of separate threaded inserts (22) in accordance with FIG. 2 is provided in the region of the blow mold (4).

Fig. 2 shows in addition to the 'blown container (2) and dashed lines drawn the preform ¹ (1) and schematically a developing container bladder (23).

Fig. 3 shows the basic structure of a blow molding machine, with a heating section, (24) and a rotating blowing wheel. (25) is provided. On the basis of a preform input (26), the preforms (1) are transported by upper gear wheels (27, 28, 29) into the region of the heating path (24). Along the heating section (24) heating radiator (30) and blower (31) are ange-. arranges to temper the preforms (l). After sufficient tempering of the preforms (1), they are transferred to the blowing wheel (25), in the region of which the blowing stations (3) are arranged. The finished blow-molded container (2) are fed by additional transfer wheels of a Ausgäbestrecke ^'(32). In order to transform a preform (1) in such a way in a container (2) ^• in that the container has properties (2) material properties, a long shelf life of the filled within the container (2) food products, especially beverages, ensure must special process steps in the heating and orientation of the preforms (1) are met. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

As thermoplastic material, different plastics can be used. For example, PET, PEN or PP can be used. , ,.

The expansion of the preform (1) during the orientation process takes place by means of compressed air supply. The compressed air feed is in a pre-blow phase in which gas, for example compressed air, is supplied at a low pressure level and subdivided into a subsequent main blow phase in which gas at a higher pressure level is supplied. During the pre-blowing phase, compressed air is typically used at a pressure in the range 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.

From Fig. 3 it can also be seen that in the illustrated embodiment, the Heizstreeke - (- 2 - * -) - au-s-e-iner- a variety of peripheral. Transport elements (33) is formed, which are strung together like a chain and guided along by deflecting wheels (34). In particular, it is thought that the chain-type arrangement would open up a substantially rectangular basic contour. In the illustrated embodiment are in the field of the transfer wheel (29) and a feed (35) facing extension of the heating (24) a single, relatively large-sized guide wheel (34) and in the range of Benach-disclosed deflections two relatively small dimension-ierte guide wheels (36) _(used. Basically but also any other guides are conceivable.

To enable a possible 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 deflecting wheels (34, 36) are positioned , in each case the smaller deflection wheels (36) in the region of the transition to the linear courses of the heating track (24) and the larger deflection wheel (34) in the immediate transfer area to the transfer wheel (29) and to the input wheel (35) , As an alternative to the use of chain-like transport elements (33), it is also possible, for example, to use a rotating heating wheel.

After a finished blowing of the containers (2) they are led out of the region of the blowing stations (3) by a removal wheel (37) and transported via the transfer wheel (28) and a delivery wheel (38) to the delivery line (32).

In the modified Heizstrek- ke shown in Fig. 4 (24) can be tempered by the larger number of radiant heaters (30) a larger amount of preforms (1) per unit time. ¹ The fans (31) introduce here cooling air into the area of cooling air ducts (39), which in each case the opposed radiant heaters (30) opposite and via discharge openings, the cooling air submit. As a result of the arrangement of the outflow directions, a flow direction for the cooling air is realized substantially transversely to a transpiration direction of the preforming rings (1). The cooling air channels (39) can in the area of the radiant heaters (30) opposite surfaces reflectors. provide for the heating radiation, it is also possible to realize via the discharged cooling air and a cooling of the radiant heater (30).

FIG. 5 shows a depiction of the blowing station (3) with respect to the illustration in FIG. T, in a viewing direction from the front. In particular is known from this illustration seen that the ¹ stretching rod (11) support the stretching rod of a supported (41) ,, composed of a support base (40) and a management over a Kupplungsele- (42) to the support base (40 ) connected roller carrier (43) is formed. The roller carrier (43) holds the guide roller (17), which serves for ^' positioning of the stretching system. The guide roller (17) is guided along a curved path, not shown. It is realized here a complete mechanical control of the stretching process.

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

Fig. 5 illustrates a locked state of the coupling element (42), in which the support base (40) and the roller carrier (43) with each other. are connected by the coupling element (42). There is thus a rigid mechanical coupling, which leads to that a positioning of the ^" guide roller (17) directly and directly in a positioning of the stretch rod

(11) is implemented. In this way, in each state of movement of the blowing wheel (25), an exactly predetermined positioning of the stretching rod (H) is present and the positioning of the stretching rod (11) is effected at a plurality of blowing stations (3) arranged on the blowing wheel (3) Blowing station (3) exactly reproduced. This exact mechanical specification of the positioning of the stretch rod

(11) contributes to a high product quality as well as to a high uniformity of the manufactured containers

(2) at ..

Fig. 5 also shows the arrangement of a pneumatic block (46) for Blasdruckversorgung the blow station (3). The pneumatic block (46) is equipped with high-pressure valves (47) which can be connected via terminals (48) to one or more pressure supplies. After a blow-molding of the container (2) is in. An environment to be discharged blast air via the pneumatic block (46) next to a silencer (49). supplied. ,

Fig. 6 shows an embodiment in which for supplying blown air, a connecting element (50) in the region of the blowing station (3) is arranged, consisting essentially of a relative to the blow mold (4) immovably arranged base member (51) and a relative to the base part (51) movably guided valve carrier (52) is formed. The valve carrier (52) extends ^' at least partially between the base part (51) and the blow mold (4). According to the embodiment in FIG. 6, the valve carrier (52) is guided with a carrier shaft (53) in a recess (54) of the base part (51). An exact guidance of the support shaft (53) in the Ausnehπiung (54) is supported by bearings ^' (55, 56). The base part (51) is bolted in the embodiment shown in Fig. 6 with a support structure (57) which may be formed as part of the blowing wheel (25). However, the use of connection elements (50) according to FIG. 6 is also possible with stationary blowing stations.

The base part (51) and the valve carrier (52) can be coupled together by springs (58, 59). The springs (58, 59) can be realized both as compression springs and as tension springs. By the springs (58, 59) is achieved that only an active positioning movement for the valve carrier (52) must be specified and that after completion of a Beauschlagung with a force of the valve carrier (52) automatically returns to a basic position. Depending on the realization of the springs (58, 59) as compression springs or as tension springs, the basic positioning can represent both a positioning of the valve carrier (52) as shown in FIG. 6 and a raised positioning of the valve carrier (52) ,

The springs (58, 59) can in recesses (60, 61) of the base part (51) and. the valve carrier (52) are positioned. This makes it possible, despite the use of the springs. (58, 59) a dense arrangement of the Bäsisteiles. (51) and the valve carrier (52) pretend. ^'' ,

In the embodiment shown in Fig. 6, a blow molding of the preforms (1) in container (2) with the mouth sections in the vertical direction is oriented downwards. However, the arrangement can also be rotated by 180 ° with respect to the illustration in FIG can be used so that the preforms (1) with ili- ren mouth sections in a vertical direction upwards in the container (2) are transformed.

Fig. 6 shows an embodiment of the connecting element '(50) such that blown air valves (63, 64)', a Blasluftrück- guide valve (65) and a vent valve (66) directly on the. Ventilträger (52) are arranged and can be positioned together with this , An interior (67) of the valve carrier (52) is connected via connecting channels (68, 69, 70, 71) to the respective valves (63, 64, 65, 66). A positioning of the valve carrier (52) can be controlled by cam so that a with the valve carrier (52) ver-connected cam roller (72) along a control cam (73) is guided. The blown air valve (63) is connected to a low pressure supply (74), the blown air valve (64) is connected to a high pressure supply (75). The blow-by air return valve (65) is connected to a return system (76) and the vent valve (66) is connected to a muffler (77).

In order to ^' support a low-loss blow pressure supply to the preforming (1), the' valve carrier (52) is provided with a seal (78) in the region of its extension facing the blow mold (4). The seal (78) can be designed as a sealing ring, which partially surrounds a nozzle (79) which can be inserted into the mouth region of the preform (1). To further avoid pressure losses, the stretch rod (11) via a seal (80) is sealed relative to the valve carrier (52). A guide of the stretching rod (11) is supported by a bearing (81) arranged in the region of the valve carrier (52). According to the embodiment shown in Fig. 6, the valves (63, 64, 65, 66) are designed as electrically controllable • valves. In particular, it is intended to be realized as electromagnetically controllable valves. In order to illustrate this functional principle, valve disks (82) are shown in FIG. 6, which are guided by connecting elements (83) in the region of control coils (84).

As an alternative to the use of electrically or electromagnetically controlled valves but also valves of any type can be used. In particular, it is also conceivable to couple the valves arranged directly on the valve carrier (52) with pilot valves arranged at a distance relative to these.

According to a typical functional sequence in the shown in Fig. 6 spatial orientation of the preforms (1) with their mouth sections in the vertical direction down after a closing of the blow mold (4) lifting the valve carrier (52) until the seal (78) is guided against the edge of the mouth region of the preform (1). Coordinated with retraction of the stretching rod (11) into the preform (1), the blowing air valve first opens, LI (63) for supplying a lower blowing pressure and after closing the blowing valve (63) opens the blowing valve (64) to supply the higher one Blowing pressure. After completing the blowing process, when using a blast air return system, the blast air recirculation valve (65) opens first, and after closing the valve, the vent valve (66) opens. The valve carrier (52) is then returned to its basic position and the blow mold (4) opens to remove the finished blown container (2) can. Advantageous in the embodiment according to FIG. 6 is in particular the axial positioning of the valve carrier (52) along a longitudinal axis of the stretch rod (11). The preform (1), the valve carrier (52) and the base part (51) each extend along the longitudinal axis of the stretch rod (11).

Claims

P a t e n t a .Ii s p r e c h e 1. A method for blow molding of containers, in which a preform is converted by a thermal molding in a blow mold by blowing pressure into the container and is introduced at the blowing gas through a connecting element into an interior of the preform, characterized in that the blowing gas by at least one of. a valve carrier (52) movably guided relative to the blow mold (4) ^• Valved valve (63, 64) is supplied. 2. The method according to claim 1, characterized in that the blowing gas is supplied from a positioned laterally on the valve carrier (52) valve _(63, 64). 3. The method according to claim 1 or 2, characterized in that the valve carrier (52) at least partially between a relative to the blow mold (4) immovable base part (51) of the connecting element (50) and the blow mold (4) is positioned. 4. The method according to any one of claims 1 to 3, characterized in that the blowing gas is supplied to the valve (63, 64) through a flexible hose therethrough. 5. The method according to any one of claims 1 to 4, characterized in that the blowing gas is supplied by at least one electromagnetically controllable valve. 6. The method according to any one of claims 1 to 5, characterized in that the valve carrier (52) is positioned by a cam control. 7. The method according to claim 6, characterized in that of the cam control only one direction of movement of the valve carrier (52) is specified. 8. The method according to claim 6 or 7, characterized in that the valve carrier (52) by at least one spring (58, 59) is returned to a basic positioning. 9. The method according to any one of claims 1 to 8, characterized in that at least one of the valves (63, 64) is connected to a pilot valve. 10. The method according to any one of claims 1 to 9, characterized in that the valve carrier (52) in the vertical direction from below relative to the preform (1) is moved. 11. The method according to any one of claims 1 to 9, characterized in that the valve carrier (52) in the vertical direction from above relative to the preform (1) is moved. 12. The method according to any one of claims 1 to 11, characterized in that the valve carrier (52) ¹ relative to the preform (1) is sealed .. 1 ^' 3. Method according to one of claims 1 to 12, - characterized in that the stretch rod (11) is sealed relative to the valve carrier (52). , " 14. The method according to any one of claims 1 to 13, characterized in that the stretch rod (11) within the valve carrier • (52) is guided displaceably. , 15. The method according to any one of claims 1 to 14, characterized in that the valve carrier (52) in an axial direction of the stretch rod (11) is positioned. 16. An apparatus for blow-molding of containers having at least one blow station with a blow mold, and in which a flow path for a blown gas for blow molding of the container by. one Terminal element extends therethrough, characterized in that the connecting element (50) has a relative to the blow mold (4) immovably arranged base part (51) and a relative to the base part (51) movably guided valve carrier (52) and that the valve carrier (52) at least one Blow valve (63, 64) holds. 17. The apparatus according to claim 16, characterized in that the blow valve (63, 64) is arranged laterally on the valve carrier (52). 18. The apparatus of claim 16 or 17, characterized in that the valve carrier (52) at least partially between a relative to the blow mold (4) immovable base part (51) and the blow mold (4) is positioned. 19. Device according to one of claims 16 to 18, characterized in that the blow valve (63, 64) is coupled via a flexible hose with at least one Blasluftversorgung. 20. Device according to one of claims 16 to 19, characterized in that the valve is designed as an electromagnetically controlled valve. 21. Device according to one of claims 16 to 20, characterized in that the valve carrier (52) is coupled to a cam control. 22. The apparatus according to claim 21, characterized in that one with the valve carrier (52) coupled cam roller (72) ^{N on} one side by a control cam (73) is guided. 23. Device according to one of claims 16 to 22, characterized in that the base part (51) ^• and the valve carrier (52) of at least one spring (58, 59) are coupled together. 24. Device according to one of claims 16 to 23, characterized in that the valve carrier (52) arranged valve is coupled to a pilot valve. 25. Device according to one of claims 16 to 24, characterized in that the valve carrier (52) at least partially below ^' the blow molding (4) is arranged. 26. Device according to one of claims 16 to 24, characterized in that the valve carrier (52) at least partially above the blow mold (4) is arranged. 27. Device according to one of claims 16 to 26, ■, characterized in that, the valve carrier (52) at least one of the blow mold. (4) facing arranged seal (78). 28. Device according to one of claims 16 to 27, characterized in that the stretch rod (11) is sealed by at least seal (80) relative to the valve carrier (52). 29. Device according to one of claims 16 to 28,. characterized in that the stretch rod (11) is displaceably guided in the valve carrier (52). 30. Device according to one of claims 16 to 29 ^' , characterized', that the valve carrier (52) is arranged positionable in an axial direction of the stretch rod (11).