DE102015208677A1 - Blow mold and method for molding plastic containers - Google Patents

Abstract

Discussed are a blow mold for plastic containers and corresponding methods for molding the containers from thermoplastic preforms in a blow mold with lateral mold halves and a mold bottom. Characterized in that the mold bottom comprises at least one inner wall portion which is movable in the closed mold halves to open and / or close at least one channel for venting the blow mold, the channel can be formed with a comparatively large cross-section and temporarily during the blowing process for venting open the blow mold. Before the container is completely blown, the channel can be substantially flush with adjacent inner wall areas, so that a container with a high-quality outer surface can be produced in a particularly efficient manner.

Description

As is known, plastic containers are produced in stretch blow molding machines by pressing previously heated preforms into blow molds against the inner wall of the blow molds by the action of compressed air and thereby obtaining their final shape. The air present in the blow molds prior to the expansion of the preforms must be passed out of the blow molds when the containers are formed. This is made possible for example by narrow gaps between the individual segments of the blow molds and / or by additional vent holes, which are formed, for example, in the area of the bottom mold and / or on particularly critical areas of the blow mold, see for example US Pat WO 2014/127903 A1 ,

The disadvantage here is that the openings of such permanently open venting channels are visible on the finished molded container and thus may only have a limited cross-section. Accordingly, the narrow ventilation channels of the outflowing air counteract a comparatively high flow resistance. As a result, a sufficient expression of container details, such as container feet, can be achieved in difficult-to-manufacture container shapes only by increasing the blowing pressure.

Known venting channels thus represent a bottleneck in the venting, which limits both the quality of the molded container and the efficiency of the blowing process.

There is therefore a need for blow molds and methods for blowing containers in which at least one of the above-mentioned problems is eliminated or at least alleviated.

The stated object is achieved with a blow mold according to claim 1. Accordingly, the blow mold is suitable for molding and in particular for filling containers. The containers are made of a thermoplastic such as PET. The blow mold comprises lateral mold halves and a mold bottom. According to the invention, the mold bottom comprises at least one inner wall section, which is movable in the case of closed, ie abutting and locked, lateral mold halves, in order thereby to open and / or close at least one duct for venting the blow mold.

The movable inner wall portion may also be referred to as a movable forming wall portion. The movable inner wall portion is a component of the forming inner wall of the blow mold, in contrast to non-closable vent holes and vent gaps, which are to be understood as recesses of the shaping inner wall. By venting is meant a displacement of air from the blow mold and / or an evacuation of the blow mold to an absolute negative pressure, such as at least 0.1 bar. The blow mold according to the invention is preferably suitable for evacuating and filling the evacuated containers.

For blowing and / or filling of the containers, a blowing unit and / or filling unit or combined blowing filling units, which can be placed on the blow mold or the mouth regions of the containers, are formed on the blow mold. Blowing units and filling units are designed, for example, as valve blocks with suitably controllable valves.

The movable inner wall section is in particular switchable between a venting position releasing the channel and a mold position substantially closing the channel, for example by automatic control. The movable inner wall portion has substantially the function of a pneumatic valve for alternately releasing and blocking a bleed flow. In the mold position of the inner wall portion with the finished molded container in contact. In the vent position, the inner wall portion may be temporarily in contact with the forming container. Likewise, the contact in the vent position can be completely avoided.

Thus, a comparatively wide venting duct for the blow mold can be temporarily provided, which can be selectively closed during molding of the container, in particular before the forming container abuts the movable inner wall section. Thus, a large part of the existing at the beginning of the blowing process in the blow mold air through the open channel with relatively low flow resistance escape. It is also possible to evacuate the blow mold in the venting position through the channel and thereby actively venting from the outside.

Preferably, the channel is formed in the mold bottom, and the movable wall portion is a valve plate for the particular airtight sealing of the channel. The opening of the channel to the interior of the blow mold is thus formed as a valve seat for the inner wall portion. The channel is then formed in particular concentrically with respect to the mold bottom, for example, corresponding to a Anspritzbereich of the preforms used and the container forming therefrom.

The movable inner wall section then closes in the retracted state, ie in the Shape position, preferably flush with each adjacent wall portions of the mold base. The transition between the movable wall portion and the adjacent areas of the mold bottom is then not visible on the finished blown container, or at least less clearly formed than in the non-closable vent opening. A valve plate that is airtight in the mold position is particularly suitable for evacuating the blow mold cavity for molding the containers and / or for filling a product into the containers.

In a further advantageous embodiment of the blow mold, the movable wall section is a bottom cup, which in the case of a completely closed blow mold, ie in the mold position, is in particular airtightly adjacent to the lateral mold halves. In the venting position then, for example, at least one substantially annular channel for venting between the bottom cup and the closed, ie abutting mold halves is formed. This makes it possible to provide a venting channel with a particularly large free cross-section. An airtight seal between the bottom cup and the mold halves is advantageous for evacuation of the blow mold interior.

Preferably, the mold bottom comprises a lockable with the lateral mold halves base for centering the mold halves and for linear guiding of the movable wall portion. The lockable base is then formed, for example, as a so-called centering prism for centering the lateral mold halves. The movable wall section can then be guided vertically precisely with respect to the mold bottom and / or the lateral mold halves.

Preferably, the blow mold further comprises a particular pneumatic or electric lifting drive for moving the inner wall portion. This makes it possible to provide a precise switchable valve for venting and closing the blow mold. The lifting drive then acts, for example, on a plunger connected to the movable wall section or the like. A pneumatic lifting drive is possible due to the existing compressed air supply with a very low technical complexity. An electric lifting drive would be conceivable.

The stated object is also achieved with a blow molding machine having a plurality of blow molds, in particular continuously circulating on a carousel, according to at least one of the preceding embodiments. However, a linear transport of the preforms / containers with respect to at least one blow mold and / or a cycle operation of the blow molding machine would also be possible. For supplying and discharging preforms and / or containers individually driven transport vehicles, such as slides, could be formed by means of linear motors. Linear motors can be integrated in particular in guide rails for the transport vehicles. It is then preferably a transport system consisting of so-called "movers" and "shuttles". The blow molding machine can be a mold filling machine in which at least one partial step of the blowing takes place by hydraulic blowing, that is to say by shaping by means of an incompressible fluid. Conceivable, for example, would be pneumatic pre-blowing and hydraulic pre-blowing of the containers.

Preferably, the blowing machine then further comprises a suction connected to the channel. As a result, the blow mold can be evacuated during and / or before the blow molding process to an absolute pressure of at least 0.5 bar, preferably at least 0.3 bar, and particularly preferably at least 0.1 bar. Consequently, the expansion of the forming containers in the blow mold is promoted.

The container may then expand substantially without resistance to an air cushion formed between the container and the blow mold. The fact that air cushion between the container and blow mold wall prevented or at least reduced, there is an improved heat transfer. Consequently, the container can be cooled more effectively, for example, which can have a positive effect on the process time. Also, this can improve the expression of container details. Furthermore, a negative pressure generated by the suction can be maintained for filling the containers with product in the blow mold, in particular also to evacuate the container to negative pressure and then to fill.

The stated object is also achieved by a method according to claim 9, wherein the container of thermoplastic preforms in a blow mold comprising lateral mold halves and a mold bottom are formed. According to the blow mold is vented after closing the lateral mold halves by at least one formed in the mold bottom channel, in particular by evacuation of the blow mold, and the channel is closed by retraction of an in particular designed as a valve plate inner wall portion in the mold bottom.

The stated object is also achieved by a method according to claim 10, wherein the containers are formed from thermoplastic preforms in a blow mold with lateral mold halves and a mold bottom, wherein the blow mold after closing the lateral mold halves by at least one channel, in particular by evacuation the blow mold, is vented, wherein the channel is formed between a formed in particular as a bottom cup inner wall portion of the mold base and the mold halves and is closed by lifting the inner wall portion against the mold halves.

Preferably, the blow mold is vented by the forming container displacing air from the blow mold and pushes out of the blow mold through the duct. The venting thus takes place by the blowing process itself, preferably without additional active external influence.

Through the open channel, the air can escape with comparatively low flow resistance.

Preferably, the channel is closed during molding of the container before the forming container contacts the wall portion. Thus, the predominant portion of existing in the blow mold at the beginning of the blowing process air with relatively low flow resistance escape through the channel, without directly affecting the finished molding of the container bottom by the movable wall section.

By timely closing of the channel, a contact between the previously extended in the direction of the preform / container movable inner wall portion, which is formed for example as a plunger, valve plate or the like, and the expanding container can be reliably avoided. However, it would also be conceivable to temporarily support the container bottom that forms with the still extended wall section in order to influence the blowing process in a targeted manner.

In the closed mold position, the movable inner wall section with adjacent wall sections acts as a substantially continuous shaping section of the inner wall.

Preferably, the channel is closed prior to mechanical stretching of the preform. This makes it possible, in particular, to prevent the wall of the preform / container from being trapped between a stretch rod introduced into the blow mold for this purpose and the inner wall section which has been moved outwards in the direction of the preform / container and is designed, for example, as a plunger, valve disk or the like , Alternatively, it would also be possible to properly close the channel during the stretching operation before the stretching rod has reached its fully extended position. However, it would also be conceivable to temporarily clamp the bottom of the preform or forming container between the stretching rod and the movable inner wall section in order to influence the blowing process in a targeted manner.

Preferably, the blow mold is vented by air is sucked through the channel, in particular in otherwise airtight closed blow mold. By evacuating the blow mold, the resistance of an amount of air existing between the expanding container wall and the inner wall of the blow mold can be further reduced. In addition, evacuation allows adequate venting of the blow mold prior to parison stretching and subsequent blowing, as opposed to venting by displacing the air with the forming container.

In addition, by evacuating the blow mold, a pressure equilibrium can be established when filling the molded container with a liquid product. For example, the interior of the container is also evacuated prior to and / or during filling with a liquid product. In order to prevent collapse of the container wall with the container evacuated, a suitable negative pressure is created around the container through the channel in the venting position.

Under an airtight closed blow mold is to be understood that, for example, the lateral mold halves and the mold base are moved and locked airtight to each other, so that a vent or suction of the blow mold only through the open channel, especially only in the venting position is possible.

Preferably, then the channel is then closed prior to molding of the container. Thus, when the containers are formed, a negative pressure prevails in the blow molds outside the preforms or containers.

In a favorable embodiment of the method, preforms / containers for the hydraulic shaping of the containers, in particular for a finished blowing of the containers, and / or for product filling in the blow mold are filled with a liquid. For the blowing of the containers, an incompressible fluid, for example water or product, is then used. Likewise, it is conceivable for the containers to be initially at least partially shaped, for example pre-blown, by means of a compressible fluid, for example by compressed air, and then to be hydraulically finished in the blow mold and / or filled with product.

By means of the switchable inner wall section, suitable pressure ratios can be generated outside the containers for the hydraulic shaping and / or filling of the containers in the blow mold.

Preferably, the container, or the partially blown container, subjected to negative pressure inside. As a result, the container in the blow mold can be filled with a liquid, in particular with a liquid product. Likewise, the partially blown container could be filled accordingly before the finished blowing.

Preferred embodiments of the invention are illustrated in the drawings. Show it:

1 a schematic section through a first embodiment of the blow mold with open and closed vent channel;

2 a schematic section through a second embodiment of the blow mold with lowered Blasformboden and fully closed blow mold; and

3 a schematic plan view of a blow molding machine with several on a carousel revolving blow molds.

As the 1 reveals includes the blow mold 1 in a first preferred embodiment, lateral mold halves 2 . 3 and a mold bottom 4 with a relatively movable inner wall section 5 For example, as a valve plate or the like for closing a mold in the bottom 4 trained channel 6 is trained.

The movable inner wall section 5 can be between a ventilation position (shown on the left) 7 for venting the cavity 1a the blow mold 1 and a (shown on the right) shape position 8th in which the inner wall section 5 at the end of the blow molding process acting on the container B, be moved. At the same time, the lateral mold halves collide 2 . 3 each against each other and are with the mold bottom 4 locked.

In the ventilation position 7 For example, at the beginning of a blowing process in which a preform V to a (in the 1 not yet finished) container B is inflated, is the movable inner wall portion 5 to the cavity 1a the blow mold 1 extended. The channel 6 is then opened so that air 9 from the cavity 1a through the channel 6 can escape, for example, by displacement by the increasingly expanding preform V or container.

Likewise, the cavity 1a in the ventilation position 7 through the channel 6 with the help of a schematically indicated suction 10 be evacuated. It then prevails after retraction of the movable inner wall section 5 in its shape 8th a vacuum 11 in the cavity 1a For example, during the subsequent complete blowing of the container B and / or when filling the container B with a liquid product.

At the blow mold 1 is also a lifting unit 12 for extending and retracting the inner wall section 5 with respect to the mold floor 4 trained to the channel 6 to open and close. The preferably pneumatically operated lifting unit 12 for example, includes one with the inner wall portion 5 mechanically connected plunger 12a or similar. For targeted control of the lifting unit 12 is a schematically indicated control unit 13 available.

The mold bottom 4 includes, for example, a base 4a for guiding the designed as a valve disk movable inner wall portion 5 and for centering the mold halves 2 . 3 , In the form of ground 4 is a valve seat 4b formed, on which the inner wall section 5 can lower controlled. The base 4a will when closing the blow mold 1 from below against the mold halves 2 . 3 driven and is locked during subsequent venting with these.

In the form position 8th is the channel 6 closed, for example by airtight completion of the inner wall section 5 with the valve seat 4b , In the form position 8th closes the inner wall area 5 preferably flush with adjacent inner wall areas 4c of the mold floor 4 from. In the form position 8th makes the movable inner wall area 5 with the surrounding wall areas 4c a continuous molding floor cup, on which finally the container bottom forms (not shown).

As the 1 further indicates, the movable inner wall section 5 preferably retracted before the forming container B, the inner wall portion 5 touched. Likewise, the inner wall section 5 preferably retracted before an integrated in the blow molding stretching operation is started. A lowered stretch rod 14 is in the 1 indicated schematically. In principle, could possibly also partially, still extended inner wall section 5 However, also be used to support the forming container bottom to specifically intervene in the blowing process.

The interior of the container B is filled during the blow molding, for example, with compressed air, so a compressible fluid. However, this known procedure could be at least partially replaced by a molding process using an incompressible fluid, for example by introducing water or product, in particular in a final step of the final molding. Furthermore, it would be conceivable that container already finished and still resting in the blow mold B to fill with a liquid product. For filling of compressible and / or incompressible molding fluids and liquid products blowing units, filling units or blow-filling units with suitably controllable valves in a conventional manner sealingly placed on the mouth region of the preforms V and container B (not shown).

This also applies to the in the 2 schematically indicated blow mold 21 an alternative embodiment, which differs from the embodiment described above substantially in that the mold bottom 24 designed as a ground cup movable inner wall portion 25 which is opposite to the locked lateral mold halves 2 . 3 lower to a substantially annular channel 26 between the mold bottom 24 and the mold halves 2 . 3 in the sense of an annular gap for venting the blow mold 21 train.

The movable inner wall section 25 can be between a ventilation position (shown on the left) 27 for venting the cavity 21a the blow mold 21 and a (shown on the right) shape position 28 in which the inner wall section 25 shaping acting on the container B, be moved. At the same time, the lateral mold halves collide 2 . 3 together and are with the mold bottom 24 locked.

In the ventilation position 27 For example, at the beginning of a blowing process in which a preform V is inflated to a container B is the movable inner wall portion 25 from the cavity 21a the blow mold 21 lowered away. The channel 26 is then opened so that air 9 from the cavity 21a through the channel 26 can escape, for example, by displacement by the increasingly expanding preform V. The annular channel 26 sets the outflowing air particularly little flow resistance, so that the blowing process can be done faster and / or with lower blowing pressure than conventional venting channels.

Likewise, the cavity 21a in the ventilation position 27 through the channel 26 with the help of a (in the 2 for the sake of simplicity) evacuation be evacuated. It then also prevails after lifting the movable inner wall section 25 in its shape 28 a vacuum in the cavity 21a For example, during the subsequent complete blowing of the container B and / or when filling the container B with a liquid product.

At the blow mold 21 is also a lifting unit 12 for lowering and lifting the inner wall section 25 with respect to the mold floor 24 trained to the channel 26 to open and close. The preferably pneumatically operated lifting unit 12 for example, includes one with the inner wall portion 25 mechanically connected plunger 12a or similar. For targeted control of the lifting unit 12 is a control unit 13 available.

For guiding the designed as a ground cup movable inner wall area 25 includes the mold bottom 24 one in the 2 only schematically indicated and stationary in the vertical direction base 24a , further for centering the mold halves 2 . 3 serves.

As the 2 On the right side, the inner wall area designed as a ground cup closes 25 with completely closed blow mold 21 preferably flush with the lateral mold halves 2 . 3 at. Thus, the appearance of the blow-mold can be seen 21 Improve prepared container B against non-closable vents / venting gaps. It can be, based on the appearance of the container produced B, seamless transition between the lateral mold halves 2 . 3 and the movable inner wall area 25 the floor shape 24 produce.

The channels described above 6 . 26 could also go to the cavity 1a . 21a towards permanently open ventilation holes and / or ventilation gaps in the side of the mold halves 2 . 3 and / or the mold bottom 4 . 24 be combined. For example, such additional vent holes and / or venting gaps could be used for final venting of the blow molds 1 . 21 when finished blowing the container B in the mold position 8th . 28 be used.

In the example of 1 becomes the cavity 1a over the open channel 6 evacuated, so after closing the channel 6 a vacuum 11 inside the blow mold 1 and outside the container B prevails. The vacuum 11 On the one hand, there is no need for further ventilation when the container B is blown out. On the other hand, the vacuum can be used 11 create a pressure equilibrium with the interior of the container B, which is applied for example for filling a product in the container B with a vacuum. In principle, the vent in both embodiments by displacing and / or suction of the air 9 possible.

As the 3 schematically indicates, comprises a preferred blowing machine 31 several at a carousel 32 circulating blow molds 1 or 21 , The preforms V are then in a conventional manner by an inlet star wheel 33 to the open blow molds 1 . 21 to hand over. The blow molds 1 . 21 are open in the transfer of the preforms V in a known manner. After the delivery of the Preforms V become the lateral mold halves 2 . 3 closed and with the mold bottom 4 . 24 locked. The inner wall sections 5 . 25 can already be in their vent position 7 . 27 be or after locking the mold halves 2 . 3 in the venting position 7 . 27 be driven.

After that, the blow molds 1 . 21 passively through the forming container B, so by displacing the air 9 from the cavities 1a . 21a , be vented and / or active by sucking off the air 9 , Preferably, before the forming container B, the movable inner wall portion 5 . 25 touched, this is in the shape position 8th . 28 drove and the canal 6 . 26 thereby closed. The channel 6 This may, but not necessarily, be airtight to the blow mold 1 . 21 be closed.

The containers B can then be in the fully closed blow mold 1 . 21 be blown ready. The finished blown container B are in a conventional manner to an outlet star 34 or the like handed over.

In the field of blow molding machine 31 The containers B could also be formed with the aid of an incompressible fluid and / or filled with a liquid product. In this case, the product could also be used to form the container B by the product is pressed with a suitable overpressure in the preforms V and in the forming container B.

Due to a reduced flow resistance in the ducts compared to conventional venting ducts 6 . 26 becomes airborne to the forming tank B. 9 in the blow mold 1 . 21 less resistance so that the overpressure required for blowing can be reduced over conventional methods.

Furthermore, the blow molds can be 1 . 21 , Especially when designed as valves inner wall sections 5 , evacuate specifically to support the blowing process. The extraction of the blow molds 1 . 21 and the stroke of the inner wall sections 5 . 25 can be done for example with the help of known vacuum sources and overpressure sources.

With the between a ventilation position 7 . 27 and a shape position 8th . 28 movable inner wall sections 5 . 25 of the mold floor 4 . 24 can be comparatively wide ventilation channels 6 . 26 generate temporarily, so that the vent accelerates compared to conventional methods and thus the process time can be reduced overall. Furthermore, the surface finish of the container B by targeted closing of the venting channels 6 . 26 improved. For example, the number and / or size in the blow mold 1 . 21 Reduce additional trained permanently open vents so far that they do not affect the appearance of the container B during molding or only insignificantly. Optionally, additional permanently open vents are also unnecessary.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2014/127903 A1 [0001]

Claims (17)

Blow mold ( 1 . 21 ) for molding, in particular further for filling, thermoplastic container (B), with lateral mold halves ( 2 . 3 ) and a mold bottom ( 4 . 24 ), characterized in that the mold bottom at least one inner wall portion ( 5 . 25 ) which is movable with closed mold halves to at least one channel ( 6 . 26 ) to vent and / or close the blow mold. Blow mold according to claim 1, wherein the duct ( 6 ) in the mold bottom ( 4 ) is formed and the movable wall section ( 5 ) is a valve plate for the particular airtight sealing of the channel. Blow mold according to claim 1, wherein the movable wall section ( 25 ) is a bottom cup which, when the blow mold is closed ( 21 ) in particular airtight to the mold halves ( 2 . 3 ) adjoins. Blow mold according to one of the preceding claims, wherein the mold bottom ( 4 . 24 ) a lockable with the mold halves base ( 4a . 24a ) for centering the mold halves ( 2 . 3 ) and for linear guiding of the movable wall section ( 5 . 25 ). Blow mold according to at least one of the preceding claims, further comprising an in particular pneumatic or electric lifting drive ( 12 ) for moving the inner wall section ( 5 . 25 ). Blow mold according to at least one of the preceding claims, further comprising a to the channel ( 6 . 26 ) connected suction ( 10 ). Blowing machine ( 31 ) with several on a carousel ( 32 ) in particular continuously circulating blow molds ( 1 . 21 ) according to at least one of the preceding claims. Blowing machine ( 31 ), in particular according to claim 7, with at least one blow mold ( 1 . 21 ) according to at least one of the preceding claims, wherein the blowing machine is further formed as a mold filling machine for pneumatic and / or hydraulic blowing and for filling the containers in the blow mold with a liquid product. Method for molding containers (B) from thermoplastic preforms (V) in a blow mold ( 1 ) with lateral mold halves ( 2 . 3 ) and a mold bottom ( 4 ), wherein the blow mold after closing the lateral mold halves by at least one channel formed in the mold bottom ( 6 ) is vented, in particular by evacuation, and the channel by retraction of an in particular designed as a valve disk inner wall portion ( 5 ) is closed in the mold bottom. Method for molding containers (B) from thermoplastic preforms (V) in a blow mold ( 21 ) with lateral mold halves ( 2 . 3 ) and a mold bottom ( 24 ), wherein the blow mold after closing the lateral mold halves by at least one channel ( 26 ) is vented, in particular by evacuation, wherein the channel between a particular formed as a ground cup inner wall portion ( 25 ) of the mold bottom and the mold halves is formed and is closed by lifting the inner wall portion against the mold halves. A method according to claim 9 or 10, wherein the blow mold ( 1 . 21 ) is vented by the forming container (B) air ( 9 ) and through the channel ( 6 . 26 ) presses. Method according to one of claims 9 to 11, wherein the channel ( 6 . 26 ) is closed when forming the container (B) before the forming container touches the wall portion. The method of claim 12, wherein the channel ( 6 . 26 ) is closed prior to mechanical stretching of the preform (V). A method according to claim 9 or 10, wherein the blow mold ( 1 . 21 ) is vented by air ( 9 ) through the channel ( 6 . 26 ) is sucked, especially in otherwise airtight closed blow mold. The method of claim 14, wherein the channel ( 6 . 26 ) is closed before molding the container (B). Method according to at least one of claims 9 to 15, wherein preforms (V) and / or containers (B) for the hydraulic shaping of the containers, in particular for a finished blowing of the containers, and / or for product filling in the blow mold ( 1 . 21 ) are filled with a liquid. Method according to at least one of claims 9 to 16, wherein the container, or the partially blown container, is subjected to negative pressure inside.

Images