DE102010004586A1 - Device for manufacturing large-sized hollow body from thermoplastic, has vacuum chamber sealing blow mold against external atmosphere, where blow mold has opening that connects inner area of blow mold with inner area of chamber - Google Patents

Abstract

The device (10) has a blow mold (16) accommodating a pre-mold (28) made from thermoplastic, where the pre-mold projects from a die head (30) of a coextrusion-device (12). The pre-mold has a foam layer, and an upper hose-closing device (36) closes an upper area of the pre-mold. A lower hose-closing device (42) closes a lower area of the pre-mold against a blow mandrel. A vacuum chamber (14) is arranged at the die head, and seals the blow mold against external atmosphere. The blow mold has a connection opening (60) that connects an inner area of the blow mold with an inner area of the chamber. An independent claim is also included for a method for manufacturing a large-sized hollow body from thermoplastic.

Description

The invention relates to a device for producing large-volume plastic hollow bodies, with a multi-part blow mold which accommodates in an opened state a hose-shaped, multilayer plastic preform dispensed by a nozzle head of a coextrusion device, wherein at least one layer of the preform is a foam layer.

Furthermore, the invention relates to a method for producing large-volume hollow body.

When using a blow molding process for producing large-volume hollow bodies, which comprise a plastic foam layer, it is advantageous if the blown air has a low pressure in the blowing process, so as not to hinder or prevent the formation of the foam structure. If, after the ejection of the preform from the coextrusion device, a pressure is applied to the still thermoplastic melt, the foam structure collapses. Therefore, efforts are made to produce only a small pressure in the blow molding inside the hollow body. If a vacuum is generated between the inner wall of the multi-part blow mold and the hollow body, only a small blow pressure for forming the hollow body in the blow mold is required in the interior of the hollow body. However, with large volume hollow bodies, it is technically problematic to maintain the vacuum because it is difficult for a multi-part blow mold to sufficiently seal the parting plane of the blow mold along a relatively long parting line.

From the EP 1 112 164 B1 the same applicant, a method and an apparatus for producing a large-volume container is known in which vacuum is used to form the hollow body. The blowing device is designed so that the hollow body around its entire circumference around a circumferential crushing edge and the squeezing closes airtight. Such a circumferential squeezing area is disadvantageous, because this results in an uneven wall thickness distribution, with the result that the weight of the hollow body increases and the desired effect of a weight reduction by using a foam structure is at least partially canceled.

From the WO 2005/097462 A1 of the same applicant, an apparatus and a method for producing tubular preforms with a multilayer structure is known. A preform made of thermoplastic material is ejected through an annular nozzle. The nozzle is opened and closed by means of a reciprocating sleeve.

It is an object of the invention to provide an apparatus and a method for producing large-volume hollow body made of thermoplastic, multilayer plastic with at least one foam layer, wherein the material used for producing a high-quality hollow body is reduced.

This object is achieved for a device by the combination of the features of claim 1. According to a further aspect of the invention, a manufacturing method is specified. Advantageous developments are specified in the dependent claims and in the description.

According to the invention, the device includes a vacuum chamber which surrounds the multi-part blow mold and the closed multi-part blow mold airtight seals against the outside atmosphere. The blow mold contains at least one connection opening which connects the interior of the blow mold with the interior of the vacuum chamber. If vacuum is applied to the vacuum chamber, the preform is pressed against the inner surface of the multi-part blow mold, with air being injected into the interior of the sealed preform via the hollow blow pin. The vacuum chamber is located at the nozzle head which ejects the tubular preform or below it. Accordingly, the vacuum chamber has an internal space which is only slightly larger than the volume of the blow mold. The vacuum to be applied to the vacuum chamber is therefore limited in volume, which gives economic advantages. With the help of the upper hose closing device and the lower hose closing device, the preform is clamped and provisionally hermetically sealed, without making high demands on airtightness. In this way, the preform is held securely in the open blow mold until it takes over the further formation of the hollow body at a later time. A long circumferential pinch edge is avoided, which reduces plastic material. The subsequent blowing process takes place in the interior of the closed vacuum chamber, which completely surrounds the blow mold and the closed preform, so that vacuum leakage losses are avoided. As a result, the formation of a uniform wall thickness, including the foam layer, favors, resulting in the production of a high quality hollow body.

According to one embodiment, the top of the vacuum chamber is completely closed in its closed state and has such a distance from the top of the blow mold that from the upper hose closing device upwardly projecting Butzenteile in a space above the blow mold and the top of the vacuum chamber are fully absorbable. The Butzenteile are after separating the expelled from the nozzle head preform on the upper hose-closing device, so that the vacuum chamber in the upper part can be completely closed and Butzenteile not hinder the closing process. In this way, a vacuum leak is avoided and a vacuum with high constancy can be formed.

In another embodiment, the top of the vacuum chamber includes an opening whose edge in the closed state of the vacuum chamber sealingly abuts the jacket of the nozzle head of the coextrusion device. The preform ejected at the nozzle head is separated by closing the nozzle gap. Its Butzenteile fall due to gravity on the upper hose-closing device and do not hinder the manufacturing process. In this embodiment, can be dispensed with an upper tube-separating device which separates the tubular preform. In this way, the device is structurally further simplified.

Another development, which relates both to the device and the manufacturing method, provides that the bottom of the vacuum chamber is arranged at such a distance from the bottom of the blow mold, that under the lower hose closing device projecting Butzenteil in a space between the blow mold and Bottom of the vacuum chamber is completely absorbable. In this way it is prevented that when closing the vacuum chamber hanging parts of parts protrude into the separation region of the divided bottom of the vacuum chamber and thus can cause a vacuum leak.

Another embodiment of the device and the manufacturing method is characterized in that the multi-part blow mold and the multi-part vacuum chamber are rigidly connected together and are moved together in the open state and the closed state. In this way, the structure of the device and the manufacturing process is further simplified.

Embodiments of the invention are explained below with reference to the drawings. Show:

1 a schematic cross section through the blow mold and the vacuum chamber, in which a tubular preform is received;

2 the device after 1 with closed vacuum chamber and closed blow mold;

3 Another embodiment of the vacuum chamber, which bears sealingly against a lateral surface of the nozzle head; and

4 the embodiment according to 3 with closed vacuum chamber and closed blow mold.

1 shows a first embodiment of the apparatus for producing large-volume hollow body made of plastic. The device 10 is seen below a coextrusion device in the vertical direction 12 arranged and includes a clam shell vacuum chamber 14 , inside of a two-shell blow mold 16 is arranged. The vacuum chamber 14 and / or the blow mold 16 can also consist of more than two parts.

The vacuum chamber 14 and the blow mold 16 are in 1 shown in the open state. Each half of the blow mold 16 is with the associated side wall of the vacuum chamber 14 rigidly connected, for example screwed. In this way they are common across the central axis 18 with the help of a right machine clamping plate 20 and a left machine platen 22 in the closed state and from there again in the open state movable. Above the top 24 the vacuum chamber 14 is a hose separator 26 arranged, which is suitable for a preform 28 to be separated from thermoplastic.

From the coextrusion device 12 is just a nozzle head 30 represented in its interior by means of a vertically reciprocable quill 32 a nozzle gap 34 opened and closed, over which the tubular, multilayer preform 28 is ejected. This preform 28 contains at least one plastic foam layer.

At the top 24 the blow mold 16 is an upper hose-closing device 36 arranged, which is movable in the transverse direction and in the open state, the preform 28 the entry into the blow mold 16 permitted (see dashed preform 28 ). In the in 1 shown closed state squeezes the upper hose-closing device 36 the tubular preform 28 together, leaving the top of the preform 28 is largely closed. A through the hose separator 26 separated part of the brush 38 comes due to its gravity on the hose-closing device 36 to lie. A gap 40 above the blow mold 16 and the top 24 the vacuum chamber 14 is so big that the slug pieces 38 be completely absorbed in it.

Below the blow mold 16 is a lower hose-closing device 42 arranged at the in 1 shown closed state the lower portion of the preform 28 against the circumference of a hollow blow pin 44 presses and the preform 28 closes air-tight in the lower section. Through the blow pin 44 can blow air 46 be blown, so that the sealed preform 28 inflates like a balloon in a preform phase, as in 1 is shown. By pinching the preform 28 in the lower area creates a lower slug 48 , A gap 50 between ground 52 the vacuum chamber 14 and bottom of the blow mold 16 is sized so that the slug 48 from the gap 50 is completely recorded.

The double-shell vacuum chamber 14 contains in its respective peripheral edge sealing means 54 , When moving together the two shells of the vacuum chamber 14 this is at the top 24 also completely closed in the middle. In the lower part of the vacuum chamber 14 contains the soil 52 an opening 56 and sealants 54 , with the help of which a seal against the mandrel 44 in the closed state of the vacuum chamber 14 he follows. By means of the circulating sealant 54 For example, a rubber seal is the closed vacuum chamber 14 airtight sealed against the outside atmosphere. A vacuum line 58 is airtight in the ground 52 inserted. About this vacuum line 58 can by means of a vacuum device (not shown) a vacuum to the interior of the vacuum chamber 14 be created. The two-part blow mold 16 contains connection openings 60 so that the vacuum in the vacuum chamber 14 also inside the blow mold 16 is available. The upper hose-closing device 36 and the lower hose-closing device 42 can be moved using mechanical slides or hydraulic devices. The moving elements may also be airtight between the interior of the vacuum chamber 14 and sealed to the outside atmosphere.

2 shows the embodiment according to 1 in the closed state of blow mold 16 and vacuum chamber 14 , Same parts are the same. When closed, the vacuum chamber is 14 about the sealant 54 completely closed airtight. The upper gap 40 and the lower space 50 take the slugs 38 . 48 completely in such a way that the closing process of the vacuum chamber 14 not hindered. The blow mold 16 has on each shell a circumferential Abquetschkante 62 in the closed state of the blow mold 16 interact and the preform 28 squeezing off. The lower hose-closing device 42 has moved apart again as holding the preform 28 and the squeezing of the Butzens 48 is no longer necessary.

Hereinafter, the manufacturing process for a large volume hollow body based on 1 and 2 explained. The coextrusion device 12 bumps over the opened nozzle gap 34 a multilayer preform 28 out, with the quill 32 in 1 in the axial direction is moved down to the nozzle gap 34 to open. At least one layer of the preform 28 is a plastic foam layer. The rigidly connected two-part vacuum chamber 14 and the two-part blow mold 16 have moved apart, so that the tubular preform 28 according to the dashed lines when ejected moves down. Also the hose separator 26 , the upper hose-closing device 36 and the lower hose-closing device 42 are in the introduction phase of the preform 28 open. When a predetermined amount of plastic material is ejected, which is a predetermined length of the preform 28 corresponds, the ejection process is stopped and close the upper hose-closing device 36 and the lower hose-closing device 42 , In the upper part of the preform 28 the still warm thermoplastic material is squeezed airtight. In the lower part of the preform 28 the squeezing takes place along the circumference of the mandrel 44 , Thereafter, with the help of the hose-separating device 26 the preform 28 separated and the parts of the parts 38 fall due to their own weight on the upper hose-closing device 36 , About the blowhorn 44 becomes the preform 28 balloon-inflated to give it some initial stability. After that, the blow mold 16 and with it the vacuum chamber 14 closed, with the pinch edges 62 squeeze the preform together and the slug parts 38 and 48 in recesses 64 be recorded ( 2 ). When moving together the two-part blow mold 16 welds the preform 28 along the pinch edge 62 , wherein in the lower area in the middle of the opening for the mandrel 44 remains free.

When closing the blow mold 16 also become the two parts of the vacuum chamber 14 moved together and there is an airtight seal along the parting plane of the vacuum chamber 14 with the help of the circumferential seal 54 , When moving together the vacuum chamber 14 hamper the slugs 38 . 48 the seal does not, because these slugs 38 . 48 completely in the interstices 40 . 50 are included. Accordingly, the length of the ejected preform is 28 so measured that the drooping slippery material 48 not too long to enter the space between the two-piece floor 52 the vacuum chamber 14 to protrude.

After the vacuum chamber 14 closed airtight and also the blow mold 16 is closed, is via the vacuum line 58 Vacuum placed on the inside and at the same time the pressure of the blown air, which is above the mandrel 44 emanates, kept to a minimum. As a result of the connection openings 60 in the blow mold 16 becomes the preform 28 through the vacuum to the inner surface of the blow mold 16 sucked as well as the differential pressure between the vacuum in the blow mold 16 and the blowing pressure inside the preform 28 pressed. This is the preform 28 due to the close contact with the walls of the blow mold 16 cooled. At the same time is over the mandrel 44 cooled cooling air into the interior of the now formed to the hollow body preform 28 blown. Due to the low air pressure inside the preform 28 The foam structure may be in the plastic foam layer of the preform 28 to train completely. Due to the high tightness of the vacuum chamber 14 There is no vacuum loss, so that a high quality and a uniform formation of the wall of the hollow body is achieved. After the end of the cooling process, the hollow body is after opening the blow mold 16 and the vacuum chamber 14 taken.

3 shows a variant of the device according to 1 , Equal parts are again denoted the same. The vacuum chamber 14 has an opening at the top 70 with a frontal seal 54 , In the closed state of the vacuum chamber 14 lies the seal 54 on a coat 72 of the nozzle head 30 at. After closing the vacuum chamber 14 This results in a hermetic seal against the outside atmosphere and inside the vacuum chamber 14 A stable vacuum can be generated without loss of leakage at the parting line. The gap 40 is in turn so dimensioned that the Butzenteil 38 is completely absorbed. A hose separator (as in 1 ) can be omitted here. By control with the help of the quill 32 the nozzle gap is opened and closed. When closing the nozzle gap 34 also the multi-layer preform is separated with.

The manufacturing process for plastic hollow body is analogous to the manufacturing process described above.

The hollow bodies may have a volume of 50 liters to 40 m ³ , preferably 200 liters to 10 m ³ . The plastic material used may preferably be polyethylene (PE), polypropylene (PP) and as a plastic foam layer PE or PP with blowing agent.

The blowing pressure in the interior of the preform for forming the foam structure of the plastic foam layer is in the range from 1 bar to 5 bar, preferably from 1 bar to 2 bar.

In the embodiments shown, the blow mold and the vacuum chamber are rigidly connected to each other and are moved together at the same time. Alternatively, blow mold and vacuum chamber can also be moved independently of each other.

LIST OF REFERENCE NUMBERS

10

Device according to the invention

12

Coextrusion device

14

vacuum chamber

16

blow

18

central axis

20

right machine clamping plate

22

left machine clamping plate

24

Top of the vacuum chamber

26

Tube separator

28

preform

30

nozzle head

32

Pinole

34

die gap

36

Upper hose closing device

38

Butzenteil

40

gap

42

Lower hose closing device

44

mandrel

46

blowing air

48

slugs

50

gap

52

Bottom of the vacuum chamber

54

sealant

56

opening

58

vacuum line

60

connecting opening

62

recess

70

opening

72

Sheath of the nozzle head

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

• EP 1112164 B [0004]
• WO 2005/097462 A1 [0005]

Claims (8)

Contraption ( 10 ) for producing large-volume hollow plastic body, with a multi-part blow mold ( 16 ), which in an open state one of a nozzle head ( 30 ) a coextrusion device ( 12 ) issued tubular, multilayer preform ( 28 ) of thermoplastic material, wherein at least one layer of the preform ( 28 ) is a foam layer, with an upper hose closure device ( 36 ), the preform ( 28 ) in the upper area, with a lower hose closing device ( 42 ), the preform ( 28 ) in the lower area against a hollow mandrel ( 44 ), with one at the nozzle head ( 30 ) or below it arranged multipart vacuum chamber ( 14 ), the multi-part blow mold ( 16 ) surrounds and the closed multi-part blow mold ( 16 ) airtightly seals against the outside atmosphere, and with a vacuum device, a vacuum to the inside of the vacuum chamber ( 14 ), wherein the blow mold ( 16 ) at least one connection opening ( 60 ) containing the interior of the blow mold ( 16 ) with the interior of the vacuum chamber ( 14 ) connects. Device according to claim 1, characterized in that the upper side ( 24 ) of the vacuum chamber ( 14 ) is completely closed in its closed state and from the top of the blow mold ( 16 ) has such a distance that from the upper hose closing device ( 36 ) upwardly projecting parts ( 38 ) in a space ( 40 ) above the blow mold ( 16 ) and top ( 24 ) of the vacuum chamber ( 14 ) is completely absorbable. Device according to claim 1, characterized in that the upper side ( 24 ) of the vacuum chamber ( 14 ) an opening ( 70 ) whose edge in the closed state of the vacuum chamber ( 14 ) on the jacket ( 72 ) of the nozzle head ( 30 ) of the coextrusion device ( 12 ) sealingly. Device according to one of the preceding claims, characterized in that the bottom ( 52 ) of the vacuum chamber ( 14 ) at such a distance from the bottom of the blow mold ( 16 ) is arranged, that one below the lower hose closing device ( 42 ) protruding part ( 48 ) in a space ( 50 ) between blow mold ( 16 ) and ground ( 52 ) of the vacuum chamber ( 14 ) is completely absorbable. Method for producing large-volume plastic hollow bodies in which a coextrusion device ( 12 ) via a nozzle head ( 30 ) a tubular, multilayer preform ( 28 ) is made of plastic, wherein at least one layer of the preform ( 28 ) is a foam layer, the preform ( 28 ) of a multi-part blow mold ( 16 ) is received in its opened state, the preform ( 28 ) in its upper region by an upper hose closing device ( 36 ), the preform ( 28 ) in its lower region by a lower hose closing device ( 42 ) against a hollow blow pin ( 44 ), the preform ( 28 ) by supplying air through the mandrel ( 44 ) is partially inflated and the blow mold ( 16 ), the closed blow mold ( 16 ) by a at the nozzle head ( 30 ) or below it arranged multipart vacuum chamber ( 14 ) is airtight sealed against the outside atmosphere, using a vacuum device, a vacuum to the interior of the vacuum chamber ( 14 ) is applied, the blow mold ( 16 ) via at least one connection opening ( 60 ) with the interior of the vacuum chamber ( 14 ), one below the lower tube closing device ( 42 ) protruding part ( 48 ) in a space ( 50 ) between blow mold ( 16 ) and ground ( 52 ) of the vacuum chamber ( 14 ) is completely absorbed. A method according to claim 5, characterized in that the tubular preform ( 28 ) above the upper hose closing device ( 36 ) by means of a hose separating device ( 26 ) and the protruding parts ( 38 ) in a space ( 40 ) above the blow mold ( 16 ) and top ( 24 ) of the vacuum chamber ( 14 ) is recorded. Method according to claim 5, characterized in that the upper side ( 24 ) of the vacuum chamber ( 14 ) in its closed state on a jacket ( 72 ) of the nozzle head ( 30 ) of the coextrusion device ( 12 ) sealingly abuts, the tubular, multilayer preform ( 28 ) by closing the nozzle ( 34 ) in the nozzle head ( 30 ) is separated and the Butzenteil ( 38 ) in a space ( 40 ) above the blow mold ( 16 ) and top ( 24 ) of the vacuum chamber ( 14 ) is recorded. Method according to one of the preceding claims, characterized in that the pressure, with the air over the mandrel ( 44 ) in the preform ( 28 ) is reduced to a predetermined minimum to form the foam structure.

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