DE202011001622U1 - Compressed gas thermoforming apparatus - Google Patents

Abstract

Pressurized gas thermoforming device for the simultaneous production of several plastic containers from thermoplastically deformable plastic films or sheets (5) with a first part (1) and with a second part (2), in which the second part (2) has several shaping cavities (3 ) and in which the first part (1) for each cavity (3) comprises an internally hollow hold-down device (4) for temporarily fixing the plastic film or plate (5) and a forming die (6) that can be displaced within the hold-down device (4) and at which the spaces (7) between the hold-down devices (4), the plastic film or plate (5) and the forming die (6) can be supplied with forming air under pressure, characterized by a piston plate (15) which combines several hold-down devices (4) and which is located inside a cylinder-like The recess (16) of the first part (1) can be moved, in particular pneumatically or hydraulically, and the associated hold-down device (4) is moved back and forth for the detachable fixing of the film (5).

Description

FIELD OF THE INVENTION

The invention relates to a compressed gas thermoforming device for producing plastic containers from thermoplastically deformable plastic films or plastic plates having the features of the preamble of claim 1. Accordingly, the device comprises a first part, such as an upper part, and a second part, such as a lower part. The second part comprises or carries a plurality of shaping cavities, which usually form part of a mold insert in the first part. The first part comprises, per cavity, a hollow holder which is hollow on the inside, in order temporarily to fix the plastic film or sheet to be thermoformed, hereinafter referred to as foil, in an edge region with respect to the lower part and there with respect to the cavity. The hold-down device for fixing the film relative to the cavity is hollow on the inside and open on its rear side. The first part further comprises a displaceable within each hold-down form stamp, which is also referred to as stretching aid or Vorstrecker. This forming punch is to be displaced within the hollow holder down against the film to be deformed in the direction of the cavity, so that it initiates the molding process. The space enclosed between the holding-down device, the film and the forming die can be supplied with so-called shaping air as a gas under overpressure in order to complete the shaping step until the film has been applied to the contour of the associated cavity.

TECHNOLOGICAL BACKGROUND

From the DE 10 2007 037 748 B3 , from which the invention proceeds, it is known to keep compressed air ready for the forming step within the inside hollow hold-down in a cylinder space separated from the forming die in order to make it abruptly available for the pressurized gas forming step. For this purpose, the hold-down is designed as a cylinder for receiving a piston plate. This creates on the back of the piston plate within the hold-down of the sealable cylinder chamber to the outside. Furthermore, a device for possibly also independent movement of the piston plate is provided. The so-equipped hold-down is used axially movable in the region of its rear wall in a cylindrical recess of a head plate of the upper part and is urged by an effective in the recess of the top plate compression spring in the hold-down position. The cylinder space of the hold-down and the recess in the top plate are maintained at a constant pressure via a permanent fluid connection in order not to influence the hold-down force. A common drive for the uniform and simultaneous process of hold-down for all simultaneously operated cavities is therefore not provided.

PRESENTATION OF THE INVENTION

On this basis, the present invention seeks to provide alternative means to allow a uniform expression of the opening edge of several plastic containers simultaneously produced in a pressurized gas thermoforming device. To solve this problem, a compressed gas thermoforming device with the features of claim 1 is proposed. Accordingly, in a generic compressed gas thermoforming device, a plurality of hold-down piston plate is provided which is within a cylinder-like recess of the first part, in particular pneumatically or hydraulically movable. The associated hold-down are thus for releasably fixing the film together and moved with uniform force back and forth and the hold-down movement significantly simplified. The pressurized surface of this piston can be kept relatively small, so that the hold-down forces can be set sensitively. This can be achieved, in particular, by using a mold air displacement body, as explained in more detail below:
The mold air displacement body is slidably received in the first part. This is done in such a way that the mold air displacement body is sealed with respect to the first part out to the outside of the upper part. The mold air displacement body are axially displaceable with the mold dies with respect to the first part. When propelling the punches is therefore the amount of air that is located after clamping the film in the space between the downers, the film and the dies, no longer, as in the past, but rather kept constant or even reduced. Once mold air is introduced into the remaining mold air space under pressure to carry out the pressurized gas thermoforming step, the gas within the mold air space may already be biased and only a relatively small residual volume of pressurized gas must be supplied under mold air pressure. The functions of the "upper part" and the "lower part" can be interchanged without leaving the invention solution.

Overall, a significant saving in pressurized mold air can be achieved. The savings potential is on the order of 30 to about 80% with respect to the volume necessary for the working stroke of the forming punch inside the hollow holder inside. Because of the mentioned possible Vorkomprimierung already before the propelling the Formstempels, the Pressure gas savings even higher than in generic solutions according to DE 103 26 670 B3 , But above all, the many additional components are saved, as in accordance with DE 103 26 670 B3 are required for the local mold air savings. This solution is independent of claim 1 of independent inventive importance.

If a hold-down support plate summarizing several hold-down, within the first part is provided, a Niederhalterwechsel can be simplified for the conversion to another product by externally operable on the first part locking elements, such as slides for releasably connecting the hold-down with the hold-down support plate, which can also be used as the plurality of hold-down piston plate summary, are provided. This solution is independent of claim 1 of independent inventive importance.

It is now possible in various ways to carry out the invention, in particular when shaping air displacement bodies are provided:
Basically, one will choose the cross section of the Formluftverdrängungskörpers so that it fills the cavity of the hollow inside hold-down to a radial residual air gap. A seal between the cavity wall of the blank holder and the Formluftverdrängungskörper is - in contrast to DE 103 26 670 B3 - dispensable, since the annular space between the outer surface of the mold air displacement body and the cavity wall of the blank holder can be reduced to an insignificant residual and therefore relatively insignificant for application to thermoforming air.

Since the cavity and possibly the hold-down and / or the forming die for molding the plastic container for different sizes and shapes must be adapted to plastic containers, at least one of these components is replaced with a product change against corresponding to the new product form-adapted components. An exchange of the mold air displacement body is often unnecessary, because on a compressed gas thermoforming machine such plastic containers are usually produced, which have a reasonably similar maximum cross-section at its opening edge and differ substantially only in terms of their container depth or with respect to the container outer contour. Therefore, the radial gap in the residual air annulus remaining between the inner wall of the blank holder and the outer surface of the mold air displacer is not too different for various plastic containers made on the same pressurized gas thermoforming machine, so that the molding air consumptions for various products do not significantly differ at comparable container height.

If the mold air displacement body carries the mold air in its interior, thereby simplifying the design of the hold-down and the upper part, because the Formluftzuführleitung can be connected directly to the located outside of the upper head of the Formluft-displacement body or its front-end holder. Elaborate air ducts within the shell and the blank holder omitted.

When the mold air displacement body has at least one mold air passage valve in its end portion near the forming die, the temperature control of the molding process is simplified. Above all, this reduces the feed time for compressed gas and thus the duration of the thermoforming process.

A further simplification of the Formluftein- and / or -ausspeisung arises when multiple mold punches and mold air displacement body summarized by means of a form-stamping support plate and with respect to the first part are moved back and forth and the forming die support plate is designed as a mold air distributor, the forms a mold air distribution assembly together with the mold air displacement bodies. The molding gas distribution arrangement preferably has individual valves for the supply of each molding gas cavity in the hold-down device with molding gas. This solution is independent of claim 1 of independent inventive importance.

If a body pierced in its longitudinal direction closure body is provided to seal the opening of the upper part of the mold air displacement body to the outside and to receive a mold-carrying piston rod slidably, thereby the mold air displacement body can be replaced with a conventional tool if necessary.

The above-mentioned and the claimed components to be used according to the invention described in the exemplary embodiments are not subject to special conditions of size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction.

Further details, features and advantages of the subject matter of the invention will become apparent from the subclaims, as well as from the following description and the associated Drawing in which - by way of example - an embodiment of a compressed gas thermoforming device is shown. Also, individual features of the claims or of the embodiments may be combined with other features of other claims and embodiments.

BRIEF DESCRIPTION OF THE FIGURES

In the drawing show:

1 a pressurized gas thermoforming device in a first embodiment in the open position of the upper part with respect to the lower part in a perspective view, partially and partially in vertical section;

2 the same compressed gas thermoforming device with closed upper and lower part before the deformation step in vertical section;

3 the same compressed gas thermoforming device with the upper and lower part closed and the mold die lowered before the pressurized gas thermoforming step;

4 the same compressed gas thermoforming device with the upper and lower part closed and the shaped punch lowered in the state of the final deformation of the film into a plastic container with pressurized gas;

5 one too 1 to 4 alternative embodiment of a compressed gas thermoforming device in the state of completed deformation;

6A / B shows a further alternative embodiment of a compressed gas thermoforming device in the phase of compressed gas filling ( 6A ) and in the phase of pressurized gas emptying ( 6B ) such as

7 of yet another embodiment of a pressurized gas thermoforming device, the upper part without hold-down.

DETAILED DESCRIPTION OF EMBODIMENTS

Out 1 to 4 is the general structure of a pressurized gas thermoforming device 100 can be seen according to the invention. It includes a top 1 and a lower part 2 which in the illustrated embodiment eight shaping cavities 3 includes, for example, in the form of interchangeable mold inserts 3A , The top 1 each cavity can have a hollow downholder inside 4 contribute to the temporary fixing of a plastic film or sheet 5 which is introduced in a mold heated to deformation temperature for each shot (production sequence) in plate or sheet form between the upper and lower part.

How out 2 Obviously, the hold-down has 4 the function, after closing the compressed gas thermoforming device by moving together upper and lower part of the plastic film or plate 5 firmly on the (overhead) shaping mouth edge of the cavity 3 hold and thereby imparting to the forming edge of the plastic container to be produced the desired surface structure. This is the hold-down 4 in relation to the upper part 1 to a short distance of z. B. 1 millimeter axially movable and corresponding in a belonging cylindrical recess of a lower half of the housing 1A the block-like shell 1 slidably fitted. In the in 1 shown rest position is located within the hold-down 4 one from the top 1 out push-forward shape stamp 6 , also known as Vorreckstempel. His function is off 3 clearly, as can be seen from the plastic film or plate by advancing the mold punch 6 to a container blank 5A is preformed, with differences in wall thickness in the deformation range of the plastic film (as usual) set.

The collapse of upper and lower part creates between the hold-down 4 , the plastic film or plate 5 as well as the forming stamp 6 a universally sealed room 7 , In these (as usual), controlled by suitable valves, under pressure known as molding air, z. B. at 4B , pressed in. This usually happens only in the 4 production phase shown, ie following the preforming of the container by the forming die 6 , The mold air then penetrates between the preformed container blank 5A and the shape stamp 6 and presses the preformed material of the container blank to the walls of the mold insert 3A at. In that regard, the process is known, as well as the subsequent separation of the individual finished container 5B from the initially contiguous plastic plate, the cooling of the mold and the ejection of the finished container 5B ,

To reduce the use of mold air as much as possible, is per cavity 3 a mold air displacement body 8th intended. This extends at least with a part of its length by at least a partial length of the blank holder 4 and the shell 1 therethrough. In the work phases according to 1 and 2 the mold air displacement body extends 8th only by an upper half of the housing 1B of the top 1 , as well as a still to be described piston plate 15 and the head area of the hold-down 4 , In the production steps after 3 and 4 the mold air displacement body extends 8th also through the bottom housing half 1A of the top 1 and all or nearly the whole length of the hold-down 4 therethrough. The shaped air displacement body 8th is at its (lower in the drawing) end via a screw thread or the like - or possibly also in one piece - with the forming punch 6 firmly connected. At its opposite, from the top 1 outstanding, end region is the mold air displacement body 8th with a known support plate 19 firmly connected, in turn, via a coupling pin 19A is movable up and down with a drive, not shown in the drawing. The top 1 , or in the embodiment of the upper half of the housing 1B , has large-bore cylinder bores 1C for sealed, slidable guidance of the cylindrical peripheral surfaces 8A the positive displacement body 8th on. With the cylinder bore 1C Aligns another cylinder bore 15C the still to be described piston plate 15 inside a cylindrical recess 16 in the upper part 1 is arranged and also allows a sealed relative to the ambient atmosphere sliding guide of the mold air displacement body. Finally, it aligns with the cylinder bores 1C and 15C a third cylinder bore 4C in the head area of the hold-down 4 , This can also lead to management tasks for the cylinder surface 8A the mold air displacement body 8th be designed.

On its predominant length is the hold-down 4 possibly with a slightly larger internal cross-section than in the area of its cylinder bore 4C provided and forms a radial gap 7A between the inner hold-down surface and the cylinder surface 8A , The narrower this, preferably annular radial gap is held, the lower the mold air consumption, as will be seen below. The gap width should be between 0.01 and 15 mm, preferably between 1 and 5 mm. Alternatively or cumulatively, the cross-sectional area ratios between the inner cross-section of the blank holder 4 and the outer cross section of the positive displacement body 8th between 1: 0.4 and 1: 0.99, and more preferably between 1: 0.8 and 1: 0.99. The largest cross-sectional area of the at the lower end of the mold air displacement body 8th subsequent form stamp 6 may have similar cross-sectional dimensions as the mold air displacement body 8th exhibit; it can also be dimensioned smaller or larger in dimensions. In this way, when advancing the forming punch 6 only as much under working pressure standing mold air volume are tracked, as it is the volume of the gap or annulus 7B equivalent. It is also possible, non-circular cross-sections for the forming die and the positive displacement body 8th to choose if z. B. a non-circular cross-section, but oval or otherwise oblong shaped plastic container to be produced. In these cases, in which even then the mouth section of the blank holder must be shaped according to the shape of the container mouth edge, the upper part changes accordingly.

The hold down 4 can be designed completely backless and thus from a tubular blank, z. B. by turning, are produced inexpensively.

In order to allow a uniform formation of the mouth edges of all in a single shot from the plastic film or plate produced plastic container, the multiple downholder summary piston plate 15 provided within a cylindrical recess 16 of the top 1 , z. B. is pneumatically or hydraulically movable. This allows all hold-downs 4 be moved back and forth together to set the plastic film or plate and release it again. For this purpose, the piston plate 15 in a cylinder space formed in the upper part (cylindrical recess 16 ) in radially sealed form slightly up and down, with a guideway of about 1 mm usually sufficient. The piston plate 15 may have an approximately rectangular cross-sectional area, wherein the corner regions are sufficiently rounded, if a simplified seal against the cylindrical recess 16 in the upper part 1 is desired. In the embodiment shown in the drawing and so far preferred embodiment, the cylindrical recess 16 in the lower half of the housing 1A of the top 1 housed and gets up from the top half of the case 1B closed, which can be designed approximately plate-shaped and thus easy to produce. The piston plate 15 has for sealingly performing the Formluftverdrängungskörper 8th correspondingly dimensioned cylinder bores 15C on, the usual sealing rings can wear. Although it is possible in principle, the piston plate 15 in any way, so also by mechanical or electromagnetic means to move, but it is preferably by a fluid and more preferably pneumatically moved up and down, the aforementioned seals the piston chamber suitably seal.

The connection between the piston plate 15 and the downers 4 can be done in any way and also be solvable. The latter is desirable when the hold-downs are to be interchangeable, be it in case of damage or be it that the embossing countries are to be changed at the lower hold-down end. To disassemble the shell here 1 To avoid this, locking means, in particular slides, can be used for this purpose 18 be provided, which can be operated outside of the upper part. This results in a simplified production of the piston plate 15 if these consist of two interconnecting sub-panels exists between which recesses are provided for receiving the locking elements. Such locking elements engage both in the piston plate and on the outer edge of the hold-down 4 a, as particularly clear 6A / 6B seen.

In the embodiment according to 5 is a perforated in its longitudinal direction closure body 11 provided to seal the opening of the upper part of the mold air displacement body to the outside sealingly and to receive a piston rod supporting the forming die in a slide-sealed manner. This allows to use in a device according to the invention older or conventional tools, the z. B. do not allow use with a Formluftverdrängungskörper.

The supply of the molding air can be done in different ways. In the embodiments according to 1 to 4 The Formluftzufuhr done in a conventional manner, by within the upper part 1 Molded air channels are incorporated, which open at the holding-down recesses in the upper part. Wall openings 4A the hold down 4 then allow the inflow of mold air into the inside of the hold-down 4 Form gas space formed 7 ,

An alternative form gas supply results 6A / B, according to which a molding gas distribution arrangement is provided which comprises a plurality of mold air displacement bodies 8th back summary molding air displacement body panel 19 and the mold air displacement bodies 8th includes. For this purpose, have the Formluftverdrängungskörper 8th an internal cavity 8B on, in the mold air from the support plate 19 flow in from above and from the mold air at the bottom, preferably above the forming punch 6 , can emanate again.

The Formgasverteilanordnung can individual valves 9 have, either in the support plate 19 or on or in the mold air displacement body 8th are provided. As a result, the molding gas consumed per production shot and held under pressure can be further reduced in terms of quantity.

Individual shaped air outlet valves 9 as they are in 6A / B, reduce the volume of mold gas to be fed particularly clearly. For this purpose, within the cavity serving as a passage for shaping air cavity 8B a combined air inlet and outlet pipe 12 be provided, which opens freely at its upper end to the atmosphere and this through the support plate 19 can be passed through. It opens with its lower end z. B. in a closure plate 8C the hollow mold air displacement body 8th and by the way also a screw connection 12E or the like for interchangeable receiving different mold punches 6 exhibit. One over the combined inlet / outlet pipe 12 pushed ring sleeve-shaped spool 9A is in sealed and slidably guided form by means of a through the support plate 19 guided by control rod 13 along the inlet / outlet tube 12 displaceable. For this purpose, all control rods 13 by means of a support plate 13A and drive means 13B be moved up and down together. The spool 9A has one or more so-called control edges 9B on that with tax holes 12A . 12B of the inlet outlet pipe 12 can interact. A stopper 12C divides the inner channel of the inlet / outlet tube 12 in two separate work areas.

The function of the shaping air outlet valve 9 is the following: In the in 6A illustrated Formlufteinlassstellung is the spool 13 in its highest working position and thereby gives at least one lower control bore 12A below the sealing plug 12C free, allowing the forming gas out of the cavity 8B the mold air displacement body 8th over a transverse distribution z. B. in the form of a transverse bore 12D from the inlet / outlet pipe 12 can escape. This transverse distribution is preferably in the region of the closure plate 8C the mold air displacement body 8th arranged and opens, preferably, there in an annular channel 8C for uniform distribution of the molding gas in all radial directions. As a result, the same flow and thus uniform cooling conditions are achieved in the Formluftauslassstellung over the container circumference. Here is the spool 9A in his lowest working position, in which he has the lower tax holes 12A opposite the cavity 8B shut off and on the other hand, the lower control bore 12A with the above the sealing plug 12C located control bore 12B combines. In this way, the initially pressurized forming gas can flow back and escape to the atmosphere.

LIST OF REFERENCE NUMBERS

1

top

1A

lower half of the housing

1B

upper half of the housing

1C

bore

2

lower part

3

shaping cavity

3A

mold insert

4

Stripper plate

4A

Wall openings

4C

bore

5

Plastic film or plate

5A

container blank

5B

finished container

6

forming punch

7

Form gas space

7A

annular gap

7B

Gap or annulus

8th

Forming air-displacement body

8A

cylindrical surface

8B

cavity

8C

closing plate

8D

annular channel

9

Form vent valve

9A

spool

9B

control edges

10

Compressed gas thermoforming apparatus

11

closure body

12

Inlet / outlet pipe

12A

lower control bore

12B

upper control bore

12C

sealing plug

12D

cross hole

12E

Screw

13

control rod

13A

support plate

13B

drive means

14

Means for passing through mold air

15

piston plate

15C

bore

16

cylindrical recess

17

Lower holder supporting plate

18

pusher

19

support plate

19A

kingpin

19B

Formluftzuführleitung

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

• DE 102007037748 B3 [0002]
• DE 10326670 B3 [0004, 0004, 0006]

Claims (11)

Compressed gas thermoforming device for simultaneously producing a plurality of plastic containers from thermoplastically deformable plastic films or plates ( 5 ) with a first part ( 1 ) and with a second part ( 2 ), in which the second part ( 2 ) several shaping cavities ( 3 ) and in which the first part ( 1 ) per cavity ( 3 ) an inside hollow holder ( 4 ) for temporary fixing of the plastic film or plate ( 5 ) and one within the hold-down ( 4 ) movable mold punches ( 6 ) and in which the rooms ( 7 ) between the holdings ( 4 ), the plastic film or plate ( 5 ) and the forming punch ( 6 ) Mold air can be supplied under pressure is characterized by a plurality of hold-down ( 4 ) summary piston plate ( 15 ), which within a cylindrical recess ( 16 ) of the first part ( 1 ), in particular pneumatically or hydraulically, is movable and the associated hold-down ( 4 ) for releasably fixing the film ( 5 ) moved back and forth. Device according to the preamble of claim 1, in particular according to claim 1, with a plurality of hold-downs ( 4 ), within the first part ( 1 ) movable back and forth hold-down support plate ( 17 ) with at least one from the outside at the first part ( 1 ) actuatable locking element, such as a slider ( 18 ), for releasably connecting the hold-down ( 4 ) with the hold-down support plate ( 17 ). Device according to the preamble of claim 1, in particular according to claim 1, characterized in that at least one mold air displacement body ( 8th ) per cavity ( 3 ) is provided that the at least one mold air displacement body ( 8th ) at least with a part of its length by at least a partial length of the blank holder ( 4 ) and the first part ( 1 ) and in that means for jointly displacing the at least one mold air displacement body ( 8th ) with the forming punch ( 6 ) with regard to the first part ( 1 ) are provided in opposite to the ambient atmosphere sealed, slidably guided manner. Apparatus according to claim 3, characterized in that the at least one mold air displacement body ( 8th ) exclusively with regard to the first part ( 1 ) is sealed. Apparatus according to claim 3 or 4, characterized in that the mold air displacement body ( 8th ) Medium ( 14 ; 8B ) for passing molding air. Device according to one of claims 3 to 5, characterized in that the mold air displacement body ( 8th ) at least one shaping air passage valve ( 9 ) having Device according to one of claims 3 to 6, characterized in that the width of a between the outer surface of the mold air displacement body ( 8th ) and the inner surface of the rest room or the hold-down ( 4 ) remaining radial gap ( 7A ) 0.01 to 15, preferably 0.1 to 5 mm, and / or that in the region of the travel path of the mold air displacement body ( 8th ) the cross sectional area ratio between the inner cross section of the rest space or the hold down and the outer surface of the mold air displacement body is between 1: 0.4 to 1: 0.999 and preferably between 1: 0.8 and 1: 0.99. Device according to the preamble of claim 1, in particular according to one of claims 1 to 7, with a plurality of mold air displacement bodies ( 8th ), with reference to the first part ( 1 ) movable back and forth mold air displacement body support plate ( 19 ), which is designed as a form gas distributor and together with the mold air displacement bodies ( 8th ) forms a molding gas distribution arrangement. Apparatus according to claim 8, characterized in that the forming gas distribution arrangement individual valves for the supply of each mold air space ( 7 ) with molding gas. Device according to one of claims 3 to 9, characterized by a pierced in its longitudinal direction closure body ( 11 ) for sealing the opening to the outside ( 1A ) of the first part ( 1 ) for the mold air displacement body ( 8th ) and for sealing, sliding receiving a die ( 6 ) carrying piston rod ( 12 ) as a substitute for the mold air displacement bodies ( 8th ). Device according to one of claims 3 to 10, characterized in that the hold-down ( 4 ) is designed without any backs.

Images