HK1146921B - Method and device for producing containers made of thermoplastic and containers so produced - Google Patents

Description

Method and device for producing containers from thermoplastic plastic and container produced in this way

Technical Field

The invention relates to a method for producing containers from thermoplastic, in which method an extruded plastic tube is introduced into a mold, the movable mold part of which has been moved into a mold-opening position, at least the mold parts forming the transition between the container body and the container bottom are closed, wherein the container bottom is welded, the tube is expanded and pressed against the walls of the mold parts by means of a pressure gradient (pressure change) acting on the tube to form the shape of the container, and the mold parts are moved into a mold-opening position to release the formed container. The invention also relates to a device for carrying out the method and to the container produced in this way.

Background

Methods of this type, e.g.Systems are widely used for manufacturing containers having different shapes, sizes and for different purposes of use. The container may in particular be a transparent, flexible container made of polyethylene or polypropylene. Many times, in an aseptic operation, both the container is manufactured and filled with a sterile filling substance, e.g. a drug, and the container is closed in one process step. This is the case in particular when expensive fillings are involved, which is the case for certain medicaments, it being important for the use properties of the relevant container that the filling can be taken out in a suitable manner. In particular, it must be ensured that, when the very expensive medium is pressed out of the flexible container by compression, it can be pressed out of the container without a residual quantity remaining and/or that a precise dose can be delivered, which is important in particular for medicaments.

Disclosure of Invention

In view of these requirements, it is an object of the present invention to provide a method for producing a container, the use properties of which are optimized with regard to the removal of the filling material.

The object is achieved according to the invention by a method which has the following features in its entirety:

method for manufacturing containers from thermoplastic, in which method an extruded plastic hose is introduced into a mould, the movable mould part of which has been moved into a mould-opening position, at least the mould parts forming the transition between the container body part and the container bottom are closed, in which the container bottom is welded, the hose is expanded and brought into abutment against the walls of the mould parts by means of a pressure gradient acting on the hose to form the container shape, the mould parts are moved into a mould-opening position to demould the formed container, characterized in that the container bottom is formed in the shape of a basin-shaped bottom part which axially lengthens the container body part, said bottom part being turned into the interior of the container to form a bottom projection which projects into the container body part, the basin-shaped bottom part being formed by the bottom mould parts, each of said bottom mould parts being movable relative to the body mould part in which the container body part is moulded and being in the closed position The bottom part is welded in and, in order to turn the bottom part, the bottom mould part is moved into a position in which the mould is partially opened, the turning of the bottom part being effected mechanically by loading the bottom part by a punch which is driven to move concentrically with respect to the axis of the container.

Accordingly, an important feature of the present invention is that in a pressIn a method of the type of system, a pot-shaped bottom part, which axially extends the container body part, is formed in a blow mold or vacuum mold and is then turned into the interior of the container, so that a bottom projection is formed, which extends into the interior of the container in the form of a pot which opens out on the container bottom. When the filling is to be dispensed in such a container in such a way that the container is compressed from the bottom, the bottom projection then acts as a pressure-discharging body which, for complete emptying of the container, can be moved into the top region of the container and will be located at the topThe volume of the filling in the region is pressed out and the remaining residual quantity is thereby minimized.

This is particularly relevant in containers in which the container body is designed as a bellows which is compressed for the discharge of the filling in such a way that the individual corrugations of the bellows abut against one another. If this state is reached during the pressing-out, the bellows has a certain absolute length/cut-off length depending on the number of corrugationsThe cut-off length cannot be shortened by further compression, so that at the end of the bellows compression process a large residual volume remains. If the bottom projection formed according to the invention is matched in shape and size to the residual volume in the optionally tapered top region of the container, the residual volume remaining when the bellows is compressed together can be minimized, even for containers with bellows.

The bottom part of the basin is preferably turned inside the container before final demoulding of the container. Since the container is now also fixed inside the mold, the turning process can be carried out without difficulty in the desired, precisely calibrated manner. Furthermore, the turning-over process can now be carried out in a controlled manner at a temperature level at which the plastic material used for forming the remaining bottom projections can still be plastically deformed in a suitable manner. In view of this, it is advantageous to carry out the inversion of the bottom portion before the container is filled with the filling, i.e. before cooling by the filling takes place.

In an advantageous embodiment of the method, the basin-shaped bottom part is formed by bottom mould parts, which are movable relative to a body mould part forming the body part of the container, and in the closed position the bottom part is welded and moved into a position partly opening the mould in order to invert the bottom part. The turning can thus also be effected by mechanical intervention between the bottom mould parts which are correspondingly moved away from each other.

In an advantageous embodiment, it can be provided that the tilting of the base part is effected mechanically by loading the base part with a punch which is driven so as to be movable concentrically to the container axis.

In this connection, it is preferably provided that the scrap located at the welding site of the bottom part is separated by a separating element before the bottom part is turned over.

The subject of the invention is also a device for carrying out the method, preferably having a movable mold part forming a blow mold, wherein a bottom mold part, which is independent of the movable mold part pair, is connected to the mold part pair forming the container body part, each of which bottom mold parts in the closed position defines a pot-shaped mold cavity for forming a pot-shaped bottom part axially extending the container body part.

The arrangement is preferably such that the bottom mould part has a welding jaw for welding the basin-shaped bottom part.

In order to invert the base part into the interior of the container, a pressure ram is preferably provided which can be driven in a reciprocating manner and can be oriented in alignment with the longitudinal axis of the container, by means of which the pot-shaped base part can be inverted into the container body part when the bottom tool parts are correspondingly opened.

In order to provide a support surface without irregularities for supporting the pressure ram, in a preferred embodiment a mechanically movable separating element is provided which can be aligned with the longitudinal axis of the container when the bottom die part is correspondingly opened, for removing bottom scrap formed at the welding site of the pot-shaped bottom part.

The subject of the invention is also a container produced by the method according to the invention according to the method according to the invention, wherein the container has a bottom projection which projects inwardly of the container body part.

Drawings

The present invention is described in detail below with reference to the accompanying drawings. Wherein:

fig. 1 shows a schematic simplified view of an open blow mould and an extrusion head located above for forming a hose from a plasticized plastic material;

fig. 2 shows the partially closed blow mould of fig. 1 in an operating state in which a hose welded on the bottom side is expanded through a blow hole in order to form a container shape;

fig. 3 shows the working condition of filling the container with the filling material;

FIG. 4 shows the working condition with the bottom mould parts partially moved away from each other for removing bottom scrap of the bottom side weld sites;

FIG. 5 shows the working condition after separation of the bottom scrap, with the bottom mold parts further moved away from each other and showing the separating element in an axially oriented position;

fig. 6 shows an operating state in which the movable pressure ram is shown in an axially oriented position;

fig. 7 shows the operating state with the bottom part inverted by the pressure punch and the filling surface thus raised with respect to fig. 6;

FIG. 8 shows the operational condition with the fill surface raised but after forming the top closure by closing the top mold parts;

FIG. 9 shows a side view of one embodiment of a container made in accordance with the present invention in the form of an axially compressible closed bellows; and

fig. 10 shows a perspective view of another embodiment of the container with the bellows tapering towards the top region.

Detailed Description

FIGS. 1 to 8 show a known method for producing plastic containers by blow moldingPart of an apparatus used within the scope of the system, in which a hose 3 is extruded from a molten plastic material by means of an extrusion device 1 between movable mould parts of a blow mould, which is shown in an open state in fig. 1 and has a top mould part 5, a container body mould part 7 and a bottom mould part 9 arranged in pairs. After extruding the hose 3 into the open mould, the hose 3 is disconnected separately between the nozzle outlet of the extrusion device 1 and the upper side of the top mould part 5. The separation line is shown in dashed lines in fig. 1 and is denoted by 8.

Fig. 2 shows an operating state in which the mould is partly closed by moving the main mould part 7 and the bottom mould part 9 together and instead of the extrusion device 1 a blow core (blastorn) 11 is moved into the upper end of the hose 3 in order to expand and to adhere the hose 3 by means of the blowing air to the mould walls of the main mould part 7 and the bottom mould part 9 and thus to form the shape of the container 13. The closed bottom mould part 9 is provided with welding clamps (not shown in fig. 1) in order to weld the hose 3 on the bottom side before blowing in blow air. The bottom scrap formed here at the welding site is designated 15 in fig. 2. The main mold part 7 has an inner mold wall which is cylindrical over the majority of its axial length except for a top region adjoining the top mold part 5, which is designated 16 in fig. 1 and tapers inwardly, while the inner mold wall of the bottom mold part 6 forms part shells (Teilschale) which define a hemispherical shape in the closed position, so that the hose 3 expanded by blowing air is shaped into a container 13 which has a pot-shaped bottom part 19 formed by the bottom mold part 9, which is connected as an axial extension to the container main part 18. The bottom mold part 9, which is shown in fig. 1 to 6 as a partial formwork with smooth mold walls, can also be stepped so that the bottom portion 19 formed has a bellows-type corrugation.

Fig. 3 shows a state in which the blowing core 11 is replaced by a filling core 17 in order to introduce a predetermined amount of flowable filler. The mould parts are now in the same position as shown in figure 2. Instead of using a special core 11 or 17 for blow moulding and filling, a combined blow-filled core can also be used.

Fig. 4 shows that, with the top mold part 5 and the body mold part 7 in the unchanged position, the bottom mold parts 9 are moved away from each other from the closed position by a distance which is sufficient to make the bottom scrap 15 accessible to a separating element 21 (shown only in fig. 5 and 6) by means of which the bottom scrap 15 is removed from the bottom section 19.

Fig. 5 shows the situation after the removal of the bottom waste 15, wherein the separating element 21, which can be a scraper pin or a scraper bar, is removed from the area of the bottom mould part 9 after the separation process has been completed. In comparison with fig. 4, the bottom die parts are moved away from each other over a greater distance, so that, after the separating element has been moved away laterally as indicated by the arrow 23, a pressure punch 25 can enter between the open bottom die parts 9 after it has been aligned in an axial orientation as indicated by a further arrow 27 with the bottom part 19 (this position is shown in fig. 6). The basin-shaped bottom part 19 is now turned into the container body part 18 by a lifting movement, which is indicated by the arrow 29 in fig. 6. As shown in fig. 7, the axial extension of the container body part 18, which is now formed by the pot-shaped bottom part 19, is thereby converted into a bottom projection 31 which projects into the container interior. Whereby the filling surface rises from a level indicated by 33 in fig. 6 to a level indicated by 35 in fig. 7. This is taken into account in determining the filling quantity during the filling process.

Fig. 8 differs from fig. 7 only in that the top cover 36 is moulded by turning the top mould part 5 into the closed position, for example by vacuum assistance in combination with a closing process by welding.

The inner wall of the body mould part 7 is shown and described in fig. 1 and 8 in the form of a smooth surface, but the blow mould can also be designed in a manner known per se so that the container body constitutes a bellows 37, see fig. 9, where an embodiment of a container 13 thus designed is shown. Such a container 13 designed as a bellows is preferably used for the discharge of the filling material by axial compression of the bellows 37. The problem of the large residual volume remaining during extrusion is even more severe in bellows, since the bellows 37 can only be axially shortened to the extent that the individual corrugations close, with a remaining cut-off length which is at least twice the wall thickness of the container times the number of corrugations. The bottom projection 31 provided according to the invention forms a pressure relief body when the bellows 37 is compressed, which releases a usually large residual volume.

This is particularly advantageous in particular for containers 13 in which the bellows 37 has a conically tapering configuration towards the top closure 36, as is the case in the embodiment shown in fig. 10. The shape and size of the base projection 31 are formed here by a corresponding configuration of the cup-shaped base part 9 during the molding process in such a way that the base projection 31 matches the inside of the compressed bellows 37 as far as possible in the top region, as a result of which the residual volume remaining when the bellows 37 is fully compressed is minimized.

For containers with a tapered neck in the region of the top, the bottom part 19 forming the bottom projection can be molded by corresponding shaping of the mold wall of the bottom mold part 9 in such a way that it tapers in the central region in such a way that the inverted bottom projection 31 has an end which is adapted to the neck of the container, so that the filling can be completely pressed out of the container.

Claims (10)

1. Method for producing containers (13) from thermoplastic, in which method an extruded plastic hose (3) is introduced into a mould, the movable mould parts (5, 7, 9) of which have been moved into a mould-opening position, at least the mould parts (7) forming the transition between the container body part (18) and the container bottom are closed, in which the container bottom is welded, the hose (3) is expanded and brought into abutment against the walls of the mould parts (5, 7, 9) by means of a pressure gradient acting on the hose to form the container shape, the mould parts are moved into a mould-opening position to demould the formed container (13), characterized in that the container bottom is designed to axially elongate the shape of a basin-shaped bottom part (19) of the container body part (18), said bottom part being turned inside the container (13), to form a bottom projection (31) projecting into the container body part (18), the basin-shaped bottom part (19) being formed by bottom mould parts (9) which are movable relative to the body mould part (7) moulding the container body part (18) and weld the bottom part (19) in the closed position, the bottom mould parts (9) being moved to a position partly opening the mould in order to invert the bottom part (19), the inversion of the bottom part (19) being effected mechanically by loading of the bottom part (19) by a punch (25) which is driven to move concentrically relative to the container axis.

2. A method as claimed in claim 1, wherein the basin-shaped bottom portion (19) is turned inside the container (13) before final demoulding of the container.

3. Method according to claim 1 or 2, characterized in that the scrap (15) at the welding site of the bottom part is separated by means of a separating element (21) before the bottom part (19) is turned over.

4. Device for carrying out the method according to any one of claims 1 to 3, having movable mould parts (5, 7, 9), characterized in that a pair of bottom mould parts (9) which are movable independently of the pair of mould parts are connected to the pair of mould parts (7) forming the container body part (18), which pair of bottom mould parts in the closed position define a pot-shaped mould cavity for forming a pot-shaped bottom part (19) axially extending the container body part (18).

5. The device according to claim 4, characterized in that the bottom mould part (9) has welding jaws for welding the basin-shaped bottom part (19).

6. Device according to claim 4 or 5, characterized in that a pressure ram (25) is provided which can be driven in a reciprocating axial movement and which can be aligned with the longitudinal axis of the container, by means of which the basin-shaped bottom part (19) can be turned into the container body part (18) when the bottom die part (9) is correspondingly opened.

7. Device according to claim 6, characterized in that a mechanically movable separating element (21) is provided which can be aligned with the longitudinal axis of the container when the bottom mould part (9) is opened accordingly, for removing bottom scrap (15) formed at the welding point of the basin-shaped bottom part (19).

8. The apparatus of claim 4 wherein said mold part forms a blow mold.

9. Container (13) manufactured by the method according to any one of claims 1 to 3 by means of the device according to any one of claims 4 to 8, having a bottom projection (31) turned inside the container body portion (18).

10. A container according to claim 9, characterized in that at least the container body part (18) is constructed in the form of a bellows (37), the bottom projection (31) being shaped and dimensioned such that it minimizes the residual volume in the top area of the container (13) when the bellows (37) is compressed.