WO1998024611A1

WO1998024611A1 - Support technique and device

Info

Publication number: WO1998024611A1
Application number: PCT/DE1997/002142
Authority: WO
Inventors: Klaus Vogel; Michael Linke; Julian Choinski
Original assignee: Krupp Corpoplast Maschinenbau Gmbh
Priority date: 1996-11-30
Filing date: 1997-09-20
Publication date: 1998-06-11
Also published as: DE19649750A1; AU4698797A

Abstract

Disclosed is a support technique and device for the outer aperture section of a blank, to be used when a thermoplastic blank is expanded by a pressurized agent inside a blowing mould. In order to avoid a widening of the aperture section during the blowing process, a support sleeve is pushed over said mouth section. The support sleeve is maintained by a supporting element which can be positionned relative to the blowing mould along the longitudinal axis of the latter.

Description

Support method and apparatus

The invention relates to a method for supporting an outer region of a mouth section of a molding during the expansion of a thermoplastic preform by applying a medium under pressure within a blow mold.

The invention further relates to a device for supporting an outer region of a mouth section of a molded article, which has at least one enclosing element and which is arranged in the area of a device for blow molding the molded article and encloses the mouth section of the molded article during the action of a medium under pressure . Devices of this type are used to protect the mouth section of preforms made of a thermoplastic material, for example preforms made of PET (polyethylene terephthalate) within a blow molding machine in the region of a blow molding station against expansion by the action of the pressure medium. An expansion would lead to problems in the area of a downstream filling machine or when screwing closures onto the external thread of the mouth sections. Typically, such a blowing machine has a heating device and a blowing device, in the area of which the pre-tempered preform is expanded into a container by biaxial orientation. The expansion takes place with the aid of compressed air which is introduced into the preform to be expanded. The procedural sequence for such an expansion of the preform is explained in DE-OS 43 40 291.

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

The preforms and the blown containers can be transported within the blow molding device with the aid of different handling devices. The use of transport mandrels on which the preforms are attached has proven particularly useful.

The use of support bodies for handling the preforms has the advantage that the preforms can be plugged with their mouth onto a coupling element of the support body and that during the further transport movements, the transport elements used only act on the support body and not directly on the preform. This prevents damage and deformation of the preform, which is soft due to the heating. In addition, material removal through direct-acting gripping elements, which could lead to dust formation, for example, is avoided.

The known supporting bodies in the form of transport mandrels have a high mechanical strength and, as a result, are highly reliable and have a long service life. In particular when using rotating transport devices, however, centrifugal forces occur which impair the handling speed.

The use of gripping tongs for handling preforms is described, for example, in FR-OS 27 20 679. A spreading mandrel that can be inserted into a mouth area of the preform for holding purposes is explained in WO 95 33 616.

According to the blow molding station, which is described in DE-OS 43 40 291, to support the mouth area of the molding during blowing, each half of a blow mold is assigned to a half of a threaded insert, which insert portion of the molding during blowing after closing the Blow station supported on the outside. However, such a support can only be used if the preform is fed to the blow molding station in such a way that it is held by a transducer mandrel inserted into the mouth of the preform, so that the outer region of the mouth section is free. When handling the moldings with the help of external attackers Holding devices, however, the use of support devices fixedly arranged in the area of the blowing station would lead to unfavorable kinematic processes during handling.

It is therefore an object of the present invention to improve a method of the type mentioned in the introduction in such a way that expanded constructive design options are provided when handling the moldings.

This object is achieved in that a support sleeve is pushed on the outside over the mouth portion.

Another object of the present invention is to improve a device of the type mentioned in the introduction in such a way that the use of gripping devices acting on the outside is supported.

This object is achieved according to the invention in that the enclosing element is designed like a sleeve and is held by a carrier which can be positioned relative to the blow mold in the direction of a longitudinal axis of the blow mold.

The use of the sleeve-like enclosing element prevents the thread area from widening during blowing. The closed design of the enclosing element means that no additional forces are introduced into the locking of the blow mold and the carriers for holding the blow mold. Due to the lowerable arrangement of the enclosing element, the outer region of the molded article is kept clear before positioning this element in the direction of the molding, so that it can be used for intended handling Available. The shaping can thus first be inserted into the blow mold by handling devices, and only after the handling element has been removed does the enclosing element become effective after being positioned in the direction of the shaping. After the blowing process has been completed, the enclosing element is removed from the area of the molding so that the finished-blown container can be removed from the blowing station.

Improved support can be achieved by providing the support sleeve with an undercut-free inner profile in the push-on direction.

Increased handling space for the shaping is particularly important if the support sleeve is lowered to perform the support function in the case of a molding positioned with its mouth in the vertical direction upward within the blow mold.

A simple mechanical implementation of movement processes can be achieved in that the support sleeve is pushed onto the mouth section before a blowing agent is supplied. Basically, however, it is sufficient to allow the support sleeve to take effect only above a certain blowing pressure, since low blowing pressures cannot yet lead to any deformation of the mouth section.

A simple mechanical construction is also supported in that the support sleeve is pushed onto the mouth section before a stretching rod is inserted into the molding. According to a possible method variant, it is also possible for the support sleeve to be pushed onto the mouth section after a stretching rod has been inserted into the molding.

Process time can be reduced by pushing the support sleeve onto the mouth section while a stretching rod is being inserted into the blank.

A particularly high support effect can be achieved in that the mouth section is supported by the support sleeve directly under an edge of a mouth opening of the molding.

A compact structure can be supported in that the carrier is designed as a connection element for blowing agent supply.

A high reproducibility in the execution of the movement processes is supported in that the connection element can be positioned together with the support sleeve by a cam control.

Integration into conventional construction concepts for blow molding machines is supported by the fact that the support sleeve is provided with a stretch rod bushing for a stretch rod.

A high mechanical stability in the implementation of the stretching rod is achieved in that a mouth insert arranged coaxially to the support sleeve has an inner diameter which is larger than an outer diameter of the stretching rod to form an annular gap. A further improvement in the support of the mouth section can be achieved in that a distance between the mouth insert and the support sleeve essentially corresponds to a maximum wall thickness of the molding in the region of the mouth section.

A loss of pressurized blowing medium can be prevented by providing the mouth insert with a seal.

Exemplary embodiments of the invention are shown schematically in the drawing. Show it:

1 is a schematic diagram of a device for blow molding when handling the moldings with the mouth oriented downward,

2 shows a partial representation of a molded article inserted into a blow molding station with an upwardly oriented mouth and associated encircling element and stretching device,

3 shows a construction modified from the embodiment in FIG. 2, in which the enclosing element is provided with an inner profile,

Fig. 4 is an enlarged partial view of an enclosing element arranged along a mouth portion of the molded article

and

Fig. 5 is an enlarged partial illustration of a molding which is inserted into a blow molding station and which is provided with marked support areas at the mouth section.

In the embodiment shown in FIG. 1, the device for blow molding containers has a heating wheel (1) and a blowing wheel (2). Preforms to be processed are fed via a feed rail (3) into the area of a turning device (4) and transported by transfer wheels (5,6,7) into the area of the heating wheel (1). In this variant, the preforms are guided hanging with their mouths oriented upwards along the feed rail (1) and rotated by 180 ° by the turning device (4). Heating in the area of the heating wheel (1) takes place in such a way that the preforms are oriented upright with their mouths facing downward. However, it is also conceivable to carry out a hanging heating without previously turning the preforms.

Heating devices (8) and cooling devices (9) are arranged along the heating wheel (1). A cooling device (9) is preferably arranged between two heating devices (8). The heating devices (8) heat the preforms with the aid of IR radiation and the cooling devices (9) blow air onto the surfaces of the heated preforms for surface cooling.

After heating and passing through a cooling section, the tempered preforms are transported from a transfer wheel (10) to the blowing wheel (2) and used here in molds (11) which are held by blowing stations (12). The blowing stations (12) can be opened and closed like a book. After the blowing process has been completed, the blown containers are removed from the blowing station (12) and from transfer wheels (13,6,14) an output section (15) fed. When the preforms are blow molded in the area of the blowing wheel (2) with a mouth orientation downward, it is particularly contemplated to arrange a further turning device between the blowing wheel (2) and the discharge section (15), so that the blown containers hang in the area of the Output route (15) can be transported.

If the preform is heated with an upwardly oriented mouth and the preform is expanded to the final container in the area of the blowing station (12) with the mouth oriented upwards, turning devices can be dispensed with. In this way, a simplified material circulation can be achieved.

Fig. 2 shows a molding (16) which is arranged in the region of the blowing station (12). In this embodiment, it is provided that the molding (16) is transferred from a gripping device (17) to the blowing station (12), which engages around the molding (16) in a threaded area (18). The threaded area (18) is arranged between a support ring (19) and an opening (20) of the molded article (16).

In the orientation of the individual components chosen in FIG. 2, a connection element (21) is arranged above the blowing station (12), which enables a supply of blown air after a relative movement in the direction of the molding (16). The connecting element (21) is designed as a connecting piston and is provided with a guide roller (22) which, by means of a cam control, positions the connecting element (21) in the direction of the molding (16) and, after the blowing process has been completed, positions it in allows an opposite direction. The connection element (21) is provided in the region of its orientation facing the molded part (16) with a support sleeve (23) which has an inner diameter (24) which is approximately an outer diameter (25) of an opening section (26) of the molded part (16 ) in an environment of the threaded area (18). The support sleeve (23) can have a transverse flange (27) which is used for holding in the region of the connecting element (21).

It is also provided that the connecting element (21) is equipped with an orifice insert (28) which has an outer diameter (29) which corresponds approximately to an inner diameter (30) of the molded article (16) in the region of the orifice section (26). To facilitate insertion of the mouth insert (28) into the mouth (20) of the molded article (16), the mouth insert (28) can be provided with a bevel (31) on the outside.

The mouth insert (28) and the support sleeve (23) are arranged essentially coaxially to one another and to a longitudinal axis (32) of the mold. The longitudinal mold axis (32) coincides with a longitudinal mold axis (33) of a molded article (16) inserted into the blowing station (12). There is also an essentially identical alignment to a longitudinal axis (34) of a stretching rod (25) which can be inserted into the blowing station (12) for the longitudinal stretching of the molding (16).

The stretching rod (25) has an outer diameter which is somewhat smaller than the inner diameter of the mouth insert (28). As a result, an annular gap is formed after the stretching rod (35) has been introduced into the molded article (36), through which blow air can be supplied. The muzzle insert (28) is preferably provided on the outside with a seal (36), for example an annular seal, in order to provide sufficient gas tightness when blowing air is supplied. The seal (36) can be embedded in an annular groove of the mouth insert (28). Assembly can be carried out in such a way that the mouth insert (28) extends with a mouth flange (37) between the connecting element (21) and the transverse flange (27) of the support sleeve (23).

The connecting element (21) is guided in a longitudinally displaceable manner in a holder (38) which carries a stop element (39) for limiting a stroke of the connecting element (21). The stop element (30) engages in a form-fitting manner in a counter-profile (40) of the connection element (21), which can be designed, for example, as a groove-shaped depression.

In the embodiment shown in Fig. 3, the support sleeve (23) is provided with an inner profile (41). The inner profile (41) is designed in such a way that on the one hand it is still possible to push the support sleeve (23) onto the mouth section (26), but on the other hand that an adaptation to an outer contour of the mouth section (26) is carried out. In particular, it is intended to design the inner profile (41) as a ring-like inner thickening.

In the case of an undefined positioning of the molded part (16) within the molds (11) relative to the longitudinal axis (33) of the mold, in the case of a ring-shaped design of the inner profile (41) in the direction of the longitudinal axis (33) of the molded part, an extension is selected which ensures that, despite the inclined profile Orientation of threads (42), it is possible to push the support sleeve (23) sufficiently far onto the blank (16). at However, if the molding (16) is positioned in the blowing station (12) exactly as it is known relative to the longitudinal axis (33) of the molding, it is also possible to adapt the course of the inner profile (41) to the limits of the threads (42).

In the embodiment shown in a greatly enlarged illustration in FIG. 4, such an adaptation of the inner profile (41) to the course of the threads (42) is realized. Without an adaptation to a rotational positioning of the molding (16) relative to the longitudinal molding axis (33), the inner profile (41) in the direction of the longitudinal molding axis (33) would have approximately half of the extent shown.

From Fig. 4 it can also be seen that the support sleeve (23) abuts at several points on the mouth section (26) in the region of its inner boundary, or at least runs at a very short distance from the mouth section (26). A widening of the mouth section (26) with a supply of blown air can hereby either be completely avoided or at least be kept in an area of elastic deformation of the mouth section (26). It is thus ensured that after the blowing process has ended, the outer dimensions of the mouth section (26) are within a predetermined tolerance range.

For further illustration, FIG. 5 shows possible support points (43) in the area of the mouth section (26), in the area of which support can be provided after the support sleeve (23) has been pushed on.

Claims

Patent claims

1. A method for supporting the outer region of a mouth portion of a molding during the expansion of a thermoplastic preform by acting with a pressurized medium within a blow mold, characterized in that a support sleeve (23) is pushed on the outside over the mouth portion (26).

2. The method according to claim 1, characterized in that the support sleeve (23) is provided in the push-on direction with an undercut-free inner profile (21).

3. The method according to claim 1 or 2, characterized in that the support sleeve (23) with a mouth (20) in the vertical direction upward within the blow mold (11) positioned molding (16) is lowered to perform the support function.

4. The method according to any one of claims 1 to 3, characterized in that the support sleeve (23) is pushed onto the mouth section (26) before a blowing agent supply.

5. The method according to any one of claims 1 to 4, characterized in that the support sleeve (23) is pushed onto the mouth section (26) before retracting a stretching rod (35) into the blank (16).

6. The method according to any one of claims 1 to 5, characterized in that the support sleeve (23) is pushed onto the mouth section (26) after retraction of a stretching rod (35) in the molding (16).

7. The method according to any one of claims 1 to 6, characterized in that the support sleeve (23) is pushed onto the mouth section (26) during the retraction of a stretching rod (35) in the blank (16).

8. The method according to any one of claims 1 to 7, characterized in that the mouth section (26) of the support sleeve (23) is supported directly under an edge of a mouth opening (20) of the molding (16).

9. A device for supporting an outer region of a mouth section of a molding, which has at least one enclosing element and which is arranged in the area of a device for blow molding the molding and encloses the mouth section of the molding during the action of a medium under pressure, characterized in that Enclosure element designed like a sleeve as a support sleeve (23) and is supported by a carrier which can be positioned relative to the blow mold (11) in the direction of a longitudinal axis (32) of the blow mold.

10. The device according to claim 9, characterized in that the support sleeve (23) an inner profile (41) on.

11. The device according to claim 9 or 10, characterized in that the carrier as a connecting element

(21) is designed for blowing agent supply.

12. Device according to one of claims 9 to 11, characterized in that the connecting element (21) together with the support sleeve (23) can be positioned by a cam control.

13. The device according to one of claims 9 to 12, characterized in that the support sleeve (23) with a horizontal bar feed-through for a horizontal bar

(35) is provided.

14. Device according to one of claims 9 to 13, characterized in that a mouth insert (28) arranged coaxially to the support sleeve (23) has an inner diameter which is used to form a Annular gap is larger than an outer diameter of the stretching rod (35).

15. The device according to one of claims 9 to 14, characterized in that a distance between the mouth insert (28) and the support sleeve (23) substantially corresponds to a maximum wall thickness of the molding (16) in the region of the mouth portion (26).

16. The device according to one of claims 9 to 15, characterized in that the mouth insert (28) is provided with a seal (36).

17. Device according to one of claims 9 to 16, characterized in that the molding (17) is arranged within the blow mold (11) with an opening (20) oriented vertically upwards.