WO1998016367A2 - Device for holding preforms and blower machine for shaping containers - Google Patents

Abstract

The invention is used to hold preforms and comprises a substantially sleeve-shaped support body, in the region of which at least one rotary bearing is disposed. The support body comprises at least one primary part and at least one secondary part. The specific weight of the secondary part is less than the specific weight of steel. The device for holding preforms can be used in the vicinity of a device for the blow-moulding of thermoplastic containers. Wear can be reduced by suitable material matching in the region of interacting surfaces.

Description

 Device for holding preforms and blowing machine for forming containers

The invention relates to a device for holding preforms, which has an essentially sleeve-shaped support body and in which at least one rotary bearing is arranged in the region of the support body.

The invention also relates to a device for blow molding thermoplastic containers, which has at least one blow molding station provided with a blow mold and a stretching device and in which an essentially sleeve-shaped support body is provided for transporting preforms to be inflated. Such a support body is described, for example, in DE-OS 43 40 291 and serves to supply preforms made of a thermoplastic material, for example preforms made of PET (polyethylene terephthalate), to different processing stations within a blow molding machine. 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 also 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 use of support bodies for handling the preforms has the advantage that the preforms can be attached with their mouths to 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 have a high mechanical strength and, as a result, are highly reliable and have a long service life. Especially at using rotating transport devices, however, centrifugal forces occur which impair the handling speed. In addition, when the carrying bodies are transported along guide devices which are arranged in the region of the blow molding machine, signs of wear appear with increasing transport speed.

The object of the present invention is to construct a device for holding preforms of the type mentioned in the introduction in such a way that handling is improved.

This object is achieved in that the support body is formed from at least one primary part and at least one secondary part and that the secondary part has a specific weight that is less than the specific weight of steel.

Another object of the present invention is to design a device for blow molding of the type mentioned in the introduction in such a way that wear caused by the transport movement of the support body is further minimized.

This object is achieved in that guide elements are arranged along at least part of a transport path of the support body, which are made of a harder material than the support body in the region of a guide surface which is provided for contact with the guide elements.

Due to the construction of the device for holding preforms, the construction weight can be reduced considerably, so that lower inertial forces occur on the one hand during braking and on the other hand it is also possible to provide higher transport speeds, in particular in the case of rotational movements in which centrifugal forces act on the holding devices.

The construction of the device for blow molding using the device for holding the preforms makes it possible to reduce wear that occurs, so that on the one hand a longer service life is made possible and that on the other hand contamination due to wear-related abrasion is avoided.

Easier handling can already be brought about by the fact that the specific weight of the secondary part is at least 10% less than the specific weight of steel.

A further increase in handling advantages can be achieved in that the specific weight of the secondary part is at least 20% less than the specific weight of steel.

A considerable variety of materials can also be used in that the specific weight of the secondary part is at least 50% less than the specific weight of steel.

When the secondary part is made from synthetic materials, it is particularly thought that the specific weight of the secondary part is at least 80% less than the specific weight of steel.

A typical application is that the secondary part is made of plastic. To ensure sufficient thermal conductivity, it is also possible that the secondary part is made of light metal.

A significant reduction in wear can also be supported in that the secondary part has an extension in the direction of a longitudinal axis of the support body which is at least equal to the extension of a guide surface of the support body, which is provided as a contact surface for guide elements along a transport path of the support body.

To support a support of the support body by magnetic forces, it is proposed that the primary part have an expansion that approximately corresponds to the expansion of magnets for mounting the support body in the area of the heating wheel in the direction of the longitudinal axis of the support body.

An embodiment variant with high stability is provided in that the secondary part is received as an insert part by the primary part.

A particularly strong reduction in inertial forces can be achieved in that the primary part is received as an insert in the secondary part.

High stability can also be brought about by the primary part being made of metal.

To ensure sufficient mobility of the transport mandrel in the area of the heating wheel, it is provided that the transport mandrel has two rotary bearings. To enable an arrangement of guide elements at different mounting heights, it is proposed that the support body be provided with at least two secondary parts made of plastic.

A low overall weight can be achieved in that the support body has a basic structure made of plastic and is provided with metal inserts.

To support the application of rotational movements by mechanical drives, it is proposed that the support body have at least one toothing.

A largely standardized mounting of geometrically differently dimensioned preforms is supported in that the support body is provided with a product element designed as a function of the product.

To reduce pressure losses, it is proposed that a sealing ring be arranged in the transition area of the attachment element in the support body.

Defined trajectories are also supported in that the support body has a guide sleeve for aligning a stretching rod which is inserted into the container to be formed by the transport mandrel.

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

1 is a schematic representation of a device for blow molding thermoplastic containers with heating wheel and blowing wheel, 2 shows a cross section through a device for holding preforms,

3 shows a cross section through another device for holding preforms,

4 shows a cross section through a further modified device for holding preforms,

Fig. 5 shows a further modified variant of the device for holding preforms

and

Fig. 6 is a schematic diagram illustrating a contact of the device for holding preforms with a guide element in the area of the device for blow molding thermoplastic containers.

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 prior turning of 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, completely blown containers are removed from the blowing station (12) and fed to a delivery section (15) by transfer wheels (13, 6, 14). 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.

Fig. 2 shows the arrangement of a transport mandrel (16) in the area of the heating wheel (1). The heating wheel (1) is provided with mandrel holders (17), in the area of which magnets (18, 19) are arranged in order to hold the transport mandrels (16). In principle, the use of a magnet (18, 19) is sufficient, but the use of two magnets (18, 19) can increase the security of the holder. The transport mandrels (16) form the device for holding the preforms.

The transport mandrel (16) is provided with a support body (20) which is profiled on the outside and is essentially sleeve-shaped. The support body holds rotary bearings (21, 22) and can be provided with teeth (23). The rotary bearings (21, 22) can be designed, for example, as roller bearings or as ball bearings that roll in the mandrel holder (17). It is also conceivable in the area of the mandrel holder

(17) Arrange rotatably mounted elements, for example balls or rollers, and the rotary bearings

(21, 22) as outer surfaces of cylindrical or sleeve-like bodies. Basically, designs as plain bearings are also possible.

The magnets (18, 19) are arranged within the mandrel receptacles (17) in such a way that an air gap between the magnets (18, 19) and associated contact segments (24, 25) of the transport mandrel (16) remains. This ensures that there is only direct material contact between the outer surfaces of the rotary bearings (21, 22) and the mandrel holder (17). This allows the transport mandrel (16) to move freely within the rotary bearing (21, 22) relative to the mandrel holder (17) despite the magnetic holder.

The support body (20) opens vertically upwards into an attachment element (26) which has a dimensioning which is selected as a function of the preform to be transported. The further area of the transport mandrel (16), however, is dimensioned in a standardized manner. The attachment element (26) can be made of steel, for example, and be provided with a sealing ring (27) against which the mouth area of an attached preform is guided. In particular, it is also possible to nitride the top element (26) in the surface area, for example with titanium nitride. Other treatments to improve the surface quality, especially smoothness, hardness or corrosion resistance, are also possible.

A connection element (28) is provided, facing away from the plug-on element (26), through which compressed air is fed in to expand the preform into an interior (29) of the transport mandrel (16).

To stabilize the positioning of the transport mandrel (16), in particular when carrying out transfers, for example after completion of the heating process with a separation of the transport mandrel (16) from the heating wheel (1), guide elements (30) are arranged in the area of the blow molding machine, depending on their positioning at different heights can support the transport mandrel (16) against lateral tilting. The guide elements (30) can also support the removal of the transport mandrels (16) from the mandrel receptacles (17).

In Fig. 2 three different positions for guide elements (30) are entered. If the transport mandrel (16) is predominantly made of metal, the guide elements (30) can be made of a plastic, for example of POM. When using secondary parts (31) of the support body (20), which are formed from a plastic, it is expedient that Guide elements (30) made of metal, for example made of hardened steel.

In the embodiment according to FIG. 2, it is provided that the secondary parts (31) have a ring shape and are arranged in the region of the transport mandrel (16) in such a way that contact regions which can come into contact with the guide elements (30) are covered. If the secondary parts (31) are made of a soft material, for example plastic, and if the guide elements (30) are made of a hard material, for example steel, contact points between the transport mandrel (16) and the guide elements (30) are due to the Rotational mobility of the transport mandrel (16) statistically distributed over the circumference of the secondary parts (31). Contact with the guide elements (30) always takes place in the same area of the guide element (30). The advantage can thus be achieved that the contact zone varies statistically in the region of the further component and that there is only a locally constant contact zone in the region of the harder component. Compared to a reverse implementation, this can significantly reduce wear.

Fig. 3 shows an embodiment in which the support body (20) is formed from a material which has a lower specific weight relative to iron or steel. For example, it is intended to use plastic or aluminum. Typical specific weights are 7.86 kg / 1 for iron or steel, 2.70 kg / 1 for aluminum and 0.9 to 2.1 kg / 1 for plastics.

In this embodiment, the connecting element (28) can also be made, in whole or in part, of a material that is lighter than steel, for example Plastic. When the contact segments (24, 25) are formed from a non-magnetic material, for example from plastic, it is in particular contemplated to embed magnetizable parts in order to be able to apply sufficiently strong holding forces through the magnets (18, 19).

4 shows an embodiment in which the add-on parts can all be pushed onto the support body (20) from one side. This can bring about a further simplification in production and it only needs to be braced on one side. The support body (20) and the connecting element

(28) are formed in one piece in this embodiment. If this one-piece supporting body (20) is made of metal, secondary parts can in turn be used

(31) made of plastic, for example, in the area of the connecting element (28) and in the area of the plug-on element (26).

Alternatively, an embodiment variant is also shown in thin lines in FIG. 4, in which the support body (20) is formed in two parts and is joined by the combination of an internal thread (32) and an external thread (33). Sealing is ensured by sealing rings (34). In such an embodiment variant, the contact segment (24) can be made in one piece with the supporting body (20).

In the embodiment in Fig. 5, a two-part embodiment of the support body (20) is also illustrated, in which the connecting element (28) in one piece with a lower region of the support body (20) and an upper contact segment (35) in one piece with an upper Area of the support body (20) is connected. This embodiment enables the product-dependent attachment element (26) to be geometrically significantly reduced in size, so that further standardization of the transport mandrel (16) can be achieved. Depending on the choice of material for the transport mandrel (16) or for selected areas of the transport mandrel (16), iron parts in plastic or plastic parts, for example, can in turn be embedded in a supporting body made of iron to enable a magnetic holder. Likewise, depending on the material stresses that occur, other material combinations are conceivable.

Fig. 6 shows the arrangement of the transport mandrel (16) within the device for blow molding containers. The transport mandrel (16) here consists of a primary part (36) made of metal and a secondary part (31) made of plastic. The transport mandrel (16) can rotate in the direction of rotation (37) with respect to a center line (38) and is moved past a guide element (40) in the transport direction (39). The guide element (40) is formed from a material that is harder than the material of the secondary part (31). For example, steel can be used.

When moving in the transport direction (39), the transport mandrel (16) first strikes the guide element (40) in a collecting area (41) which is widened like a funnel. Due to the predetermined transport movements, the same point of impact (42) always results in the area of the collecting area (41). In the area of the transport mandrel (16), the corresponding counterpart (43) is due to the rotational movement of the transport mandrel (16), the corresponding counterpart (43) is based on the rotational movement of the Transport mandrel (16) distributed statistically along an outer circumference (44). The further transport mandrel following the illustrated transport mandrel (16) thus hits the guide element (40) again exactly at the same point of impact (42). The transport mandrel (16) shown, however, strikes another counterpart (43) in the area of its outer circumference (44) in a subsequent guide element (40). It can also be assumed statistically that the transport mandrel (16) assumes a different position from the rotational position shown after the end of its orbit and when it hits the guide element (40) again.

Basically, it is intended to construct the transport mandrel (16) by means of the material pairings provided in such a way that there is a pressure stability of at least 40 bar. The choice of materials also ensures that temperature resistance up to a temperature of at least 80 ° C is ensured. If the transport mandrel (16) is made of plastic in certain areas, it is also possible to carry out at least partial coating or vapor deposition with metal. In this way, on the one hand, heating can be avoided by reflection, and, in addition, heat dissipation is supported when heat is absorbed. Metal vapor deposition also prevents dust accumulation, since electrostatic charges are dissipated.

When the connecting element (28) is made of a relatively soft material, it is contemplated that a lower lead-in area be formed by an insert made of a firmer material so that impact stresses caused by pneumatic connecting elements can be tolerated.

Claims

Patent claims 1. Device for holding preforms, which has a substantially sleeve-shaped support body and in which at least one rotary bearing is arranged in the region of the support body, characterized in that the support body (20) from at least one primary part (36) and at least one secondary part (31 ) is formed and that the secondary part (31) has a specific weight that is less than the specific weight of steel. 2. Device according to claim 1, characterized in that the specific weight of the secondary part is at least 10% less than the specific weight of steel. 3. Device according to claim 1 or 2, characterized in that the specific weight of the secondary part is at least 20% less than the specific weight of steel. 4. Device according to one of claims 1 to 3, characterized in that the specific weight of the secondary part is at least 50% less than the specific weight of steel. 5. Device according to one of claims 1 to 4, characterized in that the specific weight of the secondary part is at least 80% less than the specific weight of steel. 6. Device according to one of claims 1 to 5, characterized in that the secondary part (31) is made of plastic. 7. Device according to one of claims 1 to 6, characterized in that the secondary part (31) is made of light metal. 8. Device according to one of claims 1 to 7, characterized in that the secondary part (31) in the direction of a longitudinal axis of the support body (20) has an extent which is at least equal to the extent of a guide surface of the support body (20) which as Contact surface for guide elements (30) along a transport path of the support body (20) is provided. 9. Device according to one of claims 1 to 8, characterized in that the primary part (36) has an extent that approximately the expansion of magnets (18,19) for holding the support body (20) in the region of the heating wheel (1) in Direction of the longitudinal axis of the support body (20) corresponds. 10. Device according to one of claims 1 to 9, characterized in that the secondary part (31) is received as an insert part of the primary part (36). 11. Device according to one of claims 1 to 9, characterized in that the primary part (36) is received as an insert part of the secondary part (31). 12. Device according to one of claims 1 to 11, characterized in that the primary part (36) is made of metal. 13. Device according to one of claims 1 to 12, characterized in that the transport mandrel (16) has two rotary bearings (21, 22). 14. Device according to one of claims 1 to 13, characterized in that the support body (20) is provided with at least two secondary parts made of plastic (31). 15. The device according to one of claims 1 to 9, characterized in that the support body (20) has a basic structure made of plastic and is provided with insert parts made of metal. 16. The device according to one of claims 1 to 15, characterized in that the support body (20) has at least one toothing (23). 17. The device according to one of claims 1 to 16, characterized in that the support body (20) is provided with a product-dependent attachment element (26). 18. Device according to one of claims 1 to 17, characterized in that a sealing ring (27) is arranged in the transition region of the attachment element (26) in the support body (20). 19. Device according to one of claims 1 to 18, characterized in that the support body (20) has a guide sleeve for aligning a through the transport mandrel (16) into the container to be formed stretching rod. 20. Device for blow molding thermoplastic containers, which has at least one blow molding device provided with a blow mold and a stretching device and in which an essentially sleeve-shaped support body is provided for the transport of preforms to be inflated, characterized in that along at least part of a transport path of the Carrying body is arranged at least one guide element (40) which is made of a harder material than the support body (20) in the region of a guide surface which is provided for contact with the guide element. 21. Device according to one of claims 1 to 20, characterized in that the support body (20) is guided in a rotatable manner. y - 22. The apparatus according to claim 20 or 21, characterized in that the guide element (40) is made of metal. 23. Device according to one of claims 20 to 22, characterized in that the supporting body (20) is at least partially formed in the region of the guide surface from a plastic.