DEVICE FOR HEATING PLASTIC PREFORMS WITH SHIELDING PLATE

Description

[0001] The present invention relates to a device and a method for heating plastic preforms. It is known in the prior art that plastic preforms are formed into plastic containers, for example by stretch blow molding. For this purpose, the plastic preforms are first heated and then, in a heated state, fed into the actual forming device. In the prior art, microwave ovens are sometimes used for heating the plastic preforms, but infrared ovens are also commonly used.

[0002] These ovens transport the plastic preforms in an upright position, heating the base bodies of the preforms for the subsequent stretching process. However, the plastic preforms also have threaded areas that should not be heated. Without appropriate equipment, these threaded areas could overheat, which would be detrimental to further processing.

[0003] Therefore, shielding plates are known from the prior art, which are usually mounted on the brackets and are intended to prevent excessive heating, especially of the threaded areas and the support rings. In the prior art, the plastic preforms are usually gripped and moved through or within openings in these shielding plates. However, this means that these shielding plates must always have a larger cross-section than the largest cross-section of the plastic preforms, which is usually located in a region of the support ring of the plastic preforms. This, in turn, creates comparatively large gaps between the plastic preforms and the respective shielding plates, through which heat can nevertheless penetrate.

[0004] In other words, the existing light gap between the shielding plate and the support ring of the plastic preforms, as found in the prior art, still leads to a certain degree of overheating of the support ring. This, in turn, can cause problems during subsequent processing, for example, with a blow molding machine, where a blow nozzle imprint can form in the support ring.

[0005] For example, AT 000 520 U1 discloses a device for producing hollow bodies from tubular, thermoplastic preforms, wherein the preforms are transported through a heating device and subsequently fed to a blow molding device. Furthermore, FR 2 950 284 A1 discloses a protective device for the thermal protection of a neck area of ​​a preform when the preforms are transported along a predetermined transport path through a furnace.

[0006] The present invention is therefore based on the objective of enabling improved heat shielding, which also protects the support ring and / or the thread of the plastic preforms in a better manner than is achieved in the prior art. This objective is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0007] An inventive device for heating plastic preforms comprises a transport device which transports the plastic preforms at least section by section along a predetermined transport path. This transport device includes a plurality of holding devices for holding the plastic preforms. Furthermore, the device includes a heating device for heating the plastic preforms at least temporarily during their transport with the transport device, wherein the device includes at least one heat shielding device which is suitable and intended to counteract heating of the opening areas of the plastic preforms.

[0008] According to the invention, the heat shielding devices comprise at least a first heat shielding element and a second heat shielding element, which are movable relative to each other and which, in at least one relative position to each other, at least partially and preferably substantially surround a section of the plastic preform to be heated in its circumferential direction. Preferably, the heat shielding devices also each comprise a first heat shielding element and a second heat shielding element.

[0009] In contrast to the one-piece heat shielding plates of the prior art, the invention proposes that these plates be designed in two parts and be movable relative to each other. This allows the shielding elements to be positioned more precisely and closer to the plastic preforms, thereby reducing the occurrence of light gaps between the plastic preform and the cross-section of the shielding plate. This also reduces unwanted heating of the opening areas of the plastic preforms.

[0010] In the context of the present invention, a heat shielding device is understood in particular to be a device which is suitable and intended to at least partially interrupt a heat flow running towards the openings of the plastic preforms.

[0011] A substantial or even largely enclosing of the plastic preforms is understood to mean an enclosure of at least 160°, preferably at least 180°, preferably at least 200°, preferably at least 220°, preferably at least 240°, preferably at least 260°, preferably at least 280°, preferably at least 300°, preferably at least 320°, and particularly preferably at least 340° and particularly preferably at least 350°. Preferably, the two shielding elements together completely enclose the plastic preform or surround it except for a very small gap. Advantageously, the two shielding elements form a hole, or in particular a partially circular hole, which is adapted to the outer contours of the plastic preform, so that the gap between the plastic preform and the two shielding elements is small.

[0012] In a further advantageous embodiment, a plurality of heating elements are arranged laterally alongside the transport path of the plastic preforms. Preferably, these heating elements are arranged in a region where the plastic preforms are conveyed in a straight line.

[0013] According to the invention, at least one shielding element, and preferably both shielding elements, can be positioned on the plastic preform by a movement perpendicular to a longitudinal axis of the plastic preform. Advantageously, the shielding elements can be positioned below a support ring of the plastic preform. This means that the support ring of the plastic preform itself is no longer heated. The shielding elements are preferably moved in a horizontal direction.

[0014] In a further advantageous embodiment, a movement device is provided which can supply the shielding elements laterally or with a movement component perpendicular to the longitudinal direction of the plastic preform. Particularly preferably, however, this supply movement is carried out by a transport chain or other circulating transport means (such as a belt) on which the shielding elements are arranged. It is conceivable that, with a straight path of this transport means, the individual shielding elements are also positioned towards each other, and with a curved path (e.g., around a deflection wheel), the individual shielding elements move apart. However, supplying the shielding elements by a separate drive would also be conceivable.It would also be conceivable that this or, more generally, a motion device is selected from a group of motion devices which includes guide curves, electric motion devices, pneumatic motion devices and hydraulic motion devices.

[0015] According to the invention, these holding devices have prongs that can be inserted into the openings of the plastic preforms. The plastic preforms are held by these prongs. Advantageously, these holding devices are active holding devices that can activate and deactivate a grip on the plastic preforms. In a further advantageous embodiment, these prongs are rotatable, so that rotation of the plastic preforms with respect to their longitudinal direction is also possible during heating.

[0016] In a further advantageous embodiment, each holding device is preferably assigned at least one, and preferably exactly one or exactly two, heat shielding elements. It is also advantageous for each holding device to be assigned receiving segments of two adjacent heat shielding elements. It is also advantageous for each plastic preform to be assigned receiving segments of two adjacent heat shielding elements. In a further advantageous embodiment, the transport device has a circulating transport means and, in particular, a circulating transport chain. The holding devices for holding the plastic preforms can also be arranged on this transport chain, and the shielding elements are also preferably arranged on this circulating transport means. Preferably, each plastic preform (or its threaded area) is shielded by exactly two consecutive shielding elements.

[0017] According to the invention, the shielding devices are arranged on the same holding device as the aforementioned gripping elements or mandrels. It would be conceivable for at least one or both heat shielding elements—that is, either the first or the second or both—to be arranged on the same holding device as the mandrels. Thus, it would be possible for both the holding device for the plastic preforms and the shielding device to be arranged on the transport chain by means of the same holding device. Preferably, at least one shielding device is arranged on the same holding device as the gripping elements; more preferably, several shielding devices are arranged on the same holding devices as the gripping elements; and most preferably, all shielding devices are arranged on the same holding devices as the gripping elements.

[0018] In a further advantageous embodiment, a transport path along which the plastic preforms are moved is curved at least in sections and preferably also straight in sections. Preferably, the shielding devices are designed such that they are closed in a straight section of the transport path and the plastic preforms are in a heated state within the shielding elements.

[0019] Preferably, adjacent shielding elements are separated from each other in the curved areas of the transport path.

[0020] Preferably, the plastic preforms are fed into the transport path in a curved section. Preferably, the plastic preforms are also removed from a curved section. Preferably, both the feeding and removal of the plastic preforms take place in the same curved section of the transport path. In a further advantageous embodiment, the shielding elements are also arranged on the transport device.

[0021] In a further advantageous embodiment, the heat shielding elements are designed in a plate-like form. These plates can then be positioned below the support rings of the plastic preforms.

[0022] In a further advantageous embodiment, at least one heat shielding element has a first recess for receiving at least one section of the plastic preform.

[0023] In a further advantageous embodiment, at least one heat shielding element and the heat shielding elements are designed from a reflective (in particular from a (heat) radiation reflecting and / or heat-reflecting) material.

[0024] In a further advantageous embodiment, at least one heat shielding element, and preferably the heat shielding elements, are made of a material suitable and intended for absorbing IR radiation. Particularly preferably, at least one heat shielding element, and preferably the heat shielding elements, are made of an aluminum alloy such as stainless steel. Alternatively or additionally, it would also be possible to use a polished material for the heat shielding element(s).

[0025] This recess is particularly preferably a trough into which a section of the plastic preform, and especially a section of its base body, can enter. Advantageously, this trough has a circular segment-shaped profile. In this way, the plastic preform can be positioned very close to the respective trough, or the heat shielding element can be placed very close to the plastic preform. A radius of curvature of this recess is particularly preferably adapted to an outer circumference of the plastic preform to be heated. It is possible for this radius of curvature to be slightly larger than a corresponding radius of curvature of the plastic preform, so that the shielding element can nevertheless be placed very close to the plastic preform.

[0026] In a further advantageous embodiment, at least one shielding element has a second recess for receiving a section of the first or a further plastic preform. In this embodiment, at least one shielding element has two such recesses. Advantageously, these two recesses are arranged on opposite sides in the transport direction or along the transport path of the plastic preforms. It is possible for the first receiving element to receive sections of a first plastic preform and the second receiving recess to receive sections of a second plastic preform, which are transported particularly adjacent to each other or one behind the other. Therefore, a specific shielding element preferably shields sections of two consecutive plastic preforms.

[0027] In a further advantageous embodiment, the first recess of the first shielding element and the second recess of the second shielding element are configured such that they interact, at least temporarily, to substantially surround a section of the plastic preform in its circumferential direction. In this embodiment, it is particularly proposed that two adjacent shielding elements be positioned relative to each other in such a way that they surround the plastic preform during its heating.

[0028] In an advantageous embodiment, at least one shielding element has a first recess for receiving a section of a first plastic preform, and a second recess for receiving a section of a second plastic preform. Advantageously, these are plastic preforms transported adjacent to each other.

[0029] In a further advantageous embodiment, at least two heat shielding elements are identical. In particular, the two heat shielding elements have the same geometric design. Preferably, two shielding elements cooperating to surround an identical plastic preform are also identical. It is also advantageous for two shielding elements successive in a transport direction or along the transport path to be identical. In a further advantageous embodiment, all shielding elements are identical.

[0030] In an advantageous embodiment, at least one of the aforementioned recesses is suitable for surrounding the plastic preform in its circumferential direction at an angle greater than 70°, preferably greater than 90°, preferably greater than 120°, preferably greater than 140°, preferably greater than 150°, preferably greater than 160°, and particularly preferably greater than 170°. Alternatively or additionally, at least one recess is suitable and designed for surrounding the plastic preform in its circumferential direction at an angle less than 270°, preferably less than 250°, preferably less than 230°, preferably less than 210°, preferably less than 200°, and particularly preferably less than 190°.

[0031] In a further advantageous embodiment, when the recesses surround a plastic preform, the area enclosed by these recesses is smaller than or equal to the cross-section of a support ring of this plastic preform. These area dimensions, and also this specific design of the respective shielding elements, allow for an efficient reduction of the gap between the plastic preform and the shielding element.

[0032] The present invention further relates to a shielding element for shielding upright transported plastic preforms from heat. This shielding element has a holding device for attaching the shielding element, at least indirectly, to a transport device for transporting plastic preforms, and a first recess which is suitable and intended for receiving at least one section of a first plastic preform, wherein this recess extends over a circumferential angle of less than 180°. According to the invention, the shielding element has a second recess which is suitable and intended for receiving at least one section of a second plastic preform, wherein this second recess extends over a circumferential angle of less than 180°.A shielding element is therefore proposed which is suitable and intended for receiving two plastic preforms and in particular two consecutive plastic preforms.

[0033] Advantageously, the shielding element has a plate-shaped section that can be inserted below the support ring of the plastic preforms.

[0034] In a further preferred embodiment, at least one recess has a circular segment-shaped profile. Preferably, both recesses, considered together, sweep an angle of more than 160°, more preferably more than 180°, more preferably more than 200°, more preferably more than 220°, and particularly preferably more than 240°, more preferably more than 260°, and particularly preferably more than 300°. In a further preferred embodiment, the two recesses point in opposite directions. Preferably, these two recesses are spaced apart from each other. In a further advantageous embodiment, the holding device has at least one (and preferably two) rod-like body, which is / are arranged, for example, screwed onto the shielding plate (which has the recesses). Preferably, this rod-like body is arranged between the two recesses.

[0035] The present invention further relates to a method for heating plastic preforms, wherein the plastic preforms are transported along a predetermined transport path by means of a transport device and are heated at least temporarily during this transport. Furthermore, heat shielding devices are used to counteract the heating of the opening areas of the plastic preforms.

[0036] According to the invention, the heat shielding devices comprise at least a first heat shielding element and a second heat shielding element which are movable relative to each other and which, in at least one relative position to each other, at least partially and preferably substantially surround a section of the plastic preform in its circumferential direction.

[0037] Advantageously, the plastic preforms are conveyed at least partially in a straight line and / or at least partially along a curved, and in particular circular, path. Advantageously, the heat shielding elements are also moved relative to one another. These heat shielding elements are particularly preferably arranged on the conveying device and are moved towards or away from each other by the conveying device itself. It is possible that adjacent heat shielding elements have a minimal distance from each other in the straight sections and a maximum distance from each other, at least temporarily, in the curved sections.

[0038] Advantageously, adjacent shielding elements move towards or away from each other in a pincer-like motion. In a further advantageous embodiment, the plastic preforms are inserted between two adjacent heat shielding elements by a movement in a direction perpendicular to the longitudinal direction of the plastic preforms. Preferably, the removal of the plastic preforms is also carried out by a corresponding movement perpendicular to the longitudinal direction of the plastic preforms.

[0039] Further advantages and embodiments are shown in the attached drawings: These show: Fig. 1 A schematic representation of a system for manufacturing containers; Fig. 2 A detailed representation of a transport device for transporting plastic preforms; Figs. 3a and 3b Two representations of shielding elements; Figs. 4a and 4b Two representations of shielding elements mounted on holding devices; Fig. 5 Another view of a device according to the invention; Fig. 6 A representation to illustrate the shielding elements.

[0040] Figure 1Figure 1 shows a schematic representation of a plant 50 for manufacturing plastic containers. Plastic preforms are fed from a storage device 52 to a heating device 1 by means of a transport device 54. This heating device 1 has a transport device 2 for transporting the plastic preforms and at least one heating unit 4, which heats these plastic preforms during their transport with the transport device 2. A forming device 58, such as a blow molding machine, is provided downstream of the heating device 1. This forms the heated plastic preforms into plastic containers, in particular plastic bottles.

[0041] Figure 2Figure 1 shows a detailed representation of the transport device 1. A multitude of shielding elements 62, 64 are provided. It can be seen that these shielding elements 62, 64 each serve to shield an opening area 10a of the individual plastic preforms 10. The shielding elements 62, 64 are arranged on chain links and are designed such that they abut each other, at least during straight-line transport in a section I of the transport device.

[0042] In this way, it is possible, on the one hand, to insert the plastic preforms into a gap between two adjacent holding elements in a deflection area of ​​the transport device, and on the other hand, to close them efficiently along a straight path. It can also be seen that the shielding element 62 has a first recess 62a as well as a second recess 62b. Likewise, the shielding element 64 also has a first recess 64a and a second recess 64b.

[0043] Reference numeral 6 designates the shielding assembly as a whole, that is, the entirety of all individual shielding elements. In a closed state, that is, particularly during straight-line transport, the recess 62a of shielding element 62 and the recess 64b of the subsequent shielding element 64 serve to surround the plastic preform in its circumferential direction. In this way, it is possible for the shielding elements to have a smaller cross-section than, for example, the support ring of the plastic preform.

[0044] The Figures 3a and 3bFigure 1 shows two illustrations of shielding elements 62. The recess 62b and the recess 62a opposite it are particularly visible. Reference numerals 66 denote support devices with which the shielding element can be attached to a holding device. Reference numeral 68 denotes a recess for locking the shielding elements to a holding device. This also allows for quick replacement of the holding elements. Due to the design, or rather the two-part design, of the shielding elements, it is possible for the holding elements to be inserted below the support ring during the transport process. This allows a very large circumferential angle of the plastic preform to be directly shaded by the shielding elements. Experiments have shown that this significantly reduces the blow molding nozzle imprint for the subsequent blow molding machine.The shielding elements described here also allow for a more favorable neck pull-out after the heating process and also more process freedom due to reduced heating of the openings of the plastic preforms.

[0045] The Figures 4a and 4b Figure 1 shows a holding arrangement 5 to which a shielding element 62 is attached. It can be seen that the shielding elements 62 are plug-in elements that can be inserted into areas of the holding arrangement 5. The reference numerals 52 denote fastening means, such as screws or the like, which serve to hold the shielding elements 62. This holding arrangement also includes (not shown) the individual holding devices for holding the plastic preforms. This holding arrangement can be mounted on a transport chain, which serves to transport the plastic preforms.

[0046] Figure 5Figure 1 shows another representation of a device according to the invention. Here it can be seen that the successive shielding elements 62 and 64 do not yet completely surround the plastic preforms, but rather a certain angular area remains unshielded. In this embodiment, a further shielding element 65 is provided, which here is designed in the form of an elongated plate and which covers the remaining area circumferentially around the plastic preforms. In this case, the shielding device 6 for each plastic preform consists of the two shielding elements 62 and 64 and the aforementioned shielding plate 65. This shielding plate 65 is preferably arranged in a stationary position, meaning that the plastic preforms move relative to this shielding plate.In contrast, the shielding elements 62 and 64 move with the plastic preforms and are therefore particularly preferably also arranged on the transport device 2, i.e., the transport chain. Preferably, at least during the transport of the plastic preforms in a straight section, the shielding elements are arranged stationary relative to the plastic preforms.

[0047] Figure 6Figure 1 shows another representation of the device according to the invention. In this representation, in addition to the recesses 62b and the shielding elements 62 and 64, the gripping element 74, which engages the plastic preforms to hold them, can also be seen. This gripping element is designed here as a mandrel that can be inserted into the openings of the plastic preforms. The carrier 66, by means of which the shielding elements are attached to their holding device, can also be seen again. These gripping elements are therefore the holding devices mentioned above for holding the plastic preforms.

[0048] The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are novel individually or in combination compared to the prior art. It is further noted that the individual figures also describe features which may be advantageous on their own. A person skilled in the art will immediately recognize that a particular feature described in a figure may be advantageous even without incorporating other features from that figure. Furthermore, a person skilled in the art will recognize that advantages may also arise from a combination of several features shown in individual or different figures. Reference symbol list

[0049] 1 Heating device 2 Transport device for transporting the plastic preforms 4 Heating device 5 Holding device 6 Shielding device 10 Plastic preforms 10a Mouth area of ​​the plastic preform 10 50 System for manufacturing plastic containers 52 Storage device 54 Transport device 56 Fastening device 58 Forming device 65 Shielding plate 66 Support devices 68 Recess for locking the shielding elements 74 Gripping element 62, 64 Shielding elements 62a First recess 62b Second recess 64a First recess 64b Second recess 66 Support 74 Gripping element, Holding device I Section of the transport device

Claims

1. Apparatus (1) for heating plastic parisons (10), comprising a transport device (2), which transports the plastic parisons (10) at least at sections along a predetermined transport path, wherein the transport device (2) has a plurality of holding devices (74) for holding the plastic parisons (10), with a heating device (4) for heating the plastic parisons (10) at least at times, while they are being transported by the transport device (2), wherein the apparatus (1) has at least one heat shielding device (6) which is suitable and intended to counteract the heating of mouth regions (10a) of the plastic parisons (10), characterised in that the heat shielding devices (6) have at least one first heat shielding element (62) and a second heat shielding element (64) which can be moved relative to one another and which, in at least one relative position with respect to one another, at least partially surround a portion of a plastic parison (10) in the circumferential direction thereof and wherein the holding devices (74) have mandrels which are introduced in to mouths (10a) of the plastic preforms (10), wherein both shielding elements (62, 64) are deliverable to the plastic preforms (10) by a movement which is carried out perpendicular to a longitudinal direction of the plastic preforms (10) and the heat shielding elements (62, 64) are arranged at the same holding device (5) as the mandrels.

2. Apparatus (1) according to claim 1, characterised in that the heat shielding elements (62, 64) have a plate-like construction.

3. Apparatus (1) according to at least one of the preceding claims, characterised in that at least one heat shielding element (62, 64) has a first recess (62a, 64a) to receive at least one portion of the plastic parison (10).

4. Apparatus (1) according to at least one of the preceding claims, characterised in that the heat shielding elements (62, 64) are made from a reflecting material.

5. Apparatus (1) according to at least one of the preceding claims, characterised in that the heat shielding elements (62, 64) can be fixed to the holding devices by a quick-change connection.

6. Apparatus (1) according to claim 3, characterised in that at least one heat shielding element (62, 64) has a second recess (62b, 64b) for receiving a portion of the plastic parison (10).

7. Apparatus (1) according to claim 4, characterised in that the first recess (62a, 64a) of the first shielding element (62, 64) and the second recess (62b, 64b) of the second shielding element (64) are constructed in such a way that they co-operate at least at times in order to substantially surround a portion of a plastic parison in the circumferential direction.

8. Apparatus (1) according to at least one of the preceding claims, characterised in that at least one heat shielding element (62, 64) has a first recess (62a, 64a) to receive a portion of a first plastic parison as well as a second recess (62b, 64b) to receive a portion of a second plastic parison (10).

9. Apparatus (1) according to at least one of the preceding claims, characterised in that at least two heat shielding elements (62, 64) have the same construction.

10. Apparatus (1) according to at least one of the preceding claims 3 to 7, characterised in that at least one recess (62a, 62b, 64a, 64b) is suitable to surround the plastic parison (10) in the direction thereof at an angle which is greater than 70°, preferably greater than 90°, preferably greater than 120°, preferably greater than 140°, preferably greater than 150°, preferably greater than 160° and particularly preferably greater than 170° and / or that at least one recess (62a, 62b, 64a, 64b) is suitable to surround the plastic parison (10) in the direction thereof at an angle which is less than 270°, preferably less than 250°, preferably less than 230°, preferably less than 210°.

11. Apparatus (1) according to at least one of the preceding claims 5 to 8, characterised in that in a state in which the recesses surround a plastic parison (10), an area surrounded by these recesses (62a, 64b) is smaller than or equal to the cross-section of a carrying ring of this plastic parison.

12. Shielding element (62, 64) for shielding heat from plastic parisons (10) which are being transported upright, with a holding device in order to fasten the shielding element (62, 64) at least indirectly to a transport device (2) for transporting plastic parisons, which has a plurality of holding devices (74), with a first recess (62a, 64a) which is suitable and intended to receive at least a portion of a first plastic parison (10), wherein this recess (64a) extends over a circumferential angle of less than 180°, characterised in that the shielding element (62, 64) has a second recess (62b, 64b) which is suitable and intended to receive at least a portion of a second plastic parison, wherein this second recess (62b, 64b) extends over a circumferential angle of less than 180° and wherein the holding devices (74) have mandrels which are introduced in mouths (10a) of the plastic preforms (10).

13. Method for heating plastic parisons (10), wherein the plastic parisons (10) are transported by a transport device (20), which has a plurality of holding devices (74) for holding the plastic preforms, along a predetermined transport path and are heated at least at times during this transport, wherein a heating of mouth regions (10a) of the plastic parisons (10) is counteracted by a heat shielding device (6), characterised in that the heat shielding devices (6) in each case have a first heat shielding element (62) and a second heat shielding element (64) which can be moved relative to one another and which, in at least one relative position with respect to one another, at least partially surround a portion of the plastic parison (10) in the circumferential direction thereof and wherein the holding devices (74) have mandrels which are introduced in mouths (10a) of the plastic preforms (10).