ITRM20110319A1 - HEATING SYSTEM PREFORMER OF CONTAINERS - Google Patents

Description

PREFORM HEATING SYSTEM OF CONTAINERS

Field of invention

The present invention relates to a container preform heating system, in particular used before the blow molding step of containers made of plastic material.

State of the art

Heating apparatuses for preforms of plastic containers are already known. Generally, the heating of the preforms takes place before the blow molding or stretch-blow molding step in such a way as to bring the material of the preform to an appropriate temperature in order to obtain a molded container of better quality.

The source of thermal energy for heating the preforms is generally constituted by infrared radiation (IR) lamps. The preforms, moved along a transfer chain equipped with pads for supporting the preforms themselves, pass through a tunnel oven along which several batteries of IR lamps are arranged.

Disadvantageously, in known heating apparatuses there is a not negligible dispersion of infrared radiation, directly emitted by the lamps, which cannot be directed towards the area where the preform passes. Furthermore, even the infrared radiation reflected by the walls of the tunnel through which the preform passes is not adequately optimized. These drawbacks determine a higher energy consumption and / or an unacceptable lowering of the production speed in order to achieve an optimal heating of the preforms.

A further disadvantage is represented by the fact that a poor penetration of heat is often obtained in the thickness of the preform, which determines an overheating of the external surface of the preform with consequent crystallization of the PET, which compromises the subsequent blowing.

The need is therefore felt to create a preform heating system that allows the above drawbacks to be overcome.

Summary of the invention

The primary purpose of the present invention is to provide a preform heating system which allows to optimize the focusing of infrared radiation towards the preform, reducing energy consumption while maintaining a very high production speed.

A further object of the invention is to provide a preform heating system which allows to optimize the penetration of heat throughout the thickness of the preform in order to make the temperature as uniform as possible along said thickness.

The present invention therefore proposes to achieve the objects discussed above by realizing a heating plant for preforms of containers which, according to claim 1, comprises at least one heating module configured so as to define at least one tunnel, arranged laterally with respect to a longitudinal plane X, for the passage of the preforms to be heated, said at least one heating module comprising a first portion provided with forced ventilation means, at least a first lateral portion, arranged on a first side of said first portion, provided with a plurality of infrared radiation lamps for heating the preforms, in which said first portion and said at least a first lateral portion are configured so as to define at least a tunnel section, delimited on a first side by said infrared radiation lamps; on a second side, opposite the first side, by at least one first plate; on a third side, transversal to said first and second sides, by at least a second plate; said tunnel section being open at a fourth side, opposite the third side, to allow the passage of the preforms; in which the at least one first plate closes the lateral ends of the first portion and is provided with a plurality of slots for the passage of air, moved by said forced ventilation means, from the first portion to the tunnel section; and in which said infrared radiation lamps are placed in respective longitudinal housings of a reflector of the lamps, each longitudinal housing having a section profile, along a vertical plane, substantially C-shaped.

The particular shape of the lamp housings, the gold coating of at least one of the reflective surfaces (lamp housings, first plates and second plates), the configuration of the slots for the passage of air contribute in a synergistic way to make the most of and at best the thermal energy emitted by the lamps, resulting in energy savings for the heating of each individual preform and a high quality of molding even at very high production speeds. Considering that the heating plant of the invention, arranged upstream of the blow molding plant, allows to operate at production speeds of up to 80,000 containers / hour, the energy savings are considerable.

A further advantage is represented by the fact that the preform heating system, object of the present invention, is equipped with a ducting system for the air flows inside it so that a uniform distribution of the air to the compartments is obtained. of the oven by exploiting the symmetries of the structure.

The dependent claims describe preferred embodiments of the invention.

Brief description of the figures

Further characteristics and advantages of the invention will become more evident in the light of the detailed description of a preferred, but not exclusive, embodiment of a preform heating system, illustrated by way of non-limiting example, with the aid of the joined tables drawing in which:

Figure 1 represents a perspective view of a heating system according to the invention;

Figure 2 represents a schematic sectional view of the heating system according to the invention;

Figure 3 represents an enlargement of part of the view of Figure 2;

Figure 4 represents an exploded view of a first part of the plant of Figure 1;

Figure 5 represents a side view of a component of the implant of the invention;

Figure 6 represents a perspective view of a second part of the plant of Figure 1;

Figure 7 represents an enlargement of part of the view of Figure 6.

The same reference numbers in the figures identify the same elements or components.

Detailed description of a preferred embodiment of the invention With reference to Figures 1 to 7, an embodiment of a heating plant for preforms of containers is shown, generally indicated with the reference numeral 1 (Figure 1). The preforms to be heated are generally made of plastic material, for example PET, PP, PLA, PVC but the plant of the invention can also be used to heat preforms or molded containers made of different plastic material, or in a combination of some of these materials.

With reference to Figures 1 and 2, the heating system 1, in this embodiment, is substantially symmetrical with respect to the longitudinal plane X, and comprises one or more modules 1, arranged in succession.

It is possible, without departing from the scope of the invention, embodiments in which the heating system comprises a single symmetrical module or one or more modules having asymmetrical shapes, i.e. with heating carried out only on one side or combinations of asymmetrical modules with symmetrical modules. These possible alternatives are not illustrated, but are easily derivable for a person skilled in the art from what is illustrated below for the preferred embodiment.

The modules 1â € ™ are configured in such a way as to define two tunnels 2, 2â € ™, arranged symmetrically with respect to the X plane, for the passage of the preforms 40 to be heated which are transported by a transfer chain equipped with backing pads (not shown). The passage of the preforms 40 from tunnel 2 to tunnel 2â € ™, or vice versa, takes place by means of a curved section 31, connecting the ends of said tunnel, which is crossed by the transfer chain. Advantageously, manifolds 30 are provided for the cooling liquid to keep the preform neck area at a lower temperature which does not need to be heated by the oven during the heating process to which the preforms are subjected. Each module 1â € ™ comprises a central portion 16 and two lateral portions 17. Each central portion 16, hollow inside it, in turn comprises: - at least one air intake filter 3, arranged on the lower wall of the central portion 16, said air coming from the environment outside the system, at room temperature;

- at least one fan 4 fixed to the upper wall of the central portion 16 and provided with an impeller 5, arranged in the hollow part 18 of the central portion 16 and substantially in the center of the module 1â € ™ between the respective tunnel portions 2, 2â € ™ of the module itself;

- two lateral ends 15 closed respectively by a first metal plate or sheet 7, provided with slots 14.

Each lateral portion 17 comprises at least one battery of IR lamps 6 for each length of tunnel 2, 2â € ™ and a relative support structure for the lamps, in the form of perforated plates 25.

Each stretch of tunnel length 2, 2â € ™ is delimited on a first side by said at least one battery of IR lamps 6; on a second side, opposite the first side, from said first metal plate 7, preferably made of aluminum; on a third side, transversal to said first and second sides, by a second metal plate or sheet 8, preferably made of aluminum. A fourth side of the tunnel, opposite the third side, is instead open to allow the preforms 40 to pass through the transfer chain.

Each battery of IR lamps 6, supported by a support structure 39, is positioned in a respective housing provided in the structure of the reflector 9, preferably in aluminum. This reflector is provided with a number of housings 10, 10â € ™ at least equal to the number of lamps 6. Each housing has a longitudinal extension or length suitable for housing each lamp 6 entirely along its longitudinal extension or length.

Advantageously, inside each section of tunnel length 2, 2â € ™ at least one of the surface of the housings 10, 10â € ™, the surface of the first plate 7 and the surface of the second plate 8 is entirely coated with gold to optimize the reflection of infrared radiation. In a variant, both the surface of the housings 10, 10 ', both the surface of the first plate 7 and the surface of the second plate 8 are entirely coated with gold.

In particular, the use of aluminum to make the reflector 9, the first plates 7 and the second plates 8, combined with the gold coating of the relative surfaces facing inside the tunnels 2, 2â € ™, made it possible to obtain an optimal reflection of infrared radiation.

The gold coating layer, preferably with a thickness comprised between 0.01µm and 0.1µm, and even more preferably equal to 0.05µm, can be made by spraying or by applying a film or by galvanic electrodeposition.

Each housing 10, 10â € ™ has a surface consisting partly of a semi-cylindrical lateral surface 12 and partly of flat surfaces 11 which extend said lateral surface 12 at both ends. Advantageously, said flat surfaces 11 allow to house entirely or almost entirely the lamps 6 in each housing, allowing to recover that part of infrared radiation which is generally dispersed, focusing it optimally towards the passage area of the preforms 40. A further advantage is represented by the fact that each housing 10 is configured so that the radius R of the semi-cylindrical side surface 12 is between 6 and 8 mm and the width L of said flat surfaces 11 is between 2 and 3 mm so that, once the lamp 6 is placed in the housing, the front ends 13 of the flat surfaces 11 are positioned so as to cover at least the vertical longitudinal center line of the the lamp 6 at least about 1 mm. In the example of Figure 3 the IR lamps 6 are entirely arranged inside the corresponding housing.

The center distance D between one housing and the next is advantageously between 14 and 25 mm.

The preferably used IR 6 lamps are of the â € œshort waveâ € type with a temperature of 2400 K. Alternatively, quartz lamps at a temperature of 1800 K of the low thermal inertia type, known as â € œmedium wave IRâ € lamps, can be used, or NIR lamps, with temperatures up to 3400 ° K. Preferably the IR lamps 6 have a diameter of 10-12 mm, even more preferably 11 mm.

The reflector 9 cooperates in correspondence with its lateral ends 29 with respective perforated plates 25, in which holes 26 are provided in correspondence with the housings 10 for the insertion of the ends of the IR lamps 6. In at least some of these holes 26 thicknesses are provided 24 removable. The removal or addition of one of these spacers 24 gives the possibility to adjust the distance of the IR lamps from the direction of advancement of the preforms.

A further advantage is represented by the fact that at least the lower housing 10â € ™ of the reflector 9 is arranged offset from the other housings 10 of the same structure. In particular, the lower housing 10â € ™ is positioned further forward, that is, more internally in the relative length of the tunnel and therefore closer to the direction of advancement of the preforms 40, compared to the other housings 10 for a distance equal to approximately 4Ã 6 mm. This implies that the lower flat surface 11â € ™ of the housing 10, adjacent to the lower housing 10â € ™, has a width L between 6 and 10 mm, greater than the width L of all the other flat surfaces 11 This technical expedient allows to optimize the infrared radiation necessary to heat the portion of the preform 40 adjacent to the neck of the preform itself, which passes in proximity to said lower housing 10â € ™. It is possible to prepare another housing having the same configuration as the lower housing 10â € ™ just described in another position, upper or intermediate of the reflector 9.

A further contribution to better focusing of infrared radiation and energy saving is given by the presence and shape of the second plate 8. The presence of this additional plate allows to close one more side of the length of the tunnel compared to known systems. . With reference to Figures 3, 6 and 7, in a preferred variant the plate 8 has a broken line profile and is fixed at one end to the upper wall of the central portion 16 of the module 1â € ™ by appropriate fastening means. The profile of the plate 8 is configured in such a way as to minimize the losses of infrared radiation, and therefore of heat, inside each length of the tunnel. In another variant each second plate 8 can be fixed at a first end to the upper wall of the central portion 16 and at a second end to the upper wall of a lateral portion 17 of the module 1â € ™.

Advantageously, the slots 14 of the first metal plates 7 allow the passage of air from the hollow part 18 of the central portion 16 to the respective tunnel portions 2, 2â € ™. The air is sucked in through the filter 3 longitudinally along the axis of the impeller 5 and then expelled by the same impeller at an angle of 90 ° with respect to said axis. First lateral flows of air 19 thus generated pass through the hollow part 18 until reaching the lateral ends 15 whereby blades of air come out of the slots 14 directed towards the area crossed by the preforms 40. Second lateral flows of air 19â € ™, on the other hand, after passing through the hollow part 18, they emerge from the central portion 16 through slits 32 (Figure 7), configured in such a way as to direct said second flows 19â € ™ towards the passage area of the neck of the preforms 40.

These lateral air flows 19, 19â € ™, once they have passed through the passage area of the preforms 40, are conveyed into at least one internal channel 33 provided in the side portions 17 and exit from the modules 1â € ™ through the grids 34.

The slots 14 are preferably formed in at least three rows along the plates 7. The slots of one row are offset with respect to the slots of the adjacent row so that the air blades are distributed as evenly as possible in the respective tunnel length section. In the example of Figure 6 the slots of the central row 20 are offset with respect to the mutually aligned slots of the side rows 21 and 22.

Advantageously, the presence of these slots 14, together with their staggered distribution on the plates 7, allows to considerably improve the penetration of heat throughout the thickness of the preforms. Cooling with this air also allows to increase the life of the IR lamps and other components of the heating system of the invention.

Claims (17)

CLAIMS 1. Heating system (1) of plastic preforms comprising at least one heating module (1â € ™) configured to define at least one tunnel (2, 2â € ™), arranged laterally with respect to a longitudinal plane (X) , for the passage of the preforms (40) to be heated, said at least one heating module (1â € ™) comprising - a first portion (16) provided with forced ventilation means (4, 5), - at least a first side portion (17), arranged on a first side of said first portion (16), provided with a plurality of infrared radiation lamps (6) to heat the preforms, wherein said first portion (16) and said at least one first lateral portion (17) are configured so as to define at least one tunnel section (2), delimited on a first side by said infrared radiation lamps (6); on a second side, opposite the first side, by at least one first plate (7); on a third side, transversal to said first and second sides, by at least a second plate (8); said tunnel section being open at a fourth side, opposite the third side, to allow the passage of the preforms (40); in which the at least one first plate (7) closes the lateral ends (15) of the first portion (16) and is provided with a plurality of slots (14) for the passage of air, moved by said forced ventilation means ( 4, 5), from the first portion (16) to the tunnel section (2); and in which said infrared radiation lamps (6) are placed in respective longitudinal housings (10, 10â € ™) of a reflector (9) of the lamps, each longitudinal housing having a sectional profile, along a vertical plane, substantially shaped by C. 2. Plant according to claim 1 in which, inside each section of tunnel length (2, 2 '), at least one of the surfaces of the housings (10, 10'), the surface of the at least a first plate (7) and the surface of at least a second plate (8) is coated with gold. 3. Implant according to claim 2, wherein the gold coating layer has a thickness of between 0.01 and 0.1 µm. 4. Plant according to any one of the preceding claims, comprising two or more heating modules (1â € ™). 5. Plant according to any one of the preceding claims, wherein each heating module (1â € ™) comprises a second lateral portion (17) equal to the first lateral portion (17) arranged on a second side of the first portion (16) opposite the first side with respect to the longitudinal plane (X), for which further tunnel sections are defined (2â € ™). 6. Plant according to any one of the preceding claims, wherein each longitudinal housing (10, 10â € ™) has a surface consisting partly of a semi-cylindrical lateral surface (12) and partly of longitudinal flat surfaces (11) parallel to each other which they are an extension of said semi-cylindrical lateral surface (12). 7. Plant according to claim 6, wherein the radius (R) of the semi-cylindrical side surface (12) is between 6 and 8 mm and the width (L) of said flat surfaces (11) is between 1 and 3 mm. 8. Plant according to claim 7, wherein the front ends (13) of the flat surfaces (11) are positioned so as to cover at least the vertical center plane of the lamps (6) by at least about 1 mm. 9. Plant according to claim 7 or 8, in which the center distance (D) between one housing and the next is between 14 and 25 mm. 10. System according to any one of the preceding claims, in which at least one end housing (10â € ™) is arranged offset with respect to the other housings (10) of the same reflector (9) so that it is positioned more internally in the respective section of length of tunnel and in proximity to the passage area of the preform portion (40) adjacent to the neck of the preform itself. 11. Implant according to claim 10, wherein said end housing (10â € ™) is positioned more internally than the other housings (10) by a distance of approximately 4-6 mm. 12. Implant according to claim 11, wherein the lower flat surface (11â € ™) of the housing (10) adjacent to said end housing (10â € ™) has a width (Lâ € ™) greater than the width (L ) of all flat surfaces (11) of the other housings. 13. Implant according to claim 12, wherein the width (Lâ € ™) of said lower flat surface (11â € ™) is comprised between 6 and 10 mm. 14. Plant according to any one of the preceding claims, in which the slots (14) are formed in at least three rows along the first plates (7) and the slots of a row are offset with respect to the slots of the adjacent row so that first blades of air are distributed evenly in the respective tunnel length section (2, 2â € ™). System according to claim 14, in which the slots (14) of a central row (20) are offset with respect to the mutually aligned slots (14) of two lateral rows (21, 22). 16. Plant according to claim 14, in which the first central portion (16) is also provided at the lateral ends (15) with slits (32) configured in such a way as to direct second blades of air towards the passage area of the package of the preforms (40). 17. System according to any one of the preceding claims, in which at the lateral ends (29) of the reflector (9) are arranged respective perforated plates (25) with holes (26) placed in correspondence with the housings (10) for the insertion of the ends of the lamps (6), at least some of said holes (26) being provided with removable shims (24).