Heating device for preforms and oven for preforms

Abstract

The present invention relates to a heating device for preforms and to an oven for preforms, in particular a heating device using monochromatic infrared radiation, preferably generated by a laser. In particular, the present invention relates to a heating device (101) for preforms (P) configured so as to be positioned outside the preforms (P) and to radiate electromagnetic radiation in the infrared range, so as to form a radiation disc in such a device according to radial symmetry with respect to the center of the preform axis.

Description

TECHNICAL FIELD

[0001] The present invention relates to a preform heating device, in particular to a heating device using monochromatic infrared radiation, preferably generated by a laser. BACKGROUND

[0002] In a packaging line of beverages in plastic bottles, a first step comprises heating preforms, which are then blown into bottles up to their softening point.

[0003] This operation is usually carried out in special ovens, through which the preforms pass in a reduced pitch, and in which infrared radiation emitting lamps, heated to the required temperature, are arranged.

[0004] The preforms are guided along a heating path by means of a mandrel, which is introduced into the preform as a result of the action of suitable cams. At the end of the path in the oven, the mandrel is disengaged from the preform by means of a lifting cam and conveys the preform to a movement system, usually a distribution star, which feeds it to the blowing machine.

[0005] These ovens have considerable dimensions, since the path of the preforms must be long enough to allow the necessary heating time. In fact, the heat is diffused by the lamps along the path of the preforms, whereby, despite the provision of adequate reflecting surfaces, the diffusion of heat into the environment is considerable.

[0006] The infrared lamps are usually tungsten filament lamps, which have a maximum emission efficiency at 3000°K. However, considering that various plastic materials have an energy absorption spectrum in a rather narrow range of wavelengths, only a small fraction of the energy is actually absorbed by the preforms, despite the fact that the tungsten filament lamps work at maximum efficiency, emitting energy at very different wavelengths, the rest of the energy being dispersed in the environment. For example, if we consider PET preforms, which represent approximately 95% of the global market, the power used for heating under these conditions has a value indicative of low efficiency compared to the power actually stored by the preforms, no more than 15% of the electrical energy introduced being effectively converted into thermal energy absorbed by the preforms.

[0007] The dispersion of the unusable thermal energy from the preforms also requires an effective refrigeration system to avoid overheating the system, which leads to further energy waste.

[0008] Therefore, there is a need to provide a preform heating system that has greater energy efficiency than the ovens currently on the market and possibly has smaller dimensions.

[0009] Furthermore, the preforms are currently heated by a grid of lamps, which generate radiation from a whole flat surface, thus not allowing homogeneous radiation of the cylindrical containers.

[0010] Therefore, the main problem of the present invention is to provide a preform heating device which solves the above-mentioned drawbacks inherent in the prior art and allows to obtain energy savings while optimizing the heating of the preform.

[0011] In particular, the present invention proposes to concentrate the radiation on a single preform, in order to avoid the dispersion of the radiation in the environment.

[0012] The present invention also uses monochromatic light sources of suitable wavelength, selected from those having an absorption coefficient for PET or other commonly used plastic materials, such as polyester resins, for example but not limited to PET (polyethylene terephthalate), PEF (polyethylene 2,5-furandicarboxylate, also defined as polyfuran dicarboxylate or polyethylene furfural), PLA (poly lactic acid or poly lactic acid resin), PEN (polyethylene naphthalate) and polyolefin resins, such as PE (polyethylene), PP (polypropylene), also with copolymers, suitable for conveniently heating the material. Such monochromatic radiation can be obtained on the basis of currently known technologies.

[0013] The heating system of the present invention follows the cylindrical geometry of the object to be heated, i.e. the preform, in order to radiate the preform from the outside according to the cylindrical geometry and to concentrate the radiation towards the inside of the preform.

[0014] Therefore, the object of the present invention is a preform heating device as set forth in the appended claims, which define an integral part of the present description. SUMMARY

[0015] The first object of the present invention is in particular a preform heating device comprising a heating element configured so as to be arranged outside the preform and to radiate electromagnetic radiation in the infrared range, which forms a radially symmetrical radiation disc in such device with respect to the centre of the preform axis.

[0016] The second object of the present invention is a heating device comprising a heating element configured to individually heat the preform from the outside, wherein said heating element is powered by a laser device.

[0017] Another object of the present invention is a diffuser of infrared radiation which passes through the inside of the preform, which diffuses the radiation according to a defined radiation geometry and intensity, in order to optimize the incidence of the radiation itself.

[0018] Still another object of the present invention is a heating device comprising a heating element configured to individually irradiate the preform from the outside and to distribute the radiation emitted by the laser source on an optical path aimed at concentrating such radiation towards the central axis of the preform. BRIEF DESCRIPTION OF DRAWINGS

[0019] Further features and advantages of the invention will become apparent from the description of some examples of embodiments given herein with reference to the following non-limiting examples of the accompanying drawings:

[0020] Figure 1 A schematic plan view is shown, viewed from above a preform oven including the heating device of the present invention;

[0021] Figure 2 A schematic side view of the preform heating device according to the present invention is shown;

[0022] Figure 3 It shows Figure 2 A cross-sectional side view of the heating shroud in the embodiment shown, indicating the expected path of the radiation rays;

[0023] Figure 4 It shows Figure 3 Detailed cross-sectional side view;

[0024] Figure 5 A perspective view of a second embodiment of the heating device of the present invention is shown;

[0025] Figure 6 A side view of a third embodiment of the heating device of the present invention is shown;

[0026] Figure 7 It shows Figure 6 A perspective view showing the details of the heating device;

[0027] Figure 8 It shows Figure 6 A perspective view of the heating device;

[0028] Figure 9 A perspective view of a rotating machine for heating preforms is shown, the rotating machine comprising... Figure 6 Heating device;

[0029] Figure 10 Side views of different embodiments of the heating device of the present invention are shown;

[0030] Figure 11 It shows including Figure 10 A perspective view of the prefabricated oven of the heating device;

[0031] Figure 12 It shows Figure 10 A perspective view of the heating device;

[0032] Figure 13 A schematic side view of the preform heating device in different variations is shown;

[0033] Figure 14 It shows according toFigure 13 optical view of the configuration of the heating radiation of the variant according to

[0034] Figure 15 shows a cross-sectional side view of a detail of Figure 13 alternative optical view of the configuration of the heating radiation of the variant according to

[0035] Figure 16 shows a cross-sectional side view of a detail of Figure 13

[0036] Figure 17 shows a view of a detail of Figure 16 highlighting the cross-sectional path of the heating radiation. DETAILED DESCRIPTION

[0037] With reference to the figures, reference 1 indicates an oven for preforms according to the present application, which is coupled with a blowing machine 5. Figure 1 The oven 1 is operatively connected at the inlet and at the outlet of the oven 1 to moving devices 2, 3 for the preforms. Such moving devices 2, 3 are usually constituted by a distribution star which comprises a series of gripping devices 4, for example notches or hollows, suitable to engage, for example at the neck, the preforms.

[0038] The moving device 3 for the preforms at the outlet of the oven 1 is in turn operatively connected to a blowing machine 5 (the term "blowing machine" used in the present description means any type of blowing machine or stretch-blowing machine) comprising a plurality of molds 6 into which the heated preforms are inserted and from which the preforms exit in the form of blown (or stretch-blowed) bottles.

[0039] The blowing machine 5 is in turn operatively connected with a distribution device 7, usually a distribution star, suitable to pick up the blown bottles at the output of the blowing machine and to transport them, through a suitable conveying system, to the subsequent operating units. For this purpose, the distribution star 7 comprises a plurality of notches 4' suitable to engage the necks of the blown bottles.

[0040] The path of the preforms is thus defined, which is indicated in

[0041] by the direction of the arrows, from the feeding of the preforms to the oven 1 to the entrance of the preforms into the molds 6 of the blowing machine 5. Figure 1 The oven 1 comprises a conveying device 8 suitable to move the preforms along the path and a plurality of heating devices 101 associated therewith so that a heating device 101 corresponds to each preform.

[0042]

[0043] ​​The conveying device 8 comprises a track 9 on which the plurality of heating devices 101 slide, each adapted to engage a preform. The track 9 comprises two substantially parallel straight stretches 13, 13' and two curved stretches 14, 14' connecting the straight stretches 13, 13' at the two ends according to a circular-arc path. Respective drive wheels 15, 15' are provided at said curved stretches 14, 14'.

[0044] The heating devices 101 can be moved along the track 9 passively, i.e. in contact with each other and each pushed by the upstream device, as happens in traditional preform ovens, or actively, i.e. arranged on a rack, on a chain or on a motorized belt.

[0045] If the heating devices 101 are moved passively, the conveying device 8 of the oven 1 further comprises a device for moving the heating devices 101 and spacing them apart. Such a moving device comprises a first auger 16A arranged in the oven at a feeding point of the preforms, between the drive wheel 15' and the first straight stretch 13 of the track 9, and a second auger 16B arranged at the junction between the second straight stretch 13' of the track 9 and the drive wheel 15'.

[0046] Both augers 16A, 16B comprise a helical groove 17 with variable pitch for interfering with a suitable thrust wheel of each heating device 101. The augers 16A, 16B are mounted in an inverted position along the direction of travel of the heating devices 101, so that the first auger 16A has the maximum pitch upstream along the direction of travel, while the second auger 16B has the maximum pitch downstream.

[0047] The augers 16A, 16B can be moved independently but in a synchronized manner by respective motorized means (not shown) or by a single motorized means provided with mechanical transmission means.

[0048] The heating devices 101 are configured to individually heat the preforms P by radially sending electromagnetic radiation from the outside towards the inside of the preforms P.

[0049] The heating devices 101, configured to receive the preforms P therein, comprise a vertically movable clamp 102, which can be in a raised position of disengagement of the preform P and in a lowered position of insertion of the preform P in a respective heating hood 103. The clamp 102 is moved by an actuator 104 able to follow a predetermined law of motion. The actuator 104 is powered and controlled by a voltage line coming from a manifold (not shown) comprising a first unit and a second unit for distributing power and control signals, respectively, to the actuator 104.

[0050] The clamp 102 is moved by two jaws 102a, 102b (in Figure 2In the case of a single jaw 102a) only, the jaw is able to grip the preform P in the cylindrical area located directly above the finishing ring, by the action of a spring or by the action of special closing cams for gripping the preform from the star 2 and opening cams for releasing onto the star 3.

[0051] The vertical movement of the clamp 102 is operated by a dedicated actuator 104 Figure 2 ), preferably by a stepper motor, a servo motor, a linear motor or a brushless motor. It is thus possible to apply specific motion laws to optimize the heating inside the preform P.

[0052] The clamp 102 is supported by a support 105, which is driven by a screw 106 and guided by a low-friction seat 107. In the case of a linear motor, the screw 106 is not present. The assembly consisting of the movable clamp 102, the actuator 104, the screw 106 and the low-friction seat 107 is mounted on a support structure 108.

[0053] As an alternative to the solution using a clamp, it is possible to make the same movement by grabbing the preform with a mandrel, which is a cylindrical body that penetrates inside the threaded portion of the preform and is not subjected to heating, or by gripping the preform from the outside. The interference required to manipulate the preform is obtained by means of elastic elements provided in the mandrel device. In Figure 10 、 Figure 11 and Figure 12 one example of this implementation is shown.

[0054] With reference to these figures, the heating device 101 comprises a sliding member 270, which comprises a body 271 into which a mandrel 272 is slidably inserted, movable along a vertical direction between a raised position and a lowered position. The mandrel 272 is configured to engage with the neck of the preform P by means of a traditional engagement device 272a.

[0055] The sliding member 270 is connected to the heating hood 103 by means of a connecting element 273, so that the heating hood 103 is aligned with the mandrel 272 and positioned below it.

[0056] The sliding member 270 comprises drive wheels 274a, 274b, 274c for sliding and aligning the sliding member 270 on the track 9 in the same way as the mandrel in a traditional oven.

[0057] On the body 271 of the sliding member 270 there is also a wheel 275, which is connected to the mandrel 272 and is movable in a slot 271a of the body 271 Figure 12), the slot is configured to interact as a driven member with a cam (not shown) for the commanded lowering / raising of the mandrel 272. Thus, the preform can be inserted into the heating hood 103 for a certain period of time and with a desired speed profile obtained by suitably configuring the cam.

[0058] In Figures 2 to 8 an embodiment of the support structure 108 in turn comprises a sliding member 270 (see Figure 2 ) along the track 9 of the oven 1, which comprises the drive wheels 274a, 274b, 274c as described above.

[0059] The heating hood 103 is also fixed to the support structure 108 by suitable connecting rods (not shown in the drawings) so as to move integrally therewith.

[0060] The heating hood 103( Figure 2 , Figure 3 , Figure 4 and Figure 13 ) comprises a substantially cylindrical hollow body 103a, a conical portion 103b provided at one end of the body 103a and a reflecting portion 103c provided at the other opposite end of the body 103a.

[0061] The heating hood 103 has an opening 109 coaxial with the axis X-X of the hood at the reflecting portion 103c, while it comprises a collimator member 110 located at the end of the conical portion 103b.

[0062] Downstream of the optical path of the collimator member 110, the conical portion 103b of the heating hood 103 comprises a first lens or axicon 111a located at the end of said conical portion 103b connected to the collimator member 110. A second lens or axicon 111b is provided in the lower segment of the cylindrical body 103a.

[0063] The lenses and axicons used are made of a material having a sufficient refractive index in the radiation used so as to form a suitable geometry of the outgoing beam of radiation in the form of a cylinder. Suitable materials are, for example, but not limited to, those listed below: quartz, silica, magnesium fluoride, calcium fluoride, silicon, germanium or rare-earth sapphire or boron glasses. The surfaces of these optical devices have the necessary treatment to reduce reflections in the direction opposite to that of the radiation. Such optical devices are well known to the person skilled in the art and will not be described in detail.

[0064] In a different embodiment of the heating hood( Figure 13), the body 103a comprises a shaped aperture 150 for blowing purified air to keep the surface of the shaft cone 111b clean. The air introduced at high pressure must be evacuated without touching the outer surface of the preform, so as not to remove the absorbed heat. For this purpose, the body 103a comprises a second aperture 151 which is connected to an air exhaust / intake system able to expel the bulk of the introduced purified air. The body 103a has an enlarged section between the second shaft cone 111b and the reflecting portion 103c, which allows better guiding of the turbulence of the blown air, thus minimizing the risk of air touching the surface of the preform.

[0065] The reflecting portion 103c comprises, internally, a series of truncated-cone-shaped surfaces coated with a reflective material, as will be better described hereinafter. In the lower part, the radiation can be introduced by a coaxial collimator along the axis of the heating mantle as in Figure 2 , or, as in the embodiment of Figure 13 , by a collimator 110a housed in a casing 103d connected to the truncated-cone-shaped portion 103b of the heating mantle 103. The collimator 110a deflects the radiation by 90° and, thanks to a rotating optical joint (as shown), can allow a relative rotation between the optical fiber and the collimator.

[0066] The reflecting portion 103c comprises a system of truncated-cone-shaped reflective surfaces 112a, 112b, 112c, comprising, in order from the body 103a towards the opening 109, a first truncated-cone-shaped reflective surface 112a which flares outwards, a second truncated-cone-shaped reflective surface 112b which converges towards the central axis X-X of the heating mantle 103 and a third truncated-cone-shaped reflective surface 112c which converges towards the central axis X-X, wherein the first, second and third truncated-cone-shaped reflective surfaces 112a, 112b, 112c are respectively inclined by an angle a, an angle β and an angle γ with respect to a respective cylindrical surface coaxial to the axis X-X.

[0067] In particular, the angle a is smaller than the angle β and greater than or equal to the angle γ.

[0068] A substantially cylindrical absorbing surface 112d, obtained by coating the upper part of the body 103a with a highly absorbing substance in the infrared range, is provided between the body 103a and the first truncated-cone-shaped reflective surface 112a. One example is a carbon or "black oxide" coating deposited on the metal from which the heating mantle 103 is made, which allows the adhesion of a highly absorbing and high-temperature resistant substance (of the order of 200°C). Another example can be a surface treatment which makes the absorbing surface 112d a "meta-surface", i.e. which is able to capture a large part of the radiation in the most superficial layer thanks to its specific structure generated by nanotechnology.

[0069] In particular, Figure 16 and Figure 17 One form of the reflecting portion 103c is shown, provided with four reflecting surfaces 112a, 112b, 112c, 112e and a vertical absorbing surface 112d. This solution allows a greater absorption of the heating radiation and a more homogeneous radiation over the thickness of the preform. As already described, the cylindrical surface 112d is highly absorbing. In this alternative, there are four truncated-cone-shaped surfaces tilted according to the angles a, b, g and d. In particular, the angle a is smaller than the angle b and greater than or equal to the angle g. The angle d is smaller than the angle a. Figure 17 The optical path of the radiation arriving parallel from the collimator member 110 is shown by way of example.

[0070] The collimator member 110 is fed by an optical fiber 113 which generates a collimated beam of infrared radiation which is refracted by two lenses or axicons 111a, 111b arranged in series, so as to generate a radiation cylinder R1( Figure 3 ) having the appropriate homogeneity. Alternatively, instead of refractive devices such as axicons and lenses, diffractive optical elements can be used, for example lattices or nanostructures which exploit the diffraction phenomenon and constructive and destructive interference.

[0071] Figure 14 and Figure 15 The paths of the heating radiation beams, seen in cross section, are shown. In these figures, the collimator member 110 comprises a collimator 110a with a 90° angle for a more compact solution.

[0072] In detail, in Figure 14 the device comprises a pair of axicons 111a, 111b, both positive, i.e. the tilted portion is everted, while in Figure 15 the axicon 111a has a negative taper. The latter solution requires an unusual axicon, but has the advantage of a more compact solution and lower radiation intensity on the central axis.

[0073] The optical fiber 113 is shown in cross section and comprises a sheath 113a, inside which the actual optical fiber 113b is composed of two dielectric materials, one inside the other, called cladding and core. At the end 113c of the optical fiber 113, the radiation propagates according to a conical symmetry that can be guided by a spherical lens provided on the end of the optical fiber. Otherwise, as known to those skilled in the art, the beam of radiation exiting the optical fiber can be collimated towards the axicon 111a by means of the more common circular lens system. In the case of the angled collimator 110a, the cone of radiation coming out of the optical fiber hits a highly reflective surface 110b with a parabolic curve, which is inclined on average at 45°, reflecting the beam of radiation in the vertical direction. In a variant of the application, the optical fiber 113 can be integral with a rotatable element 110c, which is connected to the housing 103d of the collimator 110a by means of a bearing or a sleeve joint. Thus, in certain embodiments of the machine in which this type of illuminator is used, it is possible to allow the rotation of the optical fiber without generating torsional loads on the optical fiber or on the structure. The beam of radiation travels upwards through the positive axicon 111a or through the negative axicon 111b. In both cases, as shown in Figure 14 and Figure 15 the radiation expands according to a hollow cone as seen in cross section, and subsequently, passes through the axicon 111b, which moves as a hollow cylinder towards the reflective surface 103c.

[0074] Another alternative is to provide an optical diffractive device instead of the negative axicon 111a, which simulates the effect of the negative axicon, i.e. it can use the phenomenon of diffraction, as well as constructive and destructive interference, to produce a cone of radiation, as known in the field of optical devices. Another alternative solution to obtain the cone of radiation R3 is to use a biaxial crystal with internal conical refraction. Crystals of this type used in industry are oxides of tungsten, potassium and gadolinium, in particular crystals of potassium and gadolinium ditungstate, KGd(W04)2, commercially defined as "MDT crystals" (Monoclinic Double Tungstate). The radiation is collimated on the lower surface of the crystal, oriented along a specific optical axis of the crystal itself, and downstream of the upper surface, a similar cone of radiation to that obtained with the negative axicon is obtained.

[0075] As shown in detail in Figure 3 the radiation cylinder R1 illuminates the second truncated conical reflective surface 112b of the reflective portion 103c and is reflected (ray R2) on the first truncated conical reflective surface 112a, then on the third truncated conical reflective surface 112c, then again reflected along rays R4 and R5. In Figure 16 and Figure 17In the embodiment with four reflecting surfaces, again according to the cylindrical symmetry, the path of the heating radiation, starting from the ray R1 of the irradiation surface 112b, then of the surface 112c, then of the surface 112a, in this case, the radiation is limited to always reflect on the surface 112a, requires a fourth additional surface 112e to limit the radiation reflected and refracted from the surface and thickness of the preform. The convenient radiation in the form of a ring of radiation required for the heating operation according to the degree required is obtained by the various reflections between the said truncated conical reflecting surfaces 112a, 112b, 112c (and on the surface 112e when present) and the refraction in the thickness of the plastic material. This succession of external and internal reflections leads to a proper absorption of the radiation and therefore to an optimal heating of the material with a much higher precision than the current lamp heating systems. The temperature distribution and the related gradients, by means of the direct thermal deposition phenomena inside the material obtained by the correct selection of the radiation, allow the system according to the present application to provide a much higher heating quality than the heating qualities available today. Finally, the band 112d with high absorption treatment placed on the metal cylinder absorbs any residual radiation that can escape from the light ring generated between the surfaces 112a, 112b, 112c, 112e, to limit the heat generation in this way to the upper part.

[0076] The reflecting surfaces can be made of a high-reflectance coating, such as, but not limited to, gold, silver, or polished aluminum, and protected by a transparent layer, or can be made of a dielectric multilayer material capable of increasing the reflectivity of the matrix. The external structure of the heating hood 103 is preferably made of a metal material, such as aluminum, ensuring proper heat dissipation, absorption of the dispersed radiation, and proper robustness.

[0077] The system of truncated conical reflecting surfaces 112a, 112b, 112c, 112e, and the relative angles of inclination a, b, g, and d, is configured to capture most of the infrared radiation in the Figure 3 radiation ring shown. In addition, the radiation path is designed to heat the preform in a proper and homogeneous way through the thickness of the preform and along the vertical direction. In addition, the so-called "hot radiation disc" has a reduced thickness so as to have a more local and precise heating. The heating of the portion of the preform P to be radiated is thus optimized, and the radiation that could return to the optical fiber 113 and from the optical fiber to the laser source is minimized, which would otherwise be lost. In order for the system of the present application not to be dependent on the specific geometry of the preform, as said, the high absorption band 112d limits the radiation to the upper part of the heating hood.

[0078] The vertical movement of the preform P, as described above, following a predetermined law of movement, not only radiates the entire preform P (except for the neck above the finishing ring), but also increases or decreases the radiation time according to the portion of the preform to be treated and the specific heating requirements.

[0079] Moreover, in addition to the variation of the sliding speed (movement law) of the preform inside the electromagnetic heating radiation ring, the laser source has its own high-precision adjustability.

[0080] The possibility of adjusting the intensity of the emitted radiation and of adjusting the movement law of the relative preform heating hood movement is a significant advantage of the device of the present application. In fact, it is known that the conical portion of the preform, arranged immediately below the finishing element, is generally subjected to greater deformations and therefore can require greater heating with respect to other areas of the preform to obtain high plasticity. Another factor that can determine a longer or shorter duration of exposure of an area of the preform to heating radiation is the variation in the thickness of the preform.

[0081] In one embodiment, the movement law will comprise the following steps:

[0082] a) introducing the bottom F of the preform P into the opening 109 of the heating hood 103;

[0083] b) relatively sliding the tubular portion T of the preform P with respect to the heating hood 103 at a first speed vi;

[0084] c) relatively sliding the conical portion C of the preform P with respect to the heating hood 103 at a second speed v2 lower than said first speed vi;

[0085] d) adjusting the intensity of the infrared radiation as a function of said speeds vi, v2 and of the thickness S of the wall of the preform P,

[0086] wherein said first speed vi and second speed v2 are inversely proportional to said thickness S for the same intensity of infrared radiation.

[0087] As previously mentioned, the variation of the sliding speed of the preform is easily obtained thanks to the drives available on the market, which drive a stepper motor or a permanent magnet or brushless motor. The operating computer / PLC of the machine then stores the specific movement law for each type of preform and for each type of container.

[0088] The embodiments described herein concern the vertical movement of the preform P, while the heating hood 103 remains vertically fixed. Alternatively, the preform P and the relative clamp 102 can remain fixed and the heating hood 103 supported by the arm 208 is moved vertically with similar actuators 104, moving screws 106 and guides 107, as described above and as shown in Figure 5 Fig. 4.

[0089] In one embodiment, the support structure has an inverted L shape and comprises a horizontal portion 108a on which the actuator 104 and the clamp 102 are fixed. The arm 208 in turn has a stepped shape and comprises a first end portion 208a connected to the screw 106 to move the heating hood 103, a second end portion 208b which supports the heating hood 103, and a connecting lifting element 208c.

[0090] In Figures 6 to 8 In the different embodiments shown, the preform P is moved in inversion, i.e. with the neck arranged underneath. In this embodiment, the heating hood 103 is fixed, while the preform P is vertically movable, but in different embodiments the preform can be fixed and the heating hood 103 can be movable, as described above.

[0091] As Figures 6 to 8 shown, the support structure 108 has an inverted L shape and comprises a horizontal portion 108a on which the actuator 104 is fixed, and the arm 208 comprises an end portion 208b which supports the heating hood 103 so that the opening 109 of the heating hood 103 faces downwards.

[0092] The clamp 102 is supported by a support element 105 which is driven by the screw 106 and guided by a low-friction seat 107. The support element 105 comprises an inversion member 210 of the preform P which is adapted to bring the preform P from a normal condition, with the preform opening upwards, to an inverted condition, with the preform opening downwards, and vice versa.

[0093] The inversion member 210 comprises a first bevel gear 211a and a second bevel gear 211b and an actuator 212, said bevel gears being meshed with each other and having mutually perpendicular axes 213, 214.

[0094] The actuator 212 is operatively associated with the axis 213 coaxial with the first bevel gear 211a, while the axis 214 coaxial with the second bevel gear 211b coincides with the longitudinal axis 215 of the clamp 102. Therefore, the rotation of the actuator 212 causes the rotation of the first bevel gear 211a, which in turn causes the rotation of the second bevel gear 211b along a perpendicular axis, and the rotation of the clamp 102, which holds the preform P, with this rotation. This mechanism is necessary if the movement devices 2, 3 of the preforms are configured at the inlet and at the outlet of the oven 1, respectively, to move the preforms P in the normal condition, i.e. with the opening upwards. If, vice versa, such movement devices 2, 3 are able to move the preforms in the inverted condition, the inversion member 210 is no longer necessary.

[0095] The oven 1 can comprise a light collector able to transfer the radiation fed from a fixed static laser source to each heating hood 103 to the corresponding heating hood 103. According to the overall dimensions, the light collector 364 can be alternatively provided in the upper part of the carousel 303. The light collector transfers the radiation from the optical fiber of the laser source to the corresponding optical fiber 113 that can move together with the heating device 101, which feeds the heating hood 101.

[0096] The light collector can be connected to a plurality of laser sources. Alternatively, a light collector can be provided that receives the radiation from a single laser source and distributes it according to the appropriate proportions as a function of time to the various heating hoods 103 in the different heating steps. In fact, the various preforms enter the oven consecutively and have a phase shift, which makes it necessary to adjust the infrared radiation for each preform P along the path in the oven 1. This adjustment of the intensity of the radiation sent to each heating hood can be made by using photonic crystals that act as switches and regulators of the intensity of the radiation that passes through the photonic crystals by means of a variable electromagnetic field applied to such crystals. Thus, the radiation supplied by a single laser source, once distributed to the various heating units, can be activated and adjusted in intensity by acting on the photonic crystals and obtaining for each preform P a separate switching on, switching off and adjustment according to its heating step and according to the specific area involved.

[0097] A variant comprises arranging a laser source for each heating hood 103, which is directly provided on the heating device 101, which allows to avoid the use of a light collector.

[0098] In a particularly preferred embodiment, the electromagnetic radiation emitted by the laser device is in the following wavelength ranges:

[0099] - 1620 nm - 2100 nm, preferably 1652 nm - 1674 nm and / or

[0100] - 1701 nm - 1880 nm and / or

[0101] - 1907 nm - 1919 nm and / or

[0102] - 1951 nm - 2000 nm and / or

[0103] - 1803 nm - 1813 nm and / or

[0104] - 1903 nm - 1913 nm and / or

[0105] - 1941 nm - 1961 nm and / or 1972 nm - 2012 nm.

[0106] Even more preferably, the electromagnetic radiation has a wavelength of 1661 nm and / or 1721 nm and / or 1908 nm and / or 1951 nm and / or 1992 nm, most preferably a wavelength of about 1940-1955 nm.

[0107] It is also possible to use an optical heating path to convey the UV-C radiation from the LED or laser device to sterilize the preform, as described in Italian patent application No. 102019000009591 filed by the same Applicant on 20 June 2019.

[0108] Many advantages can be obtained with the heating system of the present application.

[0109] In fact, the heating system of the present application allows to obtain:

[0110] - high energy efficiency, by using the absorption wavelengths in the predetermined band and by limiting the heat losses both by the presence of the reflective elements associated with each preform;

[0111] - maximum precision of the heating curve, since the heating hood 103 generates a series of external and internal reflections (this is studied by the geometry of the truncated cone surfaces 112a, 112b, 112c, 112e), which leads to a proper absorption of the radiation and, as a consequence, to the optimal heating of the material, with a precision much higher than the current heating systems with lamps. The temperature distribution and the related gradients allow the present application to provide a much higher heating quality than the heating qualities available today, thanks to the heat deposition phenomenon obtained directly inside the material by the correct penetration of the radiation selected. Finally, the band 112d with high absorption treatment placed on the metal cylinder absorbs any residual radiation that can escape from the light ring generated between the surfaces 112a, 112b, 112c, 112e, and thus limits the heat production to the upper part;

[0112] - the heating time reaches one order of magnitude lower than in the current systems, depending on the power of the laser source used, which allows to limit the size of the oven and thus to a lower thermal diffusion.

[0113] - wide adjustability of the heating by varying the intensity of the laser source and by varying both the motion of the preform P or of the heating hood 103;

[0114] - absence of thermal inertia, which allows to restart immediately and thus makes the entire production line more efficient;

[0115] - possibility to adjust the machine speed according to the trend of the production line during the operating step, a feature not obtainable in the ovens currently on the market, also thanks to the absence of thermal inertia and to the variability of the radiation intensity due to the high dynamic response of the laser source;

[0116] - the possibility of integrating a UV-C radiation source in the same optical path to pair the sanitization of the preforms with the heating;

[0117] - the heat dissipation is significantly reduced, with the result of saving cooling energy to maintain the working environment of the machine at the correct temperature and to avoid very hot surfaces, which are therefore potentially dangerous for the operators;

[0118] - the size of the heating system can be reduced while maintaining the same production capacity with respect to a traditional preform oven;

[0119] - there is no ionizing radiation (unless coupled with a UV-C radiation source) because the laser source is monochromatic in the infrared range, which prevents the formation of harmful substances inside the plastic of the preforms.

[0120] It is clear that only some specific embodiments of the present application have been described, and that the person skilled in the art will be able to make all the necessary changes to adapt it to specific applications without departing from the scope of protection of the present application.

[0121] For example, the heating device 101 described here can also be inserted into a rotary heating system, such as the one described in Italian patent application No. 102019000012549 in the name of the same Applicant, of 22 July 2019, or into a continuous linear system.

[0122] Figure 9 An example of a rotary system is shown in Fig. 6, in which the heating device 101 of the present application is installed, in particular in the embodiment of Figures 6 to 8 Fig. 5.

[0123] The heating device 101 is installed on a turntable 250 that rotates by means of motorized means 251. The lower part of the turntable is arranged in a container base 252, which also comprises a light collector 253, which is connected upstream to a laser source (not shown) and downstream to the heating hood 103, as previously described. The turntable 250 is synchronized with a distribution star (not shown) that moves the preforms P into and out of the turntable 250.

Claims

1. A heating device (101) for a preform (P) configured so as to be positioned outside the preform (P) and to radiate electromagnetic radiation in the infrared range, so as to form in such device a radiation disc radially symmetrical with respect to the center of the preform axis, said heating device comprising heating hoods (103) configured to receive the preform (P) in said hoods, and said heating device comprising a laser device for each heating hood (103), wherein, The electromagnetic radiation emitted by the laser device is in the wavelength range 1620-2100 nm, wherein the heating hood (103) comprises a substantially hollow cylindrical body (103a) and a conical portion (103b) arranged at one end of the cylindrical body (103a), and wherein the heating device comprises a collimator member (110) connected to an optical fiber (113) to convey a collimated beam of the electromagnetic radiation, wherein, downstream of the optical path of the collimator member (110), the heating device (101) comprises a first lens (111a) arranged at the end of the conical portion (103b) connected to the collimator member (110) and a second lens (111b) arranged in a lower segment of the cylindrical body (103a) so as to generate a radiation column (R1) with proper homogeneity.

2. The heating device (101) according to claim 1, comprising a plurality of reflecting surfaces (112a, 112b, 112c, 112e), each of which is configured to radiate a preform (P) individually from the outside.

3. The heating device (101) according to any one of claims 1 or 2, wherein The laser device is a device with diode light source, semiconductor light source or fiber optic light source.

4. The heating device (101) according to claim 1, comprising a clamp (102) vertically movable so as to assume an elevated position in which the preform (P) is disengaged from the heating hood (103) and a lowered position in which the preform (P) is inserted into the heating hood (103), the clamp (102) being moved by an actuator (104) configured to follow a predetermined motion law.

5. The heating device (101) according to claim 2, comprising a clamp (102) vertically movable so as to assume an elevated position in which the preform (P) is disengaged from the heating hood (103) and a lowered position in which the preform (P) is inserted into the heating hood (103), the clamp (102) being moved by an actuator (104) configured to follow a predetermined motion law.

6. The heating device (101) according to claim 4 or 5, wherein The actuator (104) is a stepper motor, a servo motor, a linear motor or a brushless motor.

7. The heating device (101) according to any one of claims 1 to 2, comprising a clamp (102) vertically fixed, the heating hood (103) being supported by an arm (208) vertically movable by an actuator (104) configured to follow a predetermined motion law so as to assume an elevated position in which the preform (P) is inserted into the heating hood (103) and a lowered position.

8. The heating device (101) according to claim 7, wherein The actuator (104) is a stepper motor, a servo motor, a linear motor or a brushless motor.

9. The heating device (101) according to claim 4 or 5, wherein The clamp (102) is supported by a support (105) which is moved by a screw (106) and guided by a low-friction seat (107), the assembly consisting of the movable clamp (102), the actuator (104), the screw (106) and the low-friction seat (107) being mounted on a support structure (108).

10. The heating device (101) according to claim 7, wherein The arm (208) is moved by a screw (106) and guided by a low-friction seat (107).

11. The heating device (101) according to any one of claims 1 to 2, wherein The heating device comprises a clamp (102), wherein the clamp (102) holds the preform (P) in a turned-over condition, i.e. with the opening of the preform facing downwards, and wherein the heating hood (103) is arranged with the opening (109) facing downwards, the clamp (102) being vertically movable so as to assume a lowered position in which the preform (P) is disengaged from the heating hood (103) and a raised position in which the preform (P) is inserted into the heating hood (103), the clamp (102) being moved by an actuator (104) configured to follow a predetermined motion law.

12. The heating device (101) according to claim 11, comprising a turning member (210) for the preform (P), which turns the preform from a normal condition, with the opening facing upwards, to a turned-over condition and vice versa.

13. The heating device (101) according to any one of claims 1 to 2, comprising a sliding member (270) comprising a main body (271) into which a mandrel (272) for the preform (P) is slidably inserted, the mandrel (272) being movable along a vertical direction between a raised position and a lowered position, the sliding member (270) being connected to the heating hood (103) by a connecting element (273) so that the heating hood (103) is aligned with and positioned below the mandrel (272).

14. The heating device (101) according to claim 5, wherein The heating hood (103) comprises a reflecting portion (103c) provided at the other opposite end of the cylindrical body (103a) and comprises an opening (109) at the reflecting portion (103c) coaxial with the longitudinal axis (X-X) of the heating hood (103), the collimator member (110) being located at the end of the conical portion (103b), wherein the reflecting portion (103c) comprises the plurality of reflecting surfaces (112a, 112b, 112c, 112e).

15. The heating device (101) according to claim 14, wherein The plurality of reflective surfaces (112a, 112b, 112c, 112e) is a system of truncated conical reflective surfaces comprising, in succession from the cylindrical body (103a) towards the opening (109), a first truncated conical reflective surface (112a) flaring outwards, a second truncated conical reflective surface (112b) converging towards the longitudinal axis (X-X) of the heating hood (103) and a third truncated conical reflective surface (112c) converging towards the longitudinal axis (X-X), and a fourth truncated conical reflective surface (112e) flaring outwards arranged between the cylindrical body (103a) and the first truncated conical reflective surface (112a), wherein the first (112a), second (112b), third (112c) and fourth (112e) truncated conical reflective surfaces are each inclined by a first (a), second (b), third (g) and fourth (d) angle, respectively, with respect to a respective cylindrical surface coaxial to the longitudinal axis (X-X), wherein the first angle (a) is smaller than the second angle (b) and greater than or equal to the third angle (g), wherein the fourth angle (d) is smaller than the first angle (a), and wherein a substantially cylindrical absorbing surface (112d) is arranged between the cylindrical body (103a) and the first truncated conical reflective surface (112a).

16. The heating device (101) according to claim 1, wherein The first lens is an axicon and the second lens is an axicon.

17. An oven (1) for preforms (P) comprising a conveying device (8) suitable to move the preforms (P) along a path and a plurality of heating devices (101) according to any one of claims 1 to 16, so that one heating device (101) corresponds to each preform (P), the oven (1) being operatively connected, at the inlet and at the outlet, respectively, of the oven (1), to the moving device (2, 3) for the preforms (P).

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