Heating device and heating method for plastic bottle blank

Abstract

The invention discloses a heating device for a plastic bottle blank, the heating device comprises a laser emitting device and a corner reflector assembly, the corner reflector assembly is arranged on the outer side of the plastic bottle blank, laser emitted by the laser emitting device irradiates the plastic bottle blank to heat the plastic bottle blank, and the corner reflector assembly is arranged on the outer side of the plastic bottle blank. The corner reflector assembly collects the laser transmitted and reflected from the plastic bottle blank and reflects the laser back to the plastic bottle blank. By arranging the corner reflectors, reflected light and transmission light which are lost originally are effectively collected and accurately reflected back to a plastic bottle blank, and therefore the energy utilization efficiency of laser is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic preforms, and particularly to a heating device and a heating method for plastic preforms. Background Art

[0002] In the field of plastic bottle production, the heating link of plastic preforms is crucial, and its heating effect directly affects the quality and efficiency of subsequent blow molding. Traditional plastic preform heating methods, such as lamp tube heating and hot air heating, have many drawbacks. When using lamp tube heating, the heat transfer efficiency is low, resulting in a long heating time, high energy consumption, and it is difficult to ensure heating uniformity. It is easy to cause local overheating or insufficient heating of the preform, thereby affecting the quality stability of the finished plastic bottle, such as uneven wall thickness and inconsistent strength of the bottle body. Although hot air heating can improve the heating uniformity to a certain extent, there is a large energy loss during the transmission of hot air, the heating efficiency improvement is limited, and the equipment structure is complex with high maintenance costs.

[0003] With the continuous development of laser technology, laser heating has gradually been applied to the field of plastic preform heating due to its advantages such as concentrated energy, fast heating speed, and easy control. However, in practical applications, it is found that when laser heats plastic preforms, a large amount of light reflected and transmitted from the preforms is wasted and fails to fully act on the preform heating, resulting in low light energy utilization rate. This not only increases the production cost but also limits the further promotion and application of laser heating technology in plastic bottle production.

[0004] Currently, some technologies attempt to use plane mirrors to recover part of the reflected light. However, due to the relatively high optical roughness of the surface of plastic preforms, the directions of the light transmitted and reflected from the surface of plastic preforms are disordered, resulting in the plane mirror being unable to comprehensively and efficiently collect the reflected light and transmitted light in different directions, thereby making the light energy utilization rate and heating efficiency low. Summary of the Invention

[0005] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a heating device and a heating method for plastic preforms to solve at least one of the above technical problems.

[0006] According to one aspect of the specification of the present invention, there is provided a heating device for plastic preforms. The heating device includes a laser emission device and a corner reflector assembly. The corner reflector assembly is arranged outside the plastic preform. The laser emitted by the laser emission device irradiates the plastic preform to heat the plastic preform, and the corner reflector assembly collects and reflects the laser transmitted and reflected from the plastic preform back onto the plastic preform.

[0007] Further, the corner reflector assembly includes at least one corner reflector; wherein, at least one of the corner reflectors is composed of a plurality of corner reflector units, and each corner reflector unit includes three mutually perpendicular reflecting surfaces.

[0008] Further, the corner reflector is made of an optical material, and a high-reflection film is plated on the surface of the corner reflector.

[0009] Further, the heating device further includes an angle and position adjuster, which is connected to the corner reflector assembly and is used to adjust the position and angle of the corner reflector assembly.

[0010] Further, the heating device further includes a temperature monitoring system, which is connected to the laser emitting device and is used to monitor the temperature data of the plastic preform in real time and adjust the light output power of the laser emitting device based on the temperature data.

[0011] Further, the laser emitting device emits corresponding laser based on laser heating parameters; wherein, the laser heating parameters are determined according to the material and target temperature of the plastic preform, and the laser heating parameters include the wavelength and power of the laser.

[0012] Further, the heating device further includes a rotating table, which is used to place the plastic preform and make the plastic preform rotate at a preset speed.

[0013] Further, the heating device further includes a beam shaper, which is used to perform beam shaping on the laser emitted by the laser emitting device.

[0014] According to one aspect of the specification of the present invention, there is provided a heating method for a plastic preform, which is implemented by using the above-mentioned heating device for a plastic preform. The heating method includes:

[0015] Determine laser heating parameters according to the material and target temperature of the plastic preform; wherein, the laser emitting device emits corresponding laser based on the laser heating parameters; the laser heating parameters include the wavelength and power of the laser;

[0016] Turn on the laser emitting device so that the laser irradiates the plastic preform; wherein, the light transmitted and reflected from the plastic preform is reflected back by the corner reflector assembly and irradiates the plastic preform again;

[0017] Real-time monitor the temperature data of the plastic preform through the temperature monitoring system, and when the plastic preform reaches the target temperature, control the laser emitting device to turn off through the temperature monitoring system;

[0018] Further, before turning on the laser emission device, the heating method further includes: adjusting the position and angle of the corner reflector assembly according to the size and shape of the plastic preform through an angle and position adjuster.

[0019] In the above technical solution, by cleverly arranging a corner reflector in the laser heating device, the reflected light and transmitted light that would otherwise be lost are effectively collected and accurately reflected back onto the plastic preform.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The present invention improves the light energy utilization rate: through the effective collection and reuse of the reflected light and transmitted light by the corner reflector assembly, compared with a plane mirror, the utilization rate of laser energy is significantly improved, the waste of light energy is reduced, and the energy consumption in the production process is lowered.

[0022] (2) The present invention enhances the universality of the equipment: Due to its unique optical performance - the corner reflector can reflect the light incident from any angle back in the original incident direction, so there is no need to accurately adjust its angle and position. Only need to install the corner reflector assembly at a certain distance in the direction of the transmitted and reflected laser of the plastic preform, and manually adjust the position and angle of the corner reflector assembly, so that the device of the present invention can adapt to the target temperature of plastic preforms of different sizes and shapes, enhancing the universality and flexibility of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural diagram of a heating device for a plastic preform provided in an embodiment of the present invention

[0024] Figure 2 It is a flowchart of a heating method for a plastic preform provided in an embodiment of the present invention

[0025] Figure 3 It is a structural diagram of a corner reflector unit provided in an embodiment of the present invention

[0026] Figure 4 It is a spectral analysis result diagram of a PP preform provided in an embodiment of the present invention

[0027] Figure 5 It is a structural diagram of a galvanometer-based beam shaper provided in an embodiment of the present invention

[0028] Figure 6 It is a structural diagram of a corner reflector provided in an embodiment of the present invention.

[0029] In the figure: 1. Laser emission device; 2. Beam shaper; 3. Corner reflector assembly; 31. Corner reflector unit; 4. Angle and position regulator; 5. Rotary table; 6. Temperature monitoring system; 100. Heating device; 200. Plastic preform. Detailed implementation manners

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0032] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the connection inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0033] In the present invention, unless otherwise clearly defined and limited, the fact that the first feature is "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the fact that the first feature is "above", "over" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The fact that the first feature is "below", "under" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or only means that the horizontal height of the first feature is lower than that of the second feature.

[0034] Please refer to the attached Figure 1, this embodiment provides a heating device 100 for plastic bottle preforms, which includes a laser emitting device 1, a beam shaper 2, a corner reflector assembly 3, a rotating table 5, an angle and position adjuster 4, and a temperature monitoring system 6. The laser emitted by the laser emitting device 1 irradiates the plastic bottle preform 200 to heat the plastic bottle preform 200. The beam shaper 2 is used to shape the laser emitted by the laser emitting device 1. The corner reflector assembly 3 is used to collect and reflect back onto the plastic bottle preform 200 the laser transmitted and reflected from the plastic bottle preform 200. The angle and position adjuster 4 is used to adjust the angle and position of the corner reflector assembly 3. The rotating table 5 is used to drive the plastic bottle preform 200 to rotate. The temperature monitoring system 6 is used to monitor the temperature of the plastic bottle preform 200. In this embodiment, the material of the plastic bottle preform 200 includes, but is not limited to, PP material and PET material.

[0035] Furthermore, the laser emitting device 1 includes a laser generator and an optical path adjustment component. The laser generator is used to emit laser, and the optical path adjustment component is used to emit the laser emitted by the laser generator along a preset path. In this embodiment, the laser emitting device 1 emits corresponding laser based on laser heating parameters; wherein, the laser heating parameters include, but are not limited to, the wavelength and power of the laser.

[0036] Please refer to Figure 3 and Figure 6 , the corner reflector assembly 3 is arranged outside the plastic bottle preform 200, and the corner reflector assembly 3 includes at least one corner reflector. Each corner reflector is composed of multiple corner reflector units 31, and each corner reflector unit 31 includes 3 mutually perpendicular reflecting surfaces. The unique structure of the corner reflector unit 31 enables it to efficiently collect the reflected light and transmitted light from any angle and reflect them back along the original direction to the plastic bottle preform 200. In this embodiment, the corner reflector is made of a high-purity and low-absorption optical material, and a high-reflection film for a specific laser wavelength is plated on the surface of the corner reflector to minimize the loss of light energy during the reflection process. In this embodiment, the number, arrangement mode, and installation angle of the corner reflectors of the corner reflector assembly 3 can be optimized and adjusted according to the shape, size of the plastic bottle preform 200, and specific requirements of laser heating, and are not limited herein. It can be understood that the number of corner reflector units required for each corner reflector is related to the size of each corner reflector unit and the size of the plastic bottle preform. Therefore, as long as the size of the corner reflector is larger than the size of the plastic bottle preform, most of the light transmitted and reflected from the plastic bottle preform can be reflected back. For example, assuming that the size of the used plastic bottle preform is about 70×23mm and the area of the corner reflector unit is 15.6mm², then at least about 70*23 / 15.6 = 104 units are required.

[0037] Furthermore, the rotary table 5 is used to stably place the plastic preform 200, and by setting the rotation speed of the rotary table 5, the plastic preform 200 can rotate uniformly at a preset speed during the heating process, so as to ensure that all parts of the plastic preform 200 are heated evenly and avoid quality problems caused by uneven local heating. It can be understood that in this embodiment, the laser scanning path is linear and needs to cooperate with the rotation of the plastic preform 200 to achieve uniform heating of the entire plastic preform 200. Preferably, the rotation speed of the rotary table 5 is 120 rpm.

[0038] Please refer to Figure 5 , the beam shaper 2 is used to shape the laser beam emitted by the laser emitting device 1 to obtain a light spot with a specific shape and size, so as to more conveniently and efficiently heat the plastic preform 200. In this embodiment, a pseudo beam shaping scheme based on galvanometer scanning is selected. The basic principle is to achieve beam scanning and plan the scanning path by quickly swinging a pair of reflectors placed orthogonally at 45°. Combining the high-frequency swing of the galvanometer can achieve any light spot shape (where the galvanometer speed can be selected in the range of 0-8000 mm / s). The advantage of this scheme is strong applicability, that is, it can be applied to plastic preforms 200 of different sizes and specifications. In some other feasible embodiments, the beam shaper 2 can also be based on a microlens array group, a diffractive optical element (Diffractive Optical Element, DOE), and an aspherical lens group to achieve beam shaping. In addition, it should be noted that the beam shaping based on the galvanometer is pseudo shaping, that is, it does not really change the light spot shape, but the laser beam forms a light spot with a specific shape and size due to the rapid movement of the path.

[0039] Furthermore, the angle and position adjuster 4 is connected to the corner reflector assembly 3. The staff can manually operate the angle and position adjuster 4 according to the heating situation of the plastic preform 200 to adjust the angle and position of the corner reflector assembly 3, thereby improving the energy utilization rate of the laser. It should be noted that due to the unique optical characteristics of the corner reflector assembly 3 - it can reflect the incident light from any angle back in the original incident direction, so there is no need to accurately adjust the position and angle of the corner reflector assembly 3. Only by roughly manually adjusting the position and angle of the corner reflector assembly 3 can the corner reflector assembly 3 catch all the reflected light or transmitted light. Preferably, the corner reflector assembly 3 is adjusted to be close to the plastic preform 200 and roughly parallel to the plastic preform 200. It can be understood that adjusting the corner reflector assembly 3 to be close to and parallel to the plastic preform 200 is not because the reflection effect is better in this way, but because the required size of the corner reflector assembly 3 can be reduced. In this embodiment, the installation distance reference range of the corner reflector assembly 3 is 20 mm - 100 mm.

[0040] Further, the temperature monitoring system 6 is connected to the angular laser emitting device 1. The temperature monitoring system 6 monitors the temperature data of the plastic preform 200 in real time to adjust the light output power of the laser emitting device 1 based on the temperature data in real time. In this embodiment, the temperature monitoring system 6 includes a temperature sensor, a data acquisition module, and a control system. The temperature sensor faces the plastic preform 200 and collects the temperature data on the surface of the plastic preform 200 in real time. The data acquisition module quickly transmits the temperature data collected by the temperature sensor to the control system. The control system intelligently regulates parameters such as the light output power of the laser emitting device 1 according to the temperature data. When the temperature sensor detects that the temperature of the plastic preform 200 is higher than the target temperature (the target temperature refers to the temperature corresponding to the plastic preform 200 reaching the target blow molding state, and the target blow molding state refers to the state where the plastic preform 200 is suitable for blow molding, and at this time, there is no need to heat the plastic preform 200 anymore), the control system controls the laser emitting device 1 to turn off. When the temperature sensor detects that the temperature of a certain part of the plastic preform 200 is much higher or much lower than other parts (that is, the plastic preform 200 is unevenly heated), the control system automatically adjusts the light output path and light output power of the laser emitting device 1 to ensure the stability and uniformity of the heating process of the plastic preform 200.

[0041] Please refer to Figure 2 , the present invention also provides a heating method for the plastic preform 200, using the heating device 100 described above to heat the plastic preform 200, including the following steps (steps S101 - S105):

[0042] Step S101, determine the laser heating parameters according to the material and target temperature of the plastic preform; wherein, the laser emitting device emits corresponding laser based on the laser heating parameters. The laser heating parameters include the wavelength and power of the laser;

[0043] In step S101, it can be understood that the staff needs to select a laser emitting device 1 with a suitable wavelength range according to the material of the plastic preform. At the same time, the light output power of the laser emitting device 1 also needs to be initially set according to the target temperature. Of course, the light output power of the laser emitting device 1 can be adjusted according to the actual heating situation of the plastic preform 200 subsequently. In this embodiment, a spectrophotometer (not shown in the figure) is used to perform a spectral absorption test on the material of the plastic preform 200 to obtain the best spectral absorption rate curve of the material of the plastic preform 200 (the result is as shown in the appendix Figure 4 . It should be noted that in actual production, spectral absorption rate analysis can be performed on any required temperature, and the appendix Figure 4The PP spectral absorption rate relationship diagram shown (which is not a limitation on the scope of the present invention), and then select an appropriate laser wavelength according to the spectral absorption rate. It should be noted that a low absorption rate indicates that the plastic preform 200 material has strong laser transmissibility at this wavelength, the interaction between light and matter is weak, and the heat conversion rate is poor. While an excessively high absorption rate indicates that the plastic preform 200 material has weak laser transmissibility at this wavelength, that is, the laser of this wavelength cannot completely penetrate the material and only interacts with the surface of the material, which in turn causes too large a temperature difference inside and outside the plastic preform 200 and uneven heating. Therefore, it is particularly important to select a laser generator with an appropriate absorption rate corresponding wavelength. Preferably, select a laser generator with an appropriate wavelength within the range of 25% - 50% absorption rate. For example, for a PP preform (i.e., a plastic preform 200 made of PP material), select a laser generator with a wavelength of 1070 nm. The absorption rate of this wavelength for the PP preform is 25.39%, the light output mode of the laser generator is continuous, and the power is 100 - 3000 w. In addition, it is also necessary to consider whether there is a mature industrial laser generator in the corresponding optimal band, and determine the wavelength of the laser generator by comprehensively considering both factors.

[0044] It should be noted that before turning on the laser emitting device 1, it is also necessary to select a beam shaping method according to the type, size and heating effect of the plastic preform 200. At the same time, the plastic preform 200 needs to be placed in the turntable 5, and the motor of the turntable 5 is turned on to make the plastic preform 200 rotate. In addition, a corner reflector assembly 3 needs to be assembled around the plastic preform 200. And according to the size and shape of the plastic preform 200, the position and angle of the corner reflector assembly 3 are adjusted by manually operating the angle and position adjuster 4 by the staff.

[0045] Step S103, turn on the laser emitting device so that the laser irradiates the plastic preform; wherein, the light transmitted and reflected from the plastic preform is reflected back by the corner reflector assembly and irradiates the plastic preform again.

[0046] In step S103, the laser emission device 1 emits corresponding laser based on the laser heating parameters. The laser passes through the beam shaper and then irradiates on the plastic preform 200 to heat the plastic preform 200. However, when the laser heats the plastic preform 200, a large amount of the laser reflected and transmitted from the plastic preform 200 is wasted and fails to fully act on the heating of the plastic preform 200. Therefore, in the present invention, by providing the corner reflector assembly 3, the reflected light and transmitted light that would otherwise be dissipated are effectively collected and accurately reflected back onto the plastic preform 200, thereby improving the light utilization rate. In this embodiment, corner reflectors with different cycle sizes can be selected for plastic preforms 200 of different sizes. The corner reflector cycle refers to the size of each corner reflector unit 31 that makes up the corner reflector. The smaller the size of the corner reflector unit 31, the smaller the corresponding light offset amount. It should be noted that the optical characteristic of the corner reflector is to reflect the incident light back in the original direction, but there will be a light offset amount in space. This light offset amount is related to the size of the corner reflector unit 31. Without considering the factor of light diffraction, theoretically, the smaller the corner reflector unit 31, the smaller the light offset amount caused, and the higher the light recovery efficiency.

[0047] Step S105, the temperature monitoring system monitors the temperature data of the plastic preform in real time. When the plastic preform reaches the target temperature, the temperature monitoring system controls the laser emission device to turn off;

[0048] In step S105, the temperature monitoring system 6 monitors the temperature data of the plastic preform 200 in real time. When the temperature monitoring system 6 monitors that the plastic preform 200 is heated to the target temperature, it feeds back a signal to the laser emission device 1, and the laser emission device 1 stops heating. In the embodiment of the present invention, an optoelectronic sensor is used to monitor the overall temperature of the plastic preform 200. In addition, in some feasible embodiments, a thermal imaging camera combined with a galvanometer can also be used to achieve segmented temperature control of the plastic preform 200.

[0049] This embodiment will be described by taking the heating of a PP preform with a laser emission device 1 as an example. At room temperature, the PP preform is in a glassy state. It transforms from the glassy state to a rubbery state at 130°C and reaches the target blow molding state at 140°C. The goal of this embodiment is to heat the PP preform to 140°C (i.e., the target temperature) and then turn off the laser emission device 1. In addition, the results show that with a corner reflector installed, the time required to heat the PP preform to 140°C is 37 s. When the corner reflector is replaced with a plane mirror and other conditions remain the same, the time required to heat the PP preform to 140°C is 42 s. Without any reflection system and with other conditions being the same, the time required to heat the PP preform to 140°C is 66 s. Compared with the plane mirror, the heating efficiency of the corner reflector is increased by 11.9%, and compared with no reflection system, the efficiency is increased by 43.94%. Therefore, by arranging a corner reflector in the heating device 200 of the present invention, the utilization rate of laser energy is significantly improved, the waste of light energy is reduced, and the energy consumption in the production process is lowered.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A heating device for a plastic bottle preform, characterized in that, The heating device includes a laser emitting device and a corner reflector assembly. The corner reflector assembly is arranged outside the plastic preform. The laser emitted by the laser emitting device irradiates the plastic preform to heat the plastic preform. The corner reflector assembly collects and reflects the laser transmitted and reflected from the plastic preform back onto the plastic preform.

2. The heating device for a plastic bottle preform according to claim 1, characterized in that, The corner reflector assembly includes at least one corner reflector; wherein, at least one of the corner reflectors is composed of a plurality of corner reflector units, and each corner reflector unit includes three mutually perpendicular reflecting surfaces.

3. The heating device for a plastic bottle preform according to claim 2, wherein, The corner reflector is made of an optical material, and a high-reflection film is plated on the surface of the corner reflector.

4. The heating device for a plastic bottle preform according to claim 3, characterized in that, The heating device further includes an angle and position regulator, which is connected to the corner reflector assembly and is used to adjust the position and angle of the corner reflector assembly.

5. The heating device for a plastic bottle preform according to claim 4, wherein, The heating device further includes a temperature monitoring system, which is connected to the laser emitting device and is used to monitor the temperature data of the plastic preform in real time and adjust the light output power of the laser emitting device in real time based on the temperature data.

6. The heating device for a plastic bottle preform according to claim 1, characterized in that, The laser emitting device emits corresponding laser based on laser heating parameters; wherein, the laser heating parameters are determined according to the material and target temperature of the plastic preform, and the laser heating parameters include the wavelength and power of the laser.

7. The heating device for a plastic bottle preform according to claim 1, characterized in that, The heating device further includes a rotating table, which is used to place the plastic preform and make the plastic preform rotate at a preset speed.

8. The heating device for a plastic bottle preform according to claim 1, wherein, The heating device further includes a beam shaper, which is used to shape the laser emitted by the laser emitting device.

9. A heating method for a plastic bottle preform, characterized in that, Implemented by using the heating device for plastic preforms according to any one of claims 1-8, the heating method includes: Determine laser heating parameters according to the material and target temperature of the plastic preform; wherein, the laser emitting device emits corresponding laser based on the laser heating parameters; the laser heating parameters include the wavelength and power of the laser; Turn on the laser emitting device so that the laser irradiates the plastic preform; wherein, the light transmitted and reflected from the plastic preform is reflected back by the corner reflector assembly and irradiates the plastic preform again; Real-time monitor the temperature data of the plastic preform through the temperature monitoring system. When the plastic preform reaches the target temperature, control the laser emitting device to turn off through the temperature monitoring system.

10. The heating method of a plastic bottle preform according to claim 9, characterized in that, Before turning on the laser emitting device, the heating method further includes: Adjust the position and angle of the corner reflector assembly through the angle and position regulator according to the size and shape of the plastic preform.

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