A method of preheating a plastic bottle blank

Abstract

This invention discloses a method for preheating plastic preforms, relating to the field of preform processing technology. The invention includes: delivering hot air through a pipeline to a feeding machine, installing a heating mechanism on the feeding machine, and utilizing the combined action of the hot air and the heating mechanism to preheat the plastic preforms within the feeding machine; setting up a temperature monitoring device to monitor and control the temperature within the feeding machine; and feeding the preheated plastic preforms, which have reached a specified temperature, into a blow molding machine for subsequent processing. This invention not only effectively reduces the overall energy consumption of the blow molding machine but also makes the temperature of the plastic preforms easier to control, effectively ensuring the production efficiency and quality of the plastic preforms.

Description

Technical Field

[0001] This invention belongs to the field of preform processing technology, and in particular relates to a preheating method for plastic preforms. Background Technology

[0002] When processing blown plastic bottles using a two-step blow molding machine, the plastic preform needs to be heated from room temperature to a highly elastic state, and the optimal orientation temperature needs to be obtained through temperature regulation (the orientation temperature of common preform materials PET is 105℃, and PP is 150℃). Taking PET preforms as an example, they generally need to be heated from room temperature to 110℃. PET has low thermal conductivity; the thermal conductivity of commonly used blow molding PET is only 0.25W / m·K, making heating by convection slow. Since common two-step blow molding machines have high blowing efficiency, they generally use infrared lamps to centrally heat the preforms (mainly through thermal radiation). The preforms spend a short time in the infrared lamp heating device, which requires a high power output from the infrared lamp heating device (the maximum heating power of the entire machine typically ranges from 20kW to 300kW). The total power of the blow molding machine is slightly greater than the total power of the infrared lamp heating device. Electricity costs account for a large portion of the entire production and maintenance lifecycle of the blow molding machine. Therefore, reducing the power consumption of the plastic preforms during heating is of great practical significance. On the one hand, infrared lamp heating devices cannot completely convert electrical energy into light energy; on the other hand, PET preforms cannot fully absorb the infrared radiation emitted by the infrared lamps, resulting in relatively high heat loss (i.e., electrical energy loss). Before entering the blow molding machine, the preforms are stored indoors, and their temperature can be considered room temperature. The typical temperature in the processing workshop is controlled between 15℃ and 27℃, with significant temperature variations throughout the year, which is detrimental to preform temperature control. Therefore, there is an urgent need to research a preheating method for plastic preforms to solve the above problems. Summary of the Invention

[0003] The present invention provides a method for preheating plastic bottle preforms, the purpose of which is to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0005] Since plastic preforms are placed in a preform feeder before entering the blow molding machine, whether the feeder is manually operated or automatically fed after centralized preformation, the preforms stay in the feeder's hopper for a relatively long time, often exceeding half an hour. Therefore, the preheating method for plastic preforms in this invention occurs during the conveying process before the plastic preforms enter the blow molding machine, specifically including the following steps:

[0006] Step 1: Hot air is piped into the feeding machine, and a heating mechanism is installed on the feeding machine. The hot air and the heating mechanism work together to preheat the plastic preforms in the feeding machine.

[0007] Step 2: Set up a temperature monitoring device. The temperature monitoring device is used to monitor the temperature inside the feeding machine and realize temperature control inside the feeding machine.

[0008] Step 3: The preheated plastic preform, having reached the specified temperature, is fed into the blow molding machine for further processing.

[0009] As a preferred technical solution of the present invention, in step one, a heating mechanism is installed on the bottom wall of the hopper of the feeding machine to achieve preheating treatment of the plastic bottle preform.

[0010] As a preferred technical solution of the present invention, in step one, hot air is delivered to the hopper of the feeder by means of thermal convection, which causes the overall temperature inside the hopper of the feeder to rise.

[0011] As a preferred technical solution of the present invention, in step one, hot air is delivered to the inclined conveying device of the feeding machine by means of thermal convection, which causes the overall temperature inside the inclined conveying device of the feeding machine to rise, thereby achieving preheating treatment of the plastic bottle preform.

[0012] As a preferred embodiment of the present invention, in step one, a turning device for agitating plastic preforms is installed in the hopper of the feeding machine.

[0013] As a preferred embodiment of the present invention, in step one, the outer periphery of the hopper of the feeding machine and the outer periphery of the inclined conveying device are both equipped with heat preservation devices.

[0014] As a preferred embodiment of the present invention, in step two, the temperature monitoring device can control the amount of hot air introduced into the feeding machine and the power of the heating mechanism according to the monitoring results, and the temperature monitoring device can also adjust the heating power of the infrared lamp heating device of the blow molding machine.

[0015] The present invention has the following beneficial effects:

[0016] 1. This invention involves installing a heating mechanism on the bottom wall of the feeding machine's hopper before the plastic preform enters the blow molding machine and while the preform is in the hopper. Hot air is then transported through the feeding machine's hopper and the inclined conveyor to preheat the plastic preform via heat conduction and convection. Finally, the preheated plastic preform is conveyed to the infrared lamp heating device of the blow molding machine. This not only makes it easier to control the temperature of the plastic preform but also effectively reduces the overall energy consumption of the blow molding machine, while ensuring the production efficiency and quality of the plastic preform.

[0017] 2. In the stage between the bottle preform leaving the feeder and arriving at the infrared lamp heating device, although the bottle preform is relatively warmer than the air, its low thermal conductivity and short conveying time result in minimal heat loss. Therefore, when the bottle preform enters the infrared lamp heating device of the blow molding machine, its temperature is much higher than room temperature and controlled within a stable range. The heating effect of the infrared lamp heating device on the bottle preform is reduced by about one-quarter to one-third. Although preheating of the bottle preform during feeding consumes energy, the slow heating method minimizes heat loss compared to the infrared lamp heating device. Overall, the energy savings are still considerable.

[0018] 3. This invention effectively prevents excessive heat damage in the hopper and the inclined conveyor by installing heat preservation devices on the outer periphery of both the hopper and the inclined conveyor, thus ensuring the preheating effect of the plastic preforms. Furthermore, by utilizing thermal convection to transport hot air into the hopper of the hopper, the heating efficiency of the hopper is further improved, further ensuring the preheating efficiency and effect of the plastic preforms.

[0019] 4. The preheating method of the present invention is simple, highly operable, and easy to improve existing equipment. It can also reduce the heating time and power of the infrared lamp heating device of the blow molding machine, and can also reduce the scale of the blow molding machine.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a control principle diagram of a preheating method for plastic bottle preforms according to the present invention. Detailed Implementation

[0023] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Example 1:

[0025] Please see Figure 1 As shown, before entering the blow molding machine, the plastic preforms are placed in the preform feeding machine. Whether the feeding is done manually or automatically after centralized preformation, the preforms stay in the feeding machine's hopper for a relatively long time, often exceeding half an hour. Although the thermal conductivity of the plastic preforms is very low, they can still be heated to a specified suitable temperature range under prolonged heating conditions. Therefore, the preheating method for plastic preforms in this invention occurs during the conveying process before the plastic preforms enter the blow molding machine, and includes the following steps:

[0026] Step 1: Hot air is piped into the feeding machine, and a heating mechanism is installed on the feeding machine. The combined action of the hot air and the heating mechanism preheats the plastic preforms inside the feeding machine. Specifically, before the plastic preforms enter the blow molding machine and while they are in the feeding machine's hopper, a heating mechanism is installed on the bottom wall of the hopper to preheat the preforms via heat conduction. The heating mechanism uses a conventional electric heating plate, which is fixedly attached to the bottom wall of the feeding machine's hopper and horizontally positioned below it. Simultaneously, hot air is delivered into the feeding machine's hopper via thermal convection, raising the overall temperature inside the hopper. Multiple conventional nozzles are fixedly inserted into the opposite side walls of the hopper, with the air inlet of each nozzle connected to... The gas supply pipeline is connected to a heat source, which can be a conventional hot air blower in this field. The gas supply pipeline is equipped with a conventional flow control valve in this field. By using thermal convection to deliver hot air to the hopper of the feeder, the heating efficiency of the hopper can be further improved, ensuring the preheating efficiency and effect of the plastic preform. After the plastic preform enters the inclined conveyor of the feeder from the hopper, hot air is delivered to the inclined conveyor of the feeder by thermal convection, causing the overall temperature inside the inclined conveyor of the feeder to rise, thereby achieving a secondary preheating treatment of the plastic preform. Among them, multiple conventional nozzles in this field are fixedly inserted into the opposite side walls of the protective shell of the inclined conveyor. The air inlet of the nozzle is connected to the heat source through a gas supply pipeline, which can be a conventional hot air blower in this field. The gas supply pipeline is equipped with a conventional flow control valve in this field.

[0027] Step 2: Install a temperature monitoring device. This device monitors the temperature inside the feeding machine to control it. Specifically, the temperature monitoring device is electrically connected to the electric heating plate, hot air blower, and flow control valve. Based on the monitoring results, the device controls the amount of hot air entering the feeding machine and the power of the heating mechanism. In other words, the temperature monitoring device can adjust the power of the electric heating plate and regulate the airflow through the flow control valve. Furthermore, it can also adjust the heating power of the infrared lamp heating device in the blow molding machine, thus facilitating control of the infrared lamp heating device.

[0028] Step 3: The preheated plastic preforms, having reached the specified temperature, are fed into the blow molding machine for further processing. During the period between the preform leaving the feeder and reaching the infrared lamp heating device, although the preform's temperature is relatively high compared to the air, its low thermal conductivity and short transport time result in minimal heat loss. Consequently, when the preform enters the infrared lamp heating device of the blow molding machine, its temperature is significantly higher than room temperature and maintained within a stable range. This reduces the heating amplitude of the preform by approximately one-quarter to one-third. Although preheating during feeding consumes energy, the slow heating process minimizes heat loss compared to the infrared lamp heating device. Overall, the energy savings are still considerable. Specific Implementation Example 2:

[0030] Based on specific embodiment one, as follows Figure 1 As shown, the outer periphery of the hopper of the feeding machine and the outer periphery of the inclined conveyor are both equipped with heat preservation devices; the heat preservation devices can be conventional heat preservation cotton in this field; by wrapping the heat preservation cotton around the outer periphery of the hopper of the feeding machine and the outer periphery of the inclined conveyor, the heat damage in the hopper and the inclined conveyor can be effectively avoided, thus effectively ensuring the preheating effect of the plastic preform. Specific Implementation Example 3:

[0032] Based on the second specific embodiment, as follows Figure 1 As shown, the feeder's hopper is equipped with a stirring device for agitating the plastic preforms. Specifically, the stirring device comprises a servo motor vertically fixed below the hopper, a rotating shaft coaxially fixed to the servo motor's output shaft and rotatably inserted into the bottom wall of the hopper, and a stirring rod radially welded to the upper end of the rotating shaft. The rotating shaft is connected to the bottom wall of the hopper via conventional roller bearings. By installing the stirring device in the feeder's hopper, the device can agitate the plastic preforms within the hopper, thereby ensuring uniform heating of the preforms.

[0033] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of preheating a plastic bottle blank, characterized by, Includes the following steps: Step 1: Hot air is piped into the feeding machine, and a heating mechanism is installed on the feeding machine. The hot air and the heating mechanism work together to preheat the plastic preforms in the feeding machine. Step 2: Set up a temperature monitoring device. The temperature monitoring device is used to monitor the temperature inside the feeding machine and realize temperature control inside the feeding machine. Step 3: The preheated plastic preform, having reached the specified temperature, is fed into the blow molding machine to enable subsequent processing of the plastic preform. The blow molding machine is equipped with an infrared lamp heating device; In step one, a heating mechanism is installed on the bottom wall of the hopper of the feeding machine to preheat the plastic bottle preform. In step one, hot air is delivered to the hopper of the feeder by means of thermal convection, which causes the overall temperature inside the hopper of the feeder to rise. In step one, hot air is delivered to the inclined conveyor of the feeding machine by means of thermal convection, which causes the overall temperature inside the inclined conveyor of the feeding machine to rise, thereby achieving preheating treatment of the plastic bottle preform.

2. A method of preheating a plastic bottle blank according to claim 1, characterized in that, In step one, the feeder is equipped with a turning device for agitating the plastic preforms.

3. A method for preheating a plastic bottle preform according to claim 1 or 2, characterized in that, In step one, heat preservation devices are installed on the outer periphery of the hopper of the feeding machine and the outer periphery of the inclined conveyor.

4. The method for preheating a plastic bottle preform according to claim 3, characterized in that, In step two, the temperature monitoring device can control the amount of hot air introduced into the feeding machine and the power of the heating mechanism based on the monitoring results. The temperature monitoring device can also adjust the heating power of the infrared lamp heating device of the blow molding machine.

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