Preform Heating Plant Air Temperature Control
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Solution Overview
Problem
Existing preform heating plants using infrared radiation lamps struggle to maintain a consistent and high temperature of the ventilating air, which is crucial for precise temperature control of plastic preforms, especially for materials like polypropylene, due to variations in ambient temperature and blower status, leading to temperature fluctuations that can affect the quality of the final containers.
Innovation Solution
A preform heating plant design that incorporates a hot air source to enhance the temperature of the ventilating air beyond what is achievable by mixing ambient and recirculated air, using a mixing member with adjustable inlets and a shutter system to regulate the air flow, and a recirculation channel to ensure consistent temperature control, even during periods without preforms being heated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a recirculation channel is used to mix ambient air with hot air from the furnace, then the temperature control is improved, but the maximum temperature reachable is limited to 30-40°C higher than ambient temperature
Solution Approach 1:
The patent combines two independent heating systems: a recirculation channel that recycles hot air from the furnace (providing baseline heating) and a supplemental heater that adds additional heating capacity. This merging allows the system to achieve temperatures beyond what either system could provide alone, resolving the contradiction between temperature control stability and maximum temperature capability.
Solution Approach 2:
The supplemental heater acts as an intermediary component between the recirculation system and the ventilating air flow. It receives the partially heated air from the recirculation channel and further heats it to the required temperature, enabling the system to overcome the temperature limitation of the recirculation-only approach while maintaining the stability benefits of recirculation.
2Manufacturing precision
If the ventilating system operates without temperature control, then the device complexity is reduced, but the temperature variations affect preform quality
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the temperature of the ventilating air and adjusts the operation of the supplemental heater accordingly. This feedback mechanism maintains precise temperature control without requiring overly complex system architecture, as it builds upon the existing recirculation infrastructure rather than replacing it with a completely new control system.
Solution Approach 2:
The system controls temperature by dynamically adjusting the operation parameters of the supplemental heater (power level, on/off timing) based on the recirculated air temperature and ambient conditions. This parameter-based control approach achieves precise temperature uniformity while keeping the overall device complexity manageable by modifying operational characteristics rather than adding complex hardware.
3Productivity
If the IR lamps operate at maximum power during blowing steps, then the heating efficiency is improved, but the temperature variations during waiting steps affect preform quality
Solution Approach 1:
The recirculation channel maintains continuous operation throughout both blowing and waiting steps, constantly circulating and retaining heat within the system. This continuous action ensures that even when IR lamps are at maximum power during blowing or reduced during waiting steps, the recirculated air provides a stable thermal baseline, smoothing out temperature variations and maintaining preform quality consistency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for higher and more stable ventilating air temperatures, minimizing temperature variations and ensuring consistent preform heating, thereby improving the quality and reducing rejects in the blow moulding process, particularly for sensitive materials like polypropylene.
Implementation Method 1
The thermal energy source for heating the preforms generally consists of infrared radiation lamps (IR). The preforms, moved by a transfer chain, cross a tunnel furnace 1 along which a plurality of IR lamps is arranged.
Implementation Method 2
A fan 2 is typically provided, which sucks an inlet air flow F1 from the ambient and generates, at the delivery, a ventilating flow F2 oriented against the preforms which cross the tunnel furnace 1. Thereby, the outer surface of the preforms is cooled
Implementation Method 3
at least one recirculation channel arranged to receive said ventilating air flow exiting from said at least one tunnel, a mixing member, including at least one first inlet for ambient air, at least one second inlet communicating with said recirculation channel for receiving said ventilating air flow exiting from said at least one tunnel
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A heating plant (10) for performs (20), comprises: - at least one tunnel (3, 3') for the passage of a plurality of preforms (20) - a plurality of infrared radiation lamps (6) along the tunnel (3, 3'); - forced ventilation means (2) for generating a ventilating air flow (F2, F3) through the tunnel (3, 3'), - at least one recirculation channel (15, 15') arranged to receive the ventilating air flow (F2, F3) exiting from the tunnel (3, 3'), - a mixing member (30), including a first inlet (31 ) for ambient air, a second inlet (32) for the ventilating air (F2, F3) and at least one mixed air flow outlet (F1), in which the mixing member (30) is shaped and arranged so as to convey the mixed air flow (F1) towards the forced ventilation means (2), - at least one mobile shutter (35) for regulating the degree of opening of the inlets (31, 32), - a hot air source (40); - flow means (45) for conveying the hot air from the source (40) towards the mixing member (30).