PTC Heated Shelf Structure for Energy-Efficient Food Vending
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Solution Overview
Problem
Existing hot food vending machines face challenges in balancing cost-effectiveness with energy efficiency, hygiene, and user safety, particularly in maintaining optimal temperature control and ease of food retrieval, while struggling to reduce energy consumption and maintenance costs.
Innovation Solution
The design incorporates laminated shelves with PTC heating elements and a modular construction, featuring insulating panels, color-coded temperature ratings, and a self-regulating heating system, along with a door mechanism that ensures safe and efficient food dispensing and easy cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If conventional heating elements are used in prior art vending machines, then food can be heated, but energy consumption is high and temperature control is inefficient
Solution Approach 1:
The patent replaces conventional mechanical heating elements with PTC (Positive Temperature Coefficient) heating elements that are integrally formed with the shelf structure. This substitution eliminates the need for separate heating mechanisms and provides automatic temperature regulation through the PTC effect, where the heating element's resistance increases with temperature, naturally limiting maximum temperature and preventing overheating. This resolves the contradiction by achieving both energy efficiency and reliable temperature control.
Solution Approach 2:
The patent employs composite shelf structures combining insulating materials with integrally formed PTC heating elements. The composite construction includes shelves made from materials that provide both structural support and thermal insulation properties, with the PTC heating elements embedded within the shelf body. This composite approach reduces heat loss to surrounding structures, improving energy efficiency while maintaining stable temperature control for food heating.
2Temperature
If multiple heating zones are provided for different food items, then temperature control is improved, but device complexity and production cost increase
Solution Approach 1:
The patent implements local quality by providing different PTC heating elements with specific temperature characteristics at different locations within the same shelf or compartment. Each PTC element can be tailored to provide the optimal temperature for specific food items placed at that location, while maintaining a unified shelf structure. This approach achieves differentiated temperature control without requiring completely separate heating systems for each zone, thus managing device complexity.
Solution Approach 2:
The patent segments the heating function by incorporating multiple independent PTC heating elements within individual shelves or compartments. Each PTC element operates independently and can be controlled separately, allowing different temperature zones to be created using the same basic shelf design. This segmentation enables versatile temperature control while maintaining manufacturing simplicity through modular design.
3Ease of operation
If door opening mechanism is simplified, then ease of operation is improved, but user safety deteriorates due to burn risk
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of a door that must be opened to access food items. The door acts as a mediator between the user and the hot food, allowing users to visually inspect food items before opening the door and making contact with hot surfaces. The door structure includes insulation and protective features that reduce direct exposure to heat, enabling easier operation while maintaining safety by controlling the timing and manner of user interaction with hot food.
4Loss of energy
If insulating panels are added to shelves, then energy efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the insulating panel function with the shelf structural component by integrally forming the PTC heating elements within the shelf body during manufacturing. The insulating material and heating elements are combined into a single integrated shelf unit, eliminating the need for separate assembly steps. This merging approach reduces heat loss to the machine's internal structures while maintaining manufacturing simplicity through integrated production processes.
Solution Approach 2:
The patent uses composite material construction where insulating materials are combined with PTC heating elements in a unified shelf structure. The composite construction allows both thermal insulation and heating functions to be achieved within a single manufactured component, reducing the number of separate parts that would need to be assembled. This approach improves energy efficiency by reducing heat loss while maintaining ease of manufacture through integrated composite production.
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 reduces energy consumption by at least 30% compared to prior art models, enhances user safety, and simplifies maintenance while providing versatile temperature control and attractive food presentation.
Implementation Method 1
at least one PTC heating element bonded between the plate and the panel
Implementation Method 2
PTC heating element
Implementation Method 3
an insulating panel of composite, dielectric material
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a hot food vending machine including: an array of shelves, each shelf defining a compartment within a housing; doors mounted to the housing, each door closing a respective one of the compartments; wherein each shelf comprises: a plate; a panel of composite, dielectric material; at least one PTC heating element bonded between the plate and the panel, and a first electrical coupling integrally formed on the panel and electrically connected to each PTC heating element, each electrical coupling including a conducting layer laminated upon the panel.