Boiler with Screen-Printed Resistor for High-Pressure Beverage Heating
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Solution Overview
Problem
Boilers for hot drink machines face challenges in quickly heating liquids to high pressures while maintaining cost-effectiveness and simplicity, as existing solutions either have high thermal inertia, are costly due to complex designs, or fail to withstand pressures required for preparing espresso coffee.
Innovation Solution
A boiler design featuring a monolithic structure with a circular longitudinal wall and concave bottom wall, reducing pressure concentrations and sealing interfaces to a single point, combined with a screen-printed resistive heating element, simplifies the structure and enhances pressure resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a metal block with embedded resistive element is used, then the boiler has high thermal inertia, but it requires a relatively long time to heat the liquid
Solution Approach 1:
The boiler is divided into two functional parts: a pressure-resistant enclosure (metal block) and a heating element (screen-printed resistive layer). This segmentation allows the metal block to provide structural stability and pressure resistance while the thin resistive heating layer provides rapid heating with minimal thermal inertia, resolving the contradiction between stability and heating speed.
Solution Approach 2:
The screen-printed resistive heating element is directly integrated onto the inner surface of the metal block enclosure, merging the heating function with the pressure-containing structure. This combination eliminates the need for separate heating chambers and thick insulating layers, enabling rapid heating while maintaining pressure resistance.
2Productivity
If screen-printed resistance type heating element with diffusers is used, then rapid heating is achieved, but the boiler cannot withstand high pressures above approximately 8 bars
Solution Approach 1:
The boiler separates the pressure-containing function (metal enclosure) from the heating function (screen-printed element). The metal enclosure is designed to withstand high pressures up to 16 bars, while the screen-printed heating element provides rapid heating. This functional segmentation resolves the contradiction between heating speed and pressure resistance.
Solution Approach 2:
The screen-printed resistive heating element is applied locally on the inner surface of the metal enclosure where heating is needed, while the bulk metal structure provides pressure resistance. This local application of different material properties allows rapid heating at the heating surface while maintaining overall structural strength for high pressure containment.
3Strength
If complex force recovery means and deformation chambers are added, then high pressure resistance is achieved, but the manufacturing cost and complexity increase
Solution Approach 1:
The pressure-resistant enclosure and heating element are merged into a single integrated structure, eliminating the need for separate force recovery mechanisms and deformation chambers. The metal block itself serves as both the pressure container and the mounting structure for the heating element, significantly simplifying the overall device complexity while maintaining high pressure resistance.
Solution Approach 2:
The complex force recovery means and deformation chambers from prior art are extracted and eliminated. Instead, the invention uses a simple screen-printed resistive heating element directly on the metal enclosure, which naturally withstands pressure without requiring additional mechanical compliance elements, thus reducing manufacturing complexity and cost.
4Reliability
If multiple sealing interfaces are provided, then pressure containment is improved, but the manufacturing cost and assembly complexity increase
Solution Approach 1:
The heating element and pressure containment structure are merged into a single integrated unit with only one sealing interface at the opening. The screen-printed heating element is applied directly on the inner surface of the pressure enclosure, eliminating the need for separate sealed heating chambers. This reduces the number of sealing interfaces from multiple to just one, simplifying assembly while maintaining reliable pressure containment.
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
The design allows for rapid heating of liquids under high pressure, reduces the complexity and cost of the boiler, and improves pressure resistance, enabling the preparation of espresso coffee while minimizing energy consumption and thermal inertia.
Implementation Method 1
a screen-printed resistive heating element
Implementation Method 2
the pressure prevailing in the heating chamber is applied partly to the longitudinal wall whose section is circular, which makes it possible to avoid pressure concentrations
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a boiler (100) for a machine for preparing beverages, for heating a liquid pressurized to at least 8 bars so as to carry out an infusion of a material by means of the heated liquid. The boiler includes: a body (1) having an outer wall (2) covered with a screen-printed resistor (14) and an inner wall (3); said inner wall (3) of the body (1) having a longitudinal wall (4) that has a circular cross-section, as well as a bottom wall (5); an inner element (30) having an outer surface (35) for defining, together with the longitudinal wall (4), at least a portion of a heating chamber (102); an inlet (10) and outlet (12) for liquid; and a mounting (20) configured to engage with the body (1) so as to form, together with the longitudinal wall (4) and the bottom wall (5), a sealed enclosure (101) that includes the heating chamber (102).