Induction Cookware Sandwich Bottom to Prevent Convex Deformation
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Solution Overview
Problem
Containers for cooking on induction plates face deformation issues due to thermal expansion coefficients differences between ferromagnetic and non-ferromagnetic materials, leading to convex bottoms and potential separation from the energy source, affecting thermal efficiency and cooking uniformity.
Innovation Solution
Incorporating a third inner element made from the same or similar material as the outer element, along with a supplementary annular portion, to minimize curvature and ensure complete contiguity between elements, allowing for a single-step impact bonding process that maintains stability and prevents deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single ferromagnetic bottom is coupled to a non-ferromagnetic bowl, then the container can be used on induction plates, but the bottom deforms convexly outward due to thermal expansion differences during cooling
Solution Approach 1:
The bottom is segmented into two separate ferromagnetic discs (first and second discs) coupled to opposite sides of the non-ferromagnetic bowl, rather than using a single ferromagnetic bottom. This segmentation allows the thermal expansion stresses to be distributed and compensated across both discs, preventing the convex deformation that occurs with a single bottom structure.
Solution Approach 2:
The container employs a composite structure consisting of ferromagnetic material discs coupled to a non-ferromagnetic bowl. By using different materials with complementary properties (ferromagnetic for induction compatibility, non-ferromagnetic for the bowl body) and arranging them in a specific composite configuration, the invention achieves both induction plate compatibility and bottom flatness.
2Stability of the object's composition
If aluminium parts are made with great thickness to contrast deformation, then bottom stability improves, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of increasing the thickness of aluminium parts, the invention segments the bottom into two ferromagnetic discs coupled to opposite sides of the bowl. This segmentation approach achieves bottom stability through the balanced thermal expansion compensation of the two discs, avoiding the need for thick aluminium sections and the associated manufacturing complexity.
3Strength
If braze welding is used to couple the bottom to the bowl, then strong bonding is achieved, but the bottom becomes deformed after cooling due to thermal stresses
Solution Approach 1:
The bottom is segmented into two ferromagnetic discs coupled to opposite sides of the bowl via braze welding. This segmentation allows the thermal expansion stresses to be distributed across both coupling points, preventing the concentrated stress that causes convex deformation in single-bottom designs while maintaining strong bonding strength.
Solution Approach 2:
The invention changes the thermal parameters of the system by using two ferromagnetic discs that experience symmetric thermal expansion and contraction. This parameter change in the thermal behavior of the bottom structure allows the braze welding to maintain strong bonding without causing the bottom deformation that occurs in asymmetric single-bottom configurations.
4Ease of manufacture
If the bottom deforms convexly outward, then manufacturing is simpler, but thermal efficiency and cooking uniformity deteriorate due to separation from the energy source
Solution Approach 1:
The segmented bottom structure with two ferromagnetic discs maintains a flat configuration that ensures continuous contact with the induction plate energy source. This segmentation prevents the convex deformation that would cause separation, thereby maintaining thermal efficiency and cooking uniformity while still allowing for straightforward manufacturing processes.
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 solution achieves a stable bottom during use, eliminating deformation and enhancing thermal efficiency and cooking uniformity by creating a sandwich structure that compensates for thermal expansion differences, while being cost-effective and rapid to produce.
Implementation Method 1
the bottom made from ferromagnetic material heats by eddy-current which are generated by effect of the magnetic field generated by the induction source
Implementation Method 2
heats by eddy-current which are generated by effect of the magnetic field generated by the induction source
Implementation Method 3
the bottom finally heats the non-ferromagnetic material parts and the brazing alloy through conduction
Implementation Method 4
The heating is carried out by means of an induction device, in which some metal coils crossed by current induce an electromagnetic field which passes through the piece being machined. Such an electromagnetic field in turn induces eddy-currents in the bottom made from ferromagnetic material which thus reaches the desired temperature
Implementation Method 5
induces eddy-currents in the bottom made from ferromagnetic material which thus reaches the desired temperature
Implementation Method 6
This phenomenon is due to the tensions exerted by the different thermal expansion coefficients of the different coupled metals
Data Source
Figure 1~4
Figure 5~7
Figure 8~9
AI summary
A container (1) for cooking food comprises a first substantially concave element (4), made from a first metal material, and a second element (5), made from a second metal material, preferably ferromagnetic, externally fixed with respect to an area (6) of the first element (4) corresponding to the bottom (2) of the container (1), the container (1) moreover comprises a third element (7) internally fixed with respect to the area (6), made from the second metal material, or from a third metal material in which the first element (4), in its unrefined state, comprises a supplementary annular portion (15) constituting a continuous solid part of the first element (4), positioned near to the perimeter of the second element (5), and foreseen for flowing and moving near to the perimeter of the third element (7) under the action of a punch (19) and of a matrix (18); also a method for making the container (1) is presented.