Refrigerator Flap Actuation Using Shape Memory Alloy Wire
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Solution Overview
Problem
Conventional household refrigeration appliances with pivotable flaps lack an efficient and energy-effective mechanism for switching between open and closed positions, particularly in managing air flow between temperature zones, leading to increased energy consumption and potential noise from motor operation.
Innovation Solution
A household refrigeration appliance utilizing a shape memory alloy wire actuated by electrical energy to pivot a flap between two positions, coupled with a bistable mechanism and spring-loaded elements, allowing for quiet operation and reduced energy use by maintaining the flap's position without continuous heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synchronous or stepper motor is used to pivot the flap, then the flap can be reliably positioned between open and closed positions, but the appliance generates operational noise and consumes more energy
Solution Approach 1:
The patent replaces the mechanical motor-driven system with a shape memory alloy wire system that uses thermal actuation instead of electrical motors. The SMA wire contracts when heated by electrical current, providing the mechanical force to pivot the flap, thereby eliminating motor noise while maintaining positioning reliability through the bistable mechanism.
Solution Approach 2:
The patent changes the actuation parameter from continuous electrical motor operation to thermal parameter changes in the shape memory alloy wire. By controlling the temperature of the SMA wire through electrical heating, the flap position is controlled without the noise associated with motor operation, while the bistable mechanism ensures reliable positioning.
2Reliability
If a synchronous or stepper motor is used to pivot the flap, then the flap can be reliably positioned between open and closed positions, but the appliance consumes more energy
Solution Approach 1:
The patent replaces the energy-intensive motor system with a shape memory alloy wire system that uses minimal electrical energy only for thermal actuation. The SMA wire requires electrical energy only temporarily to heat and contract for position changes, whereas motors require continuous energy for holding positions, significantly reducing overall energy consumption while maintaining positioning reliability.
Solution Approach 2:
The patent employs periodic action by applying electrical energy to the SMA wire only when position changes are needed, rather than continuous energy consumption. The bistable mechanism maintains positions without energy input, and the SMA wire is heated only periodically to transition between states, minimizing energy usage while ensuring reliable positioning.
3Use of energy by moving object
If a shape memory alloy wire is used to pivot the flap, then energy consumption is reduced and operation is quieter, but the mechanism requires additional components like heating elements and control systems
Solution Approach 1:
The patent merges the electrical connection and heating function into a single integrated system. The electrical contacts that provide power to the SMA wire also serve as the heating elements, eliminating the need for separate heating components. This integration reduces device complexity while maintaining the energy efficiency and quiet operation benefits of the SMA wire system.
4Stability of the object's composition
If the wire made of shape memory alloy is heated continuously to maintain flap position, then the flap remains in the desired position, but energy consumption increases significantly
Solution Approach 1:
The patent employs periodic action by applying electrical energy to the SMA wire only when position changes are needed, rather than continuous energy consumption. The bistable mechanism maintains positions without energy input, and the SMA wire is heated only periodically to transition between states, minimizing energy usage while ensuring reliable positioning.
Solution Approach 2:
The bistable mechanism provides self-service by maintaining the flap in its positioned state without requiring continuous external energy input. Once the SMA wire contracts to change the position, the bistable mechanism holds that position automatically, eliminating the need for continuous heating and significantly reducing energy consumption while maintaining position stability.
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 enables efficient air flow management between temperature zones, reduces energy consumption, and provides quiet operation by using a shape memory alloy wire and bistable mechanism to pivot the flap, maintaining positions without constant heating.
Implementation Method 1
The wire made of a shape memory alloy is designed in such a way that it contracts when heated, ie shortens its length, and thereby pivots the flap from its first position into its second position
Implementation Method 2
If electrical energy is applied to the wire made of a shape memory alloy, so that an electrical current flows through it, in particular, it heats up
Implementation Method 3
The wire made of a shape memory alloy is designed in such a way that it can be drawn back to its original length in its cooled state by applying a force, e.g. This makes it possible, in particular, for the flap to pivot back into the first position
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
The invention relates to a domestic appliance, in particular a domestic refrigerator (1), and to a method for operating the domestic appliance. The domestic appliance has a panel (21), which is pivotably arranged between at least two positions relative to a pivot axis (23), and a moving device (9), which is designed to pivot the panel (21) back and forth between the at least two positions. The moving device (9) comprises a wire (24) which is coupled to the panel (21) and is made of a shape memory alloy, said wire being shortened upon heating and thus pivoting the panel (21) from a first position into a second position.