Normally Closed Switch Positive Stops for Reliable Circuit Opening
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Solution Overview
Problem
Existing normally-closed switches in refrigerators and freezers often fail to consistently open the circuit when the door is closed, leading to a persistent interior light due to improper installation and resistance between terminals.
Innovation Solution
A normally-closed switch with positive stops, where a push button rotates into a housing, forcing an internal post member to apply pressure and break contact between terminals, and includes stops to prevent further movement, ensuring consistent circuit opening and closing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stationary terminal is allowed to move with the moveable terminal during disengagement, then the terminal movement is more flexible, but the circuit opening becomes unreliable and the interior light may remain on
Solution Approach 1:
The stationary terminal is pre-positioned with a stop mechanism that limits its movement range before disengagement occurs. This preliminary positioning ensures that when the moveable terminal needs to break contact, the stationary terminal cannot move beyond the predetermined position, guaranteeing reliable circuit opening while maintaining controlled flexibility in terminal movement
Solution Approach 2:
A stop mechanism acts as an intermediary element between the stationary terminal and the housing. This intermediary component prevents the stationary terminal from moving excessively with the moveable terminal during disengagement, ensuring that the circuit opens reliably while allowing controlled terminal movement within the stop's constraints
2Productivity
If the gap between the liner and the door is not precisely controlled during installation, then the installation process is simpler and faster, but the switch may fail to open the circuit properly
Solution Approach 1:
The switch assembly is pre-configured with the stationary terminal positioned at a predetermined location within the housing, establishing the correct gap distance before installation. This preliminary positioning ensures that when the switch is installed in the refrigerator door, the stationary terminal is already at the optimal position to prevent excessive movement and ensure reliable circuit opening, eliminating the need for precise gap adjustment during installation
Solution Approach 2:
The switch design incorporates the stationary terminal position and stop mechanism as self-adjusting features that automatically compensate for installation variations. The pre-positioned stationary terminal with its built-in stop self-regulates the gap between the liner and door, ensuring reliable circuit opening without requiring precise installation measurements or adjustments by the installer
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 ensures reliable opening and closing of the circuit, eliminating resistance and ensuring the interior light turns off when the door is closed, addressing the issue of persistent lighting caused by improper installation and terminal movement.
Implementation Method 1
the moveable terminal has sufficient resilience that it also functions like a leaf spring, providing a biasing force against the internal post member that returns the push button to the extended position
Data Source
AI summary
A normally-closed switch comprises: a housing; a push button that is mounted for movement with respect to the housing; a stationary terminal; a moveable terminal that, when in contact with the stationary terminal, completes a circuit; and one or more positive stops that engage the stationary terminal. When a force is applied to the push button, the moveable terminal breaks contact with the stationary terminal, thus opening the circuit. The one or more positive stops apply pressure to and maintain a predetermined position of the stationary terminal, but do not interfere with or impede the moveable terminal.