Appliance Latch with Toggle Lever to Reduce Rotational Friction
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Solution Overview
Problem
Existing latching mechanisms for household appliances, such as dishwashers and washing machines, face challenges in reducing friction to prevent accidental hook dislodgment and ensuring proper sealing of the door gasket, while maintaining low activation force and preventing premature release of the latch.
Innovation Solution
A latching mechanism utilizing a pivoting lever to hold the hook in an over-center position, reducing friction by eliminating sliding contact and incorporating a floating pivot with a swing arm structure to accommodate accidental activations, allowing for spring-biased re-engagement of the hook and catch element, and an electrical switch for proper closure indication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotating hook cam is held by a stop abutting an outer surface, then the hook is held in its energetic state, but high forces generate significant friction making it difficult to release
Solution Approach 1:
A lever element is introduced as an intermediary between the stop and the hook cam. The lever pivots about a pivot point and transfers the holding force from the stop to the hook cam, converting high-force sliding contact into lower-force pivoting motion, thereby reducing friction while maintaining reliable holding
2Force
If a rotating wheel is used for the stop to reduce sliding friction, then friction is reduced, but the hook may accidentally shift in position independent of engagement
Solution Approach 1:
The lever element provides dynamic control of the hook cam position. The lever can pivot to accommodate small positional variations while maintaining the holding function, and the pivot point geometry ensures that accidental shifts are prevented while still allowing intentional release through catch element engagement
3Force
If a lever is used to hold the hook in over-center position, then friction is greatly reduced, but the mechanism complexity increases
Solution Approach 1:
The lever element is integrated with the existing latch structure by pivotally connecting it to the latch frame and coordinating its motion with the hook cam and catch element. This merging approach adds the necessary pivoting function while minimizing the increase in overall mechanism complexity
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 significantly reduces friction, prevents accidental dislodgment of the hook, ensures reliable door closure, and allows for easy resetting of the latch, enhancing the operational reliability and user experience by minimizing the risk of premature release and ensuring proper sealing of the door gasket.
Implementation Method 1
A bi-stable spring mechanism energizes a spring as the door is opened and holds that energy until the door is closed again. When the door closes past a balance point, the spring releases its energy in a manner to pull the door fully closed.
Implementation Method 2
The use of the lever element, rather than sliding contact between the cam surface and a stop, greatly reduces the friction that must be overcome to release the hook
Data Source
AI summary
An appliance latch provides a hook that may be energized against a spring force to receive a catch element which releases the hook to pull the catch element into engagement. A toggle arm may be used to hold the hook in the energized state before receipt of the catch element to provide for a sensitive and predictable release of the spring force with rotation of the hook. The hook may be mounted on a floating pivot both to accommodate the toggle arm operation and to permit re-engagement of the catch element with the hook in the event that the hook is released from its energized state without engagement of the catch element, for example, by inertial forces.