Trigger Switch Waterproof Sealing for Brushless Motor Tools
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Solution Overview
Problem
Conventional trigger switches for brushless motor-mounted power tools are prone to water ingress around the revolving shaft of the switching lever, leading to erroneous operations due to water propagation to contact elements on the sliding circuit board, and corrosion occurs due to leaks between electrodes.
Innovation Solution
A waterproof packing, such as a rubber-like resin, is used to cover the periphery of the revolving shaft and the top surface of the revolving shaft storage chamber, and a drip-proof device like a low-resistance film or slits between contact elements is employed to prevent water adhesion and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the revolving shaft is exposed without protective measure, then the switching lever can operate freely, but water enters around the revolving shaft and propagates to contact elements causing erroneous operation
Solution Approach 1:
A waterproof packing made of flexible rubber-like resin is fitted around the revolving shaft to create a water-tight seal. This flexible membrane allows the shaft to rotate freely while preventing water from penetrating to the contact elements, thus maintaining both operational freedom and reliability.
2Ease of operation
If the contact elements are coated with resister, then sliding operation is enabled, but water entry causes leak between electrodes accelerating corrosion
Solution Approach 1:
The waterproof packing creates a protective barrier that prevents water from reaching the resister-coated contact elements, allowing the sliding operation to function while protecting against water-induced corrosion and electrical leaks.
3Reliability
If waterproof packing is added around the revolving shaft, then water ingress is prevented, but device complexity increases
Solution Approach 1:
A single rubber-like resin waterproof packing is used to provide comprehensive water protection around the revolving shaft. This simple yet effective solution achieves reliable waterproofing without requiring complex multi-component sealing systems.
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 effectively prevents water ingress and subsequent corrosion, ensuring reliable operation by sealing the revolving shaft area and protecting contact elements on the sliding circuit board.
Implementation Method 1
a waterproof packing, such as a rubber-like resin, is used to cover the periphery of the revolving shaft
Implementation Method 2
a drip-proof device like a low-resistance film or slits between contact elements is employed to prevent water adhesion and corrosion
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a trigger switch having a normal and reverse switching lever configured to switch the direction of rotation of a motor, a case (12) is formed with a speed control unit storage chamber (19) for storing a speed control unit (44), a revolving shaft storage chamber (21) for storing a revolving shaft (29) of the switching lever (26) and a contact strip member storage chamber (22) with continuing from the revolving shaft storage chamber (21) through a shielding member therebetween for storing contact strip member of the switching lever, the revolving shaft storage chamber (21) is formed with a revolving shaft engaging hole (23) configured to allow the revolving shaft (29) to be inserted in an engaged state on an upper portion thereof on the side of the trigger lever (11), and a waterproof device for covering at least a gap between the switching lever (29) and the revolving shaft engaging hole (23) is provided to prevent entry of water therein.