Concentric Sealing Rings for Electric Tool Lever Water Ingress
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Solution Overview
Problem
Conventional sealing structures for operating levers in electric tools, such as trigger switches, rely on a short sealing surface distance between the ring-shaped packing and the switch case, resulting in an unreliable sealing property due to a line contact, which is inadequate for preventing water ingress.
Innovation Solution
The proposed solution involves a sealing structure where a plurality of concentrically disposed sealing rings is sandwiched between the bottom surface of a fitting recess and the ceiling surface of the guard portion of the operating lever, increasing the pressure-contact points and lengthening the sealing surface distance, with optional features like a cyclic gap, position regulating grooves, and uplift regulating ribs to enhance the sealing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring-shaped packing is used in a conventional waterproof structure, then the sealing structure is simple, but the sealing reliability is poor due to line contact and short sealing surface distance
Solution Approach 1:
The single ring-shaped packing is segmented into multiple sealing rings arranged concentrically. Each sealing ring creates a separate sealing interface, transforming a single line contact into multiple surface contacts. This segmentation increases the sealing reliability by providing redundant sealing paths and longer cumulative sealing surface distance, while the modular concentric arrangement keeps the structural complexity manageable.
Solution Approach 2:
The sealing approach transitions from a single-dimension line contact (ring packing against housing) to a multi-dimension solution by stacking multiple sealing rings concentrically along the radial dimension. This creates extended sealing surfaces in the axial direction, transforming the sealing from line contact to surface contact across multiple concentric cylinders, thereby increasing sealing reliability without excessive complexity.
2Reliability
If a single sealing ring is used, then the structure is simple, but the sealing surface distance is short resulting in poor sealing property
Solution Approach 1:
Multiple sealing rings are nested concentrically within the fitting recess, similar to nested dolls. Each sealing ring is positioned at a different radial location but shares the same central axis. This nesting arrangement extends the sealing surface distance in the radial direction without requiring a proportional increase in axial length, thereby improving sealing property while maintaining a compact structure.
Solution Approach 2:
The sealing solution moves from extending sealing surface distance in the axial direction (single long seal) to extending it in the radial direction through concentric stacking. This dimensional change allows achieving longer effective sealing surface distance within a compact axial footprint, improving sealing reliability without excessively increasing the overall component length.
3Object-affected harmful factors
If the guard portion does not cover the fitting recess, then the structure is open and accessible, but water can easily invade and collect in the fitting recess
Solution Approach 1:
The guard portion is designed to cover only the critical fitting recess area where sealing is most vulnerable, rather than enclosing the entire operating lever assembly. This localized coverage provides targeted protection against water invasion at the sealing interface while maintaining accessibility and operational functionality elsewhere, thus reducing water harm without excessive structural complexity.
Data Source
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AI summary
An aspect of the present invention provides a highly reliable operating-lever sealing structure having a long surface distance between a sealing ring 86 and a housing 11. The operating-lever sealing structure is applied to a sealing structure of an operating lever 80 that is turnably attached to the housing of a trigger switch. A shaft portion 85 projected immediately below a guard portion 80a of the operating lever is turnably supported in an operation hole 22 made in a bottom surface of a fitting recess 21 of the housing, and the sealing ring is sandwiched between the bottom surface of the fitting recess and a ceiling surface of the guard portion of the operating lever.