Sealed Slide Control Switch for Dust-Prone Electrical Tools
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Solution Overview
Problem
Existing multi-way switches for electrical devices, particularly in tools and household devices, are prone to malfunction due to contamination at low voltages and currents, leading to disruptions in the control circuit, especially when air pressure changes allow dust and dirt to enter the switch housing.
Innovation Solution
A switch design where the operating element is inserted and extracted through sealed bushings, preventing air pressure changes and thus reducing dust and dirt ingress, with a sealed contact space that minimizes contamination, and using a linear potentiometer or capacitive travel sensor without additional encapsulation for signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the operating element is moved in and out of the switch housing during activation, then the slide control can be adjusted, but air pressure changes occur that draw dust and dirt into the housing through tiny openings and cracks
Solution Approach 1:
The operating element is nested within the switch housing in such a way that it moves inside a sealed contact space rather than entering and leaving the housing. This nesting prevents the operating element from creating pump effects that would draw dust and dirt into the housing through openings and cracks.
Solution Approach 2:
A membrane is used to seal the contact space, creating a flexible barrier that prevents dust and dirt from entering while allowing the operating element to move within the sealed space. The membrane maintains the seal during operation without requiring rigid enclosures with openings.
2Ease of manufacture
If open contact surfaces are used on the printed circuit board for switching elements, then manufacturing costs are reduced, but dust and dirt can modify the transition resistance and disrupt switch functioning
Solution Approach 1:
The switch housing is divided into separate sealed compartments, with the contact space being a distinct sealed region. This segmentation allows open contact surfaces to be used within the sealed contact space while preventing dust and dirt from reaching them, thus maintaining both low manufacturing costs and high reliability.
Solution Approach 2:
The contact space is sealed to create a protected environment that excludes dust and dirt, effectively creating an inert atmosphere for the electrical contacts. This sealed environment allows open contact surfaces to function reliably without contamination while maintaining cost-effective manufacturing.
3Object-affected harmful factors
If the operating element is sealed through bushings without volume change, then dust and dirt ingress is prevented, but the design complexity increases
Solution Approach 1:
Instead of sealing the operating element itself, the approach is inverted by sealing the contact space and allowing the operating element to move freely within it. This inversion simplifies the sealing design while still preventing dust and dirt ingress into the critical contact area.
Solution Approach 2:
The membrane acts as an intermediary element that seals the contact space while allowing the operating element to move within it. This intermediary solution provides effective contamination prevention without requiring complex sealed bushings for the operating element itself.
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 contamination and ensures reliable operation by preventing dust and dirt from entering the contact space, enhancing safety and reducing manufacturing costs while maintaining functionality at low voltages and currents.
Implementation Method 1
The operating element of the slide control is inserted in all adjustment positions of the operating element, in sealed fashion, through by a first bushing, into a contact space of the switch housing, and is extracted from the contact space, in sealed fashion, through a second bushing
Implementation Method 2
The slide control can be designed as a linear potentiometer, by at least one sliding contact of the linear potentiometer being directly or indirectly fastened on the operating element, and by the sliding contact interacting with resistance tracks applied to the printed circuit board
Implementation Method 3
The slide control can be designed as a capacitive travel sensor and by a slide of the capacitive travel sensor, arranged depending on the adjustment position of the operating element in places between at least two electrodes, being fastened directly or indirectly on the operating element
Data Source
AI summary
The invention relates to a switch for an electrical device, in particular for an electrical tool, comprising a slide control for setting a rotational speed of the electrical device, a switch housing, and at least one circuit board arranged in the switch housing for holding electrical components of the slide control. According to the invention, a movably supported operating element of the slide control is inserted into a contact chamber of the switch housing in a sealed manner through a first feed-through and is led out of the contact chamber in a sealed manner through a second feed-through in all adjustment positions of the operating element. Thus, a switch that ensures reliable function even under ambient conditions of high contamination is provided.