Variable-Speed Controller With Membrane Contact Surface
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Solution Overview
Problem
Conventional speed control mechanisms in electric power tools, such as potentiometers with thin carbon film resistors, suffer from wear and tear and contamination issues, leading to inaccurate and erratic speed control due to direct sliding contact and exposure to particles.
Innovation Solution
A variable-speed controller design featuring a membrane with conductive surfaces and a slider that moves along a second membrane contact surface, allowing the first membrane contact surface to engage with a variable resistor element in multiple contact configurations, reducing direct contact and wear, and using a spacer element to maintain separation and prevent contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a potentiometer with thin carbon film is used for speed control, then speed control functionality is achieved, but wear and tear occurs due to repeated sliding movement of conductive wipers
Solution Approach 1:
A membrane with conductive contact surfaces is introduced as an intermediary between the slider and the variable resistor element. The membrane transfers the sliding motion while protecting the carbon film from direct contact with contaminants and reducing wear on both the wiper and the carbon film surface, thereby extending the service life and improving reliability of the speed control mechanism.
Solution Approach 2:
A flexible membrane with conductive contact surfaces is used to replace the traditional direct sliding contact. The thin film structure allows for smooth sliding motion while protecting the underlying carbon film resistor from wear and contamination, solving the durability issue of conventional potentiometers.
2Reliability
If conductive wipers slide directly on thin carbon film, then variable resistance is achieved, but contaminant particles cause short-circuiting and exacerbate wear
Solution Approach 1:
The membrane serves as a protective intermediary layer between the external environment (contaminants) and the carbon film resistor. It allows electrical contact to be made through the membrane's conductive surface without exposing the carbon film directly to contaminant particles, preventing short-circuiting and reducing wear from particulate contamination.
Solution Approach 2:
The flexible membrane with conductive contact surface acts as a protective barrier that shields the carbon film from contaminants while still allowing for electrical contact and mechanical sliding motion, thereby preventing contamination-related failures.
3Reliability
If a membrane with spacer element is used, then wear and contamination are reduced, but device complexity increases
Solution Approach 1:
A thin flexible membrane with an integrated spacer element is used to maintain a precise air gap between the contact surfaces. This single-component approach protects the carbon film from wear and contamination while maintaining a simple overall structure that does not significantly increase device complexity.
Solution Approach 2:
The spacer function is integrated directly into the membrane structure, combining the protective membrane and the spacing function into a single component. This merging of functions protects the carbon film from wear and contamination without requiring separate spacer components, thereby minimizing the increase in device 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
This design enhances the reliability and stability of speed control by minimizing wear and preventing short-circuiting, resulting in more accurate and consistent motor speed operation over time.
Implementation Method 1
a membrane including a first membrane contact surface spaced-apart from the variable resistor element contact surface by a spacer element, and, a second membrane contact surface; a slider configured for slidable movement along the second membrane contact surface wherein responsive to the slider slidably moving along the second membrane contact surface, the first membrane contact surface is able to be urged into contact with the variable resistor element contact surface
Data Source
AI summary
A variable-speed controller for use with an electric device including: a variable resistor element having a variable resistor element contact surface; a membrane including a first membrane contact surface spaced-apart from the variable resistor element contact surface by a spacer element, and, a second membrane contact surface; a slider configured for slidable movement along the second membrane contact surface wherein responsive to the slider slidably moving along the second membrane contact surface, the first membrane contact surface is able to be urged into contact with the variable resistor element contact surface in a plurality of contact point configurations whereby the effective resistance of the variable resistor element is configured to change in response to the first membrane contact surface being urged into contact with the variable resistor element contact surface in each of the plurality of contact point configurations.