Optical Rotary Position Sensor for Hand Power Tools
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Solution Overview
Problem
The production and mounting of scanning printed circuit boards in electric hand power tools are complicated, leading to increased costs, and existing scanning methods are vulnerable to moisture, dust, and vibrations, which can result in inaccurate measurements.
Innovation Solution
An optical scanning apparatus using binary scanning elements and a coding disk with reflective marks or apertures, employing Gray code to determine the rotary position of the control element with high resolution, minimizing errors and installation space, and integrated with a digital controller for intuitive control of the drive device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sliding contact and scanning printed circuit board are used to determine rotary position, then the control element can be electrically scanned, but the production and mounting become complicated and costs increase
Solution Approach 1:
The patent replaces the mechanical sliding contact system with an optical scanning system. Instead of using physical sliding contacts that require complex printed circuit boards, the invention uses optical elements (light sources, light barriers, reflective marks) to detect rotary position. This substitution eliminates the need for complex electrical scanning infrastructure while maintaining measurement precision.
Solution Approach 2:
The patent uses optical copying principles where reflective marks or apertures on a coding disk create optical patterns that are detected by light barriers. The rotary position information is copied from the physical disk position to optical signals, simplifying the scanning apparatus by replacing complex electrical contacts with optical pattern recognition.
2Measurement precision
If sliding contacts and printed circuit board contacts are exposed to the environment, then electrical scanning can be performed, but moisture and dirt affect measurement accuracy
Solution Approach 1:
The patent replaces electrical sliding contacts with an optical system that uses light sources and light barriers. This substitution creates a non-contact measurement method where light beams pass through or reflect off coding elements without physical contact, eliminating the problem of moisture and dirt accumulation on electrical contacts.
Solution Approach 2:
The patent introduces light as an intermediary medium between the control element and the scanning apparatus. Instead of direct electrical contact, light serves as the mediator that carries position information across the measurement gap, making the system immune to environmental contaminants like moisture and dirt.
3Measurement precision
If conventional binary coding is used for rotary position, then position can be determined, but incorrect measurements may occur with errors up to the most significant binary digit
Solution Approach 1:
The patent changes the coding parameter from conventional binary code to Gray code. This parameter change ensures that only one binary digit changes between adjacent rotary positions, eliminating the possibility of multiple digit changes that cause large measurement errors. The Gray code transformation maintains the same resolution but dramatically improves reliability by limiting maximum error to the least significant bit.
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 optical scanning system effectively suppresses disturbances from moisture, dust, and vibrations, providing accurate rotary position determination with reduced production costs and increased compactness of the hand power tool.
Implementation Method 1
an electric scanning apparatus which is arranged on the device section and is intended to determine a rotary position of the control element, the scanning apparatus being set up to optically scan the rotary position
Data Source
AI summary
An electric hand power tool includes a cylindrical device section, a control element displaceable about the cylindrical device section, and an electric scanning device disposed at the device section and configured to determine a rotary position of the control element. The scanning device is configured to optically scan the rotary position.