Magnetic Trigger Assembly for Wear-Resistant Power Tool Control
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Solution Overview
Problem
Physical connections on input devices of power tools, such as triggers, wear over time, reducing the operational life of the tool.
Innovation Solution
A contactless trigger assembly using a movable plunger, arm, and magnets to sense magnetic fields, converting linear movement into rotational movement, and using sensors to control the power tool output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical connections are used in input devices, then the device structure is simple and reliable, but the connections wear over time reducing operational life
Solution Approach 1:
The patent replaces mechanical contact connections with a contactless magnetic sensing system. A magnet attached to the movable plunger interacts with a magnetic sensor (such as a Hall effect sensor or magnetoresistive sensor) to detect plunger position without physical contact. This eliminates wear from friction and contact degradation, significantly extending operational life while accepting increased device complexity through the addition of magnetic components and signal processing circuitry.
2Duration of action of stationary object
If contactless sensing is used, then wear is reduced and operational life increases, but the device complexity increases
Solution Approach 1:
The patent introduces a magnetic field as an intermediary between the movable plunger and the sensing system. The magnet on the plunger generates or modulates the magnetic field, which is then detected by the magnetic sensor. This intermediary allows information transfer about plunger position without direct mechanical contact, reducing wear while managing complexity through the use of well-established magnetic sensing technologies and signal processing.
3Measurement precision
If physical connections are used, then the device structure is simple, but measurement precision may be limited due to wear and contact degradation
Solution Approach 1:
The patent replaces mechanical contact-based position detection with contactless magnetic field sensing. The magnetic sensor detects changes in the magnetic field caused by the magnet's position on the plunger, providing precise measurement of plunger displacement without the degradation associated with mechanical wear. This enables higher measurement precision while accepting the increased complexity of magnetic sensing systems and their signal processing requirements.
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
Reduces wear on input devices by eliminating physical connections, thereby increasing the operational life of the power tool and providing precise control over its output.
Implementation Method 1
an arm including a first side that is moveably connected to the second end of the moveably plunger and a second side that is coupled to a magnet. The trigger assembly also includes a sensor configured to sense a magnetic field of the magnet.
Implementation Method 2
the sensor may be configured to sense a change in the magnetic field of the annular magnet in response to the annular magnet rotating
Data Source
AI summary
A trigger assembly for a power tool includes a housing, a moveable plunger extending from a surface of the housing, the movable plunger includes a first end disposed externally from the housing and a second end disposed internally within the housing. The trigger assembly further includes a trigger shoe coupled to the first end of the moveable plunger, and an arm including a first side that is moveably connected to the second end of the moveably plunger and a second side that is coupled to a magnet. The trigger assembly also includes a sensor configured to sense a magnetic field of the magnet. Movement of the trigger shoe rotates the magnet, and alters the magnetic field sensed by the sensor.