String Trimmer Head With Centrifugal Auto Line Feeding
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Solution Overview
Problem
Current string trimmers lack accurate automatic line feeding mechanisms, leading to inefficient line usage, user inconvenience, and unreliable line release, especially under varying working conditions.
Innovation Solution
A trimmer head design with a transmission member and mating portion that maintains equilibrium states based on centrifugal and friction forces to automatically adjust line length, ensuring consistent line feeding without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If manual control or sensor-based automatic feeding is used to release the trimming line, then line feeding can be achieved, but the reliability is poor and the line cannot be accurately controlled to the required length
Solution Approach 1:
The trimmer head automatically senses when the trimming line needs feeding through the transmission member's centrifugal force mechanism and performs line feeding without user intervention or external sensors. The system serves itself by using the rotational dynamics of the spool and transmission member to detect line length and trigger feeding automatically.
Solution Approach 2:
The patent replaces sensor-based electronic detection with a purely mechanical detection system. The transmission member's position and centrifugal force generation provide mechanical feedback about line length, eliminating the need for sensors and electronic control while improving reliability through mechanical robustness.
2Productivity
If a large speed difference is created between the head housing and spool to achieve line feeding, then automatic feeding can be realized, but the trimming line may be released too long or not at all
Solution Approach 1:
The patent uses dynamic equilibrium between centrifugal force and friction force to control line feeding. The transmission member's position is determined by the balance of forces during rotation, allowing precise control of line release length through force equilibrium rather than fixed speed differences.
Solution Approach 2:
The patent changes the control parameter from speed difference to force balance (centrifugal force vs. friction force). By adjusting the equilibrium of forces on the transmission member, the system precisely controls the amount of line released without the overshoot or failure issues associated with speed-based control.
3Stability of the object's composition
If the trimmer head rotates at constant speed during working state or line-feeding state, then operational stability is improved, but the transmission member must reliably distinguish between working and feeding states
Solution Approach 1:
The transmission member provides mechanical feedback about the trimmer head's state through its position and centrifugal force generation. When the line needs feeding, the transmission member's position changes, creating a detectable mechanical signal that distinguishes the feeding state from the working state, even at constant rotation speed.
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 design ensures reliable and efficient line feeding, maintaining optimal line length without user input, enhancing operational convenience and reducing resource waste.
Implementation Method 1
the transmission member generates a centrifugal force along a straight line, and the mating portion contacts the driving portion and imparts an acting force to the driving portion
Implementation Method 2
the acting force has a first component force along the direction perpendicular to the straight line and a second component force along the straight line direction, and the second component force is also opposite to the direction of the centrifugal force so as to prevent the transmission member from moving in the direction of the straight line
Data Source
AI summary
A string trimmer includes a trimmer head and a driving device having a motor for driving the trimmer head to rotate around a rotation axis. The trimmer head includes a spool, a head housing formed with an accommodating space, and a transmission member mounted to the spool. The spool is at least partially accommodated in the accommodating space. The transmission member includes a driving portion. The head housing is formed with a mating portion to mate with the driving portion.