String Trimmer Cutting Head Automatic Line Feed
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Solution Overview
Problem
Existing grass trimmer cutting heads require manual adjustment and lengthening of the cutting line, which is inconvenient and prone to breakage, especially when the line wears out or is subjected to wear and tear during use.
Innovation Solution
A cutting head mechanism that automatically lengthens the cutting line when the grass trimmer is stopped or braked, utilizing a pivoting lever with a center of gravity arrangement that shifts into a tracking position to allow relative rotation between the spool and housing, ensuring the line is lengthened by a specified increment, reducing wear and tear, and incorporating a U-shaped eyelet for easy line insertion and a spool thread hold-down device for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual adjustment of cutting line is required, then device complexity is reduced, but ease of operation deteriorates and loss of time increases
Solution Approach 1:
The cutting line lengthening mechanism operates automatically without user intervention. When the cutting head is stopped or braked, the pivoting lever shifts to the tracking position, allowing the spool to rotate relative to the housing and feed cutting line through the eyelet, thereby self-adjusting the line length without manual operation
Solution Approach 2:
The mechanism is designed to proactively lengthen the cutting line before wear causes functional issues. By automatically feeding line through the eyelet during stopped/braked conditions, the system maintains optimal line length continuously rather than reacting to wear problems after they occur
2Reliability
If cutting line is manually lengthened, then reliability is improved, but loss of time increases and ease of operation deteriorates
Solution Approach 1:
The system automatically detects when cutting line needs lengthening and performs the operation itself. The pivoting lever mechanism responds to stopped/broken conditions by shifting to the tracking position, enabling automatic line feeding through the eyelet without user intervention or time loss
Solution Approach 2:
The automatic lengthening mechanism ensures continuous operational readiness. By maintaining the cutting line at optimal length through automatic feeding during stopped/braked conditions, the system eliminates interruptions for manual adjustment and maintains continuous productive operation
3Object-affected harmful factors
If cutting line is not automatically lengthened, then device complexity is reduced, but wear and tear increases
Solution Approach 1:
The mechanism proactively feeds cutting line through the eyelet during stopped or braked conditions, preventing wear-related issues before they occur. This preliminary action maintains optimal line tension and length, reducing stress on the cutting line and eyelet area
Solution Approach 2:
The pivoting lever mechanism responds to operational conditions (stopped/broken states) by automatically shifting to the tracking position, creating a feedback loop that detects when line feeding is needed and activates the appropriate mechanism to prevent wear
4Reliability
If pivoting lever center of gravity is positioned at specific radial distance, then automatic lengthening reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The pivoting lever's center of gravity is positioned at a specific radial distance from the rotation axis to create the necessary moment arm for automatic lengthening. This parameter optimization ensures reliable automatic operation while using standard manufacturing tolerances through careful design of the lever geometry and mass distribution
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 mechanism ensures continuous and comfortable operation by maintaining the cutting line at an ideal length, reducing manual effort, minimizing breakage, and distributing wear evenly, thus enhancing user convenience and tool longevity.
Implementation Method 1
Depending on centrifugal force and/or acceleration (particularly when braking), a relative rotation between the spool and the housing is made possible for the purpose of thread adjustment or lengthening.
Data Source
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AI summary
The invention relates to a cutting head (42) for a string trimmer (10). The cutting head (42) is designed to automatically stretch a cutting wire (44). The cutting head has a pivot lever (820) which is mounted in a pivotal manner about a pivot lever rotational axis (822). In a locked position of the pivot lever (820), in particular in which the cutting wire (44) is not stretched, the distance between the center of gravity (886) of the pivot lever (820) and the rotational axis (60) of the cutting head (42) in the radial direction is approximately the same or greater than the distance between the pivot lever rotational axis (822) and the rotational axis (60) of the cutting head (42).