String Trimmer Line Feed via Motor Braking Inertia
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Solution Overview
Problem
Existing string trimmer line feed mechanisms, such as bump feed and automatic feed systems, are inefficient and prone to waste, as they either require user-induced wear on the spool housing or are delicate and prone to accidental line feeding, leading to unnecessary line wear and user frustration.
Innovation Solution
A user-actuated button activates a motor braking mechanism to halt the spool rotation, generating a large force that unlocks a lever to feed additional line only when needed, eliminating the need for user-induced spool housing impact and improving line management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bump feed systems are used, then line feed is achieved by user action, but the spool housing wears out and accidental line feeding occurs
Solution Approach 1:
The patent replaces the mechanical bump feed system with an electronic motor braking system. The controller activates the motor brake to rapidly decelerate the spool motor, generating inertial force that feeds the cutting line. This substitution eliminates mechanical impact on the spool housing while providing controlled line feed operation.
Solution Approach 2:
The system uses the motor's own braking action to generate the force needed for line feed. When the controller activates the motor brake, the spool's rotational inertia creates the necessary force to release and feed the cutting line without requiring external mechanical impact or additional force-generating components.
2Extent of automation
If automatic feed systems are used, then line feed occurs when forces become unbalanced, but the system is delicate and prone to accidental line feeding
Solution Approach 1:
The system incorporates a button input that provides user feedback control for line feed activation. The controller monitors the button state and only activates the motor brake when the button is pressed, ensuring that line feed occurs only when explicitly requested by the user. This feedback mechanism prevents accidental line feeding while maintaining automation of the force generation process.
Solution Approach 2:
The patent replaces the delicate mechanical force-balancing system with an electronic control system using motor braking. Instead of relying on mechanical pivoting arms and force thresholds that are prone to accidental activation, the system uses electronic control of the motor brake to generate precise, on-demand inertial force for line feed.
3Extent of automation
If automatic feed systems are used, then line feed is automated, but cutting line is fed out when not needed or not properly fed when needed
Solution Approach 1:
The system uses button-activated feedback control to ensure line feed occurs only when the user explicitly requests it. The controller monitors the button state and activates the motor brake only during button press events, providing reliable user-controlled automation that prevents both premature and missed line feed operations.
Solution Approach 2:
The system employs periodic, discrete line feed actions triggered by button presses rather than continuous or automatic periodic feeding. Each button press initiates a controlled motor brake activation that feeds a specific amount of line, allowing the user to request line feed at appropriate intervals based on actual usage needs.
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 solution ensures that additional cutting line is fed out only when required, reducing waste and enhancing user experience by providing a more reliable and controlled line feed mechanism.
Implementation Method 1
activates a motor braking mechanism that rapidly halts rotation of the motor, which in turn generates a large force within the spool assembly to initiate the line feed
Data Source
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AI summary
The present invention is directed to a string trimmer line feeding mechanism having a sliding lever (31) that locks a spool (30) relative to the spool housing (28), and only feeds additional cutting line when the user actuates a button (22). This brakes a motor (15), which generates a force acting on the spool (30) to move the lever (31) into an unlocked position, allowing the spool (30) to rotate relative to the spool housing (28) and feed additional cutting line.