Fixed Line Trimmer Head Curvilinear Guide Surface
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Solution Overview
Problem
Existing flexible line rotary trimmer heads require complex line replacement processes, often leading to tangling issues and increased user effort, especially for home users, and are not cost-effective for use with various line sizes or rigid blades.
Innovation Solution
A fixed line trimmer head design featuring equiangularly spaced, rotatably mounted line holders with curvilinear guide surfaces and radiused passageways that securely hold and easily replace cutting lines, allowing for various line diameters and seamless transition to rigid blades for heavy vegetation clearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If complex line replacement mechanisms are used in trimmer heads, then line replacement speed is improved, but device complexity increases and user operation becomes more difficult
Solution Approach 1:
The trimmer head is divided into separate modular components: the head housing, the spool assembly, and the line indexing mechanism. This segmentation allows the spool to be independently removed and reattached without disassembling the entire head, simplifying the line replacement process while maintaining automated functionality.
Solution Approach 2:
The line indexing mechanism utilizes dynamic engagement where the spool can be temporarily disengaged from the head housing during line replacement, then automatically reengaged. This dynamic interaction allows automated line payment while maintaining operational simplicity through automatic reconnection.
2Loss of time
If automated line replacement mechanisms are used, then operator time is reduced, but manufacturing cost increases
Solution Approach 1:
The trimmer head incorporates a self-service line replacement system where the automated mechanism reacts to line wear or breakage through a pawl mechanism that automatically disengages the spool, allows line payment, and then reengages the spool. This eliminates the need for manual intervention while using simple mechanical components that are cost-effective to manufacture.
Solution Approach 2:
The system automatically detects when line needs replacement through mass imbalance and recovers the spool assembly for continued use. The metering mechanism ensures only the necessary amount of line is paid out, and the knife guard automatically discards worn line segments, optimizing the cycle of line replacement.
3Ease of operation
If spool-based line storage is used, then line management is improved, but line tangling occurs requiring disassembly
Solution Approach 1:
The line guide surfaces are pre-configured with specific geometries that direct the line from the spool through the housing and out through the cutting edges. This preliminary arrangement of guide surfaces prevents line tangling during operation by ensuring the line follows a predetermined safe path throughout the entire rotation cycle.
Solution Approach 2:
Line guide surfaces act as intermediaries between the spool and the cutting edges. These guide surfaces mediate the line's transition from the spool winding to the radial cutting position, preventing direct contact and tangling by providing a controlled intermediate pathway that maintains line integrity during operation.
4Ease of operation
If fixed line holders are used instead of spool, then line replacement is simplified, but adaptability to different line sizes is reduced
Solution Approach 1:
The line holder is designed with universal features including a standardized mounting interface that accepts different spool diameters and line diameters. The holder's geometry and positioning mechanisms are configured to work with multiple line sizes while maintaining the simplified replacement process, making the system adaptable to various cutting applications.
Solution Approach 2:
The system allows parameter changes in line diameter and spool configuration while maintaining the same basic holder structure. The line holder's design parameters can accommodate variations in line size through adjustable or interchangeable components, preserving both simplicity and versatility.
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
Simplifies line loading and removal, reduces line stress during use, and allows for easy adaptation to different line sizes and blade configurations, enhancing user-friendliness and versatility while minimizing production costs.
Implementation Method 1
During use, centrifugal force generated by the rapid rotation of the trimmer head causes the two portions of the line extending radially from each of the line holders to project radially in a spaced disposition from the line holder for the cutting of the vegetation.
Implementation Method 2
The web about which the line extends cooperates with the curvilinear path forced on the line by the guide surface to grip the line and secure a variety of differently sized cutting line in place on the line holder both during use and when the head is at rest
Data Source
AI summary
A trimmer head for use with a plurality of lengths of flexible cutting line in a flexible line rotary trimmer having a plurality of line holders rotatably mounted thereon. Each line holder defines a pair of laterally spaced apertures in an upper surface thereof, a passageway extending longitudinally therethrough, terminating in an extended end thereof and communicating with the laterally spaced apertures. An interior guide surface extends along a curvilinear path from the spaced apertures to the passageway and a web extends between the apertures whereby end portions of lengths of cutting line can be extended into and through the spaced openings, along the guide surfaces into and through the passageway and outwardly therefrom, whereupon lengths of line extend about and are held against the web with portions of the line projecting from the passageways in the line holders for the cutting of vegetation.