Rotatable Clamp Housing for String Trimmer Cutting Head
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing string trimmer cutting heads often break strings when encountering solid objects due to stress concentrations and require time-consuming re-stringing processes, especially with thin strings and heavy spool designs.
Innovation Solution
A cutting head with rotatable clamp housings that minimize stress concentrations by rotating when encountering solid objects, using spring-biased clamping members to grip strings without disassembly, and allowing easy re-threading with pre-cut strings of any gauge thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If spring-biased clamping members are used to grip strings, then string clamping force is improved, but string breakage occurs when encountering solid objects due to stress concentrations
Solution Approach 1:
The clamp housing is made rotatable about the string axis, transforming a static clamping structure into a dynamic one. When the string encounters a solid object, the clamp housing can rotate to relieve stress concentrations, preventing string breakage while maintaining effective clamping force during normal operation
Solution Approach 2:
The solution adds rotational freedom in the third dimension (around the string axis) to the clamping mechanism. This dimensional change allows the clamp to respond to radial forces from solid objects by rotating, thereby distributing stress and preventing string failure
2Reliability
If weave-type cutting heads with grooves and cut-outs are used, then string anchoring is improved, but re-stringing becomes time-consuming and requires disassembly
Solution Approach 1:
The cutting head is divided into modular components: a reusable hub with integrated clamp housings and removable spools. This segmentation allows the spool to be easily removed and replaced without disassembling the entire cutting head or manipulating strings through complex grooves, dramatically reducing re-stringing time
Solution Approach 2:
The string storage function is extracted into a separate removable spool that can be taken out and replaced independently from the cutting head hub. This extraction eliminates the need to disassemble the cutting head for re-stringing, as the spool can be simply removed and a new one inserted
3Adaptability or versatility
If thin strings are used to navigate through grooves and cut-outs, then string flexibility is improved, but string strength decreases leading to increased breakage
Solution Approach 1:
The string is extracted from the complex groove system and held simply by clamp members within the rotatable clamp housing. This eliminates the need for thin, flexible strings to navigate through twists and turns, allowing the use of stronger, thicker strings that are less prone to breakage
Solution Approach 2:
The rotatable clamp housing dynamically adjusts to string thickness variations, allowing both thin and thick strings to be effectively clamped without requiring the string to be flexible enough to navigate fixed grooves. This dynamic adaptation enables the use of stronger, less flexible strings
4Ease of operation
If tap-and-go head with spool is used, then re-stringing ease is improved, but operator fatigue increases due to carrying heavy spool weight
Solution Approach 1:
The string storage system is segmented into lightweight removable spools that can be easily carried and replaced. This segmentation reduces the weight burden on the operator compared to carrying a large integrated spool, while maintaining the ease of re-stringing through simple spool replacement
Solution Approach 2:
The design changes the weight parameter of the spool by using lightweight materials and optimizing spool geometry. This allows the spool to remain easy to carry and replace while still providing sufficient string capacity for operation
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 solution reduces string breakage by minimizing stress concentrations and allows for quick, tool-free re-stringing without bending or twisting, enabling efficient operation with both thin and thick strings and reducing operator fatigue.
Implementation Method 1
Spring-biased clamping members are provided to clamp the strings within the cutter head, with the clamping force being provided by the springs
Implementation Method 2
the clamping force being provided by the springs and possibly supplemented by centrifugally generated force moments
Data Source
AI summary
A cutting head for a string trimmer is provided which accommodates any string gauge thickness and may be easily and quickly re-threaded upon failure of a string previously disposed therein. The cutting head has spring-biased clamping members which are each mounted within a rotatable clamp housing within the head, such that, as a string encounters a solid object, the clamping member and its associated housing are rotated about a generally vertical axis so as to obviate or minimize the development of a stress concentration in the string in the vicinity at which it is engaged by the clamp housing.