Single-Piece Crankshaft Layout for Compact Hedge Trimmer Drives
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Solution Overview
Problem
Multi-piece crankshaft constructions in handheld power tools like hedge trimmers are large and prone to high stresses, necessitating a more robust and compact design.
Innovation Solution
A single-piece crankshaft mechanism with an integrally connected input and output section, featuring spaced engaging members that drive cutting implements along and transverse to the rotational axis, allowing for efficient conversion of rotational motion into linear motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multi-piece crankshaft construction is used, then the crankshaft can be assembled from separate input and output sections, but the overall size increases and stress resistance decreases
Solution Approach 1:
The patent merges the input section and output section into a single integrally formed crankshaft body. This eliminates the need for separate assembly of multiple sections, reducing the overall volume while maintaining manufacturability through single-piece casting or forging processes.
Solution Approach 2:
The patent positions engaging members in three-dimensional space, spaced apart both along the rotational axis and in transverse directions. This spatial arrangement allows compact packaging of multiple functional elements within the single-piece structure, optimizing volume efficiency.
2Ease of manufacture
If a multi-piece crankshaft construction is used, then the crankshaft can be assembled from separate input and output sections, but stress endurance decreases due to joints and connections
Solution Approach 1:
The patent combines the input and output sections into one monolithic structure, eliminating joints, welds, or fasteners that would create stress concentration points. The integral construction ensures uniform stress distribution and superior endurance under cyclic loading conditions.
Solution Approach 2:
The patent employs material selection and construction methods that enhance the inherent strength of the single-piece crankshaft, ensuring it can withstand high stresses without requiring additional reinforcement at joint interfaces.
3Productivity
If engaging members are spaced apart in multiple directions, then cutting implements can be driven efficiently, but the crankshaft design becomes more complex
Solution Approach 1:
The patent designs the single-piece crankshaft body to perform multiple functions simultaneously: it provides structural support, houses multiple engaging members spaced in three dimensions, and converts rotational motion to linear motion for multiple cutting implements. This multi-functionality is achieved through integrated design rather than separate components.
Solution Approach 2:
The patent utilizes three-dimensional spacing of engaging members along and transverse to the rotational axis, allowing efficient drive transmission to multiple cutting implements while maintaining a compact overall design. This spatial distribution optimizes productivity without proportionally increasing complexity.
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 single-piece crankshaft construction enhances stress endurance while reducing volume, enabling more efficient operation and assembly of handheld power tools like hedge trimmers.
Implementation Method 1
crankshaft and/or scotch yoke mechanisms to convert the rotational motion of a small engine into translational motion
Data Source
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AI summary
Crankshaft for handheld power tools is provided. A crankshaft (200) includes an input section (402) configured to be coupled to a motive device and an output section (404) comprising first and second engagement members (412, 416). The first and second engagement members (412, 416) are configured to drive a first and second cutting implement (102, 104), wherein the first and second engaging members (412, 416) are spaced apart from each other in a direction along a rotational axis (406) of the crankshaft (200) and in a direction transverse to the rotational axis (406) of the crankshaft (200), and wherein the first and second cutting implements (102, 104) are each coupled to the crankshaft (200) by translating relative to the crankshaft (200) in a direction along the rotational axis (406).