Reciprocating Impact Tool With Slotted Spindle Dry-Firing Control
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Solution Overview
Problem
Conventional power tools experience inefficiencies due to dry-firing and increased tool wear when not in contact with a workpiece, necessitating complex parking features that increase tool length and manufacturing complexity.
Innovation Solution
A power tool design incorporating a retainer and protruded wall in the spindle to limit anvil travel, eliminating the need for a parking feature, and utilizing a slotted spindle geometry to reduce overall tool length and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power tools are designed without travel limiting features, then the anvil can move freely during operation, but this causes dry-firing occurrences and increased tool wear when not in contact with a workpiece
Solution Approach 1:
The patent extracts the travel limiting function from a complex parking feature system and implements it through simple geometric constraints (protruded wall and retainer) that passively limit anvil movement. This eliminates the need for active parking mechanisms while preventing dry-firing.
Solution Approach 2:
The anvil's own movement during operation naturally engages it with the protruded wall and retainer, which automatically limit travel without requiring external control systems. The system self-regulates anvil position through its operational dynamics.
2Reliability
If parking features are added to prevent dry-firing, then tool wear is reduced, but the tool length and manufacturing complexity increase
Solution Approach 1:
The patent removes the need for extended parking features by extracting the travel limiting function into compact geometric elements (protruded wall and retainer) that are integrated into the existing spindle structure, maintaining a compact tool form factor.
Solution Approach 2:
The travel limiting features are merged with the existing spindle and anvil assembly, combining multiple functions (support, movement guidance, and travel limitation) into a unified compact structure rather than adding separate parking mechanisms.
3Reliability
If complex parking features are implemented, then dry-firing is prevented, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the travel limitation function from complex active parking mechanisms and implements it through simple passive geometric features (protruded wall and retainer) that are easier to manufacture and integrate.
Solution Approach 2:
The solution uses simple, inexpensive geometric features (protruded wall and retainer) rather than complex mechanical systems, prioritizing ease of manufacture and simplicity over elaborate protective mechanisms.
4Length of stationary object
If the spindle geometry is modified to include slots and travel limits, then tool length is reduced, but the structural complexity of the spindle increases
Solution Approach 1:
The spindle is segmented into functional zones with slots creating discrete movement paths for the anvil, allowing compact packaging of movement freedom while maintaining overall structural simplicity and reducing tool length.
Solution Approach 2:
The patent uses slots to constrain anvil movement in specific dimensions while allowing freedom in others, creating a compact three-dimensional arrangement that reduces overall tool length without overly complicating the spindle structure.
Data Source
AI summary
A power tool includes a motor, a spindle defining a first end with a slot, and a crankshaft including a counterweight and a crank pin that are rotated by the motor about a crank axis so that at least one of the counterweight and the crank pin is rotated through the slot. The spindle includes a second end opposite the first end and defines a third distance taken between the first end and the second end of the spindle. The spindle further includes an anvil seat between the first end and the second end and defines a fourth distance between the anvil seat and the first end of the spindle. The power tool further includes an anvil received in the spindle, and the anvil defines a bit seat configured to receive a tool bit.