Reciprocating Saw Blade Rake Pattern for Burr and Wear Tradeoffs
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Solution Overview
Problem
Prior art reciprocating saw blades with negative rake angles fail to provide long blade life and generate excessive burrs when cutting metal workpieces, which are undesirable and require additional deburring efforts.
Innovation Solution
A reciprocating saw blade design featuring a repeating pattern of cutting teeth with a leading tooth having a negative rake angle and trailing teeth with less negative or positive rake angles, reducing burr formation and enhancing blade life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If negative rake angles are used on cutting teeth to make the blade robust, then blade life is improved, but excessive burrs are generated
Solution Approach 1:
The patent applies different rake angles to different teeth within the same repeating pattern. The leading tooth has a more negative rake angle for robustness and blade life, while the trailing tooth has a less negative rake angle for reduced burr generation. This local differentiation of tooth geometry resolves the contradiction between blade life and burr generation.
Solution Approach 2:
The cutting edge is segmented into multiple teeth with different rake angle characteristics within each repeating pattern. By dividing the cutting function across teeth with varying rake angles (leading tooth with more negative rake, trailing tooth with less negative rake), the patent achieves both robust blade life and reduced burr generation simultaneously.
2Strength
If negative rake angles are used on cutting teeth, then the blade becomes more robust, but cutting speed decreases
Solution Approach 1:
Different teeth within the repeating pattern have different rake angles optimized for different functions. The leading tooth's more negative rake angle provides robustness, while the trailing tooth's less negative rake angle maintains cutting speed, resolving the contradiction between blade strength and cutting speed.
Solution Approach 2:
The repeating pattern of teeth with alternating rake angle characteristics creates a periodic cutting action. Each pattern cycle includes both robust leading teeth and speed-optimized trailing teeth, maintaining overall blade robustness while preserving cutting speed through the alternating sequence.
3Duration of action of stationary object
If negative rake angles are used on cutting teeth, then blade life is improved, but additional deburring effort is required
Solution Approach 1:
The trailing tooth's less negative rake angle is specifically optimized to reduce burr generation, directly addressing the deburring time issue while the leading tooth maintains blade life through its more negative rake angle.
Solution Approach 2:
The patent converts the potential harm of burr generation into a benefit by using the trailing tooth's geometry to minimize burrs. The trailing tooth's less negative rake angle acts as a burr-reduction mechanism, transforming what would be a harmful byproduct into an advantageous feature that reduces deburring requirements.
Data Source
AI summary
A recip blade has a cutting edge defining a cutting direction and a repeating pattern of cutting teeth. Each repeating pattern includes (i) a leading tooth with respect to the cutting direction that includes a rake face defining a first rake angle that is negative, and (ii) a trailing tooth following the leading tooth with respect to the cutting direction that includes a rake face defining a second rake angle that is less negative than the first rake angle.