Safety Utility Knife Resin Coupling Groove
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Solution Overview
Problem
Existing safety utility knives face increased manufacturing costs and labor due to the use of 3-gate type molds, and suffer from higher cutting resistance and hand fatigue due to resin parts covering the blades, leading to rough cut ends.
Innovation Solution
A safety utility knife design featuring a grip part, a blade with a through-hole, and a coupling part within the blade that couples the grip and head parts together, allowing for manufacturing using a 1-gate type mold, reducing costs and labor, and maintaining blade thickness to prevent increased cutting resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin parts cover the blade to couple grip and head parts, then manufacturing is simplified and costs are reduced, but cutting resistance increases and cut quality deteriorates
Solution Approach 1:
The harmful resin material is extracted and removed from the blade cutting surface area. The resin coupling part is positioned only in the non-cutting region, specifically in the groove between the blade and the workpiece, thereby eliminating the negative effect of resin on cutting while preserving the manufacturing benefits of integral molding.
Solution Approach 2:
The coupling part is repositioned from a surface-level coverage on the blade to a subsurface location within a groove. This spatial relocation in the vertical dimension allows the resin to perform its coupling function without interfering with the cutting action at the blade edge.
2Manufacturing precision
If 3-gate type mold is used to manufacture separate resin parts, then manufacturing precision is maintained, but manufacturing labor and cost increase
Solution Approach 1:
Multiple separate resin parts (grip part, head parts, and coupling part) are merged into a single integral resin component. This allows all parts to be molded simultaneously in one injection process using a simpler 1-gate type mold, eliminating the need for multiple molding operations and subsequent assembly steps.
Solution Approach 2:
The single resin component performs multiple functions simultaneously: it forms the grip part for user handling, the head parts for blade support, and the coupling part for structural connection. This multi-functionality is achieved through integral molding, simplifying the manufacturing process while maintaining structural integrity.
3Strength
If coupling part extends on the blade surface, then grip and head parts are coupled together, but blade thickness increases causing rough cut ends
Solution Approach 1:
The blade assembly is segmented into distinct functional zones: the cutting edge area where the blade contacts the workpiece, and the coupling zone where the resin connects the grip and head parts. The coupling part is confined to the groove in the non-cutting zone, preventing interference with cut end quality while maintaining coupling strength.
Solution Approach 2:
The coupling part is nested within a groove structure on the blade assembly. This nesting arrangement allows the resin coupling material to be housed within the groove, preventing it from extending beyond the blade surface and interfering with the cutting action, while still providing adequate coupling strength.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A safety utility knife includes a resin-made grip part 31, a blade 50a, 50b projecting from the grip part, and a resin-made head part 33a, 33b arranged at a tip of the projecting blade. The blade is formed with a through-hole so that a resin-made coupling part 35 lying within the through-hole couples together the grip part 31 and the head part 33a, 33b that are made of resin. Since the safety utility knife of the present invention allows the three resin-made parts to be joined together, it can be manufactured easily and at low cost using a 1-gte type mold. Also, there is no unnecessary increase in the blade thickness, preventing an increased cutting resistance and a rough cut end from occurring.