Wood Screw Countersunk Head Milled Pocket Curved Edge

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Solution Overview

Problem

Existing wood screws with countersunk heads and milled pockets face challenges in effectively creating a countersink in materials like wood and plastic while minimizing weakening of the screw head and transition area.

Innovation Solution

A wood screw design featuring a countersunk head with axially adjoining truncated cones, rotationally symmetric milled pockets, and a cutting edge configuration that includes a curved and straight section for the front edge, which enhances the milling effect and reduces weakening by optimizing the cutting edge's engagement and chip formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If milling pockets are added to the underside of the countersunk head to improve machining effect and countersink creation, then the cutting action is enhanced, but the screw head becomes weakened due to material removal

Engineering Contradiction:
Improvemachining effectVSAvoidscrew head strength
Core Design Contradiction:
ProductivityVSStrength

Solution Approach 1:

The patent applies local quality by creating milling pockets only in specific regions of the countersunk head underside, concentrating the material removal where it is most effective for chip formation while preserving head strength in critical load-bearing areas. The pockets are positioned to optimize cutting action without compromising overall structural integrity.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent employs curved leading edges on the milling pockets instead of sharp angular transitions. This curvature distributes stress more evenly and prevents stress concentration that would otherwise occur at sharp corners, thereby maintaining screw head strength while still achieving effective material removal for countersink creation.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Productivity

If the milling pockets are made deeper to improve chip formation, then the machining effect is enhanced, but the screw head is significantly weakened

Engineering Contradiction:
Improvechip formationVSAvoidscrew head strength
Core Design Contradiction:
ProductivityVSStrength

Solution Approach 1:

The patent implements partial action by creating milling pockets with controlled depth that is sufficient for effective chip formation but not excessive. The pockets extend only far enough to achieve the desired machining effect while stopping before reaching critical structural zones that would compromise head strength if removed.

Inventive Principle:
Principle #16Partial or excessive action

Solution Approach 2:

The patent optimizes the depth parameter of the milling pockets to achieve the right balance between chip formation capability and structural strength. By carefully controlling the depth parameter within specific ranges, the design achieves effective machining without over-removing material that would weaken the head.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If the leading edge of the milling pocket is made curved to improve chip flow, then the machining effect is enhanced, but the manufacturing complexity increases

Engineering Contradiction:
Improvechip flowVSAvoidleading edge geometry
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent applies curvature to the leading edges of the milling pockets to improve chip flow and reduce chip jamming. This curved geometry allows chips to flow more smoothly along the pocket contours, enhancing the machining effect while the curvature radius is chosen to balance performance improvement with manufacturing feasibility.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Data Source

PatentEP3807545B1Screw
Publication Date: 2023.06.21 FISCHERWERKE ARTUR FISCHER GMBH & CO KG
  • EP3807545B1 patent drawingFigure 1

AI summary

The invention relates to a screw (1), in particular a wood screw, having a countersunk head (4) with the shape of two truncated cones. The invention proposes that front edges (9), as viewed in a direction of rotation during screwing in, are formed by milling pockets (7) having a curvature in the direction of rotation during screwing in, with the result that the milling pockets (7) are extended in the circumferential direction, with the result that an engagement of cutting edges (8) in, for example, wood is improved.