Countersunk Head Screw Convex Groove Geometry

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Solution Overview

Problem

Existing countersunk head screws face challenges in cost-efficient manufacturing due to early wear of forming tools and require either a cutting or locking effect, which is not easily switchable without altering the screw geometry, and the geometry leads to material displacement issues and reduced durability.

Innovation Solution

A countersunk head screw design featuring conical partial surfaces with adjustable inclination and cone angles allows for simple manufacturing with carbide tools, preventing edge wear and enabling either a cutting or locking effect without changing the geometry, using a design where the relationship 2*α+β is varied to achieve desired effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional groove geometry with concave curves is used, then cutting edges are formed, but material displacement during stamping increases and tool service life decreases

Engineering Contradiction:

Improvecutting edge formationVSAvoidstamping complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the traditional concave curved grooves with convex curved grooves that bulge outward. This curvature reversal simplifies the stamping process by reducing material displacement requirements while still forming effective cutting edges at the groove bottoms, directly resolving the contradiction between cutting edge formation and manufacturing ease

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent modifies the groove geometry parameters by inverting the curvature direction from concave to convex and adjusting the groove depth distribution. This parameter change allows for simpler stamping tools with extended service life while maintaining the necessary cutting edge functionality, addressing both manufacturing precision and ease of manufacture

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If steel stamping tools are used, then manufacturing is simple, but tool service life is very short

Engineering Contradiction:

Improvetool manufacturingVSAvoidtool service life

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The patent changes the geometric parameters of the grooves to convex curves with optimized depth profiles, which significantly reduces the mechanical stress and wear on stamping tools during production. This parameter optimization enables the use of steel tools to achieve service lives comparable to carbide tools, resolving the contradiction between tool manufacturing simplicity and tool service life

Inventive Principle:

Principle #35Parameter changes

3Duration of action of stationary object

If carbide tools are used, then tool service life is high, but tool manufacturing becomes complicated

Engineering Contradiction:

Improvetool service lifeVSAvoidtool manufacturing complexity

Core Design Contradiction:

Duration of action of stationary objectVSEase of manufacture

Solution Approach 1:

The patent optimizes the groove geometry parameters to convex shapes that are more tolerant to manufacturing variations and impose lower stresses on tools. This allows steel tools to achieve high service lives without requiring the complexity of carbide tool manufacturing, effectively resolving the contradiction between tool service life and manufacturing complexity

Inventive Principle:

Principle #35Parameter changes

4Manufacturing precision

If grooves are recessed with concave curve, then cutting edges are formed, but material displacement increases

Engineering Contradiction:

Improvecutting edge geometryVSAvoidmaterial displacement

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent inverts the groove curvature from concave to convex, which fundamentally changes the material flow pattern during stamping. The convex geometry allows material to flow more smoothly into the groove form, significantly reducing the amount of material displacement required while still creating sharp cutting edges at the groove bottoms, directly resolving this contradiction

Inventive Principle:

Principle #14Spheroidality (Curvature)

5Manufacturing precision

If high notch stresses are generated at edges, then cutting edges are formed, but edge durability decreases

Engineering Contradiction:

Improvecutting edge sharpnessVSAvoidedge durability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent uses convex curved grooves that distribute stresses more evenly along the groove walls compared to sharp concave corners. This curvature design reduces stress concentration at the groove edges while maintaining sharp cutting edges at the bottoms, resolving the contradiction between edge sharpness and edge durability

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The convex groove geometry acts as a stress-distributing feature that prevents the formation of high notch stresses before they can cause edge breakage. By designing the groove shape to inherently distribute loads, the patent prevents durability issues while maintaining cutting effectiveness

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8231320B2Countersunk head screw

Publication Date: 2012.07.31 LUDWIG HETTICH

AI summary

The invention relates to a countersunk head screw comprising a cylindrical shaft (2) and an essentially conical countersunk head (4) comprising at least two edges (15) on the lower side. Said countersunk head screw is characterized in that the edges each mark an end of a partial surface (10) located on the lower side, each of the partial surfaces lying on a non-concave separate surface of revolution.