Pliers Joint Pin Toroidal Clearance Design

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Solution Overview

Problem

Existing pairs of pliers with crossing legs and fixed joints suffer from a notch effect due to high forces, which can lead to structural instability and dirt accumulation, especially in the conical regions of the joint pin and lug.

Innovation Solution

The introduction of a second mouth portion on the joint pin that overlaps the first mouth portion, forming a toroidal clearance, reduces the radial dimension and conical widening, thereby minimizing the notch effect and allowing for a narrower structural design while maintaining stability, and incorporating a toroidal clearance to prevent dirt accumulation and facilitate lubricant distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the joint pin is designed with a conical portion that widens as far as into the broad face of the pliers leg, then the notch effect is minimized and structural stability is improved, but the radial dimension and structural complexity increase

Engineering Contradiction:

Improvestructural stabilityVSAvoidstructural complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The joint pin is segmented into multiple functional portions: a first conical portion for bearing on the second conical portion of the joint lug, a first mouth portion for reduced radial dimension, and a second conical portion with second mouth portion for overlapping engagement. This segmentation allows each portion to perform its specific function optimally while maintaining overall stability without excessive complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the joint pin are given different local geometries tailored to their specific functions. The first conical portion provides bearing surface, the mouth portions provide reduced radial dimension, and the overlapping second conical portion provides additional stability. This local differentiation resolves the contradiction by applying complexity only where needed rather than uniformly throughout the structure.

Inventive Principle:

Principle #3Local quality

2Device complexity

If the second conical portion in the pliers leg transforms into a first mouth portion that does not radially widen further as far as into the outer surface, then the structural design is simplified, but the notch effect increases due to interrupted conical extent

Engineering Contradiction:

Improvestructural designVSAvoidnotch effect

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The first mouth portion acts as an intermediary element between the first conical portion and the outer surface of the pliers leg. It provides a transition zone that maintains the reduced radial dimension while the overlapping second conical portion compensates for the interrupted conical extent, thereby minimizing the notch effect without requiring continuous radial widening to the outer surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If a toroidal clearance is formed between the first and second mouth portions, then dirt accumulation is prevented and lubricant distribution is improved, but the radial dimension of the joint pin increases

Engineering Contradiction:

Improvedirt accumulationVSAvoidradial dimension

Core Design Contradiction:

Object-affected harmful factorsVSLength of moving object

Solution Approach 1:

The toroidal clearance extracts or removes the harmful factor of dirt accumulation by creating a space that prevents dirt from becoming trapped in the joint pin structure. The clearance acts as a drainage path that allows lubricant to flow through and carry away contaminants, thereby preventing dirt accumulation without significantly increasing the overall radial dimension of the joint pin.

Inventive Principle:

Principle #2Taking out (Extraction)

4Stability of the object's composition

If the joint pin is designed with overlapping first and second mouth portions, then the notch effect is reduced and stability is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvejoint stabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The overlapping mouth portions are designed as preliminary structural features that are formed during the manufacturing process itself, rather than requiring post-manufacturing assembly or adjustment. The conical portions and mouth portions are integrated into the joint pin geometry from the outset, allowing the overlapping engagement to be achieved through standard machining or forming operations, thereby reducing manufacturing complexity despite the enhanced stability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10751857B2Pliers

Publication Date: 2020.08.25 KNIPEX WERK C GUSTAV PUTSCH KG

AI summary

A pair of pliers having two pliers legs that are arranged in a crossing manner, wherein a fixed joint is formed, having a joint pin. The joint pin has a first conical portion that widens towards the outer side, wherein, the pliers leg is assigned a second conical portion which bears on the first conical portion and transitions into a first mouth portion that leads into the outer side of the pliers leg. The joint pin has a second mouth portion which, starting from the outer side of the pliers leg and perpendicularly to a joint axis, overlaps the first mouth portion. The first and second mouth portion, bound a circular clearance between one another, the radial dimension of the clearance corresponding to 0.05 to 0.15 times the radial dimension, measured from the joint axis of the joint pin in the region of the second mouth portion.