Cardan Shaft Connecting Device Helical Thread Reducing Deformation

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Solution Overview

Problem

The existing connections for cardan shafts, particularly the joint yoke and shaft connections, suffer from geometrical deformation due to the broaching process, which affects the positional accuracy of the cardan shaft.

Innovation Solution

A connecting device featuring a joint yoke with a recess having a continuous helical internal thread and a shank with axial teeth, allowing for a radial toothing that absorbs production forces, reducing deformation and enhancing positional accuracy through a non-positive and form-fitting connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a broaching operation is used to create teeth on the connecting surfaces, then a positive connection is achieved, but considerable forces cause geometrical deformation of the components

Engineering Contradiction:

Improveconnection strengthVSAvoidpositional accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Instead of cutting teeth radially into the joint yoke (conventional approach), the patent inverts the approach by forming longitudinal grooves axially in the joint yoke and then inserting corresponding protrusions from the shaft. This reversal of the manufacturing sequence avoids the high radial forces of traditional broaching that cause deformation, while still achieving a positive mechanical connection through the interlocking grooves and protrusions.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The connection is segmented into two separate forming operations: first creating longitudinal grooves in the joint yoke, then creating corresponding protrusions on the shaft. This segmentation allows each component to be prepared independently with lower forces, avoiding the deformation caused by simultaneous high-force broaching of both components.

Inventive Principle:

Principle #1Segmentation

2Strength

If radial teeth are arranged in the recess of the joint yoke, then connection strength is improved, but deformation during assembly and production increases

Engineering Contradiction:

Improveconnection strengthVSAvoidgeometrical deformation

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The patent inverts the conventional radial tooth arrangement by forming longitudinal grooves axially in the joint yoke instead. This axial groove configuration maintains connection strength through the interlocking mechanism while distributing forces more evenly during formation, thereby reducing geometrical deformation of the joint yoke recess.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If high one-sided forces are applied during broaching, then tooth formation is achieved, but positional accuracy deteriorates

Engineering Contradiction:

Improvetooth formation capabilityVSAvoidpositional accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Instead of applying high one-sided forces to broach teeth radially, the patent uses a two-step process with lower forces: first forming longitudinal grooves axially in the joint yoke, then inserting pre-formed protrusions from the shaft. This inverted approach achieves the same tooth formation result while maintaining positional accuracy by avoiding excessive deformation forces.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP2769109B1Connecting device and method for producing it

Publication Date: 2015.03.18 THYSSENKRUPP PRESTA AG

Figure 1~3
Figure 4~5

AI summary

The invention relates to a connecting device comprising a joint fork (10) and a shank (11), wherein, in a recess (17), the joint fork has a toothing system which runs transversely with respect to a longitudinal axis and the shank (11) has a longitudinal toothing system. Furthermore, the invention relates to a method for producing a connecting device of this type.