Working Cylinder Coupling Ring Design for Fatigue Strength

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Solution Overview

Problem

Existing working cylinders face challenges in achieving high fatigue strength and tightness, especially under alternating loads, due to complex production processes and material inaccuracies associated with traditional connection methods like screwing and welding, which also lead to high costs and potential sealing element failure.

Innovation Solution

A working cylinder design featuring a first and second coupling partner with annular grooves and an elastically tensionable coupling ring that provides a form-fitting and frictional connection, allowing for easy assembly and preventing axial relative movements, thereby enhancing fatigue strength and reducing production costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If screwing or welding is used to connect cylinder components, then connection strength is improved, but manufacturing complexity and cost increase

Engineering Contradiction:
Improveconnection strengthVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The connection system is segmented into a coupling ring and two coupling partners (cylinder tube and closure element), each with annular grooves. This segmentation allows the connection to be achieved through simple groove engagement rather than complex screwing or welding processes, reducing manufacturing complexity while maintaining connection strength.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The coupling ring acts as an intermediary element between the cylinder tube and closure element. It provides the connecting function without requiring direct screwing or welding between the main components, thereby simplifying the manufacturing process while ensuring reliable connection strength.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If welding is used to connect cylinder components, then non-detachable connection is achieved, but material inaccuracies and fatigue strength are worsened

Engineering Contradiction:
Improveconnection permanenceVSAvoidfatigue strength
Core Design Contradiction:
Stability of the object's compositionVSStrength

Solution Approach 1:

The thermal welding process is replaced with a mechanical coupling system using annular grooves and a coupling ring. This mechanical substitution eliminates heat input that causes material inaccuracies and fatigue strength reduction, while still achieving a permanent non-detachable connection through the interference fit and geometric locking.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If coupling ring with undersize is used, then assembly is simplified, but axial play increases causing sealing element wear

Engineering Contradiction:
Improveassembly easeVSAvoidsealing element reliability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The coupling ring's dimensional parameters are optimized so that its axial length slightly exceeds the annular groove width. This parameter change eliminates axial play while maintaining ease of assembly, preventing sealing element wear without requiring complex adjustment mechanisms.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The coupling ring is designed with sufficient axial length to preemptively prevent any axial movement between coupling partners. This beforehand cushioning approach ensures sealing elements are protected from wear by eliminating the possibility of axial play before it can cause damage.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution provides a cost-effective, high-fatigue-strength connection that maintains positional conformity under load changes, preventing sealing element damage and extending the working cylinder's service life while simplifying the production process.

Implementation Method 1

The coupling ring (4.1), under elastic deformation in its radial clamping direction, is completely accommodated by the annular groove of a coupling partner

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

The coupling ring, under elastic deformation in its radial clamping direction, is completely accommodated by the annular groove of a coupling partner... providing a form-fitting and frictional connection

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP2898224B1Working cylinder
Publication Date: 2019.07.17 BUMACH ENG INT BV
  • EP2898224B1 patent drawingFigure 1
  • EP2898224B1 patent drawingFigure 2
  • EP2898224B1 patent drawingFigure 3

AI summary

The invention relates to a working cylinder having a first coupling partner and a second coupling partner. The first coupling partner is designed as a cylindrical tube, the second coupling partner is designed as a closing element and one coupling partner is inserted axially into the respective other coupling partner. The working cylinder is characterised in that each of the coupling partners has an annular groove, the annular groove of the inserted coupling partner being formed by an external groove, the annular groove of the other coupling partner being formed by an internal groove and the annular grooves of the coupling partners lying opposite one another so that they correspond. The working cylinder is also characterised by a coupling ring which can be spring-loaded, which, when deformed in the tensioning direction, can be fully accommodated by the annular groove of one coupling partner and which, when deformed in the release direction, engages in the annular grooves of both coupling partners. The engagement of the coupling ring in the annular grooves of both coupling partners produces a form-locking connection between said partners. The working cylinder is also characterised in that the inserted coupling partner is oversized in relation to the other coupling partner, thus providing an additional frictional connection.