Hook-Crimp Tube Fitting for High-Pressure Leak Resistance
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Solution Overview
Problem
Existing tubing connections in air conditioning and refrigeration applications fail to securely fasten tubes at high pressures above 40 bar, leading to potential disconnection and leakage, as they are not robust enough to withstand increased fluid pressures.
Innovation Solution
The use of annular hook elements that form a circumferential crimp on the outer surface of the tubular element or inner surface of the fitting, providing a form-fit and force-fit connection that resists pressures up to 200 bar without weakening the structure, and can be pre-formed or formed using a press tool, ensuring a secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crimping connections are used, then the connection is sufficient for low pressures, but the connection becomes loose when pressure increases above 40 bar
Solution Approach 1:
The hook element is designed with a curved, hook-shaped geometry that engages with the crimp on the tubular element. This curved shape allows the hook to wrap around and interlock with the crimp, creating a mechanical interlocking connection that resists high pressure forces better than conventional linear crimping interfaces.
Solution Approach 2:
The connection mechanism transitions from a simple radial crimp interface to a three-dimensional interlocking structure where the hook element engages with the crimp in multiple directions. The hook shape provides engagement in both radial and axial dimensions, preventing disconnection under pressure.
2Strength
If cutting blades or tooth elements are used to increase connection force, then the connection strength increases, but the structural integrity of the tubular element is weakened
Solution Approach 1:
The crimp is pre-formed on the tubular element before the fitting is assembled. This preliminary action creates a ready-to-engagement feature that does not require cutting or damaging the tube during assembly. The hook element then engages with this pre-formed crimp, providing strong connection force without compromising the tube's structural integrity.
Solution Approach 2:
Instead of using cutting blades that remove material and weaken the structure, the invention uses a pre-formed crimp that deforms the tube surface locally without removing material. The deformation is controlled and localized, providing engagement strength while preserving the overall structural integrity of the tubular element.
3Reliability
If a secure connection at high pressure is achieved, then reliability improves, but the device complexity increases
Solution Approach 1:
The hook element serves multiple functions: it provides mechanical interlocking with the crimp, resists axial separation forces, and guides the assembly process. This single component achieves what would otherwise require multiple separate features, maintaining simplicity while ensuring high pressure resistance.
Solution Approach 2:
The hook element and crimp form a self-locking mechanism where the geometry of the hook naturally engages with the crimp and prevents disengagement under pressure. The connection secures itself through the interlocking geometry without requiring additional locking mechanisms or complex assembly steps.
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 hook-based connection effectively secures the tube to the fitting at high pressures, preventing disconnection and leakage, even at pressures exceeding 200 bar, and allows for the use of various materials such as metals and plastics, ensuring reliability in ACR applications.
Implementation Method 1
the hook element (21) engages with the crimp (7) on the tubular element (5) in a form-fit and force-fit manner
Implementation Method 2
the end section (9) is pressed with a pressing tool such that the diameter of the end section (9) is at least partly reduced
Implementation Method 3
a crimp (7) forming a second crimp on the outer surface of the tubular element (5)
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a fitting (3, 3') for connecting to a tubular element (5, 5') having a first end section (9, 9') comprising at least one first connection element (21, 21'), wherein the diameter of at least a part of the first connection element (21, 21') can be reduced in a radial direction in order to produce a connection, wherein the first connection element comprises at least one first hook element (21, 21') and/or at least one first crimp configured to be connected in force-fit and/or form-fit manner to at least one second crimp (7, 7') and/or at least one second hook element formed on the outer surface of the tubular element (5, 5'), when the diameter of at least a part of the first connection element is reduced, as well as a tubing connection and a method for connecting a fitting to a tubular element.