Press Fitting Stop Ring Geometry for Low-Force Sleeve Assembly
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Solution Overview
Problem
Existing press fittings face challenges in forming a secure connection between the press sleeve and fitting body, requiring high assembly forces and often damaging components due to complex interconnections and manufacturing difficulties.
Innovation Solution
A press fitting design featuring a stop ring with snap elements and hooks that provide a form-fit connection, reducing assembly forces through a combination of snap elements with larger recess angles and outward expanding collars, along with a segmented inner contour for injection molding ease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the press sleeve is inserted into the undercut of the retaining ring to form a secure connection, then the connection strength is improved, but the assembly force required increases and the retaining ring may be damaged
Solution Approach 1:
The retaining ring is segmented into multiple snap elements (typically 3-6) arranged circumferentially around the press sleeve. Each snap element independently engages with the press sleeve, distributing the connection strength across multiple points while reducing the force required at each individual engagement point compared to a single deep undercut.
Solution Approach 2:
The snap elements are designed with specific geometric parameters including a guiding angle (typically 15-30 degrees) for easy insertion and a recess angle (typically 45-90 degrees) for secure locking. The depth of the undercut is optimized to provide sufficient holding force while minimizing insertion force requirements, balancing connection strength and assembly ease.
2Reliability
If the retaining ring is designed with a deep undercut to firmly hold the press sleeve, then the connection reliability is improved, but the manufacturing difficulty increases
Solution Approach 1:
Segmenting the retaining ring into multiple discrete snap elements simplifies manufacturing compared to creating a single deep undercut. Each snap element can be formed as a separate feature or in smaller groups, reducing tooling complexity and making the molding or machining process more manageable while achieving the same holding reliability through distributed engagement.
Solution Approach 2:
Instead of requiring one extremely deep undercut, the design uses multiple shallower undercuts (snap elements) that collectively provide sufficient holding force. This partial action approach distributes the required engagement depth across multiple features, making each individual feature easier to manufacture while maintaining overall connection reliability.
3Strength
If the press sleeve is directly attached to the fitting body with high mounting forces, then the connection strength is improved, but the assembly complexity and potential for damage increases
Solution Approach 1:
The retaining ring acts as an intermediary component between the press sleeve and the fitting body. It provides a standardized interface with multiple snap elements that simplify the attachment process, distributing mounting forces across multiple engagement points and reducing the complexity of direct attachment while maintaining connection strength.
4Force
If slots are provided in the press sleeve to reduce pressing forces, then the assembly force is reduced, but an additional manufacturing step is required
Solution Approach 1:
Instead of modifying the press sleeve with slots (which would require additional manufacturing steps), the design extracts the force-reduction function to the retaining ring's snap elements. The snap elements are designed with appropriate angles and geometries that inherently reduce the pressing force required, eliminating the need for slots in the press sleeve while achieving the same force-reduction effect.
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B~2C
AI summary
Press fitting (100) for a pipe connection, comprising a fitting body (120), a press sleeve (140) comprising a substantially cylindrical press area (140) and an outward expanding first collar (144) at a first end (146) of the press sleeve (140), and a stop ring (160) interconnecting the press sleeve (140) and the fitting body (120). The stop ring (160) comprises a groove (162) for accommodating the outward expanding first collar (144) of the press sleeve (140), and a plurality of snap segments (164) formed in a first part (166) of an inner contour (168) of the stop ring (140) and delimiting the groove (162), the snap segments (164) being arranged, in an insertion direction (ain) of the press sleeve (140), in front of the groove (162) to form an undercut (170), a recess angle (β) of each snap segment (164) being larger than a guiding angle (a) of the respective snap segment (164).