Bearing Retaining Cage Spherical Cylindrical Pockets
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Solution Overview
Problem
Bearing units with traditional polymer retaining cages face issues with stress concentration at sharp edges, leading to damage at low temperatures and production defects during injection molding, especially when using composite plastic materials.
Innovation Solution
The design incorporates a retaining cage with pockets featuring a combination of radially adjacent spherical and cylindrical surfaces, reducing stress concentration and improving injection molding by ensuring the cylindrical surface forms an angle of at least 90° with the base rib, and flexible tenons for enhanced torsional flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a sharp edge is used along the inner surface of the pocket, then the structural rigidity of the base rib is improved, but stress concentration occurs leading to damage at low temperatures
Solution Approach 1:
The patent replaces the sharp edge with a rounded corner having a radius of curvature R1. This curvature eliminates the stress concentration that occurs at sharp edges, particularly under low temperature conditions, while maintaining the structural rigidity needed for the base rib.
Solution Approach 2:
The patent applies different geometric characteristics to different locations: the rounded corner with radius R1 is applied specifically at the critical inner surface location where stress concentration would occur, while other portions of the base rib maintain their original geometry to preserve overall structural rigidity.
2Strength
If a sharp edge is used along the inner surface of the pocket, then the structural rigidity of the base rib is improved, but production defects occur during injection molding
Solution Approach 1:
The rounded corner geometry with radius R1 eliminates sharp edges that create air traps and flow disturbances during injection molding. This allows polymer material, especially composite materials with glass fibers, to flow smoothly and fill the mold cavity completely, preventing production defects.
Solution Approach 2:
The rounded corner is applied specifically at the pocket inner surface where material flow convergence occurs during injection molding, improving local filling quality without compromising the overall structural rigidity of the base rib.
3Stability of the object's composition
If the tenons are made rigid, then the cage maintains its shape, but the tenons cannot open for insertion of balls
Solution Approach 1:
The tenons are designed with elastic properties, allowing them to deform dynamically. During ball insertion, the tenons can open elastically to accommodate the balls, and then return to their original position to maintain cage shape stability during operation.
Solution Approach 2:
The tenons are designed with specific elastic parameters that allow controlled deformation during ball insertion while maintaining sufficient rigidity to hold the balls in position during bearing operation. The elastic modulus and geometry are optimized to balance these requirements.
Data Source
AI summary
Bearing unit (30) has a central axis of rotation (X) and a retaining cage (40) for a plurality of rolling bodies (34) interposed between a radially outer ring (31) and a radially inner ring (33). The retaining cage (40) has a base rib (41), a plurality of tenons (42) that are spaced apart circumferentially and rigidly connected to the rib (41), and a plurality of pockets (43). Each pocket (43) is delimited by the rib (41) and by a respective pair of adjacent tenons (42). Each pocket (43) is defined by a respective radially outer spherical surface (44) and by at least one respective radially inner cylindrical surface (45) radially adjacent to the spherical surface (44).