Ball Socket Retention Structure for High Axial Load Swing
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Solution Overview
Problem
Existing ball joint designs face challenges in supporting heavy negative axial loads without increasing manufacturing costs or restricting the swing of the ball stud, particularly when using plastic bearings that expand under load.
Innovation Solution
A cartridge-style ball joint with a metal housing and a cover plate that includes a torus-shaped top surface and angled surface-to-surface contact area to reinforce the plastic exit bearing against radial expansion, allowing for increased swing angle and load resistance without high-strength materials, combined with a thrust washer and backing bearing for low friction interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cross-sectional size of the metallic cover plate is increased to support heavy negative axial loads, then the load-bearing capacity is improved, but the manufacturing cost increases and the ball stud swing is restricted
Solution Approach 1:
The patent employs a composite structure combining a plastic bearing with a metallic reinforcement cage. The plastic material provides low-friction bearing surfaces while the metallic cage provides structural strength to handle negative axial loads. This composite approach achieves the required load-bearing capacity without needing a large, expensive metallic cover plate, thus resolving the contradiction between strength and manufacturing cost.
Solution Approach 2:
The bearing assembly is segmented into distinct functional components: the plastic bearing material for friction reduction and the metallic reinforcement cage for structural support. This segmentation allows each component to be optimized for its specific function, enabling the system to achieve high load-bearing capacity with a smaller, more cost-effective cover plate design.
2Strength
If the thickness or strength of the cover plate is increased to support large negative axial loads, then the load-bearing capacity is improved, but the manufacturing cost increases
Solution Approach 1:
The metallic reinforcement cage acts as an internal structural support that enables the use of a thinner, less expensive cover plate. The cage bears the primary structural loads while the cover plate provides containment and additional support, allowing cost reduction through reduced cover plate thickness without sacrificing load-bearing capacity.
Solution Approach 2:
The metallic reinforcement cage serves as an intermediary structural element between the plastic bearing and the cover plate. It transfers and distributes the negative axial loads through its rigid structure, preventing the cover plate from needing to be excessively thick or strong, thus reducing manufacturing costs while maintaining load-bearing capacity.
3Strength
If a metallic cover plate is used to restrict axial movement of the ball stud and plastic bearing, then the load support capability is improved, but the ball stud swing is interfered with or restricted
Solution Approach 1:
The reinforcement cage is segmented into radial bars spaced apart from one another, creating gaps that allow the ball stud to swing freely through the bearing assembly. This segmented structure provides axial load support through the rigid bars while maintaining rotational freedom for the ball stud, resolving the contradiction between load support and ease of operation.
Solution Approach 2:
The reinforcement cage functions as a flexible skeletal structure that can deform slightly to accommodate ball stud movement while maintaining its load-bearing function. The open framework design allows the ball stud to articulate freely while the cage structure provides the necessary rigid support for negative axial loads.
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 effectively supports high loads while minimizing material costs and maintaining the ball stud's articulation range, enhancing the ball joint's strength and durability without resorting to costly materials, and reducing axial movement and pullout strength issues.
Implementation Method 1
the plastic material can expand under load due to a contact angle between the bearing and the ball stud
Implementation Method 2
combined with a thrust washer and backing bearing for low friction interfaces
Data Source
Figure 1
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Figure 3
AI summary
The ball socket assembly includes a housing (22) that is made of a monolithic piece which includes a lower wall. A ball portion of a ball stud is disposed in an inner bore of the housing. An exit bearing (50), which is made of a polymeric material, is disposed in the inner bore and is in slidable contact with at least one hemisphere of the ball portion. The exit bearing has an upper surface (64) which faces towards an open end (32) of the housing. A cover plate (52) is in direct contact with the upper surface of the exit bearing along a surface-to-surface contact area. The surface-to-surface contact area is angled (alpha) towards the open end from its radially outermost end to its radially innermost end for supporting the exit bearing against radial expansion in response to axial loads being applied on the exit bearing from the ball portion of the ball stud.