Metal Holding Element Geometry for Torque in Plastic Housings
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Solution Overview
Problem
Existing metallic holding elements for plastic housings face challenges in providing adequate anchoring without weakening the plastic, requiring minimal metal and weight, being cost-effective, and compatible with lead-free materials, while also simplifying plastic housing production and avoiding increased size when pressed in.
Innovation Solution
A metallic holding element with 3 main corners connected by convex edges and no concave incisions or undercuts, produced from lead-free material by cold forging, which engages with the plastic edge to displace material and features a cylindrical bore, internal thread, or pin for screw fastening, allowing for reduced mechanical stress on the plastic housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional holding elements with undercuts or notches are used to improve torque absorption, then anchoring strength is improved, but production complexity and cost increase
Solution Approach 1:
The invention extracts the problematic undercuts and notches from the holding element design, eliminating the need for complex forming operations. Instead, it uses a simplified cylindrical shape with external threading that achieves torque absorption through the thread engagement with the plastic housing, separating the anchoring function from complex geometric features.
Solution Approach 2:
Rather than creating undercuts or notches that require material displacement and complex forming, the invention inverts the approach by using external threading on the cylindrical surface. The torque absorption is achieved through the threaded engagement where the threads cut into or engage with the plastic material, reversing the conventional approach of using internal undercuts.
2Strength
If strong forming is applied to create undercuts for better anchoring, then torque absorption is improved, but the risk of plastic housing damage increases
Solution Approach 1:
The invention removes the strong forming process entirely from the manufacturing method. The holding element is produced without requiring displacement forming or undercut creation, and instead uses a straightforward cylindrical shape with external threads that are formed through simpler processes, eliminating the harmful high-stress forming action on the plastic housing.
Solution Approach 2:
The invention changes the fundamental parameter of how anchoring is achieved - from material displacement through strong forming to threaded engagement. The external threading allows torque absorption through screw-thread mechanics rather than through plastic deformation and material displacement, significantly reducing the risk of housing damage.
3Strength
If holding elements are pressed with greater oversize to improve anchoring, then torque absorption is improved, but the plastic housing size and weight increase
Solution Approach 1:
The invention changes the anchoring mechanism parameter from relying on oversized press-fit to threaded engagement. The external threading allows a smaller diameter holding element to achieve the same or better torque absorption through the mechanical advantage of the thread profile, reducing the overall size and weight of the plastic housing required.
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 enables effective torque absorption with reduced plastic housing stress, smaller size, and cost-effectiveness, allowing for larger holding elements without risking plastic dome wall tears, while maintaining structural integrity and environmental compatibility.
Implementation Method 1
a metallic holding element for pressing into an opening (21) in a plastic housing (2) and for absorbing or introducing a torque in the plastic housing (2)
Implementation Method 2
when the holding element is introduced or when the force acts on the holding element
Data Source
Figure 1a~1b
Figure 2a~2c
Figure 3~5
AI summary
The invention relates to a metal holding element (1) for receiving or introducing a torque into a plastic housing (2), wherein in the holding region (111), the holding element has a cross section having three, four, or five main corners (11), which among each other are connected to one another by way of rectilinear or concave edges (12). Overall, the edges (12) have preferably a concave dome shape due to one or more obtuse-angled intermediate corners (14).