Injection Molded Cover Thick Portions Prevent Ejection Dents
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Solution Overview
Problem
Thinning of the ceiling wall in synthetic resin covers for electronic devices to reduce outer dimensions while maintaining internal space strength is compromised by stamp-like dents generated during ejection from molds, as the ejection pin presses on the surface before the product is fully hardened, leading to potential strength deficiencies.
Innovation Solution
Incorporating thick portions on the ceiling wall at positions corresponding to ejection pin locations, which protrude inward and are relatively thicker than adjacent normal portions, to ensure a minimum thickness and prevent strength decrease even if dents form during ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the ceiling wall thickness is reduced to minimize outer dimensions, then the compactness of the electronic device is improved, but the strength of the cover is compromised due to stamp-like dents generated during ejection
Solution Approach 1:
The patent applies local quality by providing thick portions at specific locations on the ceiling wall where ejection pins contact during molding. These localized thick portions (with thickness of 0.5-2.0mm) are positioned at predetermined ejection locations, while other areas of the ceiling wall can maintain thinner dimensions (0.3-1.5mm). This allows the cover to achieve compact overall dimensions while maintaining sufficient strength at critical ejection points where dents would otherwise occur.
2Volume of stationary object
If the ceiling wall is made thinner to secure internal space, then the space utilization is improved, but the surface integrity deteriorates due to dent formation during ejection
Solution Approach 1:
The patent implements local quality by creating thick portions at specific ceiling wall locations corresponding to ejection pin contact points. These localized reinforcements (0.5-2.0mm thickness) prevent surface dents during ejection, while the remaining ceiling wall area can be thinner (0.3-1.5mm) to maximize internal space. This selective thickening maintains surface integrity at critical points without sacrificing overall space utilization.
3Reliability
If ejection pin pressure is increased to ensure proper release from mold, then the ejection reliability is improved, but the dent depth increases causing greater local thinning
Solution Approach 1:
The patent applies local quality by providing thick portions at ejection contact locations with thickness of 0.5-2.0mm. These localized reinforcements allow the ejection pin to apply sufficient pressure for reliable mold release without creating excessive dents, because the thick portion absorbs the pressing action. The thick portion acts as a buffer that maintains local thickness even under ejection pressure, preventing the local thinning that would occur in thinner wall sections.
Solution Approach 2:
The patent implements beforehand cushioning by pre-forming thick portions at ejection contact locations before the ejection process occurs. These thick portions serve as a cushion or buffer that absorbs the pressing action of the ejection pin, preventing excessive dent formation and local thinning. The thick portions are created during the molding process itself, providing proactive protection against ejection-induced damage.
Data Source
AI summary
A cover (5) of an electronic device has side walls (8) and a ceiling wall (9), and is molded by injection molding using a mold. The ceiling wall (9) has a flat plate shape. Disk-shaped thick portions (21) that locally protrude inward so as to be relatively thicker than an adjacent normal portion of the ceiling wall (9) are provided at a plurality of positions of the ceiling wall (9) corresponding to respective positions of ejection by ejection pins (25). Although a circular dent (22) is formed at a middle of the thick portion (21) due to the thick portion (21) being pressed by a tip of the ejection pin (25), even at this dent (22) portion, a thickness equal to or greater than that of the normal portion of the ceiling wall (9) is secured.