Container Neck Finish Ramp Intersection to Prevent Cross-Thread
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Solution Overview
Problem
Existing container neck finishes are susceptible to cross-threading issues due to the design of locking lugs, which can lead to sealing failures and child resistance issues during stacking and opening.
Innovation Solution
A container neck finish with a cylindrical outer surface, an axially facing sealing surface, a bead, and circumferentially spaced retention elements, including a first cam portion, an upturned portion, and a stop portion with a ramp that converges within ten angular degrees of the parting line, minimizing the likelihood of cross-threading by providing a precise engagement mechanism for the closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional locking lugs with circumferentially truncated ramp portions are used, then clearance for neck ring equipment is provided, but cross-threading susceptibility increases
Solution Approach 1:
The ramp portion angle is changed from traditional designs to specifically 45 degrees, and the ramp portion extends to intersect the parting line rather than being truncated. This parameter change allows the ramp to provide both the necessary clearance for neck ring equipment and the precise engagement needed to prevent cross-threading.
Solution Approach 2:
Instead of truncating the ramp portion to provide clearance (which causes cross-threading), the invention inverts the approach by extending the ramp portion to intersect the parting line. This inversion allows the ramp to define the parting line position, thereby providing both clearance and preventing cross-threading simultaneously.
2Strength
If locking lugs with circumferential overlap are used, then structural strength is improved, but cross-threading resistance deteriorates
Solution Approach 1:
The locking lugs are designed with asymmetric features where each lug has a ramp portion that extends to intersect the parting line at specific locations. This asymmetric configuration provides structural strength through the lug design while the precise intersection with the parting line prevents cross-threading by defining clear engagement zones.
Solution Approach 2:
The neck finish is segmented into multiple locking lugs spaced circumferentially around the neck, with each lug independently featuring a ramp portion that intersects the parting line. This segmentation provides both the structural strength of multiple engagement points and the cross-threading resistance of precisely defined engagement zones.
3Reliability
If ramp portions are extended to intersect parting line, then cross-threading is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The ramp portion design inherently defines the parting line position through its intersection point. During manufacturing, the parting line is automatically established by the mold halves, and the ramp portion's geometry self-aligns to this parting line, reducing the need for additional precision adjustments or post-processing.
Solution Approach 2:
The ramp portion is pre-formed during the molding process with its intersection point with the parting line built into the mold cavity design. This preliminary action ensures that the precise alignment needed to prevent cross-threading is achieved during forming, rather than requiring high-precision assembly or adjustment afterward.
Data Source
Figure 1A
Figure 1B~1C
Figure 2~3
AI summary
A container neck finish (20) includes an outer surface (56) of the neck finish having a parting line (60b), an axially facing sealing surface (64), a bead (66) projecting radially outwardly from the outer surface and axially spaced from the sealing surface, and circumferentially spaced retention elements (30a, 30b, 30c) projecting radially outwardly from the outer surface, and being located axially between the sealing surface and the bead. At least one of the retention elements includes a stop portion (114') including a ramp portion (130') that extends circumferentially toward the parting line and radially inwardly toward the neck finish outer surface and converges therewith at a location within ten angular degrees of the parting line.