Volatile Material Refill Neck Chamfer to Reduce Stress Cracking
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Solution Overview
Problem
Volatile material dispensing devices experience stress cracking in the neck of the refill due to hoop or circumferential stress, which compromises the yield strength of the polymer and leads to crack initiation and fracture, particularly when the plug and wick are inserted and the cap is attached.
Innovation Solution
The refill design incorporates a chamfered surface on the inner surface of the neck rim, angled between 2 and 9 degrees, to reduce tensile hoop stress and minimize stress cracking by redistributing high interference locations away from the neck tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plug and wick are inserted into the bottle neck and a cap is attached, then a fluid seal is maintained, but tensile hoop stress increases causing stress cracking in the neck
Solution Approach 1:
The patent applies local quality by creating a chamfered surface at the specific location where the plug contacts the bottle neck. This localized geometric modification concentrates the sealing function at the chamfered surface while redistributing stress away from the vulnerable neck region, allowing effective sealing without compromising overall neck strength
Solution Approach 2:
The chamfered surface is pre-formed on the bottle neck before plug insertion. This preliminary geometric preparation ensures that when the plug is inserted and cap attached, the stress distribution is already optimized to prevent cracking, rather than relying on the assembly process itself to create stress concentrations
2Strength
If the neck geometry is modified to reduce stress cracking, then neck strength improves, but sealing effectiveness may be compromised
Solution Approach 1:
The patent changes the geometric parameters of the neck interior surface by introducing a chamfer at a specific angle (between 10-45 degrees). This parameter modification simultaneously achieves stress redistribution to prevent cracking while maintaining adequate contact area between the plug and bottle for effective sealing
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 chamfered surface design significantly reduces stress cracking in the neck by up to 20% and maintains effective seals, ensuring the volatile material remains contained during assembly and use.
Implementation Method 1
The chamfered surface is tapered at an angle of between about 2 and about 9 degrees with respect to the longitudinal axis... significantly reduces stress cracking in the neck by up to 20%
Implementation Method 2
The volatile material is moved from the bottle, through the first end of the wick to an end of the wick by capillary action
Data Source
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AI summary
A refill for dispensing a volatile material includes a bottle having a body defined by at least one sidewall and a neck extending outwardly from the at least one sidewall. The neck includes a rim at an upper end thereof, the neck being defined by an inner surface, a top surface, and an outer surface. The refill further includes a plug and a wick having a first end positioned within the bottle and a second end extending out of the bottle, the wick further defining a longitudinal axis. The plug is coupled to the neck of the bottle, the plug retaining the wick within the bottle. At least a portion of the inner surface of the rim is tapered at an angle of between about 2 and about 9 degrees with respect to the longitudinal axis.