Discharge Head Bellows Spring for Accurate Liquid Dosing
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Solution Overview
Problem
Existing discharge heads for pharmaceutical liquids, particularly those used for nasal applications, face challenges in achieving high dosing accuracy and recyclability due to the relaxation of plastic springs, which affect the reliability of liquid dispensing.
Innovation Solution
A discharge head design featuring a fixed pump piston and a plastic bellows spring with an expanding shape, combined with a movable cylinder component, ensures consistent liquid discharge and recyclability by utilizing a non-linear spring characteristic and a 'lost motion' mechanism to maintain dosing accuracy despite spring relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a plastic spring is used instead of a metal spring to improve recyclability, then the environmental friendliness is improved, but the reliability deteriorates due to spring relaxation over time
Solution Approach 1:
The patent changes the geometric parameters of the plastic spring, specifically designing it with an expanding shape where the diameter increases from the fixed end to the free end. This parameter change creates a non-linear spring characteristic with progressive stiffness, where the spring force increases more rapidly during compression. This design compensates for relaxation effects and maintains dosing accuracy while using recyclable plastic material.
2Reliability
If the spring force increases rapidly to compensate for relaxation, then the dosing accuracy is improved, but the ease of operation deteriorates due to increased actuation force
Solution Approach 1:
The patent employs a dynamic spring design where the stiffness is not constant but varies during compression. The expanding geometry creates a progressive spring characteristic where the force increases gradually at first and then more rapidly towards the end of compression. This dynamic behavior allows easy initial actuation while ensuring accurate dosing near the end of the stroke, balancing ease of operation with dosing precision.
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 design achieves consistent dosing accuracy and recyclability by using a plastic bellows spring with an expanding shape, counteracting spring relaxation effects and ensuring reliable liquid dispensing, even as the spring weakens over time.
Implementation Method 1
a return spring (90) designed as a plastic bellows spring, which, when the cylinder component (50) is displaced in an actuating direction relative to the pump piston (32), exerts a counteracting return force on the cylinder component (50)
Implementation Method 2
By reducing the size of the pump chamber, the liquid contained therein is pressurized and discharged through a discharge opening
Data Source
AI summary
A discharge head for dispensing liquids and for attachment to a liquid reservoir. The discharge head has a discharge head base with a coupling device for connecting to the liquid reservoir, a discharge opening and a pump device for conveying liquid from the liquid reservoir to the discharge opening. The pump device has a pump cylinder and a pump piston guided in a sealing manner along a cylinder sliding surface. The pump piston is fixed relative to the discharge head base, and the pump cylinder is formed by a cylinder component movable relative to the discharge head base. A return spring, configured as a plastic bellows spring exerts a counteracting return force on the cylinder component when moved in an actuating direction relative to the pump piston.