Cage Spring Return Mechanism for Liquid Dispenser Pump
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Solution Overview
Problem
Existing pump units for liquid dispensers face challenges in finding a material that balances actuation force and restoring force, with known designs being difficult to implement in compact dispensers and prone to material relaxation, especially when using tension springs.
Innovation Solution
The design of a pump unit with a return spring as a cage spring, which stores energy primarily through bending deformation, allowing for precise control of deformation and reduced material relaxation, and is made from polyolefin materials for ease of recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal return spring is used in the pump unit, then the desired restoring force and actuation characteristics are achieved, but recycling becomes difficult due to the need to separate metal components from plastic
Solution Approach 1:
The patent changes the material parameter from metal to plastic (polymer), transforming the return spring into a plastic component that can be easily recycled with other plastic parts. This material substitution maintains the functional requirements while solving the recycling problem.
Solution Approach 2:
The patent employs composite plastic spring materials or plastic-metallurgical composites that combine the elastic properties needed for spring function with plastic material characteristics, enabling both functional performance and ease of recycling.
2Ease of manufacture
If a plastic return spring is used to facilitate recycling, then recycling becomes easier, but finding a material that balances actuation force and restoring force becomes difficult
Solution Approach 1:
The patent modifies material parameters by selecting specific plastic polymers with appropriate elastic moduli and stress-strain characteristics, or by adjusting plastic spring geometry parameters (wire diameter, coil spacing, pitch) to achieve the required force characteristics while maintaining recyclability.
3Reliability
If the return spring extension is made less than the pump piston travel as disclosed in US 2002/043540 A1, then material relaxation is reduced, but the dispenser becomes large and difficult to implement in compact designs
Solution Approach 1:
The patent changes the spring extension parameter to be substantially equal to or greater than the pump piston travel distance, which increases the spring's ability to maintain tension throughout the full stroke and reduce relaxation, while accepting the resulting increase in dispenser dimensions.
Solution Approach 2:
The patent positions the return spring in a longitudinal arrangement along the pump piston travel path, utilizing the linear dimension efficiently to achieve the required spring extension without significantly increasing the overall dispenser volume in other dimensions.
4Ease of operation
If a tension spring design is used with parallel individual strands or circumferentially closed sleeve bodies, then the pump unit can be actuated, but the design becomes difficult to implement in compact dispensers and prone to material relaxation
Solution Approach 1:
The patent modifies the spring geometry parameters including the arrangement of individual strands, the configuration of circumferentially closed bodies, or the lattice structure parameters to achieve compact dimensions while maintaining adequate spring tension and minimizing relaxation during operation.
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
This design provides a stable and efficient actuation mechanism with reduced material relaxation, enabling a high degree of deformation without damage and ensuring consistent functionality over time.
Implementation Method 1
The return spring (70) is designed, at least in sections, as a cage spring... elastic elongation is not caused exclusively by material expansion, but to a significant extent by bending deformation
Implementation Method 2
a cage spring, elastic elongation is not caused exclusively by material expansion, but to a significant extent by bending deformation
Implementation Method 3
pressurize it for discharge through a discharge opening... During the actuation-induced reduction of the pump chamber volume, fluid is pumped from the pump chamber toward a discharge opening
Implementation Method 4
The inlet valve can be opened depending on the negative pressure in the pump chamber or depending on the travel distance
Data Source
Figure 1A~2
Figure 3A~3B
Figure 4A~4C
AI summary
The pump unit (10) comprises a pump cylinder (30) and a pump piston (50) which is movable relative to the pump cylinder (30) between an unactuated end position and an actuated end position. The pump unit (10) further comprises an inlet valve (16) at a fluid inlet (14) and an outlet valve (20) at a fluid outlet (18), as well as a return spring (70) by means of which the pump piston (50) is subjected to force in the direction of the unactuated end position. It is proposed to design the return spring (70) as a tension spring and to arrange it such that, when the pump chamber (12) is reduced in size, a cylinder-side end (72) of the return spring (70) and a piston-side end (74) of the return spring (70) are spaced apart from each other in a longitudinal direction, thereby generating or increasing a state of tension in the return spring (70).The return spring (70) is designed, at least in sections, as a cage spring, which has a wall (77) with a cylindrical or conical basic shape. The wall (77) of the cage spring has a structure formed by openings (78) with nodes (82) and spring bars (79) connecting the nodes (82).