Frustoconical Helical Spring for Needleless Injector
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Solution Overview
Problem
Existing needleless injection devices require increased height to enhance trigger stroke and compression force, which complicates design and increases device size, and existing springs generate friction noise and do not allow for efficient calibration.
Innovation Solution
A frusto-conical helical compression spring with axially fitting coils that reduce vertical space and allow for adjustable calibration without affecting trigger travel, providing stability and minimizing friction noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the space between spring coils is increased to enhance trigger stroke, then the trigger stroke is improved, but the overall height of the device must be increased
Solution Approach 1:
The spring coils are designed to nest within each other during compression, with each coil fitting into the space of the previous coil. This nesting arrangement allows the spring to achieve the required compression distance (trigger stroke) while maintaining a compact overall height, as the coils utilize the radial space rather than requiring additional axial space when compressed.
Solution Approach 2:
The spring geometry transitions from a uniform cylindrical shape to a frustoconical shape where the coil diameter varies along the axial direction. This dimensional change allows the spring to accommodate larger coil spacing at the base for stability while reducing the height requirement at the top during compression, effectively trading radial dimension for axial dimension to resolve the height-stroke contradiction.
2Force
If the wire diameter of the spring is increased to enhance compression force, then the compression force is improved, but the overall height of the device must be increased
Solution Approach 1:
The spring wire diameter is not uniform but varies along the axial length of the spring. The wire diameter is larger at the base where higher compression force is needed and gradually decreases toward the top. This local variation in quality allows the spring to generate sufficient compression force at the point of application while maintaining a compact overall height, as the thicker wire section is localized rather than extending throughout the entire spring length.
Solution Approach 2:
The spring design employs a frustoconical geometry where both the coil diameter and wire diameter are parameters that change continuously along the axial direction. By adjusting these geometric parameters, the spring achieves optimal compression force at the base while minimizing the height required, resolving the contradiction between force generation and compact dimensions.
3Force
If coils are added to increase compression force, then the compression force is improved, but the triggering stroke is affected
Solution Approach 1:
The spring coils are designed to nest within each other during compression, with each coil fitting into the space of the previous coil. This nesting arrangement allows the spring to achieve the required compression distance (trigger stroke) while maintaining a compact overall height, as the coils utilize the radial space rather than requiring additional axial space when compressed.
Solution Approach 2:
The spring design employs a frustoconical geometry where both the coil diameter and wire diameter are parameters that change continuously along the axial direction. By adjusting these geometric parameters, the spring achieves optimal compression force at the base while minimizing the height required, resolving the contradiction between force generation and compact dimensions.
4Reliability
If the spring coils are in contact during sliding, then the spring provides continuous support, but friction noise is generated
Solution Approach 1:
The design extracts or eliminates the harmful friction noise by ensuring that the spring coils do not contact each other during the sliding motion. The frustoconical geometry with properly spaced coils allows them to move independently without rubbing against adjacent coils, thereby removing the source of friction noise while still providing the necessary mechanical support and energy storage function.
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 solution enables a compact design with adjustable force settings between 5 and 45 Newtons, maintaining trigger stroke length and reducing noise, enhancing user experience and device stability.
Implementation Method 1
a compression spring which is interposed axially, along the injection axis, between the body and the hood, to compress the user's skin tissues during the application of the nozzle to the skin
Implementation Method 2
a gas generator, a percussion device which is designed to strike the gas generator
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a needleless injector (10) comprising a cap (50), an injection system, a body (12) mounted so as to slide upwards in relation to the cap (50) along an injection axis (B) between a rest position and an injection position, a compression spring (60) axially intercalated along the injection axis (B) between the body (12) and the cap (50) to compress the skin tissue of the user when the nozzle (28) is applied to the skin, characterised in that the compression spring (60) is a frustroconical helical spring which extends along the injection axis (B) and comprises a plurality of turns designed to nest axially the ones inside the others.