Needleless Injection Device Sealing Membrane Axial Creep
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Solution Overview
Problem
The existing needleless injection devices with elastically deformable membranes suffer from axial creep and potential seal damage between the membrane and the device body, leading to leaks during the injection process due to geometrical manufacturing tolerances and axial displacement of the annular disk.
Innovation Solution
Incorporating an annular washer between the annular disk of the membrane and the upper collar of the reservoir, which extends radially to the tubular wall of the housing, limits axial creep and enhances the seal by reducing the space for membrane deformation, ensuring a tighter fit between the membrane and the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the annular disk of the membrane is compressed axially between the upper end of the reservoir and the seat formed by the body to ensure sealing, then the seal between the reservoir and the body is improved, but the annular disk creeps axially and overflows between the reservoir and the tubular wall of the housing, causing leaks
Solution Approach 1:
An annular anti-extrusion washer is introduced as an intermediary element between the membrane disk and the reservoir. This washer has a peripheral edge that engages with the tubular wall of the housing to prevent axial creep of the membrane disk, while allowing the membrane to maintain its sealing function. The washer acts as a mediator that resolves the conflict between sealing compression and shape stability.
Solution Approach 2:
The solution addresses the axial creep problem by introducing a radial constraint mechanism. The peripheral edge of the washer extends radially to engage the tubular wall, creating a constraint in the radial dimension that prevents axial displacement. This dimensional approach converts the problem from purely axial to a combination of radial and axial constraints.
2Ease of manufacture
If geometrical manufacturing tolerances of the reservoir and body are considered, then the assembly is easier to manufacture, but the space for membrane deformation increases, leading to potential seal damage
Solution Approach 1:
The invention changes the geometric parameters of the assembly by introducing the washer with specific dimensional relationships. The washer's peripheral edge is positioned to engage the tubular wall at a predetermined radial distance, creating a geometric constraint that compensates for manufacturing tolerances. This parameter change ensures that even with tolerance variations, the membrane disk remains constrained and the seal integrity is maintained.
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 annular washer effectively prevents axial displacement of the membrane disc, maintaining a secure seal and preventing leaks, even under high injection pressures, thus ensuring reliable delivery of the active ingredient.
Implementation Method 1
The displacement of the body in the cover allows the triggering of the gas generator, generating a pressurized gas which moves the pistons to inject the active ingredient through the patient's skin
Implementation Method 2
The tubular part of the membrane is designed to expand axially under the effect of pressurized gas, in order to drive the pistons in displacement
Implementation Method 3
the annular disk of the membrane is compressed axially between the upper end of the reservoir and the seat formed by the body of the device
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a needleless injection device (10) having a body (12) forming a receptacle (44) which is delimited by a tubular wall (46) and which extends axially from an upper radial seat (48), a gas generator (16), a tubular reservoir (24) which encloses an active principle (26) and which extends axially in said receptacle (44) from an upper end forming an upper flange (40) to a lower end (36), an elastically deformable membrane (50) in the general shape of a T, which comprises a radial annular disc (52) that is interposed axially between the upper flange (40) of the reservoir (24) and said seat (48), and a tubular part (54) which extends axially in the reservoir (24), characterized in that it has an annular washer (64) which is interposed axially between the annular disc (52) of the membrane (50) and the upper flange (40) of the reservoir (24).