Medication Cartridge Plunger with Nested Force Distributor
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Solution Overview
Problem
Resilient plungers in medication cartridges are susceptible to local compression, which can lead to undesired contact with the cartridge barrel, affecting fluid-tight sealing and glide force, and rigid elements used to mitigate this often increase friction or lengthen the plunger assembly.
Innovation Solution
A medication cartridge plunger design featuring a resilient sealing member with a recessed hollow rear end and a complementary force-distributing back plate made of a more rigid material, with a radial periphery arranged transverse to the axial direction, reduces the likelihood of undesired contact and distributes expelling forces effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid element is added to distribute load over a larger surface area, then local compression is reduced, but frictional resistance increases due to undesired contact with the cartridge barrel
Solution Approach 1:
The rigid back plate is nested within the hollow recess of the sealing member, allowing the force distributing member to be contained within the sealing member's hollow region. This nesting arrangement enables the rigid plate to distribute load effectively while its peripheral edges remain constrained within the hollow, preventing undesired contact with the cartridge barrel and reducing frictional resistance.
Solution Approach 2:
The hollow recess acts as an intermediary space that separates the rigid back plate from the cartridge barrel. By providing this intermediate hollow region, the design allows the rigid plate to perform its force distribution function while preventing direct contact between the plate's peripheral edges and the barrel, thereby eliminating the source of frictional resistance.
2Reliability
If the diameter of the rigid element is increased to improve force distribution, then load distribution effectiveness improves, but the plunger assembly length increases
Solution Approach 1:
The rigid back plate is nested within the hollow recess of the sealing member, utilizing the existing hollow space to accommodate the force distributing member. This nesting arrangement allows the rigid plate to have sufficient diameter for effective force distribution without extending the overall plunger assembly length, as the plate is contained within the hollow region rather than extending beyond the sealing member's outer dimensions.
3Object-affected harmful factors
If the rigid element is placed on the rear end face without extending into the hollow, then contact with the barrel is reduced, but the plunger assembly becomes longer than desired
Solution Approach 1:
Instead of placing the rigid back plate externally on the rear end face, the design nests the plate within the hollow recess of the sealing member. This nesting approach allows the rigid plate to be positioned effectively for force distribution while containing it within the hollow region, thereby avoiding extension of the plunger assembly length beyond the sealing member's outer dimensions.
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 minimizes frictional resistance and allows for larger radial dimensions while maintaining a fluid-tight seal, enabling accurate and efficient medication administration.
Implementation Method 1
The sealing member is formed of a resilient material and includes a body with a forward end, a rearward end, and a length that extends in an axial direction between the forward and rearward ends
Implementation Method 2
The force distributing member is attached to the sealing member and formed of a material more rigid than the resilient material. The force distributing member is shaped complementary with the sealing member to distribute to the recessed surface a medication expelling force that may be applied to the force distributing member by an external drive element
Data Source
AI summary
A medication cartridge plunger including a sealing member, which is formed of a resilient material, and a force distributing member, which is attached to sealing member and formed of a material more rigid than the resilient material. The force distributing member is shaped complementary with the sealing member to distribute to the sealing member a medication expelling force that may be applied to the force distributing member by an external drive element to drive the plunger forward. The force distributing member includes a radial periphery fit within a hollow of the sealing member. The radial periphery has a plurality of apex regions connected by spanning regions, which apex regions are disposed along a common circle centered on an axial center of the medication cartridge plunger. The spanning regions are disposed within the common circle, and each apex region, relative to the common circle, is not in diametric alignment with any of the other apex regions.