Medication Delivery Device Resilient Member Piston Relaxation
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Solution Overview
Problem
Medication delivery devices often experience medication 'weeping' after dose delivery, leading to inaccurate dosing and potential bruising, especially with drugs like heparin, due to uncontrolled piston relaxation and pressure retention.
Innovation Solution
A medication delivery device with a resilient member that moves the drive member and piston rod proximally after dose delivery, reducing pressure on the piston and creating space for relaxation, thereby minimizing unintended medication dispensing and bruising risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the piston rod maintains pressure on the piston after dose delivery, then the medication can be delivered accurately, but the piston cannot relax properly causing medication weeping
Solution Approach 1:
The resilient member is pre-loaded during dose delivery to maintain pressure on the piston for accurate medication delivery. After dose delivery, the resilient member automatically releases this pressure, allowing the piston to relax and preventing medication weeping. This preliminary action ensures both accurate dosing and prevents harmful weeping.
Solution Approach 2:
The system dynamically transitions from a high-pressure state during dose delivery to a low-pressure state after delivery. The resilient member enables this dynamic pressure adjustment, maintaining force when needed and releasing it when dose delivery is complete, thus preventing continuous pressure that would cause weeping.
2Object-generated harmful factors
If the piston rod is moved proximally after dose delivery, then the piston can relax and reduce weeping, but the device complexity increases
Solution Approach 1:
The resilient member automatically performs the function of moving the piston rod proximally after dose delivery without requiring external control or additional complex mechanisms. The stored elastic energy in the resilient member self-driven the pressure release and piston relaxation, preventing medication weeping while maintaining device simplicity.
Solution Approach 2:
The resilient member acts as an intermediary between the drive member and the piston rod, mediating the pressure transmission. It transfers force during dose delivery and then releases it to allow piston relaxation, simplifying the overall control mechanism while effectively preventing medication weeping.
3Stress or pressure
If a resilient member is added to move the drive member proximally, then pressure on the piston is reduced, but the device complexity increases
Solution Approach 1:
The resilient member serves multiple functions: it maintains pressure on the piston during dose delivery for accurate dosing, automatically releases pressure after delivery to prevent weeping, and drives the proximal movement of the drive member. This multi-functionality reduces the need for separate mechanisms, offsetting the added complexity with functional consolidation.
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 enhances dose accuracy and reduces medication 'weeping' and bruising by allowing the piston to relax in the proximal direction, ensuring precise and safe administration of pre-set doses without the need for electric energy.
Implementation Method 1
a resilient member which is arranged to move the drive member in a proximal direction with respect to the housing after dose delivery, thereby reducing pressure of the piston rod on the piston
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
A medication delivery device (1) comprises a housing (4) having a proximal end (P) and a distal end (D), a cartridge (3) for holding a medication (M), the cartridge (3) having an outlet (2), a moveable piston (5) being retained within the cartridge (3), a drive member (17) moveable in a proximal direction with respect to the housing (4) for setting a dose of medication (M) to be delivered and in the distal direction with respect to the housing (4) for delivering the dose and a piston rod (10) adapted to drive the piston (5) in a distal direction with respect to the cartridge (3) for delivering the dose. The drive member (17) is releasably coupled to the piston rod (10). The medication delivery device (1) further comprises a resilient member (21 ) which is arranged to move the drive member (17) in the proximal direction with respect to the housing (4) after dose delivery, thereby reducing pressure of the piston rod (10) on the piston (5).