Medication Delivery Piston Rod Reset Mechanism
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Solution Overview
Problem
Existing medication delivery devices face challenges in easy and unambiguous dose setting, low dispensing force requirements, and the need for a reset mechanism that does not contaminate the drive mechanism, especially for users with impaired vision or dexterity, and ensure no pre-pressurization of the medication cartridge during cartridge replacement.
Innovation Solution
A medication delivery device with a piston rod having two threaded sections, where a reset element is engaged with the piston rod to prevent proximal movement during operation and allows resetting by rotating and moving the piston rod proximally when the cartridge is replaced, without the user touching the drive mechanism, ensuring no movement of the cartridge bung and thus no pressurization of the medication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drive mechanism is exposed for user operation, then ease of operation is improved, but the risk of contamination and damage increases
Solution Approach 1:
The cartridge holder serves as an intermediary component that the user interacts with to operate the device. When the user rotates the cartridge holder, it indirectly actuates the piston rod through the reset element and threaded connection, without the user's fingers needing to touch the piston rod or drive mechanism directly. This mediator approach maintains ease of operation while preventing contamination of sensitive internal components.
2Ease of operation
If the piston rod can move freely during cartridge replacement, then ease of cartridge replacement is improved, but pre-pressurization of the medication cartridge occurs
Solution Approach 1:
The reset element is designed to maintain engagement with the piston rod during cartridge replacement, performing a preliminary protective action. By keeping the piston rod constrained through the threaded connection with the reset element, the system prevents premature movement of the bung and avoids pre-pressurization of the medication cartridge before the user intends to deliver a dose.
Solution Approach 2:
The reset element and its threaded connection with the piston rod create a preliminary counteracting force that opposes any unintended movement of the piston rod during cartridge replacement. This preliminary anti-action prevents the harmful effect of pre-pressurization by maintaining the piston rod in a controlled, constrained state until the user deliberately initiates dose delivery.
3Ease of repair
If the reset mechanism requires direct user contact with the drive mechanism, then resetting can be performed, but the drive mechanism may be damaged through contamination
Solution Approach 1:
The cartridge holder acts as an intermediary that the user manipulates to reset the device. By rotating the cartridge holder, the user indirectly drives the piston rod proximally through the reset element's threaded connection, without direct contact with the piston rod or drive mechanism. This maintains resetting capability while protecting the drive mechanism from contamination and damage.
4Measurement precision
If the piston rod is constrained during operation, then medication delivery accuracy is improved, but resetting becomes more complex
Solution Approach 1:
The reset element serves multiple functions: it constrains the piston rod during medication delivery to ensure accuracy, and simultaneously enables resetting by allowing proximal movement when the cartridge holder is rotated. The threaded connection provides a universal mechanism that maintains control during operation while permitting controlled resetting, reducing overall device complexity compared to separate constraint and reset mechanisms.
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 device allows for easy and unambiguous dose setting and resetting without direct contact with the drive mechanism, reducing the risk of contamination and ensuring accurate medication delivery by preventing pre-pressurization of the cartridge, making it suitable for users with impaired vision or dexterity.
Implementation Method 1
The piston rod comprises two threaded sections, wherein a first threaded section is provided for threaded engagement with a reset element and a second threaded section is provided for threaded engagement with the drive device
Data Source
AI summary
A medication delivery device comprising a housing, a medication receptacle, a piston rod which is moveable distally, and a drive device for rotating the piston rod in a first rotational direction. The piston rod comprises two threaded sections, a first threaded section for threaded engagement with a reset element and a second threaded section for threaded engagement with the drive device. In an operational state, the reset element is prevented from rotating and the piston rod prevented from moving proximally. In a resetting state, the reset element is allowed to rotate, such that the delivery device is resettable by rotating the piston rod and the reset element in a second rotational direction and moving the piston rod proximally.