Drug Delivery Drive Mechanism with Bidirectional Coupling
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Solution Overview
Problem
Existing drug delivery devices face challenges in achieving accurate dose delivery due to potential unintentional movement of the piston rod during dose setting, which can lead to inconsistencies in the amount of drug dispensed.
Innovation Solution
A drive mechanism with a stop member and a drive member that converts rotational movement into lateral movement of the piston rod, featuring a bi-directional coupling system for setting and dispensing, and a reset mode to prevent unintentional proximal movement, ensuring precise dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the drive member is allowed to rotate freely during dose setting, then the device structure is simpler, but the piston rod may move unintentionally in the proximal direction reducing dose accuracy
Solution Approach 1:
The stop member acts as an intermediary element between the drive member and the housing. It selectively prevents rotational movement of the drive member during dose setting while allowing rotation during dose delivery. This mediator component resolves the contradiction by enabling precise control over when the drive member can rotate, thereby preventing unintentional proximal movement of the piston rod during setting while maintaining operational simplicity.
2Reliability
If the first coupling portion is permanently coupled to the drive portion, then the drive mechanism is more reliable, but the drive portion cannot be reset
Solution Approach 1:
The coupling between the first coupling portion and the drive portion is made dynamic rather than static. The coupling state changes based on operational mode: coupled during set and dispense modes for reliable force transmission, and decoupled during reset mode to allow repositioning. This dynamic coupling mechanism resolves the contradiction by providing both reliability when needed and adaptability when needed through state-dependent connection.
3Manufacturing precision
If the stop member prevents all rotational movement of the drive member, then dose accuracy is improved, but the drive member cannot rotate during dose delivery
Solution Approach 1:
The stop member applies preliminary anti-action by preventing rotational movement of the drive member during the dose setting phase. This pre-prevents potential errors in piston rod positioning before dose delivery begins. The stop member's selective engagement ensures that this restrictive action is applied only when needed (during setting) and removed when needed (during delivery), thus resolving the contradiction between precision and operability.
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 drive mechanism enhances dose accuracy by preventing rotational movement during dose setting and allowing controlled distal movement of the piston rod, ensuring that the intended dose is consistently delivered.
Implementation Method 1
a drive mechanism of the drive member is adapted to convert rotational movement of the drive member into a, preferably lateral, movement of the piston rod in the distal direction with respect to the housing
Data Source
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AI summary
A drive mechanism for a drug delivery device (1) comprises a housing (13, 17, 40) having a proximal end (8) and a distal end (7) and a piston rod (12), which is adapted to be displaced in a distal direction with respect to the housing when dispensing a drug dose. A drive member (20) is adapted to be rotated when dispensing the drug dose, wherein the drive mechanism is configured to convert rotational movement of the drive member (20) into a movement of the piston rod (12) in the distal direction with respect to the housing (13, 17, 40). A stop member (26) is adapted to prevent a rotational movement of the drive member (20) with respect to the housing when setting a drug dose. The drive member (20) comprises a drive portion (200) being coupled to the piston rod (12) and a first coupling portion (202) which couples the drive portion (200) and the stop member (26), wherein the drive mechanism is configured to be switchable between a set and dispense mode of operation and a reset mode of operation, and wherein, in the set and dispense mode, said first coupling portion (202) is bidirectionally coupled to the drive portion (200) for setting and dispensing the drug dose, and wherein, in the reset mode, said first coupling portion is decoupled from the drive portion (200) to allow a reset operation to be performed for the drive mechanism.