Medication Delivery Piston Rod Ratchet Stop Mechanism
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Solution Overview
Problem
Existing medication delivery devices face challenges in providing user comfort, safety, and reducing manufacturing costs while minimizing errors, particularly in setting and delivering precise doses without accidental overdosing or underdosing.
Innovation Solution
The design incorporates a rotatable piston rod with ratchet teeth for dose setting, a stop member for distal locking after dose delivery, and a priming mechanism to ensure accurate dose delivery, preventing unintended further dosing and featuring a compact, error-reduced design with minimal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotatable piston rod with ratchet teeth is used for dose setting, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The piston rod integrates multiple functions: it serves as both the plunger for medication delivery and the dosing member for dose setting. The ratchet teeth are directly formed on the piston rod itself rather than being separate components, merging the dosing mechanism with the delivery mechanism to reduce overall device complexity while maintaining ease of operation.
Solution Approach 2:
The piston rod performs multiple functions: it acts as the plunger to push medication, the dosing member with ratchet teeth for rotational dose setting, and the component that engages with axial blind guides for both dosing and delivery operations. This multi-functionality reduces the number of separate components needed in the device.
2Measurement precision
If axial blind guides of different lengths are used for dose delivery, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The axial blind guides are segmented into different lengths, with each length corresponding to a specific dose amount. This segmentation allows for precise dose measurement through the selection of appropriate guide lengths, while the standardized design of these segmented guides facilitates manufacturing.
Solution Approach 2:
The device is designed as a single-use disposable unit. The axial blind guides are pre-set to specific lengths during manufacturing, and the entire device is discarded after one use. This approach eliminates the need for high-precision adjustable mechanisms, as the dose is determined by the fixed length of the axial blind guide in the disposable unit.
3Reliability
If a stop member is added for distal locking after dose delivery, then reliability is improved, but device complexity increases
Solution Approach 1:
The stop member is pre-positioned within the device structure. After the piston rod delivers the medication and reaches the end of its travel, it automatically engages with the pre-positioned stop member, which then prevents further rotation or movement. This preliminary positioning ensures reliable locking without requiring additional active components or complex control mechanisms.
Solution Approach 2:
The piston rod automatically engages with the stop member through its own movement during the dosing process. The rotation and axial movement of the piston rod during normal operation cause it to naturally contact and lock against the stop member, providing self-service locking functionality without requiring separate actuating mechanisms.
4Reliability
If a priming mechanism is implemented to prevent accidental overdosing, then safety is improved, but ease of operation decreases
Solution Approach 1:
The priming mechanism requires the user to perform a preliminary action before the actual dosing can occur. The piston rod must be rotated to a specific priming position and held there for a predetermined time to ensure proper priming of the medication delivery system. This preliminary step prevents accidental overdosing by ensuring the device is properly prepared, but it adds an extra step to the operation sequence.
Data Source
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AI summary
An assembly for a medication delivery device (1) is described comprising a body (3), a piston rod (4) adapted and arranged to be rotated with respect to the body (3) for setting a dose of a medication (10) and to be axially moved in a distal direction with respect to the body (3) for delivering the set dose of the medication (10), wherein, as seen in cross-sect ion, the piston rod (4) comprises a plurality of ratchet teeth (24) adapted and arranged to enable rotation of the piston rod (4) during setting of a dose of the medication (10), and at least one stop member (18) secured against axial and rotational movement with respect to the body (3), wherein the stop member (18) is adapted and arranged to mechanically cooperate with the piston rod (4), wherein when setting the dose of the medication (10), the piston rod (4) becomes aligned with the stop member (18), wherein when delivering the set dose, the piston rod (4) is moved in the distal direction towards the stop member (18) such that the piston rod (4) and the stop member (18) abut at the end of the dose delivery operation and such that further distal movement of the piston rod (4) is prevented after the set dose of the medication (10) was delivered. Furthermore, a medication delivery device (1) comprising the assembly is described.