Medicament Applicator Drive Mechanism Last Dose Blocking
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Solution Overview
Problem
Existing medicament applicators lack a reliable mechanism to prevent the setting of doses larger than the remaining medicament volume in the cartridge, leading to potential underdosing, and require modifications to existing components, increasing costs and complexity.
Innovation Solution
A drive mechanism with a last dose blocking system that includes a rotatable and axially non-translatable clutch element, a piston rod with internal and external threads, and blocking elements to prevent excessive dose setting, allowing precise dose setting and correction without modifying the applicator's core components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blocking mechanisms are added to prevent setting doses larger than remaining medicament volume, then reliability of dose delivery is improved, but device complexity increases
Solution Approach 1:
The blocking mechanism is merged with the existing dose setting assembly and piston rod structure. The blocking element integrates with the piston rod's threaded structure, combining the dosing function and blocking function into a unified mechanism rather than adding a separate independent blocking system.
Solution Approach 2:
The piston rod serves multiple functions: it translates axially to deliver medicament, rotates to set the dose volume, and incorporates blocking elements that prevent over-setting. The threaded structure on the piston rod serves both for axial translation and for engaging with blocking elements on the shaft, providing multi-functionality that reduces overall device complexity.
2Reliability
If blocking elements are integrated into piston rod and shaft, then last dose blocking reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The blocking elements are pre-positioned on the piston rod and shaft during manufacturing. The threaded structures are designed with predetermined pitch and engagement points that automatically provide the correct blocking position based on the total dose volume, eliminating the need for complex adjustable positioning mechanisms during assembly.
Solution Approach 2:
The blocking mechanism is self-regulating through the threaded engagement between the piston rod and shaft. As the piston rod rotates to set the dose, the blocking elements automatically engage at the correct position based on the number of rotations, providing self-service blocking without requiring external control or precise manual adjustment.
3Adaptability or versatility
If the piston rod is made hollow with internal thread and shaft with external thread, then adaptability of the mechanism is improved, but device complexity increases
Solution Approach 1:
The shaft with external thread is nested inside the hollow piston rod with internal thread. This nested configuration allows both components to cooperate through their threaded structures while occupying the same spatial envelope, providing adaptability for dose setting and correction without requiring additional external components.
Solution Approach 2:
The relative rotation and axial translation between the hollow piston rod and nested shaft are dynamically controlled during dose setting. The threaded engagement allows the shaft to rotate relative to the piston rod to adjust the blocking position, providing dynamic adaptability for different dose volumes while maintaining a relatively simple structural configuration.
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
Enables precise and reliable last dose blocking, preventing underdosing by limiting the translation of the piston rod and shaft, ensuring accurate medicament delivery and reducing manufacturing costs through compatibility with existing applicator designs.
Implementation Method 1
a drive element and a drive spring, wherein when a dose is being set by means of the knob, the clutch element is rotated so that the drive spring is loaded, while the drive element and the piston rod are immobilized, and when the dose is being delivered, the drive spring is being released causing the drive element to rotate together with the piston rod
Implementation Method 2
a shaft having an external thread for cooperation with the internal thread of the piston rod is located within the piston rod, the shaft being coupled in rotation with the clutch element so that during the setting of each subsequent dose the shaft is rotated in relation to the piston rod and translated axially in a proximal direction
Data Source
AI summary
A drive mechanism for an applicator for delivering a dose of a medicament, comprising: a dose setting assembly (N), a knob (1), a rotatable and axially non-translatable clutch element (2) coupled in rotation with the knob (1) and cooperating with the dose setting assembly (N), a rotatable piston rod (3) having an external thread (3.2), the piston rod (3) being located inside the clutch element (2), a drive element (4) and a drive spring (5), wherein when a dose is being set (1) by means of the knob (1), the clutch element (2) is rotated so that the drive spring (5) is loaded, while the drive element (4) and the piston rod (3) are immobilized, and when the dose is being delivered, the drive spring (5) is being released causing the drive element (4) to rotate together with the piston rod (3), the piston rod (3) being moved axially in a distal direction, wherein the piston rod (3) is hollow and has an internal thread (3.3) and a shaft (21) having an external thread (21.2) is located within the piston rod (3), the shaft (21) being engaged in rotation with the clutch element (2) so that during the setting of each subsequent dose the shaft (21) is rotated in relation to the piston rod (3) and moved axially in a proximal direction, while during the delivery of the dose the shaft (21) is immobilized in relation to the piston rod (3), and wherein the total translation of the shaft (21) in relation to the piston rod (3) caused by the setting of a defined number of doses is limited by means of blocking elements (B) located respectively on the piston rod and the shaft. An applicator for delivering a dose of a medicament, the applicator comprising the disclosed drive mechanism.