Drug Delivery Piston Rod Adjustment Member Axial Clearance
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Solution Overview
Problem
Existing drug delivery devices face challenges in consistently eliminating axial clearance between the piston rod and piston, leading to variations in dose accuracy and manufacturing inefficiencies, particularly due to manufacturing tolerances.
Innovation Solution
The introduction of a drive mechanism with a piston rod and adjustment member featuring a contour system with axially facing steps and radially disposed protrusions, allowing for precise adjustment and potential elimination of axial clearance, enabling predictable and uniform dose dispensing without the need for extensive control measurements during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional piston rod and piston assembly is used without adjustment mechanism, then device construction is simple, but axial clearance cannot be eliminated leading to dose accuracy variations
Solution Approach 1:
The adjustment member is segmented into multiple axial positions defined by contoured surfaces, allowing selective positioning to eliminate clearance. The piston rod assembly is divided into adjustable components that can be positioned relative to each other through the contour system.
Solution Approach 2:
The adjustment member acts as an intermediary element between the piston rod and piston, providing a contoured surface system that mediates the clearance elimination. This intermediary component enables precise axial positioning without requiring direct modification of the piston rod or piston.
2Manufacturing precision
If clearance reduction is performed manually for each device, then dose accuracy is improved, but manufacturing time and cost increase
Solution Approach 1:
The contoured surface system is pre-configured on the adjustment member with multiple axial positions defined during manufacturing. This preliminary action eliminates the need for manual adjustment during final assembly, as the clearance elimination positions are already prepared and defined.
Solution Approach 2:
The adjustment member is designed to self-position at the correct axial clearance elimination position through the contour system, without requiring external manual intervention. The mechanism serves itself by using the predefined contoured surfaces to automatically establish the correct position during assembly.
3Adaptability or versatility
If multiple material types are used in device construction, then functional requirements are met, but manufacturing complexity and disposal difficulty increase
Solution Approach 1:
The adjustment member serves multiple functions: it provides axial clearance elimination, defines dose delivery positions, and acts as a structural component of the piston rod assembly. This multi-functionality reduces the need for separate specialized components and material types.
4Manufacturing precision
If priming operation is required for each device, then dose accuracy is ensured, but user time and complexity increase
Solution Approach 1:
The axial clearance is eliminated during the manufacturing process through the adjustment member's contoured surface system, performing the clearance elimination action in advance. This preliminary action removes the need for users to perform priming operations to establish proper clearance, as it is already done during assembly.
Data Source
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AI summary
The present invention relates to a drug delivery device that houses a piston equipped cartridge and a drive mechanism comprising a piston rod (170) configured for axially moving the piston in a distal direction. An adjustment member (150) connects to the member (150) comprises a first contour system (175) defining a plurality of steps (175´, 175´´, 175´´´) being circumferentially disposed and arranged axially offset from one another. The other of the piston rod (170) and the adjustment member (150) comprises at least one radially disposed protrusion (155). For eliminating an axial clearance between the piston rod (170) and the piston of the cartridge the at least one radially disposed protrusion (155) axially engages a selective one of said plurality of steps (175´, 175´´, 175´´´) so that the relative rotational position between the piston rod (170) and the adjustment member (150) is decisive for the axial position of the adjustment member (150) relative to the piston rod (170).