Plastically Deformable Piston Rod for Drug Delivery Device
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Drug delivery devices, such as pen-type injectors, often require users to prime the device before use, which can lead to inaccuracies in the first dispensed dose due to manufacturing tolerances between components like the piston rod and cartridge bung, potentially resulting in incorrect dosing.
Innovation Solution
A method involving a plastically deformable piston rod that is adjusted to eliminate gaps by applying force, allowing it to abut the bung, thereby eliminating the need for user priming and ensuring accurate dosing without increasing stress or loads within the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manufacturing tolerances are reduced to eliminate gaps between piston rod and cartridge bung, then dosing precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The piston rod material's physical state is changed from rigid to plastically deformable through temperature control or material selection, allowing the rod to be compressed and permanently deformed to eliminate gaps. This parameter change enables tolerance compensation without requiring ultra-precise manufacturing tolerances.
Solution Approach 2:
The piston rod is pre-deformed during assembly to anticipate and compensate for manufacturing tolerances before the device is used. By performing the gap elimination action during manufacturing rather than requiring user priming, the system ensures accurate dosing from the first use.
2Ease of manufacture
If a priming step is required to close gaps, then ease of manufacture is improved, but reliability of dosing is worsened due to user error
Solution Approach 1:
The piston rod performs self-adjustment through plastic deformation during normal operation, eliminating the need for user priming. The material's inherent plasticity allows the rod to automatically close gaps and adapt to tolerance variations without requiring user intervention or special priming procedures.
Solution Approach 2:
The piston rod material is selected or treated to exhibit plastic deformability under operational conditions, enabling automatic gap closure. This parameter change transforms the rod from a rigid component requiring manual adjustment to a self-adjusting component that ensures reliable dosing.
3Measurement precision
If the piston rod is made plastically deformable to eliminate gaps, then dosing precision is improved, but the risk of fracture or damage increases
Solution Approach 1:
The piston rod is designed with localized plastic deformability at specific regions while maintaining overall structural integrity. The material or cross-section is engineered to allow controlled deformation at the deformation zone while preserving sufficient strength in load-bearing areas to prevent fracture.
Solution Approach 2:
The piston rod undergoes controlled plastic deformation during assembly before being subjected to operational loads. This preliminary deformation eliminates gaps and sets the rod in its final position, ensuring that subsequent operational stresses do not cause fracture but rather maintain the established fit.
4Manufacturing precision
If force is applied to plastically deform the piston rod, then gap elimination is achieved, but stress and loads within the rod increase
Solution Approach 1:
The piston rod material's yield strength is modified through temperature control or material selection to enable plastic deformation at lower applied forces. By changing the material's physical parameters, the deformation can be achieved with forces that do not create excessive internal stresses or residual loads.
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
This method ensures accurate and reliable delivery of the first dose by adjusting the piston rod to match the cartridge bung, eliminating the need for user priming and addressing manufacturing tolerances, thus enhancing user-friendliness and dosing precision.
Implementation Method 1
a force is applied on the piston rod in a state wherein at least a part of the piston rod or at least a part of the area being manufactured from a plastically deformable material allows plastic deformation. Upon applying the force on the piston rod, the piston rod is plastically deformed
Data Source
Figure 1
Figure 2~3B
Figure 4A~5B
AI summary
A method for assembling a drug delivery device comprising a body (2) retaining a piston rod (3) and a cartridge (5) retaining a bung (6) and holding a drug, said body (2) having a distal end (11) and a proximal end (12), comprises the following steps: A) Providing the cartridge (5) and the body (2) retaining the piston rod (3), wherein the piston rod (3) is plastically deformable, at least a part of said plastically deformable piston rod being manufactured from a plastically deformable material, B) Applying a force on the piston rod (3), at least a part of the piston rod (3) being in a state that allows plastic deformation, so that the piston rod (3) is plastically deformed and an element of the piston rod (3) abuts the bung (6), C) Applying conditions in order to bring the plastically deformed piston rod (3) of step B) into an altered state wherein no further plastic deformation takes place, D) Securing the cartridge (5) to the body (2).