Drug Delivery Piston Rod Automatic Reset Mechanism
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Solution Overview
Problem
Existing reusable drug delivery devices face challenges in efficiently resetting the piston rod after cartridge replacement, requiring manual intervention and lacking an easy and automatic mechanism for facilitating drug container changes.
Innovation Solution
A drive mechanism featuring a piston rod with a biasing member, such as a helical spring, that is loaded during drug delivery and automatically resets the piston rod to its initial position when the cartridge holder is removed, utilizing a lock nut and activation pin for rotational engagement and disengagement to facilitate easy cartridge replacement and automatic reset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual reset of the piston rod is used after cartridge replacement, then the device structure can be simpler, but the ease of operation deteriorates due to requiring manual intervention
Solution Approach 1:
The piston rod automatically resets itself through the biasing member when the cartridge holder is removed, eliminating the need for manual reset intervention by the user. The system serves itself by utilizing the mechanical connection between the cartridge holder and piston rod to trigger the reset action.
Solution Approach 2:
The biasing member is pre-loaded during the normal operation phase when the cartridge holder is attached, storing energy that is automatically released to reset the piston rod when the cartridge holder is removed. This preliminary loading enables the automatic reset action without requiring additional user input.
2Ease of operation
If automatic reset mechanism is implemented, then the ease of operation improves, but the device complexity increases due to additional components
Solution Approach 1:
The lock nut serves multiple functions: it provides rotational locking of the piston rod during normal operation, acts as a guide for the biasing member, and enables the automatic reset mechanism. By making one component multi-functional, the patent avoids adding separate dedicated components for each function.
Solution Approach 2:
The patent combines the reset mechanism with the existing cartridge holder and lock nut components rather than adding completely separate mechanisms. The biasing member is integrated into the space between these existing components, merging the reset function with the structural elements already present in the device.
3Productivity
If the piston rod is not automatically reset, then the device complexity remains low, but the productivity deteriorates due to time loss during cartridge replacement
Solution Approach 1:
The automatic reset mechanism allows the piston rod to quickly return to its initial position through the biased movement when the cartridge holder is removed, skipping the time-consuming manual reset step. This rushing through of the reset action significantly reduces the total time required for cartridge replacement.
4Reliability
If manual reset procedure is used, then the manufacturing precision requirements are lower, but the reliability deteriorates due to potential user error
Solution Approach 1:
The biasing member provides continuous mechanical feedback to the piston rod, ensuring it returns to the correct initial position relative to the drive member. The pre-loaded spring acts as a feedback mechanism that automatically corrects any positioning deviations and ensures consistent reproducible positioning after cartridge replacement.
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 easy and automatic reset of the piston rod, simplifying the process of changing drug containers and ensuring the device is ready for the next use, while also protecting the internal components from damage.
Implementation Method 1
A spiral spring of the mechanism is attached to the body of the device and to a reset nut, which rotates together with the piston rod. The spring is loaded by the rotation of the piston rod and the simultaneous rotation of the reset nut during dose setting and generates a rotation of the piston rod in the opposite direction when the cartridge holder is removed and the piston rod is released.
Implementation Method 2
The spring is loaded by the rotation of the piston rod and the simultaneous rotation of the reset nut during dose setting and generates a rotation of the piston rod in the opposite direction when the cartridge holder is removed and the piston rod is released.
Data Source
Figure 1
Figure 2~3
AI summary
The drive mechanism for a drug delivery device comprises a piston rod, which is displaced in a distal direction for a delivery of a dose and in a proximal direction for a reset, and a rotatable drive member, which is threadedly engaged with the piston rod and rotates during the delivery of the dose. A biasing member is provided, which is loaded by the rotation of the drive member during the delivery of the dose and tends to rotate the piston rod with respect to the drive member in such a way that the piston rod is screwed into the drive member and is thereby advanced in the proximal direction. The drug delivery device is provided with such a drive mechanism.