Unidirectional Shaft Drug Reservoir Loading Mechanism
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Solution Overview
Problem
Conventional drug delivery systems face issues with unintended drug delivery due to the siphoning effect, require complex circuitry for motor-driven systems, and have difficulties in accommodating partially filled cartridges, especially when replacing drug reservoirs, which involves reversing the lead screw or manual reset mechanisms.
Innovation Solution
A drug reservoir loading and unloading mechanism using a unidirectional rotated shaft, where the piston rod is connected to the shaft with a flexible nut segment that disengages from the threads when the lid is opened, allowing for easy removal and replacement of the reservoir without reversing the shaft, and incorporating a ratchet mechanism for increased torque and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lead screw mechanism is used to drive the plunger, then the drug reservoir can be securely connected and driven, but the system requires complex circuitry for motor reversal and additional switches when replacing reservoirs
Solution Approach 1:
Instead of reversing the lead screw direction to disengage the plunger, the invention inverts the approach by using a ratchet mechanism that allows the lead screw to rotate freely in the reverse direction while preventing reverse rotation only during the driving phase. This eliminates the need for complex motor reversal circuitry while maintaining secure connection during drug delivery.
Solution Approach 2:
The invention extracts the reversal function from the motor control system by introducing a mechanical ratchet mechanism that passively allows free reverse rotation during reservoir replacement. This separates the driving function (requiring secure connection) from the replacement function (requiring free rotation), simplifying the overall system complexity.
2Ease of operation
If the lead screw is reversed to insert a new reservoir, then the piston engagement returns to the starting position, but this requires additional switches and complex circuitry
Solution Approach 1:
The ratchet mechanism provides self-service by automatically allowing the lead screw to rotate freely in reverse when the plunger is disengaged during reservoir replacement. This eliminates the need for additional switches or complex control circuitry to manage the reversal process, as the mechanical structure itself enables the required motion.
3Adaptability or versatility
If manual reset configuration is used, then the threads can be engaged and disengaged, but the housing becomes more complex and the mechanism requires sophisticated nut design
Solution Approach 1:
The invention applies the disposable principle by making the plunger and its connection to the lead screw temporary and single-use. The plunger is designed to be easily disconnected from the lead screw after drug delivery, eliminating the need for complex reusable reset mechanisms. This allows simple housing design while maintaining the ability to engage and disengage threads for reservoir replacement.
4Reliability
If the plunger is physically connected to the lead screw, then the drug reservoir is secured, but unintended drug delivery occurs due to the siphoning effect
Solution Approach 1:
The invention applies preliminary action by ensuring the plunger is firmly secured to the lead screw through the ratchet mechanism before drug delivery begins. This pre-securing action prevents any unintended movement or siphoning effect during the delivery process, as the mechanical connection is established and locked in place before the harmful effect can occur.
Data Source
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AI summary
A drug delivery device (10) comprises a shaft (20); a drive system (30) operably connected to the shaft and configured to only rotate the shaft in a first direction; a drug reservoir (12) having a plunger (16) used to adjust a volume of the drug reservoir; a piston rod (14) operably connected at a first end to the plunger and providing threads (70) on an exterior surface thereof, the piston rod being operably connected to the shaft, wherein said drug delivery device provides a secured position which permits the rotation of the shaft to drive the piston rod and move the plunger to adjust the volume of the drug reservoir, and an unsecured position which permits the drug reservoir to be removed unobstructed from the drug delivery device and replaced without having to rotate the shaft in a direction opposite to the first direction. Said drug delivery device further comprises a partially threaded nut (74) that is spring (84) biased, which allows engagement with the threads of the piston rod in a first position to permit plunger (16) movement via rotation of the shaft, and which disengages with the threads of the piston rod in a second position, thereby preventing plunger movement with or without shaft rotation.