Rack and Pinion Drive for By-Pass Cartridge Mixing
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Solution Overview
Problem
Existing pharmaceutical delivery systems, such as dual-chamber syringes with by-pass channels, face challenges in ensuring complete mixing of powdered drugs with diluents due to the risk of the inner piston being pushed too far past the by-pass channel, leading to incomplete fluid transfer and difficulty in correction, and lack of controlled mixing.
Innovation Solution
A device with a by-pass type cartridge featuring a plunger rod with a rack gear engaging a pinion gear, driven by a wheel, which ensures slow and steady advancement of the plunger to facilitate complete mixing of the diluent with the powdered drug, utilizing a gas permeable hydrophobic membrane to retain the liquid and evacuate air, reducing the likelihood of the piston moving past the by-pass channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual mixing procedure is used, then simplicity of device is maintained, but mixing completeness and drug utilization are worsened
Solution Approach 1:
The patent replaces manual mechanical mixing with an automated rack and pinion driven plunger system. The pinion gear engages with the plunger rod's rack gear to automatically advance the plunger through the by-pass channel at a controlled rate, eliminating manual intervention and ensuring complete mixing of drug powder with diluent.
Solution Approach 2:
The patent changes the control parameter from manual user action to mechanically controlled incremental movement. The rack and pinion mechanism converts rotational motion into linear plunger movement at a controlled rate, ensuring the plunger advances slowly and steadily through the by-pass channel to achieve complete mixing without rushing past the channel.
2Speed
If rapid piston advancement is used, then delivery speed is improved, but mixing completeness deteriorates
Solution Approach 1:
The patent employs a dynamic control mechanism where the rack and pinion gear system allows for controlled advancement speed. The engagement between the pinion teeth and rack gear naturally regulates the plunger's movement speed, enabling slow steady progression during mixing phase while maintaining the ability to accelerate during delivery phase.
Solution Approach 2:
The mechanical engagement of the rack and pinion provides inherent feedback control. As the plunger advances through the by-pass channel, the gear teeth meshing ensures controlled incremental movement. The system self-regulates the advancement rate based on the mechanical interaction between the pinion and rack, preventing过快 advancement that would compromise mixing.
3Productivity
If outer piston is pushed vigorously, then transfer speed is improved, but piston control and fluid transfer completeness deteriorate
Solution Approach 1:
The patent replaces direct manual pushing of the outer piston with a rack and pinion driven mechanism. The pinion gear on the drive shaft engages with the rack gear on the outer piston rod, converting rotational motion into controlled linear advancement. This mechanical substitution eliminates the risk of overly vigorous application that causes loss of control.
Solution Approach 2:
The rack and pinion mechanism serves as an intermediary between the user's rotational input and the linear motion of the piston. This intermediate mechanical transmission system provides controlled force application, preventing direct vigorous pushing while maintaining efficient transfer speed through gear-driven motion.
4Reliability
If inner piston is pushed past by-pass channel, then complete fluid transfer is achieved, but correction difficulty increases
Solution Approach 1:
The patent applies preliminary anti-action by using the rack and pinion mechanism to prevent the inner piston from being pushed too far past the by-pass channel. The controlled mechanical advancement ensures the piston reaches the channel at the correct position and progresses through it at a regulated rate, preventing the harmful action of overshooting that would make correction difficult.
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
The solution effectively prevents the piston from being pushed too far past the by-pass channel, ensuring complete transfer of the diluent and even mixing of the pharmaceutical constituents, allowing for efficient and controlled delivery of the active ingredients.
Implementation Method 1
A driving device including a pinion gear is provided on the syringe body for driving the plunger rod, which in turn has a rack gear engageable with said pinion gear
Implementation Method 2
utilizing a gas permeable hydrophobic membrane to retain the liquid and evacuate air
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A device for mixing a substance comprised of two constituents contained in a cartridge (12) and having a cartridge holder (32) thereabout, the device comprising a plunger rod (46) for pushing a closure member (20) to permit the transfer of a diluent in a second chamber (28) through a by-pass channel (24) to mix with a constituent in a first chamber (26), the plunger rod (48) being driven by means of a rack (48) and a pinion gear (50) arrangement to prevent overly rapid movement of the plunger rod (46).