Medical Injector Ratcheting Plunger Dose Control
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Solution Overview
Problem
Medical injectors face challenges in controlling the linear displacement of plungers, leading to difficulties in managing dose size, and existing pen injector mechanisms are complex with multiple parts, increasing costs and complexity.
Innovation Solution
A medical injector with a displaceable plunger featuring spaced-apart ratchet teeth and an indexer that allows unidirectional distal movement while preventing proximal movement, coupled with a rotatable actuator that engages and disengages ratchet teeth to control plunger displacement, minimizing the number of cooperating parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct linear force is applied to advance the plunger, then the injection function is achieved, but precise control of plunger displacement and dose size becomes difficult
Solution Approach 1:
The patent replaces direct linear mechanical force application with a rotational mechanical system. The actuator rotates the plunger, and ratchet teeth convert this rotational motion into controlled linear displacement. This substitution enables precise control of plunger displacement through rotational positioning, directly resolving the contradiction between measurement precision and ease of operation.
2Ease of operation
If a lead screw or rotating plunger with multiple mechanical connections is used, then plunger control is achieved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the plunger itself. The plunger incorporates both the drive mechanism (ratchet teeth) and the indexing system (protrusions engaging with recesses) directly on its body. This integration eliminates the need for separate lead screws and multiple cooperating parts, achieving controlled plunger movement while minimizing device complexity.
3Reliability
If ratchet teeth are provided on the plunger, then proximal movement is prevented, but the mechanism complexity increases
Solution Approach 1:
The patent combines the ratchet teeth and indexing features directly on the plunger body, merging multiple functions into a single component. The ratchet teeth prevent proximal movement while the protrusions and recesses provide indexing, eliminating the need for separate mechanisms and reducing overall complexity.
4Reliability
If multiple cooperating parts are used in pen injector mechanism, then reliable operation is achieved, but manufacturing costs increase
Solution Approach 1:
The patent integrates multiple functions (ratchet mechanism, indexing system, drive mechanism) directly into the plunger component. This merging reduces the total number of parts that need to be manufactured and assembled, directly lowering manufacturing costs while maintaining reliable operation through the integrated features.
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 solution enables precise control over plunger displacement and dose size with a simplified mechanism, reducing complexity and costs while ensuring accurate medicament delivery.
Implementation Method 1
The plunger includes a plurality of spaced-apart ratchet teeth disposed along the length thereof. At least one indexer is provided and is formed to engage the plunger, wherein the indexer is configured to allow the plunger to displace distally toward a distal end of the body but not proximally toward a proximal end of the body.
Data Source
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AI summary
A medical injector has a body with a displaceable plunger, which has a plurality of ratchet teeth along its length. An indexer is provided to engage the plunger, wherein the indexer is configured to allow the plunger to displace distally. The medical injector also includes an actuator having an engagement portion formed to engage the ratchet teeth. The.actuator is displaceable to a ready state, the engagement portion being displaced proximally relative to the plunger with the actuator being displaced to the ready state. The indexer prevents proximal movement of the plunger, thereby allowing the engagement portion to bypass one or more of the ratchet teeth with the actuator being displaced to the ready state. The plunger is slidably displaceable relative to the body, and rotatable relative to the body to selectively engage and disengage ratchet teeth engaged with the indexer and the actuator.