Rotatable Collar Torque Conversion for Auto-Injector Activation
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Solution Overview
Problem
Existing auto-injector devices require high activation and hold forces, which can lead to user discomfort, incorrect device activation, and partial drug delivery.
Innovation Solution
The injection device incorporates a plunger with recesses, toothed beams, and a rotatable collar with cam tracks, allowing for the conversion of biasing force into torque, reducing the peak activation force required for device operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a needle cover spring is used to automatically extend the needle cover for shielding, then needle shielding is provided automatically, but high activation force and hold force are required from the user
Solution Approach 1:
The collar is designed to rotate dynamically during needle cover retraction, converting the user's retraction force into rotational motion that drives the toothed beams to release the plunger. This dynamic conversion reduces the linear force required compared to direct axial compression of the spring.
Solution Approach 2:
The solution transitions from one-dimensional axial force application to two-dimensional rotational motion. The collar rotation and cam track mechanism convert the retraction force into angular displacement, which then actuates the plunger release through the toothed beams, reducing peak force requirements.
2Extent of automation
If high activation force is applied to compress the needle cover spring, then the device can be activated, but user discomfort and incorrect device activation occur
Solution Approach 1:
The collar and cam track mechanism serve as intermediaries between the user's retraction action and the plunger release. Instead of directly compressing the spring, the user retracts the needle cover which rotates the collar, which then actuates the toothed beams to release the plunger. This intermediary mechanism smooths the force profile and improves ease of operation.
3Stability of the object's composition
If the user must hold the device at the injection site during drug delivery, then injection stability is maintained, but high hold force causes pain and discomfort
Solution Approach 1:
The collar rotation mechanism provides dynamic stabilization during injection. As the collar rotates during needle cover retraction, it maintains engagement with the toothed beams, providing continuous mechanical coupling and stability throughout the drug delivery process without requiring excessive holding force.
4Extent of automation
If high activation force is required, then the needle cover can be pushed into the device, but inadvertent early removal or wet injection site occurs
Solution Approach 1:
The cam track geometry provides mechanical feedback during needle cover retraction. The shaped cam track guides the collar rotation through specific angular positions that correspond to different stages of needle cover retraction, ensuring complete retraction and reliable plunger release while preventing premature activation.
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 design reduces the peak activation force, making the device easier to use, minimizing user discomfort, and ensuring complete drug delivery.
Implementation Method 1
biasing means for applying a biasing force to bias the plunger in a distal direction of the injection device
Implementation Method 2
each of the one or more plunger recesses is shaped to urge a tooth of the corresponding toothed beam outwards when the biasing force is applied to the plunger
Implementation Method 3
the one or more collar recesses are shaped to cooperate with a tooth of a corresponding toothed beam to apply a torque to the rotatable collar when the corresponding toothed beam is urged outwards
Implementation Method 4
The cam track is shaped to guide the shroud pin from an initial position to a hold position and cause the collar to rotate relative to the injection device body during retraction of the needle shroud
Data Source
AI summary
An injection device comprising: an injection device body; a plunger comprising one or more plunger recesses; biasing means for applying a biasing force to bias the plunger in a distal direction of the injection device; a casing at least partially enclosing the plunger, the casing comprising one or more toothed beams each comprising a tooth engageable with a corresponding plunger recess of the one or more plunger recesses; and a rotatable collar at least partially enclosing the casing and comprising one or more collar recesses on an inner surface of the rotatable collar.