Injection Device Drive Assembly Force Control
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Solution Overview
Problem
Existing injection devices face issues with the force exerted during needle insertion potentially damaging the syringe and the increased width due to components extending rearward from the syringe carrier to the delivery driving assembly.
Innovation Solution
The injection device features a drive assembly with an insertion tube, a firing cartridge, and a delivery driver, utilizing a helical movement mechanism and stop positions defined by meshing teeth to manage the force and prevent rearward movement, along with a biasing member for an audible click indication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a strong insertion spring is used to drive needle insertion, then the needle insertion force is sufficient, but the syringe may be damaged when it bottoms out against the housing
Solution Approach 1:
A velocity regulator mechanism is incorporated that limits the velocity of the syringe during insertion. This regulator activates before the syringe bottoms out, controlling the speed and force of insertion to prevent damage while still achieving sufficient penetration force. The mechanism provides progressive resistance that cushions the final impact.
2Ease of operation
If actuating mechanism components extend rearwards from the syringe carrier to the delivery driving assembly, then the delivery function is achieved, but the device width increases
Solution Approach 1:
The actuating mechanism is redesigned to operate within the longitudinal dimension of the device rather than extending in the lateral dimension. The plunger and delivery driver are arranged to move primarily along the longitudinal axis, with compact positioning that prevents rearward extension beyond the syringe carrier, thereby maintaining a compact device width while achieving the delivery function.
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 minimizes the risk of syringe damage and maintains a compact device structure by controlling the force distribution and movement of components, ensuring efficient needle insertion and drug delivery.
Implementation Method 1
The actuation mechanism may comprise a delivery actuator (for example a compression spring) which is held in an energised (or primed position) prior to release
Implementation Method 2
The initial static friction or 'stiction' between the bung and syringe resists forward movement of the piston relative to the syringe
Data Source
AI summary
Injection device including a casing, a syringe carrier located within a proximal end of the casing and being movable along a longitudinal axis of the device between a stowed position and a needle insertion position, a drive assembly located within a distal end of the casing and being movable by an insertion driver in order to move the syringe carrier and a loaded syringe from a stowed position to a needle insertion position; a first formation fixed relative to the casing and a second formation fixed relative to an insertion tube of the drive assembly, the first and second formations defining a plurality of stop positions for the insertion tube relative to the casing, spaced along the direction of said longitudinal axis, to prevent significant rearward movement of the insertion tube along said axis when a plunger of a firing cartridge is released from a reaction assembly of the cartridge.