Autoinjector Radially Flexible Blocking Means Prevent Needle Bounceback
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Solution Overview
Problem
Autoinjectors face issues with needle bounceback during needle exposure, leading to potential syringe damage and risk of medicament leakage or incorrect dosing due to inadequate control of forward axial forces.
Innovation Solution
An autoinjector design featuring radially flexible blocking means that prevent forward axial movement of the syringe before actuation, using an interference fit with the outer housing or end cap to maintain the syringe in place until needle exposure is complete, allowing automatic movement to a non-blocking position for injection, thus minimizing syringe movement and preventing bounceback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the syringe is allowed to move axially forward during needle exposure, then the needle can be exposed beyond the end of the nozzle for injection, but the syringe may bounce back against internal components causing damage and medicament leakage
Solution Approach 1:
The blocking means are designed to be moveable between a first blocking position and a second non-blocking position. During needle exposure, the blocking means are in the first position to prevent syringe movement. During injection, they automatically move to the second position to allow syringe forward movement. This dynamic transition resolves the contradiction by providing stability when needed and mobility when required.
Solution Approach 2:
The blocking means act as an intermediary component between the syringe and the outer housing. They transmit and control the forces acting on the syringe, blocking forward axial forces during needle exposure while allowing controlled movement during injection. This intermediary mechanism prevents direct harmful interactions between the syringe and internal components.
2Reliability
If the blocking means remain in the blocking position during injection, then the syringe is protected from bounceback, but the syringe cannot move forward to deliver the injection
Solution Approach 1:
The blocking means automatically transition from the first blocking position to the second non-blocking position upon actuation of the autoinjector. This dynamic change ensures that the blocking means provide protection during needle exposure but do not obstruct the injection process when the syringe needs to move forward to deliver medicament.
3Strength
If the radially flexible fingers are made rigid to provide stronger blocking, then the syringe is more securely held in place, but the blocking means cannot automatically move to the non-blocking position during injection
Solution Approach 1:
The blocking means comprise radially flexible fingers that can be deflected radially inward and outward. These flexible fingers provide sufficient blocking strength during needle exposure while being capable of automatic radial deflection during injection to clear the axial path of the syringe. The flexibility allows the blocking means to adapt to different operational phases.
Solution Approach 2:
The blocking means utilize changes in radial position of the flexible fingers to transition between blocking and non-blocking states. During needle exposure, the fingers are in a radially outward position to block the syringe. During injection, they deflect radially inward to clear the path. This parameter change (radial position) enables both strong blocking and automatic movement.
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 effectively reduces the risk of syringe damage and ensures controlled medicament delivery by maintaining the syringe in place until injection, preventing needle-stick injuries and ensuring accurate dosing.
Implementation Method 1
said blocking means comprising one or more fingers that are radially flexible substantially into and out of the axial path of said syringe or syringe holder; characterised in that in the first blocking position, the radially-flexible fingers are flexed inwardly by means of an interference fit with said outer housing, an end cap or a needle cover, and in moving from the first blocking position to the second non-blocking position, the radially-flexible fingers spring radially out of the axial path
Data Source
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AI summary
An autoinjector comprising an outer housing in which can be mounted a syringe for holding a volume of medicament, the syringe for holding medicament having a needle at one end thereof, a syringe holder for supporting the syringe in an axial position relative to the outer housing, and an intermediate housing at least part of which is located within said outer housing, characterised in that said intermediate housing is provided with a blocking means capable of abutting the syringe or the syringe holder so as to be capable of preventing forward axial movement of the syringe when a forward axial force is applied to said needle before actuation of the autoinjector to deliver an injection, but incapable of preventing forward axial movement of the syringe during actuation of the autoinjector to deliver an injection.