Autoinjector Needle Retraction Control via Switching Cam
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Solution Overview
Problem
Existing injection devices, particularly auto-injectors, often result in incomplete administration of medicaments due to inefficient needle retraction mechanisms, leading to drug loss and inaccuracies in dose delivery, especially with expensive medicines.
Innovation Solution
The injection device incorporates a mechanism with a switching cam and actuating sleeve that allows the user to control the retraction of the needle by adjusting the contact pressure, ensuring complete product dispensing and accurate dose administration through a dynamic blocking window mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the needle is automatically retracted into the housing immediately after dispensing, then the device operation is simplified, but drug loss occurs and dosing accuracy deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the needle retraction timing controllable and adaptable. The switching cam mechanism allows the needle to remain extended during a controllable waiting period after dispensing, enabling the user to optimize the retraction timing based on the specific injection scenario. This dynamic control resolves the contradiction by allowing automatic operation while preventing premature retraction that would cause drug loss.
Solution Approach 2:
The patent implements feedback through the switching cam mechanism that responds to the actuating sleeve position. The cam profile is designed to automatically transition the needle from extended to retracted position based on the dispensing cycle completion. This feedback mechanism ensures the needle retracts at the optimal moment after dispensing, preventing both premature retraction (causing drug loss) and delayed retraction (complicating operation).
2Measurement precision
If the needle remains extended after dispensing to allow complete product distribution, then dosing accuracy improves, but the device complexity increases due to controlled retraction mechanism
Solution Approach 1:
The patent applies preliminary action by pre-configuring the switching cam mechanism to automatically control the needle retraction timing. The cam profile is designed in advance to maintain the needle in the extended position during the critical waiting period after dispensing, ensuring complete product distribution. This preliminary design of the retraction timing eliminates the need for complex user controls while maintaining dosing accuracy.
Solution Approach 2:
The patent implements self-service through the automatic switching cam mechanism that autonomously manages the needle retraction based on the dispensing cycle. The cam mechanism automatically transitions the needle position without requiring user intervention or complex controls. This self-service approach maintains dosing accuracy by ensuring the needle remains extended long enough for complete product distribution while avoiding the need for overly complex user-controlled mechanisms.
3Measurement precision
If a switching cam mechanism is introduced to control needle retraction timing, then dosing accuracy improves, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the switching cam mechanism to serve multiple functions: it controls the needle retraction timing, ensures complete product distribution, and automatically transitions between extended and retracted states. This multi-functionality reduces the need for separate controls and mechanisms, thereby improving dosing accuracy without proportionally increasing device complexity.
Solution Approach 2:
The patent utilizes parameter changes by varying the cam profile geometry to control the timing and duration of needle extension. By adjusting the cam parameters (such as the waiting period duration and retraction triggering point), the system optimizes dosing accuracy for different injection scenarios. This parameter-based control allows precise regulation of needle position without requiring complex mechanical structures.
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 users to determine the optimal time for needle retraction, ensuring complete product distribution and reducing drug loss, thereby providing economic and dosing advantages by allowing for better control over the needle's position and retraction timing.
Implementation Method 1
an elastic means such as a spring element or a spring can be provided, which can be tensioned by the movement of the actuating sleeve in the proximal direction and/or with which the actuating sleeve can be driven for movement in the distal direction
Implementation Method 2
The elastic means preferably serves to return an actuating sleeve that has not been moved back sufficiently in the proximal direction to trigger a switching process to the starting position
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to an injection device, especially autoinjector, which comprises: a) a housing (1), b) an actuating sleeve (6) which is mounted to be movable relative to the housing (1) and which can be placed on a point of injection of a patient with the distal end of the injection device, c) an injection needle (4) which protrudes over the distal end of the injection device when in the position of insertion and which can be moved back into the interior of the injection device, d) an actuating cam (17) which is arranged in an axially fixed manner relative to the injection needle (4) and which engages in a locking recess (20) when in the position of insertion to prevent the injection needle (4) from being retracted into the interior of the injection device, e) said actuation cam (17) being releasable from the engagement with the locking recess (20) by means of the actuating sleeve (6), thereby releasing the injection needle (4) for the retracting movement.