Injection Device Actuator Unlatching Mechanism
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Solution Overview
Problem
Existing injection devices face challenges in compact design due to tolerance stack-up, leading to inefficient release mechanisms that may fail to retract the syringe completely, resulting in incomplete dosing or 'wet' injections, and require increased device length to accommodate actuator movement past the syringe.
Innovation Solution
Defining nominal unlatching positions relative to the syringe instead of the device casework, allowing the actuator to move past the syringe and reducing the device's length by enabling the actuator and unlatching mechanisms to move forward with the syringe, thus reducing the initial distance between the actuator and syringe plunger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actuator moves past the syringe to activate unlatching mechanisms, then the device length increases, but the release mechanism reliability improves
Solution Approach 1:
Instead of moving the actuator past the syringe to reach fixed unlatching mechanisms, the invention inverts the approach by making the unlatching mechanisms move forward with the syringe. The nominal unlatching positions are defined relative to the syringe rather than the device casework, allowing the actuator to engage them at the correct position without excessive travel.
Solution Approach 2:
The invention transitions from a static configuration where unlatching mechanisms are fixed relative to the casework to a dynamic configuration where the nominal unlatching positions move forward with the syringe during actuation. This dynamic positioning ensures reliable engagement while minimizing actuator travel distance.
2Reliability
If the safety margin for release mechanism activation is increased, then the syringe discharge completeness improves, but the risk of post-retraction discharge increases
Solution Approach 1:
The invention uses the syringe's own position as feedback to control the unlatching mechanism activation. By defining nominal unlatching positions relative to the syringe, the system automatically activates release at the correct moment based on syringe displacement, ensuring complete discharge without excessive safety margin that would cause post-retraction discharge.
3Ease of manufacture
If the actuator and unlatching mechanisms are positioned to minimize device length, then manufacturing cost and ergonomics improve, but the release mechanism may fail to operate reliably
Solution Approach 1:
The invention makes the unlatching mechanisms dynamic by allowing them to move forward with the syringe. This enables the actuator to engage the unlatching mechanisms at optimized positions that minimize device length while ensuring reliable operation, as the engagement point moves to meet the actuator rather than requiring the actuator to travel past the syringe.
Data Source
AI summary
An injection device (210; 110) is described. A housing (212; 112) receives a syringe and includes a return spring (226; 126) for biasing the syringe from an extended position in which its needle (218; 118) extends from the housing (212; 112) to a retracted position in which the it does not. A drive spring (230; 130) acts on a first drive element (232; 132) and a second drive element (234; 134) acts upon the syringe to advance it from its retracted position to its extended position and discharge its contents through the needle. The first drive element (232; 132) is capable of movement relative to the second (234; 134) once a nominal decoupling position has been reached. A release mechanism is activated when the first drive element (234; 134) is further advanced to a nominal release position, to release the syringe (214; 114) from the action of the drive spring (230; 130), whereupon the return spring (226; 126) restores the syringe (214; 114) to its retracted position. The nominal decoupling and release positions are defined relative to the syringe (214; 114). This may be achieved by interaction between a moving component and a decoupling component (162; 262) that moves with the syringe as it is advanced.