Telescopic Plunger Indicator for Reliable End-of-Dose Feedback
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Solution Overview
Problem
Existing injection devices face challenges in providing a reliable end-of-dose indication, particularly for high viscosity drugs or small needle diameters, which can lead to premature termination of medicament delivery and underdosing due to false indications.
Innovation Solution
An injection device with a telescopic plunger and an indicator system that includes a radially inwardly extending portion and a recessed trailing portion, providing increased mechanical coupling and resistance to prevent premature movement, and utilizing a resilient member and kinetic impact for audible and tactile feedback when the plunger reaches its forwardmost position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact indicator is provided within the injector, then the overall size of the injection device is reduced, but the reliability of the end-of-dose indication may be compromised
Solution Approach 1:
The indicator is nested within the trigger arrangement, utilizing the existing structural space. The indicator comprises an aperture with a radially inwardly extending portion that fits within the trigger's internal geometry, allowing the indicator to be housed compactly without increasing the overall device volume while maintaining functional reliability through the resilient member mechanism
Solution Approach 2:
The indicator incorporates a resilient member that allows dynamic movement between a first position (during plunger extension) and a second position (at end of dose). This dynamic capability enables the indicator to provide reliable end-of-dose indication through movement and engagement with the syringe barrel, while the compact design is maintained by utilizing the existing trigger arrangement space
2Reliability
If the indicator is held in a stressed position by the trailing portion of the plunger, then premature indication is prevented, but the mechanical coupling complexity increases
Solution Approach 1:
The plunger is segmented into a leading portion and a trailing portion, with the trailing portion specifically configured to interact with the indicator. The trailing portion comprises a recess defined by a portion of reduced diameter that receives the radially inwardly extending portion of the indicator's aperture. This segmentation allows the trailing portion to hold the indicator in the stressed position reliably while keeping the mechanical coupling straightforward through the recess-portion interface
Solution Approach 2:
The trailing portion of the plunger is pre-configured with a recess that is arranged to receive the radially inwardly extending portion of the indicator's aperture. This preliminary configuration ensures that as the plunger extends, the trailing portion automatically engages with and holds the indicator in the stressed position, preventing premature indication without requiring additional complex mechanical coupling mechanisms
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
The solution ensures accurate end-of-dose indication, minimizing the risk of premature termination and underdosing by maintaining the indicator in a stressed position until the plunger reaches its maximum extension, thus providing reliable feedback through audible and tactile cues.
Implementation Method 1
the indicator is biased towards the indicating position and the trailing portion of the plunger is arranged to hold the indicator against said bias
Implementation Method 2
utilizing a resilient member and kinetic impact for audible and tactile feedback when the plunger reaches its forwardmost position
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An injection device (1) for the delivery of medicament has an indicator (50) for providing an end of dose indication. The device comprises a housing (10), an extendable plunger (40), an actuation mechanism (30), a trigger arrangement (15), and an indicator (50). The extendable plunger (40) comprises a leading portion (42) and a trailing portion (48) configured to allow the plunger (40) to extend from an initial length to a maximum extended length, the plunger portions ((42),48) being slidably mounted within the housing (10). The actuation mechanism (30) is configured to move the leading portion (42) of the plunger (40) forwardly relative to a syringe (20) so as to express medicament from the syringe (20). The trigger arrangement (15) is moveable in use to release the actuation mechanism (30). The indicator (50) is responsive to the forward movement of the plunger (40) and is configured to provide an audible and/or tactile and/or visual indication of the end of dose when the plunger (40) reaches or approaches its forwardmost position.