Injection Device Trigger Lock Friction Reduction
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Solution Overview
Problem
Existing auto-injectors face issues with friction in their locking mechanisms, which can cause discomfort to users, prevent the sleeve from returning to its engaged position, and lead to accidental activation due to snagging on the housing rim, resulting in unsafe and wasteful operation.
Innovation Solution
A contact surface, such as a flange, is provided to facilitate easier engagement and disengagement of the locking mechanism, reducing point pressure and friction, and an arm or sleeve design that fits within the exit aperture to prevent snagging, along with a release mechanism that ensures safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the locking mechanism uses a sleeve surrounded by the housing, then the locking mechanism is compact and integrated, but friction acts against movement causing user discomfort and potential failure to return
Solution Approach 1:
The locking mechanism is segmented into a sleeve component and a separate contact surface (flange) component. The contact surface is disposed outside the housing while the sleeve operates within the housing, separating the friction-prone internal movement from the user interaction point.
Solution Approach 2:
The contact surface acts as an intermediary between the sleeve and the user's finger. When the user presses the locking mechanism, force is applied to the contact surface which then transmits force to the sleeve, reducing direct friction contact and improving movement smoothness.
2Ease of operation
If the sleeve protrudes from the housing to enable engagement, then the locking mechanism can be easily activated, but the rim may catch on the housing rim preventing automatic return
Solution Approach 1:
The locking mechanism is divided into the sleeve (which may protrude) and a separate contact surface (flange). The contact surface is positioned to extend beyond the housing rim, providing a large contact area for user engagement while the sleeve geometry is optimized to avoid catching on the housing rim during retraction.
Solution Approach 2:
The contact surface extends in a direction perpendicular to the sleeve's movement axis, creating a two-dimensional engagement surface. This allows the user to apply force effectively while the sleeve itself maintains a profile that prevents snagging on the housing rim.
3Ease of operation
If the locking mechanism applies force directly to tissue, then activation is achieved, but point pressure causes user discomfort and pain
Solution Approach 1:
The force application is segmented between the contact surface (flange) and the sleeve. The contact surface is designed with a larger area that distributes the applied force across a broader region of the user's finger, reducing point pressure and discomfort.
Solution Approach 2:
The contact surface is designed to deform or flex under applied force, dynamically adapting to the user's finger pressure distribution. This flexibility helps distribute stress and reduce localized pressure points that cause discomfort.
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 enhances user safety by reducing discomfort and preventing accidental activation, ensuring the locking mechanism disengages smoothly and re-engages correctly, maintaining device functionality.
Implementation Method 1
The sleeve is biased into its extended position by a resilient spring mechanism
Implementation Method 2
The sleeve is surrounded by the housing of the injection device which causes friction to act against movement of the sliding sleeve
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
An injection device comprises a housing adapted to receive a syringe having a discharge nozzle, the syringe being moveable in the housing on actuation of the injection device along a longitudinal axis from a retracted position in which the discharge nozzle is contained within the housing and an extended position in which the discharge nozzle of the syringe extends from the housing through an exit aperture (138). There is an actuator and a drive adapted to be acted upon by the actuator and in turn act upon the syringe to advance it from its retracted position to its extended position and discharge its contents through the discharge nozzle. A locking mechanism (119) is moveable from an engaged position in a direction into the housing at the exit aperture into a disengaged position. The locking mechanism is adapted to prevent actuation of the device when it is in its engaged position and permit actuation of the device when it is in its disengaged position. The exit aperture is defined by a rim (128a) located on an edge of the housing and the locking mechanism comprises a contact surface (119a) which is adapted to extend over or around at least a part of the rim.