Bayonet Cap Removal Mechanism for Injection Device
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Solution Overview
Problem
Existing injection devices pose difficulties for patients with rheumatoid arthritis, elderly, or those with limited manual dexterity in removing the boot from the syringe due to the need for twisting and pulling actions, which can lead to improper handling and separation of syringe components.
Innovation Solution
An injection device with a housing and closure member featuring guides and splines that require rotation to break a frangible joint before axial removal, ensuring the boot is twisted off before being pulled, preventing cap removal without twisting and maintaining component integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the boot is designed to be removed by pulling or twisting, then the boot can be removed from the syringe, but users with limited manual dexterity (rheumatoid arthritis, elderly, weak patients) find it difficult to perform the removal action
Solution Approach 1:
The patent combines the twisting and pulling actions into a single integrated operation. The slot in the housing closure member is oriented at an angle to the longitudinal axis, so that when the user pulls the closure member off the housing, the angled slot automatically induces a twisting motion that breaks the frangible joint while simultaneously removing the boot from the syringe. This merging eliminates the need for separate twisting and pulling steps, making the operation easier for users with limited dexterity.
Solution Approach 2:
The angled slot is pre-configured in the housing closure member to automatically perform the twisting action before complete removal. As the user begins to pull the closure member off, the angled geometry of the slot immediately engages with the protrusion and initiates the twisting motion that breaks the frangible joint, ensuring the correct sequence of actions occurs automatically without requiring the user to consciously perform separate steps.
2Ease of operation
If the boot is removed by pulling without twisting, then the removal action is simple, but the frangible joint cannot be broken and the boot remains on the syringe
Solution Approach 1:
The patent merges the twisting and pulling actions into a single integrated operation. The slot in the housing closure member is oriented at an angle to the longitudinal axis, so that when the user pulls the closure member off the housing, the angled slot automatically induces a twisting motion that breaks the frangible joint while simultaneously removing the boot from the syringe. This merging eliminates the need for separate twisting and pulling steps, making the operation easier for users with limited dexterity.
Solution Approach 2:
The angled slot is pre-configured in the housing closure member to automatically perform the twisting action before complete removal. As the user begins to pull the closure member off, the angled geometry of the slot immediately engages with the protrusion and initiates the twisting motion that breaks the frangible joint, ensuring the correct sequence of actions occurs automatically without requiring the user to consciously perform separate steps.
3Ease of operation
If the slot runs perpendicular to the housing axis, then the closure member can be easily pulled off, but the boot cannot be twisted to break the frangible joint
Solution Approach 1:
The patent employs asymmetry by orienting the slot at a specific angle (not perpendicular) to the longitudinal axis of the housing. This asymmetric orientation is crucial: it creates a component of force in the rotational direction when the closure member is pulled off, which generates the twisting motion needed to break the frangible joint. The asymmetric angle transforms a simple pulling action into a combined twisting-and-pulling operation.
Solution Approach 2:
The patent adds a rotational dimension to the removal action by angling the slot. Instead of the slot running purely in the axial direction (one dimension), it is oriented at an angle that introduces a rotational component (second dimension). This dimensional change allows a single linear pulling motion to simultaneously produce both axial separation and rotational twisting, breaking the frangible joint while removing the boot.
4Reliability
If the slot turns towards the housing axis, then the boot can be twisted and pulled off in sequence, but the device complexity increases with multiple slot sections
Solution Approach 1:
The patent employs asymmetry by orienting the slot at a specific angle (not perpendicular) to the longitudinal axis of the housing. This asymmetric orientation is crucial: it creates a component of force in the rotational direction when the closure member is pulled off, which generates the twisting motion needed to break the frangible joint. The asymmetric angle transforms a simple pulling action into a combined twisting-and-pulling operation.
Solution Approach 2:
The patent adds a rotational dimension to the removal action by angling the slot. Instead of the slot running purely in the axial direction (one dimension), it is oriented at an angle that introduces a rotational component (second dimension). This dimensional change allows a single linear pulling motion to simultaneously produce both axial separation and rotational twisting, breaking the frangible joint while removing the boot.
Data Source
AI summary
An injection device 110 is described having a housing 112 and a housing closure means 130. The injection device 110 houses a syringe 114 having a needle 118 which is sealed by a boot 117. The housing closure means 130 is arranged so that the boot 117 can be connected to the housing closure means 130 simply, but cannot be removed from the housing closure means 130. The housing 112 and housing closure means 130 are arranged so that upon rotation of the housing closure means 130, the housing closure means 130 member first rotates relative to the housing and then moves away from the housing. The injection device is simple to use and manufacture.