Mechanical Interlock for Automatic Injection Device
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Solution Overview
Problem
Automatic injection devices can be accidentally fired before the needle boot is removed, leading to wasted medicine, as users may not be able to visually confirm the boot's removal, especially in auto-injectors where the needle and boot are not readily visible.
Innovation Solution
Incorporating a mechanical interlock mechanism that prevents the trigger from being actuated until the boot is removed, which can be achieved through various configurations such as a boot remover integrated with the device, separate components, or a mechanism that locks the trigger cover in place until the boot is removed, ensuring the boot is removed before the device can be fired.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the boot remover is integrated with the housing, then the device structure is more compact and easier to manufacture, but the device complexity increases due to the mechanical interlock mechanism
Solution Approach 1:
The boot remover is integrated with the housing to form a single piece, eliminating the need for separate boot remover components and simplifying assembly. The mechanical interlock mechanism is built into the housing structure itself, combining multiple functions (boot removal, trigger protection, and interlocking) into one integrated component.
Solution Approach 2:
The integrated boot remover serves multiple functions: it acts as a boot removal tool, a trigger cover, and part of the mechanical interlock system. This multi-functionality reduces the total number of components needed in the device while maintaining safety and operational requirements.
2Loss of substance
If a mechanical interlock is implemented to prevent trigger actuation, then medicine waste is prevented, but the ease of operation is reduced due to additional steps required
Solution Approach 1:
The boot must be removed before the trigger can be actuated, creating a preliminary action sequence. This ensures that the needle is exposed and ready for injection before the injection process begins, preventing accidental firing and medicine waste while maintaining a logical operational flow.
Solution Approach 2:
The mechanical interlock acts as an intermediary mechanism between the boot removal action and trigger actuation. It mediates the transition from a protected state to an active state, ensuring that trigger actuation is only possible after proper boot removal, thus preventing medicine waste without completely complicating the operation.
3Reliability
If the trigger is made accessible only after boot removal, then accidental firing is prevented, but the device complexity increases due to additional locking mechanisms
Solution Approach 1:
The trigger cover and mechanical interlock are combined into the boot remover assembly, creating a single component that performs multiple safety functions. This integration reduces the number of separate locking mechanisms needed while maintaining reliable prevention of accidental firing.
Solution Approach 2:
The mechanical interlock system is designed to automatically engage and disengage based on the boot removal state. When the boot is in place, the interlock automatically prevents trigger access; when the boot is removed, the interlock automatically allows trigger access. This self-regulating mechanism maintains reliability without requiring additional complex control systems.
Data Source
AI summary
An automatic injection device for delivering a dose from a medicine containing syringe includes a housing for containing the syringe, a force applicator for applying a force to eject medicine from the syringe, a trigger coupled to the force applicator for releasing the force applicator to cause an injection, a boot covering a needle attached to the syringe to protect and maintain sterility of the needle, and a mechanical interlock. The mechanical interlock prevents actuation of the trigger prior to removal of the boot. When the boot is removed, the mechanical interlock allows for actuation of the trigger.