Force Containment in Automatic Injector Receiving Frame
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Solution Overview
Problem
Automatic injectors face challenges in immobilizing cartridges during drug delivery, leading to potential discomfort for patients due to unwanted movement of the needle, especially with cartridges having bent fluid paths that translate rotational movements into axial translations.
Innovation Solution
A receiving frame within the injector mounting plate is designed to immobilize the cartridge by reducing both axial and rotational movements through a unitary frame that contains forces generated by the plunger driver and motor, ensuring the cartridge remains fixed during operation, thereby preventing needle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple connection between cartridge and injector is used, then device complexity is reduced, but cartridge stability deteriorates leading to needle movement
Solution Approach 1:
The connection structure is divided into multiple independent elements: interference elements for axial positioning, snap elements for lateral securing, and a driver mount for force containment. Each element addresses a specific degree of freedom, collectively achieving complete cartridge immobilization without requiring a single complex monolithic structure.
Solution Approach 2:
The interference elements and snap elements are integrated within the receiving frame structure, with the driver mount nested within the frame. The cartridge itself contains the plunger driver, creating multiple nested levels where each component is contained within or supported by the next, achieving compact force containment while maintaining simplicity.
2Ease of operation
If the cartridge is freely movable for easy installation, then ease of operation is improved, but patient comfort deteriorates due to needle movement during injection
Solution Approach 1:
The connection mechanism transitions from a static rigid connection to a dynamic multi-stage engagement process. The cartridge is first guided into position by the interference elements, then secured by the snap elements during a single continuous motion, allowing easy installation while ensuring complete immobilization before injection begins.
Solution Approach 2:
The receiving frame acts as an intermediary structure between the cartridge and the injector housing. It provides a transition zone where the cartridge is received, positioned by interference elements, and secured by snap elements, mediating between the need for easy installation and the requirement for complete stability during injection.
3Device complexity
If forces from plunger driver are not contained, then device structure is simplified, but cartridge integrity deteriorates leading to breakage
Solution Approach 1:
The driver mount provides localized force containment specifically at the point where the plunger driver interacts with the cartridge. This localized approach concentrates the force containment function in a specific region rather than requiring the entire cartridge or injector structure to bear the loads, simplifying the overall device while protecting cartridge integrity.
Solution Approach 2:
The driver mount converts the potentially harmful forces generated by the plunger driver into beneficial contained forces. By providing a dedicated force containment structure, the high forces from plunger operation are channeled and dissipated in a controlled manner, protecting the cartridge from breakage while maintaining device simplicity.
Data Source
AI summary
An automatic injector for delivering a pharmaceutical substance from a reservoir of a cartridge, the cartridge interconnected to a needle at its distal end and mechanically coupled to a plunger driver at its proximal end, the injector comprising a connecting feature on the cartridge a contact surface for contacting an injection site a frame connected to the contact surface, the frame having an interference element with a distal stop, the interference element sized to slidably link to the connecting feature and allow the cartridge to slide up to the distal stop, a snap element allowing the interference element to receive the connection feature, but inhibiting disconnection of the cartridge; the frame further comprising a driver mount, for fixedly containing a plunger driver, the driver for driving a plunger to empty the reservoir of the cartridge through the needle to inject fluid from the reservoir into the injection subject.