Injection Safety Device Spring Creep Prevention
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Solution Overview
Problem
Existing safety devices for injection devices can become faulty due to wear and creep of retractable tabs under stress during long-term storage, leading to potential accidental triggering or failure to operate properly.
Innovation Solution
A safety device with a protective sheath driven by return means, featuring retractable means that are deactivated during storage to avoid tension, using a cap or storage member to exert greater stress on the return means, preventing the retractable means from being subjected to stress, thus reducing creep and ensuring proper operation after long storage periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the safety device is stored in the injection position with the spring under stress, then the device is ready for immediate use, but the retractable tabs suffer from creep and wear over time, leading to potential malfunction
Solution Approach 1:
The device transitions from a static stored position to a dynamic injection position. The retractable tabs are designed to be dynamic, moving between engaged and disengaged states. During storage, the tabs are disengaged from the spring, eliminating stress. During injection, they engage to control spring movement, resolving the contradiction between readiness and reliability.
Solution Approach 2:
Before storage, the device is prepared by disengaging the retractable tabs from the spring, placing the system in a preliminary state that prevents wear during storage. This preliminary action ensures that when the device is later used, the tabs are fresh and reliable, while the spring can be re-engaged for the actual injection function.
2Ease of manufacture
If the retractable tabs are made of flexible plastics material to enable retraction, then the device is easier to manufacture and operate, but the material creeps under tension from the compressed spring over time
Solution Approach 1:
The harmful stress element is extracted from the retractable tabs during storage. By designing the mechanism so that tabs are disengaged from the spring during storage, the problematic tensile load is removed. The tabs only experience stress during the brief injection phase when they actively control the spring, preventing cumulative creep damage while maintaining manufacturing simplicity.
Solution Approach 2:
The stress state parameter of the retractable tabs is changed from continuous tension to intermittent engagement. During storage, the tabs are in a stress-free state; during injection, they temporarily engage to control spring movement. This parameter change allows use of flexible plastics material without creep issues, as the material never experiences prolonged tension.
3Speed
If the spring is kept compressed during storage to ensure immediate injection capability, then the device is ready for use, but the compressed spring exerts stress on the retractable tabs causing wear
Solution Approach 1:
The system uses dynamic engagement of the retractable tabs rather than continuous compression. During storage, the spring remains compressed but the tabs are disengaged, creating a dynamic state where potential energy is stored without harmful stress on retention components. During injection, the tabs dynamically engage to control spring expansion, achieving fast response without degradation over time.
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 the safety device remains functional after long storage, reduces the risk of accidental triggering, and allows for the use of less robust and less expensive materials for the retractable means, enhancing reliability and safety.
Implementation Method 1
The sheath is driven by a spring that is compressed while the sheath is in the injection position and that is expanded while the sheath is in the safe position
Implementation Method 2
the retractable tabs are often made of a flexible plastics material and can suffer a certain amount of creep over time, particularly since they are subjected to tension from the compressed spring applying a certain amount of stress thereto
Data Source
AI summary
A safety device for an injection device including a protective sheath driven by a spring, the safety device being capable of taking an injection configuration in which the sheath allows an injection needle to be left uncovered, and a safe configuration in which the sheath enables the injection needle to be covered; retractable catches for retaining the spring, the retractable catches retaining the spring under stress in such a manner as to hold the safety device in the injection configuration; and deactivation mechanism for deactivating the retractable catches, enabling the safety device to take a storage configuration in which the retractable catches are not subjected to stress from the spring.