Anti-Needle Stick Guard Trigger Finger Spacing
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Solution Overview
Problem
Conventional anti-needle stick safety devices for prefilled syringes often require significant force for assembly, leading to stress on the syringe flange and increased risk of breakage, and may result in partially activated devices due to geometrical incompatibilities between the syringe flange and trigger fingers.
Innovation Solution
The design includes a body with syringe capture features featuring angled surfaces to reduce assembly force and prevent trigger finger unseating, along with a spring mechanism and elongated trigger finger heads to accommodate various syringe tolerances, and retention features that flex laterally to securely hold syringes with small round flanges during use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional passive anti-needle stick safety devices are used, then needle stick prevention is achieved, but significant force is required for assembly causing stress on the syringe flange and increased risk of breakage
Solution Approach 1:
The patent modifies the geometric parameters of the trigger fingers, specifically increasing the distance between them to exceed the syringe flange diameter. This parameter change allows the trigger fingers to clear the flange during insertion without excessive flexing, thereby reducing assembly force and preventing flange breakage while maintaining the safety function.
Solution Approach 2:
The trigger fingers are designed with flexible properties that allow them to dynamically adapt during the assembly process. The increased spacing combined with flexible material properties enables the trigger fingers to flex minimally during insertion and then seat properly against the plunger rod, reducing stress on the brittle flange while ensuring reliable activation.
2Volume of moving object
If the distance between trigger fingers is less than the syringe flange diameter, then the safety device structure is compact, but the trigger fingers must be flexed outwardly during insertion causing unseating and partially activated devices
Solution Approach 1:
The patent changes the critical parameter of trigger finger spacing from being less than the flange diameter to being greater than the flange diameter. This parameter change eliminates the need for excessive flexing during insertion, prevents unseating of trigger fingers, and ensures complete and reliable activation while the trigger fingers return to their seated position after clearing the flange.
3Stability of the object's composition
If significant force is applied to insert the medicine cartridge into the safety device, then the syringe is securely held in place, but the medicine cartridge flange is stressed and at risk of breakage
Solution Approach 1:
The patent modifies the geometric parameter of trigger finger spacing to be greater than the flange diameter, which fundamentally changes the insertion mechanics. Instead of requiring large lateral forces to flex the trigger fingers aside, the flange simply passes between the spaced trigger fingers, dramatically reducing insertion force while maintaining secure holding through proper trigger finger seating against the plunger rod.
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
This solution reduces the risk of syringe flange breakage during assembly, ensures complete activation of the safety device, and enhances the reliability and manufacturability of the safety device while improving ergonomics and holding strength.
Implementation Method 1
The embodiments provided herein relate generally to anti-needle stick safety systems for injection devices such as medicine cartridges, syringes and the like, and more particularly to a needle guard for an injection device such as a medicine cartridge, a syringe and the like, that includes a passively activated shield for covering a needle of the injection device
Implementation Method 2
The design includes a body with syringe capture features featuring angled surfaces to reduce assembly force and prevent trigger finger unseating
Implementation Method 3
retention features that flex laterally to securely hold syringes with small round flanges during use
Data Source
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AI summary
A safety device for a medicine cartridge comprising a body for receiving a cartridge, a guard for covering a used needle, a plunger to dispense medicine from the cartridge and a spring for activation of the guard. The trigger fingers of the guard are spaced to avoid or minimize contact with the syringe flange during assembly to avoid trigger finger unseating. An elongated trigger finger head enables the device to activate for all known syringe and syringe plunger tolerances. The spring end coils have larger diameter than the inner coils to reduce the likelihood of the spring end coil end interfering with the cartridge subassembly. Syringe capture features are configured to retain a syringe having a small round or conventional cut flange in place during use and reduce the stress on the syringe flange during insertion while maintaining the ability to hold the syringe in place during use.