Safety Syringe Rotational Sheath Deployment Mechanism
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Solution Overview
Problem
Safety syringes with larger diameter barrels face challenges in preventing stick injuries due to the increased distance the sheath needs to extend past the needle, which can also increase the overall stroke length, making operation difficult and potentially leading to incomplete drug delivery.
Innovation Solution
The sheath is configured with an aperture smaller than the barrel diameter, positioned forward of the shoulder, and coupled with a safety plunger that deploys to cover the needle without increasing the stroke length, using a rotational mechanism to control sheath deployment and prevent needle exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sheath extends further past the needle to prevent stick injuries, then safety is improved, but the stroke length increases making operation difficult
Solution Approach 1:
The patent introduces a rotational dimension to sheath deployment. Instead of only linear extension, the sheath rotates around the barrel axis during deployment, allowing it to cover the needle effectively while maintaining a shorter overall extension distance, thus improving safety without excessively increasing stroke length
Solution Approach 2:
The sheath deployment is made dynamic through rotational motion controlled by a spiral groove mechanism. The sheath rotates and extends in a controlled manner during the plunger's inward stroke, optimizing the coverage of the needle while minimizing the increase in overall stroke length
2Reliability
If the sheath extends further past the needle to prevent stick injuries, then safety is improved, but the stroke length increases potentially leading to incomplete drug delivery
Solution Approach 1:
By adding rotational motion to the sheath deployment, the patent achieves effective needle coverage with a shorter linear extension. This dimensional change ensures that the sheath can protect against stick injuries without requiring excessive extension that would interfere with complete drug delivery
Solution Approach 2:
The sheath deployment is synchronized with the plunger stroke through the spiral groove mechanism. The sheath begins to rotate and extend during the drug delivery process itself, ensuring that needle coverage is achieved without delaying or interfering with complete drug expulsion
3Length of moving object
If the aperture at the forward end of the sheath is reduced in size, then the sheath extension distance is reduced, but the sheath must still effectively cover the needle
Solution Approach 1:
The patent uses rotational motion to achieve comprehensive needle coverage. Even with a smaller aperture, the rotating sheath can sweep across and cover the entire needle length, maintaining effective protection against stick injuries without requiring a large extension distance
Solution Approach 2:
The continuous rotational motion of the sheath during deployment ensures that the smaller aperture still achieves complete needle coverage. The rotation allows the aperture to sweep across the needle, providing continuous protection throughout the deployment process
Data Source
Figure 1
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AI summary
A safety syringe comprising a barrel having an opening at an end thereof and a bung positioned in the barrel and creating a volume between the opening and the bung. The safety syringe also comprises a handle portion secured to the barrel and a syringe plunger slidably engaged with the handle portion and moveable within the barrel on an inward stroke to drive the bung forwards within the barrel to cause a substance within the volume to be expelled from the opening. The safety syringe further comprises a rotation mechanism configured to rotate the syringe plunger within the barrel at a point during the inward stroke when the syringe plunger is in contact with the bung, such that a rotational force is applied to the barrel and a brake connected to the handle portion and configured to provide a frictional force to resist the rotational force applied to the barrel.