Safety Needle Creep-Resistant Spring Mechanism
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Solution Overview
Problem
Existing safety needles with polymeric springs face issues with creep over time, leading to a loss of stored energy and unreliable return to the locked position, compromising their ability to automatically cover the needle tip after use.
Innovation Solution
A safety needle design featuring a hollow needle with a slidable sleeve and a pre-loaded spring member, such as a circumambient annular ring or elastomeric sheath, that generates a restoring force to move the sleeve into an extended position and lock over the needle tip upon removal, preventing creep and ensuring reliable locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-loaded polymeric spring is used to ensure reliable return of the slidable sleeve to the locked position, then the stored energy is sufficient for reliable operation, but the device must be stored in an unstressed condition which causes creep over time and loss of spring potential
Solution Approach 1:
The patent changes the physical state of the spring from a pre-loaded compressed state to an uncompressed state by inverting the needle hub, while maintaining the pre-loaded condition through the biasing force of the spring against the deformable membrane. This parameter change (inversion) allows the device to be stored in a stable, uncompressed state while still having the spring ready to provide the necessary force for operation.
Solution Approach 2:
The patent performs preliminary action by pre-loading the spring during manufacturing, then inverting the device before use to activate the safety mechanism. The spring is pre-loaded against the membrane, and the inversion action prepares the device for automatic sleeve return without requiring the device to be stored in a stressed compressed state, thereby preventing creep.
2Force
If the slidable sleeve is stored in a pre-loaded position, then the restoring force is maintained, but creep occurs over time causing loss of stored energy
Solution Approach 1:
The patent changes the configuration parameter of the spring from compressed to uncompressed by inverting the needle hub. The spring remains pre-loaded in terms of its biasing capability, but the physical compression is removed, eliminating creep while maintaining the restoring force potential for the duration of storage.
Solution Approach 2:
The patent introduces a deformable membrane as an intermediary between the spring and the sleeve return mechanism. The spring biases against this membrane, which in turn provides the restoring force for sleeve return. This intermediary allows the spring to be pre-loaded without being in direct contact with the sleeve, enabling storage in an uncompressed stable state while maintaining force potential.
3Stability of the object's composition
If the device is stored in an unstressed unloaded position, then creep is prevented, but the stored energy is insufficient for reliable sleeve return
Solution Approach 1:
The patent performs preliminary action during manufacturing by pre-loading the spring against the deformable membrane. The device is then inverted before use, which activates the pre-loaded spring to provide the necessary restoring force for reliable sleeve return, while the device can be stored in a stable uncompressed state.
Solution Approach 2:
The patent makes the system dynamic by inverting the needle hub to activate the safety mechanism. The spring transitions from a static pre-loaded state during manufacturing to an active restoring force state during use, while allowing the device to be stored in a stable uncompressed inverted position.
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 effectively resists creep and ensures the needle tip is reliably covered after use, maintaining the safety mechanism's effectiveness over a long storage life without requiring additional user actions, enhancing safety and usability.
Implementation Method 1
A spring member is mounted to the slidable sleeve proximate the mounting end. A displacement force urges the slidable sleeve toward the retracted position generating a restoring force within the spring member. The restoring force urges the slidable sleeve to move axially toward the injection end of the needle hub and into the extended position upon removal of the displacement force.
Data Source
Figure 1~1d
Figure 2~2a
Figure 3
AI summary
A safety needle for automatically covering a needle tip following removal of the needle from a patient includes a hub mounted to the needle. A slidable sleeve is slidably mounted to the hub and has an extended position in which a tip of the needle is located inside the slidable sleeve and a retracted position in which the tip of the needle projects from the slidable sleeve. An outer surface of the hub deflects the slidable sleeve in a radial direction as the slidable sleeve slides in an axial direction toward a receiving end of the hub. A spring member is mounted to the slidable sleeve proximate the mounting end. A displacement force urges the slidable sleeve toward the retracted position and generates a restoring force within the spring member. The restoring force urges the slidable sleeve to move toward the injection end of the needle hub and into the extended position upon removal of the displacement force.