Biopsy Needle Slider Clearance for Jamming Reduction
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Solution Overview
Problem
Existing biopsy guns face issues with jamming and deformation due to manufacturing tolerances, requiring strong springs for cannula propulsion, which increases user effort and reduces the number of shots, and are difficult to handle with one hand due to misalignment of the stylet and cannula.
Innovation Solution
The device features a stylet slider with a support device and guide device having a clearance, allowing for easy sliding of the cannula along the stylet, decoupling support and guidance functions, and using a single arming button for both cannula and stylet arming, reducing transversal forces and friction, enabling easier handling and reduced jamming risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a relatively powerful spring is used for the cannula to propel it effectively, then the cannula can be propelled in an effective way, but a greater force is required to arm the device and the needle may jam and bend
Solution Approach 1:
The arming mechanism is divided into two independent stages: first arming the cannula, then arming the stylet. This segmentation allows the spring force to be applied progressively rather than all at once, reducing the peak force required from the user while maintaining effective propulsion.
Solution Approach 2:
The cannula is armed in advance before the stylet. The arming button first retracts the cannula to its shooting position and locks it, then subsequently arms the stylet. This preliminary action ensures the cannula is ready and secured before the stylet is armed, distributing the arming effort over time.
2Reliability
If tight manufacturing tolerances are used for the stylet and cannula to ensure optimal sliding motion, then the sliding motion is optimal, but the parts made from plastic become difficult to manufacture and may still jam
Solution Approach 1:
The guide device provides localized guidance at specific points along the stylet and cannula, rather than requiring uniform tight tolerances throughout. The guide rails and guide surfaces are precisely formed only where contact occurs, allowing standard plastic molding tolerances elsewhere while maintaining reliable sliding motion at critical interfaces.
3Stability of the object's composition
If the stylet and cannula are closely fitted to ensure proper alignment, then alignment is improved, but friction increases and jamming risk increases
Solution Approach 1:
The guide device acts as an intermediary between the stylet and cannula, providing a controlled interface that maintains alignment while reducing direct friction. The guide rails and guide surfaces mediate the interaction, allowing the stylet to slide smoothly within the cannula without requiring tight clearance fits that would increase friction.
4Ease of operation
If a single arming button is used for both cannula and stylet arming to enable one-handed operation, then one-handed handling is enabled, but the mechanism becomes more complex
Solution Approach 1:
The single arming button performs multiple functions: it arms the cannula, locks the cannula in place, arms the stylet, and locks the stylet in place. This multi-functionality is achieved through a sequence of mechanical interactions where the button's movement triggers different stages of the arming process, reducing the number of separate controls needed.
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 allows for easier one-handed operation, reduces jamming and deformation risks, and increases the number of samples that can be taken without requiring excessive force, as the device is designed to accommodate manufacturing tolerances and maintain precise guidance of the cannula along the stylet.
Implementation Method 1
a spring (35) for propelling the stylet slider (30) towards the front of the body (11)
Implementation Method 2
reduces transversal forces and friction
Data Source
AI summary
This invention relates to a device (10) for taking at least one sample of soft tissue from an organ, said device comprising a body (11) and a needle (12) arranged in the body and extending at least partly outside the body through the front end of the body, the needle is formed by a stylet and a cannula coaxial with said stylet. The device comprises a mechanism for arming the needle, designed for sequentially moving the stylet and then the cannula from a rest position to a shooting position wherein the stylet and the cannula are retracted towards the rear end of the body, and a triggering mechanism designed to release the stylet then the cannula and to allow their displacement from the shooting position to the rest position. The cannula is coupled to a cannula slider (24) comprising at least one retaining element (26) for maintaining the cannula slider in a shooting position. The stylet is coupled to a stylet slider (30) comprising at least one retaining element (32) for maintaining the stylet slider in a shooting position and means for unlocking the cannula slider. This device is characterized in that the stylet slider (30) comprises a support device (41) integral with the stylet and a guide device (42) mobile in the body (11) of the device, in that the displacement of the guide device (42) leads to the displacement of the support device (41) and in that the support device (41) and the guide device (42) have a clearance between each other.