Reload Assembly Knife Carrier Retention Mechanism
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Solution Overview
Problem
Conventional circular stapling devices face difficulties in retaining the knife carrier in a retracted position after firing, making it challenging to safely remove the tissue donut and avoid clinician injury during manipulation and disposal.
Innovation Solution
The reload assembly incorporates a one-way collar and snap-ring mechanism that engages to securely retain the knife carrier in the retracted position, using a snap-ring that deforms to allow advancement but returns to obstruct readvancement, ensuring the knife remains within the shell housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the knife carrier is allowed to move freely after firing, then the tissue donut can be removed from the cavity, but the knife may readvance and cause injury to the clinician
Solution Approach 1:
The snap ring is pre-configured to automatically engage with the collar and prevent readvancement of the knife carrier. This preliminary protective action is built into the mechanism before the tissue donut removal step, ensuring that while the knife carrier can move distally to allow donut removal, it cannot readvance to injure the clinician.
Solution Approach 2:
The collar acts as an intermediary component between the knife carrier and the clinician. It allows controlled distal movement for tissue donut removal while blocking proximal movement through engagement with the snap ring, thus mediating the conflicting requirements of ease of operation and safety.
2Object-affected harmful factors
If a retention mechanism is added to prevent knife readvancement, then clinician safety is improved, but the device structure becomes more complex
Solution Approach 1:
The retention function is segmented into separate, simple components: a snap ring and a collar. Rather than adding a complex integrated retention system, the function is divided into these two discrete elements that work together through a simple engagement mechanism, minimizing added complexity while achieving the safety function.
Solution Approach 2:
The snap ring and collar form a simple, potentially disposable retention mechanism that is easier and cheaper to manufacture than complex retained mechanisms. This approach prioritizes clinician safety through a reliable but structurally simple solution.
3Ease of operation
If the snap ring is designed to deform for advancement, then the knife carrier can advance during firing, but the snap ring must be sufficiently strong to prevent readvancement
Solution Approach 1:
The snap ring is designed with dynamic properties that allow it to deform elastically during the forward firing motion, accommodating the advancement of the knife carrier. However, the same elastic properties enable it to spring back and engage with the collar to prevent reverse motion, thus satisfying both advancement and retention requirements through material dynamics.
Solution Approach 2:
The physical state of the snap ring changes during operation: it transitions from a rigid retention structure to a deformed state during advancement, then returns to its original configuration to provide retention. This parameter change in the snap ring's physical state allows it to fulfill both conflicting requirements of allowing advancement and preventing readvancement.
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 design effectively prevents the knife carrier and knife from readvancing, safely retaining the knife within the shell housing, minimizing the risk of injury during reload assembly manipulation and disposal, and facilitating easy removal of the tissue donut.
Implementation Method 1
a snap-ring that deforms to allow advancement but returns to obstruct readvancement
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A reload assembly includes a shell housing, a knife carrier, and a one-way collar. The knife carrier is movably positioned about an inner housing portion of the shell housing between retracted and advanced positions and supports a snap-ring. The one-way collar is movably supported about the inner housing portion of the shell housing from a retracted position to an advanced position in response to movement of the knife carrier from its retracted position to its advanced position. The snap-ring is movable with the knife carrier to a position proximally of the one-way collar when the one-way collar is in its advanced position to obstruct movement of the knife carrier back towards its advanced position.