A-Frame Splines for Circular Stapling Device Alignment
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Solution Overview
Problem
Circular stapling devices face issues with staple malformation due to spline crashing, which damages the alignment structures and prevents proper alignment of staple forming pockets with staple receiving pockets, leading to malformation during firing.
Innovation Solution
The introduction of A-frame splines with secondary channels in the shell assembly, designed to fracture and allow anvil splines to pass into these channels upon engagement, ensuring proper alignment and minimizing staple malformation by allowing the splines to align even when they crash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional splines with single tapered surfaces are used, then the alignment structure is simple, but the splines may crash head-on causing damage and preventing proper alignment
Solution Approach 1:
The spline structure is segmented into multiple functional surfaces: a first tapered surface for initial engagement and a second tapered surface for final alignment. This segmentation allows the spline to handle alignment in stages, preventing head-on crashes while maintaining a relatively simple overall structure.
Solution Approach 2:
Different portions of the spline have different geometric properties - the first tapered surface has a specific angle for initial engagement, while the second tapered surface has a different angle for final alignment. This local differentiation of geometric properties allows each surface to perform its specific function optimally without requiring complex mechanisms.
2Manufacturing precision
If splines engage head-on causing crash, then the engagement is direct and simple, but the splines become damaged preventing proper alignment
Solution Approach 1:
The first tapered surface performs a preliminary engagement action that guides the splines toward proper alignment before the final engagement. This preliminary action prevents the splines from crashing head-on during the final engagement, thereby preserving spline integrity while ensuring precise staple formation.
Solution Approach 2:
The first tapered surface acts as a cushioning element that absorbs the initial impact and guides the splines into proper alignment before the final engagement. This beforehand cushioning prevents the harmful head-on crash while maintaining the strength and integrity of the splines for precise staple formation.
3Reliability
If the spline structure is made more complex to prevent crashing, then alignment reliability improves, but the device complexity increases
Solution Approach 1:
The spline is segmented into multiple surfaces with different taper angles, allowing each surface to perform a specific function. This segmentation provides reliable alignment without requiring complex mechanisms, as each surface is simple in design but effective in function.
Solution Approach 2:
The spline structure is designed to be dynamic in its engagement process, transitioning from initial engagement on the first tapered surface to final alignment on the second tapered surface. This dynamic behavior ensures reliable alignment while maintaining structural simplicity.
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 reduces the likelihood of staple malformation by ensuring that the anvil and shell assemblies remain aligned, even when the splines engage head-on, maintaining the integrity of staple formation during the stapling process.
Implementation Method 1
The splines on the anvil shaft and on the shell housing of the shell assembly include left and right tapered ends that define an apex. When the tapered ends of the splines of the anvil assembly engage the tapered ends of the shell assembly, the anvil assembly is cammed into rotation to align the staple forming pockets of the anvil assembly with staple receiving pockets of the staple cartridge of the shell assembly.
Implementation Method 2
The A-frame splines with secondary channels in the shell assembly, designed to fracture and allow anvil splines to pass into these channels upon engagement
Data Source
AI summary
A surgical stapling device includes an anvil assembly and a shell assembly having a shell housing including a plurality of shell splines having an A-frame configuration. The shell splines include a triangular tip that defines an apex and is positioned to engage splines on an anvil shaft of the anvil assembly to properly align the anvil assembly with the shell assembly. The A-frame splines are spaced from each other to define primary channels that are dimensioned to receive the splines of the anvil assembly to properly align the anvil assembly with the shell assembly. The A-frame splines also define secondary channels that are positioned proximally of and in axial alignment with the apex of the A-frame splines. In situations in which an apex of the splines on the anvil assembly “crash” into the apex of the A-frame splines of the shell assembly, i.e., the apexes of the splines meet head on, the A-frame splines of the shell assembly are constructed to fracture to allow the splines of the anvil assembly to penetrate into the A-frame splines and pass into the secondary channels of the A-frame splines to properly align the anvil assembly with the shell assembly of the stapling device.