Surgical Shaft Assembly With Axial Stops for Insulating Sheath Alignment
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Solution Overview
Problem
Existing electrosurgical instruments face issues with axial displacement of insulating sheaths due to differing thermal expansion properties of materials, leading to axial gaps and potential damage to the instrument shaft assembly, which can cause damage to the instrument shaft, which is not addressed by the instrument shaft, during sterilization processes.
Innovation Solution
A shaft assembly for surgical instruments, particularly electrosurgical instruments, featuring an insulating sheath made of PEEK that is axially displaceable on the instrument shaft, with proximal and distal axial stops to limit movement, and a pressure element like a helical spring to maintain alignment, ensuring compatibility with different sheath diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulating sheath is made axially movable to accommodate thermal expansion differences, then the instrument can be sterilized without damage, but axial displacement occurs creating gaps between the sheath and shaft
Solution Approach 1:
A proximal axial stop and distal axial stop are introduced as intermediary elements between the insulating sheath and the instrument shaft. These stops act as mediators that allow the sheath to expand axially during sterilization while preventing excessive displacement that would create harmful gaps. The axial stops maintain the sheath in a defined position range, reconciling the need for movement with the need for precision alignment.
Solution Approach 2:
The axial position of the insulating sheath is allowed to change within controlled limits during thermal processing. The axial stops define parameter boundaries (proximal and distal limits) that accommodate thermal expansion while preventing parameter deviations that would compromise alignment. This controlled parameter change enables sterilization safety while maintaining manufacturing precision through defined boundaries.
2Manufacturing precision
If the insulating sheath is fixed axially to prevent displacement, then alignment is maintained, but thermal expansion during sterilization causes damage to the shaft assembly
Solution Approach 1:
The insulating sheath transitions from a fixed axial position to a dynamically adjustable position that can accommodate thermal expansion. The axial stops provide dynamic boundaries that allow the sheath to move axially during sterilization while maintaining controlled alignment. This dynamic approach prevents structural damage by allowing necessary movement while preserving functional alignment through defined limits.
3Reliability
If axial stops are added to limit sheath movement, then alignment is maintained during sterilization, but device complexity increases
Solution Approach 1:
The axial stop function is extracted as a separate, modular component that can be independently designed and positioned. By taking out the alignment control function into discrete proximal and distal axial stops, the system achieves sterilization safety without requiring a complete redesign of the shaft assembly. This modular extraction minimizes complexity by adding only the essential elements needed for reliable operation.
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 ensures the insulating sheath maintains proper alignment and prevents axial gaps during sterilization, enhancing safety and compatibility with various sheath diameters, thus ensuring reliable operation and sterility of the instrument.
Implementation Method 1
a pressure element, particularly in the form of a spring, preferably a helical spring, which axially preloads the proximal axial stop
Implementation Method 2
axially preloaded in a distal direction
Implementation Method 3
individual components of the shaft assembly that expand differently according to their material-dependent thermal expansion properties
Data Source
Figure 1
Figure 2~3
Figure 4~7
AI summary
The invention relates to a surgical shaft assembly (6) of or for a surgical instrument (2) and to a surgical instrument (2), in particular a minimally invasive shaft-type electrosurgical instrument (2), comprising the shaft assembly (6), wherein the shaft assembly (6) has a proximal axial stop (36, 50, 52, 74), which is received on an instrument shaft (12) in an axially movable manner and which is axially pretensioned in the distal direction, for limiting a proximally oriented axial movement of an insulating sheath (16) relative to the instrument shaft (12). (Fig. 4)