Surgical Instrument Coupling with Wedge Lock for Play-Free Rotation
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Solution Overview
Problem
Existing surgical instruments face challenges in providing a cost-effective, space-efficient, and play-free coupling mechanism for connecting the shaft and handle, which allows for rotation while maintaining secure engagement, and are not easily adaptable to different handle types.
Innovation Solution
A surgical instrument with a coupling device featuring a wedge-like engaging element that moves between engaging and release positions, utilizing a trapezoidal profile to compensate for manufacturing tolerances and ensure play-free, non-rotatable connection between the shaft and handle, facilitated by a rotary handle part and a spring element for easy actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking bracket with circumferential collar is used to couple shaft to handle, then the connection is free of play and secure, but the component is expensive and requires increased space
Solution Approach 1:
The coupling device is divided into separate functional elements: a retaining ring for axial retention and a wedge-shaped engaging element for radial engagement. This segmentation allows each component to perform its specific function efficiently, reducing overall complexity while maintaining security.
Solution Approach 2:
The invention extracts the essential coupling function from the complex locking bracket and implements it through simpler elements. The wedge-shaped engaging element isolates the radial engagement function, while the retaining ring handles axial retention, eliminating the need for a complex integrated bracket structure.
2Reliability
If spherical locking bodies are used in a sleeve-like housing part, then the shaft can be fixed securely, but the enclosed region is large and difficult to clean and sterilize
Solution Approach 1:
The coupling elements are extracted from the enclosed sleeve-like housing and positioned in open configurations. The retaining ring and wedge-shaped engaging element are arranged such that they do not create enclosed cavities, allowing cleaning and sterilization fluids to access all surfaces effectively.
Solution Approach 2:
Instead of enclosing the coupling elements within a housing that creates cleaning difficulties, the design inverts the approach by arranging the elements in an open configuration where the housing does not enclose the coupling mechanism, thereby facilitating cleaning and sterilization.
3Strength
If a connecting pin with engaging lugs is used to secure handle to shaft, then the connection is strong, but the pin protruding from housing allows accidental release during use
Solution Approach 1:
Instead of having the engaging elements protrude from the housing which allows accidental engagement, the design inverts the approach by positioning the wedge-shaped engaging element and retaining ring in a configuration where the coupling is secured from the interior, preventing accidental release while maintaining connection strength.
Solution Approach 2:
The wedge-shaped engaging element acts as an intermediary that transfers the coupling force securely. Combined with the retaining ring, it creates a mediation mechanism that maintains strong connection while preventing accidental release by designing the engagement geometry to resist disengagement forces during use.
4Manufacturing precision
If an engaging element with wedge-like engaging section is used, then manufacturing tolerances are compensated and play is eliminated, but the engaging plane length must correspond to recess length
Solution Approach 1:
The wedge-shaped engaging element utilizes parameter changes in its geometry to compensate for manufacturing tolerances. The wedge angle and dimensions are designed such that variations in manufacturing tolerances result in acceptable clearance and engagement forces, eliminating play without requiring extremely tight tolerance control.
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 provides a secure, play-free, and adaptable coupling mechanism that allows for shaft rotation, reducing the risk of accidental disengagement and simplifying cleaning and sterilization processes.
Implementation Method 1
a spring-loaded engaging element with a trapezoidal profile to securely attach the shaft to the handle
Implementation Method 2
the engaging element has at least one wedge-like engaging section which has an engaging plane E, the length of which along the longitudinal axis A corresponds to a length of the recess along the longitudinal axis A
Data Source
AI summary
A surgical instrument has a hollow shaft defining a longitudinal axis, a handle arranged at the proximal end of the shaft, and a force-transmission element mounted in the shaft and connected to a tool on the distal side and to the handle on the proximal side. The surgical instrument has a coupling device for releasably connecting the shaft and handle, the coupling device being an engaging device with an engaging element that moves between an engaging position wherein it engages with at least one recess at the proximal end of the shaft and a release position wherein it does not engage with the recess. The engaging element has at least one wedge-like engaging section with an engaging plane, the length corresponding to a length of the recess along the longitudinal axis so that the engaging section is received in the recess up to the engaging plane in the engaging position.