Surgical Instrument Shaft Threaded Actuation
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Solution Overview
Problem
Existing surgical instruments for robots rely on complex cable mechanisms that require high precision and regular pre-tensioning maintenance, which can lead to operational issues over time.
Innovation Solution
A surgical instrument with a simplified design featuring a shaft and actuation unit with non-rotatable but axially movable wheels, allowing direct force transmission and independent movement in two degrees of freedom, eliminating the need for pre-tensioned cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cable mechanism is used for force transmission, then the instrument can achieve movement control, but the structure becomes complex and requires regular pre-tensioning maintenance
Solution Approach 1:
The patent removes the cable mechanism entirely from the transmission system. Instead of using cables that require pre-tensioning and maintenance, the invention uses a direct mechanical connection through a shaft that is threaded into the actuation unit, eliminating the intermediate cable elements and their associated maintenance requirements.
Solution Approach 2:
The patent replaces the cable-based mechanical transmission system with a direct threaded mechanical connection. The shaft with external threads engages with the internally threaded actuation unit, creating a direct force transmission path that eliminates the need for cables, pulleys, and pre-tensioning mechanisms.
2Ease of operation
If cables are used for force transmission, then movement control is achieved, but pre-tensioning slackens over time requiring regular checks
Solution Approach 1:
The threaded connection between the shaft and actuation unit is a self-retaining mechanism that maintains its mechanical engagement without requiring external pre-tensioning or periodic adjustment. The threads inherently maintain the connection geometry, eliminating the need for manual pre-tensioning and reducing maintenance time to zero for this specific function.
3Device complexity
If a threaded engagement between shaft and actuation unit is used, then the structure is simplified and maintenance is reduced, but the mechanism must support both rotational and axial movements
Solution Approach 1:
The patent employs a dynamic design where the shaft can simultaneously rotate around its axis and move axially relative to the actuation unit. The threaded engagement allows the shaft to rotate for torque transmission while also permitting axial displacement, and the connection to the end effector allows swiveling movement, providing multiple degrees of freedom through a single simplified mechanical interface.
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 maintenance-friendly, reliable transmission mechanism that ensures consistent operation by directly transmitting forces and allowing for precise movement of the end effector, reducing the risk of mechanical failure due to pre-tensioning issues.
Implementation Method 1
the first shaft is axially displaceable in relation to the first wheel and is in threaded engagement with a second wheel which is axially immovable in relation to the first wheel
Implementation Method 2
A torque can be transferred to the first shaft via the connection, non-rotatable but freely moveable in an axial direction, with the first wheel, causing said first shaft to rotate around its axis
Implementation Method 3
The first shaft advantageously has a flexible region which extends at least partially through the swivel mechanism and which follows a swivelling movement of the swivel mechanism. The flexible region is preferably elastic, so that a restoring force caused through the elasticity is exerted on the swivel mechanism
Data Source
AI summary
The invention relates to an instrument (30) with an elongated first shaft (42), an end effector which is arranged on a distal end of the first shaft (42) and an actuation unit (19) arranged on the proximal end of the first shaft, wherein the actuation unit (19) comprises a first wheel (32) which is connected non-rotatably with the first shaft (42). The first shaft (42) is axially displaceable in relation to the first wheel (32) and is in threaded engagement with a second wheel (33) which is axially immovable in relation to the first wheel (32).