Split Nut Drive for Manual Retraction in Medical Devices
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Solution Overview
Problem
Medical device drive systems face challenges in enabling manual retraction of surgical tools without the need for computerized control systems, particularly during robot-assisted surgery, where disengagement from the lead screw is necessary without rotating the screw.
Innovation Solution
A medical device drive system incorporating a split nut with pins and oblique slots that allow for selective engagement and disengagement with the lead screw, enabling manual retraction by sliding the nut housing relative to the lever body, which biases the pins to disengage the nut from the lead screw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional nut is used to engage with the lead screw, then the drive system maintains stable engagement, but manual retraction without computerized control is not possible
Solution Approach 1:
The nut is divided into two separable halves that can be positioned to engage or disengage from the lead screw. This segmentation allows the drive system to transition between engaged and disengaged states manually, enabling retraction without computerized control while maintaining stable engagement when the halves are positioned together.
Solution Approach 2:
The nut housing is made movable relative to the lever body, allowing dynamic transition between engaged and disengaged states. This dynamic configuration enables manual control of the drive system's engagement state, providing flexibility for retraction while maintaining reliability during active engagement.
2Adaptability or versatility
If the nut is made disengageable from the lead screw, then manual retraction is enabled, but the complexity of the drive system increases
Solution Approach 1:
The first and second nut halves are combined within a single nut housing structure that moves together relative to the lever body. This merging approach enables engagement/disengagement capability while reducing the complexity that would result from completely separate control mechanisms for each nut half.
Solution Approach 2:
The oblique slots in the nut housing automatically guide the pins during movement, causing the nut halves to engage or disengage from the lead screw based on the housing's position relative to the lever body. This self-service mechanism reduces the need for additional control components, balancing adaptability with structural simplicity.
3Reliability
If pins are used to connect the nut halves to the lead screw, then engagement is maintained, but manual disengagement requires overcoming pin resistance
Solution Approach 1:
The pins are positioned in oblique slots that allow dynamic adjustment of the pin positions during housing movement. This dynamic slot configuration enables the pins to naturally transition between engagement and disengagement positions, reducing the effort required for manual disengagement while maintaining stable engagement when the housing is in the engaged position.
Solution Approach 2:
The oblique slots act as intermediaries between the pin connection mechanism and the housing movement. They mediate the transition from engaged to disengaged state by guiding the pins through a controlled path, reducing the direct resistance that would otherwise be encountered during disengagement while preserving engagement stability.
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 solution allows for manual retraction of surgical tools without computerized control, enhancing flexibility and usability in minimally invasive surgical procedures by enabling the disengagement of the nut from the lead screw, allowing for axial movement of the drive member and surgical instrument without rotating the lead screw.
Implementation Method 1
The medical device drive system can include a spring in the lever body cavity. The spring can be sized and shaped to exert a drive gear turns biasing force on the first nut housing and the lever body.
Implementation Method 2
The first nut can have a first slot, and a lead screw interface sized and shaped to engage with the engagement portion of the lead screw
Implementation Method 3
The pin can be slidable in the first slot of the first nut
Data Source
AI summary
A medical device drive system including a lever body having portions defining a lever body cavity, a nut housing in the lever body cavity, and a first nut at least partially in the first nut cavity. The first nut is slideable in the first nut cavity between an engaged position in which the lead screw interface is engaged with the engagement portion of the lead screw, and a disengaged position in which the lead screw interface is not engaged with the engagement portion of the lead screw. The lead screw interface of the first nut is selectively engageable with the engagement portion of the lead screw by sliding the lever body and pin relative to the first nut housing.