Rotary Stop Mechanism for Compact Shaft Rotation Constraint

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Solution Overview

Problem

Existing constraint mechanisms for tools like surgical instruments are bulky, unreliable, and prone to unintentional activation, failing to effectively restrict rotational motion within a predefined range while occupying excessive space.

Innovation Solution

A rotational stop mechanism that transitions between states to constrain shaft rotation, utilizing a rotary device with stop surfaces and notches to interact with protrusions on the shaft, allowing rotation in one direction until a midpoint is reached, then restricting further rotation in that direction, and optionally in the other direction, without requiring a circumferentially surrounding structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional constraint mechanisms are used to restrict rotational motion, then reliable movement restriction is achieved, but the mechanism occupies excessive space within the tool

Engineering Contradiction:

Improvemovement restrictionVSAvoidspace occupied by constraint mechanism

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The constraint mechanism is segmented into discrete elements: a shaft with protrusions at specific positions and a rotary device with corresponding notches and stop surfaces. This segmentation allows the mechanism to achieve reliable rotational constraint through localized interactions rather than requiring a continuous circumferential structure, thereby reducing the overall volume occupied by the constraint system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from a two-dimensional circumferential constraint approach to a three-dimensional point-contact approach. By using protrusions positioned at specific locations on the shaft that engage with notches in the rotary device, the mechanism achieves rotational constraint through discrete point contacts in three-dimensional space, eliminating the need for a bulky circumferential structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If constraint mechanisms are reduced in size, then space efficiency is improved, but the mechanism becomes prone to unintentional activation

Engineering Contradiction:

Improvespace occupied by constraint mechanismVSAvoidactivation control

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The shaft features protrusions at asymmetric positions (first, second, and third positions) rather than uniform distribution. This asymmetric arrangement creates specific engagement sequences with the rotary device's notches, ensuring that rotation can only proceed in the intended direction through defined midpoints. The asymmetric geometry prevents unintentional activation by making reverse or random rotation mechanically impossible without proper engagement of the stop surfaces.

Inventive Principle:

Principle #4Asymmetry

3Reliability

If a circumferentially surrounding structure is used for constraint, then comprehensive rotation control is achieved, but the tool diameter must be increased

Engineering Contradiction:

Improverotation controlVSAvoidtool diameter

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The invention extracts the essential constraint function from a complete circumferential structure and implements it through discrete, localized elements. Instead of surrounding the shaft with a continuous constraint structure, the design uses specific protrusions at selected positions that engage with corresponding notches in the rotary device. This extraction approach maintains comprehensive rotation control while significantly reducing the tool diameter requirement.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If the rotational range is extended, then versatility is improved, but the constraint mechanism becomes more complex

Engineering Contradiction:

Improverotational rangeVSAvoidconstraint mechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The rotary device is designed with multiple notches and stop surfaces that can engage with different protrusions on the shaft at various positions. This multi-functional design allows a single constraint mechanism to control rotation through multiple defined ranges and midpoints, accommodating extended rotational versatility without requiring separate constraint mechanisms for each range, thereby avoiding proportional increases in complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12257700B2Constraint mechanisms, systems, and methods

Publication Date: 2025.03.25 INTUITIVE SURGICAL OPERATIONS INC

AI summary

A tool includes a transmission mechanism, a shaft, and a rotary device. The shaft is rotatable with reference to the transmission mechanism through a defined range of rotational motion about a first axis of rotation and includes a protrusion extending from the shaft in a direction normal to the first axis of rotation. The rotary device includes a first stop surface, a second stop surface, and a notch between the first stop surface and the second stop surface, with the notch configured to receive the protrusion extending from the shaft. Rotation of the shaft through a midpoint of the range of rotational motion causes the protrusion to enter the notch of the rotary device and rotate the rotary device from a first position to a second position.