Catheter Actuator Mechanical Advantage via Offset Pivot
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Solution Overview
Problem
Steerable medical devices, such as electrophysiology catheters, require increased mechanical advantage to deflect the distal end effectively, necessitating a mechanism to adjust input force proportionally with deflection amount and direction, while maintaining clinician comfort and control.
Innovation Solution
A pull wire actuator system comprising a drive wheel, pull wire arm guide plate, and a bendable pushing member, where the drive wheel is pivotable and includes thumb bosses for rotation, and the pull wire arm is slidably mounted in an arm channel with an arcuate pin groove, allowing for increased mechanical advantage as the catheter is deflected, thereby reducing the required input force and providing feedback to the clinician.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of deflection at the distal end of the medical device is increased, then the steering capability and positioning precision are improved, but the force required to deflect the distal end increases excessively
Solution Approach 1:
The actuator incorporates a dynamic mechanical advantage system where the drive wheel rotates on a pivot pin that is offset from the drive wheel's axis of rotation. As the drive wheel rotates, the effective lever arm length changes dynamically, providing increased mechanical advantage as the catheter deflects from neutral. This dynamic adjustment allows the system to maintain acceptable input force levels across the full range of deflection motion while achieving the required positioning precision.
Solution Approach 2:
The invention introduces a lateral offset dimension by positioning the pivot pin laterally away from the drive wheel's axis of rotation. This dimensional offset creates a varying moment arm as the drive wheel rotates, transforming the force application geometry. The lateral displacement of the pivot pin relative to the rotation axis enables the mechanical advantage to vary with deflection angle, resolving the force-p precision contradiction.
2Device complexity
If a fixed mechanical advantage is used in the actuator, then the structure is simple, but the input force does not adjust proportionally with the deflection amount
Solution Approach 1:
Rather than using a complex adjustable mechanism, the invention achieves variable mechanical advantage through the dynamic geometry of a rotating drive wheel with an offset pivot. The system naturally adapts its mechanical advantage ratio as the drive wheel rotates through its range of motion, providing force adjustment capability that is proportional to the deflection amount without requiring additional actuators or complex control systems.
Solution Approach 2:
The invention changes the geometric parameters of the actuator mechanism during operation. Specifically, the effective lever arm length changes as the drive wheel rotates, with the moment arm varying proportionally to the deflection angle. This parameter change enables the mechanical advantage to adapt to different deflection requirements while maintaining a simple fixed-structure actuator design.
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 system provides a mechanical advantage that increases as the catheter is deflected, reducing the force needed to steer the device and offering improved control and feedback to the clinician, allowing for precise positioning and reduced fatigue during procedures.
Implementation Method 1
The bendable pushing member can be positioned in the arcuate pin groove between the pushing pin and the distal end of the pull wire arm. In this way, the bendable pushing member can provide mechanical advantage that increases as the catheter is deflected from a neutral position
Implementation Method 2
a first bendable pushing member slidably positioned in the first arcuate pin groove between the first pushing pin and the distal end of the first pull wire arm
Data Source
AI summary
Catheter actuators providing a mechanical advantage are disclosed. The actuators include a pull wire arm guide plate and a drive wheel attached around the pull wire arm guide plate and pivotable relative to the guide plate, the drive wheel comprising at least one thumb boss for pivoting the drive wheel about a drive wheel axis of rotation. The drive wheel mechanically engages at least one pull wire arm slidably mounted in a pull wire arm channel in the pull wire arm guide plate. A mechanism transfers drive wheel input into longitudinal motion of the at least one pull wire arm. The mechanism may include, for example, a pin pushing against a bendable pushing member riding in an arcuate pin groove in a top surface of the guide plate, or a pin pushing against a surface of a cam arm pivotably mounted on the top surface of the guide plate.