Steerable Sheath Deflection Mechanism Using Bevel Gears
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Solution Overview
Problem
Conventional steerable sheath deflection mechanisms are limited by large handle size and length requirements for high deflection, leading to ergonomic issues and compatibility problems with other therapy devices, and are not MR compatible due to metallic components, which cause friction and assembly complexity.
Innovation Solution
A steerable sheath deflection mechanism using a tubular shaft with bevel gears and flexible polymer wires, allowing for compact handle design, MR compatibility, and reduced component complexity, with a keystone component to maintain handle assembly integrity and a wire-bridge component to connect metallic and polymer wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rotation to linear translation mechanism (lead screw or rack) is used to achieve high degree of tip deflection, then the pull wire can be translated to a large degree, but the control handle geometry must accommodate the corresponding large degree of linear translation which requires the sheath handle to have a very long length and sometimes a larger outer diameter
Solution Approach 1:
The patent replaces the traditional rotation-to-linear-translation mechanism (lead screw or rack) with a direct rotation mechanism where the control knob directly rotates the pull wire. This substitution eliminates the need for intermediate linear translation components, thereby achieving high tip deflection without requiring a long handle length. The pull wire is directly coupled to the control knob, allowing rotational movement to be efficiently transmitted to achieve the desired deflection angle.
2Force
If the pitch of the thread on the knob and linear mechanism is about 0.4 or 0.5 inches, then friction force is manageable, but more than one knob rotation is required to fully deflect the sheath which can cause hand fatigue
Solution Approach 1:
The patent eliminates the threaded mechanism entirely and uses a direct rotation coupling between the control knob and pull wire. This allows for a much larger effective pitch equivalent, where a single knob rotation (or fraction thereof) can achieve the full required pull wire translation for maximum deflection. The direct mechanical coupling maintains manageable friction forces while requiring only one knob rotation, thereby preventing hand fatigue.
3Strength
If metallic pull wires are used in the transfer assembly, then tensile strength is achieved, but the assembly is not MR compatible
Solution Approach 1:
The patent employs a composite material strategy by using a polymeric pull wire with an embedded metallic core or coating. This composite structure combines the high tensile strength of metallic materials with the MR compatibility of polymeric materials. The metallic component provides the necessary mechanical strength to transmit the deflection force, while the polymeric exterior ensures MR compatibility by preventing magnetic interference and heating issues during MRI procedures.
4Object-affected harmful factors
If polymeric pull wire is used to achieve MR compatibility, then MR compatibility is achieved, but it is extremely difficult to bond the polymeric pull wire to a metallic pull ring
Solution Approach 1:
The patent uses a composite pull wire structure where the polymeric pull wire has an integrated metallic component (core or coating) that facilitates bonding to the metallic pull ring. This metallic interface within the composite structure provides a compatible bonding surface for metallurgical or mechanical attachment to the pull ring, while the polymeric exterior maintains MR compatibility. This eliminates the bonding difficulty between dissimilar materials.
5Strength
If a thicker walled polymeric pull ring is used to achieve the strengths of a metallic pull ring, then strength is achieved, but the outer diameter of the sheath increases which is not ideal
Solution Approach 1:
The patent employs a composite pull ring structure combining metallic and polymeric materials. The metallic component (core, reinforcement, or coating) provides the high strength and stiffness required for effective force transmission, while the polymeric component maintains MR compatibility and can be made thinner than a fully polymeric ring would require. This composite construction achieves the necessary mechanical strength with a reduced outer diameter compared to a thick-walled polymeric ring.
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 enables high-degree deflection with a shorter, more ergonomic handle, MR compatibility, and reduced assembly time and cost, while preventing hand fatigue and improving tensile strength.
Implementation Method 1
A steerable sheath deflection mechanism using a tubular shaft with bevel gears and flexible polymer wires
Implementation Method 2
the pull wire is connected to the tip of the sheath, usually via a pull ring. When the pull wire translates linear proximal direction, the tensioning force is transferred to the pull ring and this in turn causes the tip of the sheath to deflect
Data Source
AI summary
A steerable sheath with a deflection mechanism assembly is provided. The assembly includes a tubular shaft that receives first and second longitudinal movement wires at a distal end. A control handle includes a main body configured to receive first and second bevel gears. The first longitudinal movement wire is coupled to the first bevel gear and the second longitudinal movement wire is coupled to the second bevel gear. A rotatable adjustment knob is engageable with the control handle and has an external geared portion matingly engageable with the first and second bevel gears and the rotatable adjustment knob is moveable between a first and second position.