Torque Limiter Coupling for Cardiac Capsule
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Solution Overview
Problem
The existing disengageable frictional coupling mechanism in implantable medical devices, such as leadless capsules, is insufficient to transmit unscrewing torque during explantation, especially when fibrosis develops at the implantation site, leading to the capsule turning loosely with the screw remaining stationary.
Innovation Solution
A disengageable frictional coupling mechanism that differentiates between screwing and unscrewing directions, featuring a one-way unscrewing blocking mechanism to prevent disengagement in the unscrewing direction while allowing rotation in the screwing direction, using conjugated plates with surface configurations forming an anti-return mechanism and an elastically deformable element for frictional coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a disengageable frictional coupling mechanism is used to limit torque during screwing, then tissue damage is prevented, but the mechanism cannot transmit sufficient torque during unscrewing when fibrosis is present
Solution Approach 1:
The coupling mechanism dynamically changes its friction characteristics based on rotation direction. During screwing, high friction transmits torque to prevent tissue damage. During unscrewing, low friction allows torque transmission to overcome fibrosis. This dynamic adaptation resolves the contradiction between protecting tissue and enabling sufficient torque transmission.
Solution Approach 2:
The coupling mechanism exhibits asymmetric friction behavior: high friction in the screwing direction to protect tissue, and low friction in the unscrewing direction to enable torque transmission through fibrosis. This asymmetry allows the same mechanism to serve two opposing functions that would otherwise be contradictory.
2Stability of the object's composition
If the capsule is securely anchored during implantation, then stability is achieved, but accidental disengagement during explantation becomes difficult to prevent
Solution Approach 1:
The coupling mechanism transitions from a high-friction locked state during implantation to a low-friction unlocked state during explantation. This dynamic state change ensures stable anchoring when implanted while enabling controlled disengagement when explanted, preventing accidental retention or unintended disengagement.
Solution Approach 2:
The coupling mechanism is segmented into distinct functional states: a locked high-friction state for secure anchoring and an unlocked low-friction state for controlled disengagement. This segmentation allows the system to reliably maintain stability during implantation while enabling controlled removal, addressing both stability and reliability requirements.
3Force
If frictional coupling is used to prevent rotation during screwing, then torque control is achieved, but the mechanism fails to transmit torque in the opposite rotation direction
Solution Approach 1:
The frictional coupling exhibits direction-dependent characteristics: high friction in the screwing direction for torque control and low friction in the unscrewing direction for ease of operation. This asymmetric design allows the mechanism to provide precise torque control during implantation while enabling smooth operation during explantation.
Solution Approach 2:
The coupling mechanism dynamically adjusts its friction properties based on the direction of applied torque. When screwing, high friction provides torque control to prevent tissue damage. When unscrewing, low friction facilitates easy operation. This dynamic adaptation resolves the contradiction between torque control and ease of operation.
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
Ensures effective transmission of unscrewing torque during explantation, preventing accidental disengagement and tissue damage by maintaining the capsule securely anchored until intentional removal, even in fibrosed conditions.
Implementation Method 1
a disengageable frictional coupling arranged at said distal end of the capsule between the front-end unit and the tubular body
Implementation Method 2
the disengageable frictional coupling comprises two conjugated plates facing each other, with i) a first plate extending radially and integral with the tubular body and ii) a second plate extending radially and integral with the front-end unit
Data Source
AI summary
The capsule comprises a tubular body and a front-end unit with an helical screw for anchoring the capsule to a wall of a patient's organ. The front-end unit is mobile in relative axial rotation with respect to the tubular body. A disengageable frictional coupling member allows this relative rotation when, for implantation, the tubular body receives an external rotational stress, and that until a predetermined limit torque triggering the disengagement. At explantation, this disengagement is prevented to allow a joint rotation of the tubular body and of the front-end unit and the unscrewing of the helical screw. It is provided for that purpose two conjugated plates facing each other, with flat surfaces such as circular sectors offset in opposite directions with respect to a radial reference plane, in such a way as to form steps providing an anti-disengagement abutment function.