Spring Torque Drive Interface for High-Speed Torque Limiting
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Solution Overview
Problem
Disposable torque-limiting devices for medical power tools fail to maintain torque specification at higher rotational speeds and have a limited number of actuations, leading to performance issues in surgical applications.
Innovation Solution
A disposable torque-limiting device with a coil spring force assembly and reduced components, featuring a cylindrical body with a partially closed distal end, upper and lower shank components, and torque-limiting interfaces that engage and disengage when a predetermined torque limit is exceeded, ensuring consistent torque delivery at high speeds over a specified number of cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If disposable torque-limiting devices are used for medical power tools, then the need for sterilization and recalibration is eliminated, but the devices fail to maintain torque specification at higher rotational speeds and have limited actuation cycles
Solution Approach 1:
The patent transitions from static friction-based torque limiting to a dynamic spring-based mechanism. The coil spring provides continuous force to maintain engagement between the drive socket and drive shaft, allowing the system to adapt to varying rotational speeds while maintaining consistent torque delivery across 50-1300 RPM ranges.
Solution Approach 2:
The invention changes the physical parameters of the torque-limiting mechanism by introducing a spring force component. The spring constant, pre-compression force, and engagement surface geometry are optimized to maintain torque specification consistency across high-speed operations, enabling reliable performance at rotational speeds up to 1300 RPM.
2Productivity
If traditional disposable torque-limiting devices operate at higher rotational speeds, then productivity increases, but torque specification is not maintained and device reliability decreases
Solution Approach 1:
The spring-based engagement mechanism dynamically adjusts to rotational speed variations. The coil spring maintains constant contact force between the drive socket and drive shaft across the operational speed range, ensuring torque limit accuracy is preserved even at high rotational speeds up to 1300 RPM.
Solution Approach 2:
The spring is pre-compressed during device assembly to establish optimal engagement force before operation. This preliminary action ensures that the torque-limiting interfaces are properly engaged from the start, maintaining torque specification consistency across the entire operational cycle from 50 to 1300 RPM.
3Measurement precision
If reusable torque-limiting systems are used, then torque precision can be maintained through calibration, but the devices require constant recalibration and sterilization which reduces ease of operation
Solution Approach 1:
The patent implements a disposable torque-limiting device that eliminates the need for recalibration and sterilization. The spring-based mechanism is designed to maintain torque precision (0.1-6 Nm) throughout its operational life without requiring maintenance, and can be disposed of after use, significantly improving ease of operation in surgical settings.
Solution Approach 2:
The spring mechanism is designed to self-maintain engagement force throughout its operational life. The coil spring's inherent elasticity automatically compensates for wear and operational variations, eliminating the need for external recalibration services while maintaining torque precision across multiple actuation cycles.
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 device maintains a predetermined torque between 0.1 and 6 Newton-meters at rotational speeds from 50 to 1300 RPM for a defined number of actuations, providing reliable performance and durability in medical applications while reducing the need for recalibration and sterilization.
Implementation Method 1
a coil spring placed above the lower shank component, at least partially around the neck and configured to apply compressive force (F) along the axis to compress the torque-limiting interfaces
Implementation Method 2
the first torque-limiting interface in contact with the second torque-limiting interface... configured to compress the torque-limiting interfaces against each other
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Disposable torque-limiting devices having an upper shank component with a torque-limiting interface, a lower shank component with a torque-limiting interface, and a spring element. Torque -limiting interfaces having a plurality of undulations arranged around an axial bore or drive socket and separated by a plurality of transition regions, with each undulation having an upslope, a peak, and a downslope. The torque-limiting interfaces are configured to engage and disengage to provide torque transmission with predetermined torque limits at various rotational speeds and for amounts of actuations while remaining within a specified operational range. The encasement provides mounts for a tool and for a drive shaft which may be connected to a powered device.