Torque-Limiting Driver Nose Cone Breakage Prevention
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Solution Overview
Problem
Current disposable torque-limiting drivers in the medical industry face challenges in imparting higher torques required for larger applications, with existing solutions often leading to plastic nose cone breakage and inconsistent torque delivery.
Innovation Solution
A disposable torque-limiting driver design featuring a torque-limiting assembly with a spring-loaded mechanism, multiple washer bearing surfaces, and a round square drive socket configuration that distributes force evenly, allowing for higher torque transmission without cracking the plastic nose cone, and incorporating a spiral tooth configuration for increased reliability and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If disposable torque-limiting drivers are used for high torque applications, then torque transmission capability is improved, but plastic nose cone breakage occurs
Solution Approach 1:
The drive socket is divided into multiple segments with rounded corners instead of a single monolithic structure. This segmentation allows the force to be distributed across multiple corner regions, preventing stress concentration that would otherwise cause the plastic nose cone to crack or break under high torque conditions.
Solution Approach 2:
The drive socket incorporates rounded corners instead of sharp corners. This curvature modification distributes the applied torque forces more evenly across the plastic material, preventing stress concentration at corner points and thereby eliminating the crack propagation pathway that leads to nose cone failure.
2Force
If torque limit is increased for larger applications, then torque transmission capability is improved, but binding and friction increase
Solution Approach 1:
The spring mechanism is segmented into multiple active regions with multiple bearing surfaces. This segmentation allows the spring to engage and disengage in stages, reducing continuous binding friction while maintaining the ability to transmit high torque pulses through controlled engagement of individual spring segments.
Solution Approach 2:
The spring acts as an intermediary element between the torque-limiting assembly and the drive socket. It provides a controlled friction interface that allows smooth torque transmission while preventing direct binding between metal components, thereby reducing energy loss from friction and binding.
3Measurement precision
If reusable drivers are used, then torque precision can be maintained, but recalibration is required which increases time loss
Solution Approach 1:
The driver is designed as a disposable single-use tool with pre-calibrated torque-limiting assembly. This eliminates the need for post-use recalibration entirely, as the torque precision is built into the disposable unit's manufacturing specifications. The trade-off is accepting lower cost and single-use nature in exchange for eliminating recalibration time and ensuring consistent torque delivery without wear.
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 the driver to transmit torques up to 17 Newton meters without nose cone breakage, providing consistent and reliable high-torque performance in surgical applications, such as orthopedic implant installation, with a ten-fold increase in torque capability and reduced binding issues.
Implementation Method 1
There is a spring for applying pressure across the upper cylindrical shank and the lower cylindrical shank
Implementation Method 2
at least one bearing surface formed between at least two washers interposed between a distal end of the spring and the upper cylindrical shank and a plastic nose cone at a distal end of the lower cylindrical shank
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A torque-limiting driver is disclosed, having a handle, a body, a torque-limiting assembly and a work-piece engaging tip. The torque-limiting assembly includes an upper and lower shank that have a plurality of teeth circumferentially spaced. The teeth have a vertical face, an inclined face, and a flat peak. There is a spring for applying pressure across the upper and lower shank with multiple washers interposed between the lower shaft and spring. In some instances, there is a round-square drive with arched catches having preselected radii to assure operation over certain cycles at selected torque and to reduce nose cone damage and breakage at a predetermined measurement of inch-pounds of torque.