Spring Washer Torque Limiter for High-Speed Surgical Tools
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Solution Overview
Problem
Disposable torque-limiting devices for medical power tools fail to consistently limit torque at high rotational speeds and maintain performance over a predetermined number of actuations, leading to inadequate performance in surgical applications.
Innovation Solution
A disposable torque-limiting device with a novel design featuring a hollow cylindrical body, upper and lower shank components with torque-limiting interfaces, and a Multiple Belleville Washer Assembly (MBWA) to apply compressive force, allowing the components to engage and disengage at a predetermined torque limit, maintaining torque control across a range of rotational speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If disposable torque-limiting devices are used for medical power tools, then cost-effectiveness and ease of disposal are improved, but torque consistency and reliability deteriorate at high rotational speeds
Solution Approach 1:
The patent applies dynamics by making the torque-limiting interface movable rather than fixed. The conically-shaped torque-limiting interface allows the lower shank component to move axially relative to the upper shank component during rotation, enabling the frictional contact to maintain consistent torque limiting across varying rotational speeds. This dynamic adjustment resolves the contradiction by allowing disposable components to reliably limit torque even at high speeds up to 1300 RPM.
Solution Approach 2:
The patent changes physical parameters by using a conically-shaped torque-limiting interface instead of a cylindrical one. The conical geometry creates a varying normal force as the components rotate, which maintains consistent frictional torque limiting across different rotational speeds. This parameter change enables disposable devices to achieve reliable torque control in high-speed medical power tool applications.
2Productivity
If disposable torque-limiting devices operate at high rotational speeds, then productivity is improved, but torque control precision deteriorates
Solution Approach 1:
The dynamic conical interface design allows the system to maintain precise torque control across a wide range of rotational speeds from 50 to 1300 RPM. The axial movement enabled by the conical shape adjusts the frictional contact in real-time, ensuring consistent torque limiting precision regardless of rotational speed variations.
Solution Approach 2:
The torque-limiting interface is segmented into multiple conical contact surfaces that engage sequentially during rotation. This segmentation distributes the torque limiting action across different portions of the conical interface, maintaining precision even at high rotational speeds where a single contact point would be insufficient.
3Measurement precision
If reusable torque-limiting systems are used, then torque precision is improved, but device complexity and maintenance requirements worsen
Solution Approach 1:
The patent implements a disposable torque-limiting driver with integrated torque-limiting functionality, eliminating the need for separate reusable torque-limiting systems. The disposable nature simplifies the overall system while maintaining torque precision through the conical interface design, resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent merges the torque-limiting function directly into the disposable driver body by forming the conically-shaped torque-limiting interface on the shank component. This integration eliminates the need for separate reusable torque-limiting attachments or systems, reducing overall system complexity while maintaining precise torque control.
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 effectively limits torque between 0.1 and 6 Newton-meters at rotational speeds from 50 to 1300 RPM over multiple actuations, ensuring consistent performance and durability within specified operational ranges.
Implementation Method 1
an MBWA placed above the lower shank on at least partially around the neck configured to apply compressive force (F) along the axis to compress the first torque-limiting interface against the second torque-limiting interface
Implementation Method 2
the two interfaces together form a torque limiting engagement
Data Source
AI summary
Disposable torque-limiting mechanisms with upper shank component with a torque-limiting interface, a lower shank component with a torque-limiting interface, and a washer assembly biasing 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.