Wear-Compensated Torque-Limiting Orthopedic Driver
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Solution Overview
Problem
Orthopedic surgical drivers experience calibration drift and reduced service life due to wear and sterilization processes, leading to inconsistent torque application and potential bone damage.
Innovation Solution
A wear-compensated, calibrated mechanical torque-limiting driver with a torque-limiting assembly that includes a cam bearing mechanism and a biasing system, distributing wear over a larger surface and adjusting force vectors to maintain precise torque control despite wear and sterilization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibrated torque-limiting driver is used for orthopedic surgical applications, then torque control precision is improved, but calibration drift occurs due to wear and sterilization over time
Solution Approach 1:
The patent converts the harmful effect of wear into a beneficial feature by designing a wear-compensated mechanism. The cam profile is intentionally designed to account for wear, where the worn surface progressively adjusts the torque limit to maintain accuracy. The cam bearing assembly with wear-compensated cam profile allows the wear to occur in a controlled manner that actually maintains torque calibration over time, transforming the harmful wear effect into a self-correcting mechanism.
2Object-affected harmful factors
If repeated cleaning and sterilization is performed on torque-limiting drivers, then surgical hygiene is improved, but calibration accuracy deteriorates over time
Solution Approach 1:
The patent applies beforehand cushioning by designing the cam bearing assembly to anticipate and accommodate the effects of repeated sterilization. The wear-compensated cam profile is pre-designed to account for the cumulative effects of cleaning and sterilization cycles, creating a buffer that maintains calibration accuracy despite these repeated exposures to harsh environmental conditions.
3Device complexity
If traditional torque-limiting mechanisms are used, then device simplicity is maintained, but service life is reduced due to wear
Solution Approach 1:
The patent applies dynamics by creating a mechanism where the cam profile dynamically adapts to wear over time. Rather than a static torque-limiting mechanism that degrades with wear, the cam profile is designed to dynamically adjust, where the worn surface progressively modifies the torque transmission characteristics to maintain accuracy. This dynamic wear compensation extends service life while maintaining relative mechanical simplicity.
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 extends the accurate calibration service life of orthopedic surgical drivers by maintaining consistent torque limits, reducing the risk of bone damage and ensuring reliable performance across repeated use and sterilization cycles.
Implementation Method 1
The cam bearing assembly has a wear-compensated cam profile... distributing wear over a larger surface
Implementation Method 2
The bearing load assembly applies a normal bias force to the cam bearing assembly... adjusting force vectors to maintain precise torque control
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A torque-limiting driver (10) for orthopedic surgical use has a housing (16) to which a torque force may be applied and transferred to a driver output shaft (18). The housing (16) encloses a cam bearing assembly (52) having a ball cage (54) disposed so that balls (56) of the ball cage (54) moves along a first vector path (Vr) radial to the axis of rotation (20). The bearing assembly also has an inner race (58) abutting the ball (56) and which inner race (58) travels along a second vector path (F) parallel to the axis of rotation (20). The first vector path (Vr) and the second vector path (F) are not co-axial. A bearing load assembly (70) applies a bias force (F) to the inner race (58) of the cam bearing assembly (52) to set the calibrated maximum amount of torque that can be transmitted via the housing (16) through the cam bearing assembly (52) to output shaft (18) of the torque-limiting driver (10).