Torque Limiter Lock Bushing Alignment
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Solution Overview
Problem
Prior art torque limiting devices for surgical applications suffer from misalignment issues, leading to inaccurate torque outputs and increased mechanical wear, particularly at low torque ranges, which can result in damage to orthopedic implants and undesirable patient outcomes.
Innovation Solution
A torque limiter device with a simplified design featuring a lock bushing and retaining ring to ensure proper alignment of components, reducing lateral movement and eliminating gear teeth to minimize binding, thereby improving accuracy and precision in torque application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior art torque limiting devices use torque gear teeth that rotate at a slight angle away from horizontal position, then the device can limit torque, but the misalignment creates frictional interference and inaccurate torque outputs
Solution Approach 1:
The patent removes the torque gear teeth entirely from the device architecture. Instead of using gear teeth that rotate at angles and create friction, the invention uses a straight shaft that rotates true without angular deviation, eliminating the source of frictional interference and improving torque output accuracy.
Solution Approach 2:
Rather than having gear teeth rotate at an angle to limit torque, the invention inverts the approach by using a straight, true-rotating shaft combined with a locking bushing mechanism. This reverses the conventional gear-based approach and eliminates the misalignment problem inherent in angled gear rotation.
2Reliability
If prior art torque limiter devices are constructed with multiple intricate components that fit precisely together, then the device can provide torque limiting function, but the complexity results in tolerance stack up and structural misalignments
Solution Approach 1:
The patent segments the device into distinct functional components: a handle, a straight shaft, a locking bushing, and a retaining ring. This segmentation allows each component to perform its specific function independently, reducing the need for multiple intricate parts while maintaining reliability through simplified assembly.
Solution Approach 2:
The straight shaft serves multiple functions: it transmits torque, provides structural support, and ensures true rotation without requiring separate alignment mechanisms. The locking bushing simultaneously provides both alignment and retention functions, reducing the overall component count while maintaining device reliability.
3Adaptability or versatility
If prior art torque limiter devices apply spring pressure axially to control torque release, then the device can adjust torque levels, but axial force application during normal use results in additional unwanted torque
Solution Approach 1:
The patent introduces a locking bushing as an intermediary component between the shaft and the torque limiting mechanism. This bushing provides a stable reference point that prevents axial forces from translating into unwanted torque, allowing torque adjustment through spring pressure while maintaining precise torque application during normal use.
Solution Approach 2:
The invention replaces the conventional spring-pressure-only mechanism with a hybrid system combining the locking bushing and retaining ring. This substitution creates a more stable mechanical reference that eliminates the coupling between axial force and torque, allowing independent control of torque levels without the harmful side effect of additional unwanted torque.
Data Source
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AI summary
A torque limiting mechanism used for securing fasteners is described. The torque limiting mechanism consists of a shaft (36), a torque gear (66) having a plurality of ball bearings (64), a thrust bearing (86) and a variable force applying subassembly (96). The torque limiting mechanism further consisting of a lock bushing (52) and retaining ring (60) placed circumferentially around the proximal end of the shaft. The lock bushing and retaining ring reduce structural misalignments and increase the accuracy of the device.