Disposable Torque-Limiting Driver with Spiral Teeth

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Solution Overview

Problem

Existing disposable torque-limiting drivers in the medical industry face challenges in delivering high torque values required for larger applications, as they are typically limited to lower torque ranges and require recalibration for reusable drivers.

Innovation Solution

A disposable torque-limiting driver design featuring a torque-limiting assembly with spiral teeth configurations and a spring mechanism that engages and disengages at a predefined torque, allowing for higher torque transmission and precise control through a combination of inclined and flat surfaces on the teeth, enabling a ten-fold increase in torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If disposable torque-limiting drivers are designed for low torque applications (4-20 inch-ounces), then reliability and ease of use are improved, but the ability to deliver higher torque values for larger applications deteriorates

Engineering Contradiction:

Improvetorque delivery reliabilityVSAvoidtorque range coverage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent employs a dynamic tooth engagement mechanism where the number of engaged teeth varies with applied torque. At low torque, fewer teeth engage; as torque increases, more teeth progressively engage, allowing the same mechanism to handle a wide torque range (4-100 inch-ounces) reliably without requiring multiple specialized drivers

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the engagement parameter from fixed to variable by designing teeth with different engagement characteristics. The spiral geometry and incremental engagement allow the system to adapt its effective tooth count based on the torque magnitude, enabling a single disposable driver to cover both low and high torque applications

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If reusable torque-limiting drivers are used, then adaptability to different torque requirements is improved, but manufacturing precision and reliability deteriorate due to calibration drift over time

Engineering Contradiction:

Improvetorque adjustment rangeVSAvoidtorque calibration accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent implements a disposable torque-limiting driver that is pre-calibrated at the factory for specific torque values. Each driver is designed for single-use, eliminating the calibration drift problem of reusable drivers. The disposable nature ensures consistent torque delivery without requiring field recalibration, while still providing adaptability through different pre-set torque options

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The torque calibration is performed in advance during manufacturing under controlled conditions. Each disposable driver is pre-set to deliver precise torque values before use, ensuring manufacturing precision is locked in at production rather than degrading over time through use and recalibration cycles

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If the tooth geometry uses only inclined faces, then ease of operation is improved, but the torque transmission capability deteriorates

Engineering Contradiction:

Improvedriver rotation smoothnessVSAvoidtorque transmission capacity

Core Design Contradiction:

Ease of operationVSForce

Solution Approach 1:

The patent applies different surface geometries to different parts of the tooth structure. The working faces use inclined surfaces for smooth engagement and ease of operation, while the peaks are made substantially flat to increase contact area and torque transmission capacity. This local differentiation allows the teeth to engage smoothly while transmitting high torque loads effectively

Inventive Principle:

Principle #3Local quality

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 provides reliable and precise high-torque delivery, suitable for applications like dental and vertebral implants, with adjustable torque settings and audible feedback, ensuring consistent torque application without over-torquing.

Implementation Method 1

There is a spring for applying pressure across the upper cylindrical shank and the lower cylindrical shank

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

The inclined face is defined by a first radius of curvature that transitions to the substantially flat peak. The teeth of the upper cylindrical shank and the lower cylindrical shank engage for relative rotation when the handle is turned and disengage when a predetermined value of torque is exceeded

Methodology Applied

Scientific EffectTorque: Torque

Data Source

PatentUS7938046B2Torque-limiting device

Publication Date: 2011.05.10 ECA MEDICAL INSTR

AI summary

A torque-limiting driver has 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. The inclined face is defined by a radius of curvature that transitions to the flat peak. There is a spring for applying pressure across the upper and lower shank. The teeth engage for relative rotation when the handle is turned and disengage when a predetermined value of torque is exceeded.