Cast Removal System With Low-Speed Shearing Wheel

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Solution Overview

Problem

Existing methods for removing orthopedic casts are noisy, generate fine debris, and can cause burns or abrasions, making them unsafe and uncomfortable for patients, especially children.

Innovation Solution

A motorized apparatus with a gear train and shearing wheel system that operates at low speed with high torque, using a combination of shearing sectors and teeth to cut through the cast material with minimal noise and debris, featuring a foot mechanism to protect the patient's skin and a handle for easy operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If powered oscillating saws are used to remove casts, then cutting speed and efficiency are improved, but noise level increases and fine debris is generated

Engineering Contradiction:

Improvecutting speedVSAvoidfine debris

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The cutting wheel is divided into multiple discrete cutting elements (teeth or shearing sectors) arranged around the circumference. Each element acts independently to cut the cast material, allowing the wheel to rotate and continuously engage the cast without generating excessive debris or noise, while maintaining efficient cutting progress.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the high-speed oscillating mechanical action of traditional saws with a low-speed rotating shearing mechanism. The cutting wheel rotates slowly with high torque, using shearing action rather than oscillating impact, which significantly reduces noise and debris generation while maintaining cutting effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If oscillating saws operate at high frequency, then cutting efficiency is improved, but risk of burns or abrasions to patient increases

Engineering Contradiction:

Improvecutting efficiencyVSAvoidburns or abrasions

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Instead of using high-frequency oscillating motion that contacts the cast and potentially the patient, the invention uses a low-frequency rotating wheel with discrete cutting elements. The cutting action occurs at the interface between the wheel and cast, away from direct contact with the patient's skin, inverting the traditional approach of high-frequency direct contact.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The cutting wheel acts as an intermediary between the motor drive and the cast material. It transfers the cutting action through its rotating peripheral elements, which engage the cast and shear it away without requiring direct high-frequency contact with the patient's underlying skin or tissue, thus reducing the risk of burns or abrasions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Force

If high torque is applied to cut through cast material, then cutting capability is improved, but risk of injury to patient increases

Engineering Contradiction:

Improvecutting forceVSAvoidinjury risk

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The invention applies cutting force in a rotational dimension rather than linear oscillating motion. The high torque is converted to rotational motion of the cutting wheel, which distributes the cutting force across multiple discrete elements around the circumference. This dimensional change allows effective cutting while reducing concentrated force application that could injure the patient.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The cutting system uses dynamic rotation of the cutting wheel rather than static or reciprocating motion. The continuous rotation allows the cutting elements to progressively engage and shear the cast material, maintaining effective cutting force while avoiding the sudden impacts or concentrated pressure points that could occur with oscillating saws, thereby reducing injury risk.

Inventive Principle:

Principle #15Dynamics

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 apparatus provides a quiet, clean, and safe method for removing orthopedic casts with reduced risk of injury, minimizing debris and ensuring efficient cutting through various cast materials.

Implementation Method 1

a gear train including a worm gear pair, the first pair providing a speed reduction and torque increase to the driving member of the gear train

Methodology Applied

Scientific EffectGear reduction: Gear

Implementation Method 2

a wheel including a plurality of shearing sectors arranged in a first pattern about a first rotational axis, each sector having a sharp edge

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentUS9168188B2Cast removal system

Publication Date: 2015.10.27 ORTHOPEDIATRICS CORP

AI summary

Apparatus and methods for cutting a material, especially with low material speed and high cutting torque. In some embodiments, the apparatus is a hand-held device for quietly cutting through an orthopedic cast with little or no generation of debris. In yet other embodiments, there is a method for automatically advancing material past a shearing surface, such that the shearing action occurs at about the same velocity as the advancement. In yet other embodiments, there is a device for cutting material between a foot and a sharp edge, with the bottom of the foot being under the sharp edge to protect the skin of the patient.