Orthopaedic Specimen Testing Apparatus with Cam-Driven Multi-Axis Motion

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Solution Overview

Problem

Conventional testing apparatuses for orthopaedic specimens, such as knee implants, are expensive due to the use of electrohydraulic actuators, which are ineffective in measuring smaller forces and lack resolution, making them unsuitable for synchronized and coordinated motion testing under ISO standards, especially when testing multiple specimens simultaneously.

Innovation Solution

A testing apparatus utilizing a drive mechanism with cams and followers to impose rotational, linear, and dynamic compressive forces on specimens, eliminating the need for electrohydraulic actuators and allowing for simultaneous testing of multiple specimens with adjustable forces and motions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrohydraulic actuators are used to impose forces and motions on test specimens, then the testing apparatus can achieve coordinated synchronized motion as required by ISO standards, but the cost of the testing apparatus becomes unduly expensive

Engineering Contradiction:

Improvecoordinated synchronized motionVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The testing apparatus is divided into multiple independent testing stations, each capable of testing a specimen individually. This segmentation allows the system to achieve coordinated synchronized motion at each station without requiring expensive electrohydraulic actuators, while maintaining the ability to test multiple specimens simultaneously under the same controlled conditions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces electrohydraulic actuators with a purely mechanical drive system consisting of drive shafts, cam mechanisms, and linkages. This mechanical substitution eliminates the need for expensive sensors and control systems while maintaining the ability to impose coordinated synchronized forces and motions on test specimens according to ISO standards

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Force

If electrohydraulic actuators are used to measure forces and motions, then the testing apparatus can impose required forces and motions, but the measurement precision for smaller forces deteriorates

Engineering Contradiction:

Improveforce imposition capabilityVSAvoidsmaller force measurement

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

The mechanical drive system with cam mechanisms and linkages provides direct mechanical coupling between the drive shaft and the test specimen, enabling precise measurement of small forces through mechanical means rather than electronic sensors. The system can dynamically adjust the mechanical advantage through cam profile selection to optimize measurement precision across different force ranges

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If multiple electrohydraulic actuators and associated sensors are used to achieve coordinated synchronization, then the required motions and forces can be imposed on specimens, but the device complexity increases

Engineering Contradiction:

Improvecoordinated synchronizationVSAvoidnumber of actuators and sensors

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple testing stations are mechanically coupled to a common drive shaft, merging the drive function into a single component that simultaneously controls all stations. This eliminates the need for multiple independent actuators and sensors, reducing device complexity while maintaining coordinated synchronization across all testing stations

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cam mechanisms serve multiple functions: they impose the required motion profiles, provide mechanical amplification for force measurement, and enable easy adjustment of testing parameters by simply changing cam profiles, thereby reducing the need for complex control systems

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Force

If electrohydraulic actuators are used for testing, then the required force magnitudes can be achieved, but the resolution for measuring smaller forces deteriorates

Engineering Contradiction:

Improvedynamic compressive forceVSAvoidforce resolution

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

The cam mechanisms can dynamically adjust the mechanical advantage ratio during the testing cycle, providing high resolution measurement capability for small forces during certain phases while maintaining the ability to impose large dynamic compressive forces during other phases, thereby achieving both high force capability and high measurement precision

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9730812B2Adjustable testing apparatus for an orthopaedic specimen such as a knee implant prosthesis

Publication Date: 2017.08.15 ORTHOPAEDIC RES LAB

AI summary

A testing apparatus for exposing an associated specimen(s) to motions along multiple axes is provided. The testing apparatus includes a test chamber and first, second, third, and fourth devices that impose different kinematic motions or forces on the specimen. A drive mechanism is connected to the first, second, third, and fourth devices so that motion from a single axis is conveyed by the first, second, third and fourth devices to deliver the desired kinematic motions and/or forces to the test chamber(s). At least one of the first, second, third, and fourth devices includes an adjustment mechanism to modify at least one of the devices.