A Form-Closed Cam-Follower Mechanism for a Breath Simulator Machine
The worldwide incidence of asthma yields 250,000 deaths annually, being almost all of these deaths avoidable. The inhalation therapy is the preferable route to deliver bronchodilator/anti-inflammatory drugs to the patient lungs. Within this route of treatment, pressurized Metered Dose Inhalers (pMDI’s) are the cornerstone devices. When coupled with a Valved Holding Chamber (VHC), its efficiency increases and the limitations almost vanish. The VHC devices efficiency is something of interest to measure. For that, it is necessary an experimental setup that evaluates the amount of drug delivered by the device. This setup shall replicate a human breath waveform as input, therefore a breath simulator machine was build. The report herein describes the project process of the form-closed cam-follower mechanism necessary to replicate the waveform. The design and dimensional constrains are input in the cam design, leading to a piston diameter of 63.0 mm and a cam base diameter of 250.0 mm. A performance analysis to the pressure angle, curvature radius and backlash impact force, is reported. It can be concluded that a larger diameter would improve the performance results substantially.
KeywordsForm-closed Cam-follower mechanism Breath simulator Synthesis
The first author would like to express his gratitude to the Portuguese Foundation for Science and Technology (FCT) through the PhD grant SFRH/BD/76458/2011. This work was financed by National Funds-Portuguese Foundation for Science and Technology, under Strategic Project PEst-C/EME/UI4077/2011 and PEst-OE/EME/UI0252/2011.
The authors are also grateful for the help of Dr. Eurico Seabra from the University of Minho with the data acquisition from the LVDT.
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