Breathing with a machine - Piezo valves in breathing apparatus

Article of 27 September 2013 

Breathing with a machine - Piezo valves in breathing apparatus

Breathing comes naturally to most people, with every breath being taken automatically. The world looks very different, however, for people with chronic respiratory ailments: ventilators and oxygen apparatus are vital to them and an essential everyday companion. Inside the machines, which are often portable, pneumatic automation components ensure a smooth ventilation process – they generate the required pressure and mix oxygen in the correct ratio if necessary.

Piezo valves help people to breathe

Piezo valves from Festo are today used in modern ventilators to supply the oxygen. They provide major benefits compared to the previously used solenoid valve technology, as they consume up to 95 % less electrical power. This is particularly important on the portable appliances – the batteries therefore last much longer, which save the patient from changing them frequently. It is also possible to ensure very fine doses with piezo valves, meaning that oxygen can be mixed in exact quantities. Last but not least, the switching operation makes almost no sound, and patients who have to be ventilated day and night are not disturbed by the much quieter operating noise.

The VEMR piezo valve
The VEMR piezo valve

How piezo technology works

Some ceramic materials are deformed when they are placed under an electric charge – two plates made of such a material and joined together are then bent, for example, in a certain direction. Festo makes use of this process for its piezo valves. They are opened and closed with the help of this small connected plate, the so-called bending actuator.

How the bending actuator in the piezo valve works
How the bending actuator in the piezo valve works

If a voltage is applied to the bending actuator, the ceramic layer contracts and hence bends the small plate upwards; the valve opens (fig. right). If the voltage is switched off, the bending actuator resumes its original shape and closes the valve (fig. left). The higher the voltage, the wider the valve opens – the rate of flow can thus be regulated. These switching operations can also run very quickly after one another on piezo valves.

Used in many sectors

Besides breathing apparatus, piezo valves are also used in many other medical areas, e.g. in decubitus mattresses to prevent bedsores, blood pressure gauges and laboratory appliances. Medical technology is just one of the application areas for the fast switching and small dimensioned valves, however. They are used in many other sectors such as the automotive industry, food production or process and industrial automation.

This film shows you how piezo valves are produced fully automatically at Festo: