The main function of an exhaust valve is to release burned gases. It closes during the initial part of the induction and it usually opens a little before the top dead centre of your car’s engine. It remains a little open after the top dead centre and as pressure increases during compression and combustion, a small amount of air-fuel mixture is forced around the edges of the exhaust valve and between the valve and the valve seat.
Exhaust valves are installed at the rod or blind end of the pneumatic cylinder to provide a quick extension and retraction of the equipment. They operate by increasing the speed of the pneumatic cylinder’s rod to expel the exhaust air at the port of the cylinder directly. One exhaust valve is used in each port of the cylinder to ensure an increase in the speed of the rod in both directions.
There are several different ways in which a valve can benefit an exhaust system. A rapid reaction where exhaust valves generally have a greater exhaust capacity compared to commonly-used four-way control valves. Thus, increasing cylinder speed and allowing for a smaller, less costly control, valve to be put into use. Under high-pressure conditions, these valves allow a quicker extension of the cylinder. They can also be used at lower temperatures to achieve retraction, save air and increase the pneumatic cylinder’s life.
In a typical application, the exhaust valve is installed in the inlet of a spring return or double-acting pneumatic cylinder. Supply air from a control valve is directed into the inlet port of the exhaust valve. The nitrile poppet seals the exhaust port and allows air to flow from the outlet port of the valve into the cylinder. The pressurized air then pushes against the piston and extends the rod, compressing the spring, until full rod extension is achieved.
When the control valve exhausts air from the exhaust valve inner port, the nitrile poppet shifts to seal the inlet port and open the exhaust port to the cylinder. The pressurized air is then allowed to exhaust directly through the exhaust valve to the atmosphere. Normally, the air must travel back to the long-air line to the control valve to exhaust. However, by mounting the exhaust valve directly on the cylinder, the piston reacts quickly since the distance to the atmosphere is very short and unrestricted.