Importance

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Abstract

A constant air pressure unit for an air handling system. The unit comprises a housing having an air inlet opening for admitting pressurized air into the housing. The housing has a top wall with a by-pass opening therein and a door is displaceably retained over the by-pass opening. The door has a predetermined load whereby the door is caused to lift away from the by-pass opening when the pressure of the air in the housing is equal to the pressure required to lift the load. The door load defines a maximum housing pressure. In the case where the pressure at the inlet opening starts to increase above the predetermined maximum housing pressure, the door lifts and by-passes the excess pressurized air and thus limits the inlet and housing pressures. In a corollary unit, an air outlet opening for releasing air is included. A pressurized airflow path is defined between the inlet opening and the outlet opening. The outlet airflow is restricted by the use of an adjustable restrictor blade which will start to increase the pressure in the housing. With the door load selected for a desired inlet pressure, the excess pressurized air is then evacuated through the by-pass opening so as to maintain a substantially constant air pressure at the inlet and thus a substantially constant inlet airflow volume rate with a variable outlet airflow volume rate.

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First Claim