Valve system particularly for apparatus for producing dry compressed air

Abstract

Apparatus for producing dry compressed air comprises a compressor which delivers air to a dry air storage tank through a cooling coil, a liquid separator comprising a housing having a cavity with a valve controlled tap opening at the bottom thereof, a screening filter and an adsorption filter connected in sequence. A pressure sensitive switch turns off the compressor when a predetermined pressure has built up in the storage tank. When delivery of air ceases, a valve control system opens the tap opening of the separator and second valve control system opens a valve to permit back flow of air from the dry air storage tank back through the adsorption filter to regenerate it and out of the tap opening if the moisture content of air in the dry air storage tank is above a predetermined level. The first valve control system which controls the opening of the tap opening comprises a diaphragm which divides the cavity of the housing into a lower chamber which comprises the liquid separator and an upper chamber, means connecting the diaphragm with the valve of the tap opening and a valve assembly connected in circuit between the separator and the adsorption filter and comprising a Borda nozzle for producing a reduced pressure in the upper chamber to close the tap opening when compressed air is being delivered, a bypass valve and check valve in parallel with said Borda nozzle and an auxiliary valve for connecting the upper chamber with the atmosphere in order to close the tap opening in the event the compressor starts up again after a short interruption.