Valve arrangement for introducing back wash air in filters for air or gas cleaning

Claim 1

An improved valve arrangement for use with duct filters in air or gas cleaning apparatus, adapted to be interposed between a filter chamber and an adjacent discharge duct, for introducing backwash air in a shock-like manner to clean the filter, comprising in combination: a. a filtered air valve having a valve seat in an opening between the filter chamber and the discharge duct; b. a backwash air duct adjacent said filter chamber; c. a backwash air valve having a valve seat in an opening between the filter chamber and the backwash air duct; d. a compressed air cylinder having a piston and couplings for supplying compressed air to the opposite sides of the piston to impart backward movement thereto for backwash cleaning or forward movement for normal discharge of filtered air through the discharge duct; e. a piston rod extending from said piston through said backwash air duct and through said filter chamber, and rigidly connected to said filtered air valve for normally maintaining the same in open position during filtering, the backwash air valve being slidably mounted on said piston rod and normally maintained in closed position due to the pressure difference between the backwash air duct and the filter chamber; and f. a helical spring mounted on and surrounding said piston rod and having one end engaging said filtered air valve connected to said piston and the other end engaging said backwash air valve slidably mounted on said piston rod; whereby on supplying compressed air to said cylinder for backwash cleaning, the piston rod moves to close the filtered air valve against its valve seat and compress said helical spring until the combined actions of the spring and compressed air suddenly open the backwash air valve from its valve seat to produce a shockwave of backwash air into the filter chamber, the cleaning action being terminated by supplying compressed air to said cylinder to move the piston rod to return the filtered air valve to normal open position.