An air cannon for removing cakes of flowable material and clearing clogged areas of flowable material in silos, heat exchanger and lines has a pressure container for storing compressed air and a pressure source connected to the pressure container. An outlet valve is connected to the pressure container. An outlet jet is connected to the outlet valve. The outlet valve has a valve housing and a piston, wherein the valve housing has a guide in which guide the piston is axially slidable. An annular channel is formed between the valve housing and the guide. The annular channel is connected to the pressure container and, in the open position of the outlet valve, forms a cylindrical opening that opens into the outlet jet. The piston has a forward end face facing the outlet jet and having an annular valve sealing surface. The rearward end face of the piston is subjected to a suddenly releasable closure pressure. A pressure present in the outlet jet acts on the area enclosed by the annular sealing surface, and a pressure of the pressurized container acts on the area surrounding the annular sealing surface.

Quick acting blast aerators having rigid accumulation tanks with internal valve assemblies comprising a tubular body, an end cap teat receives air through an inlet controlled by solenoids, and an internal piston that contacts a valve seat during filling, and retracts to expose exhaust vents upon firing. The valve calp comprises a ring groove and an O-ring check valve. An internal dampening passageway vertically extends through the cap. Internal air passageways extend form the passageway to the air-control groove, admitting air into the tank by dislodging the O-ring. The high temperature piston slides between a tank-fill position bearing against the valve seat and a retracted position exposing the exhaust vents. An internal return spring extends between a deep, annular recess in the piston, and a groove formed in the bottom of the end cap. A dampener projecting from the piston is received within the passageway traversing the end cap.

A quick acting blast aerator comprising a spring-less actuator triggered by an exhaust valve. The actuator valve comprises a tubular body, an exhaust vent defined in the body, a dampening passageway, and a piston slidably disposed therewithin for movement between a tank filling position and a displaced, air discharge position. Preferably the piston has a projecting dampener which engages the dampening passageway. The trigger valve comprises a rigid, cylindrical housing with a hollow interior having a plurality of vent orifices radially disposed about its periphery. A pair of resilient bands surrounding the housing cover the vent orifices to form a one-way check valve. A resilient, hollow piston coaxially, slidably disposed within the trigger housing has a hollow internal chamber containing a ball valve. Mutual cooperation of the trigger piston and its internal valve govern pneumatically control the actuator.

An externally-mounted, quick-acting trigger assembly for firing blast aerators, air cannons, or the like. The trigger assembly is ideal for high temperature applications involving environmental factors such as excessive heat, humidity, and mechanical shock. The trigger comprises a symmetrical, ventilated housing that internally mounts a hollow piston. A plurality of vent orifices are radially disposed about the housing periphery, and normally covered by a resilient band forming a check valve. The trigger piston comprises a generally cylindrical base and an integral, generally conical bottom that is displaced into and out of contact with a mechanical valve seat. An air passageway through the piston is controlled by a deflectable spherical valve element that is captivated within the piston, for selectively blocking air passage through the piston by contacting an internal valve seat. This construction with internal air passageways facilitates trigger function. The base comprises a circumferential groove for seating an appropriate O-ring.

A positive pressure actuated aerator valve assembly adapted to discharge compressed gas into the chamber of a bulk material handling structure. The aerator valve assembly includes a housing and positive pressure actuated valve. The housing includes a chamber adapted to receive compressed gas and a discharge piston slideable between an extended position and a retracted position. The valve includes a valve body having an actuator piston seat and a fluid vent passageway in fluid communication with the actuator piston seat. An actuator piston is slideable with respect to the valve body between a retracted position and an extended position. A positive displacement force is applied to the actuator piston, such as by the supply of pressurized gas to the valve, to slide the actuator piston from the retracted position toward the extended position whereupon gas within the chamber of the housing flows through the fluid vent passageway and the discharge piston is moved from the extended position to the retracted position by gas within the chamber to thereby place the chamber of the housing in fluid communication with the fluid passageway of the piston seat.