Patent ID: 7494521

Claim:
A trigger mechanism for triggering release of filter bag cleaning pulses of compressed air from an air tank communicating with a radial air distribution arm rotating about an arm axis within a filter apparatus including a plurality of filter bags positioned in circumferentially spaced groups, said tank including a tank valve controllable to release said pulses of compressed air through said air distribution arm which includes a plurality of nozzles arranged thereon to periodically register with said groups of filter bags, said tank valve being a tank diaphragm valve and being controlled to release said pulses in response to reduction in air pressure on one side of said tank valve, said trigger mechanism comprising: (a) a fixed gear secured in coaxial relation with said arm axis; (b) a trigger frame secured to said distribution arm to rotate therewith; (c) a trigger assembly mounted on said frame to enable movement between a sealing position and a release position, said trigger assembly being urged toward said sealing position by a combination a trigger spring member and by compressed air and being engaged with said tank valve in such a manner as to cause said tank valve to open when said trigger assembly is moved to said release position, thereby releasing said air pressure acting against said trigger assembly and causing said reduction in air pressure on one side of said tank valve; (d) a rotary trigger cam journaled on said frame and including a trigger gear meshed with said fixed gear whereby rotation of said arm causes rotation of said trigger cam relative to said frame, said trigger cam having two diametrically opposed cam lobes which periodically engage said trigger assembly in such a manner as to periodically push said trigger member from said sealing position to said release position; and (e) said fixed gear and said trigger gear being relatively sized and synchronized in such a manner as to time engagement of said cam lobes with said trigger assembly substantially simultaneous with registration of said nozzles with a selected group of said filter bags whereby said bag cleaning pulses of air are periodically applied to each of said filter bags.