suitable electrical mechanical control means known to those skilled in the art to achieve proper positioning of shuttle block 40 during operation slots 52 allow pins 42 reference fig6 a b to extend down to make contact with shuttle block 40 fig8 is a flow chart describing the method of removing a spent cartridge and replacing it with a fresh cartridge in step 100 a computer program interrupt generated by a flow sensor signal programmed elapsed time signal or user command signals microprocessor 65 to initiate a filter change out operation the interrupt is usually based on a flow sensor measurement of reduced volumetric flow below a user defined low flow level but also is frequently initiated by a user initiated filter change command in step 110 microprocessor 65 initiates disengagement of used filter cartridge 10 from cam 5 typically this is performed by removing a vacuum condition within cam 5 that holds cartridge 10 in place in step 120 a signal from controlling microprocessor 65 initiates movement of shuttle block 40 that contains used spent filter cartridge 10 from cam 5 along transport insert 50 until shuttle block 40 reaches discharge container 30 during this movement shuttle block 40 engages pins 42 and pushes latch piece 45 away from feed container 20 allowing the stack of replacement cartridges to move down in step 130 once centered over discharge container 30 used filter cartridge 10 simply drops into discharge container 30 from shuffle block 40 in.