Filter apparatus for fluids to be cleaned

Filter apparatus comprising:

• a stationary housing having a supply channel for fluid to be filtered, a discharge channel for filtered fluid, and a washing channel;
• and
• a screen carrier member guided for reciprocal movement in said housing and having a screen nest positioned therein, said screen nest comprising two perforated plates having a filter layer therebetween, said screen nest having an upstream side that receives fluid to be filtered and a downstream side that discharges filtered fluid, said carrier member further including a storage space which is connected with a space at the downstream side of said screen nest, said storage space having a piston reciprocally movable therein and means for moving said piston in said storage space for pressing said filtered fluid in said storage space in a backwashing direction through said screen nest,
• means for reciprocally displacing said screen carrier member in said housing between
• an operating position wherein a space at said upstream side of said screen nest is connected with said supply channel for receiving fluid to be filtered, and said space at said downstream side of said screen nest is connected with said discharge channel for discharging filtered fluid which has passed through said screen nest and with said storage space for introducing filtered fluid therein, said washing channel being closed by said carrier member when said screen carrier member is in said operating position,
• a washing position wherein said space at said upstream side of said screen nest is connected with said washing channel, said filtered fluid in said storage space being pressed in a backwashing direction through said screen nest and being discharged through said washing channel, said supply channel and said discharge channel being closed by said screen carrier member when said screen carrier member is in said washing position, and
• a screen exchange position wherein said screen carrier member protrudes from said housing such that said screen nest is accessible for a screen changing process.