Patent ID: 8585897

Claim:
A cylindrical backwash purifying device, comprising a main body within which a cylindrical through hole is transversely provided, wherein a plunger closely fitted with and axially slidably coupled with the through hole is disposed within the through hole, and a feed channel and a discharge channel which are connected with the through hole are provided in the main body, the cylindrical backwash purifying device having a cylindrical periphery of a fore portion of the plunger is depressed inwards and forms an annular cavity with an inner wall of the through hole, the annular cavity is communicated with the feed channel, an L-shaped hole communicated with the discharge channel is made in the plunger from front to back of the plunger in an axial direction, filter holes communicated with the annular cavity and the L-shaped hole are made in the depressed periphery of the plunger in a radial direction, and a detachable filter screen is coupled to the depressed periphery of the plunger, wherein a spacer bar in contact with the inner wall of the through hole is axially disposed in the annular cavity on the plunger, and a semi-ring shaped groove is disposed on an external surface of the plunger around two sides of the discharge channel.