Filter underdrain assembly and method of producing same

Claim 2

A filter underdrain assembly comprising a tubular straiNer body having a perforated sidewall with an exterior surface providing a multiplicity of circumferentially extending recessed portions therein; a fabric covering of filaments plaited directly upon said exterior surface and extending entirely about said strainer body over substantially the entire length thereof, said fabric covering conforming closely to the contour of said strainer surface to interengage with said body in said recessed portions and to resist relative axial movement between said covering and said body; and means communicating with the interior of said body for connection to a pump, said fabric covering effecting the removal of entrained particulate matter from liquids passing through said covering and said sidewall of said body into the interior thereof.

Claim 3

The assembly of claim 1 wherein said body is generally cylindrical with an outside diameter that alternates along the length thereof between a relatively large and a relatively small diameter, to provide a series of circumferential recesses therein extending entirely about said body.

Claim 4

The assembly of claim 2 wherein said connection means is adjacent one end of said body and wherein said assembly additionally includes an end plug inserted into the other end of said body and bonded to the inside surface of said sidewall to seal said other end of said body, said fabric covering extending about said body at least between said connection means and the area of bond with said plug to necessitate passage through said fabric covering of the entire volume of liquid entering into the interior of said body.

Claim 5

The assembly of claim 1 wherein said body and said fabric covering are each fabricated of synthetic resinous materials.

Claim 6

The assembly of claim 1 wherein the synthetic resinous material of said fabric is a polyester.

Claim 7

In a method for producing a filter underdrain assembly, the steps comprising: a. fabricating a tubular strainer member having a perforated sidewall with an exterior surface providing a multiplicity of circumferentially extending recesses therealong; b. plaiting a fabric covering of filaments directly upon and in close conformity to the contour of said exterior surface with said fabric covering extending entirely about said strainer member over substantially the entire length thereof, said close conformity causing interengagement of said fabric covering with said strainer member in said circumferential recesses to resist relative axial movement therebetween; and c. providing on said strainer member means communicating with the interior thereof for connection to a pump, said fabric covering being capable of effecting the removal of entrained particulate matter from liquids passing through said fabric covering and said sidewall of said strainer member into the interior thereof.

Claim 8

In a method for producing a filter underdrain assembly, the steps comprising: a. fabricating a tubular strainer member having a perforated sidewall with an exterior surface providing a multiplicity of circumferentially extending recesses therealong; b. plaiting a fabric covering of filaments directly upon and in close conformity to the contour of said exterior surface with said fabric covering extending entirely about said strainer member over substantially the entire length thereof, said close conformity causing interengagement of said fabric covering with said strainer member in said circumferential recesses to resist relative axial movement therebetween; and c. providing on said strainer member means communicating with the interior thereof for connection to a pump, said fabric covering being capable of effecting the removal of entrained particulate matter from liquids passing through said fabric covering and said sidewall of said strainer member into the interior thereof.

Claim 9

The method of claim 6 wherein said strainer member is provided in said fabricating step with an outside diameter that alternates along the length thereof between a relatively large and a relatively small diameter to provide a series of circumferential recesses extending entirely about said body, said fabricating step additionally involving extrusion of a synthetic resinous material through a generally annular die opening to produce a generally cylindrical strainer member.

Claim 10

The method of claim 6 wherein said strainer member and covering are relatively long, and additionally including the steps of applying a length of water-impermeable material about said strainer member and said fabric covering intermediate the ends thereof, severing said length of material, fabric covering and strainer member intermediate said ends to produce a plurality of underdrain subassemblies, and of providing one of said communicating means on each of said subassemblies to produce a strainer assembly therefrom.

Claim 11

The method of claim 7 wherein there are included the additional steps of mounting connection means adjacent one end of said strainer member and of sealing the other end of said strainer member by inseRting an end plug thereinto and bonding said plug to said inside surface of said sidewall of said strainer member.