Back pressure resistant filter element

Claim 2

A filter element comprising, in combination a support core having a plurality of apertures for the passage of fluid therethrough; a corrugated filter sheet formed in a closed configuration extending about the core, with the corrugations extending longitudinally of the core, and the inner tips of the corrugations being disposed in proximity to the core; and a foraminous softenable plastic bonding sheet disposed between the core and the filter sheet and bonded only to the inner tips of corrugations of the filter sheet, the inner tips of the corrugations being bonded in situ to the bonding sheet by displacement of the plastic material about at least a portion of the inner tips of the corrugations with the corrugations disposed about a central axis in a fixed radial relationship to each other and with the inner tips of the corrugations being fixed against displacement.

Claim 3

A filter element in accordance with claim 1, in which the foraminous bonding sheet is made of thermoplastic material.

Claim 4

A filter element in accordance with claim 1, in which the bonding sheet is made of polypropylene.

Claim 5

A filter element in accordance with claim 1, in which the bonding sheet has up to about 30 percent open area.

Claim 6

A filter element in accordance with claim 1, in which the core is made of a thermoplastic material.

Claim 7

A filter element in accordance with claim 5, in which the core is made of polypropylene.

Claim 8

A filter element in accordance with claim 1, in which the core has a series of circumferential troughlike indentations.

Claim 9

A filter element in accordance with claim 1, in which the corrugated filter sheet is made of paper.

Claim 10

A filter element in accordance with claim 1, in which the filter sheet is made from a material that comprises a porous base having a microporous layer adhered thereto.

Claim 11

A filter element in accordance with claim 1, in which the side edge portions of the corrugated filter sheet are positioned in a juxtaposed relationship and in which a portion of the bonding sheet is positioned between said side edge portions so as to bond the side edges to each other and thereby form a side seam.

Claim 12

A filter element in accordance with claim 10, in which the side edge portions are bonded to each other by a radially extending border strip of the bonding sheet.

Claim 13

A filter element in accordance with claim 1, including a sheet of separating material, disposed between the core and the foraminous bonding sheet.

Claim 14

A filter element in accordance with claim 12, in which the separating material is paper.

Claim 15

A filter element in accordance with claim 1, in which the foraminous bonding sheet is soluble in a solvent, and the core is soluble in the same solvent.

Claim 16

A filter element comprising, in combination, a generally tubular thermoplastic support core having a series of circumferential indentations along its length, and having a plurality of apertures disposed in the indentations for the passage of fluid therethrough; a separator sheet disposed about thE core; a corrugated filter sheet formed in a generally tubular closed configuration, disposed concentrically on the core over the separator sheet, the corrugations of said filter sheet extending longitudinally of the core and the inner tips of the corrugations being disposed in proximity to the core; and a foraminous thermoplastic bonding sheet disposed between the separating sheet and the filter sheet, said bonding sheet being bonded to the inner tips of the corrugations to fix them in position, but not being bonded to the core, such that the corrugated filter sheet cannot flex away from the core, although it is not bonded to the core.

Claim 17

A filter element comprising, in combination, a generally tubular thermoplastic support core having a series of circumferential indentations along its length, and having a plurality of apertures disposed in the indentations for the passage of fluid therethrough; a separator sheet disposed about thE core; a corrugated filter sheet formed in a generally tubular closed configuration, disposed concentrically on the core over the separator sheet, the corrugations of said filter sheet extending longitudinally of the core and the inner tips of the corrugations being disposed in proximity to the core; and a foraminous thermoplastic bonding sheet disposed between the separating sheet and the filter sheet, said bonding sheet being bonded to the inner tips of the corrugations to fix them in position, but not being bonded to the core, such that the corrugated filter sheet cannot flex away from the core, although it is not bonded to the core.

Claim 18

A filter element in accordance with claim 15, in which the side edge portions of the corrugated filter sheet are positioned in a juxtaposed relationship, and in which a portion of the foraminous bonding sheet is positioned between the side edge portions so as to bond the side edge portions to each other in a side seam.

Claim 19

A filter element in accordance with claim 15, in which the thermoplastic core and the thermoplastic bonding sheet are made of polypropylene.

Claim 20

A filter element in accordance with claim 1, in which the foraminous softenable plastic bonding sheet is a perforated sheet.