Method and structure for sealing tubular filter elments

Claim 2

In a tubular filter element comprising a pleated microporous membrane disposed for fluid flow therethrough from its upstream side to its downstream side and having its ends sealed in solidified liquid sealer, said membrane comprising a sheet material having pores between about 0.1 and 25 microns in size and about 50-80% voids by volume, the improvement wherein each end of the membrane on its upstream side includes a barrier strip of non-porous pleated film, one portion of the strip being joined fluid-tight to the membrane and the other portion being free from the membrane to permit relative movement therebetween, the solidified sealer terminating on the other portion of the film and sealing fluid-tight to the film and downstream side of the membrane, whereby the membrane may flex away from the other portion of the strip in response to upstream pressure.

Claim 3

A tubular filter element according to claim 1 wherein at least a portion of said sealer extends inwardly from the end of the element a greater distance on the upstream side of the membrane than on the downstream side thereof.

Claim 4

An element according to claim 2 wherein said membrane and end strips comprise a substantially common thermoplastic material, one portion of each strip being welded fluid-tight to the membrane independently of said sealer.

Claim 5

An element according to claim 3 wherein the portion of the membrane forming said weld has its pores collapsed, a portion of the membrane on its downstream side adjacent said weld remaining porous and having said sealer extending into said pores.

Claim 6

An element according to claim 1 wherein said sealer extends into the pores of the membrane on the downstream side and seals the element free of leaks larger than said pore size.

Claim 7

An element according to claim 1 wherein said membrane and strips comprise polyvinylidene fluoride.

Claim 8

A tubular filter element comprising a microporous membrane filter disposed for fluid flow therethrough from its upstream side to its downstream side and having at least one end sealed in solidified liquid sealer, said membrane comprising a sheet material having pores between about 0.1 and 25 microns in size and about 50-80% voids by volume, said end of the membrane on its upstream side including a barrier strip of non-porous film, one portion of the strip being joined fluid-tight to the membrane and the other portion being free from the membrane to permit relative movement therebetween, the solidified sealer terminating on a portion of the film of the upstream side of the membrane and the sealing fluid-tight to the film on the downstream side of the membrane, at least a portion of said sealer extending from the end of the element a greater distance on the upstream side of the membrane than on the downstream side thereof, said membrane at said sealer portions being free to flex away from a portion of the film strip in response to pressure.

Claim 9

A tubular filter element comprising a microporous membrane filter disposed for fluid flow therethrough from its upstream side to its downstream side and having at least one end sealed in solidified liquid sealer, said membrane comprising a sheet material having pores between about 0.1 and 25 microns in size and about 50-80% voids by volume, said end of the membrane on its upstream side including a barrier strip of non-porous film, one portion of the strip being joined fluid-tight to the membrane and the other portion being free from the membrane to permit relative movement therebetween, the solidified sealer terminating on a portion of the film of the upstream side of the membrane and the sealing fluid-tight to the film on the downstream side of the membrane, at least a portion of said sealer extending from the end of the element a greater distance on the upstream side of the membrane than on the downstream side thereof, said membrane at said sealer portions being free to flex away from a portion of the film strip in response to pressure.

Claim 10

A filter element according to claim 7 wherein the membrane is a pleased cast film, the membrane having over its downstream side a separate permeable support layer the end of which is embedded in said sealer said sealer extending into the pores of the membrane on its downstream side to seal the element free of leaks larger than said pore size.

Claim 13

The method according to claim 9 wherein said barrier strip is formed by collapsing the pores at one edge of a microporous membrane sheet of thermoplastic material and folding the collapsed edge over the membrane.

Claim 14

The method according to claim 10 wherein the contacting surfaces adjacent the fold are bonded together.

Claim 15

The method according to claim 9 wherein said barrier strip is of thermoplastic material and is bonded to the membrane.

Claim 16

The method according to claim 9 wherein the membrane and barrier strip are of substantially similar thermoplastic materials and are joined together by welding.

Claim 17

The method according to claim 9 wherein said element is formed by pleating and sealing together the longitudinal edges to form a seam, and wherein both ends of the element are identically sealed.

Claim 20

The method according to claim 15 wherein said pleated membrane is formed into a cylinder with its two free longitudinal edges adjacent each other, one of said free edges providing said contiguous surface, and wherein barrier strips and sealer are applied substantially identically to each free edge.

Claim 21

The method according to claim 9 or 15 wherein said membrane has a fibrous support on each of its upstream and downstream sides, each barrier strip being located between said membrane and upstream support.