Process for making hermetically sealed filter units

• US 5,688,460 A
• Filed: 06/20/1996
• Issued: 11/18/1997
• Est. Priority Date: 04/26/1994
• Status: Expired due to Term

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Filtertek Inc. (Illinois Tool Works Inc.)
• Inventors: Ruschke, Rick R.
• Primary Examiner(s): ORTIZ, ANGELA Y
• Application Number:
  US08/667,005
• Time in Patent Office: 516 Days
• Field of Search: 264/263, 264/328.1, 264/DIG. 48, 264/266, 264/274, 264/249, 264/271.1, 264/275, 210/232, 210/445, 210/446
• US Class Current: 264/263
• CPC Class Codes: A61M 1/3627 Degassing devices; Buffer reservoirs; Drip chambers; Blood filters
• CPC Class Codes: A61M 1/3633 Blood component filters, e.g. leukocyte filters
• CPC Class Codes: B01D 2201/4084 Snap or Seeger ring connecting means
• CPC Class Codes: B01D 27/005 Making filter elements not provided for elsewhere
• CPC Class Codes: B01D 27/08 Construction of the casing
• CPC Class Codes: B01D 29/012 Making filtering elements making bag, cage, hose, tube, sleeve or like filtering elements B01D29/111
• CPC Class Codes: B01D 29/05 supported
• CPC Class Codes: B29C 2045/14319 bonding by a fusion bond
• CPC Class Codes: B29C 45/14467 Joining articles or parts of a single article B29C45/14377, B29C45/14385, B29C45/14581, B29C45/14614 and B29C45/006 take precedence
• CPC Class Codes: B29L 2031/14 Filters optical filters B29L2011/0066, sieves or screens B29L2031/737
• CPC Class Codes: Y10S 264/48 Processes of making filters

Abstract

A process for the manufacture of hermetically sealed filter units and a product made thereby. The process comprises aligning a porous filter element between two housing parts and a thermoplastic skirt that overlaps the edge of at least one housing part to shield the edge of the filter element disposed adjacent to the skirt, pressing the housing parts together and then injection molding a thermoplastic overmold band around the outer portions of the housing parts to form a hermetic seal at the edge of the filter element.

Claims

1. A method for hermetically sealing a filter element within a housing, comprising the steps of:

(a) aligning a filter element between a first and a second housing member defining a filter cavity;

(b) disposing a thermoplastic skirt adjacent to a peripheral edge of the second housing member to surround an entire peripheral edge of the filter element located between the first and second housing members;

(c) applying pressure to the first and second housing members; and

(d) injection molding a thermoplastic overmold over the skirt and a periphery of the housing members, wherein a temperature and pressure of the injection molded overmold causes the skirt to melt and mix with the overmold to infuse the edge of the filter element.

2. The method of claim 1 wherein the skirt depends from a peripheral edge of the first housing member.

3. The method of claim 1 wherein the housing members are thermoplastic.

4. The method of claim 3 wherein the overmold is injection molded at a temperature and pressure to cause the skirt and a periphery of the second housing member to fuse together and to infuse the peripheral edge of the filter element to form an integral hermetic seal between the housing members, the overmold and the peripheral edge of the filter element.

5. The method of claim 1 wherein the first and second housing members have opposing surface portions, the filter element has peripheral surface portions, said filter element is aligned such that the peripheral surface portions of the filter are disposed between the opposing surface portions of the housing members, said pressure is sufficiently applied to the housing members to cause the opposing surface portions to contact the peripheral surface portion of the filter element and form a seal sufficient to prevent the melted thermoplastic from inwardly infusing into the filter element beyond the opposing surface portion during the overmold injection molding step.

6. The method of claim 4 wherein the periphery of the second housing member has a lip extending outwardly disposed adjacent to the skirt.

7. The method of claim 1 wherein the first housing member comprises a filter element support and an outlet port, and the second housing member comprises an inlet port.

8. The method of claim 1 wherein the first housing member comprises an inlet port, and the second housing member comprises a filter element support and an outlet port.

9. The method of claim 1 wherein at least one alignment tab extends from the periphery of the first housing member.

10. In a method for hermetically sealing a filter element within a thermoplastic housing wherein a filter element is aligned between two thermoplastic housing members, the housing members are pressed together and a thermoplastic overmold is injection molded over a periphery of the housing members and on a peripheral edge of the filter element to form an integral seal, the improvement comprising:

providing a first housing member with a skirt depending from a periphery of said first housing member whereby the skirt and an outside peripheral edge of a second housing member are configured such that the entire peripheral edge of the filter element is protected from direct initial contact with overmold thermoplastic during the overmold process, and

injection molding the thermoplastic overmold at a temperature and pressure to cause the skirt to melt during the overmold process to infuse the peripheral edge of the filter element and to fuse with the peripheral edge of the second housing member to form therewith an integral hermetic seal between the filter element and the housing members.

11. A method for sealing a filter element, comprising the steps of:

(a) supporting a first thermoplastic housing member on a lower mold half, the housing member comprising a filter element support, a periphery, an aperture for passage of fluid and a skirt depending from the periphery;

(b) aligning a filter element over the aperture and the support of the first housing member such that a peripheral edge of the filter element is disposed adjacent to the skirt of the first housing member;

(c) placing a second thermoplastic housing member over the filter element such that a peripheral edge of the second housing member is disposed adjacent to an inside surface of the skirt defining a filter cavity, the filter element is encased within the housing members;

(d) placing an upper mold half over the lower mold half, the mold halves having portions which contact and apply pressure to the housing members, the mold halves defining a channel around the periphery of the housing members;

(e) injection molding a thermoplastic overmold over the periphery of the housing members to form an integral seal between the housing members and the filter element, the thermoplastic overmold injection molded at a temperature and pressure to cause the skirt of the first housing member and the peripheral edge of the second housing member to fuse together and to infuse the edge of the filter element; and

(f) separating the mold halves and ejecting the filter unit.

12. The method of claim 11 wherein an outer diameter of the second housing member is about the same size as an inner diameter of the skirt of the first housing member such that the skirt may slidably engage the peripheral edge of the second housing member.

13. The method of claim 11 wherein the thermoplastic overmold is injection molded at a temperature and a pressure to cause the periphery of the housing members to melt and infuse the peripheral surface portion of the filter element.

14. The method of claim 11 wherein the first and second housing members have raised opposing surface portions disposed on the filter element aligned therebetween, the pressure applied to the housing members is sufficient to cause the opposing surface portions to compress the filter element to prevent melted thermoplastic from inwardly infusing into the filter element and into the filter cavity beyond the opposing surface portions.

15. The method of claim 11 wherein the periphery of the second housing member has a lip extending outwardly that is disposed adjacent to the skirt, at least two alignment tabs extend from an end of the skirt, the alignment tabs have a foot at a distal end extending inwardly, an inner diameter across the first housing member at the foot is less than an outer diameter of the lip of the second housing member, the alignment tabs being semi-rigid and sufficiently flexible to allow the foot to slide over the lip when the second housing member is placed over the first housing member, the foot being substantially rigid to hold against the lip when the housing members pull apart such that the housing members and filter element hold together.