Hub assembly for use in the filtration of fluids and method of making the same

A hub assembly for use in the filtration of fluids therethrough comprising:

• a hub having a bore extending therethrough, said bore being substantially circular in cross-section and tapered in generally frusto-conical fashion thereby defining a large opening at the proximal end thereof and a small opening at the distal end thereof, said hub including a section extending from said distal end, said section having a substantially cylindrical passage therethrough communicating with said small opening, said passage adapted to receive a hollow needle for conducting fluid from said bore therethrough;
• a substantially flat flexible filter membrane in said bore, said filter membrane having a first, substantially circular portion extending transversely across said bore, said filter membrane having a second, annular portion being an upturned annular flange extending from said first portion and facing towards said large opening, said flange having an outside surface and an inside surface, said outside surface being in substantially circular contact with said hub around said bore;
• and a retaining ring having an opening therethrough, said ring having a substantially circular cross-section smaller than said large opening but larger than said small opening and extending transversely across said bore with a flat surface of said ring in contact with said first portion of said filter, said ring being in annular contact with said inside surface of said flange, said ring being inserted in said tapered bore to secure said filter membrane therein by pressing said flange tightly against said hub around said bore at the position whereat said ring diameter and said bore diameter are substantially equal.

A method of fabricating a filter membrane and inserting the same into a hub having a bore extending therethrough, said bore being substantially circular in cross-section and tapered to define a large opening at the proximal end thereof and a small opening at the distal end thereof, comprising:

• forming a substantially flat, circular filter membrane;
• inserting said filter membrane into the large opening of said tapered bore so that a first portion thereof is substantially perpendicular to the longitudinal axis of said bore, and a second portion of said membrane is formed, said second portion being an annular flange extending from said first portion along said hub around said bore and facing said large opening;
• advancing said filter membrane a sufficient distance in said bore and applying a force radially outwardly to press against said flange so that said first portion is rendered taut by the wiping action of said flange along said hub around said bore;
• and stopping the advance of said filter membrane when the combination of said tapered bore and the force pressing against said flange provide a secure fit of said filter membrane in said bore.

A method of fabricating a filter membrane and inserting the same into a hub having a bore extending therethrough, said bore being substantially circular in cross-section and tapered to define a large opening at the proximal end thereof and a small opening at the distal end thereof, comprising:

• forming a substantially flat, circular filter membrane by punching out a section from a blank of filter medium, said filter membrane having a diameter larger than said large opening of said bore;
• placing said filter membrane over said large opening of said bore so that said flat surfaces are substantially perpendicular to said longitudinal axis of said bore;
• placing a retaining ring over said filter membrane, said retaining ring having a circular cross-section smaller than said large opening, but larger than said small opening of said bore, and advancing said ring and said filter membrane into said bore so that a first portion of said filter membrane is formed in surface to surface contact with said ring and extending transversely across said bore, and a second portion of said membrane is formed, said second portion being an annular flange extending from said first, flat portion along said hub around said bore and facing said large opening, said flange portion lying between the annular surface of said ring and said hub;
• and
• advancing said filter membrane and said ring a sufficient distance into said bore to the position intermediate the ends thereof whereat the diameter of said ring and the diameter of said bore are substantially equal, whereby said ring exerts a radially outward force against said flange thereby providing a secure fit of said filter membrane in said bore.