Friction welding process and filter formed thereby

A filter comprising:

• a) two thermoplastic housing parts each comprising cup-shaped top and base members and each having extended flange portions connected at their periphery to enclose a volume, the volume having an inlet and an outlet, the flanges each including an opposing projecting rib and at least one of the flanges including an interfering rib spaced from the opposing projecting rib and projecting toward the other flange;
• b) fibrous filtration media disposed within the volume between said inlet and said outlet;
• and
• c) a frictional weld joint formed between the interfering rib and the opposing surface of the said other flange hermetically sealing the periphery of the filter, said opposing projecting ribs sealingly capturing the edges of the filtration media so as to prevent fluid passing from the inlet through the volume from bypassing the media before exiting through the outlet.

A process for forming a hermetically sealed filter, comprising the steps of:

• a) providing thermoplastic filter housing parts capable of being joined together at their periphery to provide a filter housing having an inlet and an outlet, said housing parts each comprising a flange, at least one of the flanges including an interfering rib thereon projecting towards the other flange and suitable for forming a vibration welding weld with the other flange, said flanges each including an opposing projecting rib spaced toward the inside of the volume from the interfering rib;
• b) providing a sheet of fibrous filtration material in a form to fit within the housing between the inlet and the outlet so that the edges of the sheet extend past the opposing projections;
• and
• c) vibration welding the housing parts together such that the interfering rib melts to form a hermetic seal with the opposing flange at the periphery of the filter housing and, simultaneously, the opposing projecting ribs bond to and form a fluid seal with the filtration material.

A method of producing a fluid flow filter comprising the steps of:

• a) providing thermoplastic housing members which, when sealed together, cooperate to form a filter housing, the peripheral edges of said housing members each comprising a flange, at least one of the flanges including an interfering rib projecting towards the other flange suitable for forming a vibration welding weld and said flanges each further including an opposing projecting rib spaced toward the inside of the housing from the interfering rib;
• b) providing a porous, fibrous filtration media;
• c) placing the filtration media between the housing members such that the edges of the media are captured by said opposing projecting ribs during assembly of the filter;
• and
• d) applying a vibratory welding process to the assembled filter sufficient to form a hermetic seal between the interfering rib and the opposing flange and to simultaneously cause the opposing projecting ribs to firmly hold the filtration media within the housing such that no fluid flowing through the filter can bypass the filtration media.

A hermetically sealed filter comprising:

• a) first and second thermoplastic filter housing parts each having peripheral flanges, the housing parts being capable of being joined together at their periphery to provide a filter housing having an inlet and an outlet, the flange of the first of said housing parts including an interfering rib projecting towards and being suitable for forming a vibration welding weld to the flange of the second of said housing parts, each of said flanges further including an opposing projecting rib spaced toward the inside of the volume from the interfering rib;
• b) a sheet of fibrous filtration material fit within the housing between the inlet and the outlet with the edges of the sheet extending past the opposing projections;
• and
• c) said interfering rib being melted to the flange of the second housing part to form a hermetic seal at the periphery of the filter housing and the opposing projecting ribs forming a fluid seal with the filtration material.