Filter element and fabrication method for the same

A filter element comprising:

• a cylindrical portion having at least one closed end and being molded of a slurry of main fibers and micro fibers;
• said main fibers having a fiber diameter of at least 5 .mu.m;
• said micro fibers having a fiber diameter of less than 5 .mu.m;
• and
• a plurality of axial grooves being formed in at least one of an outer surface and an inner surface of said cylindrical portion,
• whereby said cylindrical portion has circumferentially thin and thick portions;
• and
• said cylindrical portion has a fiber density gradient in its circumferential direction such that said thick portion has a low density and said thin portion has a high density.

A method of fabricating a filter element which includes a cylindrical portion having at least one closed end and molded of a slurry of main fibers and micro fibers, said main fibers having a fiber diameter of at least 5 .mu.m and said micro fibers having a fiber diameter of less than 5 .mu.m, said method, comprising the steps of:

• feeding in a liquid tank said slurry including said main fibers and said micro fibers;
• and
• drawing said slurry into a suction unit immersed in said slurry;
• and
• wherein said drawing step draws said slurry through a plurality of suction openings formed on said suction unit, density of said openings being changed in a circumferential direction of said suction unit.

A method of fabricating a filter element which includes a cylindrical portion having at least one closed end and molded of a slurry of main fibers and micro fibers, said main fibers having a fiber diameter of at least 5 .mu.m and said micro fibers having a fiber diameter of less than 5 .mu.m, said method, comprising the steps of:

• storing a first slurry including said main fibers in a tank;
• feeding into said tank a second slurry including said micro fibers;
• drawing a mixture of said first slurry and said second slurry into a suction unit immersed within said tank;
• and
• wherein said feeding step uses a plurality of feed nozzles arranged around said suction unit to feed said second slurry into said tank, said suction unit and said feed nozzles being changed in circumferential positional relation therebetween during said feeding step and said drawing step.

A method of fabricating a filter element comprising the steps of:

• drawing a slurry through an inner mold of a suction unit immersed in a tank to stack fibers suspended within said slurry on a surface of said inner mold to form a molded body,
• said inner mold having a predetermined opening ratio;
• using said inner mold as a reference to hold and position said molded body during subsequent fabrication steps;
• said inner mold being cylindrical in shape and having open ends at both axial sides;
• and
• wherein said inner mold is formed on its outer periphery with a plurality of axial fins, and said fins define a space at said axial sides of said inner mold, said space being closed by said fibers.

A method of fabricating a filter element comprising the steps of:

• drawing a slurry through an inner mold of a suction unit immersed in a tank to stack fibers suspended within said slurry on a surface of said inner mold to form a molded body,
• said inner mold having a predetermined opening ratio;
• using said inner mold as a reference to hold and position said molded body during subsequent fabrication steps;
• wherein said inner mold is formed on its outer periphery with recesses and ridges, a slurry drawing position of said inner mold being changed from said recesses to said ridges during said drawing step;
• wherein said suction unit includes a suction cylinder disposed inside said inner mold and having a plurality of suction openings;
• and
• wherein a relative position between said inner mold and said suction cylinder is changed so as to change a relative position of said openings to said inner mold during said drawing step.

A method of fabricating a filter element comprising the steps of:

• drawing a slurry through an inner mold of a suction unit immersed in a tank to stack fibers suspended within said slurry on a surface of said inner mold to form a molded body,
• said inner mold having a predetermined opening ratio;
• using said inner mold as a reference to hold and position said molded body during subsequent fabrication steps;
• wherein said suction unit includes a suction cylinder received inside said inner mold and formed with a plurality of suction openings, said suction openings being substantially uniformly arranged over an entire cylinder surface;
• and
• wherein an opening rate of said suction cylinder is lower than that of said inner mold.

A filter element comprising:

• an inner mold used to draw a slurry of fibers therethrough and to stack said fibers thereon;
• a molded body formed by said stacked fibers, said molded body being kept integrally with said inner mold;
• said inner mold being cylindrical in shape and has open ends at both axial sides;
• said inner mold being formed on its outer periphery with a plurality of axial fins defining a space at said axial sides of said inner mold;
• and
• said space being closed by said molded body.