Method of making membrane-type filter and product thereof

A method of making a membrane filter for use in separation of extremely small particles, said method comprising the steps of:

• (2) providing a non-porous membrane material;
• (2) supporting said membrane material such that said membrane is capable of being perforated;
• (3) perforating said membrane material at least one time with at least one piercing means by relatively moving said piercing means with respect to said supported membrane material to form at least one pore therein;
• said step of perforating said membrane material includes a piercing means having a plurality of elongated probes, each probe having a straight-sided untapered body portion which extends from a tapered piercing end portion, said probes being bundled together such that each of said untapered body portions abut untapered body portions of parallel adjacent probes and said method including the further step of establishing the spacing of the pores formed by said piercing means by selection of the cross-sectional dimensions of said abutting untapered body portions;
• whereby a membrane filter is formed having a predetermined controlled porosity.

A membrane filter for use in separating extremely small particles, said filter formed by the process of piercing tapered pores into a membrane with a plurality of piercing means comprising:

• a membrane having a plurality of pores therein with each of said pores having a predetermined controlled shape and dimension between the entry and exit sides of said membrane and a substantially tapered cross-sectional configuration so that the cross-sectional area of said pores at said entry side is greater than the cross-sectional area of said pores at said exit side;
• said pores being spaced from one another at predetermined locations;
• whereby said membrane material has a predetermined controlled porosity and flow rate and whereby said tapered pores act as pre-screens at said entry side and final screens at said exit side;
• and
• said tapered pores being formed by a plurality of tapered piercing means perforating a membrane material, said tapered piercing means being bundled together to control the spacing between said tapered pores and controlling the depth of penetration of said tapered piercing means such that the cross-sectional area of said pore at said exit and entry side may be controlled.