# US 5,348,660 A · Filter apparatus and method with filter evaluation by sample solutions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,348,660 A - Document ID: US5348660A - Status: Granted - Kind: A - Application number: 08/012,778 - Filed: 1993-02-03 - Granted: 1994-09-20 - Earliest claimed: 1992-02-05 - Assignees: Fuji Photo Film Co., Ltd. - Inventors: Shingo Fujikata - Web page: https://patentgrep.com/patent/US5348660A ## CPC - G11B 5/848: Coating a support with a magnetic layer by extrusion - B01D 29/114: {arranged for inward flow filtration (B01D29/15, B01D29/33 take precedence)} - B01D 29/52: in parallel connection - B01D 37/00: Processes of filtration (processes specially adapted for filtering gases B01D46/00) - B01D 2201/0438: mounted substantially vertically on plates at the lower side of the filter elements - B01D 2201/0476: mounted substantially vertically on collector tubes at the lower side of the filter elements - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract A filter apparatus and coating method particularly adapted for thixotropic coating solutions and which yet permits the dead space within the housing of the filter apparatus for the secondary region to be reduced under a broad range of conditions at all times. The improved filter apparatus has a filter provided within a housing in such a way that it divides the interior of the housing into a primary region into which a coating to be filtered is supplied and a secondary region which receives the coating solution after it is filtered. The apparatus filters the coating solution just before it is coated on a flexible base. The apparatus is characterized in that the housing for the secondary region is designed in such a way that an index for measurement of the dead space within the housing satisfies the relation T/.tau.> 0.95, where .tau. is an experimentally determined dimensionless number for the indicial response time of the housing and T is a dimensionless number of theoretical time. ## Claims ### Claim 1 A method for evaluating a filter apparatus for use in filtering a thixotropic fluid, said filter apparatus having a housing with an interior volume V, and a filter provided within the interior of the housing in such a way that the filter divides the interior into a primary region and a secondary region having a dead space, the method comprising the steps of: providing a first solution; providing a second solution which differs from the first solution in one characteristic so that the first solution can be distinguished from the second solution; placing said first solution in every part of said housing; displacing said first solution in every part of said housing with said second solution; recovering a filtered solution from said secondary region; measuring a duration of time, .THETA., required for said filtered solution to change from consisting of only said first solution to consisting of only said second solution; calculating a mean residence time H, where H=V/v and where v is a flow velocity in the filter apparatus for said first and second solutions; calculating an index .THETA./H; and accepting said filter apparatus only if said index .THETA./H>0.95. ### Claim 2 A method for filtering a thixotropic fluid using a filter apparatus having a housing with an interior volume V, a filter provided within the interior of the housing in such a way that the filter divides the interior into a primary region and a secondary region having a dead space, said filter apparatus having an index .THETA./H>0.95, which is determined by: providing a first solution; providing a second solution which differs from the first solution in one characteristic so that the first solution can be distinguished from the second solution; placing said first solution in every part of said housing; displacing said first solution in every part of said housing with said second solution; recovering a filtered solution from said secondary region; measuring a duration of time, .THETA., required for said filtered solution to change from consisting of only said first solution to consisting of only said second solution; calculating a mean residence time H, where H=V/v and where v is a flow velocity in the filter apparatus for said first and second solutions; calculating the index .THETA./H; supplying said thixotropic fluid to said filter apparatus; and passing said thixotropic fluid from said primary region through said filter into said secondary region. ### Claim 3 (depends on 2) The method according to claim 2, wherein said step of supplying said thixotropic solution to said filter apparatus comprises supplying a thixotropic solution having a viscosity variable with shear rate, wherein .eta..sub.1 is the viscosity of said thixotropic solution at a shear rate of 20 cm.sup.-1 and .eta..sub.2 is the viscosity of said thixotropic solution at a shear rate of 46,500 cm.sup.-1 and where a relation .eta..sub.1 /.eta..sub.2 .gtoreq.250.