Process for making composite porous elements

Claim 1

A PROCESS FOR MAKING A COMPOSITE POROUS ELEMENT HAVING AT LEAST TWO DISTINCT LAYERS OF DIFFERENT POROSITY ADHERED TOGETHER, EACH OF SAID LAYERS COMPOSED OF METALLIC GRAINS AND BINDER AND THE GRANULOMETRY OF THE GRAINS IN EACH OF SAID LAYERS BEING IN DIFFERENT RANGES, THE GRAINS IN ALL OF SAID LAYERS HAVING A SUBSTANTIALLY COMMON RANGE OF SINTERING TEPERATURE, SAID PROCESS COMPRISING: (1) PREPARING A FIRST PASTE OF METALLIC GRAINS OF A SPECIFIED GRANULOMETRY RANGE AND A FUGITIVE BINDER, (2) PREPARING A SECOND PASTE OF METALLIC GRAINS OF A SPECIFIED GRANULOMETRY RANGE DIFFERING FROM SAID FIRST RANGE AND A FUGITIVE BINDER, (3) SPREADING SAID FIRST PASTE INTO A FIRST SELF-SUPPORTING LAYER CAPABLE OF BEING MECHANICALLY DEFORMED, (4) DISPOSING SAID SECOND PASTE UPON SAID FIRST LAYER TO FORM A SECOND SELF-SUPPORTNG LAYER CAPABLE OF BEING MECHANICALLY DEFORMED DISTINCT FROM SAID FIRST LAYER, (5) SIMULTANEOUSLY FABRICATING SAID FIRST AND SECOND LAYERS AT SUBSTANTIALLY AMBIENT TEMPERATURE WITHOUT INTERPENETRATION OF METALLIC GRAINS TO ADHERE SAID LAYERS TO FORM SAID COMPOSITE ELEMENT, AND (6) HEATING SAID COMPOSITE ELEMENT AT A TEMPERATURE IN SAID SINTERING TEMPERATURE RANGE TO FORM A COMPOSITE BODY HAVING DISCRETE ZONES OF DIFFERING POROSITIES CORRESPONDING TRO THE INITIAL LAYERS OF DIFFERING GRANULOMETRY.