Method for uniformly distributing discrete particles on a moving porous web

A method for substantially uniformly distributing a layer of discrete particles along a predetermined portion of the uppermost surface of a moving porous web traveling at a first velocity so that said particles occupy less than 100% of said predetermined portion of the uppermost surface of said moving web, said method comprising the steps of:

• (a) feeding said particles in a substantially uniform stream to the inlet of a gas eductor;
• (b) entraining said particles in a moving gaseous stream;
• (c) passing said gaseous stream through a conduit having a nozzle exit positioned adjacent the uppermost surface of and oriented so as to discharge said gaseous stream containing said entrained particles in a direction substantially parallel to the direction of travel of said moving porous web;
• (d) mixing said particles entrained in said gaseous stream inside said conduit to provide a substantially uniform distribution of said particles, as measured across the width of said nozzle exit of said conduit in a direction perpendicular to the direction of travel of said moving porous web;
• (e) discharging said gaseous stream containing said uniformly distributed entrained particles from said conduit adjacent said predetermined portion of the uppermost surface of said moving porous web at a second velocity which is greater than said first velocity;
• and
• (f) maintaining the fluid pressure adjacent the lowermost surface of said moving porous web at a level below the fluid pressure adjacent the uppermost surface of said moving porous web in an area coinciding in width to said predetermined portion of said web and located near the nozzle exit of said conduit, whereby the uniformly distributed particles entrained in said discharged gaseous stream are substantially uniformly deposited on said predetermined portion of the uppermost surface of said moving porous web as the bulk of the gas in said gaseous stream is drawn from the uppermost to the lowermost surface of said web.

An apparatus for substantially uniformly distributing a layer of discrete particles along a predetermined portion of the uppermost surface of a moving porous web traveling at a first velocity so that said particles occupy less than 100% of said predetermined portion of the uppermost surface of said moving web, said apparatus comprising:

• (a) means for feeding said particles in a substantially uniform stream to the inlet of a gas eductor;
• (b) means for entraining said particles in a moving gaseous stream;
• (c) conduit means for passing said gaseous stream through a nozzle exit positioned adjacent the uppermost surface of and oriented so as to discharge said gaseous stream containing said entrained particles in a direction substantially parallel to the direction of travel of said moving porous web;
• (d) means for mixing said particles entrained in said gaseous stream inside said conduit to provide a substantially uniform distribution of said particles, as measured across the width of said nozzle exit of said conduit in a direction perpendicular to the direction of travel of said moving porous web;
• (e) nozzle exit means at the discharge end of said conduit means for discharging said gaseous stream containing said uniformly distributed entrained particles from said conduit adjacent said predetermined portion of the uppermost surface of said moving porous web at a second velocity which is greater than said first velocity;
• and
• (f) means for maintaining the fluid pressure adjacent the lowermost surface of said moving porous web at a level below the fluid pressure adjacent the uppermost surface of said moving porous web in an area coinciding in width to said predetermined portion of said web and located near the nozzle exit of said conduit, whereby the uniformly distributed particles entrained in said discharged gaseous stream are substantially uniformly deposited on said predetermined portion of the uppermost surface of said moving porous web as the bulk of the gas in said gaseous stream is drawn from the uppermost to the lowermost surface of said web.