Gear pump for high viscosity materials

Abstract

A pump 10 for materials having a viscosity up to about 3.0.times.10.sup.5 cps, such as cellulose acetate, has a pump body 12 formed with a gear receiving means and, mounted thereon for closing the gear receiving means 13, a pair of side plates 16, 18 having bearing receiving cavities 21. The side plates 16, 18 have pressure relief means 50 for relieving pressure that builds-up in the intermesh of gears 14 when highly viscous material, such as cellulose acetate, is being pumped. This means of diverting the pressure buildup enables the pump 10 and component parts, such as shafts 22, 24 and plain bearings 20, to resist premature failure due otherwise to the resultant load caused by residual pressure buildup. In the preferred embodiment, wear resistant ceramic plain bearings 20 are press fitted in the bearing cavities. Grooves or channels 30 in the interior walls 32 of bearings 20 provide a means to lubricate shafts 22, 24 rotatably supported in the bearings 20. Wear resistant coatings, such as, thermally sprayed tungsten carbide, are coated on the shafts 22, 24 and surface 46 of side plate 16, 18 to promote wearability and increased life of the apparatus 10.

Dependencies are inferred from the claim text.