Gear wheel pump with feed passage of constant hydraulic cross section

Claim 1

In a gear wheel pump adapted for the pumping of viscous melts from a vessel maintained at subatmospheric pressure, a pump casing comprising three plates stacked together in face-to-face relationship, the middle plate thereof having two, partially intersecting, transverse bores next to one another, said bores together providing a pumping chamber with a rectangular entrant opening, a pair of intermeshing toothed gear wheels rotatably mounted in the respective bores, shaft means for driving rotatably one of said gear wheels, said rectangular entrant opening having a cross section at least equal in cross section area to the product of the distance between the axes of rotation of said gear wheels times the tooth length of said gear wheels, said middle plate further having therein a feed passage and a discharge passage respectively intersecting opposite sides of said pumping chamber, and said feed passage having at its end adjacent said entrant opening of said pumping chamber a rectangular cross section corresponding to the rectangular entrant opening and further, with its hydraulic croSs section remaining constant, being transformed gradually toward a circular entrant opening in said middle plate, said hydraulic cross section being expressed as 16F3/U2 wherein F denotes the flowthrough cross section throughout the feed passage area and U is the wetted perimeter of the corresponding part of said passage.