Low energy recovery compounding and fabricating apparatus for plastic materials

A gear pump for pumping highly viscous media provided to the pump in rope-like strand form comprising:

• housing means defining an inlet passage at one end, an outlet passage at an opposite end and a chamber therebetween;
• a pair of pump gears located within said chamber having intermeshing teeth and being rotatably mounted in said housing, said chamber and said pump gears defining a media free space;
• said chamber and each of said gears defining gear sealing zones adjacent said outlet passage, each sealing zone having a minimum length equal to the circumferential distance between two adjacent gear teeth across the full axial length of the gears at the outside diameter of said gears;
• said media free space expanding from the end of said seal zones remote from said outlet passage such that an increasing hydraulic radius is produced at least to the plane of the tops of said gears, said increasing hydraulic radius being produced by a dimension of the chamber measured in a plane parallel to the plane passing through the axes of said gears, said dimension increasing from the end of said seal zones remote from said outlet passage to the plane of the tops of said gears, whereby a pressure gradient is created to fill the gear cavities with said viscous media;
• said outlet passage adjacent said sealing zones having a cross-sectional area of from 0.2 to 2.0 times the product of the gear width and the gear tooth height;
• said chamber increasing in cross-sectional area above the tops of said gears to the top of said chamber, thereby enhancing the pumping capacity and volumetric efficiency of said gear pump;
• and a pair of feed rollers rotatably mounted in said chamber upstream of said gears, the axis of each roller being substantially parallel to the axis of the associated gear and said rollers being spaced apart to define a media nip substantially coplanar with the mesh line of said gears, and means for rotating said gears and rollers, whereby said rope strand is drawn into and feeds the gear cavities and thereafter pumped by said gears.