Plasticating apparatus screw having grooves of varying angles and depths

Abstract

A screw for a plasticating apparatus has one or more helical flights. A portion of the screw has a plurality of advancing grooves arranged in a noncontinuous helix cut in the screw. The advancing grooves are dimensioned to receive material therein as the material is conveyed through the barrel. The screw has a plurality of noncontinuous cross-cut grooves traversing one or more of the advancing grooves. The cross-cut grooves have a second helix angle greater than the first helix angle and less than ninety degrees; and/or one or more of the cross-cut grooves have a third helix angle of about ninety degrees.

What is claimed is: 
     
         1 . A screw for a plasticating apparatus, the screw comprising:
 a longitudinal axis, the screw being rotatably supportable in a barrel for rotation about the longitudinal axis, the screw having a core and at least one helical flight extending along a length of the screw, the helical flight extending in a first threaded direction and defining a first helical path of a first helix angle measured relative to a reference line perpendicular to the longitudinal axis, the first helix angle being less than ninety degrees; the helical flight defining a helical channel; and   a longitudinal portion of the screw having a plurality of advancing grooves with each having at least one closed-end, the plurality of advancing grooves being arranged in a noncontinuous helix cut in the screw core in the helical channel of the screw, each of the plurality of advancing grooves forming a second helical path in the helical channel and being arranged entirely between adjacent helical flights and extending substantially parallel to the helical flights, and the plurality of advancing grooves being dimensioned to receive material therein as the material is conveyed forward through the helical channel;   the longitudinal portion further having a plurality of noncontinuous cross-cut grooves traversing at least one advancing groove; the plurality of cross-cut grooves comprising:   at least one first cross-cut groove being oriented in the first threaded direction common to that of the helical flight and having a second helix angle measured relative to the reference line perpendicular to the longitudinal axis, wherein each cross-cut groove passes through the helical flight not more than two times so that the material can back flow and recirculate within the longitudinal portion, and the second helix angle is less than ninety degrees; and   at least one second cross-cut groove having a third helix angle measured relative to the reference line perpendicular to the longitudinal axis,   wherein the first helix angle, the second helix angle, and the third helix angle are different.   
     
     
         2 . The screw of  claim 1 , further comprising at least one third cross-cut groove having a fourth helix angle measured perpendicularly to the longitudinal axis that is different from the first helix angle, the second helix angle and the third helix angle. 
     
     
         3 . The screw of  claim 1 , wherein at least one of the plurality of cross-cut grooves is located axially downstream from the at least one second cross-cut groove. 
     
     
         4 . The screw of  claim 2 , wherein the fourth helix angle is about ninety degrees measured relative to the reference line perpendicular to the longitudinal axis. 
     
     
         5 . The screw of  claim 1 , wherein the second helix angle and the third helix angle are greater than the first helix angle. 
     
     
         6 . The screw of  claim 5 , wherein the fourth helix angle is greater than the third helix angle and the second helix angle. 
     
     
         7 . The screw of  claim 6 , wherein the third helix angle is different from the second helix angle. 
     
     
         8 . The screw of  claim 1 , wherein the at least one second cross-cut groove is located axially downstream from the at least one first cross-cut groove. 
     
     
         9 . The screw of  claim 2 , wherein the at least one second cross-cut groove is located axially downstream from the at least one first cross-cut groove, and the at least one third cross-cut groove is located axially downstream from the at least one second cross-cut groove. 
     
     
         10 . The screw of  claim 1 , wherein:
 at least one of:
 at least one of the plurality of advancing grooves comprises an advancing groove depth taper; and 
 at least one of the plurality of cross-cut grooves comprises a cross-cut groove depth taper. 
   
     
     
         11 . The screw of  claim 10 , wherein the advancing groove depth taper of the at least one of the plurality of advancing grooves is different from the advancing groove depth taper of another of the plurality of advancing grooves. 
     
     
         12 . The screw of  claim 10 , wherein the cross-cut groove depth taper of at least one of the plurality of cross-cut grooves is different from the cross-cut groove depth taper of another of the plurality of cross-cut grooves. 
     
     
         13 . The screw of  claim 10 , wherein the cross-cut groove depth taper of at least one of the plurality of cross-cut grooves is different from an advancing groove taper of at least one of the plurality of advancing grooves. 
     
     
         14 . The screw of  claim 10 , wherein at least one of the cross-cut grooves has an increasing depth taper extending longitudinally along the cross-cut groove in a direction of flow in the cross-cut groove. 
     
     
         15 . The screw of  claim 10 , wherein at least one of the cross-cut grooves has a decreasing depth taper extending longitudinally along the cross-cut groove in a direction of flow in the cross-cut groove. 
     
     
         16 . The screw of  claim 10 , wherein at least one of the advancing grooves has an increasing depth taper extending longitudinally along the advancing groove in a direction of flow in the advancing groove. 
     
     
         17 . The screw of  claim 10 , wherein at least one of the advancing grooves has a decreasing depth taper extending longitudinally along the advancing groove in a direction of flow in the advancing groove. 
     
     
         18 . A screw for a plasticating apparatus, the screw comprising:
 a longitudinal axis, the screw being rotatably supportable in a barrel for rotation about the longitudinal axis, the screw having a core and at least one helical flight extending along a length of the screw, the helical flight extending in a first threaded direction and defining a first helical path of a first helix angle measured relative to a reference line perpendicular to the longitudinal axis, the first helix angle being less than ninety degrees; the helical flight defining a helical channel; and   a longitudinal portion of the screw having a plurality of advancing grooves with each having at least one closed-end, the plurality of advancing grooves being arranged in a noncontinuous helix cut in the screw core in the helical channel of the screw, each of the plurality of advancing grooves forming a second helical path in the helical channel and being arranged entirely between adjacent helical flights and extending substantially parallel to the helical flights, and the plurality of advancing grooves being dimensioned to receive material therein as the material is conveyed forward through the helical channel;   the longitudinal portion further having a plurality of noncontinuous cross-cut grooves traversing at least one advancing groove; the plurality of cross-cut grooves comprising:   at least one first cross-cut groove being oriented in the first threaded direction common to that of the helical flight and having a second helix angle measured relative to the reference line perpendicular to the longitudinal axis, wherein each cross-cut groove passes through the helical flight not more than two times so that the material can back flow and recirculate within the longitudinal portion, and the second helix angle is less than ninety degrees; and   at least one second cross-cut groove having a third helix angle measured relative to the reference line perpendicular to the longitudinal axis,   wherein at least two of the first helix angle, the second helix angle, and the third helix angle are different.