Clay extruder
The clay extruder includes a drum 2 having a screw 4 having a rotary shaft 6 , a spiral rotary blade 5 for feeding the clay under pressure while kneading the clay fed into the screw, a pressure raising portion 10 to feed the clay under pressure while kneading the clay, and a rectifying portion 11 provided on the side of an extrusion port 20 in the drum 2 to rectify the clay into a columnar shape. The rectifying portion 11 has a rectifying rotary blade 7 whose intervals being longer than that of the rotary blade; an angle formed between the face on the side of the extrusion port in a sectional shape of the rectifying rotary blade cut along the central line of the rotary shaft 6 and the central line gradually decreases, as the rectifying rotary blade comes close to the extrusion port.
1. A clay extruder comprising:
a drum including a supply port for feeding a clay,
an extrusion port through which the clay is extruded to form a columnar or a rectangular-columnar article, and
a screw having a rotary shaft and a spiral rotary blade extending along the rotary shaft which feeds the clay under pressure while kneading the clay fed into the screw by a rotation of the rotary blade,
wherein the screw has a pressure raising portion in a supply port side of the drum to feed the clay under pressure while kneading the clay, and a rectifying portion in an extrusion port side of the drum to rectify the clay fed under pressure along the rotary shaft into the columnar shape,
the rectifying portion has a rectifying rotary blade configured so that a rotary blade angle gradually decreases as the rectifying rotary blade approaches the extrusion port, the rotary blade angle being formed between a face of the rectifying rotary blade that faces the extrusion port and a central line of the rotary shaft
the rectifying rotary blade extends beyond an end of the rotary shaft in a direction toward the extrusion port and is configured so that the sectional shape of the rectifying rotary blade cut along the direction perpendicular to the rotary shaft is gradually reduced outwardly in a diametric direction of the drum, and expands along an inner wall of the drum, as the rectifying rotary blade comes close to the extrusion port,
the end of the rotary shaft is tapered, and
an interval of the rectifying rotary blade in a rotary shaft direction is longer than that of the rotary blade of the pressure raising portion in the rotary shaft direction.
2. The clay extruder according to claim 1 , wherein the interval of the rectifying rotary blade in the rotary shaft direction gradually increases, as the rectifying rotary blade comes close to the extrusion port.
3. The clay extruder according to claim 1 , wherein the rectifying rotary blade comprises two blade members configured so that the sectional shapes of the blade members cut along the direction perpendicular to the rotary shaft are rotationally symmetrical with respect to the central line of the rotary shaft.
4. The clay extruder according to claim 3 , wherein the rectifying rotary blade is configured so that the sectional shape of the rectifying rotary blade cut along the direction perpendicular to the rotary shaft is gradually reduced outwardly in a diametric direction of the drum, and expands along an inner wall of the drum, as the rectifying rotary blade comes close to the extrusion port.
5. The clay extruder according to claim 1 , wherein the rectifying rotary blade is configured so that the sectional shape of the rectifying rotary blade cut along the direction perpendicular to the rotary shaft is gradually reduced outwardly in a diametric direction of the drum, and expands along the inner wall of the drum, as the rectifying rotary blade comes close to the extrusion port, and so that the sectional shape becomes a circular arc in the extrusion port.
6. The clay extruder according to claim 3 , wherein the rectifying rotary blade is provided so that the sectional shape of the rectifying rotary blade cut along the direction perpendicular to the rotary shaft is gradually reduced outwardly in a diametric direction of the drum, and expands along the inner wall of the drum, as the rectifying rotary blade comes close to the extrusion port, and so that the sectional shape becomes a circular arc in the extrusion port.
7. The clay extruder according to claim 1 , wherein the rectifying rotary blade is configured so that a volume of the clay fed under pressure to the extrusion port is kept at a constant level for one cycle of the rotation of the rectifying rotary blade in a range of 5 to 30 cm from the extrusion port.