Andritz Sprout-Bauer, Inc.

Oszkar Bittner

The double tapered die mount defines a channel to support the die shoulder. No contact occurs between the die and die housing. The die shoulder is machined to be in generally congruent relationship with the channel shape of the die mount of the invention. In the prior art, the die shoulder is perpendicular to both the inner radial surface and the outer radial surface of the die mount. In the preferred embodiment, the die shoulder is tapered from the inner radial surface toward the die edge to define an inner die taper. The die shoulder also tapers from the outer radial surface to the die edge to define an outer die taper. The side walls of the channel defined by the die mount of the invention taper inwardly to be congruent with tapered surfaces of the die shoulder. The inner channel wall, i.e., the channel wall closer to the axis of rotation of the die, contacts the inner die taper. The outer channel wall, i.e., the channel wall farther from the axis of rotation of the die, contacts the outer die taper. The inner channel wall and the outer channel wall taper toward each other in the direction toward the base of the channel. The edge of the die shoulder does not contact the bottom of the die mount channel, and therefore, a gap exists between the bottom of the die mount channel and the die edge. Both radial forces and torque forces resulting from operation of the pelletizer are taken up by the mated tapered surfaces.

Double tapered die mount

The single tapered die mount employs a radially inner surface at an angle to the axis of rotation of the die mount, die and die holder. The radially inner surface of the die mount acts on an annular shoulder of the die to support and position the die in the die holder. The die mount of the invention is located between the radially outer surface of the die and the extended lip of the die housing. In the preferred embodiment of the invention, the radially inner surface of the die mount in contact with the radially outer surface of the die shoulder has an angle of a modified Morse taper. The radially outer surface of the die shoulder is machined to a matching angle.

Single tapered die mount

The present invention employs a main shaft cantilevered from a frame. A die holder is disposed around the outside of the shaft, and in the preferred embodiment rotates by the use of adjustable tapered roller bearings around the shaft. Fixed to the die holder is a die, and the die and die holder define a pelletizing chamber. The shaft supports a roller frame with a plurality of rollers within the pelletizing chamber. The resulting construction is a pelletizer shaft support structure that uses only a single set of bearings. In the preferred embodiment, the main shaft is comprised of an inner shaft and an outer shaft. The inner shaft is located coaxially within the outer shaft and supported within the outer shaft by static bushings. The roller frame and rollers are mounted to the inner shaft. The inner shaft and the outer shaft are both fixed to the frame structure. The outer shaft is fixed in a permanent manner while the inner shaft is fixed to the frame by use of a shear pin to allow rotation under emergency circumstances. During operation of the mill, should binding of the roller mechanism in relation to the die result in undue torque being placed upon the inner shaft, the shear pin will shear and allow the inner shaft and the outer shaft to rotate relative to each other to protect the mechanism from further damage.

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Muncy, PA, United States of America

Oszkar Bittner