Agitating – Rubber or heavy plastic working – With specified feed means
Reexamination Certificate
1999-01-07
2001-02-13
Soohoo, Tony G. (Department: 1723)
Agitating
Rubber or heavy plastic working
With specified feed means
C366S076600
Reexamination Certificate
active
06186655
ABSTRACT:
DISCLOSURE
This invention relates generally as indicated to an over fed extruder, and more particularly to a reclaim extruder and the feeding of such extruder which greatly increases the rate or through-put of the extruder.
BACKGROUND OF THE INVENTION
In the manufacture of extruded foam products such as styrene sheet, board or billets, the extruded products are subjected to cutting and trimming, and defect or off grade rejections, particularly on start-up of the continuous extrusion line. The operations produce a substantial amount of scrap, which can range from large pieces to sawdust. The scrap is economically recycled.
Large pieces of scrap are run through a scrap chopper, collected in a storage silo, and then the smaller particulate material is run through a reclaim extruder. The material is remelted and the melt extrudate is chopped and cooled to form feed pellets which are then added to the virgin raw material supply of the continuous extrusion line.
The chopped reclaim material from the scrap chopper or silo has the consistency and low density of fluff. The material is so light that it is often conveyed from the silo to the reclaim extruder with forced air conveyors or grain conveying augers.
The reclaim extrusion rate or output is a direct function of the mass of the material entering the feed throat of the reclaim extruder. Thus the lighter the density of the material, the lower the through-put or extrusion rate. The through-put or rate is normally measured in pounds per hour.
Many attempts have been made to improve the through-put of reclaim extruders. These usually involve the use of a force-feed section in the throat of the reclaim extruder. These force-feed sections generally take the form of one or more augers, supposedly designed to push or compress the light fluffy material into the feed section of the reclaim extruder. One prior attempt involved three rotating augers driven by a DC motor and drive chains. The three auger device was extremely complex and a nightmare to maintain. The rate, when operating properly, only increased about 50 to 200 pounds per hour for a total rate of about 500-700 pounds per hour, depending on the density of the fluff material entering the extruder. One of the problems was overpacking the feed throat, and this would lead to “rat holing,” where the auger simply forms a hole in the overpacked material. This would then cause loss of feed to the reclaim extruder. It has been characterized as pushing marshmallows with a bulldozer, since the system had no feel or ability to react to the light density material.
On the other hand, when heavier density material was introduced, the system could quickly become overloaded and stall, also shutting down the system completely. Accordingly, with rat holing, frequent stalling, complexity in structure, difficulty in maintenance, and, more importantly, minimal or no improvement in through-put, the three auger system was abandoned as unworkable.
Accordingly, it would be desirable to have a system which would be more rugged in design, easier to maintain and operate on a continuous and reliable basis, but, more importantly, one which would substantially increase the output rate of the reclaim extruder.
SUMMARY OF THE INVENTION
A reclaim extruder is provided with an improved force feed section which has three rotating augers, two of one hand and one of opposite hand, which are each driven at different speeds and torques. Each auger has an individual compression tube which closely surrounds the auger. The augers are driven by a common belt drive and a proportional speed train for control of compaction into the feed throat of the reclaim extruder. A drive package provides continuous torque and can be stalled under load without overdriving the material beyond the load ability of the extruder.
The force feeder of the reclaim extruder comprises two right (one) hand and one left (opposite) hand force feed auger screws. The augers are pointed at and intersect the axis of the extruder screw, and the ends of the augers are positioned close to the flights of the extruder screw. The augers are driven by a common timing belt that serpentines around the respective drive pulleys of the augers. The serpentine arrangement causes two of the augers to turn in a common direction, while the other turns in the opposite direction. However, because of the right hand and left hand augers, the reclaim fluff material is advanced forward for all three augers. The screws are driven by an AC variable frequency drive, and a simple right angle gear box. The AC drive is set such that a torque setting limits the compaction rate and has the ability to stall the force feeder system under full load. The force feeder augers can also restart as material is taken from the reclaim extruder feed throat, which is important in assuring that the feed throat does not become over-packed.
A feature of the invention is the respective compression tubes for each auger which allows material to enter the force feed augers and also provides a resistance while the material is being advanced. These tubes surround each feed auger and have feed openings that allow the material to enter the flights of the augers. The resistance and restraint of the tubes causes the density to increase for a given volume. Another feature is that the force feeder augers have a mechanical proportional speed train that helps control the compaction into the reclaim extruder. The auger with the largest pulley turns at a proportional slower rotational speed as compared to the force feed auger with the smallest pulley. The auger turning at the slowest speed adds material at the beginning or upstream section of the reclaim extruder screw; the second turning at an intermediate speed adds more; and then the third turning at the fastest speed adds the final material at the down stream end of the throat prior to entering the reclaim extruder barrel. The material density just prior to the barrel entry is important since it is the actual feed rate of the reclaim extruder itself. The proportional train also assists in the proper compaction for various densities that enter the reclaim extruder as noted above. For lighter densities, the force feeder avoids the problems of overpacking and “rat holing” the material thus causing a loss of feed to the extruder. On the other hand, when heavier density material is introduced, if the system becomes overloaded with too much material, it will stall and automatically restart when the overloading portion moves into the extruder barrel. This helps control the compaction across the linear face of the reclaim extruder screw.
The system also has a diverter plate which maintains the compaction deep into the feed throat. This plate prevents material from escaping the feed throat and also provides a directional feed for the fluff material as it enters the force feeder augers from the upper side.
The force feeder is mounted at an angle through the wall of a collection box which houses the force feeder assembly and is placed to project into the feed throat of the extruder. The direction of the reclaim screw extruder with respect to the force feeder position is important in that the force feeder is placed to cause the fluff material to be pinched against the feed throat as it enters the machine and reclaim screw turns.
To the accomplishment of the foregoing and related ends, the invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
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patent: 731073 (1903-06-01), Rust
patent: 1977515 (1934-10-01), Klippel
patent: 3645505 (1972-02-01), McLeod, Jr. et al.
patent: 3746319 (1973-07-01), Blach
patent: 3865355 (1975-02-01), Eauclaire
patent: 3868093 (1975-02-01), Sokolow
patent: 3892390 (1975-07-01), Eauclaire
patent: 3907259 (1975-09-01), Leclercq
patent: 4039
Brookes Sean R.
Mendel Kilian
Sadinski Robert L.
Chi Anthony R.
Eckert Inger H.
Owens Corning Fiberglass Technology, Inc.
Soohoo Tony G.
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