US3506415A - Fuel log producing apparatus - Google Patents

Description

April 14, 1970 P. P. PALADINO I FUEL LOG PRODUCING APPARATUS Filed Feb. 27, 1967 INVENTOR.

Patrick P Paladino BY 9% ,BMA,WW

' Attorneys United States Patent 3,506,415 FUEL LOG PRODUCING APPARATUS Patrick P. Paladino, 1932 Key Blvd., El Cerrito, Calif. 92269 Filed Feb. 27, 1967, Ser. No. 618,761 Int. Cl. C101 5/22; B30b 11/00 US. Cl. 44-13 8 Claims ABSTRACT OF THE DISCLOSURE In the production of fuel logs by compressing a mixture of cellulose material in finely divided form and a flowable binder (wax), the mixture is advanced through a barrel by a screw having, at its discharge end, a lobe extending radially out beyond the screw core throughout only a part of the core circumference and projecting forwardly beyond the end of the core, for beating and mixing and causing it to fill the otherwise hollow core at the center as the compacted, solid log is forced forwardly.

The invention relates to apparatus for producing fuel logs from a mixture of ligno-cellulose material in finely divided form (commonly sawdust) and a flowable binder, such as wax, wherein the mixture is advanced through a barrel by a screw of special construction; it further relates to the screw.

It is known, e.g., from US. Patent No. 3,232,722, to produce fuel logs from such materials by advancing the mixture through a compaction barrel by a screw and forcing it as a compacted log beyond the discharge end of the screw to a discharge barrel, such as a second barrel, sometimes called a barrel extension, which receives the compacted material and produces a high pressure at the end of the screw by friction of the compacted log against the barrel extension. Several difliculties were encountered in prior operations among which are: It was necessary to provide a relatively large mixing device, wherein the cellulose material and binder were mixed for an extended time before being supplied to the com paction barrel, often up to 25 or more minutes, to insure that the binder penetrates the cellulose material. Further, it was diflicult to cause the material to flow radially inwards in the section of the barrel beyond the screw for filling completely the void core produced in the compacted log by the screw core. Such radial flow is possible only when the mixture has sufficient fluidity and is under sufliciently high pressure; however, it is diflicult to maintain the necessary pressure and fluidity in the portions of the barrel at and immediately downstream from the discharge end of the screw. A further difliculty has been the compaction of the mixture into large, dense chunks, which burn only at the boundaries of the chunks when they fall apart.

The present invention overcomes the above-stated drawbacks of the prior practice in providing a screw which is rotated at the high speed and has, at its discharge end, a lobe which acts as a hammer and beats the mixture, acting or successive, small increments thereof.

In summary, according to the invention, the screw has an axially elongated core which terminates at the discharge end of the screw, and a screw flight extending radially outward from the core, and, at the discharge end, a lobe of short axial extent which extends radially outwards from the core throughout only a portion of the core circumference and has a part of the lobe projecting axially beyond the front end of the core, said projecting part being displaced wholly from the axis of the screw, so that there is left in front of the core empty space into which the material can flow.

The screw is mounted, at least in part, within a compaction barrel having a feed end, the lobe of the screw being situated wholly within the barrel and displaced from the feed end in the direction of movement of the mixture. The screw is rotated at a high speed and the mixture which is supplied to the feed end is advanced to the discharge end by the screw flight and is there beaten and mixed intimately. This feeding occurs continuously but the mixture is beaten by the lobe in successive increments. This pulsates successive increments so as to promote radially inward flow and forms the compacted log so as to cause cracks to develop when the log is burned; these cracks expose more surface area of the log to the fire which in turn increases the flame.

Preferably, the screw flight has a lesser pitch adjacently to the lobe than farther toward the rear, so that the material is fed only slowly to the lobe and the pressure increases along the screw to the discharge end; further, there is normally provided a discharge barrel or barrel extension beyond the discharge end of the screw for receiving the compacted log and imposing the back pressure by virtue of friction between the log and the barrel extension. In this manner, the mixture is under pressure at the discharge end of the screw, and the beating action of the lobe on successive increments of the mixture occurs under pressure. This beating action under pressure replaces the preliminary mixing operation, necessary in the prior practice before the mixture entered the barrel, and promotes penetration of the binder into the lignocellulose material; further, this beating action vibrates the material sufliciently to cause it to flow radially inward from the barrel wall under pressure to fill the central core, thereby filling the void space which would otherwise occur.

The invention will be further described with reference to the accompanying drawings forming a part of this specification, wherein:

FIGURE 1 is a longitudinal sectional view of the apparatus;

FIGURE 2 is a plan view of the feed end of the apparatus;

FIGURE 3 is a transverse sectional view, taken on the line 33 of FIGURE 1;

FIGURE 4 a fragmentary, enlarged view of the discharge end of the screw; and

FIGURE 5 is an end view of the screw.

The apparatus includes a compaction barrel 10 having at one end a feed opening 11 which is connected to a supply hopper 12. A barrel extension 13 is connected to the discharge end of the barrel 10 in coaxial relation and may be surrounded by a jacket 14 for the circulation of the cooling fluid. The hopper 12 has a rounded bottom and contains a feed device 15 which has feeder arms 16 and is rotatable on a transverse axis by means of a drive shaft 17, journalled in the hopper.

The barrels 10 and 13 may be of any desired cross section, which need not be uniform. In the embodiment shown, these barrels are rectangular, spec., square, except for slightly rounded corners, throughout their lengths. It is desirable that the internal cross section of the barrel 10 3 be noncircular at least at the section denoted by the section line 33 in FIGURE 1.

The barrel 10 contains a feed screw having a core 18 and a screw flight 19, 20, extending radially outward therefrom. The screw preferably includes a rear section near the feed end of the barrel and remote from the discharge end 21 of the screw, wherein the flight 19 has a steep pitch, and a front section wherein the flight 20 has a lesser pitch. Although a screw wherein the core 18 has a uniform diameter of cylindrical shape was shown, and the flights 19 and 20 are shown to be spaced with ample clearance from the wall of the barrel 10, and the clearance shows the preferred construction, neither of these features is essential and screws of other configurations may be used. Because the portion of the screw near the discharge end 21 is subject to more rapid wear than the other part to the screw, it is desirable to form it as a replaceable part. To this end, the screw (FIGURES 4 and includes a rear or base part 22 and a separate tip part 23 which is detachably and coaxially mounted on the base part by a bolt 24. The rear of the tip part 23 has an integral lug 25 which fits into the slot in the base part 22 for preventing relative rotation and insuring alignment of the screw flights on the several parts. The tip part is advantageously hard-faced to increase its wear-resisting characteristics. The tip part 23 has formed integrally therewith a camshaped lobe 26 which extends radially outwards from the core throughout only a fractional part of the core circumference. This lobe preferably has a first lateral wall 27 which is convex and of gradually increasing radius, and a second lateral wall 28 which is flat and of abruptly decreasing radial extent. The lobe includes a part 29 which projects axially beyond the end of the core 18 and the front face 30 of this part is preferably inclined to the plane which lies perpendicular to the axis of the screw, so that the forward projection of the lobe is greatest at its maximum radius. The lobe 26 is of limited axial extent and the screw flight 20 extends along the rear end of the lobe, preferably merging therewith. In other words, the maximum radial extent of the lobe 26 is equal to the radial extent of that portion of the flight 20 which is immediately adjacent to the lobe. When, as is preferred, the lobe has a greater radius than most of the screw flights, said portion, indicated at 31, may be of gradually increasing radius, as appears in FIGURES 4 and 5; this insures a more positive feeding of the mixture to the lobe. The portion 31 of changing radius may extend throughout one full turn, as shown, to insure that the mixture is engaged near the lobe and forced forwardly.

It will be noted that the lobe 26 and its projection 29 lie wholly outside of the core 18 and the geometrical, cylindrical surface defined by its forward extension. Thereby there is left unoccupied a space situated radially inside of the projection 29, near the axis of the screw into which the material which forms a fuel log can move.

In operation, the materials forming the fuel long are mixed continually and supplied to the hopper 12. A typical composition includes, per log, 4 pounds of sawdust as the ligno-cellulose material, 2.3 pounds of a flowable binder, such as slack wax (which may contain about 18 to 25 percent oil) or wax without oil, and 2 ounces a chemical binder for preventing falling apart of the log during heating, such as ammonia or sodium lignin sulfonate, available under the trade name Orzan. A small amount of an ignitor, such as sodium nitrate, may also be included. The binder is preheated to make it flowable; however, the mix ing period need not, with the apparatus of the invention, be extended for time sufliciently to effect complete penetration of the binder into the sawdust.

The shaft 17 is driven to insure entry of the mixture into the barrel by means of the feeder arms 16 and the screw core 18 is driven at relatively high speed, e.g., 1700 to 3000 revolutions per minute. The screw flight 19 advances the material toward the discharge end 21, the material being compressed and fed slowly by the flight 20. Upon reaching the discharge end of the screw, the material is beaten by the lobe 26, the screw being rotated in the direction shown by the arrows in FIGURES 3 and 5, so that the convex face 27 leads. The lobe engages successive increments of the mixture as it is applied by the screw flight 20. This beating action occurs under high pressure, such as 30 pounds per square inch, and the material is pulsated and forced outwardly into the corners of the barrel 10, as appears in FIGURE 3. Moreover, some of this material is deflected by the barrel wall to enter the empty space in front of the core 18 whereby the resulting log is solid throughout its cross section. The screw supplies the mixture in increments to the lobe, thereby avoiding large cohesive chunks and insuring separation of the log into pieces providing ample burning area as was noted above.

The log is pushed forwardly by the following mixture into the barrel extension 13, and attains an elevated temperature due to friction and the work of the lobe 26. This temperature is controlled by cooling fluid circulated through the jacket 14. Friction of the log against the walls of the barrel extension 13 promote the high pressure at the discharge end 21 of the screw. The apparatus produces a continuous log, the axial extent of the barrel extension 13 preferably exceeding that of an individual log. Therefore, this continuous log is subsequently cut into sections suitable for packaging and marketing. Such cutting mechanism being not germane to the invention is not described herein.

I claim:

1. A screw for operation within the barrel of an apparatus for producing fuel logs from a mixture of lignocellulose material and a flowable binder, comprising an axially elongated core terminating at the discharge end of the screw, a screw flight extending radially outward from said core for advancing said mixture forwardly to the discharge end, and a cam-shaped lobe of short axial extent at said discharge end extending radially outward from said core throughout only a portion of the core circumference, said lobe when viewed in end elevation having solid front and leading and trailing side faces, said leading face having a gradually increasing radius as said face progresses radially outwardly and said trailing face having an abruptly decreasing radius as such face progresses radially inwardly.

2. A screw as defined in claim 1 wherein said screw includes a rear section remote from said discharge end and a front section that extends to the discharge end, and the pitch of said flight is less in the front section than in the rear section.

3. A screw as defined in claim 2 wherein said screw flight has, at the discharge end of the screw, a radius equal to the maximum radius of the lobe and which extends along the end of the lobe that is rearward from the discharge end.

4. A screw as defined in claim 2 wherein said sections are formed as separate members, and means for detachably connecting said members coaxially against relative rotation.

5. A screw as defined in claim 1 wherein said lobe projects axially beyond the end of the core and said leading and trailing faces meet at a radially outwardly disposed juncture and said front face is inclined forwardly from the core to said juncture.

6. Apparatus for producing fuel logs which comprises an axially elongated barrel, means for admitting a mixture of ligno-cellulose material in particulate form and a flowable binder to the feed end of said barrel, a screw as defined in claim 1 mounted coaxially and at least partially within said barrel for rotation therein, said lobe being situated within the barrel and remotely from said feed end, and means for rotating said screw at high speed for beating and mixing said material and binder by the action of said lobe.

'7. Apparatus as defined in claim 6 wherein the cross section of at least the portion of said barrel which contains said lobe is noncircular.

5 6 8. In combination with the apparatus as defined in 2,803,038 8/1957 Holland et al. claim 7, a barrel extension joined coaxially to the said 3,227,530 1/1966 Levelton 44--1 barrel beyond the discharge end of the screw for receiving the mixed materials as a solid log and creating DANIEL E, WYMAN, Primary E i r back pressure by friction of the solid log on the walls of the barrel extension. 5 C. F. DEES, Assistant Examiner References Cited US Cl XR UNITED STATES PATENTS 44 30; 1,906,245 5/1933 Bowling 44-13 10

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