US2815858A - Particle classifier for refuse screenings and the like - Google Patents

Description

C. E. RICH Dec. 10, 1957 PARTICLE CLASSIFIER FOR REFUSE SCREENINGS AND THE LIKE Filed April 16, 1956 INVENTOR. Ckf/Wd 22 1F 56%.

United rates PARTICLE CLASSIFIER FOR REFUSE SCREENINGS AND THE LIKE Application April 16, 1956, Serial No. 578,482 4 Claims. (Cl. 209-138) My invention relates generally to separators or classifiers for use in grain elevators, feed mills and the like, and more particularly to devices for classifying refuse screenlugs.

It is common practice in storage elevators and grain processing plants to use dust collecting systems in connection with separators, classifiers and other equipment which is utilized to remove varying quantities of foreign material from the grain. Much of this foreign material comprises minute particles which are thrown into the atmosphere as dust, and which is normally removed by dust collecting systems and conveyed to a storage bin together with the larger particles of foreign material such as, sand, pieces of leaf, tiny hairs or awns, skin particles from theg rain, and the like. Inasmuch as the smaller dust particles, when floating in the air in quantity, present a definite explosion or fire hazard, the same is removed by the dust collecting system at the several places where such dust is caused to be air-borne. Then, when a predetermined quantity of the refuse, screenings and collected dust has accumulated in the storage bin or bins therefor, the same is conveyed to a suitable vehicle for ultimate disposal. In the storage bin, the collected airborne dust is deposited together with the heavier particles of refuse screenings. Heretofore, the handling of the refuse screenings during conveying of the same from the storage bin by conveyor belts, bucket elevators, and the like, has presented a definite fire or explosion hazard. it has been found that the smaller sized dust particles are more liable to ignition and explosion that the larger sized particles, and particles of a size sufliciently small to pass through a 150 mesh screen are apt to explode in the presence of a spark. It has also been found that the percentage of particles sufiiciently small to pass through a 150 mesh screen varies between 14% and 36% of a given quantity of refuse screenings. It has also been determined that particles larger than those above mentioned can be handled with relative safety from fire or explosion due to sparks and the like. The primary object of my inventino, is therefore, the provision of novel means for separating the finer particles from the refuse screenings so that the same may be otherwise disposed of before such screenings are transported to the point of ultimate disposal.

Another object of my invention is the provision of novel mechanism as set forth which may be easily and accurately adjusted for various operating conditions.

Still another object of my invention is the provision of classifying mechanism of the type and for the purpose set forth which is relatively simple and inexpensive to produce and install, which occupies a minimum of space, which is highly efficient in operation, and which is rugged in construction and durable in use.

The above and still further highly important bojects and advantages of my invention will become apparent from the following detailed specification, appended claims and attached drawings.

Referring to the drawings which illustrate the invendischarge end of the screen 11 is provided with a depend-/ 2,315,.h5ii Patented Dec. 16,

ice

tion, and in which like characters indicate like parts throughout the several views:

Fig. 1 is a view in side elevation of my novel classifier, some parts being broken away and some parts shown in section;

Fig. 2 is an enlarged transverse section taken substantially on the line 22 of Fig. l; and

Fig. 3 is a fragmentary detail in section of one of the valves utilized in my improved mechanism.

Referring with greater detail to the drawings, the numeral 1 indicates in its entirety a housing structure comprising a lower generally rectangular housing section 2 having opposed end walls 3, opposed side walls 4, an open top, and a closed bottom wall 5. The housing struc ture 1 further includes an upper housing section or hood 6 comprising end walls 7, opposed sidew alls 8 and a top wall 9, the upper section having an open bottom. The lower marginal edge portions of the upper housing section are upwardly spaced from the upper marginal edges of the lower housing section 2. A band 10 of airtight flexible material encompasses the adjacent marginal edges of the lower housing section 2 and the hood 6, and is secured thereto to provide a flexible substantially airtight joint therebetween.

A flat horizontally disposed generally rectangular screen 11 is mounted in a rectangular frame 12 that is secured to opposite side portions and one edge portion of the flexible band 10 between the adjacent marginal edges of the upper and lower housing sections whereby to provide a substantially airtight joint therebetween. The screen 11 cooperates with the side and end walls of the upper and lower housing sections to define therewith upper and lower chambers 13 nad 14 respecitvely. The screen 11 is carried by a plurality of hanger bars or the like 15 that are pivotally secured at their lower ends to the opposite side of the screen frame 12 as indicated at 16. The upper ends of the hanger bars 15 are pivotally secured to bearing brackets or the like 17 rigidly secured to a means of support such as a frame or ceiling 18. The hanger bars 15 prevent the weight of the screen 11 from being carried by the flexible sealing band and permit limited reciprocatory movement of the screen 11 longitudinally of the housing structure 1. Means for imparting such reciprocatory movement to the screen 11 is conventional, and is shown as comprising a motor 19, a crank element 20 on the drive shaft of the motor 19 and a pitman arm 21 pivotally connected one end to the crank element 20 and at its other end to the adjacent end of the screen frame 12.

Means for introducing material to be classified, such as refuse screenings, to the screen 11 comprises a chute 22 extending downwardly from the storage bin therefor, not shown, and into a receiving hopper 23 having suitable. valve means 24 therein for controlling delivery of material to the adjacent underlying end of the screen 11. Such a valve structure is shown in Fig. 3 and is operative to introduce material to the screen 11 while substantially sealing the adjacent end of the upper chamber against atmosphere. With reference to Fig. 1 it will be seen that one end of the screen underlies the inlet hopper 23 and valve 24, and slopes slightly downwardly toward the opposite end of the housing structure 1. A discharge chute or the like 25 is mounted on the opposite end of the housing structure and extends downwardly from the adjacent end of the screen 11 to receive relatively heavy particles or tailings from the screen 11 and conduct said tailings to a point of alternate disposal, not shown. It will be noted that a second feeding valve 26 identical to the feeding valve 24 is operative to cause discharge of the tailings through the discharge outlet 25 and seals the interior of the upper chamber 13 against atmosphere. The

ing flexible curtain 27 that engages the adjacent end wall 3 and portions of the discharge chute to prevent movement of air between the upper and lower chambers through the upper end of the discharge chute 25.

The screen 11 is a woven mesh of smooth resilient threads of plastic material preferably nylon, the threads of said screen being woven together to define apertures sufficiently large to permit free passage of air therethrough. but of insuflicient size to permit passage therethrough of any of the particles delivered to the screen 11 through the chute 22 and valve 24. Preferably the screen mesh is finer than a so-called 150 mesh screen so that few if any dust particles are capable of passing downwardly therethrough during feeding reciprocation of the screen 11.

A conventional fan or blower is interposed in a conduit 29 one end of which communicates with the lower chamber 14 as indicated at 30, and the other end of which communicates with a header 31 of an air filter indicated in its entirety at 32. The filter 32 is of a type in common usage and is shown as comprising a housing 33 containing one or more tubular filter elements 34 the interiors of which communicate with the header 31. A conduit 35 is connected at one end to one end of the hood 6 and at its other end to the filter 32 adjacent the upper end thereof. Operation of the blower 28 causes air to be drawn from the header 31 and introduced to the lower chamber 14 from whence it moves upwardly through the screen 11 and the chamber 13 of the hood 6, and from thence through the conduit 35 to the interior of the housing 33. The dust laden air passes through the filter elements 34 which remove substantially all of the dust from the air, so that only filtered air is delivered to the lower chamber 14 by the blower 28. Dust removed by the filter 32 is discharged therefrom through a suitable discharge outlet 36 having a delivery valve 37 therein, said delivery valve 37 being similar to the valve 24 shown in Fig. 3.

A perforate equalizer plate 38 is mounted in the lower chamber 14 in downwardly spaced substantially parallel relationship to the screen 11 and diffuses the filtered air entering the chamber 14 from the conduit 29 so that upward movement of the filtered air through the screen 11 is substantially equal over the entire area of the screen 11. For the purpose of adjusting the volume and velocity of air moving upwardly through the screen 11, I provide a plurality of partition elements 39 which converge downwardly to define upwardly tapering compartments 40 which communicate with the upper portion 41 of the chamber 13 through restricted openings 42. With reference to Fig. 1 it will be seen that the conduit 35 communicates with the upper end portion 41 of the chamber 13 above the restricted openings 42, and that the lower edges of the partitions 39 are in upwardly spaced relation to the screen 11. A plurality of dampers 43 are mounted one each in a different one of the openings 42 and are operable to effectively enlarge or reduce the size of the several openings 42. The downward spacing of the screen 11 from the lower ends of the partitions 39 permits air passage upwardly through the screen 11 over the entire area thereof even when one or more of the dampers 43 is in a position to close its respective opening 42. With reference to Fig. 1 it will be seen that a branch conduit 44 is connected in communication with the conduit 29 between the blower 28 and the chamber 14, and that a conventional damper valve 45 is mounted at the junction between the conduit 29 and the branch conduit 44-. The damper valve 45 may be regulated to control the amount of filtered air introduced to the lower chamber 14. With the damper valve 45 in the position shown by dotted lines in Fig. 1, a portion of the filtered air will be exhausted to atmosphere or delivered to any desirable point.

In operation, the motor 19 is energized to cause reciprocatory movements to be imparted to the screen 11, the blower 27 is caused to operate, and material to be classified is caused to be fed downwardly through the chute 22 and delivery valve 24 onto the adjacent end of the screen 11. As the material is carried by the screen 11 toward the discharge outlet or chute25, it is violently agitated by reciprocatory movements of the screen 11 and air blowing upwardly therethrough causes the finer particles to be separated from the material and to become entrained and carried through the conduit 35 to the filter 32. The violent agitation imparted to the material by the screen 11 causes the finer and lighter particles to become dislodged from the coarser particles to which they might adhere and to become more easily entrained. Inasmuch as many of these finer particles include elongated awns and skin particles having tiny barbs and other projections thereon, it has been found that the use of a conventional cloth screen becomes quickly choked with such needle-shaped particles. Thus, after considerable experimentation it has been found that a woven screen made from extruded resilient plastic threads is highly successful in remaining free from being choked by the smaller particles which contact the screen before being carried away by the air stream. Plastic threads such as nylon are devoid of the usual projecting fiber ends generally found in cotton threads and the like, and have a smooth outer surface to which the barbs or projections on the dust particles have difficulty in adhering. Furthermore, the resiliency of the nylon threads permits a substantial amount of flexing thereof so that particles caught between adjacent threads are quickly dislodged and become air-entrained.

My invention has been thoroughly tested and found to be completely satisfactory for the accomplishment of the objectives set forth; and while I have shown and described a preferred embodiment of my novel classifier, it will be understood that the same is capable of modification without departure from the spirit and scope of the invention as defined in the claims.

What I claim is:

1. In a particle classifier for refuse screenings, a housing structure comprising a lower housing section and a hood in overlying spaced relation to said lower section and an airtight flexible band encompassing the adjacent marginal edges of said lower section and hood and providing a flexible substantially airtight joint therebetween, a generally horizontally disposed fiat woven mesh screen of smooth resilient threads of plastic material within said housing structure, said screen cooperating with said lower housing section to define a lower chamber and with said hood to define an upper chamber, the marginal edges of said screen being secured to said flexible band to prevent air from passing therebetween from one of said chambers to the other thereof, means at one end of said housing defining a screenings inlet for materials to be classified overlying one end of said screen and a tailings outlet underlying the opposite end of said screen, means for imparting reciprocatory movements to said screen to agitate material delivered thereon and feed the same toward said tailings outlet, said screen defining apertures of suflicient size to permit free movement of air therethrough but of insuflicient size to permit passage therethrough of the particles of said material, an air filter, means including a blower and a cooperating conduit communicating with said lower chamber and said filter for delivering filtered air to said lower chamber and upwardly through said screen with suflicient volume and pressure to cause separation of particles on said screen and entrainment and removal of the finger particles upwardly through said upper chamber, and a disposal conduit for guiding air and the entrained particles away from said upper chamber.

2. The structure defined in claim 1 in further combination with a plurality of generally upstanding partitions mounted in said hood and dividing said upper chamber into a plurality of upwardly tapering compartments, the lower edges of said partitions being upwardly spaced from said screen, and damper means defining the upper ends of said compartments and operative to vary the volume and velocity of air upwardly through said screen.

3. The structure defined in claim 1 in which said disposal conduit is coupled to said filter for delivery of entrained particles thereto, the filtered air from the upper chamber being delivered to said lower chamber by said blower and cooperating conduit.

4. In a particle classifier for refuse screenings, at housing structure, a generally horizontally disposed flat woven mesh screen of smooth resilient threads of plastic material within said housing and dividing the interior thereof into upper and lower chambers, means at one end of said housing defining a screenings inlet for material to be classified overlying one end of said screen and a tailings outlet underlying the opposite end of said screen, means mounting said screen for reciprocatory movements in a direction to feed material from said inlet toward said outlet, said screen defining apertures of suflicient size to permit free movement of air therethrough but of insuflicient size to permit passage therethrough of the particles of said material, means for imparting reciprocatory movement to said screen to agitate said material and feed the same toward said tailings outlet, an air filter, conduit means con necting said upper chamber to said air filter, means in- 6 4 eluding a blower and a cooperating conduit communicat-' ing with said lower chamber and said filter for delivering filtered air through said lower chamber and upwardly through said screen with suflicient volume and pressure to cause separation of particles on said screen and entrainment and removal of the finer particles outwardly through said conduit means to said filter, partition means in said upper chamber dividing said upper chamber into a plurality of compartments, said screen defining the bottoms of said compartments, and damper means for each of said compartments operative to vary the volume and velocity of air upwardly through said screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,132,961 Morgan Oct. 11, 1938 2,206,337 Steele July 2, 1940 2,586,223 Harmon Feb. 19, 1952 FOREIGN PATENTS 428,495 Italy Dec. 19, 1947

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