US3768740A

US3768740A - Reclamation of molded sand

Info

Publication number: US3768740A
Application number: US00214700A
Authority: US
Inventors: J Carpenter
Original assignee: J Carpenter
Current assignee: Pangborn Corp
Priority date: 1972-01-03
Filing date: 1972-01-03
Publication date: 1973-10-30
Anticipated expiration: 1990-10-30
Also published as: CA970525A; GB1362600A; IT974166B; JPS4874418A

Abstract

Lumpy molded sand from a shake-out operation is fed onto the upper section of an endless conveyor which moves the material through a stream of projected abrasive particles thereby granulating the lumps. The granulated sand and abrasive particles are conveyed to a separator which removes the grains of sand from the abrasive particles.

Description

te States Patent 1 Carmen Get. 30, 1973 RECLAMATION 0F MOLDED SAND [76] Inventor: James H. Carpenter, 212 Pangborn B1vd., Hagerstown, Md. 21740 [22] Filed: Jan. 3, 1972 [21] Appl. No.2 214,700

[52] US. Cl. 241/68, 241/301, 241/DlG. 1O [51] int. Cl. B02c 19/00 [58] Field 01 Search 241/5, 22, 68, 69,

241/77, 263, 265, 273.1, 274, DIG. 10, 301;

[56] References Cited UNITED STATES PATENTS 894,272 7/1908 Jorn, Jr 51/14 1,907,198 5/1933 Hull 5l/14 2,261,947 11/1941 Bamebl et al. 241/DlG. 10 2,924,912 2/1960 Schulte 51/14 Primary Examiner-Granville Y. Custer, Jr. Attorney-David E. Dougherty et al.

[ 5 7 ABSTRACT Lumpy molded sand from a shake-out operation is fed onto the upper section of an endless conveyor which moves the material through a stream of projected abrasive particles thereby granulating the lumps. The granulated sand and abrasive particles are conveyed to a separator which removes the grains of sand from the abrasive particles.

10 Claims, 4 Drawing Figures 3.768.740 sum 2 n? 5 PATENTED U61 3 0 I975 PATENTEU BB! 3 0 I915 SHEET 30F 3 ll H H RECLAMATION OF MOLDED SAND BACKGROUND OF THE INVENTION The present invention relates to apparatus for the reclamation of sand used to produce molds for foundry castings.

Reconditioning of used sand involves reducing used core elements and molded sand lumps to grains. It is necessary to remove metallic particles, sintered clusters of sand grains, excess fines and tramp material from the sand prior to reuse. The quality of reclaimed sand must be comparable to that of new sand so that it may be satisfactorily substituted for new sand in core and molding sand mixtures without appreciable change in sand practice. Thus, it is usually necessary to remove accumulated coatings from around individual sand grains.

Recently, foundries are converting to a practice which utilizes quality sand. In this practice a chemical binder and a catalyst are mixed together and hardened into a solid cake at ambient temperatures to form a chemically bonded mold. Since baking is not required, this process is known in the art as no-bake molding. The no-bake molding process has distinct advantages such as ease of making a mold, a cleaner environment, ease of handling a completed mold, and improved casting finishes and casting tolerances.

Despite the numerous advantages, there are a number of disadvantages such as the increased cost for 'quality grade sand. Efficient and effective reclamation of the used sand is necessary to make the no-bake process economically attractive. Reclamation systems of the prior art such as hammer mills, ring crushers, jaw or roll crushers generally subject moving parts to excessive wear and large stresses, thereby decreasing machine life and increasing machine breakdowns. The large quantity of dust created by prior apparatus is not only an undesirable pollutant but is evidence that the lumps are crushed to such an extent that a good yield of granulated sand is sacrificed. Heretofore, apparatus of the prior art has not effectively and efficiently reclaimed sand from lumps.

SUMMARY OF THE INVENTION A feed mixture of lumps of molded sand together with contaminants such as spent abrasive, rods, and fines from a shake-out operation is fed onto the upper section of an endless conveyor which provides for a positive drive of the feed material through a stream of projected abrasive particles. The endless conveyor is of the type having a plurality of perforated slats held between a pair of laterally aligned endless chains. The abrasive particles and sand pass through the perforations in the slats and are conveyed to a separator in which the granulated sand is removed for further processing or recycling. Trash, core rods, and feed material of a larger size than the perforations in the slats are discharged by the conveyor.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view showing one embodiment of the present invention;

FIG. 2 is an end elevational view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view along the line 3-3 of FIG. 1; and

FIG. 4 is a cross-sectional view along the lines 44 which are shown in FIG. 3.

DETAILED DESCRIPTION A feed mixture from a shake-out operation which includes lumps of molded sand and may include core rods, hangers, tramp iron of various sizes, sweepings and spillage is fed into a hopper 11 positioned above the conveyor I3.

One method of forming the feed mixture comprises projecting abrasive particles against a mold with the casting therein to remove the sand and rods from the casting and clean the exposed casting in one operation. This is accomplished in a blast chamber with the sand, rods, spent abrasive, fines and other contaminants falling through the bottom of the chamber from where it is conveyed onto the conveyor 13.

In general, the feed mixture from the hopper 11 drops onto slats 15 which form the upper, running surface of the conveyor 13. The slats 15 are held between a pair of spaced parallel chains 17. The upper surface of the conveyor l3 passes through a trough 19 which includes the inlet section communicating with the hopper 11 and an enclosed blasting chamber 2!. On either side of the blasting chamber 21, the trough 19 includes a plurality of rubber curtains 23 which hang from the top of the trough 19 to prevent the escape of projected abrasive particles.

A stream of abrasive particles is projected in a path toward the upper or running surface of the conveyor 13 within the blasting chamber 21. The blasting path extends along the length of the trough 19 and the upper surface of the conveyor 113. A centrifugal blasting wheel 25 which is mounted on the shaft of a motor 27 has a shot path disposed lengthwise with respect to the flow of lumps. In this case, the hottest area of the blast stream is aimed downwardly toward the trough 19. To permit an increased width of the conveyor 13 and an increased flow of feed material through the path of projected abrasive particles, it is preferable to have centrifugal blasting wheels 25 mounted side by side. The lumps of molded sand are granulated in the blasting chamber 21.

The granulated sand and abrasive particles pass through the perforations 29 in the floor 31 of respective slats 15 and are pushed along the bottom of the trough 19. The granulated sand and abrasive particles are discharged through an opening into a hopper 33. Trash, core rods, and material larger than the perforations 29 in the slats 15 are discharged from the upper surface of the conveyor 13 onto the floor as the slats l5 begin their return run. This material can be removed by suitable means such as another conveyor or stored in a receptacle.

The sand and shot mixture which passes into the hopper 33 flows through a conduit 37 to a conditioner 39 which subjects the mixture containing sand to a scouring treatment thereby removing accumulated coatings on the sand grains. The conditioner 39 includes a centrifugal throwing wheel which projects the sand and shot against an impact plate. After scouring the sand is conveyed via elevator 41 into an air wash separator 43 which separates the sand from the shot. Although FIGS. 1 and 2 illustrate an embodiment wherein the mixture including sand and shot is passed through a conditioner 39 prior to separation, it is contemplated that the mixture including sand and shot can be conveyed directly to the air wash separator 41 without passing through a conditioner 39. This latter arrangement is preferable when it is desirable to separate the sand from the shot prior to conditioning the sand.

Advantageously, at least a pair of separators 413 of the air wash type such as described and illustrated in U.S. Pat. No. 3,368,677 are utilized. In general, the air wash separator 43 subjects the falling mixture to a cross current of air. A number of skimmer plates are provided in a separating chamber to facilitate a separation of the mixture into individual streams in accordance with their weight. in this respect the abrasive particles are heavier than the sand which in turn is heavier than the tines. Thus, the abrasive particles fall generally directly downwardly into a discharge conduit 45 while the tine grain sand is slightly diverted and received in other discharge conduits 47. Other discharge conduits 48 are conveniently provided for fines and other contaminants.

The substantially pure abrasive particles are received in conduit or hopper 45 for reuse by centrifugal blasting wheels 25. The granulated reclaimed sand passes through conduit 47 to a magnetic drum separator 49 to remove the small quantity of metal abrasive that may be mixed with the otherwise substantially pure sand. From the magnetic separator 49 the pure sand flows through outlet 51 to a bin 53 for storage or directly to a sand molding area for reuse.

in some cases, especially with green foundry sand, it is desirable to recycle the pure sand from the outlet several times through a conditioner 39 to obtain the desired organic level or clay content. To achieve this end, the sand from the outlet can be recycled into the elevator 41. However, in many cases, the rate of sand flow will not allow this extra load on the conditioner 39 and separators 43. if considerable recycling is required, the sand may be fed into an auxiliary conditioning system including a plurality of conditioners arranged in series.

According to the principles of the present invention, the upper or conveying surface comprises a plurality of perforated slats extending between laterally aligned endless chains 17 which are trained about a plurality of sprockets 55. The sprockets 55 are rotatably mounted on a frame 57. A suitable drive means such as an electric motor 59 is in driving engagement with a pair of the sprockets 55 which serve as drive sprockets while the remaining sprockets 55 are idler sprockets. The upper section of the conveyor moves through the trough 19 so as to move lumps of molded sand through the blasting station 21. At least some of the slats 15 include an upper rib 63 which extends upwardly across the slat 15. The upper rib 63 functions to hold the lumps against the force of the blast stream so as to drive the lumps through the blast stream. The perforations 29 in the floor 31 of each of the slats 15 are of sufficient size to permit the passage of granulated sand and abrasive particles. The floor 31 is spaced from the bottom of the trough 19 so that granulated sand and shot drop to the bottom of trough 19. At least some of the slats 15 include a lower rib 61 extending downwardly across the floor 31. The bottom edge of the lower rib 61 is spaced just above the bottom end of the trough 19 and conforms therewith so as to push or scrape granulated sand and spent abrasive particles along the bottom of the trough 19.

Each slat 15 includes a pair of side walls 65 which contain projected and ricocheting abrasive particles.

The lower portion of each of the side walls 65 overlap the respective sides 67 of the trough 19 so as to contain abrasive particles and sand within the trough 19. The upper portion of each of the side walls 65 is secured to a slat support member as by suitable means such as bolts. The slat support member 69 includes a vertically extending plate portion 73 which extends above the side walls 65.

The trough 19 includes a channel 75 exterior and on either side of respective sides 67 for housing respective chains 17. The support member 69 includes a lower portion having a pair of depending members 77 with each of the members 77 disposed on a respective side of the chain E7. The bottom of depending member 77 forms a support on which brackets 79 are mounted. The brackets 79 are mouned to every other link of the chain 17 by a pin 83. Each of the brackets 79 on a respective side of the chain 117 is secured to the support member 69 by bolts 85. Each of the chains 17 rides on a track 81 secured to the bottom of the channel 75.

A scrapper member 87 in the form of a plate is mounted on either side of the track 81 to respective depending members 77 of the support member 69. The bolt 85 holds respective scrapper members 87 in place. The scrapper members 87 are provided for cleaning the channel 75 of any abrasive or sand which might become deposited therein.

The outer wall 89 of the channel 75 extends exterior to the support member 69 so as to enclose the support member 69 and associated parts. The upper end of the outer wall 89 of the channel '75 is provided with an overlapping member 73 so as to contain abrasive within the trough 19.

In operation, the feed material is conveyed along the upper surface of the conveyor 13 through the blast chamber 21. The granulated sand and abrasive particles which pass through the perforations 29 in the slats 15 are pushed along the bottom of the trough 19 by the lower ribs 61. In the interest of efficiently minimizing the wear throughout the system, it is preferable to maintain a steady flow of feed material at a maximum capacity. in this case, the abrasive particles are projected against the material held within the slats 15 rather than the slats l5 themselves. Therefore, the wear on the slats 15 will be minimized. To achieve this end, it is preferable to use a hopper 1 l at the entrance of the conveyor for providing a reservoir of lumps to insure a steady influx of feed material.

Preferred embodiments of the present invention having been described herein, it is to be recognized that modifications, variations and changes therein will be apparent to one of ordinary skill in the art. it is contemplated that the claims appended herewith will cover such modifications, variations and changes that are within the broad spirit and scope of the present invention.

What is claimed is:

1. Apparatus for granulating lumps of molded sand comprising: (a) a trough; (b) an endless conveyor having a running surface passing through said trough and spaced from the bottom thereof; (0) means for project ing abrasive particles in a path toward said running surface for granulating lumps of molded sand thereon,-said running surface being perforated to permit granulated sand and abrasive particles to pass therethrough to the bottom of said trough; and ((1) means for removing said granulated sand and abrasive particles from the bottom of said trough.

2. Apparatus according to claim 1 wherein said endless conveyor includes a plurality of ribs extending upwardly from said running surface for holding lumps of 5 molded sand against the force of projected abrasive particles.

3. Apparatus according to claim 1 wherein said removing means comprises a plurality of ribs extending downwardly from said running surface to push sand and abrasive particles along the bottom of said trough.

4. Apparatus according to claim 1 wherein said projecting means comprises a centrifugal throwing wheel.

5. Apparatus according to claim 1 wherein said endless conveyor comprises a plurality of slats forming the running surface, each slat being perforated.

6. Apparatus according to claim 5 wherein at least some of said slats include an upper rib for holding the lumps of molded sand against the force of projected abrasive particles.

7. Apparatus according to claim 5 wherein at least some of said slats include a lower rib for pushing sand and abrasive particles along the bottom of said trough.

8. Apparatus according to claim 5 wherein said trough includes an enclosed blasting chamber housing said projecting means, an inlet for lumps of molded sand, and an opening in the bottom of the trough for discharging sand and abrasive particles.

9. Apparatus according to claim 5 wherein said endless conveyor comprises a plurality of slats forming the running surface and a pair of spaced parallel chains for holding said slats therebetween, said trough including a channel along each side thereof for housing a respective chain.

10. Apparatus for reclaiming sand from a feed mixture including lumps of molded sand comprising: (a) a trough; (b) an endless conveyor having a running surface passing through said trough and spaced from the bottom thereof; (c) means for projecting abrasive particles in a path toward said running surface for granulating lumps of molded sand thereon, said running surface being perforated to permit granulated sand and abrasive particles to pass therethrough to the bottom of said trough; (d) means for removing said granulated sand and abrasive particles from the bottom of said trough; and (e) a separator for removing the granulated sand from the mixture of granulated sand and abrasive particles.

Claims

1. Apparatus for granulating lumps of molded sand comprising: (a) a trough; (b) an endless conveyor having a running surface passing through said trough and spaced from the bottom thereof; (c) means for projecting abrasive particles in a path toward said running surface for granulating lumps of molded sand thereon, said running surface being perforated to permit granulated sand and abrasive particles to pass therethrough to the bottom of said trough; and (d) means for removing said granulated sand and abrasive particles from the bottom of said trough.

2. Apparatus according to claim 1 wherein said endless conveyor includes a plurality of ribs extending upwardly from said running surface for holding lumps of molded sand against the force of projected abrasive particles.