US3694964A

US3694964A - Abrasive blast cleaning system

Info

Publication number: US3694964A
Application number: US89181A
Authority: US
Inventors: Joseph E Bowling Jr
Original assignee: Carborundum Co
Current assignee: Pangborn Corp
Priority date: 1970-11-13
Filing date: 1970-11-13
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

An abrasive blast cleaning system includes a pair of separators for separating sand from abrasive particles in conjunction with a no-bake molding procedure with crushing rollers being provided between the separators to crush small lumps of pea size sand.

Description

United States Patent 1151 3,694,964 Bowling, Jr. 1451 Oct. 3, 1972 [54] ABRASIVE BLAST CLEANING SYSTEM 3,055,150 9/ 1962 Greenberg et al. ..5 H3 19 X 72 I t I h E. Bo Ii 3,097,450 Freeman fit 3.] X l 1 fiz w Jr 3,097,451 7/1963 Freeman et al ..51/319 x 3,368,677 2/ l 968 Bradley ..209/135 1 Asslgnee= h Carbonmdum Company, 3,540,156 11/1970 Stebbins et a1 ..51/320 x Niagara Falls, NY. 2,962,230 11/1960 Dilley ..24l/77 X 22 i N 13 1970 2,996,261 8/ 1961 Picalarga ..241/77 [2]] 89181 Primary Examiner-Donald G. Kelly I AttomeyDavid E. Dougherty and Robert E. Walter [52] US. Cl ..51/9 51 Int. Cl ..B24c 3/08 ABSTRACT [58] Field of Search 3 2 5 An abrasive blast cleaning system includes a pair of separators for separating sand from abrasive particles in conjunction with a no-bake molding procedure with [56] References cued crushing rollers being provided between the separators UNITED STATES PATENTS to crush small lumps of pea size sand.

1,954,111 4/1934 Wilks ..51/8 7 Claim, 2 Drawing figures ABRASIVE BLAST CLEANING SYSTEM BACKGROUND OF INVENTION A recent development in the casting industry is the use of chemical bonded molds. Essentially this practice utilizes quality sand, a chemical binder and a catalyst which are mixed together and hardened into a solid cake at ambient temperatures. Accordingly, baking is not required for such molds and the practice is, therefore, known in the art as no-bake molding. Generally the base binder used in no-bake molding is either an acid base such as a chemical binder with phosphoric acid as the activator or is an oil base. In practice the nobake mold pattern is disposed in a topless frame on, for example a support table with the no-bake ingredients being added to form a cavity corresponding to one portion of the casting and with rigidifying rods added thereto. The mold is then inverted and the complementary portion of the no-bake mold is formed thereon so that the resultant composite cavity corresponds to the casting. Suitable gating is of course also provided. This practice is generally similar to standard foundry techniques but thus differs in at least one major respect, namely, the no-bake molding equipment does not require a heavy flask in which to house the sand when the molten metal is subsequently applied to the cavity. Even the topless frame used initially in the process is not needed during the casting forming step.

The no-bake molding process potentially represents a significant advancement in the foundry art since it offers a number of distinct advantages. For example the molds are easier to make without requiring a skilled molder. There is a cleaner environment with less dust and spillage than with green sand molding. The nobake technique is quicker since jolt mechanisms are not required. Simple form boxes or topless frames are merely necessary to shape the mold rather than the conventional heavy flasks. The molds can be handled without breaking apart by providing a grid plate or strapping and thereby the mold with its casting can be moved to a shaker or cleaning process without breaking apart. It has been suggested that the mold shell or sand can be removed by blasting and in such case the mold shell and core can be handled to the interior of a blast machine where the sand and dust can be contained and shakeout noise eliminated. Moreover, the casting finish is thereby improved and casting tolerances can be tightened with the castings matching the pattern. The castings can go directly to numerically controlled machines, thereby obviating the need for rough cuts on manual machines.

Despite, the numerous advantages such as indicated above which are possible with no-bake molding, there are a number of serious disadvantages which might cause this process to meet stiff acceptance by the foundry art. These disadvantages include the increased costs for quality grade sand which might cost three or four times more than the cost of green sands. Since quality sand is used this sand must be reclaimed for reuse to make the entire process economically feasible.

Although attempts are being made at reclaiming and reusing the sand, experts cannot agree on the percentage of reclaiming possible with a system nor the qualities needed or obtained by a system. The publication, Foundry, September 1970, pages 8389, for example, describes one such attempt at sand reclamation. The

reclaimed sands with the present systems, however, are not uniform in qualities. In this respect the build-up of fines and/or organics seriously affects the molds using reclaimed sands. Moreover, proposed reclaiming systems require shakers, crushers or Muller type units which are noisy and dusty and also require rather large floor space and head room with high maintenance and capital costs.

SUMMARY OF INVENTION An object of this invention is to provide an abrasive blasting system which includes means for effectively separating sand from abrasive particles.

A further object of this invention is to provide such a system which is particularly adapted to be used in con junction with the no-bake molding process.

In accordance with this invention an abrasive blast cleaning system includes a pair of separators for separating sand from abrasive particles in conjunction with a no-bake molding procedure with crushing rollers being provided between the separators to crush small lumps of pea size sand.

The separators may be of the air wash type which include skimmer plates for dividing the mixture passed thereto into the individual streams. The lowermost separator of each pair need only include one skimmer plate since the mixture passed through that separator contains only sand and abrasive particles. The crushing rollers may be made of a wear resistant material such as polyurethane.

THE DRAWINGS FIG. 1 is a side elevation view schematically showing one embodiment of this invention and FIG. 2 is a cross-sectional elevation view on an enlarged scale of a portion of the embodiment in FIG. 1.

DETAILED DESCRIPTION Recently filed application Ser. No. 108,417, filed Jan. 21, 1971, in the names of James H. Carpenter and Joseph E. Bowling, Jr., is concerned with a comprehensive abrasive blast cleaning system used in conjunction with the no-bake mold process. The system of that application generally includes means for the granulation and scouring of the sand used in a no-bake mold for ultimate reuse of the sand. In conjunction with that system separating means are disclosed for effectively separating the granulated sand from abrasive particles. This application is concerned with a particular aspect of that system, namely, the means for assuring complete separation of the sand from the abrasive particles by the inclusion of crushing means between a pair of air wash separators for crushing pea sized lumps of sand discharged from the first separator and prior to its passage into the second separator.

FIG. 1 illustrates the general arrangement of the system disclosed in the copending application. As indicated therein a no-bake mold 12 is held in an open frame 14 and conveyed on monorail 16 into blast chamber 18. As is conventional with such no-bake molds rigidifying rods 20 as well as a casting 22 are embedded in the sand 24. Means 26 are provided to suspend the casting when the sand is later removed.

Blast chamber 18 is provided with a plurality of centrifugal throwing wheels 28 which project abrasive particles against the mold to remove the sand and rods therefrom and thereby clean the then exposed casting in one operation. When the sand is removed from the mold it has been found that about percent of the sand is in lump form while the remaining 75 percent is in granular form. The falling sand, rods, spent abrasive, fines and other contaminants fall through the bottom 30 of chamber 18 and are received on oscillating conveyor 32. To facilitate the discharge of this mixture of sand, abrasive, etc., from chamber 18 the floor of the chamber is made with maximal open area. Ideally chamber 18 would be completely floorless. It is generally desired, however, to have some structural members at the bottom of chamber 18 to permit workmen to enter for various purposes. Thus as shown in FIG. 1 spaced I-beams 34 are provided so that the mixture 36 can be received on the oscillating conveyor 32 by falling through the large open areas between I- beams 34.

The entire mixture 36 is conveyed on oscillating conveyor 32 until the mixture reaches a portion of the conveyor which includes a screen 40 of appropriate mesh size to permit the fine grain abrasives, fines, and other contaminants to fall into hopper 42 and thence to screw conveyor 44 where it is received by elevator 46 for separation as later described. The remaining portion of mixture 36 which includes lumps, rods, and any other elements which may be carried with the mixture is conveyed to the end of oscillator 32 and drops onto generally perpendicular oscillating conveyor 48 until it reaches the second blast station 50.

Blast station 50 includes a conventional centrifugal throwing wheel 80 which uses generally large size metal shot projected at a high flow rate at for example 1,200 to l700 rpm or lower. The metal shot strikes the lumps to granulate them while also knocking the organics off the grains of sand. Advantageously the sand which had been separated by the separators 54 and 68 (as later described) is also passed into the blast stream from wheel 80 so that the organic binder is removed from this sand. For example the falling sand from conduit 78 may drop between the blast stream from wheel 80 and a strike plate 84. In this manner the abrasive particles from a portion of the blast stream hit the falling sand and causes the sand grains to strike each other and to ricochet against the strike plate 84. The resulting impacts effectively remove the organic binder. In the meantime the remaining portion of the .blast stream granulates and scours the lumps 86 and cleans the rods 20 which are moving on oscillating conveyor 48. A portion of oscillating conveyor 48 is provided with a screen deck of appropriate mesh size to permit the granulated sand and abrasive particles to fall into hopper 89 to screw conveyor 90. The larger rods, however, continue to flow on oscillator 48 and are ultimately discharged and collected in any suitable receptacle (not shown). Thus the rods are received from blast station 50 in a cleaned condition for reuse.

From screw conveyor 90 the mixture of granulated reconditioned sand and abrasive particles are fed to elevator 92 and then to separator 94 which also is of the air wash type previously described including air curtain inlet 96 and skimmer plate 100 in separation chamber 98. The mixture is thereby divided into one stream of abrasive particles which is received in spout 102 and conveyed back to abrasive blast wheel 80 while the stream of reconditioned sand is received in spout 104 and discharged from outlet 106 and into any suitable receptacle (not shown) for reuse.

Prior to discharge from outlet 106 the sand may pass through magnetic drum separator 107 to remove the small quantity of metal abrasive that may be mixed in with the otherwise substantially pure sand.

As previously described a portion of the mixture is received in elevator 46. This portion is discharged into screw conveyor 52 and into any suitable number of separators 54. FIG. 2 shows the details of this portion of the arrangement, of which this invention is particularly concerned. As shown therein separators 54 are of the air wash type such as described and illustrated in U. S. Pat. No. 3,368,677 the details of which are incorporated herein by reference thereto. In general the air wash separator 54 subjects the falling mixture to an air curtain supplied for example at inlet 55. Anumber of skimmer plates 58 are provided in the separating chamber 60 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 fines. Thus the abrasive particles fall generally directly downward into discharge conduit 62 while the time grained sand is slightly diverted and received in discharge conduit 64. Discharge conduit 65 is provided for the fines and other contaminants, while dust in the air curtain exits through outlet 56 to a dust collector (not shown).

It has been found that the sand in the mixture fed to separators 54 is not always of the desired size of fineness but frequently is in smaller lumps 61 which may be termed pea size. Generally such pea sized lumps are about 3/16 V4 inch in diameter. Since this pea size lumps of sand is heavier than the fine grain size lumps of, the pea size sand 61 will also go into conduit 62 with the abrasive particles 63 which are large size metal shot. Accordingly, it is necessary that this sand be separated from the abrasive particles if the sand recovered is to be maximized not only for reuse of the sand but also for reuse of the abrasive particles. Accordingly, the mixture of pea size lumps of sand 61 and abrasive particles 63 undergoes a second separation process. This second separation process includes feeding the mixture of abrasive particles and pea size lumps of sand through pairs of juxtaposed rollers 66 which may be made of wear resistant polyurethane. The cylindrical rollers 66 may be mounted on shafts 77 in housing 67 at the mouth 69 of spout 62. The closely positioned rotating rollers crush the pea size lumps of sand 61 into its fine granular form 71 while of course permitting the abrasive particles 63 to retain their normal size. This mixture of crushed sand and abrasive particles is then fed into separator 68 which is of the air wash type similar to separators 54 except that only one skimmer plate is necessary since the mixture will be divided into only two streams. Air is supplied through inlet 73 and is discharged along with any airborne contaminants through outlet 75. The substantially pure abrasive particles are received in spout 72 for reuse by blast wheels 28 by conveyance through pipes 74 (FIG. 1). The fine grain sand is received in hopper 76 where it mixes with the fine grain flowing from conduits 64 and is conveyed through conduit 78 to the blast station 50 (FIG. 1).

What is claimed is:

1. An abrasive blast cleaning system comprising abrasive blast means for removing a casting from a no bake mold and creating a mixture which includes fine granulated sand and pea size lumps of sand and abrasive particles, separating means, conveying means for transporting at least a portion of said mixture to said separating means, said separating means comprising a first separator for receiving the portion of said mixture and separating it into individual streams which includes one stream of abrasive particles and pea size lumps of sand, a second separator under said first separator, crushing means between said first separator and said second separator for granulating the pea size lumps of sand in the one stream and feeding the one stream to said second separator, and said second separator separating the one stream into individual sub-streams of abrasive particles and granulated sand.

2. The system of claim 1 wherein said crushing means includes a pair of juxtaposed rotatable rollers.

3. The system of claim 2 wherein each of said first and said second separators is an air wash separator with an air curtain inlet and an air curtain outlet.

4. The system of claim 3 wherein said first separator includes a plurality of skimmer plates, and said second separator including a single skimmer plate.

5. The system of claim 4 wherein each of said separators includes discharge means for discharging a stream of granulated sand, and both of said discharge means communicating with a common hopper.

6. The system of claim 5 wherein said rollers are made of wear resistant polyurethane.

7. The system of claim 6 wherein said second Separator includes means for feeding its stream of abrasive particles to said abrasive blast means.

Claims

1. An abrasive blast cleaning system comprising abrasive blast means for removing a casting from a no-bake mold and creating a mixture which includes fine granulated sand and pea size lumps of sand and abrasive particles, separating means, conveying means for transporting at least a portion of said mixture to said separating means, said separating means comprising a first separator for receiving the portion of said mixture and separating it into individual streams which includes one stream of abrasive particles and pea size lumps of sand, a second separator under said first separator, crushing means between said first separator and said second separator for granulating the pea size lumps of sand in the one stream and feeding the one stream to said second separator, and said second separator separating the one stream into individual sub-streams of abrasive particles and granulated sand.