US3759451A

US3759451A - Apparatus for granulating molded sand

Info

Publication number: US3759451A
Application number: US00214611A
Authority: US
Inventors: H Good
Original assignee: Carborundum Co
Current assignee: Pangborn Corp
Priority date: 1972-01-03
Filing date: 1972-01-03
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18
Also published as: GB1362599A; JPS4874417A; CA978508A; IT974164B

Abstract

In an apparatus for granulating molded sand, a first conveying surface discharges lumps of molded sand onto a lower conveying surface and into the path of a stream of projected abrasive particles which granulate the lumps of sand.

Description

United States Patent 1 [111 3,759,451 Good 1 Sept. 18, 1973 [54] APPARATUS FOR GRANULATING MOLDED 1,907,198 5/1933 Hull 51/14 SAND --2,261,947 11/1941 Barnebl et al. 24l/DlG. 10

[75] Inventor: Harper W. Good, Waynesboro, Pa.

[ Assigneer Tl'le carbolllndllm P Y, Primary ExaminerGranville Y. Custer, Jr.

Niagara Falls, N.Y. Attorney-David E. Dougherty et al. [22] Filed: Jan. 3, 1972 [21] App]. No.: 214,611

[57] ABSTRACT [52] US. Cl. 241/77, 241/263 [51] Int. Cl. B02c 19/00 5s 1 Field of Search 241/5, 22, 68, 69, In an apparatus for granulatmg molded sand, a first 241/77 263, 264, 265 2731, 274, conveying surface discharges lumps of molded sand 51/9, 14 onto a lower conveying surface and into the path of a stream of projected abrasive particles which granulate [56] References Cited the lumps of UNITED STATES PATENTS 894,272 7/1908 Jorn, Jr 51/14 12 Claims, 2 Drawing Figures I" Q; (27 i I lLe ew aanakak I 25 I w I I 479 g I Y 7 I Y 5i i 1 23 g 7 PATENTED 3 5 SHEU 1 OF 2 BACKGROUND OF THE INVENTION The present invention relates to the reclamation of sand used to produce molds for foundry castings.

Reconditioning of used sand involves reducing molded sand lumps to individual sand grains and removing the metallic particles, sintered clusters of sand grains, excess fines and other tramp and objectionable material. The quality of reclaimed sand must be comparable to that of new sand so that it may be satisfactorily substituted for new sand and sand mixtures without appreciable change in sand practice.

Foundries are adopting a practice utilizing quality sand, a chemical binder and a catalyst which 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. Therefore, the effective and efficient reclamation of sand can play a significant part in making the no-bake molding process economically attractive. One of the steps in the reclamation of sand used in no-bake molding is the reduction of lumps of molded no-bake sand. Prior art apparatus such as hammermills, 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 According to the present invention there is provided an apparatus for granulating lumps of molded sand comprising:

a. a first surface having an end for discharging lumps of sand;

b. a second surface spaced below said first surface for receiving lumps of sand discharged from said first surface;

0. means for projecting abrasive particles in a path toward said second surface and adjacent the discharge end of said first surface; and d. means for oscillating first and second surfaces to transport lumps of molded sand into the path of abrasive particles thereby granulating the lumps of molded sand.

The use of the apparatus of the present invention results in a good yield of granulated sand from no-bake lumps. This is achieved without excessive wear on costly parts since the lumps of sand receive the direct impact of the projected abrasive particles. The core rods, trash and other objectionable material can be conveniently removed from the granulated sand and spent abrasive particles with the apparatus of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the apparatus of the present invention shown in section; and

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

trough 11 having a closed bottom and an open top is supported for horizontal oscillation. A plurality of wheels or rollers 13 mounted on the bottom of the trough 11 ride on a track 15 which is supported by a frame 17.

A substantially horizontally disposed surface 19 is provided in the upper portion of the trough 11 between the vertical sides thereof. A feed mixture including lumps of molded sand to be granulated is deposited on the upper surface 19 by a suitable means such as a conveyor.

-One method of forming the feed mixture comprises projecting abrasive particles against the 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 sand, rods, spent abrasive, fines and other contaminants falling through the bottom of the blast chamber for where it is conveyed to the surface 19 in the trough 11.

Oscillation of the surface 19 causes the feed mixture to move forwardly along the surface 19 to a discharge end 21. The feed mixture drops from the discharge end 21 and is conveyed through a stream of abrasive particles which granulate the lumps of molded sand. The granulated sand passes through apertures 23 in a lower surface 25 which is supported between the sides of the trough 11. The granulated sand and shot are carried along the bottom of the trough 11 by the oscillation thereof and exit via the open end 27 of the trough 11, while particles of a size larger than the apertures 23 in the lower surface 25 are conveyed along the surface 25 for discharge into a suitable receptacle for storage or further processing. W

Preferably the sand and shot mixture discharged from the bottom of the trough is passed through an air wash separator of the type described in US. Pat. No.

3,368,677 wherein the falling-mixture of sand and shot is subjected to an air curtain. 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 fines. The abrasive particles fall generally directly downwardly into a discharge conduit while the sand is slightly diverted and received in another discharge conduit. Thus an effective separation of the shot from the reclaimed sand is attained. The core rods, trash and other material which are discharged from the lower surface 25 can be reused or disposed of.

According to a preferred embodiment of the present invention, the upper surface 19 comprises a plurality of The oscillations of the trough 11 cause the feed material to moveforward. The lumps of material are pushed forward by the leading edge of respective serrations 29 as the trough 11 moves forward. As the trough 11 moves backward during an oscillation, the feed material tends to slide over the inclined support surface 31. Therefore, a general forward motion is imparted to the feed material deposited on the upper surface 19.

The lumps are discharged from one end of the upper surface 19 and drop toward the lower surface 25. The lower surface 25 is substantially horizontally aligned and extends between the vertical walls of the trough. The lower surface 25 can be a wire mesh screen of a wear-resistant material of an appropriate mesh size to permit abrasive particles and sand to pass therethrough.

A stream of abrasive particles is projected in a path 33 toward the lower surface 25 and adjacent to the discharge end 21 of the upper surface 19. The length of the path 33 extends across the width of the trough 11. Preferably an abrasive throwing wheel 35 mounted on the shaft of a motor 36 has a shot path 33 disposed crosswise with respect to the flow of lumps. in this case,

the hottest area of the wheel stream is aimed downwardly toward the middle of the trough 11 and forward the discharge end 21. By providing a trough 11 with sufficiently high side walls, abrasive particles from the head stream and tail stream ricochet off the side walls and downwardly into the lumps to increase the effectiveness of the wheel stream at points remote from the hottest area. It is contemplated that a plurality of abrasive throwing wheels can be mounted together to increase the width of the blast pattern.

The upper 19 and lower 25 surfaces are oscillated back and forth rapdily in a horizontal direction. As illustrated in the drawings, the oscillation of the trough l1 accomplished by a power device 37 connected at one end to the frame 17 and at the other end to the trough 11. The power device 37 is in the form of a hydraulic cylinder and piston rod with the piston rod connected to a member 39 rigidly secured to the bottom of the trough 11. At the extended position of the piston rod, there is provided a stop 41 attached to the frame 17 and having a yieldable member 43 secured thereto for limiting the forward stroke of the power device 37. Another stop 45 with a yieldable member 47 is also provided for limiting the backward end of the stroke. The motion of the member 39 secured to the bottom of the trough 11 is limited by the stops 41 and 45. Preferably the oscillating motion is such that the trough 11 moves backwardly more rapidly than it moves forwardly. At the forward end of the stroke there is preferably a sudden reversal which allowsthe sand lumps to continue moving forward due to their momentum while at the backward end of the stroke there is preferably a deaccelerating backward motion followed by an accelerating forward motion. Any suitable controls wellknown in the prior art can be used to control the power device 37 to produce this motion.

Any suitable means such as a mechanical, electrical, pneumatic or hydraulic means can be used to oscillate the trough l l. The conventional mechanical oscillators generally use positive eccentric drives while the electrical oscillating systems operate on a release cycle or push pull cycle using electro and/or permanent magnets. lt is contemplated that any suitable type of oscillating means known in the prior art can be used to produce the oscillating motion.

There is provided a shoulder 49 disposed between the discharge end of the upper surface 19 and the lower surface 25 for blocking the backward flow of lumps of material. The shoulder 49 can be in the form of a vertically extending metal plate which is attached at either end to the side walls of the trough 1 1. Lumps are therefore trapped in a pocket when they drop from the upper surface 19. As the trough l1 quickly reverses, lumps fall from the upper surface 19 and are in turn pushed forward under the path of abrasive particles by the shoulder 49 when the trough 11 again moves forward.

Another surface 51 which is positioned above the lower surface 25 and below the upper surface 19 receives the lumps from the discharge end 21. Surface 51 is horizontally disposed across the width of the trough 11 and extends substantially across the path 33 of the abrasive particles. Surface 51 is preferably a wearresistant plate which is placed immediately above the lower surface 25 and is suspended in a fixed horizontal position from the frame 17 by a suitable support member 53. The surface or plate 51 extends under the upper surface 19 and holds the sand lumps falling from the upper surface 19. The plate 51 may be solid or perforated as desired. In operation, plate 51 provides a stationary surface on which the lumps are resting while being blasted. As the shoulder 49 moves toward the blast stream, the lumps are caused to slide across the plate 51 to a position under the stream of abrasive particles. While the lumps are being blasted, the force of the abrasive in the stream tends to pin the lumps downwardly against the plate 51. When the plate 51 moves away from the stream of abrasive particles, it creates a void into which the lumps from the edge of the last serration on the upper surface 19 may fall. Without the plate 51, the lumps under the stream of abrasive particles tend to move back with the lower surface 25 as a result of being pinned thereto by the blast force. In this latter case, the lumps moving backwardly remain in the corner defined by the shoulder 49 and the surface 25, new lumps falling from the edge of the upper surface must fall into the wheel stream by rolling over the lumps remaining in the corner just described. Thus, the new lumps are not subjected to the full force of the abrasive particles. To alleviate this effect, the stationary plate 51 is provided.

The vertical drop between the upper 19 and lower 25 surfaces should be maintained at a minimum so as not to hinder the flow of core rods through the conveyor, but must be sufficiently high so that lumps do not bridge from one surface to another to the extent that sand flow volume is retarded.

The length of the oscillating strokes should be set so that lumps will not be pushed all the way through the wheel stream in one oscillation. The lumps should receive two or more pushes while passing through the stream. Concentration of abrasive is lightest along both sides of the stream pattern and heaviest along the center area of the pattern. By causing the lumps to stop along the lighter edge area first, then along the denser, more concentrated middle area and again along the lighter area at the opposite side of the blast pattern, better use is made of the entire wheel stream.

It is also contemplated that the lower surface may comprise a plurality of serrations in place of a screen.

The serrations can be separated to allow sand to fall through to the bottom of the trough from where it is conveyed for further processing. It is also contemplated that the lower surface be gently sloped downward so as to permit an increased flow of material. In the interest of efficiency minimized wear throughout the system and proper flow of sand lumps, it is preferable to maintain a steady flow of lumps at a maximum capacity. Therefore, it is preferable to use a hopper at the entrance end of the conveyor for providing a reservoir of lumps to insure a steady influx of feed material. Another modification, which can be beneficial in certain circumstances, is the inclining of the wheel stream toward the shoulder 49 in such a way that the stream strikes the surface 51 adjacent to the shoulder 49. This tends to keep all lumps along the edge which is formed by these two surfaces. Lumps therefore remain trapped by the stream until disintegrated.

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 first surface having an end for discharging lumps of sand;

0. means for projecting abrasive particles in a path toward said second surface and adjacent the discharge end of said first surface; and

d. means for oscillating said first and second surfaces to transport lumps of molded sand into the path of abrasive particles thereby granulating the lumps of molded sand.

2. Apparatus according to claim 1 comprising a shoulder disposed between the discharge end of said first surface and said second surface for blocking the flow of lumps.

3. Apparatus according to claim 1 wherein said first surface comprises a plurality of serrations, each serration having an inclined support surface.

4. Apparatus according to claim 1 wherein said second surface includes a plurality of apertures to permit granulated sand to pass therethrough.

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

6. Apparatus according to claim 1 wherein said oscillating means comprises means for moving said first and second surface back and forth rapidly in a horizontal direction.

7. Apparatus according to claim 6 wherein said oscillating means is adapted to move said first and second surface backwardly more rapidly than said first and second surface are moved forwardly.

8. Apparatus according to claim 1 including a trough, said first and second surfaces supported by said trough, and said oscillating means being operably associated with said trough.

9. Apparatus according to claim 8 wherein said trough includes a bottom for receiving granulated sand passing through said second surface.

10. Apparatus according to claim 1 including a third surface positioned above said second surface and below said first surface so lumps of molded sand from the discharge end of said first surface fall onto said third surface, said third surface being stationary with respect to said first and second surfaces.

11. Apparatusaccording to claim 10, wherein said third surface extends substantially across the path of the abrasive particles.

12; Apparatus according to claim 10 including a shoulder extending toward said third surface to push lumps on said third surface through the path of abrasive particles and into said second surface when said surface is oscillating.

Claims

1. Apparatus for granulating lumps of molded sand comprising: a. a first surface having an end for discharging lumps of sand; b. a second surface spaced below said first surface for receiving lumps of sand discharged from said first surface; c. means for projecting abrasive particles in a path toward said second surface and adjacent the discharge end of said first surface; and d. means for oscillating said first and second surfaces to transport lumps of molded sand into the path of abrasive partIcles thereby granulating the lumps of molded sand.

11. Apparatus according to claim 10, wherein said third surface extends substantially across the path of the abrasive particles.

12. Apparatus according to claim 10 including a shoulder extending toward said third surface to push lumps on said third surface through the path of abrasive particles and into said second surface when said surface is oscillating.