Surface blasting apparatus
1A. RELATED APPLICATION 
     This application is a continuation-in-part of Wayne E. Dickson U.S. patent application Ser. No. 498,846, filed May 27, 1983, now abandoned, the details of which are incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to surface cleaning equipment, and more particularly to a surface blasting apparatus which recovers blasting abrasive and debris from the treated surface, and provides means for separating the debris from the abrasive. 
     2. Brief Description of The Prior Art 
     A number of types of surface blasters have been heretofore devised which recover abrasive and debris from the treated surface and utilize various methods to separate debris from the abrasive, so that the cleaned abrasive can be reused. Some of such surface blasting apparatus utilize mechanical pickup of the abrasive from the treated surface and a conveying system to carry the abrasive back to an abrasive storage hopper. 
     The prior surface blasters use a variety of methods to clean the abrasive so that the abrasive can be reused without frequent interruptions in service. One method of such cleaning is to use an air wash which passes through the abrasive carrying dust and debris away. A problem is that this air wash does not provide adequate cleaning of the abrasive, so that frequent stops to manually clean the abrasive are required. Also, the prior blasters do not adequately clean the air which is discharged from the machine which results in undesirable dust problems for the operator and passersby. 
     The apparatus of the present invention provides a means of adequately air cleaning the abrasive and filtering the dust and debris from the air stream. 
     BRIEF DESCRIPTION OF THE PRESENT INVENTION 
     The surface blasting apparatus of the present invention comprises magnetic receiving means for receiving abrasive rebounded from the treated surface which removes all kinetic energy therefrom, a baffle system or means for allowing air flow therethrough without passage of abrasive therethrough for a first abrasive cleaning operation, and means to draw air through the apparatus so that is passes through a falling curtain of abrasive for a second abrasive cleaning operation. 
     The apparatus also comprises means for removing heavy foreign debris picked up from the treated surface, heavy dust removing means in the form of a prefilter and light dust removing means in the form of a filter. The surface blaster also comprises an auger system which provides means for transferring the debris and dust to a common opening for removal from the apparatus. 
     One object of the present invention is to provide a baffle means for allowing air flow therethrough while preventing abrasive flow therethrough so that the air may remove dust and debris from a stream of abrasive rebounded from the treated surface. 
     A further object of the invention is to provide an auger means for removing large debris from the abrasive and transferring said large debris to a cleaning compartment for removal therefrom. 
     Still another object of the invention is to provide a means of air cleaning a flow of abrasive at two positions in the apparatus and filtering dust and debris from said air flow. 
     An additional object of the invention is to provide means for transferring all dust and debris removed from the abrasive and air streams to a single location in the apparatus for removal therefrom. 
    
    
     Additional objects and advantages of the invention will become apparent as the following detailed description of the preferred embodiment is read in conjunction with the accompanying drawings which illustrate such preferred embodiment. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial longitudinal cross-section of the surface blasting apparatus of the present invention. 
     FIG. 2 is a partial cross-section taken along lines 2--2 in FIG. 1. 
     FIG. 3 is a cross-section taken along line 3--3 in FIG. 1. 
     FIG. 4 is a view taken along lines 4--4 in FIG. 1. 
     FIG. 5 is a cross-sectional view taken along lines 5--5 in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly to FIG. 1, abrasive stored in a storage hopper is supplied to a rotary blast wheel and thrown to the surface to be treated. A stream of abrasive 400 rebounds from the treated surface through abrasive return chute 402 of substantially uniform cross-section. A deflector plate 404 at the exit of chute 402 directs abrasive 400 toward a magnetic receiving means in the form of vertically disposed magnets 406. Because the abrasive is ferrous, an envelope 408 of abrasive forms around magnets 406. As the stream of abrasive 400 strikes abrasive envelope 408, the abrasive is arrested and then falls downwardly, eventually coming to rest adjacent lower abrasive auger 410. The abrasive is moved transversely with respect to the surface blaster toward the lower end (not shown) of a bucket-type conveyor 412 of a kind known in the art. The abrasive is carried upwardly by conveyor 412 to a position above the hopper and discharged therefrom into upper abrasive compartment 414. 
     Referring now to FIGS. 1 and 3, abrasive falls downwardly in compartment 414 toward an open end 416 of an upper abrasive auger 418. The abrasive is then moved transversely by auger 418 toward filter screen 420 which encloses a second portion 422 of auger 418. As viewed in FIG. 3, the abrasive moves in a leftward direction. Filter screen 420 includes a plurality of openings 424 which are sized such that abrasive may fall therethrough. However, large debris, such as foreign material picked up from the treated surface, will not fall through openings 424 but is instead moved further transversely to fall from open end 426 of filter screen 420 into large debris chute 428. 
     As abrasive falls through openings 424 in filter screen 420, the abrasive enters abrasive return chute 430 and continues downwardly toward abrasive control valve 432. Abrasive control valve 432 is weighted, and when sufficient abrasive builds up in abrasive return chute 430, the valve will automatically open and abrasive will be allowed to fall downwardly toward the hopper, forming a curtain 434 of abrasive. 
     Referring still to FIG. 1, air is drawn into the lower end of corridor 402 adjacent the treated surface, as indicated by arrow 436, by a fan hereinafter described. The air flows upwardly through chute 402 with abrasive 400 and then passes upwardly through a baffle assembly 438. Referring now to FIGS. 4 and 5, baffle assembly 438 is shown in detail. In the preferred embodiment, baffle assembly 438 includes a lower baffle 440, a control baffle 442 and an upper baffle 444, but it will be clear to those skilled in the art that the number of baffles may be varied. 
     Lower baffle 440 defines a plurality of longitudinal slots 446 therethrough and, in an alternate embodiment, also has a plurality of longitudinally disposed magnets attached to a lower surface 450 thereof substantially parallel to slots 446. Central baffle 442 also has a plurality of parallel magnets 454 attached to lower surface 456 thereof. Similarly, upper baffle 442 has a plurality of slots 458 therethrough and, in the alternate embodiment, corresponding magnets 460 attached to lower surface 462 thereof parallel to the slots. Slots 446 in lower baffle 440 and slots 458 in upper baffle 444 are in substantial alignment, and slots 452 in central baffle 442 are staggered with respect to slots 446 and 458. Thus, any abrasive that might have a tendency to be carried upwardly with the flow of air which passes through baffle assembly 438 will be prevented from significant movement. Upwardly moving abrasive passing through slots 446 in lower baffle 440 should impinge against lower surface 456 of central baffle 442 rather than passing through slots 452. However, any abrasive that does pass through slots 452 in central baffle 442 should impinge, and be stopped by, lower surface 462 of upper baffle 444. In the alternate embodiment of baffle assembly 438, upwardly carried abrasive moving toward slots 446 will most likely be attracted, and stopped, by magnets 448, but any abrasive that does pass upwardly through slots 446 will almost certainly impinge against magnets 454 and be retained thereby, or at least stopped so that it can fall downwardly toward lower auger 410. Similarly, any abrasive that by chance passes through slots 452 should impinge magnets 460. Thus, in either embodiment, baffle assembly 438 provides a passage for air flow that should prevent any appreciable upward movement of abrasive therethrough. However, the air moving upwardly through baffle assembly 438 will carry dust and nonferrous light debris from the treated surface, thus, providing a first cleaning of the abrasive. 
     Referring again to FIG. 1, air, and the dust and debris contained therein, which exits baffle assembly 438 moves rearwardly with respect to the surface blasting apparatus as indicated by arrow 464 and is directed through the falling abrasive curtain 434 as indicated by arrow 466. This further removed debris from the abrasive, providing a second cleaning thereof. The flow of air and debris is controlled by air valve 468 and moves upwardly and rearwardly through air duct 470 to enter first cleaning chamber 472. 
     Referring now to FIGS. 1 and 2, the air and debris in first cleaning chamber 472 enters at least one prefilter 474. In the preferred embodiment, prefilter 474 is a cyclonic separator of the type disclosed in co-pending U.S. patent application Ser. No. 498,846. Heavy dust and debris is discharged from prefilter 474 so that it falls downwardly toward large debris auger 476 positioned at the lowermost end of first cleaning chamber 472. Large debris chute 428 also exits into first cleaning chamber 472 so that the large debris entering the chute from filter screen 420 falls downwardly towards auger 476 along with the heavy dust from prefilter 478. 
     The air and some light dust still contained therein exits first cleaning chamber 472 through discharge conduit 478 and enters second air cleaning chamber 480. The air and dust then flow through at least one filter 482 which removes essentially the remainder of the dust. Clean air exits the apparatus through discharge opening 484. Dust cleaned by filters 482 falls toward dust auger 486 located at the lowermost portion of second cleaning chamber 480. This is also similar to the filtering disclosed in co-pending application Ser. No. 498,846. 
     It will be seen that large debris auger 476 and dust auger 486 are mounted on a common shaft 488 which is driven by motor 490. The pitch of blades 492 on auger 476 and blades 494 on auger 486 are in opposite directions. Thus, as motor 490 turns shaft 488, augers 476 and 486 act as an auger means by which the debris and dust are moved transversely in both first and second cleaning chambers 472 and 480 toward divider wall 496 between the chambers. The lowermost portions of first cleaning chamber 472 and second cleaning chamber 480 adjacent wall 496 define a common opening 498 covered by a movable door 500 actuated by hydraulic cylinder 502. Door 500 can be opened when desired to remove dust and debris from the first and second cleaning chambers through opening 498. 
     Air is continuously drawn through abrasive chute 402, baffle assembly 438, air duct 470, first cleaning chamber 472 and second cleaning chamber 480 by a rotary fan (not shown) of a kind known in the art such as described in co-pending application Ser. No. 498,846. 
     It can be seen, therefore, that the surface blasting apparatus of the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as those inherent therein. While a presently preferred embodiment of the invention has been described for the purposes of this disclosure, numerous changes in the construction and arrangement of parts can be made by those skilled in the art. All such changes are encompassed within the scope and spirit of this invention as defined by the appended claims.