US2449745A - Shot blasting machine - Google Patents

Description

Sept. 21, 1948." w. E. JEWELL 2,449,745

SHOT BLAS TING MACHINE Filed pril 1, 1947 2 Sheets-Sheet 2 INVENTOR. M17256 5. 02/1/ BY b Patented Sept. 21 1948 UNITED snares rum TING MHCHINE Walter. E..Jewell, LosvA-n gcles; Calif Application April '1, 1947; Serial No; 738,5'16' 4iGlaims:

inventionqrelates tolshotr blasting'machines;

and more particularly toa shotib-lasting'ma-chine wherein the workpieces. are tumble-d While; being exposed: to the stream ofi a. centrifugal shotth -rowingwwheeli Shotblasting is widely: used for-the cleaning of? hard objects -such as ceramics ormetal, and assuch is often used ast-hecquivalent: oil sandblasting. or as. a: replacement for sand'eblasting operations; Shot" blasting isparticularlyuseful for cleaning sand; castingszan di forgings; the impactnofi' the shot knocking looseadhering sand particles or scale,- as the casexmay be. All surrfaces of the workpieces may: be exposed tothe shotzblast by tumblingvthe workpieces in any con ventional manner as by: placingthem 'inside of a rotating drum.

Prion shotr blasting" machines hav generally employeclz a stream of air foncarrying the shot torthe objects to be blast'ed. Machines emplow ing. airb-last's accordingly may include a=plurality of: moyableon fixed" nozzleswhi'ch can be directed from. a .varietyrof: angles towards i workpieces: that are:v generally carried on a conveyor belt or-may be disposed upon a. rotatablev fixture; Also stream of shot fon shot blasting have been ob"- tainect. from: rotating wheels having paddlesor blades thereon that could centrifugally throw shot that is fed towardsthe centenofthewheel from; any convenient. source; such'as a chute. These centrifugal; wheels are more efficient than the: air blasts. ofshot, and' employa mucl'tmore simple. mechanism thanthat required forair blasts.

While ;severali attemptsthave been made to -combine: centnifugal shot-throwing wheel's withltumblers so-that allisurfacesofi the workpiecesmay be exposedato the shotblast, these in-general have not: been successful. The principal -difficultyhas apparently been. due to the: fact that no suitable mechanism: on device could=be obtained for di-- recting the shot into the tumbl'er. Forexampl'e; tumblers have. been. formed of drums mounted for rotation. upon a. generally inclined or verti-- calaxis; and the workpieces tumbled in the.-

drums. have been; exposed to, the: blast. of shot by having one end of the drum 011811.: These strum tures, however, are. not. particularly satisfactory;

since only a smallquantity. of tumbled efliciently atonetime work-pieceslmay be invention, seeks. to overcome these. defects.v

ofiprion shot blasting machinles by providing tumbias for workpieces that may include rotatable drums mountedon. generally horizontal axes so theta large tumbling. capacity be obtained.

Further; instead ofi: opening' one" and off the drum so'ethats. an outside source of-ishoi'. ..may be utilized; Lhaveprovidedia shot-throwing mechanism; that marcbe disposedwithinlth e tumbler itself; Inesmuchra-st-suchi shotv blasting mechanism-s am'particularly: bulky. and:v would. interfere with the mounting of a, drum that is supported upon a shaf-il;.lI have arrangedumy: tumbling drum-so that vitamay be supported :at" its p-eriphery only upon driving rollers. H'I hisa structure also-per mits the utilization of an extremely large chargingyidoor: for; the drum which: door may be situated at the. end; of the: drumiopposite from: that inrwhich. the shoteth'rowing. device is disposed;

Thee in'senti-ona on 8;: shotsthrowing dcviceinto the interior of a tumbling drum raises the asd'cled problem; of; adequately covering; theentire axial lflngt-lh ofrthe: :drumrzwitln the shot blast so as to obtain a uniform and efficient blasting of the tumbledi workpieces. While ibwl'S theoretically possible; tmaligm an elongatedicshot-throwing wheel. with; the'raxis ofzithedrum and" to throw shot fromtheientine lengthz ofit-he Wheel so as to cover: thez entine axiah lengthz of lthe drum, this structurezisinot practical; at. present. My invention', howeyen, includes. means for employing a simplea-shot-throwinge wheel having: a relatively thin: widthitoi the radiali shot -throwing pattern in suchta manner that; the. entireaxial lengthof. the drumvwillz be: adequatelysblasteds This structure may. include. earshot-throwing wheel havihgits axis; oitrotationat "an." angle to the axis of rotati'on ofi1the drum,- and when the wheel is" dis posed on? the interiorof" the drum; it will direct a shot pattern generally aligned with the diagonal corners of the drum;

in; ordinary tumbling operations, the workpiecespreferably cover only "the." bottom portion of the tumbled drumsc that. all surfaces of the workpieces may be. exposedjtm ashot blast with the fewest number of rotations. Accordingly; therefore, the shotrthrowingwheel must. be (ilesigned. to. deliver. shot onlyloverz-that part of the. interior surface? of.. the .;drum: occupied; by the; workpieces; inasmuch as any shotthat is directed. towards parts of the drum not covered bythe workpieces will; quickly erode away the drum and render it unserviceable: My. inventionaccordingly: includes: an improved: shot-throwing wheel: structure having a very; directive shot pattern so that the life; of the drum will. be greatly extended. l

It. is a: principal objectroi my. invention to-prowide an. improved: shoti blasting machine wherein an improved shot-throwing device for. shot blast-.

ing machines.

Other objects and advantages of my invention will be apparent in the following description and claims, considered together with the accompany ing drawings, in which Fig. 1 is an elevation front View of a shot blastother things, the mechanism for delivering shot from the bottom of the machine to the top of :the

machine; l y

Fig.3 is-a sectional view along the-line III-III ofv Fig. l'showing the location and relative dis-- position ofthe shot-throwing wheel and the tumblingdrum; l

r Fig. 4 is a sectional view through the tumbling drum taken along the'line IVIV of Fig. 3;

Fig. 5 is an elevation view of one side of the shot-throwing wheel astaken along the line VV Fig. 6 is a sectional view through the shotthrowing wheel as taken along the line VI-VI of Fig. 5; and

Fig. 7 is a sectional view through a chilled surface type ofwmold for casting the shot-throwing blades of the shot-throwing wheel of Fig. 5.

While my invention may be embodied in apparatus comprising essentially a drum, shotthrowing wheel,. and means for feeding shot to the shot-throwing wheel, I prefer to add refinements thereto that increase the utility and efficiency of my shot blasting machine. Accordingly, referring to Figs. 1, 2, and 3, a shot blasting machine [B may include a rectangular frameworkl l formed of angle irons or other structural shapes of great strength. The entire rectangular frame. H may be enclosed with sheet metall2 so as to form a dust proof case about the shot blasting machine, and the dust may be removed by any suitable mechanism, for example by a suction exhaust pipe I3. A suitable door in the sheet metal case l2 may be provided forpermitting access to the tumbling drum.

The tumbling drum may be in the form of a steel cylinder l4 having a plurality of perforations 16 in the cylindrical wall thereof. The drum may be'mounted for rotation on, and may be driven by, a plurality of flanged driver wheels l1, and each end of the drum l'4 may be provided with heavy steel tires 18 for engagement with these drivers l1.

,The drivers I! may be mounted upon two shafts I9 generally parallel to the axis of the drum l4, and these shafts may be journaled 'in suitable bearings 2| mounted upon horizontal portions of the frame I, I.- These shafts -l9 may-project from the rear of the sheet metal dust case [2 for a driving engagement by a geartrain driven by a motor 22 which is preferably electric. .A suitable reduction in speed between the motor 22 and the drum [4 must be obtained inasmuch as the rotation of the drum is preferably on the order of about 1 R. P, M. Accordingly a small sprocket 23 on the motor 22 may engage a large sprocket 24 secured to a reduction gear box 26 from which may lead suitable belts or chains having a driving engagement with one of the shafts 19. The two shafts l9 may be interconnected by a belt or chain drive 21 so that all four wheels I! will drive the drum l4.

The drum l4 may be charged with workpieces by means of a large charging door 28 hingedin any suitable manner, as by a rod 29, to the drum itself. An inspection door 31 may be provided in this charging door if desired. Accordingly the door 23 may be opened and workpieces placed within the drum l4 and the door 28 may then be closed and securely locked. Thereafter the drum will be rotated and the workpieces will tend to rotate with'the drum until they reacha point on 4 their upward travel where the forces of gravitywil-l cause them to roll down over the .pile of workpieces within the drum and thus give rise to the tumbling action. The shot with which the-workpieces are blasted, and the blasted particles of sand, scale, or other coating may fall through the small holes ['6 into a hopper 32. The shot may roll from the hopper 32 into thebottom part 33a of an elevator shaft 33 so that the .bottom part 33a of the shaft acts as abin for the shot. If desired, an air'inlet opening may be formed adjacent the bin portion 33a, of the elevator. shaft 33 so that air-will be sucked upwardly within the'dust casing l2 to the exhaust pipe I3 and thereby clean the shot of scale and line particles. The shot-throwing mechanism is shown in general in Fig. 3, and has as its essential part a shot-throwing wheel 4| which will be described in more detail. with referenceto Figs. 4 through 7, inclusive. zThe wheel 4| may be mounted'upon a generally horizontal shaft 34 journaled in bearings 35. The shaft may be driven by an electric motor 36.mounted upon aplatform 31 disposed atthe rear of the shot blasting machine Ill. A drive may be effected between the motor 36 and the shaft 34 by any suitable device such as pulleys and; one or more belts or chains 38.

.Also it will be noted that-the rear end of the drum 14 may be centrally relieved so that only an annular end portion l4a remains. Project-4 ing into the central opening formed by the annular end plate l4a, may be a generally tubular member42 to which the inner bearing 35 is secured, and this tubular member may be secured in turn to upright portions of the frame I l. The horizontal shaft-34 may be located generally in the same horizontaliplane that includes the axis of the rotatable drum 14, but variations of smallv amounts may be made therein as will be apparent to those skilled in the art.

Shot maybe supplied to the throwing wheel 4i by. means of .a continuous supply mechanism disposed within the elevator shaft 33. For example,

an endless belt maybe employed for'this purpose having buckets secured thereto as shown in Fig. 2; Accordingly pulleys 43 may be journaled in the bottom and top of the'elevator shaft'33, and an endless belt 44 may be passed about the pulleys and may have buckets 46 secured thereto which will dip into a'pile of shot 4'! formed in the bin portion 33a-of "the shaft 33. The upper pulley 43' may bedriven' by any suitable mechar'iisni' suchas a sprocket 48"co'nnected by a chain 49 to 5 sprocket, 51:- mounted on a1 crosss'shafti having avlargeipulley 52. driven; by; an electric. motor: 53.

the endless :belt. moves. about. pulleys;v it

will? pick up shot: at, the bottom. of. the; shaft 33 and. deliver; it-at the: top'ofs the shaft to: 3.151111 ableisupply mechanism such as an tube 54 (Fig.

4!) leading from the top: of the. elevatorgshaft to the; sho-t'l-throwinga wheel M. The: rate; of. supply of sh'ot torthe centrifugal. wheel. 4 I maybe. .reguelatecli by placing? a. sliding plate; 3-llr or: similar mechanism between the hopper 32 and thfi botr tomw33a' of. theelevator" shaft 33... l

- The construction of theshot-throwingwheel 41-- mayrbe best explained: with=reference1to Figs.

31.4 ,5; and- 6. Referring to Fig. 3, it willibe: noted that/i a.relatively thick and: heavy wear plate 5.6 may be. secured: to: the endgofi the tubular projectiom 42;. and? the shot supply tube 54-- may pass through an opening in thiswea-r plate to. deliver shot-t'oflthe wheel 41. Apertured square plates 51: may be'spacedifrom the end of. the tubular portion 42 to trap shot that t'end's-to ride along the shaft 34 to the outside: of the machine. The wheel; may include anxannular hub 581 resting upon: a 'shoulder on the end of the shaft and a grooved: plate: 59 may be secured against the hub 58 by a washer 6:! and remitv 62-. Blades: 63. may be secured to-the circular plate 59 and may be partially disposed withinthe grooves of the. plate 59. r

The detailed construction of the centrifugal WheelJH is best illustrated in Figs. 5' and 6; whereinlit will beinoted that. the blades G3 may include a: generally channel-shaped: member '64: having a ribbed transverse boss 96 integrally formed thereon. One'edge ofthe channelshape may be disposed withintliegrooves of the plate 5.9, which grooves may be'designated as 59a. A bolt 61- may pass through the transverse boss Strand. through the plate 59" to securely fasten thenblades 63" to the circular plate: 59f The pl'ate59 isdesignedt'o rotate at a high rate-of speed, for example 2 000 R. P. M., and: as the shotxrolls.outwardly on the blades 63* they bear thereagainst very heavily due to the increased angular acceleration- Whilethe balls move outwardly with some rolling action, there is also a considerable sliding action, and the blades 6-3 are accordingly subject toistrong forces that tend to wear the blades.

Accordingly I prepare the blades 63' to accommodate these Wearing tendencies, and I have found that a chill casting of the wear surface performs quite-satisfactorily when the blades 63 are formed from high carbon iron. This casting technique is illustrated in Fig. 7,.wherein a mold mayinclude asandporti'on 68 for the main body of the-blades 63; but the portion of the mold. forming the channel' of the blades may be formed of a metal as at.69.z Therefore if a high carbon ironalloy is used, for example cast-iron, the surface of the channel will be chilled during this casting operation due to the high thermal conductivity of the metal portion 68 of the mold. This chilling action will cause an alignment of metal grains perpendicular to the channel that give rise to great wear resistance.

The operation of the mechanism may be initiated by opening the chargin door 28 and inserting therein any material that is to be shot blasted. For example, a tumbling drum approximately four feet in diameter and about three feet in axial length may be loaded with eight hundred to two thousand pounds of metal objects, and the door 28 may then be closed and securely locked. A supply of hard steel shot may be disposedlinz the: bott om of the elevator. shaft; 33 until ax. substantial pile isaformed as indicated at 4:1 (Fig. 29;, The: drum rotating motor 22 may them be started; the.shot thro wingm otor-3flfimay then be started; andl the elevator motor- H may nextsbe started: Also a suitable exhaust fan may be omrated to Withdraw air from the exhaust 'staclr: I53 (Fig: ll); The endless belt' M there after continuously moves on the pulleys-43 and ther buckets E6 on the beltd'cliver-"shotto the top of the elevator shaft 33. whereupon-the shot is dumped into the delivery pipe 54; Thed'eliveryi pipe- 51! passes through the wearplate 56 (Fig. 30 and deliversshot totherapidlywhirling wheel d ll The blades- 63 of this wheel'take the shot which is delivere'd at their most inward end and: give it a: very rapid angular acceleration-dhe tothe highrate ofrot'ation ofthe wheel ll-which may be-aof the order of 2 :000R. P: Thisamgular acceleration gives-riseto' a radial -m'ovement of the shot,causing the shot to skid or roll along the channel= portions of the blades 63 until they are delivered with-a tangential trajectory to the interior of' the drumfl M The angular spread of the tangential trajectory may beadiusteol by any suitable means to substantially that shown by arrowsl llfiinlFig. 44 The. chargewithinthe drum M which is slowly rotating will occupysubstantially this angular portion of the interior of 'th'e drum l4, an'd accordinglywill be blastedibythe shot with verylittle o'f the shot-striking theidrum interior itself-of the drum: l t? The spent shot; together with the" particles knocked offdue to the impact with the work: pieces, will pass through the' holes: F6 i-n the drum to be collectedby the hopper: 3-2: Any suitable mechanism (notxshowm may beutilize'd for separating the blasted' material from ther's-hoi'i; which shotmay-then be re-usedi for a great cycles. This re cycling of the shotoccunsit I OuS fI'Ol'l'L the hopper-32: down intethe lower end of the elevator shaft 33 to formtheshot pile 47'. The operation-is continuousfor'any dcsired! length. ofti me; and: the usual blasting times are from: filve to twenty minutes, depending upon the: type. of. material: being clean'ed or treated; When. its is desired; tobremove the. chargerat, the end. of the. run, the. motors. are turned olii the charging doorwzlli opened and the material removed from the drum it which may beeasi'ly affected,, for. example by. raking: .the: matenial from thedrum-intio a waiting= truck orother receptacle; The operation of. the machinemay be entirely,

dust freedue to the enclosure-of the drum Mlby the case l2, togethenwith the exhausting operation performed by the stack. 11:3... The machine accordinglymaybe placed in any type of; shop without interfiering with nearby, operations reiquiring substantial freedom firomdustand grit-1..

By referringto Eig. 3; itwill'be noted: that the shot-throwing Wheel 4| is disposed at an angle to the axis of the drum M. Also by referring to Fig. 4 it will be noted that the angle between the shot-throwing limits 10 is such that the shot will be delivered from one corner of the drum and diagonally across the drum to the other corner. Thus all portions of the workpieces within the drum will be treated simultaneously. At one corner of the drum the pieces on the highest end of the constantly tumbling pile of workpieces will be treated, and the line of shot will traverse the pile until at the other diagonal corner of the drum the lower end of the tumbled pile will be blasted. As noted in Fig. 4, the relation of the feed tube 54 with respect to the centrifugal wheel 41 is such that the drum M should be rotated in an opposite direction to'obtain proper coverage.

Hard steel shot is preferred as the blasting medium, and the wheel 4| may ive this a velocity sufficient so that the shot is able to penetrate a WOOdGIl board, but not excessive so that it will mar the charge-being cleaned. The positioning of the shot-throwing mechanism directly within the tumbling drum gives the most direct contact of the shot-with the workpieces, and makes possible very close control of shot velocity with respect to the charge being treated. In this connection I have found that shot-throwing wheels employing two blades are greatly superior to those having a greater number ofblades insofar as delivering a clean and direct shot pattern is concerned. This positioning of the shot thrower within the tumbler is made possibleby mounting of and rotation of the drum upon driving wheels rather than by an axial shaft.

The drum I4 is preferably formed of heavy steel such as one-half inch steel, and the holes l6 therein may be drilled or punched. The heavy tires I8 which engage the driving wheels I! may be made with considerable accuracy compared to the drum itself. In this connection it should be noted that the drum may be made of plates Welded together into a general cylindrical shape, or may be formedof one or more sheets rolled into a circular cylindrical shape. The drivers I! are preferably formed of very hard material such as chilled cast-iron. The moving parts are relatively few in number and when made with extreme ruggedness the final machine is free of operational breakdowns and the only substantial maintenance operation thereupon need be the replacement of the blades 63 on the centrifugal Wheel 4|, Further, the shot-throwing wheel is so constructed as to handle blasting particles other than shot. For example, the conventional grits often used in place of round shot may be employed.

While I'haVe described my invention with respect to a particular embodiment thereof, I do not limit myself to this embodiment, since it is obvious that various modifications could be made therein without departing from the true spirit and scope of the invention. Accordingly I limit m invention only by the terms of the following claims.

I claim:

1.- A shot blasting machine comprising a rotatable tumbling drum having a generally horizontal axis, a generally horizontal rotatable shaft projecting into the drum at one end thereof and at an acute angle to the drum axis, and a narrow shot-throwing wheel disposed on the shaft inside of the drum so that a shot pattern may be thrown diagonall across the drum to cover the entire axial length of the drum.

2. A shot blasting machine comprising a rotatable tumbling drum having a generally horizontal axis, a generally horizontal rotatable shaft projecting into the drum at one end thereof and at an acute angle to the drum axis, a narrow shotthrowing wheel secured tothe shaft insideofthe drum and characterized by having two shotthrowing blades, and means for supplying shot to the shot-throwing wheel 'sothat a shot pattern may be thrown that coversthe entire axial length of the drum but at an angle to the axis of the drum.

3. A shot blasting machine comprising a rotatable tumbling drum having a generally horizontal axis, a generally horizontal rotatable shaft projecting into the drum at one end and at an acute angle to the drum axis, a narrow shot-throwing wheel disposed on the shaft inside of the drum, rotatable wheelscontacting the outer periphery of the drum for supporting and rotating the drum, means for supplying shot to the shot-throwing wheel, and a large charging door disposed in the other end of the drum.

4. A shot blasting machin comprising a framework, at least four rotatable Wheels mounted within the framework, means for driving at least one of the wheels, a perforated drum disposed on the wheels and having a generally horizontal axis, a generally horizontal rotatable shaft projecting into the interior of the drum through one end thereof, means for rotating the shaft at a high rate of speed, a shot-throwing wheel disposed upon the shaft within the drum for throwing a pattern of shot diagonally across the drum, a hopper disposed below the drum for receiving shot that-falls through the perforations of the drum, a dust-tight case secured to the frame about the drum and connected to the hopper, an elevator secured to the framework for lifting shot from the bottom of the hopper to a point abovethe shot throwing wheel, a chute connecting the top of the elevator with the shot-throwing wheel, and means for passing air through the hopper and the dust-tight case, whereby foreign particles and dust may be removed from the shot and from the dust-tight case, WALTER E. JEWELL.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Date

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