US2204587A - Centrifugal abrasive blasting machine - Google Patents

Description

' J. E. GUENDLING CENTRIFUGAL ABRASJ IVE BLASTING MACHINE June 18, 1940.

Filed June 25, 1 938 2 Shee'ts-Sheet 1 (law/g Y 4- TToRNEY lNVENTO Ja/m 1576a I w E; w M

June 18, 1940- J. E. GUENDLING 2,204,587

' CENTRIFUGAIL ABRAS IVE BLAS'IING MACHINE Filed June 25. 1938 2 Sheets-Sheet 2 INVENTOR PatentedJune 18, 1940 UNITED STATES PATENT OFFICE cau'rnrrocu lig e s rva anas'rmc John E. Guendllng, South Bend, 1nd. mm: to The American Foundry Equipmcnr'company, Mlshawaka, 11111., a corporation oi Delaware Application June 25, 1938, Serial No. 215,753

4 Claims.

This invention relates to centrifugal abrasive blasting machines and more particularly to an abrasive throwing wheel having improved abrasive supply means-associated therewith whereby c increased abrasive capacity and operating emciency of this unit of the machine may be realized.

Centrifugal abrasive throwing wheels of the type now in general use comprise a rotor head 1' mounted upon a high speed shaft, the rotor head ly extending abrasive throwing blades mounted thereon, the blades extending inwardly short of the axis of the rotor to provide a central space within which a device for controlling the direction of discharge of the abrasive is positioned. To reduce windage and consequent loss of power, the blades may be positioned between and supported by the rotor head and aside wall plate which are rigidly secured together. The control device comprises a tubular member inserted into the central space within the wheel, which tubular member is supported in relatively stationary position and is provided with a discharge opening in the peripheral wall thereof through which the abrasive is discharged onto-the inner ends of the blades as they successively rotate past the discharge opening. Means, such as a bladed impeller fixed to the rotor head, is provided for 3 forcibly projecting theabrasive fed into the tubular control member through the discharge 'opening thereof. The abrasive material generally used in abrasive throwing machines of this type comprises steel shot or steel grit and occasionally hard quartz sand. 1

Means must be provided for conducting this abrasive material into the tubular control member in such manner that it will be properly projected by the impeller through the discharge 49 opening in the side wall of the tubular control member. Abrasive throwing wheels of this general type are normally constructed from eighteen to twenty inches in diameter and arerotated at a speed of 2200 to 2600 R, P. M., developing a pcripheral velocity of from 11,000 to 15,000 lineal feet per minute. It will be appreciated that when a wheel having eight blades and constructed as above indicated is rotated at 2200 R. P. M., a blade will move past the discharge opening in the con- 59 trol member over 17,000 times every minute. 1 Thus, even when very large quantities of abrasive are fed into the control member, only a small quantity of abrasive will be ejected into the inner end of each blade as it passes the discharge open- 55 ing therein. Assuming, for example, that a cubic on having a plurality of spaced substantially radialouter end of the blade.

' mately only of a cubic inch of abrasive would be fed onto each throwing blade during each revolutlon thereof, which small charge is ejected from the blade before a second charge is placed there- 10 It will thusbe appreciated that the capacity of an abrasive throwing wheel is to a large extent controlled by the amount of abrasive which can be conducted into and fed into the rotating im-. peller within the tubular control member.- The throwing blades in the wheelshould preferably be made of substantial length so that the abrasive may be picked up on theinner end of each blade while the abrasive is moving at a relatively low velocity and thereafter may be gradually accelerated as it moves along the'iace of the blade until it has gained an abrading velocity of 11,000 to 15,000 lineal feet per minute as it leaves the Thus, it is appreciated that the diameter of the tubular control member as well as the impeller positioned within the tubular control member must be made relatively small. The abrasive can be most eifectively conducted into the path of rotation of the impeller vanes by providing a central opening in the impeller into which the abrasive is conducted bythe feed spout. However, the diameter of the feed spout through which the abrasive moves by. gravity must then be no greater than the. diameter of the central open space within the impeller and consequently the inside diameter of the feed spout is correspondingly limited. Furthermore, the feed spout should not be completely filled with abrasive since this'would result in a definite retardation of the velocity flow 40 through the feed spout and into the impeller and an actual decrease in the amount of abrasive conducted into the impeller measured in pounds per minute. 7 a

I have discovered that improved operating resuits and a substantial increase in abrasive capacity are accomplished by providing an air vent opening adjacent the discharge end of the feed conduit, which air vent opening is guarded by a baiiie which prevents the abrasive flowing through the feed conduit from falling out or discharging from the vent opening. The feed capacltyof .the feed spout may thus be increased from 20% to 50% and upwards. The air vent adJacent the discharge end of the feed conduit an improved means gal abrasive throwing wheel showingmy improved also prevents the settling of the fine abrasive particles and dust along the interior lower wall of the feed conduit as often occurs in the prior art structures. Further, the air vent effects a thorough mixing of the flne and coarse abrasive particles and also effects a more uniform flow of abrasive through the 'wheel and a more even distribution 'of abrasive over the full width of the throwing blades.

An object of this invention is to provide a centrifugal abrasive throwing wheel having ossociated therewith improved abrasive supply means whereby increased abrasive capacity and abrading efliciency may be attained.

Another object of this invention is to provide for supplying abrasive to a centrifugal abrasive throwing wheel whereby settling of the fine abrasive material in the feed supply means is prevented and a uniform mixing of the fine and coarse abrasive particles injected into the wheel may be obtained.

'A further object of thisfinvention is to provide an improved feed spout for conducting the,

abrasive into an abrasive throwing wheel whereby the abrasive-feeding capacity of the feed spout may be substantially increased without an increase in the diameter, the gravity drop or the length thereof.

Other objects of this invention will become apparent as the-disclosure proceeds.

Various other features and advantages of the invention will become apparent as the disclosure proceeds.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out'in the claims appended hereto. the invention itself, as to its objects and advantages, and the manner in which it maybe carried out, may be better understood by referring to the following description taken in connection'with the accompanying drawings-forming a part thereof, in which Fig. 1 is a front elevational view of a centrifuspout for supplying abrasive to the wheel associated therewith;'

Fig. 2 is a transverse cross-sectional view of the centrifugal abrasive throwing wheel and associated abrasive supply conduit, this view being taken on line' 2-2 of Fig. 1;

Fig. 3.is an enlarged front elevational view of ,the improved feed spout;

Fig. 4 is an enlarged'side elevational view of i the improved feed spout;

proved feed spout, certain parts being. broken Fig. "5 is an enlarged top plan view of .the imaway to more clearly illustrate the internal construction thereof; and. 3 I

Fig.6 is an enlarged fragmentary cross-sectional view of the'feed spout adjacent the discharge end thereof, this view being taken on line 6-6 of Fig. 3.

Similar reference characters refer to similar parts throughout the several views of the drawings and the specification. I

For ajbetter understanding of this invention, there is shown in Figs. 1 and 2 one type of abrasive throwing wheel with which my improved abrasive supply means may be associated. The wheelcomp'rises a'rotor' head I which may be suitably mounted upon a highspeed shaft 2 by means of a hub 3 which is keyed to the shaft and secured to the rotor head I by bolts 4. Channelshaped abrasive throwing blades 1:, shown in. Figs. 1 and 2, are provided which are radially arranged are supported.

-pro'ximately 30 to 90.

a, ,w: p r

in spaced relationship and are suitably mounted parallel spaced relationship by suitable shoul dered stud elements 8, the ends of which are iixedlysecured to the rotor head I and side wall plate 2. the rotor head I and the sidewall plate 5 by the provision of parallel extending grooves 1 in the rotor head I, and the side .wall plate '5, within which the side edges of the blades b extend and Each of the blades b is generally channelshaped in transverse cross-section and comprises abottom wall portion I and side flange portions III which extend forwardly in the direction of rotation of the rotor. The flange portions IOI,

serve to confine the. abrasive flowing over the blade between the flanges l'l and on the bottom wall IIIII of the blade. The blades extend substantially from the outer periphery of the rotor head I, inwardly along a substantially radial line to a point spaced from the axis of rotation of the wheel so as to provide a central space 8 within which a tubular control member I0 extends. Each I of the blades 1) may be held in position by a suitable set screw 9 which is screwed into'a threaded aperture in the side wall plate 5, the inner end 90 of the set screw being tapered so as to seat within a corresponding shaped recess 91) provided in the side edge of the blade b. Each blade b may be removed when worn by retracting the set screw 9 and drawing the blade outwardly through the periphery of the wheel. Thev position of the inner end of the blade when located in the wheel may be fixed and determined by a centering plate I II, which is'generally circular in shape and is so located that the outeredge I2 thereof overhangs the adjacent inner ends of the blades b so as to provide an abutment which limits the distance the blades may be inserted into the wheel. The centering plate II may be fixed to rotate with the rotor head I by means of a pair ped alined holes cut in the centering plate I and the hub 3.

The tubular control member III is provided with'a discharge opening I5 in the tubular side wall I4 thereof, the side edges of the opening I5 being confined between the flanges Illl of the blades 1). The opening I! ispreferably-of limited circular sidewall plate 5 I The blades b may be suspended between of dowel pins each seating within corresponding peripheral length,v extending around the tubular wall I4 of the control member a distance ap- The tubular control member II is rigidly'supported in stationary position during operation of the wheel upon a suitable supporting member It to which the tubular control member may be secured as by bolts I1 extending through elongated slots I8 in that portion of the tubular wall ll of the control member'which extends exterior to the side wall plate 5.

The abrasive fed into the tubular control member II is forcibly ejected through the dischargeopening I! thereof bymeans of an impeller 20 v which may comprise spaced side wall plates 2| and 22 having impeller vanes 24 extending therebetween. Preferably, the impeller vanes 24 are equal in numberto the throwing blades b, each vane being positioned in'the wheel slightly in advance of its corresponding throwing blade. The i p l er vanes 24 also preferably extend inlower interior face ofgthe ieed spout 3| where it hole in the end 01' the shaft 2.. The rear face or a the side wall plate 2| may be provided with a transverse rib 21 which seats ,within a corresponding slot 28 provided in an inwardly projecting circular boss 29 provided on the wear plate ll.

Thus the impeller vanes 24 are held properly centered with respect to the discharge opening II in the tubular control member Hi. The-tubular con- 5 trol member Ill may be provided with an inwardly extending lip II which seats behind the impeller and overlaps the rear side wall 2| thereof. The front wall plate 22 of the impeller is provided with a central-opening 23 for the admission of the l abrasive into the peller.

In an abrasive firing wheel of. the type above described, it will be appreciated that the wear exerted by the abrasive on the parts of the mai chine is dependent upon the speed at which the abrasive is moving at that particular point It is desirable to reduce the wear on the impeller 2|) and the tubular control member to a minimum and to concentrate the wear as-much as i possible on the removable and replaceable throwing blades 1). To effect this desired result, the diameter of the tubular control member 3 should be kept to a minimum and for practical purposes should be in the nature of four and not over six inches in diameter.

blades 12 can thus be correspondingly increased in length and in practical operation are generally made from flve to eight inches in length.

It will thus be appreciated that with a tubular control member ID of relatively small diameter,

the diameter of the impeller 20 is correspondingly small and for practical uses is generally 3 to. 5 inches in outside diameter. Furthermore, the impeller vanes 24 of the impeller 20 must be of suflicient. length to pick up the abrasive ejected over the inner ends thereof and to forcibly throw it out through the discharge opening l5, so that the diameter oi. the openspace 25'within the impeller should preferably be kept within two to three inches in diameter. With thecentral feeding space 25 within the impeller thus definitely limited, it will be appreciated that the discharge end of the feed spout 3| which conducts the abrasive into the impeller must be kept within the diametrical limits of the central space 25 of the impeller and its diameter also is definitely limited.

Since the impeller side wall 22 is set a substantial distance within the outer edge of the tubular control member ill, it is necessary ,that the abrasive supply conduit 3| which conducts the abrasive into the impeller be provided with a bend to avoid obstructing the rotating wheel. Thus a straight gravity drop or the abrasive through a. truly vertical feed spout isnot possible. Furthermore, due to the break-up of the abrasive particles resulting from the terrific impact shocks the abrasive receives in striking the metal articles under treatment, the abrasive is gradually reduced insize, which fine abrasive. is re-cycled through the feed spout and into the wheel. The abrasive fines or dust have a tendency to pack or settle along surfaces with which it comes into contact, with the result that there is a decided tendency for the abrasive fines to settle along the generally circular inside contour. spout 3| may be rigidly supported upon a suitable central space 25 within the im-' wardly flared ears 4| and The abrasive throwing slide gate 5| sons to close departs from the vertical drop, which obstructs the free flow of the abrasive into the central receiving space'25 of the'impeller.

I have discovered that the abrasive-feeding capacity or the feed spout 3| which conducts the abrasive into the wheel may be substantially increased by providing an air admission opening in the lower side wall of the feed spout at a point adjacent to the discharge end thereof or at points where it departs from a vertical drop. As shown in Figs. 1 to '6 inclusive of the drawings, the feed spout 3| is of. generally tubular form having a The feed bracket 32 aifixed thereto, which bracket may be secured to a rigidly supported standard 33 as by bolts 34. The discharge end 35 of the feed spout 3| is centered with respect to the central receiv-v ing space 25 of the impeller 20, and may be provided with an outwardly flared lip or flange 36 which overlaps the side wall plate 22 of the impeller and is positioned closeiy'adjacent to the side wall plate 22 with-suflicient clearance only as not to obstruct the free rotation of the impeller 20. The flange 35 should also extend sub- 'stantially to the interior surface of the tubular control member In. The abrasive is supplied to thereceiving end 3'! of the feed spout 3| by a funnel 33. The tunnel 38 is supported by a bracket 39 fixed thereto, which bracket is secured} as by bolt 40' to the standard 33. The upper end oi the feed spout 3| may be provided with outthe bracket 39 may also be provided with corresponding outwardly flared cars 42 through which securing bolts 43, as shownin Fig. 1, may extend and thus secure the feed spout 3| to the bracket 39.

Abrasive may be supplied to the funnel 38 by a'supply line 44 leading from the abrasive elevator' (not shown) to the funnel. The volume of discharge from the supply line 44 maybe controlled by a gate 45 hinged to swing on the end of the supply line 44 as by pins 46. A suitable baille plate 41 may be positioned within the funnel to prevent spillage of the abrasive leaving the line 44 and emptying into the funnel 33. The

open mouth of the funnel 33 may be covered by a suitable wire mesh screen which collects particles of metal and other foreignmatter cycled through the abrasive supply system, preventingsuch foreign matter from entering the abrasive supply pipe 3| and passing into the rapidly rotating wheel. The screen 50 is of sufficient mesh to freely pass the abrasive particles a ejected from the supply line 44. The abrasive g dropped into the funnel 38 passes from the funnel into the feed conduit 3| and thence into the impeller 20.

To control the abrasive flow from the funnel 38 into the feed pipe 3|, a gate 5| may be provided which slides within a corresponding slot 52 cut through the bracket 39 and the wall of the funnel 38. The gate 5| is provided with an aperture 53 of such size as to pass the desired amount of abrasive. The aperture 53 during operation of the wheel ,is positioned over the receiving mouth 31 of the feed pipe 3|. The abrasive ow into the spot 3| may be cut off by shifting the oil the receiving end 31 of feed pipe 3|. v

The abrasive-conducting capacity of the feed pipe 3| having a predetermined diameter may be substantially and measurably increased. by the extending through provision of an opening 55 iii I for the admission of a stream of air a which will the lower inclined wall of the feed conduit 5i flow into the wheel along with the abrasive; As shown more particularly in Figs. 3 to 6 inclusive,

the air inlet opening 55 may be formed by cutting a -v-shaped opening in the lower wall or belly. of'the feed conduit 3|. .The opening may thus be defined by a generally upwardly extending edge 56 and a generally horizontally extending abrasive flows,"the shelf of the feed e'dge'5'l defining therebetween an air inlet area The with afeedconduit having an air inlet opening 55 protected by a baffle 58, unexpected and substantially improved operating results are "obtained. It has been found that the abrasiveconducting capacity of the feed conduitof apredetermined size may be increased from to by the provision of an air inlet opening and associatedbaflie of the type heretofore described. The air stream a drawn through the opening by the suction effect produced by the rapidly rotating wheel breaks up and destroys any tendency of the abrasive fines and dust to settle in the conduit. The settling of dustandabrasive fines in the conduit, which has the effect of slowing the abrasive flow through the feed conduit,

is thus overcome.

Bymeans of the feed conduit herein described, the abrasiveis fed into the impeller with greater uniformity and is more evenly distributed over the impelling vanes 24 thereof, resulting in a more even distribution or spread of the abrasive over the entire width of the advancing face-of the bottom wall I00 of the blade and a/more uniform distribution of the thrown abrasive over the workpiece. The blades are also worn more uniformly and consequently have increased wear .life. r

The air vent or inlet opening 55 need not be limited to the particular shape shown in Figs. 3 to 6 inclusive but may assume other shapes. Further, one or more-air inlet openings may be located along the lower wall or belly of the feed .pipe at such points as there appears to be a tendency for the abrasive fines to settle or where the flow velocity of the abrasive becomes reduced. The shelf or baffle 58 may be concave, convex or substantially fiat in cross-sectional contour, and. should be so constructed as to permit the abrasive to flow freely thereover and to permitti ie free entry of a stream of air flowing in the directlon of the abrasive throwing wheel. Preferably,

theair inlet 55 should be positioned along the lower side wall or belly of the conduit so that the abrasive will flow over the inlet and the stream of air will flow inwardly into the conduit and generallyunder the abrasive stream flowing over the baffle 58. I e

' It will be appreciated that the improved 'abrasive feeding means herein disclosed may be asso-- ciated with abrasive throwing wheels of dif ferent sizes and modified forms, and that the.

' wheel shown in Figs. 1 and 2 of the drawings is presented only as an illustration of one type of abrasive throwing wheel in which ,my improved abrasivesupply means .may be advantageouslyassociated. While certainnovel have been disclosed herein, out in the annexed claims, it that various omissions, maybe made by those skilled in the art without departing from the spirit of the invention.

What I claim is I a 1. In combination with a centrifugal abrasive throwingwheel having rotatably mounted abrasive throwing blades, a normally stationary tubular control member having a discharge opening in the side wall thereof adapted to direct abra sive onto the inner end of the rotating blades, and air impeller having lmpelllng v'anes positioned within said tubular control member and fixed-to rotate ,with said blades, of means for supplying a-stream of abrasive particles to said impeller for ejection by said impeller through said discharge op n g in the tubular control member and onto the inner end of said blades, said. abrasive supply means including an abrasive supply pipe arranged in inclined position having the lower discharge end thereof closely adjacent to said impeller, an air admission opening in said abrasive supply pipe located in the underside of said abrasive supply pipe immediately above a lower substantially horizontally. extending discharge portionthereof, and a. guard adjacent said opening operative to guide the flowing abrasive over said air admission opening and prevent the abrasive from escaping therethrough 2. A centrifugal abrasive throwing machine including, a rotor head mounted to be rotated a1 high speed, radially arranged abrasive throwing blades mounted on said rotor head, a normally stationary control member having a dis charge opening therein positioned to direc abrasive into the path of rotation of said blades a rotatably mounted impeller positioned withil said control member operative when. rotated t1 eject abrasive through the discharge opening'il said control member, and means for supplyinl abrasive particles to said, impeller, said abrasiv and are pointed willbe understood supply means including an inclined abrasive sup ply conduit extending from a point above sail impeller downwardly to a point adjacent sai impeller, a funnel adjacent the upper end of sai supply conduit, said conduit having an air ad mission opening located in the underside an adjacent the discharge end thereof, and a she] element within said conduit overhanging sai opening, said shelf element being operative i guide the abrasive flowingdown the conduit ove said air admission opening and prevent th abrasive from escaping through said opening. .3. A centrifugal abrasive throwing machir including, a plurality of spaced rotatably mouni ed abrasive throwing blades, a normally statior ary tubular control member having a discharl opening therein through which abrasive may l conducted into the path of rotationof sa blades, a rotatably mounted impeller within sa tubular control member, an abrasive-receivii hopper positioned above said impeller, an abr: sive supply conduit extending from said hopp downwardly to said impeller, means for 001 trolling the flow of abrasive from said hopp through said supply conduit, said conduit havi: an air admission opening located in the unde side and immediately above acurved-genera' horizontally extending discharge portion thei of, and a. shelf element within said conduit ove ,hanging said opening, said shelf element bei features of the invention substitutions and changes 2,204,687 operative to guide the abrasive flowing down the conduit 'over said air admission opening and present the abrasive from escaping through said opening.

4. A centrifugal abrasive throwing machine including, a plurality of spaced rotatably mounted abrasive throwing blades, a normally stationary tubular control member having a discharge opening therein through which abrasive may be conducted into the path of rotation of said blades, a rotatably mounted prising an air intake port in said impeller within said tubular control member, a gravity feed abrasive 5 supply conduit extending from a point above said impeller to said impeller, and means for increasing the volumetric abrasive-conducting capacity of said teed conduit. said'means comconduit located in the underside and adjacent the discharge end thereof, and an element overhanging said port operative to guide the abrasive flowing down said conduit over said port and prevent the abrasive ,from escaping through said port.

JOHN E. GUENDLING.

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