US2304041A

US2304041A - Centrifugal blasting machine

Info

Publication number: US2304041A
Application number: US345035A
Authority: US
Inventors: Chester E Unger
Original assignee: American Foundry Equipment Co
Current assignee: American Foundry Equipment Co
Priority date: 1940-07-12
Filing date: 1940-07-12
Publication date: 1942-12-01
Anticipated expiration: 1959-12-01

Description

Dec. l, 1942. c. E. UNGER CENTRIFUGAL BLASTING MACHINE.

Filed July l2, 1940 2 Seet-S-Sheet l INVENTOR flmser E @er All ATTORNEY Dec. 1, 1942. c. E. UNSER v-'-"23302041 GENTRIFUGAL BLASTING `MACHINEW Filed .my 12. i940v 2 sheefcs-sneet 2 Ws *"a ATTORNEY Patented Dec. l, 1942 CENTRIFU GAL BLASTIN G MACHINE Chester E. Unger, Mishawaka, nd.,. assignor to The American Foundry Equipment Company, Mishawaka, Ind., a corporation of Dela- Ware Application July 12,1940, serial No. 345,035

' 15 claims. (01.51-9) This invention relates to centrifugal blasting machines, and more particularly to that type of blasting machine which comprises a bladed rotor having means positioned centrally thereof for directing the abrasive into the path of rotation of the blades of the rotor whereby the abrasive thrown by the blades may be directed in a coniined or concentrated stream against the article undergoing v treatment positioned at one side thereof.

In accordance with this invention, the centrifugal blasting machine embodies a bladed rotor which may comprise a pair of spaced side Wall discs rigidly connected together and fixed to the end of a high speed shaft. Abrasive throwing blades are positioned between and supported by the side wall discs and are arranged in spaced generally radially extending relationship with the inner ends of the blades extending short of the axis of rotation of the rotor to provide a central space therein.

An important feature of this invention comprises the provision of a tubular impeller positioned within the central space of the bladed rotor and fixed to rotate therewith, which is so designed as to effect substantially even distribution of the abrasive over the full width of the advancing face of the blades. The abrasive is fed into the tubular impeller by a suitable stationary feed spout which discharges the abrasive onto the inside surface of the tubular impeller. The tubular side wall of the impeller is provided with a plurality of discharge ports or slots whose side edges are positioned between the side flanges of the channel shaped blades. tent of each slot is relatively short so that the slot is relatively narrow in axial extent. The number of slots employed are preferably equal in number to the abrasive throwing blades and each slot is preferably positioned slightly in advance of its corresponding blade. The abrasive deposited on the interior surface of the tubular side wall of the impeller is held in hugging relationship to the inside surface by centrifugal force. Agitating lugs fixed to the inside surface of the impeller may in some cases be provided to assist in bringing the abrasive deposited therein up-to peripheral speed. These lugs also serve to assist the distribution of the abrasive between the narrow discharge ports so that substantially uniform discharge of the abrasive through the full axial width of the discharge ports is effected. Y.

When the bladed rotor is rotated at blasting 'Ihe peripheral ex- A speeds the blades thereof exert a fan action which Mi normally produces high velocity air movements within the central space of the wheel.

A baille plate or deflector segment is positioneds within the tubular impeller and serves to baiile the air currents generated by the rapidly rotating blades within the central space of the rotor, so that the ports of the tubular impeller when rotating through 'an area which is generally opposite the arcuate side wall and the heel of the deilecting segment, appear to experience a high velocity inow of air through the ports, which prevents any substantial quantity of abrasive escaping outwardly through the ports as they rotate through this area. This area, through which the air flows at high velocity through the ports of the tubular impeller inwardly into the same, might be referred to as a pressure area. velocity air currents escape from the interior of the rotating tubular impeller through the ports thereof when they move over a relatively short peripheral area which is adjacent but,slightly in advance of the tip end of the deiiector segment, which area might be termed a suction area. The outflowing air at the suction area obviously does not obstruct but facilitates the discharge of abrasive through the discharge ports of the impeller as they move through the suction area. The inside surface of the arcuate side wall of the deflector segment also serves to guide any abrasive thrown thereagainst along the inside surface until it is free to discharge from the tip end of the deflector segment. 'Ihe narrow discharge ports in the tubular impeller which -have an axial width approximating that of the throwing surface of the blades perform the highly important function of effecting substantially uniform distribution of the abrasive directed onto the inner ends of the advancing blades through substantially the full abrasive throwing width thereof. y

Another feature of this invention is the provision of a spiralling rib or iange xed to the outer periphery of the end portion of the feed spout which extends into the tubular impeller. This spiralling rib further facilitates the distribution of the abrasive within the tubular impeller so that the abrasive will discharge substantially uniformly throughthe full axial width of the narrow discharge ports thereof. This spiralling sive within the tubular impeller so that the abrasive is more effectively brought under the inuence of the controlled and deflected air currents The `highgenerated by the bladed rotor within the tubular impeller.

Various other features `and advantages oi the invention will be apparent from the following particular description and from an inspection of the accompanying drawings.

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 may be 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 across-sectional view of a centrifugal blasting machine having the abrasive deflecting device positioned within the tubular impeller, this view showing the machine as it appears when looking in the direction of the arrows along line I-I of Fig. 2;

Fig. 2 is a cross-sectional view of this machine as it appears when looking in the direction of the arrows along the line 2-2 of Fig. 1;

Fig. 3 is a perspective view, partly in section, of the abrasive impeller device associated with this machine; 't

Fig. 4 is a perspective View of a normally stationary deflector employed to effect directional control of the abrasive from the bladed rotor of the machine shown in Figs. 1 and 2;

Fig. 5 is a cross-sectional view of a centrifugal blasting machine having modified means for feeding and controlling the direction of abrasive discharged from the bladed rotor, this View being taken along line 5-5 of Fig. 6;

Fig. 6 isa cross-sectional view of this centrifugal blasting machine as it appears when looking in the direction of the arrows along line 6--6 of Fig. 5; and

Fig. '7 is a perspective view of the abrasive deiiecting device employed to effect directional control of the abrasive fired by the bladed rotor forming a part of the machine shown in Figs. 5 and 6.

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

The centrifugal blasting machines which have been shown in the drawings to illustrate embodiments of this invention, generally comprise a bladed rotor I mounted on the end of a high speed shaft which has associated therewith a device or devices for giving to the abrasive supplied thereto through a suitable feed spout an initial velocity in the general direction of rotation of the blades of the rotor and a device or devices disposed generally centrally of the bladed rotorA for controlling the direction of discharge of the abrasive fired by the rapidly rotating blades of the rotor. l

Generally speaking, the bladed rotor, constructed of suitable metal, may comprise a pair of spaced side wall forming discs 2 and 3 which are held in xed spaced relationship by means of suitable studs or spacers 4 which are welded or otherwise rigidly fixed` to the side wall discs 2 and 3. The bladed rotor is mounted upon a sturdy shaft 5 which rotates within suitable spaced bearings, the shaft being suitably connected to a suitable power source so as to be rotated at high speed. A hub 6 is fixed to the end of the shaft 5 as by means of a suitable spline 1 and the hub flange is suitably secured as by bolts 8 to the adjacent side wall disc 2. vThe front side the side wall discs 3 and 2 respectively. As thus constructed, the inner ends of the blades b and circular opening 'of substantially the same diameter defined by an inner circular edge 9'.

A plurality of throwing blades b,`general1y formed of wear resistant metal, are radially arranged in spaced relationship between the metal side wall discs 2 and 3. Four to eight such blades b are generally provided. 'I'hese blades are preferably channel shaped in cross-section, definingan abrasive receiving bottom wall III and a pair of side flanges II t'o retain the abrasive within the confines of the advancing face of the bottom wall I0. Each blade is inserted into paired slots or grooves formed in the side wall discs 2 and 3, which grooves support the blades in radial spaced arrangement. The

inner ends I2 of the blades are generally in approximate alignment with the peripheral edges 3 and 9' which define the central openings in the circular openings in the side wall discs 2 and 3 define a central space I5 within the bladed rotor within which .the abrasive impelling and controlling devices may be positioned. 'I'he blades b are removed when worn and fresh blades inserted through the periphery of the rotor, and may be held in operative position by set screws I3 threaded into the side wall plates 2 and 3, the inner ends of these set screws extending into suitable recesses I4 in the side edges of the blades. By manipulating the set screws I3 the blades b can beeasily withdrawn through the periphery of the rotor.

Referring more particularly to the abrasive blasting machine illustrated in Figs. 1 to 4 inclusive, a generally cylindrical impeller device 20, cast from wear resistant metal, is positioned within the central space of the rotor. This impeller device, shown separately in Fig. 3, comprises a cylindrical wall 2| which is closed at the inner end by end wall 22. This end wall may be designed to seat against the inside face of the hub 6 and may be fixed to rotate with the bladed rotor by means of a bolt 21 which extends through the end wall 22 of the impeller device and is threaded into a threaded opening in the end of the drive shaft 5. The front end of the impeller device 20 may be provided with an intumed fiange 23 which defines a circular opening 24 into which the discharge end of the abrasive supply spout 40 may be inserted. -The tubular wall 2I of the impeller device may be provided with a plurality of spaced discharge openings 25 preferably equal in number to the number of blades b of the rotor. The outer periphery of the tubular side wall 2| of the impeller extends closely adjacent the inner ends I2 of the blades b.

The tubular impeller device is preferably so positioned that each discharge opening 25 is positioned slightly in advance of the corresponding blade b of the rotor so that the abrasive will discharge from the opening 25 with the least interference with the inner ends I2 of the blades b. The tubular impeller device is alsoso positioned that the side edges of the opening 25 extend generally between the side flanges I I of the blades b. The openings 25 are preferably relatively narrow or short in their peripheral extent so that in this machine substantially unlform quantities of abrasive will discharge through each opening. The inside surface 2l of the tubular impeller device provides a circular rotating shelf upon which the abrasive is deposited as it discharges from the discharge end 4| of the abrasive supply spout 4|.l.l The abrasive a deposited on the shelf 28 dened between the end wall 22 and the adjacent side edges of the openings 25 rotates with this shelf and collects thereon in a ring-shaped pile until its angle of repose is overcome, when it drops out through the narrow openings 25. To bring the abrasive up to a speed approaching the peripheral speed of the shelf 28, a plurality of radially extending agitating lugs 28 are preferably secured to the inside face of the end wall 22.

In order that a central space may be provided within the bladed rotor deep enough to receive the tubular impeller and provide an adequate abrasive supporting shelf 28, the hub 6 may be provided with an internal circular recess. Such a circular recess may be made by providing as a part of the hub a circular plate 43 having a circular opening 44 on the inside face thereof, which is secured to the side wall disc 2 of the rotor by the bolts 8. It will be appreciated that, if desired, the plate portion 43 may be formed as an integral part of the hub.

apertures 53 through which securing bolts 63 extending through spaced apertures 63 in the bottom wall 6| of the dish-shaped member 58 extend. The spaced h'oles or slots,63 in the bottom wall 8| may be arranged in a circle s o that the securing screws 63 may be selectively inserted through these openings or slots to attach the control cage segment in any desired operative position.

Abrasive supplied to the feed spout 48 discharges from the inner end 4| thereof into the tubular impeller 28 where it collects upon the inside surface of the tubular wall 2| thereof. The control cage segment 58 serves to baille the high velocity air currents so that during high speed rotation of the bladed rotor air is drawn through the ports during a predetermined clockdial position during rotation thereof, .so as to prevent escape of any substantial quantity of abrasive at this point. The segment 50 operates to force the air out through the ports 25 during the remaining predetermined clockdial position during rotation so as to permit escape of abrasive at this area.

The abrasive supply spout 40 is supported upon a suitable bracket 42 fixed to a suitable stationary mounting. The abrasive a supplied to the feed spout 40 discharges from the inner end 4| thereof and drops upon the shelf 28 of the tubular impeller. The abrasive dropped on the shelf 28 quickly assumes the speed of rotation of the shelf, assistedby the agitating lugs 26, and collects on this shelf until the angle of repose of the pile of abrasive deposited thereon is overcome.

Directional control of the thrown abrasive is effected by the provision of an arcuate baille plate or segment which is positioned within the tubular impeller in the manner illustrated in Figs. 1 and 2.

The control cage segment 50 may be formed as illustrated perspective in Fig. 3, comprising an arcuate baille wall portion 5| having an arcuate contour of such a nature that it can be positioned within and generally conform to the circular contour of the inside face of the tubular side wall 2| of the impeller. The baille wall 5| is illustrated as being approximately 90 in length, approximately the minimum length at which it should be made to eiect a fair degree of directional contr'ol. More accurately defined directional control can be obtained if the baille wall 5| is made up to 120 or 180 or more in that the direction of discharge of the thrown abl rasive may be controlled. As shown in Fig. 2, a suitable support for the control cage segment may comprise a supporting plate 55 having a central opening within which a dish-shaped plate 58 is positioned. The plate 58 is provided with an outturned flange portion 59 secured to the supporting plate 55 as by screws 68. wall 6| 4of the dish-shaped supporting member is provided with a central opening 62 through which the discharge end 4| of feed spout 40 extends. The control cage segment 50 may be provided with a U-shaped formation 64 so designed as to extend around the inturned flange 23 of the tubular impeller 28. The U-shaped formation 84 presents a ilange portion 64 having threaded The bottom The control cage segment 50 positioned within the tubular impeller as illustrated effects a measurable degree of directional control of the thrown abrasive. The direction of discharge of the thrown abrasive may be regulated by shifting the I tip end 54 of the control cage segment 50 to the proper clockdial position.

There is shown in Figs. 5 and 6, an abrasive blasting machine which includes a bladed rotor and a tubular abrasive impelling device similar to that illustrated in Figs. 1 and 2. In this construction, the abrasive supply spout 48 is provided with means for scraping the abrasive out through the discharge ports 25 in the tubular impeller 20 and an abrasive deecting device 80 which extends into the tubular impeller 20 and is adjustably supported in normally stationary position.

The abrasive deilecting device 80, illustrated in perspective in Fig. 7, may be formed from cast metal having a generally arcuate body portion 8| and a trailing end portion 82. A foot portion 85 adjacent the side edges thereof is provided with threaded openings 18 through which extend the securing bolts 63 extending through a selected pair of spaced openings 63 in the bottom wall portion 6| of the dish-shaped supporting plate 58. It will be noted that the inner side edge 81 of the deector plate 88 is longer and of greater radius than the outer side edge 88 thereof, so that when the deector plate is mounted in position Within the tubular impeller 20 it assumes the position generally illustrated in Figs. 5 and 6. The tip end 83 and the trailing end 84 extend generally parallel to the axis of the rotor. The baille member serves to baille the air currents generated Within the rapidly rotating rotor so that the abrasive will be discharged into the path of rotation of the blades b in a direction determined by the clockdial position of the tip end 83 of the deilector member.

It will be noted by referring to Fig. 6 that the end portion 19 of the feed spout extends into the tubular impeller 20 for a substantial distance and that a spiralling vane 89 is integrally or otherwise fixedly secured to the outer periphery thereof. The spiralling vane 89 is shown as comprising three complete turns, each turn increasing in diameter toward the open inner end ofthe spout extension 19. It is appreciated that the vane 89 is normally stationary during rotationof the bladed rotor. The vane 88 serves to movable collar guide the abrasive discharged into the tubular rotating impeller 28 from the inner end thereof to a position where it may bev discharged through the full axial width of the ports 25 of the impeller 28. It will be noted from Figs. 5.and 6, that the arcuate body portion 8| of the detlector member 88 is so positioned that its inner surface is relatively closely adjacent the periphery of the erable to throw a concentrated stream of abraspiralling vane 89 and also that the periphery l .eration of the machine by means of a suitable supporting device such as the bracket 42. A re- I85, having an opening |06 through which the feed spout extends, closes the enlarged opening 62 in the dish-shaped supporting member 58. Bolts 83 extending through openings in the collar may be screwed into threaded apertures in the bottom wall 8| of the dishshaped support to retain the same in position.

In operation, abrasive is supplied to the supply spout 40 and discharges from the end of the end extension 19 into the rapidly rotating tubular impeller 20 which is fixed to and rotates with the bladed rotor i. The spiral vane 89 scrapes the abrasive deposited on the inner surface of the tubular side wall 2| of the impeller 20 forwardly so that the abrasive is discharged through substantially the full axial width of the discharge ports 25 therein. The shield member 80 acts to direct the abrasive onto the inner ends of the blades at a predetermined position.

It will be noted by referring to Fig. 5 that the trailing end 84 of the baille member 80 is positioned close to the interior surface of the tubular wall 2| of the impeller 20, while the tip end 83 thereof is positioned close to the periphery of the spiral vane 89. The baille member 80 as illustrated in Figs. 5 and 6 has an arcuate length of 90, which is the shortest length that should be employed to achieve a fair measure of directional control. This baiie member 80 may be made up to 300 in arcuate length with correspondingly improved directional control results. The bale member 88 serves to baiile the air currents so that a stream of air at relatively high velocity ows into the tubular impeller through the impeller ports 25 during that portion of their path of rotation which is opposite the baiile and adjacent the trailing end 84 thereof, producing through the discharge ports 25 when moving through this pressure area. The high velocity air stream and the abrasive escape from the tubular impeller outwardly through the ports 25 during that portion of their path of rotation which is adjacent but in advance of the tip end 83 of the deecting member 80, producing what might be termed a suction area. The spiralling vane 89 presents a generally conical shaped peripheral edge which also cooperates with the arcuate conical portion 8| of the baille member 80 to effect directional control results.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made -by those skilled in the art without departing from the spirit of the invention.

what is claimed is: 1. A centrifugal abrasive blasting machine opsive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality oi spaced radially extending abrasive throwlngblades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein for a suiiicient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof, an abrasive supply spout for conducting abrasive into saidV tubular impeller, and a normally stationary control device having an arcuate shaped side wall portion extending into said impeller and overlapping a limited arcuate section o f the tubular side wall of said impeller and covering the ports in said section, said control device being operable to direct the abrasive through certain of the uncovered ports of said impeller and into the path of rotation of the inner ends of said blades during a predetermined limited arc of rotation thereof.

2. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades sup- Iported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a.tubular impeller -positioned'within said central space fixed to rotate with said rotor, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof, an abrasive supply spout for conducting abrasive into said tubular impeller, a normally stationary tubular control cage extending into said central space and enclosing the discharge ports of said impeller, said control cage having a discharge opening in the tubular side wall of hunted peripheral extent positioned between the side edges of said blades operable to direct the abrasive into the path of rotation of the inner ends of said blades during a -predetermined limited arc of rotation thereof, and means for adjustably supporting said control cage in normally stationary position.

3. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high4 speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a centralspace, a tubular impeller positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein for sufficient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof, each of said ports having the side edges thereof positioned between the, channel confines of the adjacent blade, said ports being relatively short in peripheral extent, a feed spout for conducting abrasive into said tubular impeller, and

a normally stationary control device having an arcaute shaped wall portion extending into said impeller and covering a limited number of the -ports in said impeller, said control device being operable vto direct the abrasive through certain of the uncovered ports in said impeller and into the path of rotation of the inner ends of said blades during a predetermined limited arc of rotation thereof.

4. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein for a sufflcient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a .plurality of vspaced abrasive discharge' ports in the tubular side wall thereof, each of said ports having the side edges thereof positioned between the channel confines of the adjacent blade, said ports being relatively short in peripheral extent, a feed spout for conducting abrasive into said tubular impeller, deecting elements xed to the interior of said tubular impeller for guiding the abrasive to the discharge ports thereof, and a normally stationary control device having an arcuate side wall portion extending into said impeller and covering a limited number of the ports in said impeller, said control device being operable to direct the abrasive through certain of the uncovered ports of said impeller and into the path of rotation ofthe inner ends of said -.blades during a predetermined limited arc of rotation thereof.

5. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotationjhaving a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positionedl within said central space xed to rotate with said rotor and operative to retain abrasive therein for a suicient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof equal in number to the number of blades carried by said rotor, each of said ports having the side edges thereof positioned between the channel confines of the adjacent blade, said ports being relatively short in peripheral extent and positioned slightly in advance of their corresponding blades, a feed spout for conducting abrasive into said tubular impeller, and an arcuate sha-ped deflector wall extending into said central space and interiorly around a limited arcuate section of the tubular side wall of said impeller and covering the ports in said section whereby the discharged abrasive will be directed through certain of the uncovered discharge ports in said impeller.

6. A centrifugal abrasive blasting machlne operable to throw a concentrated stream of abray sive over a predetermined limited arc including 1n combination, a rotor head mounted for high speed rotation having a plurality of spaced ra-v the rotor to provide a central space, a tubularl impeller positioned within said central space 'fixed to rotate with saidirotor, said impeller having a'- plurality of spaced abrasive discharge ports in the tubular side wall thereof, each of said ports having the side edges thereof positioned between 4the channel confines of the adjacent blade, said ports being relatively short in peripheralextent,

a feed spout for conducting abrasive into said tubular impeller, an arcuate shaped deflector plate extending into said impeller and overlapping a limited arcuate section of the tubular side wall of said impeller and covering the ports in said section whereby the discharged abrasive will -be directed through certain of the uncovered discharge ports in said impeller, a normally stationary supporting plate positioned exterior to said impeller and having an aperture through which the discharge end of said feed pipe extends, and

means associated with said supporting plate and 1 said deector plate for adjustably securing said deilector plate to said supporting plate.

7. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, va rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positioned Within said central space xed to rotate with said rotor and operative to retain abrasive therein for a sulcient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof equal in number to the number of blades carried by said rotor, said ports being relatively short in peripheral extent and positioned slightly in advance of their corresponding blades, a feed spout for conducting abrasive into said tubular im-peller, and an arcuate shaped deilector section extending into said impeller and covering a limited -arcuate ported section of the tubular side wall of said impeller whereby the discharged abrasive will be directed through certain of the uncovered discharge ports in said impeller. 8. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positioned within said central space and having a tubular side wall and a closed rear end wall fixed to said rotor head to rotate therewith and operative to retain abrasive therein for a suiiicient interval to transmit to the abrasive al the tubular side wall thereof, a feed 'spoutr for conducting abrasive into said tubular impeller, an arcuate shaped deilector plate extending into Asupporting plate.

9.'A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, an impeller positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein -for a suflilcient interval to transmit to the abrasive a centrifugal speed corresponding tothe speed of rotation of the impeller, said impeller having a tubular side wall comprising a generally tapered the ports in said section, said control device being operable to direct the abrasivethrough certain of the uncovered discharge ports of said impeller and into the path of rotation of the inner ends of said blades during a predetermined limited arc of rotation thereof.

l0. A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a said impeller and into the path of rotation of the rotor and operative to retain abrasive therein for a sumcient interval to transmit to the abrasive a centrifugal speed' corresponding to the speed of rotation of the impeller, said impeller having a tubular side wall comprising a generally tapered side wall portion and a generally cylindrical side wall portion adjacent the inner ends of said blades, said cylindrical portion having a plurality of spaced abrasive dis- Charge DOI'S therein. deflecting elements fixedl l to the interior of said tapered side wall portion for guiding the abrasive to the discharge ports thereof, and a normally stationary control device having an arcuate shaped side wall portion extending into said impeller and covering a limited number of 'the ports in said impeller, said control device being operable to direct the abrasive through certainv of the uncovered ports of inner ends of said blades during a predetermined limited arc of rotation thereof.

l2. A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a -predetermined limited are including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending predetermined limited arc including in combinathe inner ends of said blades extending inwardly short of the axis of rotation of the; rotor to provide a central space, an impeller positioned within said central space ilxed to rotate with said rotor and operative to retain abrasive therein for a sutilcient interval to transmit to the abrasive a centrifugal vspeed corresponding to the speed of rotation of the impeller, said impeller having a tubular side wall comprising a generally tapered side wall portion and a generally cylindrical side wall portion adjacent the inner ends of said blades. said cylindrical portion having a plurality of spaced abrasive discharge ports therein, and an arcuate shaped deiiector plate extending into said central space and interiorly covering a limited arcuate ported section of the tubular side wall of said impeller whereby the discharged abrasive will be directed through certain o f the uncovered discharge ports in said im-peller.

1l. A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of s paced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the -axis of rotation of the rotor to provide a central space, an impeller positioned within said central space fixed to rotate with said inwardly short of the axis of rotation of the rotor to provide a central space, a generally tubular shaped impeller having a closed end wall and a tubular side wall positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein for a sumcient interval to transmit to the abrasive a centrifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof equal in number to the number of blades carried by said rotor, an abrasive supply spout for conducting abrasive into said tubular impeller, a spiralling rib extending around the innei end of said feed spout for deilecting the abrasive for discharge substantially through the full axial width of said'discharge ports, and a normally stationary control device comprisinga baille plate extending into and covering a limited number of the ports in said impeller operable to direct the abrasive through certain of the uncovered ports of said impeller and into the path of rotation of the inner ends of said blades during a `predetermined limited arc of rotation thereof.

13. A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends ofsaid blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a generally tubular shaped impeller having a closed end wall and a tubular side wall positioned within said central space fixed to rotate with said rotor and operative to retain abrasive therein for a sumcient interval to transmit to the abrasive a cen- .trifugal speed corresponding to the speed of rotation of the impeller, said impeller having a plurality of spaced abrasive discharge ports in the tubular side wall thereof equal in number to the number of blades carried by said rotor, an abrasive supply spout for conducting abrasive into said tubular impeller, a spiralling rib extending around the inner end of said feed spout for defiecting the abrasive Afor discharge sub'- stantially through the full axial width of said discharge ports, and an arcuate shaped deflector plate extending into said central space and interiorly around a limited arcuate ported section of the tubular side wall .of said impeller whereby the discharged abrasive will be -directed through certain of the uncovered discharge ports in said 4 impeller.

14. A centrifugal blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced radially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of'rotation of the rotor to provide a central'space, a generally tubular shaped impeller having. a closed end Wall and a tubular side wall positioned Within said central space fixed to rotate with said rotor and operative to retain abrasive therein -for a suiiicient interval to transmit to the abrasive a centrifugal speed a spiralling rib having atapering periphery extending around the-inner end of said feed spout for deflecting the abrasive for discharge substantially through the full axial width of said discharge ports, and-a control device having an yarcuate shaped deilector section extending into directed through certain of the uncovered discharge ports in said impeller.

15. A centrifugal abrasive blasting machine operable to throw a concentrated stream of abrasive over a predetermined limited arc including in combination, a rotor head mounted for high speed rotation having a plurality of spaced ra.- dially extending abrasive throwing blades supported thereby, the inner ends of said blades extending inwardly short of the axis of rotation of the rotor to provide a central space, a tubular impeller positioned within said central space and having a tubular side wall anda closed rear end wall xed to said rotor head to'rotate therewith, said impeller having a plurality of spaced abrasive discharge ports. in the tubular side wall thereof, an abrasive. supply spout for conducting abrasive into said tubular impeller, and a normally stationary abrasive control device having an arcuate shaped wall portion extending intosaid impeller and overlapping a limited arcuate section of the tubular side Wall ofsaid impeller and covering the ports in said'` section, said control device having means operable to direct the abrasive through certain of the uncovered p orts 'of said impeller and into the path of rotation of mined limited arc of rotation thereof.

CHESTER E. UNGER.