US2358322A - Blasting machine - Google Patents

Description

Sept; l9, 1944. 'J. E. FOSTER BLASTING MACHINE Filed A ril 18, 1942 3 Sheets-Sheet l Sept. 19, 1944. J. E. FOSTER BLASTING MACHINE Filed April 18, 1942 3 Sheets-Sheet 2 v INVENTOR. dc/4 as E. Fosrsx? Patented Sept. 19, 1944 UNITED STATES PATENT OFFICE (Granted under the act of. March 3, 1883, as amended April 30, 1928; 3'10 0. G. 757) 12 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to blasting machines, particularly intended for projecting an abradant material, such as shot or grit or the like, in a predetermined direction.

One object of my invention is to provide a blasting machine of the centrifugal type, in which an abradant material is supplied to the machine and is then centrifugally accelerated and projected by and from the machine in a definite pre-selected direction.

Another object of my invention is to provide a blasting machine of the centrifugal type in which the directional control may be easily and readily established by controlling the point of feed of the abradant material to an accelerating and throwing part of the machine, such as a radial slinger blade. 7

Another object of my invention is to provide a method of and a structure for feeding the abradant onto an accelerating surface of the machine, in such manner that the abradant will approach the accelerating surface in a curved path that will engage the accelerating surface relatively smoothly and substantially tangentially, so the wearing efiect of the abradant particles on the accelerating surface will be a minimum.

Another object of my invention is to provide a blasting machine of the foregoing character, in which the feeding of the abradant material may be easily and variably controlled by the operator, to vary both the position and the quantity of feed, so the quantity of the blasting material will be subject to the control of the operator, without excessive changes in the structural assembly of the machine.

Another object of my invention is to provide a blasting machine in which measured quantities of the abradant material may be supplied to the projecting or throwing part of the machine, for projection by the machine at a pre-determined point.

One modification of a blasting machine, that is contructed in accordance with the principles of my invention, consists of a rotatable head or rotor shaped like a wheel and provided with several radially disposed slinger blades. lhe outer ends of the slinger blades are open and the blades are held in, fixed position on a rotor disc or spider. The abradant material is supplied to the inner end of each slinger blade when that blade reaches a pre-determined position in its cylinder.

path of travel, so the abradant material, will be accelerated and projected and discharged from the outer end of that blade when the blade moves through a pre-determined angle beyond the position at which the abradant material has been supplied to the plate. Since the centrifugal force acting on the abradant material, to move the material along the surface of the projecting plate, is relatively constant, the time interval required for the abradant material to move from the inner end of the plate to the outer or projecting end of the plate will be uniform. By co-ordinating such time interval of movement of the material along the plate with the angle through which the plate will move in the same period of time, the abradant material may be supplied to the inner end of the blade at the proper angle in advance of the line of projection, or discharge, to ensure that the abradant material will be thrown from the rotor at the proper point. 4

The abradant material is fed to the inner ends of each of the radial slinger blades by a distributor through which themachine is supplied with the abradant material. The distributor consists of a cylinder disposed like a hub, con;-

centrically near the inner ends of the blades. The innerends of the blades do not touch the cylinder, as a hub, however. The'cylinder is provided 'with several passages or openings through the cylinder wall, one passage being adjacent the inner end of each of the blades. The transfer of abradant material, through each of those openings, to the associated slinger blade, is controlled through a valve, at the proper predetermined position.

In this case each valve consists of a pivoted roller nested in a longitudinal groove in the outer surfaceof the cylinder, and communicatingwith the transfer opening through the wall of the The roller is provided with two co-- aXial end journals that are supported for rotation in two end bearings that are mounted on the outer surface of the cylinder. 7

The roller is provided with a longitudinal groove, or pocket, atone zone in its periphery, where the pocket will communicate with the slot in the cylinder, when and While the roller is in normal or loading position. When the roller is,

turned to unloading position, the pocket is moved away from and out of communication with the slot.

to a slinger blade, the roller of the corresponding associated valve is turned through a suflicient angle to shift the roller pocket away from the slot and to unloading position, at which the abradant material in the pocket is spilled over the edge of the roller pocket in response to centrifugal force, and the abradant material then falls'onto the slinger blade.

The angular movement of the roller of the valve is controlled through a bell-crank that is also pivotally supported on the outer surface of the cylinder. a fork secured on the roller shaft, and'serves to move the roller to either of its operating positions, that is, either to normal loading position, or to operated unloading position.

The other arm of the bell-crank carries a magnetizable plate at its end, so disposed that the plate will pass adjacent to an energized e1ec tro-magnetic core structure. When the plate moves into the effective magnetic flux field 'of the electro-magnet, the plate is attracted by the magnet, and is so held as to be retarded momentarily. Such momentary, retardation of that arm of the bell-crank imparts an angular movement to the bell-crank to turn the valve roller through an angle sufiicient to move the roller from loading'position to unloading position, and

thereby to spill or feed the abradant material in the pocket of the roller onto the inner end of the associated slinger blade. 7

When the armature plate at the end of the bell-crank is moved out of the effective magnetic flux 'zone of the electro-magnet, by the continuing rotation of the rotor, centrifugal force acts on the fork-and on the operating arms of that valve, so the abradant particles discharged by the roller will move through a curved path onto the blade with a relatively smooth continuous movementthat approaches the surface of the slinger blademore or less as a tangent to the curved path of the abradantmaterials.

Figure 1 is a side view, particularly inrelevation, and partially in section, of a blasting machine rotor' embodying this invention;

Figure 2 is an enlarged longitudinal vertical sectional view, partially in elevation, and with parts broken away, to show the distributor on the rotating head of the blaster, and the stationary support for the control electro-magnet;

Figure 3 is a plan view of the electro-magnet core structure showing the location of the control armature;

One arm of the bell-crank fits into of the valve roller with a portion of the valve roller and of the distributor cylinder broken away, to show the shape of the pocket in the roller, and its relative disposition adjacent the slot in the cylinder; and

Figure 9 is a transverse view of the cylinder and the roller, with the roller shown in loading and in unloading positions, to illustrate the manner inwhich the discharged particles'from the roller move in a curved path onto the slinger blade.

As shown in the drawings, a blasting machine I I], constructed in accordance with the principles of my invention, is shown as comprising, briefly, a rotatablehead or rotor I I, mounted at one end of a drive shaft I2 that is supported, for rotation, between two supporting bearings I3 and I4. The drive shaft I2 is provided with a suitable driving pulley I 5 at the other end of the shaft, by means of which the shaft may be driven from any suitable source of motive power, to rotate the shaft and the rotor at high speed. I

The rotatable head. I I comprises briefly a spider, or back disc plate I6, provided with a hub I1 by means of which the disc plate may be keyed to the drive shaft I2 with a suitable means such as a key I8. The disc I6 carries several slinger blades 20 that are radially disposed on, and

fixedly secured to, the disc I6, by anchoring plates 2| that are bolted to the disc I6 to hold the slinger blades in place by fitting over edge flanges 22 on the edges of the blades 20 that rest against the disc I6. The anchoring plates are anchored to the disc I6 by bolts 23.

The drive shaft is driven at a relatively high speed to rotatethe disc I6 and the rotor slinger blades 20 at the same high angular velocity, in order to impart a high velocity to the abradant material by the time itis moved out. to the end of the respective slinger blades and projected and discharged by and from those blades in a predetermined direction, against an object or surface that is to be b1asted.

Figure 4' is an end elevational view, partially schematic, of the distributor cylinder, showing the valve rollers,the control electro-magnet for the valve rollers, and the slinger blades shown in part, to show their'relative location adjacent the valve rollers; Figure 5 is a plan development of a part of a roller, its operating arm, and the associated bellcrank;' 'Figure 6 is a partial and broken end View of a slinger blade showing its disposition on its supporting disc; 7 i 7 Figure '7 is an end elevational view of a roller bearing for a valve roller, asnested in a groove inthe distributor cylinder;

; Figure 8 is a transverse view through the'shaft' The accelerating surface 25 of each slinger blade '20 is relatively smooth and continuous, so the abradant material can move freely along the full length of the slinger blade without inter-' ference of any kind that would diminish the momentum of the accelerated abradant material,

and absorb some of the kinetic energy from that material. The free uninterrupted passage of the abradant matterial along the inner surface of the slinger blade tends to maintain a uniformity of traveling time interval of the abradant material on each one of the blades, so the discharge point will be uniform and constant on the several blades, when the several blades are fed with the abradant material at the same point on the orbital path traversed by the inner ends of those blades.

The abradant material is fed to the inner ends of the blades 20 by and through a distributor 30.

As shown in the drawings, the distributor 30 comprises a supply cylinder 31 co-axially secured to the end of the drive shaft I2 and concentrically disposed in a centrallopening on the rotor adjacent the inner ends of the slinger blades. The distributor cylinder 3I is provided with four slotted openings or transfer passages 32, 33, 34, and 35. The transfer passages from 32 to 35 inclusive are equally spaced around the periphery of the cylinder, each passage being located in the zone generally adjacent but slightly in advance of the inner end of an associated slinger blade or plate- 20.} Each'slotted passage 32 to 35 is sub;

stantially rectangular in cross-section andhas substantially straight radial side walls to permit the abradant material to move readily through those openings from the inside of the cylinder 3|. The outer surface of the cylinder 3| is also provided with shallow fluted grooves 36 to 39, inclusive each axially and symmetrically aligned with the corresponding slotted transfer passage 32 to 35 inclusive. The shallow grooves 36 to 39 are of greater length than the slotted transfer passages 32 to 35, but less than the full length of the cylinder 3|.

The fluted grooves 36 to 39,.inclusive, are respectively provided to receive a control roller 48 which serves as a control valve to transfer a measured amount of abradant material from the cylinder distributor to its associated radial slinger plate 28.

The roller 40- is provided with two end shafts or journals 4| and. 42, and with a long recess or pocket 43 at a central region on its peripheral surface. The pocket 43 is substantially triangular in cross-section, and the length of the pocket 43 is less than the length of the roller body, but

is preferably greater thanthe length of any of the slotted transfer passages 32 to 35, through the wall of cylinder 3|.

The roller 46 and the arcuate or fluted groove surface 36 in. the cylinder wall are concentric so the roller will substantially nest or seat itself in the groove 36.

Each roller 4!) is mounted for angular movement on the distributor cylinder 3|, and is supported on the distributor cylinder 3! between two ball bearings 44 and 45 that are anchored to the cylinder 3| by suitable anchoring straps 41 and 48. The straps 41 and 48 may be welded to the cylinder 3| or secured thereto by bolts.

In order to impart a turning movement to the roller 48 to move the pocket 43 from its normal loading position, where it communicates with the transfer passage 32, to its unloading position, at which the pocket 43 will be separated and disconnected from the transfer passage 32, an operating fork58 is keyed to roller shaft 4|.

The operating fork 58 is illustrated briefly as comprising an upper housing section 5| and a lower housing section 52 respectively provided with fork arms 53 and 54. The two body sections 5! and 52 of the fork are clamped together by bolts 55 and 56 and keyed to the shaft 4| of the roller" by a key 51.

The fork 58 is arranged to be operated by means of a bell-crank 68, having an operating arm 6|, and a control arm 62. is pivotally supported for its angular movement, between two spaced side walls 63 and 64 of a bracket 65, that is provided with a base 66 that is suitably secured to the distributor cylinder 3|, either by Welding or by bolts 61.

The operating arm 6| of the bell-crank 68 is provided with a small fork 68 that supports an anti-friction roller or roller bearing 69 on a small pivot shaft 18.

The roller or roller bearing 69 fits in the fork 50 on the shaft of the valve roller 46. Whenthe valve roller 40 is in normal loading position, with its pocket communicating with the transfer pase sage through the wall of the distributor cylinder 3|, the fork 50 and the bell-crank 68 will be in the position shown in Figure 4, in their respective outermost limit positions.

Disregarding friction for the moment, the valve roller fork 50 and the-bell-crank arm 6| will be biased towards their outermost positions by the The bell-crank centrifugal force developed during rotation of the rotor and the distributor cylinder. In order to limit the outward movement of the fork 50 and of the bell-crank arm. 6|, a stop lug 1| extends from the walls'of the bearing bracket 65, for the bell-crank pivot shaft, to serve as a stop to define the outer limit positionof the bell crank arm 6| slightly behind the radius line from the center axis.

of the distributor cylinder 3|. through the axis of the bell crank. I

The outer end of the bell-crank arm 62 carries a magnetizable plate 15 that is to serve as an armature to be attracted by an adjacent control electro-magnet 1'6. The armature plate 15 is symmetrically supported on the bell crank arm 62, and the center of gravity on the bell-crank'arm 62 and the plate 15 is therefore also behind the radius line from the center of the rotor distributor axis through the pivot axis of the bell-crank. Consequently, during rotation of the rotor, centrifugal force further tends to turn the bell-crank to move the'bell-crank arm 6| to its outermost position, and thereby move the valve. roller '40 to loading position.

r The control electro-magnet 16 is shown as comprising a magnetic core structure 11 of substantially U-shape with an energizing coil 18. The core structure 11 has two pole faces Biland 8| that are separated by an air gap 82. The two pole faces and 8| are partially recessed to embody inwardly facing shoulders 83 and 84 that are to be directly underneath the armature plate 15 at the end of the bell-crank during rotation of the rotor. The air gap' space between the lower or outer surface of the armature'plate 15 and the shoulder surfaces 83' and 84 of the electro-magnet may thus be made'relatively small.

The two faces also embody the outer side walls 85 and 86 at the outer edges of the shoulders 83 and 84. The space between the inner wall surfaces of the side walls 85 and 86 is slightly larger pivotal than the corresponding dimensions of the armatureplate 15 when the armature plate is moved through that space at the endof the bell crank, during rotation.

By means of the shoulder and side wall arrangement, a magnetic attractive force is impressed upon the armature plate 15 irrespective of its position during its turning movement on its pivotally supported bell-crank.

In order to permit sufficient clearance between the armature plate 15, at the end of the bellcrank, and the shoulder surfaces 83 and 84, the electro-magnet is spaced a suflicient distance away from the main axis of rotation of the rotor to be free of the armature plate 15 when the armature plate is in its furthermost radially extended position.

The angle through which the bell-crank must be moved, by the retarding magnetic friction force of the electro-magnet on the armature plate 15, depends upon the angle through which the valve roller must be turned, to shift the pocket on the roller from the normal loading position of the valve to its unloading -position, at which the abradant particles are released from the pocket of theroller to move onto the adjacent surfac of theslinger blade.

As shown in Figure 9, when the valve is in the normal loading position, the bottom or lag ging surface of the pocket in the valve roller is inclined-slightly upwardly from aline through i the bottomcorner of the pocket and parallel to -a tangent to the cylinder 3!.

In order to permit the abradant materials or particles to fall free from the pocketonto the slinger blade, when the valve is moved to unloading position, the roller should be moved through a sufficient angle to bring the bottom surface of the pocket to an angle below the tangent parallel, as shown in Figure '9.

c -That angle constitutes the operating angle of the valve and determines the angle through which the fork 50 must be moved by the bell-crank to establish a desired operation of the valve to feed abradant to a slinger plate.

Since turningmovement of the fork will tend to turn the upper fork arm 53 towards the cylinder surface, which would limit the-fork movement, the initial or normal positionof the fork during the loading operation of the valve will be somewhat underinclined from the horizontal line to the valve roller axis, when the line between the valve axis and the rotor axis is considered vertical. 'of the valve roller and'the pivotal axis of the The distance between the axis which the particles may move with a minimum of friction in response to the centrifugal force that is moving them outwardly along the slinger plates surfaces.

Each slinger blade or plate is supplied with the abradant material from its'own valve, and, in order to reduce attrition of the plate to a minimum, each plate is mounted a short distance behind its valve so the trajectory of the abradant particles, whenthey leave the valve'roller, will approach the slinger blade surface as an asymptote or substantial tangent. I 7

For that reason, it is alsotherefore preferable to supply the abradant particles at a zone of low speed, which is the center of rotation, and then to feed the abradant particles from the central low-velocity zone of the rotor onto the slinger blades or plates, in the same general direction which those particles are to take as they are fed to the plates for acceleration and projection. By means of the construction illustrated, each valve roller is provided with a substantially measured amount of the abradant particle to be supplied to each slinger blade during each opera tion. The dimensions of the pocket may be varied according to the quantity or volume of each charge that it is to be supplied to each blade. In order to permit easy rotation of the roller 7 of the valve to unloading position, the pocket in the roller is made somewhat longer on both sides than the slot in the cylinder wall, and the pocket is centrally located relative to transfer passage 32 in the cylinder wall, through which the abradant material is supplied to the pocket of the valve. Consequently, when the valve roller isturned through the'small angle to unloading position, someof the abradant particles in: the

pocket shift over towards the ends of the pocket and remove the sustaining pressure from the central portion'of the charge of abradant in the middle zone of the pocket.

In order to control the point at which the valve rollers will be operated to discharge the quantity of abradant material in each pocket, the electro-magnet is mounted on a ring bracket that is concentric with the rotor. The electromagnet is adjustably mounted on the ring bracket 90 so it may be adjustably positioned on .the ring bracket, and then fixed in such position which the entire blasting mechanism is mounted.

The trough support 92 is also provided with a ring shaped bracket 93, that serves as a stationary hearing within which the ring bracket 99, for the electro-magnet, may be rotatably supported, for short angular adjustments of the supporting co-axial shaft 9|, by means of a handle 94 on the outer end of the shaft 9|.

When a substantial angular adjustment of the electro-magnet is desired, the entire bracket 95 for the electro-magnet is adjustably shifted on the ring bracket 9!}, and then securely tightened in place by a suitable bolt 91. v

For simplicity, the electro-magnet is shown as supported on a'shelf at the lower'end of the adjustable bracket 95 that is mounted onthe ring 90. Since the entire adjusting and supporting mechanism forthe electro-magnet is co-axially disposed with respect to the main cylinder distributor, any adjustment of the electro-magnet will keep it in proper position with respect to the armature plates associated with each of the valve rollers.

As shown in Figure 4, the inwardly extending shoulders on the side walls of the electro-magnet are concave and have a curvature that is concentric with the distributor cylinder, so the armature platesmay move freely between the two pole pieces of the electro-magnet.

As illustrated in Figures 8 and 9, the pocket in each roller, when in loading position, is directly underneath the slot'inthe distributor cylinder, so it may receive a charge of abradant material. When the cylinder is turned to unloading position, as shown in Figure 9, the abradant material spills out of the roller pocket in a trailing slip stream 99, in a substantially parabolic curved path, that approaches the accelerating surface of the slinger blade directly behind it,-with a smooth tangential contact.

By thus arranging the valve, slightly in advance of the slinger blade, so the material may be supplied from the valve to the slinger blade in a path of movement having substantially no component, or a very small component, in a direction perpendicular to the surface of the slinger blade, the effects of attrition of the abradant material on the slinger blade surfaces is reduced to a minimum.

As shown in Figures 4' and 6, the slinger blade 7 20 is arranged to be held in position on and against the main back disc plate l6, by the on the edge of the plate that rests against the disc. The radial edge surfaces, of the slinger blade 20, that is engaged by the anchoring plate 2I, may be slightly angularly convergent, with the corresponding surfaces or edges on the anchoring plate 2| divergent, outward from the center of rotation, so the slinger blades will be held by a wedging action between the anchoring plates 2I.

- As shown in Figure l, the abradant material is supplied to the distributor cylinder through a conduit 98 that constitutes the lower end of a feed hopper. This conduit 98 extends through the space in the trough 92 and then through the ring bracket 90 and the bearing bracket 93 to the distributing cylinder.

For extensive angular adjustments of the electro-magnet, the supporting bracket 95 for the electro-magnet may be loosened at the bolt 91, and the bracket 95 then adjustably shifted to substantially the position desired on the ring bracket 90, and the bolt then re-tightened to lock the bracket 95 in position on the supporting ring bracket 90. Finer angular adjustments of the ring bracket 90 may then be made to locate the electro-magnet, by means of the handle on the shaft 9| that is secured to the supporting ring bracket 90 on which the bracket 95 is secured. By such adjustable positioning of the magnet, the direction of the stream of discharged abradant may be controlled.

As shown in Figure 2, the distributor cylinder and the valve rollers are supported on the end of the main shaft 12 by means of a cylinder cap bracket I00.

The cylinder cap bracket I is provided with a portion IOI that fits over the end of the main drive shaft I2 and that is keyed thereto by a key I02. A similar cylindrical portion I03 extending in the opposite direction extends over one end of the distributor cylinder, and is secured thereto by suitable bolts I05.

The cylinder cap I00 is secured to the main drive shaft I2 by an anchor bolt I06 which is threaded into the end of the drive shaft I2, and presses against a pressure plate I01 that is concentrically seated on and against the center wall I04 of the cylindrical bracket I00. A lock washer I08 holds the bolt I06 against casual displacement.

As shown in Figure 1 and in Figure 2, the inner end edge of the slinger blade is spaced a short distance from the distributor cylinder, and a short distance behind the associated valve roller. With this arrangement the distributor cylinder and its control rollers may be handled as a unit for assembly and for removal, if necessary.

As is shown in Figure 1, the edge 20a of the slinger blade is spaced sufiiciently from the main rotor disc IE to bring that edge 20a out far enough to receive all of the abradant material that is spilled out of the pocket of the valve roller.

My invention is not limited to the specific details of construction that are illustrated since various modifications might be made in those various details without departing from spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. A blasting machine comprising a rotor having a plurality of radial slinger blades; means for supplying abradant particles to the machine; and means individually associated with each blade for measuring out a quantity of the abradant particles and for feeding those measured particles to the associated blade; and electro-magnetic means adjustably positionable adjacent the rotor to operate the feeding means at a pre-determined point, thereby to control the zone of discharge from the blades.

2. A blasting machine comprising a rotor having a plurality of radial slinger blades; means for supplying abradant particles to the machine; a distributor including a central cylinder, concentric with the radial blades for receiving the particles, and spaced valves on the cylinder, one valve for each blade, fortransferring particles from the cylinder to the associated blade; and electr c-magnetic means adjustably positionable to operate the valve to feed the particles to the blades at a selected point of the pathof the blades.

3. A blasting machine comprising a rotor having a plurality of radial slinger blades; means for supplying, abradant particles to the ma chine; a distributor including a central cylinder concentric with the radial blades for receiving the'particles, and spaced valves on the cylinder, one valve for each blade, for transferring particles from the cylinder to the associated blade; each said valve comprising a roller with end shafts, the roller being pivotally supported and being seated in a longitudinal groove of arcuate section on the outer surface of the cylinder, with a slot in the groove extending through the cylinder wall, the roller having a longitudinal pocket registering with the slot in the cylinder wall when the roller is in particle-receivingposi tion, and being out of communication with the slot when oscillated to unloading'position; bearings on the cylinder to support the roller for rotation; means normally biasing the roller to receiving position; and means for angularly moving the roller to unloading position.

4. A blasting machine comprising a rotor having radial slinger blades; 'a distributor cylinder concentrically disposed and secured to the rotor; the cylinder having, in its outer surface, adjacent the inner end of each blade, a longitudinal fluted groove with a shorter central radial slot through the cylinder wall; means for supplying abradant particles to the inside of the cylinder; and means for transferring abradant particles from the cylinder to each slinger blade, said means consisting of a roller to seat and fit into the fluted groove, the roller having a longitudinal pocket in its periphery to register with the slot in the cylinder groove and to receive a quantity of abradant particles while in such registering loading position, the roller being supported for angular movement to move the roller pocket to non-communicating unloading position and to permit the particles to be centrifuged out of the pocket onto the associated blade, to be thence accelerated and thrown by and from the blade;

means for pivotally supporting the roller; and 7 means for moving the roller to its loading and to its unloading positions.

5. A blasting machine as in claim 4, in which the pocket in the roller is substantially triangular in section, with one side of the triangle disposed to forma departing angle with a. tangent to the cylinder, when the roller is turned to unloading position.

6. A blasting machine as in claim 4, in which the roller-moving means include a pivoted arm supported on the cylinder and provided and adapted to turn the roller to unloading position;

and an electro-magnet for actuating the pivoted arm to turn the roller to that unloading position.

7. A blasting machine as in claim 4, in which the roller-moving means includea pivoted arm to turn the roller; an electro-magnet to actuate the arm; and means for adjustably positioning the electro-magnet to pro-determine the posi-, tion at which the arm will be actuated to turn the roller to unloading position, to feed abradant to the associated slinger blade.

8. A blasting machine as in claim 4, in which the slot in the cylinder groove is shorter than the pocket in the roller to provide over-flow spaces for the charge of abradant in the pocket, when the roller is turned to move its pocket froin the slot.

9. A blasting machine comprising a rotor for projecting an abradant material centrifugally at high velocity from several spaced peripheral zones; a central cylindrical container for receiving a supply of abradant material, and secured to the rotor to rotate with it; auxiliary vessels for receiving a quantity of the abradant from the container; and electro-magnetic means for tilting the vessels for transferring all or part of such quantity to the rotor at a pre-determined position of the rotor to enable the abradant to be shifted to, and thrown from, the peripheral zones of the rotor, at a pre-determined point in the peripheral path.

10. A blasting machine comprising a rotor having means establishing several spaced passageways from th center of the rotor to the periphery; a cylindrical container concentrically disposed in the center of the rotor and secured to rotate therewith, said container having openings through its wall to feed the several spaced pas-.

sageways in the rotor; means for supplying abradant particles to the container; and means pivotally supported on the outer surface of the container and movable to a loading position to receive a quantity of particles from the container, and movable to supply the particles to the passagewayswhile closing the feeding openings; means biasing the pivoted means to loading position; and means adjustably positionable to shift the pivoted means to unloading position.

11. A blasting machine comprising a rotor having a plurality of radial slinger blades spaced to provide a central opening; a distributor consisting of a cylinder concentrically disposed in the opening to receive a supply of abradant particles to be fed to the blades; an orifice in the cylinder wall adjacent the inner end of each blade; a valve for the orifice, said valve embodying an element pivotally supported on the cylinder on an axis parallel to the cylinder axis; and means to operate the valve element through a small angle to an unloading position to permit some abradant particles to pass out through the orifice while controlling the orifice to limit the passage of abradant therethrough, said operating means consisting of a pivoted bell-crank on the cylinder, the bell-crank having one arm disposed to turn the valve through said angle and having the other arm normally extending in a general radial direction from the main rotor axis, that arm being adapted to be operated, externally and independently of the rotor, through an angle to correspondingly turn the valve element to unloading position. 7

12. A blasting machine as in claim 11, in which an electro-magnet is providedrto be adjustably positioned adjacent the paths of travel of the outer end of the bell-crank to attract and to retard that end of the bell-crank, and thereby to apply an effective turning force that will oscillate the bell-crank through the desired angle to turn the valve element.

' JULIUS E. FOSTER.

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