US 2176577 A
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Description (OCR text may contain errors)
Oct. 17, 1939. L. L.. TIRRELL 2,176,577
SANDBLAST DEV-ICE Filed April 3, 1937 2 Sheets-Sheet 1.
L. L. TIRRELI.
sANDBLAsT 15EvIcE Oct. 17, 1939.
Patented Oct. 17, 1939 sANnBLssr nevica Leslie L. Tirrell, Benton Harbor, Mich., assigner to The Hydroblast Corporation, Chicago, lili., a
corporation of Illinois Application April 3, 1937, Serial No.113d,692
This invention relates to improvements in sandblast guns and more particularly to a sandblast gun that is operated by hydraulic pressure.
In the art of cleaning and abrading, it has been customary to use steam or air as the motive power for projecting the abrasive from a sandblast gun. The use of water or kother liquid, however, is more desirable than the use of steam or air since it costs less, prevents silicosis, effectively removes core sand from castings, washes back the used abrasive to a point where it can be collected and reemployed, avoids burning the surface being blasted; and provides better vision for the operator. 'Water or liquid, having higher surface tension and greater density than-air or steam, also provides a more forceful and easily Acontrolled stream. In the past, the use of water has generally been regarded as impractical, since a large amount of water has been required to project a relatively small amount of abrasive. This is because a stream of water projecting from one jet to another through a sand injection chamber in the gun is not easily penetrated by the abrasive particles. Consequently, only a small amount of abrasive is incorporated into the liquid stream.
The principal object of this invention is to provide a practical method for driving the abrasive particles into the liquid stream. A further object is to provide a method in which a small solid stream of water under high pressure can be employed to project a relatively large amount of abrasive. Other objects and advantages willA appear hereafter in this specification.
I have found that a very small substantiallysolid stream of water or other liquid when employed under sufciently high pressure, can be kused to project a relatively large amount of abrasive, provided the abrasive can be driven into 40 the stream. This I accomplish by so proportioning and shaping the mixing chamber that the abrasive particles mixed with air are rotated at high velocity and are thereby driven into the liquid stream by the resulting centrifugal force. The air in this mixture becomes incorporated with the water stream and aids the entry of the abrasive particles thereinto in a manner to be described.
For the purposes of illustration, I have shown one form of apparatus in which the method may be satisfactorily used. This apparatus is shown in the accompanying drawings, in which the various parts are always designated by the same gg numerals throughout the several views.
Fig. 1 ls a longitudinal sectional view of a gun embodying this Inventiom- Fig. 2 is an elevation of the gun connected to a feeder in a sand bucket, the bucket being shown in section; 5
Fig. 3 is a partial sectional view of the sand feeder;
Fig. 4 is a partial sectional View of an alternative sand feeder; and
Fig. 5 is a partial sectional view of another l@ alternative sand feeder.
Fig. 6 is a fragmentary sectional view of a portion of the gun shown in Fig. l and includes a .erresentation of the liquid jet and abrasive parc es.
In the drawings, the gun 5 consists of a tube made up of the axially aligned sections I0, I2, I4, I6 and It. Within this tube are a nozzle 20, ,a chamber 22, a nozzle 24, and a water valve 26.
The nozzle Isof substantially cylindrical 90` section with a tapered axial hole 28 extending therethrough. 'I'his hole 28 is smallest at the forward end and increases in size gradually as it extends rearwardly until it reaches a point near its rear end from where it flares outwardly g5 to the periphery of the nozzle. 'I'his nozzle 20 has an external annular ridge 30 that is clamped between the sections I0 and I2 of the nozzle casing when they are screwed together,
The nozzle casing consists of the two sections I0 80 and I2 which when fitted together form a sleeve with an axial hole 32 to iit the nozzle 20 and an annular groove 3d to hold the ridge 30, so
. that the nozzle 2@ will not be forced from the gun by the projected abrasive and water mixture. 85
Behind the nozzle 2l! is the section I4 containing an annular recess 22 that is largest at a point near its center and is rounded inwardly toward bothends, so that it is of less diameter at its ends than in the center. 4@
Into the lower side of this chamber 22 the` abrasive is brought through the nipple 36, which is connected to the sand hose 38.
Fitted to the rearward side of the section I4 is the bushing I6 provided with an internal thread into which is fitted the rear nozzle 24. Extending rearwardly through` the bushing I6 is a water passage 42.
The rear nozzle 26 has a cylindrical opening 4d therethrough which cones outwardly and rearwardly from a point 46 near its center. 'Ilhe external forward face tof the nozzle 2 substantially continues the curve of the chamber 22, so that the inside surface of the chamber 22 plus 5g the contiguous surface 68 of the nozzle 26 fe a modlned toroidal surface.
The bushing i6 is joined' at its rearward end to section i8 which contains a rearwardly extending recess 52 containing a valve 2@ which is of well known construction; extending obliquely outwardly from the recess 52 is a. water inlet passage 56 provided with a thread 5@ at its outward end for attaching a water hose 6d. Near the forward end of the section i@ is a valve seat t2 against which is forced a valve washer t@ when a knob 65 is turned to the right, thereby cutting oif the flow of water through the gun.
The sand hose 38 is connected to a feeder @8 which consists oi a sand pipe i@ joined to the hose and extending for an inch or two into some sand 12 in a barrel 18. Fastened to this pipe 1li is a tube 1t which is open to the air at the top and extends through an opening 11 in the sand pipe 10 at a point near its lower end. The lower end of the tube 16 is approximately one-half inch from the bottom of the pipe 1t.
Since in operation the part of the tube i6 that is inside the pipe 'i0 is cut away in time by the abrasive particles, I prefer to join the two together by clamps or friction tape, so that the tube 16 can be easily removed from the pipe 1@ and a new tube substituted.
In Figs. 4 and 5 are shown two alternate feeders that may be substituted for the above described feeder 6B. Both of these alternate forms have a sand pipe connected to the hose 38 to supply sand thereto, and differ from the feeder 68 only in the manner in which air is mixed with the sand particles.
In Fig. 4 a sand pipe 18 is surrounded by a sleeve 18, the inside diameter of which is somewhat larger than the outside diameter of the pipe 18. The sleeve 19 projects about one-half inch below the end of the pipe i8 and is secured in spaced relation thereto by means of bolts 80, nuts 8| and spacing washers 82, thus providing an annular space 83 for the passage of air.
In Fig. a sand pipe 85 is provided with a tube 86 open to the atmosphere at the top and which extends downwardly along the pipe 85 and at the end thereof is curved inwardly and upwardly so that the opening 81 of the tube faces upwardly and is about one-quarter inch below the surface of the pipe.
When it is desired to operate the apparatus,l
the gun is connected to a relatively high pressure water supply, in the nature of '100. pounds per square inch, and to the sand hose 38. The feeder 68 is thrust into the sand 12 about an inch or so.
When the valve 26 ls opened by turning the knob 66, the water ows through the chamber 56, around the valve 26, and into the passage 42. As illustrated in Fig. 6, the water passes through the opening 44 in the nozzle 24 and comes out as a jet moving at great velocity. This -jet of water passes through the abrasive injection chamber 22 and the front nozzle opening 28.
Since the nozzle opening 44 is cylindrical, the
water passing therethrough will encounter con-` siderably more friction along the surface than in the center. This friction causes the surface of the jet to be retarded with respect to the center, thereby causing the jet of water to expand as it passes through the chamber 22, and produce a depression therein and within the sand hose 38. Consequently air will ow downwardly through the tube 16 and into the sand pipe 10. This jet of air strikes the sand at the lower end of the pipe and agitates it. The air then ows up atraer? inside of the pipe 1B to the gun, carrying the sand along insuspension. Because of the resistance oiered to the now of air by the tube 16 and by the weight of the sand particles in the pipe 10 andA hose 33, the air enters the chamber 22 in a rareed condition.
If the sand feeder shown in Fig. 4 is used, the operation is similar to that described above, ex-
. cepting that here the .air iiows downwardly are desired, or if the sand must be lifted a greatV distance.
As illustrated in Fig. 6, when the sand and air strike the water stream in the gun, the particles lsuch as 90 are driven forwardly, then outwardly,
then rearwardly, and then inwardly, as indicated by dotted arrows Si. This is, the particles travel at a high speed which is dependent upon or proportional to the jet speed and in smoke-rng like manner. The centrifugal force produced by this movement of the particles is in substantially the direction illustrated by the arrows such as 92 and drives the sand particles into the liquid stream.
Since these abrasive particles are moving much more slowly than the water stream at the instant of impact, their inertia causes them to resist the accelerating force of the stream. Consequently, as each particle strikes lhe jet of water and is accelerated up to jet velocity, it causes a partial vacuum to be formed on the side of the particle toward the front of the gun. The many small vacuum spaces thus formed are in turn lled by the rareed air which has been brought into the chamber 22 along with the sand. As the stream of water continues through the chamber 22 these pockets or bubbles of rareed air provide an easily penetrable surface for additional sand particles, and likewise, sand drawn into the nozzle 20 along the surface of the jet easily nds its way into the central portion of the porous stream. Therefore, as the jet of water flows through the chamber 22, it will be seen that abrasive particles are incorporated therein both by the centrifugal force developed and also by the filling of the rarefied air bubbles with the abrasive particles.
From the chamber 22 the homogeneous mixture of water, sand, and rareed air is projected from the nozzle 20 in the form of a jet which is highly eil'ective in cleaning and abrading operations.
As far as my knowledge goes, past attempts to use water as a motive force in an abrading gun have resulted in the failure of the abrasive to penetrate to the center of the stream. This is because the stream of dense liquid having suri'ace tension and under such high pressure presents a medium that is rather hard and that is not easily penetrated by the abrasive particles.
In accordance with my invention, and as illustrated in Fig. 6.a small stream under high pressure is provided, and the chamber 22 is so shaped that the abrasive particles carried in the rareed air travel at high velocity in paths similar to those in which particles travel in a smoke-ring. 'I'he centrifugal force acting upon the sand particles by virtue of their movement throws them into the stream. The stream also becomes pene-v trable because of the rareiled` air which is also taken in with the sand, as described above,l to form a homogeneous mixture of sand, water, and rareiled air in which a small amount of water carries a suitably large quantity of abrasive. 'I'his mixture when projected isl highly eilicient in cleaning and abrading surfaces both because can be'made therefore while utilizing the inven of its abrasive effect and because of the washing A properties of the water.y
While in the foregoing specification, I have given a preferredembodiment of my device and suggested certain pressures as desirable, it will be understood that the invention may be em ployedunder various conditions with changes in pressures to accommo'date the process to different classes of work. Also, it will be understood that the dimensions suggested are forthe purpose of illustration only, and wide variations tion.
The foregoingdetailedfdescription has been" given for the" purpose of clearness of understanding only, and no unnecessary limitations shoul be understood therefrom.
. Having described my invention, what 1' man as new and useful and desire to protect by Letters Patent is: f y
i1. A method for blast-treating a surface, comprising: passing a non-compressible liquid in a single confined stream and under a high pressure 'through a loading zone and thence to the sur face to be blasted, supplying granular abrasive by suction to said zone, transferring said granular 'abrasive from said zone intona-intimate mixture with said stream, the transference be- .air by the force of the jet 'centrifugal force, and and entrained granular abrasive as a second high 25 vdeveloped by rapidly moving said granular abrasive in vortex rings within the loading zone by the force of lsaid conned stream. 5
2.F The method of admixing abrasive with` a rapidly moving liquid stream comprising the steps of projecting the liquid stream, mixing abrasive particles with air, 4whirling the mixed'` abrasive particles and air in a space surround-jm ing' the projected stream to drive the abrasive particles and air into the liquid stream by centrifugal force to form a porous stream, and co1- lecting more abrasive particles in the open l spaces in the porous stream. 15 3. The method of projecting granular abrasive comprising the steps of mixing granular abrasive with'air, projecting water as a high velocity jet, whirling the mixture of granular abrasive andin planes passing through the axis of the jet in a coniinedspace l .surrounding said jet and at suiicient speed that the granular abrasive is thrown into the jet by reprojecting the water` velocity jet.
V4. The method of projecting grammar abrasive comprising the steps of projecting a highvelocity jet of fluid carrying medium through a conned space, introducing a mixture of granular abra- 30 sive and air into the said confined space, whirling th'e mixture of granular vabrasive and air within the ccnned space by the force of the jet and at a speed dependent upon the speed of the jet, so that centrifugal force throws the granu- 35 lar abrasive/into, the :|et, and reprojecting the fluid carrying medium and entrained granular abrasive as a second high velocity Jet.