US2652662A - Blast cleaning - Google Patents

Description

Sept. 22, 1953 F. NEWELL BLAST CLEANING Filed Nov. 5, 195o INVENTOR. F/P/M//f NEM/[M Patented Sept. 22, 1953 FrankNewell,l Chicago', Ill., assigner to Pagborn; Corporation,.Hagcrstown, Md., a corporation o1 Maryland ppicati-GiiNbv'emh'er 3, 1950, Serial N0. 193,903

1 rIhis invention relates te the cleaning otrmaterials and more particularly to a pressure bla-sting machine and method for projecting astream of soft abrasive particles or grit against ai surface! to remove superuous materials such as grease's, carbon and dirt therefrom- Soft'grit'iolasting of fragile electrical andY motor parts, etc., vas a means` of removing heavy, hard. coating of grease,` carbon, dir-t, etc., is of great interest to industry. The widespread trend tcward greater industrial plant safety hasv given impetus to`l the use of.so'ft Agrits' due to the toxic hazards ofv previouslyl used solventv typev chemicals'.. Typical soft grits arev celluloisc'- materials such as ground corn. cubs, wood particles'y (saw dust), riceA hulls,.- ground' walnut or pecan shells or' ground. pits of fruits Alike peach, apricot, etc., and are usually particles of about to e0 mesh or smaller.V

The use of prior art blasting equipment to blast theseusoft grits has not. been satisfactory, particularly with` the smaller sized particles which are more. desirable by reason ofthe better and more economical cleaning they effect. These particles do not feed themselvesproperly to the blasting mechanism` Whether pressure,` suction, gravity or combinations of these forces areused to carryl them to the. mechanism. Instead of moving smoothly the particles have -a tendencyI to bridge or pack (jam): in the passageway theyv move through. As azresult the: flow oi particles is cut off and, where the feeding; force isv large enough, the jammed particlesV suddenly break` loose in excessive amounts. Thisfeast-or-famine operation continues inl` short cycles. and` necessitates careful attention to assure thorough cleaning.

It is among the objects of this invention tof provideA an improved?. blasting machine and method for proiectinga stream of soft abrasives without the: above diniculties- Another.' object' of the invention is to. provide-V Va machine that willi allow a small flow of soft grit at high` pressure, or a heavy solid now ofv soft grit at low pressure for'cleaning; heavy grease or light oil lm'seiiiciently from: various machine with reference i tov f the lappended drawings whereinz.'

lig. 1A isi a" frontvie'w of. a pressure blasting.V machine of the presenti invention, yportions of ther.

machinev being; broken away to-show details,vv`

Fig. 2 is a plan View ci*` the machine shown in Fig. 1,:

Figs. 3 and 4 are vertical cross-section views of a mixing chamber portion of the machine of Figs. 1 andl 2`, thev chamber being shown Iinv different. operating positions, and

Fig. 5 is a vertical cross-section view at right anglesrto those of Figs. S'and. 4 of the mixing and projecting portions' or the apparatus of' Figs. 1 and2.

The machine o'i the iig'nrescomprises a tani: t@ for receiving and storing a quantity of abrasive particles.v The bottom portion ofthe tank le is in the `forni of a hopper. I2`having an opening ifi (see Fig. 5) forV discharging the abrasive. Agitating means te', consisting; preferably of a condui't f6 having a pluralityof' downwardly directed holes iB; extends withinK and across the tank iii for` discharging aplurality of; uid streams 2e into the abrasive holding` hopper i2 in order to' assure that the abrasive particles are uniformly discharged andy doi not` jam theu hopper i2 or the opening t4". This opening is' connected through an abrasivey control: valve mechanism i2? to" a mixing chamber' 21 where the particles dischargedfromI thel hopper are mixed with the propeliant fluidi in thiscas'e air. Mixing chamber22- has an opening 24i for'receivin'g'- a stream of air under pressure'ffor imparting" a projecting forceL upon' said abrasive particles discharged from* hopper t2", `and a dis'e'ha.1geV opening 25?: for directing they impelled stream` ci' abrasive particles andi a-ir (seefiig. 515

The; machine. sncvm in Figs. rana' a induces. a erst conduit `ai for delivering. uuid' to agitar-ieg.

' ber 22, and iromthenuidfsupply (not shown) respectively. A nozzle 134 is connected-.by an ado'litionalA conduit to2., `shown asa flexible hose, .to the. outflow opening 26 ofv chamber 22. The iiexiblei conduits are attached in place by any suitablexarrangement such as the wood screws Hill, or theelamps- HH.v Toprevent the. carrying baokof the'blasting particles to thefval-ves @dal a set of check valves 98, 99 are desirably inserted in conduits 30, 32:.

Thel` pressure; blasting 4.machine ofV Figs. i anc-1 2 is of the portable type supported on wheels 50, 52 mounted on axle 56 suitably secured to the tank Ill. Framework 54 also secured to the tank forms a stand to support the machine when it is rolled tothe desired position. This or an additional framework 55 can also be used to carry a coiled up length of hose |32 or a source of compressed fluid.

A funnel 66 is provided in the top of tank I6 for guiding the abrasive supply into a loading opening I3 in a concave top portion II forming the upper wall of the sealed-in tank storage space. A valve I1 seats in opening |3 for the purpose of opening and closing tank I to the flow of abrasive from funnel 60. Handle means is connected as by flexible cable 62 or chain to operate valve I1.

An abrasive control valve lever 13 is also provided at the top of tank I0 and connected through vertically extending rod 14 to arm 16 pivoted at 18 to the upper portion |23 of the abrasive control valve mechanism. |22. This portion is hollow and has an upper flange 92 clamped to a plate 94 at the bottom of the hopper, as by bolts |40, and a gasket |24 seals this joint. Member |23 tapers down at its lower end to a small tube 96 seated against a deformable rubber valve ring |05 held in a socket |06 in the upper portion of the mixing chamber 22. An upward movement of arm 16 moves a U-shaped clamp 11 about hinge 18 and compresses the valve ring forcing it from the open position shown in Fig. 4 to the closed position shown in Fig. 3. For regulating the required movement of U clamp 11 a. compression adjustment screw 83 is also provided. Modifications of this valve control mechanism can be made as indicated in U. S. patents numbered 2,025,247 granted December 24, 1935, and 2,146,917 granted February 14, 1939.

A clean out plate |36 fastened over an external opening |39 in hollow member |23 is made readily removable and carries a valve slider |31 (partly broken away in Fig. 1) which can be received in grooves |38 of enlarged portion |23 to shut off the supply of abrasive. The mixing chamber 22 can be removed from the tube portion 96, and when this is done it is advisable to first remove the plate |36, and then reverse and replace it so that slider |31 is in cut-off position. To improve the cut-off operation, the grooves |38 can be located against the upper wall of member |36 so that abrasive cannot flow out over the top of slider |31 and through opening |39 when the plate |36 is not fully seated. Such a construction is shown in the above-mentioned U. S. Patent No. 2,146,917. Plate |36 can also be removed to permit convenient inspection and cleaning of this member. An exhaust valve 2| for selectably opening tank I0 to the atmosphere facilitates its cleaning and opening when required. A capped handhcle 88 (Fig. 2) at about mid-tank height, enables the insertion of a hand or suitable cleaning or exploring tool into substantially all portions of the tank interior.

Mixing chamber 22 has a converging passageway |26 through which it carries the stream of fluid under pressure and in which is mixed the abrasive particles. This convergence which may be about 5 to 10 degrees assures that there is no blocking offset in the abrasive-carrying bore where the mixing chamber 22 meets the conduit A feature of the above machine is the maintenance of above-atmospheric pressure in the tank III) during the blasting. This is provided by the fluid under pressure that is admitted through conduit 30. To assist in controlling the pressures, meters 95, 96 are conveniently connected to the conduits 30, 32.

With a blast hose |32 having a one-inch diameter, a nozzle |34 having a 1% inch diameter, and an air source of at least 60 pounds per square inch, the following operational instructions have been found highly effective.

Setting of air control valves: Before loading abrasive into the tank,

(l) place lever 13 in closed" position.

(2) Pull handle 10 to out position, hold while turning on valve 44.v The slightest build up of pressure will hold the filling valve I1 in closed position, at which time the hand may be released from handle 1D.

(3) Adjust valve 46 to 6() lbs. per square inch.

(4) Hold the nozzle end of the hose |62 while adjusting valve 42 to 35 lbs. per square inch.

(5) Close valve 44.

(6) Open valve 2| which will exhaust the air from the tank, and permit opening of valve I1. After the pressure in the tank has come down to atmospheric, valve 2| is closed.

This completes preliminary setting of control valves, before abrasive is placed in the tank.

To fill the machine with abrasive:

(7) Check the interior of the tank for any foreign material by removing the bail and cap of handhole 88 and inserting a hand and arm into the tank and probing to determine if there is any refuse at the bottom of the cone. A flash light may also be used to see the interior. Replace all parts carefully.

(8) Handle 10 is pushed in so that the filling valve drops to its lowest position.

(9) Pour about 5 cu. ft. of abrasive into the top of the tank. The abrasive should not contain any coarse particles such as paper, match stems, lint from cloth bags, etc.

(l0) The blast hose |02 should be held by the operator for blasting, before the next operation.

(l1) Pull handle 16 to close the filling valve, hold until valve 44 is turned on.

(12) Turn valve 44 on which admits air to the tank and hose line. (Valves were set at preliminary setting.)

(13) When tankA pressure is up to 60 lbs. per square inch, the control lever 13 may be pulled down to open position.

Abrasive should now be flowing from the nozzle.

The gauges will show a differential pressure of approximately 5 lbs. per square inch, while blasting. The gauge on the tank pressure will be 45-50 lbs., and the gauge on the blast line pressure will be approximately 40-45 lbs. For soft abrasives it is necessary that the tank pressure be higher than the blast line pressure.

For pressures other than 60 lbs. per square inch, the dierential pressure will be in approximately the same proportion.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that this invention is not limited to the specific embodiments hereof, except as defined in the appended claims. Thus, the conduit I6 can be positioned in the hopper I2, and as far down as the lowest portion of the tank.

The height of the conduit is only limited by the ability of the available fluid pressure to effect agitation of the soft grits adjacent the tank bottom, and about two feet is the practical maximum. The directing holes I8 of the conduit need not be pointed straight down, but can be tilted about 80 degrees up in any direction, although the agitation produced with such a construction is not quite as eilicient.

What is claimed is:

1. A pressure blast machine for projecting a stream of soft abrasive particles, said machine comprising a tank for receiving and storing a quantity of said particles, the bottom portion of said tank forming a hopper in free communication with the upper portion of the tank for discharging said particles, a mixing chamber secured to said hopper for receiving said discharged particles, said mixing chamber having an opening therein for receiving a stream of luid, under pressure, for imparting a projecting force upon said discharged particles, and a blasting opening for receiving and directing said particles and said stream of fluid, tank pressurizing structure connected for introducing fluid under pressure into said tank, said structure including agitating means within said tank for discharging at least one stream of lluid, under pressure, into said hopper to agitate said particles, and iluid pressure regulating elements connected to said mixing chamber and controlling the iluid operating pressure under which the projecting fluid is received, and maintaining this pressure below that at which fluid is introduced into said tank to assure that the particles are uniformly discharged and do not jam in the bottom of the hopper, said tank including a first conduit for carrying fluid to said agitating means, a second conduit for carrying fluid to said mixing chamber, a third conduit common to both said rst and said second conduit for carrying fluid to each from a common supply of fluid under pressure, the fluid pressure regulating elements are connected at least in said second conduit, and the second conduit also has a check valve to resist the movement of particles from the mixing chamber to the pressure regulating elements under the influence of the high tank pressure.

2. In a method of blasting articles with finely divided soft abrasive particles, the steps of maintaining the particles in a container, injecting into the container a fluid under pressure to agitate the particles, supplying a stream of blastant fluid under a lower super-atmospheric pressure, mixing the agitated particles in the tank with the blastant stream at their respective pressures to cause the particles to be carried along with the stream, and directing said stream at the articles to be blasted.

3. A pressure blast machine for projecting a stream of soft abrasive particles, said machine comprising a tank for receiving and storing a quantity of said particles, the bottom portion of said tank `forming a hopper infree communication with the upper portion of the tank and terminating in an outlet through which it moves said particles, a mixing chamber secured to said outlet for receiving said moved particles, said mixing chamber having a supply line opening therein for receiving stream of fluid, under pressure, to impart a projecting force upon the particles received by the chamber, and a discharge opening for directing said particles and said stream of fluid, tank pressurizing structure connected for introducing uid under pressure into said tank, said structure including agitating means within said tank for discharging at least one stream of fluid under pressure into said hopper to agitate the particles therein, and a pressure regulating valve connected in said line to hold substantially fixed the projection-imparting pressure and maintain it below the pressure at which fluid is introduced into the tank, to assure that the particles are uniformly discharged and do not jam in the bottom of the hopper.

FRANK NEWELL.

References Cited in the flle of this patent UNITED STATES PATENTS Number Name Date 979,897 Steedman Dec. 27, 1910 1,297,223 Mott Mar. 11, 1919 '1,433,302 Rothchild Oct. 24, 1922 1,730,195 Davis Oct. 1, 1929 2,146,917 Rosenberger Feb. 14, 1939 2,324,425 Rasmussen July 13, 1943 FOREIGN PATENTS Number Country Date 359,343 France Jan. 18, 19,06

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