US2380738A - Art of sandblasting - Google Patents

Description

July 31, 1945.

A. H. EPPLER ART OF SAND BLASTING Filed July 29, 1940 5 Sheets-Sheet 1 INVENTOR /7z rm/e H. EPPAEZ MMZWM /ATTORNEYJ".

July 31, 1945. A. H. EPPLER 8 ,7 8

ART OF SAND BLASTING Filed July 29, 1940 3 SheetSSheet 2 INVENTOR HETHUZ H.EFF E K ATTORNEY;

M 1 AAA MA A. H. EPPLER 2,380,738

ART OF SAND BLAS'IING Filed July 29, 1940 July 31, 1945.

3 Sheets-Sheet 3 INVENTOR Her/40E H. EPPLEK ATTORN EYS.

7 practical. v

More specifically, it is an object of the inven- Patented July 31,

um'rao STATES PATENT I OFFICE ART OF Arthur H. Eppler, Milwaukee, Wis. applicationllzllz SSH-8 1%. 348,130

word "sand being employed genericallyfor the purposes of this description.

It is the obiect of the invention to provide an improved means and method for sand blastin and simultaneously inhibiting the corrosion or oxidation of the freshly cleanedsurface while at thesametimemakingthesandblastmoreef- 1 fective and enabling the use of cheaper grades of sand than have heretofore been regarded as tion to provide a sand blasting method and apparatus in which minute quantities of a liquid carrier for chemical material are sprayed with the pneumatically propelled sand at the surface to becleaned. In the past it has been thought necessary for efi'ective high speed sand blasting work to employ special grades of sharp sand entirely free from dust, but in the .use of my invention I find that I am able to use inexpensive common sand from practically any source without dust hazard, and to make such common sand out even more rapidy than the best sand heretofore available. It is my theory that the dust present in common sand has in the methods and apparatus of the prior art operated to cushfion the action of the sharp particles upon the work. I have found that even a minute proportion of water will not only carry the rust inhibiting chemicals but will minimize the menace of silicosis by laying the dust, and because cheap sand used in my apparatus cuts at least as effectively as the highest grade sand in prior art structures, I believe that the mist or vapor delivered through the sand blast nomle in my de-; vice accomplishes this result by segre ating the dust and either increasing its mass and its velocity to match the mass and velocity of the larger particles, or by removing the dust from the home during intervals when the sand is not Btillotheroblectsoftheinventionhavctodo with the mountin of conventional sand blast nouie tips interchangeably on the handle portion of the hostile.

A still further oblect is to obtain the aforesaid advantages while at the same time sufiiciently moistening the abrasive so as to preclude the building up of a positive magnetic charge upon ferrous metal objects which are treated, such a charge being a deterent to machining as well as to the magnetic fiux testingof the metal. Such a charge is frequently the result of dry sand blasting of ferrous metals, It is not present in hydraulic sand blasting but the hydraulic sand blasting has other disadvantages avoided by the use of the invention herein disclosed.

Other objects will be apparent to those skilled in the art upon study of the following specification of my invention.-

In the drawings:

Fig. i is a side elevation of those portions of the apparatus which are relatively stationary path of the larger particles, or by enveloping line I particles of sand in globules of liquid to produce the results. noted. I Further objects of the invention have to do 1 with means for successfully mixing the chemi- 'aboutoverthegrmindiikeastofieboat orm'ay shown at II is a conventional'commercial sand and by which the nozzle is supplied.

Fig. 2is aviewonanenlargedscaleshowing the nozzle apparatus largely in longitudinal section.

Fig. 3 is a longitudinal valve which controls the supply nossle.

Fig.4isaviewtakeninsectiononlinel-l of Fig. 2. Y Fig.5 is a view taken in section on line 8-5 of Fig. 2. v I

Fig. 6 is an enlarged detail view-in axial sectionthrough the water pump and metering arrangement.-

Figfllisaviewonanenlargedscaleinaxial section through the pneumatically operated chemical pump and metering arrangement.

Like parts are identified by the same reference characters throughout the several views.

The apparatus shown in Fig. i k mounted for convenience on a base I, whichf may be pulled section through the be carried on the chassis of a truck. The device blast generator. It includes a large tank or hopper .ll within which the sand is contained, and a mixer I I in which there is a cut-oi! valve (not shown) actuated by the control lever II. Air

. from the compressed air line Ills supplied subiect to the main control valve II to a pipe I.

which leads to the generator. a portion of the of liquid to the" trol cut-oil valve ll and a check valve ll.

2", through the hose 2 with the sand blast hose 2|.

The metering valve m is of the type which may either be shut oi! completely oropenedonly to a predetermined and very slight extent. Because of the introduction of water into the nozzle in the manner hereinafter to be described, the water might accumulate in the nozzle and mix with sand therein to cause the sand to cake and stop the nozzle ii it were not for this by-pass which, eventhough the valve controlled by lever ll may be momentarily closed, will nevertheless permit a sufficient quantity of air to flow through the hose 20 to keep the nozzle open and to keep the water moving toward the nozzle discharge.

On a separate sub-base 22 are mounted a pressure tank 23, the pneumatically operated water metering pump 2|, the pneumatically op rated chemical metering pump 25, and the chemical storage tank 28.

The water supply pipe 21 communicates with the chemical storage tank 2! by means of valve 20 only for the purpose of facilitating the filling of the chemical tank for the dilution of the chemicals placed therein. The main purpose of the water connection at 21 is to supply'the pump 24 by means of pipe 2! with whichpipe 21 communicates subject to an automatic pressure concut-oi! valve 22 is self-closing and is held open only by the pressure of air admitted to its con- The trol chamber 32 through pipe 32 from the air I supply pipe 3| which communicates with the main air pipe ll. When the main control valve II is cut oil, the water valve ll closes itself. When the control valve II is open, the air pressure also opens the water valve to leave theapparatus in condition for operation.

Pipe 24 not only supplies the control chamber 32 01' the automatic valve ll, but also supplies the pressure tank 28 and the pump by means of pipes II and l! respectively, both of which are subject to the control of the regulating or reducing valve 31. The valve Il may be adiusted to a fixed setting which will automatically compensate or equalize pressures according to the hose lengths and sizes of hoses used in the apparatus to arrive at a negative pressure or partial vacuum at the point where the liquid enters the gun at 81. Pipe 2! is provided with a normally closed cut-oi! valve which is only opened to build up a sumcient'head or air in the top of tank 23 a ainst which the water and chemical admitted to the tank may operate.

The pump 24, shown in detail in Fig. 6, is likewise of conventional commercial design and hence will be described but briefly. In addition to the air admission pipe it and the water admission pipe 20 previously described, the pump has a. pipe 3. communicating with the chemical pump 25 and a pipe SI which serves as an airdischarge pipe and which, for the purposes of this invention. leads to a point below the surface of the chemicals in tank 2|. such tank being i'reely vented to the atmosphere whereby the air cscaping through the submerged outlet ll aerates and mixes the chemicals.

The construction and operation of the pneumatically driven water pump are as follows:

In the control head 4. is an air exhaust valve ll and an air inlet valve 2 mounted on the same stem 0 and connected with a diaphragm M. The diaphragm has its opposing faces exposed to the chambers 48 and 46 respectively. Chamber 46 communicates through duct II with the dis-I charge conduit 48 which-leads to the air exhaust pipe 38. Thesame chamber II at the right hand side of the diaphragm as viewed in Fig. 6 communicates through a duct 49 with a tubular post 50 and thence subject to the control of valve II with the interior of the pump chamber 82. 4

The float i3 reciprocates on the guide post 5.. At its lower extreme of movement it operates the lever 54 which opens valve ll, the valve being closed by spring 55. At its lower extreme of movement the float 53 also engages a ring it connected by link 51 with lever 58 which displaces the ball valve 59 which is normally seated by gravity to cut oflf communication between the pump chamber 52 and the diaphragm chamber a ll. Diaphragm chamber 45 has restricted communication through the annular clearance around the valve stem 43 with the inlet chamber 80.-

through pipe 28 subjectto the control of check valve n, the float will he in contact with lever '58 which will thereupon be displaced to permit the seating of valve 59. When valve 59 is closed the air leaking around the valve stem from inlet chamber into diaphragm chamber ll will act on the diaphragm in a direction to seat the air exhaust valve II and to open the air inlet valve 42, thereby letting air flow from the supply pipe 38 into the water chamber 52 through duct ii.

The air pressure exerted on the surface of the water will expel the water from chamber 82 through the water discharge pipe 82, thereby lowering the float II. In the lowermost position oi. the float the float will open valve ll and valve II as above described, thus permitting the pressure in the tank or chamber 82 to pass upwardly through'the post II into diaphragm chamber 40, thus equalizing the pressure in the diaphragm chamber 40 with that in chamber 48 and permitting the air pressure on the exhaust valve to displace the valve assembly-to a position where .the inlet will be closed and the outlet valve U will be open. The water supply under pressure through pipe 21 will now open the check valve 3| and enter the bottom of tank I2, thus displacing the air therefrom through duct ii and discharge pipe 32, raising the float to the point where the cycle will be repeated in the manner above described. N

As previously indicated, the air discharged from the pump through exhaust pipe 30 is used elevated position as shown in Fig. "1. Pipe a communicates with the air cylinder CI- above piston l' l. Both cylinders. between the respective pistons. are vented through duct II. The chemical from tank 28 is admitted through pipe The chamber a: being full of water admitted 12 subject to the control of a check valve 18 and is discharged through pip I4 subject to the control of a check valve I8, pipe 14 leading to the outlet pipe 82 from the water pump and thence communicating through pipe 16 with the pressure tank 28.

In actual practice the water pump displaces 2 gallons of water in each operation and the chemical pump 25 displaces /4 pint of chemical in each operation. It will, of course, be understood that the water pump 24 may be used for pumping any suitable solvent or rust resistin chemical, the term "water being used herein for the purpose of description and not of limitation.

It will be apparent from the foregoing that the operation of the chemical pump is entirely automatic, being controlled by the operation of the water pump. When air is admitted to the water chamber 52 to expel the water therefrom, the air pressure is communicated through pipe 88 to the air cylinder 85 of the chemical pump, thereby forcing piston 61 downwardly whereby piston 68 expels the charge of chemical from the displacement cylinder 88 of the chemical pump. Thus the chemical and the water flow together from pipes 82 and 14 respectively, into pipe 18 and thence to the storage tank 23 where the mixture is stored under a head of approximately 20 pounds more or less of air which is confined in the top of said tank.

When the exhaust valve 4| in the water pump is opened to relieve the pressure of air in tank 82, the pressure on piston 81 of the chemical pump is likewise relieved through pipe 38, whereby the spring 18 lifts the piston assembly in the chemical pump to introduce a fresh charge of chemical through pump 12 and check valve 13 into the displacement cylinder 88.

From the bottom of the storage tank 23 the liquid line 11 leads to an atomizing fitting in the nozzle subject to the control of a diaphragm valve 18 which is shown in detail in Fig. 3. While this valve is of conventional manufacture it is important to use a valve of this general type because no other valve has been found to be as satisfactory and as free from clogging in a device where sand is used. This valve has an inlet passage at 18 and a discharge passage at 18' ber tween which there is a partition at 88 upon which the diaphragm 8| may be forced to seat by the pressure member 82 actuated by a screw 83.

The liquid supplied through pipe 11 subject to the control of valve 18 is admitted through a ported boss 84 to the interior of the handle portion 85 of the nozzle. Within this handle, in registry with the boss, is a sleeve 88 having an annular peripheral channel coacting with the tube of the handle to comprise a closed passage through which the water is distributed to the various orifices at 81 through which the water may pass sleeve 86 into the annular mixing chamber at 88.

.A special fitting at 88 is secured in the end of sleeve 88 and has a stem portion 8| projecting centrally through sleeve 88 to guide the sand blast therethrough. The inner bore 82 traversed by the sand blast is counterbored at 85 to provide a tapered inlet. Externally the fitting is tapered near its discharge end at 88. The diameter of this bore will be varied according to the size of the nozzle. Roughly its cross sectional diameter is approximately twice that of the nozzle. For example, I use a fitting with a /4" bore when I employ a nozzle, and I use a fitting with a /8" bore for a $41 to 1%" nozzle.

The nozzle proper as indicated at 81, is of generally conventional design. It is, however, provided with a, novel arrangement for interchangeably mounting it on the handle tube 88. For this purpose the nozzle stem 88 is Provided with a flange 88 having an external peripheral diameter adapting it to fit reasonably closely within the handle tube 85. At its end the handle tube is provided with an annular nut I88 and between this nut and the flange 88 I interpose a rubber sleeve |8| which is placed under compression when the nut is turned up upon the end of tube 85. The rubber sleeve not only holds the nozzle stem 88 in position, but also serves as a packing to prevent leakage while permitting an immediate change of nozzles. It is not even necessary to use tools, for the pressure which can be exerted in tightening the nut I88 by hand is entirely adequate to hold the nozzle in place and to distort the rubber packing |8| in such a way as to pack the device adequately. The internal bore through the nozzle stem 88 is counterbored to provide a tapered inlet or mixing chamher at I82 which is maintained in the proper desired relationship to the tapered end 88 of fitting 8| by the pressure contact of flange 88 with the end of sleeve 86. The air and sand passing across the gap between fitting 8| and the nozzle stem 88 aspirates into the stream the mist of chemically treated water which has been delivered through the fine apertures 81 into the annular space at 88.

As previously explained, throughout the period when the device is in use a small amount of air by-passed through the hose 2 is continually flowing through the nozzle whether or not the main stream of sand and air is flowing. This relatively small amount of air is suflicient to keep up the aspiration of water from the annular passage 88 under all circumstances, thus preventing any accumulations of water within the handle and also tending toprevent sand from clogging the water passages.

By introducing the chemical into the pneumatically carried stream of sand prior to the discharge thereof, I ensure the thorough commingling of the chemical with the sand carried by the blast so that each particle of sand is believed to be a carrier for the chemical at the time of discharge, thus ensuring the treatment of the sand blasted surface with the chemical at the very instant when it is cleaned.

The protective or rust inhibiting chemicals may be varied according to the requirements of the work. For cleaning steel forgings or castings and for much other work I have used with great success a chemical preparation made up by using in every 100 gallons of water in the chemical tank 3 to 5 ounces of the following preparation:

Pounds Trisodium phosphate 100 Zinc oxide (this being used only where the water supply is alkaline) 2 Neutral sodium dichromate (more being used for painting old steel and less for new steel) 4 to 6 Lead phosphate 1' Chemically pure lime (less being used for new steel than for old steel) 6 to 10 Using a nozzle a device made in accordance with the present invention will discharge approximately 450 lbs. of sand per hour in 80 cubic feet of air per minute at 90 lbs. air pressure but it will only require gallons of water or rust-inhibiting liquid, or less, in an hour.

As compared with pneumatic sand blasting as heretofore known, this small amount of water or rust-inhibiting liquid is adequate to lay the dust, thus substantially completely removing the danger of silicosis. In so doing it renders the blast much more effective. The sand ordinarily used in sand blasting averages approximately $7.50 per ton in cost. With the apparatus herein disclosed it is possible to use cheap sand at approximately $2.50 per ton with equal or better results. As above noted, I' ascribe the improved results in part to the fact that the water apparently adheres to the dust particles, possibly giving them increased momentum but more probably removing them completely from the blast and preventing them from cushioning the cutting action of the heavier and sharper particles.

At the same time the amount of water or rustinhibiting liquid used is not such that the disposal of waste is a problem. The chemicals are carried to the work and left on the surface without being washed away by sluicing quantities of water. Where such small quantities of water are used it is feasible to incorporate chemicals in the sand blast, whereas otherwise it would not be feasible to do so, because the cost would be prohibitive. By mixing the chemicals with the sand blast I ensure the treatment of the surface at the instant when the scale is removed, thus leaving no interval of time between the cleansing and polishing of the surface and the treatment thereof to prevent oxidation. This leaves a much brighter and more permanently rust free surface than has heretofore been possible to achieve.

My improved apparatus has been used in the Far West where water is scarce, and there also the small quantity of water used is significant. While the device actually uses in the neighbor hood of 15 gallons of water per hour when a 1%" nozzle is employed, I should regard gallons per hour as being a small quantity for such a nozzle within the meaning of the aforesaid description. A greater quantity would create disposal problems, be wasteful of chemicals, and make the chemical treatment less effective. It will, however, be understood that in reference to the amount of water discharged from the nozzle 1 am referring to the chemically treated water as stored under pressure in tank 23.

It will be apparent to those skilled in the art that my process does not involve hydraulic sand blasting as that term has previously been known. The small amount of water used is merely a fine mist and the compressed air is still relied upon to furnish the impetus by which the sand blasting operation is conducted.

The sand blasting method herein disclosed constitutes an improved means of cleaning and cutting viscous surfaces. It is adapted to clean light gauge or frail metal parts without warping or buckling thereof, and avoids the generation of heat in the cleansed articles such as commonly results from dry sand blasting thereof, this being particularly important where the treatment is applied to a surface of viscous material which would soften and run when heated.

My improved treatment is also important in completely removing foreign greases or oils from the articles being treated, and in scouring the surfaces of such articles while at the same time leaving such articles free of rust for substantial periods so that they do not require immediate painting for their protection. My improved method is further advantageous in that it is successfully used on wet surfaces without requiring the preliminary drying of such surfaces as has heretofore been necessary in ordinary pneumatic sand blasting.

My improved method is further advantageous in the cleamng of concrete so that new concrete work added thereto will result in a. stronger and water-tight bond or union.

The abrasive, including the dust therein contained, is confined by themoisture to the immediate vicinity of the work and does not float in the air but drops to the ground about the work and stays there.

I claim:

1. In a sand blast system, the combination with a sand blast generator and an air supply pipe therefor provided with a control valve, of a connection to said pipe controlled by said valve, a water supply pipe, a chemical supplymeans, and pumps provided with operating means actuated by said air connection for operation to deliver water and chemicals in predetermined quantities when said valve is open, and means for discharging said water and chemicals with a sand blast from said generator.

2. Sand blast apparatus comprising the combination with a sand blast generator, a nozzle, and means including a hose affording communication between the generator and the nozzle, of means including an aspirating device for introducing a liquid into said last mentioned means in the proximity of the nozzle, a liquid supply tank, a chemical meter provided with means for delivering chemical to the liquid supply tank, and means for pneumatically operating said meter, said pneumatic operating means and said generator having a common source of air supply and a common control valve.

3. Sand blast apparatus comprising the combination with a generator and a nozzle, of a water pump, a chemical pump, means for the pneumatic operation of said pumps, means for delivering the eflluent of the pumps to the sand blast in proximity to the nozzle, an air supply common to the generator and the means for pneumatic operation of the pumps, a water connection to the water pump, and valve means controlled by said air supply for opening said water connection to said pump when said air supply is elfective to actuate the water pump.

4. Sand blast apparatus, comprising the combination with a manually controlled source of elastic fluid supply, a mixing nozzle provided with a main inlet and auxiliary atomizing inlets, a receiver for abrading material, a mixing chamber associated with the receiver and adapted to receive sand therefrom, manually controlled means for directing the elastic fluid to the nozzle either through the receiving and mixing chambers or through a by-pass, and means for delivering chemically charged liquid through the atomizing inlets of said nozzle, whereby said liquid may be utilized for coating particles of sand entrained by the elastic fluid delivered through said nozzle, and for charging the by-passed elastic fluid with rust resisting chemical material.

5. In a sand blasting apparatus provided with a sand container, an associated mixing chamber and a nozzle, the combination therewith of valved pipe connections adapted for delivery of an elastic fluid under pressure to the sand and mixing chamber, and means dependent upon elastic fluid delivery through said pipe connections for charging water with a rust resisting chemical and jetting it into said nozzle in predetermined proportions to the film of elastic fluid passing therethrough.

6. In a sand blasting apparatus provided with a sand container, an associated mixing chamber and a nozzle, the combination therewith of valved pipe connections adapted for delivery of an elastic fluid under pressure to the sand and mixing chamber, means dependent upon elastic fluid delivery through said pipe connections for charging water with a rust resisting chemical and jetting it into said nozzle in predetermined proportions to the film of elastic fluid passing therethrough, and valved by-pass connections for delivering the elastic fluid to the nozzle and water supply means independently of delivery of sand from the sand container and the mixing chamber.

7. The combination with a pneumatically operated sand blasting apparatus having an air inlet pipe, an outlet .pipe provided with an aspirating nozzle and an associated blast nozzle for delivery of air and sand to a surface to be cleaned, of pneumatically operable pumping mechanism adapted for delivery of chemically charged liquid to the aspirating nozzle, said pumping mechanism having power connection with the air inlet pipe, whereby the pumping mechanism may be automatically operated during sand blasting operation.

8. A combination as set forth in claim 7, in which the pumping mechanism has its outlet connected with an annular series of atomizing nozzles leading through the wall of the aspirating nozzle to the annular space about the sand blast, and adapted to atomize the liquid chemical preparatory to its exposure to the suction of the aspirating nozzle and mixture with the sand passing through such nozzle.

9. Sand blast apparatus, comprising the combination with a sand blasting generator, a mixing nozzle and a pipe connection between the generator and the nozzle, of means for metering and supplying to the mixing nozzle, under pressure, atomized liquid charged with rust resisting chemical material in predetermined quantities substantially equal to those required for coating the particles of sand generally with such material, whereby the surface to be cleaned may be coated with the chemical material simultaneously with the impact of the sand particles thereon.

10. A sand blasting process, consisting in gencrating a dry sand blast, metering, pumping and uniformly distributing quantities of liquid rust resisting chemical material to the particles of sand in particle coating proportions immediately prior to contact of the blast with the surface to be cleaned.

11. A sand blasting process, consisting in generating a dry sand blast, metering, pumping and atomizing quantities of liquid rust resisting chemicals into the sand blast in definitely predetermined proportions to the volume of the blast, and in quantities substantially equal to those required for coating the surface against which the blast is projected.

V ARTHUR H. EPPLER.

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