US2290979A - Sandblasting device - Google Patents

Description

R. L. LUCE SANDBLASTING DEVICE Filed June 14, 1941 July 28, 1942.,

Kay L. L zzce Patented 'July 28, 1942 Roy L. Luce, Chicago, Ill., assignor to The Hydro- Blast Corporation, Chicago, 11]., a corporation of Illinois Application June 14, 1941, Serial No. 398,002

7 Claims.

The present invention relates to sand blasting devices and is particularly concerned with the provision of a sand blasting gun that for certain types of work is an improvement over the sand blasting gun shown in Leslie L. Tirrell Patent No. 2,200,587, patented May 14, 1940, for Method and apparatus for sand blasting."

It will be understood that sand is used in this specification in its generic sense and includes all suitable abrasive materials normally used in sand blasting operations.

The gun of the present invention is intended to make use of water, under high pressure as the sand propellent and may be used with the other apparatus shown in the above mentionedTirrell patent in place of the gun there shown,

Whereas the gun shown in the Tirrell patent is primarily intended to be used in cleaning articles having, a comparatively coarse surface, such as ferrous sand castings, for instance, and

is particularly well adapted for removing sand.

cores from such castings, the device of the present invention is intended for cleaning surfaces of a type requiring a more delicate and less concentrated abrasive action than that produced by the before mentioned Tirrell gun.

In general, it can be said that in the before mentioned Tirrell patent, one of the problems solved was to provide an arrangement for the efficient use of a high pressure liquid stream for projecting a large quantity of sand at high veloc- Still another object of'the present invention is to provide an improved sand blasting gun which accomplishes the above objectives and which is interchangeable in the apparatus described in the before mentioned Tirrell patent with the gun there shown.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention taken in conjunction with the accompanying drawing, in

which:

Fig. 1 is a diagrammatic representation of a device incorporating the present invention shown connected to a pair of hose lengths which may be considered as being connected at their opposite en to a high pressure water supply and to a sand and water feeder of the type shown in the above mentioned Tirrell patent;

Fig. 2 is a diagrammatic front end view of the sand blasting gun shown in Fig. 1. This figure shows in general the shape of the pattern of the abrasive and water stream projected by this ity in a confined jet having a high impact force.

In the present invention, however, one of the important problems solved is to provide an arrangement for the eflicient use of a high pressure liquid stream for projecting alarge quantity of sand over a comparatively large area in such a manner that the impact force at any point on the work is comparatively small, while at the same time maintaining a high velocity and hence a great abrasive action of the individual -sand grains incorporated in the stream.

It is, therefore, a primary object of the present invention to provide a novel liquid sand blasting method and apparatus for efllciently and rapidly cleaning comparatively extensive areas.

A further object of the present invention is to provide a novel method and apparatus for removing scale from such objects asferrous forgings and heat treated articles without alteration of the dimensions of the work so treated.

Still another object of the present invention is to provide an improved sand blasting gun that projects an intimately mixed sand andoliquid stream at high velocity in a fan-like pattern.

gun.

Fig. 3 is a horizontal medial sectional view through the sand blasting gun shown in Fig. 1, while Fig. 4 is avertical transverse sectional view which may be considered as taken in the direction of the arrows substantially along the line 4-4 of Fig. 3.

Referring to the drawing in which'similar characters of reference refer to similar parts throughout the several views, it will be seen that the gun comprising the present invention pro- 3 jects a fan-shaped stream which covers a. comparatively large area of the work being treated and thus reduces the impact force of the stream against any isolated area of the work. It is well adapted, therefore, for rapid cleaning of sheet metal objects or delicate surfaces of a type that might be injured by. use of the gun she in the before mentioned Tirrell patent.

In Fig. 1 of the drawing, I have shown a sand blasting gun of this type, indicated generally by the numeral it, connected to a high pressure water hose l2 and a'sand hose H. The high pressure water hose I2 is connected at its opposite end to a source of water under high pres-.

sure, preferably of the order of 1,000 to 1,200 pounds per square inch. The sand hose I4 is connected at its opposite end to a feeder oi the type shown in the Tirrell patent, so that a sand and water slurry can be fed from a sand tank through the hose M to the gun I by means of suction produced in the body of the sun in a manner to be described presently. This sand and water mixture from the hose I4 is intimately mixed with and propelled by the liquid under high pressure from the forward end of the gun in a fan-shaped stream against the work to be cleaned. It will be appreciated that although the pattern of the stream is such that a comparatively large area of the work is covered by the stream at one time, thus reducing the impact force against any given point on the work, still the impact force of the individual abrasive particles carried within the stream will be substantially as great as is the impact force of the abrasive particles in the more confined stream projected by the before mentioned Tirrell gun.

As shown in Fig. 3, the gun I comprises a body portion l6, preferably formed of corrosion resistant material such as bronze. Although this body portion could be formed in diiferent manners, the one shown comprises a bronze casting.

In general, this casting is rectangular in shape,-

being somewhat longer than it is wide and a matter of twice or so as wide as it is thick. The rearwardportionof this casting is internally threaded at 20 and is secured by these threads to a hose coupling l8.'- Directly inwardly of the coupling l8, the body portion is provided with a water distributing chamber 22. This chamber communicates with the rearward end of a rearward nozzle 24. threaded into complementary threads 28 formed in the gun body. A passage 28 extends longitudinally through the nozzle and confines-the liquid stream, thus causing the liquid under high pressure to issue from this nozzle as a pencil-like jet which passes through a sand loading chamber 38 and into a forward nozzle 32.

An axial passage 33 extending through this forward nozzle 32 is somewhat larger than the similar passag through the rearward nozzle 28.

This is because it should conform generally to the external contour of the liquid stream which had been expanded after leaving the rearward nozzle 28 by the addition of the before mentioned abrasive slurry to this stream. The action of the liquid jet in passing from the nozzle 28 into the forward nozzle 32 produces a 'subatmospheric pressurewithin' the chamber 30. Thesuction effect thus induced causes the sand and water slurry'to fiow upwardlythrough the hose l4 and intathis chamberwhere this slurry is drawn along with and becomes intimately mixed with the high pressure jet. The mixed jet, therefore, issuesfrom the forward nozzle 32 at high velocity and in a pencil-like form.

In order to enhance the wear resisting properties of the gun comprising this invention, I prefer that the sand mixingchamber 3|! be formed by providing the bronze casting with a cylindrical opening therein into which is pressed an annular stainless steel liner 34. This stainless steel liner, which is much more resistant to the abrasive action of the sand grains than is the bronze casting-greatly increases th life of the sand blasting gun. The sand hose l4 communicates with the interior of this chamber through a nipple 38 to which the hose I4 is connected and which is threaded transversely through the bronze body It and into the stainless steel liner 34. This nipple therefore aids in preventing the liner 34 from being forced from the gun body.

Th forward portion of the stainless steel liner 34 is externally threaded at 38 and this threaded portion is surrounded by a recess 38 formed in the forward end of the gun body l8. The internal forward portion of the liner 34 has a recess of somewhat larger diameter than that of the rearward portion which forms the sand chamber 30, and thus provides a shoulder 40 against which the rearward end of the forward nozzle can seat.

This forward nozzle 32 fits within the forward recess in th liner 34 with its rearward end against the shoulder 40. The forward portion of the nozzle is of reduced external diameter and has a conical shoulder 44, by means of which the nozzle is secured in place by a retainer sleeve 48 provided with a complementary shoulder and which at its rearward end is provided with internal threads threaded to the external threads 38 upon the liner 34. Thus, the nozzle 32 can be slipped in place and the retainer sleeve 48 slid endwise thereover and threaded to the threads 38. By tightening this retainer sleeve 48 the nozzle 32 is rigidly secured within the gun body.

The forward nozzle 32 is formed of two elements which comprise a brass sleeve 48 and a liner 58 pressed thereinto. In order toprevent the liner from being projected from the sleeve by the force of the liquid stream, the sleeve at its forward end extends inwardly somewhat over the end portion of th liner 58 to form an annular cap 52. Preferably, the liner 5!! is formed of a substance having an extremely high resistance to erosion. For this purpose I have found that cemented tungsten carbide is to be preferred over other substances with which I am at present familiar.

Directly to each side of the forward portion of the front nozzle 32 I have arranged a pair of auxiliary jet spreading nozzles 54. Each of these auxiliary nozzles is arranged with its axis at an angle of about 40 degrees to the central jet and is so positioned that jets from these two auxiliary nozzles intersect the central jet upon opposite sides in a position slightly ahead of the nozzle 32. The impact upon opposite sides of the central jet produced by these small high velocity liquid jets flattens the central jet, thus causing the central jet to expand upwardly and downwardly considerably. The fan-shaped jet thus produced comprises an intimate mixture of ranular abrasive' material and liquid and is admirably adapted for the specified types of cleaning requirements.

The small nozzles 54 producing these jets are threaded into the gun body and are connected by means of longitudinally and transversely extending passages 58 and 58, respectively, to the wardly from opposite sides of the casting to intersect the chamber 22 and by drilling other longitudinally extending holes from the rearward end of the casting through the passages 58 and up to the forward end of th gun where they communicate with tapped holes into which the nozzles 54 are threaded. The openings in the rearward portion of the gun body, where the passage forming drills entered, are closed by threaded plugs 58.

In use, the high pressure liquid stream entering through the fitting I8 is divided in the chamber 22. A portion of this stream passes outwardly through the transverse extending passages 58, through the longitudinal extending passages 55 and through the forward small auxiliary nozzles 54. The jets from these nozzles project obliquely inwardly and strikereach other and the central stream at a point slightly ahead of the forward nozzle 32. Meanwhile, a portion of the water under high pressure passes through the rearward nozzle 28, through the sand loading chamber I0, and through the forward nozzle 32. The partial vacuum thus produced in the sand loading chamber 30 causes the sand and water mixture to flow upwardly through the hose I4 and into this chamber where it is intimately mixed with the high pressure liquid jet and is projected with this stream from the nozzle 32. As the round jet thus projected is struck upon each side by the jets from the auxiliary nozzles 54, these side jets flatten the round jet and spread it outwardly in a vertical direction, thus producing the fan-like pattern that is characteristic of this sand blasting gun. This fan-shape cleaning jet is moved'slowly across the work to be cleaned so -that the rapidly traveling sand grains will have an opportunity to remove the scale or other surface coating desired to be abraded from the work being treated. As soon as a particle of surface coating is loosened by the abrasive action of the sand grains, it is quickly washed away by the liquid component of the jet.

I have found that with a gun of this type it is possible to clean forgings so as to remove the scale therefrom without endangering the surface beneath this scale. In like manner I have used thisdevice to clean the scale formed upon automobile difl'erential gears by heat treatment without damaging the surface of the gears thus cleaned. I have found also that gears cleaned in this manner can be cleaned more economically. have a superior finish and are lessv deleteriously affected than similar gears from which the heat treatment scale has been removed by pickling. I have found, too, that not only are scales of this type, as well as other surface finishes, removed very rapidly by a device such as that described, but that material suchas sheet metal of comparatively light gauge can be similarly cleaned without distortion.

Having described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. In a sand blasting device, means providing an inlet for liquid under high pressure, a nozzle communicating at one end with said inlet. means providing a sand loading zone adjacent the opposite end of said nozzle, means to deliver a sand and liquid mixture to said loading zone under the influence of reduced pressure created therein, 7

a second nozzle positioned ahead of said zone in substantially axial alignment with the first said nozzle, a pair of jet spreading nozzles positioned upon opposite sides of said second nozzle, means providing passages connecting said jet spreading nozzles with said inlet, said jet spreading nozzles being inclined to each other and to the said second nozzle so that liquid atlhigh velocity projected from said jet spreading nozzles will impinge against opposite sides of the sand and liquid jet projected from said second nozzle so as to flatten the latter jet to produce a fan-like pattern.

' '2. In a sand blasting device, means providing an inlet for liquid under high pressure, a nozzle communicating at one end with said inlet, means providing a sand loading zone adjacent the opposite end of said nozzle, means to deliver sand 'jet spreading nozzle with said inlet, said jet spreading nozzle being inclined to the said second nozzle so that liquid at high velocity .projected from said jet spreading nozzle 1 will impinge against the side of the sand and liquid jet projected from said second nozzle so as to change the characteristice of the latter jet.

3. In a sand blasting device, means providing an inlet for liquid under high pressure, a nozzle communicating at one end with said inlet, means providing a sand loading zone adjacent the opposite end of said nozzle, means to deliver a sand and liquid mixture to said loading zone, a second nozzle positioned ahead of said zone in substantial axial alignment with the first said nozzle, a pair of jet spreading nozzles positioned upon opposite sides of said second nozzle, means to supply liquid under high pressure to said jet spreading nozzles, said jet spreading nozzles being inclined to each other and to the said second nozzle so that liquid at high velocity projected from. said jet spreading nozzles fwill impinge against opposite sides of the sand and liquid jet projected from said second nozzle so as to flatten the latter jet to produce a fan-like pattern.

4. In a sand blasting device, means to project at high velocity a pencil like mixed jet composed of sand and a liquid vehicle, and means to project a supplementary high velocity liquid jet against the side of said pencil-like jetto change the characteristics of said pencil-like jet.

5. In a sand blasting device, means to project at high velocity 9. pencil-like mixed jet composed of sand and a liquid vehicle, and means to project a pair of supplementary high velocity liquid jets'against opposite sides of said pencil-like jet to spread the latter into a fan-like pattern.

6. The method of blast treating surfaces which comprises projecting a high velocity liquid stream through a loading zone to produce a reduced pressure therein, feeding a sand and water slurry to said loading zone under the influence of the reduced pressure therein, mixing the slurry with the high velocity liquid stream within said zone and projecting the mixture in the form of a substantially round jet, projecting a pair of liquid jets againstopposite sides of the high velocity jet to cause spreading of said high velocity jet in a plane substantially bisecting a line between said pair of jets, and finally applying the resulting jet to the surface of the work to be treated.

"I. The method of blast treating surfaces which comprises projecting a high velocity liquid jet through a loading zone to produce a reduced pressure therein, feeding sand to said loading

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