US2755598A

US2755598A - Rotary blast nozzle

Info

Publication number: US2755598A
Application number: US421456A
Authority: US
Inventors: William N Van Denburgh
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-04-06
Filing date: 1954-04-06
Publication date: 1956-07-24
Anticipated expiration: 1973-07-24

Description

y 1956 w. N. VAN DENBURGH 2,755,598

ROTARY BLAST NOZZLE Filed April 6, 1954 2 Sheets-Sheet 2 55 -0 M 24 Ed 4 4 ji z jib III I l r El E I E- 41: INVENTOR.

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United States Patent O ROTARY BLAST NOZZLE William N. Van Denburgh, Kent, Wash.

Application April 6, 1954, Serial No. 421,456

3 Claims. (Cl. 51-11) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.

This invention relates to abrasive blast cleaning and, more particularly, to the structure and operation of jet nozzles such as are used in these cleaning operations.

One of the most efficient manners of cleaning all sorts of articles or surfaces, both small and large, is by means of abrasive blasting or, more descriptively, by the use of compressed air to direct a jet of abrasive particles, such as sand or steel grit, against the particular surface to be cleaned. In the development of this art many different types of nozzles have been suggested in an effort to produce a blast which will clean the surface in the most expeditious manner and, as might be expected, different nozzles are to be preferred depending upon the particular type of work at hand, as well as the particular material used as a cleaning agent.

One of the more important cleaning jobs required of these nozzles is that of preparing a large surface area, such as the deck or side of a ship, for painting. In such work, it will be appreciated that the area to be covered demands a nozzle which will have a blast pattern that covers the widest possible deck section so that the job itself can be accomplished in a relatively fast time. Customarily, the operation of cleaning these wide surfaces is performed with sand blasters which are adapted to be manually directed and manually moved from one section to the next, although some recent developments contemplate a large blast cabinet in which the nozzles are mounted and the cabinet itself mechanically moved by remote control across the surfaces. Such cabinets are particularly desirable because it is possible to vacuumize their interior so that the spent grit and waste material can be safely removed instead of being permitted to fly freely about and becoming a safety hazard. However, whether the nozzle is to be manually directed or mechanically moved into operative position, it nevertheless is most desirable that the particular blast pattern of the nozzle be as wide as possible so as to minimize the requisite movements. On the other hand, while a wide blast pattern most certainly is a desirable asset, it also can be realized that the maximum spraying width of the pattern must be reduced to such a point that the blasting will be effective, since, as can be appreciated, the wider the blast spray, the less actual force there will be behind each particle. On the other hand, if a blast spray is directed perpendicularly into the surface to be cleaned, another difficulty arises in that the particles, instead of gouging away the paint or the scale and other foreign material to be cleaned, simply will dig into the surface and lose a substantial portion of their eficacy by being pulverized. In effect, such perpendicular blasting creates a hammer action which, if carried on for a suflicient length of time, forms minute pockets which eventually become corrosive sources.

In the prior art, most of these nozzles emitted a narrow jet blast which normally would strike the surface at a perpendicular angle, and the efficiency of the cleaning operation was left up to the skill of the operator in that he was required to so manipulate the impact angle of the blast that it would produce a cutting or gouging action instead of the pulverizing hammering effect. Further, in these prior art nozzles, it apparently was felt preferable to use the narrow blast instead of a wider spray pattern, probably because of the cutting force sacrificed when a spray is produced. As a result, so far as is presently known, the available nozzles are most inefficient for cleaning unusually wide fiat surfaces both because of their narrow blast patterns and because of the fact that the most effective use of these patterns is dependent upon the skill or constant attention of the operator.

It is, therefore, a fundamental objective of the present invention to provide a blast nozzle which has a wide blast pattern, as well as a pattern in which each blasted particle has substantially as great a force as that which is capable of being applied to a particle directed perpendicularly of the surface to be cleaned.

Another important object is to provide a blast pattern in which the particles necessarily are directed at the surface in an angular path as will achieve a cutting or gouging action correlative to this object, the invention also contemplates the elimination of the operator previously employed to so manipulate the nozzle as to achieve this cutting action.

Other objects are to provide a sturdy, easily maintained and economic blast nozzle which is capable of producing the widest possible effective blast pattern.

in accordance with the invention, the apparatus provided is formed with a nozzle housing in which is rotatably mounted a nozzle and, preferably, this nozzle is mounted for rotation about a longitudinal axis of the housing and it is driven by a rotor secured to its inlet end portion and adapted to be driven by a source of fluid pressure supplied through the housing. To achieve a wide blast pattern, the nozzle is formed with at least one longitudinally extending jet passageway, the outlet portion of which is disposed angularly to the rotational axis of the nozzle so as to jet the particles outwardly in an arcuate path. In the preferred form, a plurality of such jet passageways are employed and, of course, each of these passageways is disposed angularly to the nozzle axis.

Another feature of the invention which materially improves the effectiveness of the cleaning operation is the fact that the rotation of the nozzle immediately applies a centrifugal force to the blast particles, which, in turn, causes the particles to be thrown from the nozzle in a spinning movement. It is surmised that the actual path of particles thus subjected to the centrifugal action is somewhat spiral in form so that the particles actually are traveling in a curved path as they strike the surface to be cleaned. Whether or not the theory of the spiral path is correct, it has become quite evident that the cleaning effect of these particles is superior to particles which are thrown in a straight linear path, and this is true even though the linear path of such particles strikes the surface at an angle. For this reason, a further feature of the i11- vention resides in a method of cleaning in which particles propelled in a straight linear path subsequently are subjected to a centrifugal force which produces a spinning motion and possibly a spiral path.

In the drawing, Fig. l is a partially-sectional side elevation of the apparatus; Fig. 2 a front end elevation showing the arrangement of jet passages; and Figs. 3 and 4 vertical sections taken along lines III.lII and IVIV respectively of Fig. 1.

Referring to the drawing, the nozzle apparatus is formed generally of a tubular housing 10 having at its front or outlet end a mouth 12, and having its rear face covered with a plate 14. No support is shown for the housing as it forms no part of this invention. However, it is apparent that the apparatus shown is adaptable for use in hand operated blasting equipment, or it may be associated in any combination with blasting cabinets or the like, which may be of the vacumized type.

Cover 14 is formed with an annularly recessed hub 13 to receive an outer coupling 19 by which an abrasivecarrying air hose 2%) may be detachably connected by coupling ears 21. ithin the cover hub is mounted a sleeve 22 which forms a stationary portion of an otherwise rotatable nozzle member to be described, sleeve 22 being aligned with hose 2% and extending partially into the housing to support one end of the rotating nozzle member assembly by means of an outer concentric bushing 23.

An air rotor casing 24 and cover 26 are clamped within the housing cover 14, the covers being suitably spaced at 28 to provide for the introduction of a lubricant at port 36 in cover 14. The foregoing described parts of the nozzle apparatus are fixed within the housing, while the remaining components are rotatable within the housing for imparting the desired rotary motion to the abrasive particles as they are propelled through the nozzle. An air rotor 32 having a plurality of radial blades 34 is positioned within casing 24, the hub of the rotor being supported on and keyed at 36 to a hollow shaft or nozzle liner 38 which is recessed at its inner end to fit over bushing 23 and rotatably supported within the housing by sealed roller bearings 44 and retained thereto by ring 41. Liner 38 preferably is made of brass and forms a carrier for a rotatable nozzle member 42 frictionally engaged within the liner and axially aligned with its counter-part sleeve half 22 to permit the unrestricted flow of air-carrying abrasive. Nozzle member 42 and sleeve 22 may be made of steel, or they may be made of a thin metal liner, such as brass, with a vulcanized rubber lining offering high wear resistance property to the abrasive particle flow.

To provide an effective abrasive spray pattern, nozzle member 42 may be drilled with one or more longitudinal jet passages 44 leading from the main nozzle passage 43 to the nozzle face, passages 4-4 preferably extending in diverging relation to the longitudinal axis of the nozzle for providing a diverging abrasive flow of increased diameter. Where a. plurality of passages are utilized they should be disposed symmetrically about the longitudinal axis to balance the rotational forces. If the abrasive air fiow is to be utilized as the rotary means, the passages may be obliquely arranged to cross the longitudinal axis r whereby air jetted through the passages will provide the force to rotate the nozzle member. It is apparent that the jet flow from each diverging passage will traverse a circular path on the surface to cover a much larger area than would result with either a passage that is coaxial with the rotational axis of the nozzle or the non-rotatable nozzles of the prior art. The path diameter, of course, will vary depending on the inclination of the passages, their diameter and the nozzle distance from the surface. In the preferred embodiment, it has been found that four passages, each 4;" in diameter and inclined about 12 from the rotational axis will give satisfactory results.

The rotatable nozzle member is provided with a flared head portion for accommodating diverging passages 44, the head portion of the nozzle being seated in a correspondingly flared head portion of liner 38, which in turn is seated in a flared portion of the housing. The nozzle member is seated within a recess in the liner by an annular restraining shoulder 45 being retained therein by a detachable split-ring 4-6 having llltgS 47 so that a worn nozzle member can be expeditiously replaced through the front end of the housing simply by removing the retaining ring with a pliers or the like. The remaining parts of the nozzle requiring less frequent replacement may be removed through the rear of the housing by disconnecting rear cover 14.

Referring now to the details of the air driven motor shown in Figs. 2 and 4, rotor blades 34 are freely slidable in radial slots 54, the blades being forced outwardly to slide on the inner casing and cover walls during rotor rotation by the combined action of centrifugal force and the operating air pressures, which may originate from the same compressed air source as the abrasive carrying air stream. It is noted that the rotational axis of rotor 32 is eccentric or off-set from the center or rotor casing 24 forming between the rotor and the casing a crescentshaped chamber (Fig. 3). As the blades slide through the chamber in flush engagement with the casing walls, they form expansion cylinders 55a to 55g, inclusive, in which the operating air is allowed to be successively expanded and vented to permit the rotor to be driven in the direction indicated. Operating air pressure is introduced into housing 10 at threaded inlet port 56 adapted to be connected to a compressed air hose, not shown, and is admitted to the base of rotor blade slots 54 through a plurality of radial passages 58 in the side walls of each casing 24 and cover 26, these passages terminating in kidney-shaped ports 6i) recessed on the interior wall of the casing and cover, the casing being shown in Fig. 4. From the base of slots 54 which are aligned with ports 60, operating air pressure is simultaneously admitted to the chamber cylinders formed by adjacent blades through oblique rotor passages 62 which extend from the base of each slot to the corresponding chamber cylinders. Ports extend in an are for a length that will permit the preceding air cylinder having been charged (for example, cylinder 5512 in Fig. 3) to be vented shortly after air pressure is blocked to that cylinder. After initial air expansion has imparted a thrust to the rotor, each cylinder is exhausted through radially drilled vents 64 in the peripheral casing wall, such vents, in turn, being connected to atmosphere through an undercut passage 66 formed on the inner periphery of casing 10 and outlet ports 68. Thus as the blades progress through chamber 55, the chamber cylinders first increase and then chamber cylinders 55c to 55g gradually decrease in size so that the expanded operating air which otherwise would be compressed by the decreasing volume of the cylinders is allowed to escape to prevent any retardation of rotor rotation. The operation of the nozzle is obvious from the foregoing description and drawing.

By the use of nozzle apparatus of this invention, the eitlciency of blast cleaning is greatly increased, a condition achieved primarily by imparting to the linearly propelled abrasive particles passing through the nozzle a rotary motion in which the particles are ejected from the nozzle in a spinning, swirling and probably spiraling path. Accordingly, the particles impinge the surface in an arcuate gouging or cutting stroke with greater momentum due to centrifugal force. The particles are less likely to be pulverized by the impingement, and, consequently, the swath in the surface is wider as well as longer due to the cutting angle. By providing a plurality of diverging nozzle passages, the abrasion is faster. A further advantage of this construction arises when the nozzle is hand directed as less movement of the nozzle is needed to cover the same surface area. The use of air-driven means to rotate the nozzle is most advantageous in that the weight of the nozzle is kept to a minimum, and a source of air pressure is always available as it is used as the abrasive-carrying medium. The nozzle apparatus is compactly constructed and readily disassembled for replacement of worn partsi Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. Blast cleaning apparatus comprising a housing pro-.

vided with a longitudinal bore having blast particle inlet and outlet ends, a nozzle rotatably mounted in said housing bore, and means carried by said housing for rotating the nozzle, said nozzle being formed with an elongate cylindrical section axially aligned with and extending through said bore to a point near said outlet end, said cylindrical section having a smooth cylindrical inner peripheral wall bifurcated at said point into a plurality of independent branches, said branches cumulatively forming a continuation of substantially all of the cross-sectional area of said cylindrical portion and of at least a major part of its said inner peripheral wall, each of said branches continuously diverging in an outwardly-flared direction with respect to said bore axis and each opening to the exterior of said apparatus at said outlet end, whereby blast particles delivered to said rotating cylindrical section are subjected to centrifugal force and said centrifugal force is applied uninterruptedly until the particles are discharged from the apparatus.

2. Apparatus according to claim 1 wherein said nozzle rotating means include a plurality of impeller blades drivably-engaged with said cylindrical nozzle section and extending radially therefrom, and pneumatic means for driving said blades, said blades being mounted in a chamber formed in said housing and said pneumatic pressure being delivered through said housing into said chamber.

3. Apparatus according to claim 1 wherein said nozzle rotating means include a plurality of impeller blades driv ably engaged with said cylindrical nozzle section and extending radially therefrom, and pneumatic means for driving said blades, said blades being slidably and eccentrically mounted in a circular chamber formed in said housing and said pneumatic pressure being delivered through said housin g into said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,951,627 Peik Mar. 20, 1934 1,953,311 Peik Apr. 3, 1934 2,303,088 Perkins Nov. 24, 1942 2,324,250 Voerge July 13, 1943? 2,334,172 Champayne Nov. 16, 1943 2,577,238 Edvinson Dec. 4, 1951