US2132431A - Irradiating method and apparatus - Google Patents

Description

Oct.ll,1938. I BOBRIE 2,132,431

IRRADIATING METHOD AND APPARATUS Filed April 27, 1934 4 Sheets-Sheet 1 Brian BY I ATTORNEY Oct. 11, 1938. B. O'BRIEN 2,132,431

IRRADIATING METHQD AND APPARATUS 4 Sheets-Sheet 2 Filed April 27, 1934 I Emjok Zrzm fl rzew @ATTORNEY Oct. 11, 1938. v Y B. OBRIEN 2,132,431

IRRADIATING METHOD AND APPARATUS Filed April 27, 19:54 4' Sheets-Sheet s ngmvrpx Elan OBrzen BY ATTORNEY Oct. 11, 1938. QBRIEN I I I 2,132,431

IRRADIATING METHOD AND APPARATUS Filed April 27, 1934 v 4 Sheets-Sheet 4 7 if v 16' 7 Z 59 E 29- i I I INVENTQR Bram 0$7-zen %z.'5 ATTORNEY Patented Oct. ll, 1938 UNITED STATES PATENT orrice 2,132,431 M nmAmA'rING rm'rnon AhfD APPARATUS Brian O'Brien, Rochester, N. Y. Application April 27, 1934, Serial No. 722,751

23 Claims.

This invention relates to a method and an apparatus for treating various products or substances, whether of solid, liquid, or gaseous form, by means of light rays or spectral emissions, for example. Both the method and the apparatus are especially suitable for the treatment of products in a fluid form, that is, in a gaseous or liquid state, and they have been used with success in, for example, the irradiation of milk by a source of ultra-violet light, though the invention is not limited to the treatment of this one product nor 11'; (tihe use of a light source of this particular An object of the invention is the provision of 1 generally improved and more satisfactory method and apparatus for carrying out the above mentioned general treatments.

Another object is the provision of a method and an apparatus which will give excellent result'snot only from a scientific or medical standpoint but also from a commercial or economic standpoint, so that the cost of the treatment will be low and the treatment can be applied generally, without anundue increase in the cost of the finished treated product.

Still another object is the provision of such apparatus of simple and compact form, and of such a character that, when properly set into operation, it will continue to operate automatically with a minimum of attention.

To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings:

Fig. 1 is a vertical section taken substantially through apparatus constructed according to one embodiment of the invention, approximately on the line l--I of Fig. 2;

Fig. 2 is a plan, with parts in horizontal section, of the apparatus shown in Fig. 1;

Fig. 3is a view similar to a part of Fig. 1 showing an alternative construction of the lower part of the apparatus;

Fig. 4 is a fragmentary vertical section through certain film forming parts of the apparatus showing them in one position of adjustment;

Fig. 5 is a similar view showing the parts in a different position;

Fig. 6 is a similar view showing the parts in still another position;

Fig. '7 is a similar view of a slightly different arrangement of film forming parts;

Fig. 8 is a similar view of still another modification of the film forming parts; Fig. 9 shows another modification of similar parts;

Fig. 10 is an alternative construction of film 8 forming parts;

Fig. 11 is a diagrammatic elevation of a film or sheet of plane form illu trating the effect of surface tension in drawin in the edges of the film;

Fig. 12 is an edge view of the parts shownin Fig. 11;

Fig. 13 is a diagrammatic view somewhat simi-w lar to Fig. 11 showing an arrangement for overcoming the narrowing effect of surface tension; 16

Fig. 14 is an edge view of the parts shown in Fig. 13;

Fig. 15 is a view similar to Figs. 11 and 13 showing a different arrangement for overcoming the effect of surface tension;

Fig. 16 is an edge view of the parts shown in Fig. 15

Fig.1! is a diagrammatic horizontal section through one form of irradiating apparatus constructed on the principles shown in Fig. 15;

Fig. 18 is a diagrammatic horizontal section through another form of irradiating apparatus, and

Fig. 19 is a diagrammatic view showing a liquid film projected upwardly.

The same reference numerals throughout the several views indicate the same parts.

In the. irradiation of liquids for the production of photochemical change, either in the liquid or in substances or particles contained there- 36 in, an important factor is the manner in which the liquid is presented to or caused to move or flow past a source of light.

If the liquid is relatively transparent to those wave lengths of light or other radiation which 40 produce the desired photochemical change, then the liquid may be caused to move past the light source in a relatively thick mass, since the effec: tive penetration of the radiation into the liquid will be great. An example of this case is the destruction of bacteria in relatively pure water by irradiation with ultraviolet light which is capable of penetrating such water for several inches without serious attenuation.

If the liquidis relatively opaque to the radiation producing the desired photochemical eifect, then the liquid must be caused t0 move past the light source in a relatively thin layer of film if all, or even a substantialfraction, of the liquid, is to receive a useful exposure to the light. An ex- 1 ampleof this is the exposure of milk to ultraviolet light for the purpose of destroying bacteria in the milk, the production of vitamin D from pro vitamin substance contained in the milk, etc.

subject matter of this present application. -The present invention is, however, not limited in its usefulness to the treatment of liquids, many features of the invention being applicable also to the treatment of solids or gases, while a number of features are useful in other fields distinct from that of irradiation.

In the following description of the invention, milk will be frequently referred to as a good example of a typical liquid product conveniently treated by the method and apparatus of the present invention, but it is to be understood that the reference to milk is intended only by way of example and not in a limiting sense.

I have found that a film of milk 0.2 mm. thick has a diffuse transmission of about 4% for ultraviolet radiation of wave length 2800 Angstrom units. If such a film could be uniformly translated past a source of light (all parts of the film moving at the same speed) a sufficient fraction of the milk could be made to receive light of wave length 2800 A. to produce a considerable amount of vitamin D in the milk without at the same time wasting largeamounts of light or of seriously overexposing those layers of the milk film nearest to the source. Unfortunately a rapid (and therefore practical) uniform motion of such a thin and uniform film presents serious difiiculties if the film is in contact with any solid object unless that object also 'moves past the source of light. Such motion of a solid object in, the form of a rotating cylinder or disk, or .a running conveyor belt, is not difiicult to achieve, but it is very difiicult, after having formed a liquid film on the surface of such movingsolid object, to remove the film eifectively from the moving object or conveyor after exposure to the source of light.

It has been proposed to spray the liquid or to allow it to drip or fall past the source of light in whatis frequently called a sheet or curtain of liquid, as shown for example in Supplee Patent No..1,81'7,936, granted August 11, 1931, and in Rohde Patent No. 1,888,472, granted Nov. 22,

1932. In these patents and in all prior devices of which I have knowledge, however, the inventors have made no provision for counteracting the effect of the surface tension of the liquid. Without adequate provision for counteracting surface tension, the falling liquid will not form a true sheet or curtain of approximately uniform thickness. If the liquid flows from a straight edge to form a plane sheet, surface tension will draw the side edges of the sheet in toward each other as illustrated diagrammatically in Fig. [11, and the sheet will become thickened and of materially reduced widthas it falls from its forming surface. Or if this does not occur, the sheet will become discontinuous and break up into a series of separate strands or streams. If the liquid flows from a circular forming edge, to tend to form a hollow cylindrical sheet, surface tension will quickly draw the sides of the cylinder in to-.

ward eachother until the liquid forms a solid rope-like stream instead of remaining a hollow cylindrical sheet. r

anginterposed film acting either It has been found that continuous sheets or curtains of liquid may be fo ed according to the present invention, howeve and may; be main?- tained in continuous form and of approximately uniform thickness free from any backing or support through a distance relatively great in com parison to the thickness of the film. This is accomplished by'giving to the liquid, as it is formed into the film, an oblique movement having a component of velocity in a direction tending to counteract the effect which the-surface tension of the liquid will have on it. It is also found that, in the practice of the present invention,films can be produced which are so truly continuous that they are even gas tight and serve as barriers for fumes or vapors. v

Such films or sheets may also be produced in many desired shapes, and with close control of thickness, while at the same time they fiow rapidly and substantially uniformly. The thickness of the film may be. varied over wide limits, ranging from a few hundredths of a millimeter to a millimeter or more. Flow velocities of a number of feet per second are easily obtainable without destroying the continuous character of the film or its substantially uniform thickness. Thus the desired conditions of a thin, substantially uniform, and rapidly moving liquid film are achieved, and if a source of light of the proper wave, length is provided in proximity to the moving film, the liquid will be irradiated in a practical and emcient manner. Since the unsupported film, out of contact with any solid supporting body through large areas, moves much more rapidly than a film Since a continuous and substantially gas tight film may be produced, such a' film may be used not only as a method of transmitting the product to be treated past the source of light, but also as a screen or filter to be interposed between the light source and the product to be treated, such to keep gases or fumes from the light source out of contact with the product to be treated, or as a lightfilter to filter out emissions of undesirable wave length, or both. It is also contemplated that the novel unsupported film of the present invention may be used as a screen, filter, or' baflie between the light source and any product to be treated, whether that product be in the form of a film of liquid or any other desired form. I

Referring now to Figs. 1 and 2 of the drawings, there is shown one form of apparatus for producing a free or unsupported moving,film of product to be treated, and also for producing such a film to act as a bafile or filter between the light,

source and the product, although it will be under,

stood. from what has been said above that either one of these films may be used without the other, without departing from the spirit of the invention.

The apparatus illustrated somewhat diagram- .matically in Figs. 1 and 2, comprises posts or standards 20 from which is supported, as by arms 22 what may be termed a bubble head or film head indicated in general by the numeral 23 and having an annular conduit or passageway 24 to which the liquid product to be treated may be supplied, .as by means of a conduit 25. Surrounding the. lower part of the film head or bubble head 23 is a lip ring 28 which is threaded on the film head, as plainly shown in the drawings, so that by turning the lip ring, its height with respect to the film head may be closely adjusted, and it may be locked in any desired adjusted position, as by means of the lock nut 29.

The outer bottom edge 30 of the member 23 projects slightly to form a lip, as shown, for cooperation with an inwardly projecting lip at the bottom edge of the. ring 28, but'above these lips there is a substantial annular space or chambine.

ber 3| between the members 23 and 28, into which the liquid may fiow through passageways 32 from the annular supply conduit 24. After reaching the annular chamber 3| the liquid flows downwardly through the space between the lip 30 and ring 26, which parts define the annular slot from which the liquid issues to form the desired film or sheet.

A substantially similar arrangement may be used for forming an innersheet or bubble to act as a barrier or film around a suitable source of light, such as an are light indicated diagrammatically at 35. This other film forming arrangement may comprise, for example, a bubble head or film head 40 having an annular conduit 4| fed with liquid through supply conduits 42. From the conduit 4|, the liquid flows downwardly through passageways 42 into an annular chamber 43 formed between the body 40 and a lip ring 44 screwed on the body 40 as in the case of the previous ring 28, and likewise held in any desired adjusted position as by means of a lock nut 45. The lower edge of the body 40 and the lower edge of the lip ring 44 have cooperating lips projecting toward each. other, as shown in the drawings, which lips define between them an annular slot or passageway from which the liquid issues to form the desired film or bubble.

The two film heads or bubble heads may operate in substantially the same 'way, and the same principles of adjustment and operation apply to both, although of course, there may be some differences either in the construction or adjustment of the two heads, if it is desired to have the inner film and the outer film of difierent shapes. Accordingly, the following discussion of the action of a film head and the various positions towhich it may be adjusted, will apply to both of the film heads except as otherwise specifically indicated.

As above stated, the effect of surface tension upon a liquid film formed in the shape of a hollow cylinder is to draw the sides of the film together into a somewhat conical shape until the sides coalesce and form a rope-like stream. This tendency is counteracted, according to the present invention, by giving the liquid acomponent of velocity in a direction tending to overcome the efi'ect of the surface tension. This component of velocity may be produced in a number of ways. One of the most satisfactory ways of securing it is to give the liquid a circular or rotary motion so that the entire liquid film swirls around its vertical axis and the centrifugal force produced by this rotary motion tends to move the sides of the film outwardly and thus counteracts the surface tension which tends to pull the sides of the film inwardly.

. To produce this rotary motion of the liquid,

the film head may be provided with vanes or nozzles somewhat similar to those used in a tur- For example, in Figs. 1 and 2 the passageways 32 between the conduit 24 and the chamber 31 are plainly shown as being formed obliquely of film or bubble which has been produced in actual practice.

Instead of obtaining the circular motion by means of the tangential nozzles 32, as shown in Fig. 2, the circular movement of the liquid might be obtained by providing vanes or deflectors at the bottoms of vertical passageways 42 through which the liquid flows, as shown in connection with the inner or lower film head in Fig. 1. These vanes or buckets 55 receive the liquid from the top through the passageway 42 and discharge it to one side, so that after passing through these vanes the liquid is caused to flow in a circular direction around the chamber 43, issuing from the film forming slot while still rotating so that any particular particle of liquid would have an oblique or somewhat spiral path of travel, asindicated at in Fig. 1. The centrifugal effect of this rotation would resist the surface tension of the liquid and would cause the film to remain of hollow form through a substantial length of travel, as indicated at 6|, instead of coalescing into a single central stream or rope.

The adjustment of the lips at the sides of the forming slot has considerable effect upon the form of the sheet or film, and the shape of the film may be varied by varying the adjustment of the lips. When the lips at the two sides of the slot are substantially flush with each other, as indicated in Fig. 4, the liquid tends to issue straight downwardly, as shown in Fig. l in connection with the inner film or bubble. If the lip ring-is raised slightly so that the inner lip is lower than the outer lip, then the liquid tends to issue with a slightly inward obliquity as indicated by the arrow in Fig. 5. I on the other hand, the lip ring be moved downwardly until it is below the inner lip, as in Fig. 6, then the liquid will issue in a slightly outward direction, as shown by the arrow 66. tends to cling to whichever lip is lower and tends to pull over to the side of this lower lip, with which it remains in contact after leaving the upper lip. While this tendency exists, the actual direction in which the liquid issues does not depend on this tendency alone, of course, but is infiuenced also by the effect of any centrifugal force which may be present, due to rotation of In other words, the issuing liquid the liquid. By adjusting the movable lip ring to various positions, bubbles or films of various shapes can thus be formed.

In Fig. 7 there is shown a similar but slightly different arrangement in which the film forming slot between the parts 400. and 44a is not vertical, as it was in Figs. 4, 5 and 6, but is inclined outwardly, the adjacent lip faces being in the form of a frustum of a cone. With this arrangement, if the apex angle of the cone be great enough, the .liquid will issue with suficient outward motion as indicated at 61, so that in many cases the efl'ect of surface tension is suificiently overcome without the necessity of employing a rotary movement of the liquid to produce a. centrifugal that centrifugal force assists in maintenance of the bubble ina stable form, and to this end a vane or bucket 55 may be employed as shown in Fig. 7, for producing'the desired rotation of the liquid.

When centrifugal force is employed, a=film or bubble may be produced having a free or unsupported length of four or more times its diameter. Whenever a bubble having a length of two or three times its diameter or longer is desired,

it is preferred to employ centrifugal force. When the length of the bubble is to be less than two or three times its diameter, however, and sometimes when it is longer than this, satisfactory results can frequently be obtained without spinning or rotation of the film, merely by causing the liquid to issue from the slot or forming surface with a sufiicient outward inclination or obliquity, as in Figs. 6, 7, and 8. The oblique angle at which the liquid issues, causes it to have a component of velocity in a direction tending to overcome the effect of surface tension.

When the spinning or rotating principle is employed, whether with or without the initial outward direction as in Figs. 6, 7, and 8, it is seen that the film issues from the slot or forming surface with a tangential component of velocity, and this tangential component, as well understood in mechanics, produces the centrifugal force present in the rotatinglbody of liquid, so that the tangential component is a componen in a direction tending to overcome the effect 0 surface tension.

It is not necessary in every case that the film be formed by liquid issuing from a slot. In many cases, the liquid can flow from one surface rather than from between two slot-forming surfaces. Such arrangements are shown in Figs. 9 and 10. In Fig 9, which shows a vertical radial section through a small fragment of a film forming head, the liquid fed through the conduit 10 into the annular chamber ll issues therefrom through the tangential nozzles l2, which give it a rotary motion, into the space l3 between the body 14 and the adjustable ring 15, then slides down the inner surface of the ring 15 and issues from the lip 16 thereof with a swirling or rotary motion so that centrifugal force is produced.

Although the space 13 forms, of course, a slot in one sense, yet in this construction the volume 'of liquid is so controlled that the issuing film does not fill the thickness of this slot, but the liquid issues only from that side of the slot formed by the lip 16, being free of the opposite or inner side of the slot. The issuing liquid, being in contact with the lip 16 and not with the body 74, will tend to be drawn slightly around the lip, and this tendency, together with the centrifugal force caused by the rotation of the liquid, will'make the film issue approximately in the direction indicated diagrammatically at ll. In Fig. 9, the lip surface from which the film is formed is at the outer side of the slot. In Fig. 10 is shown a similar arrangement in which the film lip is at the inner side of the slot. Here, the liquid is supplied through a conduit 80 to an annular chamber 8| whence it flows through a nozzle 82, (arranged preferably substantially tangentially) which directs it against a surface 83 on an adjustable ring 84. The liquid slides down this surface 83 to the lip 85 thereon, without being in contact with the opposite side of the slot, and is thus drawn slightly around the lip 85. The combined effect of this tendency to draw the liquid around the lip and the centrifugal force produced bythe rotary motion of the liquid, causes the film to leave the lip substantially in the direction indicated-at 86. After leaving the lip, the liquid is free of the inward drawing influence of the lip, and the outward centrifugal force then comes into full play, causing the diameter of the film to increase somewhat as it descends, with the result that the film may have a shape somewhat like an hour glass.,

In connection with the constructions shown in Figs. 9 and 10, it should be pointed out that whenever the film or sheet is formed by liquid flowing over a surface contacting with only one side of the film, the length of fiow between the point where the liquid firlsg; strikes the' forming surface and the point Whe e the liquid leaves the forming surface should b as short as practicable. If the liquid is required to fiow over the forming surface for any considerable distance, a type of flow is produced which is similar to that described in the above mentioned copending application, Serial No. 654,649. In this type of flow, the portion of theliquid film next to the solid surface moves very slowly compared to the outer portions of the film farthest from the solid surface, and thus it is impossible for the liquid to form a satisfactory film or sheet as it leaves the edge of the solid forming surface. in order to obtainan equal volume of fiow, it is generally necessary that the thickness of a film flowing in contact with a solid surface be far greater than the thickness of an unsupported or free film-as herein disclosed. Thus even when a more or less continuous sheet is formed by liquid leaving a forming surface after flowing for some-distance aiong'that surface, the unsupported film is necessarily verythick and is movingrelatively slowly. Its resultant velocity, as well as the component thereof tending to overcome surface tension, is small, and control of the film ,is-unsatisfactory. For this reason, in constructions such as that shown, for example, in

' Fig. 10, the liquid should be projected against the forming surface 83 only a short distance from the edge 85, as otherwise the liquid would move so slowly or would have to be so thick that it would turn sharply tothe right instead of leaving the forming edge in the direction of the arrows 86. Preferably the distance from the point where the liquid strikes the forming surface to the point..... I where it leaves the forming surface is not more than about 100 or 206 times the thickness of the film flowing over the surface, and it should be less than this if possible. The liquid also should issue from the jets or nozzles (such as 1.2 or 82), under substantial pressure, of at least about one pound per square inch and preferably several pounds per square inch, in order that the velocity of flow over the forming surface may be as fast as possible. 3 3 I Conditions are somewhat different, however,

when the liquid to form the film or sheet issues Moreover,

from a slot between twoconfining surfaces, for here the liquid canbe forced out under pressure and made to fiow much more rapidly than when it flows overa single surface, where-pressure is obviously impossible. Hence it is desirable I in most cases that a slot or nozzle be used so that better control of the-film or sheet can be attained, and the arrangements shown diagram- 'matically in Figs. 13 to 16 preferably include suitable slots or nozzles from which the liquid issues under pressure while confined at both sides.

The liquid passageways leading to the forming slot or nozzle are preferably of substantially greater cross sectional area than the cross sectional discharge area of the forming slot, so that the liquid flows easily and unimpededly to the actual slot. The walls of the passageways narrow down to form the slot only a short distance from the discharge edge of the slot, as readily seen in Figs. 1 to 8, in order that the frictional resistance to flow may be reduced as much as possible. Best results as to formation and control of the liquid film or sheet are secured when the liquid issues from the forming slot under substantial pressure, usually at least one pound per square inch and preferably several pounds per square inch.

When forming slots are used, they should be accurately and carefully machined and finished so as to have smooth lips or edges with auniform clearance distance between them, so far as can be practically attained within the usual limits of precision machine work. Good results have been obtained in practice from a forming slot having a width or clearance of 0.01 of an inch, or about 0.25 of a millimeter. The film formed by a slot is somewhat thinner than the width of the slot, the average thickness of the film or sheet being usually about eighty per centum of the width of the slot. 1

When the liquid issues from the forming edge or slot under a pressure of several pounds'per square inch, the force of gravity upon the thin film is relatively small in comparison to the other forces involved. Consequently gravity places no serious limitation on the direction which the film or sheet may take, and it may be shot upwardly or laterally from the forming means, as well as downwardly. Films with upward and with lateral direction of flow, formed as described in this application, have actually been produced and have been found'to be entirely practicable, so that their production is not merely an untried theory. When a hollow circular film (like the films 50 and BI in Fig. 1, for example) is shot upwardly, it can be made to turn either inwardly or outwardly at its upper end, depending upon the shape and adjustment of the forming slot.

In Fig. 19, there is shown diagrammatically I such an upwardly projected film or bubble which turns outwardly at i s upperend. Here, 'theforming head containing the forming slot is indicated at 20l. The film 202 is projected upwardly from the head, turns outwardly at its upper end and is caught in the annular'ring 203, from which the liquid is discharged at 204.

Since in each case the film is formed by a sheet of liquid leaving a solid surface, the film is in continuous gas tight engagement with the solid surface which constitutes the forming edge. If. desired, the opposite or free end of the film may j becaught or recoveredin a manner'which preserves its gas tight properties, but for some uses it is not necessary that the film be maintained .sociated film head 40.

gas tight. For example, in the irradiation of a liquid, if the source of light be placed within an enclosing film which is gas tight, there is no necessity for maintaining gas tightness'in the outer film of product being treated, so long as the film .is substantially uniform in thickness over most of itslength, so that it receives proper irradiation. Under such circumstances, a certain amount of splashing or even splitting of the film might be tolerated at its lower extremity.

But in other cases, and especially in the case of an inner or bafile film surrounding an open are light, it is desirable that the film be maintained gas tight throughout, in. orderlthat it may beeffective in preventing undesirable gases or vapors from the light source from-coming'into contact with the product being treated.

It is possible to catch the free end of the flowing film in such a manner as to preserve its gas tight properties, and this can be done in the manner indicated in the lower part of Fig. 1, in which an inverted conical sleeve I M is provided with its upper and open end having a diameter slightly greater than the diameter of the lower end of the inner or baflle film 6|. The lower end of the film impinges upon the inclined side walls of the member I0! and flows downwardly over them and out through any suitable discharge conduit I 02.

Similarly, the product film 50 can likewise be caught in a conical member I05, which at the same time is extended far enough upwardly so that it, together with an upper removable part I06, forms a casing forenclosing the entire bubble or film. The lower end of the bubble film 50 impinges upon the conical walls of the member I05 and flows down these walls and out through any suitable discharge conduit IOBa.

With this arrangement, both the baffie and screen bubble, and the product bubble, are caught in a gas tight manner, particularly if the outflow down so that an appreciable depth of liquid is maintained at the bottom of the apparatus, for

example, up to the levels indicated respectively by the lines I03 and I07. The film 6i thus forms an enclosure for the light source and prevents any ozone formedby the light or any other undesirable gases or vapors formed thereby, from head or film head II for forming the bubble GI ispreferably of hollow or annular shape, and a sleeve III connected to and rising from it may form a stack through which vapors from the light source are conducted upwardly away from any possible contact with theproduct. Electrode holding means orother suitable supporting means may also be placed within or project downwardly from the space within the sleeve III and its as-;

As the liquid in the .filrn50 run'sdownthe coni- .cal sides I05, the viscous drag exerted by the moving film upon the adjacent ai'r or other gas will cause some air or gas to be entrained in the acute angle I20 between the filrn'and the wall I05. Small bubbles of gas "will thus be carried down and will breakinto the space I2l. Y In this manner, the film acts as a pump slowly pumping through the conduits I02 and l06a is throttled gas from the space surrounding the film 'into space within the film, and the same is true of the barrier film 6|.

If there isa suitable outlet from the space place in a reverse direction, so that the film pumps gas from the space inside it to the space outside it, then obviously all that is necessary is for the lower end of the film to be caught on a surface inclined in the opposite direction; that is, extending obliquely downwardly from the inside to the outside of the film.

A self compensating or adjusting arrangement, which may be employed for either or both of the two films 50 and GI, is shown in Fig. 3. Here, a ring shaped ridge I25 tapering upwardly to a relatively sharp upper edge I26 is placed so that the film normally strikes on or very close to thisedge. If for any reason the gas pressure within the film should increase slightly above that outside the film, this would slightly expand the diameter of the film and cause the lower end of the film to strike outside the apex I26, on the outer inclined surface of the ridge I25. This would cause the film to commence a pumping action, pumping gas out from the space within the film so that the excess pressure within the film would be relieved and the film would re- .turn to its normal size, striking approximately 7 on the apex I26. One the other hand, if the gas pressure within the film should fall below the exterior pressure, the diameterof the film would be slightly decreased so that it would strike on the inner inclined side of the ring I26, and thus a pumping-action would take place, pumping gas from the space surrounding the film into the space within the film, until the two pressures were equalized.

As an example of the remarkable gas tight properties of films which can be produced with apparatus such as shown in Fig. 1, it may be mentioned that in tests the space within the film has been filled with any visible gas, or with tobacco smoke, and the openings at top and bottom have been corked up so that the smoke could not escape through these openings. Under these circumstances, the smoke has been maintained within the space within the bubble for many minutes, without any visible escape.

While the films or bubbles produced by the apparatus shown in Fig. 1 would be in the form of surfaces of revolution of various shapes (depending upon the construction and adjustment "of.the forming edge or slot, as for example in Figs."4 to 8), it is notnecessary that the film be always a surface of revolution, and the main principles of the invention can be applied also to films of various other shapes, such as plane sheets, or open or closed sheets of any form.

In the. case of a plane sheet formed by water flowing over a simple straight forming edge, from any suitable water supply I50 (Figs. 11 and 12), the effect of surface tension is to draw in the sides of the sheet, as indicated at I5I in Fig-11, so that the sheet rapidly narrows down after leaving the forming edge, and thickens. Such a sheet would not be satisfactory for irradiation work.

But by giving the liquid a component of velocfiow approximately straight downwardly, but to each side of the center the liquid is given a divergent direction as it leaves the forming means I60.

The outward component of velocity, away from the center, counteracts the effect of surface tension which tends to narrow the sides of the film,

as in Fig. 11, with the result that a large unsupported area of film of substantially uniform thickness can be produced. A film of this kind exhibits the curious phenomenon. however, that a thickened edge I62 forms along the film of increasing size in a downward direction. Since the liquid in this thickened edge does not receive the same intensity of irradiation as the liquid in the much thinner film, the thickened edge may be separately caught in receiving channels I63 and recirculated through the apparatus, or allowed to waste, while the main portion of the film, of the netting at greatly reduced velocity.

desired thin form, is caught in a receiving channel I64.

Still another form of film is indicated in Figs. I5 and I6, where a liquid supply and film forming means is indicated in general at I10, and a series of guide wires or rods III is provided, extending downwardly in the direction of film flow, so that the film contacts with these wirespr guides as it flows. The effect of surface tension is to make the film cling to the guides so that it does not tend to narrow and thicken, as inFig. l1. -It is I to be pointed out, however, that these guides III are relatively far apart in a direction across the film, and that no cross or transverse members need be provided between the film forming surface and the film catching or receiving chamber, so that this construction is to be clearly distinguished from a screen or netting, which has --no resemblance to it from a practical standpoint.

In the arrangement shown in Figs. 15 and 16, the guides I'll have very slight efi'ect in slowing up the velocity of the film, so that it moves rapidly and unimpededly in the wide spaces between the guides, whereas liquid flows over a screen or In Fig. 1'7 there is shown a form of irradiating apparatus in which the film is of plane form,

instead of in the form of a surface of revolution.

Here the source of radiation (such as an arc light) is illustrated diagrammatically at I80, and the product to be treated flows past the source of radiation in a thin film I8I of substantially uniform thickness, formed or maintained in any of the ways above described. For example, it may be maintained by guide wires J", as described in connection with Fig. 15.

In Fig. 1'7 there is also shown a. filter or barrier film I02 which, as above explained, is preferably of a continuous gas tight form, so that undesirable vapors or gases formed by the source I00 do not come into contact with .the product film I8I. A film I82 may likewise be formed and maintained in any of the ways above described,

1 guide wires "I being useful for this purpose. A casing I83 extends from one edge of the barrier source I00, so that all of the gases and vapors from this light source are kept between the barrier film I82 and the casing I83 and allowed to escape therefrom only through a suitable 'controlled outlet so that they do not come into contact with the product film H.

A slightly different form of apparatus is shown in Fig. 18, in which the product to be treated is in the form of a thin film I90 formed and maintained in any of the ways above describedv and having, for example, edge guides IlI acting as set forth in ,connection with Fig. 15. Here, two sources of radiation are provided, indicated at I9I and I92, on opposite sides of the film I90, each of these being, for example, an are light. Barriers or filters I93 may surround the sources I9I and I92, these barriers orv filters being of. any suitable form, solid or liquid. For example, they may be formed by a liquid film, such as the film 6| described in connection with. Fig. 1.

A casing I95 surrounds the product film I90 and both sources of illumination.- The ends of this casing I95 are curved as plainly indicated in the drawings; being preferably arcuate in form, with radii I96 swung about centers I91. The centers and radii are so chosen that they will reflect the radiations from the sources I9I and I92 to a sufficient extent so that the reflected radiations plus the direct radiations will give the product film substantially uniform intensity of treatment throughout the entire width of the film. As an example of satisfactory dimensions for accomplishingthisuniform treatment, the light sources I.9l and I92 may each be 9 inches from the center line of the film 190, the radii I96 may each be 8 inches,- the centers I91 may each be offset 1 inch laterally from a center line joining the two lightsources I9I and I92 at a distance 4 inches from the adjacent light source and 5 inches from the film I90, and the width of the film I90, between the edges I'lI, may be inches.

It is obvious from Fig. 18 that the central portion of the film, being closer to each source of radiation than the other part of the film will re- I ceive the greatest intensity of direct radiation from the sources. As one considers zones of film progressively farther and farther from its center line toward either side edge, it is seen that such zones will receive less and,less intensity of direct radiation becausev of their increasing distances from the sources of radiation and the smallerangles of incidence of the direct rays of radiation; hence, such zones farther toward the edges should receive more and more of the reflected radiation.

From the dot-dash lines I98 shown in Fig. 18, it is apparent that the greatest intensity of reflected radiation will be focused upon the edge zone of the film and progressively less and less intensity will be focused upon the portions of the film closer to the center, so that the'sum total of the reflected radiation plus the direct radiation is sub stantially constant across the entire width of the film, when the reflectors are made of the peculiar shape illustrated in Fig.18.

A further advantageous feature, in the apparatus shown inFig. 18, isto run the two sourcesof radiation I9I- and I92 on a two phase electrical current in which the two phases are 90 out ofv phase with each other. Thus one source of illumination will be at its maximum intensity when r the current in the other source is at z'ermand vice versa, so that the-two sources complement each other and the film as ,a whole receives substanr for the barrier or filter.

' be formed inthe manner taught by this application; that the product to be treated may be in the form of such a film; that such a film may be used as a barrier or filter; and that two films may be employed, one for the product and one It'is also apparent that such films are useful not only in irradiation, but also in other fields, as, for example, wherever it may be desirable to use a film of liquid, either as a light filteror as a gas barrier, or the like. The liquid used in the barrier or filter film may obviously have any desired chemicals or substances added to it to make it of any desired color, or to change its light transmitting properties "or'filtering characteristics in any desired way. It is also seen that the use of such a film for the product to be,treated is not necessarily confined to irradiation treatments, as such a film may also beuseful where it is desired to bring .the liquid to be treated into contact with a gas or vapor. When this is desired, the product film would simply fiow incontact with the desired gas or vapor, which could be on either one or both sides of the film. If desired, the product may be treated by contact with gas or vapor, Whileat'the same time it is also being irradiating light source, for example,

solidsiespecially in the form of falling grains,

flakes, or powder) ,and gases may also be treated, as well as liquids.

Apparatus substantially as shown in Fig. 1, has been constructed and tested under actual working conditions and is foundto operate satisfac-.

torily and efliciently in the manner above described. A few detailsfof such actual working apparatus maybe mentioned by way of example, purely as an illustrationof what is possible with apparatus 'of this kind, and not in a limiting In the above mentioned apparatus, the inner I or screen bubble or film is approximately 3 inches in diameter, and 8 inches long, and.0.17

of a millimeter in thickness. It fiows at the rate of about 1700 pounds of water per hour. The outer or product'bubble, which is of 'milkin the actual apparatus above' mentioned, is approximately 8 inches in diameter at-its top, about 9 inches in diameter at its bottom, about 15 inches long, and about 0117 of a millimeter to 0.20

of a .millimeter in thickness. It normally flows at the rate of approximately 4000. pounds of milk per hour, but it has been run satisfactory at a rate as high as 5000 pounds per hour, and as low as 2000 pounds per hour.

When speaking of thickness inthe figures given byway of example, the average thickness of the film is to be understood. Observation of the apparatus in actual use shows that there is some variation in thickness'in different parts of the film, but not enough to cause serious complications in the treatment of the liquid. It is found, for example, that ridges form in the liquid in a direction parallel orapproximately parallel to the direction of motion of the liquid. That is,

for example, with a bubble or film which is rotating or spinning as described'in connection lth n'i the bubble 6| in Fig. 1, the ridges would forin in an oblique or spiral direction approximately as indicated by the arrows 60. In the extreme condition, such ridges may at times be even twice as thick as the portions between the ridges, but even in such cases the amount of the liquid in these thickened ridges is so small and the maximum thickness of the ridges is so small that all of the liquid as a whole is adequately treated.

It isalso found by close observation that small ripples tend to form in the film in a direction obliquely across the ridges, but such ripples are not large and present no serious dimculties.

Applicant has been able to produce bubbles or films about 8 or 9 inches in diameter with a free or unsupported length of 18 inches, and with *an average thickness of Thus it is seen that it is possible to I about 0.15 of a millimeter. produce a film having an unsupported dimension in one direction several hundred times the thickness of the film. In general, however, the thickness of the film and its unsupported length will, in practice, depend on the character of the liquid forming the film, the desired capacity of flow, the length of time during which the film is to be subjected to the influence of irradiations or other treatment, and other conditions. In-

general, however, it may be said that the present invention is intended to include theproduction ofany film having an unsupported dimension in one direction of about fifty or more times the averagethickness of the film.

While in various forms of apparatus above de-.

scribed it is not necessary to have the solid parts of the apparatus move, nevertheless movement of the solid parts is in many cases not objectionable. Thus the parts constituting the forming surface or defining the forming slot may rotate or be other- In Fig. 1, for example,

might be rotated as a comprises providing a source of rays in proximity to a substance to be irradiated, and interposing between said source and said substance a freely flowing continuous film of liquid unsupported through a distance in the direction of flow many times greater than the thickness of said film and flowing-with a velocity having a component in a direction tending to counteract the tendency of surface tension of the liquid to break or contract 1 the film. I v

2. The method of forming a, continuous thin film of flowing liquid, free of any solid support throughout a distance in the direction-of flow of many times the average thickness of the film, which comprises from a forming edge with a velocity havinga component in a direction tending to counteract the effect of surface tension on saidfllm. I

3. The method of forming a continuous thin film offlowing liquid, free of any solid support throughout a distance in the direction of flow of I many times the averagethickness of the film and of approximately uniform thickness throughout said distance, which comprises forcibly projecting the liquid from true of the outer filmforcibly projecting the liquid a forming edge with a velocity .having a component in a direction tending to counteract the effect of surface tension on said film, the direction of said velocity being such that it does not cause rapid and marked thinning of the film in the area of the film near said forming edge.

I 4; The method of producing a continuous thin liquid film unsupported throughout a substantial area, which comprises causing liquid to leave a film-forming surface in an oblique direction with a component of velocity in a direction tending to counteract the effect of surface tension on said,

film.

5. The method of producing a continuous thin .liquid film unsupported throughout a substantial area, which comprises causing liquid to leave a film-forming surface in a direction having a component of velocity oblique to the main direction of movement of the film, to tend to counteract the effect of surface tension thereon.

" v 6. The method of producing a continuous thin film of flowing liquid free of any solid support throughout a large distance in the. directionof fiow relatively to the thickness of the film; which comprises causing liquid to leave a film-forming edge with a velocity having a component in a directionalong said edge to tend to counteract the effect of surface tension in said film, as well as a I component in a direction away from said edge.

7. The methbd of producing a continuous thin film of flowing liquid free of any solid support throughout alarge distance in the direction-of flow relatively to the thickness of the film, which comprises forcibly projecting liquid from a film- 'forniing slot with a velocity having a component in a direction along said slot tending to counteract the effect of surface tensionin said film, as well as a component in a direction through said slot.

8. The method of forming a continuous thin film of flowing liquid having a maximum thickness of less than a millimeter throughout an area of several centimeters in each direction and free or any solid support throughout said area, which comprises projecting liquid from a forming edge with a substantial velocity having a component in a direction tending to surface tension on said film, and said velocity having such direction that it does not cause rapid and marked thinning of the film in said area.

' 9. The method of forming a continuous thin film of flowing liquid of hollow approximately-annular form and free of any solid support throughout a large distance in the direction of flow relatively to the thickness of the film and throughout counteract the effect of a length approximately equal to or greater than the greatest diameter of the hollow film, which comprises causing the liquid to be projected from an approximately. annular formingmember, and counteracting-the tendency of surface tension to contract or break the resulting'film by'imparting to the liquid arotary motion around the forming.

member, to cause the liquid counteract said tendency of the surface tension. 10. The method of treating substances which comprises providing a source of radiation and moving the product to be treated past said source of radiation in the form of a continuous thin film any 'solid support I throughout an area of relatively large sizeand of flowinggliquid free of having a component of velocity in a direction tending to counteract the efiect of surface tension on said film.

11."I'he method of treating substances which comprises providing a source of radiation, moving the product to be treated pastsaid source of film to swirl around /lts axis to produce centrifugal force to tend to and with a velocity component radiation in the form of a substantially continuous thin film of flowing liquid free of any solid support throughout an area of relatively large size, and interposing between said source of radiation' and said product film a. substantially continuous thin barrier film offiowing liquid free of any solid support throughout an area of relatively large size, each of said films flowing with a velocity having a component'in a direction. tending to counteract the efiect of surface tension on the film.

12. Apparatus for forming a thin film of fiowing liquid which is continuous and free of any solid support. and of approximately uniform thickness throughout a relatively great distance in the direction offlow in comparison to the thickness of the film, said apparatus comprising walls forminga slot extending in a direction generally transverse to the length of the film to be formed, and means for moving liquid through said slot under pressure with a velocity having a component in a direction tending to overcome the tendency of surface tension to contract or break the film.

13. Apparatus for forming a thin film of flowing liquid which is continuous and free of any solid support and of approximately uniform thickness throughout a relatively great distance in the direction of fiow in comparison to the thickness of the film, said apparatus comprising a substantially circular forming edge, and means for supplying liquid to said edge to be projected therefrom and causing said liquid to move in a direction rotating around said circular edge as it leaves said edge, so that. centrifugal force produced by said rotary motion will tend to counteract the eifect of surface tension on a film formed by said liquid.

14. Apparatus for forming a thin film of flowing liquid which is continuous and free of any solid support and of approximately uniform thickness throughout a relatively great distance in the direction of fiow in comparison to the thickness of the film, said apparatuscomprising means forming a substantially annular passageway having a substantially circular continuous slot opening therefrom, and means for introducing liquid 'into said passageway under pressure in a circular di-X rection around said passageway, so that said liquid will issue from said passageway through said slot with a velocity component along said slot as well as a velocity component in a direction leavfirst passageway through said slot with a velocity component in a direction along said slot as well as a velocity component in a direction leaving said slot, and will form a hollow-spinning film,

the spinning motion thereof causing centrifugal impinge upon' said surface and fiow along said surfaceto make a gas-tight seal therewith.

1'7. Liquid film controlling apparatus comprising means. for forming .a continuous liquid film, and receiving means including a tapered ridge having a relatively sharp apex substantially at the normalline of incidence of the film, so that any difierence in gas pressure on opposite sides of the film will tend to cause the film to fallupon said ridge on one side or the other'of said apex, and so that when the film thus falls on one side or theother, it will tend to pump gas to restore the balance of gas pressure on opposite sides of the film.

18. Apparatus for forming a thin film of fiowing liquid which is continuous and free ofany solid support and of approximately uniform thickness throughout a relatively great distance in the direction of flow in comparison to the thickness of the film, and for receiving such a film' in a substantially gas-tight manner,- said apparatus comprising means forming a substamtially annular passageway having a substantially circular continuous slot'opening therefrom, means forintroducing liquid into said passageway under pressure and with a velocity component in a circular direction aroundsaid passagewawso that a said liquid will issue from said passageway through said slot with a vel city component along said slot as well as a velocity component in a di-.-

. rection leaving said slot, and will form a'hollowv spinning film, the spinning motion thereof causing centrifugal force which will tend to counteract the effect of surface tension, and means formingasubstantially solid film-receiving surface of approximately annular form approximately concentricwith 'and substantially spaced from said I slot, said surface being inclined 'to the axis of said film and so placed that said spinning film will impinge upon said surface and flow along force which will tend to counteract the effect of surface tension.

15. Apparatus for forming a thin film of flowing liquid which is continuous and free of any solid support and of approximately uniform thickness throughouta relatively-great distance in the direction of flow in comparison to the thickness of the film, said apparatus comprising means forming a substantially annular passageto said first passageway-and ther by acquire a' velocity component in a circular direction around said first passageway and will issue from said said surface to form a substantially gas-tight seal therewith.

19. The method of treating substances which comprises providing a source of radiation and a product to be treated in proximity toeach other,"

and causing liquid to leave a film-forming surface in an oblique direction so. as to form,.interposed between said source and said product, a

- 20. The method of treating substances, which comprises providing a source of radiation and causing a liquid to be treated tov leave a film-forming surface in an oblique direction with a component' of velocity in a direction tending to counteract the effect of surface tension on the liquid film thus formed, to provide a continuousthih film of flowing liquid moving past said source of radiation and free of any solid support throughout an area of relatively large size.

21. Product treating apparatus comprising a source of radiation, a forming edge, and means for moving liquid over said edge with a velocity having a component in a direction along said interposing between said source and said substance'a substantially continuous gas-tight film of moving liquid free of any supporting surface throughout an area relatively large in comparison to the thickness of the film and through a distance in the direction of flow of 50 or more times the thickness of the film, and flowing with a velocity having a component in a direction tending to counteract the tendency of surface tension of the liquid to break, or contract the film.

23. The method of forming a continuous thin film oi flowing liquid free of any solid support throughout a distance in the direction of flow of many times the average thickness of the film, which comprises projecting a film of liquid from a support with a velocity having a component in a direction tending to counteract the eflect ofv surface tension on said film.

BRIAN OBRIEN.

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