US 3238635 A
Description (OCR text may contain errors)
March 1965 T. E. GRAVENSTRETER 3,
METHOD AND APPARATUS FOR TREATING SHEET AND WEB MATERIAL Filed Jan. 7, 1963 3 Sheets$heet 1 IN V EN TOR. fia/vzas E'rarezzsfrefar Mard'l 1966 T. E. GRAVENSTRETER 3,238,635
METHOD AND APPARATUS FOR TREATING SHEET AND WEB MATERIAL Filed Jan. 7, 1963 3 Sheets-Sheet 2 TIIIIIIIIIIIIIA IN VEN TOR. 730127.45 I, Grarezzsfrefel' March 8,- 1966 1'. E. GRAVENSTRETER 3,238,635
METHOD AND APPARATUS FOR TREATING SHEET AND WEB MATERIAL Filed Jan. 7, 1965 3 Sheets-Sheet 5 FIG. 6.
United States Patent 3,238,635 METHOD AND APPARATUS FOR TREATING SHEET AND WEB MATERIAL Thomas E. Gravenstreter, Indianapolis, Ind., assignor to Interchemical Corporation, New York, NY. Filed Jan. 7, 1963, Ser. No. 249,951 2 Claims. (Cl. 34-23) This is a continuation-in-part of application Serial No. 835,294, filed August 21, 1959, now abandoned.
This invention relates to a method and apparatus for applying gaseous or vaporous material to a sheet or web. The invention especially relates to a method and apparatus for applying moisture to a sheet or web of paper, cellophane or the like.
A primary object of the invention is to provide a simple means of efiiciently applying gaseous material to a sheet or web of material. A more specific object of the invention is to provide a simple but efficient means of applying moisture to a moving sheet or web of paper. Another specific object of the invention is to provide a simple but eflicient means of applying moisture to a web of freshly printed paper to set the ink, in the case of moisture setting inks, or to condition the paper when it has been dried out by the drying of an ink by heat.
Several methods are proposed in the prior art for applying moisture or steam to moving web material. In general, these methods involve the use of expensive and cumbersome equipment that eject jets of steam onto the web. The apparatus employed requires large energy input to function and even then the performance is not always satisfactory. In many printing operations, it has been found that the temperature of the applied steam, about 212 F, or higher has a very harmful effect on the paper web being printed upon, causing drying up and v cracking of the paper. Typical prior art apparatus and methods are disclosed in United States Patents Nos. 2,464,119; 2,627,667 and 2,718,065.
I have now found a novel method of applying water vapor to a moving web which does not have any of the disadvantages of the aforementioned steam-jet methods. In accordance with my invention, I generate a humid atmosphere by a method of thoroughly mixing water vapor with the air of the atmosphere. This humid atmosphere is then applied to the moving web. This thorough mixing is accomplished through an initial step of premixing the water vapor with air. This is followed by a final mixing step in which the premixture is emitted into the path of an air blanket carried along by the moving web. The web is passed in close proximity to the point of emission of the premixture so that the movement of the web creates a turbulence as it passes the point of emission and thus provides efficient mixing of the premixture with the blanket of air traveling with the web. The humid atmosphere thus produced is then drawn into contact with the web by the motion of the web.
It should be noted that even where steam is used as the initial source of water vapor being premixed, the final mixture is so complete that the steam loses all identity as such in the created humid atmosphere. This is in marked contrast to the conventional steam-jet method where the steam is impelled against the web in a substantially undiluted state, the only air being mixed is that incidentally entrained in small quantities along the periphery of the jet stream. Likewise, in marked contrast to the streamjet method, the emitted premixture is not impelled or jetted against the web. Rather, the premixture is emitted at a pressure only sufficient to carry it into the path of the air blanket moving along the web. It is actually the motion of the Web which draws the final mixture into contact with the moving web. This results in a much 3,238,635 Patented Mar. 8, 1966 "ice more uniform distribution of moisture than in the jet devices, The invention will be more clearly understood by reference to the description of the accompanying drawings in which:
FIGURE 1 is a diagrammatic cross section of a general embodiment of this invention.
FIGURE 2 is a fragmentary prospective view of one embodiment of this invention.
FIGURE 3 is a side view of the embodiment shown in FIGURE 2.
FIGURE 4 is a prospective view of another embodiment of this invention with the top and one side removed.
FIGURE 5 is a fragmentary prospective view of still another embodiment of this invention.
FIGURE 6 is a diagrammatic cross-section of the embodiment of FIGURE 5, showing the various gaseous currents.
In FIGURE 1 of the drawings, 11 represents a supply source of treating gas, such as water vapor for treating a web of paper that has been freshly printed with a moisture setting printing ink. The moist air feeds through slot 12 at such rate that the feed through is at least as great as the volume of air to be displaced. A good safety factor is to use a feed through of treating gas that is approximately twice the volume of air being displaced from the web. A moving web is represented at 13. i The web should pass as close to the outlet slot 12 as is practical and still avoid occasional dragging of the web against the outlet; usually one-fourth inch distance is sufficient to avoid such dragging and, for this reason one-fourth inch is preferred as the nearest limit of approach of the web to the opening. The upper limit of distance of the web from the outlet slot is not particularly critical; however, since the turbulence created by the moving web decreases as this distance increases it is preferred that the distance be not greater than about one inch. Another factor that affects the turbulence of air 14 moving with the web is the speed of the web. Thus, the greater the speed of the webin other words, the faster the speed of printingthe more turbulence there will be.
The moving web 13 may come directly from a printing roller or it may pass over various intermediate guiding rollers or cooling rollers 15. Similarly the web, after being treated can be passed over any desired path as chill roll 16.
In the practice of the invention, it has been found that optimum mixing or turbulence is obtained if outlet slot 12 is no wider than the traveling web. Of course, if the slot is not as wide as the web then a portion of the web will not receive the same treatment as the remainder of the web.
In calculating the amount of treating gas to use, it is assumed that the Web carries along with it a blanket of air equal to the width of the web and having a thickness equal to the distance between the web and the outlet. Thus if the web is three feet wide and is traveling onehalf inch from the source at a rate of 400 feet per minute the volume of air carried along by the blanket would be 50 cu. ft. per minute. As a safety factor to allow for leakage around the web and source, the total feed of treating a gas should be approximately doubled, or about cu. ft. per minute.
Any convenient source of treating gas can be used. If the gas is a substance that can normally exist as a liquid at the temperature and pressure of application it is desirable to remove substantially all of the unvaporized substance before application of the vaporized portion to the web. Thus where the invention is being employed to set moisture setting printing inks the preferred temperature of application of the moisture will be below 190 F.
.and most: preferably about to F. In this instance, precautions should be taken to supply the humidifying gas as free from water droplets as is practical to achieve. This is because the addition of Water droplets onto the web of paper is objectionable in that it results in sporadic moisture addition rather than uniform addition.
FIGURES 2, 3 and 4 of the drawing illustrate two specific devices for generating a humid atmosphere that is relatively free from water droplets.
Housing 21 defines an enclosure which is divided into chamber 23 and chamber 24 by centrally located apertured plate 22. Except for the apertures 25 contained in plate 22, chamber 23 is substantially airtight. \Vater vapor is fed into chamber 23 through tube 26 which longitudinally runs through the chamber. Tube 26 has a plurality of openings 27 formed therein through which the water vapor enters chamber 23. Surface heater 28 comprises a tube which also passes through chamber 23 parallel to tube 26 and is heated by a constant stream of hot air or gas passing through the heater. Surface heater 28 maintains the temperature in chamber 23 at a level sufficient to substantially prevent any condensation of water vapor contained in said chamber. It will be understood that a surface heater having an extended surface may be used in place of tubular heater 28 if desired. Chamber 24 is defined by top 29, bottom 30, and side walls 31 and 32 of housing 21, apertured plate 22 and grill 33 which comprises a plurality of longitudinal parallel bars 34. The operation of the humid atmosphere generating device will be better understood by referring to FIGURE 3 together with FIGURE 2.
Moving web 35 moves traversely of grill 33 under the conditions previously described with respect to FIG- URE 1. The distance between grill 33 and web 35 is subject to the conditions considered in the description with respect to FIGURE 1. Water vapor which enters chamber 23 through tube 26, is maintained above its condensation temperature by the heating action of surface heater 28. The water vapor then passes through the apertures in apertured plate 22 into chamber 24 wherein it becomes mixed with some air. The water vapor air mixture passes between bars 34 of grill 33 into the path of the blanket of air carried with the web thereby creating a turbulence which results in the blanket of air being displaced by a water vapor-air mixture as previously stated. In order to insure complete displacement of the air blanket, it is preferable to have the water vapor emerge from the generating device under a very slight pressure. This pressure is achieved by having the apertures 25 in plate 22 of a number and size selected to provide watervapor emerging from chamber 23 under slight pressure. The placement density and the proportions of bars 34 of grill 33 are selected to guide the water vapor-air mixture emerging from chamber 24 into the path of the air blanket traveling with the web 35. The generating device of FIGURES 2 and 3 is preferably used with a vertically moving web as shown in FIGURE 3. It has been found that some slight condensation of water-vapor may occur within chamber 24. However, because of the verticle positioning of the web, the condensed water-vapor can not contact the moving web and thus has no etfect on the operation. Whatever moisture does condense is readily eliminated through drain 36 opening into drain pipe 37. Bottom is slightly inclined toward drain 36 so that any condensed droplets will flow toward the drain.
On the other hand, where the humid atmosphere generating device is positioned above a horizontally moving web, even slight condensation of water vapor results in droplets which may drip on to the web causing adverse effects. This invention, accordingly, provides a humid atmosphere generating device which provides a droplet free water vapor. Reference is made to FIGURE 4 which shows such a device with one wall and top removed. Housing 41, which comprises bottom 42, front wall 43, rear wall 44, and side wall as well as a top and a second side which have been removed to expose the internal structure, defines chamber 46. Bottom 42 has formed therein slot 47 which traverses the width of the bottom. Housing is constructed of a heat insulating material and with the exception of slot 47 is substantially airtight. Input of Water vapor into chamber 46 is accomplished by means of water vapor carrying tube 48 mounted in wall 44 and having formed therein a plurality of apertures 49 which open into chamber 46. The temperature of the chamber is maintained above the condensation level of water vapor by suitable heating means which in this embodiment comprises surface heater 50.
The device is mounted above horizontal moving web 51 so that bottom 42 is between A and /2 inch above said web. Moving web 50a moves traversely of slot 47, the length of which is preferably equal to the width of said web.
Water vapor entering the chamber is prevented from condensing by the temperature level maintained in the chamber by heater 50 as well as the insulated walls of the housing. Water vapor which accumulates within chamber 46 emerges droplet free through slot 47 into the path of the air blanket carried by moving web thereby creating a turbulence which results in the displacement of the air blanket by a mixture of air and water vapor.
Referring now to the method and apparatus shown in FIGURES 5 and 6, housing 51 of which the front and portions of the top and sides are broken away completely encloses premixing chamber 52. Housing 51 traverses web 53 and is parallel thereto. Slot 54 in the base of housing 51 completely traverses web 53. Heater 55 comprising tube 56 containing a suitable heated fluid and parallel fins 57 is situated proximate to slot 54. A series of aligned spaced apertures 58 are formed in the side wall of the housing away from the slot. Hollow conduit 59 is positioned in parallel spaced relationship to the apertured side wall of housing 51 so that the series of aligned spaced apertures 60 in conduit 59 are in spaced registration with the corresponding apertures 58 in housing 51. Water vapor from conduit 59 is driven through apertures 60 and through corresponding apertures 58 into premixing chamber 52. The driven water vapor will entrain air from the atmosphere into chamber 52. The proportion of air to water vapor carried through apertures 58 will vary directly with the size of apertures 58 (which are larger) in relation to the size of apertures 60 (which are smaller). For example, if the size of apertures 60 remains fixed, increasing the size of corresponding apertures 58 will increase the amount of air entrained and consequently the proporition of air in the premixture. The proportion of air with respect to water vapor will determine the temperature at which the water vapor will condense or dew point of the mixture. The desired condensation point will vary with the nature of the application of the generated humid atmosphere. For example, in moisture set printing best results are obtained if the premixture has a dew point of about to F. The relative sizes of the apertures may be fixed for given applications.
Following a cycle in the operation of the embodiment of FIGURES 5 and 6, water vapor 61 which may be steam is driven into conduit 59 from a source not known. The water vapor is then driven from apertures 60 through corresponding apertures 58 into premixing chamber 52 carrying air along through apertures 58. In chamber 52 there is extensive premixing of the air and water vapor. The cooling efiect of this premixing tends toward some condensation of the water vapor. However, any condensed water vapor is entrained by the incoming stream of water vapor and air past heater 55 where the premixture is heated to prevent condensation of water vapor as well as to evaporate any condensed water vapor. The heated premixture is then passed through slot 54 which is most preferably at an acute angle into the path of air blanket 62 which is carried along the surface of moving web 53. The resulting turbulence brings about the final mixture of the premixture with the air blanket, and the resulting humid atmosphere is drawn into contact with the web by the motion of the web. It has also been found that if the speed of the web is increased requiring a greater amount of humid atmosphere to be generated, this can be accomplished solely by increasing the pressure in conduit 59 and consequently the rate at which water vapor is driven from apertures. More air is entrained through apertures 58 so that the proportion of air:water vapor remains constant irrespective of the rate of feed of water vapor into premixing chamber 52. Thus, the amount of humid atmosphere generated may be varied without atfecting the aircwater vapor ratio.
Heater 55 operates by a heated fluid 63 which passes through tube 56 from a source not shown.
It will be understood that I intend to cover all changes and modifications of the embodiments, herein described for purposes of illustration, which do not constitute depar-ture from the spirit and scope of the invention,
What is claimed is:
1. In moisture set printing, a method of providing moisture to a printed moving web which comprises generating a humid atmosphere having .a temperature of from about 140 to 180 F. by (1) premixing air with water vapor in a zone, (2) heating said premixture .to prevent moisture loss by condensation, (3) restricting the air being carried along by said moving Web to a blanket extending for a distance from A to 1 inch from said web, (4) emitting said premixture into the path of said air blanket whereby a turbulence is created which causes a final mixture of said air blanket and said premixture, the humid atmosphere created thereby being drawn into contact with the moving web by the motion of said web.
2. An apparatus for uniformly mixing water vapor with the atmosphere surrounding a moving web and applying said uniform mixture to the moving web comprising a housing enclosing a chamber, said housing being spaced from said web and having formed therein at least one slot-like opening traversing the width of the web in a position substantially parallel to said web at a distance of from A inch to 1 inch from said web, means for introducing water vapor and air into said enclosed chamber to effect a premixture of said gases prior to the premixture being moved through said slot-like opening into the path of the air blanket being carried along by the web to create turbulence whereby the exiting premixture and the air blanket are mixed into a final mixture prior to being applied to the web and heating means within said enclosed chamber for heating the premixture to prevent condensation of water vapor, said means for introducing water vapor and air into the chamber comprising a series of aligned apertures in said housing, a conduit for carrying said water vapor positioned outside of said housing in adjacent spaced relationship to said series of apertures and a series of aligned apertures formed in said conduit corresponding to and in spaced registration with the housing apertures, the apertures in said conduit being smaller than the corresponding apertures in said housing, whereby water vapor passing from said conduit apertures through the corresponding housing apertures entrains air from the space separating the conduit and housing apertures into the housing.
References Cited by the Examiner UNITED STATES PATENTS 2,346,186 4/1944 Poesl 34-155 2,613,603 10/ 1952 Ireton 34-23 2,627,667 2/1953 Gillis 3423 2,731,732 1/1956 Harris et-al 34160 2,838,982 6/1958 Dupasquier 34155 WILLIAM F. ODEA, Primary Examiner.
NORMAN YUDKOFF, Examiner.