Apparatus for applying liquid to a web
United States Patent 1191 1111 3,874,331 Kirsen Apr. 1, 1975 [54] APPARATUS FOR APPLYING LIQUID TO A 1,508,469 9/1924 Osgood 118/D1G. 15 WEB 2,057,509 10/1936 Bauer 118/228 2,605,684 8/1952 Nagels et a1. 118/227 X [75] Inventor: B rnar Klr n, Lon ngl 2,926,628 3/1960 Black et a1 118/227 x [.73] Assigneez GAF Corporation, New York, NY 3,000,287 9/1961 Heldens 118/227 X [22] Filed: Nov. 1 1972 FOREIGN PATENTS OR APPLICATIONS 481,284 2/1952 Canada 118/227 1211 P N04 302,745 926,952 5/1963 United Kingdom 118/249 Related US. Application Data [63] Continuation-in-part of Ser. NO. 107,278, Jan. 18, Primary EXaminerJ9hn McIntosh I971, abandoned. Attorney, Agent, or Firm-Walter C. Kehm; Samson B.  
  Leavitt; Arthur Dresner [30] Foreign Application Priority Data Oct. 16, 1972 United Kingdom 47635/72 57 ABSTRACT 52 us. c1 118/227, 118/249, 118/262 A backing roller adapted to apply a liquid to a Web of [51] Int. Cl. B05c 1/08 material is Provided Where Such roller is formed with [58] Field of Search 8/227, 228 224, 212,&#34; a plurality of side-by-side resilient vertical application lug/DIG 15, 249, DIG 23 95/89 surfaces or protuberances. By metering controlled 354/318, 297 amounts of liquid on to the web, even distribution is assured. The density of the pro&#39;tuberances varies from [56] References Cited 60 to 100 per square inch, with the sides sloping t0- UNITED STATES PATENTS Ward one another- 1,112,134 9/1914 Hansing Il8/DIG. I5 10 Claims, 6 Drawing Figures APPARATUS FOR APPLYING LIQUID TO A WEB The present invention is a continuation-impart of my co-pending application, U.S. Ser. No. 107,278, filed Jan. 18, 1971, now abandoned entitled LAMINA LIQ- UID FILM APPLYING APPARATUS. This invention relates to means for depositing liquid on a face of a lamina or web passing between two rollers, wherein one of the rollers employed has a surface configuration as hereinafter described.  
  More particularly, the instant invention employs rol lers between which pass a lamina or web, where at least one of the faces of the lamina or web is wetted by liquid disposed on the contacting roller (hereinafter referred to as the applicator roller) and usually transferred thereto by a transfer roller. Such apparatus is used for a variety of purposes, for instance for the application of inks, lacquers, emulsions or photographic fluids, and especially in the diazo reproduction processes, of the so-called semi-dry type, wherein, an exposed diazo paper sheet is passed through a pair of squeeze rollers ofa multiple roller system, which roller system picks up development fluid from a source thereof, and transfers it to paper passing through the squeeze rollers.  
  Of concern in carrying out the aforementioned is to ensure that controlled amounts of liquid are applied to the side of the paper remote from that to which the developing fluid is applied. In so doing, curling of the sheets of paper is obviated after passing through the rollers, and when such paper is subsequently dried.  
  With such diazo processes, and indeed with other procedures wherein a particular side of the web or sheet is to be wetted, not only must a controlled amount of liquid be applied by the backing roller, but also the liquid must be applied evenly, and no tear or other markings be apparent thereon after the sheet has passed through the rollers.  
  Hitherto backing rollers have been used having hard or resilient surfaces which may be smooth or slightly roughened, or alternatively may have a ribbed configuration. Thus the surface may be grooved either radially or transversely, or be wound with wire whereby a spiral groove is provided.  
  The practice of using a roller upon which a filament is wound is not new, but such rollers employing a relatively heavy gauge filament or where the filament is wound as a more or less open helix tend to flood the web with an excess of liquid or they may cause a pattern of light and heavy coverage by the liquid. The roller contacting the image side of the web, the so-called applicator roller, is often a smooth roller. Such a roller, by virtue of its uninterrupted even exterior displaces more liquid than is needed for a satisfactory development. An alternative prior art design provides minute transverse grooves also called micro grooves, along the entire length of the applicator roller. These grooves work by capillary action and are satisfactory at low speeds. At higher speeds, however, the liquid from the saturated roller is flung radially outward which produces a print so heavily soaked that drying becomes a major problem.  
  Accordingly, the main object of the present invention is to avoid the defects of the prior art.  
  Another object of the present invention is to provide a liquid applying apparatus capable of uniformly applying liquid to a web of material.  
  Still a further object of the present invention is to provide a roller configuration having a backing roller adapted to meter out controlled amounts ofliquid onto a web passing in proximity thereto.  
 A further object of the present invention is to provide a backing roller with a plurality of protuberances extending therefrom adapted to apply liquid to a web of material. Still another object of the present invention is to provide a backing roller having an array of protuberances extending diagonally with respect to the applicator roller.  
  With the foregoing and other objects in view, there is provided an apparatus for applying a film of liquid developer to moving lamina including: a liquid pick-up roller, liquid supply means for applying a film of liquid to the said liquid pick-up roller; a liquid transfer roller having a surface adapted to retain liquid rotatably in contact with the said liquid pick-up roller; a liquid applicator roller a lamina supply means adapted to cause the lamina to move against said liquid applicator roller; and a roller train disposed and arranged to supply liquid to a surface of said lamina moving past the said applicator roller on the surface thereof, remote from said applicator roller by means of a backing roller having contoured surfaces in the form of a plurality of protuberances in side by side relationship.  
  It has now been discovered, however, that if backing rollers are used having a surface which is covered by a plurality of protuberances, the distribution and configuration ofwhich is hereinafter defined, then liquid may be applied from the tops of the protuberances, whereby the web or lamina is wetted in a controlled manner, without the appearance of uneven surface markings after leaving the machine.  
  Furthermore, backing rollers according to the inven tion, are characterized by the provision on the surface thereof of an array of substantially frusto-conical protuberances having a density of from 60 to protuberances per square inch, the protuberances having a height of not less than one&#39;sixteenth inch, the spacing of the protuberances from each other being not less than half the depth.  
  Particularly good results are obtainable with such surface configurations wherein the sides of the protuberances slope towards each other. The angle of the sides of the protuberances may be such that the space between them is substantially V-shaped, and the tops of the protuberances may be flat, curved or pointed.  
  Particularly good results are obtainable with an array of protuberances disposed diagonally with respect to the roller axes. It is preferred that the protuberances are made of a resilient material, e.g. natural or synthetic rubber, or other plastics material.  
  Backing rollers according to the invention are of particular use for the controlled wetting of the non-image side of diazo papers in a diezo developing machine using rollers as hereinbefore described Accordingly, a rustless wire filament not exceeding about .012 inch in diameter is wound so closely upon a rustless metal core that its diameter equals the pitch of the winding. By this means a precise roller component is obtained serving a threefold function, i.e., transferring a more than adequate supply of liquid to the applicator roller, spreading the liquid supply evenly over the entire length of itself and of the applicator roller, and balancing the demand of liquid.  
  The array of protuberances on backing rollers according to the invention may be applied thereto by a cutting operation or by a moulding operation. Thus a moulded sleeve may be applied to the smooth surface of a metal roller. Such a sleeve may be produced for example by hardening a layer of a rubber latex or a polymerizable plastics, material on a cut master roller, stripping the hardened sleeve therefrom, turning the sleeve inside out and applying it to the surface of the a backing roller.  
  The small amount of liquid picked up by the sheet is then dried by a dryer which also constitutes part of this invention.  
  A true cylinder of metal or other heat resisting material revolves around a heating element. In contrast to other drying devices where radiated or convected heat is employed at a relatively low degree of efficiency, this cylinder dries a web in direct contact at a far greater efficiency and at a speed in step with the capability of the developer unit. The energy requirements of this drying cylinder are considerably reduced compared with other drying devices so that a machine incorporating this invention may be operated without the usual ducting. A sensing or indicating means provides control over the maintenance of an optimum mum temperature.  
  The invention is more particularly described and illustrated in the accompanying drawings, in which:  
  FIGS. la and 1b are longitudinal sections of protuberances on the surface of a backing roller of the invention.  
  FIG. 2 is a schematic representation of protuberances on a backing roller according to the invention.  
  FIGS. 3a and 3b are transverse sections of protuberances according to the invention on backing rollers, and  
  FIG. 4 is a schematic representation of a dizao apparatus employing backing rollers according to the invention. Referring to FIGS. 1a and 3a an array of frustoconical protuberances l are formed on a backing roller made for example of a rubbery material of about 40 Shore hardness, each have a rounded top portion 2, the valley 3 between adjacent protuberances also being rounded. The sides 4 of the protuberances are inclined so that the sides of adjacent protuberances taper towards each other towards the root of the protuberances.  
  Alternative exemplary configurations of the protuberances are shown in FIGS. lb and 3b, wherein in FIG. 1b the tops 5 of the protuberances are flat and the sides of the protuberances are flat and the sides of the protuberances are inclined so that adjacent surfaces meet at a point 6. In FIG. 3b the tops 5 of the protuberances are pointed and the sides inclined at an angle of approximately 45 to meet in pointed valleys 6.  
  As hereinbefore described, the protuberances may be integral with the backing roller or may be moulded on a substrate which is subsequently attached to a metal backing roller.  
  Referring to FIG. 2, the backing roller 7 is provided with an array of protuberances 8 according to the invention, in which the lines of protuberances in the array are disposed diagonally to the longitudinal axis of the roller.  
  Referring to FIG. 4, the arrangement for a diazo copying machine shown therein is contained in a frame (not shown), and comprises an inlet means 9 for sheets of exposed diazo copying paper, and two reservoirs 10,  
 10 for diazo developing liquid. A first pick-up roller 11 is disposed partly in reservoir 10 in rotating contact with a transfer roller 12 which in turn is in rotating contact With an applicator roller 13.  
  A second liquid pick-up roller 14 is disposed partly in reservoir 10, and a backing roller 15 according to the invention disposed in rotatable contact therewith.  
  The applicator roller 13 and backing roller 15 are so disposed in relation to each other to form a nip for diazo papers passing&#39;therebetween, for instance by one or more spring biasing means.  
  A heated rotating drum 16 is provided above the rollers 13 and 15, and a web guiding, semi-circular, fixed drum 17 is provided adjacent the drying drum. Delivery rollers 18 are provided at an exit stage of the arrangement.  
  In operation, the path of successive diazo papers in passing through the machine is shown by the broken line. The pick-up rollers during rotation pick up developing fluid from reservoirs 10, 10&#39;, transfer it to adjacent rollers, and thereafter it is applied by applicator roller 13 to the exposed side of a diazo paper as it passes through the nip of rollers 13 and 15. At the same time, fluid is applied to the other side of the diazo paper by backing roller 15 according to the invention in a&#39; controlled and even manner.  
  After leaving the roller nip, the moist diazo papers pass over the heated drying drum whereby development of the image and drying of the paper take place simultaneously, and subsequently are guided by driving bands over the semi-circular drum 17, and finally they are discharged from the apparatus between delivery rollers 18.  
  With the small amount of liquid deposited on the image side it becomes possible to reduce the amount of liquid at the back of the web to a fraction of the frontal deposit without causing undue curl. With a plain backing smooth roller a meniscus would form during such periods when no web is passing through the rollers and would spread its liquid over some distance after the leading edge-of the web or sheet. This undesirable effect would occur on every sheet travelling through the rollers. Other forms of backing rollers with fins or corrugations have been tried which although minimizing the uncontrolled wetting of the rear of the sheet, tend to fill with liquid when the spacing is close, thus producing wet streaks, or tend to leave corrugations on the web or sheet when the spacing is wide. The backing roller of this invention is unique, inasmuch as it provides the necessary support to the web whilst the liquid is being applied, without ever causing a meniscus to accumulate. This is achieved by the disposition on a roller of a multiplicity of points of a yielding material in diagonal pattern both in a left to right as in a right to left direction.  
  While the invention has been disclosed in conjunction with certain particular embodiments, it is not confined to the details of construction herein set forth and this application is intended to cover such departures or modified arrangements as may come within the purposes of the improvements or the scope of the following claims.  
 What is claimed is:  
  1. In an apparatus for applying a film of liquid developer to both sides of a moving web of exposed photosensitive material of the type having means for advancing such web, first and second liquid pick-up rollers, liquid supply means for applying a film of liquid to said first and second liquid pick-up rollers, a liquid transfer roller having a surface adapted to retain liquid in rotatable contact with the first liquid pick-up roller, and a liquid applicator roller in rotatable contact with said liquid transfer roller and adapted to apply liquid to the exposed surface of said moving web, the improvement comprising a backing roller in rotatable contact with the second liquid pick-up roller to receive liquid therefrom, and arranged to cooperate with the applicator roller to define a nip through which the web is advanced&#39;, said backing roller having an array of evenly spaced protuberances having sides thereof inclined at an angle to a line normal to the surface of said backing roller and sloping toward each other, integrally formed on the surface thereof and arranged in a diagonal pattern with respect to the rotational axis of said backing roller to uniformly apply a controlled amount ofliquid to the unexposed surface of said web to prevent curling.  
  2. In an apparatus as claimed in claim 1, wherein: the density of said protuberances varies from 60 to 100 per square inch.  
  3. In an-apparatus as claimed in claim 1, wherein: the height of said protuberances is greater than onesixteenth inch.  
  4. In an apparatus as claimed in claim 1, wherein: each of said protuberances are spaced from one another by a distance not less than one-half the depth of such protuberances.  
  5. In an apparatus as claimed in claim 1, wherein: the spacing between the protuberances is substantially V- shaped.  
  6. In an apparatus as claimed in claim 1, wherein: the top portions of said protuberances are flat.  
  7. In an apparatus as claimed in claim 1 wherein: the top portions of said protuberances are curved.  
  8. In an apparatus as claimed in claim 1 wherein: the sides of said protuberances are inclined at an angle of 45 with respect to the backing roller surface.  
  9. In an apparatus as claimed in claim 1, wherein: the surface of the backing roller having said protuberances is formed of a resilient material.  
 10. In an apparatus as claimed in claim 9, wherein:  
 said resilient material has a shore hardness of about 40.  
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