US 2813506 A
Description (OCR text may contain errors)
Nov. 19, 1957 E. E. JOHNSTON APPARATUS FOR APPLYING COATINGS 0R MASTICS TO FLEXIBLE WEBS Filed June 23, 1953 INVENTOR Z e/zeZfJZfim/z ATTORNEY APPARATUS FOR APPLYING COATHWGS OR MASTICS TO FLEXIBLE VVEBS Eugene E. Johnston, Lockport, N. Y., assignor to The Patent and Licensing Corporation, New York, N. Y., a corporation of Massachusetts Application June 23, 1953, Serial No. 363,455
3 Claims. (Cl. 118-101) This invention relates to methods of and apparatus for applying coatings or mastics to flexible webs or sheets of fibrous material.
More particularly the invention is concerned with methods of and apparatus for applying coatings of bituminous material or the like to continuously moving webs or sheets of fibrous material, whereby not only to improve the coating operation per se, but also to make possible the production of coated sheets or webs of this type, of improved quality.
While the invention is by no means limited thereto, it is of particular advantage in connection with the application of filled asphaltic coatings to the surfaces of felted fibrous sheets, wherein it is important that the coating be in the form of a smooth, uniform film of predetermined thickness over the entire surface of the sheet. Coated sheets of this character find a wide variety of commercial use. An illustrative example of the use of such sheets is found in the so-called deadening felts to be adhered to the surfaces of the metal panels or other parts of automobile bodies for vibration-damping or sound-absorbing purposes.
The coating method and apparatus of my invention are likewise of advantage in laminating one felted fibrous sheet to another as is necessary in many instances in order to satisfy special requirements in usage of the resultant product. Laminated, felted fibrous sheets possessing sound-absorbing or vibration-damping properties are used extensively in the construction of automobile bodies and for other purposes. The manufacture of laminated felted fibrous sheets has, however, sufiered a number of drawbacks, stcmmingfrom the fact that presently known methods of laminating such sheets by means of bituminous material, especially the so-called filled or mastic coatings, fail in many instances to result in the application of smooth, uniform films of the desired thickness to the surface or surfaces of porous or bibulous felted fibrous sheets or webs especially where it is necessary that the applied coating be in the form of a relatively thick, heavy film. By the term porous or bibulous in referring to felted fibrous sheets or webs .I mean such possessing substantially the following physical characteristics:
Weight 50 to 75 lbs. per 480 sq. ft.
Caliper 0.050 to 0.075 inch.
Tensile strength"--- 5 across machine direction, with machine direction.
Porosity 10 to 25.
In order to coat fibrous sheets of the foregoing types or characteristics with bituminous coatings, such as those generally referred to as filled or mastic coatings, it is necessary that the coating material be applied in heated, molten state, since these coating materials are relatively hard at normal atmospheric temperatures. The tempera ture to which the material must be heated and maintained in order to reduce it to the moltenstate required for con- States Patent the moving sheet of felt or the like.
2,813,506 iPatented Nov. 19, 1957 tinuous application thereof as a coating to felted, fibrous sheets, depends primarily upon the physical properties, more especially the melting point and penetration characteristics, of the coating material.
Typical of bituminous coatings employed for the purposes above stated are asphalts having a melting point between say 200 F. and 275 F. and apenetration gram needle, 5 seconds) of say 8 to 20 at 77 F. As phalts of this range of melting point and penetration require heating to temperatures of the order of 350 F. to 400 F in order to reduce them to a viscosity and fluidity to enable them to be applied as films to continuously moving sheets of felted fibrous material. When such asphalts are combined with suitable fillers to form socalled mastic or filled coatings, the resultant increase (depending upon the nature and relative amount of such filler) in the melting point and other physical properties of the filled coating, even higher temperatures are re quired for melting the coating and maintaining it at the viscosity or fluidity desirable for enabling it to be applied as a film to continuously moving sheets offelted fibrous material.
From a practical standpoint, particularly where such coatings are to be applied only to one surface of a moving sheet of fibrous felt, the coating operation requires the use of a coating roll or drum partially submerged and rotating within a bath or supply vat of the coating material heated to a temperature so as to be maintained at the desired fluidity or viscosity. The rotating roll or drum picks up a layer of themolten coating material during its rotation in the bath and carries the layer out of the bath and into contact with the desired surface of Since the coating drums or rolls in commercial practice are required to be of relatively large diameter, the layer of coating material picked up thereby from the bath must travel a substantial distance between the surface of the bath of coating material and the surface of the sheet to be coated. In consequence, there is an unavoidable substantial drop in the temperature of the layer of coating material during its travel between those two points, and hence an unavoidable reduction in its viscosity or fluidity (the amount of the reduction depending upon the physical characteristics of the coating material and upon the distance of its travel as a relatively thin layer on the surface of the coating roll) such as to render it difiicult, if not impossible, to apply the layer of coating material to the sheet in a film that will be smooth and uniform, and of predetermined thickness, over the entire surface of the sheet. In many cases this ditficulty is accompanied or manifests itself by the tendency of the coating material to form into strings or filaments, or to take on a streaky or corrugated condition on its surface.
Attempts have been made to remedy the aforementioned difliculty and the resultant undesirable effects by maintaining the coating material in its supply bath at higher temperatures, such that the layer of the coating will be sufliciently fluid or of low enough viscosity at the time it is brought into contact with the surface of the sheet. That practice, however, results in serious detrimental effects upon the physical properties of the coating material thus applied to the sheet.
The principal object of the invention is to provide an improved method of and apparatus for applying bituminous or like coating films to felted fibrous sheets of the Another object of the invention is to provide a method of and apparatus for coating felted fibrous material with bituminous coating material, which will make it possible to utilize felted fibrous sheets of relatively lower tensile strengths than have heretofore otherwise been possible in commercial practice.
Still another object of the invention is to provide a method of and apparatus for coating, as aforesaid, which will make it possible to apply such bituminous coatings to felted fibrous sheets in films of substantially greater thicknesses or weights than would otherwise be possible, especially when felted fibrous sheets having relatively low tensile strengths are to be employed.
Still another object of the invention is to provide a method of and apparatus for applying to the surface of a sheet of felted fibrous material a coating of bituminous material in the form of a film of predetermined thickness, uniformly smooth over the entire surface, and wherein such film functions as a bonding layer for laminating the thus coated sheet with another sheet of felted fibrous material of the same or similar physical character.
Owing to the more effective reinforcement of the fibrous sheets, particularly those possessing exceptionally low tensile strengths, imparted by the coating material when applied thereto according to my invention, further advantage thereof resides in making possible the coating of such sheets at relatively higher speeds of operation.
The foregoing and other objects and advantages of the invention will be readily apparent from the following more detailed description, and from the accompanying drawing, wherein the single figure is a fragmentary view, partly in side elevation and partly in cross-section, illustrating one form of apparatus that may be employed in the practice of the invention.
Referring more specifically to the drawing, the numeral indicates a suitable framework comprising vertical supports 11 and horizontal supports 12 extending therebetween. Suitably fixed to or otherwise mounted upon the horizontal supports 12 is a vat or supply box 15 for the bituminous coating material to be employed, the coating material being fed to and maintained at a desired level in the vat indicated at 16, by any suitable means (not shown).
The coating roll or drum is indicated at 18, this roll being mounted upon a rotatable shaft 19 in any convenient fashion so as to rotate in the direction indicated by the arrows shown in the figure.
As will be readily apparent, during rotation of the roll 18, a layer of the coating material in the vat will be picked up on the surface 20 of the roll or drum 18 so as to be carried thereby upwardly for application to the surface of the sheet to be coated. This sheet is indicated at A, and may be fed to the apparatus from any suitable supply roll (not shown) around guide rolls 21, 22 by means of draw rolls 23, 24, in the direction indicated by the arrows. As will be noted, the arrangement is such as to enable the sheet to be brought into contact with the surface of the coating roll it; at substantially the uppermost point 3ft in the course of its rotation. The layer of coating material carried on the surface 20 of the roll, is thus applied to the downwardly extending surface of the sheet A.
Suitably fixed to the framework it) may be arcuate plates 32, slotted as at 33. These plates are constructed and arranged to support forwardly extending arms 35, fulcrumed as indicated at 37 upon which are mounted a transversely extending doctor roll 39 adjacent the surface of the roll 18 in the path of its travel between the coating material in the vat l5 and the point indicated at 30.
Notwithstanding that it is general practice to employ a doctoring device, such as the doctor roll 39, in conjunction with coating operations of the type with which the invention is concerned, for doctoring off some of the coating material picked up on the surface of the coating roll, this doctoring of the coating layer has not enabled such coatings to be applied to the sheets in films of predetermined uniform thickness, free of strings, streaks or corrugations.
In accordance with the invention, I have found that by conducting the coating operation in such a way as to form a pocket or pool of the coating material immediately adjacent to the point where the sheet in its forward travel leaves the surface of the coating roll 18, the coating material accumulated in the pool or pocket at that point will enable the coating to be deposited on the surface of the sheet in a smooth and uniform layer of predetermined thickness, with no tendency on the part of the coating to streak, corrugate or form strings.
More specifically, by thus forming a pocket or pool of coating material immediately adjacent the point of departure of the sheet from the moving surface of the coating roll, the sheet is caused to float on the surface of the pocket or pool of coating, the latter thereby also serving to loosen the sheet from the surface of the coating roll and facilitate the continued, uniform, forward travel of the sheet. Furthermore, the coating material may thus be applied to the downwardly facing surface of the sheet in a smooth, uniform film of predetermined thickness or weight, the thickness or weight being controlled by regulating the position of the doctor roll 39 in relation to the surface of the coating drum 1%.
in the specific embodiment of the invention illustrated in the drawing, the aforementioned pocket or pool of the coating material is formed by positioning a transversely extending, steam-heated tube 40 on the side of the roll 18 opposite that on which doctoring roll 39 is positioned, and adjacent the path of travel of sheet A from the surface of the coating roll to the draw roll 24, the arrangement being such that tube 40 will barely rest on the surface of the coating roll 18.
Conveniently, the steam-heated tube 40 may be of a diameter of approximately 2 inches, the coating roll 1'8 may be of a diameter of 12 to 15 inches or more, and the doctor roll 39 may be of a diameter of approximately 3 inches.
As will be evident, the pool or pocket 42 of the coating material formed between the surface of the coating roll and the heated tube 40 may be formed by other suitable means. Thus, in lieu of the steam-heated tube 40 there may be employed a heated bar or similar member constructed and arranged to rest upon the surface of the rotating coating roll so as to cause the coating material to accumulate in a pool at the point of departure of the sheet from the coating roll and to cause the sheet to fioat thereon and be loosened thereby from the surface of the coating roll.
As hereinabove set forth, the invention finds particular utility in the manufacture of laminated sheets of fibrous material, such as sheets of porous or bibulous fibrous felt used for sound deadening automobile bodies, and like purposes. These types of products may be produced readily and with advantage by delivering a second sheet B from any suitable supply roll (not shown) around guide rolls 50, 51 and draw rolls 24, 23 so as to be brought into contact with sheet A after the film of coating is applied to the surface of sheet A and thereby be laminated to sheet A as the two sheets pass together around the surface of the draw roll 24.
As a specific example of a felted fibrous product produced in accordance with the invention, there may be cited a laminated sheet of automotive sound-deadening felt composed of a felted fibrous sheet A weighing approximately 60 pounds per 480 square feet and a felted fibrous sheet weighing approximately pounds per 480 square feet. These sheets were laminated to each other with a film of coating material, in the manner above described, the coating comprising a bituminous composition made of a mixture of approximately 55 percent, by weight, of asphalt (having a melting point of about 240 F, and a penetration of about 14 at 77 F.) and approximately 45 percent, by weight, of mineral filler. The filled composition had a melting point of about 270 F., and a penetration of 9 at 77 F.
In the production of the above illustrative laminated product, the film of the bituminous coating material was smooth and uniform throughout the sheet. It had a thickness of approximately 0.070 inch and weighed approximately 260 pounds per 480 square feet. The speed of travel of the sheet was at the rate of approximately 125 lineal feet per minute.
Bearing in mind especially that the tensile strength (as measured by a Scott tensile tester) of sheet A in this specific illustration was of the order of only about 10 (with machine direction) the coating thereof at satisfactory speed with a smooth film of bituminous composition of the character and in the amount specified has not heretofore been practical, so far as known to me. The advantages of the invention will be readily apparent, therefore, to those skilled in the art.
Having described the invention what I claim is:
1. Apparatus of the character and for the purpose set forth, comprising a coating roll rotatable in a supply of coating material, means for moving a sheet of felted, fibrous material over and into contact with the upper surface of said roll, adjustable means arranged to doctor coating material carried by said coating roll during its travel from said bath to the point of contact of said roll with said sheet, and means for accumulating a pool of said coating material beneath said sheet adjacent the point of departure thereof from said surface of the coating roll, said last-named means comprising an elongated member having its longitudinal axis substantially parallel to the longitudinal axis of said roll and being positioned substantially to rest on the surface of said coating roll and in the path of travel of said sheet beyond said point of departure thereof from said surface of the coating roll.
2. Apparatus as defined in claim 1 wherein the elongated member comprises a heated member.
3. Apparatus as defined in claim 1 wherein the elongated member comprises a steam-heated tube.
References Cited in the file of this patent UNITED STATES PATENTS 1,994,066 Denning Mar. 12, 1935 2,001,339 Wood May 14, 1935 2,176,093 Merrill Oct. 17, 1939 2,396,946 Grupe Mar. 19, 1946 2,676,563 Montgomery et al. Apr. 27, 1954