Method and apparatus for manufacturing wallboard

April 8, 1941. J. κ. duncan 2,238,017

METHOD AND.......APPARATUS FOR MANUFACTURING WALLBOARD

Filed Oct. 23, 1937

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Patented Apr. 8, 1941

2,238,017

UNITED STATES PATENT OFFICE

Claims.

This invention relates to methods and apparatus for manufacturing, in a continuous manner, wallboard of the type having a cementitious or composition core encased in fibrous liners or cover sheets. More specifically, the invention relates to the formation of wallboards of this character having beveled or recessed ends, and has for an object the provision of an improved method and apparatus of this character.

The manufacture, in a continuous stream or sheet, of wallboard having a cementitious or composition core, and paper or fibrous liners or cover sheets, is, of course, well known. It is likewise well known to produce, in a continuous manner, such wallboard having beveled or depressed longitudinal edges, so that when the wallboards are assembled in a wall structure a more perfect joint between the boards may be formed by applying suitable joining tape and sealing cement to the recess formed by adjacent edges of the board.

While a similar advantage is to be found in wallboards having their transverse ends beveled or depressed, particularly when the boards are to be erected with the long dimensional boards horizontal, no entirely satisfactory method has heretofore been proposed for manufacturing such beveled or recessed-end boards.

It has been proposed to form such recessed-end boards by depressing portions of the board after ³⁰the board has been cast or formed. This procedure is not entirely satisfactory, since the pressing operation is usually detrimental to the core of the board. It has likewise been proposed to produce such recessed-end boards by forming parallel rows of projections in the outer surface of one of the cover sheets by punching the cover sheet before the board is formed and severing the continuous board stream between the rows of projections after the board is formed. It will be apparent that boards formed by this latter method have a series of projections spaced along the depressed or beveled portions, and that these projections seriously interfere with the application of joining tape and sealing cement when a wall structure is being erected from the boards. Numerous other objections are also found in recessed-end boards of this type having projections along the recessed-end portions. ¹

It is a further object of my Invention to provide an improved method and apparatus for forming, in a continuous manner, wallboards of this character having recessed-end portions.

Tn carrying out my invention in one form, one of the cover sheets is embossed or creased prior to

2,238,017

METHOD AND APPARATUS FOR MANUFACTURING WALLBOARD

James K. Duncan, Chicago, Ill., assignor to United States Gypsum Company, Chicago, III., a corporation of Dlinois

Application October 23, 1937, Serial No. 170,513 (Cl. 154—2) the formation of the board to provide spaced, transversely extending projections on one surface of the board, which projections are effective to space adjacent portions of the cover sheet and > of the composition core from the supports therefor during the formation of the board, and during the passage of the board over the setting conveyors. After the core of the board has set, the continuous board stream is severed along opposite sides of the projections entirely to remove the projection from the board and to provide boards of predetermined length having uniformly beveled or recessed-end portions. If desired the continuous board stream may be severed along the center lines of the projections and the ends of the boards thus formed may be then trimmed to provide uniform beveled ends.

As a further aspect of my invention, means are provided for applying to the projections, before the application of the plastic mass or core, a suitable stiffening medium so as to prevent deformation of the projections during the board-forming operation. This stiffening medium may have moisture-proofing characteristics if desired. In certain cases the embossing of the cover sheet is carried out in such a manner that the depth of the projections is less than the thickness of the cover sheet, so that a continuous layer of fiber is provided to improve the resistance of the projections to deformation when subjected to tension or pressure. In forming wallboards of the type in which one of the cover sheets is folded around the edges of the plastic mass or core, the projection or embosture extends only across that portion of the cover sheet which is to form the bottom surface of the board so that no creasing or embossing is effected in the portions of the cover sheet to be folded about the core.

For a more complete Understanding of my invention reference should now be had to the drawing, in which:

Figure 1 is a somewhat diagrammatic representation of board-forming apparatus embodying my invention;

Fig. 2 is a fragmentary perspective view of a portion of the scored or creased cover sheet;

Fig. 3 is a fragmentary side view of a section of the continuous board stream before the severing operation has been performed;

Fig. 4 is a fragmentary elevational view of a . recessed-end board formed In accordance with my invention:

Fig. 5 is a detail view of a portion of the scored sheet shown in Fig. 2;

Fig. 6 is a similar detail view of a portion of a cover sheet formed in. accordance with a further embodiment of my invention; and

Fig. 7 is a transverse sectional view of a scored cover sheet constituting a further embodiment of my invention.

Referring now to Fig. 1 of the drawing, I have shown my invention as applied to a board-forming apparatus comprising a pair of embossing rolls 10 and I 1, respectively, provided with intermeshing projections 12 and recesses 13 for engaging a fibrous cover sheet or liner 14 as it is continuously advanced to the forming means of the apparatus. The embossing rolls 10 and II are driven in synchronism by suitable means, not shown, and are arranged to emboss or crease the sheet 14 at predetermined intervals so as to provide projections 15 extending outwardly from one surface of the sheet. As shown best in Fig. 2, these projections 15 extend transversely entirely across the cover sheet 14 and are preferably channel-shaped, the side walls of the projections extending substantially at right angles to the surface of the cover sheet.

As shown, the projections 12 and the recesses 13 are so arranged that sufficient space is left between each projection and its cooperating recess to permit the cover sheet 14 to pass therebetween with substantially a pressure fit, so that the cover sheet is crimped into the sharp comer projection 15. In some cases it may be desirable to coat the inner surface of the projection 15 with a suitable moisture resisting and stiffening medium such as lacquer or wax, and for carrying out this coating operation I provide a coating wheel 16 supported on a movable arm 17 i and arranged sequentially to engage the projections 12 on the scoring roll 10 so as to apply the stiffening medium to the projections. As shown, the roll 16 is supported so as to engage the periphery of a cooperating roll 18 which is rotatable in a suitable reservoir IS containing a bath of suitable stiffening medium. The feature of applying stiffening medium is of particular importance where very thin cover sheets or liners are used which would otherwise be incapable of supporting the plastic mass when the thin sheet is moistened.

After the cover sheet 14 has been provided with projections or embostures as described above, it passes over a casting table or support 21 and a plastic mass 21 is applied to the upper surface thereof from any suitable source of supply, as for example the supply spout 22, the plastic mass 21 preferably being gypsum plaster or other suitable composition material in a plastic or manageable state. After the plastic mass 21 is applied to the upper surface of the sheet 14, the plastic mass and the sheet 14 pass between a pair of forming rolls 23 and 24 which operate to form the plastic mass into a core of desired thickness, a top cover sheet 25 being applied to the upper surface of the core^- by the forming roll 24.

From the forming rolls 23 and 24 the formed board passes over suitable setting conveyors one , of which is represented by the reference numeral 28, and it will be apparent that the projection 15 is effective, during the formation of the board stream and during its passage over the setting conveyors, to space adjacent portions of the ' cover sheet 14 from the setting conveyor so as to form recesses 27 and 28 in the lower surface of the formed board on opposite sides of the projection. The setting conveyors 26 support the board stream for a sufficient time to 75

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2,238,017 permit the plastic mass or core 21 to set, and after setting of the core the board stream is advanced to suitable cutting mechanism by means of which the projections 15 and the portions of the board stream immediately thereover are entirely removed. Thus, in Fig. 1, I have shown the cutting means as comprising two pairs of cooperating cutting knives 29 and 30, which are arranged to sever the board stream » along the opposite transverse edges of the projections 15. These cutting knives are of course operated in synchronism with the travel of the board stream so as to sever the board at the proper instant, that is, just as the projection ; 15 reaches the position shown in Fig. 1 with respect to the knives 29 and 30. As indicated above, a single pair of cutting knives may be used in place of the knives 29 and 30, and these knives may be arranged to sever the board 1 stream along the center lines of the projections 15 thus separating the stream into a plurality of recessed-end boards having ridges or uneven edges along the transverse recessed-ends. These uneven edges or ridges may then be removed by grinding or sawing so as entirely to_; remove the portions of the board stream formed by the projections 15 and to provide uniform recessedend boards.

The character and formation of the board stream as it passes over the setting conveyors is illustrated most clearly in Fig. 3, and the character of the transverse end of the board produced after the projection 15 has been removed is illustrated in Fig. 4.

Fig. 5 shows the preferred shape of the projections 15 in the sheet 14 before the plastic mass is applied to the upper surface of the cover sheet, and although the dimensions of the channel-shaped projections 15 may be varied so that the recesses 27 and 28 produced thereby in the formed board are of suitable depth and length, I have found that a very satisfactory product is obtained if the depth of the recesses indicated by the letter a in Fig. 4 is approximately .03 inch and if the length of the recessed or beveled end indicated by the letter b in Fig. 4 is approximately 1½ inches.

In Big. 6 there is shown a cover sheet 31 having a projection 32 which is formed by embossing or creasing the sheet 31 to a depth less than the thickness of the sheet. As will be understood by those skilled in the art, embossing or creasing the sheet 31 in this manner provides a continuous horizontal layer of fiber, indicated by the broken line 33 in Fig. 6, which is instrumental In increasing the strength of the embossed or rigid sheet and in resisting deformation or flattening of the projection 32 when the sheet 31 is subjected to tension during the board-forming operation.

In the embodiments of my invention thus far described, the plasterboards formed are of the open or raw-edge type, and it is sometimes desirable to provide boards of the type having closed edges, which boards are produced by folding a portion of one of the cover sheets around the plastic mass or core during the board-forming operation. In providing beveled or recessed ends on boards of this type, in accordance with my invention, the bottom cover sheet or liner is formed as shown in Fig. 7, the cover sheet 84 there shown being provided with a continuous channel-shaped projection 35 which extends only across that portion of the cover sheet which is to constitute the bottom surface of the finished board, Thus the edge portions 36 of the liner·

2,238,017

31, which are ίο be folded around the core as indicated by the broken lines in Fig. 7, are left free of any projections and accordingly may be readily folded. Inasmuch as suitable means for folding the.edge or marginal portions of the toot- 5 tom cover sheet, to provide closed-edge boards of the type referred to above, are well· known in the art, it is not believed necessary to illustrate or further describe the construction and operation of board-forming apparatus provided with such folding means.

While I have shown particular embodiments of my invention, it 'will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.