US2523861A - Method of finishing end edges of plasterboard - Google Patents

Description

p 1950 G. A. BUTTRESS 2,523,861

METHOD OF FI NISHING END EDGES 0F PLASTER BOARD Filed April 2, 1946 Patented Sept. 26, 1950 UNITED METHOD OF FINISHING END EDGES F PLASTERBOABD George A. Buttress, Los Angeles; Calif.

Application April 2, 1946,'Serial No. 658,952

2 Claims. (Cl. 154-87) This invention relates to plaster board of the type wherein a sheet-like body or filler of hardened plastic material is faced with card-' board or similar sheets to produce a board for use as a base for plaster on walls and ceilings or as sheeting in finishing walls and ceilings, and more particularl pertains to th finishing of such board so that critical margins of the plastic sheet-like body are covered by the facing sheets and the board is given a particular shape and finished appearance along margins thereof to provide advantages which will be hereinafter pointed out.

In the manufacture of plaster board, cardboard or like facing sheets are fed in long strips over a table or on a conveyor while a soft and wet plastic material is applied therebetween whereby a long strip of plaster board stock may be formed subject to being cut into desired lengths when the plastic material has set. Later methods provide for bending or folding the facing sheets around the longitudinal edges of the long strip of stock board during the forming thereof so that the plaster board lengths cut from the strip will have certain opposite edges thereof in finished and protected form with the plastic body sheet covered along said edges by the cardboard facing sheets. However, in so far as I am aware, the transverse edges of these board lengths are square, expose the dry plastic filler and present an unfinished appearance. Exposure of the dry plastic body sheet in this manner is objectionable in that when plaster is applied over a number of such boards or a wall or ceiling, the exposed edges of the dry plastic body sheet will absorb moisture from the applied plaster at the joints of said boards and weaken the plaster at the most critical points, namely, the joints in the base formed by the boards, thereby impairing the monolithic characteristic of the body of applied plaster'and often causing cracking and discoloration thereof. Moreover, these ordinary squarecut edges of the board when opposed in an assembly of plaster boards on a wall or ceiling donot afford an eliective keying of the applied plaster and present an unfinished appearance especially when the boards are used as finishing sheeting on walls and ceilings.

It is the primary object of this invention to provide a method and an apparatus for producing finished, cardboard-covered edges of board lengths of plaster board of the character described, incident to the severing of such lengths from a long strip of the plastic board stock with the edges produced by such severing given a particular shape and treatment to facilitate the keying of plaster applied to a plurality of the boards,

-give the boards, finished appearance, and reinforce and add to the strength thereto.

Another object of this invention is to provide a method of finishing plaster board of the character described while the cardboard facing sheets and the plastic filler thereof are yet wet as before the setting of the latter, which consists in first applying to the facing sheets along a line extending across both sides of the board, a pressure such that the plastic filler will be laterally displaced and the facing sheets forced inwardly and caused to form grooves and to adhere to one another along the bottoms of said grooves, and then forcibly continuing the pressure in such manner that the adhered portions of the facing sheets are severed, whereby successive applications of the aforesaid pressures at spaced points along the plaster board stock will produce desired lengths of plaster board each having the plastic body along the severed edges covered by the adhering portions of the facing sheets and being given a predetermined beveled or tapered form at such edges.

Another object is to provide a finishing apparatus for plaster board wherein opposed dies are first pressed against opposite sides of the wet unhardened stock length of plaster board to form transverse grooves in opposite sides of the board with the cardboard facing sheets forced together and adhered to one another along the bottoms of said grooves, and then forcibly moved toward one another so as to sever the facing sheets along the adhering portions thereof whereby the result ant edges are sealed by said adhered portions of such sheets and are beveled on opposite sides and given a finished appearance.

With the foregoing objects in view, together with such other objects and advantages as may subsequently appear, the invention resides in the parts and in the combination, construction and arrangement of parts hereinafter described and claimed, and illustrated by way of example in the accompanying drawing, in which:

Fig. l is a fragmentary side elevation of an apparatus embodying the present invention and constituting one means by which the method hereof may be carried out, the apparatus being shown in readiness for operation;

Fig. 2 is a sectional view taken on the plane of line 2-2 of Fig. 1, showing in cross section the apparatus of Fig. 1 and in addition the confining elements which extend along the longitudinal appear during the finishing operation but before.

the facing sheets and the stock" have been severed;

Fig. 4 is asectional view similar to Fig. 3 showing the die members and board as when a severing operation has been completed; and

Fig. 5 is a fragmentary side elevation of a finished plaster board as produced with the method and apparatus hereof.

The method of this invention is-preferably carried out in connection-with plaster board which in being formed in long stock strips subject to having suitable lengths or pieces cut therefrom has its longitudinal edges covered by one or both of the cardboard facing sheets, so that the plastic body sheet of the board is sealed-in and covered along such edges before it sets. This arrangement protects the longitudinal edges of the plaster body sheet to which the cardboard facing sheets are adhered and prevents exposure of the plastic material at the longitudinal margins of the board and consequent objectionable absorption of moisture from plaster applied over such edges. However, the method hereof may be carried out to advantage with plaster board in which the plastic body is exposed along the longitudinal edges of the board, inasmuch as the other edges of the plastic body produced in cutting of lengths of board will be covered and finished in accordance with invention and .to that extent the product will be considerably improved as compared to board in which all the margins of the plastic body are exposed.

In carrying out the method hereof, a length of plaster board stock A in nearly complete form, that is, after the plastic filler B has been applied between the cardboard facing sheets C and the assembly has been pressed into substantially its finished sheet or board form and before the plastic material has set and while the facing sheets are still wet or damp, is subjected to pressure on opposite sides along a line extending transversely thereof as by means of opposed die members D and E so as to press portions of the facing sheets toward one another and squeeze and displace the soft plastic material laterally until a groove of a somewhat arcuate cross section is formed to extend across in each side of the board, and the pressed-in portions of the facing sheets abut and adhere to one another along the bottoms of said grooves. The board now appears as shown in Fig. 3 with adhering portions of the facing sheets substantially equal in width to that of the bottoms of said grooves.

The next step in the method hereof consists in continuing the pressure so that it is forcefully applied in such manner along the longitudinal medial lines of the portions of the facing sheets which are adhered to one another, that said adhering portions will be severed along said medial lines. This parting or severing operation produces like sealed and finished edges as shown in Fig. 4, with the plastic filler sealed-in along such edges by the lip-like portions of the facing sheets which remain adhered to one another on opposite sides of the line on which such sheets are severed.

Upon repeating these method steps at another point longitudinally spaced from the first finishing and severing point, there will be produced a finished plaster board of desired dimensions and on which the edges formed in severing the board as aforesaid, will be beveled on opposite sides with the plastic filler covered and sealed-in by the portions of the facing sheets which adhere to one another. Thus produced the cut-off lengths of plaster board are ready for use when the plastic filler sets and the facing sheets are dried out in any suitable manner.

It should be noted that due to the cardboard sheets being damp or Wet and the plastic material being soft when the forming and severing operations hereof are performed, and the manner in which the pressure is applied to form grooves in the board then sever it along the longitudinal center lines of the grooves, the cardboard portions are converted at the severed edges and adhered to one another and remain in continuity with the facing sheets propen'with the plastic material compressed, increased in density and therefore strengthened at said edges. It should be noted that at least one of the sealed lengths of board being formed by this methodis maintained under pressure and confined between the table I and the pressure plate 8 as well as-between the side retaining members ll, while having a transverse edge thereof sealed and cut, thus maintaining the board length in uniform fiat formation free from bulges or deformations which would otherwise occur due to displacement of the plaster when forming the sealed transverse edges.

Apparatus embodying the present invention as her shown includes a support I such as a table or the like adapted to support the stock length A of plaster board which is to be cut into smaller pieces or lengths to form a plurality of plaster boards.

The dies D and E hereinbefore referred to, for forming and severing the board A are disposed above and below the upper surface of the table 1 respectively, in superposed relation for movement towards and away from one another. The die D is supported on a transverse edge of a pressure plate 8 which is normally disposed above and clear of the stock length A of plaster board whereas the die E is mounted on a plate or support 9 disposed below the table and adapted to be moved through a transverse slot I 0 in the table into contact with the underside of the board at the same time that die D is moved into contact with the upper side of the board.

Any suitable means, not shown, may be employed for moving the plates 8 and 9 so that the dies D and E will be forcibly engaged with the board A to first form the groove in opposite sides thereof, cause the facing sheet C to adhere to one another as shown in Fig. 3; and then sever said adhering sheets and finally be moved back into out-of-the-way position shown in Figs. 1 and 2.

As here shown retaining members II are mounted along opposite sides of the table I so that when the dies D and E are moved into forming and severing positions, the board A will be confined under pressure and held against displacement and deformation by means of the plate 8, table I and side members I I, except where the dies are contacted therewith.

The dies D and E are of such length as to extend fully across the board A and have the edges thereof opposed to the board A, of special formation so that when forced against oppositesides of the board they will form the like grooves C of arcuate cross section and cause the facing sheets to abut and adhere to one another before being severed. As here shown said opposed edges of the dies are provided with like slightly concaved or inwardly curved faces l2 converging so as to form somewhat rounded ridge-like severing edges 13. This shape of the dies is such that the edges of the finished board provided by the severing operation will be somewhat rounded and the portions of the facing sheets which cover said edges will form a small protruding lip where adhered to one another along such edges.

The roundingpof the severing edges 13 of the dies assures that the aforesaid shaping and adhering operations will take place before severing the facing sheets on the longitudinal center line of the adhering portions, the object being to prevent the severing operation from taking place before the plastic material while yet soft is displaced, compressed and given a definite form and the two sheets are brought into abutting relation and caused to adhere to one another.

It will now be apparent that upon successive applications of the dies D and E and hereinbefore noted at spaced intervals along the length of plaster board stock A before the plastic filler B has set, there may be provided in an eflicacious manner a plurality of plaster boards in which the edges formed by such applications of the dies are covered by integral portions of the facing sheets so as to seal in the plastic 'filler B and give a shape to such edges affording a better keying action when plaster is applied to such boards as well as reinforcing such boards and providing the other advantages herein noted in a particularly efllcacious manner.

This invention embraces a new form of plaster board wherein the severed edges are given a particular form and are sealed by portions of the facing sheets.

While I have shown and described a specific embodiment of my invention, I do not limit myself to the exact details of construction set forth, and the invention embraces such changes, modifications and equivalents of the parts and their formation and arrangement as come within the purview of the appended claims.

I claim:

1. The method of finishing edges of plaster board before setting and hardening of the plastic body of such board and to which body cardboard facing sheets are adhered; which consists in pressing inwardly opposed portions of the facing sheets of a stock length of such board so as to displace the plastic body and cause said pressed-in portions of said sheets to abut and adhere to one another along a line extending transversely of said board, restraining the entire area of opposite sides and the longitudinal edges of a given length of the board during the pressing of said sheets into abutting relation, to prevent deformation of such given length of board incident to said displacement of said plastic body, then severing said adhering portions along a line which is intermediate the side edges of said adhering portions whereby the edges of the plastic body formed by such severing will be covered and sealed by portions of said facing sheets which are adhered to one another along said edges.

2. The method of producing finished edges of plaster board which edges are produced in severing given lengths of plaster board from a stock length of such board; which consists in pressing and confining against displacement the entire area of opposite sides and the longitudinal edges of a given length of the board while pressing in- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 700,805 Paine May 2'7, 1902 1,353,524 Fleming et a1 Sept. 21, 1920 1,417,117 Tyler May 23, 1922 1,464,360 Hicks Aug. '7, 1923 1,874,922 Delaney Aug. 30, 1932 1,884,708 Jeneson Oct. 25, 1932 1,949,692 Pavesi Mar. 6, 1934 2,134,862 Dunnam Nov. 1, 1938 2,142,505 Gammeter Jan. 3, 1939 2,168,803 Page Aug. 8, 1939

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