US2047982A - Wallboard joint - Google Patents

Description

July 21, 1936. PAGE 2,047,982

WALLBOARD JOINT Filed Sept. 15, 1934 I 20 21 Q C] l v.

INVENTOR JOHN I AQE- E 5 BY ATTORN E Patented July 21, 1936 PATENT OFFICE WALLBOARD JOINT John Page, Evanston, Ill., assignor to United States Gypsum Company, Chicago, 111., a corporation of Illinois "Application September 13, 1934, Serial No. 743,847

7 Claims.

This invention relates to building constructions and has reference more particularly to wallboard joints and their method of preparation.

In the history of the building industry, various proposals have been made for treating the joints of wallboards when attached to studs with their edges abutting. One of these joint treatments is covered in patent to Green No. 1,703,667, in which a perforated metal tape is adhesively secured over the wallboard joint, the perforations being provided to permit drying out of the adhesive and also to somewhat improve the bond of the tape to the face of the boards. sulting joint is covered with a plastic paint, wall paper, or other decorative covering.

Cloth tapes and paper tapes have also been used. Cloth tapes have low transverse tensile strengths and high stretch so that they are apt to rupture andpermit cracks to form in the decorative coatings. The same is true of the paper tapes which have heretofore been used. In addition paper tapes heretofore proposed have a high transverse and longitudinal expansion on wetting so that wrinkling due to application of adhesive prevents the tape from lying fiat on the surfaces of the wallboards and also produces hair line cracks along the edges of .the tape as it dries and shrinks.

In order to obtain sufficient cross tensile strength to prevent cracking at joints with ordinary papers it is necessary to use a paper of considerable thickness. This is unsatisfactory for two reasons. First, the thick tape makes a thick bulging joint which is diflicult if not impossible to hide. Second, due to the excessive thickness and resultant stiffness ofthe tape it will not shrink down properly into depressions in the joint as the adhesive dries out. This meansunbonded areas of tape over these depressions which will during painting swell slightly and form blisters. When the paint dries these blisters will not entirely straighten out and will remain as small lumps which will make the joint unsightly.

In my preferred method of application the joint is first filled flush with the surface of the board, covering nail heads, and if necessary building up low spots. After drying, the rough spots and lumps are lightly sanded off to form as even as possible a flat bed for the tape. Next,

The re-- a thick heavy bodied adhesive is applied-over the filled joint. The tape is then placed'over this and pressed down firmly into it. The excess adhesive is squeezed out by this pressure and is scraped off. The adhesive is made heavy for two reasons. First, to have sufficient body to hold down the edge of the tape and prevent it from curling. Second, in squeezing the excess of the heavy bodied adhesive out from under the tape the adhesive flows and fills every crevice and depression in the surface of the board, incompletely filled nail heads, etc. Then as the adhesive dries, due to its tackiness and body, it pulls the tape down into these depressions and bonds it to the board over the entire area of tape. If this type of adhesive were not used, there would be a hollow spot behind the tape over each depression. Later when dampened by water paint, the tape over this area will swell and blister. This is exactly what happened in previous tape systems where a thin adhesive or an adhesive previously applied to the back of the tape was used.

After the adhesive has dried and pulled the tape down into the depressions a finishing or feathering cement is used to fill up these depresg5 sions and feather off the edges of the tape. When dry this cement is sanded down to give a smooth even surface which when properly paintedor treated with other conventional decorative materials is substantially invisible.

An object of this invention, therefore, is to provide an improved tape for application over the joints of wallboards.

Another object of the invention is to provide an improved paper tape for joint treatment which has a high modulus of elasticity, a low transverse and longitudinal expansion on wetting, a high transverse tensile strength and freedom from edge cracking when applied in a wall construction. 40

Another object of the invention is to produce an improved method of applying paper tape to wallboard joints.

A further object of the invention is to provide an improved wall construction embodying my improved joint tape; also to improve joint tapes and wallboard joints in other respects hereinafter specified and claimed.

Reference is to be had to the accompanying I I drawing forming modified form of the joint tape.

In preparing a wall, ceiling or partition, it is customary to-provide studs or joists ill to which wallboards II areattached by nails 12a. The wallboards II are often made with a gypsum core l2 faced on both sides with paper cover sheets l3 which are folded about the edges of the core I! to form folds 14 forming protected edges. The wallboards Il may also be made of vegetable fibers, such as the wood fiber insulating boards which are well known to the art. The wallboards may which will produce a joint having a transverse tensile strength substantially equal to'that of the board itself so that no cracks will be formed in the coating II at the joint due to expansion and contraction-of the board because of changes in temperature or warping of the studs II. This maybeaccomplished inpart by utilizing a paper made in a paper machine which accomplishes a crossing of a substantial proportion of the fibers of which the paper is composed. This imparts to the paper a'high transverse tensile strength, a low stretch, a high' breaking load, and a high modulus of elasticity. The tape also has a low transverse and longitudirial expansion on wetting so that it lies perfectly fiat on the wall surface during application and during the drying of the adhesive. My improved method of application of the tape also contributes in securing the above results.

In order to show the comparative strength of my improved tape compared to other tapes previously' used, the following data is given-:

Ratio lon- Ratio cross Cross tentensile Longitudk isha? Transverse Thickness sile mo- Oross tenstrength n81 tensile strength stretch Material 0! mm dulus oi sllestrength 01mm, strength of m oi ta at was a is /s 1224..., or .Bzr .5

lbs/inch 1 .001 m. l -f fg cent thickness thickness Paper tape No. l -Q. 0. 045 71, 000 24 5. 3 49 10.9 Paper tape No 2 0.005 50,000 5.0 56 11.2 Paper tape No 3. 0. 007 39. 285 33 4. 7 81 ll. 5 Paper tape N o 4- 0.005 70,000 6. 0 49 9. 8 Paper tape No 5. 0. 0145 129, 000 '60 4. 14 145 l0. 0 Kraft wrapping paper- 0. 005 85, 000 27 5. 4 7. 0 Wallboard paper 0. 021 57, 600 32 1. 5 105 5. 0 Improved paper tape.- 0.0095 185,000 60-81 6. 3-8. 4 144-110 15. 2-12. 2 Perforated metal tape- 0. 004 95 Cloth tape No. 1------ 0.000 -49 Cloth tape No. 2 sized 0. 013 23 also be the wellknown paper pulp boards.

In the joint between the wallboards, I preferably apply a crack filler cement having about the following composition:

Pounds Casein 48 High calcium lime 22 Bor 10 Mica--- 100 Marble flour- 820 This cement is smoothed oil level with the faces of the boards and allowed to dry.

An adhesive I 5 is then applied to the surface of the board over the joint, this adhesive preferably having about the following formula:

Pounds Cas i 850 Bora 42 Trisodiumphosphatennl 102 Tribromophenol 6 After the adhesive is dried, a decorative coating I8 is applied to the exposed surface of the boards completely concealing the joint, this decorative coating being paint, wall paper or the like.

It will be noted from the above data that my improved paper tape is characterized by low stretch at breaking load, high modulus of elasticity, and high transverse and longitudinal strengths, which make it ideal as a joint tape over wallboard joints. In this connection, I consider that a paper joint tape should have a cross tensile modulus of elasticity of at least 100,000 lbs/111.

My improved tape is also noteworthy in its unusually low transverse and longitudinal expansion on wetting. The following data on expan-.- sion after a 2 min. immersion in water at 70 F.

- illustrates this point:

I Expansion T Expansion 1 acrosstape y Percent Percent Improved paper tape 0.78 0.25 Paper tape No. 6-- 2. 34 0. 52 Paper tape No. 7.. 2.3 0.5 Paper tape No. 8-- I 2.6 0.25

I consider that a paper tape should have a maximum transverse expansion on wetting of 1.5%

.and maximum longitudinal expansion of 0.5% in order to provide satisfactory application characteristics.

Of course, a high strength and low stretch at breaking load of the finished joint and its resistance to rupture due to thermal expansion and contraction and warping of the studs, are essential, and in this my improved joint system excels.

The following data shows the superiority of my joint system:

Stretch at Ultimate Joint breaking strength load Lbalinch ofjoint Inchu Improved joint tape 99 0 Perforated metal tape 82 0 Cloth tape No. 1--. 76 96 Cloth tape No. 7. 60 K:

The superior bond between the improved paper tape and the wallboardsis partly responsible for the superior strength of the resulting joint.

In addition to the advantages of the improved joint as above set forth, I have so formed the edges of the paper tape, that all cracking of the decorative coating at the edges of the tape has been practically eliminated. In the form of tape shown in Figs. 1 and 3, the edges of the tape have been serrated to provide irregular saw tooth projections 20. These projections 20 distribute the load at the edges of the tape where danger of rupture between the tape and feathering cement or wall finish is greatest. In the form of tape shown in Fig. 4. the edges of the tape are irregular by wavy projections 2| which may be formed by cutting or tearing. Tearing of the V edges can be accomplished by, saw tooth rolls instead of the conventional roll and knife. In the form of tape shown in Fig. 5, bevels 22 are formed on the edges of the tape which serveto secure a better adhesion between the edges of the tape and the faces of the wailboards, as well as permitting a i better feathering out of the overlying cement and decorative coating to form a smooth and in visible joint. These edge treatments combined with other advantageous characteristics of the improved tape, provide a crackless and smooth joint not heretofore obtained.

I would state in conclusion, that while the examples described constitute practical embodiments of my invention, I do not wish to limit myself precisely to these details since manifestly, the same can be considerably varied without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:-

1. A paper tape suitable for adhesive attachment to wallboard joints, comprising a strip of paper having a substantial proportion of crossed fibers extending transversely of said strip, the

longitudinal edge portions of said strip of paper being weaker than the central portions thereof to retard the formation of edge cracks along said tape when applied to said wallboard joint.

2. In a wallboard construction, the combination with wallboard having the edges thereof attached to supporting framework-in substantially abutting relation to form a wallboard joint, of a strip of thin paper tape adhered thereto having a large portion of its fibers extending transversely of said joint.

3. In a wallboard construction, the combination with wallboard having the edges thereof attached to supporting framework in substantially abutting relation to form a wallboard joint, of a strip of paper tape adhered thereto in which a large proportion of the fibers extends transversely of the tape and of the joint, the edge portions of the tape being weaker than the centre portions thereof. I 4. In a wallboard construction, the combination with wallboard having the edges thereof attached to supporting framework in substantially abutting relation to form a wallboard joint, of a strip of paper tape adhered thereto in which a large proportion of the fibers extends transversely of the tape and of the joint, the edges of the tape being feathered so as to retard the formation of edge cracks along the tape edges.

5. In a wallboard construction, the combina- 3c --tio n with wallboard having the edges thereof attached to supporting framework in substantially abutting relation to form a wallboard joint, of a strip of paper tape adhered thereto in which a large proportion of the fibers extends. transversely of the tape and of the point, the edges of the tape being serrated so as to retard the formation of edge cracks along the tape edges.

6. In a wallboard construction, the combination with wallboard having the edges thereof attached to supporting framework in substantially abutting relation to form a wallboard-joint, of a strip of paper tape adhered thereto in which a large proportion of the fibers extends transversely of the tape and of the joint, the edges of which tape being sufiiciently irregular to retard the formation of edge cracks along the tape edges, the tape having a. minimum cross tensile modulus of elasticity of 100,000 pounds per square inch.

7. A wallboard construction as in claim 2 in which the tape is not substantially thicker than CERTIFICATE OF CORRECTION.

Patent No. 2,047,982. July 2 1956.

JOHN PAGE.

It is hereby certified that error appears in the printed specificatio'n'of the above numbered patent requi-ringvcorrection as follows: Page 3, second column, lihe 67, 'claim 5, for the word "point" read joint; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of September, A. D. 1936.

Henry Van Are dale

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