CA2058466A1 - Corner bead for drywall construction - Google Patents

Abstract

IMPROVED CORNER BEAD FOR DRYWALL CONSTRUCTION
Abstract of the Disclosure A corner bead for drywall construction has a galvanized steel core strip which is formed with a central portion, side flanges, and shoulders joining the central portion and side flanges. The front face of the core strip is covered with a paper layer having an outer protective coating thereon overlying the central portion adjoining said shoulders. A paper reinforcing layer covers the back of the core strip in one embodiment to minimize the thickness of the core strip.

Description

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escri~tion IMPROVED CORNER BEAD FOR DRYWALL CQNSTRUCTION

~chnical Field The present invention relates to corner beads for drywall construction, and particularly to those having an outer paper layer.

Backqround of the i.~vention In ~he corner bead ~or :dr~wall cons~ruction art two types of beads have been commonly used, the "nail-on"
type and th2 "tape-~n" type. Nail-on beads commonly take the form of an angle strip of metal wi~h side flanges meeting at a center corner rib providing shoulders against which spackle or ~oin~ cement can be dressed when feathered from the adjoining wall surfaces: to cover the edges a~d outer ~aces of the side ~langes and the heads of the nails securing ~hese ~ flanges to thf~ :wall structure.
These nails are usually driven through the bead flanges at intervals of no more than eight inches.
Another form of nail-on bead has a rounded nose section between side flanges ~and presents step-down shoulders at the ~ tures of the: rounded :nose and the side flanges. The nails~ are driven through the side flanges and~ the spa~kle or joint cement covering the flanges is dressed:to th~ shoulders, leaving ~he rounded nose section exposed to be pain~ed later. For purpos~s of later discussion, corner beads wi~h an abrupt corner will ~ 3S be referred to as the ~'hard line~ type, and the corner beads with a rounded~nose will be re~erred to as the "soft-line" type.

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Tape-on corner heads utilize paper wings to secure a metal corner angle in position rather than using nails. Thase wings are lateral extensions o~ a paper cover strip which is bonded by a hot melt glue or other suitable adhesive to the metal corner angle, usually on the outer ~aces o~ the side ~langes. The metal corner angle can be shaped as the hard-line type or so~t-line type. Spackle or joint cement and wall paint ~or dressing and finishing the corner, normally adhere significantly better to tAe paper cover strip o~ tape-on beads than to the e~posed metal of nail~on beads. Also, normally drywall corners covered with nail-on heads are more susceptible to developing crack lines along the outer edges of the side flanges than when tape-on beads are used. On the other hand, nail-on beads have the advantage of requixing less skill to apply.
Preparatory to painting the wall board adjoining a corner covered by a corner bead, the spackle or joint cement spread from the wall surface on~o the corner bead is sanded to provide a smooth continuous sur~ace from the wall board to the corner bead. In the case of tape on beads the exposed por~ion of the out~r paper layer is co~monly scuf~ed during the sanding operation, thereby mak~ng it more dif~icult to later obtain a smooth painted sur~ace at the corner. This -scuffing is usually most prono~nced at the corner rib of a hard-line bead, and at the two shoulders adjoining the rounded nose o~ a soft-line bead.

Summary Q~ the Invention The present invention provides an improved nail~
on corner bead having advan~ages of tape~on beads and which can be produced economically. The invention also provides: a solution to the scu~ing problem o~ tape-on bQad5.
In accordance with the present invention, a metaI corner element (hard-line or so~t-line) is covered .

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on the outs~de with a paper laye~ which is folded around - the outer edges of the corner element and is bonded to the corner element. The back side of the metal corner element is preferably provided with a reinforcing layer of paper between the folded-around portions o~ the ~ront paper layer. This permits the metal corner element to be of thinner material. The overall cost of the thinner m~tal and reinforcing bacXing paper provides a structure currently mor~ ~conomical to produce than when metal alone is used of a thickness normally currently found (0.012-0.013 inches) on all-metal nail-on corner beads. The corner element has a pair of shoulders as currently provided on hard-line and soft-line types, respectively, of nail-on heads. The portion of the paper layer covering and adjoining each shoulder is provided with a protectiva coating making it ~ar more resistant to scuffing during the sanding operation in preparation for paintin~. The protective coating has a composition to which paint will readily adhere. As part o~ the inve~tion thi5 protective coating is also applied to the pater cover layer o~ tape-on corner be~ds.

f Descri ~ion o~ the Drawinas Figure 1 is a transverse cross-sectional view o~
a hard-line corner bead made in accordance with the present invention, and with the thic~ness of the eleme~ts being exaggerated for illus~rative purpos~s;
Fiqure 2 is a detail sectional view to an enlaxg2d scale~ of the cixcled portion indicated in Figure 1;
. Figure 3 is a transverse cross-sectional view:Qf a soft-line corner bead made in accordance with the prPsent invention, and with ~he thickness o~ the elements being exaggerated ~or illustrative purpases;
Fiqure 4 is a detail sectional view to an enlarged scale of the circled portion indicated in Figure 3; and . ~' : '' ~ ' . .,' . ' ' :, ' 2 ~

Figures 5 and 6 are ~ragmentary transverse cross-sectional views of a hard-line corner bead and soft-line corner bead, respectively, of the tape-on type provided with the protective coating in accordance with this invention.

DetaiLed_~escription of the_Invention Referring to ~he drawings, it is seen that finished hard-line and sofk-line nail-on corner beads 8, 9 made in accordance with the present invention have a respective core strip 10, 11 and a respective paper cover strip 12 or 13. The core strip is preferably a galvanized steel strip which has been roll-~ormed to the hard-line shape 10 having a corner rib lOa and side flanges lOb, or to the so~t-line shape 11 havin~ a rounded nose lla, a pair o~ step-down sloped shoulders llb, and side flanges llc. A typical hard-line core strip 10 will have its side flanges lOb at ninety degrees to one another and about one inch wide, and a typical soft-line core strip 11 will have its rounded nose lla Rhaped with a radius in the range of about 3/4 to }~ inrhes, and its side flanges llc at a right angle relative to one another and about one inch wide. The corner rib lOa on the hard-line unit will typically be about O. 0625 inches high and about 0.125 inches wide. Each of the shoulders llb on the soft~line unit will typically be about O.125 inches wide and have a drop of about O.0625 inches from the corresponding outer edge of the rounded nose section lla and the adjoining side flange llc.
The cover strips 12,~ }3 have their outer edge portions 12a and 13a folded back over the outer edges of the respective core skrips 10, 11 a distance of about G.2S
inches. For economy of construction, respective reinforcing backing strips 14, 15 o~ paper ~ay be applied to the core strips 10, 11 between the folded-back edge portions 12a, 13a of the respective cover strips 12, 13.
The cover stxips 12, 13 may be 80 to 90 pound bleached ' ::
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'', ~ ' 2 ~ 6 s kraft paper like ~hat commonly used for wall~oard joint tape, and the bac~ing strips 14, 15 may be kraft paper about O.016 to 0.017 inches thick like that commonly used ~or backing paper on wallboard. When the backing strips 14, 15 axe not used, the core strips 10, 11 will normally be about 0.012 to 0.013 inches thick, whereas the core strips need only be a~out O.oo1 to o.oos inches thick when the backing strips are included. ~ot melt glue or other suitable adhesive (not shown? is used to bond the entire back sur~ace of the cover strips 12, 13 and backing strips 14, 15 to the core strips lo, 11.
- In accordance with the present invention a center ba~d 16 o~ a protective coating is applied to the outer ~ace of the cover strip 12, and a pair of bands 17 of a protective coating is applied to the portions of the outer face of t~e cover strip 13 which cover ~he pair of shoulders llb and are adjacent thereto. The protective bands 16, 17 preferably extend about 0.~25 inches beyond-both si~e edges o~ the corner rib lOb and the shoulders llb. Although for production economy it is preferred to have relati~ely narxow protective bands, it will ~e appreciated that in the case of the soft-line bead 9 a protective band may extend over the entire width o~ the nose lla between the pair o~ shoulders llb.
Figures 5 and 6 show the prote tive bands 16 and 17 applied to standard tape-on beads 8' and 9' with hard-line and soft-line con~igurations in which the paper cover layers are numbered 12' and 13'j and the metal core strips are identified by 10' and 11', respectively. The portions of the core strips are identified in the same manner as in Figures 2 and 3, except ~hat a prime has been added.
The bands 16, 17 o~ protec~ive coating preferably result ~rom treatment o~ the outer paper layers 1~, 13 (~2', 13') with a material which penetrates the fibers of the paper to rein~orce thë paper and provide sur~ace protection against abrasion. For example, the coating material ~or the bands 14 15 may comprise a ~ine "' '~ - ' ' ,' , ' ' ~ , ' ' particle size, acrylic, water-~ased emulsion such, for examplet as Synthemul~ synthetic resin emulsion 40-4~3, produced by Reichhold Chemicals, Inc., Dover, Delaware, diluted 50% with water. This material may be applied by a brush, roller or spraying apparatus. When the coating has dried, the surface of the pater area to which the coating material has been applied will normally have an acrylic film or layer about .001 inches in thic~ness. This surface film or layer can be increased in thickness to about .005 inches by using a suitable primer sealer for the protective coating. For example, the same acrylic resin can be u~ilized with the ~ollowinq additional ingredients:
INGREDIENT
Nater 8.00 Ethylene Glycol 1.00 Cellulosic thickness solution 16.00 Potassium Tripolyphosphate0.10 ~e~oamer 0.40 Surfactant 0.40 Aluminum Silicate 12.00 Titanium Dioxide ~.50 Calcium Carbonate lS.00 Microbial Agent 0.10 Acrylic ~esin 39.50 A typical cellulosic thickener is Natrosol 250 HR solution (1~
In applying the hard-line and soft-li ne embodLments o~ the nail-on beads 8 9, nails are driven at regular intervals through the outer cover strips 12, 13 underlying ~langes lOb, llc of the core strips, and backing strips 14, lS, and ~hen spackle or joint cement is feathered ~rom the outer face Or the underlying wall~oard to the rib lOa and shoulder~ llb so as to cover the outer 3 5 edges o~ ~he corner beads and ~he nails, as indic:ated in - phantom in Figures 2 and 4. Since the outer edges o~ each core ~trip 10, 11 and the outer ~aces thereo~.are covered .
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with paper there is good adherence of the spac~le or joint cement to the corner beads. When the spackle or joint cement is later sanded the protective bands 16, 17 prevent adverse scuffing of the paper 1~ covering the corner rib lOa and the paper 13 covering ~he rounded nose lla adjacent the shoulders 11~. Covering o~ the relatively sharp outer edges o~ the metal core strips 10, 11 with the paper covering 12, 13 has the added advantage o~
protecting workers from hand Guts while hand~ng ~he corner beads.
The hard-line and so~t-line corner beads 8'-9' of ~he tape-on type are applied~in the conventional manner for tape-on beads. When the joint cement sovering ~he outer paper layer 12~ from the cornex rib lO'a to the outer edge of the paper 12~ on the hard-line tape-on bead 8', and covering ~he outer-paper layer 13' from th~
rounded nose ll'a to the outer edge of ~he paper 13' on the soft-line tape-on bead ~', is sanded to dress khe joint cement to the rib lO'a and nose ll~a, the protective 2C bands 16', 17' prevent adverse scuffing of the outer pa~er layers 12', 13'.
It will be appreciated that the thicXness of the protective coatings 16, 17 have been somewhat exaggerated in the drawings ~or illustrative purposes. . The portions 25 of the outer paper layer in figures 2, 4, 5 and 6 adjoining the protective coatings 16, 17 have been dotted to indicate impregnation of the paper by ~he coating material.
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Claims (7)

1. A corner bead for drywall construction, comprising:
a core strip having a central portion, two side flanges extending laterally at about a right angle relative to one another, and respective shoulder portions joining said central portion and said side flanges;
a front paper layer covering the outer face of said core strip and bonded thereto; and a thin protective coating on said front paper layer at said should portions and an adjoining portion of said central portion along the length of said core strip, said protective coating penetrating some of the fibers of said front paper layer and having a thickness on the front surface of said front paper layer of about .001 to .005 inches, said shoulder portions, front paper layer, and protective coating collectively providing outer most exposed shoulders so that joint cement or the like can be applied over the paper-covered flanges and dressed to said exposed shoulders after the corner bead is applied to a drywall corner, said protective coating being substantially more resistant to abrasive action than joint cement.

2. A corner bead according to claim 1 in which said front paper layer has doubled back portions behind said core strip and covering the outer edges of said side flanges.

3. A corner bead according to claim 1 in which said central portion comprises a rounded nose between said shoulders.

4. A corner bead according to claim 1 in which said central portion and shoulders comprise a rib at the longitudinal center line of said core strip.

5. A corner bead according to claim 2 in which a back paper reinforcing layer covers most of the back of said core strip between said doubled back portions of said front paper layer.

6. A corner bead according to claim 5 in which said core strip is galvanized steel having a thickness of about 0.007 to 0.009 inches.

7. A corner bead according to claim 1 in which said protective coating contains an acrylic resin.