Back blocking device

#The present invention relates to drywall construction and, more particularly, to an improved back blocking device for providing a smooth flat finished butt joint.

#In the construction of buildings, interior walls and ceilings typically consist of a layer of gypsum wallboard attached to construction beams made of wood or other materials. The joining of adjacent edges of two pieces of wallboard is accomplished by the application of a plaster-like material to the joint with an embedded layer of paper tape to inhibit cracking of the finished joint. Usually the longer edges of the wallboard are pre-beveled to receive the plaster so that the finished joint is flat and smooth. The ends of the wallboard, however, are not beveled. Additionally, when it is necessary to cut a portion of the wallboard away when fitting it into a smaller space, the pre-beveled edges are frequently removed. In such cases, the finished joint necessarily bulges out of the plane of the wall and is unsightly. An example of such a structure is illustrated in FIG. 1 where the nonbeveled two adjacent edges of two pieces of wallboard 10 and 12 are positioned in alignment with the center of a wooden construction beam 14 and nailed in place with nails 16. Several layers of plaster 18 and an embedded layer of paper tape 20 are applied to the area to form the butt joint. The plaster leaves a bulge 22 that extends away from the plane 24 of the wallboard, as shown. The plaster is feathered outwardly on either side of the joint for about 24 to 36 inches to render the bulge less obvious. This requires a substantial amount of skill and experience and, more importantly, the finished joint is unsightly. This is especially apparent when a glossy finish is applied to the finished surface.

#In an effort to overcome this problem, the edges of the two pieces of wallboard to be joined are positioned between two adjacent construction beams. Joint support devices that extend from one construction beam to the other are positioned at intervals along the butt joint and are spaced slightly away from the surface of the wallboard so that when the edges of the wallboard are attached to the support devices, the edges are pulled toward the support device and out of the plane of the wallboard. This provides a recessed area along the joint for receiving the plaster material in a manner similar to that of pre-beveled edges. Examples of such joint support devices are disclosed in U.S. Pat. No. 4,237,669 that issued Dec. 9, 1980 to Hunter and U.S. Pat. No. 4,392,336 that issued Jul. 12, 1983 to Ganssle. Both of these devices have metal structures that extend from one construction beam to the other and are attached to the outwardly facing edges of the beams so that when the wallboard is installed, portions of the support devices are necessarily sandwiched between the mounting surfaces of the beams and the surfaces of the wallboard. These devices cause several problems. First, once the wallboard is held in place preparatory to nailing to the construction beams, the joint support devices are no longer visible, and since they are made of metal, they may interfere when nailing the wallboard to the beams. Further, the portion of the metal structures that are sandwiched between the mounting surfaces of the beams and the wallboard cause bulges in the wallboard and can damage the inner surface of the wallboard if, when nailing, a hammer blow inadvertently strikes the wallboard near an edge of the metal.

#The invention will now be described by way of example with reference to the accompanying figures in which:

#FIG. 1 is a cross-sectional view through a construction beam showing a typical prior art joint.

#FIG. 2 is an isometric view showing a first embodiment of the back blocking device of a first embodiment of the present invention.

#FIG. 2 shows a first embodiment of a back blocking device 10. The back blocking device 10 is an elongated member 12 having a longitudinal axis 14 and a first and second side 20, 30, respectively. The first side 20 having a first outer surface 22 and a second outer surface 24. The second side 30 having a first inner surface 32 and a second inner surface 34. The first outer and inner surfaces 22, 32 extend from a first end 16 of the elongated member 12 to the longitudinal axis 14, and the second outer and inner surfaces 24, 34 extend from a second end 18 of the elongated member 12 to the longitudinal axis 14.

#The elongated member 12 is made of 18 to 24 gauge galvanized steel or any other suitable rigid material such as aluminum, or plastic, etc. It will also be appreciated by one skilled in the art that the thickness of the material may be varied depending on the desired dimension of the back blocking device. The length L of the elongated member 12 is preferably longer than the length of the butt joint, and preferably overlaps each end of the butt joint. For example, when the butt joint is 48 inches long, the elongated member 12 should be approximately 54 inches long. It will be appreciated by one skilled in the art, however, that the length L of the elongated member 12 does not have to be longer than the length of the butt joint or has to overlap each end of the butt joint to achieve a similar result. The width W of the elongated member 12 is such that it can be accommodated between two parallel construction beams 11, 15, preferably without causing the first and second ends 16 and 18 to contact the construction beams 11, 15. A plurality of apertures 40, shown in FIG. 2, span the length of the elongated member 12 and are positioned adjacent to the longitudinal axis 14 to form attachment surfaces 26, 28, 36, 38, shown in FIGS. 4 and 5, for attachment of a first and second piece of wallboard 71, 73. The apertures 40 are stamped from the elongated member 12 and sized and shaped for receipt of a standard machine screw, drywall screw, or other fastener. The apertures 40 are arranged so that the fastener may be easily inserted at any given position, simplifying attachment of the wallboard 71, 73 to the elongated member 12.

#As shown in FIGS. 2 and 3, the elongated member lies in plane P. The first outer surface 22 of the elongated member 12 is bent or molded to have raised portions 52, 54 and recessed portions 50, 51 therebetween. The recessed portions 50, 51 are positioned toward the second side 30 of the plane P of the elongated member 12, and the raised portions 52, 54 are positioned toward the first side 20 of the plane P of the elongated member 12. Moving from the first end 16 of the elongated member 12 toward the longitudinal axis 14, the first end 16 of the elongated member 12 is positioned toward the first side 20 so that the first end 16 creates the first raised portion 52. The elongated member is then formed to create the first recessed portion 51 by bending or molding the elongated member 12 toward the second side 30. The first recessed portion 51 is followed by the second raised portion 54. The first recessed portion 51 forms an angle between the first and second raised portions 52, 54. The first raised portion 52 is positioned at a distance greater from the plane P than the second raised portion 54. A central recessed portion 50 centered at the longitudinal axis 14 is then formed by converging the first outer surface 22 with the second outer surface 24 at a position toward the second side 30 of plane P. The first recessed portion 51 is positioned at a distance greater from the plane P than the central recessed portion 50.