Abstract:
A one-piece rigid connector allows a nominal construction wood member to slip axially while fixed at its distal end, to accommodate the naturally occurring shrinkage of lumber. The connector surrounds the wood member and attaches to a second wood member to secure the members together. The connector may be slightly larger radially than the first member to accommodate natural movement. In one embodiment, the connector is made of a light gauge sheet metal and attaches a vertical baluster to the horizontal lower deck rail of an elevated wood deck guard rail system. The connector secures the baluster horizontally, but allows the baluster to move vertically to accommodate expansion or contraction of the baluster after construction. The distal end of the baluster is secured using conventional wood screw attachment. The connector includes tabs on each side to allow fastening of the connector to the lower deck rail using conventional wood screws.

Description:
FIELD OF INVENTION 
     This invention relates to rigid connectors for joining two intersecting rigid members. This invention relates particularly to a rigid one-piece connector that perpendicularly joins two rigid wood members while allowing slip movement in one of the members. 
     BACKGROUND 
     Wood beams, posts, joists, balusters, and the like, referred to collectively herein as “members,” naturally shrink and expand due to the composition of the wood. A wood member can decrease and increase in length due to shrinkage and expansion in the direction of the wood grain. Frequent fluctuations of 3% are common, and fluctuations of as much as 18% may occur depending on the moisture content of the wood and the surrounding environment. Radial dimension changes also occur, although typically less drastically than length fluctuations. Despite the widespread knowledge of the natural dimensional fluctuations of wood members, conventional construction techniques largely ignore them, often to significant structural detriment. 
     In particular, it is often necessary to attach two wood members perpendicular to each other. Typically, the members are attached with a fastener, such as a nail or screw. Other known attachment devices include metal plate connectors that conform to the shape of the joint between the members. These metal plates are attached with fasteners to both members to create a “strong” or “rigid tie” that does not account for the dimensional fluctuations in the members. Once construction is complete, over time these fluctuations impart considerable tension forces on the members, the attachment devices, and related attached structural components. The tension forces may loosen the attachments across the joint, damage the wood, and otherwise warp the original shape and support capabilities of the constructed members. 
     While there are indeed requirements that some connections be rigid, in many instances the anticipated shrinkage of the wood member must be a consideration within the design and construction of wooden member connections. In particular, wood balustrades, as typically seen on balconies and decks, would benefit from a wood member connector that addresses the natural dimensional fluctuations. A balustrade is composed of several vertically-oriented balusters attached to top and bottom rails and spaced evenly apart so as to act as a guard rail or other barrier. Typically, the balusters are attached by nails or screws driven through each baluster at the upper and lower ends. The balusters then strain against the fasteners due to the dimensional fluctuations. Eventually, the fasteners begin to pull out, the wood splinters, or the contraction pulls the rails out of alignment, leading to significant safety hazards. A connector for balusters that accommodates the dimensional fluctuations is needed. 
     Therefore, it is an object of this invention to provide a device to attach two wood members to each other while accounting for the expected natural dimensional fluctuations of one or both members. It is a further object that the device provide a perpendicular attachment of the wood members. It is another object of the invention to provide a method of constructing structures with wood members that accounts for dimensional fluctuations in some or all of the wood members. 
     SUMMARY OF THE INVENTION 
     A bracket connector attaches a first wood member to a second wood member while allowing for a slip movement by the first member to accommodate dimensional fluctuations in the first member while it is securely fixed at one end. The connector fits around the perimeter of the first member, leaving a clearance gap that is thin enough to secure the first member laterally but wide enough to allow for natural radial and longitudinal expansion of the first member. The connector attaches to the second member with one or more nails, screws, or other fasteners. The connector does not securely attach to the first member, which allows for the slip movement along the first member&#39;s longitudinal axis. The several illustrated embodiments show the bracket connector as a u-shaped thin metal bracket sized to fit around a deck baluster, a ceiling joist, or a square support post, but applications to other wood members are contemplated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top rear left isometric view of a first embodiment of the present invention. 
         FIG. 2  is a top view of the first embodiment of the present invention. 
         FIG. 3  is a front view of the first embodiment of the present invention. 
         FIG. 4  is a right side view of the first embodiment of the present invention. 
         FIG. 5  is a diagram of a stamping pattern for fabricating the first embodiment of the present invention. 
         FIG. 6  is a top front right isometric view of the first embodiment of the present invention placed over a baluster. 
         FIG. 7  is a front view of a portion of a balustrade constructed using the first embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of the balustrade taken along line  8 - 8  of  FIG. 7 . 
         FIG. 9  is a top front left isometric view of a second embodiment of the present invention. 
         FIG. 10  is a top front left isometric view of the second embodiment of the present invention placed over a baluster and a lower deck rail. 
         FIG. 11  is a diagram of a stamping pattern for fabricating the second embodiment of the present invention. 
         FIG. 12  is a top front right isometric view of a third embodiment of the present invention placed over a cross beam. 
         FIG. 13  is a top front right isometric view of a fourth embodiment of the present invention placed over a cross beam. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-5 , there is illustrated a first embodiment of the present invention designated generally as  10  which is a one-piece bracket connector used to attach a first wood member to a second wood member while allowing the first wood member to fluctuate dimensionally according to the environment and the natural properties of the wood. A front portion  11  is attached to, and preferably integral with, a left portion  12  and a right portion  13  to form a three-sided brace. Preferably, the left and right portions  12 ,  13  are perpendicular to the front portion  11  and parallel to each other so that the brace is u-shaped. See  FIG. 2 . Alternatively, one or both of the left and right portions  12 ,  13  may intersect the front portion  11  at an acute or obtuse angle to accommodate non-square, non-rectangular first wood members, such as trapezoidal beams. The left and right portions  12 ,  13  may alternatively intersect each other to form a triangular beam having an apex at the intersection of the portions  12 ,  13  instead of a front portion  11 . Left and right tabs  14 ,  15  are attached to, and preferably integral with, the left and right portions  12 ,  13 , respectively, at the rear edge of each portion  12 ,  13 . The tabs  14 ,  15  project laterally from their respective portions  12 ,  13  substantially parallel to the front portion  11 . Preferably, the tabs  14 ,  15  are narrower than the left and right portions  12 ,  13  and are centered along the rear edge of the portions  12 ,  13 . The tabs  14 ,  15  are preferably coplanar so that the tabs  14 ,  15  together make flush contact with the planar attachment surface of the second wood member as described below. One or more apertures  16  are disposed through each tab  14 ,  15 . The apertures  16  each receive a fastener, preferably a screw, for securely attaching the device  10  to the second wood member. In the preferred embodiment, the apertures  16  in each tab  14 ,  15  are offset from each other, most preferably by placing one aperture  16  at the top of its tab and the other aperture at the bottom of its tab. The offset positioning minimizes the potential for the second wood member to split along its grain when the fasteners are driven into it. 
     The device  10  is preferably formed from a single piece of sheet metal, rendering each of the device  10  components substantially planar. The illustrated first embodiment of the device  10  may be stamped out of the sheet metal as shown in  FIG. 5 . Stress relief punches  17  may be formed at each juncture of the components to facilitate bending of the sheet into the proper device  10  configuration without imparting undue stress on the components along the bend lines. Preferably, the stamped metal is folded at 90 degree angles up out of the page at first and second up-fold lines  21 ,  22 , and folded at 90 degree angles down into the page at first and second down-fold lines  23 ,  24 . Each bend requires a material bend allowance to maintain proper final dimensions after bending of the part is accomplished. Rear corners  20  of the left and right portions  12 ,  13  may be linearly cut or rounded to prevent damage or injury from the sharp corner. Alternatively, the device  10  may be die stamped, cast, molded, or extruded, and may be a structural composite material instead of metal. The preferred metal is galvanized steel, which may be untreated or treated with one or more coatings, such as a colored powder coating. 
       FIGS. 6-8  illustrate the first embodiment of the present invention used to attach a baluster  51  within a typical wood deck having the following components: deck planks  57  are attached to one or more structural joists  59 ; vertical support posts  53  extend upward from the deck planks  57 ; a fascia  56  is attached to the ends of the joists  59  and may further be attached to the lower ends of the support posts  53  to hide the joists  59  from view; a guard rail, or balustrade, is formed with an upper rail  55  and lower rail  52  attached between support posts  53  parallel to the deck planks  57 , and a plurality of balusters  51  attached perpendicularly to the upper and lower rails  55 ,  52 ; a top plate  54  is attached to the support posts  53  and may further be attached at intervals to the upper rail  55 . In a typical deck construction, the balusters  51  are attached with a rigid securement, typically one or two nails or screws driven through the baluster  51 , to each rail  55 ,  52  on the face of the rails  55 ,  52  that faces away from the deck surface. As described above, the rigid securement prevents natural dimensional fluctuations and imparts tension forces on the baluster  51 , the fasteners, and any attached components. The resulting failures of this construction include the drawing downward and bowing of the upper rail  55  from the top plate  54  between the support posts  53 ; and securement failure of the balusters  51 , potentially leading to serious consequences in the event of a foreseeable user fall event. With the balusters  51  mounted on the outside of the deck surface, the failure of the lower baluster  51  securement will often not be noticed by the home or cabin owner, particularly in instances of high elevation decks. 
     The device  10  mitigates the above time-dependent baluster  51  failure, as the device  10  provides for vertical tension relief of the baluster  51  during foreseeable and anticipated baluster  51  shrinkage. The vertical tension relief also allows for minor baluster  51  expansion during periods of wetness for outdoor deck railings. With the upper end of the baluster  51  conventionally secured to the upper deck rail  55  by a rigid connection, such as by one or more securement screws  58 , the device fits around the baluster  51  and is secured to the lower deck rail  52  using two wood screws  19  driven through the apertures  16  of the device  10  into the attachment surface of the lower deck rail  52 . With a rigid attachment at the upper end and no rigid attachment at the lower end, the baluster  51  is allowed any amount of slip movement resulting from dimensional fluctuations along its longitudinal axis, which in this embodiment is perpendicular to the ground. Further, the dimensions of the front, left, and right portions  11 - 13  are selected to leave a slight clearance gap  40  between the device  10  and the baluster  51  to allow longitudinal and radial movement of the baluster  51  while still horizontally securing the baluster  51  to prevent the baluster  51  from being kicked out by an impact force. The contained baluster  51  is thus allowed dimensional variation under conditions of contraction or expansion caused by commensurate wood moisture evaporation or absorption. 
       FIGS. 9-11  illustrate a second embodiment of the device  10 , which may also be used to secure balusters  51  in a balustrade. The front portion  11  is attached to or integral with the left and right portions  12 ,  13  as in the first embodiment. The left and right tabs  14 ,  15  of the first embodiment are modified in the second embodiment to comprise a parallel section  14 A,  15 A and a perpendicular section  14 B,  15 B. The parallel sections  14 A,  15 A are attached to or integral with their corresponding portions  12 ,  13  at the rear edge of each portion  12 ,  13 . The parallel sections  14 A,  15 A project laterally from their respective portions  12 ,  13  substantially parallel to the front portion  11 . The parallel sections  14 A,  15 A are preferably coplanar so that the parallel sections  14 A,  15 A together contact the side of the second wood member. Preferably, the top edge of each parallel section  14 A,  15 A aligns with the top edge of its corresponding portion  12 ,  13 . A perpendicular section  14 B,  15 B is attached to or integral with each corresponding parallel section  14 A,  15 A and extends to the rearward aspect of the device  10  perpendicularly from the parallel section  14 A,  15 A. 
     One or more apertures may be disposed through each of the parallel sections  14 A,  15 A and perpendicular sections  14 B,  15 B. Preferably, one aperture  16  is disposed through each of the perpendicular sections  14 B,  15 B, allowing fasteners to be driven into the top of the second wood member. In this configuration, forces imparted on the screws by the baluster  51  will be shearing forces rather than tension forces. Typically, screws and nails are configured to withstand much greater forces in shear than in tension. Preferably, the position of each aperture  16  is offset with respect to the positions of the other apertures  16  to reduce or prevent splitting of the second wood member as described above. 
     The illustrated second embodiment of the device  10  may be stamped out of sheet metal as shown in  FIG. 11 . Stress relief punches  17  may be formed at each juncture of the components to facilitate bending of the sheet into the proper device  10  configuration without imparting undue stress on the components. Preferably, the stamped metal is folded at 90 degree angles up out of the page at first and second up-fold lines  21 ,  22  and third and fourth up-fold lines  31 ,  32 , and folded at 90 degree angles down into the page at first and second down-fold lines  23 ,  24 . Each bend requires a material bend allowance to maintain proper final dimensions after bending of the part is accomplished. Rear corners  20  of the right and left portions  12 ,  13  may be linearly cut or rounded to prevent damage or injury from the sharp corner. 
     The inventive device  10  may be applied in any scenario where restricting the dimensional fluctuations of the first wood member is best avoided.  FIG. 12  illustrates a third embodiment of the device  10  used to attach a rectangular first wood member, such as a wall stud or ceiling joist  41 , to a second wood member, such as a floor plate or joist  42 . In this embodiment, the axis of the first wood member, and therefore the axis of the device  10 , is horizontal rather than vertical. Further, the dimension of the device  10  from front to rear aspect is longer to accommodate the additional width of the first wood member. In a fourth embodiment, illustrated in  FIG. 13 , the device  10  secures a larger square support beam  43  to a wide support beam  44 . 
     While there has been illustrated and described what is at present considered to be the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made and equivalents may be substituted for elements thereof without departing from the true scope of the invention. Therefore, it is intended that this invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.