Abstract:
An engineered wood handrail for use in stairways and balustrade systems. The engineered handrail includes a top layer, two lower side layers and a lower middle layer which are glued and laminated together. The three layers and core include short lengths or planks of wood which are glued together using finger joints to produce long pieces of material. A modified finger joint known as a staggered shoulder joint is used to improve the outer appearance of the handrail by allowing most of the finger joints to be hidden between the layers.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 61/956,585 filed on Jun. 12, 2013 and is incorporated herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to engineered handrail products and more particularly to engineered handrails configured to improve the outer appearance of the handrail especially with respect to visible joints. 
       BACKGROUND OF THE INVENTION 
       [0003]    Throughout the years the wooden interior stair balustrade system has performed two important functions in residential and commercial construction. Through the combination of treads, newels, balusters, handrails, and handrail fittings in accordance with a system of rules, a means of safe passage from floor to floor and proximity to balconies is provided. The combination of the various elements within the balustrade system can enhance or evoke a strong statement of period style, providing this is done with an adherence to what is considered architecturally correct. This is highly significant as the staircase tends to be the focal point of a structure. The requirement for a handrail calls for a blank or billet of sufficient width and thickness to be cut to a particular profile shape. This shape is determined by both accepted rules as to grasp-ability and traditional design styles. The shaped handrail must be of sufficient length to span the distance between supports. By this system of rules, level spans in balconies are much less than those required for stairs. Therefore, a significant requirement for longer length handrails exists. 
         [0004]    Historically, defect free solid wood pieces of sufficient size and length have been utilized to produce handrails. Construction of multi-story structures has greatly increased while the availability of forest resources has declined: To satisfy the need for long, defect free solid pieces and to help control costs, alternative methods of construction of the handrail have been developed. To overcome the lack of availability of full thickness pieces, several pieces of less costly and more available, defect free, thinner lumber are cut to width and laminated to achieve sufficient thickness. This addresses the problem of adequate thickness but does not address the problem of length. Trees, and in particular, hardwood trees, yield only a small percentage of long length lumber due to the growth of branches in close proximity to the ground. The location of each branch yields a corresponding defect in the sawn board which mitigates the availability of long clear components. In an effort to overcome the lack of long components, various methods and types of joinery are used to create the required long components from shorter pieces. 
         [0005]    Wood components are kiln dried to remove moisture and create stability with regard to movement prior to shaping and assembling into a final product. As a wooden component loses moisture, shrinkage occurs and, depending on the grain structure, can bow, warp or twist. It is the nature of wood to acclimate to its&#39; environment by exchanging moisture to achieve equilibrium. Because of this, it is possible to see additional distortion after final machining and assembly. The solid wood piece shows the greatest tendency for this occurrence because there is nothing to interrupt the grain over the full length. Thinner solid wood pieces are less susceptible because the lamination process adds some stability. Thinner pieces composed of shorter blocks that have been connected together by some method of joinery are better still but, depending on the method, may not be aesthetically acceptable. 
         [0006]    The system of accepted rules governing installation states that the span of handrails must not be interrupted in sloped applications. This means that as long as the staircase is rising or descending, the handrail span must be continuous. Thus, longer lengths of material are required. The only associated components connected to the sloped rail are the balusters. While providing vertical support to the location of the handrail, balusters provide little in the way of lateral support. The lateral straightness of the handrail is accomplished only through the straightness of the grain and stability of the individual components and the construction method. 
         [0007]    Currently handrails are provided in some combination of solid and finger jointed wood plies which are horizontally laminated to achieve proper thickness. The solid plies have more of a tendency to induce bowing and, due to limited availability, do not fulfill the long length requirement. While finger jointed plies can be manufactured to any required length and are more stable, aesthetically, they are far less desirable. 
         [0008]    Wood is stronger when stressed along the grain (longitudinally) than when stressed across the grain (radially and tangentially). Wood is a natural composite material; parallel strands of cellulose fibers are held together by a lignin binder. These long chains of fibers make the wood exceptionally strong by resisting stress and spreading the load over the length of the board. Furthermore, cellulose is tougher than lignin, a fact demonstrated by the relative ease with which wood can be split along the grain rather than across the grain. 
         [0009]    Glue is highly effective for joining wooden pieces when both surfaces of the joint are edge grain. A properly glued joint is often as strong as or stronger than a single piece of wood. However, glue is notably less effective when gluing two pieces of wood end to end. 
         [0010]    DESCRIPTION OF THE RELATED ART 
         [0011]    U.S. Pat. No. 6,582,021 by Chung for ARMREST WITH OAK VENEER LAYER which issued on Jun. 24, 2003 teaches an armrest made from wooden planks and having a center layer, a left layer, a right layer and a top layer all glued to one another to form the armrest. The top, left and right layers are made of oak wood while the center layer is a cheaper wood. The three layers of oak wood serve as veneers to cover the less expensive center layer. There is no requirement for long lengths and no mention of short pieces attached end on end by finger joints to provide longer pieces which comprise the four layers. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention provides an improved engineered wood handrail for use in stairways and balustrade systems demonstrating means for maintaining or increasing the strength of multiply handrails while hiding the finger joints to provide an appearance of a smooth, uninterrupted, continous length of rail. The engineered handrail includes a top layer, two lower outerside layers and at least one lower middle inner layer or core disposed between the side layers which are affixed by adhesion means such as by glue and laminated together. The layers and core include short lengths or longitudinal lengths of wood which are glued together using finger joints to produce long pieces of material. A modified finger joint known as a staggered shoulder joint is used to improve the outer appearance of the handrail by allowing most of the finger joints to be hidden between the layers. 
         [0013]    In accordance with the present invention, there is provided one preferred embodiment of a handrail for use on staircases and balconies comprising, consisting of, or consisting essentially of at least four layers or plies of planks or strips of wood glued together. The lower middle or center layer defines a first layer containing longitudinal planks of wood is connected at the ends with horizontal staggered shoulder finger joints, the first layer oriented in a vertical position. The lower left layer or second layer including longitudinal planks of wood is connected at the ends with horizontal shouldered finger joints containing only one shoulder and wherein the fingers are oriented at the right side of the second layer. The second layer is oriented in a vertical position and the right side of the second layer is glued to the left side of the first layer. The lower right layer or third layer including longitudinal planks of wood is connected at the ends with horizontal shouldered finger joints containing only one shoulder and wherein the fingers are oriented at the left side of the third layer. The third layer is oriented in a vertical position and the left side of the third layer is glued to the right side of the first layer. The last layer is a top layer including longitudinal planks of wood connected at the ends with horizontal shouldered finger joints containing only one shoulder and wherein the fingers are oriented at the bottom of the top layer. The top layer is oriented in a horizontal position and is equal in width to a total width of a combination of the third layer, the first layer and the second layer. The bottom surface of the top layer is glued to the top sides of the third layer, the first layer and the second layer. The glued combination of the top layer, the third layer, the first layer and the second layer is milled to a profile on the top, the left side and the right side to give a pleasing appearance and comfortable feel. 
         [0014]    More particularly, the handrail comprises or consists of a first lower interior longitudinal member having a first end connecting with a second end of a second longitudinal member with cooperatively engaging vertical staggered shoulder finger joints, the first layer being oriented in a vertical position. A second side outer longitudinal member having a first end connecting with a second end of a second longitudinal member with cooperatrively engaging horizontal shouldered finger joints containing a second side outer shoulder and a plurality of fingers extending horizontally inwardly therefrom, the second side outer longitudinnal member aligned with and adhesively atttaching to a lateral side of the first lower interior longitudinal member. A thrid side outer longitudinal member having a first end connecting with a second end of a third longitudinal member with cooperatrively engaging horizontal shouldered finger joints containing a third side outer shoulder and a plurality of fingers extending horizontally inwardly therefrom, the third side outer longitudinnal member aligned with and adhesively atttaching to a lateral side of the first lower interior longitudinal member opposite the second side outer longitudinal member. A fourth top longitudinal member having a first end connecting with a second end of a fourth top longitudinal member with cooperatively engaging horizontal shouldered finger joints including a top shoulder extending thereacross having a plurality of finger joints disposed at a bottom portion of the the top layer, the top layer covering the frist side outer longitudinal member, the second side outer longitudinal member and the third side outer longitudinal member, the fourth top longitudinal member having a bottom surface adhesively affixed to the frist side outer longitudinal member, the second side outer longitudinal member and the third side outer longitudinal member, the fourth top longitudinal member. 
         [0015]    It is contemplated that the middle layer or core could comprise a plurality of strips of material glued together, a wood/plastic or synthetic composite material, or even an web type of material composed of plastic and/or wood material. 
         [0016]    Several key factors that aid in improving the straightness of the handrail product within the constraints of maintaining market appeal are included in the above-identified prefereed embodiment of the present invention. A lower block is produced with a shouldered finger joint central core (first layer) and two lateral layers (second and third layers), one on each side of the central core. The depth of the large flats of the shoulders of the central core can be adjusted to create a ply that exhibits a very high degree of straightness. A cap ply is laminated to the lower block perpendicular to the grain direction of the lower block which works to counteract the movement that occurs with all horizontal laminations. The central ply of the lower block is laminated to lateral plies that are also produced with shouldered vertical finger joints. The shoulders have sufficient depth as to keep the finger joints concealed within the finished handrail, resulting in the more desirable butt jointed appearance. If, by virtue of length, the cap ply contains finger joints, a heavy shoulder is located at the top of the handrail so that the finger joint portion is only visible on the relatively short sides of the cap. By incorporating a single lower block, the resulting appearance is a cap and single jointed lower ply. When compared with the cap and multiple jointed plies available today, the handrail of the present invention appears to be an integral continuous length of rail and is much more desirable in appearance. 
         [0017]    It is an object of this invention to provide a handrail product that, due to the method of manufacture, is superior in straightness to those currently in use while maintaining a desirable aesthetic quality. 
         [0018]    It is an object of this invention to provide a handrail product that is configured to hide most finger joints within the handrail and to minimize the amount of finger joints that are visible. 
         [0019]    It is an object of this invention to provide a handrail product that is configured to provide strength and stability which is comparable or superior to that of non-laminated handrails and other laminated handrails commonly used today. 
         [0020]    It is an object of this invention to provide a handrail product that is manufactured in a way which is at least as economical and environmentally sound as methods used today, while providing a handrail with a superior appearance. 
         [0021]    It is an object of the present invention to provide a stronger handrail with hidden joints appearing to be an integral continuous unit. 
         [0022]    It is an object of the present invention to provide a handrail with hidden joints that will accommodate inner core material of a less expensive wood product while maintaining the requisite structural strength and maintaining a pleasing appearance minimizing the visibility of the joints. 
         [0023]    Other objects, features, and advantages of the invention will be apparent with the following detailed description taken in conjunction with the accompanying drawings showing a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts throughout the views wherein: 
           [0025]      FIG. 1  is a prospective view of a tool used to make finger joints in a wooden plank. 
           [0026]      FIG. 2  is a side view of the ends of two boards containing staggered shoulder vertical finger joints. 
           [0027]      FIG. 3  is a side view of the ends of two boards containing staggered shoulder horizontal finger joints. 
           [0028]      FIG. 4  is a side view of the ends of two boards containing a single shoulder horizontal finger joint. 
           [0029]      FIG. 5  is a perspective view of a handrail including top layer and three bottom layers combined wherein each layer contains finger joints but only the finger joints in the top layer are visible. 
           [0030]      FIG. 6  is a perspective view of the four component layers of the handrail of  FIG. 5 . 
           [0031]      FIG. 7  is a perspective view of an alternative embodiment of the handrail wherein the lower middle or core layer contains horizontal instead of vertical finger joints. 
           [0032]      FIG. 8  is a perspective view of a horizontal finger joint. 
           [0033]      FIG. 9  is a perspective view of a vertical finger joint. 
           [0034]      FIG. 10  is a perspective view of a handrail  10  before the milling and shaping process. 
           [0035]      FIG. 11  is a perspective view of the handrail embodiment of  FIG. 7  showing the staggered joints prior to adding the top layer. 
           [0036]      FIG. 12  is an alternate handrail embodiment showing an exterior design. 
           [0037]      FIG. 13  is an alternate handrail embodiment showing an exterior design 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    In accordance with the present invention,  FIGS. 1-13  show a wooden handrail  10  for use along stair cases, walkways or balconies to provide a safety barrier and a grab rail for a user to hold while walking on the stair cases, walkways or balconies.  FIG. 10  shows the handrail  10  before the milling process. After the milling process, the handrail  10 , as shown in  FIG. 5 , has a new and more desirable profile. Handrail  10  includes a top layer  12 , a lower middle or core layer  16  and two lower side layers  14  and  18 . 
         [0039]    In  FIG. 5  the four layers  12 - 18  are glued together along respective side surfaces. Further, the four layers are made of shorter length planks which have had fingers  20  shown in  FIG. 4  cut into the ends and glued together to make longer planks. When the fingers of the ends of two planks are glued and pushed together to join the two planks, the resulting joint is called a finger joint. Two common types of finger joints are shown in  FIG. 8  and  FIG. 9 . 
         [0040]      FIG. 1  shows a tool  102  used to cut fingers  20  into wooden planks by milling out parallel grooves or slots  22  in the planks. Two common types of finger joints are referred to either as either horizontal or vertical. Referring to  FIG. 8 , a finger joint is a horizontal finger joint if, when the joined planks are lying horizontally on a surface, the fingers are visible on the side of the joined planks rather than on the top surface. It can be seen that if the joint is pulled apart, the fingers are horizontal along their lengths. Finger joint  30  in  FIG. 8  is a horizontal finger joint. 
         [0041]    A finger joint is a vertical finger joint if, when the joined planks are lying horizontally as shown in  FIG. 9 , the fingers are visible on the top surface. It can then be seen that when this joint is pulled apart, the fingers are vertical along their lengths. Finger joint  32  is therefore a vertical finger joint. 
         [0042]    In order to determine whether a joint defines a vertical joint or horizontal joint, it is necessary to view the joined planks lying flat or horizontally, and to then determine if the joint is oriented vertically or horizontally. For example, in  FIGS. 6 and 7 , joints  178  and  186  are horizontal finger joints even though the joint appears to be oriented vertically. The joint must oriented with the joined plank lying horizontally. The finger joint  167  in  FIG. 6  is a vertical finger joint. 
         [0043]    As shown in  FIG. 3 , finger joints may also include shoulders  25 . Instead of cutting fingers from top to bottom of the plank, as was done in  FIG. 1 , a portion of the plank remains intact, and that portion is referred to as the shoulder. Planks  40  and  42  with two such ends can be joined as shown if  FIG. 3 . The flat end  24  of the shoulder  25  abuts against the flat portion  26  of the adjoining plank. Such a joint is referred to as a staggered shoulder joint because the two shoulders are staggered with respect to one another. 
         [0044]    The handrail  10  of  FIG. 5  includes four layers or plies, vertical layers  14 ,  16  and  18  and top layer  12 . The only finger joint which is visible is finger joint  126  which is contained within top layer  12 . The shouldered finger joint  126  includes only one shoulder and the fingers are advantageously positioned at the bottom of the joint as shown in  FIGS. 4 and 5 . Looking at  FIG. 5 , the fingers are visible only at the outer edge of the top layer  12  and not on the larger top surface. Only the shoulder butt joint is visible. This creates a better appearance than if the fingers were visible all along the top surface. 
         [0045]    No other finger joints are visible in  FIG. 5 , due to the advantageous placement of the shoulders.  FIG. 6  shows a breakdown of the layers and the pieces assembled to make the layers. Second layer  14  includes members  144  and  142  joined with horizontal shoulder joint  146 . Third layer  18  includes members  182  and  184  joined with horizontal shoulder joint  186 . It can be seen that the shoulders of both joints  146  and  186  are located towards the outer surface of the planks and that the milled surfaces of the planks do not expose the fingers. It can also be seen that joints  146  and  186  include both fingers and a shoulder. In particular, joint  186  includes fingers  187  and a shoulder  188 . 
         [0046]    In  FIG. 6  the first middle or core layer  16  includes staggered shoulder vertical finger joints  167  which are completely covered by the outer layers  14  and  18  when the handrail  10  is assembled. 
         [0047]    Another preferred embodiment of the handrail is shown in  FIG. 7 . The lower middle or core layer  17  includes staggered shoulder horizontal finger joints  178  rather than vertical joints. It can be seen that the fingers of joint  178  will be exposed on the bottom side of the handrail in  FIG. 7 . However, because of the installation height of handrails, a user would have to bend or kneel to view the bottom surface of the handrail and to see the exposed finger joints. Therefore, the fact that these fingers are visible on the bottom surface does not detract from the appearance of the handrail as viewed from a normal viewpoint. The fingers in joints  146  and  186  are also visible at the bottom of the completed handrail  10  in both embodiments, but, as with joint  177 , this does not cause an appearance problem. 
         [0048]    The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modification will become obvious to those skilled in the art upon reading this disclosure and may be made upon departing from the spirit of the invention and scope of the appended claims. Accordingly, this invention is not intended to be limited by the specific exemplification presented herein above. Rather, what is intended to be covered is within the spirit and scope of the appended claims.