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[0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/872,010, filed Aug. 30, 2013. 
     
    
     FIELD OF THE PRESENT INVENTION 
       [0002]    The present invention pertains to the field of wood siding for buildings, and more particularly, it pertains to a wood siding system that has a relatively thin overlap, and ventilation gaps around every board to prevent a retention of moisture behind the wood siding boards. 
       BACKGROUND OF THE PRESENT INVENTION 
       [0003]    An old-fashion wood clapboard is approximately ¼ inch thick at the lower edge tapering to a very thin top edge. Old-fashion wood clapboards were made to match the exposed surface and thickness of traditional cedar shingles. Wood clapboards were easier to install and to paint than shingles, and therefore this type of wall cladding became very popular during the last century. 
         [0004]    Old-fashion clapboard-like siding is coming back in style with speciality wood products that are available at the present time. Wood siding products are being manufactured with stained or pre-painted wood boards, and with other torrefied or pressure treated wood products. 
         [0005]    Experience gained with old-fashion clapboards, however, has dictated a number of improvements to be applied to the newer siding products. A first improvement is to install the wood boards without nail to avoid cracking the boards along the thin edges of the boards. A second improvement is to provide ventilation between the siding boards and the supporting structure to prevent the absorption of moisture into and behind the boards. Such moisture is known to cause expansion of the boards, wood decay and discolouration and blistering of the painted surfaces of the boards. 
         [0006]    A search in the prior art has not given any suggestion for a contemporary wood siding system including all the desired improvements, while maintaining the appearance of old-fashion clapboards. As examples, the following documents describe the various siding systems that have been found in the prior art.
   U.S. Pat. No. 2,276,170, issued to A. Elmendorf on Mar. 10, 1942;   U.S. Pat. No. 2,292,984, issued to A. Alvarez, Jr., on Aug. 11, 1942;   U.S. Pat. No. 2,308,129, issued to S. H. Tummins on Jan. 12, 1943;   U.S. Pat. No. 2,354,639, issued to H. T. Seymour on Jul. 25, 1944;   U.S. Pat. No. 2,928,143, issued to L. J. Newton on Mar. 15, 1960;   U.S. Pat. No. 3,015,193, issued to J. Amoruso on Jan. 2, 1962;   U.S. Pat. No. 3,173,229, issued to E. Weber on Mar. 16, 1965;   U.S. Pat. No. 3,237,360, issued to T. W. Mills on Mar. 1, 1966;   U.S. Pat. No. 3,261,136, issued to T. L. Abner et al., on Jul. 19, 1966;   U.S. Pat. No. 3,866,378, issued to G. Kessler on Feb. 18, 1975;   U.S. Pat. No. 4,117,644, issued to R. N. Weinar on Oct. 3, 1978;   U.S. Pat. No. 4,281,494, issued to R. N. Weinar on Aug. 4, 1981;   U.S. Pat. No. 5,501,050, issued to R. Ruel on Mar. 26, 1996;   U.S. Pat. No. 5,564,245, issued to R. J. Rademacher on Oct. 15, 1996;   U.S. Pat. No. 6,055,787, issued to M. Gerhaher et al., on May 2, 2000;   U.S. Pat. No. 6,298,626, issued to E. P. Rudden on Oct. 9, 2001;   U.S. Pat. No. 6,843,032, issued to S. Hikai on Jan. 18, 2005;   U.S. Pat. No. 7,748,188, issued to T. Ito on Jul. 6, 2010;   U.S. Pat. No. 7,797,902, issued to S. Hikai et al., on Sep. 21, 2010;   US Publication 2002/0046536, by R. Hotta, dated Apr. 25, 2002;   US Publication 2009/0241459, by B. Bryan, dated Oct. 1, 2009;   US Publication 2010/0263316, by L. Bruneau, dated Oct. 21, 2010;   CA Patent 1,283,522, issued to K. Kelly on Apr. 30, 1991;   CA Patent 2,167,097, issued to R. Ruel on Dec. 14, 1999;   CA Patent Application 2,290,914, by M. Watanabe on May 30, 2005;   CA Patent Application 2,649,123, by J. Koessler et al., on Jul. 21, 2009;   CA Patent Application 2,663,469, by L. Bruneau on Oct. 21, 2010.   
 
         [0034]    In view of these documents, it is believed that there remains a market demand in the field of wood siding industry for a wall siding system that has the appearance and stiffness of old-fashion clapboards; which can be installed without nails through the boards, and which has aeration gaps between and behind the siding boards. More particularly, there is a market demand for a wall siding system that retains its appearance of high-quality old-fashion wood siding despite expansion or shrinkage. 
       SUMMARY OF THE PRESENT INVENTION 
       [0035]    In the present invention, there is provided a wood siding system that has air circulation gaps between overlapping siding boards and between the siding boards and the supporting wall. The wood siding system has the appearance of old-fashion clapboards; a limited flexibility that closely imitates a solid wall, and means to control the direction of shrinkage of the boards to preserve the visual appeal of the wood siding. 
         [0036]    In a first aspect of the present invention, there is provided a wood siding system comprising upper and lower wood siding boards mounted to a supporting wall. Each of the wood siding boards has a front surface, a back surface, an upper edge; a lower edge, and a tapered cross-section. The lower edge of each board has an apron strip and a shoulder. The apron strip of the upper wood siding board overlaps the upper edge of the lower wood siding board. The apron strip of the upper wood siding board is held at a distance for the front surface of the lower wood siding board such that a ventilation gap is maintained under the apron strip and above the front surface of the lower siding board. 
         [0037]    The back surfaces of the wood siding boards are held parallel and in a same plane with each other and at a same distance from the supporting wall, such that a ventilation space is maintained behind the boards. 
         [0038]    The shoulder of the upper wood siding board is held at a distance from the upper edge of the lower wood siding board such that an air circulation gap is maintained between the upper wood siding board and the lower wood siding board. Because of these air circulation gaps, a good ventilation is maintained between and behind the wood siding boards, to keep the siding boards and the supporting structure dry. 
         [0039]    Because the back surfaces of the siding boards are held parallel to the supporting wall, a relatively thin ventilation gap can be maintained such that the supporting wall provides a backing support to the siding boards for preventing excessive deflection in the siding boards. When a siding board is accidentally pushed inward, a slight deflection causes it to rest against the supporting wall, suggesting that the siding boards are part of a solid structure. 
         [0040]    In another aspect of the present invention, a metal retainer is mounted between the upper and lower wood siding boards. This metal retainer has a gauge lip extending vertically and forming a spacing gauge between the shoulder of the upper siding board and the upper edge of the lower siding board for maintaining an ideal distance between the shoulder of the upper siding board and the upper edge of the lower siding board. Because of these metal retainers and gauge lips, the upper siding board is easily installed over the lower siding board, without the need for a measuring tool. The metal retainers are simply loosely placed and spaced apart along the upper edge of a first siding board and nailed to the supporting wall. The shoulder on the bottom edge of a next wood siding board is manually force-fitted down into the metal retainers, and the process is repeated for the next wood siding board. 
         [0041]    In another aspect of the present invention, the gauge lip on each metal retainer has a sharp edge for penetrating the upper edge of the lower wood siding board during swelling of the lower wood siding board. The metal retainer also has a tight-fit ridge therein, extending along the shoulder of the upper wood siding board for retaining the shoulder into the metal retainer, during shrinking of the upper wood siding board. 
         [0042]    In yet another aspect of the present invention, a wood grain pattern on the front surface of the upper wood siding board is a mirror image of a wood grain pattern on the front surface of the lower wood siding board. 
         [0043]    This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following description of the preferred embodiment thereof in connection with the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  is a partial perspective view of the siding system according to the preferred embodiment of the present invention, under construction; 
           [0045]      FIG. 2  is an end view of a wood board and a preferred separation thereof into two siding boards; 
           [0046]      FIG. 3  is a first end view of a metal retainer that is used in the wood siding system according to the preferred embodiment of the present invention; 
           [0047]      FIG. 4  is an end view of two siding boards in the wood siding system according to the preferred embodiment of the present invention; 
           [0048]      FIG. 5  is an enlarged view of the overlap between the two siding boards as shown in  FIG. 4 . 
           [0049]      FIG. 6  is a second, enlarged end view of the metal retainer illustrated in  FIGS. 1 ,  3 - 5 ; 
           [0050]      FIG. 7  is an assembly of three extrusions snappily engaged to each other for shipping, handling and for cutting to length therefrom, a plurality of metal retainers. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0051]    The preferred embodiment of the wood siding system according to the present invention is described herein below with reference to the attached drawings. 
         [0052]    Referring to  FIG. 1 , the overall arrangement of the preferred siding system is illustrated. The wood siding boards  20  have straight back surfaces  22  that are held in a coplanar arrangement with each other, parallel to the supporting structure  24 . The wood siding boards  20  are held to the supporting structure  24  by spaced-apart metal retainers  26 . The metal retainers  26  are preferably installed at intervals of 12 to 24 inches along the top edge of each wood siding board  20 . A continuous length of metal retainer  26  (not shown) can also be used to support the bottom edge  28  of the lowermost wood siding board  20  on a wall. 
         [0053]    Each wood siding board  20  has a tapering front surface  30  with a thicker lower edge. The lower edge has a shoulder  32 , a slot  34  and an apron-like strip  36  formed thereon, on its front surface. The apron-like strip  36  herein after referred to as the apron strip  36  has the thickness of an old-fashion clapboard. This thickness is approximately ¼ inch. The apron strip  36  of one siding board  20  overlaps the upper edge of a lower siding board  20 . The thickness of this overlap is the thickness of the apron strip  36  plus the thickness of an air circulation gap that is maintained under the apron strip  36 . This air circulation gap will be explained later. The vertical length of this overlap is a same distance or slightly more than the projection of the overlap; that is ¼ inch plus the thickness of the air circulation gap. 
         [0054]    The shoulder  32  has substantially a same thickness as the upper edge  38  of the siding board  20 , such that when the siding boards  20  are mounted on a supporting wall  24 , their back surfaces  22  are straight, coplanar and parallel to the supporting wall  24 . 
         [0055]    In order to further enhance the visual appearance of the preferred siding boards  20 , pairs of grain-matching siding boards  20  are sawn from a single wood board  40  as shown in  FIG. 2 . For example, a one inch thick by 5½ inch wide board  40  can be profiled on a moulder and sawn by thin-kerf bandsaw along the saw line  42 . The saw line  42  corresponds to the front surfaces  30  of both siding boards  20 . It is believed that the aforesaid overall overlap projection  44  of about 5/16 inch or slightly more together with the board width of about 5½ inch, give the appearance of old-fashion clapboard siding. 
         [0056]    The preferred method of sawing of siding boards  20  as illustrated in  FIG. 2  produces pairs of siding boards with one board having a wood grain pattern that is a mirror image of the other. These mirror images are especially apparent when the boards are made of pine, ash or oak wood species for examples. These mirror images are referred to herein as “matching wood grain patterns”, and such “matching wood grain patterns” carry an impression of a carefully selected base material for manufacturing the preferred siding boards  20 . “Matching wood grain patterns” technique is well known in the field of high quality cabinet making and furniture manufacturing. When applied to wood siding as explained above, this technique carries a similar attribute of quality craftsmanship. 
         [0057]    Both boards in a pair of “matching wood grain pattern” boards follow each other closely in the manufacturing process and remain at close proximity of each other in bundles of wood siding boards delivered to clients. It becomes relatively easy for a carpenter to find boards in a same pair and install them at close proximity from each other to obtain the aforesaid high quality craftsmanship appearance. It becomes relatively easy for a carpenter to install each board above, alongside, staggered or in alternate row from its “mirror image” match for example, to obtain a “signature” or “trademark” siding appearance. 
         [0058]    Referring now to  FIG. 3 , the preferred metal retainer  26  will be described. The metal retainer  26  is preferably cut from a bar of extruded aluminium profile. Several bars can be used in their full lengths to retain the lower siding board  20  on a wall as mentioned before. Bars of extruded aluminium profile are cut to individual short pieces as desired, to obtain metal retainers  26  of shorter lengths. Metal retainers  26  of two inches long, spaced apart twelve to twenty four inches are considered appropriate for most applications. Slightly longer metal retainers  26 , say three inch length or more, may be used to support vertical joints in the siding boards. 
         [0059]    Each metal retainer  26  has a H-like formation. This H-like formation is made of a pair of U-shaped cavities  50 ,  52  superimposed over one another with the bottom one 52 being oriented downward. Both U-shaped cavities  50 ,  52  have a same opening width. These U-shaped cavities  50 ,  52  are made to enclose the shoulder  32  and the upper edge  38 , respectively, of overlapping wood siding boards  20 . 
         [0060]    Each metal retainer  26  has a backing structure  58  which is made of two superimposed C-shaped formations  60 ,  62 . The top C-shaped formation  60  extends above the upper U-shaped cavity  50 . The top C-shaped formation  60  faces forward and has a nail-guiding groove  64  therein. The top C-shaped formation  60  has sufficient depth to conceal the heads of nails that are used to fasten the metal retainer  26  to a wall  24 . 
         [0061]    The purpose of both C-shaped formations  60 ,  62  is to provide a backing structure  58  that has stiffening ribs and a sufficient thickness “A”. The thickness “A” is preferably about ⅛ inch. The thickness “A” of the metal retainer&#39;s backing wall  58  constitutes the thickness of the air circulation gap  68  between the siding boards  20  and the supporting wall  24 . 
         [0062]    The common front wall  54  of both U-shaped cavities  50 ,  52  is a planar wall with a thickness “B” of about 1/16 of an inch or slightly less. In use, the upper half of this front wall  54  is nested in the aforesaid slot  34 , and the lower half of this front wall  54  constitutes a spacer to form an air circulation gap  56  between the apron strip  36  of one siding board  20  and the front surface  30  of the siding board  20  underneath. It will be appreciated that the air circulation gap  56  mentioned above extends between the metal retainers  26 . The thickness of the front wall  54  is preferably kept at 1/16 inch or slightly less such that the total projection of the overlap  44  does not exceed about 5/16 inch, and such that the appearance of old-fashion clapboard siding is maintained. 
         [0063]    The function of the upper portion of the front wall  54  and the associated slot  34  in which this portion is fitted, is to retain the lower shoulder  32  of the upper wood siding board to the supporting wall  24 . The function of the lower portion of the front wall  54  is to retain the upper edge  38  of the lower siding board to the supporting wall  24 . 
         [0064]    The advantage of this installation is that the air gap  68  between the siding boards  20  and the supporting wall  24  can be maintained to a very small distance to prevent excessive or uneven deflection in the siding boards  20 , should they be accidentally pushed against the supporting wall  24 . 
         [0065]    Referring again to  FIG. 3 , the lower U-shaped cavity  52  has a gauge lip  66  formed on the bottom thereof. This gauge lip  66  is used as a spacing gauge to obtain a proper spacing between the shoulder  32  of one siding board  20  and the top edge  38  of the siding board  20  below it. When a wall is being covered with wood siding boards  20 , the metal retainers  26  are loosely placed on the top edge  38  of the last-installed siding board  20 , and it is nailed to the supporting wall  24  without measurement. 
         [0066]    The gauge lip  66  ensures that a proper air circulation spacing  70  is maintained between rows of siding boards  20  to allow for swelling of the boards in high humidity conditions for example. This vertical air circulation gap  70  between siding boards  20  also constitutes an air passage communicating with the air circulation gap  56  and the vertical gap  68 . 
         [0067]    The gauge lip  66  has a depth “C” that is a function of the total board width, and the potential swelling of each siding board  20 . The gauge lip  66  has a relatively sharp lower edge for penetrating the upper edge  38  of a siding board  20  with ease, during swelling of that siding board  20 , without splitting the upper edge  38  of that board. 
         [0068]    Referring now to  FIGS. 4 and 5 , the air circulation gaps between and behind the siding boards  20  will be explained. Because the back surfaces  22  are held in a coplanar arrangement parallel to the supporting wall  24  at a very small distance from the supporting wall surface  24 , an effective ventilation (without air flow resistance) of the siding boards  20  is achieved. The arrow  72  in  FIG. 5 , illustrates the air flow pattern through the air circulation gap  56 , through the board spacing  70  and along the vertical air circulation gap  68  along the supporting wall  24 . 
         [0069]    Also because the back surfaces  22  are held in a coplanar arrangement, parallel to the supporting wall  24 , at a very small distance from the supporting wall surface  24 , an effective backing support against excessive bending or twisting is obtained. When a siding board  20  is pushed inward toward the supporting wall  24 , it quickly touches the supporting wall  24  to prevent breaking or splitting of the siding board  20 . 
         [0070]    Another feature that is provided to enhance the visual appearance of the present wood siding system, is that the apron strip  36  of each siding board  20  overlaps the front wall  54  of a metal retainer  26  by a distance “D” as illustrated in  FIG. 5 , of about ⅛ inch. Because of this overlap “D”, the metal retainers  26  are not visible at a glance when looking at a wall made with the wood siding system according to the preferred embodiment of the present invention. 
         [0071]    Also for the purpose of maintaining a high quality appearance of the wood siding, a tight-fit ridge  80  is provided along the inside edge of the upper U-shaped cavity  50 . The purpose of this ridge  80  is to create a tight fit in the U-shaped cavity  50  for receiving and retaining by friction force, the lower shoulder  32  of a board inside the cavity  50 . Because of these tight-fit ridges  80 , the bottom edges of all wood siding boards  20  are held down relative to the metal retainers  26  for concealing the metal retainers  26  from view even when there is some degree of shrinkage along the height of the wood siding boards  20 . 
         [0072]    In another feature of the preferred metal retainers  26 , the front wall  54  thereof has a width ‘F’ that is a same dimension as the width inside the C-shaped formation  62 . As can be seen in  FIG. 6 , this C-shaped formation  62  has ridges  82  and  84  on respective edges thereof, for snappily receiving and retaining the front wall  54  of another metal retainer  26  inside the C-shaped formation  62 , substantially as illustrated in  FIG. 7 . Several extrusion profiles  86  can be assembled together as a bundle as shown in  FIG. 7 , to facilitate the handling and shipping of the extrusions to a client, or for handling the extrusion profiles in a cut-off saw when manufacturing metal retainers  26  of a same length.

Summary:
The wood siding system has air circulation gaps between overlapping siding boards and between the siding boards and a supporting wall. The wood siding system has the appearance of old-fashion clapboards; a limited flexibility that closely imitates a solid wall, and metal retainers with installation gauge, and lips and ridges to control the direction of shrinkage and swelling of the wood boards to preserve the visual appeal of the wood siding. A wood grain pattern on the front surface of each siding board is a mirror image of a wood grain pattern on the front surface of another siding board.