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BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    My invention pertains to building construction, specifically constructing decorative and protective corners of building surfaces. 
         [0003]    2. Related Art 
         [0004]    Vinyl siding is a popular material for constructing the surfaces of buildings, due to its reasonable cost and low maintenance. However, in the past, the corners of most buildings with vinyl siding or other cladding have been simple vertical strips with little adornment. I invented and patented a vinyl-siding corner block to enhance the look of those buildings. See my U.S. Pat. No. 5,836,123. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Though my vinyl-siding corner blocks worked well, I more recently realized they could be even better. Builders had to attach them to a building one at a time. Also, though they could fit together, they were not secured together, allowing careless builders to misalign the blocks and expose the underlying building to the elements. The wedge-lock quoin corner assembly disclosed herein, composed of locking quoin blocks, solves these problems. 
         [0006]    The locking quoin block of the present invention is made of a resilient, semi-rigid polymeric material. It is advantageously produced as a unitary product, molded as a single piece, though alternative embodiments may be assembled from separate parts. In preferred embodiments, the material is calcium-carbonate-filled, UV-stabilized, no-break co-polymer polypropylene. In some embodiments, the material is a vinyl polymeric material suitable for exterior construction. 
         [0007]    My locking quoin block includes locks that are configured to join vertically adjacent blocks without needing to use for this purpose additional connecting tools (such as hammers or screwdrivers) or connecting means (such as nails, glue, screws, bolts, staples, etc.). The locks ensure the blocks are properly aligned and securely connected prior to installation and throughout the useful life of the structure. 
         [0008]    The methods of locking such blocks, of unlocking them when disassembly is required, and of the installation of them on buildings are further aspects of my present invention. 
         [0009]    My invention provides a locking quoin block for assembling a column to be secured to a corner of a structure. The block comprises a sheet of semi-rigid polymeric material (e.g. polypropylene copolymer, vinyl, or other suitable formulation), the sheet formed as a pair of wings connected at a right angle along a corner axis, each wing having a top edge, a bottom edge, a vertical distal edge, and an exterior surface. A side flange (adapted to be nailed to the structure, optionally provided with holes for nails) extends from the distal edge of each wing. A vertical groove, adapted to mate with the ends of typical siding, is provided in the distal edge. 
         [0010]    The exterior surface of each wing desirably produces the look of a traditional quoin corner by having a raised portion, below which is a recessed portion bounded by the bottom edge of each wing. Alternative embodiments of my invention may be designed to have wings with a generally planar exterior surface, or some other configuration for a different visual effect. 
         [0011]    The top edge of each pair of wings has a horizontal groove bounded by a pair of interior groove surfaces that are substantially vertical. A horizontal lip extends from the top of one of the interior groove surfaces over and above the groove and is somewhat spaced apart from the other of the interior groove surfaces. 
         [0012]    A ridge extends from the bottom edge of each pair of wings. The ridge has a front surface. The ridge and the horizontal groove are constructed so that when the ridge of a first block of my invention is inserted downwardly into the horizontal groove of a second block, they will matingly engage. 
         [0013]    My invention provides a locking function by providing at least one wedge extending from the front surface of the ridge below each wing, configured so that, when force is applied to insert the ridge of the first block into the horizontal groove of the second block, the wedges deform the lip over the top edge of the horizontal groove, permitting the wedges to slide past the lip and to continue to a position where the lip is entrapped between the top of each wedge and the bottom edges of the wings, whereby the ridge of the first block matingly engages with the groove of the second block, and the two blocks are locked together. 
         [0014]    In some embodiments of the invention, there are four wedges, two on each wing of the block, and other configurations may optionally be designed if desired. In some embodiments, the wedges have a regular trapezoidal shape when the wing is viewed from the front, i.e., with two pairs of congruent angles. Desirably the wedges are thickest at the top in the center and thinnest on the bottom and sides. 
         [0015]    The method of locking a pair of my quoin blocks involves aligning the bottom of an upper block with the top of a lower block, then applying force to bring the blocks together so that portions of the lip extending horizontally above the lower block are entrapped by the wedges to the upper block, while the ridge of the upper block matingly engages the groove of the lower block. 
         [0016]    The method of unlocking two locked quoin blocks, such as for repair or to cure a mistake in assembly, involves deforming a portion of the side of a wing of a lower block near its top edge, then applying force to an upper block, as if to turn the upper block&#39;s top edges towards the lower block&#39;s exterior surfaces. 
         [0017]    In preferred embodiments of the invention, the method of installing the blocks as a quoin corner of a building structure involves creating a secure column or tower of blocks through repeated use of the aforementioned locking method until the desired number of blocks is reached, aligning the column with the building, and then attaching the column to the building, generally with nails. If required by the height or other characteristics of the construction, the installer may modify one or more of the blocks, preferably the bottom one, by cutting off a portion. 
         [0018]    Optionally, each of the blocks of the present invention (or in certain instances, just the topmost block of a particular column) would be provided with a top flange adapted to be secured to the top of the corner of the structure by nails, screws, or other means of attachment. 
         [0019]    My invention includes the method of assembling a column of locked-together quoin corner blocks. This method is performed by aligning the ridge of a first locking quoin block with the horizontal groove on the top edges of a second locking quoin block; and applying force (e.g. manually or by suitable mechanical means) to cause the ridge of the first block to enter the horizontal groove on the top edges of the second block, so that the wedges deform the lip of the horizontal groove, permitting the wedges to slide past the lip and to continue to a position where the lip is entrapped between the top of each wedge and the bottom edges of the wings, whereby the two blocks are locked together. These steps are repeated until the predetermined number of blocks for an assembly are locked into an assembled column, ready for attaching to the corner of a building structure. 
         [0020]    As mentioned above, sometimes it will be desired to detach one or more blocks from an already-constructed column. In that event, my invention provides the following method: applying force to deform the distal edge of a wing of the lower block near a groove of the top edge, the force directed away from the exterior surface of the wing; and applying force to the upper block, the force directed as if turning the top edges of the upper block towards the exterior surfaces of the lower block. 
         [0021]    In addition, my invention includes a preferred method of installing a column of my blocks as the corner of a building structure. First an installer determines the desired height of a column of locking quoin blocks and then shapes a first such block to fit a column to the building. Then the installer aligns the ridge of a second such block with the horizontal groove on the top edges of the first block and applies force to cause the ridge of the second block to enter the horizontal groove on the top edges of the first block, so that the wedges deform the lip of the horizontal groove, permitting the wedges to slide past the lip and to continue to a position where the lip is entrapped between the top of each wedge and the bottom edges of the wings, whereby the two blocks are mated as described above and remain locked together. The installer then repeats the step with a third block and as many additional blocks as are appropriate until the desired height of the column is achieved. Then the column of locked-together quoin corner blocks of my invention are secured to the building structure by conventional means such as nails, screws or an appropriate formulation of glue. 
         [0022]    Desirably, two or more corners of a building structure are provided with quoin corner assemblies of my present invention, and polymer siding or other cladding (e.g. of vinyl, polypropylene or other desired material) is installed between them. This is achieved in accordance with my invention by inserting an end of a panel of the cladding into the groove of a distal edge of a locking quoin corner of the assembled and mounted column and nailing or otherwise securing the panel of cladding to the building structure. 
         [0023]    Typically, an installer would repeat the previously described steps to mount another assembled column to another corner of the building, so that the two columns are at opposite ends of a wall of the building structure, and panels of cladding would be installed between both columns of quoin corner blocks. The ends of those panels of cladding that are coterminous with the ends of the structure defining the wall between the columns would be inserted matingly into the respective grooves of a distal edge of a second locking quoin corner of the second assembled column constituting a quoin corner assembly of the present invention. 
         [0024]    Another aspect of the present invention is a quoin block comprising a sheet of semi-rigid polymeric material, the sheet being formed as a pair of wings, the pair of wings comprising a first wing and a second wing connected at a right angle along a corner axis, each wing having a top edge, a bottom edge, a distal edge, and an exterior surface; 
         [0025]    a side flange extending from the distal edge of each wing, the side flange being adapted to be nailed to a structure; the exterior surface of each wing having a raised portion and a recessed portion bounded by the bottom edge of each wing; the distal edge of each wing being parallel to the corner axis and having a vertical groove; the top edge of each pair of wings having a horizontal groove with a horizontal lip formed over the groove; a ridge extending from the bottom edge of each pair of wings, the ridge having a front surface; the ridge and the horizontal groove being adapted to matingly engage when the ridge of a first locking quoin block is inserted into the horizontal groove of a second locking quoin block, the improvement which comprises providing locking functionality supplied by the addition of two wedges extending from the front surface of the ridge below each wing, the wedges configured so that, when force is applied to insert the ridge of the first block into the horizontal groove of the second block, the wedges deform the lip over the top edge of the horizontal groove, permitting the wedges to slide past the lip and to continue to a position where the lip is entrapped between the top of each wedge and the bottom edges of the wings, whereby the two blocks are locked together. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective view of a locking quoin block of the present invention, looking upwards from below the block. 
           [0027]      FIG. 2  is a perspective view of locking quoin blocks of the present invention after being assembled into a column and attached to a building. 
           [0028]      FIGS. 3   a  and  3   b  are perspective views figuratively depicting the assembly of three locking quoin blocks into an assembled column. 
           [0029]      FIGS. 4   a ,  4   b , and  4   c  are partial vertical cross-sections of a pair of locking quoin blocks showing successive steps in their assembly and locking together. 
           [0030]      FIG. 5  shows how a pair of locked quoin blocks may be disassembled. 
           [0031]      FIG. 6   a  is a perspective view of a locking quoin block of the present invention showing a bottom block for an assembled column. 
           [0032]      FIG. 6   b  is a perspective view of a locking quoin block of the present invention showing the cutting of a block which an installer desires to shorten. 
           [0033]      FIG. 7  is an elevation view of a locking quoin block of the present invention, looking at the exterior surface of a wing. 
           [0034]      FIG. 8  is an elevation view of a locking quoin block of the present invention, looking along the side flange into the distal edge of a wing. 
           [0035]      FIG. 9  is a plan view from the top of a locking quoin block of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    With reference to the accompanying drawings,  FIG. 1  shows an example of a locking quoin block  101  of my invention, with two wings  103  extending at right angles from a corner axis  102 . Each of the wings  103  has a top edge  106 , a bottom edge  107 , a side flange  113  extending from its distal edge  112 , and an exterior surface  105 . The exterior surface  105  includes a raised portion  108  and a recessed portion  109 . (Alternatively, the exterior surface may have a continuous decorative portion.) Also shown is a ridge  111  extending from the bottom edge  107  of the wing, from which two wedges  115  protrude. There is a slot  122  between the top of the wedge  115  and the bottom edge  107 . 
         [0037]    In the embodiment illustrated, the faces of wedges  115  are shaped as regular trapezoids (i.e., having two pairs of congruent angles), with the long edge of the trapezoid at the top of the wedge and the short edge at the bottom. The wedges  115  are desirably shaped to be thickest at the top center of the wedge, and thinner at the wedge&#39;s sides and bottom. The wedges  115  are further shaped so that the top of the wedge is parallel to the bottom edge  107 . Also shown is a top flange  117  extending upwardly from portions of the wings  103  near the corner axis  102 . The top flange  117  is provided with holes  119  for permitting nails, screws or the like to attach the quoin block  101  to the corner of a supporting structure. 
         [0038]    In alternative embodiments of the invention, the number of wedges  115  on each wing  103  may be as few as one or as many as three, four or more for increased locking strength. The faces of each wedge  115  need not be trapezoidal, e.g., they could be rectangular or semi-circular or triangular. In alternative embodiments, the thickness distribution of the wedges  115  may also be different from the illustrated embodiment, i.e., the sides may be as thick as the center. In preferred embodiments, the wedges  115  are integrally molded to the ridges  111 . 
         [0039]    Typically the corner axis  102  of each block is 12 inches in length, which defines the uniform height of each locking quoin block  101 . The length of each of the wings  103  (that is, from corner axis  102  to distal edge  112 ) is also typically 12 inches, but may be any length deemed by the designer to be visually pleasing and structurally sound. Typically the raised portion  108  is 10 inches long along the corner axis  102 , and the recessed portion  109  is 2 inches long along the corner axis  102 , but other design choices may be made as desired. The raised portion  108  is also typically raised 0.5 inches past the recessed portion  109 , and recessed portion itself is typically raised 0.125 inches past the front surface of the ridge  111 . 
         [0040]    In other embodiments of the invention, the illustrated top flange  117  may be omitted when the locking quoin block  101  is formed. Alternatively, top flange  117  may be removed from a locking quoin block. 
         [0041]      FIG. 2  shows an example of a vinyl siding residential structure to which an assembled column of locking quoin blocks  220  have been attached. 
         [0042]      FIGS. 3   a  and  3   b  show how a set of locking quoin blocks  220  are adapted to be assembled into a column in accordance with the present invention. Once assembled, the locking quoin blocks resist separation, making the column rigid enough to be used as one piece.  FIG. 3   a  shows three separate blocks  220  and the direction that force should be applied in order to lock the blocks together, shown here as locking force  302 . A locking force  302  is applied (manually or mechanically) to connect the middle block  305  to the bottom block  306 , and locking force  302  is also applied to connect the top block  304  to the middle block  305 . Typically, the bottom two blocks are first joined by the application of locking force  302 , then another block is joined atop the column that was created by the initial application of locking force  302 , and so on up the column until the topmost block has been thereby joined to form a completed column of locking quoin blocks  220 , such as is shown in  FIG. 3   b . The installer will then secure the column to the building, by nailing the column to the building through the side flanges of its blocks. 
         [0043]    The exterior surfaces of the locking quoin blocks which together constitute the column  220  show alternating raised portions  108  and recessed portions  109 . The raised portions  108  are desirably formed to resemble stone blocks. The recessed portions  109  are formed to resemble a surface of recessed stone. 
         [0044]      FIG. 3   b  also shows the ridges  111  and the wedges  115  on the bottom block  306  of the column  220 , whereas the ridges  111  and wedges  115  of the other blocks  304 ,  305  are no longer visible, as they would have been before assembly, e.g., as shown in  FIG. 3   a.    
         [0045]      FIG. 3   b  shows the top flange  117  with its holes  119  on the top block  304  of the column  220 , and also shows that the top flanges  117  of the other blocks  305 ,  306  are no longer exposed, as they would have been before assembly, e.g., as shown in  FIG. 3   a . Optionally, the blocks of the present invention may be assembled in any desired order. Note that the three blocks shown in  FIGS. 3   a  and  3   b  are representative of any number of desired blocks, depending on the height of the column to be provided with a quoin corner assembly in accordance with the present invention. 
         [0046]    As previously mentioned, each of the blocks  304 ,  305 ,  306  is of a uniform height, typically 12 inches. To construct an assembly with a height that is other than an integral number of feet, an installer would desirably trim an appropriate height off the bottom-most block, here shown as block  306 . As will be discussed below, such a trim is depicted in  FIGS. 6   a  and  6   b.    
         [0047]      FIGS. 4   a ,  4   b  and  4   c  show a partial cross-section (that is, a close-up) of successive positions of locking elements during the assembly of a column of locking quoin blocks of the present invention. Each of  FIGS. 4   a ,  4   b  and  4   c  shows an upper locking quoin block  401  and a lower locking quoin block  402  that have been positioned in proper alignment for locking. Also shown are parts of the raised portions  108  of the upper locking quoin block  401  and the lower locking quoin block  402 , the recessed portion  109  of the upper locking quoin block  401 , the ridge  111  on the bottom edge  107  of the upper locking quoin block  401  with one of its wedges  115 , and the groove  410  with a front wall  440  and a back wall  445 . Also shown is a lip  405  extending over the groove from the front wall  440 . The groove  410  and the ridge  111  are made so that they matingly engage when the ridge  111  is inserted in the groove  410 . Also shown is the slot  122  between the wedge  115  and the bottom edge  107 , where the lip  405  will be entrapped. In preferred embodiments, the lip  405  is about 0.125 inches thick, and the slot  122  is about 0.125 inches wide. 
         [0048]      FIG. 4   a  shows a first position, when an installer is beginning to apply locking force  302  intended to connect the upper locking quoin block  401  and the lower locking quoin block  402 . 
         [0049]      FIG. 4   b  shows a successive position of these elements, wherein the lip  405  extending from the front wall  440  of the groove  410  is pushed by the wedge  115  and thereby caused to temporarily deform a tiny amount in the direction of the arrow  408 , allowing the wedge  115  to slide by in the downward direction. 
         [0050]      FIG. 4   c  shows the final respective position of these elements, wherein the blocks have become locked together. Note that as soon as the wedge  115  has passed downwardly below the edge of lip  405 , the lip  405  snaps back, attempting to return to its original position and shape. In preferred embodiments, this locking movement of lip  405  produces an audible click. A benefit of my invention is that this click signals to the construction installer that the pair of blocks have become locked together and that no further locking force  302  need be applied. The lip  405  is now trapped in the slot  122  between the wedge  115  and the bottom of the recessed portion  109 . The ridge  111  is locked into the groove  410 . 
         [0051]    However, all work does not necessarily proceed smoothly at every construction site. One of the blocks may become damaged and so need to be replaced before the column is secured to the corner of the structure. Or perhaps the height wasn&#39;t properly measured at first. So my invention also includes a method for unlocking a pair of locked quoin blocks. As shown in  FIG. 5 , two locking quoin blocks, an upper block  401  and a lower block  402 , were locked together but are being undone. In the move shown here, an installer uses the left hand  504  to apply a deforming force  508  to the side flange  113  of the lower locking quoin block  402 . Note the holes  519  in the side flange  113  for securing the block to a building. The deforming force  508  deforms the side flange  113  of the lower locking quoin block  402  towards the fingers of the installer&#39;s left hand  504 . The installer simultaneously uses the right hand  503  to apply a turning force  510  to the upper locking quoin block  401 . As depicted in this  FIG. 5 , the turning force  510  is counter-clockwise, the installer trying to bring the top edges  106  of the wings  103  of the upper locking quoin block  401  towards the bottom edges  107  of the lower locking quoin block  402 . The wedges  115  of the upper block  401  are now visible. 
         [0052]    Note that that the installer may similarly unlock a pair of quoin blocks of the present invention by using different hand positions and/or reversing the roles of the left and right hands by flipping the blocks over. 
         [0053]    Note also that in the embodiment of quoin blocks  401  and  402  shown in  FIG. 5 , there is no structure corresponding to top flange  117  of some other of the embodiments shown. As mentioned above, such a top flange is optional. 
         [0054]      FIGS. 6   a  and  6   b  show alternative versions of a bottom block for a column of locking quoin blocks. 
         [0055]      FIG. 6   a  shows a locking quoin block  101  that has been manufactured without the recessed portions, ridges, or wedges as shown in other embodiments. This would desirably provide a wider bottom so that the block may rest on the ground more stably, to supporting a higher column than otherwise. 
         [0056]    In  FIG. 6   b , a cut line  605  shows where an installer may provide a locking quoin block such as in any of the previously described embodiments, and then trim away the lowermost section, e.g. removing the recessed portions, ridges, and wedges. This step could be performed in order to create a wider bottom edge for supporting the column while it is being affixed to the structure and/or simply to match the height of the column of quoin blocks to the height of the structure. (The style of the depicted cutting element  610  is for illustration and not limitation.) Those skilled in the art will be familiar with appropriate cutting methods. 
         [0057]      FIG. 7  shows an elevation view of a locking quoin block, facing the exterior surface  105  of a wing  103 . This locking quoin block has been manufactured with the optional top flange  117  and its holes  119  for receiving attachment means. Also shown is a ridge  111  with its wedges  115 . The side flange  113  is visible, as is the side flange&#39;s holes  519  for permitting nails, screws, and the like for securing the block to a building. The raised portion  108  and recessed portion  109  are also clearly visible. The bottom edge  107  and the top of the wedges  115  form the slot  122  where the lip of another locking quoin block will be entrapped. 
         [0058]      FIG. 8  shows an elevation view of a locking quoin block, facing the side flange. The back of the wing is visible. This locking quoin block has been manufactured with the optional top flange  117  and its holes  119  for receiving attachment means. Also shown is a ridge  111  with its wedges  115 . The side flange  113  is visible, as is the side flange&#39;s holes  519  for permitting nails, screws, and the like for securing the block to a building. The raised portion  108  and recessed portion  109  are shown. The groove  410  with its lip  405  is also shown. 
         [0059]      FIG. 9  is a plan view of a locking quoin block of the present invention. The wings  103  are set at right angles to each other along a corner axis  102 . The top edges  106  of the wings are visible. The raised portion  108  of the wing  103  is visible. The groove  410  with its lip  405  is shown. The top of the side flange  113  is also shown. Also shown is the top of the top flange  117 . 
         [0060]    While preferred embodiments of the disclosed subject matter have been described, so as to enable one skilled in the art to practice the disclosed subject matter without undue experimentation, the preceding description is intended to be exemplary. It is not intended to limit the scope of the invention as recited in the appended claims.

Summary:
This prefabricated locking quoin block is used to construct the surface of buildings. The surface of the block has decorative portions resembling brick, stone, wood, or other construction materials. Preferably the surface of each block has both a raised and a recessed decorative portion, so as to form, when assembled, a quoin corner assembly resembling sawn or quarried stone blocks. Installers can attach the assemblies to conventional building structures and install cladding materials such as vinyl siding without needing to alter the blocks other than to adjust the base block for height. The block includes wedge locks to securely connect adjacent blocks matingly to each other. Installers thereby are able to assemble a secure stack of quoin corner blocks and attach it to a building with few additional steps, saving time, labor, and cost in construction.