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This application is a continuation of U.S. application Ser. No. 11/117,638, filed Apr. 28, 2005, now U.S. Pat. No. 7,641,178 B2, which claims the benefit of provisional application Ser. No. 60/566,628, filed Apr. 29, 2004, the contents of each of which are hereby incorporated by reference herein. 
    
    
     FIELD OF INVENTION 
     A block for use in a system of interlocking modular blocks is described. In particular, blocks suitable for forming columns are described. 
     BACKGROUND OF THE INVENTION 
     Columnar structures used for decoration or as support for fence panels, gates or other such structures have required a considerable amount of skill and effort to erect. Conventional systems primarily include mortared masonry blocks. Columns or pillars also have been made from stone, but this requires skilled craftspeople to ensure proper structural completion. 
     Modular blocks have also been used to build columns or pillars. Such blocks can be installed without special skill. The advantages to such blocks are that they are a convenient size, a consistent size, and installation costs are less because of the lack of dependence on skilled labor. Blocks known in the art use construction adhesive to strengthen connection between layers and may be used with mortar to simulate the appearance of a more conventional block and mortar column. 
     An important feature of the building blocks is their appearance. The look of weathered natural stone is very appealing for columns and other similar structures. The art provides several methods to produce concrete blocks having an appearance that to varying degrees mimics the look of natural stone. According to one well-known method, blocks are individually formed in a mold and the surfaces are textured by removal of the mold. Additional machine texturing processes can then be applied. The look of smooth cut stone can also be very attractive for columns and other structures. The smooth texture provides a more straight edge, formal, geometric shape for the block and overall structural appearance. 
     A need in this art remains for blocks that can be used to construct mortarless, sturdy, reinforceable columns that have a desired appearance. 
     SUMMARY OF THE INVENTION 
     This invention is a system of blocks configured to be compatible with each other in the construction of a columnar structure. Each block has four faces that can either be textured in a manner resulting in an appearance like that of natural stone, or can be smooth to give a more formal appearance. All four faces of the block generally have the same dimensions. The faces of the block also may contain a slot to give the block a more aesthetic appearance by simulating the appearance of multiple blocks. 
     The blocks are provided with at least one interlocking element that permits a positive connection between courses of the blocks when the interlocking element is received in an overlying block. In one embodiment, the blocks interlock when there is a 90 degree rotation about a vertical axis of each block with each course. The blocks may be placed over a pipe or post-tensioning rod that is anchored into a foundation element in the ground. The core and the interlocking elements may be shaped to accommodate such a pipe and or post-tensioning rod. The blocks can be used to construct a column with a natural stone-like appearance or smooth appearance depending upon which type of block was used. Cores of stacked blocks form a passage through which vertical reinforcement can be used. This building block system is designed to be easy to install and structurally sound. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a building block according to this invention. 
         FIG. 2  is a top view of the building block of  FIG. 1 . 
         FIG. 3  is a bottom view of the building block of  FIG. 1 . 
         FIG. 4  is a side view of the building block of  FIG. 1 . 
         FIG. 5  is a perspective view of another embodiment of a building block of this invention. 
         FIG. 6  is a side view of the block of  FIG. 5 . 
         FIG. 7  is a top view of the block of  FIG. 5 . 
         FIG. 8  is a perspective view of yet another embodiment of a building block of this invention. 
         FIG. 9  is a top view of the block of  FIG. 8 . 
         FIG. 10  is a side view of the block of  FIG. 8 . 
         FIG. 11  is a perspective view of still another embodiment of a building block of this invention. 
         FIG. 12  is a top view of the block of  FIG. 11 . 
         FIG. 13  is a side view of the block of  FIG. 11 . 
         FIGS. 14 and 15  are perspective views of a column of blocks according to this invention. 
         FIG. 16  is a side view of a fence having columns of blocks according to this invention. 
         FIGS. 17A and 17B  are perspective views of two types of brackets used in conjunction with a block of this invention. 
         FIG. 18  is a perspective view of another type of bracket used in conjunction with a block of this invention. 
         FIG. 19A  is a side view of a fence system of this invention and  FIG. 19B  is a top view of the fence system of  FIG. 19A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this application, “upper” and “lower” refer to the placement of blocks as a column is constructed. The lower or bottom surface of blocks is the surface that faces the ground in a column. The first course of the column is formed by placing one block so that its lower surface is face-down. Subsequent courses are formed by stacking blocks so that an interlocking element or projection from one block fits into an indentation or void of an overlying block. “Top” and “bottom” surfaces are defined as those most conventionally used for these blocks, however, the blocks can be used with tops and bottom reversed. 
     The blocks of this invention may be made of a rugged, weather resistant material, such as concrete, especially if the columnar structure is constructed outdoors. Other suitable materials include plastic, reinforced fibers, wood, metal and stone. The surface of the blocks may be smooth or may have a roughened appearance, such as that of natural stone. The blocks typically are formed in a mold and various textures can be formed on the surface, as is known in the art. 
     Each block has four faces which can either be textured in a manner resulting in an appearance like that of natural stone, or can be smooth to give a more formal appearance. All four faces of the block may have the same dimensions. One or more faces of the block optionally may contain one or more slots that will be visible in the columnar structure to give a column of blocks a more aesthetic appearance. 
     In typical use, the interlocking element extends above the top surface of the block and projects into an indentation in an overlying block. In a preferred embodiment, the indentation is the core; that is, the core extends through the thickness of the block. In one preferred embodiment, two interlocking elements extend above the top surface of the block into the core of the overlying block, thus producing positive interconnection between facing surfaces. In a preferred embodiment, each successive block is rotated by 90 degrees about its vertical axis thus causing the interlocking elements to project into the core of the block above it. The interlocking elements hold the blocks in place and eliminate the need for mortar when constructing the column. 
     Rotation of each block about its vertical axis also varies the location of the slot, if present, resulting in a more eye-pleasing pattern for the column. Rotation of the blocks as a column is built also serves to produce a straight column. Because block molding processes may result in uneven blocks, stacking the blocks all in the same orientation may cause a column to tilt or lean. This problem is usually solved by shimming the blocks to make them level. With the block system of this invention, shimming is unnecessary. 
     The blocks can be used to form various types of columns, such as free standing, decorative columns, gate columns, or columns for use with fence panels. 
     Turning now to the drawings, the blocks of this invention are described.  FIGS. 1 to 4  show block  100 , comprising top or upper surface  112 , bottom or lower surface  113 , first and second opposed sides  114  and  116 , and third and fourth opposed sides  115  and  117 . Top surface  112  is spaced apart from opposing lower surface  113 , thereby defining a block thickness. Opposed sides  114 / 116  and  115 / 117  have substantially the same surface area. The top and bottom surfaces  112 ,  113  together with the first through fourth sides  114 ,  115 ,  116  and  117  form block body  100 . 
     The surfaces of the block meet to form edges and corners. The corners may be beveled, chamfered or rounded to give a more weathered natural stone-like appearance. 
     Block  100  has optional slot  118  on each side. The slot is a trough on the side and top surfaces, extending from the bottom surface to the core. The slot results in a desirable appearance of stacked blocks, aids in positioning the block when forming a column, and allows the top surface to receive a bracket so that the block can be attached to a fence segment, as described further below. 
     Block  100  is provided with core  120  located in the center of the block. Core  120  extends the thickness of the block and is desirable because a core results in reduced weight for the block. The core is also useful when forming a column because vertical reinforcement can be inserted through the vertically aligned cores to lend stability to the columnar structure. For example, concrete grout and rebar, steel pipe, or post-tension rods can be used to fill the core and strengthen the structure. 
     Core  120  is generally rectilinear, having walls generally parallel to the side surfaces. On opposing inside corners of core  120  are located two interlocking elements  122 . These elements extend the thickness of the block, and project above the top surface of the block. They are essentially co-planar or parallel with the bottom surface of the block, that is, the bottom surface of the block is essentially co-planar or contiguous with the bottom surfaces of these elements. 
     Although neither the interlocking elements nor the core need extend the thickness of the block, typically it is simpler to manufacture the blocks this way. In any event, the interlocking elements extend a distance above the top surface of the block. This distance is sufficient to provide adequate interlocking between blocks when a second block is stacked on a first block. 
     Block  100  has interlocking elements that are mirror images of each other on a diagonal plane of symmetry through the block. These interlocking elements are positioned to permit the alignment of blocks directly over one another when rotated 90 degrees about the vertical axis of the block. The interlocking elements also help to lock blocks into place, thus adding stability to a column of the blocks. Most preferably, the interlocking elements are shaped so that a pipe or post-tensioning rod can be installed vertically in the center of the block and through the center of the column. That is, as shown in the figures, the portion of the projection facing the center of the core is curvilinear. 
     It is to be emphasized that it is generally preferred that the blocks be used in the orientation described above, but there is nothing precluding the use of the blocks wherein the projections extend into the core of an underlying block. 
       FIGS. 5 to 7  illustrate another block  200  of this invention. Block  200  is substantially the same as block  100 , except that slots  218  are located at a midpoint on two opposing sides of the block. The slots extend from the bottom of the block to the core. 
     Block  200  comprises top or upper surface  212 , bottom or lower surface  213 , first and second opposed sides  214  and  216 , and third and fourth opposed sides  215  and  217 . Top surface  212  is spaced apart from opposing lower surface  213 , thereby defining a block thickness. Opposed sides  214  and  216  and  215  and  217  have substantially the same surface area. The top and bottom surfaces together with the first, second, third, and fourth sides form a block body. 
     Core  220  extends the thickness of the block. Core  220  is generally rectilinear, having walls generally parallel to the side surfaces. On opposing inside corners of core  220  are located two interlocking elements or projections  222 , which project above the top of the block and are parallel with the bottom of the block. The remaining descriptions of the various features of block  100  apply equally to corresponding features of block  200 . 
       FIGS. 8 to 10  show another embodiment of a block, similar to block  200 , but having recessed areas opposed to each other on the top surface of the block. The recesses accept variously-shaped brackets and permit the blocks to stack evenly, as will be described further below. 
     Block  300  comprises top or upper surface  312 , bottom or lower surface  313 , first and second opposed sides  314  and  316 , and third and fourth opposed sides  315  and  317 . Top surface  312  is spaced apart from opposing lower surface  313 , thereby defining a block thickness. Opposed sides  314  and  316  and  315  and  317  have substantially the same surface area. The top and bottom together with the first, second, third, and fourth sides form a block body. The top edges  334  and  335  of the block are beveled to produce a desired appearance. In addition, the sides meet at beveled corners  333 . 
     Slots  318  are located at a midpoint on two opposing sides of the block, and the slots open onto the top and bottom surfaces of the block. Block  300  has recessed areas  323  on the top surface of the block. Whereas in blocks  100  and  200 , the slots ( 118  and  218 , respectively) continue on the top surface of the block, in block  300 , instead of the slots, there are recessed areas  323 . Recessed areas  323  extend from the sides of the block and open onto the core. 
     Core  320  extends the thickness of the block. Core  320  is generally rectilinear, having walls generally parallel to the side surfaces. On opposing inside corners of core  320  are located two projections or interlocking elements  322 , which project above the top surface of the block. Use of block  300  in the construction of a fence will be described further below. The remaining descriptions of the various features of block  100  apply equally to corresponding features of block  300 . 
       FIGS. 11 to 13  illustrate another embodiment of the block of this invention, in which there are four recesses in the top of the block. These permit the use of a bracket during construction of a fence, as will be described later herein; the bracket can be used on any side of the block. 
     Block  400  comprises top or upper surface  412 , bottom or lower surface  413 , first and second opposed sides  414  and  416 , and third and fourth opposed sides  415  and  417 . Top surface  412  is spaced apart from opposing lower surface  413 , thereby defining a block thickness. Opposed sides  414  to  417  have substantially the same surface area. Top edges  434  and  435  of the block are beveled and the sides meet at beveled corners  433 . 
     Slots  418  are located at a midpoint on two opposing sides of the blocks and extend from bottom surface  413  to (and through) beveled edge  434 . Recessed areas  423  extend from the core toward the beveled top edges but not to the sides of the block. In this way, each side of the block has a desirable appearance for use in any orientation in a column. On the opposite side of the core from each recessed area is projection or interlocking element  422 . 
     Core  420  extends the thickness of the block. Core  420  is generally rectilinear, having walls generally parallel to the side surfaces. On opposing inside corners of core  420  are located two interlocking elements or projections  422 , which project above the top surface of the block. 
     As shown in  FIGS. 11 and 12 , region  425  on the top of the block is adjacent to both the side surface (i.e.,  414  or  416 ) and the recessed area  423 . Region  425  is useful in preventing the flow of caulk or construction adhesive to the outside of the block when used in recessed area  423 . When using a bracket with block  400 , it may be desirable to remove region  425  to reduce its height to that of recessed area  423 , thus allowing a bracket to fit across the recessed area and allowing stacked blocks to lie flat, as will be described further below. For example, when a block comprises concrete, the installer chips this portion away. 
     The blocks of this invention can be manufactured to any desired dimension; typically, the thickness is about half the width of the block. The width of the block (i.e., the distance between two opposing sides, as measured at a midpoint) typically varies from about 12 inches (30.4 cm) to about 18 inches (45.7 cm). A convenient thickness (i.e., in terms of utility and appearance) is from about 6 inches to about 8 inches (about 15.2 to 20.3 cm). Block dimensions are selected not only to produce a pleasing shape for the desired column, but also to permit ease of handling and installation. Typically, blocks of one thickness are used to construct a column. 
     The presence of the core serves not only to provide a space for interlocking elements to fit when the blocks are stacked, but it also reduces the weight of the block. It may be desirable to further reduce the weight, to make the blocks easier to handle. This can be done by adding cores in the block. For example, one or more cores can be formed near the corners of the block when the block is molded. 
       FIG. 14  shows column  500  formed of blocks  100 . A first block is set upon base  510 . This base typically comprises concrete and may range in diameter from about 18 to 24 inches (45.7 to 61 cm). The particular foundation element (e.g., the base) is determined based on the load, the soil condition, and other factors by a qualified engineer. Of course, larger diameters may be used to support greater horizontal and vertical loads. The base may be formed by using a tubular form or mold or by other methods as are known in the art. 
     Base  510  is set into the ground to at least 24 inches (61 cm) or to frost depth as determined by local building codes. The first block is set down and each subsequent block is rotated 90 degrees about its vertical axis and stacked upon a lower block. Thus, the interlocking projections on the upper surface of a block below fit into the core of a block above. The presence of slots  118  is decorative, resulting in a pleasing appearance. 
     Column  500  is shown with a vertically aligned pipe as an optional interior reinforcement. As a practical matter, the pipe is placed into the foundation element (in the ground), and then a form is built around it for base  510 . The blocks are stacked over pipe  520 . Pipe  520  is preferably made of galvanized steel and has an outer diameter of about 2.375 inches (about 6 cm). 
       FIG. 15  shows column  500  (in phantom) with a different reinforcement from that of  FIG. 14 . This reinforcement is a post-tensioning system comprising post-tensioning rod  521 , which is tightened after it is installed. There is one mating pair of connectors at the base and another pair of mating connectors at the top of the column. The first mating pair comprises ring  522  and hook  524 . Ring  522  is formed into base  511 , which typically is formed in place out of concrete. The blocks are stacked, and then a tension rod having hook  524  on the end is threaded through the block cores and hooked onto ring  522 . The second mating pair of connectors comprises compression plate  526  and washer/nut  527 / 529 . The tension rod fits through a hole in the plate. Compression plate  526  is placed onto the tension rod at the top of the block column along with nut  529  and washer  527 . Nut  529  is turned to produce a specified tension on rod  521 . 
       FIG. 16  illustrates a side view of fence  990  wherein fence posts  900  are columns comprising the blocks of this invention. Each column  900  is formed on base  910 . Preferably, there is reinforcement, such as the pipe of  FIG. 14  or the tension rod of  FIG. 15 , extending through the cores of adjacent blocks in the column to provide additional strength to the column. Cap layer  930  closes the top of each column. The columns are attached to fence panels  940 . The fence panels may comprise wood, vinyl, steel, wrought iron, aluminum, plastic, fiberglass, precast concrete, glass, plexiglass, and the like. The panels may be in the form of a picket fence or railing, or they may be solid. 
     Various ways may be used to attach fence panels to the columns, as illustrated in  FIGS. 17 and 18 .  FIG. 17A  shows a single block  300 , with pipe  520  centered in core  320  and U-shaped bracket  530  that attaches to a fence panel. U-shaped bracket  530  comprises base portion  532 , which fits over recessed area  323 , arm  534  which lies inside the core of the block, and arm  536 , to which are attached extensions  538 . Though two extensions are shown, one extension would suffice, and such a bracket. Nails or screws are used through holes  539  to attach bracket  530  to a fence panel. 
     Bracket  540  is shown in  FIG. 17B . For simplicity, no block is shown. This bracket has base portion  542  attached to arm  544 , which is attached to ring clamp  545 . The ring clamp is affixed around pipe  520  that runs through the cores of the blocks in the column. Arm  546  extends from base portion  542  and has extensions  548  with holes  549  through which nails or screws are placed to attach the bracket to a fence panel. 
       FIG. 18  shows another kind of bracket  550  that has curved segment  554  that fits around pipe  520  (shown in phantom). Straight portion  552  fits through slot  118  through the top or upper surface  112  of block  100 , shown partially in phantom, and terminates at perpendicular segment  556 , which fits into holder  945  mounted on fence panel  940 . Bracket  550  is thus sandwiched between courses of blocks. This bracket also could be used with block  300 , fitting anywhere in the recessed region  323 , and could be used with block  400  if a portion of the region  425  were removed. However, the advantage to this bracket  550  is that it fits within a slot on top surface of the block (such as slot  118  in the top surface  112  of block  100  or slot  218  in the top surface  212  of block  200 ). No additional recessed area is needed to stack blocks evenly in the presence of a bracket. The bracket preferably is made of galvanized steel and has a length sufficient to span the distance from a pipe at the center of the block to a fence panel. 
       FIG. 19A  illustrates a side view of a portion of fence  992  wherein columns  900  comprise blocks  300  and form fence posts for the fence. Each column  900  is formed on base  910  (shown in phantom). Pipe  520  (also shown in phantom) extends through the cores of adjacent blocks in each column and is embedded in base  910 . Brackets  530  join fence segments  942  to the columns. Each column is capped with capping block  930 .  FIG. 19B  illustrates a top view of the fence, showing placement of the block without the cap layer in place. This view illustrates how the fence segments are positioned relative to the columns. 
     Blocks of this invention also may be used with other blocks having interlocking elements, such as those described in commonly assigned, co-pending U.S. application Ser. No. 11/117,640, filed on Apr. 28, 2005, herewith entitled “Columnar Block Fence System,” which claims the benefit of commonly assigned, co-pending U.S. Provisional application Ser. No. 60/566,590, filed Apr. 29, 2004 entitled “Columnar Block Fence System,” both of which applications are hereby incorporated herein by reference. 
     Although particular embodiments have been disclosed herein in detail, this has been done for purposes of illustration only, and is not intended to be limiting with respect to the scope of the claims. In particular, it is contemplated that various substitutions, alterations and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims. For instance, the choice of materials or variations in the shape or angles at which some of the surfaces intersect are believed to be a matter of routine for a person of ordinary skill in the art with knowledge of the embodiments disclosed herein.

Summary:
A system of blocks is configured to be compatible with each other in the construction of a columnar structure. Each block has four faces and all four faces may generally have the same dimensions. The width of the blocks may generally be about twice their height. The faces of the block also may contain a slot to add an aesthetic appearance to the column. The blocks have certain constructions features that mate with specially constructed brackets in attaching a fence panel to the completed column. 
     The blocks have interlocking elements or projections that permit positive connection between courses of blocks. Projections of one block extend into the core another block. Adjacent blocks can be rotated 90 degrees relative to each other about a vertical axis of each block with each course. The blocks can be used to construct a column that is easy to install and structurally sound.