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RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 60/090,438, filed on Jun. 24, 1998, and U.S. Provisional Application No. 60/099,144, filed on Sep. 4, 1998, the entire teachings of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Conventional concrete blocks have the advantages in construction of low material cost, durability, strength and simplicity. However, assembly into a useful wall requires considerable time, skill and almost continuous use of mortar. Workers must set each block on top of a bed of mortar, and then tap the block until the block is plumb, flush with the wall and at the correct height. Thus, block stacking is time-consuming and requires considerable training. Moreover, rain or subfreezing weather conditions can prevent proper curing of the mortar. Measures can be taken to allow construction in such weather conditions but can be economically unfeasible. As a result, work is usually suspended during adverse weather conditions. 
     Various attempts have been made to produce mortarless or dry-stack blocks where blocks are stacked to form walls with no intervening mortar in order to avoid the problems associated with the use of mortar. A problem with mortarless blocks is that conventional block making equipment cannot consistently manufacture blocks with height tolerances of less than {fraction (1/16)} inch. In a block wall having a running bond pattern (each block resting on two blocks below), such height variations are too large for building stable mortarless walls. Typically, in conventional block walls, the mortar compensates for the height variations in the blocks. Most current mortarless blocks have designs which compensate for height variations but are either uneconomical to manufacture or require too much skill and time to assemble, thereby defeating the advantages of mortarless blocks. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a block system that does not require mortar and is economical to manufacture and assemble. The block system includes first and second blocks each having an outer surface with a first pair of locking channels formed within the outer surface. The locking channels are spaced apart from each other. Each locking channel has a narrower outer slot portion extending through the outer surface and a wider inner slot portion extending from the outer slot portion into its respective block. A first pair of locking members are provided for coupling the blocks together by insertion into the locking channels of the blocks with the locking channels of the first block being positioned to join with the locking channels of the second block. The locking members have a cross-section with wider outer edges dimensioned to fit in the inner slot portions and a narrower mid-section dimensioned to fit in the outer slot portions. 
     In preferred embodiments, the blocks are made of concrete and are rectangular with corners. Each locking channel is positioned close to a corner. The locking members have a continuous outer surface and are preferably solid with tapered ends. Each block further includes a second pair of locking channels. In one embodiment, the first and second pairs of locking channels are on opposite sides of the blocks. Each pair of locking channels are positioned on a web. The web is adjacent to a cavity extending through the block and is thicker near the locking channels. In another embodiment, the first and second pairs of locking channels are at right angles to each other. In addition, in another embodiment, a pair of locking passages extend through each block and are capable of engaging the locking members, thereby enabling the first and second blocks to be stacked in an offset manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
     FIG. 1 is a perspective view of a preferred block of the present invention. 
     FIG. 2A is a perspective view of the locking member or fastener for securing the blocks together. 
     FIG. 2B is a top view of the fastener of FIG.  2 A. 
     FIG. 2C is a side view of the fastener of FIG.  2 A. 
     FIG. 3 is a perspective view of a partially assembled wall. 
     FIG. 4 is a perspective view of a preferred corner block. 
     FIG. 5 is a perspective view of a preferred half block. 
     FIG. 6A is a perspective view of another preferred fastener with the ends cut diagonally side-to-side. 
     FIG. 6B is a perspective view of still another preferred fastener with the ends tapered toward the center. 
     FIG. 6C is a perspective view of a preferred hollow fastener. 
     FIG. 6D is a perspective view of another preferred fastener having a ribbed vertical surface. 
     FIG. 6E is a perspective view of a preferred short fastener with a raised area around the exterior surface half way up the length of the fastener. 
     FIG. 7A is a top view of a preferred block with notched edges along the top surface. 
     FIG. 7B is a side view of the block of FIG.  7 A. 
     FIG. 8 is a perspective view of a preferred block with vertical locking holes extending through the center web. 
     FIG. 9 is a perspective view of a partially assembled wall constructed of the blocks of FIG.  8 . 
     FIG. 10 is a perspective view of a preferred block with slots that widen as they approach the top of the block. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, block  100  is a molded concrete block consisting of two parallel concrete face shells  1  and two parallel end webs  2 , which are perpendicular to face shells  1 . Two cavities or cells  5  extend vertically through block  100  and are separated from each other by a center web  3  that is parallel to end webs  2 . The face shells  1  and webs  2 / 3  surround cells  5 . Each end web  2  has two locking channels or slots  6  running vertically up the outside face, each a short distance from the edges of web  2 . In horizontal cross section, each slot  6  is wider some distance behind the outside surface of the web  2  than it is at the surface of the web  2 . The web  2  is thicker in the areas  7  surrounding a slot  6  to maintain the strength in that area. In preferred embodiments, the height of the face shells  1  and the webs  2  (referred to as the “height of the block”) is about 8 inches, and the length of the face shells  1  (“length of the block”) is 16 inches. This contrasts with a conventional mortared block, where the corresponding dimensions are 7⅝ and 15⅝ inches, respectively. 
     Referring to FIGS. 2A,  2 B and  2 C, fastener or locking member  102  is employed for locking blocks  100  together. Fastener  102  is preferably a solid plastic elongate member with a cross-section consisting of two rounded sections  8  and  9  connected by a thinner mid-section  10 . The resulting cross-section approximates a figure eight. The top and bottom surfaces  11  are angled from the outside edge of one rounded section  8  to the outside edge of the other rounded section  9 . Surfaces  11  are angled to be parallel to one another. The angled surfaces  11  allow for easier insertion of fasteners  102  into slots  6  and also serve to lock vertically adjacent fasteners  102  together. The length of fasteners  102  is about the same as the height of block  100 . Although fastener  102  is preferably plastic, fastener  102  can also be made of steel. 
     Referring to FIG. 3, the preferred pattern for stacking blocks  100  into a wall includes placing the blocks  100  in adjacent abutting vertical courses such as ( 15 ,  16 ,  17 ) and ( 13 ,  14 ). A series of fasteners  102  are inserted end to end within mating slots  6  so that in central areas of the wall, each fastener  102  simultaneously engages the slots  6  of both horizontally and vertically adjacent blocks  100 , for example, blocks  16 ,  17  and  14 . Fastener  102  is shaped so that it fits precisely into the space defined between two slots  6  of abutting blocks  100  placed end to end to lock the blocks  100  together. Since the slots  6  are wider at points away from the surface of the ends of the blocks  100  than they are at the surface, the fasteners  102  can only be pulled out of the slots  6  horizontally with a pulling force sufficient to break the block  100  or deform the fastener  6 . Each fastener  102  is inserted within slots  6  in a manner where approximately half of its height is situated in the slots  6  of two vertically adjacent blocks  100  such as in blocks  13  and  14 . To make this possible, the bottom fasteners  102  within the bottom blocks  100  are cut to half their length. 
     Thus, during construction, the workers set the first course of blocks  100  and then insert fasteners  102   a  that are cut to half of their length into slots  6 . A second set of fasteners  102  are then inserted into slot  6  so that the final set of fasteners  102  protrude upward from the tops of the blocks  100  by approximately half their length (about 4 inches). The second course of blocks  100  can then be set with the slots  6  engaging the protruding fasteners  102 . The process of inserting fasteners  102  and setting blocks continues until the wall is completed. As can be seen, each fastener  102  overlaps the joints between vertically adjacent blocks  100 . In addition, the slots  6  of horizontally adjacent blocks  100  are locked in face-to-face relation by fasteners  102 , with about half the cross-section of fastener  102  being in the slot  6  of each block  100 . Although fasteners  102  are preferably about the height of block  100 , alternatively, it is possible to use special fasteners  102  which are about 1½ times the normal length (about 12 inches). 
     Vertical stacking of blocks  100  avoids the height variation problem between blocks  100  encountered in a running bond pattern. The use of paired fasteners  102  between adjacent blocks  100  enforces straight alignment of the wall between horizontally adjacent blocks  100 . The placement of the slots  6  near the edges of blocks  100  allows the center of the webs to be reduced in height if desired to accommodate reinforcement or insulation. 
     Referring to FIG. 4, corner block  104  is a preferred block for use at the corners of walls and includes slots  6  on only one end web  2 . Two slots  6  are positioned on a face shell  1  at a right angle to the slots  6  on web  2  and are dimensioned the same as the slots  6  on the end web  2 . This allows two blocks  100  to be connected to web  2  and face shell  1  of corner block  104  at right angles to each other. 
     Referring to FIG. 5, half block  106  is a preferred half block which differs from block  100  in that half block  106  is 8 inches long instead of 16 inches. In addition, half block  106  has only one cell  5  and no center web  3 . Half block  106  allows the length of walls to be built to the closest 8 inches instead of the closest 16 inches. 
     Referring to FIG. 6A, fastener  108  is another preferred fastener and has ends  11  that are sloped at an angle from the extreme points  21  on one side of the surface of the end  11  to the extreme points  22  on the other side. Fastener  108  is cut at an angle at each end that is perpendicular to that shown for fastener  102 . Thus the highest point of the fastener  108  at an end would occur to the extreme left (or right) of the figure eight, and the lowest point would occur at the extreme right (or left). 
     Referring to FIG. 6B, fastener  110  is another preferred fastener which has ends  23  tapered to points  24 , with one point  24  at the end of each rounded section  8  and  9 . As a result, each end of fastener  110  has a pair of points. 
     Referring to FIG. 6C, fastener  112  is another preferred fastener with a hollow  25  having a constant horizontal cross section and the wall of material  26  around the hollow  25  being of approximately constant thickness. The hollow  25  increases the flexibility of fastener  112  for insertion purposes. 
     Referring to FIG. 6D, fastener  114  is another preferred fastener and has a modified horizontal cross section such that the entire vertical surface consists of a series of vertical ribs  27  which can make fastener  114  slide into slots  6  more easily. 
     Referring to FIG. 6E, fastener  116  is another preferred fastener which is shorter than the height of block  100 . Fastener  116  includes a raised portion  28  around the outside of the fastener  116  approximately equidistant from either end  11 , at which the horizontal cross section of the fastener is somewhat greater in all directions. Preferably fastener  116  is shorter than eight inches long and it is slightly wider halfway up its height, for example from a raised band running around the outside. The reduced height makes the connection of fastener  116  and block  100  easier. The raised surface holds the fastener  116  securely so that half of its length can protrude downward into the block  100  below and the other half can protrude upward into the block  100  above. 
     Referring to FIGS. 7A and 7B, block  118  is another preferred block which differs from block  100  in that block  118  includes a notch  29  along the interior and exterior of the top surface of the block  118 . The resulting depressed edging around the perimeters of the top surface of the block reduces the probability of imperfections along the edges that might make the top surface uneven and therefore make a stacked wall less stable. In addition, the depressions surrounding each slot  6  provides space for a raised surface around the shaft of a fastener  116 . 
     Referring to FIGS. 8 and 9, block  120  is another preferred block which differs from block  100  in that block  120  contains vertical locking holes  33  extending through the center web  3  with a constant cross section similar to fastener  102  for engaging fastener  102 . Vertical holes  33  are midway between slots  6  in webs  2  and have the same spacing between holes  33  and slots  6 . The center web  3  is also thicker in the areas  34  to either side of the holes  33 . 
     Locking holes  33  in the center web  3  allow the block  120  to be stacked in a running bond. Each hole  33  aligns with a pair of abutting slots  6  in the two blocks  120  below, and in two blocks  120  above. Fasteners  102  span the pair of slots  6  below (or above) and a hole  33  in a center web  3  above (or below). In the preferred pattern, the blocks comprising one course, such as  35 ,  36 , and  37  are offset horizontally from the blocks, such as  38 ,  39 , and  40 , comprising the course below or above by the length of one-half block. The fasteners, therefore protrude halfway down (or up) into the cavity formed by the adjacent slots of two abutting blocks, such as  35  and  36 , on the same course, and protrude halfway up (or down) into the hole  33  of the block, such as  38 , on the course above (or below) that spans the other two blocks on the adjacent course. 
     Referring to FIG. 10, block  122  is another preferred block which differs from block  100  in that block  122  includes slots  6  with cross sections that become gradually wider near the top of the block, creating approximately funnel-shaped portions  37  of the slots  6 . The funnel  37  in the top of the slot  6  makes it easier to insert fasteners into the slots  6  or, if the block  122  were turned upside down, set the block  122  over protruding fasteners below. 
     Although specific dimensions have been given for blocks  100 ,  104 ,  106 ,  118 ,  120  and  122 , as well as fasteners  102 ,  108 ,  110 ,  112 ,  114  and  116 , those dimensions can be varied accordingly to accommodate different applications. Although the material for the blocks is preferably concrete, the materials for all parts can be made from any suitable materials such as any plastic, metal, plastic composite, or concrete with unconventional aggregates. 
     EQUIVALENTS 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
     For example, the cross sections of the slots and fasteners can be any of various shapes so long as the fasteners have greater dimensions off their cross sectional center, and the slots have shapes that mate on at least some surfaces with the fasteners. Analogous slots may be applied to almost any of the common variations on the conventional concrete block (beyond the corner block and half block already described) to use for special situations in stacking a mortarless wall joined by the fasteners, including, but not limited to, a half-high block, a bond beam block, an end block, a jamb block, a sash block, a splittable block, blocks of different thicknesses, a reduced-web insulated block, and almost any variety of architectural block.

Summary:
The present invention is directed to a block system including first and second blocks. Each block has an outer surface with a pair of locking channels formed within the outer surface. The locking channels are spaced apart from each other. Each locking channel has a narrower outer slot portion extending through the outer surface and a wider inner slot portion extending from the outer slot portion into its respective block. A first pair of locking members are provided for coupling the blocks together by insertion into the locking channels of the blocks with the locking channels of the first block being positioned to join with the locking channels of the second block. The locking members have a cross-section with wider outer edges dimensioned to fit in the inner slot portions and a narrower mid-section dimensioned to fit in the outer slot portions.