Abstract:
A method of making a wall block and a mold box therefore. The wall block design maximizes the use of the mold box. The method produces wall blocks having a large surface area front face compared to the front face size of prior art blocks. The blocks have about one third more front surface area. This results in faster construction of walls and a faster construction sequence. The method of making the blocks makes efficient use of mold space and material, resulting in higher production yields and/or higher total daily production square footage.

Description:
[0001]    This application is a divisional of pending prior application Ser. No. 10/754,454, filed Jan. 9, 2004, which is a continuation-in-part of Application Ser. No. 29/186,712, filed Jul. 21, 2003, now U.S. Pat. No. D501,935 S, issued Feb. 15, 2005, the contents of each of which are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to retaining wall blocks and a method for making these blocks. 
       BACKGROUND OF THE INVENTION 
       [0003]    Numerous methods and materials exist for the construction of retaining walls. Such methods include the use of natural stone, poured in place concrete, masonry, and landscape timbers or railroad ties. In recent years, segmental concrete retaining wall units which are dry stacked (i.e., built without the use of mortar) have become a widely accepted product for the construction of retaining walls. Such products have gained popularity because they are mass produced, and thus relatively inexpensive. They are structurally sound, easy and relatively inexpensive to install, and couple the durability of concrete with the attractiveness of various architectural finishes. 
         [0004]    It is desirable to build a wall from such blocks quickly and without the need for special skilled labor. The efficiency of building a wall can be measured by determining how fast the front face of a wall is constructed. Clearly, this depends on the size of the blocks used and ease of stacking the blocks. 
         [0005]    It is standard practice in the prior art to use similarly sized mold boxes to produce various styles of block. For example, a standard size box has a block molding area of about 18 inches by about 24 inches (about 45.7 cm by about 61 cm), and produces a block about 8 inches (20.3 cm) thick.  FIG. 1A  illustrates retaining wall block B 1  in mold box M. This block is symmetrical about a centrally located vertical plane of symmetry. Block B 1  has pin holes PH, pin receiving cavities PC, and two cores C 1  and C 2 . The sides generally converge from the front to the back of the block. Front face F is produced by the removal of waste portion W after the block has formed. This portion is split off to form a roughened surface. The block of  FIG. 1A  is manufactured one block at a time so that the yield per cycle is one square foot (1 sq ft or 929 sq cm) of front face. A typical weight for this block is about 110 lbs (50 kg). 
         [0006]    Other prior art blocks are shown in  FIGS. 1B and 1C  in mold box M. This block is similar to that described in WO 02/101157 (MacDonald et al.). This block also has similarities to block B 1 , as it is symmetrical about a centrally located vertical plane of symmetry. Block B 2  has pin holes PH, pin receiving cavities PC, and core C. Preferably, the blocks are formed so that front face F will have a roughened appearance. Block B 2  is made in a mold box two at one time. This provides a good use of mold space, producing about two square feet (1858 sq cm) of front face per manufacturing cycle.  FIG. 1B  illustrates that the blocks can be formed two at a time and separated at the back faces. In this case, the front surface of the block is textured by texturing elements T that contact the front surface as the block is removed from the mold box.  FIG. 1C  shows blocks that are molded together at front face F. The front faces of these blocks will be separated, or split apart after curing. The splitting of such blocks is used to form the desirable surface appearance. When manufactured in this manner, each block has a front face of about one square foot (1 sq ft or 929 sq cm). Thus, the yield per cycle is two square feet of front face. A typical weight for this block is about 85 lbs (38.6 kg). 
         [0007]    A third type of prior art block in its mold box M is shown in  FIG. 1D . Block B 3  is a rectangular block, shown having two cores or cavities C. The long dimension of the block typically is used to form the face of a wall. Thus, this type of block produces a useful front surface about 24 inches long, rather than the 18 inch long surface of blocks B 1  and B 2 . The surface area (for the same thickness block, i.e., about 8 inches) is about 33% greater than the surface area of blocks B 1  or B 2 . However, this block weighs about 250 lbs (113.6 kg) and must be set in place using mechanized means. 
         [0008]    Accordingly, a need in the art remains for wall blocks that make the most use of a mold box&#39;s area while producing a block with a large front surface area. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is a mold box and a method of making a wall block that maximizes the use of the mold box and produces wall blocks having a large surface area front face that are lightweight and easy to handle when constructing a wall. This results in faster construction of walls and a faster construction sequence, because for each block, the front face surface area is larger than blocks known in the art. The method of making the blocks makes efficient use of mold space and material, resulting in higher production yields and/or higher total daily production square footage. 
         [0010]    In one aspect, this invention is a mold box for making first and second wall blocks comprising first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; and a divider plate having a first end connected to the first end rail and a second end connected to the second end rail, the divider plate dividing the mold cavity into a first mold section for forming the first block and a second mold section for forming the second block. 
         [0011]    In another aspect, this invention is a mold box for making first and second wall blocks comprising first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; and a divider plate having a first end connected to the first end rail and a second end connected to the second end rail, the divider plate dividing the mold cavity into a first mold section for forming the first block and a second mold section for forming the second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail. 
         [0012]    In another aspect, this invention is a mold box for making first and second wall blocks comprising first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; and a divider plate having a first end connected to the first end rail and a second end connected to the second end rail, the divider plate dividing the mold cavity into a first mold section for forming the first block and a second mold section for forming the second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail, the divider plate being shaped in a non-planar configuration such that a maximum first block depth measured between the first side rail and the divider plate along a line generally perpendicular to the first side rail is greater than d 2 /2 and a maximum second block depth measured between the second side rail and the divider plate along a line generally perpendicular to the second side rail is greater than d 2 /2. 
         [0013]    In another aspect, this invention is a method of making wall blocks comprising providing a mold box having first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; dividing the mold cavity into a first mold section for forming a first block and a second mold section for forming a second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail; filling the first and second mold sections with a desired block material; and removing the block material from the first mold section to form the first block and from the second mold section to form the second block, the first block having a maximum depth measured between the front face and a rear face along a line generally perpendicular to the front face which is greater than d 2 /2 and the second block having a maximum depth measured between the front face and a rear face along a line generally perpendicular to the front face which is greater than d 2 /2. 
         [0014]    In another aspect, this invention is a method of making wall blocks comprising providing a mold box having first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; dividing the mold cavity into a first mold section for forming a first block and a second mold section for forming a second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail; filling the first and second mold sections with a desired block material; and removing the block material from the first mold section to form the first block and from the second mold section to form the second block, the front faces of the first and second blocks each having a length approximately equal to d 1 . 
         [0015]    In another aspect, this invention is a method of making wall blocks comprising providing a mold box having first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; connecting a divider plate between the first and second end rails to divide the mold cavity into a first mold section for forming a first block and a second mold section for forming a second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail; filling the first and second mold sections with a desired block material; and removing the block material from the first mold section to form the first block and from the second mold section to form the second block. 
         [0016]    In another aspect, this invention is a method of making wall blocks comprising providing a mold box having first and second opposed end rails and first and second opposed side rails, the end rails and side rails together forming a mold cavity, the first and second end rails being spaced apart a distance d 1 , the first and second side rails being spaced apart a distance d 2  which is less than distance d 1 ; connecting a divider plate between the first and second end rails to divide the mold cavity into a first mold section for forming a first block and a second mold section for forming a second block, the first mold section being configured such that a front face of the first block is formed adjacent the first side rail, the second mold section being configured such that a front face of the second block is formed adjacent the second side rail, the divider plate being non-planar and having a first mold surface and a second mold surface, a rear face of the first block being formed adjacent the first mold surface and a rear face of the second block being formed adjacent the second mold surface, the divider plate being configured such that the rear faces of the first and second blocks overlap when they are formed in the mold cavity; filling the first and second mold sections with a desired block material; and removing the block material from the first mold section to form the first block and from the second mold section to form the second block. 
         [0017]    In another aspect, this invention is a wall block comprising a front portion including opposed top and bottom surfaces, opposed side surfaces and a front surface, the front surface having a length equal to the distance between the side surfaces and a height equal to the distance between the top and bottom surfaces. The at least one leg extends from the front portion in a direction opposite the front surface and has a rear surface, a distance between the front surface and rear surface comprising a maximum block depth. The at least one leg is positioned such that when a plurality of the blocks including first and second blocks are packaged for shipment the first and second blocks can be positioned on a common surface with their front surfaces oriented in opposite directions with the at least one leg of the first block overlapping the at least one leg of the second block so that the first and second blocks occupy an area on the common surface which is less than the length of the front surface times twice the block depth. 
         [0018]    In another aspect, the invention is a wall block comprising a front portion including opposed top and bottom surfaces, opposed side surfaces and a front surface, the front surface having a length equal to the distance between the side surfaces and a height equal to the distance between the top and bottom surfaces. The at least one leg extends from the front portion in a direction opposite the front surface and has a rear surface, the at least one leg being positioned such that when a wall is formed from multiple courses of the blocks which are offset from course to course by about one half the length of the front surface the legs in each course of blocks align vertically. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1A  is plan view of the mold box configuration for a first Prior Art block.  FIG. 1B  is a plan view of a first mold box configuration for a second Prior Art block.  FIG. 1C  is a plan view of a second mold box configuration for a second Prior Art block.  FIG. 1D  is a plan view of a mold box configuration for a third Prior Art block. 
           [0020]      FIG. 2  is a plan view of the configuration of the block of this invention in a mold box. 
           [0021]      FIG. 3  is a perspective view of the block of this invention. 
           [0022]      FIG. 4A  is a top view and  FIG. 4B  is a bottom view of the block of  FIG. 2 . 
           [0023]      FIGS. 5A and 5B  are side views of the block of  FIG. 2 . 
           [0024]      FIG. 6  is a back view of the block of  FIG. 2 . 
           [0025]      FIG. 7  is a perspective view showing stacked blocks of  FIG. 2 . 
           [0026]      FIG. 8A  is a perspective view and  FIG. 8B  is a top view of another block of this invention. 
           [0027]      FIG. 9  is a perspective view of another block of this invention. 
           [0028]      FIG. 10  is a top view of the block of  FIG. 9 . 
           [0029]      FIG. 11  is a perspective view of another block of this invention. 
           [0030]      FIG. 12  is a top view of a mating pair of the blocks of  FIG. 11 . 
           [0031]      FIGS. 13A and 13B  are partial top views of a row of blocks comprising the blocks of  FIGS. 9 and 11 . 
           [0032]      FIG. 14  is a partial view of a wall of blocks constructed with the blocks of  FIGS. 9 and 11 . 
           [0033]      FIG. 15A  is a bottom perspective view of another block of this invention. 
           [0034]      FIG. 15B  a top perspective view of stacked blocks of  FIG. 15A . 
           [0035]      FIG. 16  is a side view of the block of  FIG. 15A . 
           [0036]      FIG. 17  is a top view of another block of this invention. 
           [0037]      FIG. 18  is a top view of two other blocks of this invention. 
           [0038]      FIGS. 19A and 19B  are partial cross sectional views of a block showing pin placement in a pin hole. 
           [0039]      FIGS. 20A and 20B  are cross sectional views of walls constructed from the blocks of this invention. 
           [0040]      FIG. 21  is a perspective view of a mold box used to form the blocks of this invention. 
           [0041]      FIG. 22A  is a plan view of the mold box of  FIG. 21  showing the divider plate and  FIG. 22B  is a plan view of the divider plate with the mold box and the blocks in phantom. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0042]    In this application, “upper” and “lower” refer to the placement of the block in a retaining wall. The lower surface faces down, that is, it is placed such that it faces the ground. In forming a retaining wall, one row of blocks is laid down, forming a course. A second course is laid on top of this by positioning the lower surface of one block on the upper surface of another block. 
         [0043]    The blocks of this invention may be made of a rugged, weather resistant material, such as concrete, especially if the wall is constructed outdoors. Other suitable materials include plastic, reinforced fibers, and any other materials suitable for use in molding wall blocks. The surface of the blocks may be smooth or may have a roughened appearance, such as that of natural stone. The blocks are formed in a mold and various textures can be formed on the surface, as is known in the art. 
         [0044]    Several embodiments are illustrated in the figures below. In one embodiment, this invention is a block comprising a front portion having two legs extending therefrom. The two legs each have a core and a back portion and the back face of each back portion is the back of the block. The cores are optional and their positions can be varied. The legs are located asymmetrically on the block. The legs have sides that define the area of the core and the leg side walls generally converge from the front toward the back. 
         [0045]    In another embodiment, this invention is a block similar to the block described above, except that one of the legs joins the front portion at right angles. This block is suitable for forming a corner structure. 
         [0046]    In another embodiment, this invention is a block having one leg extending from the front face where the leg is located at one side of the front face. 
         [0047]    In another embodiment, this invention is a block having multiple curvilinear legs, all legs extending away from the front surface. 
         [0048]    The blocks of this invention may be provided with a connection means for connecting blocks in adjacent courses. The connection means may comprise pin holes and pin receiving cavities. The cavities in a second or top block accept the head of a pin placed in a pin hole of a first or bottom block. Alternatively, the bottom surface of this block may be provided with a channel configured to accept the head of a pin placed in a pin hole in an underlying block. The appearance of the front face of the block may be varied as desired. 
         [0049]    The advantage to the design of blocks described herein is that the blocks provide good structural stability with a maximum amount of block front face and a minimum use of material. Not only are the blocks easy to handle, but the manufacture of the blocks is efficient in its use of space and material, which can be seen, for example, by the illustration of  FIGS. 22A and 22B , discussed further below. The blocks are made by forming matching pairs of blocks in a single mold designed so that one or more legs on a first block interweave or overlap with one or more legs on a second block. In this way the blocks nest together. The length of the front face of the block is generally about twice the distance from the front of the block to the back face of a leg. This has been found to maximize the volume of mold space used. Molding the blocks in this manner is also an advantage when it comes to shipping the blocks since the blocks are removed from the mold, pallatized and shipped in the same overlapping or nested configuration. This overlapping configuration takes up less space and is easier to handle than blocks molded in a conventional manner. The depth of the block (i.e., the distance from front to back surfaces) is greater than half the mold box depth. It should be understood, however, that other lengths or dimensional relationships of the blocks can be used within the scope of the invention. 
         [0050]    This block design maximizes the area of the front face of the block while minimizing the weight of the block. As a result, the block manufacturer is able to produce more wall area per manufacturing or mold cycle and gain greater yield of wall blocks per a given volume of raw materials while at the same time manufacturing the blocks in a configuration which saves space and is easy to handle and to ship. The wall installer is able to install more face area of wall each time a block is placed and the blocks generally weigh no more or just slightly more than prior art blocks having a smaller front surface area. 
         [0051]    It is useful to compare the block of the present invention to prior art blocks, such as those illustrated in  FIGS. 1A to 1D  above.  FIG. 2  shows the present inventive blocks  100  in a mold box. This figure can be compared directly with  FIGS. 1A to 1D . The mold box illustrated is a standard size for the industry, about 18 by 24 inches, and produces a block about 8 inches thick. Blocks  100  each weigh about 95 lbs (43.2 kg). The front surface (F) of the block is the dimension of the long dimension of the mold box, i.e., about 24 inches. Thus this block has a larger surface area (24 by 8 inches, 192 sq in, or 1.33 sq ft) than the surface area (18 by 8 inches, 144 sq in, or 1 sq ft) of the prior art blocks shown in  FIGS. 1A to 1C . This equals a 33% increase in front surface area. Yet the weight increases only about 11%, to 95 lbs from 85 lbs (43.2 to 38.6 kg), still a handleable weight. 
         [0052]    In addition, an even greater manufacturing advantage is realized because the inventive blocks are made two at a time. Thus, one production cycle produces 2.66 sq ft (2470 sq cm) of front surface area per manufacturing cycle. This compares to the production of one sq ft for Prior Art block B 1 , two sq ft for Prior Art block B 2 , and 1.33 sq ft. for Prior Art block B 3 . In addition, in all cases for the present block, the capacity of the mold box is maximized or at least increased substantially. 
         [0053]    Various embodiments of the blocks of this invention are shown in the drawings. 
         [0054]      FIGS. 3 to 7  illustrate block  100 .  FIGS. 8A and 8B  illustrate block  100   a , which is substantially similar to block  100  except that block  100   a  has rounded corners and fewer pin holes. Similar features of these blocks will be referred to by the same numbers. Block  100  has parallel top face  102  and bottom face  103 . Front face  104  has optional bevel or chamfer  108  adjacent the top and sides of the block to provide a desirable appearance. The length of face  104  is defined by the distance between corners  106  and  107 . Extending from front portion  110  are two legs  120  and  130 . Cores  121  and  131  are located primarily in the legs, though they extend into front portion  110 . It should be noted that the shape of the cores as shown in the figures is a convenient shape for manufacturing, however, any suitable shape can be used. Legs  120  and  130  extend to rear portions  124  and  134 , respectively, having rear faces  125  and  135 , respectively. 
         [0055]    Front face  104  and rear faces  125  and  135  each extend from top face  102  to bottom face  103 , as shown in  FIG. 6 . The distance between faces  102  and  103  defines the thickness of the block. 
         [0056]    Legs  120  and  130  are separated by void  140 . Each leg  120  and  130  has two side walls  122 ,  123  and  132 ,  133 , respectively. These side walls generally converge from the front to the back of the block. The side walls extend from top face  102  to bottom face  103 . In a preferred embodiment, legs  120  and  130  are positioned such that, when stacking blocks one on top of another in a wall, a leg of one block is placed over a leg in an underlying block and a running bond pattern is created. The alignment of legs is desirable because it adds to the structural stability of a wall, and also permits the introduction of vertical reinforcement or filler materials that would extend through the cores and voids of adjacent legs. 
         [0057]    Side  111  of block  100  is shown in  FIG. 5A  and side  113  is shown in  FIG. 5B . Side  111  comprises the side surfaces of leg side wall  122  and back portion  124 , and the side of front portion  110 . Side  113 , as shown in  FIG. 5B , comprises the side surfaces of leg side wall  133  and back portion  134 , and the side of front portion  110 . 
         [0058]    Front portion  110  ( FIG. 3 ) includes front face  104  and also includes pin holes  112 ,  114 ,  115 , and  116  and pin receiving cavities  117  and  118  ( FIG. 4A ). 
         [0059]    It should be noted that the shape of the cores as shown in  FIGS. 3 to 8  is a convenient shape for manufacturing, however, any suitable shape can be used. The cores serve to reduce the weight of the block. When a block is manufactured, a core is tapered from top to bottom to ease stripping the block from the mold, as known to one of skill in the art. Cores are optional but may be desirable since they reduce the amount of material required to make the block, and they allow more blocks to be shipped since weight is usually a constraint on how many blocks may be shipped at one time. In addition, a lower weight block is easier for those who handle the block when constructing a wall. Further, the size and shape of the legs and voids can be varied. 
         [0060]    Pin receiving cavities  117  and  118  are positioned at any desired location along the front portion of the block and may have any desired shape. The placement of cavities in conjunction with pin holes  115  and  116  can be used to form a running-bond pattern in a wall of blocks. The pin receiving cavities may extend from the top to the bottom of the block, which aids in minimizing block weight, or may only partially extend toward the bottom of the block. However, they also could be depressions in the block rather than passageways. 
         [0061]    Pin holes  112 ,  114 ,  115  and  116  extend from the top face  102  to bottom face  103 . Four pin holes are shown, but more or fewer pin holes may be used. The holes are tapered to ease the removal of forming elements from the molded block. These pin holes are sized to receive a connecting element, such as a pin. 
         [0062]    The pin may be a shouldered pin, in which case the pin hole may be substantially the same diameter for the thickness of the block, or the pin holes may be truncated to allow a portion of a headless pin to sit above the surface of the block. Various pins are described further below. 
         [0063]    Block  100  is shown stacked in a running bond pattern in  FIG. 7 . These blocks are configured so that the back portion of a block above rests on at least a part of the back portion of the block below. Optimally, a leg of one block is placed on the leg of an underlying block. This adds stability to a wall formed from these blocks and increases the frictional connection of the blocks. 
         [0064]    Block  100   a  in  FIGS. 8A and 8B  is similar to block  100 , having curvilinear back portions  124   a  and  134   a  that extend from legs  120  and  130 . Curvilinear shapes frequently are more desirable due to the ease of removal of the block from a mold. 
         [0065]      FIGS. 9 and 10  illustrate another embodiment of the block. Block  200  is similar to blocks  100  and  100   a  of  FIGS. 3 to 8 , except that there are no chamfers on the front of the block. The absence of chamfered edges and corners is that the top and the bottom of the block are interchangeable, that is, if block  200  is flipped over, it is a mirror image of another block  200 . By contrast, the minor image of block  100  would have to be manufactured separately if it is desired to use the block in more than one orientation when constructing a retaining wall. 
         [0066]      FIGS. 9 and 10  show block  200  having parallel top face  202  and bottom face  203 . The length of face  204  is defined by the distance between corners  206  and  207 . Extending from front portion  210  are two legs  220  and  230 . Cores  221  and  231  are located primarily in the legs, though they extend into front portion  210 . Legs  220  and  230  extend to rear portions  224  and  234 , respectively, having rear faces  225  and  235 , respectively. Front face  204  and rear faces  225  and  235  each extend from top face  202  to bottom face  203 . The distance between faces  202  and  203  defines the thickness of the block. 
         [0067]    Legs  220  and  230  are separated by void  240 . Each leg  220  and  230  has two side walls  222 ,  223  and  232 ,  233 , respectively, generally converging from the front to the back of the block. Block side walls  211  and  213  extend from top face  202  to bottom face  203 . Pin holes  215  and  216  and pin receiving cavities  217  and  218  are located on the front portion of the block. 
         [0068]      FIGS. 11 and 12  illustrate another embodiment of the block of this invention and  FIG. 12  shows how the blocks form a mating pair.  FIGS. 13A ,  13 B and  14  show block  300  along with block  200  in a course of blocks and in a wall. Block  300  is similar to block  200 , but one of the legs forms right angles at the front and the back of the block. Since there are no chamfers on the front of the block, the block can be used in any orientation, i.e., the bottom and top surfaces are interchangeable. 
         [0069]    Block  300  has parallel top face  302  and bottom face  303 . Face  304  extends between corners  306  and  307 . Extending from front portion  310  are two legs  320  and  330 . Cores  321  and  331  are located primarily in the legs, though they extend into front portion  310 . Legs  320  and  330  extend to rear portions  324  and  334 , respectively, having rear faces  325  and  335 , respectively. Front face  304  and rear faces  325  and  335  each extend from top face  302  to bottom face  303 . The distance between faces  302  and  303  defines the thickness of the block. 
         [0070]    Legs  320  and  330  are separated by void  340 . Each leg  320  and  330  has two side walls  322 ,  323  and  332 ,  333 , respectively. Leg side wall  322  joins front portion  310  and back portion  324  at right angles. Therefore, side  311  is perpendicular to the front face  304  and back face  325 . Side  313  is substantially similar to side  213  in block  200 . Side walls  332  and  333  generally converging from the front to the back of the block. The side walls extend from top face  302  to bottom face  303 . Pin holes  315  and  316  and pin receiving cavities  317  and  318  are located on the front portion of the block. 
         [0071]      FIGS. 13A and 13B  show blocks  200  and  300  in a course of blocks for the construction of a wall.  FIG. 13A  shows course  980 , in which block  300  is used as the corner block in the orientation as shown in  FIGS. 11 and 12 . Block  300  is flipped over in  FIG. 13B , which shows course  981 . During construction of a wall, courses  980  and  981  would be adjacent so that the wall would have an offset or running bond pattern. 
         [0072]      FIG. 14  shows wall  985  formed from these two types of blocks. 
         [0073]      FIGS. 15A and 15B  show another block embodiment, in which pin receiving cavities are absent and the front portion of the block is provided with a channel.  FIGS. 15A and 15B  illustrate the bottom and top perspective views of block  400 . In  FIG. 15A , the block is shown in the orientation as it is manufactured, that is, with the bottom surface facing up, and  FIG. 16  shows a side view of the block, with pin holes and core shown in phantom.  FIG. 15B  shows the block stacked together with other blocks. 
         [0074]    Block  400  has parallel top face  402  and bottom face  403 . Front face  404  extends between chamfered corners  406  and  407  and has chamfered top edge  408 . Extending from front portion  410  are two legs  420  and  430 . Cores  421  and  431  are located primarily in the legs, though they extend into front portion  410 . Legs  420  and  430  extend to rear portions  424  and  434 , respectively, having rear faces  425  and  435 , respectively. Front face  404  and rear faces  425  and  435  each extend from top face  402  to bottom face  403 . The distance between faces  402  and  403  defines the thickness of the block. 
         [0075]    Legs  420  and  430  are separated by void  440 . Each leg  420  and  430  has two side walls  422 ,  423  and  432 ,  433 , respectively, generally converging to the back surfaces. Side  411  comprises the side surface of side wall  422  and the side of front portion  410 . Similarly, side  413  comprises the side surface of side wall  433  and the side of front portion  410  and has a complex geometry. Side walls  432  and  433  generally converge from the front to the back of the block. The side walls extend from top face  402  to bottom face  403 . 
         [0076]      FIG. 15B  shows the top perspective view of block  400 , illustrating that there are two pin holes. Pin holes  415   a ,  415   b ,  416   a  and  416   b  are located on the front portion of the block. A set of pinholes (e.g.,  415   a  and  415   b ) are aligned in a plane generally perpendicular to the front face of block  400 ; this same plane passes through the core (e.g., core  421 ). It is to be noted, however, that the pin hole position may be varied as desired. Channel  444  spans the length of the block on the bottom surface near the front face. Channel  444  is configured to receive the head of a pin extending from a pin hole in a block underneath.  FIG. 15B  also illustrates that back portion  424  rests on back portion  434  of an underlying block. This coincidence of back portions adds to the stability of a wall. 
         [0077]      FIG. 16  shows pin holes in phantom and illustrates that pin holes  416   a  and  416   b  extend from the top to the bottom of the block with substantially the same diameter, though it is to be noted that passageways through a block thickness typically taper from the bottom to the top in the block (as-manufactured), for ease of removal of mold elements.  FIG. 16  also shows pin hole  416   a  opens into channel  444 . This type of pin hole is used with shouldered pins, to that the head of the pin lies within the channel. 
         [0078]    Another embodiment of the block of this invention is shown in  FIG. 17 . The block is similar to the block embodiments described above and has correspondingly similar elements, and not every element is numbered for this block. Block  500  has one leg  520  extending from front portion  510  to back portion  524 . Leg  520  comprises two side walls  522  and  523 , which join together with the front and back portions to form core  521 . The core is optional but preferred because it results in a lower weight block. 
         [0079]    Pin holes  515  and  516  and pin receiving cavities  517  and  518  are located near the front face of the block.  FIG. 17  demonstrates that a pair of blocks can be formed in the mold such that mold space is maximized. Convenient dimensions for block  500  are those in which the front face is about 24 inches (60.1 cm) wide and 8 inches (20.3 cm) high. The depth of the front portion is about 4 inches (10.1 cm), and the depth of leg  520  is about 8 inches (20.3 cm). 
         [0080]    Blocks  600  and  700  are shown as a mating pair in  FIG. 18  and for clarity are shown moved apart from their position in a mold box. The formation of a mating pair results in one block having three legs ( 620 ,  630 ,  680 ) and the other having four legs ( 720 ,  730 ,  780 ,  790 ). Each leg has a core ( 621 ,  631 ,  681  and  721 ,  731 ,  781 , and  791  respectively). Block  600  is provided with pin holes ( 615   a / 615   b ,  616   a / 616   b ) and channel  644  that extends the length of the block on its bottom surface. Similarly, block  700  is provided with pin holes ( 715   a / 715   b ,  716   a / 716   b ) and channel  744  that extends the length of the block on its bottom surface. The legs have a curvilinear shape. The legs of block  600  extend from the front portion in equally spaced intervals, essentially dividing the block into thirds. 
         [0081]      FIG. 18  illustrates that blocks having this curvilinear shape can be formed in a matching pair, thus maximizing the mold space and minimizing the amount of material needed for each block. 
         [0082]    Regardless of the block embodiment, various pin configurations can be used, and two are shown in  FIGS. 19A and 19B . If it is desirable to use a straight pin, the pin hole should be tapered or truncated so that the pin will not slide to the bottom of the block. Thus, as shown in  FIG. 19A , pin  840  is in pin hole  116  of block  100 . The pin hole is provided with a taper about half way through the thickness of the block. 
         [0083]      FIG. 19B  shows pin  850  having head  852  attached to straight portion  854 . Head  852  rests on the top surface of block  400 . Pin hole  416   b  has substantially the same diameter throughout the thickness of the block. 
         [0084]      FIG. 20A  shows a cross sectional view of a wall wherein blocks are stacked on top of each other, interlocked by pins  850 , which are placed in forward pin hole  815 . Head  852  fits within a channel (e.g., channel  444  in block  400 ) on the bottom surface of a block above. This arrangement produces a substantially vertical wall.  FIG. 20B  illustrates a wall in which blocks are set back from each other by placing pin  850  in the rearward pin hole of an underlying block. A wall having positive set back is frequently desirable because of both appearance and structural stability. 
         [0085]      FIGS. 21 ,  22 A, and  22 B illustrate mold box  900 , having first and second opposing end rails  902  and first and second opposing side rails  904 . The first and second end rails are spaced apart a distance d 1  and the first and second side rails are spaced apart a distance d 2 . Distance d 2  is less than distance d 1 . A third distance, d 3 , is the height of the mold box and defines the thickness of the block. The mold box sits on a bottom plate (not shown). The bottom plate, end rails and side rails together form a cavity in which blocks are molded. In order to form the blocks of this invention, the mold box is prepared by installing divider plate  950 . The divider plate thus forms first and second mold sections in the mold cavity. This plate preferably is machined from steel into the desired shape and dimensions and is bolted at either end to each side rail.  FIG. 22A  shows the divider plate bolted into mold box  900  with bolts  955 .  FIG. 22B  shows the divider plate with the bolts, the mold box, and the blocks shown in phantom. 
         [0086]    Forming elements (not shown) for the cores, pin holes, and pin receiving cavities are hung over the mold box, and a concrete mix is poured into the mold box. The box is vibrated to compact the concrete mix, which solidifies it. The blocks can then be pressed out of the mold box, and away from the divider plate and forming elements, by a stripping shoe or head that presses on the block as the bottom plate moves away. The stripping shoe is designed to pass over all the forming elements and the divider plate to facilitate removal of the block. The block, on the bottom plate, is then moved, typically by a conveyor belt, to an oven, where it is heat cured. 
         [0087]    Typically, the blocks are shipped in the same orientation in which they are manufactured. This is desirable because each handling step increases the cost of the block. This results in another desirable feature of the present invention. Since the blocks are manufactured in an overlapping configuration they form a compact and efficient package which is easy to handle and requires less space for shipping. 
         [0088]    The front surface of the block may be provided with a desired appearance or pattern by treating the surface as it is removed from the mold, just after it has been removed from the mold, or after curing. The surface appearance can be made to be smooth, corduroy, molded, fluted, ribbed, sand blasted, or fractured, as is known to one of skill in the art. Chamfers or other edge detail can be included in this molding process, as desired, or a block can be treated after curing to round the edges, by methods known to those of skill in the art. A fractured or split appearance is desirable because the surface then has the appearance of natural stone. Mechanical means can be used to treat the surface of a block after it has been cured and such is very effective in producing the appearance of natural stone. Such means are described in commonly assigned, co-pending application U.S. Application Publication No. 2003-0214069 (Ser. No. 10/150,484, filed May 17, 2002), hereby incorporated herein by reference. 
         [0089]    Though the blocks illustrated in the Figures may have any desired dimension, block  100 , for example (as in  FIGS. 3 to 8 ) typically has a thickness (i.e., the distance between surfaces  102  and  103 ) of about 8 inches (20.3 cm) and a length (i.e., the distance from corner  20   a  to corner  21   a ) of about 24 inches (60.1 cm). The length is determined by distance d 1  of the mold box. 
         [0090]    For those blocks described above having a length of about 24 inches (60.1 cm), a depth (i.e., from the front surface to a back surface) of about 12 inches (30.5 cm), and a thickness of about 8 inches (20.3 cm), the weight is about 95 pounds. This translates to about 60 pounds per square foot of front face surface area. This is a convenient weight to use when positioning the blocks in a retaining wall and compares favorably to the weight of Prior Art blocks in terms of handling. Thus the blocks offer an advantage over the Prior Art blocks in terms of their higher front surface area per unit weight. 
         [0091]    The blocks of this invention are efficient to use in constructing walls because the relatively larger face size, compared to the face size of prior art blocks, results in about one third more area when building a wall. 
         [0092]    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.