Abstract:
A resilient mold including a plurality of cavities in which a plurality of concrete blocks are cast. Cured concrete blocks are demolded from the mold by supporting the inverted mold on a support surface, engaging two opposing edges of the mold and separating the mold from the support surface so that the mold bends or sags to release the blocks from the mold cavities. The mold includes at least one wall extending in a direction between the two opposing edges between two adjacent mold cavities. One or more resilient support rods is embedded in the wall. The support rods are shaped to bend in a first direction while resisting bending in a direction perpendicular to the first direction. The rods are oriented in the wall for preventing the wall from deforming as the adjacent mold cavities are filled with concrete, while permitting the wall to bend during demolding.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    Not Applicable. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a mold for casting concrete blocks. 
       BACKGROUND OF THE INVENTION 
       [0003]    Concrete blocks have been cast in resilient molds formed, for example, from polyurethane. The molds have an open top in which the liquid concrete is poured. After the concrete has sufficiently cured, the cast block is demolded by inverting the mold. The inverted mold is on a pallet or other support surface which will receive the demolded blocks. In some cases, the blocks are not easily demolded due to surface shapes and textures. One process for demolding the blocks involves engaging opposite edges of the inverted mold and separating the mold from a support surface. The weight of the blocks causes the mold to sag and stretch sufficiently to allow the blocks to fall from the mold onto the support surface. After the cured blocks are demolded, the mold is turned upright and ready for casting additional blocks. 
         [0004]    A mold may have a number of cells or cavities for simultaneously casting a number of blocks. The cells are filled with concrete either one at a time or a row at a time. If the wall between adjacent cells is too small, the cell wall between a cell being filled and an adjacent empty cell may bend or deflect into the empty cell, causing a deformities in blocks cast in the deformed cells. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    According to the invention, the risk of producing deformed concrete blocks cast in a multi cell resilient mold is reduced by incorporating elongated support or reinforcement members in the mold walls. The reinforcement members are formed from a resilient material such as graphite spring steel. The rods are shaped and of a size which will minimize mold wall deformity as the mold cells are filled with concrete, while permitting the mold to flex or sag as the hardened concrete blocks are released from an inverted mold. 
         [0006]    Various objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a top plan view of an exemplary prior art mold for casting  8  concrete blocks, showing deflection of side walls of two cells or cavities; 
           [0008]      FIG. 2  is a side elevational view of a mold during demolding of cured cast blocks; 
           [0009]      FIG. 3  is a perspective view of a reinforced mold according to the invention for casting  9  concrete blocks; 
           [0010]      FIG. 4  is a an end perspective view of the mold of  FIG. 3 ; 
           [0011]      FIG. 5  is a side cross sectional view of the mold as taken along line  5 - 5  of  FIG. 4 ; and 
           [0012]      FIG. 6  is a fragmentary perspective view of the reinforcement member embedded in the mold of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIG. 1  of the drawings, a top view of an exemplary prior art mold  10  is shown. The mold  10  is formed from a tough, resilient material which will withstand repeated use for casting concrete blocks, such as polyurethane. In the illustrated mold  10 , 8 cells or cavities  11 - 18  are shown for simultaneously casting  8  blocks. During casting, the bottom of the mold is typically supported on a rigid support surface, such as a steel plate, and the exterior sides of the mold may be supported by a rigid frame (not shown). Bottom surfaces  19  of the cavities  11 - 18  may be textured to form textured faces on blocks cast therein. Depending on the intended application for blocks cast in the mold  10 , the cast blocks may have rectangular shapes, having parallel sides and parallel ends, or ends of the blocks may be angled where, when viewed from the top, the blocks will have a trapezoid shape with the textured face of each block being wider than the back of the block. When the blocks have angled ends, the angled ends of the cavities  11 - 18  are arranged in the mold  10  to face the mold sides  22  and  23  to facilitate demolding. The angled sides permit the blocks to be arranged side-by-side forming either a straight wall or a curved wall with the faces of adjacent blocks abutting. Since the textured faces of the blocks are formed at the bottom of the cells or mold cavities and they are wider than the backs of the blocks which are formed at the open tops of the cavities  11 - 18 , they are more difficult to the cured blocks demold. The broken lines  20  in  FIG. 1  show extended ends of the faces  19 , forming longer block faces than the width of the backs of the blocks. 
         [0014]    One known method for demolding block cast in the mold  10 , as shown in  FIG. 2 , involves placing a support surface  22  on top of the mold, and then inverting the mold  10  and blocks  21  and the support surface  22 , engaging two opposite edges  23 ,  24  of the mold and raising the mold above a support surface, either by lifting the mold  10  or by lowering the support surface. As the mold  10  is separated from the support surface  22 , the resilient mold  10  will sag and stretch to allow the blocks  20  to fall onto the support surface. For blocks  21  which are difficult to demold, pressure may be placed on the inverted bottom of the mold to help push the blocks from the mold. For ease of demolding, the resilient mold  10  must have sufficient resiliency to allow the mold  10  to sag with the help of the weight of the blocks  20  and release the cast blocks during the demolding step. This process is shown, for example, in U.S. Pat. No. 8,968,623 entitled Process And Apparatus For Demolding And Palletizing Cast Concrete Blocks, the disclosure of which is incorporated herein. 
         [0015]    Referring again to  FIG. 1 , it should be appreciated that the mold cells or cavities  11 - 18  will are normally not be simultaneously filled with concrete at the same rate. The cavities  11  and  12 , for example, may be filled with concrete prior to filling the cavity  13  with concrete. Due to the resiliency of the mold  10 , the weight of the concrete in the cavity  11  can cause the wall between cavity  11  and cavity  13  to bulge or deflect into the cavity  13 , as shown by the dashed lines  25 . Similarly, the weight of the concrete in the cavity  12  can cause the wall between cavity  12  and cavity  13  to bulge or deflect into the cavity  13 , as shown by the dashed lines  26 . The bulging will cause deformities in the blocks cast in the cavities  11 ,  12  and  13 . Problems with the cavity walls deforming can be reduced by designing the mold with thicker walls between adjacent mold cavities. However, this will reduce the number of blocks that can be cast in a mold, unless the mold is made larger. This will add to the cost for casting concrete blocks. 
         [0016]      FIGS. 3-5  show details of a mold  30  constructed according to the invention for casting a plurality of concrete blocks. The mold  30  will have at least 2 cavities, with 9 cells or cavities  31 - 39  shown in the exemplary mold  30 . The multiple cavities may be of the same size or of different sizes, as shown in the exemplary mold. The cavities are arranged in the mold for efficient use of the space. The illustrated mold  30  is rectangular when viewed from the top and has opposing sides  40  and  41  and opposing sides  42  and  43 . The block cavities extend either singly or in rows with the longitudinal directions extending between the sides  40  and  41 . Shorter block cavities  31  and  32 , for example, are aligned in a row which is parallel to the longer cavity  33 . A mold wall  45  extends between the larger cavity  33  and the smaller cavities  31  and  32 . 
         [0017]    Prior to demolding cured concrete blocks from the mold  30 , a support surface such as a rigid steel plate, is placed over the top of the mold  30  to cover the openings to the cavities  31 - 39  and the mold  30  and the support surface are inverted together so that the cured blocks rest on the support surface. During demolding of cured blocks from the mold  30 , the opposing mold sides  43  and  44  are gripped by the demolding machine, such as is shown in U.S. Pat. No. 8,968,623. The mold  20  and the mold  30  and/or the support surface are moved apart. The weight of the blocks cause the mold to sag, allowing the blocks to fall from the mold onto the support surface. If necessary, pressure may be applied to the upper surface of the inverted mold to help push the blocks from the mold. 
         [0018]    In the illustrated mold  30 , five walls  44 - 48  extend between the mold sides  42  and  43  in addition to the mold sides  40  and  41 . One side of the cavities  31  and  32  is formed by the mold side  40  and the wall  44  forms an opposite side to the cavities  31  and  32 . The cavities  33  and  34  are located between the walls  44  and  45 . The cavity  35  is located between the walls  45  and  46 . The cavity  36  is located between the walls  46  and  47 . The cavities  37  and  38  are located between the walls  47  and  48 , and the cavity  39  is located between the wall  48  and the mold side  41 . 
         [0019]    According to the invention, one or more elongated reinforcement members or rods  49  are illustrated embedded in mold walls  44 - 48 . If the mold sides  40  and  41  are subject to deforming as the adjacent mold cavities are filled with concrete, one or more rods  49  also may be embedded in these mold sides. If the mold sides  40  and  41  are supported by a rigid frame during the casting and curing process, these optional rods may be omitted. In  FIGS. 4 and 5 , two of the rods  49  are shown embedded in each of the walls  44 - 48 . However, only a single support rod  49  or more than two support rods  46  may be used, depending on the dimensions of the mold  30  and the amount of support needed. Preferably, the rods  49  are completely embedded in the mold  30  and do not extend to the walls  42  and  43 . 
         [0020]    The support rods  49  are formed from a resilient material, such as carbon fiber or a spring steel, and are elongated and are shaped in cross section to resist bending in one direction and to be more flexible when bent in a perpendicular direction. This may be achieved, for example, by constructing the support rod  49  to be relatively flat with a rectangular cross section, as shown in  FIG. 6 , with a wide side  50  and a short side  51 . Optionally, corners between adjacent sides  50  and  51  may be rounded as shown in  FIG. 6 . to reduce the risk of sharp corners inducing tears in the adjacent mold  30  when the mold bends during the demolding process. The support rods  49  will easily bend in the direction of the arrow  52  and will resist bending in a perpendicular direction shown by the arrow  53 . The flat support rods  49  are embedded in the mold  30  with the flat sides parallel to a top surface  50  and a bottom surface  51 . In this arrangement, the support rods  49  do not inhibit bending and sagging of the inverted mold  30  during demolding. However, when a mold cell is filled with concrete, the support rods  49  restrict the mold walls  44 - 48  from deforming as the cavities are individually filled with concrete. The support rods  49  permit construction of the mold  30  with thinner walls between adjacent block forming cavities, which in turn permits forming more block cavities for the same size mold, which in turn reduces the cost of manufacturing blocks and increases the output of cast blocks. 
         [0021]    It will be appreciated that various modifications and changes may be made to the above described preferred embodiment of a mold for casting concrete blocks without departing from the scope of the following claims. For example, the reinforcement rods may be replaced with other types of members which are rigid in one direction while bending with minimal resistance in a 90 degree direction, such as, for example, a roller chain similar to a bicycle chain which is quite flexible in one direction while stiff in a 90 degree direction, or a tough flexible fabric having short rigid parallel rods embedded therein.