Abstract:
A method and apparatus for forming a concrete block in form having a resilient insert forming a cavity in which the block is cast and a rigid support for the resilient insert. After the block has cured, the form is inverted. One or more areas of the insert are tethered to the support so that at least a portion of the insert can fall a short distance from the support. The weight of the cast block sufficiently deforms the insert to allow the block to fall free from the insert. When the form is again inverted to its upright position, the insert falls back into the support and returns to its original shape.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   TECHNICAL FIELD 
   The invention relates to a method and apparatus for casting concrete blocks. 
   BACKGROUND OF THE INVENTION 
   Concrete blocks may be formed with textured sides which may have undercuts. Because of the irregular surfaces, these blocks are not easily released from the form cavity in which they are cast. The shapes of the form cavity walls are such that the cured concrete block is locked within the form, even if the form is inverted. One method for releasing blocks with irregular surfaces from the form cavity is to hinge the side walls of the cavity so that the form walls may be pivoted away from the cast block after the concrete has sufficiently cured. This allows the block to be lifted from the form. Another method is to provide form walls which can be manually disassembled and separated from the block after it has cured, and reassembled for casting another block. The manual labor required to release or move the form sides from the each block so that it can be removed from the form adds to the cost for manufacturing the blocks. It has been particularly difficult to manufacture large concrete blocks having highly irregular surfaces which have the appearance of natural stone. It is desirable to form some surfaces of the blocks with deep undercuts which imitate natural characteristics of stone. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention relates method and apparatus for casting concrete blocks in which at least some of the surfaces of the block may be irregular. The cast concrete blocks may simulate natural stone blocks which have sufficiently irregular sides with recesses or shapes which are not easily released from conventional concrete block molds. 
   The apparatus may include a form having a rigid support frame and a resilient insert which forms a cavity in which the block is cast. The surfaces of the insert which define the cavity are textured to form the surfaced of blocks cast in the cavity, and may include portions which project some distance into the cavity. The frame provides support for the resilient insert when concrete is poured into the insert cavity and while the concrete cures. When the form is turned upside down, a sufficient relief angle is provided between the frame and the insert to allow the insert to fall freely from the frame. Edges or corners of the insert are loosely secured to the frame, for example, with cables, chains, bolts or rods, so that when the frame is inverted, the insert will fall only a short distance from the frame. After a concrete block cast in the mold insert cavity has cured, the support frame is inverted so that the mold insert will fall a short distance from the frame. The weight of the block causes the resilient insert to distort and bend away from sides of the block, allowing the block to fall freely from the insert. 
   In one embodiment, a forklift is used to invert the form for separating the cured block from the form. The forklift may include a second set of tines or a plate which can be moved to a short distance from the form for catching the block as it falls from the form and for transporting the block either to a storage area or to a vehicle for transportation. It will be appreciated that other equipment may be used to invert the form for removing the block. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  a perspective view as seen from the upper front left of a retaining wall block which imitates a highly weathered sandstone block made according to the invention; 
       FIG. 2  is a perspective view of a paving stone which may be made according to the invention; 
       FIG. 3  is a perspective view as seen from an upper side of a form for casting concrete blocks in accordance with one embodiment of the present invention; 
       FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 3 ; 
       FIG. 5  perspective view as seen from a bottom side of the form of  FIG. 1  inverted for removing a cast block from the form; 
       FIG. 6  is a perspective view of a fork lift for use in the method of the invention; 
       FIG. 7  is a perspective diagrammatic view showing forklift tines placing a form in which concrete has been poured on a stack of forms; 
       FIG. 8  is a fragmentary diagrammatic front view showing the form with a cured block as it is picked up by forklift; 
       FIG. 9  is a fragmentary diagrammatic front view showing the form of  FIG. 7  inverted on the forklift and separated from the cast block; 
       FIG. 10  is a fragmentary side elevational view showing a portion of two forms stacked according to a modified embodiment of the invention; 
       FIG. 11  is an enlarged fragmentary side elevational view showing the brackets for aligning the forms in  FIG. 10  when they are stacked; and 
       FIG. 12  is an enlarged fragmentary left side elevational view of the brackets of  FIG. 11 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following description of the invention, certain terminology will be used for the purpose of reference only, and are not intended to be limiting. Terms such as “upper” and “lower” refer to directions in the drawings to which reference is made. Terms such as “top”, “bottom”, “horizontal”, and “vertical” describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology will include the words specifically mentioned above, derivatives thereof, and words of similar import. 
     FIG. 1  of the drawings illustrates an exemplary cast concrete retaining wall block  10  which is formed to simulate a highly weathered sandstone block or other types of highly textured rock. The sides  11 , front  12 , top  13  and bottom  14  surfaces of the block may have numerous irregular undercuts which simulate fissures and erosion patters in the block. For the illustrated block  10 , a back surface  15  is the surface formed by the surface of the wet concrete when it is poured into a form cavity. The back surface  15  will be generally flat. It will be appreciated that blocks may be formed to simulate other types of stones, and that they may be formed with any desired surface patterns, Or the invention may be used to cast blocks or articles which do not simulate stone blocks. The invention is particularly useful for casting concrete articles with shapes having undercut surface areas which make it difficult to remove the cast articles from a conventional mold cavity. The invention also may be used for casting flat concrete paving stones and steps, such as the paving stone  16  illustrated in  FIG. 2  which has a generally flat top  17  and bottom  18  and generally rounded or irregular sides  19 . The sides may prevent the paving stone  16  from releasing from a mold cavity. Blocks, paving stones, or other articles formed according to the invention may be relatively small, having a weight less than 100 pounds, or they may be quite large, having a weight greater than 2000 pounds. 
     FIGS. 3 and 4  show an exemplary form  20  in which a concrete block, such as the exemplary block  10 , is cast in accordance with one embodiment of the present invention. The form  20  includes a rigid frame  21 , a rigid support  22  which supports a resilient insert  23  while a block is cast in a cavity  24  formed in the insert  23 . Surfaces  25  of the resilient insert  23  which define the cavity  24  are shaped and textured to impart a desired shape and surface configuration to blocks cast in the cavity  24 . The support is designed to prevent flexing or distortion of the resilient insert while a block is cast in the cavity  23 . According to the invention, the shape and size of the support  22  will depend on the shape, size and strength of the insert  23 . 
   If the block cast in the cavity  24  is an imitation of a weathered natural stone, for example, the insert cavity surfaces  25  may be highly irregular with a number of projections for defining erosion grooves on the cast block surface. The cavity  24  has a top opening  26  through which the concrete is poured. Typically, the surface of the block at the top opening  26  will either be the back of a retaining wall block where the back is not visible, or the bottom of a block which is used where both front and back sides will be visible. As shown in  FIG. 4 , the cavity top opening  26  may have dimensions in some areas which are smaller than the maximum dimensions of the cast block. 
   Preferably, the frame  21  is made from steel since it must be rigid and support the weight of the cast block. However, it should be understood that the frame  21  may be made of any other suitable material having the required strength and durability. If the invention is used for casting small blocks, for example, wood or a plastic may be acceptable for the frame  21 . 
   The exemplary frame  21  includes a base  27  having front and rear rails  28  and  29 . The front and rear rails  28  and  29  provide longitudinal support and stability to the frame  21 . The base  27  includes two spaced, parallel channels  30  and  31  which extend perpendicularly between the front and rear rails  28  and  29 . The channels  30  and  31  have a rectangular cross section, closed sides and open ends for receiving the spaced tines of a forklift (not shown) used to transport and to invert the form  20 , as is discussed in detail below. It should be appreciated that other constructions configurations may be used. 
   The exemplary frame  21  is show as including four posts  32 - 35  which extend generally vertically from the base  27 . The posts  32 - 35  provide vertical support and stability to the frame  21 . Each post  32 - 35  is provided with a flat top  36  and an upwardly and outwardly flared edging  37 . The posts  32 - 35  are sufficiently high to allow the forms  20  to be stacked. The flared edging  37  helps to align the forms  20  as they are stacked. It should be understood, however, that the form  20  may have other configurations which cooperate with any portion of another form to stabilize and support the other from when stacked. 
   The frame  21  is illustrated as having two spaced, parallel side channels, tubes or rails  40  and two spaced, parallel side channels, tubes or rails  41 . The channels  40  and  41  are connected together and to the corner posts  32 - 35  to form a rectangle which provides lateral support and stability to the frame  21 . It should be understood that the frame  21  may include any number of support rails, tubes, channels, etc. in any suitable configuration the frame  21  with the necessary strength. 
   The rigid support  22  is shown formed from a plurality of steel panels  42  which are welded together. The number and arrangement of panels  42  will depend on the exterior shape of the resilient insert  23  and the amount of support which the insert requires to maintain its shape while an article is cast in the insert. The plates  42  may be secured to the frame  21  rather than to each other and may only support areas of the insert which require support. The support  22  also maybe formed in any other suitable manner, such as a one piece stamping or a mold. If the insert  23  has a low height, as when casting paver blocks, it may be only necessary to support the bottom of the insert  23 . 
   The rigid support  22  is connected to the frame  21  by welding, mechanical fasteners, or any other suitable mechanism that will secure the support  22  to the frame  21 . The insert  23  has an outer surface  43  that generally conforms to and is supported by the interior of the support  22  without being retained by the support  22 . In other words, there must be a sufficient relief angle where the insert  23  contacts the support  22  to allow the insert  23  to fall freely from the support  22  when the form  20  is inverted. 
   The resilient insert  23  may be composed of an elastomer, e.g. natural or synthetic rubber. It must be understood, however, that resilient insert  23  may be composed of any material suitable to support concrete during casting and with sufficient resilience to allow the material to be pulled away from the concrete and to return to it original shape when positioned in the support  22 . 
   At least one or more points on the resilient insert  23  are tethered, i.e. moveably connected, to the frame  21  or to the support  22 . The tethers may be, for example, in the form of cables, ropes, strings, wires, lose bolts, or any other element suitable to tether the insert  23  to the frame  21  or the support  22 . In the illustrated form  20 , the tethers are five flexible, plastic coated wire cables  44 . At a front side of the form  20 , cables  44  are secured between the front corners of the insert  23  and the front channel  40  of the frame  21 . Three rear cables  44  are shown secured between the rear corners and the rear center of the insert  23  and a rear bar  45  of the frame  21 . The cables  44  or other forms of tethers may be secured by any desired method depending on the type of tether used and the strength required, such as by knots or conventional cable clamps for wire cables or rope, or welding for chain, or nuts for bolts. 
   The insert  23  may have outwardly extending edges  47  which surround the cavity opening  26 . The edges may be rectangular and the cables  44  or other form of tethers may be secured to points adjacent the corners. Preferably, to extend the life of the resilient insert  23  reinforcing members  46  are embedded in the edges  47  of the insert  23  to reduce the risk that the insert will tear when a block is dumped from the form  20 . The tether reinforcing members  46  disperse forces exerted between the cables  44  and the insert  23 . The members  46  may be made of steel or of high density plastic or of any other material suitably to reinforce the insert  23  without unduly interfering with the resiliency of the insert  16 . 
   Referring to  FIG. 5 , a cured concrete block is removed from the form  20  by inverting the form  20  above a surface which will catch the block. When the form  20  is inverted, the resilient insert  23  will fall from the form  20  to the extent permitted by the wire cables  44  or other type of tether. Due to its resiliency, the insert  23  will be stretched from its corners and edges and will deform sufficiently to allow the block to fall from the insert cavity  24 . 
   For large blocks which have a heavy weight, preferably a forklift is used to implement the method of the invention. A preferred type of forklift  50  is illustrated in  FIG. 6 . A basic conventional forklift has a pair of parallel tines which may be moved up and down on a generally vertical mask which may be tilted over a limited range. On some forklifts, the tines also may be moved to change the spacing between the tines. The forklift  50  has an added feature of a mechanism  51  mounted on a mask  52 . The mechanism  51  can be moved up and down on the mask  52  and can be rotated on the mask  52 . A pair of tines  53  are mounted on the mechanism  51 . In addition, a flat support plate or a second pair of tines  54  are mounted on the mechanism  51  for movement towards and away from the tines  53 . A fork lift of this type is commercially available. 
   Referring to  FIG. 7 , a form  58  is shown being stacked on top of a stack of three forms  59 - 61 . As the forms  58 - 61  are filled with wet concrete, they may be easily stacked while blocks cast in the forms cure. Either the forklift  50  or a basic forklift which only has tines which may be raised and lowered may be used to stack the forms  58 - 61 . Only the tines  62  of the forklift are shown in  FIG. 7 . The flared edging  37  on the tops of the corner posts of the stacked form  59  facilitate alignment of the form  58  with the form  59 . 
     FIGS. 8 and 9  are fragmentary diagrammatic views show the process for removing a cured block  63  from a form  64  using the forklift  50  of  FIG. 6 . The form  64  is picked up by inserting the forklift tines  53  into the channels  65  on the form  64  and lifting. The second tines  54  are moved against the form  64  so that the form  64  is clamped between the forklift tines  53  and the second tines  54 . The forklift mechanism  51  is then rotated 180° and the second tines  54  are lowered, as shown in  FIG. 9 . This allows a form insert  66  to fall from the form by the length of the tether and the cured block  63  to fall from the insert  66  to the second tines  54 . The weight of the block  53  stretches and deforms the insert  66  so that any surface projections on the insert cavity surface will pull away from the block  63 . The forklift may then be used to move the cured block to a storage area or to a transportation vehicle. Preferably, the block  63  overhangs edges  67  of the second tines  54 . The overhanging may be lowered on blocks which space the block  63  above a support surface so that it can easily be picked up at a later time with a forklift. 
     FIGS. 10-12  show a modified arrangement for stacking forms  69  either when not in use or while blocks cast in the forms  69  cure. Each form includes at its bottom two parallel channels  70  and  71  which are spaced for receiving forklift tines (not shown) for lifting, stacking and inverting the forms  69 . A bracket  72  is welded or otherwise secured to an outer side  73  adjacent each end of each channel. A post  74  extends vertically from each channel  70  and  71  to an upper end  75  adjacent the top of each form  69 . A bracket  76  is secured adjacent the upper end  75  of each post  74 . As seen in  FIGS. 10 and 11 , the brackets  76  have upwardly and outwardly angles surfaces  77  which, when an upper form  69  is stacked on a lower form  69 , center the forms so that the channels  70  and  71  are supported on the posts  74  and brackets  76  on the lower form  69 .  FIG. 12  is a fragmentary left side elevational view showing additional details of the brackets  72  and  76 . The brackets  76  have a bend  78  which forms an upwardly and outwardly angled surface  79 . The bracket  72  is secured to the outer side  73  of the channel  70  so that a surface  80  on the bracket  72  forms substantially the same angle as the angle of the upper surface  79  on the bracket  76 . The angled surfaces  79  and  80  cooperate to align the stacked forms  69  in a front to back direction. Other arrangements for aligning the stacked forms also will be apparent to those skilled in the art. 
   It should be appreciated that the illustrated components of the frame  21  and of the rigid support  22  may be varied, combined or eliminated, so long as sufficient support is provided for the resilient insert  23  while a block or other article is cast and allowed to cure in the resilient insert, and so long as the resilient insert  23  with a cast block and the support can be inverted and the resilient insert is allowed to at least partially fall from its inverted support and deform to release the cast block. It also will be appreciated that various other modifications and changes may be made to the above described preferred embodiment of without departing from the scope of the following claims.