Patent Publication Number: US-6991206-B1

Title: Concrete block mold with improved stripping ability

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application relates to and claims priority from provisional U.S. Patent Application Ser. No. 60/432,951 filed Dec. 12, 2002. 

   FIELD OF THE INVENTION 
   This invention relates to an improved mold for forming concrete blocks and, more specifically, pertains to an improved mold for forming concrete blocks in which one or more surfaces of the block are irregular in appearance, providing a rough texture resembling that of a split block. 
   BACKGROUND AND SUMMARY OF THE INVENTION 
   In the manufacture of concrete blocks, it is known to split a cured composite block module along one or more splitting planes to provide an irregular surface to the block. 
   It is also known to form such a split-type block by utilizing a mold that has a number of projections extending inwardly into the cavity. Such a method and mold are shown in my U.S. Pat. No. 5,078,940 issued Jun. 7, 1992, which is herein incorporated by reference. Molds such as that shown in the &#39;940 patent utilize projections and a lip to form the irregular face on the block. As the concrete block is stripped from the mold, concrete collects on and between the projections and the irregular pattern is formed. It has been found that excessive amounts of concrete would collect on and between the projections and the lip, thus increasing the amount of force needed to strip the concrete block from the mold. This increased force did not present an insurmountable problem in single face blocks, but in multiple face blocks stripping was made very difficult, if not impossible. 
   The present invention eliminates any spaces or gaps between the projections and the lip for the concrete to gather in, thus making stripping of the concrete block much easier. It has also been found that with the use of this improved mold, both the feed time and the finish time can be increased, resulting in a superior product. 
   It has further been realized that the amount of material wasted during forming of the block can be reduced by as much as 50 percent. 
   It is a general object of the present invention to provide a block forming mold which has improved stripping ability, and is capable of more quickly and efficiently forming an irregular split-type block surface. 
   It is one object of the present invention to provide a block forming mold which markedly reduces wasted block material. 
   It is an additional object of the present invention to provide a block forming mold which lessens disturbance to the block by reducing friction during stripping and contributes to a decrease in cracking of the formed block. 
   It is a further object of the present invention to provide a block forming mold which enables the formation of a stronger, harder product exceeding increased use specifications. 
   It is also an object of the present invention to provide a block forming mold which produces a block which is cleaner in appearance and dimensionally correct. 
   In one aspect of the invention, a mold is provided for forming concrete block. The mold includes a plurality of interconnected vertical walls defining a block material forming cavity having a top opening and a bottom opening with at least one of the walls having a plurality of spaced projections extending inwardly from the wall into the cavity, and a lip at a bottom of the wall beneath the lowermost of the projections extending inwardly into the cavity. The lip has a top surface, a bottom surface and an inwardly extending lip extension disposed along the bottom surface. The invention is improved with the lip being formed with an upper vertical inner surface extending from the top surface to the lip extension. The invention is further improved with the lowermost of the projections having a bottom surface in abutment with the top surface of the tip, and a vertical inner surface coplanar with the upper vertical inner surface of the lip. 
   In another aspect of the invention, a mold used in a concrete block forming process includes a plurality of interconnected vertical walls defining a cavity having a top opening and a bottom opening adapted to receive concrete block forming material containing aggregate through the top opening, and to discharge formed block material in the form of the concrete block having a length, a width, and a height. At least one of the walls has a number of spaced projections extending inwardly from the at least one wall into the cavity. The at least one wall further includes a lip at a bottom of the wall beneath the lowermost of the projections extending inwardly into the cavity with the lip having a top surface and an inwardly extending lip extension disposed along a bottom surface of the lip. The lip is formed with an upper vertical surface extending from the top surface of the lip to the lip extension. The lowermost of the projections has a bottom surface in abutment with the top surface of the lip, and a vertical inner surface coplanar with the upper vertical surface of the lip. A shoe is engaged with an upper surface of the block forming material and is mounted for sliding movement relative to the vertical walls during the concrete block forming process. The shoe has at least one edge adjacent the projections and is spaced from the lip extension to define a surfacing gap through which waste material from the concrete block forming process will fall. The surfacing gap is determined substantially by a largest size of the aggregate in the block forming material, and the height of the concrete block to be formed. 
   Various other features, object and advantages of the invention will be made apparent from the following description taken together with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
       FIG. 1  is a sectional view of a prior art concrete block mold; 
       FIG. 2  is a sectional view similar to  FIG. 1  showing the use of the prior art mold; 
       FIG. 2A  is a view similar to  FIG. 1  showing an alternative prior art mold; 
       FIG. 3  is a top view of the concrete block mold constructed in accordance with the present invention; 
       FIG. 4  is a perspective view of a face plate of the present invention; 
       FIG. 5  is a sectional view of the face plate of  FIG. 4 ; and 
       FIG. 6  is a sectional view like  FIG. 2  showing the face plate of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Prior Art 
   Referring now to  FIGS. 1 ,  2  and  2 A, thereshown is a prior art concrete block forming mold  10  which is well known. Mold  10  includes a face plate  12 , a rear portion  14  and a lower plate  16 , all of which cooperate along with side walls (not shown) to form a cavity  18  adapted to receive therein a block forming material  20 . Material  20  is a standard mix of sand, native aggregate, cement, mortar and water as is well known in the block forming art. 
   Face plate  12  includes a rearwardly extending lip  22  with a lip extension  23  at a bottom thereof, and a series of rearwardly facing projections  24   a – 24   d  above the lip  22  extending into a first portion of the cavity  18  to retain material  20  therein. An upwardly and downwardly moveable shoe  26  is slidably mounted in the mold  10 . When mold  10  is in the position shown in  FIG. 1 , material  20  is deposited and vibrated in the cavity  18 , after which the shoe  26  is placed against the top of the poured material  20  to form and compact a flat top surface of the material  20 . The material  20  sets for a short interval and then face plate  12  and rear wall  14  of mold  10  and the lower plate  16 , are moved relative to each other to form the block  30  as seen in  FIG. 2 . At the same time, the shoe  26  is moved against the top of the material  20  to urge the block forming material  20  out of the mold  10 . When this occurs, the volume of material  20  contained in the first portion of cavity  18  defined by face plate  12  remains in place due to projections  24   a – 24   d . This action essentially shears or splits the material  20  providing an irregular split-type surface  28  to the block shown at  30 . Some fragmentation of material  20  occurs during the forming action, causing waste material  31  to fall through a surfacing gap  32  to be discussed further hereafter. When the upper surface of formed block  30  has cleared the bottom of the mold  10 , the shoe  26  is retracted and lower plate  16  is removed to carry block  30  to a curing area. 
     FIG. 2A  shows an alternative face plate  12 ′ which also has been used to form a concrete block. 
   It is extremely important to acknowledge the criticality of gap  32  which is formed between the end of the lip extension  23  and the edge of the shoe  26  adjacent the face plate  12  or  12 ′. This gap  32  is generally defined according to the largest size of the native aggregate used in the block forming material  20 , and a desired height of the block  30  to be formed in the mold  10 . Typically, the larger the aggregate used and the higher the height of the block  30  desired dictates a correspondingly sized, larger gap  32 . If the gap  32  is not properly chosen, the block forming process will incur too much friction and waste material  31  being sheared will not be properly relieved from the mold  10 . 
   When forming blocks  30  using the face plates  12  and  12 ′, it has been found that concrete block forming material  20  tends to collect in the spaces  33  between the lowermost projections  24   d  and the lip  22  as well as on a sloping face  34  of the lip  22  or an extension  34   a  ( FIG. 2A ). Such accumulation of material  20  increases the amount of force required to strip the block  30  from the mold  10 . This undesirable material retention negatively impacted on the efficiency of the block forming method and affected the quality of the block as discussed in the Background of the Specification. 
   The Present Invention 
     FIG. 3  shows an improved concrete block mold  35  including a plurality of interconnected vertical walls  36   a – 36   f  forming a central cavity  38 . 
   At least one vertical wall  36   b  and preferably several of the vertical walls  36   a – 36   f  is a face plate. Each vertical wall and face plate, such as shown at  36   b  in  FIG. 4 , is provided with a plurality of projections  40   a – 40   d  extending inwardly in the cavity  38 . Vertical wall and face plate  36   b  is also provided with a lip  42  located at a bottom thereof and extending into the cavity  38 . Lip  42  is provided with an inwardly extending lip extension  44  disposed along a bottom surface of the lip  42 . In accordance with the invention best seen in  FIGS. 5 and 6 , the lowermost row  40   d  of projections  40   a – 40   d  has its bottom surface in abutment with the top surface of the lip  42 , and a vertical inner surface  46  coplanar with a vertical inner surface  48  extending between top surface of the lip  42  and the lip extension  44 . 
   This design thus eliminates any spaces  33  or sloping faces  34  or extensions  34   a  where block forming material  20  tended to deleteriously accumulate. With this construction, the ability to strip the formed blocks  30  from the mold  35  is vastly improved resulting in a more efficient method and a significantly enhanced product. More particularly, the formed blocks  30  produced from the new mold  35  exhibit less cracking, are cleaner in appearance and more dimensionally correct, and are clearly stronger, denser products. The improved mold thus operates to avoid the drawbacks of the prior art by preventing formed blocks  30  from hanging up in the mold  35  and then dropping down onto the lower plate or support surface  16 . Thus, the amount of impaired or damaged blocks is minimized. 
   While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only and should not be deemed limitative on the scope of the invention set forth with the following claims.