Patent Publication Number: US-2005116389-A1

Title: Apparatus and methods for making a masonry block with a roughened surface

Description:
FIELD  
      This invention relates to an apparatus and method for making a masonry block, such as a retaining block, in which one or more surfaces have a roughened texture resembling that of a split block or natural stone.  
     BACKGROUND  
      Masonry products, such as blocks or bricks for constructing walls, have been made for many years by molding processes. A typical molding process involves the use of what is commonly known as a static block-making machine. Pallets made from metal or wood are fed by a conveyor into the block-making machine, which generally comprises a mold, a stripping device, a vibration mechanism, and a device for filling the mold with a cementitious mix. After the pallet has been located, the mold is lowered onto the pallet to form a mold cavity defined by the upper surface of the pallet and the inside surfaces of the side walls of the mold. A cementitious mix is then introduced into the mold cavity through the open top of the mold while simultaneously vibrating the mold and/or pallet. A compression or compacting head is lowered onto the cementitious material in the mold to facilitate densification of the cementitious material. The molded cementitious material is then stripped from the mold by raising the mold while the compacting head remains stationary relative to the mold, thereby pushing the molded block through the open bottom of the mold.  
      It is common to split off a portion of the cured block, such as with a splitting machine or a hammer and chisel, so as to create a decorative face on a surface of the block that resembles the surface texture of natural stone. The face created by the splitting process is often referred to in the industry as “split face” or “rock face.” The splitting of cured blocks, however, involves additional equipment and manufacturing steps and results in material wastage. In order to avoid the shortcomings of conventional splitting processes, there have been efforts to achieve the same “split face” texture without additional splitting steps.  
      There are a number of patents, which disclose methods and apparatuses for producing a roughened surface on an uncured block during the molding process. For example, U.S. Pat. No. 3,981,953 to Haines is understood to disclose a method of forming a roughened block face in which cementitious material is placed in a mold cavity, with a grid-like series of elements being disposed in the cavity and suspended from a top plate. After the block material is compacted into the cavity, the side walls and top plate are drawn off the molded but uncured block. Upward movement of the top plate lifts the grid-like series of elements, and the block material between the elements and the lower plate is broken off from the lower block material in the mold, forming a roughened texture on the top face of the block. A drawback to this arrangement is that the pattern of the elements is cast in the top face of the block.  
      U.S. Pat. No. 3,940,229 to Hutton is understood to disclose a mold in which a small lip is formed on the inner, lower edge of a vertical wall of the mold. As the densified, composite material is stripped from the mold, the lip moves vertically up an adjacent side wall of the block, and tears some of the composite material away from the surface of the block. The lip temporarily retains this composite material in place against a portion of the mold wall as the mold is stripped. The retained material is thus dragged, or rolled, up the surface of the adjacent side wall of the block as the mold is stripped, creating a roughened texture on the side wall of the block.  
      The process of the &#39;229 patent tends to produce a textured face having horizontal striations so as to provide what may be referred to as a “shingled” appearance. In addition, the textured face is slightly tapered or sloped, as a result of the lip retaining fill material as the mold is stripped from the block.  
      Another example of an alternative to splitting is shown in U.S. Pat. Nos. 5,078,940 and 5,217,630 to Sayles. These patents are understood to disclose a mold having a lower lip on a vertical wall of the mold, similar to that shown in the &#39;229 patent. In addition, the mold employs a plurality of projections on the vertical wall above the lip, and a vertically oriented reinforcing mesh above the lip and spaced from the projections. When the mold is initially filled, the cementitious material fills in between the mesh and the wall, and around the projections. The combination of the lip, mesh and projections holds a large mass of compacted material against the mold as the mold is moved vertically upward to strip the uncured block from the mold. These patents appear to show the retained mass of material shearing from the rest of the material, and thus creating a roughened face on the molded block.  
      In the process of the &#39;940 and &#39;630 patents, the use of the projections holds a much larger mass of material against the mold side wall than is the case in the &#39;229 process, and does this in a fashion so as to retain that material in the mold from cycle to cycle. Consequently, frequent stoppages in production may be required to clean the mold of material accumulated between the projections. Further, cleaning of the mold may be complicated by the presence of the screen.  
      Yet another apparatus for producing a block with a roughened surface is shown in U.S. Pat. Nos. 5,879,603 and 6,138,983 to Sievert. The &#39;603 and &#39;983 patents are understood to disclose a mold having generally parallel upper and lower lips on a vertical wall of the mold. As the mold is moved vertically to strip the uncured block from the mold, fill material is retained in the space between the upper and lower lips. Like the process of the &#39;940 and the &#39;630 patents, the retained material is sheared from the uncured block, thereby creating a roughened surface.  
      U.S. Pat. No. 6,209,848 to Bolles discloses an apparatus that is similar to the apparatus of the &#39;603 and &#39;983 patents. The &#39;848 patent discloses a mold in which a lip is formed along the bottom edge of at least one wall of the mold, wherein a series of grooves are formed along the length of the lip.  
      Finally, U.S. Pat. Nos. 6,113,379 and 6,224,815 to LaCroix are understood to disclose a mold having two mold cavities separated by a metal grate. The grate has openings to permit fill material to flow through the openings and form a single molded article in the mold. When the molded article is discharged from the mold, the article is separated into two masonry units by the grate, with each masonry unit having a roughened surface where the units were previously joined.  
      Despite the foregoing processes, there exists a continuing need for new and improved methods and apparatus for producing a masonry block that does not involve splitting but which creates a textured surface that resembles the “split face” look that can be achieved with a conventional splitting process.  
     SUMMARY  
      According to one aspect of the invention, an apparatus for making a masonry block with at least one roughened surface is provided. In one representative embodiment, a mold comprises a plurality of walls defining at least one mold cavity adapted to receive block-forming material. The mold defines an opening through which a formed, uncured block may be removed from the mold. At least one wall of the mold has a plurality of projections extending into the mold cavity so as to contact an adjacent surface of the uncured block in the mold cavity. The projections are positioned such that when the uncured block is removed from the mold, the projections texture the adjacent surface of the uncured block.  
      Desirably, the projections taper as they extend away from the wall of the mold. In a disclosed embodiment, the projections are generally frusto-pyramidal in shape and desirably are oriented on the wall with two side surfaces facing in a generally-upward direction and two other side surfaces facing in a generally downward direction. Desirably, although not necessarily, the two generally upwardly facing side surfaces of each projection have a slope that is less than the slope of the two generally downwardly facing side surfaces. In addition, at least some of the projections are located between the top and bottom of the mold. In one example, the projections may be positioned in plural rows of projections along the wall of the mold, with the projections being in contacting relationship with other at their bases so as to minimize spacing between adjacent projections.  
      In addition, the mold may have a separating wall for separating the mold into first and second mold cavities, each of which is adapted to receive block-forming material for forming first and second blocks, respectively. A first major surface of the separating wall may have a plurality of projections extending into the first mold cavity for texturing a surface of the first block. A second major surface of the separating wall may have a plurality of projections extending into the second mold cavity for texturing a surface of the second block.  
      According to yet another representative embodiment, an apparatus for molding masonry blocks comprises a mold. A plurality of mold walls define an interior space of the mold. A separating member separates the interior space into first and second mold cavities, each being adapted to receive block-forming material for forming first and second blocks, respectively. The separating member has first and second major surfaces, with the first major surface forming an interior surface of the first mold cavity and the second major surface forming an interior surface of the second mold cavity. A plurality of projections are disposed on one of said mold walls and extend into the first mold cavity. A plurality of projections are also disposed on another of the mold walls and extend into the second mold cavity. In addition, the first and second major surfaces of the separating member have a plurality of projections extending into the first and second mold cavities, respectively. The projections are positioned such that when the first and second blocks are removed from the mold, the projections produce a roughened texture on at least two surfaces of the first and second blocks.  
      According to another aspect of the invention, a wall for use in a mold for making a masonry block with a roughened surface is provided. The wall, in one configuration, comprises a body having first and second major surfaces. At least one of the first and second major surfaces has a plurality of block-texturing members extending outwardly from the body. Desirably, the block-texturing members taper as they extending away from the body. In another configuration, both the first and second major surfaces have a plurality of block-texturing members. In either case, the body and the block-texturing members may be of a unitary construction, or alternatively, the block-texturing members may be configured to be removable from the body.  
      The block-texturing members in an illustrated embodiment are generally frusto-pyramidal in shape. Desirably, although not necessarily, the block-texturing members may have a side surface that has a slope greater than that of another side surface. In addition, the block-texturing members may be positioned side-by-side in contacting relationship with each other along one or both of the first and second major surfaces.  
      According to another aspect of the invention, a method for making a masonry block having at least one roughened surface is provided. In one specific approach, block-forming material is introduced into a mold cavity having plural inwardly extending projections located between the top and bottom of the mold cavity. An uncured block is formed in the mold cavity, after which the mold cavity is moved relative to the uncured block. The relative movement of the mold cavity causes the projections to produce a roughened texture on a surface of the uncured block. Typically, moving the mold cavity for producing the roughened texture on the block comprises moving the mold cavity (e.g., raising the mold cavity) until the uncured block is removed, or stripped, from the mold cavity. The projections desirably are configured to avoid retaining block-forming material in the spaces between adjacent projections as the uncured block is removed from the mold.  
      These and other features of the invention will be more fully appreciated when the following detailed description of the invention is read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a front elevational view of a mold wall according one embodiment for use in a mold for forming a masonry block, showing a plurality of frusto-pyramidal shaped projections extending outwardly from one major surface of the wall.  
       FIG. 2  is a cross-sectional view of the mold wall of  FIG. 1  taken along line  2 - 2  of  FIG. 1 .  
       FIG. 3  is a cross-sectional view of the mold wall of  FIG. 1  taken along line  3 - 3  of  FIG. 1 .  
       FIG. 4  is a cross-sectional view of an apparatus, including a mold filled with cementitious material, according to one embodiment for molding a masonry block, in which the forward and rear walls of a mold have the same general configuration as the mold wall shown in  FIG. 1 .  
       FIG. 5  is a cross-sectional view of the apparatus of  FIG. 4  showing a formed, uncured block being removed from the mold.  
       FIG. 6  is a horizontal cross-sectional view of the mold of  FIG. 4  taken along line  6 - 6  of  FIG. 4 .  
       FIG. 7  is a cross-sectional view of an apparatus, including a mold filled with cementitious material, according to another embodiment for molding two masonry blocks, in which a divider plate or wall separates the mold into first and second mold cavities for forming first and second blocks, respectively. 
    
    
     DETAILED DESCRIPTION  
      According to one aspect, the invention provides an apparatus and method for making masonry units or blocks having one or more roughened surfaces without using conventional splitting techniques. The invention can be adapted for use with different types of molds to produce various types of blocks, such as decorative architectural blocks, paving stones, landscaping blocks, retaining wall blocks and the like.  
      Referring first to  FIGS. 4-6 , there is shown a schematic illustration of a block-forming apparatus  60 , according to one embodiment, for forming a masonry unit or block having at least one roughened surface. The apparatus  60  in the illustrated configuration comprises a generally rectangular-shaped mold  62  supported on a suitable support surface, such as a pallet  70 . As shown, the mold  62  comprises vertically upright opposed forward and rear walls  10 ,  10 ′, respectively, and opposed side walls  64 ,  66 , extending between respective ends of the forward and rear walls  10 ,  10 ′ ( FIG. 6 ). The walls  10 ,  10 ′,  64  and  66  collectively define a mold cavity  68  adapted to receive fill material (also referred to herein as block-forming material) for forming a block  72 . The walls  10 ,  10 ′,  64  and  66  are desirably generally impervious to block-forming material so that block-forming material is retained in the mold cavity  68  by the walls. The mold  62  has an open top through which fill material may be introduced into the mold cavity  68  and an open bottom through which the formed, uncured block  72  may be removed, or stripped, from the mold cavity  68 .  
      A substantially horizontal pusher plate  74  may be provided to facilitate compression of the fill material during the block forming process and removal of the formed, uncured block  72  from the mold cavity  68 . The pusher plate  74 , which is shaped so as to be able to fit slidably within the mold cavity  68 , is operable for movement between a raised position above the mold  62  ( FIG. 4 ) and a lowered position within the mold cavity  68  for compressing the fill material and for removing the formed, uncured block from the mold cavity  68  ( FIG. 5 ). The pusher plate  74  may be coupled to any suitable mechanism for moving the pusher plate  74  between the raised and lowered positions and for pressing the pusher plate  74  against the top surface of the block  72 . For example, the pusher plate  74  may be coupled to a hydraulic ram, as generally known in the art.  
      The shape of the mold cavity  68  defines the plan shape and size of the block  72  (i.e., the shape and size of the block when viewed from above or below), with each wall  10 ,  10 ′,  64  and  66  forming an adjacent vertical surface of the block  72 . The bottom and top surface of the block  72  are formed by the upper surface of the pallet  70  and the lower surface of the pusher plate  74 , respectively. The walls  10 ,  10 ′, which, in the illustrated embodiment, are identical in construction, have interior surfaces configured to texture adjacent surfaces of the block  72  as it is removed from the mold cavity  68 , as explained in greater detail below. The mold cavity  68  in the configuration shown in  FIGS. 4-6  has a generally rectangular plan shape to provide a block having the same shape. However, the shape of the mold cavity  68  can be varied to provide blocks having other geometrical plan shapes. For example, one or more of the walls defining the mold cavity  68  can be configured to intersect an adjacent wall at an angle that is greater than or less than 90°. In addition, one or more of the walls of the mold cavity  68  may be curved or rounded. Alternatively, a wall may comprise plural segments interconnected to each other at angles. Moreover, the mold cavity  68  may have greater than or less than four vertical walls.  
      Although the mold  62  of  FIGS. 4-6  is shown as having two walls for texturing opposed surfaces of the block  72  (walls  10 ,  10 ′), in other embodiments, only one such wall may be used, or alternatively, two adjacent such walls may be used, or more than two walls for texturing the surfaces of a block may be used.  
       FIGS. 1-3  illustrate in greater detail the wall  10  of the mold  62  shown in  FIGS. 4-6 . As mentioned, the wall  10 ′ is identical in construction to wall  10 . Thus, the following description, which proceeds in reference to the wall  10 , is also applicable to the wall  10 ′. The wall  10  in the illustrated configuration comprises a body  12  having first major surface  14 , which serves as an interior surface of the mold cavity  68 , and second major surface  16 . A plurality of abutting block-texturing members, or projections,  18  extend outwardly from the first surface  14 . As shown in  FIGS. 4 and 5 , the projections  18  on the walls  10 ,  10 ′ project into the mold cavity  68  and contact an adjacent surface of the block  72 . As the mold  62  is moved vertically with respect to the block  72  for removing the block  72  from the mold cavity  68 , as indicated by arrow A in  FIG. 5 , the projections  18  produce a “scraping,” or “tearing,” action on the respective adjacent surfaces of the block  72 , thereby creating an irregularly roughened surface for those sides of the block  72 .  
      As shown in  FIGS. 1-3 , the projections  18  desirably taper as they extend outwardly from the first surface  14 . In the illustrated embodiment, for example, each projection  18  is generally “frusto-pyramidal” in shape, that is, each projection  18  has a square-shaped base  28  at the first surface  14 , a flattened, square-shaped end surface or crest  30  spaced from the base  28 , and four flat side surfaces  20 ,  22 ,  24  and  26  that converge as they extend from the base  28  to the end surface  30 . However, it is contemplated that other tapered or non-tapered shapes may be used for the projections  18 . For example, the projections  18  may be pyramidal, conical, frusto-conical, rectangular, square, cylindrical, or any of other various shapes.  
      Desirably, the projections  18  are distributed uniformly throughout the surface area of the first major surface  14 . As best shown in  FIG. 1 , the projections  18  desirably are arranged side-by-side in diagonal rows extending across the first surface  14  without spacing between projections or between adjacent rows of projections. Although less desirable, in other embodiments, the rows of projections  18  may extend horizontally across the first surface so as to form a “checkerboard” pattern of projections. In addition, in other embodiments, the projections  18  may be spaced apart in the direction of the rows of projections. In still other embodiments, the rows of projections may be spaced from each other.  
      As shown in  FIG. 1  and except for those projections bordering the edges of the wall  10 , the base  28  of each projection  18  adjoins the base  28  of an adjacent projection to minimize spacing between the crests  30  of adjacent projections. The side surfaces  20 ,  22  of each projection  18  face in a generally upward direction and the side surfaces  24 ,  26  of each projection  18  face in a generally downward direction. Thus, it can be seen that the side surfaces  20 ,  22 , along with the end surface or crest  30 , of each projection  18  produce the scraping action against the adjacent surface of the block  72  as the wall  10  is moved vertically with respect to the block  72  in the direction of arrow A.  
      In the illustrated embodiment, the side surfaces  20 ,  22  of the projections  18  have slopes that are less than the slopes of the side surfaces  24 ,  26 . It is believed that this minimizes the likelihood of fill material being retained in the spaces between adjacent projections as the block  72  is being removed from the mold cavity  68 .  
      In the embodiment of  FIGS. 1-3 , the wall  10  and the projections  18  are of a unitary, monolithic construction. The wall  10  may be formed by machining the projections  18  into one surface of apiece material used to form the mold wall. In one specific implementation, the projections  18  are machined in a ½ inch thick piece of material (e.g., steel) to a depth of about ¼ inch. The width of each projection is about 0.87 inch at their respective bases  28  and about 0.19 inch at their respective end surfaces  30 .  
      In other embodiments, the projections may be separately formed and then coupled or otherwise mounted to the mold wall, such as by welding or with conventional releasable fasteners (e.g., bolts). If releasable fasteners are used, projections that are worn-out can be removed and replaced with new projections.  
      In still other embodiments, the walls  10 ,  10 ′ can be used as “inserts” for an existing mold. When used in this manner, the walls  10 ,  10 ′ are coupled to the interior surfaces of existing walls of a mold.  
      Explaining the operation of the apparatus  60 , according to one specific approach, and referring initially to  FIG. 4 , the mold  62  and the pallet  70  can be moved into place under the pusher plate  74 , such as by way of a conveyor (not shown). The mold  62  is then loaded with a flowable, composite cementitious fill material through the open top of the mold. Composite fill material generally comprises, for example, aggregate material (e.g., gravel or stone chippings), sand, mortar, cement, and water, as generally known in the art. The fill material also may comprise other ingredients, such as pigments, plasticizers, and other fill materials, depending upon the particular application.  
      The mold  62 , or the pallet  70 , or a combination of both may be vibrated for suitable period of time to assist in the loading of the mold  62  with fill material. The pusher plate  74  is then lowered into the mold cavity  68 , against the top of the mass of fill material. The pusher plate  74  desirably is sized so as to provide a slight clearance with the projections  18  of the walls  10 ,  10 ′ when lowered into the mold cavity  68 . Additional vibration, together with the pressure exerted by the pusher plate  74  acts to densify the fill material and form the final shape of the block  72 .  
      After the block  72  is formed, the formed, uncured block  72  is removed from the mold such as by raising the mold  62  (as indicated by arrow A in  FIG. 5 ), while maintaining the vertical position of the pusher plate  74  and the pallet  70  so that the block  72  is pushed through the open bottom of the mold  62 . Alternatively, the block  72  can be pushed through the mold  62  by moving the pusher plate  74  through the mold  62 , while simultaneously lowering the pallet and maintaining the vertical position of the mold  62 . In either case, the action of stripping the block  72  from the mold  62  creates a roughened texture of the walls of the block that contact the projections  18  on walls  10 ,  10 ′. Since the mold is not configured to retain fill material for the purpose of creating the roughened surfaces of the block, unlike some prior art devices, the mold  62  does not require frequent stoppages in production to clear material from the walls of the mold.  
      Because the projections  18  do not retain fill material as the block  72  is stripped from the mold  62 , the block  72  maintains its dimensional tolerances. Thus, the roughened surfaces of the block  72  will be substantially perpendicular to the top and bottom of the block  72  and the block  72  will have a substantially constant cross-sectional profile from top to bottom.  
      The mold filling time, the vibration times and the amount of pressure exerted by the pusher plate  74  are determined by the particular block-forming machine being used, and the particular application. After the block is removed from the mold  62 , it may be transported to a suitable curing station, where it can be cured using any suitable curing technique, such as, air curing, autoclaving, steam curing, or mist curing.  
      The mold  62  may be adapted for use with any conventional block-forming machine.  
      Referring to  FIG. 7 , there is shown an apparatus  100  for forming two masonry blocks. In this embodiment, the apparatus  100  comprises a mold  102  supported on a suitable support surface, such as a pallet  104 . The mold  102  comprises vertically upright opposed forward and rear walls  10 ,  10 ′, respectively, and opposed side walls (not shown), extending between respective ends of the forward and rear walls  10 ,  10 ′. The walls of the mold  102  define a first mold cavity  106  and a second mold cavity  108 , separated by a vertically upright separating wall  110  (also referred to herein as a separating member), which extends between the side walls of the mold  102 . The first and second mold cavities  106 ,  108  are adapted to receive fill material for forming first and second blocks  116 ,  118 , respectively. A first pusher plate  112  and a second pusher plate  114  may be provided to facilitate compression of the fill material in the first and second mold cavities  106 ,  108 , respectively, and removal of the blocks from their respective mold cavities. Other configurations for mold  102  also may be used. For example, the first and second mold cavities  106 ,  108 , respectively may have different shapes so that blocks of different shapes can be made.  
      The separating wall  110  has a first major surface  120  and a second major surface  122 . As shown, the first major surface  120  helps define and serves as an interior surface of the first mold cavity  106  while the second major surface  122  helps define and serves as an interior surface of the second mold cavity  108 . The wall  10  has a plurality of projections  18  extending into the first mold cavity  106  for texturing an adjacent surface of the first block  116 . Similarly, the wall  10 ′ has a plurality of projections  18  extending into the second mold cavity  108  for texturing an adjacent surface of the second block  118 . In addition, both the first and second major surfaces  120 ,  122  of the separating wall  110  have a plurality of projections  18  extending into their associated mold cavities  106 ,  108 , respectively, for texturing respective adjacent surfaces of blocks  116 ,  118 . Thus, the apparatus  100  of  FIG. 7  can be used to produce two blocks, each having at least two opposed roughened surfaces.  
      In other embodiments, either the wall  10 , the wall  10 ′, or both of the walls  10 ,  10 ′ can be conventional mold walls (i.e., walls without projections  18 ), in which case one or both blocks would have only a single roughened surface formed by the separating wall  110 . Still alternatively, more than two walls of one or both mold cavities  106 ,  108  can be provided with projections  18  to produce roughened surfaces on more than two surfaces of a block. Also, only one surface  120  or  122  of the separating wall  110  may be provided with projections  18 , in which case one of the two blocks produced would have a different number of roughened walls than the other.  
      The walls  10 ,  10 ′ ( FIGS. 4-7 ), as well as wall  110  ( FIG. 7 ), are “self-cleaning” in that they are configured to avoid retaining block-forming material as the uncured block(s) are removed from the molds. Consequently, increased production throughout can be achieved because the mold walls do not have to be cleaned between each cycle. In addition, as noted above, because the projections do not retain block-forming material, the resulting blocks maintain their dimensional tolerances.  
      The invention has been described with respect to particular embodiments and modes of action for illustrative purposes only. The present invention may be subject to many modifications and changes without departing from the spirit or essential characteristics thereof. We therefore claim as our invention all such modifications as come within the scope of the following claims.