Abstract:
A method of forming a concrete stamp. The method includes forming a positive mold representative of a natural surface and providing a mold base having a first portion and a second portion. The method further includes attaching the positive mold to the first portion and positioning the second portion in contact with the first portion to at least partially define a cavity. The method also includes injecting a material into the cavity.

Description:
BACKGROUND  
       [0001]     The present invention relates to a concrete stamp suited to forming patterns in concrete. More particularly, the present invention relates to a method of manufacturing a concrete stamp suited to forming patterns in concrete.  
         [0002]     Concrete stamps have become very popular in recent years. The stamps are used to produce the appearance of a natural surface (e.g., slate, flagstone, brick, cobblestone, wood, and the like) in a poured concrete surface. The stamps are pressed into the concrete as the concrete sets to create the appearance of the natural surface. Coloring agents can be applied to further enhance the illusion of a natural surface.  
         [0003]     Prior concrete stamps were manufactured by creating a mold around the natural surface to be copied, and filling that mold with a setting material, such as thermosetting plastic. After several hours, the material sets and is removed from the natural surface. This process is very slow and costly. In addition, it is difficult to quickly and inexpensively create multiple stamps that include varying patterns.  
       SUMMARY  
       [0004]     The present invention provides a method of forming a concrete stamp. The method includes forming a positive mold representative of a natural surface and providing a mold base having a first portion and a second portion. The method further includes attaching the positive mold to the first portion and positioning the second portion in contact with the first portion to at least partially define a cavity. The method also includes injecting a material into the cavity.  
         [0005]     The invention also provides a method of forming a concrete stamp. The method includes forming a negative mold representative of a natural surface, forming a positive pattern using the negative mold, and forming a casting mold using the positive pattern. The method also includes casting a mold insert using the casting mold, the mold insert including a metal portion, and attaching the mold insert to a first mold portion. The method further includes positioning a second mold portion in contact with the first mold portion to define a cavity and injecting a plastic material into the cavity at high pressure.  
         [0006]     The invention also provides a mold suitable for use in injection-molding a concrete stamp. The mold includes a first mold portion, a second mold portion, and an insert that includes a cast portion having a surface that is a substantial copy of at least a portion of a natural surface. The insert is coupled to the second mold portion. The first mold portion, the second mold portion, and the insert cooperate to define at least a portion of a cavity corresponding to the concrete stamp.  
         [0007]     The invention further provides a method of forming a concrete stamp. The method includes forming a negative mold representative of a natural surface and forming a positive pattern using the negative mold by positioning a thermosetting material in intimate contact with a surface to be copied such that the negative mold is a substantial copy of the surface to be copied. The method also includes forming a sand casting mold using the positive pattern, casting a first metal mold insert using the casting mold, and forming a second metal mold insert representative of a second natural surface different from the first natural surface. The method further includes attaching one of the first metal mold insert and the second metal mold insert to a first mold portion and forming a third mold insert corresponding to the one of the first metal mold insert and the second metal mold insert attached to the first mold portion. The method also includes attaching the third mold insert to a second mold portion, positioning the second mold portion in contact with the first mold portion to define a cavity, and injecting a plastic material into the cavity at high pressure using an injection-molding process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The description particularly refers to the accompanying figures in which:  
         [0009]      FIG. 1  is a perspective view of a natural surface to be copied;  
         [0010]      FIG. 2  is a perspective view of a first mold;  
         [0011]      FIG. 3  is a perspective view of a first positive pattern;  
         [0012]      FIG. 4  is a schematic illustration of a casting mold;  
         [0013]      FIG. 5  is a perspective view of an injection-molding mold including a mold insert;  
         [0014]      FIG. 6  is a perspective view of a concrete stamp in use;  
         [0015]      FIG. 7  is a flowchart illustrating one manufacturing process suitable for use in manufacturing a concrete stamp; and  
         [0016]      FIG. 8  illustrates another concrete stamp having a second surface texture. 
     
    
       [0017]     Before any embodiments of the invention are explained, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof is meant to encompass the items listed thereafter and equivalence thereof as well as additional items. The terms “connected,” “coupled,” and “mounted” and variations thereof are used broadly and encompass direct and indirect connections couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.  
       DETAILED DESCRIPTION  
       [0018]     With reference to  FIG. 1 , a walkway  10  formed from an arrangement of natural stones  15  is illustrated.  FIG. 1  illustrates one pattern and type of stone  15  that can be used for such a walkway  10  with many other patterns and textures being possible. A walkway  10  of this type can be expensive and time consuming to build, as the stones  15  must be individually placed and fit, usually by a skilled artisan.  
         [0019]     A walkway  12  (shown in  FIG. 6 ) that appears nearly identical to the walkway  10  of  FIG. 1  can be produced quickly and inexpensively using a concrete stamp  20  as illustrated in  FIG. 6  and formed as described herein. The stamp  20 , illustrated in  FIG. 6 , matches the shape of one of the stones  15  in the walkway  10  of  FIG. 1 . Additional stamps  20  could be produced to match other stones  15 , or multiple stones  15  could be copied in one stamp  20  to allow for the creation of many different patterns. For example, one construction uses a stamp  25  that copies cobblestone, as shown in  FIG. 8 . In this construction, a large stamp  25  that includes multiple cobblestone copies is employed. As one of ordinary skill will realize, many different size patterns could be employed. The size of the stamp being employed depends on many factors including the pattern being copied.  
         [0020]     The stamps  20  are manufactured such that they include at least one surface that is a substantial copy of an existing natural surface (e.g., slate, flagstone, cobblestone, brick, pave stones, granite, sandstone, wood, and the like). Thus, the surface of the stamp  20  appears to include wood grain, cracks, crevices, indentations, bumps, chips, and/or any other variations commonly found on natural surfaces. Generally, these features are somewhat random and are too complex to accurately model with a computer, or to machine with present machine tools. As such, the surfaces generally must be copied directly to be reproduced.  
         [0021]     To manufacture the concrete stamp  20  illustrated in  FIG. 6 , a mold  30  is first positioned around the natural surface to be copied. In this case a single stone  15  is being copied. However, in other constructions a square, rectangular or other shaped area may be copied. Once the mold  30  is positioned, a liquid material is pored into the mold  30 . The liquid material is of a viscosity and consistency that allows the liquid to flow into the many cracks, crevices, indentations, and other surface features of the stone  15 . Generally, a thermosetting plastic, such as polyurethane, is used as the liquid. Once the material sets, it defines a negative mold  35  that can be removed from the mold  30 . The negative mold  35 , illustrated in  FIG. 2 , is representative of the natural surface, in that low spots in the natural surface appear as high-spots in the mold  35 . In addition, the surface features and the surface texture is captured by the negative mold  35 .  
         [0022]     The negative mold  35  is used to make a positive pattern  40 , or copy of the original stone  15 , as shown in  FIG. 3 . Many materials can be used to form the positive pattern  40 . For example, thermosetting plastic could be poured into the mold  35  to produce the copy.  
         [0023]     In some constructions, the formation of the negative mold  35  and the pattern  40  can be omitted and the actual stone  15  itself is used as the positive pattern. Of course, this construction is limited to single stones  15  or simple patterns of stones.  
         [0024]     The pattern  40  is used to form a casting mold  45 , such as the sand-casting mold illustrated in  FIG. 4 . The pattern  40  is positioned within the sand-casting mold  45  and sand is distributed around the pattern  40 . The sand is such that it makes intimate contact with the surface features of the pattern  40 , thereby allowing for a fairly accurate reproduction of most of the surface features. Once the sand is positioned as desired in the two halves of the mold  45 , molten metal (e.g., aluminum, iron, steel, and the like) is poured into the mold  45  to form a mold insert  50 . In other constructions, other casting methods, such as investment casting, are employed.  
         [0025]     The mold insert  50  is removed from the mold  45  and machined if necessary to allow for its attachment to a first injection mold portion  55 , as illustrated in  FIG. 5 . In preferred constructions, a standard attachment portion is formed as part of, or is attached to, the second pattern  50 . The standard attachment portion allows the mold insert  50  to be inserted into the injection mold portion  55 . For example, a number of fasteners arranged in a predefined pattern could be employed to attach the mold insert  50  to the mold portion  55 . The use of a standard attachment portion allows for additional mold inserts to be manufactured and used with a common mold portion  55 .  
         [0026]     A second injection mold portion  60  is machined or otherwise formed to receive the mold insert  50  when the first mold portion  55  and the second mold portion  60  are closed. Thus, the first mold portion  55  and the second mold portion  60  cooperate to define an injection mold  65 . For complex patterns, such as the one illustrated in  FIG. 5 , a second cast insert  68  may be required. The second cast insert follows the outer contour of the insert  50 , but is offset such that the insert  50  acts as a core, while the second cast insert  68  defines the outer most surface of a cavity  70 . The second cast insert  68  is made in much the same manner as the mold insert  50 . In addition, the second cast insert  68  is installed into the second mold portion  60  in much the same manner as the mold portion  55 .  
         [0027]     In the closed position, the two mold portions  55 ,  60 , the pattern  50 , and the second cast insert  68  cooperate to substantially define the cavity  70  that corresponds to the finished concrete stamp  20 . As such, additional features, such as handles  72 , may be defined in one or both of the mold portions  55 ,  60  such that the completed concrete stamp  20  includes these features.  
         [0028]     With the mold portions  55 ,  60  positioned in the closed position, plastic, in a substantially liquid state is injected into the mold  65  under high-pressure. The plastic fills the cavity  70  and begins to cool and solidify. Once solidified, the mold  65  is opened, the plastic concrete stamp  20  is removed, and the injection molding process is repeated. Thus, the injection molding process allows for the mass production of concrete stamps  20  that have substantially identical surface patterns.  
         [0029]     To manufacture concrete stamps  20  having a different surface pattern, the mold  65  is opened and the mold insert  50  is removed. A second mold insert (not shown) having a surface texture corresponding to the different surface pattern desired is installed in the mold  65 . The mold portions  55 ,  60  are then closed and the injection molding process continues. Thus, the process described is able to quickly transition from manufacturing a concrete stamp  20  having a first surface texture, to a concrete stamp having a second surface texture, such as the concrete stamp  25  shown in  FIG. 8 , with little loss in manufacturing time.  
         [0030]      FIG. 6  illustrates one of the concrete stamps in use to form the walkway  12 . The walkway  12  is similar to the walkway  10 , which is illustrated in  FIG. 1 . As shown, concrete is first poured and leveled. The stamps  20  are then positioned as desired on the concrete, depressed, and removed to leave a positive copy of the original stone  15 .  
         [0031]      FIG. 7  is a flowchart that illustrates the steps involved in making the concrete stamp  20 . The first step  75  is to determine if the actual surface being copied can be used as a pattern, or if it must first be copied. If it must be copied, the surface is framed and the negative mold  35  is made as shown at steps  80 ,  85 , and  90 . In the next step  95 , the positive pattern  40  is made using the negative mold  35 . The positive pattern  40 , or the actual stone, is then used to form the casting mold  45  at step  100 . The next step  105  is to cast the mold insert  50 . The mold insert  50  is then inserted into the mold  65 , as shown at step  110 , to allow injection molding to begin at step  115 .  
         [0032]     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.