Abstract:
An improved volumetric cement mixer has bins, containers, and troughs formed from UHMW material reinforced with expanded metal. A metal skeletal frame supports the UHMW walls of the sand and gravel bins, while mininizing the weight of the mixer. The UHMW troughs for the boot mixer and discharge chute improve product flow and mixing, and simplifies cleaning of the troughs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. § 119 of a provisional application Ser. No. 60/773,517 filed Feb. 15, 2006, which application is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Generally, there are two types of cement mixing systems used in the cement industry, a continuous volumetric mixer, or a batch ready mix mixer. A volumetric mixer normally includes separate bins for holding the sand, aggregate, and Portland cement which are discharged onto a conveyor and transported in a dry state to a mixing boot or chute wherein water is added to form the concrete mix. In comparison, a ready mix mixer, such as a cement truck, includes a rotating drum or tank wherein the sand, aggregate, Portland cement, and water are mixed before discharge into a chute. A volumetric mixer is normally stationed at the job site, wherein the ingredients are loaded into the respective mixer bins, whereas a ready mix mixer travels to the job site as the ingredients are mixed. 
         [0003]    Prior art volumetric mixer bins normally are constructed of steel. Stainless steel bins are also known, though are much more costly than steel bins. A major problem with steel bins is rusting, caused by the corrosive nature of sand, limestone, other aggregates, and Portland cement. Rusting in the bin leads to reduced product flow and bridging. Therefore, the prior art volumetric mixer bins include vibrators to prevent bridging and maintain product flow. 
         [0004]    A primary objective of the present application is the provision of an improved volumetric mixer which overcomes the problems of the prior art. 
         [0005]    Another objective of the present application is the provision of a volumetric cement mixer having non-corrosive bins. 
         [0006]    Still another objective of the present application is the provision of an improved volumetric cement mixer having bins which maintain product flow and prevent bridging of product within the bins, without the use of vibrators. 
         [0007]    A further objective of the present application is the provision of an improved volumetric cement mixer having reinforced plastic bins, mixing boot, and discharge chute. 
         [0008]    Yet another objective of the present application is the provision of an improved volumetric cement mixer having bins and a mixing boot made from UHMW plastic with expanded metal imbedded therein. 
         [0009]    A further objective of the present application is the provision of an improved volumetric cement mixer having bins, a mixing boot, and discharge chute which are strong, lightweight, and durable in use. 
         [0010]    These and other objectives will become apparent from the following description of the invention. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed towards an improved volumetric cement mixer. The mixer includes multiple bins for the concrete ingredients, including a sand bin, an aggregate bin, and a Portland cement bin. The bins may be formed as a large container with dividing walls or as separate independent bins. The walls of the bin are made from reinforced plastic, which preferably includes expanded metal bonded between two layers of ultra high molecular weight (UHMW) plastic. The bins are supported by a metal skeletal frame so as to provide a strong, yet lightweight structure for the storage of the concrete ingredients. 
         [0012]    The mixer also includes a mixing boot wherein the ingredients are mixed with water and a discharge chute. Preferably, the mixing boot and discharge chute are also made of the same reinforced material having expanded metal sandwiched between two layers of UHMW plastic. 
         [0013]    The reinforced plastic has a lower coefficient of friction than steel or stainless steel conventionally used in cement mixers. Therefore, the reinforced plastic eliminates bridging problems in the bins, reduces the power requirements for mixing and discharge, and simplifies clean up. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side elevation view of one embodiment of the volumetric cement mixer of the present invention. 
           [0015]      FIG. 2  is a perspective schematic of the sand and aggregate bins of the mixer according to the present invention. 
           [0016]      FIG. 3  is a top plan schematic of the sand and aggregate bins of the mixer. 
           [0017]      FIG. 4  is a sectional view taken along lines  4 - 4  of  FIG. 2 . 
           [0018]      FIG. 5  is an end view of the mixer boot, which is similar to an end view of the discharge chute, showing the UHMW reinforced plastic used in the cement mixer according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0019]    The volumetric cement mixer is generally designated in  FIG. 1  by the reference numeral  10 . The cement mixer  10  is shown to be mounted on a truck chassis so as to be portable. However, it is understood that the volumetric cement mixer of the present invention may also be built at or transported to a job site and set on the ground or other support structure so as to be non-portable. 
         [0020]    The cement mixer  10  includes a pair of bins  12 ,  14  for holding sand and gravel or other aggregate, as well as a separate container or bin  16  for storing Portland cement. The bins  12 ,  14  and container  16  are positioned above a conveyor  18  for receiving the concrete ingredients or materials from the bins  12 ,  14  and container  16 . The conveyor  18  discharges the sand, gravel and Portland cement into a mixer boot  20 . A water tank  22  supplies water to the mixer boot  20 . An auger (not shown) resides within the mixer boot  20 , and is driven by any convenient means so as to mix the sand, gravel, cement, and water within the boot  20 . When mixing is complete, the wet concrete is expelled through and outlet chute  24  on the end of the boot  20 . 
         [0021]    The walls of the bins  12 ,  14  are made from reinforced ultra high molecular weight (UHMW) plastic. More particularly, the walls of the bins  12 ,  14  include two layers of UHMW plastic with expanded metal embedded therein so as to provide structural support to the walls. The expanded metal also minimizes thermal effects on the UHMW material, such as shrinkage in cold weather and expansion in hot weather. The reinforced UHMW walls are supported by a metal skeletal frame  26 . The frame  26  provides structural integrity to the bins  12 ,  14  while minimizing the weight of the mixer  10 . 
         [0022]    As seen in  FIG. 2 , the bins  12 ,  14  may be formed from an enlarged container having opposite side walls  28 , opposite end walls  30 , and a central dividing wall  32 . Preferably, the side walls  28  included lower sloped portions  34  which allow the sand and gravel to flow by gravity through lower openings  36 ,  38  into the conveyor  18 . As seen in  FIG. 3 , support braces  40  extend between the central dividing wall  32  and the opposite side walls  28 . 
         [0023]    As an alternative construction, the bins  12 ,  14  can be formed separately from one another, with each bin having its own perimeter walls. 
         [0024]    The reinforced UHMW walls with embedded expanded metal may also be used as the walls of the Portland cement container  16 . Furthermore, the lower troughs  42 ,  44  of the mixer boot  20  and discharge chute  24  are preferably made of similar UHMW material layers with expanded metal sandwiched therein. As seen in  FIG. 5 , the reinforced material is preferably formed from an outer plastic layer  46 , and inner plastic layer  48  and a sheet of expanded metal  50  embedded between the layers  46  and  48  and bonded thereto. The openings in the expanded metal facilitate bonding of the UHMW plastic to the embedded metal. It is understood that the reinforced walls  28 ,  30 ,  32  have a similar structure as shown in  FIG. 5 , though flat or planar, rather than curved. 
         [0025]    The reinforced UHMW walls  28 ,  30  and  32  of the bins  12 ,  14  minimizes or eliminates bridging of material within the bins, and eliminates the need for vibrators for breaking up such bridge product bridging. The plastic surface of the UHMW material used for the bins  12 ,  14 , container  16 , boot trough  42 , and discharge chute trough  44  is not subject to corrosion and simplifiers cleanup of the surfaces of the cement mixer  10 . The reduced coefficient of friction of the plastic surface also minimizes the auger horse power requirements in the mixing boot  20 , since the mixture moves or flows more readily through the boot, as compared to the prior art boots. The embedded expanded metal in the reinforced UHMW material provides additional rigidity for the boot trough  42 , as compared to prior art rubber boots, and thus provides for more uniform mixing of the ingredients by the auger. 
         [0026]    Thus, the improved volumetric cement mixer of the present invention accomplishes at least all of the stated objectives.