Abstract:
A system for forming a cementitous slurry comprising at least water or other liquid and at least one flowable particulate mass such as sand or cement has computerized control of loading the ingredients into a mixing chamber. The mixing chamber has a scale that provides a signal indicating the current weight of the mixing chamber. The computer monitors the weight of the mixing chamber as these ingredients are individually loaded into the mixing chamber. When the desired weight of a particular ingredient has been loaded, the computer halts the delivery of that ingredient. Ingredients are loaded first at a relatively high rate, and then as the desired weight of material in the mixing chamber approaches, the rate slows.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part application filed under 37 CFR §53(b) claiming priority under 35 U.S.C. §120 of co-pending U.S. patent application Ser. No. 12/276,044 filed on Nov. 21, 2008, which is a regular application filed under 35 U.S.C. §111(a) claiming priority, under 35 U.S.C. §119(e)(1), of provisional application Ser. No. 60/991,116, previously filed Nov. 29, 2007 under 35 U.S.C. §111(b). 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention is directed to transportable mixing apparatus for cement operated at the construction site. 
       BRIEF DISCUSSION OF THE RELATED ART 
       [0003]    Gypsum is a frequently-employed material for constituting building floor underlayments and other non-structural purposes. Gypsum is to be distinguished from concrete in that it has a different chemical formulation and different characteristics after mixing and before hardening. One important difference is its high fire resistance compared to concrete&#39;s low resistance. 
         [0004]    Gypsum is formed by mixing water, gypsum powder, and sand in the correct proportions, and allowing the slurry so formed, to harden. Once mixing is complete, the gypsum slurry&#39;s useful life is very short (typically, less than 45 min.) as opposed to at least 90 min. for concrete. Therefore, gypsum must usually be mixed at the actual job site, whereas concrete can be mixed at a central plant and delivered to the job site. 
         [0005]    The mixed slurry is then poured into the desired area and quickly leveled. The slurry soon hardens into an underlayment forming the desired floor, or possibly other surface. 
         [0006]    Hardened gypsum material (hereafter “final product”) is a composite made up of a filler (i.e., sand), the gypsum powder binder, and a small amount of residual water. The binder glues the filler together to form a stable, fire-resistant material. 
         [0007]    To form the final product, water and gypsum powder are first mixed. Adding the filler, usually fine or coarse aggregates of sand, to the water and gypsum mixture, and then stifling the material for a suitable period completes the mixing process and produces a pourable slurry. Typically, 60-80% by weight of the final product is aggregate. 
         [0008]    Water is a key ingredient when producing the gypsum slurry. When water is mixed with gypsum a chemical process called hydration causes the slurry to harden to a solid final product with the gypsum binding the aggregates together. The water to gypsum ratio is a critical factor in determining the quality of the ultimately produced final product. Too much water reduces final product strength, while too little water will make the slurry difficult to work and shape into a desired configuration. Accordingly, it is important that the appropriate water to gypsum ratio be achieved when mixing the precursor slurry. 
         [0009]    Different applications require different hardness of the final product. The hardness is typically varied by adjusting the concentrations of sand and water relative to the concentration of gypsum in the slurry mixture. Typically, a greater relative concentration of gypsum results in greater underlayment hardness. Underlayment hardness is typically varied between 1,000 psi to 7000 psi, with more demanding applications (e.g., areas that will experience relatively high foot traffic) requiring a harder underlayment. 
         [0010]    It is often desirable to select the hardness for a particular installation since installations often require a specific hardness. For example, a floor intended to be covered by vinyl typically requires a hardness of 2,500 psi. Where a construction project requires a specific hardness of the underlayment, the contractor will usually prefer to provide underlayment with no more hardness than required so as to contain costs. However, accurately controlling the ingredient proportions for the underlayment has been difficult because measuring the amount of each of the ingredients being added is difficult to accurately control. Because of this inexact processes employed for creating and mixing gypsum underlayment, it is often highly difficult to produce a desired psi hardness with any degree of precision or accuracy, especially when attempted in the field. 
       SUMMARY OF THE INVENTION 
       [0011]    A system for forming a cementitous slurry comprising at least water or other liquid and at least one flowable particulate mass such as sand or cement uses a computer to control loading of the ingredients into a mixing chamber. The mixing chamber has a scale that provides a signal indicating the current weight of the mixing chamber. The computer monitors the weight of the mixing chamber as these ingredients are individually loaded into the mixing chamber. When the desired weight of a particular ingredient has been loaded, the computer halts the delivery of that ingredient. 
         [0012]    Such system delivers preselected weights of a liquid and at least a first particulate mass material to the mixing chamber. The system comprises at least sources for the liquid and the particulate mass and a mixing chamber. 
         [0013]    First and second delivery devices sequentially and separately transport the liquid and the at least one particulate mass material to the mixing chamber responsive to first and second delivery control signals. Each delivery control signal has a second value causing the associated delivery device to transport the associated material to the mixing chamber, and a first value stopping the associated delivery device from transporting the associated material to the mixing chamber. 
         [0014]    A scale supports at least a portion of the mixing chamber, and providing a mixer weight signal indicating the current weight of the mixing chamber. 
         [0015]    A controller receives from an external source such as an operator, a liquid weight signal encoding the preselected liquid weight, a first particulate mass weight signal encoding the preselected particulate mass weight, and the mixer weight signal from the scale. The controller records the current weight of the mixing chamber as the first starting mixer weight, and then provides the first delivery signal with the second value thereof to the first delivery device. Then the controller periodically records the current weight of the mixing chamber, and responsive to the current mixer weight less the first starting mixer weight equaling or exceeding one of the preselected liquid and particulate mass weights, provides the first delivery signal with the first value thereof to the first delivery device 
         [0016]    The controller also records the current weight of the mixing chamber as the second starting mixer weight, and provides the second delivery signal with the second value thereof to the second delivery device and periodically recording the current weight of the mixing chamber. Responsive to the current mixer weight less the second starting mixer weight equaling or exceeding the other of the preselected liquid and particulate mass weights, the controller provides the second delivery signal with the first value thereof to the second delivery device. 
         [0017]    In this way, precise weights of these two ingredients are delivered to the mixing chamber. 
         [0018]    Weight of a third ingredient loaded into the mixing chamber can be measured using the same mechanism. This makes the system particularly well suited for creating a gypsum slurry having preselected weights of water, gypsum powder, and sand as its ingredients. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    These and other features and a more thorough understanding of the present invention may be achieved by referring to the following description and claims, taken in conjunction with the accompanying drawings, wherein; 
           [0020]      FIG. 1  is a first side view of the portable cement mixing system of the present invention mounted on a flat-bed truck; 
           [0021]      FIG. 2  is a detailed side view, similar to  FIG. 1 , of the portable cement mixing system of the present invention; 
           [0022]      FIG. 3  is a detail side view, similar to  FIG. 1 , of the portable cement mixing system of the present invention showing different details of the invention; 
           [0023]      FIG. 4  is a side elevational view of the crane; 
           [0024]      FIG. 5  is a view illustrating the cement bin and auger; 
           [0025]      FIG. 6A  is a view illustrating an end view of the sand bin; 
           [0026]      FIG. 6B  is a view illustrating a side view of the sand bin; 
           [0027]      FIG. 7  is a view illustrating an end view of the mixer; 
           [0028]      FIG. 8  shows the side view of the mixer; 
           [0029]      FIG. 9  shows the mixer outlet; 
           [0030]      FIG. 10  shows the blender outlet; 
           [0031]      FIG. 11  shows the blender; 
           [0032]      FIG. 12  shows the end side view of the apparatus 
           [0033]      FIG. 13  shows a cross-section of the blender; 
           [0034]      FIG. 14  shows an end view of the blender and scales; and 
           [0035]      FIG. 15  shows a list of activities for precisely controlling the ingredient proportions of a cementitious slurry. 
           [0036]      FIG. 16  is a block diagram of a system for controlling operations pertaining to ingredient management and delivery of a cementitiuous slurry. 
           [0037]      FIGS. 17A ,  17 B and  17 C together comprise a flow chart for software or firmware executed by the system of  FIG. 16  for controlling the ingredient proportions of a cementitious slurry. 
           [0038]      FIG. 18  is a flow chart for software or firmware executed by the system of  FIG. 16  for controlling the delivery of a cementitious slurry to a job site. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]      FIGS. 1 ,  2  and  3  show the major elements of portable mixing system  100  mounted on a motorized vehicle  102 . Vehicle  102  has a bed  104  on which in mounted mixing system  100  for easy transport to any desired job site. Mixing system  100  may also be mounted on a trailer for towing to the job site. 
         [0040]    These arrangements provides mobility for system  100 . Either arrangement permits cement mixing system  100  to be transported to a construction site, where the ingredients of a cementitious slurry can be measured and mixed for placement at the desired site. “Cement” refers here to both gypsum powder used to form gypsum underlayer and to Portland cement, used to make concrete. 
         [0041]    System  100  delivers accurately measured weights of water, cement, and sand to a mixer  106 . Water stored in a tank  138  on vehicle  102  passes through a pipe or hose  128 A to a hydraulically operated pump  128 B. Another pipe or hose  128 D carries water from pump  128 B to mixer  106 . Pump  128 B may be considered a delivery device for the water required for the slurry to be formed. If flow of water is under control of a valve, then that valve would be a delivery device. 
         [0042]    Vehicle  102  includes a hydraulic pump  103  driven by the engine of vehicle  102  that supplies pressurized hydraulic fluid through a hose  105  for operating the motor  136 B that drives a cement auger  136  and a motor  140 F ( FIG. 6B ) that drives a sand conveyor  140 . Auger  136  and sand conveyor  140  and their cooperating element may also be considered delivery devices for the cement and sand ingredients of the slurry for system  100  to form. 
         [0043]    Pump  103  also provides pressurized hydraulic fluid for other devices forming a part of system  100 . Valves to be described later control the flow of the pressurized hydraulic fluid to motors  136 B and  140 F and to these other devices. 
         [0044]    Controller  116 , shown in more detail in  FIG. 16 , provides control of system  100 . Controller  116  includes all the components and capabilities of current general-purpose computers including a keyboard  116 A, display  116 B and printer  116 C. Keyboard  116 A permits the operator to enter a variety of inputs to the apparatus in the field. Display  116 B permits the operator to observe the various operating parameters and printer  116 C permits generating a permanent record of selected results during the operation of the apparatus. 
         [0045]    Keyboard  116 A can be used to input cement mixing parameters and other requirements and data. The parameters and data can relate to the hardness of the concrete, the weights of the various ingredients or any other parameter. Controller  116  is linked with, and individually controls, all operations of the apparatus. 
         [0046]    Controller  116  has a mixing control program stored in memory that orchestrates the operation of the entire system in response to stored cement mixing parameters and various measured information. This information permits controller  116  to precisely control the apparatus and also permits avoiding potential problems in the operation of the system, described hereinafter. 
         [0047]    The system operation can be initiated either manually by keyboard or by calling up a previously prepared and entered program, either of which provides data to controller  116  giving the desired concrete characteristic requirements. This includes the amounts of the various ingredients for the specified concrete characteristic. 
         [0048]    A setup mode of operation for controller  116  may prestore the various cement mixing parameters, formulae, processes, and related ingredient weights. These various formulae can be selected by the operator in the field by relatively simple keyboard entries. An alternate mode of operation permits the operator to change any or all of the above parameters in the field relating to different formulae by keyboard entries using interface  116 A. While more time consuming, this has the advantage of permitting use of the mixing system  100  for any operation within its operating range regardless of previously prestored data. This addition provides maximum flexibility in the field. 
         [0049]    Controller  116  interprets this data using the active program to determine the amount of weight of the various ingredients needed for each ingredient to achieve the desired hardened product characteristics. Using this approach the total will then indicate only the weight of the currently transferred ingredient and will be interpreted in that manner. 
         [0050]    All of the ingredients are mixed together in mixer  106 , described below. Mixer  106  mixes the various ingredients in the mixer for a predetermined period of time set by controller  116  and the mixing control program. In one method, the quantity of each ingredient is determined by weighing mixer  106  immediately before and while the ingredient is conveyed to the mixer  106 . Determining the weight of mixer  106  and its contents before the new ingredient is added and then subtracting their weight during the transfer will determine the amount of the ingredient that has been transferred. When the required weight of a given ingredient has been added, controller  116  stops that particular conveyor from conveying any more of that particular ingredient to mixer  106 . Typically, controller  116  directs mixer  106  to commence mixing when the required amount of water has been added to mixer  106 . Mixing continues while the other ingredients are added to mixer  106 . After the ingredients have all been added, further mixing for a predetermined time occurs until controller  116  sends a stop signal to mixer  106 . 
         [0051]    Mixing system  100  and controller  116  can also be configured to perform a number of other complementary activities. As one example, controller  116  may provide a signal that indicates the completion of mixing to the operator. This signal could include an audible signal, or a visual sign such as a light turning on, and similar arrangements. These are representative of the variety possible other responses. 
         [0052]    Controller  116  interfaces with all operating elements and precisely regulates the weight of any given ingredient (e.g., cement, water, sand, etc.) introduced into mixing system  100  as well as the various operating times and/or conditions. 
         [0053]    Controller  116  also monitors various parameters relating to the ongoing system status to avoid potential problems. This includes such things as monitoring the quantity of slurry in a blender  108 , described later. Mixer  106  transfers the mixed slurry from mixer  106  to blender  108  for further blending, and more importantly, for temporary storage or buffering, the flow of slurry to the placement site. Weight measuring means, described later, determines the weight of blender  108  and its contents to both avoid overfilling or underfilling. Controlling the weight of slurry in blender  108  avoids problems of spillage caused by overfilling and pumping problems arising from underfilling. 
         [0054]    Turning to  FIG. 16 , controller  116  therein is a data processing device such as a personal computer. Appropriate connections between controller  116  and various elements of the described apparatus tie the entire mixing system  100  together to permit controlling various operations of the system. 
         [0055]    The block diagram in  FIG. 16  for controller  116  shows major functional elements and the relevant signals supplied to and by controller  116  for controlling the operation of system  100 . It is conventional knowledge that computers comprise electrical circuits. As such, the portion of the invention that the controller  116  comprises is simply a complex electrical circuit the uses software or firmware to modify and control operations to provide the required functionality. 
         [0056]    One may consider the circuitry of controller  116  while executing the various instructions for controlling system  100 , as sequentially becoming one and then another of the various functional elements shown in  FIG. 16 . Thus, these functional elements typically exist sequentially rather than simultaneously, but that does not matter for purposes of defining the invention in apparatus claims. 
         [0057]    One should also note that the instructions for controller  116  are held in a physical memory  116 F. These instructions themselves create a unique physical structure in memory  116 F, in that the bytes comprising the instructions cause physical alterations of the memory cells themselves. Granted, the changes are sub-microscopic, but the patent law imposes no size limit on the subject matter of an invention. Thus, this programmed controller  116  is simply a complex machine and should be considered as such when evaluating claims addressing the control functions of controller  116 . 
         [0058]    As previously mentioned, controller  116  comprises the standard components for a computer: control element  116 D, display element  116 A, keyboard  116 B, and memory  116 F. Controller  116  also has communication functionality allowing sending and receiving of signals from external devices. Memory  116 F stores the various instructions that configure controller  116  as the various functional elements needed to operate system  100 . Memory  116 F includes as one element of the invention, a mixer weight register (MWR)  116 G that stores the current weight of mixer  106 . Memory  116 F also includes as a further element of the invention, a blender weight register (BWR)  116 H that stores the current weight of blender  108 . Registers  116 G and  116 H are of course physical structures within memory  116 F. 
         [0059]    Mixer weight monitor  116 C and blender weight monitor  116 E are two functional elements shown as a part of controller  116  in  FIG. 16  and that form a part of the invention. Weight monitors  116 C and  116 E actually are integral with control element  116 D, and exist only during the time that instructions specific to the stated weight monitor function execute within control element  116 D. 
         [0060]    Controller  116  uses the communication functionality to provide a water start/stop signal AW on a data path  108 A, a cement powder delivery fast/slow/stop signal AG on a data path  108 B, and a sand delivery fast/slow/stop signal AS on a data path  108 C. The AW, AG, and AS signals control the delivery of these masses in terms of speed at, and time during, which the specified ingredient is loaded into mixer  106 . 
         [0061]    As stated, mixer weight monitor  116 C comprises a functional element of controller  116 , and receives on paths  107 A and  107 B, MW 1  and MW 2  signals from scales  106 E. The MW 1  and MW 2  signals encode the weight of mixer  106 . Scales  106 E support mixer  106  and provide the MW 1  and MW 2  signals. Scales  106 E may comprise commonly available electronic load cells. Mixer weight monitor  116 C uses the MW 1  and MW 2  signals to continuously calculate the actual current weight of mixer  106 , and store that weight in MWR  116 G. 
         [0062]    Three different delivery means provide the different ingredients to mixer  106 . The ingredients for this embodiment include cement powder (previously defined as gypsum or Portland cement), water, and sand. Controller  116  directs the delivery means to provide the ingredients in the proper weights and order to mixer  106  where they are mixed together. Controller  116  interfaces with and controls the operation of, mixer  106  and the various ingredient conveyors. Controller  116  controls each conveyor device sequentially and determines that the required quantity of each ingredient is transferred to mixer  106  as previously described. 
         [0063]    Mixer  106  is shown in  FIGS. 7-9 . Here various ingredients are mixed together within two interfacing cylindrically shaped segments  106 A which together form a double drum housing having a  10  cubic foot capacity. 
         [0064]    Two rotors  106 C, one located within each segment  106 A, are each powered by a hydraulic motor  106 B attached to one end of each rotor. Each rotor  106 C has three equally spaced outwardly extending paddles  106 D which counter rotate relative to an adjacent rotor to completely mix any ingredients located within interfacing drum segments  106 A. Interfacing drum segments  106 A contain a volume of about 10 cubic feet. While motors  106 B operate hydraulically using power provided by vehicle  102 , other power sources and motor types can be employed. 
         [0065]    Conveyors  136  and  140  ( FIGS. 5 and 6B ), described hereinafter, transport their respective ingredients into the open top of mixer  106 .  FIG. 8  shows the two supporting scales  106 E located at opposite ends of mixer  106  for monitoring mixer  106  weight. With this arrangement, scales  106 E form weight sensing means for measuring the weight of mixer  106  and any ingredients within segments  106 A. Scales  106 E send their outputs on signal paths  107 A and  107 B to mixer weight monitor  116 C, which interprets the mixer weight signals and stores the latest mixer weight in memory  116 F at the MWR location  116 G. 
         [0066]    As will be explained in connection with the flow chart of  FIG. 17 , controller  116  monitors the weight of mixer  106  while ingredients are added. Recording (or zeroing) the starting weight held in MWR location  116 G, and then monitoring the current weight of mixer  106  while an ingredient is added, allows the weight of this ingredient in mixer  106  to be determined in real time. When the required weight of an ingredient has been added to the mixer  106 , control module  116 D halts flow of the ingredient to mixer  106  on the pertinent one of signal paths  108 A,  108 B, or  108 C. 
         [0067]    The MX signal on path  108 E from control element  106 D controls mixer operation. The MX signal has in this embodiment, three values that cause mixer  106  to mix either fast or slow. Stopping the mixer  106  is normally under manual control. 
         [0068]    After adding the ingredients and the mixing of them is finished, the slurry is ready for dispensing. Mixer  106  has an outlet  142  allowing the contents of mixer  106  to empty into a blender  144 . A cover  142 A operated by a hydraulic cylinder  142 C with a ram or piston  142 B, opens and closes outlet  142 . With piston  142 B extended from cylinder  142 C as shown in  FIG. 8 , cover  142 A seals mixer outlet  142  preventing slurry flow from mixer  106 . When cylinder  142 C retracts piston  142 B, outlet  142  opens to allow slurry flow into blender  144 . Outlet  142  is on the low side of mixer  106 , thereby permitting slurry to flow under gravity from mixer  106  through outlet  142  into blender  144 . 
         [0069]    The MV signal on path  108 D from control element  106 D sets the position of piston  142 B. In the simplest type of control, control element  106 D simply holds outlet  142  either open or closed. In this way, control element  106 D can control the flow of slurry from mixer  106  into blender  144 , and the slurry level in blender  144 . 
         [0070]    Blender  144  is shown in  FIGS. 10-14 . Blender  144  comprises a hopper for holding slurry temporarily until delivered for placement. Blender  144  receives the slurry mixture flow from mixer outlet  142  into an upper opening  144 E when cover  142 A of mixer  106  is moved from outlet  142 . Blender  144  has a hydraulic motor  144 A that drives a shaft  144 B by chain  144 B  1  to rotate paddles  144 C to further stir the slurry to keep it fluid and the solids properly suspended. Motor  144 A operates under control of a BM signal on path  108 F that has a first value that commands motor  144 A to turn paddles  144 C rapidly, for slow turning of paddles  144 C, and a third that stops paddles  144 C. 
         [0071]    The slurry exits through outlet  144 D propelled by motor  144 H driving a pump  144 G which delivers the slurry to the emplacement site through a hose or other conduit  144 G. Controller  116  provides a BP signal on path  108 G. The BP signal has a first value that enable pump  144 G to operate under control of the person who is directing the delivery of slurry to the point of deposition. When slurry is needed for deposition that person can use a separate control (not shown) for activating pump  144 G. A second value of the BP signal disables pump  144 G. 
         [0072]    An electronic scale  144 F is arranged to determine the weight of blender  144  and its contents. Scale  144 F provides a blender weight signal BW on a signal path  107 C to the blender weight monitor  116 C, see  FIGS. 14 and 16 . 
         [0073]    Controller  116  operates cover  142 C, scale  144 F, and pump  144 G to assure that the level of slurry in blender  144  does neither overflow nor fall so low that air can enter pump  144 G. Controller  116  further operates to prevent pump  144 G operation when no more slurry is available in mixer  106  and the level of slurry in blender  144  will allow air to enter pump  144 G. 
         [0074]    As shown in  FIGS. 1-3 , a water supply system  128  provides water to mixer  106 . Water supply system  128  includes a reservoir  138  with a  200  gallon capacity, for example. It is coupled to mixer  106  through pipe  128 A, pump  128 B, and pipe  128 C. Cap  138 A, which mates with an opening on the top of reservoir  138 , provides an upper opening for filling the reservoir. 
         [0075]    Water pump  128 B uses hydraulic power to pump water from reservoir  138  to mixer  106 . A water pump control (W) signal is carried from control element  116 D on a signal path  108 A to control the operation of pump  128 B. In one embodiment, the W signal may have three levels, pump  128 B fast, pump slow, and pump off when operating to supply water to mixer  106 . In this way control element  116 D can turn pump  128 B on and off and control the rate at which water is added to mixer  106 . 
         [0076]    Cement handling device  120  shown in  FIG. 4 , transfers cement from cement bags  118  to cement bin  134  prior to operating the apparatus to load mixer  106 . Cement handling device  120  transports individual cement bags  118  from bed  104  to cement bin  134 . Cement bags  118  are conventional cement bags, each containing a predetermined amount of mixing-ready gypsum or Portland cement powder. Bags  118  are positioned on bed  104  in a location accessible by crane  126 , as described hereinafter. 
         [0077]    As described hereinbefore, device  120  pre-loads bin  134  with bags  118  stored on bed  104  before operating mixing system  100 . Device  120  has a base  124 , a boom  126  and a two axis boom controller  129 . The functions of device  120  can be performed, for example, by the Auto Crane, model  8406 H telescoping crane. 
         [0078]    Boom  126  can be inclined to different angles around generally horizontally oriented pivot axis  126 A by a hydraulically powered cylinder  126 C and slewed hydraulically by rotating mount  126 B under manual control using two axis controller  129 . Pump  103  provides pressurized hydraulic fluid to operate crane  120 . Inclining boom  126  at varying angles changes the horizontal spacing of the object being transported by device  120  from mount  126 B. These two degrees of freedom of movement of the boom  126  with respect to bed  104  permits the boom to transfer cement bags  118  both on and off bed  104  of vehicle  102  to cement bin  134 . 
         [0079]    Boom  126  has on the end thereof, a line  130  which suspends each cement bag  118 . Line  130  may be rope, metal wire, polymeric fibers, or any other material capable of extending from the boom  126  and securing a bag  118  and having the necessary strength to support the bag. A proximal end of line  130  opposite bag  118  is wound about a spool  132  driven by a hydraulic motor to extend or retract the line  130 . The opposite, distal end of line  130  terminates in hook  126 C. Any other arrangement that can readily capture a concrete bag  118 , however, can be used. Valves control the flow of hydraulic fluid for operating cylindrical  126 C and slewing boom  126 . 
         [0080]    While device  120  is shown as using a boom for lifting and carrying bags  118 , other mechanisms capable of providing the desired two degree of freedom movement for bags  118  may also provide this function. 
         [0081]    Cement bin  134 , shown in  FIG. 5 , can have a capacity of 70 cubic feet. Cement bin  134  has a rectangular upper opening  134 A, and the cross-rotational area is gradually reduced downwardly along tapered portion  134 B. Upward opening  134 A is located and oriented to receive the contents of a cement bag  118  transported by boom  126 . A bag  118  is positioned above upward opening  134 A and lowered into the opening  134 A where the bag is cut open by the inverted V structure  134 C. The contents of bag  118  then fall into cement bin  134 . Bin  134  should be loaded with as many bags  118  as necessary for the next slurry batch. Cement bags  118  can, alternatively be loaded for transfer to mixer  106  through an optional port  134 D. 
         [0082]    Cement bin  134  works in conjunction with a cement conveyor  136  to transfer cement from bin  134  to mixer  106 . Conveyor  136  is shown as having a rotating auger  136 A that moves the cement from bin  134  to mixer  106 . 
         [0083]    Auger  136 A is powered by a hydraulic motor  136 B with oil from pump  103  supplied by hose  105 . An AG signal, see  FIG. 5 , provided by control element  116 D to motor  136 B, governs the speed of motor  136 B. In one embodiment, the AG signal can specify fast, slow, and stopped operation for motor  136 B. The AG signal may operate a valve for example that controls flow rate of hydraulic fluid from hose  105  to hydraulic motor  136 B. While conveyor  136  is shown as utilizing an auger  136 A to transfer cement to mixer  106 , any other appropriate apparatus and power source capable of transporting cement from bin  122  to mixer  106  can be utilized. 
         [0084]    As shown in  FIGS. 1-3 , a water supply system  128  provides water to mixer  106 . Water supply system  128  includes a reservoir  138  with a  200  gallon capacity, for example. It is coupled to mixer  106  through pipe  128 A, pump  128 B, and pipe  128 C. Cap  138 A, which mates with an opening on the top of reservoir  138 , provides an opening for filling the reservoir. 
         [0085]    Hydraulically powered water pump  128 B pumps water from reservoir  138  to mixer  106 . The water (AW) signal is carried from control element  116 D on a signal path  108 A to control the operation of pump  128 B. In one embodiment, the AW signal may have three levels, pump  138 C fast, pump slow, and pump off when operating to supply water to mixer  106 . In this way control element  116 D can turn pump  138 C on and off and control the rate at which water is added to mixer  106 . 
         [0086]    Sand conveyor system  112 , shown as part of an overall system in  FIGS. 2 and 3  and shown separately in  FIGS. 6A and 6B , is used to transfer sand or a similar ingredient and/or filler (e.g., crushed limestone, gravel, crushed recycled concrete, or similar material) to mixer  106 . Sand conveyor system  112  includes a sand bin  140 A that in the embodiment shown is detached from vehicle  102 . Sand bin  140 A is mounted on four legs  140 B and may have a capacity of 125 cubic feet. 
         [0087]    Sand bin  140 A has an upper opening  140 C with downwardly and inwardly inclining sides and a bottom opening  140 E. A conveyor arm  140  extends from below the bottom opening  140 E to above upper mixer opening  106 F. Conveyor belt  140 B extends along the length of arm  140  from one end to the other and is driven by a hydraulic motor  140 F mounted at the bottom of arm  140  at a speed set by the AS signal. In the embodiment shown, motor  140 F has fast and slow speeds and a stopped mode, specified by fast, slow, and stop values for the AS signal. 
         [0088]    Motor  140 F drives the belt in the direction which will convey sand from below sand bin  140 A to above mixer  106 . The sand reservoir is shown located adjacent vehicle  102 , but it could be mounted on bed  104  of vehicle  102 . Vehicle  102  carries a valve  107  (see  FIG. 3 ) that receives the AS signal on path  108 C from control element  116 D. The AS signal controls the setting of valve  107  to set motor  140 F speed at either the fast or slow speed, or to stop motor  140 F. 
         [0089]    If conveyor  140  is of the type that is detached from vehicle  102 , then a detachable hydraulic hose  140 G connects from a hydraulic valve  107  to motor  140 F. Signal path  108 C carries the start/stop signal S to motor  140 F. In this way, controller  116 D can turn the motor  140 F on or off as required to transfer the amount of sand required by the program and as measured by scales  106 E. 
         [0090]    Printer  116 C can be used to record all relevant parameters during system operation for the particular mixture being produced by mixing system  100 . This record can include all of the above data fields and all related concrete parameters. For example, these records can including the date and selected time intervals to record the date, the water weight, the cement weight, the sand weight or any other relevant system parameters. 
         [0091]    System  100  can be configured to permit introduction of additional ingredients into the mixture for other products. These can include such things as fly ash, super elasticizers, retarding admixtures, accelerating admixtures, and other ingredients related to the particular product being produced. 
         [0092]      FIG. 15  is a chart which illustrates the sequence of a typical procedure for a cement mixing method in accordance with the present invention. Alternatively, the various target weights can be given. Such an alternative method essentially mirrors the procedures shown in  FIG. 15 . 
         [0093]    The Batch Set Procedure begins at  202  of  FIG. 15 , the Select batch design step, Example  1 . 9  mix. In this step the user inputs desired concrete characteristics data into the system controller  116  using keyboard  116 A. Controller  116  interprets this data to determine the required weight of each ingredient. In accordance with one example, the program requires that the final concrete product have a hardness of 2,500 psi. Based on such a requirement, controller  116  calculates predetermined volumes for all of the required ingredients. In the example, these ingredients are, sequentially, water, the cement product and sand. Controller  116  then converts the volumes calculated into a weight for each ingredient. An inflow rate of water is initiated based upon target weight for the initial water component. This initial flow rate is followed by a slow target rate where the ingredient is fed into the mixer at a slower rate to avoid an excessive amount being introduced. This is followed by the trim weight rate of flow necessary to achieve the final required weight. The target weight, slow target weight and trim weight are shown successively for water  140 #,  120 # and  5 #. The flow rates for a cement product are  320 #,  280 # and  5 #, and for sand are  760 #,  720 # and  5 #. 
         [0094]    A required mix time of 30 seconds, for the example, is also determined by controller  116 . These weights and mixing time are merely by way of example and are different for other types of concrete. 
         [0095]    Batch Mix Procedure begins at an Enter mix design step. Prior to this procedure, a cement bin  134  has been loaded with cement typically by using crane  120  which has been employed to transfer cement bags  118  from bed  104  to cement bin  134 . Bags  118  are automatically opened by knife  124 C. Sand bin  140 B has also been loaded with sand. Sand conveyor system  112  has been positioned as shown in  FIGS. 1-3 . Water reservoir  138  has been filled with water prior to initiation of water flow into the mixer  106  in accordance with step  202 . 
         [0096]    The Batch Mix Procedure begins the process. Enter mix design, and Enter batch count by controller  116  are followed by Enter start, which begins the process. The next step, Prints time and date of batch etc., is documented by printer  116 C for the record. The scale zero&#39;s step subtracts any reading attributable to the mixer scales  106 E in order to weigh only the added ingredient. The steps follow such that, as previously described, water starts at high flow and the mixer speed is low. The water switches to low flow until the target amount is reached, and the mixer remains at low speed. Water amount is printed using printer  116 C. The scale zero&#39;s step then follows. The product starts at high flow with mixer at high speed. The following steps are then sequentially performed: 
         [0097]    Product switches to low speed to finish with mixer low. 
         [0098]    Product amount is printed using printer  116 C. 
         [0099]    Scale zero&#39;s. 
         [0100]    Sand starts at high flow with mixer at high speed. 
         [0101]    Sand switches to low flow to finish with mixer speed low. 
         [0102]    Sand amount is printed using printer  116 C. 
         [0103]    Prints total amount of ingredients by summing the individual ingredient weights. 
         [0104]    Mix time runs to set time with the mixer speed high. 
         [0105]    Mixer door opens with the mixer speed high. 
         [0106]    Mixer empty, door closes with the mixer speed low. The determination of when the mixer is empty is also determined by the mixer weight scales  106 E. 
         [0107]    Start new batch. 
         [0108]    After cement has been conveyed to bin  122 , it is then transferred to the mixer  106  by auger  136 , as at step  208 . After the required amount of cement has been transferred as indicated by the data from scales  106 E at step  210 , weight is determined by the controller  116 . Until the required amount of cement has been transferred, the method  200  continues step  208  until the correct weight has been attained. Once the required amount of cement has been introduced, the method  200  continues with step  212 . Water is transferred from the reservoir  138  to the mixer  106 . Again, before step  214  has been performed, step  212  is continued. After the required amount of concrete has been added, step  216  is entered and sand is then added to mixer  106 . Again, before step  218 , step  216  is continued until the required amount of sand has been added. Once the required amount of sand has been added, mixer  106  mixes the ingredients in step  220 . After mixer  106  has mixed the ingredients for a predetermined length of time, step  222  is then entered and pourable concrete is output to blender  144 . 
         [0109]    Note that the method described hereinbefore is merely representative of one way of programming controller  116 . Depending upon the particular type of cement, the ingredients required, the various mixing times, the method of determining the quantity of the ingredient being transferred and the specific hardness, different programs could be employed. The ability of controller  116  to coordinate an essentially unlimited variety of requirements quickly and accurately by merely using a different program gives this apparatus great flexibility. 
         [0110]    Keyboard  116 B is provided, as shown, as an operator interface to permit the entry of pertinent information in the field. This could be supplemented by a touch screen or a specialized interface that permits input of only certain data fields such as concrete hardness, concrete quantity and volume, and other related parameters. 
         [0111]    In addition to providing portability, this system also provides accurate control over the quantity of the various ingredients providing for concrete hardness and the operating times of critical functions. This obviates a lack of precision and different concrete hardnesses with current mixing apparatuses. 
         [0112]      FIGS. 17A ,  17 B, and  17 C form a flow chart of the software that configures control element  116 D as a mix control device that loads desired weights of ingredients into mixer  106  in the proper order and mixes them to form the desired slurry. One can consider that the instructions comprising each flow chart element for each period of time that these instructions execute within control element  116 D, actually configure control element  116 D as a physical, electronic element performing the function indicated in the flow chart element. 
         [0113]    In general, control element  116 D executes the  FIGS. 17A-17C  instructions at intervals sufficiently short to assure that the correct weights of the ingredients are provided to mixer  106 . Often, control elements maintain a list of all routines active at any given time, and each routine is executed in order. The mix control device software of  FIGS. 17A-17C  comprises activity elements such as element  307  and decision elements such as element  317 . Activity elements perform some sort of data manipulation, such as moving data, adding two values, etc. Decision elements select one of two paths for instruction execution based on some type of mathematical test. On occasion, some data manipulation may form a part of a decision element. 
         [0114]    Turning first to  FIG. 17A , element  303  is the starting point for the mix control software. Activity element  305  then sets the MX signal on path  108 D to set the mixer speed to low. 
         [0115]    Element  307  symbolizes software that causes control element  106 D to clear the mixer weight register (MWR)  116 G and sets the desired ingredient weight values W, G, and S for water, cement (gypsum), and sand respectively. Element  307  may include inputs from keyboard  116 B provided by an operator that set the desired ingredient weights. 
         [0116]    Element  310  symbolizes the instructions that cause control element  116 D to issue the AW signal to pump  128 B with a high flow level to start pump  128 B adding water to mixer  106 . Instruction execution then proceeds to activity element  314 , which essentially configure control element  116 D to function as blender weight monitor  116 C. Monitor  116 C reads the MW 1  and MW 2  signals, digitizes them, and stores them in the MWR  116 G. 
         [0117]    Decision element  317  tests the value in MWR  116 G against 0.9×W. If the MWR  116 G value is less than 0.9×W, then execution of instructions returns to activity element  314 . The test of MSR against the 0.9×W value allows the system to slow the flow of water during the final stage of loading the water. Slowing the water flow toward the end of the water delivery interval allows for more accurate measurement of the final delivered water weight. The 0.9 factor is nominal and somewhat arbitrary.  FIG. 15  shows this value to vary between (approximately) 0.8 and 0.95. 
         [0118]    Eventually, as water continues to flow into mixer  106 , the MWR  116 G value exceeds 0.9×W, and instruction execution continues to activity element  320  which slows the flow of water to mixer  106 . The instructions of decision element  323  then test whether the MWR value is ≧W. If so, then the desired weight of water has been loaded into mixer  106  and execution proceeds to activity element  326 , which sends the AW signal with the level that stops water flow to mixer  106 . If the MWR value is &lt;W, instruction execution returns to activity element  314 . 
         [0119]    After the activity element  326  instructions have executed, control element  116 D starts the actions to load cement into mixer  106 . The instructions of activity element  330  execute to issue the MX signal on path  108 E, to run the mixer  106  at low speed. Then the instructions of activity element  333  cause control element  116 D to issue the AG signal on path  108 B with the level that runs the cement auger motor  136 B at high speed. Cement starts moving to mixer  106  from bin  134 , which has been preloaded with cement powder. 
         [0120]    Element  336  connects the instructions that  FIG. 17A  shows to the instructions of  FIG. 17B . Execution of instructions on  FIG. 17B  starts at the connection element A  347  and then proceeds to activity element  350 . Element  350  reads the MW 1  and MW 2  signals on paths  107 A and  107 B and then updates the MWR value in memory element  116 G. 
         [0121]    Then decision element  353  tests whether W+(0.9×G) is less than the MWR value. If true then execution returns to connector element A  347  and weight is recalculated. 
         [0122]    If W+(0.9×G) is not less than the MWR value then instruction execution proceeds to activity element  356 , which sets the rate of cement flow to the slow level. Here too, the 0.9 factor is nominal, and simply provides an interval at the end of cement delivery with a slow delivery rate to allow more accurate weighing and final cement weight. 
         [0123]    The instructions of activity element  358  slow the mixer  106 , which also allows scales  106 E to more accurately weigh mixer  106 . Next, the instructions of decision element  360  test whether the value in the MWR is greater than W+G. If not true, then execution returns to connector element A  347  and weight is recalculated. If true, then execution proceeds to the instructions of activity element  363 , which causes control element  116 D to set the AG signal to the value that stops flow of cement to mixer  106 . 
         [0124]    Next, the activities to load sand into mixer  106  occur. Activity element  366  sets the MX signal to cause elevator  140  to set the speed of mixer  106  to high. The instructions of activity element  365  cause control element  116 D to set the sand flow signal AS on path  108 C for high flow causing elevator  140  to add sand to mixer  106  at the higher rate. Connector element  368  indicates that instruction execution then moves to connector element B on  FIG. 17C . 
         [0125]    The instruction elements  373 ,  375 ,  376 ,  377  and  379  in  FIG. 17C  perform control functions for loading a desired amount of sand into mixer  106  that are very similar to those of  FIGS. 17A and 17B  that load water and cement. First, the mixer runs at its high speed and the elevator  140  delivers sand at its higher rate to mixer  106 . 
         [0126]    When control element  106 D executes instructions that sense the amount of sand present in mixer  106  is close to its desired weight S, then the instructions of decision element  375  cause control element  106 D to execute instructions that slow the mixer  106  and slow the sand delivery. The activity element  391  instructions change the AS signal level to stop the sand conveyor motor  140 F after the desired weight of sand has been loaded into mixer  106 . Typically, at this point, the mixer  106  stifling rate is increased and the mixer  106  runs until the slurry is completely mixed and is ready for placement. 
         [0127]      FIG. 18  is a flow chart that explains control of the slurry level in blender  108 . As mentioned, it is important that blender  108  not overflow or on the other hand, the level therein fall so low that the blender pump  144 G intake is above the slurry level in blender  108 . Controller  116  also provides this level control functionality. 
         [0128]    Two levels for the slurry in blender  144  exist, and these are functions of its design. One depends on the maximum allowable level of the slurry in blender  144 , specified by a BSW MAX  weight value, the other by the minimum allowable level of the slurry in blender  144 , specified by a BSW MIN  weight value. These values must be prestored in memory  116 F prior to operation of slurry pump  144 G ( FIG. 11 ). 
         [0129]    Blender  144  control starts at connection element  390  and then continues with the instructions of activity element  393 . Element  393  places the appropriate value of the BP signal on path  108 G to enable operation of the motor  144 H that drives slurry pump  144 G. This enablement only allows the user on site to start and stop actual motor  144 H operation, and does not cause pump  144 G to operate. 
         [0130]    Execution then proceeds to the instructions of activity element  402 . These instructions read the blender weight (BW) from scale  144 F, which is carried on path  107 C, and the mixer scale weight on paths  107 A and  107 B. These values are then stored in memory locations  116 H and  116 G respectively. 
         [0131]    Next, control element  116 D executes the instructions that decision element  397  symbolizes, to determine if any slurry remains in mixer  106  that can be moved to blender  144 . If slurry remains in mixer  106 , then instruction execution transfers to decision element  406 . If not, then the instructions that decision element  411  symbolize are executed. 
         [0132]    Decision element  411  test whether any slurry remains in blender  144  is still available for placement. If so, then execution proceeds to decision element  406 . If not then the slurry pump motor  144 H is disabled, so that a user cannot activate pump motor  144 h through error. These instructions thus make two tests, to determine if controller  116  should allow pump  144 G to operate. 
         [0133]    The decision element  406  instruction execution begins after decision element  397  has determined that slurry still remains in mixer  106 . Decision element  406  tests whether the slurry level in blender  144  is too high. If so, then control element  116 D executes the instructions of activity element  409  which sets to close the MV signal that path  108 D carries to the mixer valve  142 . If untrue, then the instructions of decision element  418  are executed. 
         [0134]    If the BSW value is less than BSW MAX , then the instructions of decision element  418  execute, to test whether the blender scale weight BSW is ≦BSW MIN . If so, then more slurry must flow from mixer  106  to blender  144 . The instructions of activity element  373  execute, to issue a MV signal with the level that opens the mixer valve  142 A. The instruction execution then returns to decision element  357 . 
         [0135]    Of course, all of these control activities can use proportional regulation, as opposed to merely on and off regulation. These are well known in control theory. 
         [0136]    The apparatus described hereinbefore can produce cementitious slurry on site with very accurately measured constituents using a minimum amount of time. It will be understood that some steps and/or equipments could be eliminated in producing cement on site, but with less precision and with more time being required. 
         [0137]    Although the invention has been described with regard to certain preferred example embodiments, it is to be understood that the present disclosure has been made by way of example only, and that the above simplifications and all other improvements, changes, modifications, details of construction, combination and arrangement of parts, control means and program steps may be resorted to without departing from the spirit and scope of the invention. Such simplifications, improvements, changes, and modifications within the skill of the art are intended to be covered by the scope of the appended claims.