Patent Publication Number: US-2010118640-A1

Title: Mobile concrete mixing plant

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. provisional application Ser. No. 61/049,951, filed May 2, 2008, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to concrete mixing plants and, more particularly, to transportable concrete mixing plants. 
     BACKGROUND OF THE INVENTION 
     Mobile concrete mixing plants are typically sized to fit on a roadable trailer, or are made up of assembled components that can be disassembled from one another and individually transported by road, such as on a semi-trailer. Typically, mobile concrete mixing plants are temporarily set up in a location near an immediate need for wet concrete, such as alongside a new road or a building project. The mobile mixing plant is supplied with concrete ingredients, such as cement, sand, aggregate, and water, which are mixed together in desired proportions and dispensed as flowable concrete. 
     SUMMARY OF THE INVENTION 
     The present invention provides a substantially self-contained transportable concrete mixing plant mounted on a roadable trailer. The transportable mixing plant may be positioned on a non-level support surface and leveled to compensate for the support surface. The transportable mixing plant receives dry concrete premix, mixes the premix with water to form liquid or flowable concrete, and pumps the liquid concrete to a location that is remote from the mixing plant. 
     According to one form of the present invention, a transportable concrete mixing apparatus is provided for supplying liquid concrete in a substantially continuous manner. The apparatus includes a transport frame, a base frame, a mixing drum, an overhead rail, a carriage assembly, and a concrete pump. The base frame is mounted to the transport frame, and the mixing drum is supported at the base frame. The overhead rail is positioned above the mixing drum and supports the carriage assembly above the drum. The carriage assembly translates along the overhead rail and supports a container of dry premix concrete, which may be positioned above the mixing drum and opened to dispense premixed concrete into the drum. The concrete pump pumps liquid concrete received from the drum to a location that is remote from the apparatus. 
     In one aspect, the base frame is pivotally supported at the transport frame, and an actuator is provided for pivoting the base frame relative to the transport frame, thereby permitting the transport frame to be positioned at a non-level location and adjusting the base frame to a level orientation with the actuator. 
     In another aspect, a winch is provided at the carriage assembly for raising and lowering the container of premix concrete. The winch may be, for example, an electric winch. 
     In yet another aspect, a pair of mixing drums is pivotally mounted to the base frame. Each of the mixing drums may be independently pivoted between a mixing orientation and a dispensing orientation. 
     In still another aspect, a water tank is provided at the base frame for supplying water to the mixing drum to facilitate the preparation of liquid concrete from the premix concrete. 
     In a further aspect, a hydraulic motor is provided for rotating the mixing drum about a longitudinal axis. Optionally, the hydraulic motor is driven by a hydraulic pump that is powered by an electric motor, which in turn is powered by an electrical generator onboard the mixing apparatus. 
     In a still further aspect, a control is provided for controlling the mixing drum, the actuator, the concrete pump, the electrical generator, the electric motor, a winch, or any combination thereof. 
     According to another form of the present invention, a method is provided for preparing pourable concrete. The method includes raising and positioning a container of premix concrete above a mixing drum with a carriage assembly. Premix concrete is dispensed from the container into the mixing drum where it is mixed with water. The mixed concrete is then dispensed into a concrete pump, from which it is pumped to a remote location. 
     In one aspect, two mixing drums are provided for mixing concrete. A first mixing drum is operable independently from a second mixing drum so that the first mixing drum can receive and mix premix concrete and water while the second drum dispenses mixed concrete into the concrete pump. The second drum then receives and mixes premix concrete and water while the first drum dispenses mixed concrete into the concrete pump. 
     Therefore, the transportable concrete mixing plant of the present invention provides a transportable and substantially self-contained concrete mixing plant that is capable of supplying a substantially constant supply of liquid concrete. Further, the transportable mixing plant of the present invention may be positioned on uneven ground and may pump liquid concrete to remote locations, thereby obviating the need for concrete-carrying vehicles. 
     These and other objects, advantages, purposes, and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a transportable concrete mixing plant in accordance with the present invention and supported upon a level surface; 
         FIG. 2  is a side elevation of the plant of  FIG. 1 , positioned on a sloped support surface; and 
         FIG. 3  is a top plan of the transportable concrete mixing plant of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and the illustrative embodiments depicted therein, a transportable concrete mixing plant  10  includes a base frame  12 , a wheeled transport frame or trailer frame  14 , and a superstructure frame assembly  16 . Transportable concrete mixing plant  10  provides a substantially self-contained concrete mixing and dispensing facility that is readily transported, such as by road, to a location near a worksite. Plant  10  is operable to supply a substantially constant flow of liquid concrete to a location spaced from the plant. 
     Base frame  12  supports a pair of mixing drums  18   a,    18   b,  a concrete pump  20 , an electrical generator  22 , a hydraulic power unit  24 , a water tank  26 , and a fuel tank  28 . Superstructure frame assembly  16 , which is mounted to base frame  12  and extends upwardly therefrom, includes a plurality of vertical members  16   a,  horizontal cross-members  16   b,  and horizontal longitudinal members  16   c.  Superstructure frame assembly  16  supports an overhead rail  30  at horizontal cross-members  16   b  and further supports a pair of supply chutes  32   a,    32   b  ( FIGS. 1 and 2 ). A carriage assembly  34  is movably mounted to overhead rail  30  for moving containers  36  of premix concrete from a loading location  38  to a discharge location  40 , as will be described in greater detail below. 
     Mixing drums  18   a,    18   b  are positioned adjacent one another above base frame  12 , and are independently vertically pivotable (about a horizontal axis) between a loading/mixing position with their open ends directed upwardly and the dispensing position with their open ends lowered from the loading/mixing position (loading/mixing position shown). As best seen in  FIG. 3 , mixing drum  18   a  is fed with dry premix concrete via supply chute  32   a,  and mixing drum  18   b  is supplied by supply chute  32   b.  At their respective loading/mixing positions, mixing drums  18   a ,  18   b  are rotatably driven about their respective longitudinal axes to mix dry premix concrete, received from respective chutes  32   a,    32   b,  with water supplied from water tank  26  until the mixture is thoroughly wetted and pourable or flowable. A metered quantity of water is pumped from water tank  26  into each drum through each drum&#39;s respective open end using a water pump. After the premix and water are suitably mixed, the mixing drum is pivoted downwardly to the dispensing position, whereupon continued rotation of the drum urges the flowable or liquid concrete into a receiving hopper  42  via a funnel  44 . Optionally, supply chutes  32   a,    32   b  may include replaceable wear plates to prevent excessive wear of the chutes. 
     In operation, mixing drums  18   a,    18   b  are independently controlled so that while mixing drum  18   a  is tilted upwardly for receiving premix and mixing the premix with water, mixing drum  18   b  is tilted downwardly for dispensing liquid concrete into receiving hopper  42 . Optionally, the time required for receiving dried premix concrete and thoroughly mixing it with water may be approximately equal to the time required to dispense the liquid concrete contents of the mixing drum into receiving hopper  42 , thereby permitting substantially continuous flow of liquid concrete into hopper  42  by alternately mixing and dispensing from mixing drum  18   a  and mixing drum  18   b.    
     Thus, mixing drums  18   a,    18   b  may be alternately sequenced so that mixing drum  18   a  is receiving or mixing dry premix from supply chute  32   a  while mixing drum  18   b  is dispensing liquid concrete into receiving hopper  42 . When mixing drum  18   a  has thoroughly mixed its contents with water to form liquid concrete, mixing drum  18   a  is tilted downwardly to dispense liquid concrete into receiving hopper  42  while mixing drum  18   b  is tilted upwardly to receive its next load of dry premix. Each mixing drum  18   a,    18   b  may be generally conventional in design, having helical mixing paddles or blades along an inner surface of each drum, whereby rotation in one direction draws concrete to the closed end of the drum for mixing, and rotation in the opposite direction directs mixed concrete toward the open end of the drum. Mixing drums  18   a ,  18   b  may be one cubic yard capacity cement mixers, for example, and rotatably and pivotally driven by actuators powered by hydraulic power unit  24 . Hydraulic power unit  24  may be a self-contained thirty horsepower unit driven by an electric motor powered by the generator  22 , for example, or other suitable power unit. 
     Overhead rail  30  is supported centrally above base frame  12  by superstructure frame assembly  16  and permits the loading and positioning of containers  36  for dispensing dry premix concrete into one of mixing drums  18   a,    18   b  via supply chutes  32   a,    32   b.  Rail  30  has a front end portion  30   a  positioned generally above supply chutes  32   a,    32   b  and a rear end portion  30   b  opposite front end portion  30   a.  Preferably, overhead rail  30  is a monorail, such as an I-beam or a C-shaped beam that supports carriage assembly  34  and permits carriage assembly  34  to translate longitudinally along mixing plant  10 . Rear end portion  30   b  of overhead rail  30  may extend rearwardly beyond a rearward extent of base frame  12  to facilitate the loading of containers  36 , as will be described in greater detail. 
     Carriage assembly  34  may be equipped with a manual or powered winch  35 , such as an electric winch, having a cable  46  that engages lift straps  48  of container  36 . Thus, carriage assembly  34  is operable to raise and lower cable  46  in order to raise and lower container  36 . Winch  35  may be a 7.5 horsepower electric winch capable of raising and lowering cable  46  at about twenty-two feet-per-minute, for example, or any other suitable powered winch. 
     Containers  36  may be made of woven fabric such as polypropylene fabric or the like, having square dimensions of 35 inches square by 51 inches high in order to hold at least about one cubic yard of dry premix concrete. Lift straps  48  are sewn to the four corners of containers  36  and may incorporate loops to facilitate attachment of cable  46  thereto. Containers  36  include a closable bottom opening  50  that is normally held closed by a draw string or other closure device. The draw string is normally released when container  36  is positioned above supply chutes  32   a,    32   b  to release dry premix concrete into one of mixing drums  18   a,    18   b.    
     Concrete pump  20  is supplied with liquid concrete from mixing drums  18   a,    18   b  via receiving hopper  42  and is operable to pump the liquid concrete to a nearby location, such as a transport vehicle, or to a distant location, such as a worksite. For example, concrete pump  20  may be powered by a 100 horsepower diesel engine and capable of pumping approximately sixty cubic yards of liquid concrete per hour a horizontal distance of up to about 900 feet and a vertical distance of up to about 290 feet through a pipe (not shown) having a diameter of about five inches. 
     Electrical generator  22  provides electricity for operation of the entire transportable concrete mixing plant  10 , such as for operating an electric motor to drive hydraulic power unit  24 , to drive the electric winch  35  and carriage assembly  34 , to power electric lights for night operation, and to power an optional control panel  64  for controlling the operation of mixing plant  10 . For example, electrical generator  22  may be powered by a diesel engine to produce approximately 80 kilowatts of electricity. 
     Water tank  26  supplies water to mixing drums  18   a,    18   b  for mixing with dry premix concrete and producing liquid concrete therefrom. For example, water tank  26  may have a capacity of approximately 500 gallons, which is sufficient for mixing approximately 16 cubic yards of premix. A pump is provided for pumping water into mixing drums  18   a,    18   b.  Fuel tank  28  supplies fuel, such as diesel fuel, to electrical generator  22 , concrete pump  20 , and any other internal combustion engine or fueled device located at mixing plant  10 . 
     As best shown in  FIG. 2 , base frame  12  is pivotally supported at a rear end of trailer frame  14  so that trailer frame  14  may be parked or positioned at an inclined support surface  52  while maintaining base frame  12  in a level or horizontal orientation. The orientation of base frame  12  is adjustable via an actuator  54  connected between trailer frame  14  and base frame  12 . For example, actuator  54  may be a double-acting hydraulic cylinder having a first end  54   a  pivotally mounted at trailer frame  14 , and a second end  54   b  pivotally mounted at a first link  56 . First link  56  is pivotally connected at a first end  56   a  to a location on trailer frame  14  spaced from first end  54   a  of actuator  54  and is pivotally mounted at a second end  56   b  to a first end  58   a  of a second link  58 . Second link  58  has a second end  58   b  pivotally connected to base frame  12 . Optionally, the various components of mixing plant may be mounted to an articulating skid, such as a steel plate, that pivots relative to the base frame and/or the trailer frame. 
     Thus, by extension and retraction of actuator  54 , a front end  12   a  of base frame  12  is urged upwardly until base frame  12  is substantially level. Referring to  FIG. 2 , an angle θ is thereby formed between base frame  12  and trailer frame  14 . Angle θ may range anywhere from zero degrees to thirty degrees or more, thus enabling mixing plant  10  to be positioned on a substantially sloped support surface  52  without affecting the operation of mixing plant  10 . 
     As best seen in  FIGS. 1 and 2 , trailer frame  14  may be equipped with one or more jack stands or outriggers  60  that are laterally and vertically extendable to support trailer frame  14  opposite one or more wheels  62  at the rear end of trailer frame  14 . Trailer frame  14  may be part of a conventional pup-style trailer and include a steel frame and wood deck, for example. Alternatively, or additionally, mixing plant  10  may be supported by a rail car, a floating barge, or other vehicle or support. 
     Accordingly, transportable concrete mixing plant  10  provides a substantially self-contained concrete mixing and dispensing facility that is readily transported to a convenient location and is operable to supply a substantially constant flow of liquid concrete to a location spaced from mixing plant  10 . Transportable concrete mixing plant  10  is first moved, typically via road, such as by connecting trailer frame  14  to a tow vehicle such as a semi-tractor. Mixing plant  10  is positioned on support surface  52  and supported in place by outriggers  60  and wheels  62 , after which the tow vehicle may be detached. If support surface  52  is sloped at angle θ, mixing plant  10  is typically oriented with its rear end and loading location  38  positioned at the higher elevation. In this manner, actuator  54  may be extended to pivot base frame  12  counterclockwise as viewed in  FIG. 2 , relative to trailer frame  14 , at angle θ so that base frame  12  is supported in a substantially level, horizontal orientation. Optionally, the base frame may be hinged to the trailer frame at their front ends so that the mixing plant may be oriented with its front end positioned at the higher elevation. 
     Containers  36  are positioned at loading location  38  behind base frame  12  and below a rear end portion  30   b  of overhead rail  30 . Cable  46  is lowered from carriage assembly  34  and attached to lift straps  48  of container  36 , after which cable  46  is drawn upwardly into carriage assembly  34 , such as with winch  35 , until bottom opening  50  of container  36  is raised above the level of supply chutes  32   a,    32   b.  Carriage assembly  34  is then urged forwardly, either manually or with a powered actuator (such as a conventional electric trolley drive unit), along overhead rail  30  until it reaches a front portion  30   a  of rail  30  so that bottom opening  50  is positioned directly above supply chutes  32   a,    32   b.  Bottom opening  50  is then opened to release dry premix concrete from container  36  into one or both of supply chutes  32   a,    3 . 2   b.  Dry premix concrete flows through bottom opening  50  of container  36  and slides or flows down into one of mixing drums  18   a,    18   b  via corresponding supply chute  32   a,    32   b.  Once empty, container  36  is removed from carriage assembly  34 , which is urged backward along overhead rail  30  toward rear portion  30   b  in order to receive the next container. Containers  36  may be discarded or reused once they have been emptied. 
     Mixing drum  18   a  or  18   b  receives water from water tank  26  and proceeds to rotate about its longitudinal axis until the water and premix are sufficiently mixed to form flowable or liquid concrete, after which the mixing drum is tilted or pivoted downwardly to dispense the liquid concrete into funnel  44 , which channels the liquid concrete into receiving hopper  42 . Once the mixing drum is emptied, it is pivoted upwardly to receive the next batch of dry premix concrete and water. 
     Liquid concrete in receiving hopper  42  is directed into concrete pump  20 , which pumps the liquid concrete away from mixing plant  10  and into a waiting transport vehicle or to the point of use. By providing a steady supply of containers  36  containing dry premix concrete, fuel, and water, concrete mixing pump  10  may be operated substantially constantly to provide a substantially constant flow of pourable liquid concrete at a work site. 
     Optionally, control panel  64  may be provided at mixing plant  10  for controlling various operations such as, for example, positioning outriggers  60 , extending and retracting actuator  54 , extending and retracting cable  46 , moving carriage assembly  34  along overhead rail  30 , controlling the tilt and rotation of mixing drums  18   a,    18   b,  controlling concrete pump  20 , controlling the water pump, controlling the electrical generator  22 , and controlling lights for operations in darkness. Control panel  64  includes a controller, such as a microprocessor board controller, which is in communication with the various components on the mixing plant. Optionally, the controller permits automated operation of mixing plant  10 . It will be understood that plant  10  may be controlled by an operator via control panel  64 , or may be fully manually operated, without departing from the spirit and scope of the present invention. 
     Changes and modifications in these specifically described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.