Abstract:
An assembly for a fracking sand trailer wherein a door can be positioned to allow a measured flow of sand to exit the assembly. The assembly can be attached to a hopper of a trailer and can stand the weight of heavy loads associated with sand. A trailer with the assembly is also described and utilizes specific construction techniques to lighten the weight of the trailer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to provisional patent application 61/895,847 which was filed on Oct. 25, 2013, and is hereby expressly incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Due to recent advancements in drilling technology that employ hydraulic fracturing or “fracking”, it is now possible to extract natural gas and oil deposits from shale rock layers deep within the earth that were once unreachable with conventional technologies. Fracking is the process that injects a highly pressurized fracking fluid, a major component being fracking sand, into the shale area to create new channels within the rock for natural gas or oil to be extracted at higher than traditional rates. With the advent of fracking and the increase in demand for fracking sand, new methods of transporting this very specialized sand is required. 
         [0003]    Conventionally, raw sand is transported over the road by steel dump trucks and end dump or belly dump style semi-trailers. These conventional sand transport methods load and dump sand in bulk and do not allow for any type of metering capabilities, especially during the unloading process. Fracking sand is a very specialized type of sand, wherein raw sand is processed and dried to meet specific characteristics and properties needed in the hydraulic fracturing process. Once processed, the sand must normally be transported to a railroad or truck terminal for further transport to the often remote drilling fields. Since one common and efficient method of transferring sand from a truck or trailer to a train car is by means of a conveyor system, metering the unloading of fracking sand is required so that the conveyor system is not overwhelmed by a sudden influx of sand being dumped upon it. 
         [0004]    In the attempt to be able to meter fracking sand, companies have tried to use dual hopper grain trailers which contain two hoppers and small bottom gates that are no more than two feet by two feet in area, but due to the abrasive and corrosive properties of the fracking sand, these trailers quickly deteriorate and have extreme maintenance costs. Though a dual hopper grain trailer has a hopper door opening that works well for low moisture content grain, it is undersized for unloading raw wet sand, so it cannot be used as a dual purpose trailer for both wet raw sand and dry fracking sand. 
         [0005]    It is an object of the invention to provide a sand trailer with an oversized hopper door opening to allow raw sand, particularly raw wet sand, to be quickly and easily unloaded. 
         [0006]    It is a further object of the invention to provide a sand trailer with the ability to control the flow rate of the fracking sand exiting the sand trailer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a bottom perspective view of the door assembly on a hopper. 
           [0008]      FIG. 2  is a bottom perspective view of the door assembly. 
           [0009]      FIG. 3  is a top perspective view of the door assembly. 
           [0010]      FIG. 4  is a bottom perspective view of the door assembly. 
           [0011]      FIG. 5  is a top perspective view of the door assembly without the motor and gears. 
           [0012]      FIG. 6  is a top perspective view of the door assembly without the motor and gears. 
           [0013]      FIG. 7  is a series of figures detailing the motor and gears of the door assembly. 
           [0014]      FIG. 8  is a bottom perspective view of the door assembly on a trailer. 
           [0015]      FIG. 9  is a top perspective view of the trailer. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present invention provides a solution to unload wet raw sand and control the flow of dry fracking sand during unloading of the trailer. Existing trailer can be retrofitted with the door assembly and new trailers can be constructed with the door assembly. 
         [0017]      FIGS. 1 through 7  illustrate an assembly  20  mounted to a hopper  8  of a fracking sand trailer  1  (see  FIG. 8 ). The assembly  20  comprises a door frame  9  with an upper subframe  22  and a lower subframe  24 , all preferably made of steel. A slidable door  4  is housed between the upper subframe  22  and lower subframe  24 . The lower subframe  24  is preferably sized such that it is twice the length of the door  4  and the upper subframe  22 . Ends  30  of the lower subframe  24  may be linked by a cross member  28 . The cross member  28  is then connected to the trailer  1  via a pair of elongated arms  26  so that the ends  30  of the lower subframe  24  are supported by the trailer  1 . The upper subframe  22  is connected to the hopper  8  of the trailer  1 . The door  4  is preferably made of steel and is reinforced with a plurality of reinforcement members  40  which span from one side of the door frame  9  to a second side of the door frame  9 . The reinforcement members  40  strengthen the door  4 . 
         [0018]    The door  4  is slidable between the upper subframe  22  and lower subframe  24  supported on rollers  13  mounted to the lower subframe  24 . The rollers  13  are preferably made of steel and bolted into place to withstand the conditions of unloading the trailer  1 . The door  4  is provided with segments of roller chain  10  which are fixed to each opposing side of the door  4  and allow the door  4  to be driven through motors  3 . Each motor  3  selectively drives a gear reducer  5  which rotates a sprocket  11  which engages the roller chain elements of the respective segments of roller chain  10 . By use of hydraulic powered motors , sufficient driving force, which may be multiplied through a gear reducer  5  applies sufficient power to overcome the friction of a hopper full of sand weighing upon the door  4 . 
         [0019]    A shield or cover  12  covers the drive shaft of each motor  3  along with an endless drive chain or belt which couples the drive shaft of each motor to drive sprockets  11 , and a chain drive gear reduction  5 . Due to the sheer weight of the sand in the trailer  1  and the conditions during unloading, the motor  3  is preferably hydraulically powered. The chain track  10 , which is also preferably steel, interacts with the drive sprockets  11  such that when the motor  3  is activated, the door  4  can be moved from a first position which is a fully closed position to a second position which is at least partially opened. Preferably the door  4  can be opened incrementally between any position between the first position and second position, that is, from an entirely closed position to a partially closed position to a completely open position. The spacing of the roller chain elements of each chain track  10  and the gears on the drive sprockets  11  will dictate the incremental positions of the door  4  relative to the opening of the hopper  8 . 
         [0020]    The assembly  20  is mounted to the hopper  8  of the trailer  1  by attaching door frame  9  to trailer frame  2  through use of lateral bolts (See  FIG. 3 ) or the assembly can be welded to the trailer  1 . The majority of the trailer  1  has portions made of a light weight material, preferably aluminum and preferably corrugated aluminum, while certain portions are made of a stronger material such as steel to reinforce the aluminum. The combination of the lightweight aluminum trailer body with a steel reinforced trailer frame allows the fracking sand trailer to be light but durable. The light weight relative to dump trucks and belly dump trailers provides some of the highest sand payloads while not exceeding highway weight limitations. The durability still allows the sand trailer to operate over the toughest road conditions. Preferably many aluminum components of the hopper and sidewalls of the trailer are welded together though rivet construction methods may be used to assemble the trailer body. 
         [0021]    The trailer  1  can be seen in detail in  FIGS. 8-9 . The trailer  1  has a top opening  51  which allows sand to be loaded into the trailer  1 . A plurality of diffusers  7  is placed at the top of the trailer  1  which traverse the trailer  1  from side wall to side wall. The diffusers  7  serve to deflect incoming sand and to decelerate it so as to protect the door  4  from incurring excess direct impact during of the loading of the trailer  1 . The diffusers  7  are preferably made of steel and provide reinforcement to the aluminum body. The trailer  1  is designed with steep angled interior walls  55  having a polymeric liner  6  that covers the hopper completely. The sidewalls  57  of the hopper  8  may be substantially perpendicular relative to the bottom of the trailer while the chute  59  includes sidewalls and end walls which converge as they approach the door  4 , though the angle of the sidewalls and end walls of the chute  59  are steep and diverge from vertical by only a small angle. The use of vertical and almost vertical sidewalls of the hopper and chute facilitate the unloading of either fracking sand or raw sand, but the large door opening of approximately four feet by four feet prevents bridging of moist sand over the opening, which is the shortfall of the use of a standard bottom dump grain trailer. The liner is preferably ⅜ of an inch in thickness and made of plastic. The hopper  8  is preferably in the middle of the trailer  1 , as shown in the figures, and extends for a distance past the bottom wall of the trailer  1 . 
         [0022]    In operation, the trailer  1  is loaded with sand from the top of the trailer  1 . If the trailer is loaded with unprocessed, wet sand, then the trailer  1  is typically transported to a site for processing. As wet sand can become stuck in existing trailers during unloading, several of the features of the present invention aid in unloading the trailer  1  when loaded with wet sand. The steep walls  55  and liner  6  assist in dropping the sand out of the hopper  8 . Additionally, the oversized bottom opening (approximately four feet by four feet) of the hopper assists in preventing wet sand from blocking the flow out of the hopper  8 . Additionally, the use of hydraulic motors  3  allow the door  4  to be opened quickly, thus allowing the wet sand to immediately exit through the oversized opening. 
         [0023]    If the trailer is loaded with processed, dry fracking sand, then the trailer  1  is typically transported to an intermodal site where rail cars are loaded with the fracking sand for transport to distant oil drilling fields. Because the rail cars are usually loaded by use of a conveyor with a below grade intake area, the trailer  1  may be moved such that door opening  61  is located over the intake area and the door  4  can be opened to the proper extent to meter output of sand from the trailer  1  such that the conveyor used to load the rail care is not overloaded and remains operating efficiently. 
         [0024]    The lightweight aluminum composition of the trailer  1  allows more sand to be loaded compared to the current state of the art trailer. A sensor  60  is provided to detect when the door is in its fully opened position and optionally a detector could be employed to determine the amount that the door  4  has been moved, such as counting the revolutions of each motor  3  from which can be derived the lateral movement of the door  1 . 
         [0025]    Because the door  4  covers an opening of approximately four feet by four feet (however a door can be constructed for a variety of sizes), raw sand will drop through the door opening quickly and efficiently without bridging the opening, while dry fracking sand can likewise be transported and emptied in a controlled operation over a loading conveyor for a rail car.