Abstract:
A tractor for hauling concrete and similar materials at a construction site. The tractor includes an engine powering two pumps connected in series. The two pumps providing hydraulic pressure to: independently power each of a plurality of wheels; to rotate at least one of the wheels to provide steering to the tractor; to raise and lower a bucket; and to release and close a latch for a gate connected to the bucket.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/148,686, filed on 30 Jan. 2009. This Provisional Application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a tractor for hauling materials or cargo, including concrete, at a construction site and, more particularly, to a tractor utilizing hydraulics. 
     2. Discussion of Related Art 
     Various tractors for hauling cargo at a construction site are known. For example the Scoot-Crete® power buggy is a device designed for hauling concrete at construction sites. The Scoot-Crete® power buggy is a two-wheel drive cart with a bucket. These carts support the cargo over the two drive wheels but, because the cargo is often very heavy, these carts can sink into soft ground and bottom out on the frame of the cart. Such characteristics may cause the drive wheels to lose traction and spin in the soft ground. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a tractor for hauling concrete and other materials including, but not limited to, soil, gravel and sand, at a construction site. In a preferred embodiment, the tractor includes a frame, an engine, a hydraulic system, a plurality of independently powered wheels, a bucket and a gate. In one embodiment, the tractor rests on three wheels connected to the frame. Two of the wheels are preferably positioned in a front of the tractor under the bucket and a third wheel is preferably positioned in a rear of the tractor under a seat for an operator. 
     The hydraulic system includes a drive subsystem, a steering subsystem and/or a bucket subsystem. Power for the hydraulic system is preferably supplied by an engine connected to two pumps in series, a drive pump and an auxiliary pump. Controls for the drive subsystem, the steering subsystem and the bucket subsystem can include, but are not limited to, a steering wheel, a joystick, an accelerator pedal and/or a brake pedal. 
     According to a preferred embodiment of the invention, the drive pump provides pressure for the drive subsystem. The drive subsystem includes a plurality of wheel motors fluidly connected to the drive pump, each of the wheel motors rotationally connected to a respective wheel. This design provides independent power to each of the wheels which reduces the possibility of the tractor getting stuck in the rough/loose/wet terrain of a construction site. The drive subsystem may also include a plurality of brakes, each brake connected to a respective wheel. The plurality of brakes can be incorporated into the plurality of wheel motors or may be separate units. 
     The auxiliary pump preferably provides hydraulic pressure to the steering subsystem and/or the bucket subsystem. In one embodiment, the steering subsystem operates to rotate the rear wheel under the seat of the operator. The steering subsystem includes a steering hydraulic cylinder with rack and pinion steering. This arrangement provides a turning radius that is up to three times smaller than prior art powered carts. 
     The bucket subsystem operates to pivot the bucket from a load position to an unload position. In one embodiment, the bucket subsystem includes a bucket tilt hydraulic cylinder and/or at least one gate latch hydraulic cylinder. The bucket tilt hydraulic cylinder is positioned between the frame and the bucket. The gate latch hydraulic cylinder operates to move a latch from an open to a closed position. The bucket is hingely connected to the frame to pivot at a front of the tractor and over the front wheels. The gate is hingely connected to the bucket to pivot at a top corner of the bucket. Pressurizing the bucket cylinder lifts a rear of the bucket causing the bucket to pivot at the front of the tractor. Activating the gate latch hydraulic cylinder moves the gate latch, releasing the gate to the open position. Gravity acting on the contents of the inclined bucket and the unlatched gate allows the contents of the bucket to be deposited in a desired location. The opening between the gate and the bucket is preferably positioned near a bottom of the tractor, this position minimizes splashing of the concrete as it is unloaded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings, wherein: 
         FIG. 1  is a side view of a tractor in a load position according to one embodiment of this invention; 
         FIG. 2  is a front view of the tractor of  FIG. 1 ; 
         FIG. 3  is a rear view of the tractor of  FIG. 1 ; 
         FIG. 4  is a top view of the tractor of  FIG. 1 ; 
         FIG. 5  is a side view of the tractor of  FIG. 1  in an unload position according to one embodiment of this invention; and 
         FIG. 6  is a diagram of a hydraulic system for the tractor according to one embodiment of this invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1-5  show a tractor  10  according to one embodiment of this invention. The tractor of this invention is a hydraulic powered tractor which can be used for hauling concrete and other materials at a construction site or other areas with an uneven terrain. The tractor  10  includes a frame  12 , a front wheel  14 , a rear wheel  16 , a bucket  18 , a gate  20 , and an engine  22  (the engine  22  is shown in  FIG. 6 , the engine  22  is blocked from view by a engine surround  23  in  FIGS. 1-5 ). In the embodiment of  FIGS. 1-5 , the tractor  10  includes three wheels, two front wheels  14  positioned beneath the bucket  18  and the rear wheel  16 . In a preferred embodiment, the tractor  10  includes a seat  24  positioned above the rear wheel  16 . 
     The frame  12 , bucket  18  and gate  20  are preferably manufactured of a strong and durable material such as steel, aluminum, titanium, and/or an alloy. The frame  12 , bucket  18  and gate  20  are preferably reinforced with additional supports such as ribs and/or tubing to better withstand loading, unloading and hauling of materials such as gravel, concrete, other materials and/or tools. 
     The bucket  18  is supported by and mounted onto the frame  12 . The bucket  18  preferably connects to a front of the frame  12  over the front wheels  14  with a bucket pivot bracket and pin  26  and to a midpoint of the frame  12  with a hydraulic bucket tilt cylinder  28 . This arrangement allows the bucket  18  to pivot from a load position, shown in  FIG. 1 , to an unload position, shown in  FIG. 5 , by actuating the hydraulic bucket tilt cylinder  28 . In an alternative embodiment, a plurality of hydraulic bucket tilt cylinders are positioned between the frame  16  and the bucket  18  to pivot the bucket from the load to the unload position. 
     The gate  20  connects to two upper corners of the bucket  18  with a pair of gate hinges  30  and hangs down to a lower edge of the bucket  18 . The gate  20  can be releaseably fixed to the lower edge of the bucket  18  with at least one and preferably a plurality gate latches  32 . Each of the gate latches  32  is moveable from a latched to an unlatched position by actuating a hydraulic gate latch cylinder  34 . In an alternative embodiment, the gate  20  can be hinged to a lower corner of the bucket  18  and latched to an upper corner of the bucket  18  allowing the gate to pivot downwards. In another alternative embodiment, the gate  20  can be hinged to one side of the bucket  18  and latched to an other side of the bucket  18  allowing the gate to pivot about a vertical axis. 
     In the load position, the hydraulic bucket tilt cylinder  28  is in a retracted state allowing the bucket  18  to lie in an essentially flat position against the frame  12  of the tractor  10 . With the bucket  18  in the essentially flat position, the gate  20  hangs against an open side of bucket  18 . The gate  20  is secured against the open side of the bucket  18  with the hydraulic gate latch cylinder  34 . To move the tractor  10  to the unload position, shown in  FIG. 5 , the hydraulic gate latch cylinder  34  is actuated to move the gate latch  32  and release the gate  20  from the bottom edge of bucket  18 . The hydraulic bucket tilt cylinder  28  is actuated to pivot the bucket  18  to an inclined position. With the gate latch  32  open and the bucket  18  inclined, the gate  20  hangs down and away from the bottom edge of the bucket  18 , allowing the contents of the bucket to be deposited on the ground. With this configuration splashing of the contents as the bucket  18  is unloaded is minimized. In a preferred embodiment of this invention, the hydraulic bucket tilt cylinder  34  and the hydraulic gate latch cylinder  34  can be activated quickly in both directions so that only a portion of the contents in the bucket  18  can be unloaded. 
     In the embodiment of  FIGS. 1-5 , the tractor  10  includes three wheels, two front wheels  14  and the rear wheel  16 . Each front wheel  14  is positioned under the bucket  18  and connected to the frame by a front wheel motor  54 . The rear wheel  16  is positioned under the seat  24  and connected to the frame  12  by a rear wheel motor  56  which is mounted on a yoke assembly  68  and the yoke assembly  68  is rotatably connected to the frame  12 . 
     Power for the tractor  10  is supplied by the engine  22 . The engine  22  powers a hydraulic system  36  of the tractor. In a preferred embodiment, the hydraulic system  36  is a closed-loop, high-pressure system which occupies a small footprint on the frame  12  of the tractor  10 . However, the hydraulic system could be an open-loop or any other hydraulic system. The engine  22  can be any type of engine which is able to provide the power requirements of the hydraulic system  36 . In a preferred embodiment, the engine  22  is a three-cylinder, four-cycle, liquid-cooled, diesel engine. 
       FIG. 6  is a diagram of the hydraulic system  36  according to one embodiment of this invention. The hydraulic system  36  generally comprises a drive subsystem  38  and an auxiliary subsystem  40 . The auxiliary subsystem  40  further comprises a steering subsystem  42  and a bucket subsystem  44 . 
     The engine  22  connects with a shaft to a drive pump  46  in series with an auxiliary pump  48 . In a preferred embodiment, the auxiliary pump  48  is smaller than the drive pump  46  and operates at a different pressure than the drive pump  46 . However, the auxiliary pump  48  may be larger than the drive pump  46  and/or may operate at the same pressure as the drive pump  46 . In a preferred embodiment, the drive pump  46  is a variable-displacement axial piston pump for a closed circuit which, according to one preferred embodiment, is able to supply approximately 3,625 psi of continuous pressure. However, the drive pump  46  is not limited to a variable-displacement axial piston pump and can be any type of pump and can supply any amount of pressure. In a preferred embodiment, the auxiliary pump  48  is a gear pump which is able to provide approximately 3,500 psi of continuous pressure and approximately 4,200 psi of maximum pressure. However, the auxiliary pump  48  is not limited to a gear pump and can provide any amount of pressure needed for an application. 
     As shown in  FIG. 6 , the drive pump  46  provides pressure to the drive subsystem  38 . The drive subsystem  38  includes the drive pump  46 , the hydraulic front wheel motors  54 , the hydraulic rear wheel motor  56 , and a hydrostatic transmission  52  including a directional control valve. The drive pump  46  provides pressurized hydraulic fluid to the hydrostatic transmission  52  and the hydraulic wheel motors  54 ,  56 . Each of the hydraulic wheel motors  54 ,  56  are rotationally connected to a respective wheel  14 ,  16  of the tractor to provide independent power to each of the plurality of wheels  14 ,  16 . In an alternative embodiment, a single front wheel motor is connected to an axle between the front wheels  14 . In a preferred embodiment, the hydraulic system  36  includes a plurality of brakes  58 , each brake  58  connected to a respective wheel  14 ,  16 . Each brake  58  can be a component of the hydraulic wheel motor  54 ,  56 , or the brake  58  can be a separate component from the hydraulic wheel motors  54 ,  56 . 
     In a preferred embodiment, each of the wheel motors  54 ,  56  include a twin lock system and the hydrostatic transmission  52  includes a directional control valve which has twin lock circuit compatibility. The hydrostatic transmission connects to a proportioning valve  60  which connects to each of the wheel motors  54 ,  56 . This arrangement, improves the traction of the tractor  10  by changing a hydraulic flow and pressure to one of the wheels  54 ,  56  when the wheel is rotating at a higher rate than the other wheels, to prevent wheel spin. 
     The auxiliary pump  48  provides pressure to the auxiliary subsystem  40 . The auxiliary pump  48  provides pressurized hydraulic fluid to a solenoid spool valve  62  which connects to each of the steering subsystem  42  and the bucket subsystem  44 . 
     The steering subsystem  42  comprises a steering hydraulic cylinder  64  connected to a rack and pinion  66 . The rack and pinion  66  connects to the yoke assembly  68  to provide rotational movement about a vertical axis to the rear wheel  16 . In a preferred embodiment, the steering hydraulic cylinder  64  is a pass-thru cylinder, however, the steering hydraulic cylinder  64  may be any type of hydraulic cylinder. 
     The bucket subsystem includes the hydraulic bucket tilt cylinder  28  and at least one and preferably at least two hydraulic gate latch cylinders  34 . In a preferred embodiment, the hydraulic bucket tilt cylinder  28  and/or the hydraulic gate latch cylinders  34  are electrically controlled double acting hydraulic cylinders. However, the hydraulic bucket tilt cylinder  28  and/or the hydraulic gate latch cylinders  34  can be any type of hydraulic cylinders. 
     After the hydraulic fluid passes through either the drive subsystem  38  or the auxiliary subsystem  40 , the hydraulic fluid preferably passes through a return line to hydraulic fluid cooler  70  and into a fluid reservoir  72  to be drawn into drive pump  46  or the auxiliary pump  48 . In a preferred embodiment, the hydraulic system  36  includes a plurality of return lines. In one embodiment, the hydraulic system  36  includes eight return lines. 
     The tractor  10  preferably includes a control system to control the hydraulic system  36 . In a preferred embodiment, the control system is a Parker Hydraulics computer module, model no. IQAN-TOC2. 
     An operator can control the concrete tractor with multiple controls. In one embodiment, the controls include a forward-neutral-reverse switch, a control pedal, a steering wheel and/or the joystick for bucket control. 
     Thus, the invention provides a tractor for hauling materials, including concrete, which utilizes hydraulics to independently drive the wheels and to tilt the bucket. This invention provides a tractor which a narrower turning radius than prior art tractors and an improved means for unloading the materials. 
     It will be appreciated that details of the foregoing embodiments, given for purposes of illustration, are not to be construed as limiting the scope of this invention. Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention, which is defined in the following claims and all equivalents thereto. Further, it is recognized that many embodiments may be conceived that do not achieve all of the advantages of some embodiments, particularly of the preferred embodiments, yet the absence of a particular advantage shall not be construed to necessarily mean that such an embodiment is outside the scope of the present invention.