Abstract:
A stump cutter configured for improved stability includes a frame structure, an engine, a boom with a proximal end and distal end, and a grinding wheel rotatably mounted to the distal end of the boom. The boom is pivotally mounted to the frame structure at its proximal end typically by means of a turntable, hydraulic actuators and ears. Preferably, the engine is pivotally mounted between the ears about a generally horizontal axis so that the engine is generally weight-balanced during pivoting. The horizontal axis preferably passes through or adjacent the engine&#39;s center of mass.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The invention relates to landscaping and tree removal. More particularly, the invention relates to a stump cutter for grinding tree stumps. Furthermore, the invention provides increased stability for a stump cutter through a weight centered power train. 
         [0003]    2. Background Information 
         [0004]    After a tree has been felled, the tree stump is usually a small remaining portion of the trunk with the roots still in the ground. Tree stumps can be very difficult to remove. They can be dug out of the ground using a pick and shovel or they can be shaved down using a stump cutter to remove the portion of the stump above the soil. After the stump is ground down below the soil line, soil can be placed over the remaining portion to allow grass or crops to grow. 
         [0005]    A stump cutter is a stand-alone power tool machine or equipment attachment that removes tree stumps by means of a rotating cutting wheel having a cutting disk and fixed rigid teeth extending radially outward therefrom which chip away the wood. Typically the grinding wheel is swept back and forth in a generally horizontal plane across the tree stump. With each sweep, the grinding wheel is lowered slightly to remove another layer of the stump with the next pass. An engine, typically a gasoline or diesel engine, located on the wheeled frame generates power to drive the grinding wheel. 
         [0006]    In one common stump cutter design, the cutter boom and engine are attached to a turntable. The turntable is free to swing side to side, and the engine sits transverse in respect to the cutter boom. Often, the engine has a belt drive going back to a jackshaft, which is a hinge point for a second portion of the cutter boom. This second hinge point allows the boom to raise and lower. The drawback to this design is that the boom is very long in order to clear the wheels of the chassis. Additionally, maintenance of the jackshaft bearings adds time and expense to this configuration. 
         [0007]    Another typical stump cutter design allows the cutter boom to support the engine. The cutter boom swings in a “pivot head” that can tilt fore and aft relative the chassis to raise and lower the cutter wheel. The engine pivots about a horizontal axis which is below and forward of the engine, which causes the engine to move a lot in relation to the chassis. This large amount of movement causes the machine&#39;s center of mass to move while in operation, which can lead to the stump cutter upsetting and rolling to its side, possibly causing injury. The larger amount of movement also leads to designing a lot of clearance beneath the engine/boom, which elevates the machine&#39;s center of mass. 
         [0008]    Thus a stump cutter is needed which maintains stability throughout the movement of the stump cutter boom and blade. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    A stump cutter comprising: a frame; a boom pivotally mounted on the frame about a substantially horizontal axis; a grinding wheel rotatably mounted on the boom; and an engine mounted on the boom and pivotable therewith wherein the horizontal axis passes through the engine. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]    A preferred embodiment of the invention illustrated of the best mode in which Applicant contemplates applying the principals, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims. 
           [0011]      FIG. 1  is a side elevational view of the stump cutter. 
           [0012]      FIG. 2  is an enlarged side elevational view of a portion of the stump cutter with the engine shown in phantom. 
           [0013]      FIG. 3  is a top plan view of the portion of the stump cutter shown in  FIG. 2  with the engine removed; 
           [0014]      FIG. 4  is similar to  FIG. 3  and shows the boom pivoting to one side. 
           [0015]      FIG. 5  is similar to  FIG. 4  and shows the boom pivoting to the other side. 
           [0016]      FIG. 6  is a sectional view taken on line  6 - 6  of  FIG. 2 . 
           [0017]      FIG. 7  is a side elevational view of the boom pivoting upwards with the engine shown in phantom. 
           [0018]      FIG. 8  is similar to  FIG. 7  and shows the boom pivoting downwards. 
       
    
    
       [0019]    Similar numbers refer to similar parts throughout the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The stump cutter of the present invention is shown generally at  1  in  FIG. 1 . Stump cutter  1  has a weight centered powertrain  3  constructed in accordance with the present invention. As shown, stump cutter  1  also includes a frame or chassis  2  supported by a plurality of wheels  4  to facilitate movement of stump cutter  1  from place to place. A control housing  6  is mounted on chassis  2  with protruding control levers  8 . 
         [0021]    Power train  3  includes an engine  10 , a boom  12  having first and second ends  11  and  13 , a clutch and brake system, a gearbox  20  and a grinding wheel  14 . Engine  10  and grinding wheel  14  are mounted on boom  12  respectively adjacent first and second ends  11  and  13 . Engine  10  is proximal housing  6  and drives the clutch and brake system, which drives gearbox  20 . Gearbox  20  drives rotation of grinding wheel  14  via a belt and chain system to provide the torque needed for the radially extending teeth  16  of wheel  14  to grind down a stump. Grinding wheel  14  is partially surrounded by a debris protector  18 . 
         [0022]    Referring to  FIGS. 1-3 , the mounting of boom  12  on chassis  2  is described in further detail. A boom platform  22  is mounted on chassis  2  and a turntable assembly  24  is mounted on platform  22 . Turntable assembly  24  includes a turntable  26 , which is typically a substantially flat horizontal plate rotatable about a substantially vertical axis A that passes through engine  10 , as well as a bearing  25  for rotational movement. As shown in  FIGS. 2-3 , a pair of axially spaced ears  34  is connected to and extends upwardly from turntable  26 . It will be understood that while turntable  26  and ears  34  are shown to be substantially separate, these elements may be fabricated as a single unit in a cradle shape. 
         [0023]    A stub plate  40  is fastened to each ear  34  by a stub bolt  41 , and securely holds a stub axle  38  to ear  34 . An ear support bracket  36  reinforces ear  34  and allows ear  34  to support a large amount of weight. First end  11  of boom  12  is pivotally connected to ears  34  via pivots or stub axles  38  about a substantially horizontal axis C passing through axles  38 . Boom  12  is attached to engine  10  by a plurality of bolts  42 , as well as stub axles  38 . Stub axle  38  holds a substantial amount of the total engine  10  weight and helps to stabilize the system by securing engine  10  weight on the generally neutral pivot axis C. 
         [0024]    A first pair of hydraulic actuators  28  are pivotally mounted adjacent first ends thereof on turntable  26  about a substantially horizontal axis B at respective pivots  27 . The opposite ends of actuators  28  are pivotally connected to boom  12  about a substantially horizontal axis D at pivots  31 . Actuators  28  enable upward and downward movement of boom  12  so that boom  12  is pivotable about axis C between a lowered position ( FIG. 8 ) and a raised position ( FIG. 7 ). A second pair of hydraulic actuators  30  is also pivotally connected adjacent respective first ends to platform  22  at pivots  32  and adjacent opposite ends thereof to turntable  26  at pivots  33 . Actuators  30  serve to rotate boom  12  laterally between a first lateral position shown in  FIG. 4  (arrows E, F, G) and a second opposite lateral position shown in  FIG. 5  (arrows H, I, J). Hydraulic actuators  28  and  30  each house a piston  29  that can extend or retract. 
         [0025]    In accordance with the present invention, axis C passes through engine  10  such that while boom  12  moves, its weight stays balanced and stable to ensure safe operation. As shown in  FIG. 6 , lateral axis C about which boom  12  rotates extends through or adjacent the center of mass of engine  10 . Vertical axis A, as shown in  FIG. 3 , extends through or adjacent the center of mass of engine  10  as well, intersecting axis C. The bulk of the weight of engine  10  is supported by stub axle  38 . With the weight evenly distributed, the engine remains relatively neutrally balanced in response to moving and pivoting of the boom  12  in any direction while in operation. 
         [0026]    In a preferred mode of operation, the user fells a tree and moves stump cutter  1  close to the stump by way of wheels  4 . The user stands behind control housing  6 , so as to manipulate control levers  8 . From this position, the operator can vary engine  10  speed, start and stop grinding wheel  14 , as well as vary cutting speed. Still from this position, the user may vertically lower and raise the grinding wheel  14  and swing the cutting wheel back and forth horizontally. 
         [0027]    After the user has positioned stump cutter  1  near a stump, he activates control lever  8  that controls gearbox  20  and starts rotation of grinding wheel  14 . Grinding wheel  14  is then lowered to a position below the level of the top of the stump, to one side of the stump. Activating one of control levers  8 , which controls hydraulic actuators  28 , retracts piston  29  and pulls boom  12  downward by pivoting on stub axle  38  to lower the boom. The vertical movement is stable and balanced due to engine  10  center of mass resting directly on or adjacent the pivot point for boom  12 . Boom  12  moves and pivots easily, while still maintaining balance as well as weight on grinding wheel  14  to dampen grinding feedback. 
         [0028]    After boom  12  is lowered and grinding wheel  14  is proximate to the stump, the user engages control lever  8 , which moves the boom  12  horizontally across the top of the stump. When the spinning teeth  16  on grinding wheel  14  come into contact with the stump, wood is chipped away by teeth  16  and removed from the stump. One of levers  8  controls actuators  30  to move boom  12  horizontally from one side of the stump to the other to remove a layer of wood. Piston  29  in actuators  30  alternately push and pull in concert on turntable  26  and move boom  12  from one side to the other, while actuators  28  hold the horizontal plane constant and steady. 
         [0029]    The user continues this procedure of grinding off layers of wood on the tree stump until the stump is level with the ground. At this point, the user will position the grinding wheel directly above the stump and vertically lower grinding wheel onto the stump, by means of actuators  28 . This will continue to grind the stump deeper into the ground, ultimately lowering the level of the top of the stump deep enough in the ground to allow a sufficient layer of topsoil to cover it. Grass seed or crops can then be planted evenly over the covered stump and the stump remains will not affect mowing or harvesting operations. 
         [0030]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0031]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.