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You are an expert at summarizing long articles. Proceed to summarize the following text: 
TECHNICAL FIELD 
   The present invention relates to digging equipment, and in particular, to equipment for trenching. 
   BACKGROUND 
   Trenchers are used in landscaping to define beds, dig ditches for the bases of walls, allow insertion of edging or irrigation tubing and the like. Landscapers often use trenchers to provide the edging around basic, simple gardens, such as ovals or rectangles. While it has long been known to provide highly elaborate garden plans, such as the formal gardens at Versailles, using a trencher to create these shapes has not been practical because of the difficult of keeping a manually operated trencher precisely on course while digging in a complicated design. Instead, the design has been manually laid out and marked, e.g., with lime, then dug in by hand with a shovel. In addition to landscape uses, trenchers are used by electricians and utilities to install cables or wiring in small trenches in the ground. 
   Trenchers come in a variety of wheel configurations, including two wheel, three wheel and four wheel. Two wheel trenchers, such as those shown in U.S. Pat. Nos. 6,874,581 and 6,938,699 can be highly steerable in very tight curves, but depend entirely on manual brute force from the operator for steering. Four wheel trenchers such as those shown in U.S. Pat. Nos. 4,195,427 and 4,896,442 may reduce the amount of brute force required for steering, but the four wheel configuration prevents a very tight turning radius. Three wheel trenchers can have a tighter turning radius than four wheel trenchers, but most, such as those shown in shown in U.S. Pat. Nos. 4,503,630 and 5,226,248, are steered from the back. This means the wheels must be off-center from the trenching arbor, since they would fall into the trench of they were in-line with the arbor, and this in turn affects their stability, particularly in very tight turns. 
   The trencher shown in U.S. Pat. No. 5,964,049 (the first two figures of which are included herein as  FIGS. 1 and 2 ) puts the steering wheel at the front of the trencher in line with the arbor, with the axis of the rear wheels in line with the arbor axis. This allows for a much tighter turning radius than the other designs, as well as stability during tight turns. However, the design as shown in the referenced patent has no drive to the wheels, so motive power still comes from the operator. In addition, the combination of the handle extending at the front of the trencher and the need for the operator to stand in front of the handle to pull the trencher limits the usefulness of the trencher in tight spaces. 
   SUMMARY OF THE INVENTION 
   The present invention improves upon these designs by providing a powered steering and drive mechanism and a control system for them. Preferably, the steering system is an electric motor mounted to a shaft extending upward from the pivot of the front wheel, and the drive mechanism is a hydraulic motor mounted to the front wheel. This configuration minimizes the total space required by the trencher, enabling its use in tight spaces. 
   The trencher also includes a control system to control the steering and drive mechanisms. This control system can take the form of a simple remote control with control knobs to allow an operator to manually regulate the power going to the different motors. Alternatively, this control system can incorporate a programmable computer, which can be programmed to steer the trencher along a specific path. In this configuration, the control system preferably is also provided with a position monitoring system to provide a feedback loop to the computer to ensure that the trencher is where expected. 
   A programmable trencher of such a design has the advantage that it can be used to cut shapes, such as logos, flowers, or any other design, into the earth. The pattern need not even be laid out and marked, just programmed into the computer. The computer then can use the position monitoring system to guide the trencher along the route needed for the design. The result is a trencher capable of doing types of digging that heretofore could only be done on a practical basis by hand. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
       FIG. 1  is a reproduction of FIG. 1 of U.S. Pat. No. 5,964,049, and is a perspective view of a trencher according to the prior art. 
       FIG. 2  is a reproduction of FIG. 2 of U.S. Pat. No. 5,964,049, and is an exploded isometric view the trencher of  FIG. 1  according to the prior art. 
       FIG. 3  is a side perspective view of the main components of a preferred embodiment of a trencher according to the present invention. 
       FIG. 4  is a front perspective view of the preferred embodiment of  FIG. 3 . 
   

   DETAILED DESCRIPTION 
   The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. 
   The prior art trencher shown in  FIGS. 1 and 2  has a main frame  10  with two rear wheels  12  rotatably mounted thereto (only the foreground wheel is visible for clarity of illustration). A front wheel  14  and steering handle  16  are mounted to a front wheel bracket  17 , which is in turn rotatably mounted to the main frame  10  via bushing  18 . The bushing  18  is located along the longitudinal center line of the main frame  10 , so that the rear wheels  12  and front wheel  14  form a balanced tripod arrangement which is readily steerable by changing the direction of the steering handle  16 . 
   An arbor housing  20  is mounted on the main frame  10  towards the rear thereof and centered between the rear wheels  12 . A deflector housing  22  is removably attached to the top of the arbor housing  20 , and preferably is reversible to deflect dirt in either direction. A rubber flap  23  or the like preferably is provided on the discharge chute  24  of the deflector housing  22  to prevent objects from being thrown. 
   An arbor pivot bracket  30  is pivotally mounted to the main frame  10  at pivot points  25 , e.g., by the use of bolts or pins. An arbor  32  is fixedly mounted to a shaft  34  which is rotatably mounted to the arbor pivot frame  30 . A pulley  26  is fixed to the shaft  34 . An engine  27  is mounted to the main frame  10 , and drives the shaft  34  and arbor  32  through a belt drive  28  and clutch  29  to the pulley  26  in the usual manner. 
     FIGS. 3 and 4  illustrate a preferred embodiment of improving upon this design according to the present invention. In  FIGS. 3 and 4 , parts which are essentially the same as in the prior design, e.g., rear wheel  12 , use the same reference numbers as in  FIGS. 1 and 2 . Many of the parts illustrated in U.S. Pat. No. 5,964,049, e.g., the deflector housing  22 , have been omitted in  FIGS. 3 and 4  for clarity of illustration, but it will be understood that they are still included in the complete embodiment. Reference may be had to U.S. Pat. No. 5,964,049 for details of those components. 
   Turning to  FIGS. 3 and 4 , a hydraulic pump  100  is mounted to be driven by engine  27 . A hydraulic motor  101  is mounted to the arbor pivot frame  30  and connected to drive the arbor through shaft  34 . The front wheel  14  is pivotally mounted in the bushing  18  by a front wheel bracket  102 . Another hydraulic motor  103  is mounted to the front wheel bracket  102  and connected to drive the front wheel  14 . A hydraulic valve box  105  is mounted to the main frame and connected via conventional hydraulic tubing (not shown for clarity of illustration) between the hydraulic pump  100 , and the hydraulic motors  101 ,  103 . 
   A mounting frame  106  is mounted to the main frame  10  in a position above the front wheel bushing  18 . A gear reducer  107  is mounted to the top of the mounting frame  106 , with an output shaft extending downward through the mounting frame  106 . An electric motor  108  is mounted to the top of the gear reducer  107 , with the shaft of the electric motor connected as the input to the gear reducer  107 . The front wheel bracket  102  includes a shaft  109  which extends upwardly beyond the bushing  18 . The output shaft of the gear reducer  107  engages the upwardly extending shaft  109  via a keyway  110 . 
   An onboard control system  111  is mounted in any suitable location and is connected via wires (not shown for clarity of illustration) to control the electric steering motor  108  and the hydraulic valve box  105 , which in turn controls flow to the hydraulic motors  101 ,  103 . A potentiometer  112  is mounted below the keyway  110  to monitor the rotational position of the upwardly extending shaft  109 , and therefore of the front wheel  14 , and provide a signal representative thereof to the onboard control system  111  via a wire (not shown for clarity of illustration). 
   In this configuration, the onboard control system  111  can control the rotational speed of the arbor by controlling the output of the hydraulic motor  101  and the longitudinal motion of the trencher by controlling the output of the hydraulic motor  103 . Preferably, the hydraulic valve box  105  includes separate valves for each of the hydraulic motors  101 ,  103 , so that the onboard control system  111  can independently control the arbor speed and the speed at which the trencher moves. In addition, the hydraulic valve box  105  preferably includes valves to allow the drive motor to be driven both in forward and reverse. The onboard control system  111  can control the steering of the trencher by controlling the electric motor  108 , using the output of the potentiometer to provide a feedback loop. 
   The onboard control system  111  preferably is itself controlled by a remote control  114 , which may be in communication by wire to the onboard control system  111 , but preferably communicates wirelessly. The remote control  114  can be a simple hand operated radio control, much like those used with a radio controlled toy car, with knobs or other controls to adjust the arbor speed, drive speed and steering direction. 
   Preferably, the remote control  114  is a programmable computer. The computer can be programmed to emulate the simple hand operated radio control for use in manually guided use of the trencher, but also can be pre-programmed to drive the trencher along a pre-selected path. To assist in this configuration, a position sensor  115  may be provided on the trencher which can determine the position of the trencher at any time. A global positioning system such as that shown in U.S. Pat. No. 6,954,999 would be sufficient for this purpose in some situations, but in most situation a more precise localized laser, optical or radio frequency triangulation position will be preferable, e.g., systems such as those shown in U.S. Pat. Nos. 5,999,131 and 6,965,344. The position information from the position sensor  115  then can be provided to the remote control  114  to use as feedback to ensure that the trencher is following the appropriate path and adjust the steering and motion appropriately to keep it on path. 
   All patents referenced herein are incorporated by reference. 
   In the foregoing detailed description, the invention has been described with reference to specific embodiments, but various changes thereto will be readily apparent to one of ordinary skill in the art. For example, while specific types of motors have been described in particular locations, it will be understood that electric, hydraulic, pneumatic or other motors could be substituted for all of them, with corresponding changes to the onboard control system. Similarly the hydraulic motor  103  could be mounted to one of the rear wheels  12  instead of the front wheel  14 . It may be appreciated that various other modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.

Summary:
A trencher has two wheels equidistant on either side of the arbor, and a third steerable wheel at the front of the trencher in line with the arbor. Speed of the arbor, forward motion of the trencher and the direction of motion are determined by motors controlled by an onboard control system. The onboard control system is controlled by a remote control, which may be a simple manual wireless controller or a programmable computer. With a programmable computer, the trencher can be pre-programmed to dig along a pre-selected path, e.g., a logo, flower or other design.