Abstract:
A walk-behind trenching implement has a side mounted rotary trenching tool for creating a profiled trench into the surface of the earth, which can also be used as an implement to edge landscape beds. The trenching implement is powered by an engine that delivers rotational power in an unbalanced manner to the wheel adjacent to the rotatable trenching tool. The wheel opposite to the trenching tool is can be non-powered to freely rotate as the implement is moved across the surface of the ground, or braked to unbalance power delivery through a differential. This unbalanced propulsion drive induces a skewing action into the operation of the implement that counterbalances the opposite skewing action resulting from the operation of the trenching tool to provide a more smoothly operating implement. A trenching tool having a configuration conducive to profile modification allows flexibility in the desired shape of the trench being formed.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to a powered utility apparatus and, more particularly, to a powered trenching apparatus that can operated from behind the implement. 
   Powered walk behind or self-propelled tools are known in the art. Examples include brush mowers, lawn mowers, rotary brooms, string trimmers and edging mechanisms. Each such implement is operably driven by a dedicated power unit. Motive power is transferred from the power unit to the drive wheels, while other power drive trains transfers operational power to the work apparatus, such as an edging mechanism. Many of these powered walk behind implements have the work apparatus positioned generally centrally and likely forwardly of the engine to provide a balanced load to the operation of the implement. Some such powered implements, like the edging mechanism for example, position the work apparatus to one side of the implement. Edging mechanisms, however, do not encounter a significant load in the operation thereof as the edging device is shaping the edge of landscape beds, and the like. 
   A trenching mechanism, such as found in U.S. Pat. No. 6,266,900, issued to Dana Bizzell on Jul. 31, 2001, has been in use for many years to dig a trench below the surface of the ground and, therefore, incurs a substantial load during the operation. Typically, a walk behind trencher is operated with the implement trailing the  operator, rather than the operator trailing the implement, as with a lawn mower or an edging mechanism. Therefore, the term “walk behind trencher” is somewhat of a misnomer. Pulling a conventional “walk behind trencher” can be an arduous task and is quite tiring to the operator. The power unit must be guided in the proper direction so that the trenching mechanism digs the trench in the desired location, while providing some motive power to the forward movement of the implement. 
   U.S. Pat. No. 6,125,943, issued to Charles Valois on Oct. 3, 2000, is directed to an edging/trenching mechanism that is of the true walk behind configuration. The work apparatus is configured to provide a narrow slit in the ground and, therefore, does not encountered the high operative loads that a conventional trencher, such as in the aforementioned Bizzell patent. In fact, the more significant the trench being formed by the work apparatus, the greater the side draft loads on the implement would be for a trencher of the Valois configuration. The handling of a side mounted trenching apparatus can be particularly burdensome as the rotation of the trenching tool is normally rotating in the opposite direction to the desired direction of travel of the implement, causing the operator to constantly skew the implement to the side to compensate for the operational load imposed by the trenching tool. Using the “pull behind” version of a side mounted trencher alleviates this problem somewhat, but performance and safety problems compromise the effectiveness and tend to exhaust the operator unduly.  
   Accordingly, it would be desirable to provide a true walk behind trenching apparatus having a side mounted trenching tool that can be operated in a manner that will enhance performance and ease the physical burden on the operator. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to overcome the disadvantages of the prior art by providing a walk-behind edger/trencher having a side mounted trenching tool that minimizes the side draft loads encountered with the operation of the ground engaging and shaping tool. 
   It is a feature of this invention that the side mounted trenching tool can be operated into the direction of travel for the implement to provide a more efficient dispersion of the unearthed soil. 
   It is an advantage of this invention that the operator of the walk behind trenching apparatus will not be burdened physically by the operation of the trenching apparatus. 
   It is another advantage of this invention that the operator can walk behind the trenching implement to allow the drive mechanism to the implement wheels to power the forward motion of the implement. 
   It is another object of this invention to provide a drive mechanism for a walk behind trenching apparatus having a side mounted trenching tool that opposes the side draft forces encountered with the operation of the trenching tool.  
   It is another feature of this invention that the forward motion of the trenching implement will be subjected to minimal course corrections due to the skewing forces imposed by the operation of the trenching tool. 
   It is still another feature of this invention that the drive mechanism compensates for the side load forces imposed by the operating trenching tool. 
   It is still another object of this invention to provide a drive mechanism for a walk behind trenching implement having a side mounted trenching tool whereby the operative power is delivered to the drive wheels in an unbalanced manner to offset the skewing action resulting from the engagement of the rotating trenching tool with the ground. 
   It is yet another feature of this invention that the unbalanced delivery of operative power can be delivered through a differential by restricting the rotation of one of the drive wheels during operation of the edging/trenching implement. 
   It is yet another advantage of this invention that the restriction of rotation of one of the drive wheels driven through a differential can be effected through a braking device that enables the operative power delivered to a differential to be passed to the opposite drive wheel in an unbalanced manner. 
   It is a further feature of this invention that the unbalanced delivery of operative power to opposing drive wheels can be accomplished through the driving of only one of the drive wheels to provide a side drive force that compensates for the side operating loads imposed by the rotating trenching tool.  
   It is still a further feature of this invention that the wheel adjacent to the side on which the rotating trenching tool is located is driven, while the wheel opposite to the rotating trenching tool is free-wheeling. 
   It is a further advantage of this invention that the single wheel drive adjacent the side loads imposed by the operating trenching tool provides a skewing force to the movement of the implement in opposition to that encountered with the trenching tool. 
   It is yet another advantage of this invention that the opposing skewing forces result in a forwardly moving trenching implement that is easy to control and has effective operation of the trenching tool. 
   It is yet another object of this invention to provide a trenching tool that can be easily constructed with different profiles to provide profiled trenches. 
   It is a further object of this invention to provide a walk behind edging/trenching implement having a side mounted ground engaging and shaping tool which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
   These and other objects, features and advantages are accomplished according to the instant invention by providing a walk-behind trenching implement having a side mounted rotary trenching tool for creating a profiled trench into the surface of the earth, which can also be used as an implement to edge landscape beds. The  trenching implement is powered by an engine that delivers rotational power in an unbalanced manner to the wheel adjacent to the rotatable trenching tool. The wheel opposite to the trenching tool is can be non-powered to freely rotate as the implement is moved across the surface of the ground, or braked to unbalance power delivery through a differential. This unbalanced propulsion drive induces a skewing action into the operation of the implement that counterbalances the opposite skewing action resulting from the operation of the trenching tool to provide a more smoothly operating implement. A trenching tool having a configuration conducive to profile modification allows flexibility in the desired shape of the trench being formed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a right side elevational view of a walk-behind trenching implement incorporating the principles of the instant invention and having a side mounted trenching tool positioned for rotation adjacent the drive wheel of the implement; 
       FIG. 2  is a top plan view of the trenching implement shown in  FIG. 1 ;  
       FIG. 3  is a schematic top plan view of the drive mechanism providing operative rotational power to a drive wheel on one side of the implement while allowing the opposing wheel to rotate freely; 
       FIG. 4  is a right side elevational view of the drive mechanism corresponding to lines  4 — 4  of  FIG. 3 ; and 
       FIG. 5  is a schematic top plan view of an alternative drive mechanism providing an unbalanced delivery of operative rotational power to one of the drive wheels through a differential. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIGS. 1 and 2 , a walk-behind version of a landscape edging/trenching implement incorporating the principles of the instant invention can best be seen. Any left or right references are used as a matter of convenience and are determined by standing at the rear of the machine where the operator would walk gripping the handlebars to effect movement of the implement in a forward direction. One skilled in the art will readily recognize that the principles of the instant invention can be applied to self-propelled or mounted versions of powered implements as well as to walk-behind versions; however, only the walk-behind version, as depicted in the drawings, will be described to exemplify the inventions.  
   A edging/trenching implement  10  is known in the art for forming a small shaped trench in the surface of the ground to bury utility lines of various kinds, such as water, gas, electrical, communications cables, sewer lines and dog fencing, and to shape the edges of landscape beds. After the trench T has been dug and the utility line, etc. placed in the trench, the trench T is usually backfilled by hand or with a separate blade device. Side mounted edging/trenching implements  10 , of the type depicted in the drawings, can also be used to shape landscape beds. The trenching tool  25  can be configured, as will be discussed in greater detail below, to provide the specific profile for the trench, against which mulch or other ground cover will be placed. Conventional landscape edgers operate somewhat similarly, though less aggressively and sometimes in the same rotational direction as the direction of travel, to maintain landscape beds after the landscape beds have been created. 
   Walk-behind implements  10  typically have a frame  11  supported above the ground G by a pair of wheels  13 ,  14  and an integral implement  40 . An engine  15  providing the operative power for the edging/trenching implement  10  is supported on the frame  12 . The engine  15  has a rotatably power output shaft  16  on which is typically mounted a pulley  17  to power a drive belt  19  for driving the trenching tool  25 . The frame  11  extends rearwardly and upwardly to form a pair of laterally spaced handlebars  12  which the operator can grasp to control the operation and direction of travel of the implement  10 . Typically, the handlebars  12  will have controls (not shown) supported thereon to control various aspects of the engine  15 .  
   The two wheels  13 ,  14  provide only two points of contact for the implement  10  with the ground G. Although a pair of front wheels could be utilized to provide positional stability for the implement  10 , a third wheel  14   a  is preferably mounted to the frame  11  at a forward location substantially in alignment with the drive wheel  14  because of the configuration of this edging/trenching implement  10  to place the trenching tool  25  on the side of the implement. This orientation of the front wheel  14   a  provides adequate stability for this particular edging/trenching implement  10  configuration. Preferably, the front wheel  14   a  is castered to permit the front wheel  14   a  to follow the direction of movement without interfering with steering or other operation of the implement  10 . 
   The frame  11  supports on the right side a tool support arm  20  that is preferably pivoted at a horizontal pivot  22  mounted on the frame  11  to permit movement of the support arm  20  in a generally vertical direction, thus moving the trenching tool  25  into and out of engagement with the ground G. The tool support arm  20  extends rearwardly from the pivot  22  and terminates at a rotatable tool spindle  24  mounted in the support arm  20 . The tool spindle  24  projects horizontally from the support arm  20  to mount the trenching tool  25 , which will be described in greater detail below. A shroud  27  is also preferably mounted at the rearward terminus of the support arm  20  to surround the trenching tool  25  to control the discharge of dirt from the operation of the trenching tool  25 . The rearward terminus of the tool support arm  20  can also have mounted thereon a gauge wheel  28  supported from an adjustable bracket  29  to control the depth to which  the trenching tool  25  will dig into the ground G. By adjusting the position of the gauge wheel  28  relative to the bracket  29 , the depth of the trench T formed by the trenching tool  25  can be varied. 
   The preferred drive mechanism  30  for the edging/trenching implement  10  is depicted in  FIGS. 1–4 . A first drive belt  19  is entrained around the drive pulley  17  to transfer rotational power from the engine power output shaft  16  to a driven pulley  32  on a right angle gearbox  31  supported on the frame  11  rearward of the front wheel  14   a . Rotational power is transferred to an output pulley  33  oriented orthogonally to the driven pulley  32  on the outboard side of the gearbox  31 . A second drive transfer belt  35  is entrained around the output pulley  33  and extends generally parallel to the tool support arm  20  to drive a tool spindle pulley  37 , which in turn drives a spindle  24  that effects rotation of the trenching tool  25 . Preferably, the pivot  22  is oriented in alignment with the axis of rotation of the output pulley  33  so that vertical movement of the tool support arm  20  does not change the tension in the second drive transfer belt  35 . 
   The propulsion drive mechanism  40  begins with a second drive pulley  41  supported on the power output shaft  16  of the engine  15 , preferably above the first drive pulley  17  providing rotational power to the trenching tool  25 . A third drive belt  42  is entrained around the second drive pulley  41  and around a trans drive pulley  44  to deliver rotational power to a hydrostatic transmission  45 . One skilled in the art will recognize that other power transfer devices could be utilized, but a transmission mechanism enables the output speed to be varied by controls (not shown) on the handle bars  12  to control the  operating speed of the implement  10 . The hydrostatic transmission  45  has an output shaft  46  that is selectively variable in rotational speed. An output gear  47  is connected to the output shaft  46  to engage an intermediate step down gear  48  that, in turn, engages a drive gear  49  mounted on the axle mechanism  50  extending between the wheels  13 ,  14 . 
   The axle mechanism  50  includes opposing first and second axles  51 ,  52  that extend from the drive gear  49  to the respective wheel  13 ,  14 . The drive gear  49  is connected to the right axle  52  by a spline  55  to accomplish a driving connection therebetween, whereas a bushing  54  lies between the drive gear  49  and the left axle  51  to prevent the drive gear  49  from causing rotation of the left axle  51 . The respective axles  51 ,  52  are supported by bearings  56 ,  57  retained by conventional snap rings  58  and washers  59 . The drive gear  49  overlaps the intersection between the respective inboard ends of the axles  51 ,  52 . With the use of the bushing  54 , there is no driving connection between the drive gear  49  and the left axle  51 , thus, the left axle is non-powered and, preferably, free wheeling to move with the movement of the implement  10 . The splined connection between the drive gear  49  and the inboard end of the right axle  52  permits the transfer of rotational power to the right axle  52  to power the rotation of the right wheel  14  in response to the output power of the hydrostatic transmission  45 . 
   An alternative drive mechanism  70  is depicted in  FIG. 5 . In the preferred drive mechanism  30 , no differential apparatus is provided between the power input, e.g. the drive pulley  17 , and the axles  51 ,  52 , thereby allowing one axle  52  to be powered while the opposing axle  51  is left unpowered. In the alternative drive mechanism  70 , a  conventional differential apparatus  71  is retained within the drive mechanism  70 , wherein a primary ring gear  72  is driven from the engine  15  to rotate pinions  73  fixed to the respective axles  51 ,  52  through planetary gears  74  in a conventional manner. The drive mechanism  70  further includes a braking device  75  operatively mounted on the left axle  51 , preferably between the axle  51  and the corresponding ground engaging wheel  13 . As a result, the differential apparatus  71  will transfer rotational power to the right ground-engaging wheel  14  to create an unbalanced drive offsetting the drag imposed by the operation of the rotating trenching tool  25 . 
   In operation, the alternative drive mechanism  70  is controlled through manipulation of a control device  77  mounted on the handlebars  12 . The control device  77  engages the brake  75  to restrict the rotation of the ground-engaging wheel  13 , thus restricting the rotation of the corresponding pinion  73 . As a result, the rotation of the planetary gears  74  with the ring gear  72  drives the opposite axle  52  and the corresponding ground-engaging wheel  14  at a faster speed to impose an unbalanced drive to the wheels  13 ,  14  and offsetting the drag imposed by the rotating trenching tool  25 . The manipulation of the control  77  can be varied to provide an offsetting skew to the implement  10  that matches the drag imposed by the trenching tool  25 , which can vary according to the characteristics of the soil being engaged and the shape and depth of penetration of the tool  25 . Alternatively, the control  77  could be interlocked with the engagement of the drive to the trenching tool  25  so that the implement  10  would be  driven in a balanced manner when the trenching tool  25  is disengaged and in an unbalanced mode when the trenching tool  25  is engaged. 
   Yet another alternative drive mechanism could include the locking of the rotation of the opposite drive shaft  51  and a selective disengagement of the corresponding ground-engaging wheel  13  to permit the opposite wheel  13  to free-wheel in response to the engagement of the drive to the trenching tool  25 . In this configuration, the differential mechanism  71  would deliver all rotational power from the engine  15  to the ground-engaging wheel  14  adjacent to the trenching tool  25 . Such a drive arrangement would involve mechanical interlocks that may not present a financially practical design. Nevertheless, alternative unbalanced drive configurations can be encompassed within the scope of the instant invention to offset the side drag forces imposed through the operation of the rotating trenching tool  25 . 
   The trenching tool  25  is configured to carve a trench T into the surface of the ground G along side of the implement  10 . The trenching tool  25  is formed from a central cup  62  preferably having a closed end detachably connected to the tool spindle  24  to be rotatably driven thereby from the entrained second drive transfer belt  35 . A series of cutting blades  62  are mounted around the circumference of the central cup  61  preferably in a spiral orientation to spread out the forces generated from the cutting blades  62  engaging the ground G. The cutting blades  62  are formed with cutting teeth  63  located along the outer periphery of the blades  62 . The shape of the cutting blades  62  will define the shape of the trench T to be created by the rotation of the trenching tool  25 .  Accordingly, differently configured cutting blades  25  can be substituted to create the desired shape of the trench T to be dug, simply by detaching the central cup  61  from the spindle  24  and re-attaching a preferred trenching tool  25  having the desired configuration. The trenching tool  25  is rotated in the direction indicated by the rotation arrow  65 , which looking at the right side of the implement  10 , as seen in  FIG. 1 , is in a counterclockwise direction with the digging motion of the trenching tool  25  in the ground G is in the same direction as the normal direction of travel of the implement  10 . 
   In operation, the propulsion drive mechanism  40  delivers rotational power from the engine  15  through the hydrostatic transmission  45  to the right wheel  14  to drive only the right wheel  14  without providing rotational power to the left wheel  13 . This one-sided driving power to the implement  10  causes a skewing of the implement to the left since the left wheel  13  is freely rotating without being driven from the engine  15 . In opposition to the skewing forces on the implement  10  from the propulsion drive mechanism  40 , the operation of the trenching tool  25  digging into the ground G pulls the implement  10  to the right. The net result of the opposing skewing forces is that the implement  10  is propelled substantially straight forwardly without undue physical exertion from the operator. The movement of the implement  10  without the trenching tool  25  being engaged with the ground G, however, requires the operator to physically compensate for the skewing forces exerted by the propulsion drive mechanism  40 . 
   To form a trench T in the ground G, the operator lowers the tool support arm  20  until the trenching tool  25  engages the surface of the ground G. The operative  power to the trenching tool  25  is engaged to start the rotation of the trenching tool  25  which will then dig into the ground G until a limit device such as the gauge wheel  28  stops the lowering of the tool support arm  20 . In this manner, the trenching tool  25  will dig a profiled trench T in the ground G extending parallel to the direction of travel over which the implement  10  is steered. Control over the position of the trench T is maintained by the operator directing the movement of the implement  10  through manipulation of the handle bars  12 . The earth excavated by the trenching tool  25  is thrown forwardly and upwardly into the shroud  27  which is shaped to deflect the excavated earth outboard of the freshly dug trench T. For new landscape beds, the trench T is formed with a sharp profile with the excavated earth being thrown onto the new landscape bed, rather than onto the area (such as the lawn) over which the implement  10  is being operated. 
   It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention.