Abstract:
A walk-behind power unit is configured to detachably mount a variety of work implements to perform a corresponding variety of operations from a single power unit. The power unit includes an implement mounting mechanism that is pivotable about a generally vertical pivot axis corresponding to the power output shaft of the engine on the power unit. An attached work implement can be moved laterally to change the operating characteristics through pivoting the implement to either side of a normal direction of travel. An landscape edger implement can be mounted so that the width of cut of the cutting disk is varied as the edger implement is pivoted. A mower implement can be attached so that the cutting path of the mower blade is offset laterally as the implement is pivoted, thus permitting the mower to mow around obstacles offset to the side of the direction of travel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims domestic priority on U. S. Provisional Patent Application Serial No. 60/283,163, filed Apr. 12, 2001, the description of which is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates generally to a powered utility apparatus and, more particularly, to a power unit that can be utilized with a variety of attachments to provide multiple uses therefor.  
           [0003]    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. It would be desirable to have the capability of utilizing a single such power unit for which different powered implements could be attached to perform the function desired. Such a power unit configuration would be more cost effective as the operator would be required to purchase only a single power unit that could be adapted for operative connection to a variety of implement attachments.  
           [0004]    Edging mechanisms such as found in U.S. Pat. No. 5,199,502 and in U.S. Pat. No. 5,156,218 are fixed at an previously defined cutting angle with respect to the direction of travel of the mechanism. Changes in the cutting angle are not contemplated by such mechanisms; however, increasing the cutting angle as defined relative to the direction of travel would widen the trench that is formed by the rotation of the powered disk member. Increasing the cutting angle would also provide a different cross-sectional profile to the trench. The different trench profiles can be combined to improve the shape of the edging trench by first digging one shaped trench and then re-shaping the side of the first trench by moving the powered disk member along a second pass engaging one side of the first trench.  
           [0005]    Furthermore, under conditions where the edge of the landscape area is covered with heavy, overgrown and/or rough sod edges, a conventional edging mechanism does not cut a trench that is wide enough to cut the sod roots adequately to permit an easy removal of the sod debris. By providing the capability of changing the cutting angle of the powered disk member, a wider trench can be formed whenever needed to solve such problems. Also, permitting the movement of the implement during operation allows the implement to be shifted in an offset direction to provide the capability of mowing under fence rails and other similar tasks.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of this invention to overcome the disadvantages of the prior art by providing a walk-behind power unit to which multiple implements can be detachably connected thereto.  
           [0007]    It is an advantage of this invention that the plurality of implements that can be attached to the power unit will enable a single power unit to accomplish a wide variety of tasks.  
           [0008]    It is a feature of this invention that an implement mounting mechanism is provided to accommodate a variety of detachable implements that can be operably powered by the walk-behind power unit.  
           [0009]    It is another object of this invention to provide an implement mounting mechanism for a walk-behind power unit in which the implement can be laterally shifted while being operated.  
           [0010]    It is another feature of this invention that the implement mounting mechanism is pivotable about a generally vertical axis of rotation to provide the ability to shift the implement attached to the power unit laterally.  
           [0011]    It is still another feature of this invention that the vertical axis of rotation of the implement mounting mechanism corresponds to the powered output shaft of the engine forming a part of the walk-behind power unit.  
           [0012]    It is another advantage of this invention that the pivotable implement mounting mechanism allows the attached implement to be operated in different configurations.  
           [0013]    It is still another feature of this invention that the implement mounting mechanism is pivotable to both the left and right of a longitudinally extending axis, corresponding to the normal direction of travel of the power unit.  
           [0014]    It is still another advantage of this invention that the operating characteristics of the attached implement can be varied by pivotally moving the implement left or right of the normal direction of travel.  
           [0015]    It is still another object of this invention that a landscape edger implement can be detachably mounted to the power unit so as to be operable to cut a trough around the edge of a landscape bed.  
           [0016]    It is yet another feature of this invention that the cutting disk of the landscape edger can be oriented with respect to the direction of travel to vary the orientation of the cutting disk with respect to the normal direction of travel of the walk-behind power unit.  
           [0017]    It is yet another advantage of this invention that the pivotal movement of the edger implement about the vertical axis of rotation of the implement mounting mechanism varies the width of cut of the cutting disk to change the characteristics of the trough cut around a landscaped bed.  
           [0018]    It is yet another object of this invention to provide a mower implement that can be detachably mounted to the implement mounting mechanism of the walk-behind power unit.  
           [0019]    It is a further feature of this invention that the mower implement can be operated along different cutting paths offset to the side of a straight-ahead orientation by pivotally moving the implement mounting mechanism about its axis of rotation.  
           [0020]    It is a further advantage of this invention that the mower implement can be moved laterally by the pivotally movable implement mounting mechanism to vary the orientation of the cutting path of the mower implement as the mower implement is being operated.  
           [0021]    It is still a further advantage of this invention that the mower implement can be moved laterally to mow around an obstacle as the implement is moved along a direction of travel with the walk-behind power unit.  
           [0022]    It is still a further feature of this invention that the drive transfer belts transferring operative rotational power from the engine on the power unit to the detachably connected implement is tensioned by the position of the driven portion of the implement.  
           [0023]    It is a further object of this invention to provide a locking mechanism to control the pivotal movement of the implement mounting mechanism.  
           [0024]    It is yet a further feature of this invention that the locking mechanism is spring-biased into a locking position to fix the implement in a pre-selected position until lateral movement of the implement is deisred.  
           [0025]    It is yet a further advantage of this invention that the spring-biased locking mechanism can be controlled from the handles of the walk-behind power unit.  
           [0026]    It is still a further object of this invention to provide a power unit operable to power the operation of a variety of detachable work implements and which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.  
           [0027]    These and other objects, features and advantages are accomplished according to the instant invention by providing a walk-behind power unit that is configured to detachably mount a variety of work implements to perform a corresponding variety of operations from a single power unit. The power unit includes an implement mounting mechanism that is configured to receive detachable work implements. The implement mounting mechanism is pivotable about a generally vertical pivot axis that corresponds to the power output shaft of the engine on the power unit. An attached work implement can be moved laterally to change the operating characteristics thereof by pivoting the implement mounting mechanism to either side of a normal direction of travel. An landscape edger implement is provide which will change the width of cut of the cutting disk as the edger implement is pivoted about the vertical pivot axis. A mower implement is provided that can laterally move the cutting path of the mower blade as the implement is pivoted about the vertical pivot axis to permit the mower to mow around obstacles offset to the side of the direction of travel.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    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:  
         [0029]    [0029]FIG. 1 is a right side elevational view of a walk-behind power unit incorporating the principles of the instant invention and having an implement mounting mechanism for the attachment of a variety of implement attachments, the vertical axis concentric with the engine output shaft being identified with a schematically imposed centerline;  
         [0030]    [0030]FIG. 2 is a top plan view of an edger implement adapted for detachable connection to the implement mounting mechanism depicted in FIG. 1;  
         [0031]    [0031]FIG. 3 is a top plan view of the power unit depicted in FIG. 1 in position to receive the edger implement shown in FIG. 2, the pivotal movement of the implement mounting mechanism being identified by an arcuate arrow;  
         [0032]    [0032]FIG. 4 is a top plan view of the power unit depicted in FIGS. 1 and 3, but having the edger implement detachably mounted thereon, the implement mounting mechanism being deployed to orient the edger implement in a straight forward direction;  
         [0033]    [0033]FIG. 5 is a top plan view of the power unit and attached edger implement as depicted in FIG. 4 but with the implement mounting mechanism being rotated to the right to orient the edger implement to change the orientation of the edging disk to cut a narrow swath;  
         [0034]    [0034]FIG. 6 is a top plan view of the power unit and attached edger implement as depicted in FIGS. 4 and 5, but with the implement mounting mechanism being rotated to the left to orient the edger implement to change the orientation of the edging disk to cut a wider swath;  
         [0035]    [0035]FIG. 7 is a top plan view of the power unit depicted in FIGS. 1 and 3 and having a mower implement detachably mounted via the implement mounting mechanism, the cutting width of the mower being depicted by spaced apart phantom lines, the implement mounting mechanism being oriented to direct the mower implement in a straight ahead orientation;  
         [0036]    [0036]FIG. 8 is a top plan view of the power unit and attached mower implement as depicted in FIG. 7 but with the implement mounting mechanism being rotated to the right to orient the mower implement for mowing in an offset path as compared to the cutting path depicted in FIG. 7;  
         [0037]    [0037]FIG. 9 is an enlarged detail view of the locking mechanism for controlling the pivotal movement of the support arm forming part of the implement mounting mechanism pivotally movable about a vertical axis concentric with the output shaft of the power unit engine;  
         [0038]    [0038]FIG. 10 is a top plan view of the power unit depicted in FIGS. 1 and 3 and having a wheeled implement detachably mounted via the implement mounting mechanism and powered through the power unit drive mechanism; and  
         [0039]    [0039]FIG. 11 is a top plan view of the power unit and attached wheeled implement as depicted in FIG. 10 but with the implement mounting mechanism being rotated to the right to effect steering of the wheeled implement by articulation of the combined power unit/attached wheeled implement about the pivot axis of the implement mounting mechanism. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]    Referring now to FIGS.  1 - 8 , a walk-behind version of a power unit 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 power unit 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.  
         [0041]    A walk-behind power unit  10  is known in the art in the form of brush mowers, edging attachments, grass mowers, tillers and other similar equipment. Walk-behind power units  10  typically have a frame  12  supported above the ground G by a pair of wheels  13  and an integral implement  40 . An engine  15  defining the operative power of the unit  10  is supported on the frame  12 . The engine has a rotatably power output shaft  16  on which is typically mounted a pulley to power a drive belt  19  for driving the integral implement  40 . The frame  12  extends rearwardly and upwardly to form a pair of laterally spaced handlebars  14  which the operator can grasp to control the operation and direction of travel of the unit  10 . Typically, the handlebars  14  will have controls (not shown) supported thereon to control various aspects of the engine  15 .  
         [0042]    [0042]FIGS. 1 and 3 depict the power unit  10  without an implement  40  attached thereto. Since the two wheels  13  provide only two points of contact with the ground, the implement  40  when attached to the implement mounting mechanism  20  or otherwise connected to the frame  12  will provide a third point of contact and, thereby, provide positional stability for the power unit  10 . FIGS. 1 and 3, however, terminate with the implement mounting mechanism  20  forming the terminus of a pivoted support arm  25  that is supported by bearings  26  housed in the frame  12  of the mower  10  to permit pivotal movement about a vertical pivot axis  29  that is concentric with the generally vertical power output shaft  16 . The support arm  25  is provided with appropriate attachment devices, such as bolt holes  22  and corresponding fasteners, or clamping devices (not shown) to connect an implement correspondingly fitted to attach to the implement mounting mechanism  20  and be carried by and powered by the power unit  20 . The pivotal movement of the support arm  25  will enable the implement to be oriented in a variety of positions relative to the power unit  10 , as will be described in greater detail below.  
         [0043]    One skilled in the art will readily recognize that the implement mounting mechanism  20  can be formed in a variety of configurations. The configuration depicted in the drawings is of a hollow support arm  25  fitted to receive a corresponding mounting arm  48  on the work implement  40 . A pair of attachment bolts  23  pass through holes  22 ,  49  formed in the respective support arm  25  and the mounting arm  48  to fix the work implement  40  to the power unit  10 . One set of the holes  22 ,  49  are preferably slotted to permit adjustable movement of the mounting arm  48  relative to the support arm  25  for tensioning the drive belt  19 , as will be described in greater detail below. Other configurations for the implement mounting mechanism  20  will permit the detachable mounting of the work implement  40  to the power unit  10 . One such configuration is described in U. S. Provisional Patent Application Serial No. 60/283,163, filed Apr. 12, 2001, from which domestic priority is claimed, the description of which being incorporated herein by reference.  
         [0044]    As best seen in FIGS. 1, 2 and  4 - 9 , a locking mechanism  30  is supported by the frame  12  to be engageable with the support arm  25  to control the pivotal movement thereof about the pivot axis  29 . While the locking mechanism  30  may take one of many similar forms, the preferred embodiment of the locking mechanism  30  includes a semi-circular bracket  32  having a plurality of teeth  33  formed therein. A key  28  is formed in the top of the support arm to be integral therewith and be movable beneath the bracket  32  as the support arm  25  is pivoted about the pivot axis  29 . The bracket  32  has as many teeth  33  or slots formed therein as pivoted positions are desired. Preferably at least five teeth  33  are formed to define a central, straight forward position and at least two different angular positions to both the left and right sides of the central position.  
         [0045]    The locking mechanism  30  is preferably spring-loaded into a lowered pivoted position in engagement with the key  28  by a spring  35  interconnecting the bracket  32  and the frame  12 . To effect pivotal movement of the support arm  25 , the semi-circular bracket  32  must first be raised to disengage the support arm key  28 . While this operation would preferably be manual in nature, remote actuation is possible, as is an interlock mechanism (not shown) that could be associated with the raising of the bracket  32  to prevent a powered operation of the attached implement  10  when the bracket is raised.  
         [0046]    The preferred embodiment of the control mechanism (not shown) for controlling the pivoting of the bracket  32  would be a conventional cable mounted on the handle bars  14  for a convenient operation by the operator and connected to the bracket  32  to force movement thereof against the force exerted by the spring  35 . An interlock mechanism is not preferred as the operation of the work implement  40  as the implement  40  is moved from side to side is preferred in some instances, such as with a mower implement  42  described in greater detail below.  
         [0047]    As depicted in FIGS. 7 and 8, the attached implement  40  could be a powered brush mower or mower implement  42  operably powered through a drive belt  19  entrained around a driven pulley  43  and a drive pulley  17  affixed to said power output shaft  16 . While a spring-loaded idler mechanism (not shown) can be supported on the mower implement  42  to engage the drive belt  19  and maintain proper driving tension therein during operation, a simpler mechanism of maintaining tension in the drive belt  19  is preferred. One such mechanism would be the use of slotted holes  49  in the mounting arm  48  of the mower implement  42  to receive the attachment bolts  23  which also pass through the holes  22  in the support arm  25 .  
         [0048]    Positioning the mower implement  42  sufficiently far from the power unit  10  will impart proper tension in the drive belt  19 . Tightening the attachment bolts  23  to fix the position of the mounting arm  48  relative to the support arm  25  will retain the tension in the drive belt  19 . The slotted openings  23  will allow for a slight positional adjustment of the mower implement  42  to adjust the tension in the drive belt  19 . An addition of a adjustment bolt  44  threadably supported in a tab on one of the support arm  25  or the mounting arm  48  and engaging a corresponding tab on the other of the support arm  25  or the mounting arm  48  would permit a finite positional adjustment of the mounting arm  48  relative to the support arm  25 , within the limits defined by the length of the slotted openings  49 , to adjust the tension in the drive belt  19 .  
         [0049]    Movement of the mower implement  42  to a position offset to either side of the central position shown in FIG. 7 is desirable with certain operations, such a mowing under fence rails and the like. Release of the locking mechanism  30  can be manual, remote or automated to provide the desired amount of convenience in operating the offset feature of the attached mower implement  42 . As represented in FIG. 8, the mower can be pivoted to either side of the central position. An attitude control link  45  pivotally interconnects the frame  12  and the mower  42  to provide a rudimentary four bar linkage in conjunction with the pivoted support arm  25  that effects a parallel offset movement of the mower implement  42  from side to side.  
         [0050]    Referring now to FIGS.  2 - 6 , one skilled in the art will recognize that the attached implement  40  could be a powered disk edging mechanism  50  having a rotatable disk member  52  that is engageable with the ground to form a shallow ditch or trough around mulching beds or landscaping areas. The edging mechanism  50  includes a formed support arm member  55  detachably mounted to the implement mounting mechanism  20  to locate the disk member  52  at a position offset to the side of the power unit  10 . The support arm member  55  includes a lateral portion  56  that extends outboard forwardly to the side of the power unit  10  and a longitudinal portion  57  that extends rearwardly to position the disk member  52  laterally to the side of the right wheel  13 . A forwardly positioned caster wheel  51  engages the surface of the ground to help support the support member  55 .  
         [0051]    A plate  59  is mounted on the support member  55  to provide support for a gearbox  60 . The drive belt  19  is entrained around the drive pulley  17  and a driven pulley  63  on the gearbox  60 . As described above with respect to the mower implement  42 , a spring-loaded idler mechanism (not shown) could be provided for the drive belt  19  and supported from the plate  59  to engage the drive belt  19  and provide tension therein for the transfer of rotational power from the drive pulley  17  to the gearbox  60 . Preferably, however, a more simple tensioning mechanism as described above with respect to the mower implement  42  would be provided.  
         [0052]    Preferably, the driven pulley  63  is mounted on a vertical input shaft  64  in a manner to be substantially parallel to the drive pulley  17 . The ninety degree gearbox  60  transfers rotational power to a horizontally disposed output shaft  66  on which is mounted a drive transfer pulley  67  having a transfer drive belt  68  entrained thereon to transfer rotational power to a driven transfer pulley  69  which powers the rotation of the disk member  52 . The longitudinal portion  57  of the support arm member  55  is formed with a yoke  58  that is pivotally attached to the plate  59  about a pivot axis  57   a  aligned with the horizontal output shaft  66 . The pivoted yoke  58  allows the disk member to move vertically as a relief against any obstacles, such as rocks or roots, that might be encountered during operation without disrupting the power transmission being effected by the transfer drive belt  68 , as the pivotal movement of the disk member  52  will not change the distance between the drive transfer pulley  67  and the driven transfer pulley  69 .  
         [0053]    Similar to the simplified belt tensioning mechanism described above with respect to the drive belt  19 , the longitudinal portion  57  of the support arm member  55  is formed in two pieces connected together by connection bolts  54  fitted through a slotted opening to permit positional (longitudinal) adjustment of the disk member  52  relative to the gearbox  60 , thereby changing the tension in the transfer drive belt  68 . Similar to the adjustment bolt mechanism described above, an adjustment bolt interengaging the two pieces of the longitudinal portion  57  of the support arm member  55  will enable a finite adjustment of the tension in the transfer drive belt  68  within the limits defined by the slotted openings in the two pieces of the longitudinal portion  57 .  
         [0054]    By manipulation of the locking mechanism  30  to allow positional adjustment of the pivoted support arm  25 , the operative angle of the disk member  52  can be varied, as is depicted in FIGS.  4 - 6 . Placement of the support arm  25  in the rightmost position, as depicted in FIG. 5, places the disk member  52  at an orientation that is next to and generally parallel with the line of travel of the power unit  10 , which is generally a transport position. The positioning of the support arm in the central, straight-away position, as is depicted in FIG. 4, moves the disk member  52  into a first operative position in which the rotatably powered disk member  52  can cut a trench into the surface of the ground. Further, a positioning of the pivoted support arm  25  in the leftmost position, as is depicted in FIG. 6, increases the angle at which the powered disk member  52  engages the ground, thereby causing the creation of a wider trench than is formed with the disk member  52  in the orientation shown in FIG. 4. The pivotal movement of the support arm  25  about the axis of the engine output shaft  16  allows the engagement angle of the disk member  52  to be varied without disrupting the power transmission of the drive belt  19 .  
         [0055]    In operation, the edging mechanism  50  is positioned adjacent a landscaped area, such as a mulch bed, where an edging trench is desired. The bracket  32  is lifted to permit the support arm  25  to be moved to a position other than the extreme rightmost pivoted position, which corresponds to the transport position as depicted in FIG. 5. For example, the pivoted support arm  25  could be located in the central position, as shown in FIG. 4, to position the powered disk member  52  at a cutting angle of approximately 20 degrees with respect to the direction of travel. If a wider trench is desired, the support arm  25  could be moved into the leftmost pivoted position to place the disk member  52  at a cutting angle of approximately 35 degrees with respect to the direction of travel. With the engine  15  running, the longitudinal portion  57  of the support member  55  is pivoted downwardly about the pivot axis  57   a  to engage the ground.  
         [0056]    A latch mechanism  70  is carried on the support member  55  to restrain the pivotal movement of the longitudinal portion  57  about its pivot axis  57   a.  When engaged, the longitudinal portion  57  is fixed in a raised inoperative, transport position. The latch mechanism  70  can also be used to control the depth on engagement of the powered disk member  52  into the ground by limiting the amount of downward pivotal movement of the longitudinal portion  57 . A handle (not shown) fixed to the distal end of the longitudinal portion  57  near the disk member  52  can be used to manually raise and lower the longitudinal portion  57  between the raised transport position and the lowered operating position.  
         [0057]    While an idler mechanism associated with the transfer drive belt  68  could be utilized to control the transfer of rotational power to the disk member  52  in addition to controlling the tension in the transfer drive belt  68 , the lack of any idler mechanism associated with either the drive belt  19  or the transfer drive belt  68  requires another device, such as a clutch, to disengage the transfer of rotational power to the disk member  52 . Such a clutch can be incorporated into either the gearbox  60  or, preferably, the engine  15  and controlled by a conventional cable control (not shown).  
         [0058]    Changing the cutting angle of the powered disk member  52  has an advantage over fixed angle edging mechanisms known in the art by allowing a wider trench profile to be formed when conditions favor the use of a wider edging trench, such as when the landscape edge is overgrown or has heavy or rough sod edges. The placement of the vertical pivot axis  29  for the implement support arm  25  in alignment with the output shaft  16  of the power unit engine  15  allows the cutting angle of the powered disk member  52  to be selectively varied without effecting the transfer of rotational power to the disk member  52 , as the entire edging implement  50  pivots about the center of the drive pulley  17 . Furthermore, the placement of the edging mechanism  50  into the above-described transport position, in which the disk member  52  presents a zero degree cutting angle with respect to the direction of travel, enables the disk member  52  to be removed and replaced by another rotary power tool (not shown) that is best used in this orientation, such as a sidewalk edger, a trencher, or a rotary cultivator.  
         [0059]    The implement mounting mechanism  20  provides the ability to utilize the power unit  10  for a variety of powered implements  40  to be attached thereto for operative connection with the engine  15 . Examples of possible implements to be attached include the mower  42  and the edging mechanism  50  shown in the drawings. Other examples of implements that could be attached would be a tiller mechanism, a snow blower, a ditching mechanism, rotary broom, string trimmer, and brush or grass mowers. Accordingly, the power unit  10  can be utilized in an effective and efficiently flexible manner. Articulation of the powered implement in a side-to-side manner can be easily accomplished, even during operation, providing operational advantages heretofore unknown in the prior art implements.  
         [0060]    As best seen in FIGS. 10 and 11, the attached powered implement  75  can be a wheeled implement that is connected to the power unit via the implement mounting mechanism  20  and driven by the drive belt  19  receiving rotational power, as described above, from the engine  15 . The powered, wheeled implement  75  can have its own secondary drive mechanism  76  to transfer rotational power delivered by the drive belt  19  to the various powered components (not shown) on the implement  75 . As depicted in FIGS. 10 and 11, the secondary drive mechanism  76  can include a gearbox  77  and other related drive components  78 . Since the implement  75  is supported by fixed wheels  79 , the lateral movement of the implement  75  cannot be accomplished through a simple pivoting of the implement mounting mechanism  20  as is described above. The combined power unit  10  and attached wheeled implement  75  form a four wheeled apparatus that is articulated by the pivoted implement mounting mechanism  20 . Accordingly, steering of the combined apparatus  10 ,  75  can be accomplished by pivoting the implement mounting mechanism  20  about the vertical axis  29  while the combined apparatus  10 ,  75  is moving, which effects steering of the combined apparatus  10 ,  75  through articulation of the apparatus  10 ,  75 , as is depicted in FIG. 11. Accordingly, the pivotal movement of the support arm  25  would preferably be controlled through a remotely controlled device accessibly mounted on the handle bars  14  of the power unit  10 .  
         [0061]    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.