Abstract:
A pruning vehicle having characteristics specifically utilizable in an orchard having rows of trees opposite each other. The vehicle is equipped with two platforms side by side which can be adjustably located vertically and horizontally in a plane perpendicular to the direction of the vehicle&#39;s motion. Each platform is controllable by an operator standing upon the platform through foot pedals incorporated thereon. Platforms are elevated above the vehicle by lifting structures designed to keep the platforms level to the ground at all times. The platforms are connected to a frame of the vehicle at a low slung central portion of the frame for added stability. Wheels of the vehicle are of a thin disc shape. Each wheel can slice through soft surfaces such as mud to attain a firm foundation for the pruning vehicle. Fins and teeth on the wheels provide added traction. Mud deflectors on the wheels prohibit mud from climbing up too high onto or bogging down the pruning vehicle. The wheels are powered by hydraulic motors which are powered by an engine mounted upon the frame of the vehicle. The engine also powers hydraulic rams which steer all four wheels of the vehicle and adjust the locations of the platforms. The motion and steering of the pruning vehicle is controllable from one of the platforms, eliminating the need for an additional operator on the vehicle to drive the pruning vehicle. One form of the invention links vertical motion of the platforms together while preserving independent horizontal motion of the platforms. In this embodiment the platforms are connected by a walkway allowing operators to pass between the platforms on opposite sides of the pruning vehicle without climbing off of or lowering the platforms.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 07/986,477 filed Dec. 7, 1992, now U.S. Pat. No. 5,427,197. 
    
    
     FIELD OF THE INVENTION 
     The following invention relates to vehicles, platforms and other systems for use in orchards to prune trees. More specifically, this invention relates to vehicles having vertically and horizontally adjustable platforms for locating workers close to the trees to be pruned. 
     BACKGROUND OF THE INVENTION 
     Throughout the history of agriculture, the financial success of the farmer has depended considerably on how efficiently and cost effectively the farmer could produce his crop. Whenever devices improve the efficiency with which the farmer can perform a required task, the size of crop the farmer can produce is increased. Also, with more efficient machines the farmer requires fewer laborers to produce the crop. Even small improvements in efficiency allow the farmer to increase his productivity, perhaps making a failing farmer into a successful one. 
     One task required of orchard farmers is that of pruning the trees. The more efficiently the orchard can be pruned, the more time the farmer will have for other tasks and the fewer laborers the farmer will need to hire in order to prune the orchard. Pruning is best accomplished while the trees are dormant or after harvest. Frequently, the terrain in the orchard is inhospitable to machinery at this time because of muddy, bog-like conditions associated with the rainy season. 
     Many devices exist in the prior art designed to improve the efficiency with which an orchard can be pruned or other tree maintenance tasks may be performed. Some devices require mounting on other vehicles or require that they be towed behind vehicles. Those that are self contained as a vehicle inadequately address the problem of maneuvering through unstable surfaces, such as mud, often prevalent in the orchard environment. These pruning vehicles also require greater numbers of operators for their use. 
     The invention of this application provides a self contained pruning vehicle designed to easily maneuver through the orchard environment, provide easily controllable access to the trees for pruning, and be operable by a small group of men or even one man alone. 
     The following prior art reflect the state of the art of which applicant is aware and are included herewith to discharge applicant&#39;s acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed. 
     
       
         
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 INVENTOR 
                 PATENT NO. 
                 ISSUE DATE 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 U.S. PATENT DOCUMENTS 
               
             
          
           
               
                   
                 Protzeller 
                 1,718,979 
                 July 2, 1929 
               
               
                   
                 Ray 
                 2,450,812 
                 Oct. 5, 1948 
               
               
                   
                 Cardiff 
                 2,601,092 
                 June 17, 1952 
               
               
                   
                 Stemm 
                 2,616,768 
                 Nov. 4, 1952 
               
               
                   
                 Mitchell 
                 2,778,694 
                 Jan. 22, 1957 
               
               
                   
                 Gregory 
                 Re. 25,746    
                 March 23, 1965 
               
               
                   
                 Kazuo Hiyama 
                 3,191,717 
                 June 29, 1965 
               
               
                   
                 Kazuo Hiyama 
                 3,311,191 
                 March 28, 1967 
               
               
                   
                 Fridley 
                 3,537,236 
                 Nov. 3, 1970 
               
               
                   
                 Johnson 
                 3,641,738 
                 Feb. 15, 1972 
               
               
                   
                 Harrison 
                 3,791,484 
                 Feb. 12, 1974 
               
               
                   
                 Carpenter, et al. 
                 3,866,713 
                 Feb. 18, 1975 
               
               
                   
                 Stokoe 
                 4,643,273 
                 Feb. 17, 1987 
               
               
                   
                 Kishi 
                 5,107,955 
                 April 28, 1992 
               
               
                   
                 Claxton 
                 5,159,989 
                 Nov. 3, 1992 
               
             
          
           
               
                 FOREIGN PATENT DOCUMENTS 
               
             
          
           
               
                   
                 Soyuzgiprostrom 
                 SU 1,416,638       
                 Aug. 15, 1988 
               
               
                   
                   
               
             
          
         
       
     
     Other Prior Art (Including Author, Title, Date, Pertinent Pages, Etc.) 
     Woods Manufacturing, Inc.; “The Tree Squirrel” brochure; no date; entire brochure. 
     Dakota “AG” Welding, Inc.; “Prune-Rite Pruning Towers” brochure; no date; entire brochure. 
     Weldcraft Industries, Inc.; no title; no date; entire brochure. 
     The Johnson patent teaches the use of a self contained pruning and picking vehicle. This vehicle requires a separate driver and uses standard rubber tires. Platforms on the Johnson device have restricted vertical motion. Some of the platforms do not move vertically at all, while others must move up and down together and cannot work independently. The vehicle of the instant application is operable without a designated driver and has wheels providing greater stability and movement. Furthermore, each platform is able to move independently vertically. 
     The patent to Stemm teaches a vehicle having two fully independent moveable platforms. The device of the present application is distinguishable from Stemm in that the vehicle may be driven from one of the platforms, has specially modified wheels, and positions the two lifting platforms in a side by side orientation making it more easily utilizable in an orchard environment where trees of adjacent rows are often directly opposite each other. 
     The patents to Gregory and Cardiff teach various lifting platforms which must be mounted to a separate vehicle to be utilized within the orchard environment. The platforms of the instant application are included in the pruning vehicle and do not necessitate the use of a separate vehicle for motivation. 
     The patent to Fridley requires the use of stairs for elevational change, while the vehicle of the present application has hydraulically operable platforms for adjustment in elevation. 
     The remainder of the prior art listed above but not specifically distinguished diverge more starkly from the invention of this application. 
     SUMMARY OF THE INVENTION 
     The pruning system is broken down into three major subparts: a chassis, wheels and a scaffold. 
     The chassis is composed primarily of a rigid frame. The frame has a forward structure, a rearward structure and a central structure. The forward structure has an axle mounted thereto which supports two forward wheels, one on each side of the frame at extremities of the axle. The forward structure also has various fillers for fluids such as oil and gas which are required by an engine located on the rearward structure. The forward structure of the frame is rigidly and fixedly attached to the central structure. The central structure is of a thinner profile, when viewed from the side, than the forward structure or the rearward structure. The central structure is lower in elevation than the forward structure and the rearward structure. 
     The scaffold is mounted on an upper surface of the central structure. The central structure is rigidly attached to the forward structure by a forward transition structure. The forward transition structure is a substantially vertically oriented rigid member to which the forward structure and the central structure are fixedly attached. By having the scaffold attached to the central structure, and having the central structure lower than the forward structure and the rearward structure, the stability of the pruning vehicle is improved. This allows the pruning vehicle to be narrower and lighter without risking tipping when platforms on the scaffold are extended horizontally and loaded. 
     The central structure is fixedly attached to the rearward structure by a rearward transitional structure there between. The rearward transitional structure is substantially identical to the forward transitional structure and is fixedly attached to both the central structure and the rearward structure. The engine is mounted above the rearward structure. An engine housing encloses the engine. Below the rearward structure is located an axle to which two wheels are attached. 
     Both the forward structure and the rearward structure have hydraulic motors integrated therein. These hydraulic motors receive their power from the engine and transmit power to the wheels through differentials interposed on each of the axles. 
     Also, on both the forward structure and the rearward structure are attached steering rams. Each steering ram is in turn connected on an opposite end to a steering ram tie rod which is attached to the wheel axle interface to turn the wheels. In this way, both forward and rearward wheels of the pruning vehicle are steerable. 
     Each of the four wheels has a substantially identical structure. These wheels allow navigation in an orchard having unstable ground conditions. The wheels are substantially disc shaped having a circular central hub which is fastenable to the axle. Circumscribing the hub at a perimeter of the wheel is a circular rim. The rim is narrower in width than the width of the hub. A circular disc is interposed between the hub and the rim and is fixedly attached to both the hub and the rim. The disc tapers from having a width similar to the width of the hub at its inner end and having a width similar to the width of the rim at its outer perimeter. Thus, in cross section the wheels taper in a manner similar to an inverted isosceles triangle from being wider near the axle to being thinner at the rim where contact with the ground is made. 
     A plurality of fins are attached to the discs on both inner and outer surfaces. The fins extend radially outward from the hub toward the rim. The fins are fixedly attached to the disc. The fins prevent the wheels from slipping when operating through soft surfaces. A plurality of side rim teeth extend axially out from the rim. Each tooth extends a distance similar to the width of the rim. The side rim teeth are located on both the inner and outer sides of the rim. The side rim teeth provide further traction for the wheels. 
     Fixedly attached to the discs on inner and outer surfaces thereof are a plurality of mud deflectors. Each mud deflector extends outwardly from the surface of the disc at an angle which slopes toward an axis collinear with the hub. The wedge shaped cross-section of the wheels allows the wheels to penetrate deeply into soft ground conditions yet not get bogged down. In this way, the wheels contact firmer ground beneath the less firm surface. Thus, the wheels reside on a firm foundation allowing operators on platforms attached to the scaffold to more easily work. 
     The scaffold of the pruning system elevates users above the vehicle and extends users horizontally away from the vehicle to provide them with better access to the trees to perform pruning and other maintenance. The scaffold is divided into two substantially identical scaffold portions, a left scaffold portion and a right scaffold portion. The lifting apparatus of the left scaffold is oriented closer to the forward structure of the frame of the chassis and the right scaffold&#39;s lifting structure is located closer to the rearward structure of the chassis. In this way, the two scaffolds may come quite close to each other without their separate lifting apparatus interfering with each other. 
     Each lifting apparatus is described as follows. A guide is fixedly attached to the central structure of the frame. Received within the guide is a horizontal slide. The horizontal slide is a rigid construct capable of sliding into and out of the guide in a horizontal direction perpendicular to the direction of vehicle motion. Fixedly attached to the slide on an upper surface thereof and at an end distant from the vehicle is located a base. The base is a rigid unitary mass. Pivotably connected to the base are two rigid links referred to as a lower driver and lower follower. The lower driver and lower follower pivotably attach on an upper end to an intermediate riser. 
     The intermediate riser is a rigid unitary mass similar to the base. The lower driver and lower follower are oriented such that they are preferably parallel to each other. The lower driver is above the lower follower. Fixedly attached to the lower driver at a point between the intermediate riser and the base is a hydraulic attachment bracket. Attached to the hydraulic attachment bracket is one end of a hydraulic ram. The other end of the hydraulic ram is pivotably attached to the base. 
     When the hydraulic ram is extended, the lower driver pivots about the base causing the intermediate riser to move upwardly. The lower follower also pivots along with the driver and causes the intermediate riser to elevate without rotating. In this way, the intermediate riser does not rotate in relationship to the base and the attached vehicle. Pivotably attached to the intermediate riser are two upper links referred to as an upper driver and an upper follower. The upper driver is higher than the upper follower. 
     On ends of the upper driver and upper follower opposite the intermediate riser is pivotably attached an upper riser. The upper riser is in turn fixedly attached to the platform. An upper hydraulic ram is pivotably mounted between the intermediate riser and the upper driver. Thus, when the upper hydraulic ram is extended, the upper driver pivots about the intermediate riser. This causes the upper riser to be elevated. The upper follower is also pivoted and causes the upper riser to elevate without rotation. 
     By extension of the upper hydraulic ram and lower hydraulic ram, the platform is elevated from a level slightly above the upper surface of the central structure of the frame to a height approximately twice the width of the vehicle. 
     Fixedly attached to the platform is a cage. The cage extends to an elevation approximately waist high above the platform. The cage allows a worker standing on the platform to work without concern of slipping off of the platform. A door is provided on one side of the cage for entrance and exit from the platform. When the cage is opened the hydraulic rams associated with the scaffold are disabled. 
     An in/out pedal is provided on the floor of the platform which when depressed causes the hydraulic ram attached to the slide to be extended or contracted. In this way a worker on the platform can cause the platform to move in (towards) and out (away) from the vehicle. 
     An up/down pedal is also provided on the platform. The up/down pedal is connected to the lower hydraulic ram and the upper hydraulic ram. Thus, when the worker on the platform wishes to move up or down he may depress the pedal appropriately causing the hydraulic rams to be extended or contracted causing the lifting structure to elevate or lower the platform. 
     One of the two platforms is provided with a steering joystick. The steering joystick is connected to the hydraulic motors which turn the wheels and the hydraulic rams which steer the wheels. Moving the joystick by one of the workers on one of the platforms causes the vehicle to move forward or in reverse and causes the vehicle to turn. In this way, the vehicle is operable without the necessity of having an extra operator to drive the vehicle. 
     The upper ram on the lifting mechanism of the platform may be replaced by a mechanical link attached to an upper end of the lower driver and a lower end of the upper driver. The mechanical link causes the upper riser to be elevated with respect to the intermediate riser when the lower hydraulic ram is extended. In this way, a single hydraulic ram is able to fully elevate the platform. 
     A modification of the scaffold has a series of four vertical base sleeves fixedly attached to the central structure of the frame of the chassis. Four base slides are sized to fit within these sleeves. A base ram is interposed between the central structure and a scaffold frame. The scaffold frame is fixedly attached to upper surfaces of the base slides and to the upper end of the base ram. Base sleeve supports extend from the forward structure and rearward structure to upper ends of the base sleeves to provide additional lateral support. When the base ram is extended, the scaffold frame is lifted vertically. 
     The scaffold frame has fixedly attached thereto a handrail and a walkway. The scaffold also has a left slide guide and a right slide guide thereon. The left slide guide is sized to receive a left slide. The left slide is a horizontally extending rigid construct which is capable of extending horizontally outward away from the vehicle. The right slide is similar in design to the left slide. The right slide is sized to fit within the right guide of the scaffold frame. 
     Cages are fixedly attached to upper surfaces of the slides on ends most distant from the vehicle. The cages have handrails which extend into the handrail fixedly attached to the scaffold frame. Each slide has a hydraulic ram interposed between itself and the scaffold frame. When the hydraulic rams are extended, the slides extend, thereby positioning the cages at a distance farther away from the vehicle in a horizontal direction. The cage handrails also extend while remaining within the fixed handrail on one end. Each cage has a moving walkway fixedly attached at a lower end thereof which slides under the fixed walkway when the cage is extended. The two moving walkways along with the fixed walkway form a single continuous platform between the left cage and the right cage. 
     Each cage has pedals which allow a worker to extend the cage toward and away from the scaffold frame in a horizontal direction perpendicular to vehicle motion. One of the cages has an additional pedal which activates the base ram causing the scaffold to be elevated or lowered. The steering joystick is connected to one of the cages for steering and driving of the vehicle by a worker within one of the cages. In this modification the vehicle is operable by a single worker having easy access to both left and right cages simultaneously. 
     An alternative modification to the vehicle which has the central scaffold utilizes an identical scaffold frame with identical handrail and walkway and left and right cages. This alternative version of the scaffold, however, is attached to the central structure through a series of scissor links. 
     In this modification, fixedly attached to the central structure is a forward and a rearward base guide. Rolling within the two base guides are guide wheels. Each guide wheel is pivotably attached to a lower end of a lower scissor link. One end of the base guides has lower ends of scissor links pivotably attached directly thereto. The four lower scissor links are pivotably attached to each other in pairs at a location directly above each base guide. Upper ends of the lower scissor links are pivotably attached to lower ends of upper scissor links which in turn are pivotably attached to each other in a middle portion and pivotably attached to the scaffold frame on upper ends thereof. Some of the upper scissor links&#39; upper ends are pivotably attached to a guide wheel which rolls within a scissor scaffold guide fixedly attached to the lower surface of the scaffold frame. The other upper ends of the upper scissor links are pivotably attached directly to the scissor scaffold guide. 
     A hydraulic ram is pivotably attached between the base guide and one of the lower scissor links. When the hydraulic ram is extended, the scissor links are pivoted and the guide wheels within the base guide and the scissor scaffold guide roll toward a middle of the base guide and the scissor scaffold guide. The scissor scaffold guide is pivotably attached directly to a scissor link. This causes the scaffold frame to be elevated without rotation. The hydraulic ram is controllable by a pedal located on the scaffold. 
     This modification allows for passage of a worker between the two cages without lowering of the scaffold. This modification also allows a single worker to operate the entire vehicle and maintain two trees at the same time without moving the pruning vehicle chassis. 
     Other alternative modifications to the scaffold include providing two separate scaffolds for each cage, the scaffolds utilizing a mechanism similar to that common in forklifts. Each scaffold in this modification has a horizontal extension mechanism with a vertical extension mechanism on a distant end of the horizontal extension mechanism. The two side-by-side horizontal extension mechanisms are interrelated in one modification allowing the two cages to be oriented in a common vertical plane orthogonal to chassis motion at all times. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to provide a pruning system which may be driven from the top of a platform attached to the pruning vehicle, avoiding the need for a separate driver. 
     Another primary object of the present invention is to provide a pruning system which includes a vehicle having special wheels which provide a solid foundation and are less likely to become stuck in an orchard environment. In fact, the instant invention benefits from adverse terrain to promulgate vehicle stability. 
     Another further object of the present invention is to provide a pruning system having a vehicle with a low slung central portion for stability and a platform fastened to the low slung portion such that when the platform is extended horizontally away from sides of the vehicle the vehicle is less likely to roll over off of its wheels. 
     Another further object of the present invention is to provide a pruning system having a vehicle with an engine which causes the wheels of the vehicle to move and which drives hydraulic motors which cause platforms on the vehicle to move upwardly and downwardly and in and out (horizontally and perpendicularly) with respect to the direction of vehicle motion. 
     Another further object of the present invention is to provide a pruning system having a vehicle with platforms of a compact structure which still may extend significantly from the frame of the vehicle. 
     Another further object of the present invention is to provide a pruning system having separate platforms which may be independently moved by workers on the platforms. 
     Another further object of the present invention is to provide a pruning system which is easy to manufacture and easy to maintain. 
     Another further object of the present invention is to provide a pruning system which can efficiently and economically prune trees within an orchard. 
     Viewed from a first vantage point it is an object of the present invention to provide an orchard pruning vehicle comprised of a frame supporting the vehicle, wheels connected to the frame and supporting the frame above ground, an engine upon the frame imparting rotation to the wheels to move the vehicle along the ground, and a plurality of platforms supported above the frame by a movable connection means moving the platforms both vertically substantially perpendicularly to the vehicle&#39;s motion and horizontally substantially perpendicularly to the vehicle&#39;s motion. 
     Viewed from a second vantage point it is an object of the present invention to provide an orchard pruning vehicle for maintenance of trees in orchards having irregular terrain and variable ground conditions comprised of a frame supporting the vehicle, a plurality of wheels attached to the frame and supporting the frame above the ground, and a plurality of platforms supported above the frame by a moveable connection means locating the platforms distant from the frame of the vehicle; and wherein each wheel is of a substantially rigid disc shape comprised of a hub fastenable to an axle connected to the frame and to an engine providing power for rotation of the wheels, a circular rim forming a periphery of the wheel surrounding the hub and coaxial with the hub, and a disc having a greater thickness near a central opening and a lesser thickness near a peripheral edge, the disc fitting between the circular rim and the hub, the disc fixedly attached to the rim at the peripheral edge and fixedly attached to the hub at the central opening, the disc being of decreased thickness as the disc extends from the hub to the rim. 
     Viewed from a third vantage point it is an object of the present invention to provide a pruning system comprising a vehicle including a frame and attached wheels, an engine upon the frame powering the pruning system, and a multiple of two platforms oriented in pairs in planes substantially perpendicular to the direction to the vehicle&#39;s motion and adjustably locatable with respect to the frame. 
     Viewed from a fourth vantage point it is an object of the present invention to provide a machine for pruning trees comprised of a frame, wheels supporting the frame above ground, a plurality of platforms supported above the frame by a moveable connection means capable of locating the platforms distant from the frame and an engine which powers hydraulic motors interposed between the engine and the wheels which in turn impart rotation to the wheels, and wherein the moveable connection means of the platforms is a series of moveable interconnected rigid supports powered by a series of hydraulic rams in turn powered by the engine, and wherein steering of the wheels is accomplished by adjustment of hydraulic rams driven by output from the engine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of the device of this invention. 
     FIG. 2 is a right side view of the device of this invention with portions cut away to reveal hid details. 
     FIG. 3 is a front view of the device of this invention with portions of the device extended in different ways. 
     FIG. 4 is a cut away sectional view of that which is shown in FIG. 1 taken along lines  4 — 4  with portions removed to reveal additional details. 
     FIG. 5 is a cut away sectional view of a portion of the device of this invention as shown in FIG. 1 taken along lines  5 — 5 . 
     FIG. 6 is a cut away sectional view of a portion of the device of this invention as shown in FIG. 1 taken along lines  6 — 6 . 
     FIG. 7 is a front view of an alternative embodiment of this invention. 
     FIG. 8 is a sectional view of that which is shown in FIG. 7 taken along lines  8 — 8 . 
     FIG. 9 is a front view of another alternative embodiment of this invention. 
     FIG. 10 is a cross-section of that which is shown on FIG. 9 taken along lines  10 — 10 . 
     FIG. 11 is an isometric view of a portion of that which is shown in FIG.  9 . 
     FIG. 12 is a cut away sectional view of that which is shown in FIG. 10 taken along lines  12 — 12 . 
     FIG. 13 is a cut away sectional view of that which is shown in FIG. 14 taken along lines  13 — 13 . 
     FIG. 14 is a right side view of another alternative embodiment of a portion of the device of this invention. 
     FIG. 15 is an isometric view of another alternative embodiment of a portion of the device of this invention. 
     FIG. 16 is a cross-section of a portion of that which is shown in FIG. 15 taken along lines  16 — 16 . 
     FIG. 17 is an isometric view of another alternative embodiment of a portion of the device of this invention. 
     FIG. 18 is a cross-section of a portion of that which is shown in FIG. 17 taken along lines  18 — 18 . 
     FIG. 19 is a cross-section of a portion of that which is shown in FIG. 17 taken along lines  19 — 19 . 
     FIG. 20 is a cross-section of a portion of that which is shown in FIG. 17 taken along lines  20 — 20 . 
     FIG. 21 is a top plan view of that which is shown in FIG.  17 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like numerals represent like parts throughout, numeral  10  refers to a pruning vehicle. The vehicle is composed of a chassis  20  which is supported above ground by wheels  50  and has extending from the chassis  20  two scaffolds  100 , one on each side of the chassis  20 . The scaffolds  100  lift operators above the ground to reach trees for pruning. 
     In essence and referring to FIGS. 1 through 6, the chassis  20  is comprised of a rigid frame  30  having various major parts attached thereto. An engine  39  and engine housing  40  (FIG. 2) are affixed to the frame  30 . A gas tank  42  is affixed to the frame  30 . Two axles  52  are attached to the frame  30  which fasten to wheels  50 . 
     The wheels  50  of the pruning vehicle  10  (shown, for example, in FIGS. 1 and 2) are each composed of a central hub  72  surrounded by a disc  82  which is in turn surrounded by a rim  78 . The hub  72  is a circular construct attachable to the axle  52 . The disc  82  is a construct of circular cross-section which fixedly attaches to the hub  72  and extends out to the rim  78 . The rim  78  forms the outermost edge of the wheel  50 . The rim  78  is fixedly attached to the disc  82 . 
     The scaffolds  100  of the pruning vehicle  10  are fixedly attached to the frame  30  on an upper side thereof as shown in FIG. 3, for example. Each scaffold  100  has a platform  130  with a cage  132  affixed thereon. The platform  130  is adjustable in relationship to the frame  30  both vertically and horizontally through a moveable connection means  125 . Each operator on each platform  130  can independently control his/her scaffold  100  while on the platform  130 . One of the operators can control the motion of the pruning vehicle  10  through the wheels  50  while upon one of the platforms  130 . Preferably, the wheels  50  are controllable by an operator on the scaffold  100  to the left of the chassis  20 . 
     More specifically, and referring to FIGS. 1 through 6, the chassis  20  is shown. The frame  30  of the chassis  20  is a rigid rectangular skeletal construct when viewed from above. The frame  30  is divided into a forward structure  32 , a rearward structure  34  and a central structure  36 . Each structure  32 ,  34 ,  36  is substantially square when viewed from above. The forward structure  32  has a leading edge  32   a on one side thereof and is attached to the central structure  36  on an opposite side thereof through a forward transition structure  33 . The forward transition structure  33  is fixedly attached to the rearward side of the forward structure  32  and forward side of the central structure  36 . The forward transition structure  33  allows the central structure  36  to be positioned below the elevation of the forward structure  32 . 
     The rearward structure  34  has a trailing edge  34   a on one side thereof and is attached to the central structure  36  through a rearward transition structure  35 . The rearward transition structure  35  is fixedly attached to a forward end of the rearward structure  34  and a rearward end of the central structure  36 . Both transition structures  33 ,  35  are disposed in a vertical plane and are substantially rectangular. A long axis  30   a of the frame  30  extends from the leading edge  32   a to the trailing edge  34   a and defines a longest dimension of the frame  30 . The central structure  36  is located within a mid-section  36   a intermediate between the leading edge  32   a and the trailing edge  34   a and is positioned below the rearward structure  34  by being attached to an opposite (lower) end of the rearward transition structure  35  as is the rearward structure  34 . In this way, the central structure  36  is positioned at an elevation below the rearward structure  34 . The forward structure  32  and rearward structure  34  are substantially in the same elevation. Gussets G may reinforce the connection of the transition structures  33 ,  35  to the forward, central and rearward structures  32 ,  34 ,  36 . 
     The central structure  36  may be subdivided into a left box beam  37  and a right box beam  38  as shown in FIG.  5 . The central structure  36  is thinner when viewed from the side than the forward structure  32  or the rearward structure  34 . The relative thinness and lower elevation of the central structure  36  allows the pruning vehicle  10  to be more stable by providing a lower center of gravity. This is especially important when the scaffolds  100  are extended, and yet the device still has substantial ground clearance. 
     The engine  39  and engine housing  40  are located on an upper surface of the rearward structure  34  of the frame  30 . The engine  39  may be one of any type of engine which can activate hydraulic motors and hydraulic rams. 
     A gas tank  42  is mounted on the frame  30  on the forward structure  32  thereof. A gas filler opening  41  is located near the gas tank  42  on the forward structure  32 . Gas lines (not shown) run within the members making up the frame  30  and then extend out to the engine  39  through a gas line connection  43 . 
     An oil filler  44  and oil filter  45  are also mounted on the forward structure  32  of the frame  30  and are connected to an oil line which extends to the engine  39  through an oil line connection  46  near the engine  39  on the rearward structure  34  of the frame  30 . The oil line and gas line associated with the connections  43 ,  46  have been removed from FIG. 1 to add further clarity to FIG.  1 . These lines extend from their connections  43 ,  46  to the engine  39  following one of a variety of possible routes, the choice of which is not critical to performance of the vehicle  10 . 
     Axles  52  are mounted beneath both the forward structure  32  and the rearward structure  34  of the frame  30 . Each axle  52  is of similar design. The axles  52  are connected to the frame  30  through axle mounts  54 . One axle mount  54  is located on each side of the frame  30  for each axle  52 . 
     A hydraulic motor  90  is mounted on both the forward structure  32  and the rearward structure  34 . The hydraulic motors  90  are of similar construction. Each hydraulic motor  90  receives power from the engine  39 . Each hydraulic motor  90  has an output shaft  91  which is rotated by the hydraulic motor  90 . The output shaft  91  of each hydraulic motor  90  extends into a differential  92  mounted on each of the axles  52 . Each differential  92  is interposed with each axle  52  so that hydraulic motors  90  may drive wheels  50  attached to each end of each axle  52 . 
     At each junction of a wheel  50  and an axle end  52  is located a universal (constant velocity) joint (not shown) and a steering collar  56  (see FIG.  4 ). The steering collar  56  is connected to the wheel  50  in a manner such that when the steering collar  56  is pivoted the wheel  50  also pivots. However, the steering collar  56  preferably does not rotate along with the wheels  50 . The steering collars  56  are attached to two wheels  50  which are attached to the same axle  52  and are connected together by a steering tie rod  58 . This connection is similar to that of many four-wheel drive or front wheel drive automobiles. 
     The constant velocity joint (not shown) connects the axle  52  to the hub  72  of the wheel  50 . Each of the two tie rods  58  are suspended beneath the frame  30  and are pivotably connected through a tie rod mount  64  to one end of a steering ram  60 . The other end of the steering ram  60  is pivotably attached through a frame mount  62  to the frame  30 . When the steering ram  60  is extended or contracted the tie rod  58  is moved to the left or to the right causing wheels  50  to be turned. 
     Each wheel  50  on the pruning vehicle  10  is of substantially the same construction. A hub  72  forms a center of the wheel  50 . The hub  72  has means for fastening to the end of the axle  52  and which allow the wheel  50  to be driven by the differential  92 . The hub  72  has a cylindrical shape with its central axis colinear with a central axis of the axle  52 . A disc  82  is fixedly attached to the hub  72  at its perimeter, extending radially outwardly therefrom. A rim  78  is located at a peripheral edge  84  of the disc  82 . The rim  78  is a toroidal rigid construct and is fixedly attached to the disc  82 . The disc  82  is itself a circular cross-sectioned rigid construct having a central opening  83  fixedly attached to the hub  72 . The hub  72  has a greater width (thickness) than the rim  78 . The disc  82  is of greater width (i.e. thickness) adjacent to the hub  72  than its width adjacent to the rim  78 . Thus, the disc  82  decreases in thickness and tapers from the hub  72  to the rim  78 . In cross-section, the disc  82  appears to have a truncated wedge shape such as that of a truncated isosceles triangle. 
     A plurality of fins  74  extend radially from the hub  72  to the rim  78  and are fixedly attached to the disc  82  on both inner and outer surfaces thereof. Each fin  74  is a rigid linear construct. The fins  74  provide both additional support to the wheel  50  and also help the wheel  50  pass through soft substances with less slippage. 
     A plurality of side rim teeth  80  are fixedly attached to inner and outer sides of the rim  78 . Each tooth  80  extends from a position adjacent to the rim  78  to a position at the edge of the disc  82  such that the tooth  80  does not extend beyond the disc  82 . The teeth  80  are all fixedly attached to the perimeter of the disc  82 . The teeth  80  provide additional traction to the wheels  50  by acting as cleats. 
     A plurality of mud deflectors  76  are fixedly attached to the discs  82  on inner and outer surfaces thereof. The deflectors  76  can be formed from angle iron. Each mud deflector  76  extends axially outwardly from the surface of the disc  82  at an angle a which slopes toward an axis of symmetry  6  of the wheel  50 . The deflectors  76  extend like chords on a circle between fins  74 . As mud collects on the disc  82  and rises up sides of the wheel  50  towards the hub  72  with progressive rolling of the wheel  50 , the mud deflectors  76  force the mud outwardly away from the wheels  50 , causing the mud to fall back to the ground. Thus the wheels  50  are somewhat self-cleaning. In this way, mud is prevented from interfering with the rotation of the wheels  50  and with the connection between the wheels  50  and ends of the axles,  52  by tending to limit the degree to which the device  10  can sink into a muddy field. The deflectors  76  coupled with the wedge-shaped taper of the disc  82  control sinking of the device  10  into mud. 
     In use and operation, the wheels  50  provide a solid foundation for the pruning vehicle  10 , even on soft surfaces. The rim  78  is thin enough to penetrate into the ground until a solid surface is impacted. The wheels  50  are thin enough to slice through soft material when rotation is imparted by the hydraulic motors  90 . This “controlled penetration” into soft earth gives greater stability to the vehicle  10 , especially during inclement weather. 
     Referring now to FIGS. 1 through 6 details of the scaffolds  100  are shown. Each scaffold  100  of the pruning vehicle  10  connects to the chassis  20  through the central structure  36  of the frame  30 . In FIGS. 2 and 5, two guides  102  are fixedly attached on an upper surface of the central structure  36 . One guide  102  is on a forward side thereof and supports the left scaffold  100 . The other guide  102  is on a rearward side thereof and supports the right scaffold  100 . Each guide  102  is a rigid member of substantially “C”-shaped cross-section which extends perpendicular to the direction of vehicle  10  motion “M” (see FIG.  2 ). The guides  102  are horizontally disposed across opposite sides of the frame  30 . A central guide  104  is located parallel and between the two guides  102  at a location near the center of the central structure  36 . The central guide  104  has two open sides of “C”-shaped cross-section facing forward and rearward while the guides  102  have open portions of their “C”-shaped cross-sections facing toward the central guide  104 . Thus, the guides  102 ,  104  open portions face each other to support two slides  106 . 
     The slides  106  are oriented between the guides  102  and the central guide  104 . The slides  106  are of a thickness equal to the interior height of the “C”-shaped cross-sections of the guides  102 ,  104 . The slide  106  is of substantially the same length as is the width of the frame  30 . 
     Having this shape, the slides  106  fit between the guides  102 ,  104  and are securely restricted from both vertical motion and horizontal motion in the direction of vehicle  10  motion M. The slides  106  are allowed to slide freely horizontally, perpendicular to the direction of vehicle  10  motion, along arrow X of FIG.  3 . 
     With reference again to FIG. 5, slide rams  108  are interposed between the box beams  37 ,  38  of the central structure  36  and outside ends  106   a  of the slides  106 . The rams  108  attach to the slides  106  and central structure  36  through attachment brackets  109 . The attachment brackets  109  allow each ram  108  to pivot somewhat but restricts ends of the ram  108  from translation. When the ram  108  is extended, the associated slide  106  slides through the guides  102 ,  104  and is extended horizontally perpendicular to the direction of vehicle  10  motion M. When the ram  108  is contracted, the slide  106  is returned to its position closer to the frame  30 . FIG. 5 shows the action of the rams  108  in detail and FIG. 6 shows the connection of the rams  108  and attachment brackets  109  in detail. 
     Lubrication layers  107  are shown interposed between the guides  102 ,  104  and the slides  106 . The layers  107  assists the slides  106  allowing them to slide more freely. An example of layers  107  may include grease, smooth solid layers of low friction hydro carbon substances or the like. 
     Bases  110  are shown in FIGS. 2 and 3 fixedly attached to upper surfaces of each of the slides  106  near outside ends  106   a of the slides  106 . The bases  110  are rigid and upwardly extending. Pivotably attached to tops of each base  110  is a lower driver  112 . The driver  112  is a rigid elongate structure. One driver  112  is attached to each base  110  at the driver&#39;s lower end through a pivot pin assembly  111 . Each assembly  111  includes a pivot pin fastened within holes formed in each base  110 . The pivot pin of the assembly  111  extends in a direction substantially parallel to the direction of the vehicle  10  motion M. The assembly  111  allows each driver  112  to pivot freely with respect to its attached base  110  (about arrow P shown in FIG. 3) while restricting the driver  112  from being displaced linearly from its base  110 . 
     A lower follower  114  is pivotably attached to a central portion of each base  110 . The follower  114  is substantially similar in characteristics to the driver  112 . One follower  114  is connected to each base  110  through another assembly  111 . Thus, each follower  114  is free to rotate with respect to its attached base  110  (about arrow P), but is not allowed to move linearly with respect to its base  110 . 
     The drivers  112  are pivotably attached at upper ends opposite the bases  110  to left intermediate risers  120 . The upper ends of the drivers  112  attach to the risers  120  at a location just below a midway point between a top and a bottom of each of the risers  120 . Assemblies  111  attach the drivers  112  to the risers  120 . Thus, the risers  120  and drivers  112  are rotatable with respect to each other but not translatable. 
     The followers  114  are pivotably attached on upper ends to lower portions of the risers  120 . Assemblies  111  are utilized to attach the followers  114  and the risers  120  together. Thus, the followers  114  and risers  120  are free to rotate about each other but are restricted from relative translation. Each driver  112  and each follower  114  is attached to the bases  110  and risers  120  in a manner such that each driver  112  is substantially parallel to its adjacent follower  114 . The drivers  112  and followers  114  are substantially the same length. Thus, four bar linkages defining parallel motion mechanisms are provided with links  112 ,  114  and captured portions of bases  110  and risers  120  therebetween. 
     Because of the geometric symmetry of the drivers  112  and followers  114  and the orientation of the drivers  112  and followers  114  on the bases  110  and the risers  120 , the risers  120  are restricted so that they may only move in a specific confined pattern. This pattern of riser  120  motion prohibits the risers  120  from pivoting with respect to the bases  110 . Thus, the risers  120  can only move vertically and horizontally perpendicular to the direction of vehicle  10  travel and may not rotate with respect to the bases  110 . 
     A lower hydraulic ram  116  is pivotably connected to a lower portion of each base  110  and a central portion of each driver  112 . Attachment brackets  117  are utilized to connect ends of each ram  116 . Thus, when one of the rams  116  is extended, the driver  112  pivots about the base  110  (arrow P) causing the riser  120  to move upwards. The follower  114  is also caused to pivot due to its attachments to the riser  120  and base  110 . The follower  114  restricts the riser  120  from pivoting with respect to the base  110 . 
     An upper driver  122  is pivotably attached to an upper end of each riser  120 . Each driver  122  is a rigid elongate structure similar in characteristics to the driver  112  but where driver  112  points in toward the center of the device  10 , driver  122  points outwardly. The drivers  122  are connected at lower ends to the upper end of each riser  120  by pivot pin assemblies  111 . The assemblies  111  allow each driver  122  to pivot freely about the adjacent riser  120  (about arrow Q) while restricting the driver  122  from translating with respect to the riser  120 . An upper end of each driver  122  is pivotably attached to an upper riser  128 . Each riser  128  is a rigid structure. The drivers  122  utilize pivot pin assemblies  111  to pivotably attach to the risers  128 . 
     A left upper follower  124  is pivotably attached on a lower end to each riser  120  at a point just above the midpoint of the height of each riser  120 . The followers  124  utilize pivot pin assemblies  111  to pivotably connect to the risers  120 . The followers  124  are substantially similar in characteristics to the followers  114 . The assemblies  111  allow the followers  124  to pivot with respect to the risers  120  while restricting the followers  124  from translating with respect to the risers  120 . 
     An upper end of each follower  124  is pivotably attached to a lower end of the adjacent riser  128 . The followers  124  are pivotably attached to the risers  128  through pivot pin assemblies  111 . In this way, the followers  124  are allowed to pivot freely about the risers  128  while being restricted from linear translation. Thus, a second set of four bar linkages defining a parallel motion mechanism are provided. 
     The drivers  122  and followers  124  are connected to each riser  120  and riser  128  in a configuration causing them to remain parallel to each other at all times. This geometric configuration causes each riser  128  to remain oriented to the adjacent riser  120  in a non-rotating relationship. Because the risers  128  does not rotate with respect to the risers  120  and the risers  120  do not rotate with respect to the bases  110 , the risers  128  do not rotate with respect to the bases  110 . 
     Upper hydraulic rams  126  are interposed between the risers  120  and the drivers  122 . Ends of each ram  126  are connected to a central portion of each driver  122  through attachment brackets  127 . The lower ends of each ram  126  are pivotably attached to mid-portions of the risers  120  through attachment brackets  127 . 
     Thus, when one of the rams  126  is extended, the associated driver  122  pivots with respect to the adjacent riser  120 , about arrow Q, causing the riser  128  to be moved vertically upwards. The follower  124  is also caused to move and restricts the riser  128  causing the riser  128  to remain oriented with respect to the riser  120  without rotation. 
     A platform  130  is fixedly attached to an upper surface of each riser  128 . The platforms  130  are a thin substantially square rigid constructs. The platforms  130  are sized to comfortably support a person thereupon. A safety cage  132  extends above and circumscribes each platform  130 . Each cage  132  has side walls  162  with an upper edge  163 . The upper edge  163  of each cage  132  is at a height near the waist of an operator standing upon the platform  130 . 
     One side of each cage  132  forms a door  134 , shown in FIG.  1 . The doors  134  provide operators with access into and out of the cages  132 . When the doors  134  are opened, the rams  108 ,  116 ,  126  are preferably disabled thereby preventing the associated scaffold  100  from moving and providing enhanced safety. 
     In/out pedals  136  are located on top surfaces of the platform  130  on a side thereof which corresponds to an operator&#39;s right foot when the operator faces away from the vehicle  10 . The in/out pedals  136  have three positions: a neutral position, an “in” position and an “out” position. When in the neutral position, the associated scaffold  100  does not move horizontally along arrow X. When the “in” portion of the in/out pedal  136  of one of the scaffolds  100  is depressed, the ram  108  of that scaffold  100  is contracted causing the slide  106  and the scaffold  100  to move toward the vehicle  10  along arrow “X”. When the “out” portion of the in/out pedal  136  of one of the scaffolds  100  is depressed the ram  108  is caused to extend. This causes the slide  106  to move outwardly away from the pruning vehicle  10 . Utilizing the in/out pedals  136 , operators on the platforms  130  may easily move the scaffolds  100  in and out, toward and away from the pruning vehicle  10 . 
     Up/down pedals  138  are located on a top surface of each platform  130  on a side thereof which corresponds to a left foot of an operator facing away from the vehicle  10 . The up/down pedals  138  have three positions: A “down” position, an “up” position and a neutral position. When in the neutral position, the associated scaffold  100  remains fixed vertically. When the “down” portion of one of the up/down pedals  138  is depressed, the ram  116  and ram  126  of the scaffold  100  are caused to contract. This causes the scaffold  100  to be lowered (along arrow “V”) from a higher position to a lower position with respect to the chassis  20 . When the “up” portion of one of the up/down pedals  138  is depressed, the ram  116  and ram  126  of the scaffold  100  are extended, causing the scaffold  100  to extend vertically (along arrow “V”) causing the platform  130  to move from a lower position to a higher position with respect to the chassis  20 . 
     A cable support stand  140  is fixedly attached adjacent to each box beam  37 ,  38  on a side thereof, shown in FIGS. 1,  2 ,  7  and  8 . The stands  140  are rigid elongate constructs which extend vertically upward and support cables connected to the scaffolds  100  through a clamp  142  and a roller  144  fixedly attached thereto. 
     Cables  143  representative of the numerous electric and hydraulic cables connecting various controls  138 ,  136  are shown routed through one of the support stands  140 . The remaining cables, such as those activating the rams  108 ,  116 ,  126  are not shown to more clearly show other elements of the chassis  20 . 
     A steering joystick  66 , shown in FIG. 8, is located on a forward side of an upper edge  163  of one of the cages  132 . Preferably, the cage  137  of the left scaffold  100  supports the joystick  66 . A frame  68  surrounds the joystick  66 . A steering apparatus cover  69  extends down a side of the cage  132 . The cover  69  contains wiring and hydraulic lines necessary to operatively connect the joystick  66  to the wheels  50  and engine  39  of the vehicle  10 . 
     The joystick  66  is free to move in all horizontal directions including forward, reverse, left and right. When the joystick  66  is placed in a neutral position the pruning vehicle  10  remains fixed in place. When the joystick  66  is moved forward the hydraulic motors  90  are activated causing the wheels  50  to turn forward causing the pruning vehicle  10  to move forward. When the joystick  66  is moved to the reverse position the hydraulic motors  90  are activated causing the wheels  50  to turn causing the vehicle  10  to move in reverse. 
     When the joystick  66  is moved to the left the forward steering ram  60  (FIG. 1) is extended causing the forward wheels  50  to turn positioning the vehicle  10  to make a left turn. The rearward wheels  50  may also turn through simultaneous contraction of the rearward steering ram  60 . When the joystick  66  is moved to the right the forward steering ram  60  is compressed and the rearward steering ram  60  is extended causing the wheels  50  to position themselves for the vehicle  10  to turn to the right. When the joystick  66  is positioned in intermediate positions between the above-described positions a combination of forward or rearward motion is combined with pivoting of the wheels  50  causing the vehicle  10  to move and turn simultaneously. 
     In use and operation, the pruning vehicle  10  is used in the following manner. First the engine  39  of the pruning vehicle  10  is started activating all of the hydraulic systems on the pruning vehicle  10 . Two operators position themselves one on each platform  130 . The operator on the left platform  130  then operates the joystick  66  to position the vehicle  10  within a row in an orchard to be pruned. Once the vehicle  10  is positioned between two trees on the orchard row, the vehicle  10  is brought to a stop. Each operator then separately operates the in/out pedals  136  and up/down pedals  138  to position the scaffolds  100  wherever the operators desire them to be located for ease of pruning. When each operator has completed pruning at the vehicle  10  position, the left operator then operates the joystick  66  to move the vehicle  10  forward. This process is continued down the row of trees in the orchard. 
     An alternative embodiment for the scaffolds of the pruning vehicle  10  is shown in FIGS. 7 and 8. The rams  126  are replaced with mechanical links  118 . The mechanical links  118  are pivotably attached between upper ends of each driver  112  and lower ends of each driver  122  through assemblies  111  on both of the scaffolds  100 . The mechanical links  118  cause the drivers  122  and followers  124  to be pivoted upwards at the same time that the drivers  112  and followers  114  are pivoted. This alternative embodiment avoids the requirement of the rams  126 . However, this embodiment restricts the ability of each scaffold  100  to be elevated to the action of only ram  116  at any one time. 
     Referring now to FIGS. 9,  10 ,  11  and  12 , another alternative embodiment of the invention is shown. The separate scaffolds  100  of the preferred embodiment are replaced with a central scaffold  210 . The central scaffold attaches to the central structure  36  of the frame  30  through four base sleeves  212 . Each sleeve  212  is an elongate rigid cylindrical hollow construct fixedly attached vertically to the central structure  36  of the frame  30 . Each sleeve  212  has a sleeve support  214  extending from the sleeve&#39;s upper end diagonally to the rearward or forward structure  32 ,  34 . Each support  214  is a rigid elongate structure fixedly attached in place. 
     Four base slides  216  are sized to fit within top openings of each sleeve  212 . Upper ends of each slide  216  are fixedly attached to a scaffold frame  220 . A base ram  218  is attached on a first end to the central structure  36  through a base attachment bracket  219  and attached through an attachment bracket  219  to the scaffold frame  220 . When the ram  218  is extended, it causes the scaffold frame  220  to move vertically upward along arrow B also causing the slides  216  to move upwards within the sleeves  212 . 
     FIG. 11 shows the operators cage area. It is a single runway allowing one operator to access both sides. It has a scaffold frame  220  and two outer cages  242 ,  252  which telescope towards and away from the scaffold frame  220 . 
     The scaffold frame  220  has two lower supports  230  each with an inner right guide  234  and an outer left guide  232 . The two outer guides  232  allow the left cage  242  to telescope while the inner guides  234  allow the right cage  252  to telescope. Details of the scaffold frame  220  are shown in FIG.  12 . 
     Each of the guide portions  232 ,  234  is an elongate construct of rectangular cross-section. The scaffold guides  230  are rigid constructs forming a rail. The left guide portions  232  and right guide portions  234  form separate rails for horizontal positioning of a left cage  242  and a right cage  252 . 
     Two left slides  240  are conformed to fit over the left guide portions  232  (FIG.  11 ). The left slides  240  slide horizontally along arrow “A”. Two right slides  250  conform to the right guide portions  234  in a manner similar to the left guide portions  232 . The right slides  250  allow the right cage  252  to slide horizontally along arrow “A”. 
     The left slide  240  has the left cage  242  fixedly attached to its upper surface. A planar walkway  248  is fixedly attached to an upper surface of the left slide  240  between the cage  242  and the left slide  240 . The cage  242  is similar in construction to the cage  132  of the preferred embodiment. The right slide  250  has the right cage  252  fixedly attached to its upper surface. A walkway  258  is fixedly attached to an upper surface of the right slide  250  between the cage  252  and the right slide  250 . The cage  252  is similar in construction to the cage  182  of the preferred embodiment. 
     A handrail  222  (FIG. 10) is fixedly attached to the scaffold frame  220 . The handrail  222  extends an appropriate distance above the scaffold frame  220  such that an operator standing on a fixed walkway  224  attached to the scaffold frame  220  will be able to grasp the handrail  222 . Handrail extensions  240  are attached on one end to one of the cages  242 ,  252  and on an opposite end telescope within the handrail  222 . 
     A left hydraulic ram  241  is pivotably attached between the scaffold frame  220  and the left slide  240 . The ram  241  can be expanded causing the left slide  240  to extend allowing the cage  242  and associated walkway  248  to provide access for an operator to a location more distant from the vehicle  10 . A ram  251  is pivotably attached between the scaffold frame  220  and the right slide  250  causing the right slide  250  and associated right walkway  258 , handrail extension  255 , and cage  252  to be extended outwardly horizontally in a direction opposite that of the left slide  240 . 
     An up/down pedal  246  is positioned on the top surface of the left walkway  248 . The up/down pedal  246  has three positions: a neutral position, an “up” position and a “down” position. The up/down pedal  246  is preferably located on a rearward side of the walkway  248  within the cage  242 . When the up/down pedal  246  is in the neutral position the scaffold frame  220  remains at a constant height above the vehicle  10 . When the “up” portion of the up/down pedal  246  is depressed the scaffold frame  220  is caused to increase in elevation along arrow B by extension of the ram  218 . When the “down” portion of the up/down pedal  246  is depressed the ram  218  is compressed causing the scaffold frame  220  to be lowered with respect to the vehicle  10 . 
     An in/out pedal  244  is located on an upper surface of the walkway  246  on the forward side thereof. The in/out pedal  244  has three positions which correspond to the three positions of the in/out pedal  136  of the preferred embodiment. The in/out pedal  244  may be utilized by the operator to move the left slide  240  in and out causing the cage  242  to extend horizontally along arrow A. 
     An in/out pedal  254  is located on an upper surface of the walkway  258  on a rearward side thereof and at end thereof distant from the scaffold frame  220 . The in/out pedal  254  has three positions which correspond to the three positions of the in/out pedal  186  of the preferred embodiment. Utilizing the in/out pedal  254 , the operator is able to move the right slide  250  and associated walkway  258 , hand rail extensions  245 , and cage  252  outward horizontally along arrow A. 
     When this embodiment is utilized, access is provided at all times between the left cage  242  and the right cage  252 . This allows a single operator to prune two adjacent trees without moving the vehicle  10  or climbing out of either cage  242 ,  252 . The joystick  66  is located on the central scaffold  210  preferably at the cage  242  in a position which corresponds to its position on the cage  132  in the preferred embodiment. 
     In use and operation this alternative embodiment is utilized in the following manner. The vehicle  10  is positioned in a manner similar to that described in the preferred embodiment. The central scaffold  210  is then boarded by one or more operators. Once the vehicle is in position between two trees of an orchard row, the operator or operators may elevate or lower the scaffold frame  220 , along arrow B, to a desired position. The operator or operators may then adjust the cage  242  or cage  252  horizontally, along arrow A, to a desired location. Once this position is achieved, pruning and other maintenance may be performed by the operator or operators. If a single operator is aboard, that operator may move between cages  242 ,  252  to perform similar maintenance or pruning. The operator may then return to the cage  242  to operate the joystick  66  to move the vehicle  10  to the next set of trees along the orchard row. 
     Another alternative embodiment, shown in FIGS. 13 and 14, involves replacement of the central scaffold  210  with a scissor scaffold  310 . The scaffold  310  utilizes a scissor scaffold frame  320  which replaces the scaffold frame  220  of the central scaffold  210 . The scaffold  310  attaches to the frame  30  of the vehicle  10  (i.e. at the central structure  36 ) above box beams  37 , 38 . The scissor scaffold  310  has identical forward and rearward construction. FIG. 14 shows only the rearward portion of the scissor scaffold  310  but is representative of the forward portion. 
     A forward base guide  312  and a rearward base guide (not shown) of complemental construction are fixed transverse to the box beams  37 ,  38  in a horizontal orientation perpendicular to vehicle  10  motion. Each guide  312  is a linear rigid construct which has an inner race upon which guide wheels  316  may roll. Also each base guide  312 , has a pivot pin assembly  319  located on right side ends of the base guide  312 . 
     Pivotably attached to both the forward and rearward assemblies  319  are two scissor links  318 . Each link  318  is pivotably connected to each guide  312  allowing rotation of link  318  without linear translation. Another pair of identical scissor links  318  are pivotably attached to the first links  318  at central locations  318   a  of each link  318  midway between distal ends thereof. A lower end of the second pair of links  318  is pivotably attached to the wheels  316  in a manner such that the wheels  316  restrict lower ends of the links  318  within the guides  312 . Thus, the pair of links  318  form a lower “X”-shaped scissor, pivotable about the junction between the two links  318 . An upper “X”-shaped scissor is pivotably attached to the lower “X”-shaped scissor. Upper ends of all four of the links  318  of the lower “X”-shaped scissor are pivotably attached to lower ends of other similar scissor links  318  of the upper “X”-shaped scissor. Each pivotable connection between links  318  is formed by a pivot pin assembly  317  similar to the assembly  111  of the preferred embodiment. Upper ends of the links  318  of the upper “X”-shaped scissor have either a pivotable attachment to a guide wheel  340  if on a left side or a pivotable attachment to a guide  330  if on the right side. The guides  330  provide races for the wheels  340  and are fixedly attached to a lower surface of the scaffold  310 . While only an upper and a lower “X”-shaped scissor are shown in FIG. 14, it is contemplated that any number of “X”-shaped scissors could be interposed between the chassis  20  and the base guide  312 . 
     A lifting ram  313  is pivotably connected between one of the guides  312  and one of the lower links  318  at a point  315  slightly above the pivot  317  which links the lower links  318  together. When the ram  313  is extended it causes the links  318  to pivot (along arrow C, for example) from a substantially horizontal extended position to a more vertical extended position. This in turn causes the scaffold frame  320  to raise to an elevated position (along arrow D). The wheels  316  roll within the guides  312  along arrow E, and within the two guides  330  located on a lower side of the frame  320 . The frame  320  is similar in design to the scaffold frame  220  except that it is fixedly attached to the guide  330  instead of to the guides  216  of the central scaffold  210  embodiment. 
     A scissor scaffold handrail  360  is fixedly attached to the frame  320  and cages  350  are located at left and right ends of the frame  320 . The locations of the cages  350  are adjustable in a manner similar to the adjustment of the central scaffold  210 . The scaffold  310  only differs from the central scaffold  210  in that it utilizes a different structure to adjust the elevation of the scaffolds  210 ,  310 . The horizontal adjustment of the cages  242 ,  252 ,  350  are not changed and therefore will not be belabored. 
     Referring now to FIGS. 15 and 16 another alternative embodiment of the pruning vehicle is shown. The scaffolds  100  of the preferred embodiment are replaced with scaffolds  400 . 
     Both the left side and right side of the scaffold  400  operate similarly and will be discussed together with the left side showing the contracted position and the right side expanded. 
     Essentially, horizontal expansion occurs through multiple stages: two stages are illustrated. Each cage  432  is attached, through vertical expansion stages, to an outer stage formed with two slides  406  braced at ends thereof and which ride in guides  406  which have facing “C”-shaped channels to accommodate the slides  406 . 
     In turn, these guides  406  have outer faces which define slides that run in outer guides  402 ,  404  and define the inner stage. As should now be evident, other stages could be similarly employed. 
     More specifically, each scaffold  400  of the pruning vehicle  10  connects to the chassis  20  through the central structure  36  of the frame  30 . Two horizontal guides  402  are fixedly attached to an upper surface of the box beams  37 ,  38 . The guides  402  are rigid members of substantially “C”-shaped cross-section which extend, along arrow F, across opposite sides of the frame  30  with open portions facing each other. Central guide  404  is located between the guides  402  at a location near a center of the central structure  36 . The central guide  404  has an “I”-shaped cross-section with open sides of its “I”-shaped cross-section facing forward and rearward. Thus, two tracks are formed, one for each scaffold  400 . A cross-bar  440  is fixedly attached between lower ends of each pair of guides  402 ,  404  on ends opposite their associated cages  432 . 
     Two outer slides  405  are formed from two elongate channels of “C”-shaped cross-section and are oriented to nest within each track formed by the guides  402 ,  404 . The slides  405  are of an exterior height substantially equal to the interior height of the “C”-shaped cross sections of the guides  402 ,  404 . The slides  405  are of substantially the same length as the width of the frame  30 . Cross-bars  442  are nested within cross-bar  440  and extend between forward and rearward sides of ends of the slides  405  distant from their associated cages  432  to hold them in a parallel configuration. 
     Having this shape, the slides  405  fit between the guides  402 ,  404  and are securely restricted from vertical motion and horizontal motion in the direction of vehicle  10  motion, but are allowed to slide freely horizontally, along arrow F, perpendicular to the direction of vehicle  10  motion. Each slide  405  has an outer end  401  comprised of a cross-bar extending between forward and rearward sides of each slide  405 . 
     Hydraulic rams  407  are interposed between each of the cross-bars  440  and the outer ends  401 . The rams  407  attach to the left ends  401  and cross-bars  440  through attachment brackets  409 . Each attachment bracket  409  allows the ram  407  to pivot somewhat but restricts ends of the ram  407  from translation. When the rams  407  are extended, the slides  405  slide through the guides  402 ,  404  and are extended horizontally along arrow F. When the rams  407  are contracted, the slides  405  are returned to their positions closer to sides of the frame  30 . 
     Inner slides  406  reside between each forward and rearward side of each slide  405 . The inner slides  406  are of an exterior height equal to the interior height of each “C”-shaped cross-sections of sides of the outer slides  406 . The inner slides  406  are substantially the same length as is the width of the frame  30 . The inner slides  406  have outer ends  403  comprised of cross-bars extending between forward and rearward sides of the inner slides  406 . Cross-bars  442  are interposed between the two portions of each inner slide  406 , maintaining them in a parallel configuration. 
     Having this shape, the inner slides  406  fit within the outer slides  405  and are securely restricted from vertical motion and horizontal motion in the direction of vehicle  10  motion, but are allowed to slide freely horizontally, along arrow F. 
     Hydraulic rams  408  are interposed between the cross-bars  442  and the outer ends  403 . The rams  408  attach to the inner slides  406  through additional attachment brackets  409 . When one of the rams  408  is extended, the inner slide  406  is caused to slide through the sides of the outer slide  405  and is extended horizontally along arrow F. When the ram  408  is contracted, the inner slide  406  is returned to its original position within the outer slide  405 . 
     A vertical guide  410  is fixedly attached to and extends above each outer end  403 . The guides  410  are rigid elongate structures comprised of two channels of substantially “C”-shaped cross-section. The guide channels&#39; open sides face each other. 
     An outer slide  412  is located within openings in the “C”-shaped channels of each guide  410 . The slides  412  are sized with a thickness and width allowing them to fit snugly within the adjacent guides  410 . Thus, the slides  412  are restricted from any horizontal motion. 
     The slides  412  are composed of two channels of “C”-shaped cross-section which have open sides facing each other. The slides  412  are substantially similar in length to the length of the guides  410 . A chain attachment bar  428  is fixedly attached between the two channels of each slide  412  on a side closest to the frame  30 . A bottom plate  434  is fixedly attached to lower surfaces of channels of each slide  412 . 
     Two hydraulic rams  413  are interposed between each outer end  403  and an upper end of the adjacent slide  412 . The rams  413  attach to the outer ends  403  through attachment brackets  416 . The rams  413  attach to the slides  412  through ram attachments  420 . 
     The ram attachments  420  are rigid constructs having two fingers  421 . Each finger  421  reaches around the outer surface of the guide  410  from a location away from the guide  410  channel interior to a location inside the channel interior where the finger  421  fixedly attaches to the slide  412 . One finger  421  goes around each side of each guide  410  channel. 
     Thus, when a pair of rams  413  are extended, the slide  412  is raised upwards along arrow H. When the rams  413  are contracted, the associated slide  412  is lowered. The rams  413  are sized and oriented to allow each slide  412  to be lowered below a bottom of each guide  410 . 
     An inner slide  414  is located within openings in the “C”-shaped channels of each outer slide  412 . The inner slides  414  are sized with a thickness and width allowing them to fit snugly within the associated outer slide  412 . Thus, the inner slides  414  are restricted from any horizontal motion. 
     The inner slides  414  are composed of two channels of “C”-shaped cross-section which have open sides facing each other. The inner slides  414  are substantially similar in length to the length of the guides  410 . Top plates  422  are fixedly attached between upper surfaces of the two channels comprising each inner slide  414 . 
     Hydraulic rams  415  are interposed between an upper surface of each bottom plate  434  and a lower surface of each top plate  422 . The rams  415  attach to the bottom plates  434  and the top plates  422  through attachment brackets  416 . 
     When one of the rams  415  is extended, the associated inner slide  414  (among other parts, as will be explained) is caused to slide through the channels of the outer slide  412  and is extended upwards vertically along arrow H. When the ram  415  is contracted the inner slide  414  is extended downwards along arrow H. 
     A platform slide  436  is located within openings in the “C”-shaped channels of each inner slide  414 . Each platform slide  436  is sized with a thickness and width allowing it to fit snugly within the associated inner slide  414 . Thus, the platform slide  436  is restricted from any horizontal motion. 
     A lubricating layer  449  is interposed between each guide  410 , outer slide  412 , inner slide  414 , and platform slide  436 . The lubricating layer  449  is similar to the lubricating layer  107  of the preferred embodiment. One alternative lubricating layer  449  includes use of thin solid hydrocarbon layers made from materials known for their low friction characteristics. 
     On a bottom end of each platform slide  436  is fixedly attached a platform  430 . The platforms  430  are rigid constructs which extend horizontally across the bottom ends of the platform slides  436  and have contours which allow the platforms  430  to avoid contacting the associated rams  415 . 
     A plurality of sprocket mounts  427  are fixedly attached to a lower surface of each top plate  422 . Sprockets  426  are pivotably attached to the sprocket mounts  427 . Chains  424  are located over each of the sprockets  426 . Each chain  424  is attached on a first end to one of the chain attachment bars  428 . Each chain  424  is attached on a second end to one of the platforms  430  on an upper surface thereof. 
     Thus, when one of the rams  415  is extended, the distance between the sprockets  426  and the chain attachment bar  428  is increased causing the chains  424  to raise the platform  430  upwards, along arrow H, with respect to the inner slide  414 . 
     The cage  432  which corresponds to the cage  132  of the preferred embodiment is fixedly attached to the platform  430 . 
     In use and operation, the platform  430  operates in the following manner. Users board the cages  432  of each scaffold  400  with none of the hydraulic rams  407 ,  408 ,  413 ,  415  extended. When one of the users desires to move a cage  432  horizontally outwards, along arrow F, the rams  407 ,  408  are extended causing the slides  405 ,  406  to more outward. When the user desires to move the cage  432  vertically upwards, along arrow H, the rams  413 ,  415  are extended causing the slides  412 ,  414 ,  436  to move upward. When the user desires to move the cage  432  vertically downwards, the rams  407 ,  408  are first extended somewhat, then the ram  413  is contracted causing the cage  432  to move downward. 
     While this embodiment includes four vertically nested supports for the cage  432 , a variety of greater or lesser groupings of supports could be utilized. Alternatively, a series of horizontally nested supports could be utilized. 
     Referring now to FIGS. 17 through 21, another alternative embodiment of the scaffolds  100  are shown. In essence, two lifts  500  position two cages  544  which are independently horizontally and vertically translatable by means of telescoping slides (horizontally) and by a hydraulic ram coupled with a chain/sheave arrangement (vertically). 
     The left side of this embodiment is shown in a retracted configuration, while the right side of this embodiment is shown in an extended configuration. The two lifts  500  are substantially mirror images of each other and hence details of each side will be described together. As shown in FIGS. 17 through 21, the left side details are referred to with (′) and the right side details are referred to with (″). 
     Each lift  500  connects to the frame  30  (FIG. 2) at the central structure  36  (FIG. 2) thereof. Specifically, two outside rails  504  and two inside rails  554  are oriented across box beams  37 ,  38  and perpendicular to box beams  37 ,  38  on extreme forward and rearward portions of upper surfaces thereof. Each rail  504 ,  554  is an elongate rigid construct of orthorhombic shape which is fixedly attached to a support plate  503 ,  505  (FIG. 20) which is in turn fixedly attached to box beams  37 ,  38  of the central structure  36  and elevated therefrom through risers  552 . One support plate  503  is rearward of the other support plate  505  with respect to the vehicle&#39;s front and rear. 
     An inner slide  508  of “C”-shaped cross-section conforms to outer contours of each outside rail  504  and each inside rail  554 . Each inner slide  508  has: a top shelf  568  resting above each rail  504 ,  554 ; an intermediate wall  572  resting along an outside edge of the outside rail  504  or an inside edge of the inside rail  554 ; and a bottom shelf  576  adjacent a bottom side of the rail  504 ,  554 . A lubrication layer  551  is interposed between each inner slide  508  and each rail  504 ,  554 . A lip  507  extends down from an end of the top shelf  568  along an upper portion of each inner slide  508 ; an inner side of each outside rail  504 ; and an outer side of each inside rail  554 . This lip  507  keeps the slide  508  on track upon the rail  504  and prevents the inner slide  508  from translating horizontally along the direction of vehicle motion M. 
     An end plate  509  (FIG. 17) seals by attachment to ends of the inner slides  508 . One end plate  509  is oriented in a vertical plane and holds the two inner slides  508 , which slide over the outside rails  504  together. The other end plate  509  is oriented in a horizontal plane and holds the two inner slides  508 , which slide over the inside rails  554  together. The outside rails  504  support the left lift  500  and the inside rails  554  support the right lift  500 . The left lift  500  and right lift  500  are identical except for their attachment to different rails  504 ,  554 . First rams  520  are interposed between each box beam  37 ,  38  and one of the end plates  509  with pivotable attachments at ends of the first rams  520 . Thus, when one of the first rams  520  is extended, the associated end plate  509  is caused to move with respect to the chassis  20 . This in turn causes one set of inner slides  508  to slide along arrow X. 
     Two outer slides  512  are shaped to conform to surfaces of each inner slide  508  of each rail  504 ,  554 . Each slide  512  has an upper portion  513  and a lower portion  514 . The upper portions  513  act as risers extending above each lower portion  514 . The lower portions  514  are “C”-shaped and similar in construction to the inner slides  508 . However, the lower portions  514  are sized with inner dimensions slightly larger than outside dimensions of the inner slides  508  to facilitate their nesting together over the rails  504 ,  554 . A gap, formed between each inner slide  508  and the associated outer slide  512 , may be supplied with a lubricant  551  to facilitate relative movement therebetween. 
     A tie  515  extends between and unites each upper portion  513  of each outer slide  512  of each lift  500  so that they move in unison. The ties  515  are rigid constructs of constant narrow width having two horizontally extending opposing ends  515   a . A central portion  515   b  of each tie  515  has vertically downward extending portions  515   c  which join the central portion  515   b  to the ends  515   a . Thus, as shown in FIG. 20, the ties  515  have an inverted “top hat”-like cross-section. 
     An “L”-bracket  517  is fixedly attached to each of the inner slides  508  and supports one end of a second ram  524  which is also connected to the tie  515  and to the associated outer slide  512 . The “L”-brackets  517  are rigid constructs which extend vertically above the inner slides  508 , and horizontally towards the risers  552 , a short distance. The lower portions of the “L”-brackets  517  are preferably located on the inner slides  508  on ends thereof distant from the associated ties  515 . 
     The second rams  524  facilitate relative motion between the outer slides  512  and the inner slides  508 . In use and operation, the rails  504 ,  554  support the inner slides  508  such that when one of the first rams  520  is extended or contracted, the inner slides  508  move relative to the rails  504 ,  554 . Likewise, when the second rams  524  are extended or contracted the outer slides  512  are caused to move with respect to the inner slides  508 . Extension of both the first ram  520  and the second ram  524  of either lift  500  causes the associated outer slide  512  to be displaced even more distant from the central structure  36  of the frame  30  along arrow X than would be possible through action of either ram  520  or ram  524  alone. 
     A vertical translation portion of each lift  500  is now described which attaches to an upper surface of each tie  515 . The vertical translation portion of each lift  500  is a mirror image of the opposite lift  500  and includes the following details generic to each lift  500 . 
     Each lift  500  has two “C”-rails  548  which are fixedly attached to an upper surface of each tie  515  at forwardmost and rearwardmost portions thereof. Each “C”-rail  548  is a rigid elongate construct having a “C”-shaped cross-section. Specifically, each “C”-rail  548  has a first wall  560  parallel to and spaced from a second wall  561 . The first wall  560  is near to a center of the frame  30  than is the second wall  561 . An orthogonal wall  564  extends from one end of the first wall  560  to one end of the second wall  561 . An open portion of each “C”-rail  548  is defined by the walls  560 ,  561 ,  564 . Open portions of each pair of “C”-rails  548  face each other and the central portion  515   b  of each tie  515 . 
     The pairs of “C”-rails  548  are united by support cross-bars  510  formed from angle iron. The support cross-bars  510  are rigid elongate constructs of “L”-shaped cross-section which are oriented horizontally, along arrow M, and are fixedly attached between each pair of “C”-rails  548  on sides thereof closest to a center of the frame  30 . Two diagonal supports  511  are interposed between each support crossbar  510  and upper surfaces of each of the upper portions  513  at ends distant from the box beams  37 ,  38 . The support crossbars  510  and diagonal supports  511  provide additional rigidity to each pair of “C”-rails  548 . 
     A chain crossbar  530  is also interposed between each pair of “C”-rails  548 . Each chain crossbar  530  is an elongate rigid construct of rectangular cross-section which is fixedly attached at distant ends thereof to each “C”-rail  548 . The chain crossbars  530  are located above the support crossbars  510 . The chain crossbars  530  extend somewhat horizontally away from the two pairs of “C”-rails  548  and closer to a center of the frame  30 . The chain crossbars  530  provide additional support for the pairs of “C”-rails  548  as well as other functions which will become apparent. 
     Two pairs of “J”-rails  546  are interposed between each pair of “C”-rails  548  with one “J”-rail  546  adjacent to each “C”-rail  548 . Thus, each “J”-rail  546  and each “C”-rail  548  resides in a plane which is substantially vertical and extends parallel to arrow M. Each “J”-rail  546  has a “J”-shaped cross-section. Specifically, each “J”-rail  546  is a rigid elongate construct of uniform cross-section. A long wall  580  and a short wall  581  are oriented parallel to each other. A perpendicular wall  584  extends between the long wall  580  and the short wall  584  and is securely attached therebetween. The perpendicular wall  584  extends from a center of the long wall  580  to an end of the short wall  581 . 
     Each “J”-rail  546  is nested within the adjacent “C”-rail  548  such that the long wall  580  of each “J”-rail  546  extends into the open portion of the associated “C”-rail  548  with the long wall  580  parallel to and slightly spaced from the first wall  560 . This orientation locates the short wall  581  in a plane parallel to the second wall  561  of the “C”-rail  548 . 
     A “C”-rail wheel  549  is located within the open portion of each “C”-rail  548  on an uppermost end thereof. The “C”-rail wheels  549  are cylindrical constructs which have an axle which allows the wheels to rotate within each “C”-rail  548  without translation linearly. Each “C”-rail wheel  549  has a diameter with sufficient clearance between the first wall  560  of the “C”-rail  548  and a radial edge of the “C”-rail wheel  549  to receive the long wall  580  of the “J”-rail  546  therebetween. Each long wall  580  is in contact with each “C”-rail wheel  549 . 
     Each “J”-rail  546  has a “J”-rail wheel  547  on a lower portion thereof which is rotatably connected to the perpendicular wall  584  of each “J”-rail  546 . The “J”-rail wheels  547  are aligned with the “C”-rail wheels  549  such that they both rotate within the same plane. However, the “J”-rail wheels  547  are displaced such that they are slightly closer to the first wall  560  than are the “C”-rail wheels  549 . A hole (not shown) is formed in the long parallel portion of each “J”-rail  546  to allow the “J”-rail wheels  547  to have a point of tangency which extends therebeyond. Thus, when each “J”-rail  546  is nested within each “C”-rail  548 , each long wall  580  is adjacent the associated “C”-rail wheel  549  on an upper portion of each “C”-rail  548 . Also, each “J”-rail wheel  547  is tangentially registered against the first wall  560  on a lower portion of each “C”-rail  548 . 
     Portions of each lift  500  above the outer slide  512  have a center of mass which is farther from a center of the frame  30  than are the “C”-rails  548 . Thus, a torque is created which causes the “J”-rail  546  to exert a force against the “C”-rail wheels  549  and causes the “J”-rail wheels  547  to exert a force against the “C”-rails  548  as a couple. The wheels  547 ,  549  support the “J”-rails  546  such that the “J”-rails  546  can be translated vertically by rolling within the “C”-rails  548 . 
     Each pair of “J”-rails  546  are spaced a distance apart on upper surfaces thereof by top plates  534 . The top plates  534  are flat rigid elongate constructs which have a length equal to a distance between each two “C”-rails  548  and are fixedly attached to upper edges of each “J”-rail  546  pair. The top plates  534  maintain the two “J”-rails  546  of each pair sufficiently distant from each other that they cannot be displaced from within the “C”-rail  548  pairs. 
     A trolley  542  is located between each pair of “J”-rails  546 . Each trolley  542  includes a bottom plate  570  and two mutually parallel side plates  574  which extend perpendicularly upward from the bottom plate  570 . A shield  540  also extends upward from the bottom plate  570  of each trolley  542  and are perpendicular to the side plates  574  of the trollies  542 . Each shield  540  is on a side of the associated trolley  542  opposite from a center of the frame  30 . Each shield  540  forms a larger surface than the plates  570 ,  574  of the trolley  542  two side plates  574  of each trolley  542  are spaced sufficiently apart and sized of a width so that they can slide within a portion of each pair of “J”-rails  546  opposite the “C”-rails  548 . To facilitate movement therein, the side plates  574  of each trolley  542  have wheels thereon which allow the trollies  542  to roll within the “J”-rail  546  pairs. 
     Two first trolley wheels  543  are oriented on uppermost and lowermost edges of each of the side plates  574  of each trolley  542  with one of the first trolley wheels  543  on a lower portion thereof on a side nearer the frame  30  and the other of the first trolley wheels  543  located on an upper portion thereof on a side away from the frame  30 . Each lower wheel  543  rolls against the long wall  580  of the associated “J”-rail  546 . Each upper wheel  543  rolls against the short wall  581 . Thus, the trollies  542  are prevented from jamming within the “J”-rails  546 . Two second trolley wheels  545  are located on each side plate  574  of each trolley  542  and rolls along the perpendicular walls  584  of each “J”-rail  546 . The second trolley wheels  545  keep the trolley  542  from rotating and jamming during movement relative to the “J”-rails  546 . 
     Two sheaves  536  extend from a lower surface of each top plate  534  such that one sheave is inboard slightly from each “J”-rail  546 . Each sheave  536  receives a chain  532  thereover. Each chain  532  is pivotably attached on one end to one of the chain crossbars  530  and on a second end to the shield  540 . Alternatively, the sheaves  536  may be replaced with sprockets. 
     A vertical ram  528  is interposed between each central portion  515   b  of each tie  515  and each associated top plate  534 . Thus, when one of the vertical rams  528  is extended, the adjacent top plate  534  is caused to be displaced upwards away from the associated tie  515 . This in turn causes the associated “J”-rails  546 , which are fixedly attached to the top plate  534 , to be displaced upwards. This also causes the attached sheaves  534  to be displaced upwards. The chains  532  are displaced about the sheaves  534  with their first ends remaining fixed to the chain crossbar  530  which is grounded to the tie  515 . The second end of each chain  532  which is attached to the shield  540  and hence to the trolley  542  causes the trolley  542  and shield  540  to roll upwards within the “J”-rails  546 . 
     A cage  544  is fixedly attached to each shield  540  on a lower surface thereof. Each cage  544  is similar to the cage  132  of the preferred embodiment. Through activation of the first ram  520 , second ram  524  and vertical ram  528 , the cage  544  may be displaced horizontally and vertically to locate a user in the position desired for performing tree maintenance within an orchard. 
     Moreover, having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.