Abstract:
A lift gate system having a first upright including a first track; a second upright including a second track, wherein the second upright is parallel to the first upright; a cross member coupled to the first upright and coupled to the second upright; a receiver bar coupled to the cross member, wherein the receiver bar is configured for detachable coupling to a receiver tube; a first carrier coupled to the first upright, wherein the first carrier is coupled to the first upright, wherein the first carrier is configured to move along the first track; a second carrier coupled to the second upright, wherein the second carrier is coupled to the second upright, wherein the second carrier is configured to move along the second track; a platform coupled to the first carrier and the second carrier; and a drive mechanism coupled to the first carrier and to the second carrier, wherein the first carrier and the second carrier move at a same velocity when the drive mechanism is activated, whereby the platform is raised and lowered uniformly when the drive mechanism is activated.

Description:
This application claims the benefit of U.S. Provisional Application No. 62/066,842, filed Oct. 21, 2014, for HITCH-MOUNTED LIFT GATE, which is incorporated in its entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a receiver-mounted lift gate, and more specifically to a removable receiver-mounted lift gate and wheeled skate body assembly. Even more specifically, the present invention relates to a single electric drive, receiver-mounted lift gate and removable wheeled skate body assembly for positioning the receiver-mounted lift gate relative to a vehicle. 
     2. Discussion of the Related Art 
     Pickup trucks and other vehicles used for transporting goods, equipment, and other cargo such as for the building, and/or agriculture industries feature cargo beds that are generally parallel to the ground, and ride a number of inches above the ground. These cargo beds have proven to be incredibly versatile, and beneficial, and have led, in part, to the popularity of vehicles such as pickup trucks for both commercial and personal uses. 
     Various means have been developed for facilitating the loading and unloading of cargo from these vehicles. For example, ramps positioned against a tailgate can be used in combination with a hand truck to facilitate loading and unloading. In the same vein, such vehicles can be backed against a loading dock for this same purpose. In addition, various technologies for lifting cargo, such as fork lifts, cranes, and the like can be employed in the loading and unloading of such vehicles. 
     Unfortunately, these above-mentioned technologies all require devices or fixtures at the site of loading or unloading to assist in this process. These devices may not be available everywhere, such that during the sequence of loading, transporting, and unlading, the operator may find him/herself without the aid of these technologies either during the loading or unloading of the cargo, or both. 
     While cranes have been installed in such vehicles, they tend to be specialized and limited to a small percentage of the overall variety of cargo types that may be transported by such vehicles, e.g., a crane may be suitable for lifting cargo that is structured or packaged with appropriate lift points, and/or positioned within the vehicle to lift and lower the cargo from and to specific positions, their application is generally limited. In addition, such cranes can create clearance problems when cargo other than that for which they are designed is to be loaded or unloaded, and must be removed in such cases, sometimes requiring additional technologies to lift the crane off of the vehicle. 
     As such, lift gates have become somewhat popular as a solution to the challenge of loading and unloading cargo from vehicles. A lift gate is positioned generally where a tailgate would be on a factory stock pickup truck or cargo truck, e.g., box truck, and generally replaces the tailgate, hence the “gate” portion of the name lift gate. In addition, the lift gate can be repositioned from a vertical orientation, where it functions as a “gate” into a horizontal orientation where it functions as a “lift.” While in its horizontal orientation, the lift gate can be lowered to the ground (or even raised to a higher level to align with a loading dock) in order to facilitate the easy loading of cargo onto the lift gate. Once loaded with cargo, the lift gate can be repositioned, such as by using an assembly of linkages and hydraulic cylinders, to a position generally coplanar with the cargo bed in order to facilitate the easy loading of cargo from the lift gate into the cargo bed, or vice versa. This lowering or raising and repositioning of the lift gate may need to be repeated multiple times for multiple batches of cargo in order to fully load the cargo bed. 
     Unfortunately, the installation of a lift gate does have its drawbacks. Most notably, because a lift gate often replaces the tailgate of the vehicle, and because it must be secured to the vehicle frame in order to both be portable and provide sufficient lifting capacity, installation of a lift gate generally requires permanent removal of the tailgate, and bumper of the vehicle, and fixation of the lift gate machinery to the frame of the vehicle, such as by welding or drilling of mounting holes. Such installation often required specialized mounting brackets suitable of installing the lift gate into the particular make/model/year of vehicle into which the lift gate is to be installed. In addition, the hydraulic cylinders of the lift gate must be supplied with a source of electrical power at 12V and, for example, approximately 100 A. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention can be characterized as a lift gate system comprising a first upright including a first track; a second upright including a second track, wherein the second upright is parallel to the first upright; a cross member coupled to the first upright and coupled to the second upright; a receiver bar coupled to the cross member, wherein the receiver bar is configured for detachable coupling to a receiver tube; a first carrier coupled to the first upright, wherein the first carrier is coupled to the first upright, wherein the first carrier is configured to move along the first track; a second carrier coupled to the second upright, wherein the second carrier is coupled to the second upright, wherein the second carrier is configure to move along the second track; a platform coupled to the first carrier and the second carrier; and a drive mechanism coupled to the first carrier and to the second carrier, wherein the first carrier and the second carrier move at a same velocity when the drive mechanism is activated, whereby the platform is raised and lowered uniformly when the drive mechanism is activated. 
     Another embodiment of the present invention can be characterized as a method of attaching a lift gate to a receiver tube comprising positioning the lift gate at a rear of a vehicle by rolling the lift gate into position on a skate body with attached wheels; aligning a receiver bar with the receiver tube by rolling the lift gate horizontally with the skate body and the attached wheels, and lifting the lift gate vertically by operating a drive mechanism; inserting the receiver bar into the receiver tube; locking the receiver bar into the receiver tube; releasing the skate body from the lift gate by unlocking a plurality of; raising the lift gate off of the skate body; and moving the skate body horizontally with the attached wheels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of several embodiments of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings. 
         FIG. 1  is a perspective view of a receiver-mounted lift gate in accordance with one embodiment of the present invention. 
         FIG. 2  is a side plan view of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . 
         FIG. 3  is a side plan view of the receiver-mounted lift gate in a raised position in accordance with the embodiment of  FIG. 1 . 
         FIG. 4  is a side plan view of the receiver-mounted lift gate in a raised position with a kick flap lowered in accordance with the embodiment of  FIG. 1 . 
         FIG. 5  is a side plan view of the receiver-mounted lift gate in a raised position with a kick flap lowered in accordance with the embodiment of  FIG. 1 . 
         FIG. 6  is a side partial cross-sectional view of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . 
         FIG. 7  is a perspective cut-away view of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . 
         FIG. 8  is a partial, exploded assembly view of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
         FIG. 9  is a rear partial cross-sectional view of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
         FIG. 10  is a partial, exploded assembly view of a winch mechanism of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
         FIG. 11  is a further partial exploded assembly view of the winch mechanism of  FIG. 10 . 
         FIG. 12  is another partial exploded assembly view of the winch mechanism of  FIG. 10 . 
         FIG. 13  is a side plan view of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  with a skate body and wheels supporting the receiver-mounted lift gate. 
         FIG. 14  is a side plan view of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  including accessories used with the receiver-mounted lift gate. 
         FIG. 15  is a side plan view of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  including a ground-mounted receiver used with the receiver-mounted lift gate. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. 
     DETAILED DESCRIPTION 
     The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of exemplary embodiments. The scope of the invention should be determined with reference to the claims. 
     Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
     Before beginning, it should be noted that the directional coordinate system used is defined from a forward facing driver&#39;s perspective; i.e. forward refers to the front of the vehicle, rear refers to the direction of the rear of the vehicle, left is defined as the driver&#39;s left, right is defined as a driver&#39;s right, up refers to the direction of the drivers head from the seat, and down refers to ground level from a driver&#39;s seat. 
     Referring first to  FIG. 1 , a perspective view is shown of a receiver-mounted lift gate in accordance with one embodiment of the present invention. The present embodiment is the removable lift gate system that includes a platform flap  22 , a platform center  24 , a kick flap  26 , two rear hinges  28   a , two front hinges  28   b , two carriers  4 , two lower linkages  32 , two upper linkages  34 , two uprights  36 , two flexible tension members  38 , two upper sheave supports  54 , two upper sheaves  50  (or pulleys), two leg outer shells  12 , two leg inner shells  14 , two leg posts  16 , and a leg drive mechanism  76 .  FIG. 1  also includes a vehicle with a cargo bed  18 . 
     The platform assembly comprises the bodies and connections including: a platform flap  22 , a platform center  24 , a kick flap  26 , two rear hinges  28   a , and two front hinges  28   b.    
     As shown in  FIG. 1 , the platform flap  22  pivotally joins to the platform center  24  via the rear hinges  28   a  located at the joint of the platform flap  22  and platform center  24 . The forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. The kick flap  26  pivotally joins to the platform center  24  via the front hinges  28   b  located at the joint of the kick flap  26  and platform center  24 . 
     Each carrier  4  is housed, either wholly or partially depending on the configuration, within its respective upright  36  so that the long axes of each body are generally vertically aligned. Each leg outer shell  12  mounts to the outside face of an upright  36  so that the long axes of each body lie generally vertically parallel. The leg outer shell  12  has a leg inner shell  14  within it in a manner such that the outside face(s) of the leg inner shell  14  concentrically align with the inside faces of the leg inner shell. Each leg post  16  sits within a leg inner shell  14  in an exact orientation as the leg inner shell  14  within the leg outer shell  12 . A leg drive mechanism  76  mounts to the leg outer shell  12  and its driving unit attaches to the leg inner shell  14 . 
     The tops of both carriers  4  pivotally connect to the end of the flexible tension member  38  of its respective side. The flexible tension member  38  begins at the carrier  4  top connection, runs generally along the central long axis of the upright  36  up to the upright&#39;s  36  top and about 180 degrees around the upper sheave&#39;s  50  groove towards the front and continues down the front face of the upright  36  in a generally vertical route. Each upper sheave  50  is pivotally connected to an upper sheave support  54 . The upper sheaves  50  are located near the top of each upright  36  with the flat faces of each upper sheave  50  parallel to the sides of the uprights  36  and the groove in-line with the flexible tension member&#39;s  38  route. 
     The platform flap  22  pivots about the rear hinges  28   a , from a position that extends to the posterior of the platform center  24  with the top surfaces of the two bodies generally parallel, approximately 180 degrees in the upwards direction so that the platform flap&#39;s  22  top surface lays over the platform center&#39;s  24  top surface. The kick flap  26  pivots about the front hinges  28   b  in an exact manner as the platform flap  22  pivots about the rear hinges  28   a . The pivoting of the platform flap  22  and kick flap  26  about hinges  28   a  and  28   b , respectively, may occur through man or mechanical power. The kick flap  26  pivoting motion is automatically controlled by a guide that pilots the kick flap  26  as the platform center  24  is lifted from ground level to the height of the vehicle&#39;s cargo bed  18 , as in the positions shown in  FIG. 2  and  FIG. 4 . At ground level, the kick flap  26  sits in the vertical position and as it lifts the guide continuously tilts the kick flap  26  towards the front until it is horizontal at the height of the cargo bed  18 . The front hinges  28   b  and rear hinges  28   a  exhibit pivot points located above the top surface of the platform center  24  that enables the kick flap  26  and platform flap  22  to pivot at least 180 degrees. The platform flap  22  is optional and the platform center  24  may be used without it. 
     The platform center  24  pivots about the carrier&#39;s  4  lower tab from a position parallel to the ground, shown in  FIG. 2  to a position vertical to the ground, shown in  FIG. 5 . When the platform center  24  sits parallel to the ground, the lower linkages  32  and upper linkages  34  lockout in tension in an extended configuration with their long axes collinear as shown in  FIG. 2 . Upon folding of the platform center  24  to the vertical position, the upper linkages  34  and lower linkages  32  rotate about their pivoting connections and collapse so that the upper linkage&#39;s  34  long axis lies vertical and parallel to the long axis of the upright while the lower linkage&#39;s  32  long axis sits at a slight rearward angle to the upper linkage&#39;s vertical long axis shown in  FIG. 5 . The upper linkage  34  and lower linkage  32  may be replaced by any flexible or collapsible members that hold tension when loaded but allows the platform center  24  to be folded to a vertical position such as, but not limited to, chain link, wire rope, or cable. 
     The carrier  4  vertically translates with respect to the upright  36  it is housed within. Depending on the height of the platform center  24 , the carrier  4  may be fully enclosed within the upright  36  or partially enclosed at its upper portions with the lower portion dropping through the bottom of the tubular cross-member  44 . Each upright  36  is tubular shaped with an open slot down the entire back face&#39;s length, see  FIG. 7 , so that tabular protrusions from the carrier  4  extend beyond the upright&#39;s  36  inside enclosure and allow the platform center  24  and upper linkages  34  to pivotally connect to the tabs without interfering with the upright  36  or carrier  4  upon pivotal motion. 
     When the flexible tension members  38  are pulled in by the drive mechanism  8 , each carrier  4  is translated in the vertical direction inside of its respective upright. 
     The leg outer shell  12  is fixedly attached to the upright  36 . The leg post  16  freely slides vertically within the leg inner shell  14  and is manually secured to the inner shell  14  through, but not limited to, a clamp, pin, or wedge when a desired position is reached. The inner shell  14  vertically translates within the outer shell  12  via a leg drive mechanism  76  that is automatically powered. The leg drive mechanism  76  can also be manually powered through a hand crank. During lifting or lowering of the platform the legs posts  16  contact the ground to act as supports. The leg inner shell  14  supports the hitch  46  by pressing the leg posts  16  against the ground, providing a reactive force to support the hitch  46 . 
     Referring next to  FIG. 2 , a side plan view is shown of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . Shown are a platform flap  22 , a platform center  24 , a rear hinge  28   a , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , an upper sheave support  54 , an upper sheave  50 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a leg drive mechanism  76 , a cross-member  44 , a mounting bracket  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52  (or pulley), a lower sheave support  56 , a hitch  46 , a hitch pin  80 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch receiver  20  of a vehicle. 
     As shown in  FIG. 2 , the platform flap  22  pivotally joins to the platform center  24  via the rear hinges  28   a  located at the joint of the platform flap  22  and platform center  24 . The forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. 
     The hitch  46  is a long tubular member that partially rests concentrically within a hitch receiver  20  and projects out towards the rear of the vehicle generally in line with the long axis of the vehicle and parallel to the ground plane. The rear portion of the hitch  46  slidably sits within a concentric, outer tubular member called the hitch sleeve  90 . A hitch drive  92  lays in line with the hitch  46  and hitch sleeve  90 . A fixed portion of the hitch drive  92  mounts to the hitch sleeve  90  with its driving end attached to the hitch  46 . 
     The cross-member  44  is a long tubular member that sits horizontal to the ground and parallel to the long axis of the vehicle&#39;s bumper. The top face of the hitch sleeve  90 , towards its rear, mounts to the bottom face of the cross-member  44  generally towards the center of the cross-member&#39;s  44  long axis. A hitch gusset  60  mounts from the underside of the cross-member  44  to the underside of the hitch  46 . The lower front face of each upright  36  mounts to the rear face of the cross-member  44 , one towards each end of the cross-member  44 , through a mounting bracket  58 . The mounting bracket  58  aligns the upright generally vertical to the ground and perpendicular to the cross-member  44 . 
     Each lower sheave  52  is pivotally mounted with a lower sheave support  56  onto the cross-member&#39;s  44  front face so that the planar face of the lower sheave  52  is parallel to the cross-member  44  front face. Each lower sheave  52  is located towards the cross-member&#39;s  44  ends in a manner that its groove generally vertically aligns with the upper sheave  50  of its respective side. The flexible tension member  38  is routed around the lower sheave  52  approximately 90 degrees towards the center of the cross-member  44  and along the cross-members  44  front face in a generally horizontal fashion until it connects to the drive mechanism  8 . 
     One flexible tension member&#39;s  38  end mounts to the upper portion of the spool  86  towards the rear in the radial direction while the other flexible tension member&#39;s  38  end mounts to the lower portion of the spool  86 , 180 degrees on the opposite side of the spool  86  in the radial direction. Starting at the axial ends of the spool  86 , each flexible tension member  38  wraps around the spool  86  at least once and works its way inwards towards the axial center of the spool  86  one flexible tension member&#39;s  38  width per wrap. 
     The spool spacer  64  mounts around the spool  86  in the space between the two flexible tension  38  member wraps generally in the center of the spool&#39;s  86  long axis. Each spool clamp  62  mounts around a flexible tension member&#39;s  38  base wraps and leaves a space between itself and the spool spacer  64  of equal or greater width to the width of the flexible tension member  38 . The flexible tension member  38  sits between the broad faces of the spool clamp  62  and spool spacer  64  and exits the spool  86  in the radial direction. 
     The front portion of the hitch  46  concentrically sits within the hitch receiver  20  and is locked into place by a hitch pin  80  that passes through the two bodies. The outer faces of the hitch  46  are firmly pressed against the inner walls of the hitch receiver  20  by a hitch lock (not shown). The hitch lock may embody, but is not limited to, a clamping mechanism that presses the outside hitch  46  face(s) firmly against the inside wall(s) of the hitch receiver  20  or a two piece hitch cut at an angle so that when the front piece draws axially towards the rear piece it climbs the rear angled surface and presses against the inner hitch receiver  46  walls and the rear hitch piece&#39;s angled surface. The hitch  46  may also rest in the hitch receiver  20  without the support of a hitch lock. 
     As shown in  FIG. 2 , the rear portion of the hitch  46  sits concentrically within a hitch sleeve  90  just as the front portion of the hitch  46  can sit in the hitch receiver  20 . The hitch sleeve  90  is able to slide axially along the hitch  46  so as to move the cross-member  44 , and thus the platform assembly, nearer or farther from the hitch receiver  20 . This motion is controlled either directly from the drive mechanism  8  or a hitch drive  92 , which can be manually or automatically powered through, but not limited to, a rotational or linear actuator. The hitch  46  may be locked into place relative to the hitch sleeve  90  by a hitch lock (not shown) similar to that described between the hitch  46  and the hitch receiver  20 , by the hitch drive  92  itself, or not at all. 
     The rear of the hitch  46  may also mount directly to the cross-member, therefore excluding the hitch sleeve  90  and hitch drive  92  from the invention and preventing any relative motion between the cross-member  44  and the hitch  46 . 
     The hitch sleeve  90  serves as a receiver that allows hitches to be attached. For example, a ball hitch may be slid into the hitch sleeve  90  and fixed in place to allow towing of a trailer while the invention is attached to a vehicle. Alternatively, another hitch receiver-sized tubular member (not shown) may be attached to the cross-member  44  and/or hitch  46  either coaxially with the hitch or in any position within the vertical plane passing through the hitch&#39;s  46  long axis while also maintaining a parallel relationship between the long axes of the hitch  46 . 
     Referring next to  FIG. 3 , a side plan view is shown of the receiver-mounted lift gate in a raised position in accordance with the embodiment of  FIG. 1 . 
     Shown are a platform flap  22 , a platform center  24 , rear hinges  28   a , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , an upper sheave support  54 , an upper sheave  50 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a leg drive mechanism  76 , a cross-member  44 , a mounting bracket  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52 , a lower sheave support  56 , a hitch pin  80 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch receiver  20  of a vehicle. 
     As shown in  FIG. 3 , the platform flap  22  pivotally joins to the platform center  24  via the rear hinges  28   a  located at the joint of the platform flap  22  and platform center  24 . The forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. 
     Referring next to  FIG. 4 , a side plan view is shown of the receiver-mounted lift gate in a raised position with a kick flap  26  lowered in accordance with the embodiment of  FIG. 1 . 
     Shown are a platform flap  22 , a platform center  24 , a kick flap  26 , rear hinges  28   a , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , an upper sheave support  54 , an upper sheave  50 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a leg drive mechanism  76 , a cross-member  44 , a mounting bracket  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52 , a lower sheave support  56 , a hitch pin  80 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch receiver  20  of a vehicle. 
     As shown in  FIG. 4 , the platform flap  22  pivotally joins to the platform center  24  via the rear hinges  28   a  located at the joint of the platform flap  22  and platform center  24 . The forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. The kick flap  26  pivotally joins to the platform center  24  via the front hinges  28   b  located at the joint of the kick flap  26  and platform center  24 . 
     Referring next to  FIG. 5 , a side plan view is shown of the receiver-mounted lift gate in a raised position with a kick flap  26  lowered in accordance with the embodiment of  FIG. 1 . 
     Shown are a platform center  24 , a kick flap  26 , rear hinges  28   a , front hinges  28   b , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , an upper sheave support  54 , an upper sheave  50 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a leg drive mechanism  76 , a cross-member  44 , a mounting bracket  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52 , a lower sheave support  56 , a hitch pin  80 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch receiver  20  of a vehicle. 
     With the hitch  46  mounted to a hitch receiver  20 , each leg post  16  and inner leg shell  14  vertically lifts off the ground so that the weight of the invention rests solely on the hitch  46 . 
     Referring next to  FIG. 6 , a side partial cross-sectional view is shown of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . 
       FIG. 6  contains a platform center  24 , a rear hinge  28   a , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , a cross-member  44 , a mounting bracket  58 , a front friction reducer  40 , a rear friction reducer  42 , a drive mechanism  8 , a tensioner  84 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52 , a lower sheave support  56 , a hitch pin  80 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch receiver  20  of a pickup truck. Note that the leg outer shell  12 , leg inner shell  14 , leg post  16 , and leg drive mechanism  76  have been removed from  FIG. 6  to reveal the carrier  4  within the sectioned view of the upright  36 . 
     As shown in  FIGS. 5 and 6 , the kick flap  26  pivotally joins to the platform center  24  via the front hinges  28   b  located at the joint of the kick flap  26  and platform center  24 . The forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. The kick flap  26  pivotally joins to the platform center  24  via the front hinges  28   b  located at the joint of the kick flap  26  and platform center  24 . 
     Each carrier  4  is housed, either wholly or partially depending on the configuration, within its respective upright  36  so that the long axes of each body are generally vertically aligned. Mounted towards the rear face of the carrier  4  is a rear friction reducer  40  and towards the front face of the carrier  4  a front friction reducer  42  is mounted. The rear friction reducer  40  contacts the inside portion of the upright&#39;s  36  rear face while the front friction reducer  42  contacts the inside portion of the upright&#39;s  36  front face so that so that the long axes of the upright  36  and carrier  4  are generally vertically aligned. 
     When the flexible tension members  38  are pulled in by the drive mechanism  8 , each carrier  4  is lifted along the respective upright  36  from the ground to the height of the vehicle&#39;s cargo bed  18 . 
     Referring next to  FIG. 7 , a perspective cut-away view is shown of the receiver-mounted lift gate in a lowered position in accordance with the embodiment of  FIG. 1 . 
     As shown in  FIG. 7  and  FIG. 1 , a slot runs along the entire length of the upright&#39;s  36  rear face that allows the pivoting connections of the platform center  24  and upper link  34  to the carrier  4  to vertically translate the upright  36  without interference. This slot may also run along the inside face of each upright  36  so long as it allows the pivoting connections mentioned before to translate the upright  36  without interference. The upright  36  may or may not have a finite slot on its front face, starting from the upright&#39;s  36  top and down some finite length, which allows the upper sheave  50  to be inset within the upright  36  for general alignment of the vertically tangential edge of the upper sheave  50  with the axial center of the carrier  4 . 
     The rear and front friction reducers,  40  and  42  respectively, may be rollers, as shown in  FIG. 7 , low friction slide pads, or any other attachment that stabilizes and eases the vertical motion of the carrier  4  within the upright  36 . A low-friction slide pad would perform the same function as a roller by mounting towards the rear and front faces of the carrier and contacting the inner walls of the upright  36 . The number of front and rear friction reducers,  42  and  40  respectively, is not fixed; any number of them may be included on each carrier  4  and mounted on any face of the carrier, whether that be the front, rear, left, right, top, or bottom face(s). 
     Shown are a platform flap  22 , a platform center  24 , a kick flap  26 , two rear hinges  28   a , two front hinges  28   b , two carriers  4 , two lower linkages  32 , two upper linkages  34 , two uprights  36 , two flexible tension members  38 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a cross-member  44 , a mounting bracket  58 , a front friction reducer  40 , a rear friction reducer  42 , and a drive mechanism  8 . 
     Each leg outer shell  12  mounts to the outside face of an upright  36  so that the long axes of each body lie generally vertically parallel. Both leg outer shells  12  have a leg inner shell  14  within it in a manner such that the outside face(s) of the leg inner shell  14  concentrically align with one another. Each leg post  16  sits within a leg inner shell  14  in an exact orientation as the leg inner shell  14  within the leg outer shell  12 . 
     A leg drive mechanism  76  mounts to the leg outer shell  12  and its driving unit attaches to the leg inner shell  14 . 
     Referring next to  FIG. 8 , a partial, exploded assembly view is shown of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
     Shown are two uprights  36 , mechanical fasteners  78 , two mounting brackets  58 , a cross-member  44 , two lower sheave supports  56 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , and a hitch pin  80 . 
     The cross-member  44  is a long tubular member that sits horizontal to the ground and parallel to the long axis of the vehicle&#39;s bumper. The top face of the hitch sleeve  90 , towards its rear, mounts to the bottom face of the cross-member  44  generally towards the center of the cross-member&#39;s  44  long axis. A hitch gusset  60  mounts from the underside of the cross-member  44  to the underside of the hitch  46 . The lower front face of each upright  36  mounts to the rear face of the cross-member  44 , one towards each end of the cross-member  44 , through a mounting bracket  58 . The mounting bracket  58  aligns the upright generally vertical to the ground and perpendicular to the cross-member  44  and secures them in place with mechanical fasteners  78  that attach the two bodies together through the mounting bracket  58 . 
     The mounting brackets  58  allow the uprights  36  to removably attach to the cross-members  44  through the use of mechanical fasteners  78 . The mechanical fasteners  78  used to mount the uprights  36  to the cross-members  44  may be of various types including but not limited to threaded fasteners, clamping fasteners, or cam-locking fasteners. 
     The mounting brackets  58  may be bypassed and the upright  36  is permanently attached to the cross-member  44  through a permanent adhering process, such as welding. In such a case, a member, like a gusset, forming a generally vertically planed rib between the front face of the upright  36  and the top face of the upright  36 , replaces the support element of the mounting bracket  58 . 
     The lower face of the upright  36  may be mounted so that it is flush with the bottom face of the cross-member  44  offset downwards towards the ground so the upright&#39;s  36  bottom protrudes vertically past the cross-member  44 , as shown in  FIG. 8 . 
     The upper sheave support  54  and lower sheave supports  56  mount the upper sheave  50  and lower sheave  52 , respectively, in the positions explained above, but the orientation and the manner in which the upper sheave  50  and lower sheave  52  are mounted are not held strictly to these positions. The lower sheave  52  may be oriented so that its planar face sits at any angle relative to the cross-member&#39;s  44  front face and it may even be mounted to the front face of the upright  36 . The upper sheave&#39;s  50  planar faces may sit at any angle relative to the upright  36  and be mounted at any position vertically along the upright&#39;s  36  front face. 
     Referring next to  FIG. 9 , a rear partial cross-sectional view is shown of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
     A single tensioner  84  slidably mounts to the cross-member  44  between the lower sheave  52  and either side of the drive mechanism  8 . The tensioner  84  reroutes the flexible tension member  38  away from a straight line path from the lower sheave  52  to the drive mechanism  8  so that the portion of the flexible tension member  38  between the lower sheave  52  and the tensioner  84  is parallel to the long axis of the cross-member  44  and the portion of the flexible tension member  38  between the tensioner  84  and drive mechanism  8  aligns at a variable angle with the cross-member&#39;s  44  long central axis in a plane generally parallel to the ground. 
     A skate body  68  is secured to the underside of each leg post  16  through skate fasteners  82  so that the leg post  16  is generally located at the center of the skate body  68  along its length. The long axis of the skate body  68  is aligned such that it is parallel to the ground and the long axis of the hitch  46 . One caster wheel  70  mounts beneath each end of the skate body  68  so that the caster wheel&#39;s  70  mounting plate contacts the lower face of the skate body  68  and the roller contacts the ground. 
     As shown in  FIG. 9  and as explained above, the flexible tension members  38  begin at the drive mechanism  8  and extend outwards to opposite lower sheaves  52 . Each flexible tension member  38  wraps approximately 90 degrees around the lower sheave of its side and reaches upward, along the upright&#39;s  36  front face, and approximately 180 degrees around the upper sheave  50  and pivotally connects to the carrier  4 . The drive mechanism  8  may also attach to one upright  36  so that the flexible tension members  38  start from the drive mechanism  8 , but one goes directly to the upper sheave  50  of that corresponding upright  36  while the other flexible tension member  38  progresses through both lower sheaves  52  and the opposite upper sheave  50 . 
     The drive mechanism  8  mounts to either the cross-member  44  or one of the uprights  36  and can be automatically powered through hydraulics and/or electricity or manually powered. The drive mechanism  8  can draw the flexible tension member  38  in or out through a rotational or linear actuator such as, but not limited to, an electric winch, lead screw, or hydraulic cylinder. 
     The drive mechanism  8  is preferably powered by, but not limited to, an electrical battery that is mounted on or near the invention, or the battery onboard the vehicle. Power may also be sourced from a wall outlet, generator or other source. 
     Referring next to  FIG. 10 , a partial, exploded assembly view is shown of a winch mechanism (or motor) of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1 . 
     Shown are the drive mechanism  8 , a spool  86 , two flexible tension members  38 , two base wraps  100 , two spool clamps  62 , and a spool spacer  64 . 
     In the case that a rotational drive mechanism  8  is used to control the feed of the flexible tension member  38 ,  FIG. 10  demonstrates a spool  86  with base wraps  100  wound around in the manner explained above. Each set of base wraps  100  is covered by a spool clamp  62  that holds the base wraps in place and separated by a spool spacer  64  as shown in  FIG. 11  and  FIG. 12 . Each flexible tension member  38  exits the spool  86  from the space between the spool spacer  64  and spool clamp  62 , one exits from the top planar surface of the spool spacer  64  and the other exits from the lower planar surface of the spool spacer  64 . The flexible tension members  38  exit tangentially from the spool in opposite directions and from opposite sides of the spool  86  in both the radial and axial directions. 
     When the drive mechanism  8  undergoes rotational motion, each flexible tension member  38  wraps around the spool  86  in a single plane that lies parallel to the planar face of the spool spacer  64  and coincident with the generally horizontal central axis of the flexible tension member  38  traveling from the drive mechanism  8  to the lower sheave  52 . As the drive mechanism  8  continues to rotate each flexible tension member  38  continually wraps around itself in this single, horizontal plane in such a manner that the width of the single-plane winding increases by two flexible tension member  38  widths per complete revolution of the drive mechanism  8 . 
     The controlled feed of the flexible tension member  38  in this single plane shape allows each flexible tension member  38  to drawn or expelled from the drive mechanism  8  at equal rates. 
     In substitution of rotational drive mechanism modification an integrally shaped spool may be formed to the modified drive mechanism assembly shown in  FIG. 12 . The spool has a central spacer that separates the two flexible tension members  38  and a small space, slightly larger than the width of the flexible tension member  38 , between planar surfaces located on each side of the central spacer. This accomplishes the same control of the flexible tension member windings along a single plane as the modified spool but does not require base wraps  100  or multiple modification pieces  62  and  64 . 
     Referring next to  FIG. 11 , a further partial exploded assembly view is shown of the winch mechanism of  FIG. 10 . 
     Shown are the drive mechanism  8 , a spool  86 , two flexible tension members  38 , two base wraps  100 , two spool clamps  62 , and a spool spacer  64 . 
     Referring next to  FIG. 12 , another partial exploded assembly view is shown of the winch mechanism of  FIG. 10 . 
     Shown are the drive mechanism  8 , two flexible tension members  38 , two spool clamps  62 , and a spool spacer  64 . 
     Referring next to  FIG. 13 , a side plan view is shown of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  with a skate body and wheels supporting the receiver-mounted lift gate. 
       FIG. 12  shows the form that the spool  86  could take. The spool  86  can be a component of the rotational drive mechanism  8  that embodies a generally cylindrical shape with two diametric groves which are approximately the width of the flexible tension member  38 . 
     Shown are a platform center  24 , a kick flap  26 , a rear hinge  28   a , a front hinge  28   b , a carrier  4 , a lower linkage  32 , an upper linkage  34 , an upright  36 , a flexible tension member  38 , an upper sheave support  54 , an upper sheave  50 , a leg outer shell  12 , a leg inner shell  14 , a leg post  16 , a leg drive mechanism  76 , a cross-member  44 , a mounting bracket  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , a lower sheave  52 , a lower sheave support  56 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , a skate body  68 , two caster wheels  70 , two skate fasteners  82 , and a hitch receiver  20  of a vehicle. 
     As shown in  FIG. 13 , the forward side faces of the platform center  24  pivotally connect to the respective carrier&#39;s  4  lower tab and the rearward side faces of the platform center  24  pivotally connect to the respective lower linkage  32 . The opposing end of each lower linkage  32  pivotally connects to an upper linkage  34 , which then pivotally attaches, at its opposite end, to the respective carrier&#39;s  4  upper tab. The kick flap  26  pivotally joins to the platform center  24  via the front hinges  28   b  located at the joint of the kick flap  26  and platform center  24 . 
     The platform center  24  pivots about the carrier&#39;s  4  lower tab from a position parallel to the ground, shown in  FIG. 2  to a position vertical to the ground, shown in  FIG. 5 . When the platform center  24  sits parallel to the ground, the lower linkages  32  and upper linkages  34  lockout in tension in an extended configuration with their long axes collinear as shown in  FIG. 2 . Prior to folding the platform center  24  to the vertical position by pivoting about the carrier&#39;s  4  lower tab, the kick flap  26  pivots about the front hinges  28   b  in such a manner that the top surface of the kick flap  26  is resting on the top surface of the platform center  24 . The platform flap  22  then pivots about the rear hinges  28   a  in such a manner that the top surface of the platform flap  22  is resting on the bottom surface of the kick flap  26 . 
     When the device is being attached to a vehicle  18  using the hitch receiver  20  interface, the device is able to move across the ground surface by the rolling action provided by the caster wheels  70 . The actuation of the leg drive mechanism  76  results in the vertical translation of the position of the hitch  46 . The leg drive mechanisms  76  are actuated until the vertical position of the hitch  46  is aligned and concentric with the hitch receiver  20 . The device is then rolled forwards until the hitch  46  sits concentric and within the hitch receiver  20 . 
     The caster wheels  70  are preferably made of a hard, durable material, such as nylon or steel, but may also be pneumatic or some other durable material. 
     The skate body  68 , caster wheels  70 , and skate fasteners  82  will hereout be collectively known as the skate assembly. The skate assembly detachably mounts to the leg post  16  and provides rolling contact between the ground and the invention. With the skate assembly attached, the invention can be translated across the ground in any direction parallel to the ground plane. 
     The skate assembly is detachably connected to the leg post  16 , which can be vertically translated within the inner leg sleeve  14 , and the inner leg sleeve  14  can be vertically translated within the outer leg sleeve  12  by the leg drive mechanism  76 . The availability of height adjustment enables the hitch  46  to be raised and lowered relative to the ground until its long axis is aligned with the hitch receiver&#39;s  20  long axis and the hitch  46  can be inserted into the hitch receiver  20 . The invention may also exist without the skate assembly. 
     Referring next to  FIG. 14 , a side plan view is shown of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  including accessories used with the receiver-mounted lift gate. 
     A platform flap  22 , a platform center  24 , a kick flap  26 , two rear hinges  28   a , two front hinges  28   b , two carriers  4 , two lower linkages  32 , two upper linkages  34 , two uprights  36 , two flexible tension members  38 , two upper sheave supports  54 , two upper sheaves  50 , two leg outer shells  12 , two leg inner shells  14 , two leg posts  16 , a leg drive mechanism  76 , an accessory  72 , accessory fasteners  94 , and the cargo bed  18  of a vehicle are shown. 
     Accessories  72  attach to the platform center  24  and/or platform flap  22  enabling the invention to lift specific objects. In the embodiment shown in  FIG. 14 , the accessories  72  are configured to serve as extension beams and are coupled to the platform center  24  by the accessory fasteners  94 . The accessories  72  may include, but are not limited to, extension beams, extension plates, handles and strap mounts that allow lifting objects including, but not limited to, a motorcycle, ATV, UTV, RTV, garbage cans, and lawn equipment. An accessory  72  may have the ability to serve as a cargo bed extender. 
     Referring next to  FIG. 15 , a side plan view is shown of the receiver-mounted lift gate in accordance with the embodiment of  FIG. 1  including a ground-mounted receiver used with the receiver-mounted lift gate. 
     An additional embodiment of the removable lift gate system is shown in  FIG. 15  and includes a platform flap  22 , a platform center  24 , a rear hinge  28   a , a carrier  4 , two lower linkages  32 , tow upper linkages  34 , two uprights  36 , two flexible tension members  38 , two upper sheave supports  54 , two upper sheaves  50 , two leg outer shells  12 , two leg inner shells  14 , two leg posts  16 , two leg drive mechanisms  76 , a cross-member  44 , two mounting brackets  58 , a drive mechanism  8 , two spool clamps  62 , a spool spacer  64 , two lower sheaves  52 , two lower sheave supports  56 , a hitch  46 , a hitch gusset  60 , a hitch sleeve  90 , a hitch drive mechanism  92 , a tensioner  84  and a non-vehicular hitch receiver  88 . 
     In lieu of coupling the removable lift gate system to the hitch receiver  20  of the vehicle, as previously shown in  FIGS. 1-14 , a ground mounted hitch receiver  88  may be provided. In the embodiment shown, a ground mounted hitch receiver  88  comprises a ground-supported vertical portion and a top portion configured to couple to the rear of the hitch  46 , for example by use of the hitch pin  80  as previously described. 
     The embodiment shown in  FIG. 15  including a ground mounted hitch receiver  88  enables the removable lift gate system to be used for non-vehicular applications, including, but not limited to, raising items to a height of a loading dock, or raising the platform center  24  and kick flap  26  to the height of a cargo vehicle which is located adjacent to but independent of the device described herein. 
     While the invention herein disclosed has been described by means of specific embodiments, examples and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.