Abstract:
A workbench assembly that may be reversibly mounted to a trailer hitch receiver of a vehicle with a stabilizer assembly that is also reversibly mounted to the trailer hitch receiver that functions to hold workbench assembly stable and free from motion relative to the trailer hitch receiver. Workbench assembly is collapsible or foldable so that it may be collapsed and folded tightly against the back of the vehicle during vehicle travel and unfolded or extended backwards from the vehicle during use of the workbench. Workbench may have rounded edges for clamping thereto by special clamps. Workbench may have one or more locking groove in its surfaces for locking or clamping thereto by special clamps. When not in use, workbench assembly may stored or mounted on the shop wall by detaching it from the trailer hitch receiver on the vehicle and remounting to a special wall mount assembly attached to the wall.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a workbench assembly, and, in particular, to a collapsible workbench assembly capable of being mounted to a trailer hitch receiver on any vehicle including pickup trucks. 
     The rear of a vehicle or tailgate of a pickup truck has long been found to be useful as a workstation. The present invention greatly improves on the usefulness of this workstation by providing a collapsible workbench capable of being mounted inside a trailer hitch receiver on a vehicle where the collapsible workbench may be folded upwards during vehicle transport and folded downwards when the vehicle is at rest to form a workstation with a wide workbench with tracking and locking groves used for mounting a wide array of mechanical such as a vise or similar and a wide array of power tools such as a chop saw or similar. 
     2. Description of Related Art 
     There are many tailgate workbenches or workbenches that are attachable to the rear of a pickup truck in the prior art. However, there are no tailgate receiver mounted workbenches in the prior art and certainly none that include the structure described below. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an aspect of trailer hitch receiver mounted collapsible workbench to comprise a workbench with a support framework that is reversibly attachable to a trailer hitch receiver on a vehicle. It is an aspect of this reversible attachment to function in the same way that a standard hitch ball mount or a standard hitch ball tongue is reversibly attached to a standard trailer hitch receiver on a vehicle where a tongue is inserted into the trailer hitch receiver on a vehicle and held inside trailer hitch receiver with a hitch pin or alternatively locked inside trailer hitch receiver with hitch lock pin. 
     It is an aspect of workbench to have a special cross-sectional shape so that the edges, upper surface, and/or lower surface of workbench function in conjunction with commercially available clamping systems and/or individual clamps to provide a workbench or platform to conveniently and securely clamp power tools, mechanical tools, and/or work objects that are fitted with the commercially available clamping systems and/or individual clamps. 
     It is an aspect of trailer hitch receiver mounted collapsible workbench to further comprise a stabilizer assembly that is rigidly reversibly attachable to the trailer hitch receiver on a vehicle, stabilizer assembly being a rigid framework that includes at least two support channels that receive, support, and rigidly hold the support framework of workbench stationary and appreciably vibrationless relative to the trailer hitch receiver during transport and use of trailer hitch receiver mounted collapsible workbench. 
     It is an aspect of the support framework of workbench to have a lower articulation point and an upper articulation point, each being an articulation point in the support framework with an axis of rotation that is parallel to the longitudinal axis of the workbench, lower articulation point allowing the workbench to be rotated downward to reduce the height of the workbench and/or rotated upwards to increase the height of the workbench, and upper articulation point allowing the workbench to be rotated into a horizontal and level position at any height or degree of rotation of the lower articulation. 
     It is an aspect of a lower articulation point to have a designated location and lock mechanism to retain or hold workbench in a reduced height location. 
     It is an aspect of a lower articulation point to have a designated location and lock mechanism to retain or hold workbench in an increased height location. 
     It is an aspect of an upper articulation point to have a designated location and lock mechanism to retain or hold workbench level and horizontal at the reduced height location. 
     It is an aspect of an upper articulation point to have a designated location and lock mechanism to retain or hold workbench level and horizontal at the increased height location. 
     It is an aspect of trailer hitch receiver mounted collapsible workbench to further comprise a wall mount assembly that is a frame structure that provides wall mounting capability of power tools, mechanical tools, and/or work objects fitted with the commercially available clamping systems and/or individual clamps that function in conjunction with the work bench. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of collapsible workbench assembly. 
         FIG. 2  is a perspective view of trailer hitch receiver mounted collapsible workbench mounted to the trailer hitch receiver on a pickup truck with the trailer hitch receiver mounted collapsible workbench in the flat or collapsed position. 
         FIG. 3  is a is a perspective view of trailer hitch receiver mounted collapsible workbench mounted to a trailer hitch receiver on a pickup truck with the trailer hitch receiver mounted collapsible workbench in the angled or work position and the tailgate of the pickup truck lowered.  FIG. 3  further depicts a chop saw locked onto the bench plate of trailer hitch receiver mounted collapsible workbench. 
         FIG. 4  is a side elevation view of collapsible workbench assembly. 
         FIG. 5  is a perspective view of stabilizer assembly mounted to the trailer hitch receiver on a pickup truck, without the collapsible workbench assembly mounted thereto. 
         FIG. 6  is an exploded view of stabilizer assembly. 
         FIG. 7  is an exploded view of collapsible workbench assembly. 
         FIG. 8  is a perspective view of a wall mount assembly attached to a wall with a chop saw clamped to the wall mount assembly.  FIG. 8  also depicts a collapsible workbench assembly mounted to the wall mount assembly. 
         FIG. 9  is a perspective view of trailer hitch receiver mounted collapsible workbench mounted to a trailer hitch receiver on a pickup truck with the trailer hitch receiver mounted collapsible workbench in the angled or work position and the tailgate of the pickup truck lowered to yield an extended payload area or truck bed depicted with several sheets of plywood loaded therein and secured with two special slideable edge tie-down brackets and a strap. 
         FIG. 10  is a cross-sectional view of best mode bench plate  210  taken at a plane perpendicular to its longitudinal axis. 
     
    
    
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 DEFINITION LIST 
               
             
          
           
               
                 Term 
                 Definition 
               
               
                   
               
               
                  50 
                 Trailer Hitch Receiver Mounted Collapsible Workbench 
               
               
                 100 
                 Stabilizer Assembly 
               
               
                 111 
                 Trailer Hitch Receiver on Vehicle 
               
               
                 112 
                 Horseshoe Plate 
               
               
                 112A 
                 Void in Horseshoe Plate 
               
               
                 113 
                 Support Channel 
               
               
                 114 
                 U-Bolt 
               
               
                 115 
                 U-Bolt Attachment Hole 
               
               
                 116 
                 U-Bolt Nut/Washer Set 
               
               
                 117 
                 Upper Safety Chain Mounting Hole 
               
               
                 118 
                 Lower Safety Chain Mounting Hole 
               
               
                 119 
                 Safety Chain Mounting Bolt/Washer Set 
               
               
                 120 
                 Safety Chain Mounting Nut/Washer Set 
               
               
                 200 
                 Collapsible Workbench Assembly 
               
               
                 210 
                 Bench Plate 
               
               
                 212 
                 Main Slab 
               
               
                 213 
                 Air Groove 
               
               
                 214 
                 Upper Locking Groove 
               
               
                 215 
                 Lower Locking Groove 
               
               
                 216 
                 Lower Rib Protrusion 
               
               
                 217 
                 Lower Rail Protrusion 
               
               
                 218 
                 Assembly Screw Hole 
               
               
                 220 
                 Bench Plate Bracket 
               
               
                 222 
                 Assembly Screw 
               
               
                 224 
                 Locking Pin 
               
               
                 226 
                 Lock Tumbler Assembly 
               
               
                 228 
                 Key 
               
               
                 230 
                 Paddle Arm 
               
               
                 232 
                 Upper Pushpin Lock Mounting Hole 
               
               
                 234 
                 Upper Pushpin Lock 
               
               
                 236 
                 Upper Axle Bushing Mounting Hole 
               
               
                 238 
                 Upper Screw Clamp Clearance Slot 
               
               
                 240 
                 Main Arm 
               
               
                 241 
                 Upper Axle Bushing Mounting Hole 
               
               
                 242 
                 Upper Pushpin Lock Clearance Hole Collapsed Position 
               
               
                 243 
                 Upper Pushpin Lock Clearance Hole Work Position 
               
               
                 244 
                 Upper Screw Clamp Mounting Hole 
               
               
                 245 
                 Upper Screw Clamp 
               
               
                 246 
                 Lower Axle Bushing Mounting Hole 
               
               
                 247 
                 Lower Pushpin Lock Mounting Hole 
               
               
                 248 
                 Lower Pushpin Lock 
               
               
                 249 
                 Lower Screw Clamp Clearance Slot 
               
               
                 251 
                 Upper Axle 
               
               
                 252 
                 Upper Axle Bushing 
               
               
                 253 
                 Lower Axle 
               
               
                 254 
                 Lower Axle Bushing 
               
               
                 255 
                 Collar Lock 
               
               
                 270 
                 T-Bar Assembly 
               
               
                 272 
                 T-Frame 
               
               
                 272A 
                 Lock Pin Clearance Hole 
               
               
                 273 
                 Ear Plate 
               
               
                 274 
                 Lower Axle Bushing Mounting Hole 
               
               
                 275 
                 Lower Pushpin Clearance Hole Collapsed Position 
               
               
                 276 
                 Lower Pushpin Lock Clearance Hole Work Position 
               
               
                 277 
                 Lower Screw Clamp Mounting Hole 
               
               
                 278 
                 Lower Screw Clamp 
               
               
                 300 
                 Wall Mount Assembly 
               
               
                 310 
                 Wall Frame 
               
               
                 320 
                 Wall Receiver 
               
               
                 330 
                 Wall Plate 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE INVENTION 
     Trailer hitch receiver mounted collapsible workbench  50  comprises a stabilizer assembly  100  and a collapsible workbench assembly  200 . Collapsible workbench assembly  200  is reversibly mounted in any standard trailer hitch receiver  111  of any vehicle. Collapsible workbench assembly  200  is reversibly mounted inside trailer hitch receiver  111  in the same way that a standard hitch ball mount (not depicted) or a standard hitch ball tongue (not depicted) is reversibly mounted to any standard trailer hitch receiver  111 . Trailer hitch receiver  111  is not a component of this invention. Collapsible workbench assembly  200  is held inside trailer hitch receiver  111  with a hitch pin (not depicted) or alternatively locked inside trailer hitch receiver  111  with hitch lock pin (not depicted) where a tongue is inserted into the trailer hitch receiver on a vehicle and held inside trailer hitch receiver with a hitch pin or alternatively locked inside trailer hitch receiver with hitch lock pin. 
     The hitch pin connection mechanism or the hitch lock pin connection mechanism between collapsible workbench assembly  200  and trailer hitch receiver  111  is not a solid and vibration free connection. To remedy this, stabilizer assembly  100  is used to help provide a more rigid, sturdy, and vibration-free reversible attachment of collapsible workbench assembly  200  to the vehicle. As stated in more detail below, stabilizer assembly  100  is reversibly mounted to the outside of trailer hitch receiver  111  and is used to effectively clamp and hold collapsible workbench assembly  200  steady, horizontal, and free from vibrations relative to trailer hitch receiver  111  during transport and during use of trailer hitch receiver mounted collapsible workbench  50 . 
     Stabilizer assembly  100  comprises a horseshoe plate  112  and at least two support channels  113 . Horseshoe plate  112  is essentially an elongated annulus shape with a notch removed from one end to yield an arced-shaped member with two elongated ends. Horseshoe plate  112  may consist of one overall plate or of several subcomponent plates connected or attached together to form a general horseshoe shaped rigid member. In best mode, as depicted, horseshoe plate  112  consists of several subcomponent plates connected together to form a general horseshoe shape. In best mode, horseshoe plate  112  further comprises a plurality of voids or drilled out areas  112 A located therein at strategic positions in horseshoe plate  112  that function to reduce the weight of horseshoe plate  112  without affecting strength or rigidity of the horseshoe plate  112 . In best mode, two of the plurality of voids  112 A also may function as attachment holes to secure the safety chains from a trailer (not depicted) to the stabilizer assembly  100 , which is securely attached to the vehicle as described below, in order to properly attach and tow a trailer with the vehicle without removing the stabilizer assembly  100  from the vehicle. However, as described below, collapsible workbench assembly  200  must be removed from the vehicle in order to properly attach and tow a trailer. 
     Stabilizer assembly  100  further comprises a trailer hitch receiver attachment means. In best mode, trailer hitch attachment means comprises a U-bolt  114 , two U-bolt attachment holes  115 , two U-bolt nut/washer sets  116 , two upper safety chain mounting holes  117 , two lower safety chain mounting holes  118 , two safety chain mounting bolt/washer sets  119 , and two safety chain mounting nut/washer sets  120 . Each of two U-bolt attachment holes  115  is a cylindrical-shaped void or hole in horseshoe plate  112  with its longitudinal axis perpendicular to the arc of the horseshoe shape, each positioned symmetrically across the longitudinal axis of the horseshoe shape, and adjacent to the concave-side of the arc of the horseshoe shape. Each of two lower safety chain mounting holes  117  is a cylindrical-shaped void or hole in horseshoe plate  112  with longitudinal axis perpendicular to the arc of the horseshoe shape, each positioned symmetrically across the longitudinal axis of the horseshoe shape, and adjacent to the convex-side of the arc of the horseshoe shape. Each of two upper safety chain mounting holes  118  is a cylindrical-shaped void or hole in horseshoe plate  112  with longitudinal axis perpendicular to the arc of the horseshoe shape, each positioned symmetrically across the longitudinal axis of the horseshoe shape, and in between upper safety chain mounting holes  117  and U-bolt attachment holes  115 . 
     Stabilizer assembly  100  must be attached to the vehicle prior to attaching the collapsible workbench assembly  200  to the vehicle. Stabilizer assembly  100  is attached or installed on a vehicle with trailer hitch receiver attachment means which is a means to firmly reversibly attach and secure horseshoe plate  112  to the exterior of trailer hitch receiver  111 . Trailer hitch receiver is a part of the vehicle that is rigidly attached to the frame of the vehicle. In best mode, as depicted, horseshoe plate  112  is attached to the lower surface of trailer hitch receiver  111  using a U-bolt  114  that is positioned to run over the top of trailer hitch receiver  111 , through two U-bolt attachment holes  115  in horseshoe plate  112 , with U-bolt nuts and washers  116  used to tighten and fasten U-bolt  114  horseshoe plate  112  firmly against the lower surface of trailer hitch receiver  111 . Best mode attachment further includes two safety chain mounting bolt/washer sets  119 , each safety chain mounting bolt  119  passing through either an upper safety chain mounting hole  117  or a lower safety chain mounting hole  118 , through a safety chain attachment hook on the vehicle&#39;s trailer hitch, and threaded into a safety chain mounting nut/washer set  120 . Safety chain mounting bolt/washer sets  119  and safety chain mounting nut/washer sets  120  are used to tighten horseshoe plate  112  firmly against the lower surface of trailer hitch receiver  111  to help attach and secure stabilizer assembly  100  to the vehicle. A choice of upper  117  or lower  118  safety chain mounting holes is required to fit the varying locations of safety chain attachment hooks on various types of trailer hitches on various types vehicles. Safety chain attachment hooks (not depicted) are normally used to attach and secure the safety chains from a trailer to the trailer hitch on the vehicle to provide a safety mechanism to catch and hold the trailer to the vehicle in the event of a failure of the primary trailer attachment mechanism. Of course with this invention attached to a vehicle, the vehicle cannot tow a trailer, so this invention can use the safety chain attachment hooks (not depicted) on the vehicle&#39;s trailer hitch to help attach and secure horseshoe plate  112  to the exterior of trailer hitch receiver  111 . Applicant has taken advantage of these existing two hook locations on every trailer hitch to provide two additional clamping points to help yield a strong vibration-free attachment of horseshoe plate  112  to trailer hitch receiver  111 , thus providing strong vibration-free attachment of stabilizer assembly  100  to the vehicle. Although only one safety chain mounting bolt/washer set  119  is depicted in the drawings, two of such sets are required to complete best mode attachment as described above. Although only one safety chain mounting nut/washer set  120  is depicted in the drawings, two of such sets are required to complete best mode attachment as described above. 
     As stated, horseshoe plate  112  must be very firmly attached to trailer hitch receiver  111  to eliminate all movement and vibrations between these members that may result from transport or use of trailer hitch receiver mounted collapsible workbench  50 . In addition to the best mode attachment described above, stabilizer assembly  100  may be attached to the upper surface of trailer hitch receiver  111 , a side surface of trailer hitch receiver  111 , or any combination thereof. Any known means of attachment may be used for trailer hitch receiver attachment means, including welding, soldering, gluing, bolting, or screwing. Best mode means described above is a specific type of attachment by bolting. 
     One support channel  113  is rigidly attached to each elongated end of horseshoe plate  112 . Each support channel  113  is a rigid three-sided trough or channel with two open ends and an open top. Support channel  113  is sized to form an exact slip fit over the exterior of T-Frame  272 . Thus, the inner dimension or width of support channel  113  is an exact dimension that allows just enough clearance for support channel  113  to slide over the outside of T-Frame  272  to form a slip-fit between these members, but not too much clearance to allow any appreciable play, movement, or vibrations between support channel  113  and T-Frame  272 . Likewise, the depth of support channel  113  is sized to allow T-Frame  272  to sit securely within support channel  113  without the possibility of T-Frame  272  falling out of support channel  113  resulting from movement or vibrations caused by travel or use of trailer hitch receiver mounted collapsible workbench  50 . This slip vibrationless exact slip fit is crucial to the proper functioning of this invention. As stated below, the upper horizontal member of T-Frame  272  may be of any particular exterior shape and where support channel  113  must be similarly shaped, but slightly larger, to form the exact slip fit with upper horizontal member of T-Frame  272 . As stated below, in best mode, horizontal member of T-Frame  272  is rectangular cuboid shaped, and thus, best mode support channel  113  is C-shaped. 
     Each support channel  113  is positioned with open ends of the channel on axis with each other and tangent to each elongated horseshoe plate  112 . The bottom of each channel on each support channel  113  is attached to and adjacent to an elongated end of horseshoe plate  112 . Thus, each open top of each support channel is in alignment with the longitudinal axis of elongated end of the horseshoe shape there attached. 
     Horseshoe plate  112  must be attached to trailer hitch receiver  111  in an exact position so that the above described channel axis of open ends is exactly horizontal and in alignment with the vehicles horizontal axis. In best mode, the above described channel axis of open ends is also in the same plane as the longitudinal axis of trailer hitch receiver  111 . The horizontal alignment intersecting the longitudinal axis of trailer hitch receiver  111  helps hold and stabilize bench plate  210  in a horizontal position, which is required for a proper workbench operation and transport. 
     Collapsible workbench assembly  200  comprises: a bench plate  210 , at least two bench plate brackets  220 , at least two paddle arms  230 , at least two main arms  240 , and a T-Bar assembly  270 . Bench plate  210  comprises a main slab  212  that is a rigid planar member in the shape of a slab, plank, or shelve that is itself the workbench component of the invention. Main slab  212  is a strong rigid member that does not flex or deflect to any appreciable degree as a result of the usual pressures applied to a workbench. Main slab  212  is a rectangular cuboid with a length that is about 3-10 feet, a width of about 3-25 inches, and a height of about 0.25-5 inches. Main slab  212  is mounted horizontally across the rear of the vehicle as depicted. Ideally, the length of main slab  212  is no more than the width of the vehicle for safety purposes. Main slab  212  comprises an upper surface, which is the primary work surface of the invention, and a lower surface, which is a secondary work surface of the invention. Bench plate  210  further comprises a plurality of assembly screw holes  218 . Assembly screw holes  218  are voids or holes through main slab  212  perpendicular to the upper and lower surfaces that are used to help attach bench plate brackets  220  to the bottom surface of bench plate  210  as described below. Assembly screw holes  218  may be tapped holes. 
     Main slab  212  further comprises rounded edges at its width that run the full length of slab  212 . Each rounded edge provides a track or clamping edge that may be used in conjunction with commercially available clamping systems and/or individual clamps. Such commercially available clamping systems and/or individual clamps can provide the ability to clamp power tools, mechanical tools, or work objects to the upper surface of main slab  212  in such a way as to allow convenient adjustability or movement along the length of main slab  212  while holding the subjects fixed in all other dimensions and the convenient locking into position at the desired location along the length of main slab  212 . This is a very important aspect of the invention.  FIG. 3  depicts a chop saw connected to main slab  212  in this way. Also, rounded edges provide a track or clamping edge that may be used in conjunction with specially made tie-down devices such as that shown in  FIG. 9  where two special slideable edge tie-down brackets are depicted that allow convenient adjustability along the length of main slab  212  and convenient locking into the desired postilion. 
     In best mode, as depicted, bench plate further comprises a plurality of air grooves  213 . Each air groove  213  is a longitudinal groove or indentation running across the upper surface of bench plate  212 . Each air groove  213  functions to facilitate easier sliding of work pieces or objects across the upper surface of bench plate  212 . As work pieces or objects are slid over the upper surface of bench plate  212 , air remains in each air groove  213 , which acts to reduce friction between the work piece or object and the upper surface of bench plate  213 , thereby making it easier to slide objects there across. In best mode, as depicted, there are four air groves  213 . 
     In best mode, as depicted, bench plate further comprises an upper locking groove  214 . Upper locking groove  214  is a specially shaped longitudinal groove in the upper surface of main slab  212  running completely across the length of main slab  212 . Upper locking groove  214  has a wide lower section and a narrow upper section as depicted. Thus, the bottom of upper locking groove  214  has a wider channel than that of the top, with a step or shoulder separating narrow upper channel from wide lower channel as depicted. This shape is such that a screw may be slid into the locking groove from either side of main slab  212  with the screw head in the wider lower channel to any position along the length of main slab  212  where the screw is remains attached and perpendicular to main slab  212  because the wide bottom of upper locking groove  214  is wide enough and tall enough to provide a clearance fit for the screw head but the narrow upper channel of the locking groove does not provide clearance for the screw head, so the screw is retained in the locking groove during all movement of the screw across the full length of main slab  212 . Upper locking groove  214  may be used in conjunction with many types of commercially available clamping systems and/or individual clamps. 
     In best mode, as depicted, bench plate further comprises and a lower locking groove  215 . Lower locking groove  215  is a specially shaped longitudinal groove in the lower surface of main slab  212  running completely across the length of main slab  212 . Lower locking groove  215  has a wide upper section and a narrow lower section as depicted. Thus, the top of lower locking groove  215  has a wider channel than that of the bottom, with a step or shoulder separating wide upper channel from narrow lower channel as depicted. This shape is such that a screw may be slid into the locking groove from either side of main slab  212  with the screw head in the wider upper channel to any position along the length of main slab  212  where the screw is remains attached and perpendicular to main slab  212  because the wide upper of each locking groove is wide enough and tall enough to provide clearance fit for the screw head but the narrow lower channel of each locking groove does not provide clearance for the screw head, so the screw is retained in the locking groove during all movement of the screw across the full length of main slab  212 . Lower locking groove  215  may be used in conjunction with many types of commercially available clamping systems and/or individual clamps. 
     Two bench plate brackets  220  are used to support bench plate  210  with one bench plate bracket  220  positioned at each end of bench plate  210 . Bench plate bracket  220  is a bracket used to rigidly attach paddle arm  230  to bench plate  210 . Any type of bracket may be used for this connection. 
     In best mode, bench plate brackets are lockable to yield a reversible lockable rigid attachment between paddle arm  230  and bench plate  210 . This allows bench plate  210  to be removed from the vehicle and hand carried to a remote work location. In best mode, each bench plate bracket  220  is a special jig or bracket assembly which functions to reversibly lockably mount paddle arm  230  to the lower surface of bench plate  210 . Best mode bench plate bracket  220  comprises a horizontal rigid planar member with an upper surface, a lower surface, and a plurality of assembly screw holes there through used to attached the upper surface of horizontal rigid planar member to the lower surface of bench plate  210 . Assembly screw holes may be tapped holes. Best mode bench plate bracket  220  further comprises a vertical rigid planar member that functions to reversibly lockably mount to the handle end of paddle arm  230 . One end of vertical rigid planar member is rigidly attached to the lower surface of a horizontal rigid planar member, perpendicular thereto, to form a rigid T-shaped member that is the “T” shape of best mode bench plate bracket  220 . Vertical rigid planar member there houses a locking pin  224  and a lock tumbler assembly  226  to form a locking mechanism actuated by a key  228  that functions to reversibly lock bench plate bracket  220  to paddle arm  230 . The turning of key  228  when inserted into the lock tumbler assembly  226  causes movement of locking pin  224  thereby locking or releasing paddle arm  230  from vertical rigid planar member. 
     A paddle arm  230  is used to support each bench plate bracket  220 . Each paddle arm  230  is a rigid planar member in the shape of a paddle, having a handle end and a paddle end. As state above, in best mode, the handle-end of paddle arm is reversibly lockably mounted to a bench plate bracket  220 . The paddle end of paddle arm  230  further comprises an upper pushpin lock mounting hole  232 , an upper pushpin lock  234 , an upper axle bushing mounting hole  236 , and an upper screw clamp clearance slot  238 . Each upper pushpin lock  234  is a typical pushpin lock comprising a lock pin and a handle where a retainer on the tip of the lock pin retracts in response to the pushing of a button on the handle of the pushpin lock. Thus, the button is pushed to retract and relocate a pushpin lock and then the button is released to lock the pushpin lock in place. An upper pushpin lock  234  is mounted in the upper pushpin lock mounting hole  232  where upper pushpin lock  234  functions in tandem with upper pushpin lock clearance holes  242 ,  243  on main arm  240  to lock and hold paddle arm  230  relative to main arm  240  at certain rotational positions designated by the location of upper pushpin lock clearance holes  242 ,  243  on main arm  240 . Upper axle bushing mounting hole  236  is a perpendicular cylindrical hole in the center of the paddle end of paddle arm  230  that functions to accept and mount an upper axle bushing  252  therein. Upper axle bushing  252  is rigidly mounted into upper axle bushing mounting hole  236 . 
     A main arm  240  is used to support each paddle arm  230 . Each main arm  240  is a rigid oblong planar member with an upper rounded end and a lower rounded end. Upper rounded end of main arm  240  further comprises an upper axle bushing mounting hole  241 , an upper pushpin lock clearance hole collapsed position  242 , an upper pushpin lock clearance hole work position  243 , an upper screw clamp mounting hole  244 , and an upper screw clamp  245 . Upper axle mounting bushing mounting hole  241  is a perpendicular cylindrical hole in the center of the upper rounded end of main arm  240  that functions to accept and mount an upper axle bushing  252  therein. Upper axle bushing  252  is rigidly mounted into upper axle bushing mounting hole  241 . Upper pushpin lock clearance hole collapsed position  242  and upper pushpin lock clearance hole work position  243  are each a perpendicular cylindrical hole in the upper rounded end of main arm  240  sized to yield a clearance fit with the lock pin of upper pushpin lock  234  with its button depressed and a interference fit with the lock pin of upper pushpin lock  234  with its button released. Upper pushpin lock clearance hole collapsed position  242  is located on main arm  240  at the rotation position of upper pushpin lock  234  when bench plate  210  is in the flat or collapsed position that is best for travel as described below. Upper pushpin lock clearance hole work position  243  is located on main arm  240  at the rotation position of upper pushpin lock  234  when bench plate  210  is in the angled or work position that is best for working as described below. 
     The upper rounded end of each main arm  240  is pivotally attached to the paddle end of each paddle arm  230 . Pivotal attachment may be accomplished with any known means. In best mode, pivotal attachment is done with at least one upper axle  251  and four upper axle bushings  252 . Upper axle  251  is a rigid cylindrical member that is an axle. Each upper axle bushing  252  is a typical bushing with an inner and outer diameter that are each capable of appreciably unhindered rotational motion relative to each other. Inner diameter of each upper axle bushing  252  is sized to make a press fit into the outer diameter of upper axle  251 . Outer diameter of each upper axle bushing  252  is sized to make a press fit into the inner diameter of upper axle bushing mounting hole  236  and upper axle bushing mounting hole  241 . Thus upper axle bushing mounting hole  236  and upper axle bushing mounting hole  241  are equivalently sized. With all four upper axle bushings  252  installed and held concentric with each other, upper axle  251  is pressed through the inner diameters of all four upper axle bushing  252  to pivotally attach the upper rounded end of each main arm  240  to the paddle end of each paddle arm  230  as depicted. 
     This pivotal attachment may further comprise a means to hold paddle arms  230  and main arms  240  in their correct positions on upper axle  251  to facilitate clearance for unhindered rotation between these members when upper screw clamps  245  are loosened and to facilitate firm clamping action between these members when upper screw clamps  245  are tightened. A plurality of collar locks  255  may be used to accomplish this where a collar lock  255  is mounted on upper axle  251  adjacent to each side of each pivotal attachment between paddle arm  230  and upper rounded end of main arm  240  to retain each paddle arm  230  at a maximum distance from each upper rounded end of main arm  240 . A collar lock  255  is an annulus shaped member that is capable of sliding over an axle at its inner diameter and capable of locking onto the axle in response to an actuation and releasing upon another actuation. Other than the use of collar locks  255 , any known means may be used to retain paddle arms  230  and main arms  240  in their correct positions on upper axle  251 . 
     Each upper screw clamp  245  is a typical screw clamp with a threaded screw end and a large head that may be rotated by hand. The width of upper screw clamp clearance slot  238  is sized above the outer diameter of threaded screw end of upper screw clamp  245  so that the threaded screw end has clearance to move within the clearance slot. However, the width of upper screw clamp clearance slot  238  is too narrow to allow passage of the large head of upper screw clamp  245 . The threaded screw end of upper screw clamp  245  is passed through upper screw clamp clearance slot  238  with a clearance fit and threaded into upper screw clamp mounting hole  244 . Upper screw clamp mounting hole  244  is a tapped hole in upper rounded end of main arm  240 . The clearance between upper screw clamp  245  and upper screw clamp clearance slot  238  and threaded arrangement between upper screw clamp  245  and upper screw clamp mounting hole  244  is such that the clockwise rotation of the large head on upper screw clamp  245  draws the upper rounded end of main arm  240  towards the large head of upper screw clamp  245  thereby clamping paddle arm  230  there in between and the counterclockwise rotation of the large head on upper screw clamp  245  separates the upper rounded end of main arm  240  from the large head of upper screw clamp  245  thereby releasing upper screw clamp clearance slot  238  to allow clearance and unrestrained rotational motion between paddle arm  230  and main arm  240  about the longitudinal axis of upper axle  251 . 
     This pivotal rotation is required for the collapsible aspect of the invention to yield a flat position for travelling and an angled position for working. The flat position is best for travelling because in this position the trailer hitch receiver mounted collapsible workbench  50  is tucked neatly against the rear or tail gate of the vehicle thereby minimizing the amount with which the trailer hitch receiver mounted collapsible workbench  50  sticks out or extends from the rear of the vehicle. The angled position is best for working because in this position the trailer hitch receiver mounted collapsible workbench  50  extends farther from the rear or tailgate of the vehicle to provide more work space behind and underneath bench plate  210  for working and because in this position bench plate  210  is lower and at the most comfortable level for working. 
     T-Bar assembly  270  comprises a T-Frame  272  and two ear plates  273 . T-Frame  272  is a rigid and sturdy tubular frame member in the shape of a “T” with a base vertical member perpendicular to and attached to an upper horizontal member. The base vertical member of T-Frame  272  is inserted and mounted inside trailer hitch receiver  111 . The outer dimensions of base vertical member of T-Frame must be sized to form a clearance fit inside trailer hitch receiver  111 . Since trailer hitch receiver  111 , by convention, is a rectangular tubular frame member, with a rectangular cuboid-shaped receiver, base vertical member of T-Frame  272  is also a rectangular tubular frame member. A rectangular cuboid-shaped exterior helps form a more stable stackable fit between these members. In best mode, as depicted, upper horizontal member of T-Frame  272  is also rectangular cuboid-shaped because generally it is easier to attach similarly shaped members together to form the “T” shape however upper horizontal member may be of any geometric shape such as cylindrical, square or triangular cuboid. 
     Base vertical member of T-Frame is reversibly mounted in a standard trailer hitch receiver  111  in the same way that a standard hitch ball mount or a standard hitch ball tongue is reversibly mounted to any standard trailer hitch receiver  111 . There is a lock pin clearance hole  272 A in base member of T-Frame that is a cylindrical void running perpendicular to the surface of base member of T-Frame and parallel to the upper horizontal member of T-Frame  272 . Lock pin clearance hole  272 A provides clearance to receive a hitch pin or a hitch lock pin. Base member of T-Frame  272  is held inside trailer hitch receiver  111  with a hitch pin (not depicted) or alternatively locked inside trailer hitch receiver  111  with hitch lock pin (not depicted). 
     Each ear plate  273  is a rigid vertical planar member with an inner surface and an outer surface. The inner surface of each ear plate  273  is rigidly attached to an end of the upper horizontal member of T-Frame  272  so that the plane of each ear plate  273  is perpendicular to the longitudinal axis of the upper horizontal member of T-Frame  272 . Attachment occurs by welding, soldering, gluing, bolting, or screwing. As depicted in the drawings, each ear plate  273  has there attached two additional plates (not numbered). These plates are added in best mode but not required. These plates are added as rock shields to shield and protect lower pushpin lock  248  and lower screw clamp  278  from damage resulting from rocks or other debris being kicked up from the road during vehicle travelling. 
     Each ear plate  273  further comprises a lower axle bushing mounting hole  274 , a lower pushpin lock clearance hole collapsed position  275 , a lower pushpin lock clearance hole work position  276 , a lower screw clamp mounting hole  277 , and a lower screw clamp  278 . Lower axle bushing mounting hole  274  is a perpendicular cylindrical hole in the center of ear plate  273  that functions to accept and mount a lower axle bushing  254  therein. Lower axle bushing  254  is rigidly mounted into lower axle bushing mounting hole  274 . Lower pushpin lock clearance hole collapsed position  275  and lower pushpin lock clearance hole work position  276  are each a perpendicular cylindrical hole in ear plate  273  sized to yield a clearance fit with the lock pin of lower pushpin lock  248  with its button depressed and a interference fit with the lock pin of lower pushpin lock  248  with its button released. Lower pushpin lock clearance hole collapsed position  275  is located on ear plate  273  at the rotation position of lower pushpin lock  248  when bench plate  210  is in the flat or collapsed position that is best for travel as described below. Lower pushpin lock clearance hole work position  276  is located on ear plate  273  at the rotation position of lower pushpin lock  248  when bench plate  210  is in the angled or work position that is best for working as described below. An ear plate  273  is used to support each lower rounded end of each main arm  240 . 
     Each lower rounded end of each main arm  240  further comprises a lower axle bushing mounting hole  246 , a lower pushpin lock mounting hole  247 , a lower pushpin lock  248 , and a lower screw clamp clearance slot  249 . Each lower pushpin lock  248  is a typical pushpin lock comprising a lock pin and a handle where a retainer on the tip of the lock pin retracts in response to the pushing of a button on the handle of the pushpin lock. Thus, the button is pushed to retract and relocate a pushpin lock and then the button is released to lock the pushpin lock in place. A lower pushpin lock  248  is mounted in the lower pushpin lock mounting hole  246  where lower pushpin lock  228  functions in tandem with lower pushpin lock clearance holes  275 ,  276  on ear plate  273  to lock and hold main arm  240  relative to ear plate  273  at a certain rotational positions designated by the location of lower pushpin lock clearance holes  275 ,  276  on ear plate  273 . Lower axle bushing mounting hole  274  is a perpendicular cylindrical hole in the center of the lower rounded end of main arm  240  that functions to accept and mount a lower axle bushing  254  therein. Lower axle bushing  254  is rigidly mounted into lower axle bushing mounting hole  274 . 
     The lower rounded end of each main arm  240  is pivotally attached to an ear plate  273 . Pivotal attachment may be accomplished with any known means. In best mode, pivotal attachment is done with at least one lower axle  253  and four lower axle bushings  254 . Lower axle  253  is a rigid cylindrical member that is an axle. Each lower axle bushing  254  is a typical bushing with an inner and outer diameter that are each capable of appreciably unhindered rotational motion relative to the other. Inner diameter of each lower axle bushing  254  is sized to make a press fit into the outer diameter of lower axle  253 . Outer diameter of each lower axle bushing  254  is sized to make a press fit into the inner diameter of upper axle bushing mounting hole  236  and upper axle bushing mounting hole  241 . Thus lower axle bushing mounting hole  226  and lower axle bushing mounting hole  274  are equivalently sized. With all four lower axle bushings  254  installed and held concentric with each other, lower axle  253  is pressed through the inner diameters of all four lower axle bushing  254  to pivotally attach the lower rounded end of each main arm  240  to ear plate  273  as depicted. Lower axle  253  runs through the center or longitudinal axis of upper horizontal member of T-Frame  272  as depicted. 
     This pivotal attachment may further comprise a means to hold the lower rounded ends of main arms  240  in their correct positions on lower axle  253  to facilitate clearance for unhindered rotation between the lower rounded ends of main arms  240  and ear plates  273  when lower screw clamps  278  are loosened and to facilitate firm clamping action between these members when lower screw clamps  278  are tightened. A plurality of collar locks  255  may be used to accomplish this where a collar lock  255  is mounted on lower axle  253  adjacent to each side of each pivotal attachment of ear plate  273  to lower rounded end of main arm  240  to retain each lower rounded end of main arm  240  at a maximum distance from each ear plate  273 . Other than the use of collar locks  255 , any known means may be used to retain paddle arms  230  and main arms  240  in their correct positions on upper axle  251 . 
     Each lower screw clamp  278  is a typical screw clamp with a threaded screw end and a large head that may be rotated by hand. The width of lower screw clamp clearance slot  249  is sized above the outer diameter of threaded screw end of lower screw clamp  278  so that the threaded screw end has clearance to move within the clearance slot. However, the width of lower screw clamp clearance slot  249  is too narrow to allow passage of the large head of lower screw clamp  278 . The threaded screw end of lower screw clamp  278  is passed through lower screw clamp clearance slot  249  with a clearance fit and threaded into lower screw clamp mounting hole  277 . Lower screw clamp mounting hole  277  is a tapped hole in ear plate  273 . The clearance between lower screw clamp  278  and lower screw clamp clearance slot  249  and threaded arrangement between lower screw clamp  278  and lower screw clamp mounting hole  277  is such that the clockwise rotation of the large head on lower screw clamp  278  draws the large head of lower screw clamp  278  towards ear plate  273  thereby clamping lower rounded end of main arm  240  there in between and the counterclockwise rotation of the large head on lower screw clamp  278  separates the large head on lower screw clamp  278  from ear plate  273  thereby releasing lower screw clamp clearance slot  249  to allow clearance and unrestrained rotational motion between lower rounded end of main arm  240  and ear plate  273  about the longitudinal axis of lower axle  253 . 
     To change trailer hitch receiver mounted collapsible workbench  50  from flat or collapsed position to angled or work position, first the lower rounded ends of each main arm  240  are rotated from collapsed position to work position. Then, each paddle arm  230  is rotated from collapsed position to work position to place bench plate  210  in the work position. This occurs as follows. 
     The lower rounded end of each main arm  240  is released by rotating each lower screw clamp  278  counterclockwise to unclamp each lower rounded end of each main arm  240 . Then, the button on each lower pushpin lock  248  is depressed to remove each lower pushpin lock  248  from a lower pushpin lock clearance hole collapsed position  275  to allow the free rotation of each lower rounded end of each main arm  240  relative to each adjacent ear plate  273  to the rotational position or angle where each lower pushpin lock  248  may be inserted into an a lower pushpin lock clearance hole work position  276  and the button on each lower pushpin lock  248  is then released to lock each lower rounded end of each main arm  240  into the angled or work position. Then, lower rounded end of each main arm  240  is firmly clamped into this position by rotating each lower screw clamp  278  clockwise to clamp each lower rounded end of each main arm  240  as described above. 
     Next, each paddle arm  230  is released by rotating each upper screw clamp  245  counterclockwise to unclamp each paddle arm  230 . Then, the button on each upper pushpin lock  234  is depressed to remove each upper pushpin lock  234  from an upper pushpin lock clearance hole work position  243  to allow the free rotation of each paddle arm  230  relative to each main arm  240  to the rotational position or angle where each upper pushpin lock  234  may be inserted into an upper pushpin lock clearance hole collapsed position  242  and the button on each upper pushpin lock  234  is then released to lock each paddle arm  230  into the flat or collapsed position. Then, each paddle arm  230  is firmly clamped into this position by rotating each upper screw clamp  245  clockwise to clamp each paddle arm  230  as described above. 
     To change trailer hitch receiver mounted collapsible workbench  50  from angled or work position to flat or collapsed position, each paddle arm  230  is first rotated from work position to collapsed position. Then, each lower rounded end of each main arm  240  is rotated from work position to collapsed position to place bench plate  210  in the collapsed position. This occurs as follows. 
     Each paddle arm  230  is released by rotating each upper screw clamp  245  counterclockwise to unclamp each paddle arm  230 . Then, the button on each upper pushpin lock  234  is depressed to remove each upper pushpin lock  234  from an upper pushpin lock clearance hole collapsed position  242  to allow the free rotation of each paddle arm  230  relative to each main arm  240  to the rotational position or angle where each upper pushpin lock  234  may be inserted into an upper pushpin lock clearance hole work position  243  and the button on each upper pushpin lock  234  is then released to lock each paddle arm  230  into the angled or work position. Then, each paddle arm  230  is firmly clamped into this position by rotating each upper screw clamp  245  clockwise to clamp each paddle arm  230  as described above. 
     Next, the lower rounded end of each main arm  240  is released by rotating each lower screw clamp  278  counterclockwise to unclamp each lower rounded end of each main arm  240 . Then, the button on each lower pushpin lock  248  is depressed to remove each lower pushpin lock  248  from a lower pushpin lock clearance hole work position  276  to allow the free rotation of each lower rounded end of each main arm  240  relative to each adjacent ear plate  273  to the rotational position or angle where each lower pushpin lock  248  may be inserted into a lower pushpin lock clearance hole collapsed position  275  and the button on each lower pushpin lock  248  is then released to lock each lower rounded end of each main arm  240  into the flat or collapsed position. Then, each lower rounded end of each main arm  240  is firmly clamped into this position by rotating each lower screw clamp  278  clockwise to clamp each lower rounded end of each main arm  240  as described above. 
     The length of main arms  240  and the locations of pushpin lock clearance holes  243 ,  276  must be such that the upper surface of bench plate  210  is exactly level with that of the lowered tailgate of a pickup truck mounted thereto when the bench plate  210  is in the angled or work position. This design ensures that when the bench plate  210  is in the angled or work position and the tailgate of the pick up truck is lowered, bench plate  210  acts to extend the bed or cargo area of the pickup truck as depicted in  FIG. 9 . Thus, in addition to providing a workbench area for working and holding power tools and mechanical tools, trailer hitch receiver mounted collapsible workbench  50  also provides a truck bed extension platform. 
     Trailer hitch receiver mounted collapsible workbench  50  may further comprise a wall mount assembly  300 . Wall mount assembly  300  is a wall frame  310  with a wall receiver  320  there attached and a wall plate  330  there attached. Wall mount assembly  300  is a means to store the power tools, mechanical tools, and/or work objects fitted with the clamping systems and/or individual clamps described above on the wall of a work shop, garage, or similar building in which work is conducted. Wall frame  310  is a rigid planar frame structure or assembly of tubular frame pieces to form a planar structure. Wall frame  310  is capable of being securely attached to a wall of a building. Wall receiver  320  is rigid tubular frame that is sized exactly like a standard trailer hitch receiver of a vehicle. Wall receiver  320  is attached to wall frame  310 , perpendicular to the plane of wall frame  310 , as depicted in  FIG. 8 . Wall plate  330  is an object that is a duplicate of bench plate  210 . Wall plate  330  is attached to wall frame  310  with is longitudinal axis horizontal and parallel to the plane of wall frame  310  as depicted. With wall mount assembly  300 , any power tools, mechanical tools, and/or work objects fitted with the clamping systems and/or individual clamps described above may be very quickly transferred from the vehicle to the shop by simply unclamping them from the bench plate  210  on the vehicle and then reclamping them to the wall plate  330  in the shop, garage, or similar.