Abstract:
A locking assembly and method of securing a dump truck tailgate to a sidewall of the dump truck, and a truck incorporating the same. The locking assembly includes a pressurized pin mechanism mounted on one of tailgate and the sidewall; and a spool mounted on the other of the tailgate and the sidewall. The spool is engageable with the pin mechanism to lock the locking assembly and secure the tailgate to the sidewall, and is disengageable from the pin mechanism to unlock the locking assembly and release the tailgate from its securement to the sidewall. A hinge assembly is provided on an opposite side of the tailgate from the locking assembly. The tailgate is selectively pivotable relative to the truck bed about a vertical axis extending through the hinge assembly or about a horizontal axis extending through both of the locking assembly and the hinge assembly.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    This invention relates generally to vehicles. More particularly, this invention relates to trucks, especially dump trucks. Specifically, this invention is directed to a locking assembly for a side-swing tailgate for a dump truck where the locking assembly includes a pressurized pin. 
         [0003]    2. Background Information 
         [0004]    Dump trucks having tailgates which swing open about either of a horizontal axis or a vertical axis are known in the art. When the vehicle is not actively being used to dump a load it is necessary to be able to secure the tailgate to the truck bed. This is especially important when the vehicle is to travel over the roads. A variety of different locking or latching mechanisms have been disclosed in the art. 
         [0005]    There is, however, always room in the art for an improved locking or latching assembly for securing truck tailgates. 
       SUMMARY 
       [0006]    A locking assembly and method of securing a dump truck tailgate to a sidewall of the dump truck, and a truck incorporating the same. The locking assembly includes a pressurized pin mechanism mounted on one of tailgate and the sidewall; and a spool mounted on the other of the tailgate and the sidewall. The spool is engageable with the pin mechanism to lock the locking assembly and secure the tailgate to the sidewall, and is disengageable from the pin mechanism to unlock the locking assembly and release the tailgate from its securement to the sidewall. A hinge assembly is provided on an opposite side of the tailgate from the locking assembly. The tailgate is selectively pivotable relative to the truck bed about a vertical axis extending through the hinge assembly or about a horizontal axis extending through both of the locking assembly and the hinge assembly. 
         [0007]    The method of engaging a tailgate to a trailer bed includes the steps of:
       providing a spool extending outwardly from a side edge of the tailgate;   mounting a bracket to a sidewall of the bed; where the bracket includes at least a first arm and a second arm, and a first gap defined between the first and second arms;   swinging the gate to a closed position so that the spool enters the first gap;   actuating a pressurized cylinder to cause a piston rod to extend further outwardly therefrom;   pivoting a pin linked to the piston rod;   moving the pin upwardly through a first aperture defined in the second arm of the bracket;   continuing the pin movement until the pin blocks off the first gap; and   securing the spool in the first gap using the pin.       
 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    A preferred embodiment of the invention, illustrated of the best mode in which Applicant contemplates applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims. 
           [0017]      FIG. 1  is a side elevational view of a dump truck having a side-swing tailgate which includes a locking assembly; 
           [0018]      FIG. 2  is a rear perspective view of the back, right-hand corner of the truck showing the locking assembly mounted on the truck bed and engaged with the tailgate; and where the locking assembly is shown in a latched position; 
           [0019]      FIG. 3  is a rear perspective view of the back, left-hand corner of the truck showing a hinge assembly engaged with the truck bed and the tailgate; 
           [0020]      FIG. 4  is an enlarged rear perspective view of the highlighted region of  FIG. 2 ; 
           [0021]      FIG. 5  is a front perspective view of the locking assembly (with the truck bed wall removed) and a portion of the tailgate engaged with the locking assembly, and showing the locking assembly in the latched position; 
           [0022]      FIG. 6  is a right side view of the hinge assembly, the left-side wall of the truck bed and a portion of the tailgate engaged with the hinge assembly; 
           [0023]      FIG. 7  is a left side cross-sectional view of the locking assembly and the portion of the tailgate, with the locking assembly in the latched position; 
           [0024]      FIG. 7A  is a top view of the locking assembly taken along line  7 A- 7 A of  FIG. 7 ; 
           [0025]      FIG. 8  is a left side cross-sectional view of the locking assembly and the portion of the tailgate, with the locking assembly in an unlatched position; 
           [0026]      FIG. 9  is a rear perspective view of the truck bed with the tailgate swung into an open position. 
       
    
    
       [0027]    Similar numbers refer to similar parts throughout the drawings. 
       DETAILED DESCRIPTION 
       [0028]    Referring to  FIG. 1  there is shown a dump truck  10  comprising a cab  12  mounted on a front region of a truck frame  14 , and an open box bed  16  mounted on a rear region of the truck frame  14 . A plurality of wheels  18  are engaged on frame  14  and are positioned to contact a road surface  20  over which the truck  10  is to travel. 
         [0029]    Bed  16  is generally rectangular in shape includes a bottom wall  22  having a front end  22   a  and a rear end  22   b . Rear end  22   b  is pivotally secured to frame  14  by a hinge  24 . Although it is not illustrated herein, it will be understood that a hydraulic lift is mounted on frame  14  and engages front end  22   a  of bottom wall  22 . The hydraulic lift is activatable to raise up the front end  22   a  of bottom wall  22  such that bottom wall  22  pivots about hinge  24  and becomes oriented at an angle relative to frame  14 . 
         [0030]    Bed  16  includes a front wall  26 , a first sidewall  28 , and a second sidewall  30  ( FIG. 2 ), each of which extends upwardly at right angles from bottom wall  22  and is fixedly engaged therewith. Bottom wall  22 , front wall  26 , and first and second sidewalls  28 ,  30  bound and define a compartment  34 . An opening to that compartment  34  is defined by the rear ends of first and second sidewalls  28 ,  30  and rear end  22   b  of bottom wall  22 . A tailgate  32  is engaged with the rear ends of first and second sidewalls  28 ,  30  and extends across the opening to compartment  34 . Tailgate  32  is engaged with the rear end of first sidewall  28  by a hinge assembly  99 , a safety latch  112  and a latch mechanism  123 . Tailgate  32  is engaged with the rear end of second sidewall  30  by a locking assembly  35  ( FIGS. 4 and 5 ), and by a latch mechanism  93 . All of these various securements will be further described herein. 
         [0031]      FIG. 2  shows the right back corner of bed  16  showing a portion of tailgate  32  in a closed position adjacent the rear end of second sidewall  30 . The portion of tailgate  32  is locked to second sidewall  30  by locking assembly  36 . A housing  36  is fixedly mounted on second sidewall  30  by a suitable means, such as by welding. Housing  36  is generally U-shaped in cross-section and includes a sidewall  36   a , a rear wall  36   b  and a front wall  36   c . A cut-out (not numbered) is defined in portions of sidewall  36   a  and rear wall  36   b  proximate a top end of housing  36 . An L-shaped bracket  37  is fixedly secured to housing  36  in this cut-out. Bracket  37  includes a first leg  37   a  and a second leg  37   b  which are disposed generally at right angles to each other and are welded to housing  36 . A first opening  36   d  ( FIG. 7 ) and a second opening  36   e  are defined in sidewall  36   a  of housing  36 . First opening  36   d  begins proximate bracket  37  and extends downwardly for a distance towards a bottom end  36   f  of housing  36 . A removable faceplate  38  is positioned over first and second openings  36   d ,  36   e  and is secured to sidewall  36   a  by way of a plurality of fasteners  42 . When housing  36  is mounted on second sidewall  30 , a chamber  40  ( FIGS. 4 &amp; 5 ) is defined between housing  36  and second sidewall  30 . Faceplate  38  is removable to gain access through first and second openings  36   d ,  36   e  into chamber  40  for maintenance of various components of locking assembly  35  housed within chamber  40  as will be later described herein. 
         [0032]    Referring to  FIGS. 4 and 7A , locking assembly  35  includes a generally L-shaped mounting block  44  which is fixedly secured to first side edge  32   a  of tailgate  32 . Mounting block  44  includes a first leg  44   a  and a second leg  44   b  that are disposed generally at right angles to each other. Although not illustrated herein, mounting block  44  preferably includes a protrusion which extends outwardly from first leg  44   a  and is received into a complementary recess in first side edge  32   a  of tailgate  32 . A plurality of fasteners  46  ( FIG. 2 ) extend through first leg  44   a  and into first side edge  32   a  of tailgate  32 . A spool  48  extends outwardly, at right angles, from an exterior surface of second leg  44   b  of mounting block  44 . Spool  48  is thus disposed generally parallel to interior surface  32   b  of tailgate  32  and is spaced a distance forwardly away therefrom. Spool  48  is secured to second leg  44   b  by a bolt  49  and is configured to be able to rotate around an axis which extends through bolt  49 . Although not illustrated herein, it will be understood that spool  48  is provided with bearings to aid it in rotating freely. Spool  48  is generally cylindrical in shape and includes a first region  48   a  of a first diameter and a second region  48   b  of a second diameter, with the second diameter being greater than the first. First region  48   a  originates proximate second leg  44   b  and extends for a distance outwardly therefrom. Second region  48   b  is disposed toward a free end of spool  48  and is thus spaced from second leg  44   b . Spool further includes an annular groove  48   c  ( FIGS. 4 and 7A ) which is defined within first region  48   a  and is of a third diameter. The third diameter is less than the first diameter. As best seen in  FIG. 7A , groove  48   c  is curved across its width and the reason for this curvature will be further disclosed herein. 
         [0033]    Locking mechanism  35  further includes a generally E-shaped bracket  50  ( FIGS. 2 ,  4  &amp;  5 ) which is mounted to L-shaped bracket  37  on housing  36 . Bracket  50  includes a first, a second and a third arm  50   a ,  50   b ,  50   c  which extend outwardly from a base  50   d . First and second arms  50   a ,  50   b  are of generally the same length but first arm  50   c  is shorter and terminates a distance inwardly from the free ends of first and second arms  50   a ,  50   b . A second gap  52  is defined between the first and second arms  50   a ,  50   b , and a first gap  54  ( FIG. 8 ) is defined between second and third arms  50   b ,  50   c . First gap  54  preferably is of a width that is smaller than the width of second gap  56 . In particular, the width of first gap  54  is substantially equal to the first diameter of first region  48   a  of spool  48 . 
         [0034]    When bracket  50  is engaged with housing  36 , third arm  50   a  is positioned adjacent an exterior surface of first leg  37   a  of bracket  37 , and base  50   d  of bracket  50  is positioned adjacent an exterior surface of second leg  37   b  of bracket  37 . A plurality of fasteners  51  ( FIG. 7 ) is used to secure base  50   d  to second leg  37   b . Preferably, each fastener  51  is recessed into an associated hole  53  defined within base  50   d  of bracket  50 . 
         [0035]    Referring to  FIG. 7 , a first aperture  56  is defined in third arm  50   a  and a second aperture  58  is defined in second arm  50   b . First and second apertures  56 ,  58  are disposed generally parallel to base  50   d  of bracket  50  and are generally aligned with each other. A hole  60  is defined in first leg  37   a  of bracket  37 . When bracket  50  is mounted on bracket  37 , first aperture  56  in bracket  50  is vertically aligned with hole  60  in bracket  37 . Hole  60  and first aperture  56  are of substantially the same diameter. Second aperture  58  is of a greater diameter than that of hole  60  and first aperture  56 . 
         [0036]    In accordance with another feature of the present invention, locking assembly  35  further includes a pin  62  which extends through hole  60  and through first aperture  56 . Pin  62  has an upper end and a lower end. The upper end of pin  62  passes through a bore of a spiral spring  64  positioned within the second gap  52  defined between first and second arms  50   a ,  50   b  of bracket  50 . A cap  66  is engaged with the upper end of pin  62 . Cap has a beveled surface  66   a , a top end  66   b  and an outer wall  66   c . Wall  66   c  is of generally the same diameter as second aperture  58  and is able to move therethrough. The diameter of wall  66   c  is such that it cap  66  is unable to move through either of first aperture  56  or hole  60 . Cap  66  includes a beveled surface  66   a  ( FIG. 4 ), a top end  66   b  and a side surface  66   c . Beveled surface  66   a  extends between top end  66   b  and side surface  66   c  and is disposed at an angle relative thereto. Cap  66  and spring  64  substantially prevent pin  62  from being withdrawn through first aperture  56  and hole  60  and into the interior chamber  40  of housing  36  during operation of locking assembly  35 . 
         [0037]    Locking assembly  35  further includes a collar  67  which is engaged with the lower end of pin  62  in a location such that when the cap  66  and upper end of pin  62  are received in bracket  50 , the collar  67  is positioned within chamber  40  a distance vertically beneath first leg  37   a  of bracket  37 . Collar  67  is of a width that is greater than the diameter of hole  60 . Collar  67  cannot pass through hole  60  and thus acts as a stop to limit the travel of pin  62  through bracket  50 . A first pivot pin  69  secures collar  67  to an upper end of a linkage arm  68 . A hook  70  is fixedly engaged with a lower end of linkage arm  68  and hook  70  is, in turn engaged with a connector bracket  72  by way of a second pivot pin  74 . The opposite end of connector bracket  72  is engaged by way of a third pivot pin  76  to a collar  78 . Collar  78  is fixedly engaged with a piston rod  80  of a pneumatic cylinder  82 . Cylinder  82  is secured to a mounting bracket  84  by a fourth pivot  86 . Bracket  84  is fixedly secured to an interior surface of housing  36 .  FIG. 5  shows that a flange  88  extends outwardly from housing  36  and a shaft  90  extends outwardly therefrom and through an aperture  92  ( FIG. 7 ) in connector bracket  72 . Linkage arm  68 , connector bracket  72 , collar  78 , piston rod  80  and pneumatic cylinder  82  and their connector components all form part of locking assembly  35 . 
         [0038]    It will be understood that instead of cylinder  82  being a pneumatic cylinder, it may alternatively be a hydraulic cylinder. It will be further understood that cylinder  82  is operatively connected to an activation assembly (not shown) that may be directly or remotely activated by the operator. When cylinder  82  is activated in a first instance the piston rod  80  is moved in a first direction relative to cylinder  82  and this movement in turn causes movement of pin  62 . When cylinder  82  is activated in a second instance, the piston rod  80  is moved in a second direction relative to cylinder  82  and this movement again results in the pin  62  being moved. Locking assembly  35  is movable between a locked position and an unlocked position. In the locked position, tailgate  32  is held adjacent the rear end of second sidewall  30  and is prevented from moving away therefrom. In the unlocked position, the tailgate  32  is free to move toward and away from the rear end of second sidewall  30 . The operation of locking assembly  35  and the manner in which it is moved between the locked and unlocked positions will be later described herein. 
         [0039]    As indicated previously, tailgate  32  is also secured to second sidewall  30  by a latch mechanism  93 . Latch mechanism  93  is provided proximate bottom end  36   f  of housing  36 . As shown in  FIG. 2 , latch mechanism  93  includes a mounting bracket  94  fixedly secured to rear side  36   b  of housing  36 , proximate bottom end  36   f  thereof, and a latch  96  which is pivotally mounted within bracket  94 . Latch mechanism  93  is operable to engage a latch pin  98  which extends outwardly from a bottom region of the first side edge  32   a  of tailgate  32 . When latch pin  98  is received within a recessed region defined by mounting bracket  94  and is retained therein by latch  96 , latch mechanism  93  is in the latched position. In this latched position, latch mechanism  93  retains the bottom region of tailgate  32  in close proximity to bottom wall  22  on bed  16 . In order to move latch mechanism  93  to an unlatched position, latch  96  is lifted manually and rotated upwardly out of engagement with latch pin  98  and tailgate  32  is pulled a short distance outwardly away from second sidewall  30  so that latch pin  98  will come to rest on the exterior surface of latch  96  when tailgate  32  is released. An operator will manually move latch mechanism  93  to the unlatched position prior to dumping a load or prior to swinging tailgate  32  open away from second sidewall  30 . 
         [0040]    Referring to  FIGS. 3 &amp; 6 , as indicated previously hinge assembly  99  engages an upper region of tailgate  32  to first sidewall  28 . A housing  101  that is substantially identical in shape to housing  36  is mounted to an exterior surface of first sidewall  28  adjacent the rear end thereof. Housing  101  includes a sidewall  101   a  and a rear wall  101   b . Housing  101  defines a cut-out in sidewall  101   a  and rear wall  101   b  in a region proximate the upper end of housing  101 . An L-shaped bracket  105  is welded to housing in this cut-out in much the same way as bracket  37  is welded to housing  36 . A vertical slot  101   c  ( FIG. 3 ) is defined in the upper end of rear wall  101   b . Slot  101   c  terminates adjacent an upper surface of bracket  105 . 
         [0041]    Hinge assembly  99  includes a hinge support  100  comprising first and second support plates  100   a ,  100   b . Hinge support plates  100   a ,  100   b  are disposed within a cavity (not numbered) defined between housing and first sidewall  28 . Specifically, hinge support plates  100   a ,  100   b  are disposed on either side of slot  101   c  and extend forward for a distance within housing  101 . Hinge assembly  99  further includes a hinge  102 . Hinge  102  includes first knuckles  102   a  and second knuckles  102   b  which are linked together by a hinge pin  110  (which passes through aligned apertures in first and second knuckles  102   a ,  102   b ). As shown in  FIG. 9 , first knuckles  102   a  extend outwardly from a leaf  103  which is fixedly secured to first sidewall  28  of trailer bed  16 . Second knuckles  102   b  are fixedly secured to tailgate  32 . A flange  104  extends outwardly from the top front edge of leaf  103  and is received through slot  101   c  of housing  101  and between hinge support plates  100   a ,  100   b . A shaft  106  ( FIG. 6 ) extends outwardly from first sidewall  28  and is received through an aperture (not numbered) in flange  104 . A link plate  107  is secured to one of the exterior surface of first sidewall  28 , first hinge plate  100   a  or second hinge plate  100   b  by way of a fastener  109 . Link plate  107  includes a detent  107   a  which is received in a slot (not numbered) in shaft  106 . Link plate  107  thereby locks shaft  106  in a specific orientation relative to flange  104 . Roller bearings  108  are provided around shaft  106  to ensure smooth operation of hinge assembly  99 . 
         [0042]    As indicated previously, a safety latch  112  engages tailgate  32  and first sidewall  28 .  FIG. 9  shows that safety latch  112  includes a pair of spaced apart mounting brackets  114  fixedly secured to first sidewall  28 . A pin  116  is pivotally engaged with mounting brackets  114  by way of a pivot rod  115  which extends vertically through brackets  114 . Pin  116  is able to pivot about a vertical axis which extends through pivot rod  115 . A pair of flanges  118  is fixedly secured to second side edge  32   c  of tailgate  32 . A gap  120  is defined between flanges  118  and this gap is complementary is size to pin  116 . Pin  116  is received into gap  120  when tailgate  32  is moved into a closed position (such as is illustrated in  FIG. 3 ). A handle  122  on pin  116  is rotated to threadably advance a sleeve  116   a  on pin  116  toward flanges  118  and thereby clampingly engage the same. When safety latch  112  is in this configuration, it is in a secured position. When it is desired to open tailgate  32 , handle  122  is rotated in the opposite direction to disengage pin  116  from flanges  118 , pin  116  may then be rotated about the pivot rod  115  to withdraw it from gap  120  and thereby release tailgate  32  from its engagement with first sidewall  28 . When safety latch  112  is in this configuration, it is in an unsecured position. 
         [0043]    As indicated previously tailgate  32  is also securable to first sidewall  28  by a latch mechanism  123 . Latch mechanism  123  includes a mounting bracket  124  which is fixedly secured to rear wall  101   b  of housing  101  proximate bottom end  101   d  thereof. A latch  126  is pivotally mounted within bracket  124  and is operable to engage a latch pin  128  which extends outwardly from a bottom region of the second side edge  32   c  of tailgate  32 . Latch mechanism  123  functions in substantially the same manner as latch mechanism  93 . 
         [0044]    Locking assembly  35  is used in the following manner. If one presumes tailgate  32  is in the closed and locked position ( FIGS. 4 ,  5 , and  7 ), then locking assembly  35  is in the locked position, latch mechanisms  93  and  123  are in the latched position, and safety latch  112  is in the secured position. Tailgate  32  is retained against the rear ends of first and second sidewalls  28 ,  30  and access to the opening to compartment  34  is prevented. 
         [0045]    If the tailgate  32  is to be configured to permit the dump truck  10  to dump a load out of compartment  34  by tilting bed  16 , the operator will first move safety latch  112  to the unsecured position (shown in  FIG. 9 ) and will move latch mechanisms  93 ,  123  to the unlatched position. (It will be understood that both safety latch  112  and latch mechanisms  93 ,  123  are moved manually to the unsecured and unlatched positions by the operator.) The locking assembly  35  remains in the locked position where spool  48  is disposed within first gap  54  of bracket  50  and pin  62  with cap  66  thereon is in its fully extended position where it projects into first gap  54 . In this fully extended position, cap  66  rests in groove  48   c  of spool  48  and keeps spool  48  in contact with the interior wall of bracket  50  which defines first gap  54 . ( FIG. 7A  illustrates the engagement of cap  66  and spool  48  and shows the curved outer surface  66   c  of cap  66  at least partially seated in the complementary curved groove  48   c  of spool  48 .) The engagement of cap  66  with spool  48  substantially prevents spool  48  from exiting first gap  54 . Thus, spool  48  is locked to bracket  50  and, consequently, tailgate  32  is locked to second sidewall  30 . When tailgate  32  is in this position, it is possible for the operator to engage an activation assembly (not shown) and thereby cause a hydraulic lift (not shown) to raise the front end of trailer  16  in the direction of arrow “A” ( FIG. 1 ) and thereby angle bed  16 . As the hydraulic lift moves front end  22   a  of bottom wall  22  upwardly in the direction of arrow “A” ( FIG. 1 ), bed  16  pivots about hinge  24  at rear end  22   b  in the direction indicated by arrow “A1”. This motion causes any load retained within compartment  34  to slide rearwardly toward tailgate  32 . While bed  16  tilts, tailgate  32  remains hanging substantially vertically. This is made possible by tailgate  32  pivoting about a horizontal axis which extends through shaft  106  in hinge assembly  102  and through spool  48  in locking assembly  35 . (It will be understood that shaft  106  and spool  48  are horizontally aligned with each other and are located vertically at substantially the same position on first and second sidewalls  28 ,  30 .) The relative motion between bed  16  and tailgate  32  opens up a gap between the rear end of bottom wall  22  and the bottom  32   d  of tailgate  32 . Thus, the load within bed  16  slides through the gap and onto the road surface upon which truck  10  rests. 
         [0046]    When the dumping operation is over, the front end of bed  16  is lowered toward frame  14  by deactivating the hydraulic lift. Bed  16  pivots in the opposite direction to arrow “A” ( FIG. 1 ) and returns to its original position shown in  FIG. 1 . When pins  98 ,  128  contact latches  96 ,  126  of latching mechanisms  93 ,  123 , they depress the same inwardly automatically and slide down the curved surfaces thereof until they come to rest in the recesses  97 ,  127 . At this point latches  96 ,  126  slide past pins  98 ,  128 , respectively, and come to rest on an exterior surface thereof, thus locking pins  98 ,  128  within locking mechanisms  93 ,  123 . The operator will then manually re-engage safety latch  112  and the truck  10  is ready to drive on road  20  once again. 
         [0047]    If, on the other hand, the operator wishes to access the load in compartment  34  without dumping the same, he or she will move safety latch to the unsecured position as previously described and will also unlatch latch mechanisms  93 ,  123  as previously described. In order to swing tailgate  32  open about a vertical axis which extends through hinge assembly  102 , the operator must also unlock locking mechanism  35 . In order to do this the operator must engage an activation assembly (not shown) which will activate hydraulic cylinder  82 . Referring to  FIG. 8 , the activation of hydraulic cylinder  82  causes piston rod  80  to be withdrawn into cylinder  82  in the direction of arrow “B”. The decrease in length of piston rod  80  causes connector bracket  72  to rotate about second pivot pin  74  in the direction of arrow “C”. The rotation of connector bracket  72  causes linkage arm  68  and therefore pin  62  to be drawn downwardly through bracket  50  in the direction of arrow “D”. Pin  62  is moved downwardly through bracket  50  until it no longer obstructs gap  54  in bracket  50 . This positioning of pin  62  coincides with the underside of cap  66  compressing spring  64  to such a degree that no further downward motion of pin  62  is possible. Once cap  66  no longer obstructs first gap  54 , spool  48  is free to slide out of the same. At this point, locking mechanism  35  is in an unlocked position and tailgate  32  is effectively released from its engagement with second sidewall  30 . The operator is then able to manually grasp tailgate  32  and rotate it to an open position. As tailgate  32  begins to rotate about the vertical axis extending through hinge pin  110 , spool  48  slides out of first gap  54  of bracket  50  and in the direction indicated by arrow “E”. Tailgate  32  is swung open in the direction indicated by arrow “F” in  FIG. 9  and the operator is then able to access the interior of compartment  34  of bed  16 . 
         [0048]    When the operator wishes to close tailgate  32 , the tailgate  32  is pivoted about hinge pin  110  in the opposite direction to arrow “F”. When first side edge  32   a  of tailgate  32  approaches second sidewall  30 , spool  48  slides into first gap  54  of bracket  50  in a direction opposite to arrow “E” ( FIG. 8 ). Latch mechanisms  93 ,  123  will also automatically move to a latched position as pins  98  and  128  engage the same as previously described. When spool  48  is seated in first gap  54 , the operator will actuate cylinder  82  once again. This causes piston rod  80  to move in the opposite direction to arrow “B” so that an increased length of piston rod  80  extends outwardly from cylinder  82 . This motion in turn causes connector bracket  72  to pivot about third pivot pin  76  in a direction opposite to arrow “C”. The motion of connector bracket  72  in this direction causes linkage arm  68  and therefore pin  62  to move upwardly in the opposite direction to arrow “D”. Additionally, the previously compressed spring  64  returns to its original shape and as it does so, it urges pin  62  upwardly through second arm  50   b . As pin  62  moves upwardly, beveled surface  66   a  on cap  66  of pin  62  engages the exterior surface of spool  48  and urges the same further into first gap  54 . Outer surface  66   c  of cap  66  enters groove  48   c  on spool  48  and thereby locks cap  66  against lateral sliding motion on spool  48 . When piston rod  80  reaches its maximum extension out of cylinder  32 , pin  62  is in a position where top end  66   b  of cap  66  is generally flush or close to a bottom surface of first arm  50   c . Cap  66  of pin  62  obstructs enough of the opening to first gap  54  to prevent spool  48  from exiting therefrom. At this point, locking mechanism  35  is in the locked position and tailgate  32  is thus secured to second sidewall  30 . Since latch mechanisms  93 ,  123  are also latched at this point; tailgate  32  is secured at both its top end and bottom end to first and second sidewalls  28 ,  30  of bed  16 . The operator will then manually re-engage safety latch  112  to ensure that latch mechanisms  93 ,  123  will not accidentally disengage during movement of truck  10 . 
         [0049]    It will be understood that while the tailgate  32  has been illustrated herein as being able to be swing open from right to left, it may alternatively be configured to swing open from left to right. If this is the case the locking assembly  35  will be engaged with first sidewall  28  and hinge assembly  102  will be engaged with second sidewall  30 . The latch mechanisms  93 ,  123  will remain in the same location, no matter which way tailgate  32  opens. Security latch  112  preferably will be moved to the first side edge  32   a  of tailgate  32  from second side edge  32   c  thereof. Still further, a second security latch  112  may be provided on tailgate  32  on the other of the first and second side edges  32   a ,  32   c,    
         [0050]    It will further be understood that while it has been disclosed that locking assembly  35  is mounted on second sidewall  30  and that the spool  48  is mounted on tailgate  32 , the locking assembly  35  may instead be mounted on tailgate  32  and the spool  48  may be mounted on second sidewall  35 . Similarly, the various hinge assembly components may be mounted on the opposite one of the tailgate  32  and first sidewall  28  from that illustrated and described herein. 
         [0051]    Still further, while the housing  36  and pressurized pin mechanism (bracket  50 , pin  62  and hydraulic cylinder  82  and all intermediate components) are disclosed as being mounted on the exterior surface of second sidewall  30 , the housing and pressurized pin mechanism may alternatively be mounted on the interior surface of second sidewall  30 . Similarly, if the housing and pressurized pin mechanism are mounted on the tailgate instead of on one of the first and second sidewalls, they may be mounted on either of the interior and exterior surfaces of the tailgate. 
         [0052]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0053]    Moreover, the description and illustration of the invention are an example and the invention is not limited to the exact details shown or described.