Abstract:
A fifth wheel includes a top plate having a throat that is adapted to receive a kingpin of a trailer. The fifth wheel is equipped with a locking mechanism including a jaw slidably connected to the top plate and slidable between a closed position where the jaw blocks passage of a kingpin out of the throat of the fifth wheel and an open position where a kingpin may pass into and out of the throat of the fifth wheel. The jaw has an edge adapted to engage a kingpin positioned in the throat of the fifth wheel when the jaw is in the closed position. A release arm is pivotally attached to the top plate and the jaw. A trigger member is pivotally attached to the release arm and has a locking head. A main spring urges the jaw towards the closed position. A locking protrusion is attached to the top plate and is engaged by the locking head of the trigger member when the jaw is in the open position so as to prevent the jaw from moving into the closed position. A release member is pivotally attached to the distal end portion of the release arm.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to fifth wheels of the type used by tractor trucks to pull trailers and the like and, in particular, to a locking mechanism for a fifth wheel. 
     BACKGROUND 
     Towing vehicles, such as tractor trucks or semi-tractors and the like, are equipped with fifth wheel hitches which receive and engage the kingpins of trailers. The fifth wheel is positioned on the back of the tractor truck and features a top plate having a central throat equipped with a latching mechanism which engages the kingpin. The throat may be, for example, provided with an open end facing the rear of the truck. The kingpin extends downward from the underside of the leading end portion of the trailer. The engagement of the trailer kingpin by the fifth wheel is the primary means by which the trailer is pivotally connected to the tractor. 
     Terminal tractors, which may be tractor trucks or other vehicles equipped with a fifth wheel, are typically used to move trailers within a cargo yard, warehouse facility, or intermodal facility, as opposed to moving trailers on public roads. Terminal tractors serve a function in the trucking industry that is similar to switch engines or shunting locomotives in the railroad industry. The fifth wheels of terminal tractors are therefore subject to much more frequent hitching and unhitching operations than highway tractors. As a result, a need exists for fifth wheel locking mechanisms for terminal tractors, and similar applications, that are very robust, reliable and quick and easy to hitch and unhitch. It is also desirable for such fifth wheels to prevent, or at least minimize, false locking cases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified side elevational view of a tractor truck having a fifth wheel and a front portion of a trailer having a kingpin suitable for use with an embodiment of the fifth wheel locking mechanism of the present invention; 
         FIG. 2  is a top perspective view of a fifth wheel in an embodiment of the invention with the locking mechanism in a closed configuration; 
         FIG. 3  is a bottom perspective view of the fifth wheel of  FIG. 2 ; 
         FIG. 4  is an enlarged isolated perspective view of the secondary lock latch of  FIG. 3 ; 
         FIG. 5  is an enlarged isolated perspective view of the assembled release arm, secondary lock latch, trigger member, manual release bar and pneumatic release cylinder of  FIG. 3 ; 
         FIGS. 6A-6C  are bottom plan views of the fifth wheel of  FIGS. 2 and 3  with the locking mechanism in an open and armed, opened and unarmed and closed configurations, respectively; 
         FIG. 7  is a bottom perspective view of the fifth wheel of  FIGS. 2, 3 and 6A-6C  with the locking mechanism in the open and unarmed configuration; 
         FIG. 8  is top perspective view of the fifth wheel of  FIGS. 2, 3 and 6A-6C  with the top wear plates removed; 
         FIG. 9  is a bottom perspective view of the fifth wheel of  FIG. 3  with a retaining bracket. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In accordance with an embodiment of the present invention, as illustrated in  FIG. 1 , a towing vehicle, such as a tractor truck indicated in general at  10 , is positioned to begin the coupling process with regard to a trailer, indicated in general at  12 . While the invention is described below in terms of a tractor truck being used as the towing vehicle and a semitrailer being used as the trailer, it is to be understood that the present invention could be applied to other towing vehicle and trailer arrangements. 
     As illustrated in  FIG. 1 , and as known in the art, the truck is provided with a fifth wheel hitch, or simply “fifth wheel” indicated in general at  20 , having a top plate  22  and a base  24  upon which the top plate is pivotally mounted. As is known in the art, the fifth wheel may be mounted in a fixed fashion on the truck frame rails or via a sliding mechanism so that the fore and aft position of the fifth wheel on the truck frame rails may be adjusted. 
     The trailer  12  features a kingpin, indicated in general at  26 . The kingpin typically extends downward from a trailer bearing plate  28  which rests upon the top surface of the top plate  22  of the fifth wheel when the kingpin is received within the fifth wheel as described below. The kingpin typically features an upper collar portion  30 , a middle shank portion  32 , which features a reduced diameter, and a bottom flange portion  34 . 
     As illustrated in  FIG. 2 , the fifth wheel top plate  22  is provided with a rearward facing, generally V-shaped opening or mouth, indicated in general at  42 , that leads to the fifth wheel throat  44 . As described in greater detail below, the fifth wheel is provided with a locking mechanism that automatically and/or manually engages and locks the trailer kingpin within the throat of the fifth wheel to couple the trailer to the tractor truck. 
     The top surface of the top plate  22  is provided with top wear plates  46   a  and  46   b , which preferably include grease grooves  48   a  and  48   b  for optimally retaining applied grease. Mouth wear plates  52   a  and  52   b  are affixed to the inside surfaces of the mouth of the fifth wheel. 
     As illustrated in  FIG. 3 , a locking mechanism is mounted to the underside of the top plate  22 . The locking mechanism uses a sliding deadbolt or jaw  54  to lock a trailer kingpin into the throat of the fifth wheel. The locking mechanism is spring loaded in the closed configuration, illustrated in  FIGS. 2 and 3 . The jaw  54  cooperates with a stationary front jaw or member  56  to hold the kingpin in place during transit. 
     In addition to sliding jaw  54 , the locking mechanism includes a release arm  58  that is pivotally connected by a proximal end to the underside of the top plate, such as by bolt  62 . The release arm  58  includes an elongated slot  61  which receives a pin  63  that is attached to the jaw  54 . As a result, as the release arm pivots about bolt  62 , the jaw  54  slides between a closed position, where the passageway between the fifth wheel mouth and throat is blocked, illustrated in  FIGS. 2 and 3 , and an open position, where the passageway between the fifth wheel mouth and throat is not blocked. 
     A secondary lock latch  64  is pivotally connected to a distal end of the release arm by a bolt  66 , which engages an opening  68  ( FIG. 4 ) formed in the latch  64 . In addition to opening  68 , with reference to  FIG. 4 , the secondary lock latch  64  includes a pull arm  72 , a secondary lock pawl  74  and an elbow portion  76 . Positioned between the pull arm and the elbow portion is a corner portion  78 . A strengthening rib  82  is preferably provided along at least a portion of the pull arm  72  and between the elbow and corner portions  76  and  78 . 
     Returning to  FIG. 3 , a trigger member  84  is also pivotally attached by a proximal end to the release arm  58  by bolt  66 . As illustrated in  FIG. 5 , the trigger member  84  includes a locking head portion  86  at a distal end that contains a locking socket  87 , having proximal wall  89   a  and distal wall  89   b . The trigger member also includes a middle portion provided with tabs  88  and  92 , both of which are provided with openings. 
     As illustrated in  FIG. 3 , a tension spring  94  has a first end connected to the opening of trigger member tab  92  and a second end attached to opening  96  ( FIG. 4 ) of the secondary lock latch  64 . A larger main tension spring  98  ( FIG. 3 ) engages the opening of trigger member tab  88  ( FIG. 5 ) at a first end, while, as illustrated in  FIG. 3 , the second end of the main spring  98  engages an eye bolt  102  secured to the top plate  22 . It should be noted that the first end of the main spring  98  is shown disconnected from the opening of tab  88  of the release member in  FIG. 3  to improve clarity of the illustration. 
     As illustrated in  FIGS. 3 and 5 , a manual release bar  104  is pivotally attached at a proximal end to opening  106  ( FIG. 4 ) of latch  64  via bolt  108  ( FIG. 3 ). The distal end of the manual release bar  104  is preferably provided with a release handle, illustrated in phantom at  110  in  FIG. 5 , that extends out from under the fifth wheel top plate  22  for access by a user. 
     A pneumatic release cylinder  112  ( FIGS. 3 and 5 ) features a piston rod  114  that is pivotally attached to opening  116  ( FIG. 4 ) of the corner portion of the latch  64 . As illustrated in  FIG. 5 , the cylinder portion  116  of the pneumatic release cylinder includes a port  118  through which pressure within the cylinder may be increased or decreased to move the piston rod. The port  118  is connected to a source of pressurized air, which may be activated or deactivated by the user to control actuation of the pneumatic release cylinder, and thus the locking mechanism, as will be described in greater detail below. The pneumatic release cylinder includes a tab  122  which is pivotally mounted to a bracket  124  ( FIG. 3 ) formed within or attached to the top plate. 
     In operation, the locking mechanism described above is initially in the open and armed configuration illustrated in  FIG. 6A . More specifically, the fifth wheel is prepared to receive the kingpin of a trailer so that the tractor truck or other pulling vehicle may be coupled to the trailer. 
     It should be noted that the main tension spring  98  is shown in  FIGS. 6A-6C  with the first end  132  disconnected from the tab  88  of the trigger member for clarity. In actuality, the first end  132  of the spring  98  is connected to the tab  88  of the trigger member and is actually held in tension when the locking mechanism is in the open and armed configuration illustrated in  FIG. 6A . In addition, the tension spring  94  of  FIG. 3  has been omitted from  FIGS. 6A and 6B  for clarity, but it should be understood that the spring is connected between tab  92  of the trigger member and the opening  96  of the secondary lock latch  64 . As a result, the spring  94  of  FIG. 3  would also be in a tension state in the open and armed configuration of  FIG. 6A . 
     When in the open and armed configuration of  FIG. 6A , due to the tension force of main spring  98 , the trigger member is pulled in the direction of arrow  134 . Motion in this direction is prevented, however, due to the engagement of the proximal wall  89   a  ( FIG. 5 ) of the locking socket ( 87  in  FIG. 5 ) of the head  86  of the trigger member with a locking protrusion  136  (also shown in  FIG. 3 ) that extends downward from the bottom surface of the fifth wheel top plate  22 . A portion of the head  86  of the trigger member extends into the throat  44  of the fifth wheel. 
     As a result of the position of the trigger member  84  illustrated in  FIG. 6A , the release arm  58  is positioned so that the jaw  54  is held in a position where it does not block the passageway between the fifth wheel mouth  42  and throat  44 . 
     As illustrated in  FIG. 1 , the fifth wheel  20  is mounted to a tractor truck or other pulling vehicle. To couple a trailer (such as  12  in  FIG. 1 ) to the pulling vehicle, the driver backs the pulling vehicle towards the trailer kingpin  26  as illustrated by arrow  140  in  FIG. 6A . As the shank portion of the kingpin  26  enters the throat  44  of the fifth wheel, the flange of the kingpin engages the locking head  86  of the trigger member  84  and moves it to the position illustrated in  FIG. 6B  (the shank portion  32  of the kingpin is indicated in phantom in  FIG. 6B ). As a result, the locking socket of the head  86  of the trigger member is moved off of locking protrusion  136 , and main spring  98  is free to pull the trigger member in the direction of arrow  134  (of  FIG. 6A ). As this occurs, the release arm  58  pivots in the direction of arrow  142  of  FIG. 6B , and jaw  54  is pushed via pin  63  to slide along sliding support  143  ( FIG. 6B ) into the closed position illustrated in  FIG. 6C  (and  FIGS. 2 and 3 ). This results in the locking mechanism being in the closed configuration with the shank portion  32  of the trailer kingpin being locked within the fifth wheel so that the pulling vehicle and trailer are coupled. A micro-switch  145  ( FIG. 6C ) detects that the jaw  54  is in the closed position and provides a signal to the driver of the pulling vehicle, such as a visual and/or audible in the cab of the pulling vehicle, so that the driver knows the locking mechanism is in the closed configuration. 
     The jaw  54  preferably includes a tapered and curved edge  144  to facilitate and ensure engagement between the jaw and the kingpin. As the trailer is pulled by the pulling vehicle, towing forces (forces in the direction of the jaw  54 ) are transmitted directly onto the curved surface  144  of the jaw that interfaces with the kingpin. These forces are distributed over the span of the jaw and transmitted into the top plate  22 . 
     While the closed configuration of  FIG. 6C  is supported by the force of main spring  98 , additional locking is provided by the secondary lock latch  64 . More specifically, as the release arm  58  moves from the position illustrated in  FIG. 6B  to the position illustrated in  FIG. 6C , the pawl  74  of the secondary lock latch is moved in a position to engage a locking notch  150  ( FIGS. 3 and 6C ) formed on the bottom surface of the top plate  22 . A torsion spring, illustrated at  152  in  FIG. 5 , features one end that engages the release arm  58  and another end that engages the pawl portion  74  of the secondary lock latch. The action of the torsion spring, in combination with the tension force of spring  94 , causes the latch  64  to pivot about the distal end of the release arm  58  in the direction of arrow  154  of  FIG. 6C  so that the pawl  74  engages the notch  150 . As a result, the release arm  58  is prevented from rotating in the direction of arrow  156  thus further locking the jaw  54  in the closed position illustrated in  FIG. 6C . This secondary locking prevents the jaw  54  from retracting from the closed position due to friction during turning or other potential jarring or impact forces. 
     An additional tertiary lock is available by way of manually inserting a locking pin  158  ( FIG. 6C ) into a hole in the top plate  22  as well as an opening  162  ( FIG. 6B ) formed in the manual release bar  104  in order to create a positive lock between the two. Engaging this tertiary lock prevents the locking mechanism from opening while in transit, even in the event that the pneumatic release cylinder is activated in the manner described below. 
     When the driver or other user wishes to uncouple the trailer from the pulling vehicle, and thus remove the kingpin from the fifth wheel, the pneumatic release cylinder  112  is activated so that the piston rod  114  moves out of the cylinder  116 . This causes the secondary lock latch  64  to rotate about the distal end of the release arm  58  in the clockwise direction (i.e. in the direction opposite of arrow  154 ). As a result, the pawl  74  of the latch is removed from engagement with notch  150 , and the release arm is rotated about bolt  62  in the clockwise direction (i.e. in the direction opposite arrow  142  in  FIG. 6B ) into the position illustrated in  FIG. 7 , and the jaw  54  is pulled to the right into the open position. In addition, the head  86  of the trigger member drops down onto the locking protrusion  136  so that the locking protrusion is positioned adjacent to the distal wall  89   b  ( FIG. 5 ) of the locking socket ( 87  of  FIG. 5 ). At this point, the locking mechanism is in the open and unarmed configuration. 
     When in the opened and unarmed configuration illustrated in  FIG. 7 , the head  86  of the trigger member rests against the flange of the kingpin and holds the mechanism open until the kingpin is removed from the fifth wheel. After the kingpin is removed, and the trailer and the pulling vehicle are uncoupled, the head  86  of the trigger member moves to the left (in the direction of arrow  134  of  FIG. 6A ) so that the locking protrusion  136  once again engages the proximal wall  89   a  ( FIG. 5 ) of the locking socket ( 87  in  FIG. 5 ). As a result, the locking mechanism is once again in the open and armed configuration illustrated in  FIG. 6A . 
     As an alternative to the use of the pneumatic release cylinder  112 , or in the event of a failure of the cylinder, there is the option of manually releasing the secondary lock and opening the mechanism via the use of manual release bar  104 . More specifically, with reference to  FIG. 6C , pulling the manual release bar in the direction of arrow  172  (with tertiary locking pin  158  removed) will cause the secondary lock latch  64  to rotate about the distal end of the release arm  58  in the clockwise direction (i.e. in the direction opposite of arrow  154 ) so as to disengage the secondary locking pawl allowing the mechanism to move into the opened and unarmed configuration illustrated in  FIG. 7  with a single pull. 
     The locking mechanism described above offers several advantages in terms of maintenance and service. The jaw  54  is replaceable while the fifth wheel is assembled to the truck or other pulling vehicle, after removal of the wear plates, which is illustrated in  FIG. 8 . The internal linkage illustrated in  FIG. 5 , including the release arm  58 , trigger member  84 , secondary lock latch  64 , manual release bar  104  and pneumatic cylinder  112 , can be replaced after the removal of a retaining bracket  174 , illustrated in  FIG. 9  as added to the fifth wheel of  FIG. 3 , and screws  62  and  176  on the bottom perimeter of the top plate  22 . The internal linkage may be dropped out the bottom of the fifth wheel and slid forward, in the direction of arrow  178  of  FIG. 9 , for removal and servicing. The stationary front jaw ( 56  of  FIG. 3 ) can be removed and replaced after removal of sliding jaw  54 , retaining bracket  174  ( FIG. 9 ) and a release bolt and detachment of the main spring  98 . 
     As shown for the top wear plates in  FIG. 8 , the mouth wear plates  52   a  and  52   b  may also be removed from the top plate  22  for repair or replacement. 
     While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.