Abstract:
A kingpin is provided for use on a trailer in a system with the tractor linked to a trailer. The kingpin includes a shank and a selectively deformable head, whereby during a trailer rollover event, the kingpin head deforms allowing the link between the tractor and trailer to be broken and the tractor to remain upright.

Description:
This invention claims the priority of provisional application 60/479,058 filed on Jun. 18, 2003, the entirety of which is incorporated herein. 

   BACKGROUND OF THE INVENTION 
   The trucking industry “keeps America moving” and trucking is in fact one of the most important modes of transportation for the movement of goods. Trucks are able to make long hauls or short hauls and can deliver to almost any location accessible by a paved road. Trucking, however, is a dangerous industry for reasons tied to this versatility. Trucks share the nation&#39;s roadways with passenger vehicles and pedestrians. Because the size of trucks almost always exceeds other vehicles, truck drivers must be especially careful to observe smaller vehicles and prevent collisions therewith. This is especially true in the case of tractor trailer combinations which exceed a common passenger vehicle&#39;s size. The inherent design for the towed trailer is long in length, narrow in width, and commonly uses its capacity to carry heavy loads at a high center of gravity. 
   Tractor trailer combinations are vulnerable to the phenomenon known as rollover which occurs typically when a truck driver attempts to avoid a collision, or obstacle through a knee jerk impulse reaction. Additionally, rollovers prevalently occur at lane changes and ramp interchanges where excessive speed is used with a change of direction maneuver. The momentum of the trailer does not allow the trailer to follow the new path dictated by the tractor. Instead, the trailer tries to continue in its original path and begins to roll over from an upright position. This is a progressive event which starts at the rear of the trailer and rapidly progresses forward to involve the towing tractor; first its drive axle and continues to involve the forward steer axle which will then have committed the whole combination. The tractor, which is linked to the trailer via a kingpin and fifth wheel system, is actually pulled over by the dominant rolling trailer. Known kingpins include a shank having a circular diameter and an integral head portion also with a circular cross section, but with a larger diameter than the shank. Combination vehicle rollovers destroy the towing tractor, are known to have caused the death of hundreds of tractor occupants and cause vast amounts of serious injuries. Thousands of these events occur annually. 
   What is desired is a system that allows a towed trailer, within a tractor trailer combination vehicle, to mechanically detach itself from the towing tractor&#39;s fifth wheel receiver when the imminent rollover event has committed the towed trailer to roll onto its side, but allows the tractor to remain upright and not follow through to destruction in these events. 
   SUMMARY OF THE PRESENT INVENTION 
   The present invention overcomes the problem of tractor rollover by providing an improved kingpin for use on the trailer. During rollover events, the kingpin on the trailer deforms, thus, breaking the link between the kingpin and the fifth wheel on the tractor. As a result the trailer becomes detached from the tractor and the tractor may remain upright even though the trailer rolls onto its side. 
   In a preferred embodiment of the invention a kingpin is provided for use on a trailer in a system with the tractor linked to the trailer. The kingpin includes a shank and a selectively deformable head, whereby during a trailer rollover event, the kingpin head deforms allowing the link between the tractor and trailer to be broken and the tractor to remain upright. 
   A method of making a kingpin of the present invention includes the reworking of a known kingpin by removing portions of the head to create two deformable ears. 
   These and other aspects of the invention are herein described in particularized detail with reference to the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a side elevational view of a tractor trailer combination; 
       FIG. 2  is a perspective view of a fifth wheel upon the tractor of the tractor trailer combination; 
       FIG. 3  is a perspective view of a kingpin of the present invention upon the trailer of the tractor trailer combination; 
       FIG. 4  is a top view of a kingpin of the present invention; 
       FIG. 5   a  is a perspective view of a kingpin known in the art; and 
       FIG. 5   b  is a perspective view of a kingpin of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The tractor  10  is shown in  FIG. 1  and includes a fifth wheel  12 . The fifth wheel  12  is shown in  FIG. 2  and includes a V-notch  18 , and locking clamp  14  having jaws  16 . The fifth wheel  12  has a tear drop shape with an upper contact surface  13  and a V-notch  18  in the narrow portion of the teardrop. Located near the center of the fifth wheel  12  and the apex of the V-notch  18  is the locking clamp  14 . The locking clamp  14  includes jaws  16  that move between an open and closed position. The jaws  16 , when open, create access from a position within the V-notch  18  of the fifth wheel  12 . The jaws  16  each define an inner surface including a semi-circular region that closes over or around the kingpin. The jaws  16  pivot upon individual pins affixed to the fifth wheel  12 . 
   Referring to  FIGS. 3 ,  4  and  5   b , the trailer  20  includes a kingpin  22  having a head  23 , shank  24 , and base  26 . The kingpin  22  extends vertically downwardly from the bottom of the trailer  20 . At an end of the kingpin  22  distal from the body of the trailer  20 , a head  23  is provided. The head  23  has a non-circular radial shape ( FIG. 5   a  and  5   b  show a comparison to a traditional kingpin having a head with a round radial shape). The head  23  includes at least one ear  28  that has a radius greater than the radius of the shank  24 . The shank  24  is located adjacent to the head  23  and extends from the head  23  toward the body of the trailer  20 . The shank  24  has a generally circular cross sectional shape. The base  26  of the kingpin  22  is located adjacent to the shank  24  and the trailer  20  body and has a generally circular radial shape. Thus, the shank  24  interconnects the base  26  and the head  23 . The base  26  has a diameter preferably that exceeds that of the shank  24 . 
   The trailer  20  defines an axis Ψ in a direction extending from the front of the trailer  20  to the rear of the trailer  20 . Preferably, a first ear  28  of the kingpin  22  extends in a direction transverse to the Ψ axis. Preferably, a second ear  28  of the kingpin  22  also extends in a direction transverse to the Ψ axis, but opposite to the direction of the first kingpin ear  28 . The kingpin  22  is preferably manufactured as an integral whole. The kingpin may be formed by forging, progressive stamping and/or machining operations. 
   The size of the kingpin ears  28  are determined by the structural strength desired before deformation and/or failure. The parameters of the ears that may be varied include the thickness “a” of the ears  28 , the distance “b” the ears  28  protrude from the center of the kingpin and the percentage of overlap “c” on a perimeter defined by an imaginary extension of the kingpin&#39;s shank  24 . The percentage overlap of a single ear to the entire perimeter of the kingpin is within a range of about fifteen percent to about forty percent. Preferably, the ears  28  are of an equal size and symmetrical. The trailer  20  is any of the known styles, such as tanker, flatbed or van styles. 
   The fifth wheel  12  functions to hold the kingpin  22  of the trailer  20  and, thus, the trailer  20  in position with respect to the tractor  10 . The locking clamp  14  and its jaws  16  close around the shank  24  of the kingpin  22  to hold the trailer  20  in place, while permitting the kingpin  22  and trailer  20  to pivot about the axis/pivot point provided by the fifth wheel. The V-notch  18  of the fifth wheel  12  allows the kingpin  22  to be brought into position within the clamp jaws  16  even when alignment between the tractor  10  and trailer  20  is initially not perfect. The clamp jaws  16  hold the kingpin  22  when in a closed position and release the kingpin  22  when in an open position. 
   As is well known, the trailer  20  functions to haul goods. The kingpin  22  is a junction and connection point between the tractor  10  and the trailer  20 . The shank  24  of the kingpin  22  fits within the jaws  16  of the locking clamp  14  upon the fifth wheel  12 . Because the shank  24  is circular the locking clamp  16  of the fifth wheel  12  may spin around the kingpin  22  without resistance. The base  26  of the kingpin  22  functions to prevent excessive downward movement of the trailer  20  with respect to the tractor  10 . The head  23  of the kingpin selectively prevents excessive upward movement of the trailer  20  with respect to the tractor  10 . However, upon a threshold amount of upward or twisting force applied to the head  23  of the kingpin  22 , the head  23  will deform allowing relative movement of the kingpin  22  and fifth wheel  12  sufficient to break the link therebetween. 
   In a manner well known in the art, the fifth wheel  12  is affixed to the tractor  10 . The notch  18  on the fifth wheel  12  points towards the rear of the tractor  10 . The kingpin  22  is attached to the trailer  20  such that it extends downwardly therefrom. The kingpin  22  is attached to a deck plate on the trailer, typically by welding. The shank  24  of the kingpin  22  fits into the clamp jaws  16  of the fifth wheel&#39;s locking clamp  14 . 
   In a manner well known in the trucking art, the tractor  10  is linked to the trailer  20  by backing the tractor  10  into position with respect to the trailer  20  such that the kingpin  22  is aligned within the fifth wheel  12 . The locking clamp  14  on the fifth wheel  12  is then closed about the kingpin shank  23 , and the tractor trailer is ready for operation. During normal operation the kingpin  22  is free to spin within the locking clamp  14  as the tractor trailer combination makes turns on the road. 
   During potential rollover situations, an atypical upward or twisting force is applied by the trailer  20  to the tractor  10  via the kingpin  22  that initiates the rollover. During the rollover, a progressive shift of orientation of the trailer causes a twisting force in the fifth wheel and kingpin joint. The rollover mechanics are different than those in an automobile rollover. The rear end of the trailer may rotate a full ninety degrees, such that the rear wheels of the trailer are off the road while all wheels of the tractor remain on the road. The twisting force inherent in this juxtaposition progresses from the rear to the front of the trailer into the fifth wheel/kingpin joint. The twisting force is transmitted by the head of the kingpin  22  against the locking clamp  14  of the fifth wheel  12 . More specifically, one of the kingpin ears  28  will be brought upwardly into engagement with the fifth wheel clamp while the other kingpin ear will be forced downwardly away from the fifth wheel clamp. 
   Depending on which way the trailer  20  rolls, force exceeding a deformation threshold is applied to either one or the other of the ears  28  upon the kingpin head  23 . When the threshold force is exceeded, a first ear and then possibly a second ear  28  on the kingpin head  23  deform in such a way as to allow the kingpin  22  to move out of the hold of the locking clamp  14 . Deformation may include a full sheering off of one or both of ears  28 . As a result, the trailer  20  is free to rollover while the tractor  10  remains in an upright position. 
   This designed failure prevents completion of a full rollover, where typically the tractor steering axle leaves the ground after the tractor frame is twisted and lifted to a forty five degree angle. 
   Although the kingpin head  23  is preferably manufactured with a non-circular radial shape, existing circular kingpins  22  may be reworked by removing portions of the head such as by grinding or machining. Further, instead of changing the shape of the head, a similar result may be achieved by cutting slots through the head so as to weaken the head to permit deformation or shearing thereof. Thus, with knowledge of the present invention, various equivalent structures may be derived by those skilled in the art. 
   Although the invention has been shown and described with reference to certain preferred and alternate embodiments, the invention is not limited to these specific embodiments. Minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the invention as claimed and equivalents.