Abstract:
A bumper system comprises a tubular roll-formed reinforcement beam. A hitch-supporting bracket has an inverted section shaped to fit downwardly onto the beam, and further has a laterally-extending second section. A hitch support tube is secured to the laterally-extending second section and has a hole for receiving a ball hitch for hauling a trailer. An energy absorber is attached to the beam, and includes a rear recess receiving the beam, a center section providing access to the hitch, and end sections that form steps on corners of the vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional of application Ser. No. 10/294,124, filed Nov. 14, 2002, entitled BUMPER WITH HITCH. 
     
    
     
       BACKGROUND OF THE PRESENT INVENTION  
         [0002]    The present invention relates to bumpers having a hitch adapted to haul a trailer or the like, and also to bumpers having energy absorbers adapted to mount accessories and form steps.  
           [0003]    Rear bumpers of vehicles, especially utility vehicles and trucks, are often adapted with hitches to haul trailers. The hitch-supporting structure is often incorporated into the bumper in order to reduce components and to provide a more compact arrangement. With stamped bumpers, the hitch-supporting structure is simply stamped into the bumper beam as the bumper components are formed and auxiliary reinforcements are added. However, it is more problematic with rollformed tubular bumper beams, since rollforming operations are not typically set up to incorporate stamping operations. Further, tubular beams often use higher-strength materials, such that it is not as easy to form a hitch-supporting structure in a tubular beam. Also, hitch-supporting structures require that the side walls of the material be cut and shaped, at a time when it is difficult to support an inside of the tube. This makes it difficult if not impossible to accurately shape the wall as desired.  
           [0004]    Sometimes, the towing strength of the hitch-supporting structure is more limited than desired. In particular, class II hitches must be able to support a tongue weight of 350 lbs., and must be able to tow a weight of 3500 lbs.; while class III hitches must be able to support a tongue weight of 500 lbs., and must be able to tow a weight of 5,000 lbs. The difference between the two hitch classes is considerable, and the structure necessary to pass the tougher class III standard is not easily achieved without significant cost, weight, and vehicle-built-in structure.  
           [0005]    In addition to the above, it is desirable to reduce the number of components required to mount accessories such as tail lights, turn signal lights, license plate illuminating lights, and the like, onto bumper systems. Further, it is desirable to form features integrally into the bumper system, such as steps and other mounting features, without the need for separate bracketry and extra parts attached to the beam. However, it is difficult to form features integrally into a rollformed beam during a rollforming process, since the process of rollforming produces a continuous cross section, while mounting features require some discontinuity, such as holes, hooks, and/or secondary mechanical deforming operations. Historically, energy absorbers made of plastic are not suitable for mounting, since the plastic is chosen to optimize energy absorption with a consistent energy-absorbing collapse (as opposed to bearing weight). Only recently have plastic materials been developed that are suitable to do both. Another problem is related to gross vehicle weight. Typically, bumper reinforcement beams are extended past the vehicle frame mounts to form bumper steps, with the beam providing the structure necessary to support the weight of a person stepping on the bumper ends. However, this results in considerable additional weight added to the bumper system, since reinforcement beams are metal and tend to be heavy. Thus, any distance that the beam extends laterally beyond the vehicle frame mounts adds undesirably to gross vehicle weight.  
           [0006]    Accordingly, a bumper system is desired solving the aforementioned problems and having the aforementioned advantages.  
         SUMMARY OF THE PRESENT INVENTION  
         [0007]    In one aspect of the present invention, a bumper system comprises a tubular bumper beam. A hitch-supporting bracket has an inverted section shaped to fit downwardly onto the tubular bumper beam, and further has a laterally-extending second section. A hitch support tube is secured to the laterally-extending second section and having a hole therein, the second section being shaped to support a ball hitch for hauling a trailer.  
           [0008]    In another aspect, a bumper system includes a tubular bumper beam that includes a center section, end sections, and bent interconnecting sections that interconnect each end section with an end of the center section, the center section being at least 25% of a length of the bumper beam and defining a longitudinal primary centerline, and the end sections being at least 15% of the length and each defining a secondary centerline that extends parallel the primary centerline. An energy absorber includes at least one rear recess shaped to receive a portion of the tubular bumper beam, and mounts adapted for attachment to a vehicle are attached to the end sections, the secondary centerline being spaced horizontally from the primary centerline when in a vehicle-mounted position.  
           [0009]    In another aspect, a bumper system includes a beam having a face and having mounts adapted for mounting to a vehicle frame, and an energy absorber engaging the face and having end sections located outboard of ends of the beam. The energy absorber is made of a structural engineering polymeric material and the end sections have flat top surfaces for forming steps outboard of the ends of the beam.  
           [0010]    In yet another aspect, a bumper system includes a beam having a face and having mounting structures adapted for mounting to a vehicle frame, and an energy absorber engaging the face and made of a structural engineering polymeric material. The energy absorber includes a honeycomb structure for absorbing energy upon a vehicle impact, and further includes accessory-mounting structures for mounting and supporting accessories on the energy absorber.  
           [0011]    In still another aspect, a bumper system includes an elongated reinforcement beam having a face and having opposing end sections adapted for attachment to mounts on a vehicle frame to support the bumper system. An energy absorber is provided made of a structural engineering polymeric material for absorbing impact forces against the beam during a collision. The energy absorber includes corner-forming sections extending outwardly from the end sections of the beam in cantilever, the corner-forming sections including top surfaces forming steps at opposite corners of the vehicle for supporting a person while being stepped upon by the person.  
           [0012]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    [0013]FIG. 1 is a perspective view of a rear bumper system embodying the present invention;  
         [0014]    [0014]FIG. 2 is an exploded perspective view of FIG. 1;  
         [0015]    [0015]FIG. 3 is a cross section taken along the line III-III in FIG. 1;  
         [0016]    [0016]FIG. 4 is an exploded view of FIG. 3;  
         [0017]    [0017]FIG. 5 is a cross section similar to FIG. 3 but of a modified bumper system; and  
         [0018]    [0018]FIG. 6 is an exploded view of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    The bumper system  20  (FIGS.  1 - 2 ) is designed for use as a rear bumper for a vehicle, such as for a sport utility vehicle or truck. The bumper system  20  includes a beam  21  and an energy absorber  22  with a recess in its vehicle-facing surface for receiving the beam  21 . A TPO plastic fascia (not specifically shown) covers the beam  21  and energy absorber  22  for aesthetics. The beam  21  may be rollformed or stamped and welded into a tubular shape, and/or hydroformed. It can have a rectangular, circular, or other cross section, but it is contemplated that the beam will be tubular for optimal torsional strength-to-weight ratio. The illustrated beam  21  is bent to include aligned opposing end sections  100  and  101 , an offset middle section  102 , and transition sections  103  and  104  that connect the end sections  100  and  101  to the middle section  102 . The end sections  100  and  101  of the beam  21  are aligned and define a first centerline  103 , and the middle section  102  defines a second centerline  104  that is spaced horizontally from the first centerline  103 . In the illustrated beam  21 , the first centerline  103  is spaced toward the vehicle on which the beam  20  is mounted. However, it is specifically contemplated that the first centerline  103  can be spaced rearwardly away from the vehicle instead, if that would be preferred. Preferably, the bends in transition sections  103  and  104  are made such that a full length of the top and bottom walls  105  and  106  is maintained in parallel horizontal planes, such that they provide good strength in a horizontal direction parallel an impact force during a vehicle crash. Advantageously, the offset position of the middle section  102  provides for a step and/or for a towing hitch and ball, as discussed below. At the same time, the shape of the beam  21  maintains a strong “foundation” for the bumper system  20 . Specifically, the mounts  26  are welded to or fastened to the end sections  100  and  101 , and the offset middle section  102  is located in the same horizontal plane as the mounts  26  but offset toward (or away from) the vehicle. Preferably, the end sections  100  and  101  are each about 15% to 20% of the beam length, and the center middle section  102  is about 25% to 30% of the beam length. These lengths provide an optimal mounting area on the end sections  100  and  101  and allow end sections  100  and  101  to be accurately positioned in an aligned condition, while also providing sufficient space on the hitch-side of the middle section  101  and also for providing accurate dimensional location of the middle section  102 . Nonetheless, the dimensions may vary depending on functional and design requirements of the bumper system.  
         [0020]    The energy absorber  22  includes an L-shaped middle section  109  defining a step, opposing transition sections  110  and  111  forming sides of the step, and corner sections  112  and  113  extending in cantilever outboard of the beam&#39;s end sections  100  and  101  that form corners of the vehicle. A fascia fits over the energy absorber  22  and is supported by the energy absorber  22 . A recess  115  is formed on a vehicle-side of the energy absorber  22  for mateably receiving the beam  20 , and includes a recess portion on a back side of the middle section  109  for receiving the middle section  102  of the beam  21  along with bracket  126  (see FIG. 3). The energy absorber  22  further includes a recess portion on a backside of the transition and corner sections  110 - 113  for receiving respective transition and end sections of the beam  21 . This creates a support structure for transferring loads to the beam  21 , both for step support and for energy absorption from impacts. Notably, it creates a corner step structure with a flat top surface located outboard of and beyond a length of the beam  21 . (See area B, FIG. 1.) This arrangement provides good corner impact strength and also provides a step located at an outer corner of the vehicle. The arrangement further provides reduced cost of low speed rear impacts, by providing a structure that is durable and less prone to dings, scratches, and corrosion than traditional stamped rear step bumpers.  
         [0021]    More specifically, the L-shaped middle section  109  (FIGS.  3 - 4 ) includes a horizontal leg  117  and an upright leg  118 . Apertures are formed in the legs  117  and  118  to reduce weight and to improve moldability. The corner section  112  and  113  are mirror images of each other, such that only corner section  112  need be described for an understanding by persons skilled in this art. The corner section  112  is not unlike the corner sections described above in regard to energy absorber  22 . The corner section  112  includes an outer “front” wall  120 , an interior “rear” wall  121 , and stiffening walls  122  that extend between the walls  120  and  121  to form a honeycomb-like structure optimally suited for energy absorption and stress distribution during a vehicle crash. The particular arrangement of the walls  120 - 122  can vary depending on functional and design requirements. For example, the walls  120 - 122  can be varied to provide mounting locations for accessories such as taillights, turn signal lights, license plate illuminating lights, and the like. This arrangement provides step support in area B (which is outboard of an end of the metal tubular beam  21 ). This arrangement also provides an integrated multiple-box-like crush cone at location A on each end of the energy absorber  22 . The crush cones of locations A are generally aligned with the vehicle frame rails, and reduce and manage loads into the vehicle frame during a rear impacts. The crush cone of area A include perpendicular parallel walls forming square tube sections  155 - 158  (i.e. “boxes within boxes”), each successive tube section being interconnected to the next with front or rear walls  159 .  
         [0022]    The illustrated energy absorber  22  (FIG. 1) is made of a structural engineering plastic, such as an ABS/PC blend (e.g. Xenoy™ made by General Electric Co) or PC/PBT blends. Because of a strength of these materials, the energy absorber  22  can include integrally formed accessory supporting structures, such as a housing  160  for supporting an electrical connector  161  adapted for connection to a trailer electrical connector plug, and/or a fascia-supporting brace  162  adapted for connection by a fastener to a lower flange of the rear end fascia to support the fascia on the vehicle, and/or wire harness retainers. The material of energy absorber  22  also allows other features to be integrated into the energy absorber  22 , such as a license plate support area including apertured bosses for receiving screws to secure the license plate to the bumper system, light housings for supporting license plate illuminating lights, cornering lighting, exterior vehicle lighting, and the like.  
         [0023]    The bumper system  20  (FIGS.  3 - 4 ) includes a hitch and ball support arrangement  125  described as follows. A hitch-supporting bracket  126  includes a U-shaped section  127  that faces downwardly and engages the middle section  102  of the beam  21 . A first leg  128  extends outwardly from a bottom edge of the outer side flange of the U-shaped section  127  at a height about equal to the bottom wall  106  of the beam  21 . A second leg  129  extends downwardly from a bottom edge of the inner side flange of the U-shaped section  127 , and optionally includes a perpendicular horizontal lip  130  at its lower end. A support bracket  131  includes a pair of spaced-apart triangularly shaped side walls  133  welded in place with welds  134  with a wide end under the bottom wall  106  of the beam  21  and that rest on the lip  130 . The support bracket  131  also optionally includes a horizontal flange  132  that connects sidewalls  133  and that abuts and supports an underside of the first leg  128  and/or abuts the leg  129  of the bracket  126 . The support bracket  131  may also include holes AA, which are appropriately sized for accepting safety chain hooks, with the support brackets  131  providing sufficient support to meet safety chain loading requirements.  
         [0024]    As illustrated in FIGS.  3 - 4 , a hitch support tube  135  extends horizontally under leg  128  of the support bracket  126 . An outer end of the hitch support tube  135  includes a radial face flange  136  for providing a blunt end on the support tube  135 . An inner end  137  of the hitch support tube  135  extends through an aperture  138  on the downwardly extending second leg  129 , with a top of the hitch tube  135  engaging the bottom wall  106  of the beam  21 , and with a bottom of the hitch tube  135  engaging and resting on the lip  130 . An L-shaped retainer  140  is welded or bolted to the inner end  137  of the hitch support tube  135  and/or a retainer bolt is extended through a hole  141  in the inner end  137  to positively and securely retain the hitch tube  135  to the beam  21  and prevent the hitch support tube  135  from being pulled out of the vehicle. On the outer end, a bolt  142  extends vertically through aligned holes  143  and  145  in the first leg  128  and the hitch support tube  135 , respectively, and a nut is threaded onto the bolt  142 . The aligned holes  143 - 145  can also receive a ball hitch  150  directly in place of the bolt  142 , if desired, such that the ball hitch is located “on” the step of the vehicle. By this arrangement, the ball hitch  150  can be mounted directly on the leg  128  and used for class III towing. For example, see FIGS.  5 - 6 , where the hitch tube  135  is eliminated, and the ball hitch  150  is supported on the leg  128 .  
         [0025]    In the arrangement of FIGS.  3 - 4 , a hitch bar  146  includes an end that fits matingly into the hitch support tube  135 , and a second end that extends horizontally outward from the vehicle and that drops downwardly a short distance. The hitch bar  146  includes a first hole that aligns with holes  143 - 145  for receiving the bolt  142  to retain the hitch bar  146  to the hitch support tube  135 . The hitch bar includes a second hole  147  for receiving the threaded stud  148  of a ball hitch  149 . This positions the ball hitch  149  rearward of the step of the bumper system  20  and also slightly lower, which is desirable in many towing situations.  
         [0026]    An important point of novelty of the present arrangement is that a hitch bar ( 146 ) is not required. Class III and higher towing is possible off of the step bumper itself, as shown in FIGS.  5 - 6 .  
         [0027]    Thus, the disclosed arrangements provide substantial torsional and tensile strength, such that they can be used for Class III towing without the use of additional add-on components and brackets. In particular, a step bumper arrangement is provided where a hitch tube is not required. (See FIGS.  5 - 6 .) Specifically, testing has shown that the present arrangements are suitable for class III towing, which requires support of a tongue weight of 500 lbs, and support of a towing weight of 5,000 lbs. Notably, this is a higher class than many previous step-bumper designs, which were class II and which supported tongue weights limited to 350 lbs. and which supported towing weights limited to only 3500 lbs.  
         [0028]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.