EP1509423A2

EP1509423A2 - Bumper with integrated energy absorber and beam

Info

Publication number: EP1509423A2
Application number: EP03757371A
Authority: EP
Inventors: Darin Evans
Original assignee: Shape Corp; Netshape Corp
Current assignee: Shape Corp; NetShape Energy Management LLC
Priority date: 2002-06-06
Filing date: 2003-06-06
Publication date: 2005-03-02
Also published as: WO2003104030B1; AU2003248628A1; AU2003248628A2; MXPA04012007A; CA2485712A1; CN1659067A; JP2005528286A; WO2003104030A3; CN100421999C; EP1509423A4; WO2003104030A2

Abstract

A bumper system includes a tubular beam with flattened end sections, and further includes an energy absorber having a rear recess mateably receiving the tubular beam in a nested relationship, with the recess also including flat mating surfaces engaging the flattened end sections. Mounts engage a rear of the flattened end sections, and fasteners secure the tubular beam and energy absorber to the mounts. In one modified bumper system, corner sections on the energy absorber are shaped to slidingly engage a side surface of the mount and simultaneously an end of the beam upon corner impact of the vehicle. In another modified bumper system, offset ends of the tubular beam fit into a recess in an energy absorber, with its center section being between vehicle mounts.

Description

BUMPERWITH INTEGRATED ENERGY ABSORBERAND BEAM

BACKGROUND The present invention relates to vehicle bumper systems, and more particularly relates to a bumper system having an integrated energy absorber and beam, novel beam constructions such as are shaped for engagement with mating energy absorbers, and to bumpers having a hitch adapted to haul a trailer or the like.

Bumper systems using integrated energy absorber and bumper beam arrangements are desired to improve assembly of bumper systems to vehicles, to minimize the number and types of mechanical fasteners overall, and to simplify tooling. In particular, it is desirable to provide a design where the beam and energy absorber can be assembled off-line of the main vehicle assembly line into a unitary subassembly, and then manipulated as a unit for attachment to the vehicle. Also, it is desirable to attach fascia to the subassembly, and to integrate and attach other components to the subassembly, such as headlights, grilles, and other functional and ornamental components. At the same time, impact durability and enhanced energy absorption continue to be high priority items in bumper systems, and accordingly, any subassembly should preferably not detract from the same.

In addition to the above, many vehicle manufacturers and some insurance groups and government entities are pressing for improved crashworthiness of vehicles, and also for bumper systems that will provide for better pedestrian safety. Longer bumper strokes with lower initial energy absorption rates have the possibility of satisfying these desires, but this can result in energy absorbers that are physically larger in size than present bumper systems, and that are not easy to package and carry at a front of the vehicle. Thus, new integrated bumper systems are desired to deal with the conflicting functional and design requirements.

Improvements are also desired in rear bumper systems on vehicles. In particular, vehicle manufacturers are looking increasingly at energy absorbers for rear bumper systems that are not dissimilar in shape and function to energy absorbers for front bumper systems. However, the energy absorber of any such rear bumper system must be integrated into the bumper system such that it does not interfere with other functional and aesthetic requirements at a rear of the vehicle. For example, many rear bumper systems include a step, and/or are adapted to support a ball hitch for hauling a trailer. 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.

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. Accordingly, bumper systems are desired solving the aforementioned problems and having the aforementioned advantages.

SUMMARY OF THE PRESENT INVENTION In one aspect of the present invention, a bumper system includes a metal tubular beam, a polymeric energy absorber, mounts and fasteners. The metal tubular beam includes front, rear, top, and bottom walls, with the front and rear walls being reformed at ends of the tubular beam to form end sections. The polymeric energy absorber has a rear surface with a recess mateably receiving the tubular beam. The recess includes mating flat surfaces engaging a front of the end sections. The energy absorber is configured to crush and absorb impact energy prior to collapse of the tubular beam. The mounts engage a rear of outer ends of the end sections. The energy absorber includes enlarged structural corner sections that extend outboard of the mounts and outboard of the outer ends of the beam for providing impact structure to a corner of the vehicle outboard of the beam and mounts. The fasteners secure the tubular beam and energy absorber to the mounts.

In another aspect of the present invention, a bumper system for a vehicle includes a metal beam, a one-piece polymeric energy absorber, mounts and fasteners. The metal beam has front, rear, top, and bottom walls defining a tubular center section and having end sections. The one-piece polymeric energy absorber has an absorber center section with a rear-facing recess mateably receiving the tubular center section and engaging portions of the front, top and bottom walls. The one-piece polymeric energy absorber further has corner sections with an interior surface located proximate an outer end of the end sections of the beam. The energy absorber is configured to crush and absorb impact energy prior to collapse of the tubular beam. The mounts engage a rear of the end sections. The interior surface of the corner sections are positioned to engage the outer end of the beam and to simultaneously engage an outer side surface of the mounts when the vehicle experiences a corner impact. The fasteners secure the tubular beam and energy absorber to the mounts.

In yet another aspect of the present invention, a bumper system for a vehicle having a passenger compartment is provided. The bumper system comprises a tubular bumper beam, an energy absorber and mounts. The tubular bumper beam 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 is at least 25 % of a length of the bumper beam and defines a longitudinal primary centerline. The end sections are at least 15% of the length and each define a secondary centerline that extends parallel the primary centerline. The energy absorber includes at least one recess shaped to receive a portion of the tubular bumper beam, with the energy absorber being configured to crush and absorb impact energy prior to collapse of the tubular beam. The mounts are adapted for attachment to a vehicle and are attached to the end sections. The secondary centerline is spaced horizontally from the primary centerline when in a vehicle-mounted position, with the center section being located partially between the mounts and closer to the passenger compartment than the end sections. The energy absorber includes enlarged structural corner sections that extend outboard of the mounts and outboard of the outer ends of the beam for providing impact structure to a corner of the vehicle outboard of the beam and mounts. An advantage of the present bumper systems is that some of the traditional front- end support structure can be simplified or eliminated. For example, the present inventive bumper system can include an energy absorber with portions that support the front-of-vehicle fascia in areas in front of the vehicle hood. This allows the front end support structure of the vehicle to be simplified, such as by eliminating fascia-supporting struts, by eliminating forwardly-extending flanges on the radiator cross support, by reducing the strength requirements on the radiator cross support and/or by eliminating or reducing strength requirements on a vehicle's front end panel.

In one aspect of the present invention, a bumper system comprises a tubular bumper beam and a hitch-supporting bracket with an inverted section fit downwardly onto the tubular bumper beam. The hitch-supporting bracket further has a laterally- extending second section with a hole therein, with the second section being shaped to support a ball hitch for hauling a trailer.

In another aspect of the present invention, a bumper system for a vehicle includes a tubular bumper beam having a center section, end sections, and bent interconnecting sections that interconnect each end section with an end of the center section. The center section is at least 25 % of a length of the bumper beam and defines a longitudinal primary centerline. The end sections are at least 15% of the length and each define a secondary centerline that extends parallel the primary centerline. An energy absorber includes at least one recess that is shaped to receive a portion of the tubular bumper beam. Mounts adapted for attachment to a vehicle are attached to the end sections. The secondary centerline is spaced horizontally from the primary centerline when in a vehicle-mounted position.

In another aspect of the present invention, a bumper system for a vehicle 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. In still another aspect of the present invention, a bumper system for a vehicle 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.

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 Fig. 1 is a perspective view of a bumper system embodying the present invention, including an energy absorber and a tubular beam with flattened ends positioned within a rear-facing recess in the energy absorber;

Fig. 2 is an exploded view of Fig. 1;

Figs. 3 and 4 are cross sections taken along lines III-III and IV-IV in Fig. 2; Fig. 5 is a fragmentary top schematic view of the bumper system of Fig. 1; Fig. 6 is an exploded perspective view of another bumper system embodying the present invention;

Fig. 7 is a perspective view of the bumper system of Fig. 6, a portion of the energy absorber being removed to better show engagement of the energy absorber with the beam;

Fig. 8 is a cross section taken along line VIII-NIII in Fig. 7; Fig. 9 is a cross section of an alternative bumper system, the cross section being similar to Fig. 8, and Fig. 9 A is a fragmentary perspective view of an apertured version of the U-beam shown in Fig. 9;

Fig. 10 is a perspective view of a rear bumper system embodying the present invention; Fig. 11 is an exploded perspective view of Fig. 10;

Fig. 12 is a cross section taken along the line III-III in Fig. 10; Fig. 13 is an exploded view of Fig. 12;

Fig. 14 is a cross section similar to Fig. 12 but of a modified bumper system; and Fig. 15 is an exploded view of Fig. 14. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A bumper system 20 (Fig. 1) includes a beam 21 with a tubular center section and flattened end sections 23 and 24, and a molded energy absorber 22 adapted to nestingly receive the beam 21 to form a unitary subassembly that can be handled and assembled as a unit to a vehicle. The flattened end sections 23 and 24 form vertically enlarged attachment members or "hands" on each end of the beam 21 that engage mating flat surfaces on the energy absorber 22. Mounts 26 abuttingly engage a rear of the flattened end sections 23 and 24, and fasteners 27 extend through the energy absorber 22 and the flattened end sections 23 and 24 to secure the tubular beam 21 and energy absorber 22 to the mounts 26. It is contemplated that the term "mount" as used herein includes a rail extending from a vehicle frame, or similar structural frame component.

The beam 21 (Fig. 1) is described in sufficient detail below for an understanding of the present invention by persons skilled in this art. Nonetheless, if additional discussion is desired, the reader's attention is directed to application Serial No. 09/822,658, filed November 1, 2001, entitled METHOD OF FORMING A ONE-

PIECE TUBULAR BEAM, and application Serial No. 09/904,066, filed March 30, 2002, entitled ROLLFORMED AND STAMPED DOOR BEAM, and also patent 5,092,512, issued March 3, 1992, entitled METHOD OF ROLLFORMING AN AUTOMOTIVE BUMPER. Different vehicle mounts can be used with the present invention. The mounts illustrated in Fig. 2 are described in sufficient detail below for an understanding by persons skilled in the art. Nonetheless, if additional discussion is desired, the reader's attention is directed to application Serial No. 09/964,914, filed September 27, 2001, entitled BUMPER CRUSH TOWER WITH RINGS OF VARIED STRENGTH. Beam 21 (Fig. 2) includes a tubular center section 28 having a square cross section defined by front, rear, top, and bottom walls. The beam 21 is rollformed to a desired tubular shape, welded along a weld bead 29 located at a middle of the rear wall, and then swept into a curvilinear shape that matches a front end (or rear end) of a selected model vehicle. It is noted that different cross sections can be used, if desired. The weld bead 29 stops short of an end of the beam 21, and about 6 to 8 inches of an end of the walls are reformed and "opened up" to a relatively coplanar flat condition to form the flattened end sections 23 and 24. A pattern of holes 30 are formed in the flattened end sections 23 and 24, which correspond to attachment holes in the mount 26. Energy absorber 22 (Fig. 2) includes an injection-molded member made from a suitable non-foam polymeric material having good properties for absorbing energy upon impact, such as Xenoy material. The non-foam material substantially forms the structure of energy absorber 22, including box-shaped sections 33, which are molded along rail 34 at strategic locations for improved impact properties, as described below. The box-shaped sections 33 include vertical sidewalls 33 ' and top and bottom walls 33 " that combine with front wall 39' to form a hollow internal cavity. The center section of the energy absorber includes horizontal upper and lower rails 34 and 35, both of which have rearwardly-facing U-shaped cross sections. The upper rail 34 defines a large portion of the rearwardly-facing recess 25 (Fig. 4), which is shaped to closely receive the center tubular section of the beam 21. The box-shaped sections 33 are molded onto top, front and bottom surfaces of the upper rail 34 at strategic locations along its length. Two such sections 33 are shown, but more or less can be used. The sections 33 provide improved energy absorbing characteristics to the bumper system 20, and further the sections 33 have an upper surface shaped to support the vehicle front fascia 36, which is typically a low stiffness or TPO material that requires support against the forces of gravity. The energy absorber 22 (Fig. 2) also includes mounting sections 38 that form integrated crush boxes over the mounts 26 at each end of the center section 28. The mounting sections 38 (Fig. 3) each include a rectangular ring-shaped planar outer front wall 39, rearwardly-extending walls 40 forming an open "C" shape that extends rearwardly from the front wall 39, a rectangular ring-shaped planar rear wall 41 that extends from the rearwardly-extending walls 40, forwardly-extending walls 42 that form a square tube shape that extends forwardly from the rear wall 41, a rectangular ring- shaped planar inner front wall 43 that extends from the forwardly-extending walls 42, and an interior stiffener flange 44 that extends rearwardly from the inner front wall 43. Additional stiffening webs can be extended between the rearwardly-extending walls 40 and the forwardly-extending walls 42 as needed for stiffness and structure in the energy absorber 22. A plurality of legs 35 ' extend below the lower rail 35, such as for supporting a bottom of the TPO fascia on a front of the vehicle. The flattened end section 23 (and 24) (Fig. 3) includes a flat front surface that mateably engages the flat rear surface of the planar rear wall 41. The mount 26 includes a tubular section 47 (e.g. a crush tower for optimal energy absorption in front impact), a rear plate shaped for connection to a vehicle, such as to vehicle frame members, and a front plate 49 shaped to mateably engage a flat rear surface on the end section 23 (and

24). Fasteners, such as bolts 50 are extended through aligned holes in the planar rear wall 41, in the flattened end sections 23 (and 24), and the front plate 49. Notably, the tubular portion of beam 21 (i.e., center section 28) extends short of the mounts 26 (see Fig. 5), and further the flattened end sections 23 (and 24) extend only to the outer edges of the mounts 26, for reasons discussed below.

The energy absorber 22 includes corner sections 52 (Fig. 2 and 5) having an apertured front wall 53, an apertured rear wall 54, and reinforcing walls 55 that extend between the front and rear walls 52 and 53 for structural support. The front wall 53 curves rearwardly at its outer edge to form an aerodynamic shape at a front of the vehicle fenders. Further, the reinforcing walls 55 include a top wall 56 shaped to structurally support portions of an RRIM fascia in the area of a vehicle front fender. Also, the corner section 52 includes a tubular canister portion 57 and canister-mounting structure 58 for adjustably securely supporting a fog lamp assembly 59 (and/or a turn signal assembly). As shown in Fig. 5, the corner section(s) 52 include a rearwardly-extending box section 60 that is outboard of the mount 26 and positioned adjacent an end of the flattened end sections 23 (and 24). During a corner impact by an object 61, forces are transmitted along lines 62 and 63 into the corner section 52. The angled forces 63 are directed through the box section 60 at an angle toward a side surface of the mount 26. The angled forces cause the corner section 52 to bend rearwardly in direction 64, sliding rearwardly slightly along line 64 ' on the mount 26 (depending on the magnitude of the forces 63). This action tends to allow the angled forces to relieve themselves, and also tends to cause the object 61 to bounce sideways off the vehicle bumper system 20.

When an object 66 is struck in a front impact directly in-line with the mounts 26, the forces 67 are transmitted directly against the mount 26 in a manner permitting the mount 26 to absorb forces in a telescoping manner like it historically is designed (i.e. , the forces are linear and permit the tubular section 47 to telescopingly crush and collapse in a predictable manner.) When the bumper system 20 is struck in a center area between the mounts 26, the impact is primarily transmitted linearly into the mounts 26, due to the strength of the beam 21. Nonetheless, it is noted that with the present beam 21 , some bending may occur, depending on a width of the impact area on the bumper system 20 and how nearly it is perfectly centered on the bumper system 20.

In the modified bumper system 20A (Figs. 6-8), a beam 21 A similar to beam 21 is provided, and a "longer stroke" energy absorber 22 A is attached to its face. The energy absorber 22A includes upper and lower U-shaped rails 34A and 35A that open rearwardly. The rails 34A and 35A are connected by vertical webs 65A that extend fore/aft, and by a rear wall 66A that extends across a back of the energy absorber 22A.

Flanges 67A and 68 A extend rearwardly from the rear wall 66A. The flanges 67 A and 68A engage and cover top and bottom walls of the beam 21A, and include fingers 67A ' and 68 A ' for snap-locking onto the beam 21 A for temporary securement of the energy absorber 22A to the beam 21 A. In energy absorber 22 A, the corner sections 52 A also form the mounting section of the energy absorber 22 A. Specifically, the corner sections

52A include a flat rear wall 70A, and perpendicular walls 71A forming a box around the flat rear wall 70A. The end section 23 A (and 24A) of the beam 21 A engage a rear surface of the flat rear wall 70A, and fasteners (e.g., bolts) are extended through aligned holes in the flat rear wall 70A, the flattened sections 23 A (and 24A), and the front plate of the mount (26) to which it is attached.

A rear "root" portion 72A of the inner wall of the rails 34A and 35A is offset slightly from the flanges 67 A and 68 A (Fig. 8), and also is offset from the corresponding top and bottom walls of the beam 21A. Upon front impact, the rails 34A and 35A are driven rearwardly. Due to the stiffness of the beam 21A, this causes the "root" portion 72A of the energy absorber 22 A to buckle and fold onto itself and onto the flanges 67 A and 68 A, as shown by arrows 73 A. The result is a much more predictable and "softer" impact. At such time as the energy absorber 22 A is completely crushed, forces from the impact are directly transmitted to the beam 21 A, providing a force versus deflection force curve increases sharply over the initial force versus deflection curve.

The bumper system 20B (Fig. 9) is not unlike the bumper system 20A (Figs. 6- 7), but in system 20B the beam 21B is U-shaped (i.e., is not tubular), and further it is insert-molded into a center of the energy absorber 22B. In the bumper system 20B, the beam 2 IB includes a plurality of apertures or holes to allow the plastic material of the energy absorber to flow through and interlock with the metal beam 2 IB, thus providing better bonding and preventing de-lamination. It is noted that the apertures 75B may reduce a bending strength of the beam 2 IB, depending on their location. The illustrated apertures 75B are located only on the vertical flange 76B of the beam 2 IB, such that they do not greatly affect bending strength in a direction parallel an impact force. Nonetheless, the location and shape of the apertures 75B can be a desirable thing by helping distribute and relieve stress in some specific vehicle applications. It is noted that a strength of the tubular portion of the beam 2 IB (or beams 21 A or 21) can be substantially increased by press-fitting within the tubular portion an internal energy absorber, such as is illustrated in Figs. 1-2 and 10-11. The internal energy absorber tends to reduce a tendency of the beam to prematurely kink or bend, resulting in a consistently higher and more predictable energy of absorption during impact.

The bumper system 20C (Figs. 10-11) is designed for use as a rear bumper for a vehicle, such as for a sport utility vehicle or truck. The bumper system 20C includes a beam 21C and an energy absorber 22C with a recess in its vehicle-facing surface for receiving the beam 21C. A TPO plastic fascia (not specifically shown) covers the beam 21C and energy absorber 22C for aesthetics. The beam 21C 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 21C 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 21C 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 21C, the first centerline 103 is spaced toward the vehicle on which the beam 21C 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 21C maintains a strong "foundation" for the bumper system 20C. Specifically, the mounts 26C 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 26C 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.

The energy absorber 22C 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 that form corners of the vehicle. A fascia fits over the energy absorber 22C and is supported by the energy absorber 22C. A recess 115 is formed on a vehicle-side of the energy absorber 22C for mateably receiving the beam 21 C, and includes a recess portion on a back side of the middle section 109 for receiving the middle section 102 of the beam 21C along with bracket 126 (see Fig. 12). The energy absorber 22C 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 21C. This creates a support structure for transferring loads to the beam 21C, 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 21C. (See area B, Fig. 10.) 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. More specifically, the L-shaped middle section 109 (Figs. 12-13) 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 22C. 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 21C). This arrangement also provides an integrated multiple-box-like crush cone at location A on each end of the energy absorber

22C. 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.

The illustrated energy absorber 22C (Fig. 10) 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 22C 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 22C also allows other features to be integrated into the energy absorber 22C, 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. The bumper system 20C (Figs. 12-13) 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 21C. 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 21C. 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 21C 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.

As illustrated in Figs. 12-13, 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 21C, 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 21C 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. 14-15, where the hitch tube 135 is eliminated, and the ball hitch 150 is supported on the leg 128. In the arrangement of Figs. 12-13, 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 20C and also slightly lower, which is desirable in many towing situations.

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. 14-15.

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. 14-15.) 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.

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.

Claims

The invention claimed is:

1. A bumper system comprising: a metal tubular beam with front, rear, top, and bottom walls, the front and rear walls being reformed at ends of the tubular beam to form end sections; a polymeric energy absorber having a rear surface with a recess mateably receiving the tubular beam, the recess including mating flat surfaces engaging a front of the end sections, the energy absorber being configured to crush and absorb impact energy prior to collapse of the tubular beam; mounts engaging a rear of outer ends of the end sections, the energy absorber including enlarged structural corner sections that extend outboard of the mounts and outboard of the outer ends of the beam for providing impact structure to a corner of the vehicle outboard of the beam and mounts; and fasteners securing the tubular beam and energy absorber to the mounts.

2. The bumper system defined in claim 1 , wherein the mounts include flat plates that engage the rear of the flattened end sections.

3. The bumper system defined in claim 1, wherein the energy absorber includes a rearwardly-facing U-shaped section of non-foam polymeric material that defines top and bottom portions of the recess.

4. The bumper system defined in claim 3, wherein the energy absorber includes foam sections of material that cover at least three sides of the rearwardly-facing U- shaped section.

5. The bumper system defined in claim 3, wherein the U-shaped section defines a horizontal rail on the energy absorber.

6. The bumper system defined in claim 1, wherein the energy absorber includes structure adapted to support headlight apparatus and further includes through-holes for passing light from the headlight apparatus.

7. The bumper system defined in claim 1, wherein the fasteners include shafts that extend through the energy absorber and through the beam ends into the mounts.

8. The bumper system defined in claim 1, wherein the energy absorber includes comer sections forming at least one honeycomb-shaped structure for absorbing impact energy during a vehicle crash, the corner sections extending around and rearward of the ends of the beam.

9. The bumper system defined in claim 8, wherein the comer sections include a portion located proximate the mounts, the co er sections being configured to flex, engage and slide on a side of the mounts during a comer impact that is directed along a line angled with respect of a length of the mounts, and being configured to engage and crush against the mounts during a front impact that is parallel a length of the mounts.

10. The bumper system defined in claim 8, wherein the comer sections of the energy absorber each include a flat top wall and reinforcing walls supporting the top wall adapted to structurally support fascia on the top wall covering the corner sections.

11. The bumper system defined in claim 1 , wherein the fasteners comprise bolts.

12. A bumper system for a vehicle comprising: a metal beam having front, rear, top, and bottom walls defining a tubular center section and having end sections; a one-piece polymeric energy absorber having an absorber center section with a rear-facing recess mateably receiving the tubular center section and engaging portions of the front, top and bottom walls; and further having corner sections with an interior surface located proximate an outer end of the end sections of the beam; the energy absorber being configured to crush and absorb impact energy prior to collapse of the tubular beam; mounts engaging a rear of the end sections, the interior surface of the comer sections being positioned to engage the outer end of the beam and to simultaneously engage an outer side surface of the mounts when the vehicle experiences a comer impact; and fasteners that secure the tubular beam and energy absorber to the mounts.

13. The bumper system defined in claim 12, wherein the comer sections include a portion located proximate the mounts, the corner sections being configured to flex, engage, and slide on a side of the mounts during a comer impact that is directed along a line angled with respect of a length of the mounts, and being configured to engage and crush against the mounts during a front impact that is parallel a length of the mounts.

14. The bumper system defined in claim 12, wherein the energy absorber includes a rearwardly-facing U-shaped section of non-foam polymeric material that defines top and bottom portions of the recess.

15. The bumper system defined in claim 14, wherein the energy absorber includes foam sections of material that cover at least three sides of the rearwardly-facing U- shaped section.

16. The bumper system defined in claim 14, wherein the U-shaped section defines a horizontal rail on the energy absorber.

17. The bumper system defined in claim 12, wherein the energy absorber includes structure adapted to support headlight cans and further includes through-holes for passing light from the headlight cans.

18. The bumper system defined in claim 12, wherein the fasteners includes shafts that extend through the energy absorber and through the beam ends into the mounts.

19. The bumper system defined in claim 12, wherein the comer sections form at least one honeycomb-shaped structure for absorbing impact energy during a vehicle crash, the corner sections extending around and rearward of the end sections of the beam.

20. The bumper system defined in claim 12, wherein the fasteners comprise bolts.

21. The bumper system defined in claim 12, wherein the top walls of the comer sections of the energy absorber each include a flat portion and including reinforcing walls adapted to structurally support fascia on the top wall covering the corner sections.

22. A bumper system for a vehicle having a passenger compartment, comprising: 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 with at least one recess shaped to receive a portion of the tubular bumper beam, the energy absorber being configured to crush and absorb impact energy prior to collapse of the tubular beam; and mounts adapted for attachment to a vehicle and that are attached to the end sections, the secondary centerline being spaced horizontally from the primary centerline when in a vehicle-mounted position, with the center section being located partially between the mounts and closer to the passenger compartment than the end sections, the energy absorber including enlarged stmctural corner sections that extend outboard of the mounts and outboard of the outer ends of the beam for providing impact structure to a corner of the vehicle outboard of the beam and mounts.

23. A bumper system comprising: a tubular bumper beam; and a hitch-supporting bracket having an inverted section shaped to fit downwardly onto the tubular bumper beam, and further having a laterally-extending second section with a hole therein, the second section being shaped to support a ball hitch for hauling a trailer.

24. The bumper system defined in claim 23, wherein the inverted section is U-shaped and shaped to straddle the bumper beam.

25. The bumper system defined in claim 24, wherein the second section includes a panel that extends horizontally when in a vehicle-mounted position.

26. The bumper system defined in claim 25, wherein the inverted section includes a long leg that extends downwardly below a height of the panel, and further including a hitch support tube that extends perpendicular to the bumper beam, the hitch support tube extending from the long leg under the bumper beam and supportingly under the panel.

27. The bumper system defined in claim 26, wherein the long leg includes a lip at its lower free end, and wherein the hitch support tube includes an end resting on the lip.

28. The bumper system defined in claim 26, wherein the end of the hitch support tube extends through an aperture in the long leg, and including a retainer that extends through the end on a back side of the long leg for retaining the hitch support tube to the bracket despite substantial towing forces acting on the hitch support tube.

29. The bumper system defined in claim 26, wherein the panel and the hitch support tube include aligned holes shaped to receive a stem of a ball hitch.

30. The bumper system defined in claim 26, including a support bracket positioned under the hitch-supporting bracket and engaging the long leg and the panel, the support bracket being shaped to support the panel in a horizontal orientation relative to the hitch- supporting bracket and including holes shaped to provide an attachment point of sufficient strength to engage and support a safety chain.

31. The bumper system defined in claim 23, including an energy absorber that substantially covers the beam and hitch-supporting bracket, and that extends outboard of ends of the beam.

32. The bumper system defined in claim 23, wherein the 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.

33. The bumper system defined in claim 32, including mounts attached to the end sections of the bumper beam, the secondary centerline being spaced horizontally from the primary centerline when in a vehicle-mounted position.

34. The bumper system defined in claim 33, including an energy absorber positioned on a face of the bumper beam, with at least a portion of the hitch-supporting bracket being located under a center of the energy absorber.

35. A bumper system for a vehicle, comprising: a tubular bumper beam having 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 with at least one recess shaped to receive a portion of the tubular bumper beam; and mounts adapted for attachment to a vehicle and that are attached to the end sections, the secondary centerline being spaced horizontally from the primary centerline when in a vehicle-mounted position.

36. The bumper system defined in claim 35, wherein the center section is located partially between the mounts and farther from the passenger compartment than the end sections.

37. A bumper system for a vehicle comprising: 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 being made of a stmctural engineering polymeric material and the end sections having flat top surfaces for forming steps outboard of the ends of the beam.

38. The bumper system defined in claim 37, wherein the beam comprises a tubular beam.

39. A bumper system for a vehicle comprising: a beam having a face and having mounting stmctures adapted for mounting to a vehicle frame; and an energy absorber engaging the face and made of a stmctural engineering polymeric material, the energy absorber including a honeycomb stmcture for absorbing energy upon a vehicle impact, and further including accessory-mounting stmctures for mounting and supporting accessories on the energy absorber.

40. The bumper system defined in claim 39, wherein the accessory-mounting stmctures include an integrally-formed molded-in stmcture shaped and adapted to house and retain an electrical accessory.

41. The bumper system defined in claim 40, including an electrical connector attached to the molded-in stmcture.

42. The bumper system defined in claim 41, including a bracket attached to and supported by the beam and forming a step.

43. The bumper system defined in claim 39, wherein the energy absorber includes end sections that extend outboard of ends of the beam, the end sections having a flat top surface and being stmctural such that the end sections form steps located outboard of the ends of the beam.

44. A bumper system comprising: a metal tubular beam with a center section having front, rear, top, and bottom walls; an energy absorber including a rail having a rear surface with a rearwardly- facing C-shaped recess mateably receiving the tubular beam therein, the energy absorber being configured to crush and absorb impact energy prior to collapse of the tubular beam; and mounts engaging a rear of the metal tubular beam.

45. A bumper system comprising: a metal tubular beam with a center section having front, rear, top, and bottom walls; an energy absorber including a rail having a rear surface with a rearwardly- facing C-shaped recess mateably receiving the tubular beam therein, the energy absorber being configured to c sh and absorb impact energy prior to collapse of the tubular beam; and mounts engaging a rear of the metal tubular beam.

46. The bumper system defined in claim 45, wherein the rear surface of the rail includes a pair of flanges that surround a rear surface of the metal tubular beam received within the rail, whereby the rail covers the front, rear, top and bottom walls of the center section of the metal tubular beam.

47. The bumper system defined in claim 45, wherein the energy absorber includes foam sections of material that cover at least three sides of the rearwardly-facing C- shaped recess.

48. The bumper system defined in claim 45, wherein rearwardly-facing C-shaped recess defines a horizontal rail on the energy absorber.

49. The bumper system defined in claim 45, wherein the energy absorber includes stmcture adapted to support headlight apparatus and further includes through-holes for passing light from the headlight apparatus.

50. The bumper system defined in claim 45, wherein the energy absorber includes comer sections forming at least one honeycomb-shaped stmcture for absorbing impact energy during a vehicle crash, the corner sections extending around and rearward of the ends of the beam.

51. The bumper system defined in claim 50, wherein the comer sections include a portion located proximate the mounts, the corner sections being configured to flex, engage and slide on a side of the mounts during a comer impact that is directed along a line angled with respect of a length of the mounts, and being configured to engage and crush against the mounts during a front impact that is parallel a length of the mounts.

52. The bumper system defined in claim 51 , wherein the comer sections of the energy absorber each include a flat top wall and reinforcing walls supporting the top wall adapted to structurally support fascia on the top wall covering the corner sections.

53. A bumper system comprising: a metal tubular beam; a polymeric energy absorber having a rear surface with a recess mateably receiving the tubular beam, the energy absorber being configured to cmsh and absorb impact energy prior to collapse of the tubular beam; mounts engaging a rear of the metal tubular beam; wherein the energy absorber includes enlarged stmctural corner sections that extend outboard of the mounts and outboard of outer ends of the beam for providing impact stmcture to a comer of the vehicle outboard of the beam and mounts; and wherein the comer sections form at least one honeycomb-shaped stmcture for absorbing impact energy during a vehicle crash, the comer sections further providing a top surface configured to support a force placed thereon.

54. The bumper system defined in claim 53, wherein the comer sections include an apertured front wall, an apertured rear wall and reinforcing walls extending between the front wall and the rear wall.

55. The bumper system defined in claim 54, wherein the front wall and the rear wall are substantially vertical and the reinforcing walls are substantially horizontal.

56. The bumper system defined in claim 55, wherein the top surface is located on a topmost one of the reinforcing walls.

57. A bumper system comprising: a metal tubular beam; an energy absorber having a rear surface with a recess mateably receiving the tubular beam, the energy absorber being configured to cmsh and absorb impact energy prior to collapse of the tubular beam; mounts engaging a rear of the metal tubular beam; wherein the energy absorber includes enlarged stmctural corner sections that extend outboard of the mounts and outboard of outer ends of the beam for providing impact stmcture to a comer of the vehicle outboard of the beam and mounts; and wherein the comer sections include a portion located proximate the mounts, the corner sections being configured to flex, engage and slide on a side of the mounts during a comer impact by an object directed along a line angled with respect of a length of the mounts, whereby the object bounces sideways off the corner section in a direction parallel to a longitudinal direction of the energy absorber upon the corner impact.

58. A bumper system comprising: a metal beam with a center section; an energy absorber including a rail having the beam therein, the energy absorber being configured to cmsh and absorb impact energy prior to collapse of the beam; and mounts engaging a rear of the metal beam; the energy absorber including a top section connected to a top portion of the rail and a bottom section connected to a bottom portion of the rail; the top section having an upwardly angled top first segment extending from the rail and a forwardly extending top second segment extending from the first segment; the bottom section having a downwardly angled bottom first segment extending from the rail and a forwardly extending bottom second segment extending from the first segment; wherein the upwardly angled top first segment folds rearwardly over a top face of the rail during a front impact of the forwardly extending top second segment; and wherein the downwardly angled bottom first segment folds rearwardly over a bottom face of the rail during a front impact of the forwardly extending bottom second segment.

59. The bumper system defined in claim 58, wherein the metal beam is tubular and includes front, rear, top, and bottom walls, and the rail has a rear surface with a recess mateably receiving the tubular beam therein.

60. The bumper system defined in claim 58, wherein the energy absorber includes a rail encapsulating the tubular beam.

61. The bumper system defined in claim 60, wherein the rail is U-shaped.

62. The bumper system defined in claim 61, wherein a front wall of the rail includes apertures therethrough.