Abstract:
An improved bumper system includes a pair of brackets connected to the spaced frame members of a motor vehicle. A support arm is pivotally connected at one end to each of the brackets. The opposite end of each support arm is connected to a transverse beam that forms separate first and second bumper sections. The brackets support the support arms and bumper sections at a desired height above the ground. Each support arm is maintained relative to the respective bracket by gravity. A shear pin provides a redundant retention of the arm relative to the bracket. The arms and bumper sections of the improved bumper system remain in position relative to the bracket even in the event of a horizontal impact. A vertical impact of one or both bumper sections by obstacles or terrain causes the shear pin to be severed, allowing the bumper section(s) to pivot relative to the bracket, rather than to bend or deform.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to rear under-ride protection for motor vehicles. In particular, the present invention relates to a hinged bumper that avoids damage to the bumper in the event of a vertical force to the bumper. 
     The U.S. Department of Transportation (“U.S. D.O.T.”), Federal Highway Administration has prescribed safety regulations for federal motor carriers which in relevant part address rear end protection for motor vehicles. Specifically, motor vehicles manufactured after Dec. 31, 1952 which have a ground clearance at the rear end of more than thirty inches from the ground are required to have a bumper substantially constructed and firmly attached to the vehicle at a height of no more than thirty inches above the ground. In addition, the bumper may not be located more than twenty four inches forward of the extreme rear of the vehicle. The objective of this regulation is to ensure that the bumpers of larger motor vehicles approximate the height of the bumpers of smaller motor vehicles and thereby prevent, in the event of a collision, the smaller vehicles from under-riding the rear end of larger vehicles. 
     One way large vehicle operators have complied with this safety regulation is by welding or bolting a metal bumper to the frame of the motor vehicle. In such a case, a pair of spaced supports which carry the bumper are attached to the frame. The length and angle of the supports are selected to properly position the bumper. The bumper itself is typically formed from a heavy gauge metal beam and is welded to the supports. 
     Damage to the bumper other than by rear end vehicle collisions can occasionally occur. For example, for motor vehicles that operate on or off road, such as concrete mixing trucks, may encounter changes in ground elevation as the trucks are backing up, or as they are moving forward, which can result in rear bumper contact. Such contact between prior art bumpers and the ground can result in a vertical force being applied to the bumper. Other conditions may also result in a vertical force being applied to the bumper. If the vertical force from the contact is sufficient, a partial or complete bending of the bumper can result, with a consequent change in its elevation from level ground or its forward position relative to the extreme rear of the vehicle. This in turn requires that the bumper be repaired, if possible, or replaced, before the vehicle is again in compliance with the federally prescribed safety regulations. Thus, while the above described prior art bumpers comply with the safety regulations, their maintenance requires considerable time and expense. There is a need for an improved rear under-ride protection device for a motor vehicle that meets federal safety regulations and minimizes the time and cost of maintaining such a device. 
     BRIEF SUMMARY OF THE INVENTION 
     The bumper system of the present invention connects to the spaced frame members of a motor vehicle frame. The bumper system comprises a pair of brackets, each bracket having a first portion that is connectable to one of the frame members, and a second portion which provides a support surface. Connected to each bracket is an arm. A first end of each arm is pivotally connected to the second portion of one of the brackets. When the bracket is mounted to a frame member, the arm is supported by the support surface when the arm is in a first position, but the arm is movable about the pivotal connection. A bumper section having first and second ends is connected to the second end of each arm 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a concrete mixing truck with a bumper known in the art. 
     FIG. 2 is a perspective view of a motor vehicle frame with a prior art bumper. 
     FIG. 3 is a rear elevation view of a motor vehicle with a prior art bumper. 
     FIG. 4 is a rear view of a motor vehicle showing the improved bumper of the present invention. 
     FIG. 4A is a flat layout of the bracket for the bumper of the present invention. 
     FIG. 5 is a side elevation view of the bumper of the present invention. 
     FIG. 6 is a rear perspective view of the motor vehicle frame with the bumper of the present invention. 
    
    
     While the above-identified drawing figures set forth preferred embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the present invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. It should be specifically noted that the figures have not been drawn to scale, as it has been necessary to enlarge certain portions for clarity. 
     DETAILED DESCRIPTION 
     FIG. 1 shows an example of a utility vehicle  10  (e.g., a concrete mixing truck) which on occasion may be used off-road. Where the rear end  12  of vehicle  10  is greater than thirty inches above the ground, a bumper  14  must be incorporated into the vehicle to lower the effective height of the rear end of vehicle  10  to no more than thirty inches above the ground. 
     As shown in FIGS. 2 and 3, bumper  14  of the prior art is comprised of spaced support members  16 A,  16 B and cross member  18 . Support members  16 A and  16 B each are formed from angle iron and are bolted to vehicle frame members  20 A,  20 B, respectively. Cross member  18  consists of a metal beam that is welded to support members  16 A and  16 B. Cross member  18  has a length greater than the distance between supports  16 A,  16 B, resulting in end portions  18 A and  18 B, which extend to within 18 inches of the width of the motor vehicle. To the extent the bumper  14  contacts an object or the ground in the area of one or the other of end portions  18 A or  18 B, a particular end portion  18 A or  18 B may be bent out of alignment with cross member  18 , or cross member  18  may be bent relative to support members  16 A,  16 B. Depending on the extent of damage to cross member  18  or end portions  18 A or  18 B, bumper  14  may be repaired by bending the end portion back into alignment, or alternatively the entire bumper  14  may be replaced. In either event, maintenance of prior art bumper  14  involves time, effort and expense, and may be required to comply with federal motor carrier safety regulations. 
     FIG. 4 is a rear view of a motor vehicle showing the improved bumper  30  of the present invention. As shown in FIG. 4, bumper  30  generally comprises a pair of mounting brackets  32 A and  32 B, which are mounted to vehicle frame members  34 A and  34 B, respectively by a plurality of bolts  36 . Brackets  32 A and  32 B are mirror images of one another, with each bracket formed by bending plate metal to form a vertical portion  38  and a box  40  having walls  42 ,  44 ,  46  and  48 . Brackets  32 A and  32 B are further reinforced by ribs  50 , which are welded between vertical portion  38 , wall  42  and a portion of wall  44  of box  40 . Vertical portion  38  serves to connect brackets  32 A and  32 B to the respective vehicle frame member  34 A,  34 B. 
     Box  40  serves as a location for connecting and holding bumper mounting arms  52 A and  52 B. Each bumper mounting arm  52 A,  52 B is formed from a length of tubular metal that is dimensioned to fit between the inner surfaces of walls  44  and  48  of box  40 . One end of mounting arms  52 A,  52 B is connected to box  40 , between walls  44  and  48 , by a bolt  54 . The opposite end of mounting arms  52 A,  52 B is connected to bumper sections  56 A,  56 B, respectively, by welding. Bumper sections  56 A and  56 B are formed of tubular metal and are connected to arms  52 A,  52 B at approximately a mid-point of each section  56 A,  56 B. Bumper section  56 A is laterally spaced from bumper section  56 B by a small gap  58 . Bumper  30  thereby is configured with a split bumper for reasons that will be apparent from the following further description of the invention. 
     FIG. 4A is a flat layout of one of brackets  32 A,  32 B (i.e., bracket  32 ). Bracket  32  is formed from a sheet  31  of ASTM A36 grade steel having a thickness of about 0.25 inch. Bracket  32  is formed by bending sheet  31  along lines  37 ,  39 ,  41  and  43  to thereby define vertical section  38  and walls  42 ,  44 ,  46  and  48 . As can be seen in FIG. 4, the difference between brackets  32 A and  32 B (i.e., being mirror images) is defined by the direction of the bends along lines  37 ,  39 ,  41 , and  43 . Each of walls  42 ,  44 ,  46  and  48  are formed by making 90° bends along lines  37 ,  39 ,  41  and  43 . Referring again to FIG. 4A, the portion of sheet  31  corresponding to walls  42  and  44  is axially aligned with vertical section  38 , with lines  37  and  39  being parallel to one another and perpendicular to the outer edges of sheet  31  at walls  42  and  44 . The portion of sheet  31  corresponding to wall  46 , however, is formed at an angle relative to wall  44 , as defined by fold line  41 . The outer edges of the portion of sheet  31  corresponding to wall  48  are formed at an angle relative to the outer edges of wall  46 , with fold line  43  being parallel to line  41 . 
     In one demonstrative embodiment, sheet  31  has a width, defined by the outer edges of vertical section  38  and walls  42  and  44 , of about 7.75 inches. Walls  46  and  48  likewise have outer edges that define a width of about 7.75 inches, albeit initially offset before the bends are made to form brackets  32 A,  32 B. As measured from the top T of sheet  31 , bend line  37  is located about 7.76 inches from top T, and line  39  is located about 10.34 inches from top T. Line  41  is located about 15.68 inches from top T along edge A and about 14.37 inches from top T along edge B. Line  43  is located about 18.24 inches from top T along edge A and about 16.93 inches from top T along edge B. The outer edges of sheet  31  corresponding to wall  46  are parallel to one another, as are the outer edges of sheet  31  corresponding to wall  48 . Edge A of wall  46 , however, is angularly offset from that of wall  44  such that the corner C formed by fold line  43  is laterally offset from edge A of wall  44  by a distance of about 0.43 inches. Correspondingly, corner D of wall  48  is laterally offset from edge A of wall  44  by a distance of about 1.21 inches. The aforementioned dimensions are but one example of how to form brackets  32 A,  32 B. The dimensions may be varied without departing from the intended scope of the invention, as will be evident to those skilled in the art. 
     FIG. 5 is a side elevation view of bumper  30  from the perspective of frame member  34 B. As shown in FIG. 5, vertical section  38  of bracket  32 B is provided with a plurality of holes  60 , which match corresponding holes in frame member  34 B, through which bolts  36  are inserted for connecting bracket  32 B to frame member  34 B. While section  38  is illustrated with a particular shape to accommodate three holes  60 , it is contemplated that section  38  may be formed in any suitable configuration. In a preferred embodiment, vertical section  38  has a length sufficient to locate box  40  at or below the lowest extent of frame member  34 B, although the function of bracket  32 B is not dependent on the particular location of box  40  relative to frame member  34 B (i.e., box  40  maybe located above the lowest extent of frame member  34 B). 
     As further shown in FIG. 5, box  40  is configured to define a space for receiving arm  52 B that in cross-section is trapezoidal, with wall  46  being formed at an angle relative to wall  42 . Thus, in a preferred embodiment, wall  46  is sloped downward relative to the forward-most edge  62  of bracket  32 B. This downward slope prevents arm  52 B from pivoting upward in response to a horizontal force. Wall  46  thereby supports arm  52 B to maintain bumper section  56 B at the required height above the ground, and prevents arm  52 B from pivoting downward in the event of a horizontal rear impact. A plate  63  dimensioned according to the size and shape of the forward-most edge  62  of walls  42 ,  44 ,  46  and  48  is welded to forward-most edge  62  for additional support of brackets  32 A and  32 B. A second rib  65  forms an upper part of plate  63 , which ties plate  63  to wall  38  of brackets  32 A and  32 B for additional structural support. Rib  50  is secured to brackets  32 A and  32 B at the rearward-facing edge  68 . 
     As shown in FIGS. 5 and 6, arms  52 A,  52 B are provided with a hole  64 , which is spaced relative to forward-facing edge  62  and corresponds with holes in walls  44  and  48 , through which a bolt  54  is inserted to connect arm  52 B to bracket  32 B. A second hole  66  is formed in arms  52 A,  52 B rearward from hole  64 , with walls  44  and  48  having corresponding holes that align with hole  66  when arms  52 A,  52 B are resting on wall  46 . Hole  66  and the corresponding holes of walls  44  and  48  are provided for a shear pin  67 , which is a redundancy for maintaining arms  52 A,  52 B relative to wall  46  (i.e., the home position). 
     In the event a sufficient vertical force F 1  or F 2  is applied to one of bumper sections  56 A,  56 B (i.e., when the vehicle is moving forward or backward over ground of changing elevation), the shear pin is severed, and arm  52 B is capable of pivoting about bolt  54 , with a range of motion defined at the lower extent by wall  46  and at the upper extent by wall  42  (at rearward-facing edge  68  of bracket  32 B). The lower corner  70  of arms  52 A,  52 B adjacent to hole  64  (FIG. 5) are formed at an angle to prevent corner  70  from contacting wall  46  as arms  52 A,  52 B pivot. 
     Assuming for purposes of illustration that bumper section  56 B is affected, when the vehicle pulls away from the object or ground contacted, gravity causes arm  52 B and bumper section  56 B return to the home position. The weight of arm  52 B and bumper section  56 B is sufficient to keep bumper  30  at the required height above the ground until the shear pin can be replaced. Thus, bumper  30  can remain in compliance with U.S. D.O.T. regulations even without the shear pin in place. Because bumper  30  is formed in two sections, only that section making contact is affected. Bumper  30  of the present invention is thus an effective bumper design for eliminating or substantially reducing the time and cost of maintaining a rear under-ride protection device of a motor vehicle.