Abstract:
A head assembly for a guardrail extruder terminal device. A head assembly is described that is lighter and more effective than prior art head assemblies. The head assembly provides a throat that receives a corrugated guardrail. The rail is flattened by a narrowing of the throat or through combined action of the throat and a curved deflector plate. A curved plate contacts the flattened rail and extrudes it away from the head assembly. The throat is constructed from a pair of side members. The first side member is an elongated plate while the second side member is a short plate. The impact plate of the head assembly is vertically elongated and presents upper and lower overhangs that assist with vehicle engagement. In addition, the impact plate is provided with flanges on either side to help stiffen the plate. The head is also asymmetrical and streamlined. When the impact head is mounted on a rail member, the central point of impact is off-center with respect to the axis of the head.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the priority of U.S. Provisional Patent Application No. 60/229,486 filed Aug. 31, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to guardrail extruder devices used with guardrail installations. In particular aspects, the invention relates to the design of impact head assemblies for such devices.  
           [0004]    2. Description of the Related Art  
           [0005]    Guardrail extruder terminals are a popular and effective end treatment for guardrail installations. During an end-on impact to a guardrail end, a guardrail extruder terminal will flatten and bend a corrugated rail member and extrude the flattened portion away from the roadway. Terminals of this type are described in U.S. Pat. Nos. 5,078,366 and 4,928,928.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides an improved head assembly for a guardrail extruder terminal device. An exemplary head assembly is described that is lighter and more effective than prior art head assemblies. The exemplary head assembly provides a throat that receives a corrugated guardrail. In preferred embodiments, the throat is a squeezing throat that is narrower at the upstream end than at the downstream end. The squeezing throat compresses a rail and flattens it. A curved plate contacts the rail and extrudes it away from the head assembly. The throat is constructed from a pair of side members. In a first described embodiment, the first side member is an elongated, S-shaped plate while the second side member is a short curved plate. Alternative head constructions are described wherein the throat is constructed from side members that are formed of flat plates rather than curved plates. The flat plates may be tapered such that the upstream end of the throat is narrower than the downstream end. Alternatively, the flat plates may be non-tapered wherein the squeezing is accomplished through combined action of the throat and curved deflector plate.  
           [0007]    The impact plate of the head assembly is vertically elongated and presents upper and lower overhangs that assist with vehicle engagement. In addition, the impact plate is provided with flanges on either side to help stiffen the plate. The head is also asymmetrical and streamlined. When the impact head is mounted on a rail member, the central point of impact is off-center with respect to the axis of the head. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is an isometric view of an exemplary guardrail extruder terminal head constructed in accordance with the present invention.  
         [0009]    [0009]FIG. 2 is a plan, cross-sectional view of the head taken along the lines  2 - 2  in FIG. 1.  
         [0010]    [0010]FIG. 3 is an exploded view of the head shown in FIGS.  1 - 2 .  
         [0011]    [0011]FIG. 4 is a plan view of the head of FIGS.  1 - 3  shown affixed to a support post.  
         [0012]    [0012]FIG. 5 is a side view of the head shown in FIG. 4.  
         [0013]    [0013]FIG. 6 is a plan, cross-sectional view of an alternative head having a throat with side members that are substantially flat and angled relative to each other.  
         [0014]    [0014]FIG. 7 is a plan, cross-sectional view of a further alternative head having a throat with side members that are substantially flat and parallel to each other.  
         [0015]    [0015]FIG. 8 is an isometric illustration of an guardrail head having an exemplary feeder chute bumper device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    FIGS.  1 - 5  illustrate a first improved head assembly  10  used for a guardrail extruder terminal of the type described generally in U.S. Pat. Nos. 5,078,366 and 4,928,928 . The general operation of guardrail extruder terminal devices is described in those two patents and they are incorporated herein by reference. The head assembly  10  is shown (in FIG. 1) positioned on the end of a corrugated, or W-beam, guardrail  12 .  
         [0017]    The head assembly  10  generally includes an impact portion  14  and an elongated rail feeder chute  16 . The rail feeder chute  16  surrounds the upstream portion of the rail member  12  and is made up of an upper, U-shaped channel member  18  and a lower, U-shaped channel member  20  which are secured in a spaced relation from one another by strap plates  22 . L-shaped brackets  24 ,  16  are affixed to the upper and lower channels members  18 ,  20 , respectively.  
         [0018]    The impact portion  14  of the head assembly  10  has, at its upstream end, an impact plate  28 . The impact plate  28  is bent on either lateral side to present flanges  30 ,  32 . The flanges  30 ,  32  lend strength to the impact plate  28 , stiffen it, and assist with engagement of an impacting vehicle.  
         [0019]    The impact plate  28  is secured by welding to a rail receiving portion  34  of the impact portion  14 . The rail receiving portion  34  includes a top plate  36  and a bottom plate  38 . The top and bottom plates  36 ,  38  are affixed by welding to left and right side members  40 ,  42 , respectively. The left side member  40  consists of a curved plate  44 , horizontal connecting plate  46 , and a lateral brace  48 . The lateral brace  48  is welded to the curved plate  44 , and the connecting plate  46  is welded to brace  48  in an abutting relation. It is noted that the curved plate  44  has an “S” shape such that it provides an upstream first curved portion  50  and a downstream second curved portion  52  at curves slightly in the opposite direction from the first curved portion  50 . The brace  48  is affixed to the curved plate  44  in between the first and second curves  50 , 52 . The right side member  42  includes a short curved plate  54  with vertical and horizontal braces  56 , 58 , respectively that are welded to the plate  54  to stiffen it. It is noted that, in this embodiment, the side plates  40 , 54  are curved. The side plate  54  is, unlike prior art designs significantly shorter in length than the plate  40 , as measured from upstream to downstream. This difference in length is due to the fact that there is no forward curved portion of plate  54  that would correspond to the curved portion  50  of the longer plate  40 .  
         [0020]    It is noted that the horizontal brace  58  extends some distance outwardly from the right side of the head  10 . This is done deliberately as the horizontal brace  58  is intended to engage and break the support post  60  during a vehicular impact to the impact plate  28  of the impact head  10  that moves the head  10  downstream upon the rail member  12 .  
         [0021]    [0021]FIGS. 4 and 5 illustrate the impact head  10  having been affixed to a support post  60  by connectors (not shown) that are disposed through the brackets  24 ,  26 .  
         [0022]    It is further noted that the impact plate  28  is vertically elongated, thereby extending both above and below the rail receiving portions of the impact portion  14 , as shown by reference numerals  62 ,  64  in FIG. 5. These overhangs permit the impact head  10  to be easily engaged by either the high bumper of trucks, SUV&#39;s and other taller vehicles and the low set bumpers of smaller cars impacting in a frontal manner, as well as engaging the vehicle frame or rocker panel to reduce vehicle intrusion when the upstream end of the head  10  is impacted by a vehicle in a sideways manner.  
         [0023]    In a preferred embodiment, when the head  10  is assembled, the curved plate  44  and short curved plate  54  are secured in a spaced relation from one another to form a squeezing throat  66 , best seen in FIG. 2. The throat  66  narrows in width as it approaches the upstream end of the impact head  10 . During collision wherein the impact head  10  is impacted by a colliding vehicle (not shown), the throat  66  squeezes and flattens the rail member  12  as the head  10  is pushed downstream by the vehicle onto the rail member  12 . The first curved portion  50  bends the flattened portion of the rail member  12  and extrudes it to the side of the head  10 .  
         [0024]    There are a number of important differences between the inventive impact head  10  and the guardrail extruder heads described in U.S. Pat. Nos. 5,078,366 and 4,928,928 . First, the portion of the head  10  that is used to bend and extrude the flattened portion of the rail  12  consists only of a single curved surface, specifically, the rail contacting surface of portion  50  on curved plate  44 . Thus, an opening is provided opposite the portion  50  upstream of the end of the small curved plate  54 . In prior arrangements, a pair of curved portions were provided by two plate members that formed a narrow opening. Elimination of one curved portion, i.e. the most downstream curved portion) reduces the extrusion force required to extrude the rail member  12  and potentially improves the trajectory of the extruded rail as it departs the head  10 . The required extrusion force is reduced at least because friction created by the removed downstream curved portion has been eliminated.  
         [0025]    Also, as FIGS. 2 and 4 illustrate, the inventive head  10  provides a reduced and streamlined profile along the traffic side (i.e., the side of the head  10  that will be directed toward a roadway). FIG. 2 illustrates a central longitudinal axis  70  that is taken along the center line of the rail member  12 . The traffic side of the head  10  (shown at the bottom portion of FIGS. 2 and 4) does not extend as far from the axis  70  as the opposite side of the head  10  (shown at the top portion of FIGS.  2  and  4 ). This streamlining is permitted by the fact that the top and bottom plates  36 ,  38  each have a flattened traffic side edge  72  as opposed to the outwardly extending, generally triangular shape of the opposite sides of those plates. The head  10  is always installed on the rail  12  so that the “traffic” side is facing roadway traffic. This streamlined design ensures that the head  10  does not extend outwardly into to the stream of traffic, thereby reducing the frequency of impacts by passing vehicles and the associated maintenance costs. The flattened traffic side edge  72  should lie approximately flush with the strap plates  22  or other portions of the feeder chute  16 , or else extend only an inch or two beyond those components in the direction of the traffic lane. This “flush-side” feature helps ensure that the head  10  is less likely to be knocked off of the rail member  12  by a reverse end impact where a vehicle impacts the head from the downstream direction.  
         [0026]    It is also noted, particularly with reference to FIG. 2, that the center of impact for the head (shown at around  74 ) is not aligned with axis  70  of the rail  12 . This non-symmetrical design actually improves the function of the head  10  during a collision. Rather than distributing the forces of the impact substantially equally to either side of the head, as in prior designs, the force is primarily transmitted via connecting plate  46  and brace  48  to the curved plate  44 . Thus, the connecting plate  46  and brace  48  serve as the axis of force transmission for the head  10 . The curved plate  44  is the portion of the head  10  that works to bend and extrude the flattened rail member  12 . Because impact force upon the impact plate is transmitted directly to the side member  44  via the axis of force transmission, the head  10  is more efficient in collapsing the rail  12  wherein the exterior of the housing played a greater role in transmitting impact forces.  
         [0027]    The impact head  10  of the present invention is advantageous because it has a substantially lighter weight and mass than prior art impact heads. The inventive impact heads typically weigh 170 pounds versus 260 pounds for many prior art heads. The reduction in weight and results in improved performance for the rail terminal since a lighter head has less inertial resistance by the head during an impact. Initial movement of the impact head and extrusion of the rail member  12  will be performed with less resistance. In addition there is less of a jolting impact to a colliding vehicle due to the reduced weight of the head. The reduction in weight and mass results from a number of changes over prior art heads, including the use of thinner metals for fashioning of the head, the removal of a largely unnecessary external housing, and the removal or change in size of various plates making up the head.  
         [0028]    Turning now to FIGS. 6 and 7, there are shown alternative heads  10 ′ and  10 ″. The heads  10 ′ and  10 ″ are similar in many respects of construction and operation to the head  10  already described except where indicated otherwise. Therefore, like components between the two embodiments are numbered alike. Head  10 ′ has left and right side plates  40 ′ and  54 ′ that form a throat  66 ′. The plates  40 ′ and  54 ′ provide essentially straight, flat sidewalls for the throat  66 ′. As can be seen, the throat  66 ′ narrows in width as it approaches the upstream end of the head  10 . Head  66 ″ has a throat  66 ″ that is formed from side member plates  40 ″ and  54 ″. The throat  66 ″ is essentially of a constant width along its length as the two side members  40 ″,  54 ″ lie substantially parallel to each other along the length of the throat  66 ″.  
         [0029]    [0029]FIG. 8 illustrates a further feature of the invention wherein a feeder chute bumper device is incorporated into the impact head. With reference once again to FIGS. 1 and 5, it may be seen that the impact head  10  has a flared downstream end  78  on the feeder chute  16 . The use of a flared end, such as end  78  is preferred because it assists in ease of placement of the head  10  onto the rail member  12 . This flared end  78  provides upper and lower extreme downstream edge portions  80 ,  82  that are formed to present an acute angle and, thus, are somewhat sharp. During an end-on impact to the head  10 , the edge portions  80 ,  82  tend to impact the support posts as the head is pushed downstream along the rail by the impacting vehicle. While the presence of such edge portions  80 ,  82  is not normally a problem when wooden support posts are used, it becomes a problem when metal support posts are used. For example, when steel wide flange support posts are used, the sharp edge portions  80 ,  82  may actually cut the flanges of the support post downstream of the head  10 . When this occurs, the support post may pull the head  10  downwardly and, thus, resist further travel of the head  10 . This is undesirable. FIG. 8 depicts a means of preventing that outcome. Pipe or round metal stock members  84  are secured by welding to the edge portions  80 ,  82  so as to provide a blunt, rounded impacting portions to the downstream end  78  of the head  10 . The pipe or round stock members  84  preferably have a length that is the same as the width of the edge portions  80 ,  82 .  
         [0030]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to other various changes without departing from the scope of the invention.