Abstract:
An energy absorbing system comprising a plurality of break-away post elements sequentially spaced to be sheared off by impact of a vehicle. Each post element individually absorbs and decelerates the impacting vehicle at a pre-determined rate that in multiple successive impacts slows the vehicle to a stop before the barrier or to an acceptable speed within the design requirements for impact with a barrier.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to energy absorption apparatus for preventing a vehicle from unrestricted impacting of a stationary roadside structure. More specifically, this invention relates to the de-acceleration of a vehicle by an energy absorbing device before it reaches a stationary structure. Such energy absorbing apparatus include impact attenuation barriers and support elements for roadway signs and the like. Support elements of this nature are characterized by break-away posts having approved shear impact characteristics that meet the vehicle de-acceleration requirements upon impact as having certain engineering design requirements as per The American Association of State Highway and Transportation Officials (AASHTO) and the FHWA&#39;s Manual of Uniform Traffic Control Devices (MUTCD) and other design codes&#39; requirement. 
     In addition, in evaluating impact attenuation systems, certain tests performance levels have been established by the federal government including the NCHRP 350 test 1, 2 and 3. Each of these test requirements of performance of vehicles impacting attenuation barrier include independent and interdependent crash performance perimeters with the primary performance characteristic requirement of an acceptable de-acceleration rate of the crash vehicle. Support elements for a roadway sign are evaluated for their break-away characteristics having been tested and approved so as to meet maximum de-acceleration rates of a vehicle upon such impact. 
     2. Description of Prior Art 
     A number of prior art devices are directed towards the problem of energy absorption of a vehicle impact with a stationary structure such as bridge abutments, parapets, traffic elements and rigid guard rails. Many of such devices provide a collapsible structure of inner engaging deformable elements such as overlying guardrail sections, honeycomb structures and crushable enclosures filled with energy absorption material. 
     All of such devices must meet government performance standards as in the National Cooperation Highway Research Program, NCHRP, Department 350 by the National Research Commission. These standards are directed towards the safety performance evaluation of highway features for longitudinal barriers, terminals and crash cushions, support structures, work zone traffic, central devices and utility poles. 
     A variety of impact attenuation systems have been developed, see for example U.S. Pat. Nos. 3,845,936, 5,660,496, 5,112,028 and 5,011,326. All of the above prior art patents rely on the energy absorption properties of material deformation and energy absorption and elaborate structural configurations placed in front of stationary barriers to be protected. 
     SUMMARY OF THE INVENTION 
     The present invention is directed towards energy absorption devices that dissipate impact forces of a vehicle before it reaches a roadway object by use of multiple break-away posts elements. Such post elements meets FHWA approval for break-away characteristics which include an acceptable meters per second de-acceleration rate of the vehicle as it impacts energy absorption device. The plurality of such posts elements are arranged to sequentially engage the vehicle wherein each posts incrementally de-accelerates the vehicle at a known rate from the initial post impact to the final vehicle resting point. Preferably the apparatus of the invention includes multiple posts extending from a central mounting base which is in turn buried in the foreground of the structure to be protected. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the preferred embodiment of the invention; 
     FIG. 2 is an enlarged partial top plan view of a post and mounting opening as seen in FIG. 1; 
     FIG. 3 is a side elevational view of the invention deployed in the ground; 
     FIG. 4 is an enlarged partial front elevational view of a post of the invention; 
     FIG. 5 is a partial cross-sectional view of an alternate mounting system for the post of the invention; 
     FIG. 6 is an alternate mounting system for the posts of the invention showing it being placed directly in the ground; 
     FIG. 7 is a graphic illustration of a preferred embodiment of the invention in a typical installation on a barrier shown in broken lines; 
     FIG. 8 is an illustration of an alternate deployment of the invention with select posts arrangement; and 
     FIG. 9 is an alternate form of the invention illustrating pairs of posts and aligned engagement arrangement. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1,  2  and  3  of the drawings the preferred embodiment of the energy impact posts system  10  (EIPS) can be seen. The (EIPS)  10  is designed and adapted to attenuate and dissipate the energy of an impacting vehicle, thus preventing the vehicle colliding unimpeded with a roadway barrier B. The (EIPS)  10  includes an elongated base element  11  which in this example chosen for illustration is of a monolithic synthetic resin (plastic) composition. The base element is cross-sectionally rectangular having an elongated top and bottom surface areas  12  and  13  and respective elongated side surfaces  14  and  15 . A plurality of longitudinally spaced mounting apertures  16  extend through the base element  11  and its top and bottom surface areas  12  and  13 . A corresponding number of post elements  17  are registerable within the respective aperture  16 . Each of the post elements  17  is of a “break-away” structural dimension having a plurality of spaced apertures  17 A within as best seen in FIG. 4 of the drawings and are designed to meet approved U.S. Federal Highway Administration safety requirements for such break-away devices. 
     The post element  17  chosen for illustration is a standard three pound/foot (3 lb. per—foot) apertured U-channel configuration that is by its very nature a “break-away” post without the addition of any other performance components. 
     The post elements  17  are of a sufficient length that they extend through the respective apertures  16  in the base element  11  with a substantial impact area extending beyond the top surface area  12  and the remaining portion of the posts extending marginally from the bottom surface  13 . The apertures  16  in the base element  11  are shaped so as to impart a high frictional interference with the post element  17  as it is inserted therethrough thus holding the post element  17  securely within as best seen in FIG. 2 of the drawings. It will be apparent to those skilled in the art that other aperture configurations can be used as long as a surface interference is maintained with the post selected for insertion therein. 
     Referring now to FIG. 3 of the drawings, the assembled (EIPS)  10  of the invention is shown in use being buried in the ground G so that the top surface area  12  is at ground level G- 1  with the post element  17  extending thereabove the top surface  12  and marginally below the bottom surface  13  so as to ensure the post break-away characteristics can be achieved upon impact by maintaining a secure mounting area within the base  11  and ground. 
     A vehicle force F illustrated by the broken lines arrow in FIGS. 1,  3  and  7  impacts the exposed post element  17  above the surface  12  in a sequential manner shearing the post off at  18  reducing the vehicle&#39;s force F to F− 1 . As subsequent post elements  17  are impacted and sheared off, incremental force reduction is achieved to a maximum level of F− 6  as illustrated in FIG. 3 of the drawings. 
     In this environment, vehicle force F is related to vehicle (speed) and by impacting with each of the post elements  17  a given speed reduction is achieved reducing the vehicle&#39;s force F to the illustrated value of F− 6 . 
     Since the FHWA approved post element  17  used will not exceed the five meter per second de-acceleration rate required during impact, it will correspondingly reduce the overall speed of the vehicle (vehicle force) by a proportional amount for a given vehicle weight upon sequential impact. 
     It will be evident from the above description that different placement patterns and numbers of post elements  17  can be used to meet different vehicle force requirements such as F+ 1  and F+ 2  corresponding to increased weight of vehicles (not shown). 
     Referring now to FIGS. 8 and 9 of the drawings, alternate post placement and numbers are illustrated to address different vehicle force requirements. In FIG. 9 of the drawings, pairs of post elements  18  extend from a mounting base  11 ′. In FIG. 8 of the drawings, a mix of post elements  18  in pairs  18 ′ on two spaced and staggered support bases  19  and  20 . The alignment of the selected posts  18  and post pairs  18 ′ between the adjacent support bases  19  and  20  maintain a staggered impact field as illustrated by the alignment lines  21  so that only one set or individual post element  18  is engaged in a sequential fashion by the vehicle force F indicated by broken arrow lines. 
     Referring to FIG. 7 of the drawings, a typical application is illustrated wherein a pair of (EPS) 10&#39;s are deployed in front of a roadway barrier B to meet safety requirements for a front impact force FIF and an angled impact force AIF. Such angle of inclination is determined by government regulations to be specifically twenty degrees spacing therebetween. 
     Alternate post mounting systems can be seen in FIGS. 5 and 6 of the drawings. In FIG. 5 of the drawings a support socket  22  is embedded partially within a base element  11 ′. The socket  22  extends from the top surface  12 ′ for receiving a standard U-shaped post element  17 ′ within. 
     In FIG. 6 of the drawings, a post element  17 ′ is driven directly into the ground G′. The alternate mounting system&#39;s performance is dependent on the ground G′ density. Such a ground base support system would still have linear space posts as set forth in the preferred embodiment so that sequential impact of the ground driven post can be achieved by the vehicle force F. The flexibility of such a ground engagement post  17  affords that different posts placement patterns can be achieved that will not depend on the longitudinal base support members  11  and  11 ′ as hereinbefore disclosed. 
     It will be apparent that by the use of multiple “break-away” post elements  17  and  17 ″ and  18  in linear sequential placement patterns, that during impact the vehicle force F will be diminished upon each post impact. Such vehicle force F reduction will slow the vehicle down to meet government standards for stationary barriers B impact as hereinbefore discussed. 
     It will therefore be seen that a new and novel impact energy absorption system has been illustrated and described and that it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention.