Patent Publication Number: US-7901156-B2

Title: Bollard having an impact absorption mechanism

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the priority date of U.S. Provisional application 61/142,775, filed on, Jan. 6, 2009, the contents of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a bollard, and more particularly to a bollard mechanism incorporated therein that transfers impact loads to an upper end of a resilient shaft where impact energy is most efficiently absorbed. 
     BACKGROUND OF THE INVENTION 
     In supermarkets and retail stores, floor fixtures such as freezer and refrigerator cases, floor shelving, and product displays, are susceptible to damage due to collisions with shopping carts, floor scrubbers, pallet jacks, stock carts, and the like. For example, freezer and refrigerator cases typically include a glass or transparent plastic door for viewing the product without opening the door. The glass can be shattered, or the plastic scratched, upon impact with shopping carts, or the like. Since the body of many of these floor fixtures is constructed of lightweight aluminum or hardened plastic, it can be easily dented or cracked by such impacts. Likewise, in industrial locations, including warehouses and manufacturing facilities, product storage, doorways, equipment, and the like, are susceptible to damage due to collisions with heavy equipment, such as delivery vehicles, forklifts, and the like. 
     A bollard protects objects from collisions with things from shopping carts to delivery vehicles or automobiles. Bollards are commonly employed inside a store to block shopping cart access to certain areas and outside a store to protect outdoor structures from collisions, to indicate parking areas, to block vehicle and heavy equipment access to a particular area, and to direct a flow of traffic. Bollards can also be used to block vehicular access for security reasons. 
     In part due to the diverse applications for bollards, the market has thusfar derived two primary types of bollards, namely, plate-mounted bollards and core-drilled bollards. Plate-mounted bollards conventionally involve a steel plate having three or four bolt holes and a bollard extending perpendicularly from one face of the plate. The plate sits on the floor and bolts are used to fasten the plate, and therefore the bollard, to the floor through the bolt holes. There is no significant disruption to the ground or floor, other than the bolt holes, which are in some instances pre-drilled. On the other hand, core-drilled bollards conventionally require a major disruption to the ground or floor with the creation of a hole 2-4 feet deep and having a larger diameter than the bollard itself (e.g., 8 inches to 2 feet, or larger). Concrete is poured into the hole and the bollard is placed in the concrete and held vertically while the concrete cures. In some instances, concrete is also poured into the hollow bollard itself Installation of a core-drilled bollard is significantly more expensive than with a plate-mounted bollard, and takes significantly more time to complete. However, there are locations where the core-drilled bollard is required due to its ability to absorb larger impacts than the plate-mounted bollard. 
     The plate-mounted bollards conventionally are utilized in areas where impacts are more likely to be less severe, and involve lighter objects, or where no significant impacts are likely and the bollard serves more as a marker. For example, inside a grocery store in front of a freezer case any impact would likely be from a shopping cart or floor polisher. Such an impact would be considered to be low-energy, or relatively minor. Accordingly, a plate-mounted bollard would be appropriate for this type of installation. Contrarily, in a warehouse with heavy equipment, such as delivery vehicles and forklifts, impacts are more likely to be more severe, or high-energy. A vehicle backing up may accidentally collide with a bollard. Accordingly, a core-drilled bollard would be more appropriate in these types of settings. 
     There are a substantial number of installations where a conventional plate-mounted bollard does not provide quite enough impact protection; however, a core-drilled bollard is significantly over-sized for the application. Yet, a core-drilled bollard is installed because the conventional plate-mounted bollard falls short of providing the required protection. Likewise, there are installations where a core-drilled bollard is necessary to provide protection against likely impacts, yet a plate-mounted bollard is installed because they are less expensive or there are logistical problems with drilling 4 foot deep holes for the core-drilled bollard installation. One of ordinary skill in the art will appreciate that there are other factors that may influence the selection of a plate-mounted bollard or a core-drilled bollard. 
     The ability of the conventional plate-mounted bollard to absorb impact energy is, to date, limited by the strength of the three or four bolts holding the plate and bollard in the ground. When a plate-mounted bollard experiences a collision with an object, the impact is absorbed primarily at the intersection between the bollard and the plate to which it is mounted. 
     Looking at  FIG. 1 , an example conventional bollard  10  coupled with a plate  12  and mounted to the ground with bolts  14  is illustrated. More specifically, a bollard  10  that is 36 inches high, for example, most often receives impact forces in the first 18 inches off the ground. This is because bumpers of equipment that most often collide with the bollards are typically in that height range. As the bollard receives an impact force (F 1 ), the bollard  10  (which is typically rigid so as to avoid damage from collisions) acts as a lever or moment arm. Due to the rigidity of the bollard, the force (F 1 ) is immediately experienced at an intersection (I) of the bollard  10  with the plate  12 , which in turn pulls upward on the bolts  14  holding the plate  12  to the ground. Magnified levels of the impact force (F 1 ) are experienced by the intersection (I) due to the moment arm phenomenon. The bolts  14  are also subject to forces sufficient in some instances to pull the bolts  14  out of the ground. There is no give, or flex, in these rigid plate-mounted bollards to absorb some of the impact forces. 
     Even with bollards that include some form of spring mechanism internally, if the bollard is mounted to the plate, the impact force (F 1 ) is typically received at the intersection thereof without much absorption of the impact force anywhere else in the bollard structure. If, alternatively, the intersection between the base plate and the bollard is hinged or pivoted and has a spring holding the bollard upward, then such a structure is unable to withstand substantial impact forces without pivoting over on its side, resulting in excessive lateral movement at the upper end of the bollard (if the top of the bollard moves a lot on impact, it may collide with the nearby structure it is supposed to be protecting). Accordingly, in conventional plate-mounted bollards, the force immediately generates a lever scenario where the impact force that results is a greater impact force than can be absorbed by the bolts, the bolts may pull out of the floor, or altogether fracture, or the floor may buckle attempting to withstand the impact. 
     A core-drilled and cemented bollard withstands such impacts as described above because a greater length of sub-floor bollard and a substantial area of concrete hold the base of the bollard in place. When the ability to absorb a larger impact is required, the convention is to utilize a core-drilled bollard. 
     Example ranges of impact forces that are typically managed by conventional plate-mounted bollards include ranges of up to about 4000 lbs with maximum lateral movement at the top of the bollard of about 3 inches due to the limitations described above. Example ranges of impact forces that are generally managed by conventional core-drilled bollards include ranges of up to about 16,000 lbs, with no substantial lateral movement of the top of the bollard at impact, or with movement of less than about 1 inch. As can be seen, the core-drilled bollards can manage substantially greater impact forces, but they require significantly more expensive and time intensive installations. 
     SUMMARY 
     There is a need for a bollard incorporating a mechanism that can absorb larger impacts than conventional plate-mounted bollards, with lateral movement at the top of the bollard within acceptable ranges, but that does not require the major disruption, time, and expense of the core-drilled bollard, that does not transfer all of the impact forces to plate intersections and mounting fasteners. The present invention is directed toward further solutions to address this need, in addition to having other desirable characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       These and other characteristics of the present invention will be more fully understood by reference to the following detailed description in conjunction with the attached drawings, in which: 
         FIG. 1  is a diagrammatic representation of a conventional plate-mounted bollard for purposes of illustrating the state of the art; 
         FIG. 2  is a perspective cutaway illustration of a bollard according to one embodiment of the present invention; 
         FIG. 3  is a diagrammatic representation of the bollard of  FIG. 2  absorbing an impact force according to one aspect of the present invention; 
         FIG. 4A  is a side view of a base plate according to one embodiment of the present invention; 
         FIG. 4B  is a side view of a base plate according to another embodiment of the present invention. 
         FIG. 5  is a diagrammatic representation of a bollard according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative embodiment of the present invention relates to a plate-mounted bollard having an internal impact absorption mechanism that enables the bollard to absorb impact forces greater than conventional plate-mounted bollards. The bollard makes use of a force transfer process that shifts impact forces to areas better able to resiliently absorb the impact forces without causing damage to the bollard, the impact absorption mechanism, or the ground in which the bollard is installed. Specifically, an internal resilient core rod is mounted to a base plate, but primarily receives impact forces at an upper and distal end of the rod from the typical area of impact. With energy from the impact force being distributed along the maximum length of the resilient core rod, the rod elastically flexes and the full length of the rod is utilized to absorb the impact force and flex. As a result, reduced forces are experienced where the rod intersects with the base plate, and the bolts or other fasteners mounting the base plate to the ground also experience reduced forces compared with conventional plate-mounted bollards. With the plate-mounted bollard of the present invention, impact forces of up to about 10,000 lbs can be absorbed with less than about 3 inches of lateral movement of the top of the bollard. This represents substantially improved performance over conventional plate-mounted bollards. 
       FIGS. 2 through 5 , wherein like parts are designated by like reference numerals throughout, illustrate example embodiments of a bollard having an impact absorption mechanism according to the present invention. Although the present invention will be described with reference to the example embodiments illustrated in the figures, it should be understood that many alternative forms can embody the present invention. One of ordinary skill in the art will additionally appreciate different ways to alter the parameters of the embodiments disclosed, such as the size, shape, or type of elements or materials, in a manner still in keeping with the spirit and scope of the present invention. 
     Turning now to a description of one example embodiment of the present invention,  FIG. 2  shows a perspective view of a bollard  20 . The bollard  20  includes a resilient core rod  22  extending from a base plate  24 . The core rod  22  can be coupled with the base plate  24  in any number of conventional mechanisms, including press mounting, welding, threading, and the like. Alternatively, the base plate  24  can be formed of the same material and from the same integral piece of metal as the core rod  22 , thereby not requiring any form of coupling mechanism or method. 
     The base plate  24  has a top surface  26 , a bottom surface  28 , and a plurality of sides or edges  30  (see also  FIGS. 4A &amp; 4B ). The sides or edges  30  form the perimeter of the base plate, and therefore the approximate shape of the base plate  24  (e.g., circle, square, rectangle, triangle, and the like). The base plate  24  further may include a plurality of pre-drilled holes  48  sized to receive bolts, screws, or other fasteners for mounting the base plate to the ground or floor, including to a concrete pad. Those of ordinary skill in the art will appreciate that the base plate  24  may not require the plurality of pre-drilled holes  48  if alternative mounting methods are utilized, such as for example, industrial adhesives. 
       FIG. 4B  illustrates an alternate base plate  24 ′ embodiment. As shown, the base plate  24 ′ has a top surface  26 ′, a bottom surface  28 ′, and a plurality of sides or edges  30 ′. A plurality of pre-drilled holes  48 ′ is also shown. In addition, a seating structure  50  can be incorporated with the base plate  24 ′. The seating structure  50  helps acts as a guide during and following an impact to the bollard  20  as described later herein. 
     The base plate  24  can be formed of a number of different materials, including metal, plastic, composite, and the like, so long as it is able to withstand forces resulting during impact of the bollard  20 , and depending in part on the purpose of the particular bollard installation. In the example embodiment, the base plate  24  is formed of A36 steel in plate form 1 inch thick and 6 inches in diameter. Again, one of ordinary skill in the art will appreciate that the present invention is not limited to this particular illustrative embodiment. 
     The resilient core rod  22  has a proximal end  32  where it meets with the base plate  24 , and a distal end  34  opposite the proximal end. The resilient core rod  22  is formed of a material that enables the core rod  22  to elastically flex when a lateral force is applied thereto and return to its original position when the force is removed. For example, the core rod  22  can be formed of a stainless steel having a 180 ksi yield strength and a 25-35 Mpsi modulus. The core rod  22  can have a circular cross-section with a diameter of about 1.25 inches. The core rod  22  can have a length of about 36 inches. It should be noted that these material properties and core rod dimensions are merely illustrative of an example implementation of a core rod  22  in accordance with the present invention. The bollard  20  of the present invention is by no means limited to having a core rod  22  having the above properties and dimensions. The properties and dimensions of the core rod  22  can be modified as needed for a particular bollard installation as would be understood by those of ordinary skill in the art. Some of the parameters that will dictate the properties, shape, and dimensions of the core rod  22  include range of impact forces the core rod  22  will be required to withstand, height or other size restrictions due to a particular installation requirement, amount of lateral movement of the top and/or middle of the core rod  22  upon experiencing the maximum design impact load, and the like. 
     The resilient core rod  22  extends substantially perpendicularly relative to the top surface  26  of the base plate  24  in accordance with one example embodiment. There may be instances where an angled relationship is required between the resilient core rod  22  and the base plate  24 , which can be accommodated. 
     A load ring  36  is disposed at or near the distal end  34  of the resilient core rod  22 . The load ring  36  can be coupled with the resilient core rod  22  using a number of different possible conventional fastening means, including a threaded connection or a bolt passing through the load ring  36  into the distal end  34  of the resilient core rod  22 , in addition to other possible coupling means and mechanisms. As depicted, a bolt and washer fastening mechanism  38  coupled with a threaded hole (not shown) in the distal end  34  of the resilient core rod  22  hold the load ring  36  to the distal end  34  of the resilient core rod  22 . The load ring  36  has a total outer perimeter, or equivalent total outer diameter, which is greater than that of the core rod  22 . This larger dimension relative to the resilient core rod  22  is instrumental in implementation of the present invention as discussed later herein. 
     The load ring  36  can be formed of a number of different materials, including metal, plastic, composite, wood, natural materials, synthetic materials, and the like. In the example embodiment illustrated, the load ring  36  is formed of a hard plastic, such as a nylon or polypropylene. 
     A hollow impact shell  40  is disposed to surround the resilient core rod  22  and the load ring  36 . Alternatively, the load ring  36  may be integrated into the hollow impact shell  40 , as depicted in a later-described embodiment. The hollow impact shell  40  has an interior surface  42  and an exterior surface  44 . The hollow impact shell  40  has an internal perimeter, or equivalent total internal or inner diameter, that is greater than the outer perimeter, or equivalent total outer diameter, of the resilient core rod  22 . This difference in dimensions creates a gap  46  between the hollow impact shell  40  and the resilient core rod  22 . The gap  46  can vary in size, but should be sufficient to prevent the interior surface  42  of the hollow impact shell  40  from making substantial contact with the resilient core rod  22  during a maximum design impact load condition. 
     The hollow impact shell  40  can be a number of different shapes and sizes. The hollow impact shell  40  may be formed using a rigid material, so that maximum design impact loads do not substantially damage the hollow impact shell  40 . For example, in an illustrative embodiment of the present invention, the hollow impact shell  40  is formed of a Schedule  40  pipe, 6 inches in diameter, and 36 inches tall or long. 
     The hollow impact shell  40  does not need to be formed of a rigid material, but can instead be formed of a material that can withstand the maximum design impact forces for the bollard  20  with no permanent deformation. For example, the hollow impact shell  40  may alternatively be made from an elastically deformable material, such as plastic. In one example embodiment, the hollow impact shell  40  is made from high density polyethylene or high density polypropylene having a thickness of about ⅜″. One having ordinary skill in the art will appreciate that these are examples only, and that other types of materials and thicknesses may be selected depending on the desired characteristics of the bollard  20 . 
     With such a construction, the bollard  20  may elastically deform on impact, thereby absorbing some of the impact force. Upon the hollow impact shell  40  receiving an impact force, the impact shell deforms in order to absorb energy from the impact force. Because the impact shell  40  elastically deforms, the impact shell  40  may absorb some of the energy of the impact. Simultaneously, energy is likewise transferred to the load ring  36 , which is further transferred to the resilient core rod  22 , as described herein. 
     Further alternatively, the hollow impact shell can experience permanent deformation upon receiving a maximum design impact force, and then be replaceable with a new hollow impact shell  40 , if for some reason the particular installation environment calls for such a design. 
     In some embodiments, the hollow impact shell  40  is not fastened with the base plate  24 , the load ring  36 , or the resilient core rod  22 . In fact, the hollow impact shell  40  is able to move in a longitudinal direction parallel to a central axis along a length of the resilient core rod  22  and away from the base plate  24 . This ability to move relative to the base plate  24 , the load ring  36 , and the resilient core rod  22 , enables the hollow impact shell  40  to transfer any impact force it experiences directly to the load ring  36  at the distal end  34  of the resilient core rod  22 , and not directly to the resilient core rod  22  at the height or area of impact on the hollow impact shell  40 . Said differently, when the hollow impact shell  40  receives an impact force (e.g., from an object colliding with the bollard  20 ) there is an initial lateral force applied to the edge  30  of the base plate  24 , but a majority of the impact force is transferred from the hollow impact shell  40  to the load ring  36  at the distal end  34  of the resilient core rod  22 . Because the resilient core rod  22  is affixed in place at its proximal end  32 , the most efficient location along the resilient core rod  22  for absorbing impact force energy is at the maximum distance along its length away from the proximal end  32 ; this location is its distal end  34 . The load ring  36  is positioned at the distal end  34  for this reason. The interior surface  42  of the hollow impact shell  40  is in contact with the load ring  36  and transfers the energy of the impact force to the load ring  36 . The load ring  36  in turn transfers the energy of the impact force to the distal end  34  of the resilient core rod  22 . As the resilient core rod  22  absorbs the impact force, it flexes, and the hollow impact shell slides upward along the load ring  36  and generally in a direction parallel to the longitudinal central axis of the core rod  22 . 
     Alternatively, the hollow impact shell  40  may include an integrated load ring, as described above, while still not fastened to the base plate  24 . In this embodiment, the integrated load ring may be slidably coupled to the resilient core rod  22 , allowing the integrated load ring to slide up and down the resilient core rod  22 . For example, slidably coupling the integrated load ring to the resilient core rod  22  may be achieved by including a hole  62  in the integrated load ring through which the resilient core rod passes. One having ordinary skill in the art will appreciate that there are a number of ways to slidably couple the integrated load ring to the resilient core rod, any of which are contemplated by the present invention. Such an embodiment is discussed below in relation to  FIG. 5 . In embodiments including an integrated load ring, the hollow impact shell  40  may be made from any of the materials described above, such as a rigid material or an elastically deformable material. 
     The hollow impact shell  40  is self seating over or on the base plate  24 . Looking at  FIGS. 4A and 4B , two different base plate  24  embodiments are illustrated.  FIG. 4A  shows the base plate  24  as depicted in other figures herein.  FIG. 4B  shows the alternate base plate  24 ′ having a seating structure  50  incorporated with the base plate  24 ′. The hollow impact shell  40  rests on the base plate  24  or on the ground upon which the base plate  24  is mounted (as depicted in  FIG. 2 ). Because the hollow impact shell  40  is not fastened to the base plate  24 , the hollow impact shell  40  can move up and off of the base plate  24  upon experiencing a sufficient impact force. After the impact force subsides, the hollow impact shell  40  is designed to fall back down onto or over the base plate  24 . In installations or environments where the hollow impact shell  40  is likely to be raised to the extent that it may not correctly self-seat over the base plate  24 , but may instead be caught on an edge  30  of the base plate  24 , the seating structure  50  can help the hollow impact shell to slide back down into the proper position over the base plate  24 . One of ordinary skill in the art will appreciate that the seating structure  50  can have a number of different configurations, dimensions, and the like, to adapt to different installation parameters. As such, the present invention is by no means limited to the specific dimensions and configurations of the seating structure  50  illustrated herein. 
     It should additionally be noted that although the hollow impact shell  40  is not fastened or mounted to the base plate  24 , the present invention is intended to encompass equivalent structures where the hollow impact shell  40  may be removably fastened to the base plate in a manner that still enables the hollow impact shell (or equivalent structure) to raise up and off the base plate  24  upon receiving an impact force of sufficient energy. 
     In operation, as shown in  FIG. 3 , the bollard  20  serves to absorb an impact force as described herein. As shown, the bollard  20  is formed of the base plate  24 , the resilient core rod  22 , the load ring  36 , and the hollow impact shell  40 . The bollard  20  is mounted to the ground or floor using appropriate fasteners. For example, as shown in  FIG. 3 , bolts  52 , such as concrete anchor bolts, mount the base plate  24  to a concrete surface  54 . The concrete surface can be supported by an underlying concrete area  56 , such as a concrete pad or poured concrete. In the example illustrated, the concrete area  56  is about 18 inches deep and about 1 foot in diameter. 
     Upon receiving an impact force (F 1 ) at the hollow impact shell  40 , the energy from the impact force (F 1 ) is transferred to the load ring  36  and some initial momentum energy is transferred to the edge  30  of the base plate  24 . The hollow impact shell  40  moves upward in the direction of arrow M, which is generally in a direction parallel to the central longitudinal axis of the resilient core rod  22 . As the hollow impact shell  40  moves upward, some of the impact energy from the impact force (F 1 ) is absorbed in that movement. In addition, the interior surface  42  of the hollow impact shell  40  slides along the load ring  36  and through contact with the load ring  36  transfers more of the impact energy from the impact force (F 1 ) to the load ring  36 . The load ring  36 , being coupled with the distal end  34  of the resilient core rod  22 , immediately transfers the energy from the impact force (F 1 ) to the distal end  34  of the resilient core rod  22 . 
     The distal end of the resilient core rod  22  is the most efficient portion of the resilient core rod  22  to receive the impact force (F 1 ) in terms of its ability to absorb that energy because it is held in place at its proximal end  32  at the base plate  24 . As the distal end  34  receives the energy from the impact force (F 1 ) it flexes the resilient core rod  22 . As long as the impact force (F 1 ) is no greater than a maximum design load, the resilient core rod  22  will not flex at its distal end  34  in the lateral direction (D) more than a desired amount. For example, a bollard  20  having a resilient core rod  22  of stainless steel 36 inches tall with a diameter 1.25 inches within a hollow impact shell  40  of Schedule  40  pipe 6 inches in diameter receiving an impact force (F 1 ) of up to about 10,000 lbs will result in lateral movement of the distal end  34  of less than 3 inches. 
     As the resilient core rod  22  flexes, the existence of the gap  46  prevents the hollow impact shell  40  from actually making contact with the resilient core rod  22 . This prevents the hollow impact shell  40  from directly transferring the impact load (F 1 ) to the middle or lower portions of the resilient core rod  22  and causing added stress on the intersection of the core rod  22  with the base plate  24 , or on the base plate  24  and its fasteners or bolts  52 . 
     Once the impact load (F 1 ) is removed from the bollard  20 , the hollow impact shell  40  falls back down on to, or over, the base plate  24 , self-seating the hollow impact shell  40  in place. 
     The installation of the bollard  20  of the present invention can be implemented a number of different ways depending on the particular requirements of the resultant installed bollard. One example installation method involves either beginning with a concrete floor, or creating a pad or section of concrete in a floor or ground surface that has the approximate dimensions of being about 1 foot in diameter and 18 inches deep. The base plate  24  and resilient core rod  22  are then mounted to the concrete surface using concrete anchor bolts. The load ring  36  is installed at the distal end  34  of the core rod  22 . The hollow impact shell  40  is then placed over the resilient core rod  22  and the base plate  24 . Installation is then complete. If desired, an additional ornamental cover (not shown) as is known in the art could be placed over the hollow impact shell  40  to improve the ornamental look of the bollard  20 . 
       FIG. 5  depicts another embodiment of a bollard  60  according to the present invention. In this embodiment, the proximal end of a resilient core rod  22  extends from the top surface of the base plate  24 . The base plate  24  is fixed to the ground as described above. A hollow impact shell  66  surrounds the resilient core rod  22 . The hollow impact shell includes an integrated load ring  68 , meaning that the shell and the load ring are a single structure, or are coupled together in a manner approximating a single structure. The integrated load ring includes the hole  62 , through which the resilient core rod  22  passes. In this way, the distal end of the resilient core rod  22  is slidably coupled to the integrated load ring  66 . As indicated previously, other slidable couplings may be utilized in such an embodiment of the present invention. 
     In one embodiment of the bollard depicted in  FIG. 5 , the hollow impact shell is made of an elastically deformable material, such as plastic. With such a construction, the bollard  60  may elastically deform on impact, thereby absorbing some of the impact force. The hollow impact shell may include a cap  64 . Although the cap  64  is depicted separately in  FIG. 5 , one having ordinary skill in the art will appreciate that cap  64  may also be integral with the hollow impact shell, meaning that the shell  66  and the cap  64  are a single structure, or are coupled together in a manner approximating a single structure. 
     Upon the hollow impact shell  66  receiving an impact force, the impact shell  66  deforms in order to absorb energy from the impact force. The hollow impact shell also transfers energy from the impact force to the integrated load ring  68 , which in turn transfers the impact force to the distal end of the resilient core rod  22 , flexing the resilient core rod. With this configuration, the impact shell  66  does not directly transfer the impact force to the middle portion or the proximal end of the resilient core rod. Because the impact shell  66  elastically deforms, the impact shell  66  may absorb some of the energy of the impact. Simultaneously, energy is transferred to the integrated load ring  68 , which is further transferred to the distal end of the resilient core rod  22 , opposite the base plate  24 . When the hollow impact shell  66  receives an impact force, the hollow impact shell  66  and the integrated load ring  68  together slide along the resilient core rod  22  due to the slidable coupling (hole  62 ) in the integrated load ring  68 . This allows some of the energy of the impact to be absorbed in the movement along the resilient core rod  22 , as described above in relation to  FIG. 3 . 
     With the structure depicted in  FIG. 5 , the bollard may have a lighter weight than a bollard with an impact shell made of a more rigid material, such as steel (but may also be made of such a rigid and heavier material, if desired). Further, because the load ring  68  is integrated into the impact shell  66 , fewer parts are required, reducing the complexity and cost of the bollard. In addition, because the bollard, in some embodiments, deforms to absorb some of the energy of the impact rather than resisting the impact based on mass and rigidity alone, the bollard  60  of  FIG. 5  may do less damage to an object that collides with the bollard  60  than a bollard with a rigid outer shell. 
     As previously indicated, the hollow impact shell  66  may constructed of a rigid material, but may include an integrated load ring  68 . In such an embodiment, the integrated load ring  68  is slidably coupled to the resilient core rod  22 , such as through the hole  62 . Upon impact, the hollow impact shell  66  may move upward, as described above in relation to  FIG. 3 . Because the load ring  68  is integral with the hollow impact shell  66 , the integrated load ring  68  moves upward along with the hollow impact shell  66 . The integrated load ring  68  slides upward along the resilient core rod  22  through hole  62  towards the distal end  34  of the resilient core rod  22 . The load ring  68 , being slidably coupled with the resilient core rod  22 , immediately transfers the energy from the impact force to the distal end  34  of the resilient core rod  22 . As the distal end  34  receives the energy from the impact force, it flexes the resilient core rod  22 , as described above in relation to  FIG. 3 . Once the impact load is removed from the bollard  60 , the integrated load ring  68  slides downward along the resilient core rod  22  through the hole  62 . Because the integrated load ring  68  is integral with the hollow impact shell  66 , the hollow impact shell  66  falls back down on to, or over, the base plate  24 , self-seating the hollow impact shell  66  in place. 
     Numerous modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure may vary substantially without departing from the spirit of the present invention, and exclusive use of all modifications that come within the scope of the appended claims is reserved. It is intended that the present invention be limited only to the extent required by the appended claims and the applicable rules of law. 
     It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.