Patent Publication Number: US-2003228191-A1

Title: Guardrail support, attachment, and positioning block

Description:
RELATED APPLICATIONS  
     [0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10,001,903, filed Nov. 15, 2001 and entitled “Guardrail Support, Attachment, and Positioning Block” which claimed priority from United States provisional application Serial No. 60/249,037, filed on Nov. 15, 2000. 
    
    
     
       TECHNICAL FIELD OF THE INVENTION  
       [0002] The present invention relates generally to highway safety systems and, more particularly, to spacer blocks for attachment of guardrails to support posts.  
       BACKGROUND OF THE INVENTION  
       [0003] Guardrails are typically installed along highways as components in roadway safety barrier systems. The guardrails commonly used are usually formed as strips of material, typically twelve (12) gauge galvanized steel Other materials commonly used in guardrail fabrication include aluminum, steel, fiberglass, or even synthetic materials. Most segments of guardrail are approximately twelve (12) feet in length and about ninety (90) pounds in weight.  
       [0004] At least one configuration of a guardrail used includes a corrugation forming an undulating cross section. The undulating cross section is employed in its capacity to absorb energy from the impact of an out of control vehicle. Such energy absorption is desired in an effort to prevent the vehicle from leaving the roadway or at least to influence the direction of the vehicle prior to it leaving the roadway. Typically, corrugated beams are about nine (9) inches wide, have two crowns and are shaped substantially like the letter “W”. An alternate corrugated guardrail embodiment is known in the industry as a thrie-beam guardrail. Thrie-beam guardrails typically have three crowns and are generally about one-third (⅓) wider than a conventional, two-crown, or “W”, guardrail.  
       [0005] In most roadway safety barrier systems, a plurality of guardrails are typically linked together at their distal ends, either end to end, or overlapping, and are supported by a plurality of vertically oriented support posts. Among the support post configurations typically used are “I-beam,” round or square posts. The support posts used may be fabricated from a variety of materials including wood, metals such as aluminum, steel, etc. Some support posts may also be formed from polymer or fiberglass materials. In place, driven into the ground a distance from the edge of the roadway and from one another, the support posts will typically yield under a certain amount of pressure either by moving within the ground or by bending in accordance with the deformation of the guardrail. Preferably, the support posts do not break off at ground level. Yielding or bending is preferred in an effort to assist the guardrail in dissipating the impact force received from an out of control vehicle.  
       [0006] In a typical roadway safety barrier system, a spacer block is disposed between the guardrail and the support post such that the guardrail may be maintained a distance from the support post. The spacing provided by the spacer block preferably helps keep an automobile&#39;s wheels from coming into contact with the support posts and initiating a roll of the vehicle. In addition, the guardrail provides a rail or track for guiding the vehicle and providing at least some response time for the driver to regain control of the vehicle.  
       [0007] Conventional spacer blocks are typically made of wood. However, wood as a material for spacer blocks has many shortcomings. Among wood&#39;s shortcomings as a spacer block material are that it deteriorates over time, it is excessively heavy, it can give installers splinters and it typically contracts and expands with seasonal changes. In addition, wood tends to leach out the chemicals typically used for pressure treatment, which chemicals may be toxic to the environment. While there are some plastic spacer block substitutes on the market, they are generally deficient in that they are typically wood block designs formed from plastic.  
       [0008] In most installation instances, it requires two to three people to attach a twelve (12) foot section of guardrailing to support posts when using conventional spacer blocks. In the effort, installation typically requires one person to hold the guardrail while another person aligns and holds the spacer block in position. A third person is often required to insert bolts or other attachment means through each system piece for securitization thereof  
       SUMMARY OF THE INVENTION  
       [0009] In accordance with teachings of the present disclosure, a guardrail support, attachment and positioning block is provided. In one embodiment, the block preferably includes a pair of side-walls coupled to a top and a bottom panel, thereby forming a generally rectangular block having first and second faces. The block preferably further includes, among other components, at least one mounting bore for coupling a guardrail to a support post. The block preferably also includes an engagement mechanism operable to engage the block with the support post and a resting mechanism operable to support the guardrail during assembly.  
       [0010] In another aspect of the present invention, a method of manufacturing a spacer block for attaching a guardrail to a support post is provided. The method preferably includes forming a block, forming a first aperture through the block and positioning an engagement mechanism on the block, the engagement mechanism preferably being operable to retain the block proximate a mounting position during assembly of a roadway safety barrier system.  
       [0011] In yet another aspect, the present invention provides a guardrail support assembly. The guardrail support assembly preferably includes a support post and a spacer block. The spacer block preferably includes, among other characteristics, a top tab operable to engage the support post and maintain the spacer block in position.  
       [0012] In a further aspect, the present invention provides a method for assembling a roadway safety barrier system. The method preferably includes, among other steps, engaging a tab on a spacer block with a support post such that the spacer block is retained proximate a mounting position. The method preferably also includes engaging at least a portion of a guardrail with a support mechanism on the spacer block such that the guardrail segment may be retained in position proximate the mounting position.  
       [0013] In another aspect, the present invention provides a roadway safety barrier system. The roadway safety barrier system preferably includes a guardrail, a support post and a spacer block coupled together by one or more attachment mechanisms. The spacer block preferably includes, among other elements, a positioning mechanism operable to depend the spacer block from the support during assembly of the roadway safety barrier system.  
       [0014] Further, the present invention provides a spacer block having improved strength, reduced weight, and competitive cost. In addition, the spacer block of the present invention, designed with the assembly process in mind, enables an individual installer to erect and install a guardrail safety barrier system using spacer blocks supported by posts.  
       [0015] Plastic properties are different from those of wood. The present invention takes advantage of these different properties through the use of a new spacer block design. The spacer block of the present invention may employ plastic (polyethylene, PVC, polypropylene polyethylene terephthalate, nylon), plastic/rubber, as well as other materials in its construction. Through the use of such materials, the present invention provides a more resilient, elastic and flexible spacer block that is generally impervious to weathering, has increased longevity, and requires little or no maintenance once installed.  
       [0016] It is an object of the present invention to provide a spacer block enabling one person to install a roadway safety barrier system.  
       [0017] It is another object of the present invention to provide a spacer block which is splinter-less, has a longer life span and is lighter than wood.  
       [0018] It is yet another object of the present invention to provide a plastic/rubber composite spacer block that meets all required specifications set forth by the Federal Highway Administration.  
       [0019] It is still another object of the present invention to provide a spacer block that is environmentally friendly and capable of being manufactured using recycled plastic, tires, and/or combinations thereof.  
       [0020] It is still another object of the present invention to provide a plastic-rubber composite spacer block that will meet or exceed the capabilities of today&#39;s wooden block.  
       [0021] Yet another object of the present invention is to provide a spacer block embodiment that may be formed from structural foam in order to optimize the weight to strength characteristics of the spacer block.  
       [0022] Other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings showing a preferred embodiment of the invention.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0023] A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:  
     [0024]FIG. 1 is a perspective view showing a two crown guardrail roadway safety barrier system according to teachings of the present invention;  
     [0025]FIG. 2 a  is a perspective view showing a guardrail support assembly according to teachings of the present invention;  
     [0026]FIG. 2 b  is an expanded view showing the engagement or positioning mechanism of the spacer block illustrated in FIG. 2 a  according to teachings of the present invention;  
     [0027]FIG. 3 is a perspective view showing a rear and side of one embodiment of a spacer block according to teachings of the present invention;  
     [0028]FIG. 4 is a perspective view of the spacer block depicted in FIG. 3 showing a front and side of the spacer block according to teachings of the present invention;  
     [0029]FIG. 5 is a perspective view showing an alternate embodiment of a spacer block according to teachings of the present invention;  
     [0030]FIG. 6 is a plan view showing the front of one embodiment of a spacer block according to teachings of the present invention;  
     [0031]FIG. 7 is a plan view showing an alternate webbing arrangement for a spacer block according to teachings of the present invention;  
     [0032]FIG. 8 is a plan view showing a spacer block for use with a thrie-beam guardrail and utilizing a webbed reinforcement arrangement similar to that used in the spacer block shown in FIG. 6 according to teachings of the present invention;  
     [0033]FIG. 9 is a plan view showing a spacer block for use with a thrie-beam guardrail and utilizing a webbed reinforcement arrangement similar to that used in the spacer block shown in FIG. 7 according to teachings of the present invention;  
     [0034]FIG. 10 is a side view of a spacer block formed from structural foam according to teachings of the present invention;  
     [0035]FIG. 11 is a top view, in section, showing a spacer block having a cellular core and an integrated solid skin on each side thereof according to teachings of the present invention;  
     [0036]FIG. 12 is a plan view, in section, of the structural foam spacer block illustrated in FIG. 10 showing a cellular core and an integral solid skin, wherein the transition from skin to cellular core is gradual, according to the teachings of the present invention;  
     [0037]FIG. 13 is a perspective view showing a portion of a two-crown guardrail roadway safety barrier system incorporating a structural foam spacer block according to the teachings of the present invention;  
     [0038]FIG. 14 is a perspective view of a guardrail support assembly incorporating a structural foam spacer block according to the teachings of the present invention; and  
     [0039]FIG. 15 is a perspective view showing a roadway safety barrier system incorporating thrie-beam guardrails according to teachings of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0040] Preferred embodiments of the invention and its advantages are best understood by referring to FIGS. 1 through 15 of the drawings, like numerals being used for like and corresponding parts of the various drawings.  
     [0041] As illustrated in FIGS. 1 through 2 b , spacer block  11  of the present invention may be mounted to a support post  30 , such as an I-beam support post, such that spacer block  11  may cooperatively engage and support a guardrail segment  14  thereon. The roadway safety barrier system  10  of FIG. 1 preferably includes a plurality of spacer blocks  11 , support posts  30  and guardrail segments  14 . An alternate embodiment of roadway safety barrier system  10  and spacer block  11  for use with thrie-beam guardrail segments  15  is illustrated in FIG. 15 and described in further detail below.  
     [0042] In FIGS. 1 through 4, spacer block  11  is shown with a removable and slidable top tab  40  for engaging a top edge of support post  30 . Side tabs  42 , illustrated in FIGS. 2 a ,  3  and  4 , for preventing lateral movement of spacer block  11  may also be included. In one embodiment, guardrail  14  preferably rests on a bottom or support tab  64 , illustrated in FIG. 4, extending from front face  12  of spacer block  11 . During installation, bottom tab  64  preferably aids in the support and alignment of guardrail  14  for attachment to support post  30  with one or more attachment mechanisms  13  (e.g., bolts) extending through holes or mounting bores  28  of spacer block  11  and support post  30 . Conventional I-beam support posts  30  generally have at least one hole punched into a flange  54  on one side of the support post  30  as illustrated in FIG. 2 a.    
     [0043] A spacer block  11  for use with conventional two crown (“W”) guardrails or other conventional longitudinal rail members is generally shown in FIGS. 1 through 6,  7 ,  10  and  12  through  14 . Such a spacer block  11  is preferably about four (4) inches wide, about seven and one-half (7½) inches deep, and about fourteen (14) inches long.  
     [0044] a spacer block  11  formed in accordance with teachings of the present invention preferably includes front face  12 . Front face  12  may be a generally flat solid surface. Alternatively, front face  12  may be webbed, curved, corrugated or formed to correspond to the shape of a guardrail  14 . Similarly, rear face  16  may be concave or include a longitudinal depression operable to fit around support posts  30 .  
     [0045] Front face  12  is preferably connected to rear face  16  by a pair of spaced apart, opposing side-walls  18  as well as a top panel  20  and a bottom panel  22 . The interconnections between side-walls  18 , top panel  20 , and bottom panel  22  may have rounded shoulders  24 , see FIGS. 1 through 4, or squared shoulders  26 , see FIG. 5.  
     [0046] As illustrated in FIGS. 3 and 5, spacer block  11  may include a top cavity  34  and a bottom cavity  36  separated by a medial wall  38  horizontally disposed between front face  12  and rear face  16 . A pair of mounting bores  28  are preferably disposed proximate to or through medial wall  38 . Corded-out cavities  34  and  36  may be reinforced with webbing, solid block materials, gel material, foam, or liquids such as water or glycol, as well as mixtures thereof to aid in the dissipation of stress or impact force.  
     [0047] As mentioned above, one embodiment of spacer block  11  preferably includes a pair of mounting bores  28  formed through medial wall  38 . Mounting bores  28  are preferably oriented horizontally, travelling between front face  12  and rear face  16 , side by side, to facilitate alignment of the one or more mounting bores  28  with the one or more offset holes  55  preformed in a typical support post  30 . Orienting mounting bores  28  as described preferably enables a single installer to position the mounting bores  28  for quick alignment and attachment of a spacer block  11  and guardrail  14  to support post  30 .  
     [0048] As illustrated, spacer blocks  11  may include at least one and preferably a plurality of mounting bores  28  extending through front face  12  for cooperative engagement of an attachment mechanism  13  extending through guardrail  14  and spacer block  11 , securing their attachment to support post  30 . In a preferred embodiment, mounting bores  28  extend through both front face  12  and rear face  16 . In addition, mounting bores  28  may extend through medial wall  38  connecting front face  12  and rear face  16 . According to teachings of the present invention, a sleeve  32  formed from a cylinder having a bore therethrough may be used as a removable spacer means for insertion between a hole formed in front face  12  and rear face  16 . Sleeve  32  preferably abuts an interior surface of front face  12 , extends through a cavity formed in the interior of spacer block  11 , interconnects with an interior surface of rear face  16  and provides additional structural support.  
     [0049] Spacer block  11 , as mentioned above with reference to FIGS. 1 through 4, preferably also includes a top tab  40  fixedly attached to top panel  20 . Tab  40  may also be provided as a removable or slidable tab having projections for cooperatively engaging grooves formed in channel  43 , such as in a tongue and groove arrangement. Tab  40  preferably extends beyond rear face  16  of spacer block  11  such that spacer block  11  may be engaged with the top of a support post  30  and depend therefrom, see FIGS. 1 through 2 b  and  13  through  15 . In alternate embodiments, positioning or engagement tab  40  may comprise a flat plate, a ring to engage a cylindrical post or any other form useful for engaging support post  30  of different configurations according to teachings of the present invention.  
     [0050] The embodiment of engagement tab  40  shown in FIGS. 1 through 5 includes projecting members or fingers  50  extending downward from tab  40 , enabling tab  40  to rest on, be positioned on, or otherwise engage the top of an I-beam shaped support post  30 . In such engagement, fingers  50  preferably extend behind flange  54  of support post  30  to thereby hold spacer block  11  proximate a mounting position on support post  30 .  
     [0051] To facilitate a movable positioning tab  40 , a groove or channel  43  may be formed or cut in top panel  20  on spacer block  11 . As shown in FIG. 4, a leg  48  that extends from a bottom surface of tab  40  and movably engages the top of the channel  43  to provide additional structural support to tab  40  may also be included.  
     [0052] As shown in FIG. 5, first and second channels,  56  and  58  respectively, may be formed in top panel  20  of spacer block  11 . Tabs  41  and  46  may be provided, attached to the top surface of top panel  20 , and preferably extend beyond rear face  16  of spacer block  11 . Similar to top tab  40 , tabs  41  and  46  are preferably flanges  45  align with one another or that there be a corresponding number of each on the respective sides of spacer block  11 . The inclusion of at least one side tab  42  or side flange  45  aids in positioning spacer blocks  11  with respect to the vertical sides or flanges  54  of support post  30 . Side tabs  42  or side flanges  45  may be integrally formed on spacer block  11  or attached by a holding means such as a screw or projection for engaging a hole (not expressly shown) formed in spacer block  11 . Spacer block  11  may be readily aligned to its proper orientation or in a mounting position through the aid of side tabs  42  or side flanges  45  and tab  40 .  
     [0053] Spacer block  11  preferably also includes a support tab  64  operable to support or rest at least a portion of a guardrail  14  thereon. As shown in FIGS. 4, 6,  7  and  10 , tab  64  may be provided as an extension from bottom panel  22  or front face  12 . Alternate positions of support tab  64  are considered within the scope of the present invention. By allowing guardrail  14  to rest on support tab  64 , the alignment of mounting bores  28  with one or more holes in guardrail  14  and support post  30 , and the installation of the same, may be simplified.  
     [0054] To permit stacking or nesting of stored spacer blocks  11 , as illustrated in FIGS. 3, 7 and  9 , a recess or notch  60  may be formed or cut into bottom panel  22 , proximate rear face  16 . Notch  60  preferably allows for the cooperative engagement of support tab  64  therewith such that spacer blocks  11  may be positioned one upon the other for storage, transport or other purposes.  
     [0055] Spacer block  11  may be formed or molded such that front face  12  is slightly shorter than rear face  16 , resulting in top panel  12  and bottom panel  22  inclining toward one another slightly (not expressly shown) at front face  12  to facilitate the removal of spacer block  11  from the mold. Notch or recess  60  of spacer block  11  may also be formed on bottom panel  22  as a declining channel extending from rear face  16  toward front face  12  and preferably does not extend through an interior surface of bottom panel  22 .  
     [0056] Spacer blocks  11  built in accordance with teachings of the present invention may be molded into specific embodiments enabling the maximization of structural integrity while maintaining controlled flexibility. These traits may be leveraged by using, among other options, reinforcing webbing, and various rubber and thermoplastic compositions.  
     [0057]FIGS. 6 and 7 show alternate embodiments of spacer block  11  of the present invention using webbing within top cavity  34  and bottom cavity  36 . Two reinforcing webbing configurations are shown in FIGS. 6 and 7. As illustrated, rear face  16  of spacer block  11  shows webbing formed by combining various lengths of lateral, longitudinal, and transverse members having cavities thereinbetween. The members are preferably positioned to increase structural strength while aiding spacer block  11  in the control of compression and flexing forces. A webbed reinforcement structure preferably also contributes to minimizing the weight of spacer block.  
     [0058] As shown in FIG. 6, one embodiment of spacer block  11  preferably includes webbing which extends from an interior surface of front face  12 , through cavity  34  and/or  36 , and having a distal end equal in length to side-walls  18 , terminating to form rear face  16 . In such a webbing configuration, preferably extending from a center of first cavity  34  from the interior surface of front face  12  is first cylindrical reinforcement member  72 . A corresponding second cylindrical reinforcement member  74  is preferably included extending from the interior surface of front face  12  through second cavity  36 . In each of cavities  34  and  36 , the webbing preferably comprises runners extending from first and second cylindrical reinforcing members,  72  and  74  respectively, to the interior surfaces of side-walls  18 , top panel  20 , bottom panel  22  and medial wall  38 .  
     [0059] Specifically as shown in FIG. 6, within first cavity  34 , first runner  76  preferably extends between top panel  20  and cylindrical reinforcing member  72 . A pair of second runners  78  preferably extend between cylindrical reinforcing member  72  and the corners connecting top panel  20  with side-walls  18 . A pair of third runners  80  preferably extend between cylindrical reinforcing member  72  and side-walls  18 . A fourth pair of runners  82  preferably extend between cylindrical reinforcing member  72  and medial wall  38 , forming a teardrop shaped cavity thereinbetween.  
     [0060] Within second cavity  36  of spacer block  11 , illustrated in FIG. 6, is a first runner  176  preferably extending between bottom panel  22  and cylindrical reinforcing member  74 . A pair of second runners  178  preferably extend between cylindrical reinforcing member  74  and the corners connecting bottom panel  22  with sidewalls  18 . A pair of third runners  180  preferably extend between cylindrical reinforcing member  74  and side-walls  18 . A fourth pair of runners  182  preferably extend between cylindrical reinforcing member  172  and medial wall  38 , forming a teardrop shaped cavity thereinbetween.  
     [0061] The spacer block  11  embodiment illustrated in FIG. 7 has dimensions, features, and webbing similar to the embodiment of spacer block  11  illustrated in FIG. 6. However, the embodiment of spacer block  11  illustrated in FIG. 7 differs from that illustrated in FIG. 6 in that the reinforcement webbing illustrated in FIG. 7 does not utilize runner  76  extending between top panel  20  and cylindrical reinforcing member  74  or the vertical runner  176  extending between bottom panel  22  and cylindrical reinforcing member  74 . In addition, the embodiment of spacer block  11  depicted in FIG. 7 includes notch  60  formed in bottom panel  22 , proximate rear face  16 . As illustrated, notch  60  preferably forms a pocket and does not cut through an exterior surface of bottom panel  22 .  
     [0062] Illustrated in FIG. 8 is an elongated embodiment of a spacer block  11  designed for use with thrie-beam guardrails. Illustration of one embodiment of a roadway safety barrier system  10  using one embodiment of a thrie-beam spacer block  11 , as shown in FIG. 8, is depicted in FIG. 15. Elongated spacer block  11  of FIG. 8 preferably includes additional third cavity  35 , medial wall  138  and mounting bores  128 , disposed between first cavity  34  and second cavity  36 . Thrie-beam spacer block  11  of FIG. 8 preferably utilizes substantially the same reinforcing webbing configuration illustrated in FIG. 6. A spacer block  11  designed for use with a thrie-beam guardrail  15 , illustrated in FIG. 15, is preferably approximately four (4) inches wide, about twenty-one (21) inches long, and about seven and one-half (7½) to eight (8) inches thick. The depth, length or other dimensions may vary to correspond with the dimensions of a selected guardrail or support post. However, the four (4) inch wide dimension, although not critical, is preferably maintained at about four (4) inches or approximately equal to the thickness of support post  30 , excluding side flanges  45  or side tabs  42 .  
     [0063] Preferably included within third cavity  35  of elongated spacer block  11  is a pair of runners  278  extending between cylindrical reinforcing member  272  and medial wall  38 , forming a teardrop shaped cavity thereinbetween. A pair of runners  280  preferably extend between cylindrical reinforcing member  272  and side-walls  18 . A pair of runners  282  preferably extend between cylindrical reinforcing member  272  and medial wall  138 , forming a teardrop shaped cavity thereinbetween.  
     [0064] The structural integrity of the various embodiments of the spacer blocks  11  of the present invention may be attributed to the lightweight composite materials and the reinforcing webbing which preferably provide for rigidity and controlled compression of spacer blocks  11  under load.  
     [0065]FIG. 9 shows a second elongated embodiment of spacer block  11  for use with thrie-beam guardrails. See FIG. 15 for one embodiment of a roadway safety barrier system  10  capable of using a thrie-beam spacer block  11  as shown in FIG. 9. As illustrated in FIG. 9, elongated spacer block  11  may include third cavity  35 , medial wall  138  and mounting bores  128 , disposed between first cavity  34  and second cavity  36 . The elongated spacer block  11  of FIG. 9 preferably utilizes substantially the same webbing configuration as the “W” guardrail spacer block  11  embodiment illustrated in FIG. 7. Similar to the elongated spacer block  11  embodiment of FIG. 8, the thrie-beam spacer block  11  illustrated in FIG. 9 is preferably approximately four (4) inches wide, about twenty-one (21) inches long, and about seven and one-half (7½) to eight (8) inches thick. As mentioned above, the depth, length or other spacer block  11  dimensions may vary to correspond to the dimensions of a selected guardrail  15  and/or support post  30 . However, the four inch (4) wide dimension, although not critical, is preferably maintained at about four (4) inches or approximately equal to the thickness of a support post  30 , excluding any side flanges  45  or side tabs  42 .  
     [0066] In addition to or in place of the webbed reinforcement structures described above, it is contemplated that all or at least a portion of a spacer block may be filled with foam, gel, finely ground solid material, or a liquid such as water, alcohol or glycol. Alternatively, one or more of cavities  34 ,  35  or  36  may contain a bag filled with one or more materials to cushion and absorb impact with a roadway safety barrier system. The materials that may be contained within spacer block  11  or included in a container inserted into the webbing or into one or more of cavities  34 ,  35  or  36  formed within spacer block  11  may be removable, such as through the use of a water bag or a deformable plastic container such as a jug. In addition, a cellular core may be used for impact absorption within cavities  34 ,  35  or  36 , just as an impact absorbing block filled with cellular material, gel, or a liquid may be disposed within one or more cavities  34 ,  35  or  36  of spacer block  11  according to teachings of the present invention.  
     [0067] As mentioned above, spacer blocks  11  made in accordance with teachings of the present invention may incorporate a variety of materials into their construction. One embodiment of a spacer block  11  incorporating teachings of the present invention incorporates structural foam into its composition. A structural foam spacer block  11  incorporating teachings of the present invention, such as the structural foam spacer blocks  11  illustrated in FIGS. 10 through 14, is preferably molded and preferably includes a cellular core and an integral solid skin, wherein the transition from skin to core is preferably gradual, as shown generally at  90  in FIGS. 11 and 12. The solid skin preferably gives a molded spacer block  11  its form and toughness, while the cellular core preferably contributes to the attainment of high strength-to-weight characteristics. In one embodiment, the skin of a structural foam spacer block  11  may be up to one-half (½) inch thick. Preferred skin thicknesses range down from one-quarter (¼) inch thick to one-eighth (⅛) inch thick.  
     [0068] In general, there are two basic types of plastics available for creating structural foam spacer blocks  11 , thermoset materials and termoplastic materials. Thermoset materials, such as polyurethane, may be produced by polyaddition of reactive components such as polyol and isocyanate. Thermoplastic materials typically require the addition of physical or chemical blowing agents to produce foam and do not undergo chemical change. Some blowing agents decompose when heated to process temperature to evolve a gas such as carbon dioxide. (During processing, the exotherm generated by the reaction vaporizes a blowing agent that causes the mixture to expand.) Often, sodium bicarbonate or ammonium carbonate is used to form cellular or sponge rubber. Halocarbons and methylene chloride may be used in urethane, pentane in expanded polystyrene, and in some cases, hydrazine for foamed plastics.  
     [0069] Spacer blocks  11  using plastic and/or rubber components are generally limited to solid wall thicknesses of about four (4) millimeters. The wall thickness of a structural foam spacer block  11  using plastic and/or rubber components, on the other hand, is preferably not less than about four (4) millimeters in order to gain full advantage of a foam webbing structure between two layers of skin. Thus, greater overall wall thickness may be obtained by using structural foam. Additionally, structural foam spacer blocks  11  have few, if any, sink marks due to residual gas pressure in the cells. This allows the material to expand internally during cooling of the part while holding the skin firmly against the mold walls.  
     [0070] Because of their cellular structure, spacer blocks formed from structural foam are virtually stress-free, resulting in bowing and warping being greatly reduced. In addition, because of its cellular structure, less resin is required during fabrication, which results in a part three (3) to four (4) times more rigid than a solid part of the same weight. Consequently, spacer blocks  11  made in accordance with teachings of the present invention may be made from commodity plastics such as polystyrene and polyethylene with or without rubber in a load bearing application.  
     [0071] Properties of a structural foam spacer block  11  depend on the base polymer, overall part density, density distribution, skin thickness, cell shape and size, among other variables. Each of these variables may be affected by the processing method, process variables, wall thickness, and mold design.  
     [0072] The density of structural foam generally varies across its cross section and is typically lowest in the core. As the distance from the center of a foam block increases, the cells generally get smaller until they “disappear” near the outer skin, see generally at  90  in FIGS. 11 and 12. One objective of such a composition is to produce a part with high skin density, low core density and without the presence of voids. The range of available densities varies in the present invention from about thirty (30) percent in the center to one hundred (100) percent at the outer skin. Also, the overall part density, density distribution, skin thickness, cell shape and size depend upon the mold cycle which may vary between one-half (½) to ten (10) minutes.  
     [0073] A preferred embodiment of spacer block  11  may be formed with a low-pressure injection molding machine using thermoplastics and/or rubber. A screw may be used to plasticate a mixture of polymer and up to one (1) percent chemical blowing agent, preferably up to one-half (½) percent, wherein the screw barrels have zones maintained at different temperatures and are arranged so that the blowing agent is maintained near the nozzle. A foamable mixture may thereby be produced, pumped under pressure to an accumulator and stored in a molten state at a pressure higher than the foaming pressure. Upon opening a valve in the nozzle, a portion of the foamable mixture may be discharged from the accumulator into the mold. The mold cavity is then filled by the gases generated by the decomposition of the chemical blowing agent, forcing the material into the shape of the mold The pressure and temperature of the material in the mold then drop, resulting in bubbles developing in the core. In a preferred embodiment, the melt is charged at about four hundred (400) degrees Fahrenheit and the melt temperature is between about three hundred and eighty (380) degrees Fahrenheit to four hundred and fifty (450) degrees Fahrenheit. It should be noted that structural foam spacer blocks  11  made in accordance with teachings of the present invention may be made from a rubber compound in combination with a plastic. Preferably, the plastic will encapsulate the rubber particles and act as a binder. The rubber preferably produces enough gas during processing under the heat and pressure of the low-pressure injection molding process that the structural foam product can be made without the addition of any type of chemical blowing agent.  
     [0074] Spacer block  11  of the present invention may be formed by injection molding, preferably low-pressure injection molding, such as is used for structural foam products. Spacer block  11  may include virgin or regrind plastic or combinations thereof without any rubber. The plastic may be selected from such polymers as polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, ABS, Acetyl, polypropylene oxide, nylon, PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone. The spacer block  11  of the present invention may be formed from a single type of polymer or mixtures of various polymers. Typically a chemical blowing agent in an amount less than five (5) percent, and preferably in an amount less than one (1) percent and preferably in an amount less than one-half (½) percent may be used with one hundred (100) percent polymer composition spacer blocks  11 .  
     [0075] A rubber and/or elastomeric compound may be incorporated in the formulation as a substitution for up to seventy (70) percent, and more preferably less than fifty (50) percent and most preferably from about forty (40) to fifty (50) percent depending upon the strength to weight ratio desired and the structural properties required for a particular application or size of guardrail. Regrind rubber is typically less expensive than plastic materials. Therefore, as much as forty (40) to fifty (50) percent regrind rubber may be used in a spacer block designed for normal impact applications or support posts  30  spaced close together. A composition with less than forty-five (45) percent rubber may be desirable for applications requiring support posts  30  to be spread further apart from one another. The type of rubber may also be an important consideration in that the rubber may be comprised of a natural rubber or synthetic rubber, either virgin material, regrind material or combinations thereof. Additives such as fillers and fiberglass may further reduce the cost of manufacture and provide the requisite strength. Because of the gases produced during injection molding of the rubber particles, the use of a chemical blowing agent is an option and is not required when processing the plastic and rubber mixed compositions.  
     [0076] One material that may be used in the construction of spacer block  11  comprises one or more polymers (such as polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, and mixtures thereof), and a polymer and rubber blend. Other plastic materials which may be used include, but are not limited to, ABS, Acetyl, polypropylene oxide, nylon PBT, polycarbonate, polystyrene, modified polyphenylene oxide, polyester, fiberglass filled nylon, fiberglass filled styrene, fiberglass filled SAN, acrylic, ethylene copolymers, ionomers, and polysulfone. Spacer block  11  may also be formed from a single polymer or mixtures of various polymers. The polymers used may be virgin material or polymers including regrind materials, such as reground polyethylene, ethylene. The rubber and/or elastomeric compound that may be incorporated may also include a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof. It is contemplated that fiberglass may also be used as an additive or substitute raw material for all or at least a portion of the plastic material. Fillers such as wood chips, sawdust, calcium carbonate may also be used. The rubber from used tires that has long been a problem for the environment may also be used as a source of rubber for the present invention. In a variety of embodiments, the spacer blocks themselves may be recyclable.  
     [0077] Another embodiment of the present invention comprises polyethylene together with regrind rubber ranging in an amount of up to forty-five (45) percent. Yet another more preferred embodiment utilizes from about thirty (30) to forty-five (45) percent regrind rubber and utilizes ethylene as the binding polymer.  
     [0078] Yet another embodiment utilizes a powdered processing aid from Polymer Process Technologies, Inc. in Akron, Ohio referred to by the trademark PPT-SYS, (PPT-SYS(R) for rubber applications and PPT-SYS(P) for plastic applications), having a specific gravity of about one and one-one hundredth (1.01), a pH of about seven (7), and a melting point range of over six hundred (600) degrees Fahrenheit. Each of these powdered processing aids is a highly effective alloying agent for compatibilizing and alloying cured rubber, virgin or regrind, to form compounds having little or no change in physical properties.  
     [0079] Still another embodiment of spacer block  11  includes a blend of at least one polymer having among its ingredients one or more of the plastic materials set forth herein mixed and molded together with at least one rubber or elastomeric material. The ability to mold large blocks of plastic containing virgin and/or regrind thermoplastics obtained from such sources as reusable containers, alone or together with virgin or grind rubber from used tires or other sources, provides a useful means for the disposal and recycling of waste products. One embodiment utilizes grind rubber in combination with one or more thermoplastics extruded or molded by low-pressure injection molding or vacuum forming. The molding process is believed to encapsulate the rubber particles with the thermoplastic melt thereby providing a stronger blended product with enhanced performance capabilities as compared to a simple mixture of thermoplastic and rubber particles compressed together under high pressure. One source of the grind rubber is used vehicle tires, as indicated above, representing a new method of disposal for used tires.  
     [0080] Another embodiment may contain a non-toxic blend of naturally occurring materials, (plant polymers, gums, and anionic salts), marketed by Polymer process Technologies, Inc., under the trademark of PPT-RNU. When added to post consumer plastics of all kinds, PPT-RNU will typically repair heat history plastics to near virgin polymer condition in addition to or instead of the PPT-SYS (R)/(P). This material has a pH of about six and eight-tenths (6.8), a specific gravity of about one and five-hundredths (1.05), a melting point flow of over six hundred and fifty (650) degrees Fahrenheit, and it&#39;s generally used in amounts of up to ten (10) percent by weight, and more preferably, from about three (3) percent to about six (6) percent by weight.  
     [0081] Another embodiment utilizes both the PPT-RNU and PPT-SYS additives with rubber and a polymer, such as polyethylene, to enhance the compatibility and performance of regrind rubber from tires being compounded with virgin or recycled polymers such as polyethylene in conventional compounding equipment at processing temperatures of from about three hundred and sixty (360) degrees Fahrenheit to four hundred and ten (410) degrees Fahrenheit which is typical for extrusion and compounding operations.  
     [0082] Although the present invention has been described with respect to a specific preferred embodiment thereof, various changes and modifications may be suggested to one skilled in the art and it is intended that the present invention encompass such changes and modifications fall within the scope of the appended claims.