Abstract:
The guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “I” beams which are driven into the ground. The spacer block keeps automobile wheels from impacting the I beams and initiating a roll of the vehicle. The spacer block is a generally rectangular block or cube including corded-out cavities to reduce weight and tabs or projections which cooperatively engage the side of the post and the edge of the guard rail to position and hold same in position for attachment with holding members such as bolts. Webbing can be used to provide structural support within the cavity. The spacer block may be formed by low pressure injection molding to form a structural foam spacer block to optimize the strength to weight characteristics of the spacer block. The spacer block may be formed of a virgin and/or recycled plastic material and/or include virgin or recycled rubber material such as from obtained from the regrind of used tires and/or another elastomeric material from other sources.

Description:
This application claims priority from U.S. provisional application Serial No. 60/249,037 filed on Nov. 15, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This device relates to spacer blocks for attachment of guard rails to support posts. 
     2. Description of the Prior Art 
     Guard rails are typically installed along highways as a roadway safety barrier system. The guard rails are usually formed as strips of material, typically extruded metal about 12 feet long and weighting about 90 pounds. A preferred embodiment comprises an elongated strip of metal, usually composed of galvanized steel, (typically about 12 gauge), aluminum, steel, fiber glass, or even synthetic materials. At least one configuration of a guard rail used includes a corrugation forming an undulating cross section in order to absorb energy upon receiving an impact from an out of control vehicle to prevent or at least control the direction of the vehicle prior to its leaving the roadway. Typically these beams are about 9 inches wide, have two crowns and are shaped substantially like the letter “W”. An alternate corrugated guard rail is known in the industry as a thrie beam which has three crowns and is about a third wider than the conventional two crown guard rail. Usually a plurality of guard rails will be linked together horizontally at their distal ends, either end to end, or overlapping, and be supported by a plurality of vertically oriented posts which are typically “I-beamed” shaped, round, or square posts which are driven into the ground spaced apart a selected distance from the edge of the road. Of course, posts are also fabricated from aluminum, wood, or other metals and could be formed from polymers or fiberglass materials. The posts are usually driven into the ground and typically will yield under a desired amount of pressure and move within the ground or bend in accordance with the deformation of the guard rail rather than break off at ground level, in order to assist the rail in dissipating force upon receiving a blow from a vehicle. 
     Typically a spacer block is disposed between the guard rail and the post to support the guard rail at a selected distance from the post to prevent an uncontrolled vehicle from hitting and entangling the posts. Thus, the spacer block keeps the automobile wheels from impacting the posts and initiating a roll of the vehicle. Moreover, the guard rail provides a continuous rail or track for guiding the vehicle providing at least some response time for the driver to regain control of the vehicle before leaving the roadway. 
     The most popular material spacer blocks are made out of is wood. Some of the problem with wood is it deteriorates over time, it is heavy, it can give installers splinters, it contracts and expands with season changes. Also, wood tends to leach out chemicals typically used for pressure treating which may be toxic to the environment. Conventional plastic blocks on the market today are typically wood block designs made out of plastic. 
     It typically requires two to three people to install a 12 foot section of guard railing to posts when using conventional spacer blocks, one to hold the guard rail and another to align and hold the spacer block in position with the post and a third person to insert bolts therethrough securing same. 
     The instant invention provides a spacer block having improved strength, reduced weight, and competitive cost. Furthermore, the spacer block of the present invention was designed with the assembly process in mind in order to enable a single individual to erect a guard rail safety barrier system on spacer blocks supported by posts. 
     SUMMARY OF THE INVENTION 
     The guard rail support attachment and positioning block or spacer block is used to space guard railing away from posts such as “I” beams which are driven into the ground. 
     The spacer block of the instant invention provides a design that is strong yet light, which makes it installation friendly, reduces the cost of manufacture, and permits one person to install a section of guardrail. In the past it might require two or three people to hold the rail and mount it to the spacer block and support post. 
     Plastic properties are different from wood and requires a design that takes advantage of the different properties. The present design is specific for plastic, (polyethylene, PVC, polypropylene polyethylene terphthalate, nylon), or plastic/rubber and will out perform the wood design in all performance specifications. Moreover, the resiliency, elasticity, flexibility, and ability to be impervious to weathering elements, extend longtivity, and require little or no maintenance are important features of the present invention. 
     A preferred embodiment to the spacer block of the instant invention is a generally rectangular block or cube including corded-out cavities to reduce weight and one or more tabs on the top and/or sides projecting outwardly for cooperatively engaging the sides and top edge of the post. A preferred embodiment is approximately 4 inches in width which is the same as conventional I-beam posts providing a lightweight, compact, high strength spacer block as compared to conventional spacer blocks made from wood or plastic typically having a width of 6 inches or more. A tab projecting outward from the face of the spacer block provides a support member to hold, steady, and even align the guard rail which rests thereon providing a means for one individual to mount the guard rail on spacer blocks, whereas conventional spacer blocks do not support the guard rail prior to attachment thereto and require at least two individuals if not three to attach the guard rail to the spacer block and post. 
     The preferred embodiment of the spacer block of the present invention comprises one or more polymers, such as (polyethylene, polypropylene, polyethylene terephthalate, nylon, polyurethane, polyvinyl chloride, and mixtures thereof), and preferably a polymer/rubber blend. Other plastic materials which may be used may be selected from 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. Of course the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers. The polymers may be virgin material or the spacer block may be composed of at least some if not all of regrind materials, such as reground polyethylene, ethylene. The rubber and/or elastomeric compound which can be incorporated in the formulation may be comprised of 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 have been a huge problem for the environment and could be utilized as the source of rubber for the instant invention. Moreover, the spacer blocks may themselves be recyclable. 
     One preferred embodiment of the present invention is a spacer block utilizing a blend of at least one polymer including one or more of the plastic materials set forth heretofore, together with at least one rubber or elastomeric materials mixed and molded together with the polymer(s). The ability to mold large blocks of plastic containing virgin, and/or regrind thermoplastics which can be obtained from reusable containers, alone or together with virgin or grind rubber from used tires or other sources providing a useful means of disposal and recycling of waste products. One preferred embodiment of the invention utilizes grind rubber in combination with a 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 reground vehicle tires, representing a new method of disposal of used tires. 
     Another important aspect of the present invention, is the molding of the spacer blocks using a structural foam process to further increase strength, reduce costs, and reduce the weight of the spacer blocks. The structural foam techniques utilizes a gas and/or chemical foaming agent injection process in the molding operation to form a foam core creating structural support webbing between solid plastic skins to increase structural strength and reduce weight and cost. The design of the block to include structural external webbing between void spaces in the spacer blocks of the instant invention further provides strength and weight advantages to the space block. The use of the blend of plastics and rubber and/or the webbing within the block cavity are unique features; however, in addition the utilization of structural foam forming the skin provides another novel feature not utilized in spacer blocks taught in the prior art. 
     These embodiments of the present invention can be utilized with a spacer block molded having solid walls as well as a spacer block molded by structural foam whereby the walls are composed of an inner and outer skin with webbing thereinbetween. 
     It is contemplated that all or at least a portion of the spacer block  10  could be filled with foam, gel, finely ground solid material, or even a liquid such as water and/or alcohol and water such as a glycol to inhibit freezing, or that the cavity could contain a bag containing same to cushion and absorb impact thereto. The material could be contained within the spacer block body or insertion of a container into the webbing or cavity formed within the spacer block could even be removable, such as a water bag or a deformable plastic container such as a jug. Moreover, a cellular core could be utilized for impact absorption within the cavities, or an impact absorbing block filled with cellular material, a gel, or a liquid could be disposed within the cavities formed in the present spacer blocks. 
     Conventional spacer block assemblies require one person to hold the wood block while another holds the guardrail section and a third person installs the bolt, which holds the entire assembly together. The instant invention includes a hanger enabling the spacer block to hang on the I beam by itself. On the bottom of the spacer block is a guard rail resting tab so that the guard rail can be lifted and placed on the resting tab for mounting to the spacer block and post. 
     One person can install a section by placing the bolt with in hands reach, it is possible for one person to lift a section of guardrail and rest it on the rail tab and install the bolt. A section of guardrail can be installed by a single person at a much faster pace than the designs of today. Therefor, it is an objective of the present invention to provide a spacer block which enables one person to mount a guard rail to a spacer block and post. 
     It is another objective of the present invention to provide a spacer block which is splinter-less, has a longer life span than wood, lighter than wood. 
     It is an object of the present invention to provide a plastic/rubber composite block which meets all required specifications set forth by the Federal Highway Administration. 
     It is an object of the present invention to provide a spacer block which is environmentally friendly and be capable of being manufactured using recycled plastic, tires, and/or combinations thereof. 
     It is an object of the present invention to provide a plastic/rubber composition which will out-last the wood blocks of today. 
     It is an object of the present invention to provide a plastic-rubber composite spacer block that will meet or exceed the requirements of today&#39;s wooden block. 
     Another important optional feature is the utilization of a plastic/rubber copolymer material to enhance the performance of the spacer block. 
     Yet another object of the present invention is to provide an embodiment which may be formed from structural foam in order to optimize the weight to strength of the spacer block. 
     Other objects, features, and advantages of the invention will be apparent with the following detailed description taken in conjunction with the accompanying drawings showing a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts throughout the several views and wherein: 
     FIG. 1 is a perspective view showing the spacer block of the present invention mounted to a post and cooperatively engaging a guard rail; 
     FIG. 2 is a rear perspective view showing the spacer block of FIG.  1  and the post; 
     FIG. 3 is a rear perspective view showing the spacer block of FIG. 1 having a cavity formed between the top, side, and medial wall, and a cavity formed between the medial side, and bottom wall; 
     FIG. 4 is a front perspective view of FIG. 1 showing the flat face of the spacer block and guard rail support and positioning tab; 
     FIG. 5 is perspective rear view showing an alternate embodiment of the spacer block utilizing a plurality of tabs removably and slidably positional within grooves formed in the top surface of the spacer block; 
     FIG. 6 is front view of an alternate embodiment of the spacer block showing webbing within the cavities; 
     FIG. 7 is front view of an elongated embodiment of the spacer block utilizing the webbing arrangement of FIG. 6 for use with a thrie beam spacer block; 
     FIG. 8 is front view of an alternate embodiment of the spacer block showing a different webbing arrangement within the cavities; 
     FIG. 9 is a side view of the spacer block of FIG. 8 formed of structural foam; 
     FIG. 10 is front view of an elongated embodiment of a spacer block utilizing the webbing arrangement of FIG. 8 for use with a thrie beam spacer block; 
     FIG. 11 is a sectional view of a portion of a block showing a cellular core and an integral solid skin on each side thereof; 
     FIG. 12 is a sectional view along Section  9 — 9  of FIG. 9 showing a structural foam segment showing a cellular core and an integral solid skin, wherein the transition from skin to core is gradual; 
     FIG. 13 is a perspective view showing the spacer block of FIG. 12 mounted to a post and cooperatively engaging a guard rail; and 
     FIG. 14 is a rear perspective view showing the spacer block of FIG.  12  and the post. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The structural integrity of the various embodiments of the spacer blocks  10  of the present invention is attributed to the lightweight composite materials and the reinforcing webbing which provides the rigidity and controlled compression of the spacer blocks  10  under load. 
     As illustrated in FIGS. 1 and 2, the spacer block  11  is mounted to a post  30 , shown as an I-beam, and cooperatively engages and supports a guard rail  14  having an “M” shaped corrugated cross section. The spacer block  11  is shown with the removable slidable top tab  40  engaging the top edge of the I beam and the optional side tabs  42  preventing lateral movement thereof. The guard rail  14  is shown resting, positioned on the bottom tab  64  extending from the spacer block  11  supporting and aligning the guard rail  14  for attachment to the post  30  with one or more bolts extending through the through holes or bores  28  of the spacer block  11 . Conventional I-beam posts  30  have a single hole punched into the flange  54  on one side of the post  30  only. 
     As shown in FIGS. 1-5, the spacer block  10  used for conventional two crown guard rails or other conventional longitudinal rail members is typically about four (4) inches wide, about seven and one-half (7½) inches deep, and about 14 inches long. The spacer blocks  10  of the present invention include a front face  12  constituting the surface for attachment of the guard rail  14 . The front face  12  is a generally flat solid surface. Of course it is anticipated that the face  12  could be webbed, curved, or even corrugated to correspond to the shape of the guard rail  14 . The front face  12  can be formed to be concave and include a longitudinal depression to fit around posts as well. 
     The front face  12  is connected to a rear face  16  by a pair of spaced apart opposing side walls  18  to a top panel  20  and a bottom panel  22 . The interconnecting side walls  18 , top panel  20 , and bottom panel  22  may have rounded shoulders  24  as shown in FIGS. 1-4 or squared shoulders  26  as shown in FIG.  5 . 
     More particularly, the spacer block  11  can include a top cavity  34  and a bottom cavity  36  separated by a horizontally disposed medial wall  38  joining the front face  12  and rear face  16 , defining a pair of sleeves having bores  18  therethrough. The corded-out cavities of the spacer block can be reinforced with webbing, solid block materials, gel material, foam, or liquids such as water, glycol, and mixtures thereof to aid in the dissipation of any stress. 
     An important feature of a preferred embodiment of the spacer block  11  of the present invention is a pair of mounting bores  28  formed in the spacer block  11  oriented along the horizontal axis, side by side, to facilitate aligning a bore  28  of the spacer block  11  with the offset hole  55  preformed in the typical metal I-beam  30 . The bore  28  can be positioned for quick alignment and attachment of the spacer block  11  and guard rail  16  to the post  30 . 
     More particularly, the spacer blocks  11  can include at least one and preferably a plurality of mounting bores  28  extending through the front face  12  for cooperative engagement of a corresponding bolt extending through the guard rail  14  and spacer block  11  for attachment to a post  30 . In a preferred embodiment, the bore  28  extends through both the front face  12  and the rear face  16 . Moreover, the bore  18  can extend through the medial wall  38  interconnecting the front face  12  and the rear face  16 . It is contemplated that a sleeve  32  formed from a cylinder having a bore therethrough could be utilized as a removable spacer means for insertion between the hole formed in the front face  12  and rear face  16  abutting an interior surface of the front face  12 , extending through the cavity formed in the interior of the block  11  to interconnect with the interior surface of the rear face  16  to provide additional structural support. 
     A feature which is very useful and adaptable to the various spacer block  11  embodiments are locating and holding means for cooperatively engaging the post  30  and/or guard rail  14 . 
     The preferred embodiments of the spacer blocks  11  can include a top tab  40  fixedly attached to the top surface of the top panel  20 . The tab  40  may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channel  43  in a tongue and groove arrangement. The tabs  43  extend from past the rear face  22  of the spacer block for holding the spacer block  11  onto the top of a post  30 . It is contemplated the tab  40  could comprise a flat plate or even a ring to engage a cylindrical post; however, the embodiment shown in FIGS. 1-5 includes projecting members or fingers  50  extending downward from the tab  40  mounted on the top of the block  11  extending past the rear face  22  enabling the tab  40  to set on top of an I-beam shaped post  30  with the fingers  50  extending behind the flanges  54  of the post  30  thereby holding the spacer block  11  securely to the post  30  for mounting. 
     Moreover, As shown in FIGS. 1-4 a groove or channel  43  can be formed or cut into the surface of the spacer block  11  top panel  20  to facilitate molding or handling of the blocks. As shown in the drawings, a leg  48  can extend from the bottom surface of the tab  40  to be supported by and preferably to connect with the top of the channel  43  in order to provide additional structural support for the tab  40 . 
     As shown in FIG. 5, a first and second channel,  56  and  58  respectively, are formed in the top panel  20  of the spacer block  13 . A pair of tabs  41  and  46  fixedly attached to the top surface of the top panel  20  extend past the rear face  22  of the spacer block for holding the spacer block  13  onto the top of a post  30 . The tabs  41  and  46  may also be provided as a removable or slidable tab having projections cooperatively engaging grooves formed in the channels  56  and  58  in a tongue and groove arrangement. The tabs  41  and  46  extend from past the rear face  22  of the spacer block  13  for holding the spacer block  13  onto the top of a post  30 . Thus, the top tab  42  allows the spacer blocks  13  to hang on the post  30  during mounting of the guard rail, post, and spacer block assembly. 
     A stop means may be incorporated within the channel or attached to the ends thereof to limit movement of a movable top tab  40 ,  41 , and  46 . 
     As shown in FIGS. 1-5, one or more optional side tabs  42  can be utilized with the spacer blocks  10  of the present invention for cooperatively engaging the post  30 . FIGS. 6-14 show the use of side flanges  45 . The side tabs  44  or side flanges  45  are spaced apart generally opposing one another and preferably in alignment with one another; however, it is not necessary that the side tabs  44  align with one another or that there be a corresponding number of side tabs on each side. Even one side tab  44  or side flange  45  aids in positioning the spacer blocks  10  with respect to the post  30 . The side tabs  44  or side flanges  45  can be integrally formed within the spacer block  10  or attached by holding means such as a screw or projection engaging a hole formed in the spacer block  10 . The spacer block  10  can be aligned in proper orientation by utilizing the side tabs  42  extending from the sides of the block  10 . 
     A support tab  64  can be provided extending from the bottom panel  22  of the front face  12  for supporting a guard rail  14  resting thereon and aiding in the alignment of the bores  28  with holes in the guard rail  14  and post  30 . 
     A recess or notch  60  can be formed or cut into the bottom edge panel  22  and rear face  16  of the spacer block  10  disposed therein for cooperatively engaging the support tab  64  permitting stacking and nesting of the spacer blocks  10  one upon the other for storage or transport. 
     The spacer blocks  10  of the present invention can be molded into specific embodiments maximizing structural integrity while maintaining controlled flexibility via reinforcing webbing and selecting particular rubber and thermoplastic compositions. FIGS. 6 and 8 show alternate embodiments of the spacer block of the present invention which utilize webbing within the top cavity  34  and bottom cavity  36  separated by a horizontally disposed medial wall  38  joining the front face  12  and rear face  16 , defining a pair of sleeves formed as cylinders having bores  18  therethrough. 
     A preferred configuration of webbing design is shown in FIGS. 6 and 8, wherein the rear end of the spacer block shows webbing formed by various lengths of lateral, longitudinal, and transverse members having cavities thereinbetween are formed to increase the structural strength while controlling compression and flexing forces and minimizing the weight of the spacer block. 
     As shown in FIG. 6, a spacer block  70  includes webbing which extends from the interior surface of the front face  12  through the cavity  34  or  36  having a distal end equal distance with the side walls  18  forming the rear face  16 . Extending from the center of the interior surface of the front face  12  and through the first cavity  34  is a first cylindrical reinforcement member  72 . A corresponding second cylindrical reinforcement member  74  extends from the interior surface of the front face  12  through the second cavity  36 . In each cavity  34  and  36  respectively, the webbing comprises runners extending radially from a cylindrical reinforcing members  72 ,  74  to intersect with the interior surface of either the side wall  18 , top panel  20 , bottom panel  22 , or medial wall  38 . 
     As shown in FIG. 6, within the first cavity  34  a first runner  76  extends vertically from the top panel  20  to intersect with the cylindrical reinforcing member  72 . A pair of second runners  78  extend radially from the cylindrical reinforcing member  72  toward the corners connecting the top panel  20  with the side wall  18 . A pair of third runners  80  radiate horizontally from the cylindrical reinforcing member  72  toward the side walls  18 . A fourth pair of runners  82  radiate downwardly from the cylindrical reinforcing member  72  toward the bores  28  in the medial wall  38  forming a tear drop shaped cavity thereinbetween. 
     Within the second cavity  36  of the spacer block  70  a first runner  176  extends vertically from the bottom panel  22  to intersect with the cylindrical reinforcing member  74 . A pair of second runners  178  extend radially from the cylindrica reinforcing member  74  toward the corners connecting the top panel  20  with the side wall  18 . A pair of third runners  180  radiate horizontally from the cylindrical reinforcing member  74  toward the side walls  18 . A fourth pair of runners  182  radiate downwardly from the cylindrical reinforcing member  172  toward the bores  28  in the medial wall  38  forming a tear drop shaped cavity thereinbetween. Moreover, spacer block  70  can be formed or molded having a front face  12  which is slightly shorter than the rear face  16  so that the top panel  12  or bottom panel  22  incline toward one another slightly at the front face  12  to facilitate removing the spacer block from the mold. The notch (not shown) of the spacer block  70  is formed on the bottom of the bottom panel as a declining channel extending from the rear face  16  toward the front face  12  which does not extend through the interior surface of the bottom panel  22 . 
     FIG. 7 shows an alternate elongated embodiment of a spacer block  84  for use with thrie beam guard rails. The elongated spacer block  84  includes an additional third center cavity  35 , medial wall  138  and bores  128 , disposed between the first top cavity  34  and the second bottom cavity  36 . The spacer block  84  utilizes substantially the same webbing configuration of the spacer block  70  of FIG.  6 . The spacer block  84  is approximately 4 inches wide, about 21 inches long, and about 7½ to 8 inches thick. Of course, the depth and length dimension could vary on any of the spacer blocks  10  depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails  45  or side tabs  42 . 
     Within the third center cavity  35  of the spacer block  84  is a pair of runners  278  radiating upwardly from the cylindrical reinforcing member  172  toward the bores  28  in the medial wall  38  forming a tear drop shaped cavity thereinbetween. A pair of runners  280  radiate horizontally from the cylindrical reinforcing member  274  toward the side walls  18 . A pair of runners  282  radiate downwardly from the cylindrical reinforcing member  274  toward the bores  128  in the medial wall  138  forming a tear drop shaped cavity thereinbetween. 
     The spacer block embodiment  86  has similar dimensions, features, and webbing to that of the spacer block  84 . As best illustrated in FIGS. 8 and 9, it differs from spacer block  84  in that spacer block  86  does not utilize runner  76  extending vertically from the top panel  20  to intersect with the cylindrical reinforcing member  74  or the vertical runner  176  extending vertically from the bottom panel  22  to intersect with the cylindrical reinforcing member  74 . Moreover, the notch  260  is formed or cut into the bottom edge panel  22  and rear face  16  of the spacer block  10  forming a pocket, and does not cut through the bottom panel  22  exterior surface. 
     FIG. 10 shows an alternate elongated embodiment of the spacer block  86  for use with thrie beam guard rails. The elongated spacer block  88  includes an additional third center cavity  35 , medial wall  138  and bores  128 , disposed between the first top cavity  34  and the second bottom cavity  36 . The spacer block  88  utilizes substantially the same webbing configuration of the spacer block  86  of FIG.  8 . The spacer block  88  is approximately 4 inches wide, about 21 inches long, and about 7½ to 8 inches thick. Of course, the depth and length dimension could vary on any of the spacer blocks  10  depending upon the dimensions of the selected guard rail; however, the four inch wide dimension, although not critical is preferably maintained at about 4 inches or equivalent to the thickness of the mounting post excluding the side rails  45  or side tabs  42 . 
     Structural Foam Spacer Blocks 
     The structural foam spacer blocks of the present invention are molded and have a cellular core and an integral solid skin, wherein the transition from skin to core is gradual as shown in FIG.  11 . The solid skin gives the molded part its form and toughness, while the cellular core contributes to the high strength to weight characteristics. The skin of the structural foam spacer blocks can be up to ½ inch thick, more preferably up to ¼ inch thick and most preferably up to ⅛ inch thick. There are two basic types of plastics available for foaming. Thermoset materials such as polyurethane is produced by polyaddition of reactive components such as polyol and isocyanate. The exotherm generated by the reaction vaporizes a blowing agent that causes the mixture to expand. Thermoplastic materials typically require the addition of physical or chemical blowing agents to product a foam and do not undergo chemical change. Some blowing agents decompsoe when heated to process temperature to evolve a gas such as carbon dioxide. Often sodium bicarbonate or ammonium carbonate is used for cellular or sponge rubber, halocarbons and methylene chloride is used in urethane, pentane in expanded polystyrene, and in some cases hydrazine for foamed plastics. 
     Spacer blocks utilizing plastic and/or rubber components formed with solid walls usually does not exceed 4 mm (0.16 inches). The wall thickness of the spacer block composed of plastic and/or rubber components is usually not less than about 4 mm in order to gain the full advantage of the foam webbing structure between the two layers of skin. Thus, thick wall thicknesses may be obtained using structural foam. Moreover, structural foam spacer blocks have few if any sink marks due to the residual gas pressure in the cells, which allows the material to expand internally while the part cools, thus holding the skin firmly against the mold walls. Because of their cellular structure the spacer blocks formed of structural foam are virtually stress-free, resulting in bowing and warpage being greatly reduced. Because of its cellular structure, less resin is used to make it resulting in a part 3 to 4 times more rigid than the solid part of the same weight. This enables the instant invention to be made of commodity plastics such as polystyrene and polyethylene with or without rubber in a load bearing application. 
     The properties of the structural form spacer block depends on the base polymer, overall part density, density distribution, skin thickness, cell shape and size. All of these parameters are affected by the processing method, process variables, wall thickness, and mold design. 
     Density of the structural foam varies across the cross section and is lowest in the core. As the distance from the center of the foamed block increases, the cells get smaller until they disappear completely in the outer skin. The objective is to produce a part with high skin density and very low core density without the presence of voids. The range of the density varies in the present invention from about 30 percent in the center to 100 percent at the outer skin. Moreover, the overall part density, density distribution, skin thickness, cell shape and size depend upon the mold cycle which may vary between ½ to 10 minutes. 
     A preferred embodiment of the spacer block of the instant invention is processed using a low pressure injection molding machine using thermoplastics and/or rubber. A screw is used to plasticate a mixture of polymer and chemical blowing agent of up to 1% and preferably up to ½ percent wherein the screw barrels has zones at different temperatures arranged so that the blowing agent in only near the nozzle. A foamable mixture is produced and pumped under pressure to an accumulator an 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 is discharged from the accumulator into the mold. The mold cavity is 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 drop resulting in bubbles developing in the core. In a preferred embodiment, the melt is charged at about 400° F. and the melt temperature is between about 380° to 450° F. It should be noted that the structural foam blocks  10  of the present invention can be made utilizing of a rubber compound in combination with a plastic. The plastic tends to encapsulate the rubber particles and act as a binder. The rubber 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. 
     The spacer block of the present invention may be formed by injection molding, and preferably low pressure injection molding such as is used for structural foam products. The spacer block can be comprised of a virgin or regrind plastic or combinations thereof without any rubber. The plastic may be selected from the following polymers: 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. Of course the spacer block of the present invention may be formed of a single type of polymer or mixtures of various polymers. Typically a chemical blowing agent in an amount of less than 5 percent, and more preferably in an amount of less than 1 percent and most preferably in amount of less than ½ percent can be used with the 100% polymer composition spacer blocks  10 . 
     A rubber and/or elastomeric compound can be incorporated in the formulation as a substitution for up to at 70 percent, and more preferably at less than 50% and most preferably from about 40 to 50 percent depending upon the strength to weight ratio desired and the structural properties required for a particular application or size of guard rail. Regrind rubber is typically less expensive than plastic materials therefor, as much as 40 to 50 percent rubber may be used in spacer blocks for normal impact applications or posts spaced closed together, whereas a composition with less than 45 percent rubber may be desired for applications requiring the posts to be spread further apart from one another. The type of rubber is also an important consideration in that the rubber may be comprised of a natural rubber or synthetic rubber, either virgin, regrind material or combinations thereof. Additives such as fillers and fiberglass may further reduce the cost of manufacture and provide the requisite strength. Moreover, because of the gases produced from injection molding 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. 
     A particular preferred embodiment comprises polyethylene together with grind rubber ranging in an amount of up to 45 percent. Yet another more preferred embodiment utilizes from about 30 to 45 percent regrind rubber and utilizes ethylene as the binding polymer. 
     Another preferred 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 1.01, pH of about 7, melting point range of over 600° F. which is a highly effective alloying agent for compatibilizing and alloying cured rubber, virgin or regrind, with plastic powder to form compounds having little or no change in physical properties. 
     Moreover, another preferred embodiment may contain a nontoxic blend of naturally occurring materials, (plant polymers, gums, and anionic salts), marketed by Polymer process Technologies, Inc, under the trademark of PPT-RNU that when added to post consumer plastics of all kinds, will repair heat history plastics to near virgin polymer condition. in addition to or instead of the PPT-SYS (R)/(P). The material has a pH of about 6.8, a specific gravity of about 1.05, a melt point flow of over 650° F. and used in amounts of up to 10% by weight and more preferably from about 3 to about 6% by weight. 
     Another preferred 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 360° to 410° F. which is typical for extrusion and compounding operations. 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modification will become obvious to those skilled in the art upon reading this disclosure and may be made upon departing from the spirit of the invention and scope of the appended claims. Accordingly, this invention is not intended to be limited by the specific exemplifications presented hereinabove. Rather, what is intended to be covered is within the spirit and scope of the appended claims.