Abstract:
A reflective pavement marker integrally molded in one piece structure having retroreflective face and structural body. The marker provide a mean to enhance agglutination to the roadway, if needed when bituminous based adhesive is used by maximizing the base area for adhesive wetting parameter. The reflective face and the structural body integrally made of high impact and abrasion resistance thermoplastic. Recessed reflective cells within the reflective face tend to minimize contact with tires and other abrasive roadway elements.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the retroreflective roadway markers that are used for traffic lane delineation and in particular, to markers with enhanced reflectivity and abrasion resistant. 
     2. Related Art 
     Roadway markers are adhered to pavements along centerlines, edge lines, lane dividers or guardrail delineators. Other roadway markers are used as temporary lane dividers in temporary constructions, detours or prior to permanent marking of newly paved roadways. 
     Since 1965, the most commonly used retroreflective roadway markers are based on Heenan U.S. Pat. No. 3,332,327 or Balint U.S. Pat. No. 3,409,344. 
     Typically, this type of markers are produced in a process consisting of four to five steps: 
     First, injection molding of a thermoplastic shell, either integrally molded with the reflective face, or the reflective faces welded on a corresponding open recesses within the shell. The reflective face, having 350 or more cube corner reflective elements on each reflective face of the shell. 
     Secondly, either the cube corner reflective elements within a shell or the entire inside surface of the shell coated with a reflective sealer by a process known as vacuum in metalizing. This metallic sealer needed to seal the cube comer reflective elements so they retain part of their retroreflectivness prior to the next step, of filling the shell with a thermosetting resinous material, such as epoxy or polyurethane. This resinous filler material encapsulate the metalized cube corner reflective elements and give the marker the structural body. 
     Finally, a layer of relatively course sand or glass beads dispersed over the top surface of the filler material (this top surface will be the marker&#39;s base) prior to solidification of the filler material. Part of the sand particles will remain partially protruding above this planar surface of the marker base, thereby increase the adhesive welding parameter of the base surface. This will improve adhesion to substrate, regardless of the type of adhesive used. This type of markers worked well for six or seven months, however, due to poor abrasion and impact resistant of the thermoplastic shell, nearly 60% of the reflectivity is lost thereafter. Also, incompatibility of the shell material to the resinous filler material, causes pealing of the reflective face or the shell, thereby losing retroreflectivity. Several attempt were made to improve abrasion resistant of the reflective face. One was the use of thin layer of untempered glass as disclosed in U.S. Pat. No. 4,340,319. Another attempt was the use of polymeric coating of the reflective face, as disclosed in U.S. Pat. No. 4,753,548 (Forrer). These abrasion resistant coating proving to be expensive and tend to reduce retroreflectivity. 
     Other major development in the pavement marker art have been made in the attempt to eliminate the use of the metalized sealer for the cube corner reflective elements. This has been achieved by dividing the inside surface of the reflective face into reflective cells, each cell will have several cube corner reflective elements, the cells isolated from each other by partition and load carrying walls. The entire reflective face welded to corresponding recesses within a hollowed body. 
     This method is disclosed in U.S. Pat. No. 4,227,772 (Heenan); U.S. Pat. Nos. 4,232,979; and 4,340,319 (Johnson et al); U.S. Pat. No. 4,498,733 (Flanagan). These markers proved to be superior in reflectivity, however, lack of structural strength and poor adhesion cause short life cycle for this type of markers. 
     This applicant successfully developed two multi-cell reflective roadway markers. One roadway marker utilizes raised rhombic shaped abrasion reducing and load transferring raised ridges which act to intercede abrasion elements and impact load, the shell filled with epoxy, the marker body having a base with large wetting parameter for shear and flexural strength , as disclosed in U.S. Pat. No. 4,726,706. The second roadway marker of this applicant, U.S. Pat. No. 5,927,897 developed a mean to increase the abrasion resistant of the reflective face by coating the reflective face with diamond-like film and by having holding pins extending from the partition walls into the body, the holding pins sealed by the filler material; this works very effectively. All of the above reflective pavement markers are incorporated herein by reference in their entireties. Applicant present goal to have a roadway marker with high reflectance, abrasion resistant, low cost, marker base area with good welding parameter and very simple yet consistent process to manufacture. 
     SUMMARY OF THE INVENTION 
     This invention provide a novel one piece raised roadway marker that comprises a monolithically injected body, together with one or two reflective faces and a base having large adhesive welding parameter for better adhesion to the pavement and higher resistance to flexural stresses . 
     The primary object of this invention is eliminate the multi steps process in prior arts for making reflective and non-reflective pavement markers while retaining maximum base surface area. Another objective of this invention is to provide a raised roadway marker made of high impact and abrasion resistant material with high impact resistance and good quality reflective index. 
     The present invention further provide a method of making one piece raised roadway marker of any desirable shape and configuration such as a marker with truncated body or one piece marker with a body having two rumble portions integrally made with two reflective faces and scalloped recess in-between with rectangular textured base. 
     In accordance with still further aspect of this invention, the marker can be made for one or two way traffic usage, having integrally built-in reflective faces, this will cost considerably less to install to the roadway, or two multi colored parts can be welded together, each with one reflective face opposite the other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages and unique features of this invention will be better understood by reference to the drawings. These drawings are schematics, no scale used. In the drawings: 
     FIG. 1 is an isometric view of one of the preferred one piece pavement marker of the invention; 
     FIG. 2 is a plan view of the pavement marker illustrated in FIG. 1; 
     FIG. 3 is another isometric view of pavement marker in FIG. 1 showing the base portion with grooved surface and the end opening for the hollow recesses; 
     FIG. 4 is a cross section view taken along the line  4 — 4  in FIG. 2; 
     FIG. 5 is an isometric view of a thin plate that can be used to seal the ends of hollow recesses; 
     FIG. 6 is a section view taken along the line  6 — 6  in FIG. 4 showing partly grooved surfaces of a hollow recess; 
     FIG. 7 is an isometric view of another preferred embodiment of one-piece marker of the invention; 
     FIG. 8 is another isometric view of marker in FIG. 7 showing the base surface; 
     FIG. 9 is an elevation view of the marker in FIG. 7 showing the cursed sides and reflective cells; 
     FIG. 10 is a cross section view taken along the line  10 — 10  in FIG. 9; 
     FIG. 11 is an isometric view of yet another embodiment of one-piece marker of the invention; 
     FIG. 12 is a plan view of the marker in FIG. 11; 
     FIG. 13 is a cross section view taken along the line  13 — 13  in FIG. 12; 
     FIG. 14 is isometric view of the marker in FIG. 11 showing the base surface and the back portion; 
     FIG. 15 is an isometric view of a sealing plate for the base of marker in FIG. 11; 
     FIG. 16 is an isometric view of two welded markers of FIG. 11; 
     FIG. 17 is a plan view of the marker in FIG. 16; 
     FIG. 18 is a cross section view taken along the line  18 — 18  in FIG.  17 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Enhanced reflectivity, durability, cost effectiveness and simplified production method can be achieved by eliminating major steps or processes used in previous arts for the manufacturing of reflective and non reflective pavement markers. This invention is satisfying the above conditions. 
     This invention eliminate the process of metalizing, the reflective face; eliminate the step of welding a backing sheet to the reflective face; eliminate filling the marker body (shell) with inert filled resinous material or welding a unitarily molded block with flattened base to a shell; eliminate a lens mounting structure and a base layer added to marker body. This invention, simply developed a process of making a reflective pavement marker in one step process. 
     Referring to FIGS. 1 through 6 represent one of the preferred embodiment of a durable one piece reflective marker designated by the number  200  which comprises an integrally cast body  210  with at least one reflective face  212 . Body  210  has a top portion  214 , two inclined sides  216 , two inclined planar faces  218  and  212  facing traffic with at least one ( 212 ) is a reflective face and a textured and grooved planar base surface  220  with an extended base portion  220   a  for added adhesion area. Marker  200  can be of any desired dimensions or shapes. 
     The inclined planar reflective face  212  integrally have planar surface  212   a,  multiple of reflective cells  230  and partition ribs  230   b  separating cells  230  from each other. Reflective cells  230  can be of any desired shape or size. Various reflective cells and cube corner reflective element designs available for use in this marker. The following U.S. Patents provide suitable cell and cube corner element designs, therefore, all of the following arts are incorporated as reference in their entireties: U.S. Pat. No. 3,712,706 to Stamm, U.S. Pat. No. 3,924,929 to Holmen, U.S. Pat. No. 4,208,090 to Heenan, U.S. Pat. Nos. 4,232,979 and 4,340,319 to Johnson, U.S. Pat. No. 4,498,733 to Flanagan, U.S. Pat. Nos. 4,726,706 and 5,927,897 to Attar. Reflective cell  230  has an outside planar surface  230   a  slightly recessed with respect to the planar surface  212   a  and the vertex of the partition ribs  230   b.  Preferably, the cell&#39;s outside surface  230   a  would be recessed anywhere between 0.005 to 0.020 inch below planar surface  212   a  to eliminate contact with automobile tires. Each reflective cell  230  have an inside surface  230   c  integrally built with multiple of protruding cube corner reflective elements. Each cell&#39;s inside surface  230   c  is isolated from each other by integrally built load carrying interior walls  310  which are tapered outwardly, integrally forming hollow recesses  300  directly beneath each inside surface  230   c  of the reflective cell  230 . Each hollow recess  300  is formed corresponding to the size and shape of the cell&#39;s inside surface  230   c  with the protruding cube corner reflective elements, said hollow recesses  300  positioned with their centerlines  500  near perpendicular to the cell&#39;s outside planar surface  230   a,  preferably this angle to be between 75 to 105 degrees. Each interior wall  310  form an angle (A) equal or less than 5 degrees with respect to each centerline  500 . 
     Hollow recesses  300   a  are used when the desired marker is to have only one side with reflective face, as shown in marker  200 . Both hollow recesses  300  and  300   a  will be tapered outwardly and open through the textured and grooved planar base surface  220  thereby forming air gab beneath each individual reflective cell  230 . Hollow recesses  300  and  300   a  can have some of the walls  310  formed with arcuate grooves  310   a  for added reflectivity, surface opaqueness, enhancing daytime reflectivity and improving the structural strength of the marker. 
     Marker  200  is made of a high impact resistance, transparent polymeric material, with ultra violet light stability. Thermoplastic such as high impact resistance acrylic, polycarbonate or any other high impact resistance engineered polymer is suitable for this marker. Reflective face  212  can have either three raw, two raw or one raw of reflective cells  230 , depending on the desired size, shape or height of marker  200  and the size and shape of the reflective cells  230  being used. 
     For applications in sunny and hot environment, where bituminous hot-melt adhesive may be used, to agglutinate marker  200  to the roadway. the low melting point of such adhesive material may lead to adhesive failure known as cookie cutter effect, where a marker agglutinated to the pavement, may be forced by traffic impact load to move away from it&#39;s intended location on the roadway. 
     The science of material welding teach us that one of the primary variables to good adhesion of two surfaces is the total surface area to be wetted by the adhesive (welding) material, this area can be called the (welding parameter), therefore, we can improve adhesion of marker  200  to a substrate and perhaps more effectively than the arts in U.S. Pat. No. 3,332,327 to Heenan or U.S. Pat. No. 5,340,231 to Steere. This improvement in welding parameter can be achieved by using one of various arcuate shapes with discontinuous length, grooved perpendicular to traffic direction. Each groove can have length of about an inch or less and textured surface, preferably by sand blasting the corresponding part of the tooling. The width or depth of such grooves should not be more than 0.10 inch in-depth. 
     It can be proving that the welding parameter can be increased considerably within the same marker base area despite the open ends of the hollow recesses  300  and  300   a,  as an example, consider marker  200  to have a base width of 4 inches and depth of 2.75 inches, therefore, the planar base surface area=2.75×4.0=11 sq. inches. In one of the preferred embodiment, assume the surface area for the same base area having 30 grooves, each having 0.09 inch diameter and 4.0 inch length, subtract 29 open end areas of hollow recesses  300  and  300   a,  each having open end area=0.08 sq. inch, hence, the net surface area=(30×4.0×0.09×3.14/2)−(0.08×29)=14.6 sq. inches. This is considerably larger than the same planar area with no grooves. Marker  200  will have even larger area as welding parameter by using short and discontinuous grooves, each near inch in length with textured surface. In addition, planar base surface  220  can have an extended portion  220   a  for added adhesive grip. 
     Yet another mean to improve the adhesive welding parameter of the grooved planar base surface  220  is by capping the open ends of hollow recesses  300  and  300   a  by a corresponding shaped plate  60  with corresponding size caps  65  and ties  66 , as in FIG.  5 . Unlike previous arts such as. in U.S. Pat. No. 5,340,231 to Steere and U.S. Pat. No. 5,667,335 to Khieu, the caps  65  used in the present invention will have textured discontinuous grooves and will be agglutinated to each corresponding hollow recess  300  and  300   a.  in such away leaving portion of each cap  65  recessed either slightly recessed or protruded within each opening of the hollow recesses  300  and  300   a  at the planar base surface  220 . The recessed depth shall be less than 0.10 inch from the planar base surface  220 . 
     In some application where the desired reflective marker is to have two opposite reflective faces integrally made within one piece body, a truncated body design can be used similar to marker  200 . 
     Another preferred embodiment is marker  100 , as shown in FIGS. 7 through 10. The body shape having one or two convex portions  40 , each having concave curve shaped front surface  41 , said front surface  41  integrally made having multiple of planar rectangular reflective cells  45 . Each reflective cell  45  integrally having an outside planar reflective surface  46 , which is slightly recessed below the vertex of partition ribs  47  separating reflective cells  45  from each other. Each integrally made cell  45  within marker body  100  having the outside planar surface  46  inclined approximately 30 degrees with respect to the marker planar base  48 . Each reflective cell  45  integrally having an inside surface  55  with protruding cube corner reflective elements. Marker  100  have two curved sides  62 . 
     The two convex portions  40  are connected with a concave portion  49 , said concave portion  49  need to be wide enough proportionately to marker&#39;s height to accommodate the space needed for the injection molding slides forming the cube corner reflective elements within each reflective cell  45  through the open end of each corresponding hollow recess  50 . Hollow recess  50  form an air gap beneath the cube corner reflective elements within the inside surface  55  of each cell. Each hollow recess is having centerline near perpendicular to the corresponding outside planar surface  46  of cell  45 . 
     Hollow recesses  50  are separated from each other by partition and load carrying walls  51 . 
     The planar base portion  48  of marker  100  has discontinuous curved grooves  48   a  with less than 0.09 inch in depth. The entire surface of the base  48  is textured to maximize the (adhesive wetting) welding parameter. The open ends of hollow recesses  50  can be capped with thin polymeric plate  52 . 
     Marker  100  may have slightly raised ridges  61  on the outside surface for added protection, such raised ridges forming either rectangular or rhombic shape grids on the convex portions  40 . The height of said raised ridges will be less than 0.010 inch. 
     In other applications where the desired marker to have two reflective faces with different color, shorter body depth, lower height or maximum welding parameter at the marker base area. In this case, an embodiment such as marker  10  and  10   a  are preferred, as illustrated in FIGS. 11 through 18. Marker  10  comprises of two identical shaped marker  10   a,  welded or glued together. The two sides of marker  10  can be of same color or two different colors. 
     Each marker  10   a  integrally consist of one inclined reflective face  110 , a top portion  121 , two multi-angled or curved sides  125 , a planar rectangular base surface  150  with textured discontinuous grooves, said base surface  150  can have an extended periphery portion  130 ; and back portion  160  forming perpendicular angle with respect to the marker planar base surface  150 , said back portion  160  have hollow cavities  165 . 
     The reflective face  110  integrally has a planar surface  110   a,  multiple of reflective cells  115  and arcuate partition ribs  115   b.  Reflective cell  115  have outside planar surface  115   a  slightly recessed below the vertex or partition ribs  115   b  and an inside surface  115   c  with protruding cube corner reflective elements. Each inside surface  115   c  is open within a hollow recess  155 . 
     Hollow recesses  115  open through the base surface  150 . The centerline of each hollow recess  155  is near perpendicular to the corresponding cell&#39;s outside planar surface  115   a.  Each hollow recess  155  separated from each other by an outwardly tapered partition and load carrying walls  155   a. It can easily be shown that marker  10  can have any desired shape or size and the reflective face can have either one raw or multipie raw of reflective cells, each cell having either hexagonal, rectangular, rhombic or circular shape or a marker with round base and spherical surface. 
     When additional welding parameter (area) is needed for the base surface  150 , the entire open ends of hollow recesses  155  can be capped by correspondingly shaped plate  60 , as in FIG. 15, with multiple caps  65  that can be welded onto it&#39;s corresponding size and shaped ends of hollow recesses  155 . 
     Caps  65  connected to each other by multiples of thin ties  66 , each with highly porous surface for adhesive penetration. 
     Marker  10  can be made welding the back side  160  of two identical parts  10   a  that can be produced connected by a thin wedge  166 . Wedge  166  can be tore apart so that two parts  10   a  with contrasted colors can be welded at the back side  160 , forming marker  10 . 
     Various embodiments of this invention can have improved abrasion resistant body, reflective cells or both, by applying one of various arts available in abrasion resistant coating. Preferably, using vacuum evaporator deposition of either silicon dioxide (SIO2) layer or a diamond like carbon layer, as in U.S. Pat. No. 5,927,897 to Attar; U.S. Pat. No. 4,060,660 to Carlson and U.S. Pat. No. 4,383,728 to Kieser, all of which are incorporated herein as reference in their entireties. 
     It is understood that various changes or modifications can be made within the scope of the appended claims to the above-preferred embodiments without departing from the scope and the spirit of the invention. Therefore, the invention can be practiced otherwise than as specifically described herein.