Patent Publication Number: US-3879148-A

Title: Grazing light reflector for roadway pavement markers

Description:
United States Patent 1 [111 3,879,148 Eigenmann Apr. 22, 1975 1 1 GRAZING LIGHT REFLECTOR FOR ROADWAY PAVEMENT MARKERS [76] Inventor: Ludwig Eigenmann, Vacallo,  
 Ticino, Switzerland [22] Filed: Mar. 19, 1974 [21] Appl. No.: 452,997  
 [30] Foreign Application Priority Data Mar. 21, 1973 Italy 21912/73 [52] US. Cl. 404/10; 404/11; 404/14; 404/16; 350/105 [51] Int. Cl. E0lc 23/16 [58] Field of Search 404/10, 11,12,14, 15, 404/ 16 [56] References Cited UNITED STATES PATENTS 1.833.124 11/1931 Rand 404/10 2,838,408 6/1958 Rindone 106/53 3.011.412 12/1961 Harrington et a1. 404/12 3.556.637 1/1971 Palmquist 350/105 Primary Examiner-Mervin Stein Assismm Examiner-Steven Hawkins Attorney. Agent. or Firm-Michael S. Striker [57] ABSTRACT There is described a retro-reflecting device designed to be structurally associated to traffic delineating signs and markers formed by tapes or layers on roadway pavements. The device improves the nighttime visibility of the sign or marker, by retro-reflecting grazing I 6 Claims, 8 Drawing Figures GRAZING LHGHT REFLECTOR FOR ROADWAY PAVEMENT MARKERS BACKGROUND OF THE INVENTION a. The Field of the Invention This invention relates to the field of traffic regulating sign or markers formed on or applied to roadway pavements, such as to delineate traffic lanes and the like. and more particularly of the reflection means designed to be associated to such markers for improving their nighttime visibility, especially in rainy weather, when the essentially sole source of light is provided by the light beams emitted by a vchicles headlamps.  
  In other words, this invention has for its specific field the art of improving the visibility by motorists of markers and signs associated to a roadway pavement and forming part of the roadable surface area, when such markers or signs are illuminated by light rays emitted in a direction forming a small or extremely small angle with generally planar roadable area, the visibility at distance of the thus illuminated marker or sign being provided essentially only by those light rays which are retro-reflected essentially along their own incident rays, towards the source of light (the headlamps) and therefore towards the motorists eyes.  
  Such type of illumination by light rays forming the said small or very small angle with the roadable surface in commonly termed by grazing light in the art. Therefore, the expression grazing light, as made use of as this specification proceeds and in the appended claims, in view of the objects and scope of the invention, is intended to encompass light beams and rays which impinge on a given part of a roadable surface, in a direction forming a small angle with said surface, alike the light emitted by a vehicle headlamps system impinges on a location or area of a roadable surface some tenths of meters at least ahead of the vehicle.  
 b. The Prior Art The problem of improving the visibility of markers formed on or applied to a roadway pavement, under grazing light, is of great interest as the traffic safety is concerned. For outmost safety to motorists, the delineation of road edges, lane separations, obstructions and bend-outs or curves should be visible to the driver well far in advance of the position of the vehicle. It is further known the visibility of such delineations is practically lost when roadways become rain swept, as a mirror-like film of water forms upon the roadable surface.  
  Three dimensional high visibility traffic delineation means have been heretofore proposed, such as various traffic buttons have been proposed as lane separators, and cast elongated pyramids or raised bars are used for channelizing the traffic. A substantial approach has been proposed and described by the present applicant in his U.S.A. Pat. No. 3,399,607 and British Pat. Specification No. 1,032,813. Reference is herein made to this prior patent literature for best knowledge of the prior art, to which this invention provides a substantial improvement.  
  Essentially, these and other prior art means comprise stationary markers arranged along the delineation to be made visible and forming, at suitable selected locations and intervals on said delineation, more or less sharply protruding reliefs having exposed side surfaces which at least in part can be impinged by grazing (relatively to the overall planar roadable surface) light, at a reasonably small angle of incidence, that is an angle well greater than that of impingement of the light rays upon neighbouring locations of the adjacent roadable surface. Said markers can be made of a tough hard plastic or resinous binder having embedded therein retroreflective glass spheres or beads.  
  It is evident that as more highly and steppingly said reliefs project above the roadable surface, as better the visibility is. On the other part, substantially high stationary reliefs on a roadable surface seriously effect the planarity thereof. They induce vibrations and serious disturbance to steering and serious and even fatal road accidents have been promoted thereby, also when such reliefs are shaped to provide a shallow curvature convex upper surface (which however provides a lower retroaeflectivity). It is to be taken into account that a vehicle wheel can impact on said reliefs when same vehicle travels at high and also very high velocity, such as running above along a traffic lane delineation lengthwise a highway, thus promoting an intense high frequency vibration in one side only of the steering mech anism (one front wheel only contacts the delineation).  
  It is therefore a principal object of this invention to provide a new device which is not subject to the above and other objections and which provides the most desirable retro-reflectivity when impinged by grazing light.  
  Another object of this invention is to provide an improved grazing light reflector as above, which is particularly adapted for being structurally associated to traffic delineation forming tape materials, say during the factory production of said known materials, so that by applying on and securing these tape materials on a road surface, the thus formed traffic delineation will be provided with the desired visibility improving means, without further operations, and ready for immediate service.  
  (Such road marking tape materials and the modes for applying same will be not described, as appertaining to current art and disclosed in patent literature. The prior Applicant&#39;s U.S.A. Nos. 3,262,375, and 3,007,838 are a few examples of such literature.)  
 SUMMARY OF THE INVENTION Essentially, the new grazing light reflector of the invention comprises, in combination with a traffic delineation providing layer having an upper planar face forming part of the roadable area, an at least partially pliable component having a first portion fixedly secured to said upper face, a second upwardly resiliently biased portion maintained by a biasing force in a first position projecting above said planar face, retroreflecting means comprising reflectorized beads on said second portion to retro-reflect grazing light rays impinging on said second portion when in its said first position, and a third intermediate portion pliably connecting said first portion to said second portion so that said second portion can be lowered in a second position essentially co-planar with said upper face when a downwardly directed force greater than said biasing force is applied to said second portion.  
  The said downwardly directed force is that applied by a vehicle wheel passing over the reflector, or by a road way sweeper machine, or by a snowplow or other mechanism which, when travelling over a roadway pavement, might impinge on any body which upwardly projects from such pavement.  
  According to a preferred embodiment of the invention, the reflector comprises a second portion consisting of an essentially flat tab including the said retroreflecting means, having a lower edge adjacent to said first portion and downwardly swingable about said lower edge until laid flat on said upper face. Preferably, said reflector is made of resiliently pliable sheet material at its said lower edge and the said biasing force is provided by the resiliency of said sheet material.  
  According to a modified embodiment of the invention, the said first portion, second portion and intermediate portion are formed by concentric outer, inner and intermediate parts ofa pliable sheet material having the said retro-reflecting means secured to at least said inner part, said outer part being secured to the said upper face of the traffic delineation, and the said inner part being upwardly biased by a resilient buffer located therebelow so that said inner part when in its said first position sharply bulges above said upper face.  
  These and other objects of the invention will be best made apparent from the following description of few embodiments thereof, illustrates in the accompanying drawing, wherein certain details have been omitted or diagrammatically indicated, as appertaining to current art.  
 THE VIEWS OF THE DRAWING FIGS. 1 and 2 are perspective diagrammatical fragmentary views of a lane delineating tape material secured on a roadway pavement and associated to visibility improving grazing light reflectors arranged according to said preferred and respectively to said modified embodiment of the invention;  
  FIGS. 3 and 4 are somewhat diagrammatical sectional views of said embodiments, taken in the planes indicated at Ill-III in FIG. 1 and respectively at lV-IV in FIG. 2;  
  FIGS. 5A, 5B and 5C diagrammatically and crosssectionally illustrate the essential steps of a procedure for forming a reflector such as illustrated in FIG. 3; and  
  FIG. 6 is a cross-sectional exploded view of the components of the reflector of FIG. 4, before its assembling with the tape material.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 to 4 there is fragmentarily shown a roadway pavement having a roadable surface 10 and having a lane delineation (or other traffic regulating sign) forming tape material secured thereon. This tape material has evidently an upper face, indicated at 12, which actually forms a part of the roadable area open to traffic. Preferably, but not critically for the invention, the tape material comprises two juxtaposed and integrally connected layers 14 and 16, the lower one ensuring the best bond with the surface 10 of the roadway pavement, and the upper one being the most desirably weather and traffic resisting composition to provide an efficient and durable delineation.  
  In the embodiment shown in FIGS. 1 and 3 the reflector comprise a flat and thin tab-like portion which, when not subject to externally applied forces, is upwardly and nearly vertically extended from a first or base portion 22 juxtaposed on and fixedly secured (by localized hot melt or by means of known solvents or adhesives) to the upper face 12 of the traffic delineation. Of course, the reflector is positioned on and secured to traffic delineation so that the flat faces of its tab portion 20 form essentially right angles with the average direction of the expected impinging grazing light. Generally, said tab portions 20 are arranged perpendicularly of the length of the traffic delineation, if the same provides a traffic lane dividing line, for example.  
  Further. in FIG. 1 there is shown a number of reflectors each extended cross-wise of the sign forming tape or layer to provide the greatest retro-reflective area for a given height of the reflector. The showing of FIG. 1 provides the best visualization of the arrangement and of the retro-reflecting action of the reflector. It has been found that reflectors provided with properly reflectorized tab portions from 10 to 20 millimeters high and from to I20 millimeters wide (that is well less than the average width of currently provided traffic lane delineations) ensure a more than suitable visibility by retro-reflection when spaced, along the delineation, at even two meters intervals. Of course, well shorter intervals can be provided, but two short intervals, such as of half of a meter or less, do not lead to a further increased brilliancy, because at distance the reflectors apparently overlap each other at the driver sight.  
  The tab portion 20 is (a) swingably connected at the base portion 22 so that such tab portion can be swung down flat as shown at 20a in FIG. 3, (b) so thin (such as two millimeter thick, for example) that does not form a noticeable bulge or relief over the surface 12, when laid down flat, and (c) upwardly resiliently biased by a force provided by the elastic nature of the components forming the lower edge of same tab.  
  Preferably, the reflector is essentially formed of a transparent highly resilient, stress resistant and wear resistant fiber reinforced resinous sheet material. The reflector of FIG. 3 can be prepared as shown in FIGS. 5A to SC. On a planar smooth surface, such as provided by a glass or a polytetrafluoroethylene plate or sheet 40, a woven or non-woven fabric 42 is laid and then an impregnating resinous layer 44 is doctored thereon, The fabric is made of well pliable and high resistance fibers, such as polyamide fibers, and the resin is selected among those very resilient and wear resistant and preferably having a refractive index equal or very near to that of the fibers, so that such fibers will disappear in the fiber reinforced sheet structure obtained by curing the resin. A commercial polyurethane resin is suitable for providing such structure.  
  Prior to complete curing of the resin, the sheet 42, 44 is detached from the plate 40, turned downwise and applied over a die forming support 50 (FIG. 58) so grooved that a bent center portion of the sheet can be fitted, leaving a space 52 in which a reflectorizing flat assembly 54 of height less than the deepness of said space 52 is forced. Such assembly preferably consists of a thin reflecting plate 56, such as of aluminum, having monolayers 58 of commercially available transparent resinous or glass beads are applied. Optionally monodirectionally retro-reflecting reflectors, say for use along one-way roads, can be more economically provided with assemblies 54 having one monolayer 58.  
  The structure is then pressed into a clamping die in the cross-sectional configuration shown in FIG. SC to provide an unitary structure. The lower edge part 60 of the tab portion 20 does not include the reflectorizing assembly and therefore is resiliently pliable. Such part acts either as a hinge for abatement of the retroreflecting tab portion as shown at 20a in FIG. 3, and as a resilient means for applying to such abated tab por tion a biasing force capable to return the same in its first nearly upright position.  
  in a structure such above described the very reflectorizing means are completely enclosed into a wear resistant transparent envelope and therefore a both efficient and durable reflector is provided.  
  The modified reflector of FIGS. 2 and 4 has, in service, a general character of a known traffic button. because it forms a reflectorized bulge 30 protruding well above the upper face 12 of the traffic delineation. or other sign on the roadway pavement 10. Such bulge is however capable to flatten down in flush with the said upper face 12, when downly urged by a substantial force and then in return in its bulging configuration when such force has been discontinued.  
  The reflector preferably consists of a disk of reinforced pliable wear and weather resistant sheet material such as that made as described with reference to FIG. 5A, and consisting of the above described reinforcing fabric 42 in a resinous layer 44, of polyamide fibers and respectively of polyurethane resins.  
  On one face of such sheet 42, 44 a monolayer 46 of beads is secured, preferably at its center portion only (a complete coating is however convenient in the case of mass production of the sheet material 42, 44, 46 in continuous ribbon form). The reflectorization can be provided by properly pigmenting the impregnating resins. For example light diffusive or light reflective fillers, such as titanium dioxide of aluminum flakes, can be added to the resin.  
  The sheet is secured at its outer portion 36 to the delineation 12, about a resilient plug or buffer 34, of rubber or of a rubbery plastic, preferably seated into a bore 48 punched out from the layer l4, 16, which provides the upwardly directed biasing force which causes the center portion 32 of the pliable sheet to provide the retro-reflecting bulge 30. The layer 46 of beads is preferably protected by a transparent protective layer. such as of polyurethane.  
 I claim:  
  1. in a reflector for roadway pavement markers, particularly for traffic regulating signs and markers which are adapted for retro-reflecting grazing light which impinges thereof and which are structurally associated with a layer superimposed on a roadway pavement which has an upper surface, a combination comprising a partially pliable component formed of a transparent fiber-reinforced resinous sheet and adapted to be bendable at its center. including a first flat portion juxtaposed on and firmly secured to the upper planar surface of the layer superimposed on the roadway, a second flat tab-like portion connected to and extending upwardly from said first portion and having an outer surface area when said component is bent at its center and having a lower edge, a resiliently pliable intermediate hinged portion located at said lower edge of said second portion and connecting said first portion to said second portion and operative to allow said second portion to assume with respect to said first portion a first position in which at least a portion of said outer surface area of said second portion is positioned to receive impinging grazing light and to assume a second position in which said outer surface area and said second portion are substantially coplanar with the upper planar surface of the layer on the roadway, and retroreflective means secured to at least part of said outer surface area of said second portion above said intermediate portion and being formed of at least one monolayer of transparent beads and a reflective sheet which back said beads so as to form a reflective surface when said transparent sheet component is bent at its center and encloses said beads and said sheet; and resiliently deformable biasing means associated with said intermediate portion for applying to said second portion a biasing force adapted to restore said second portion from said second position to said first position, whereby said impinging grazing light is reflected when said second portion is in said first position and whereby the planarity of the roadway surface is not substantially affected when said second portion is in said second position.  
  2. In a reflector for roadway pavement markers, particularly for traffic regulating signs and markers which are adapted for retro-reflecting grazing light which impinges thereon and which are structurally associated with a layer superimposed on a roadway pavement which has an upper planar surface, a combination comprising a partially pliable component including a first flat circular portion juxtaposed on and firmly secured to the upper planar surface of the layer superimposed on the roadway, a second portion formed of a substantially planar pliable sheet having an outer surface area including a circular portion concentric with said first flat circular portion, a pliable intermediate portion connecting said first portion to said second portion and operative to allow said second portion to assume with respect to said first portion a first position in which said circular portion of said outer surface area of said second portion is positioned to receive impinging grazing light and to assume a second position in which said outer surface area and said second portion are substantially coplanar with the upper planar surface of the layer on the roadway, and retro-reflective means formed with a monolayer of reflectorized beads secured to at least a part of said outer surface area of said second sheet portion; and resiliently deformable biasing means associated with said intermediate portion for applying to said second sheet portion a biasing force including a compressible body located below said second sheet portion and operative to upwardly urge said outer surface area of said second sheet portion into a bulging configuration with sufficient strength so as to restore said second sheet portion from said second position to said first position after a vehicle has passed, whereby said impinging grazing light is reflected when said second portion is in said first position and whereby the planarity of the roadway surface is not substantially affected when said second portion is in said second position.  
  3. The reflector of claim 2, wherein said component is formed of a fiber reinforced resinous sheeting.  
  4. The reflector of claim 3, wherein said sheeting consists of a polyurethane resin impregnated network of polyamide fibers.  
  5. The reflector of claim 2, wherein said monolayer of beads is transparent and is backed by a reflectorizing surface.  
  6. The reflector of claim 5, wherein said monolayer of beads has a protective coating of wear resistant transparent resins.  
 * l III