Reflective substrate surface system, reflective assembly, and methods of improving the visibility of a substrate surface

This application claims priority to U.S. provisional patent application No. 61/302,594, filed on Feb. 9, 2010, and incorporated by reference herein.

This invention relates to a system for use in improving the visibility of a surface, such as reflective substrate surface elements and other reflective articles, and more particularly to a system in which the optical elements for the reflective article are stored and dispensed in combination with a binder drying agent.

Reflective elements are incorporated in traffic signs, pavement markings and apparel. Pavement markings, for example such as those on the centerline and edge of a roadway, provide visual guidance for motor vehicle drivers. The visibility provided by these pavement markings is particularly vital for night time navigation and for navigation during inclement weather conditions.

U.S. Pat. No. 6,127,020 to Bacon, Jr. et al. teaches that such pavement markings typically include glass microspheres that are partially embedded in a binder layer containing reflective pigment particles such as titanium dioxide (TiO 2 ) or lead chromate (PbCrO 4 ). As light from the headlamp of a vehicle impinges upon the microsphere, it is refracted towards the reflective pigment. Refraction as used herein refers to the deflection of light from its original pathway. The light passes through the optical element and is scattered by the pigment-containing pavement paint. A portion of the scattered light is directed back through the optical element and is directed back along the original path towards the driver, increasing the visibility of the markings. This results in a retroreflective effect wherein the most intense light travels back along the illumination axis, which is the centerline between the headlamp and the microsphere, and the light becomes dimmer the farther it is viewed from the illumination axis. Retroreflection as used herein refers to the tendency of light to travel back along its original pathway upon hitting certain surfaces.

The intensity of the light returning to the driver depends upon, among other things, the effective refractive index of the pavement marking. Refractive index as used herein refers to the magnitude by which the speed of light is reduced within a medium. The microspheres have an inherent refractive index; however, U.S. Pat. No. 6,796,740 to Chiron et al. explains that a lower effective refractive index will result if a film of water from recent rainfall has covered the pavement marking. The angle of incidence with which the light impinges upon the microsphere also bears upon the intensity of the light reaching the driver's eyes. Furthermore, retroreflectivity may diminish as traffic erodes the pavement marking surface, if the traffic causes the microspheres to become dislodged from the binder.

In order to maintain retroreflectivity, it has been suggested to use a reflective marking system wherein a first layer of binder is applied to the surface of the substrate, and a first layer of optical elements is partially embedded in the top surface of the first layer of binder. A second layer of binder is applied to cover the first layer of optical elements such that the first layer of optical elements defines a plurality of undulations in the second layer of binder and a second layer of optical elements is partially embedded in the top surface of the second layer of binder and has an exposed-lens surface portion. As the top layer of optical elements and binder is eroded, the underlying layer optical elements will be exposed, thereby maintaining retroreflectivity. Such a system is described in U.S. patent application Ser. No. 12/428,117, filed Apr. 22, 2009, which is incorporated by reference herein in its entirety.

In order to enhance the application of the pavement marking, drying agents are applied to the binder. These drying agents allow the pavement to be marked during damp conditions and also speed up the application process, thereby minimizing the restriction to full utilization of the roadway. The typical application of paint, drying agent and beads is as follows:

1. Paint is applied to the pavement surface; 2. Paint drying accelerant is applied on top of the paint; 3. Anti-skid glass grains are applied on top of the paint; and 4. Retroreflective glass beads are applied and embedded in the paint.

In use, it is often difficult to adequately intermix the drying agent with the binder in order to achieve optimum results. In addition, the drying agent generally is formulated as beads which have a tendency to coagulate and block the dispensing mechanism. This clogging requires periodic cleaning and causes unscheduled delays in the pavement marking. The clogging also prohibits the accurate metering of the dispensed drying agent.

It is highly desirable to provide a reflective marking system which provides a high degree of retroreflectivity, allows for improved intermixing of the drying agent and binder, and also minimizes the clogging of the drying agent dispenser.

The present invention provides a marking system adapted for coating a surface of a substrate in which a drying agent is used. According to a first aspect of the invention, a drying agent and the optical elements to be applied to the surface are stored in a common hopper and dispensed together in an intermixed composition. In operation, a binder layer, such as paint, is applied to the surface. The intermixed drying agent and optical elements are dispensed together into the spray of the binder and become incorporated with the binder on the substrate surface. The combination of the drying agent and the optical elements prevents the drying agent from agglomerating and provide a clean and unhindered dispensing of the drying agent.

In a second aspect of the invention, a binder layer, such as paint, is applied to the surface. A combination of optical elements and a drying agent which are stored in a common hopper are dispensed into the spray of the binder and become incorporated with the binder on the substrate surface. The mixture of optical elements and drying agent prevents coagulation of the drying agent and the resulting clogging of the dispenser. If desired, additional optical elements or other components may be subsequently applied to the binder/drying agent/optical element layer.

The combination of the drying agent and optical elements can also be used with a hand walker striping apparatus. In such an application, binder is first applied to the surface and the blend of the intermixed drying agent and optical elements is dropped onto the binder. A second layer of binder is then applied and a layer of optical elements are then dropped onto the second binder layer.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawing:

FIG. 1 is a schematic representation of a dispensing system in accordance with the present invention.

FIG. 2 is a schematic representation of a hand walking dispensing system in accordance with the present invention.

While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

The present invention is directed to reflective surface marking systems and reflective elements and methods of applying the reflective marking system to a substrate such as roadway pavement by means of a truck-mounted line striping apparatus or a hand walking striping apparatus. Reflective marking systems according to the present invention include a first layer of binder, optical elements, such as glass beads, which are embedded in the binder, an optional second layer of binder and an optional second layer of optical elements embedded in the second layer of binder. Methods of applying a reflective marking to a substrate according to the present invention include applying a first layer of binder, dispensing a mixture of optical elements and drying agent into the binder stream for application onto the substrate, optionally applying a second layer of binder onto the first layer of optical elements and optionally applying a second layer of optical elements onto the second layer of binder.

In order to enhance drying times of the binder, especially in wet conditions, a drying agent or accelerator, preferably DOW Fastrack QS-2, is applied to the binder. The drying agent improves the ability of the binder to dry even in wet conditions and will speed up the surface marking process in both wet and dry conditions. Other suitable drying agents include silica gel.

It has been found that the performance of the drying agent is enhanced if it is incorporated into the binder prior to application on the roadway surface. To accomplish this, the drying agent is dispensed directly into the spray of the binder. The binder and drying agent are stored in separate bins, and the dispenser gun for the drying agent orients its spray directly into the spray path of the binder, allowing the binder and drying agent to mix prior to the binder being applied to the surface. Such a dispensing system is well suited for use in connection with a truck-mounted line striping apparatus.

The most common drying agent is a spherical plastic bead designed to absorb water. Because of its absorption properties, the drying agent tends to coagulate into clumps which hinder the ability to dispense a consistent and even stream of the beads into the binder and prohibits the accurate metering of the dispensed drying agent.

It has been found that the intermixture of the optical elements and the drying agent allow for a clean and unhindered dispensation of the drying agent onto the substrate. A presently preferred ratio of intermix glass beads to drying agent is 2:1 by weight. This ratio can be adjusted depending on the thickness of the binder layer which typical is within the range of 7 to 60 mils (0.2 to 1.5 mm).

Suitable intermix glass beads have been found to be Potters Safety Marking Spheres of M247 Type 1 size coated with a dual coating. A suitable drying agent includes VISILOK® traffic pavement dryer provided by Potters Industries which has been found to accelerate the drying time of the binder, approximately halving the cure time, in order to assure extended high performance of the marking system. Suitable optical elements include Potters VISIMAX® safety marking spheres, Potters FLEX-O-LITE Type III 1.9 RI glass beads, and Potters VISIBEAD and Safety Marking Spheres glass beads. Glass beads of other sizes can be utilized. The size ranges of the various optical elements are outlined in Table I below:

In order to prevent clumping of the drying agent, the optical elements and drying agent are stored together in the same bin. It has been found that this intermixing of the drying agent and optical elements prevents the drying agent from coagulating into large clumps. It has been found that the drying agent beads will form a thin layer around the optical element spheres, thereby allowing easy passage of the drying agent and optical element through the dispenser.

The binder material can be a water-borne paint such as Ennis High Build Waterborne or Vogel UC 3588. The binder material and drying agent/optical element mixture can be applied to a substrate such as a roadway using a GRACO LineLazer IV 200HS retrofitted by A-1 Road Lines.

In a presently preferred method, the dispenser for the drying agent/optical element mixture will direct the mixture directly into the binder dispensing steam. FIG. 1 is a schematic representation of a preferred dispensing system 10 . As shown in FIG. 1 , the mixture of drying agent and optical elements is stored in bin 12 . Dispenser 14 applies the binder to the roadway. Dispenser 16 applies the mixture of drying agent and optical elements and is oriented such that dispenser 16 dispenses the stream of the drying agent and optical element mixture directly into the stream of binder from dispenser 14 . If desired, additional dispensers 18 and 20 for applying optional additional layers of binder and reflective elements, respectively, can be utilized. Dispensers 18 and 20 are adapted to apply the option layers of binder and reflective elements after dispenser 12 and dispenser 14 have applied the binder, drying agent and optical elements.

In an alternative embodiment, the optical elements can be dispensed separately from the drying agent. In this embodiment, bin 12 would contain only the drying agent. A separate bin and dispenser of standard configuration (not shown) would separately apply the optical elements onto the binder/drying agent layer already applied to the roadway.

Several experiments were conducted to test the dispensing system of the present invention.