Road structure – process – or apparatus – Apparatus – Material distribution means
Reexamination Certificate
1999-12-13
2003-01-28
Will, Thomas B. (Department: 3671)
Road structure, process, or apparatus
Apparatus
Material distribution means
C404S014000, C239S455000
Reexamination Certificate
active
06511259
ABSTRACT:
TECHNICAL FIELD
The present invention relates to dispensing devices and systems that are used for dispensing and applying particles or granulated material onto the surface of a substrate while the dispenser is moved relative to the substrate. In particular, the present invention relates to particle dispensers to be mounted to a vehicle so that during movement of the vehicle particles can be dispensed through the dispenser nozzle onto the surface of road pavement, such as to enhance pavement markings with retroreflective particles.
BACKGROUND OF THE INVENTION
Pavement marking or striping is typically conducted by applying paints, resins, tapes or the like to the road surface by relative movement of a vehicle with respect to the road surface. That is, markings or stripes are applied over a pavement surface in the direction of movement of such a vehicle. Typical paint or resin application systems comprise spray devices, other contact painting devices, such as rollers or brushes or resin extruders. Tapes are typically provided by unwinding tape from a source roll and applying it to the pavement by way of an application roller. In any case, paint, resin or tape is to be supplied to the dispensing point and applied to the pavement surface in a controlled manner so that the proper amount of paint, resin or tape is provided based upon the demands of usage and required coverage.
In addition to any of the above materials utilized for providing markings or stripes, pavement markings now widely use reflective particles as well. Such paints, resins (e.g. thermoplastics or epoxies) and tapes may contain reflective particles, such as transparent microspheres within their composition. Preferably, the resultant pavement markings are retroreflective so that motor vehicle drivers can vividly see the markings at nighttime. Retroreflective pavement markings have the ability to return a substantial portion of incident light toward the source from which the light originated. Light from motor vehicle headlamps is returned toward the vehicle to illuminate road features, e.g., the boundaries of the traffic lanes, for the motor vehicle driver.
More recent development of optical elements for retroreflective pavement markings are directed to optical elements with greater retroreflectivity at low angles of incidence. Transparent optical elements, such as glass beads, on the one hand each act as a spherical lens so that incident light can be reflected back to the motorist after it passes through an optical element and strikes pigment particles within the marking material. An example of a specialized glass microsphere is described in U.S. Pat. No. 5,853,851.
To reflect more incident light back to the motorist for improved marking visibility, reflective vertical surfaces are being incorporated into pavement markings. For example, raised pavement markers may be provided at intervals along a pavement marking line, such as disclosed in U.S. Pat. Nos. 3,292,507 and 4,875,798. Another example is the use of embossed pavement marking tapes such as disclosed in U.S. Pat. Nos. 4,388,359, 4,069,281, and 5,417,515. Yet other examples comprise the provision of composite retroreflective elements or aggregates that typically include a core material with any number of optical elements embedded to the core surface. Such composite elements may be irregular in shape or may be shaped into spheres, tetrahedrons, discs, square tiles, etc. Such composite retroreflective elements are advantageous because they can be embedded into inexpensive paints and resins. Such composite retroreflective elements are known to comprise polymeric and/or ceramic core compositions. An example of durable retroreflective elements comprising a ceramic core can be found in U.S. Pat. No. 5,774,265. A retroreflective element comprising a multi-sided retroreflector and a clear thermoplastic resin is described in U.S. Pat. No. 5,835,271. Each of the above-noted U.S. patents is fully incorporated herein by reference.
Whether or not the retroreflective optical elements utilized in a pavement markings comprise conventional glass beads or composite optical particles, such optical elements can be incorporated into the pavement marking either as part of the composition of the material that is applied as the pavement marking or they may be dispensed onto the pavement marking material after it is applied but while it is capable of permitting particles to at least partially embed therein, i.e. while the marking material is still sufficiently tacky, wet or soft. In the case of a tape, the optical elements are typically formed into the tape during the tape-making process. But, with paints and resins, optical elements can be mixed into the paint or resin before application, mixed with the paint or resin just prior to application, or dispensed onto the pavement marking material after it has been applied to the pavement surface. Of these, the latter technique is generally preferred because the optical elements are assured of being present at the surface of the pavement marking where their retroreflectivity is functional. Particles within the thickness of the marking may be subsequently utilized after the pavement marking wears down. Also, optical elements dispersed within a paint or resin before or during application may not be retroreflective at all, depending on the transmissivity of the paint or resin, and on whether the entire element is coated with that paint or resin.
Examples of pavement marking painting and bead dispensing systems are described in U.S. Pat. Nos. 4,319,717, 4,518,121, 5,203,923, and 5,294,798. In each of these, the bead dispenser is located on a movable vehicle that also carries the paint or resin applicator, so that an appropriate quantity of beads are dispensed onto the width of the marking in accordance with predetermined marking characteristics. Of these, the device disclosed in U.S. Pat. No. 4,518,121 is directed to a bead dispenser whereby optical beads are deflected into the paint spray so that paint and beads are deposited together on a pavement surface to form a reflective stripe. The others are directed to bead dispensers that apply the beads to the marking paint or resin after it is applied to the pavement surface while still sufficiently wet. Moreover, in these bead applicators that spray beads onto the marking material, the beads are directed from a dispensing unit comprising a nozzle in a downward direction aimed toward the pavement. In U.S. Pat. No. 4,319,717, the disclosed spray gun includes an air nozzle for increasing the impact of the beads to the marking material than would be experienced under gravity alone. The dispensers described in U.S. Pat. Nos. 5,203,923 and 5,294, 798 are described as having the ability to dispense the tiny beads under air pressure through the dispensing valve. That is, the beads are supplied to the dispenser by virtue of a volume of air under pressure that not only moves the beads to the dispenser, but also causes the beads to be dispensed at a higher exit velocity than if simply dropped under the force of gravity.
Other dispensers, including nozzles oriented other than directly toward the pavement surface, are also known. For example, a dispensing nozzle connectable to a pressurized supply of beads is known that includes a plate for directing the beads in an opposite direction as the direction of movement of the vehicle utilized in applying the marking material and the glass beads.
A disadvantage of all of these prior art dispensers and nozzles is that the beads are dispensed onto the pavement marking material at a relative velocity compared to the pavement marking. Where the beads are dropped directly onto the pavement marking, the relative velocity equals the velocity at which the vehicle, whether manual or motor driven, is moving over the pavement. Where the dispensing nozzle faces in the opposite direction than the direction of movement, the relative velocity can be reduced. This depends on whether the beads exit the nozzle with any component of movement in a direction opposite to the direction o
Khieu Sithya S.
Marty John L.
May David C.
Zender Mark D.
3M Innovative Properties Company
Addie Raymond W.
Lilly James V.
Will Thomas B.
LandOfFree
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