Patent Application
20240271374
The present invention generally related to a pavement marking system for applying retroreflective markers to a roadway, and more particularly, to a pavement marker dispenser for more accurately spacing the markers when applied to the pavement of the roadway.
Over at least a ten-year period, a pavement marking system was developed and improved by one of the inventors of the present application. The pavement marking system is described in detail in the following U.S. Pat. Nos. 8,123,430; 8,425,144; and 8,465,223, all of which are incorporated herein by reference. The pavement marking system is shown in
More specifically, with reference to
A liquid applicator 1006 having a spray or extrusion head 1009 is mounted to the carrier 1000. As the carrier 1000 advances, the liquid applicator 1006 applies thermoplastic paint 1012 to the roadway surface 903 through the spray head 1009. The thermoplastic paint 1012 comprises thermoplastic pavement marking material that has been heated to a molten state at between 400 degrees and 425 degrees on the Fahrenheit scale. After application, thermoplastic paint 1012 forms the base line 906 for the roadway striping.
Also mounted to the carrier 1000 is a pavement marker dispenser 1015. In this embodiment, the pavement marker dispenser 1015 comprises an upwardly extending feed tube 1018, a disc actuator 1021, and a delivery chute 1024. The feed tube 1018 holds an vertical upwardly extending stack of the pavement markers 100, the stack being supported by a supporting surface 1027. The disc actuator 1021 is configured to deliver pavement markers 100 to the delivery chute 1024 at predetermined time intervals based on the speed of the carrier 1000. Thus, the disc actuator 1021 may be controlled by a commercially available skip timer.
In the embodiment of
The pavement markers 100 are loaded in the upwardly extending feed tube 1018 with their effectively flat base surfaces facing down toward engagement with the upwardly facing opposed surfaces of the pavement markers next below. By the operation of the pushing mechanism 1030, the pavement markers 100 are given a forward velocity in the direction of arrow 1032 and are received by the delivery chute 1024. The pavement marker dispenser 1015 is designed to keep the pavement marker 100 positioned with its effectively flat base surface 103 in contact with the parts of the pavement marker dispenser 1015, and, in particular, delivery chute 1024. Such positioning tends to avoid abrasive wear that might be caused by the light reflective beads 112 engaging the delivery chute, thereby prolonging the life expectancy of the pavement marker dispenser 1015.
In some embodiments, the delivery chute 1024 may be equipped with a damper 1033 to dampen the impact of the pavement marker 100 at the surface of the delivery chute 1024 and to reduce bouncing of the pavement marker 100 when applied at a high rate of speed. Bouncing of the pavement marker 100 may lead to imprecise placement into the molten base line 906. The damper 1033 may comprise, for example, rubber bushings or a surface affixed to the delivery chute 1024 by a flexible material, such as silicone or foam.
When the pavement marker 100 engages the delivery chute 1024 or damper 1033, the gravitational force pulls the pavement marker 100 downward as shown by arrow 1036. While sliding down the delivery chute 1024 in the direction of arrow 1039, the pavement marker 100 gains a horizontal component of velocity in the direction rearward of the movement of the carrier 1000. Accordingly, when released by the delivery chute 1024 for embedding into the base line 906, the pavement marker 100 has a forwardly directed component of velocity less than that of the carrier 1000.
The pavement marker dispenser 1015 and the delivery chute 1024 are positioned on the carrier 1000 and configured so that the pavement marker 100 is released to the molten base line 906 as close to the spray head 1009 as possible, preferably within 10 inches of the spray head 1009. This positioning is desired because the thermoplastic paint 1012 cools very rapidly and the molten base line 906 needs a sufficiently high temperature to produce a bond between the pavement marker 100 and the molten base line 906. Preferably, the temperature of the molten base line 906 will be sufficiently high to partially melt the material of the pavement marker 100 so that the partially melted pavement marker 100 will fuse with the molten base line 906.
A reflective bead applicator 1042 having a dispensing head 1045 may be mounted to the carrier 1000. The reflective bead applicator 1042 releases light reflective beads 1048 through the dispensing head 1045 onto the molten base line 906. The light reflective beads 1048 may be the same as or different from the light reflective beads 112 used in the manufacture of the pavement markers 100. The light reflective beads 1048 thereby become embedded into the molten base line 906 with embedded pavement markers 100, producing a reflective base line 1051.
In an attempt to improve the wet night retro-reflectivity of the marker, a new decagonal-shaped marker was developed and patented under U.S. Pat. No. D 737,165, which is incorporated here by reference. This marker is illustrated in
Disclosed are various embodiments of a pavement marker dispenser for a pavement marking system that dispenses retroreflective markers for a roadway with more accurate spacing than prior art embodiments.
One embodiment, among others, is a pavement marker dispenser that includes an elongated curvilinear feed tube that houses a generally vertical curvilinear stack of pavement markers. The feed tube has top and bottom openings to respectively receive and dispense the markers in a downwardly vertical direction. The feed tube has a nonlinear curvature along its length to produce the curvilinear stack of markers so that a downwardly vertical stacking force imposed on a bottommost marker to be dispensed is reduced. The feed tube has first and second curved portions so that the nonlinear curvature is generally serpentine in shape. A disc actuator having a pushing arm extends perpendicular to the feed tube to push the bottommost marker in a rearward and downward direction towards the delivery chute, which dispenses the markers in a rearward and downward direction.
Another embodiment, among others, is a pavement marking system for applying retroreflective markers to a surface of a roadway. The system comprises (a) a liquid applicator having a spray or extrusion head, the liquid applicator capable of applying thermoplastic paint to the roadway surface through the spray or extrusion head; (b) a pavement marker dispenser; and (c) a mobile carrier that transports the pavement marker dispenser and the liquid applicator along the roadway.
The dispenser in this embodiment includes an elongated feed tube that houses a generally vertical curvilinear stack of pavement markers. The feed tube has top and bottom openings that respectively receive and dispense the markers in a downwardly vertical direction. The feed tube has a nonlinear curvature to produce the curvilinear stack of markers so that a downwardly vertical stacking force imposed on a bottommost marker to be dispensed is reduced.
The dispenser further includes a disc actuator having a pushing arm that extends perpendicular to the feed tube to push the bottommost marker in a generally rearward and downward direction and that unextends to advance the stack of markers downwardly in the vertical direction so that a next marker that was situated adjacent to the bottommost marker is in a position to be dispensed next.
Finally, the dispenser includes a delivery chute that receives the markers from the pushing arm and deposits the markers onto the thermoplastic paint in a molten state on the roadway surface.
Yet another embodiment, among others, is a method that employs the system of the previously described embodiment to form roadway markings on a paved roadway. The roadway markings include a base line and reflective pavement markers applied at intervals to the base line with the pavement markers having an effectively flat base surface and an opposed surface. The method can be summarized by the following steps:
Other embodiments, systems, apparatus, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional embodiments, systems, apparatus, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
In order to determine the effectiveness of the new pavement marker dispenser 1050 (
As the data reflects in Table A, the consistency of the time it takes each marker 100 to exit the dispenser 1015 needed improvement. Video taken of the markers 100 leaving the dispenser 1015 showed that some markers 100 would juggle for a short period of time, while others did not in the transition from moving forward before dropping on the slide, or chute, 1024. Others might bounce on the slide itself, slowing the rearward exit of the marker from the dispenser 1015. To prevent this, the forward motion step was eliminated, and the marker 100 was pushed directly rearward and downward in the direction of the slide 1024. The speed at which the marker 100 is dispensed can be controlled via a flow control valve on the incoming air supply. Performance was modestly better. A second air cylinder was added to increase the force available to be applied, and modest improvement was found again.
After testing under various conditions, the inventor determined that the dispenser consistency improved when the stack of markers 100 was fewer, and there was less weight on the marker 100 at the bottom of the stack that was being dispensed. Unfortunately, a stack of up to two hundred markers 100 is often required to provide a safe distance away from the roadway for an operator to load new markers 100 into the feed tube to replace those that have been dispensed onto the roadway. A stack of one hundred markers 100 was weighed with the feed tube supported, and the bottommost marker 100 exhibited 9.5 lbs. of force on a weight scale.
Two slight bends were placed in the feed tube that houses the stack of markers 100 to create a curvilinear stack. The curvilinear stack of markers 100 offset the weight of the stack on the feed tube itself, rather than on the bottommost marker 100 being dispensed. The first attempt at this concept by the inventor created several misfeeds, but the angles were reduced, and the distance between the angles was increased until acceptable feeding was obtained, resulting in the final design for the new pavement marker dispenser 1050 (
As is demonstrated by the above data, the new pavement marker dispenser 1050 of the present disclosure is capable of dispensing markers five times more accurately than the any previous version. Furthermore, a road test was conducted and all markers 100 that were measured were within one inch of the desired spacing of 30 inches between markers 100.
The architecture and operation of a preferred embodiment of the pavement marking system 1000 of the present disclosure will now be discussed.
Referring now to
A liquid applicator 1006 having a spray or extrusion head 1009 is mounted to the carrier 1000. As the carrier 1000 advances, the liquid applicator 1006 applies thermoplastic paint 1012 to the roadway surface 903 through the spray or extrusion head 1009. The thermoplastic paint 1012 comprises thermoplastic pavement marking material that has been heated to a molten state at between 400 degrees and 425 degrees Fahrenheit. It is understood that different paint materials may require different application temperatures. Furthermore, although the term “paint” is used, “paint” is understood herein to refer to any type of pavement marking material. After application, thermoplastic paint 1012 forms the base line 906 for the roadway striping.
Also mounted to the mobile carrier 1000 is a pavement marker dispenser 1050. In this embodiment, as illustrated in
In the preferred embodiment of
The pushing arm 1062 is mechanically connected to and movable by one or more piston rods 1063 that extend and unextend from one or more cylinder barrels associated with one or more pneumatic and/or hydraulic cylinders, respectively. Each piston rod 1063 moves linearly in and out of a respective cylinder barrel associated with the respective pneumatic and/or hydraulic cylinder.
In the preferred embodiment, the pushing arm 1062 is mechanically connected to the two generally parallel piston rods 1063a, 1063b associated with two parallel pneumatic air cylinders 1064a, 1064b, respectively, via suitable mechanical linkage 1066 so that the pushing arm 1062 is moved between the firing position and the idle position, as illustrated in
In an alternative embodiment, the disc actuator 1054 may be an air-actuated sliding shoe. In other embodiments, the disc actuator 1021 may implemented by, for example but not limited to, a rotating helical surface configured to support the stack of pavement markers 100 in the feed tube 1052 and to rotate to allow a pavement marker 100 to drop down and be received by the delivery chute 1056.
The elongated feed tube 1052 is designed to house the pavement markers 100 in a generally vertical curvilinear stack. The feed tube has top and bottom openings that respectively receive and dispense the markers 100 in a downwardly vertical direction. The feed tube 1052 has a nonlinear curvature to produce the curvilinear stack of markers 100 so that a downwardly vertical stacking force imposed on the lowermost (or bottommost) marker 100 to be dispensed is reduced. In the preferred embodiment, as best shown in
When each pavement marker 100 engages the delivery chute 1056, the pavement marker 100 has a horizontal component of velocity in the direction rearward of the movement of the carrier 1000. Accordingly, when released by the delivery chute 1056 for embedding into the base line 906, the pavement marker 100 has a forwardly directed component of velocity less than that of the carrier 1000. Preferably, the pavement marker 100 will have a forwardly directed component of velocity less than 1 mph when the pavement marker 100 contacts the molten base line 906. By having a net forward ground speed less than that of the mobile carrier 1000, surfing and skidding of the pavement marker 100 on the base line 906 are reduced.
When the pavement marker 100 is released from the delivery chute 1056, the base surface 103 is sloped facing downwardly and forwardly of the pavement marker dispenser 1050. A slight tilt of between 20 and 35 degrees helps to prevent a number of defects from occurring.
The angle of the delivery chute 1056 may be selected based on the desired speed of the mobile carrier 1000. For example, the mobile carrier 1000 may be moving at a speed of between 2 and 7 mph. It has been observed that roadway striping crews prefer to apply pavement markings at a speed of between 3 and 5 mph. Therefore, the length and angle of the delivery chute 1056, and the corresponding rearward velocity may be fixed for the common case, as depicted in
The pavement marker dispenser 1056 and the delivery chute 1056 are positioned on the carrier 1000 and configured so that the pavement marker 100 is released to the molten base line 906 as close to the spray or extrusion head 1009 as possible, preferably within ten inches of the spray head 1009. This positioning is desired because the thermoplastic paint 1012 cools very rapidly, and the molten base line 906 needs a sufficiently high temperature to produce a bond between the pavement marker 100 and the molten base line 906. Preferably, the temperature of the molten base line 906 will be sufficiently high to partially melt the material of the pavement marker 100 so that the partially melted pavement marker 100 will fuse with the molten base line 906.
Optionally, but preferably, a reflective bead applicator 1042 having a dispensing head 1045 may be mounted to the carrier 1000. The reflective bead applicator 1042 releases light reflective beads 1048 through the dispensing head 1045 onto the molten base line 906. The light reflective beads 1048 may be the same as or different from the light reflective beads 112 used in the manufacture of the pavement markers 100. The light reflective beads 1048 thereby become embedded into the molten base line 906 with embedded pavement markers 100, producing a reflective base line 1051.
It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible nonlimiting examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention.
