Patent Application
20230407581
This invention relates generally to the field of a road surface marking apparatus, and in particular to horizontally positioned kettles mounted on a truck chassis used for melting thermoplastic material, and a device for applying thermoplastic molten material to a road surface.
Road surface markings vary in form: surface level permanently affixed, surface level temporarily but not permanently affixed, higher than road surface markers, and/or even mechanical devices. They are designed to inform motorist and pedestrians. Their designs range from merely a daytime or nighttime visual presentation to a raised pavement marker that advises motorist by light reflection or vehicle vibration resulting from contact between the vehicles tires and the raised marker. Efforts to improve road marking systems exist in the realm of the application of such markings, adding retro-reflectivity, increasing longevity, and lowering installation cost.
More specifically, two distinctions exist for road surface markings: mechanical and non-mechanical markings. Mechanical devices may be raised or recessed into the road surface, and either reflective or non-reflective. Most mechanical road surface markings are permanent; however, some are movable. Mechanical devices include, but are not limited to Botts' dots, rumble strips, and reflective markers. Botts' dots, low rounded white dots, generally are used to mark the edges of traffic lanes, frequently in conjunction with raised reflective markers. Rumble strips are typically a series of simple troughs that are ground into the asphalt. They can be used across the travel direction to warn of hazards ahead or along the travel direction to warn of hazards of not staying within a specific lane. They create a strong vibration when driven over in order to alert a driver to various upcoming hazards both by sound and the physical vibration of the vehicle. Reflective markers are used as travel lane dividers to mark the median or to mark exit slip-roads. By incorporating a raised retro-reflective element, they are typically more visible at night and in inclement weather than standard road marking lines.
Non-mechanical markings include, but are not limited to paint, thermo-set, tape, and thermoplastic pavement markings. Paint, which sometimes includes additives such as retro-reflective glass beads, is generally used to mark travel lanes, spaces in parking lots or special purpose spaces for disabled parking, loading zones, or time-restricted parking areas. Paint is a low-cost application, and is usually applied right after the road has been paved. The road is marked commonly by a truck called a “striper.” These trucks typically contain hundreds of gallons of paint stored in huge drums which sit on the bed. The markings are controlled manually or automatically by a controller who sits on the truck bed. Paint is directed through a series of hoses under pressure and applied to the roadway surface along with the application of glass beads for retro-reflectivity. Painted symbols, such as turn-lane arrows or HOV lane markers, may be applied manually or using stencils.
Thermoplastic is one of the most common types of road surface marking based on its balance between cost and performance longevity. It is durable, easy to apply, and reflective. For low traffic areas, traffic paint is suitable and will last for a year or so. However, in higher traffic areas, paint simply cannot handle the wear and will disappear in just a few months. The longevity of thermoplastic makes it a very cost effective traffic delineation solution. Thus, the use of thermoplastics over paints has increased; mainly due to the performance benefits of increased durability, retro-reflectivity, and a lack of volatile organic compound (VOC) solvents. Furthermore, municipalities like these features because they can budget for a thermoplastic job once every several years instead of having to budget for paint striping every year or less.
Thermoplastic is stored and shipped in a solid state, is environmentally friendly, and is a user safe compound. It combines with a mixture of glass beads, pigments, binders, and filler materials. Its composition offers a variety of positive features: the glass beads provide the retro-reflectivity necessary for its bright night time appearance; pigments provide the color and opacity; the binder mixture provides toughness, flexibility, and bond strength while holding all the components together; and fillers, such as calcium carbonate, sand and/or other inert substances provide bulk.
Thermoplastic markings are applied using specially equipped trucks. The thermoplastic mix, usually in a brick or pellet form, is heated in the truck to about 400° F. (200° C.) before being fed to the application apparatus, which is often a screed box, spray dispenser, or ribbon gun. Temperature is a most important factor for the proper mixing, melting and bonding of thermoplastic. The thermoplastic mix is heated to a temperature between 400° F. and 440° F. and agitated, causing the thermoplastic compound to become a homogenized liquid. When applied at this temperature, the thermoplastic melts into the upper surface of the asphalt, forming a strong thermal bond. When installed on porous surfaces, such as open-graded asphalt or tined concrete, the hot liquid thermoplastic fills the voids, creating a strong mechanical lock on concrete.
The apparatus conventionally employed to apply thermoplastic marking material, known as a pavement striping apparatus, includes walk behind systems, systems that are pulled on trailers, or systems that are built on vehicle chassis. The pavement striping apparatus includes one or more large capacity melter hoppers or kettles that maintain a relatively large volume of thermoplastic marking material in a molten state. Existing hoppers or kettles are oil-jacketed and diesel or propane fired, and can keep as much as 2,000 pounds or more of thermoplastic marking material in a molten state. Although this method is very effective, it does present certain drawbacks. For example, it takes a significant amount of time to melt the relatively large volume of thermoplastic marking material kept in the kettle. This can cause delays before the pavement marking operation can be commenced. It also takes a significant amount of energy to keep a relatively large volume, more than 2,000 pounds of thermoplastic marking material, in a molten state. For this reason, the apparatus conventionally employed to apply thermoplastic marking material to pavement surfaces further includes one or more “preheaters” that are used to melt an additional volume of thermoplastic marking material before it enters the melting kettles. Unfortunately, other drawbacks still exist.
Once melted, the thermoplastic marking material must be continuously stirred to keep the various components of the material from separating and to prevent the thermoplastic material from undergoing thermal degradation. Additionally, should the thermoplastic material remain in the kettle for too long, the material will begin to overheat and scorching may occur. Thermoplastic material that reaches and exceeds its flashpoint must be cooled rapidly for two reasons: firstly, superheated material can ignite causing serious consequences when exposed to air; and secondly, the thermoplastic can break down from the effects of this heat in a short time and thus become waste material. Overheated or super heated material in the kettle can be cooled by the addition of unheated material to the kettle, but material added to the kettle has a low efficiency of cooling.
In the case of heavy duty commercial equipment, pavement striping apparatus or systems are built on the chassis of large trucks and can include one or more large capacity kettles. Such kettles can be quite tall and provided with various structures, such as platform steps, ladder rungs, bridges, etc., which enable operators or tenders to access and add material into the tops of the melter kettles. There is an obvious inherent danger in a tender carrying large volumes of thermoplastic up a platform. The tender lifts or otherwise transfers plastic bags of granular thermoplastic material up to the kettle and introduces the material therein. The material free falls into the melter kettle in its packaged or solid state. Mechanical agitators in the melter kettle then mix the material into a molten format. The opening at the top of the melter kettle into which the thermoplastic material is poured can be a hinged lid or any number of various designed chutes with baffle doors. The hinged lid offers the tender no protection against back splash of molten material or blow back of flames from super heated material. When the melter kettle lid is opened, while the thermoplastic is above its flashpoint temperature, oxygen is sucked into the melter kettle and may ignite with an explosive force. Serious injury to anyone in the vicinity of the blast can occur. Various designed baffle chutes offer some protection against splash back of material; however, blow back of flames from super heated material remains a constant danger, especially when a tender is situated in a raised position, such as on a ladder. These hazards are serious deficiencies that need to be addressed.
There are additional problems that can occur when material is fed into melter kettles. If the material is added in solid form, it will melt slowly. This is because only the relativity small mass of the surface area of the material is in contact with the heated walls and floor of the melter as well as the molten material in the kettle. The agitators in the kettles do not have the ability to break the solid material into smaller pieces. Thus, this material can only melt from its outer surface. This slow process increases both production time and job cost. Furthermore, if material is added into a hopper, only the material fed into the hopper is melted in the kettle, and only the molten material within the kettle can be dispensed onto a pavement surface, thus resulting in a lag time.
Applicants U.S. Pat. No. 10,883,232 is directed to a pavement striping device for heating and applying thermoplastic material to a road surface. The pavement striping device includes: a hopper for holding a supply of particulate thermoplastic marking material in a non-molten state, an air or oil-heat transfer medium melting kettle having a series of coaxial conveyored or unconveyored conduits within, a plastic extruder for transporting the thermoplastic particulate from the hopper to the series of coaxial conveyored or unconveyored conduits with the air or oil-heat transfer medium melting kettle, a heating mechanism for heating the air or oil-heat transfer medium melting kettle and the plastic extruder to a temperature suitable for melting thermoplastic, and a means for driving the stream of molten thermoplastic through the series of coaxial conveyored or unconveyored conduits to a sprayer or extrusion die, all of which form a means by which the molten thermoplastic is directed to the pavement surface.
What is desired is a further improvement to the Applicant's prior pavement striping device for rapidly heating and applying thermoplastic material to a road surface in a continuous manner by use of a laterally disposed kettle.
An improvement to surface marking devices for heating and applying thermoplastic material to various surfaces including roads, parking lots and the like is provided. The surface marking device is comprised of a laterally disposed oil-jacketed melting kettle having a rotatable auger extending from a first end to a second end. The first end having an open inlet for receipt of particulate thermoplastic marking material in a non-molten state. The second end coupled to a thermo pump for transfer of the thermoplastic marking material in a molten state. A heating mechanism for heating the laterally disposed oil-jacketed melting kettle and thermoplastic marking material placed therein to a temperature suitable for melting the thermoplastic.
Placement of the oil-jacketed melting kettle in a horizontal or near horizontal position allows the place of a surface above the melting kettle, ideally available to hold a platform for carrying pallets of thermoplastic marking material. The pallets that hold individual bags are deposited into an open inlet of each kettle wherein an auger transports the material which is converted from the non-molten state to a molten state during transfer. In one embodiment the molten thermoplastic is directed to a spray or extrusion die together with glass beads for application of the molten thermoplastic to the pavement surface. In another embodiment the molten thermoplastic is directed to an auxiliary vehicle or application cart for application to the payment surface.
Accordingly, it is an objective of the present invention to provide a pavement striping device that provides real-time heating and melting of thermoplastic particulate for application to a road surface using laterally disposed tanks.
It is another objective of the present invention to provide a laterally disposed oil-heat transfer medium melting kettle to provide an area for storage of thermoplastic material allowing for continuous real time road marking.
Still another objective of the invention is to increase the amount of kettle heating volume, and increase the amount of storage, on a vehicle.
A further objective of the present invention to provide a vehicle having a platform positioned over heated melting kettles allowing pallets holding thermoplastic bags to be placed at a position above an open inlet to each kettle wherein the bags of thermoplastic material stored on the pallets can be deposited into the open inlet eliminating the need for lifting of the bags into a raised opening as required with a vertical disposed melter.
It is yet a further objective of the present invention to provide a heating mechanism to the kettle to provide heating zones that increase temperature of the kettle from the first end to the second end where the molten thermoplastic exits.
It is a further objective of the instant invention that the auger provides agitation for proper mixing of the thermoplastic, as well as ensures even disbursement and uniform temperatures throughout the thermoplastic material mass.
Still another objective of the invention is to allow a continuous flow of material to be applied by eliminating the need for a kettle to prepare a batch of molten thermoplastic material.
Yet still another objective of the invention is to increase the safety to workers by eliminating the need to work above a vertically disposed kettle.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred, albeit not limiting, embodiment with the understanding that the present disclosure is to be considered an exemplification of the present invention and is not intended to limit the invention to the specific embodiments illustrated.
Now referring to the figures, a pavement striping device 10 for heating and applying thermoplastic material to a road surface is illustrated. The pavement striping device 10 is comprised of a support base 12 having an upper surface 14 extending the width W of a vehicle 16, the base having a front edge 17 and a rear edge 19. The vehicle 16 includes a first set of laterally disposed oil-jacketed melting kettles 22, 24 fluidly coupled to a burner 26 for providing hot oil to the kettles. For ease of illustration, a single kettle 22 is depicted in
In the preferred embodiment, a second set of kettles may be used, allowing one set of kettles to heat yellow thermoplastic material and the second set to heat white thermoplastic material. In this embodiment, the vehicle includes third and fourth laterally disposed oil-jacketed melting kettles 54, 56 having an adjoining burner 60 providing hot oil to the kettles. Again, for ease of illustration, the kettle 22 depicted in
It is noted that each inlet 36, 62, 64 and 66 is positioned flush with the upper surface 14 of the support base 12, wherein the marking material 40 can be placed on the deck using shipping pallets 70. A worker can slide the individual thermoplastic 40 bags into the appropriate inlet. The inlets include an open top suitable for easily pouring pelletized or ground thermoplastic therein. The inlets preferably include tapered sidewalls, which direct the granulated or pelletized thermoplastic to the inlet of the auger placed within the thermal heat kettle.
As with each of the kettles 22, 24, 54, 56, the second end 72 of the kettle 54 is coupled to a thermo pump 44 for transfer of the thermoplastic marking material in a molten state from the kettle 54 to an application directly to the pavement surface or to an auxiliary vehicle or cart for pavement surface application. The thermo pump 44 is used for driving a stream of molten thermoplastic to a sprayer or extrusion die, all of which form a means by which the molten thermoplastic is directed to the surface to be marked. In a preferred embodiment, the transfer thermo pumps 44 are hydraulic based with an engine driven hydraulic pump 80 for supplying the required fluid pressure. In a preferred embodiment, the hydraulic pump 80 drives a first hydraulic motor 81 mounted to an end of an auger wherein a sprocket 83 rotates the individual augers.
Material 40 is placed within the appropriate inlets to the kettle in a non-molten state wherein the auger 34 is constructed and arranged to transport the thermoplastic material 40 through a kettle having a hot oil jacket. In at least one embodiment, the kettle is heated to a temperature suitable for melting thermoplastic with the auger continually scraping the inner side walls of the kettle 22 to prevent molten material from backflowing to the inlets. Holding tanks 50, 65 store the retro-reflective glass beads for subsequent application during application of the molten thermoplastic to an auxiliary cart or vehicle. In a preferred embodiment, the auger 34 is constructed and arranged to direct the molten thermoplastic directly to a thermoplastic pump or extrusion die (not shown) for sizing and controlling the flow of the molten thermoplastic and retro-reflective glass beads for the application on the pavement surface. The pavement striping device 10 may be built on a vehicle chassis, pulled on a trailer, or used to provide molten material to a secondary vehicle or cart without departing from the scope of the invention.
Gravity forces the particulate 40 in the auger 34 that is placed through the inlet 36, 62, 64, 66. Preferably, the amount of particulate 40 that is required by a sprayer in real-time is transferred through the auger 34 at the appropriate rate. In that manner, any number of devices may be used for monitoring the volume of thermoplastic heated through the kettles. The monitoring devices would cause an operator to alternate between feeding material and not feeding material to the melting kettles.
In some embodiments, the rotating auger 34 further acts to scrape the molten plastic from the sidewall of the kettle and agitate the thermoplastic material as it is forced toward the rear end 20 and controlled by a knife gate 21. Within the embodiments, each kettle may provide heating zones within the kettle that gradually increase the temperature of the kettle 22 from the front end to the rear end. In at least one embodiment, the auger 34 utilizes a screw shape such as those utilized in plastic extrusion machines. This auger shape is constructed and arranged to timely move the material 40 as it is conveyed through the kettle. In this manner, the screw may be constructed to pre-heat or melt the thermoplastic as it is transferred along the conveyor, reducing the heat that would need to be transferred to the thermoplastic for application to a road surface.
Each kettle is generally capable of melting thermoplastic road marking materials to a suitable temperature to allow flow through a nozzle or extrusion die. The melting kettle is comprised of a shell of unitized construction to maximize heat efficiency.
The auger 34 serves to control the speed of transfer of the material as it moves through the kettle, as well as directing the plastic to the surface of the heating tubes for optimum heat transfer. The auger assists in proper mixing of the thermoplastic, as well as ensures even disbursement and uniform temperatures throughout the thermoplastic material mass. A sensing means, not shown, maintains and monitors the temperature of each kettle. In a preferred embodiment, a burner 26 should provide the kettle 22 with a temperature above 400° F. but not exceeding 600° F. The heating mechanism utilizes oil as a heat transfer medium wherein oil is transfers from a reservoir 51 by a hot oil pump 53 to the burner 26 having an oil jacket 32. The oil is passed through the kettle 22 and recirculated back to the oil reservoir 51. A thermo pump 44 transfers the molten thermoplastic through a manifold 55 for distribution through thermo guns 57, the excess molten plastic returned 59 to the kettle 22. It should be noted that hot air or other fluids suitable for transferring the heat without combusting or deteriorating may be utilized without departing from the scope of the invention.
There are various devices that may be attached to the nozzle to apply or contain molten thermoplastic onto the pavement surface such as, but not limited to, a ribbon dispenser, spray dispensing device, screed extrusion device, or the like, not shown. The ribbon dispenser is heated and suspended above the road surface, applying a forced-extrusion, well-defined thermoplastic line. The spray dispensing device results in a thermoplastic spray pattern that is a uniformly thick, well-defined, and securely bonded stripe. Compressed air must be dry when mixing with the molten thermoplastic. The extrusion device has a dispensing shoe that rides directly on the road surface, and a continuous line is formed by a three-sided die with a control gate set to a pre-determined thickness.
An actuation means, not shown, is in communication with the auger and an actuation means that actuates the motors drive motors when the sprayer is operated to dispense molten thermoplastic. The actuation means allows for real-time melting of the thermoplastic particulate to molten thermoplastic upon trigger of the sprayer means. In this manner, thermoplastic particulate in a non-molten state is inserted into a kettle inlet, wherein the auger moves the thermoplastic particulate further into the kettle through friction and heating, by the series of coaxial tubes of oil-heat transfer medium, whereby the thermoplastic is driven there through and heated to a suitable melting temperature to form a molten thermoplastic. The molten thermoplastic is pumped directly through a sprayer means that directs the molten thermoplastic to the pavement surface together with the glass beads, or to an auxiliary vehicle/cart for application to a pavement surface.
The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus 5%. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes” or “contains” one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes” or “contains” one or more features, possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.
One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary, and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention, which are obvious to those skilled in the art, are intended to be within the scope of the following claims.
This application is related to U.S. Patent Registration No. 10,883,232, issued Jan. 5, 2021 the contents of which are incorporated herein by reference in its entirety. In accordance with 37 C.F.R. § 1.76, a claim of priority is included in an Application Data Sheet filed concurrently herewith. Accordingly, the present invention claims priority to U.S. Provisional Patent Application No. 63/366,043 entitled “LATERALLY DISPOSED THERMOPLASTIC MELTING KETTLE AND SURFACE APPLICATOR”, filed Jun. 8, 2022. The contents of the provisional application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63366043 | Jun 2022 | US |
