Abstract:
A single-phase portable device melts and sprays thermoplastic using 120-V power. The device includes a vessel for receiving and storing thermoplastic, and heated hollow rod circulators that draw melted thermoplastic upward and redistribute it within the vessel to facilitate rapid and even melting. The device includes a heated hose and nozzle for spraying the material, hose storage area, and wheels and handle for moving device and spraying in multiple locations as desired.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application 61/669,218, filed Jul. 9, 2012. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to thermoplastic handling devices and methods of using them, and more specifically, to a portable device and method of heating thermoplastic materials and subsequently spraying them. 
     2. Description of the Prior Art 
     Thermoplastic coatings are often used in various mechanisms and machine parts in order to keep the system in good working order. For example, bearings on conveyor belts in the mining industry are often coated with thermoplastic. An example of such a thermoplastic is ENVIROPEEL E170 from A&amp;E Systems of Malaysia. 
     The conventional system of accomplishing this is to heat the thermoplastic in a static tank having a heated bottom, relying on all heat to transfer upwardly from the bottom. Melted thermoplastic is then sprayed using a 230V 3-phase system. One example of such a system is the sprayer available through the aforementioned A&amp;E Systems of Malaysia. However, this system has shortcomings. For one, the conventional system requires 230V, which is not always readily available. In addition, it requires at least two hours to achieve full tank melt because the melting vessel is, in essence, a large high-temperature slow-cooker. In addition, the system is large and cumbersome, and therefore is not reasonably moved from one location to another. This is problematic because it isn&#39;t always feasible to remove mechanical parts, bring them to a sprayer to be coated, then reinstall those coated parts afterwards. 
     As can be seen, there is a need for a self-contained device for heating and spraying thermoplastics. It is desirable that this system is capable of running off a standard 120 V source, and is single phase. It is also desirable that the system is capable of melting thermoplastic relatively quickly, and relatively energy efficiently. It is also desirable that this system is portable insofar as it can be used in one location; unplugged, replugged, transported and used in another location; and so forth. 
     SUMMARY OF THE INVENTION 
     The present invention includes a portable device for use with thermoplastic materials. The device includes a vessel for receiving solid-form thermoplastic, a series of heaters and fluid circulators, and a hose and nozzle for spraying melted thermoplastic. The system also includes a control panel for selecting desired operating parameters such as temperature, circulation speed, pressure for spraying, and so forth. 
     One novel feature of the present invention is hollow rod heaters which use a valve assembly and pump to draw melted thermoplastic from the vessel, transfer it upward through the heated hollow tube, and discharge it from the top of the hollow tube. This action facilitates even melting by moving material throughout vessel and constantly circulating material past heaters, and by allowing melted material to mix with solid-form material, thereby facilitating ongoing even heat transfer. The result is a system that uses about half the energy, and half the time, to bring a given mass of solid-state material to the melted state for spraying. 
     The device also desirably includes a heated hose and a nozzle for spraying the melted material, as well as the associated compressor, tank and pump. The device includes a storage compartment sized to retain the hose when not in use. A set of wheels and a handle assist in moving the device from one location to another as desired. In this manner, one batch of solid-form thermoplastic may be melted, and the device can be moved to multiple locations, for example within a mining operation, to spray various parts with thermoplastic. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a device according to an embodiment of the present invention, without a lid and motor assembly; 
         FIG. 2  also depicts a top view, except with a lid and motor assembly; 
         FIG. 3  is a side view of the invention; 
         FIG. 4  is a side view showing the inner components; 
         FIG. 5  is a front view 
         FIG. 6  is a side view including a hose and nozzle; and 
         FIG. 7  includes some engineering parameters. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     The following structure numbers apply among the various FIGS:
           10 —Sprayer device (“device”);     12 —Wheels;     14 —Handle;     20 —Drive motor;     30 —Vessel;     32 —Hollow rod;     34 —Solid rod;     40 —Hose storage;     45 —Hose;     47 —Nozzle;     50 —Compressor;     52 —Tank;     60 —Recirculation valve assembly;     65 —Pump; and     70 —Control panel.       

     Broadly, an embodiment of the present invention provides a portable device  10  including heating and spraying functionality.  FIGS. 1 and 2  depict top views of an embodiment of device  10 , including wheels  12 . In use, one tilts device  10 , with handle  14 , and rolls using wheels  12 . This is best depicted in  FIG. 3 . The device is single phase, and connects to a 110 V electrical source using a standard connection such as a cord. 
     Device  10  includes various components. Referring to  FIG. 4 , going generally from top to bottom, device  10  includes drive motor  20 , which is electromechanically connected to pump  65  and recirculation valve assembly  60 . The drive motor preferably has an AC induction motor having a torque of 56 lb. and horsepower of 0.06. An example of a suitable drive motor is the Leeson D12B gear motor, which is commercially available from Grainger, Inc. of Indianapolis, Ind. 
     Vessel  30  includes hollow rod  32  and solid rods  34 , all of which are heating elements configured to melt thermoplastic placed inside vessel  30 . Vessel  30  preferably has a capacity of approximately 20 to 30 pounds of thermoplastic. Rods can be heated to various temperatures, typically in the range of 300° F. to 375° F., with 330° F. to 340° F. being preferred, depending on the characteristics of the specific thermoplastic. However, heating 75° F. to 450° F. is also within the scope of this invention. Once the desired temperature is met, melted thermoplastic is continuously pumped with pump  65  through recirculation valve assembly  60  through hollow rod  32 . This process transports melted thermoplastic from the bottom of vessel  30 , up through the insides of hollow rod  32 , where it comes out the top, thereby heating thermoplastic located in the upper portion of vessel  30 . This expedites the melting process by evenly distributing the heat throughout vessel  30  via the melted thermoplastic. This can be conceptualized as a heated thermoplastic fountain of sorts. Solid rods  34  heat the thermoplastic, but don&#39;t provide a longitudinal path through which melted thermoplastic may travel, as the hollow rods do. As the thermoplastic is uniformly melted, it moves more easily through hollow rod  32 . Rods  32  and  34  maintain uniformity of melted thermoplastic while in device  10 . The result is that thermoplastic is ready for use in approximately 1 hour, versus 2 hours for conventional systems. In addition, thermoplastic is ready for use with approximately 50% less energy than is required by conventional systems. 
     Device  10  also includes spraying capability. More specifically, hose storage  40  contains heated delivery hose and application head connected to recirculation valve assembly  60 . Recirculation valve assembly  60  is connected to pump  65 . It is preferred that heated hose is approximately 12 feet long, and has a diameter of approximately 1″. An example of a suitable delivery hose is Dynaflex from ITW Dynatec of Hendersonville, Tenn. Tank  52  is attached to a separate air line inside of heated delivery hose and delivers pressurized air to assist in certain application methods. 
     As shown in  FIG. 5 , functions are controlled by control panel  70 , which contains main power switch, drive motor control and compressor controls, and through which an operator sets parameters such as melting temperature, and spray force. Control panel  70  may also serve as a display insofar as it displays actual system temperature and heating sequences, when thermoplastic is uniformly melted, and when power switch is on. 
     In use, an operator puts a quantity of solid-form sprayable thermoplastic material into vessel  30 , enters proper settings into control panel  70 , and allows device  10  adequate time for uniform melting to occur. Referring to  FIG. 6 , once thermoplastic is ready, hose  45  is taken from hose storage  40 , attached to valve  60 , and compressor  50  is turned on. Although not shown, compressor  50  is in fluid communication with the hose and nozzle. The user then coats the desired parts by spraying them using nozzle  47 , in accordance with standard procedures. When coating is complete, device  10  is rolled to the next location for subsequent spraying of those desired parts. Once all coating is complete, device  10  is shut down and cleaned. 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. It should also be understood that ranges of values set forth inherently include those values, as well as all increments between.