Abstract:
A shut-off system that is semi-automatic or fully automatic shuts off the mechanism for flowing resin, air and filler to a miniaturized convergent spray gun so as to stop the flow of the ingredients of being sprayed and purging the spray gun so that the residue ingredients do not cure and destroy the gun.

Description:
CROSS REFERENCES 
     This invention relates to the subject matter disclosed in a co-pending patent application contemporaneously filed that is entitled “Portable Convergent Spray Gun Capable of Being Hand-Held” filed by Scarpa et al, commonly assigned to the assignee and identified by Ser. No. 09/394,289, filed Sep. 10, 1999 and is incorporated herein by reference. 
     TECHNICAL FIELD 
     This invention relates to portable convergent spray guns for applying coatings to a surface and particularly to a portable spray gun that is miniaturized so as to be capable of being hand-held or having the option of being either hand-held or robotically-held for use with a portable system that includes a shut-down system for purging the spray gun when it is shut-down and the method of accomplishing the same. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,565,241 granted to Mathias et al on Oct. 15, 1996 entitled “Convergent End Effector”, U.S. Pat. No. 5,307,992 granted to Hall et al on May 3, 1994 entitled “Method And System For Coating A Substrate With A Reinforced Resin Matrix” and U.S. Pat. No. 5,579,998 granted to Hall et al on Dec. 3, 1996 entitled “Method For Coating A Substrate With A Reinforced Resin Matrix” of which the inventor Jack G. Scarpa is a co-inventor and which these patents are commonly assigned. These references disclose a spray gun that utilizes a nozzle that is designed to configure the spray emitted by the nozzle into an atomized convergent plume of liquid resin and targets the plume with reinforced filler material immediately downstream of the nozzle to mix and wet the filler just prior to being applied to the surface of the substrate. In other words, the reinforcing material is entrained around the atomized liquid resin flow and is caused to be captured thereby, mix therewith and become an homogeneously wetted coating material that after impact with the substrates becomes cured into a substantially reasonably thick coating exhibiting good strength and resistance characteristics. The gaseous transport stream together with the eductor deliver the ingredients in the proper proportions and the air stream for causing the atomization and mixing to provide the proper amounts of material to assure that the coating is uniform and consistent. Heating is applied in the proper sequence to assure that the viscosity is at the proper level to assure evenness of flow. 
     As one skilled in this technology would appreciate, the heretofore known spray application equipment for spraying of highly loaded paints and coatings which require the addition of a high volume of solid large granular materials such as cork, glass micro spheres, granular or powdered materials in the 3 to 300 microns range require large amounts of solvents to dilute solid contents down to a level where it can be sprayed effectively. This, of necessity, requires special spray equipment designs that need to be significantly large in order to effectively spray these materials. Such systems have heretofore been designed to operate in a room or compartment that include a robot that was programmed to hold the spray gun and apply the spray. An additional room houses the supply of materials to be mixed and sprayed, the various valves, hoppers, proportioning devices and the like are separated from the spray gun room and a separate room housed the computer equipment and controls that served to control the various valves, proportioning devices etc, to automatically effectuate the spraying. 
     These special very large spray equipment designs leads to very low actual transfer efficiencies for spraying these coating materials. These low transfer efficiencies have a significant impact on the quantities of materials, solvents and volatile organic compounds that are released into the environment. As one skilled in this technology will appreciate, from an ecology standpoint these conditions are not preferred as is recognized by the Environmental protection Agency and Occupational Safety and Health Administrations that are tightening regulations that mandate change. 
     While the sized the gun of this invention retains all of the features of the heretofore known convergent spray gun utilizing the end-effector, this spray gun is capable of supplying the same amount of coating for each pass of these heretofore known spray guns. This spray gun is characterized as being portable and capable of being held by one hand in the same way that a commercially available paint spray gun is handled. In this mechanism concentric tube assembly is added to a modified commercially available spray nozzle, such as spray nozzles produced by Binks, Franklin Park, Ill and Grace, Detroit, Mich. that provides an inner tube that transports the resin and an outer tube that transports the air for atomizing the mixture and the dry powdered nozzle and its convergent cap. This arrangement of the concentric tubes allows the dry powdered nozzle that transports the dry powder material into a manifold to be propelled into the resin/air atomization plume. The dry granular materials and atomized resins become entrained at this point and thoroughly mix together outside the gun before being deposited on the substrate. 
     This patent application constitutes an improvement over the structure described in the U.S. Pat. Nos. 5,5645,241, supra 5,307,992, supra and 5,579,998. Essentially these patents are designed in a closed room environment where the spraying is done in a separate room from where the controls and ingredients are held and the spray gun is held by a robot so that the size and weight are not critical. As a matter of fact, the heretofore known designs of the convergent type of spray gun described above is much too heavy to be hand operated. 
     This invention is directed to a portable system where all of the controls, computers, valves, hoppers, eductors, proportioners and ingredients are contained in a portable cart and a hand-held spray gun is utilized with this system. Obviously, making the system portable increases the flexibility of the system and permits use of the system in different areas and locations. While the heretofore known systems include mechanism for purging the spray gun, this is not a particular concern where the system is in place and non-portable. Because of the portability of the system a more positive shut-off system was required to assure that the resin didn&#39;t remain in the gun and become hardened over a period of time when the spray gun was not in use. This invention provides a positive shut down system that shuts the system down when the spray gun is turned off. A back-up alarm system is utilized to warn the user that the gun has not been purged after a given period of time. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a shut-down system for a portable convergent type of spray gun of the type that includes an end-effector. 
     A feature of this invention is to provide on the handle of the spray gun a proximity switch that is actuated when the handle is placed in a predetermined position to relay a signal to provide a proper sequence of shut-down of the system. 
     The shut down system of this invention is characterized as being easy to fabricate, simple in design, relatively inexpensive and reliable. 
     The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the miniaturized spray gun of this invention; 
     FIG. 2 is an exploded view showing the component parts of the invention comprising the miniaturized convergent spray gun of FIG. 1; 
     FIG. 3 is a diagrammatic view in section of the concentric tube assembly of this invention; 
     FIG. 4 is a partial view partly in section and partly in elevation taken along the longitudinal axis of the concentric tubes of FIG.  1 . 
     FIG. 5 is plan view of the front end of the dry powdered nozzle of the spray gun depicted in FIG. 1; 
     FIG. 6 is a plan view of the aft end of the dry powdered nozzle of the spray gun depicted in FIG. 1; 
     FIG. 6A is a is a sectional view of an alternate embodiment of the dry powdered nozzle for use with the spray gun depicted in FIG. 1; 
     FIG. 7 is a perspective view of the spray gun depicted in FIG. 1 and a schematic illustration of the system utilized therewith; and 
    
    
     These figures merely serve to further clarify and illustrate the present invention and are not intended to limit the scope thereof. 
     DETAILED DESCRIPTION OF THE INVENTION 
     To better understand this invention the nomenclature of the component parts are defined as follows: 
     Convergent End Effector nozzle—is the discharge end of the gun where the resin and air are atomized and converged and the dry powder is introduced through the dry powdered nozzle. 
     Dry powdered nozzle is the nozzle that feeds the dry powder into the plume of the atomized resin. 
     Convergent cap is the cap mounted on the end of the dry powdered nozzle that defines the discharge orifice. 
     Nozzle is any discharge orifice that discharges flow in a prescribed manner. 
     The invention can best be understood by referring to FIGS. 1-7 which shows the convergent spray gun generally illustrated by reference numeral  10  as being comprised of a commercially available Binks gun or of the type of gun described in U.S. Pat. No. 2,971,700 granted to Peeps on Feb. 14, 1961 entitled “Apparatus For Coating Articles With Chemically Reactive Liquids” (which is incorporated herein by reference) generally illustrated by reference numeral  12  and modified for meeting the requirements of this invention, the dry powered nozzle  14  and the concentric tube assembly generally illustrated by reference numeral  16 . The commercially available Binks gun is modified to accommodate this invention by including a receiving box  18  that includes fittings for transmitting air into inlet  20  and then into the inlet  21  of the spray gun  10 , fittings for transmitting the dry powder into inlet  22  where it is split by any type of splitter (not shown) into two streams for flowing the dry powder through the discharge fittings  23  and  25  and the valve  24  (see FIG.  3 ). Trigger  30  is suitably mounted adjacent the handle  31  and is conveniently available for operation for actuating the gun to turn the spray of coating on and off. The fitting  38  serves to receive the mixed resin delivered thereto from a suitable pressurized source and flows through a passage formed in the spray gun  10  and discharges though the central orifice  26  as will be described in detail hereinbelow. In addition to the modification of the Binks gun described above, a fluid tip of the type known as a Paasche that is commercially available and as best seen in FIG. 3 is designed to include valve  24  that is manually operated by the trigger  30 . Valve  24  is located adjacent to the central orifice  26  discharging the resin and includes seat  28  surrounding the orifice  26  and the valve body  27  connected to the valve stem  29  for rectilinearly movement by actuation of the trigger  30  for opening and closing the discharge orifice  26  of the spray gun  10 . Optionally, the valve  24  can be located at the nozzle  40  (FIG. 3 ). 
     Referring next to FIGS. 4-6, the dry powdered nozzle  14  mounted on the concentric tube assembly  16  includes a pair of diametrically opposed fittings  32  and  34  adapted to receive suitable tubing for conveying the dry powder flowing through the fittings into the manifold of the dry powered nozzle that will be described hereinbelow. 
     As was mentioned above, the spray gun  10  is capable of being miniaturized from the heretofore known convergent spray guns not merely because the components are made smaller, which is partially the case, but because of the modification to the Binks type of gun and the addition of the inner and outer extension tubes of the concentric tube assembly  16  which will be described in more detail hereinbelow. As best seen in FIG. 3, the modified Binks gun  12  includes the central orifice  40  that is fluidly connected to the inlet of the fitting  38  for flowing the resin toward the discharge end of the spray gun. The outer tube  42  includes a large diameter hollow conically shaped portion  44  that fairs into a smaller diameter tubular portion  46  that extends axially toward the fore end of the spray gun. The aft end of the outer tube  42  is threadably connected to the end of the modified Binks gun by the complementary threads  49  so that the cavity  48  defined by the conically shaped large diameter portion  44  surrounds the tip  50  of the modified Binks gun. Inner tubular member  58  is threadably attached to the outer tube  44  by the complementary threads  52  and, like the tubular portion  46  of the outer tube  42 , extends axially toward the tip of the spray gun  10  and lines up with orifice  40  to continue the flow or resin toward the central discharge orifice  26 . As is apparent from the foregoing the resin is transported toward the tip of the spray gun  10  through the inner tubular member  58  and atomizing air discharging from the circumferentially spaced air discharge holes  60  and  62  of the Binks gun is transported through the outer tubular member  42  via the centrally disposed drilled passages  64  and the annular passage  66 . The tip of the spray gun  10  is defined by the fluid tip element  70  that includes a central passage  72  terminating in a discharge central orifice  26  and the air cap  90  (the air cap may be a commercially available air cap of the Paasche type), both of which serve to create a conically shaped convergent plume A (see FIG. 4) at the exterior thereof. The fluid tip element  70  includes a main body  78  which is circular in cross section and is dimensioned so that its diameter is substantially equal to the inner diameter of the tubular portion  46  and several (up to four) segments or secants to the circular cross section are milled or cut at the larger diameter portion  80  to form flats that leave a gap between the fluid tip element  70  and the annular passage  66  (See FIG.  3 ). This meters and directs and atomizes the air in the annular passage  66 . As can best be seen in FIG. 3, the aft end  82  of the fluid tip element  70  extends axially rearwardly and is threaded to complement the threads formed on the end of the inner tubular member  58  to form a tight fit and communicate the central orifice  84  with the passage  86  formed in the fluid tip element  70  which, in turn, communicates with the passage  68  of the inner tubular member  58  for flowing resin through central orifice  84 . 
     Air cap  90  includes a conical inner surface  92  and a threaded aft end  94  that threadably engages the complementary threads formed on the outer end of the outer tubular member  46  and serves to surround the fluid tip element  70 . The air cap  90  serves to converge the atomized air toward the discharge end of central orifice  84  so that the resin flowing through passage  68  into the reduced diameter portion of central passage  86  to increase the dynamic head of the resin and cause it to be accelerated and expand as it is being discharged. The air discharging from the convergent surface  92  of air cap is formed in a highly atomized spray that mixes intensely with the resin as it discharges from orifice  84  and forms a stream of small particles accelerating toward the target. The mixed atomized air and resin are discharged so as to define a plume immediately downstream of the central aperture  26  formed in the air cap  90  where the dry powder is injected as will be explained hereinbelow. 
     The dry powdered nozzle  14  as shown in FIGS. 4-6 consists of a main cylindrically shaped body  102  having angularly disposed extension portions  104  and  106  and includes a central straight through bore  109  communicating with the drilled passages  108  and  110  angularly disposed relative thereto formed in the extension portions  104  and  106 , respectively. The dry powdered nozzle  14  is fitted over the sleeve  116  that is concentrically and coaxially disposed relative to the fluid tip  70  and the tubular member  46  and tubular member  58  of the concentric tube assembly  16 . Convergent cap  120  is frictionally fitted or fitted in any suitable manner at the aft end of the dry powdered nozzle cap  14  and includes a nozzle  122  defined by the convergent cap  120  that contains the flow of dry powder from the dry powdered nozzle  14  into the plume A ( as shown in FIG.  4 ). The annular space between the sleeve  106  and the inner diameter of the main body  102  of the dry powdered nozzle  14  define an annular manifold  116  where the powder is transmitted and streamlined just prior to being injected into the low pressure area caused by the atomized plume A (FIG.  4 ). These elements just described, namely the air cap  90 , fluid tip  70  and dry powdered nozzle  14 , form the end-effector of the convergent spray gun. While the end-effector of the present invention functions similarly to the end-effector shown in U.S. Pat. No. 5,307,992, supra, because of the incorporation of the concentric tube assembly  16 , the dry powdered nozzle  14  and convergent cap  120  is made significantly smaller than the heretofore designs while at the same time being comparable to the volume of flow of the ingredients emitted at the discharge end of the spray gun. 
     FIG. 6A exemplifies another embodiment of the dry powdered nozzle  14   a  that includes the central passage  240  (the same reference numeral with a subscript is used to depict similar parts in all the Figures) for flowing the liquid resin that discharges through central orifice  202 , the annular air passages  206  that discharge the air through the annular orifice  210  at an angle to converge with and atomize the resin and the diametrically opposed dry powdered passages  215  and  218  that directly feed into the low pressure zone of the plume of the atomized air/resin stream. It will be appreciated that the a configuration of the dry powdered nozzle  14  depicted in FIGS. 5 and 6 is designed to accommodate the larger granular sized particles of dry powder, while the dry powdered nozzle  14   a  depicted in FIG. 6A is preferably designed for a finer dry powder granular. 
     In operation, and as seen in FIG. 7, the system for supplying the materials to the spray gun  10  consists of a standard PC computer  200  and process control software that operates and controls monitors, the various valves, proportioner, eductor, resin and catalyst pumps. Preferably, the components of the system are mounted on a portable cart for providing a portable coating apparatus including the hand-held gun that can be utilized without the requirement of fixed rooms and/or compartments. As best seen in FIG. 7, the computer controls the various solenoid control valves, the pneumatic control, the dry powder control system, the PLC/Process Monitoring, and heating of the materials, when or if needed. Actuation of the system turns on the compressor for feeding air to the eductor  211 , the resin pump  212  and the catalyst pump  214 . The pump and flow meters coupled with the process control software controls resin flow ratio and will also monitor the system for performance. 
     As is apparent from the foregoing, the resin and catalyst is fed to the manifold  220  where they are combined and fed to the mixer, which may be any well known static or dynamic type, where it is mixed and fed to the gun  10  via hose  128 . The dry powder, such as cork or glass micro spheres contained in the dry hopper  222 , which is a loss-in-weight or mass loss feeding system is transported to the spray gun  10  via the eductor pneumatic tubes  213 , hose  126 , the receiving box  18 , and then, hoses  130  and  132 . High pressure air is fed directly to spray gun  10  via the hose  124 , receiving box  18  and inlet  21 . The coating material is emitted from the spray gun  10  by releasing and depressing trigger  30  of spray gun  10 . In accordance with this invention, the shut down system for purging the spray gun  10  is activated by releasing trigger  30 . Proximity switch  146 , which is commercially available from Pepperl+Fuchs Inc. of Twinsburg, Ohio, generates a milliampere signal when the trigger comes into close proximity with the proximity switch  146 , which, in turn relays a signal to the computer via the control  230 . The computer includes a time delay that activates either an electric light bulb or noise generator to warn the operator that the resin will harden if left in the gun. A manual operated control valve  232  opens the connecting line  143  to flow of a suitable solvent via the manifold  220  into the mixer  138  and then, the spray gun  10  for purging the lines. It is apparent from the foregoing that the valve  232  can be made to operate automatically upon receiving a signal from the proximity switch  146  as shown by the line  231  which would send a signal directly to an actuator for automatically turning the valve while the computer has relayed signals to the system for ceasing flow of the ingredients to the gun. The saline solution for purging the spray gun is at sufficient pressure to force the valve  24  to open so that the captured resin is discharged through the nozzle as the saline solution flows therethrough. 
     The use of the proximity switch  146  which is mounted on the handle  31  in close proximity to the trigger  30  is a simple, inexpensive, yet efficacious manner for initiating control  230 . 
     Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.