Abstract:
A microprocessor controlled arc metalizing unit includes a wire cassette and a drive mechanism cassette engaged in a separable manner. By disengaging the wire cassette and drive mechanism cassette, an operator has much greater control of the unit since the wire loaded wire cassette is fixed and the operator need only maneuver the lightweight drive mechanism cassette. To improve the safety of the arc metalizing unit, a “dead-man” switch acts to automatically shut down the arc metalizing unit should any number of preestablished safety conditions be breached. In addition, one or more composite housings enclose the operational components of the arc metalizing unit to improve safety. Reliability is improved through a tension control unit that eliminates any rotational fluctuations associated with wire spools. The arc metalizing unit further incorporates a touch pad control with a display for operating the unit and displaying the status of the unit.

Description:
FIELD OF THE INVENTION 
   The embodiments of the present invention relate generally to arc metalizing units. More particularly, an arc metalizing unit which incorporates several unique features, including at least a “dead-man” switch and light-weight, non-conductive composite casing(s), which improve the efficiency, ease of handling and overall safety of operating the arc metalizing unit. 
   BACKGROUND 
   The art of metalizing has been traditionally used to protect metallic surfaces from corrosion. The basic functions of an arc metalizing unit are to liquify a material, typically metal, and then to propel the molten material onto a subject surface. The applied metal coatings act to cathodically protect the surface from corrosion and erosion for up to 100 years. 
   Commonly, an arc metalizing unit operates by subjecting a pair of metal wires to an electric current and then directs the ends of the metal wires to a common point within an arc metalizing unit spray gun. Near, or at, the common point, an arc of electricity liquefies the wire ends. A powerful stream of gas focused at the common point atomizes the molten metal and propels the molten particles depositing them on a subject surface. The metal coating bonds to the subject surface then protects the surface from external elements. 
   Although issued U.S. patents protect many different features of arc metalizing units, several drawbacks of conventional arc metalizing units remain unaddressed. First, wire loaded arc metalizing units are heavy and cumbersome for operators to maneuver. Second, the use of large electric currents, high pressure air and molten metal creates an inherently dangerous unit. Third, the current metalizing units fail to operate properly when fitted with hard wire. These drawbacks and the ability to work in confined spaces are addressed by the embodiments of the unique arc metalizing unit disclosed herein. 
   SUMMARY 
   Accordingly, the embodiments of the present invention include a wire cassette and drive mechanism cassette engaged in a separable arrangement. Traditionally, an arc metalizing unit is a single unit which is heavy and cumbersome to maneuver. Much of the weight of the arc metalizing unit is attributable to the spools of metal wire being used to feed wire to the unit. Thus, by separating the wire cassette from the drive mechanism cassette, the arc metalizing unit becomes much easier to maneuver. The wire cassette and drive mechanism cassette are each supported by wheels for providing independent mobility of each cassette. Under the embodiments of the present invention, the drive mechanism cassette may be independently operated up to twenty feet or more from the wire cassette. In this manner, the metalizing spray gun can be utilized up to 35 feet or more from the drive mechanism thereby making the unit suitable for use in confined spaces or remote areas. 
   To eliminate the problem of wire unraveling, the wire cassette incorporates a wire spool support and a unique cam-lock device that prevents unwanted movement of the feed wires. Normally, the feed wire, particularly hard wire, has a tendency to unravel from its spool during operation of an arc metalizing unit. By providing a wire spool support, in communication with a tension control device, the tendency to unravel has been overcome. The wire spool support eliminates both “back-roll” and “over-roll” of the wire spool during the application of hard wire such as stainless steel. Moreover, a cam-lock positioned immediately prior to the wire exiting the wire cassette eliminates the potential for a loose wire to unravel from the spool. 
   Reliability and safety of the arc metalizing unit are improved by shrouding a drive motor with an insulated non-conductive composite cover to eliminate the potential of motor failure due to electrical arcing or dust contamination during operation of the arc metalizing unit. The non-conductive composite acts like a jacket that covers and insulates the drive motor. 
   Several features of the embodiments of the present invention overcome the safety concerns with respect to the inherently dangerous elements of arc metalizing units. A “dead-man” switch provides an automatic means for ceasing the operation of the arc metalizing unit should the operator become incapacitated or interfere with the path of the molten metal, high-pressure air stream or DC current. A second safety feature provides for the enclosure of both the wire cassette and drive mechanism cassette in non-conductive composites, which act like a jacket by covering and insulating the internal components, thereby eliminating operator contact with the high energy potential of the metalizing wire and power supply cables. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a cross-sectional block diagram side view of an arc metalizing unit; 
       FIG. 2  illustrates a side view of a single wire drive an open position for accepting wire; 
       FIG. 3  illustrates a side view of the wire drive in a closed position to feed wire; 
       FIG. 4  illustrates a rear view of the dual wire drive mechanism; 
       FIG. 5  illustrates a side view of a wire spool from which wire is pulled by the wire drive mechanism for guidance to a spray gun; 
       FIG. 6  illustrates a cam-lock device; 
       FIG. 7  illustrates a perspective view of a wire spool support and retaining clip; 
       FIG. 8  illustrates a cross-sectional block diagram view of the spray gun; 
       FIG. 9  illustrates a perspective view of the spray gun; 
       FIG. 10  illustrates a top view of the spray gun; 
       FIG. 11  illustrates a spray gun carrier plate; 
       FIG. 12  illustrates a side and rear view of feed tips; and 
       FIG. 13  illustrates a touch pad control unit. 
   

   DETAILED DESCRIPTION 
   Reference is now made to the figures wherein like parts are referred to by like numerals throughout.  FIG. 1  shows a cross-sectional block diagram side view of an arc metalizing unit generally denoted as reference numeral  25 . A wire cassette  30 , a drive mechanism cassette  50  and a spray gun  70  (not shown in  FIG. 1 ) comprise the major components of the arc metalizing unit  25 . Moreover, a source of compressed air and a power source provide the necessary compliment to the previously described components of the unit  25 . It is noted that in practice the wire cassette  30  and drive mechanism cassette  50  may be fully enclosed by housings, but the drawings herein illustrate the housings as only partially enclosed for the sake of illustrating details of the present invention. 
   As shown in  FIGS. 5–7 , the wire cassette  30  includes a housing  32 , two wire spools  34  (only one is shown) holding wire  35 , a spool support  36  for each spool  34 , a variable tension control device  38  for each spool  34  and a cam-lock device  42 . As shown in  FIGS. 1–4 , the drive mechanism cassette  50  includes a housing  52 , a drive motor  54  and two wire drives  56  (only one is shown). The wire cassette  30  and the drive mechanism cassette  50  are separate units such that they may move on wheels  95  as a single unit or may be disengaged to move independent of one another. The independent movement provides an operator with a great degree of versatility and mobility in difficult environments. As shown in  FIGS. 8–10 , the spray gun  70  includes an air coupling  72 , an air venturi tube  74 , a gun body  76 , a power connection  78  and a carrier plate  80 . 
   In practice, the wires  35  are pulled from each of the wire spools  34  by the powered wire drives  56  and guided to the spray gun  70 . At specific points during their movement, the wires  35  are each subjected to opposite electrical charges by the electricity source. The two oppositely charged wires  35  are then guided to a common point within a spray gun nozzle  82 . At, or near, the common point the electrically energized wires  35  create an arc of electricity that liquefies the ends of each wire  35 . A stream of high pressure air then propels the liquified metal against a subject surface. Any metal, including zinc, aluminum, copper and stainless steel, which can be obtained in metal wire form can be liquified and sprayed using the embodiments of the present invention. 
     FIG. 2  illustrates a single wire drive  56  in an open position for receiving the wire  35 . The wire drive  56  is powered by the motor  54  which acts to pull the wire  35  from its spool  34 . The wire drive  56  is comprised of two upper gears  57  and two lower gears  58  driven by a single powered gear  59 . The wire  35  passes through several wire guide tubes  60  designed to maintain the wire  35  in the proper orientation. Also shown in  FIG. 2  are gear brackets  61 , tension spring studs  62 , tension adjust knobs  63  and tensions springs  64 . 
     FIG. 3  illustrates the single wire dive  56  in a closed position. In the closed position the upper gears  57  are engaged with the corresponding lower gears  58  such that the driving gear  59  acts to drive the upper gears  57  and lower gears  58  in opposite directions thereby pulling the wire  35  from its spool  34 . The wire drive  56  is closed by lowering the gear brackets  61  and locking them in place by tightening the tension adjust knobs  63 . In this manner, the wire drive  56  is able to accept wire of any size. 
   Also shown in  FIGS. 2 and 3  is a power coupling  65  which facilitates moving the wire  35  to the spray gun  70  and the wire guide tubes  60  ensure the wire  35  enters and exits the wire drive  56  in a stable and proper orientation. 
   Now referring to  FIG. 4 , a rear view of dual wire drives  56  illustrate a dual wire drive arrangement. The two wire drives  56  are symmetric and otherwise identical in design. 
   A speed controller  69  (shown in  FIG. 1 ) may reside proximate the drive mechanism cassette  50  and allows an operator to control the speed of the wire drives  56 . Alternatively, the speed can be controlled by a touch pad control unit  100  (as shown in  FIG. 13 ). The speed of the wire drives  56  is dependent on the nature of the particular application and the specific wire being used. For example, the use of hard wire may require that the speed of the wire drives  56  be reduced to allow the wire to be liquified adequately prior to being propelled onto a subject surface. Also, different surfaces may be more or less susceptible to coating than others such that the application speed of the metal must be increased or decreased, respectively. 
     FIG. 5  illustrates a spool  34  which maintains the wire  35  until it is pulled off the spool  34  by the wire drive  56 . As shown in  FIG. 7 , a wire spool support  36  is designed to receive an opening of the spool  34 . A retention clip  37  maintains the spool  34  in place on the support  36 . The wire spool support  36  also incorporates a tension control device  38  for controlling the tension of the spool  34 . Common spool fluctuations include “back-roll” and “over-roll” which can cause the wires  35  to unravel from the spool  34 . The tension control device  38  acts as a positive spool lock to prevent any undesired forward and rearward spool rotation. In addition, the adjusted tension and drive motor  54  allow an operator to regulate the rate at which the spool  34  rotates thereby optimizing the operation of the arc metalizing unit  25 . For example, light-weight wire may require more tension to prevent the spool  34  from rotating too quickly and thus preventing the wire  35  from uncontrollably unraveling from the spool  34 . 
   Ideally, the housing  32  of the wire cassette  30  incorporates two apertures  39  for allowing the passage of the wire  35  from each spool  34 . The apertures  39  should be of a size to generally control the wire  35  as it exits the housing  32  through the apertures  39 . In other words, the apertures  39  should not be much larger than the diameter of the wire  35  being used. Of course, to be efficient the apertures  39  should be adequately sized to allow various standard-sized wires to be used with the same housing. As shown in  FIG. 6 , a cam-lock device  42  for placement adjacent each aperture  39  further provides a means for controlling the movement of the wire  35 . The cam-lock device  42  comprises two separated gear-like members  43 , having teeth  44 , secured to a platform or a housing floor depending in the position of the apertures  39 . The gear-like members  43  are designed to rotate in only one direction (clockwise as shown) thereby preventing the wire  35  passing therebetween from reversing direction. In addition, the teeth  44  act to control the speed of the passing wire  35  thereby preventing too much wire from being pulled from the spool  34 . 
   As described above, in one embodiment the wire cassette  30  and drive mechanism cassette  50  can act independently thereby providing certain benefits. When loaded with spools of wire, the entire arc metalizing unit  25  may weigh in excess of one hundred and fifty pounds such that it can be cumbersome to maneuver between various field locations. By disengaging the wire cassette  30  from the drive mechanism cassette  50 , an operator need only control the weight of the drive mechanism cassette  50  which accounts for approximately twenty-five pounds of the overall unit  25  weight. In this arrangement, the drive mechanism cassette  50  can be independently maneuvered while the bulky wire cassette  30  remains stationary. 
     FIG. 8  illustrates a cross-sectional block diagram view of the spray gun  70 . The spray gun  70  includes an air coupling  72 , an air venturi tube  74 , a gun body  76 , a power connection  78  and a carrier plate  80 . Feed tips  91  (shown in  FIG. 12 ) direct the two wires  35  into the spray gun body  76  so that the wires approach a common point so that the electric arc is created thereby facilitating the operation of the arc metalizing unit  25 . 
   To increase the effectiveness of propelling the molten metal particles, the high-pressure air stream is passed through the air venturi tube  74  which increases the air velocity and causes the air move in a non-turbulent circular pattern. The circular pattern reduces the metallic dusting that can occur due to uncontrolled or turbulent air flow which is generated at, and which is exacerbated over distance, the air discharge point upstream of the wire common point. 
   The air venturi tube  74  operates by reducing the cross-sectional area of the air path over a predetermined length thereby increasing the speed of the air. Once the path has reached minimum cross-sectional area the path is widened to control the air flow. Upon exiting the air venturi tube  74 , the air flows at a high speed in a controlled pattern thereby maximizing the effectiveness of the propelled molten metal particles. The increased air velocity causes the molten metal to be propelled onto the subject surface at an accelerated rate. The accelerated rate results in lower porosity and increased plasticity of the deposited metal. Moreover, the increased velocity results in shorter travel times for the molten particles thus improving the overall efficiency of the arc metalizing unit  25 . More particularly, shorter travel times produce less dusting or overspray associated with cooling of the molten particles prior to their impact with the subject surface. The shorter travel times also enhance the appearance of the metalized surface while reducing the amount of coating material required to complete a full coating of the subject surface. 
   Another feature of the spray gun  70  illustrated in  FIG. 8  is a removable deflector  77  implemented at an exit of the spray gun body  76 . The deflector  77  re-directs the flow of the molten metal at a preestablished angle (e.g. 90 degrees) to allow the molten metal to reach irregular locations. For example, the deflector  77  is ideal for metalizing I-beams which have many surfaces at varying angles to one another. The deflector  77  is easily removed and installed in the field to provide a versatile unit  25 . 
   Now referring to  FIG. 9 , a perspective view of the spray gun  70  shows the air coupling  72 , the gun body  76 , the power connection  78  and a carrier plate  80 . Wire guides  82  direct each of the wires  35  to a common point within the gun body  76 . A supply of high-pressure compressed air is attached to the gun body  76 , namely the air coupling  72 . While any gas may be used, air is the most readily available gas and it lends itself to the operation of the arc metalizing unit  25 . The compressed air is directed through the air coupling  72 , gun body  76  and the air venturi tube  74 . Upon exiting the air venturi tube  74 , the high pressure air then propels molten metal, created at the wire common point within the gun body  76 , onto the subject surface. Power is provided to the spray gun  70  by the power cables  84 .  FIG. 9  shows a top view of the spray gun  70  with the non-conductive feed tubes  67  in place. The feed tubes  67  extend from each wire drive  56  to the spray gun  70 . 
     FIG. 11  illustrates the carrier plate  80  having attached thereto a retainer arm  85  for supporting wire guides  82  and a power cable and wire guide carrier  86 . As shown in  FIGS. 8 and 9 , the retainer arm  85  and wire guide carrier  86  act to secure the wire guides  82  in place. Screws  87  or the like are used to adjustably join the retainer arm  85  to the wire guide carrier  86 . Similarly, one or more screws  88  or the like are used to retain the power cables  84  to the power cable and wire guide carrier  86 . 
     FIG. 12  illustrates wire feed tips  91  which direct the wires  35  to the common point within the gun body  76 . A single wire feed tip  91  is inserted under the retainer arm  85  of each carrier plate  80  such that the retainer arm  85  secures the feed tip  91  in a position generally adjacent to the gun body  76 . 
   The use of electrical current, high pressure air flow and molten metal create an inherently dangerous machine. A “dead-man” switch  125  (shown in  FIG. 8 ) incorporated on the spray gun  70  provides an automatic means for preventing safety mishaps. In a first embodiment, the “dead-man” switch  125  is activated by the relative position of an operator&#39;s hand, wrist or arm with respect to the spray gun  70 . As shown, a ball  126  is attached to an operator&#39;s hand, wrist or arm via a tether  127 . Should the distance between the spray gun  70  and the operator&#39;s body part become greater than the length of the tether, the ball  126  exits its position and allows a switch arm  128  to contact a conductive wall  129  thereby automatically shutting down the arc metalizing unit  25 . Alternatively, the ball  126  completes an electric circuit such that upon the exit of ball  126  the circuit is open thereby shutting down the arc metalizing unit  25 . In another alternative, the “dead-man” switch may be facilitated by an inserted key, pin, clip or other means in place of the ball  126 . 
   The “dead-man” switch  125  allows an operator the necessary freedom of operation but automatically shuts down the arc metalizing unit should the operator&#39;s hand move too close to a danger zone (e.g. molten metal path), should the operator become incapacitated or should the spray gun  70  be dropped. The “dead-man” switch  125  also allows for the remote placement of the touch pad control unit  100 . The remote location of the controls reduces the potential for failure or malfunction due to the harsh environment near the metalizing process. 
   The operation of the arc metalizing unit  25  is controlled by a processing unit (not shown) such as a microprocessor. The processing unit is in communication with the touch pad control unit  100  shown in  FIG. 13  via electrical wiring (not shown). The touch pad unit  100  incorporates a display device  101  for displaying relevant information, including the state, of the arc metalizing unit  25  and touch controlled buttons  102  for allowing a user to enter commands or retrieve information. In practice, the touch pad control unit  100  may be implemented in any location on the arc metalizing unit  25 , but ideally the control unit  100  is positioned remotely from the spray gun  70  to minimize damage to the control unit  100 . For example, the control unit  100  may be positioned near the wire spools  34 . The control unit  100  may control and display among other things, drive motor jog, air valve (open and close), machine start-up, machine speed, machine self-diagnosis, machine fault mode, daily and total operational hours, record operational hours for lease purposes and operational status. It is also contemplated that an operator will be able to control machine voltage settings as well. The list presented herein is not exhaustive and it is understood that the control unit  100  may be used to control and display any machine function and information, respectively. 
   Although the invention has been described in detail with reference to various embodiments, additional variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.