Plasma torch with identification circuit

#The invention relates to the art of torches for cutting, welding, brazing and other purposes and more particularly to a plasma torch of the type including an arc for creating a plasma which torch is employed for the purposes of cutting, welding, etc. More specifically, the invention relates to a torch of the type which includes a system for automatically identifying the torch.

#The invention is primarily applicable for use in a plasma arc torch and it will be described with particular reference thereto; however, the invention has much broader applications and may be used with various torches which are connected to a universal control station or power supply for the purpose of directing power and/or gases to the torch in desired amounts for the purposes of welding, cutting, brazing and other heat related processes. When using plasma for heat processing, a torch is connected to a universal control station which directs the arc current, plasma gas and auxiliary cooling gas, together with electrical current from the universal control station to the torch body or housing. A torch or torch assembly includes the housing on one end, a long flexible cable and a plug on the other end. The cable is employed with the end plug for connecting the torch housing or body onto the control station which includes both the power supply and the supply of gaseous material. The station also contains the microprocessor or other control system for operating the power supply, gas supply and torch itself. Consequently, it is somewhat standard practice to provide the end plug with a specific arrangement of nipples and electrical connectors or terminals for connecting the plug to the stationary universal control station with the gas lines, arc current leads and control conduits all automatically connected in unison.

#An operator obtains a torch housing, hose and connector as an assembled unit and manually connects the plug or connector of this assembly onto the power supply or universal control station. The mere connection of the plug to the power supply or control station implements the desired operation of the torch in accordance with the settings of the control station. A unique torch assembly is required for a particular plasma operation. As the operation changes a different torch assembly may be necessary. For this reason, when each connection of the plug to the power supply is made, the operator must adjust the power, gas flow and other desired operating parameters for the specific torch being employed. The operator will thus be assured that the proper settings are made at the power supply.

#FIG. 1 is a pictorial view of a plasma system to which the present invention is used;

#FIG. 2 is a schematic view and wiring, or plumbing, diagram of the preferred embodiment of the present invention;

#FIG. 3 is an enlarged side elevational view taken generally along line 3--3 of FIG. 1 showing the plug and power supply socket used in the preferred embodiment of the present invention as shown in FIG. 2;

#Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIG. 1 shows a somewhat standard plasma system wherein a power supply PS is used as a universal control station for a variety of plasma torches PT. The torch is used to cut, weld or otherwise process a workpiece, not shown, which is grounded by a standard clamp 10. Plasma torch PT has a normal construction which includes a housing 20 with an outlet 22 and trigger 24 for selectively actuating the torch. A flexible cable 30 extends from housing 20 to plug or connector 32 which mates with and is connected to an appropriate socket 34 fixedly mounted onto control station PS. The control station is employed for the purpose of directing electrical energy to housing 20 of torch PT and also includes gas and, optionally, water inlet conduits which are directed to appropriate conduits in flexible cable 30 from plug 30 to housing 20 in accordance with standard practice. In operation, clamp 10 is manually attached to the workpiece and the power supply PS is energized. Trigger 24 is depressed to cause a plasma to issue from outlet 22 for the purpose of performing the desired heating function. Torch assembly PT includes housing 20, flexible cable 30 and plug 32; however, housing 20 is sometimes referred to as the torch. An operator manually connects plug 32 with socket 34 and actuates power supply PS by either the high current switch 36 or the lower current switch 38. In addition, the amount of air or gas to outlet 22 is adjusted by knobs 40, 42. Each time a different torch is employed, the current is selected by switches 36, 38 and the current is adjusted by either knob 36a or knob 38a. In addition, the knobs 40, 42 adjust the gas flow and/or air flow which is directed to housing 20 for creating the plasma that issues from outlet 22. As can be seen, whenever a particular torch PT is connected to the power supply, appropriate adjustments must be made by the operator. If the wrong torch is selected, it can be seriously damaged or will operate inefficiently. To prevent such occurrences, elaborate systems are now employed for coding the various plasma torches for identification by the operator when the torch is connected to the power supply PS.

#Referring now to FIGS. 2 and 3, more details of plasma torch PT are illustrated. In accordance with normal practice, the torch includes a nozzle 44 and a central electrode 46. Conduit 50 directs cooling gases in the passage between housing 20 and nozzle 44. In accordance with standard practice, conduit 52 directs a plasma sustaining gas in the passage between electrode 46 and nozzle 44. The arc between nozzle 44 and electrode 46 is maintained by the negative voltage on line or conductor 60 and a more positive voltage is applied to line 70. The voltage differential between lines 60, 70 maintains the arc, which arc ionizes the gas in conduit 52 for forming the plasma at outlet 22. Male connectors are located on the terminal end of plug 32, as schematically illustrated in FIGS. 2 and 3. Conduit 50 terminates in nipple 50a that inserted into female receptacle 50b when plug 32 is attached to socket 34. In a like manner, nipple 52a is inserted into receptacle or female coupling 52b when the plug and socket are assembled. In accordance with standard practice, connectors or terminals 62, 72 are received in companion receptacles 64, 74 of socket 34. A variety of electrical lines 80, 82 and 84 are also electrically connected when plug 32 is manually inserted into socket 34. The electrical lines, together with the gas conduits and plasma power lines, are shown for illustrative purposes. A variety of electrical lines 80, 84 could be employed in operating plasma torch PT. In the illustrated embodiment, line 80 is a conductor in a safety circuit connected to housing 20, whereas lines 82, 84 form a series circuit with trigger 24 for selectively operating the plasma torch upon command of the operator. All of these electrical and gas connections can be varied and arranged in a fixed pattern dictated by the standard socket 34. The various electrical lines and fluid conduits do not form a part of the present invention, except they are automatically connected in unison as plug 32 is inserted into socket 34 and they must be set to match the torch PT. By appropriate adjustment of the electrical power and gas flow when a particular torch assembly is mounted on the power supply PS, normal and efficient operation of the plasma system is realized.

#In accordance with the present invention, there is provided an identification circuit carried on the torch assembly so that the torch assembly can be identified automatically by power supply PS when plug 32 is attached to socket 34. In accordance with the preferred embodiment of the present invention, as shown in FIGS. 2 and 3, identification circuit ID is located in plug 32. This is part of the torch or the torch assembly PT so that the circuit is carried with the torch as it is brought to the power supply PS for the purposes of use in plasma cutting, welding, etc. Identification circuit ID includes an electrical characteristic or property which can be selected so that it is unique with a given torch assembly PT or a given type of torch assembly. In accordance with the preferred embodiment of the present invention, identification circuit ID is a resistor network including two selected resistors 100, 102 connected to outlet terminals 100a, 102a, respectively. A common terminal 104 connects the inwardmost end of resistors 100, 102 to the input terminal 110 in socket 34. This terminal is grounded so that a current through output terminal 112 will sense the voltage across resistor 100. In a like manner a known current from output terminal 114 will allow reading of the voltage across resistor 102. By applying a current to terminals 112, 114, in sequence, the resistance of the resistors 100, 102 can be individually read and inputted into the microprocessor or onboard computer of power supply PS. Thus, the voltage at lines 112, 114 can be read in sequence and stored as digital numbers for subsequent processing. Consequently, a combination of the resistance or resistors 100, 102 can give a substantial number of individual identification readings for torch assembly PT. Each of these values can be read as a voltage V.sub.A or a voltage V.sub.B at terminals 112, 114. By knowing voltage V.sub.A and voltage V.sub.B, the identification circuit ID is read and the identity of the particular torch assembly PT is determined. In the illustrated embodiment, identification circuit ID is located in the torch assembly at plug 32. In the present unit it is located in cable 30.