Abstract:
A wire drive system includes a wire feed motor for feeding welding wire in a continuous welding process. The wire drive system further includes a controller connected to the wire feed motor for driving the motor responsive to a command signal. The controller is capable of detecting the source of power from which the wire feed motor is driven wherein a first possible source of power is taken from the welding arc and wherein a second possible source of power is taken from the welding power supply.

Description:
TECHNICAL FIELD 
     The present invention pertains to wire feeders for welding power supplies, and more particularly, to wire feeders that automatically switch between power sources. 
     BACKGROUND OF THE INVENTION 
     Wire feeders are commonplace in the field of welding. As is well known, they are used in conjunction with a welding power source for feeding a wire electrode to a workpiece during the welding process. The electrode may include solid wire, which in some instances is coated depending on the application. Other applications utilize flux cored wire. The wire is continuously fed at a rate which may vary during the welding process. Such processes include, for example, FCAW and self-shield FCAW arc welding. 
     Manufacturers construct welding accessories for use with a particular application or a specific type of welding machine. In the case of wire feeders, it is known for a manufacturer to construct a unit which draws power from the welding arc. These types of wire feeders may be especially useful for construction site or field use where welding frequently occurs away from the welding power source. Other wire feeders draw power from a separate regulated power supply, since some applications require greater precision and may be adversely affected by power drawn from across the arc. Pulse welding is one example. This type of wire feeder utilizes a separate cable to conduct power from the regulated power supply, which may reside in the welder. In the present state of the art, these systems are not directly interchangeable. 
     BRIEF SUMMARY 
     The embodiments of the present invention are directed to devices and methods of arc welding, including wire feeder drive systems that can be easily connected to receive power from different power sources and from different types of arc welders without having to significantly modify the wire feeder. The invention will be described with particular reference to wire feeders in association with MIG or TIG welders. However, it will be appreciated by persons of ordinary skill in the art that the embodiments described herein can be utilized in any type of welder requiring a continuous feed of wire. The wire feeder may include electrical circuitry that can detect and activate the wire drive system responsive to different sources of power as, for example, from a regulated power supply or from the welding arc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of welding power source and wire feeder according to the embodiments of the present invention. 
         FIG. 2  is a schematic wiring diagram of the wire feeder motor and the controller according to the embodiments of the present invention. 
         FIG. 3  is a block diagram schematically showing the control and flow of power to the wire feeder according to the embodiments of the present invention. 
         FIG. 4  is a schematic representation of one embodiment of a sensing circuit. 
         FIG. 5  is a schematic representation of a switching circuit according to the embodiments of the present invention. 
         FIG. 6  is a schematic representation showing contactors according to the embodiments of the present invention. 
         FIG. 7  is a partial perspective view of a cable for communicating power to the wire feeder from a regulated power supply according to the embodiments of the present invention. 
         FIG. 8  is a schematic representation of a rectifying circuit according to the embodiments of the present invention. 
         FIG. 9  is a block diagram showing the steps of connecting power to the wire feeder from between first and second substantially different power sources according to the embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same,  FIG. 1  shows a wire feeder depicted generally at  10 . The wire feeder  10  may be used in conjunction with a welding power source  13  as manufactured by, for example, the Lincoln Electric company in Cleveland, Ohio. The welding power source  13  may receive electrical input power from an outside source that is directed to a transformer  16  having primary and secondary windings in a manner well known in the art. Output from the secondary windings may be directed to a rectifier, not shown, providing DC supply power to the output terminals or studs  19 ,  20 . It is noted that in an alternative embodiment, output power from the welding power supply may be supplied in the form of AC type power. The welding power source  13  may include a power controller, not shown, designed to control output power at the studs  19 ,  20 . In one mode of operation, the power controller may function to maintain constant current; useful in certain manual applications where arc length varies. Conversely, the power controller may operate in a constant voltage mode. The welding power source  13  may additionally include a separate regulated power supply  21  for delivering electrical power to a welding accessory, which may be a wire feeder  10  as will be discussed further in a subsequent paragraph. Welding cables, designated generally at  23 , may be connected to the welding power source  13 , and more specifically to the studs  19 ,  20  for delivering welding current to a work piece  29  through an electrode  35  and work piece connector  49 . The electrode  35  may include welding wire  37  supplied from a continuous source and fed through the wire feeder  10 . The welding cables  23  may be connected through the wire feeder  10  as shown in  FIG. 1 . In one embodiment, the wire feeder  10  may draw power to operate the wire feeder motor  18  from the open circuit voltage of the welding power source  13  and subsequently through closed circuit voltage once the welding arc has been established. Additionally, power to operate the wire feeder  10  may come from the separate regulated power supply  21 . An external cable  25  may be required to connect electrical power to the wire feeder  10  from the regulated power supply  21 . It is noted that the embodiments of the subject invention are not limited to the type of welding power source  13  and/or power controller. Rather, any type of welding power source  13  may be utilized that functions to allow power to be taken from across the arc for operating the wire feeder motor  18 . 
     With continued reference to  FIG. 1  and now also to  FIGS. 2 and 3 , the wire feeder  10  may include a wire feeder motor  18 , also termed drive motor  18 , which feeds the welding wire  37  drawn from a continuous source like a wire reel  32  or drum. A wire feeder controller  12  may also be incorporated to control the drive motor  18  along with other components of the wire feeder  10 , like for example a gas solenoid or other circuitry. In one embodiment, an on-board power supply, not shown, may be included that filters and stores operating power from across the arc, or other power source, for use by various electrical circuits during intervals of time when available operating voltage falls below a minimum level, which may be 35 Volts. It is noted that power may be stored in one or more sets of capacitors as needed. Prior to welding, i.e. establishing an arc, the open circuit voltage may supply power to the on-board power supply, as well as to the drive motor  18 . During welding, an arc is established between the electrode  35  and workpiece  49 , and the closed circuit voltage supplies power to the wire feeder  10 . At times, available power may be less than the requisite minimum, in which case power from the capacitors may then be used. 
     Welding parameters frequently change due to fluctuations in the work piece configuration and/or the electrode position. As a result, the rate at which welding wire  37  is fed through the welding gun  47  may change. Accordingly, the drive motor  18  may be a variable speed drive motor  18  for feeding the wire electrode at different rates. In one embodiment, the drive motor  18  may be a variable speed DC drive motor  18 ′. Power supplied to the drive motor  18  may be modulated to control its speed. In an exemplary manner, Pulse Width Modulation may be used to control the speed of the drive motor  18  via one or more switching circuits, which may comprise power MOSFETs or any other switching device chosen with sound engineering judgment. The switching circuits may be included within wire feeder controller  12  for switching power on and off to the drive motor  18  in a series of pulses. The switching circuits may function to rapidly switch power to drive motor  18  from between substantially zero volts to a nominal operating voltage in a series of pulsed waves. Varying the duty cycle of this signal, i.e. the amount of time that the pulsed waves are on relative to how long it is off, alters the average power delivered to the drive motor  18 . In this way, the wire feeder controller  12  adjusts the speed of the drive motor  18  by selectively controlling activation of the switching circuits. However, it is contemplated that other types of drive motors and motor controllers may be used to control the speed of the drive motor  18  including but not limited to other types of DC motors, or AC drive motors and variable frequency drive controllers. 
     With reference to  FIGS. 1 and 7 , a power cable  25  may be utilized to communicate power from the power supply  21  for operating the drive motor  18 . As previously noted, the power supply  21  may be located within the welding power source  13 . Accordingly, the power supply  21  may draw power from the output of the transformer  16  and further condition or regulate that power for use by the drive motor  18  in a manner consistent with the embodiments described herein. In one exemplary manner, the regulated power supply  21  may deliver substantially 42 V AC . However, other magnitudes of voltage may be delivered without departing from the intended scope of coverage of the embodiments of the subject invention. Alternative embodiments are contemplated where a power supply  21 ′ is distinctly separate from and/or located outside of the welding power source  13 . The separate power supply unit  21 ′ may draw power from any external source, regulating its output in a similar manner. In either type of supply  21  or  21 ′, power to operate the drive motor  18  and other wire feeder components may be communicated through the power cable  25 , which may include one or more electrical conductors and respective connector ends  27 . Accordingly, power to operate the wire feeder  10  may be drawn from one of multiple disparate power sources. 
     With reference now to  FIGS. 1 ,  3  and  8 , in one mode of operation, power from a first source may be taken directly from across the welding arc, i.e. the open circuit and closed circuit voltage of the studs  19 ,  20 . Separately, power from a second source may be taken from a regulated power supply  21  or  21 ′. However, both sources of operating power may be channeled through the wire feeder controller  12 . Power from each source may be conditioned before reaching the drive motor  18 . In one embodiment, power from each source may be rectified before reaching the wire feeder controller  12 . In an exemplary manner,  FIG. 8  shows first  40  and second  41  bridge rectifiers that connect to the power sources via connectors  42  and  43  respectively. Subsequently, the rectified power may be filtered as accomplished by on-board capacitors, which may also be used to store supply power during time periods when supply power falls below the requisite minimum. The rectified and filtered power may then be directed to the wire feeder controller  12  for modulation as described above. It is to be understood that any other means of storing and/or conditioning the power, and more specifically rectifying the power, may be chosen with sound engineering judgment. It is also contemplated in an alternate embodiment that DC power may be delivered to the wire feeder controller  12  thereby eliminating the need for the rectifiers and accompanying components. Still, other power configurations will become apparent to those skilled in the art. All such variations are to be construed as falling within the scope of the appended claims. 
     With reference now to  FIGS. 2 and 3 , the wire feeder controller  12  may include a logic processor  55  for controlling operation of the wire feeder  10 . The logic processor  55  may perform logical operations on the input data, and output timing or sequencing information for operating the wire feeder components. In one embodiment, the logic processor  55  may comprise a microprocessor  55 ′ incorporating circuitry that can be programmed to execute a succession of instructions. The microprocessor  55 ′ may be accompanied by additional support circuitry as needed, like for example static and dynamic memory. Although, any type peripheral support circuitry may be included as is appropriate for use with the embodiments of the subject invention. As mentioned above, the wire feeder controller  12  may activate, or deactivate, the switching circuits (not shown in the figures) used to adjust the speed of the drive motor  18 . In one embodiment, the logical processor  55  may control output to the switching circuits as well as other components of the wire feeder  10  as will be discussed below. It is noted that any number of logic processors or any circuit configuration of logic processors may be incorporated into the wire feeder controller  12  without departing from the intended scope of coverage of the embodiments of the subject invention. 
     With reference now to  FIGS. 3 and 4 , a sensor or sensing circuit  60  may be situated between the wire feeder controller  12  and the regulated supply power  21  or  21 ′. In particular, the sensing circuit  60  may be incorporated into the wire feeder controller  12  for use in conjunction with the logic processor  55 . However, the configuration and location of the sensing circuit  60  should not to be construed as limiting. Rather any physical representation or placement of the sensing circuit  60  may be chosen with sound engineering judgment. The sensing circuit  60  may include one or more inputs  63  and may have at least one output  66 . In an exemplary manner, the input to the sensing circuit  60  may be taken from the conductors of the power cable  25  and the output  66  may be electrically communicated to the logic processor  55 . In this way, the sensing circuit  60  may function to detect the presence or absence of electrical power on the power cable  25  and subsequently signal the logic processor  55  to respond accordingly by switching between the first and second power sources, as will be discussed further below. 
     With continued reference to  FIGS. 3 and 4 , as mentioned, the one or more inputs  63  of the sensing circuit  60  may be electrically communicated to the power cable  25 . That is to say that the voltage potential across the conductors of the power cable  25  may comprise the input to the sensing circuit  60 . The sensing circuit  60  may include one or more circuit portions that condition the input signal. In one embodiment, the sensing circuit  60  may include a rectifying circuit  61  that inverts the input signal and a voltage divider circuit  62  that scales the signal to within a particular range. The conditioned signal may then be compared to a predetermined value for subsequent output to the logic processor  55 . In an exemplary manner, the scaled signal may be compared to a threshold voltage, which may be 5 Volts. As such, the output of the sensing circuit  60  may comprise a logical “true” or “false” based on the comparison of the conditioned input signal with the threshold voltage. It is noted that the threshold voltage may correspond to the minimum voltage needed to operate the drive motor  18 . The default output signal from sensing circuit  60  may comprise a logical zero (0) or “off,” which corresponds to an input signal, i.e. power cable voltage, that falls below the threshold voltage. Conversely, a logical one (1) or “on” represents voltage on the power cable  25  that meets or exceeds the threshold voltage. Stating it another way, a logical zero (0) may indicate that the power cable  25  is not connected to the wire feeder  10 , while a logical one (1) indicates that the power cable  25  is connected and operable to deliver power to operate the drive motor  18 . Thus, the sensing circuit  60  functions to detect when the power cable  25  is connected or disconnected from the wire feeder  10 . It will be appreciated that when the operator electrically connects the power cable  25  to the wire feeder  10 , the wire feeder controller  12  automatically detects the presence of the alternate power source and automatically switches the source of power supplied to the drive motor  18 . It follows that when the operator disconnects the power cable  25 , the sensing circuit  60  detects that power is no longer available from the alternate or second power source and signals the wire feeder controller  12  to switch the power supplied to the drive motor  18  back to the first source of electrical power. It is noted that the output of the sensing circuit is discrete in nature, namely “on” or “off”, indicating the status of supply power from the power cable  25 . Other embodiments are contemplated where a magnitude of the available power, i.e. voltage level, on the power cable  25  is communicated to the logic processor and/or to the operator via a display. Still, it is to be construed that the sensing circuit  60 , and in particular the signal conditioning circuit portions, as described herein are exemplary in nature. Others circuit configurations and/or sensors may be realized and implemented that fall within the scope of the appended claims. 
     It is expressly noted that embodiments of the present invention are contemplated that do not use sensing circuits directly connected to the conductors of the power cable  25 . Other sensing means of detecting the presence of power from the power cable  25  may be incorporated including, but not limited, non-contact sensors. Additionally, it is contemplated that the trigger for switching to an alternate power source may be accomplished by mechanical means. For example, a mechanical switch may be employed that detects the physical connection of the power cable  25 . While additional circuitry may be required to detect the voltage potential across the power cable  25  conductors, automatic switching between power sources may be initiated by actuating the mechanical switch, which occurs when the power cable  25  is attached to the wire feeder  10 . Still, any manner of detecting the presence of a connected power cable and automatically switching between power sources may be chosen with sound engineering judgment. 
     With reference now to  FIGS. 6 and 8 , means for switching between power sources may include components that electrically connect or disconnect the electrical pathways of the various power sources respectively, which may be implemented by a physical break in or direct contact of electrical conductors. One example of such a device comprises a set of contactors  67  that is employed to switch power being supplied to the drive motor  18  from between power taken from across the arc and power drawn from the regulated power supply  21  or  21 ′. Contactors  67  may be utilized to isolate the power connections as determined by the connection of the power cable  25  so described above. By isolating power connections it is meant that only one of the power sources is electrically connected to deliver power to the motor  18 . The alternate power source is therefore disconnected, or switched out of electrical connection with the drive motor  18 . Even if power is available from the alternate power source, the contactors  67  may be configured to prevent that power source from delivering power to the motor  18 . In one example, power from across the arc may be connected to rectifying circuit  40 . The rectified signal is then directed to contactors  67 , shown in  FIG. 6 , through connector J 9  where electrical current flows through the set of normally closed contactors  67  and subsequently to the motor via one or more additional connectors. This may comprise the default source of power for the drive motor  18 . When power cable  25 , having an ample supply of power, is connected to the wire feeder  10 , the normally closed contactors open responsive to the activation of a switch  75 , as will be subsequently described. Power available from across the arc is thereby automatically disconnected from delivering power to the drive motor  18 . In this mode of operation, power from power cable  25  flows through connector  43  to a second rectifying circuit  41  and subsequently through connector  42  for powering the drive motor  18  in a manner consistent with that described above. It is noted in the current embodiment that the circuitry conveying current from power cable  25  remains electrically connected at all times. Isolation of power from power cable  25  is facilitated by the physical disconnection of the power cable  25  to the wire feeder  10 , and not by the opening/closing of contactors (or activation/deactivation of other switching means). However, it is to be construed additional sets of contactors may be employed to isolate connection of the power cable  25  as well. It is to be understood that the particular circuit components described herein and the manner of isolating power connections so described are exemplary in nature and not to be construed as limiting. Other devices, including but not limited to solid state devices, and other methods for selectively connecting power from disparate power sources may be utilized without limiting the scope of coverage of the embodiments of the subject invention. 
     With reference once again to  FIGS. 3 and 6  and now also to  FIG. 5 , the contactors  67 , or other switching means, may be selectively activated by an electrical switch, illustrated generally at  75 . In one embodiment, the electrical switch  75 , also termed switch  75 , may include a solid state device like for example a transistor  77 , which may be connected in series with one or more coils  69 , although it will be appreciated that any type of electrical switch  75  or switching circuit may be utilized; solid state or otherwise. The coils  69  may be electromagnetically coupled to the contactors  67  and thus activated or deactivated in synchronous with the coils  69 . The coils  69  and contactors  67  may therefore comprise a control relay. Multiple relays may be utilized, of which three (3) are included in the current embodiment: CR 1 , CR 2  and CR 3 , for isolating power connections to the drive motor  18 . It will be readily seen that power drawn from the transistor  77  flows through the circuit thereby energizing the coils  69  and activating the contactors  67 . The trigger to the switch  75 , or the transistor  77  as in the current embodiment, may be input from the logic processor  55 . When signaled by the sensing circuit  60  that the power cable  25  is present and active with available power, the logic processor  55  may output a signal that triggers the switch  75 , and consequently the contactors  67 , to break the electrical path connecting power from across the arc to the drive motor  18 . As mentioned above, the electrical pathways conveying power between the power cable  25  and the drive motor  18  may be continuously connected. Accordingly, power from the power cable  25  is immediately conveyed to the drive motor  18  upon connection of the power cable  25 . Conversely, isolation of the power source  21 ,  21 ′ is accomplished by physically removing the connector  27  of the power cable  25  from the wire feeder  10 . 
     An alternate embodiment is contemplated wherein the ability to switch between power sources is manually controlled by an end user or operator. In this embodiment, the selection of power sources may be initiated by a manually operated device, such as selector switch  73 . In other words, a selector switch  73  may be included and configured to allow power to be drawn from a single source, which may be from across the arc or from a regulated power source. The selector switch  73  may take one of several different forms like a mechanical switch having contactors, an electrical switch using solid state circuitry or any type of switching device suitable for use with the embodiments of the subject invention. It will be appreciated that the selector switch  73  may be used in conjunction with the sensing circuit  60 . However, it is to be construed that the selector switch  73  may also be used in replacement of the sensing circuit  60  as a means for manually selecting the source from which the drive motor  18  draws power. In one exemplary manner, output from the selector switch  73  may be communicated to the logic processor  55 . In other embodiments, the selector switch  73  may directly control the contactors  67  and/or power directed to transistor  77 . Still any type of selector switch  73  or any connection of the selector switch  73  may be chosen with sound engineering judgment. In this manner, when it is desired to utilize power from the across the arc, the selector switch  73  may be set to one operating position wherein power is drawn from the open and closed circuit voltage of the power supply. Alternatively, the operating position of the selector switch  73  may be set to a second operating position to allow power to be drawn only from a separate regulated power source. 
     With reference to all of the Figures, operation of the wire feeder  10  will now be discussed. The wire feeder  10  may be connected to the welding power source  13  via the welding cables  23 . Power for operating the wire feeder  10  may be taken directly from studs  19 ,  20 , first from the open circuit voltage and subsequently from the studs after the welding arc has been struck. In this manner, the wire feeder  10  operates in a first mode, or default mode of operation. When the operator connects the power cable  25  from the regulated power supply  21 ,  21 ′ to the wire feeder  10 , the wire feeder controller  12  via the sensing circuit  60  detects the presence of the second power source and automatically connects or switches to that source of power for operating the drive motor  18 . The wire feeder  10  thereby operates in a second mode of operation. The reverse situation also applies. When the operator disconnects the power cable  25 , the wire feeder controller  12  switches the source of supply power to re-establish the supply of power from across the arc. 
     The invention has been described herein with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alternations insofar as they come within the scope of the appended claims or the equivalence thereof.