Abstract:
A grounding system is provided for welding applications. The system comprises a pair of contacts that are brought into close grounding contact with a workpiece, and a measurement circuit coupled to the contacts. The contacts may be urged into intimate contact with the workpiece by a biasing structure that pulls the contacts tightly against the workpiece. The measurement circuit may include a center-tap transformer having a secondary coupled to a ground lead and to the contacts. A primary winding of the transformer is coupled to an oscillator that executes a measurement test. The system may provide an indication of the quality of the ground in the form of an operator perceptible notification, a digitized value, or any other suitable form.

Description:
BACKGROUND 
       [0001]    The invention relates generally to welding systems, and more particularly to improved grounding connections for pipe welding and other welding applications. 
         [0002]    An essential part of welding practice is properly grounding the workpiece. This ensures that the workpiece is at or very near the same potential as a ground terminal of a power supply so that a circuit can be completed through the workpiece to establish and maintain a welding arc. Consequently, a primary source of compromised welds is faulty ground connection to the workpiece. Traditionally, grounding is done through a work clamp that clamps onto the workpiece (or a fixture to which the workpiece is mounted) and which is grounded through a cable extending back to a welding power supply. However, work clamps are only suitable for workpieces of limited size and shape, such as those with straight or flat sides and of manageable size. However, using work clamps is unfeasible for pipe welding, or for other unwieldy shapes due to limited contact areas (e.g., where two joints of pipe are closely positioned end-to-end). Unfortunately, commonly used grounding techniques for pipe welding are to insert a grounding device into the gap between the two pipe joints or to place a grounding device on top of the two pipe joints, often being secured only through gravity. These grounding devices may just be pieces or blocks of conductive material, most of which are not specifically designed for the function of creating a good ground connection. The existing grounding techniques establish fragile contact angles that only touch a small surface of the workpiece. These weak connections result in a higher level of resistance as current is restricted, which can weaken the integrity of the weld and cause defects. 
         [0003]    Additionally, the existing grounding techniques do not include a convenient means of measuring critical parameters such as current, voltage, and resistance, which can be used to verify an acceptable connection. This is an important function because the point of grounding contact on the workpiece may not always provide a sufficiently conductive surface. It is not uncommon for the workpiece to be corroded or soiled at the point of contact with the ground connection, preventing a solid ground connection. For example, there may be rust or other nonconductive debris between the conductive material of the workpiece and the grounding device. The result is a faulty or high resistance ground connection, potentially compromising the quality of the weld. Without a means of measuring and indicating ground connection quality, the operator has no knowledge of the poor connection and therefore may continue to weld with a faulty ground connection. A lack of feedback makes it difficult or impossible to detect and correct a poor ground connection. This is especially problematic in advanced process equipment as the current flow is precisely controlled to achieve optimal results. 
         [0004]    There is a need for an improved grounding device that is capable of establishing a robust grounding connection as well as a means to verify that connection. 
       BRIEF DESCRIPTION 
       [0005]    The present disclosure summarizes a newly developed welding ground connection system and method that fulfills these needs. The system involves a grounding device with which the workpiece is grounded via two conductive prongs with a centertap ground lead. 
         [0006]    In accordance with one aspect of the present disclosure, a welding ground connection system and method make use of prongs that may be forced into intimate contact with one or more workpieces, and which also function as sensor leads. The prongs are coupled to an electronic circuit capable of having a user interface, taking characteristic measurements, outputting indications, and any combination of these, as well as other functions that may be desired. 
         [0007]    In accordance with further aspects of the present disclosure, a grounding system body is secured to the workpiece by a magnet, though it can also by secured through other means of fastening the grounding system to the workpiece. A two pronged connection is created, which is ensured by the securely fastened body, significantly increasing the quality of the ground connection in comparison to existing solutions. Furthermore, the present disclosure discloses a method for grounding a workpiece while simultaneously taking and outputting measurements indicative of the quality of the ground. 
     
    
     
       DRAWINGS 
         [0008]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0009]      FIG. 1  is a diagrammatical representation of an exemplary welding system utilizing aspects of the disclosed welding ground connection system; 
           [0010]      FIG. 2  is a detailed side view of the disclosed welding ground connection system for use with the welding system; 
           [0011]      FIG. 3  is a detailed top view of the disclosed welding ground connection system for use with the welding system; and 
           [0012]      FIG. 4  is a diagrammatical representation of the electronic circuitry of the disclosed welding ground connection system. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates an exemplary welding system  10  utilizing the disclosed welding ground connection system. The system  10  is designed to produce a weld  12  on a workpiece  14 . The system includes a power supply  16  that will typically be coupled to a gas source  18  and to a power source  20 , such as the power grid, although generators, engine-driven power packs, batteries, and so forth may all serve as power sources, particularly in more remote welding locations. A wire feeder  22  is coupled to the power supply  16  and supplies welding wire, shielding gas from the gas source, and welding power from the power supply to a welding gun  24 . In the illustrated embodiment, the power supply  16  will include power conversion circuitry  26  coupled to control circuitry  28  that regulates operation of the power conversion circuitry to produce power output suitable for the welding operation. The power supply may be designed and programmed to produce output power in accordance with a number of processes, welding regimes, and so forth, including constant current processes, constant voltage processes, pulsed processes short circuit transfer processes, and so forth. The power supply may also include valving  32  for regulating the flow of shielding gas from the gas source  18 . In the presently contemplated embodiment, an operator interface  30  allows a welding operator to alter both the welding process and the process settings. The power supply  16  also provides a ground terminal for a ground connection  42  of the grounding assembly  44 . 
         [0014]    It should be noted that, while throughout the present discussion reference is made to a “ground” connection, this term should be understood generally to include a work connection at any desired potential. As will be appreciated by those skilled in the art, welding processes may call for positive or negative designations for the electrode and workpiece, although in all processes intended to be used with the present grounding techniques, a workpiece connection will be made, and advantageously with the systems and methods described. 
         [0015]    The wire feeder  22  typically includes control circuitry  34 , which regulates the feed of welding wire from a spool  36 . The spool  36  contains welding wire, which serves as the electrode for the welding process and is advanced into the torch  24  by a drive assembly  38 . Welding wire, gas, and power are provided to the torch  24  via a weld cable  40 . 
         [0016]      FIG. 2  and  FIG. 3  show an exemplary grounding assembly  44  in relation to the workpiece in this embodiment. In the illustrated embodiment, the workpiece comprises two end-to-end positioned joints of pipe forming a first side  46  and a second side  48  separated by a gap  50  wherein a weld is to be formed. Typically, a gap  50  is left between the first side  46  and the second side  48  to allow full penetration of welding material, though a gap  50  is not necessary in order to use the grounding assembly  44 . The joint  12  may be configured in many different ways, with the ends of side  46  and side  48  having different configurations, including but not limited to a bevel as shown in  FIG. 2 . 
         [0017]    In the illustrated embodiment, the grounding assembly  44  comprises a body  52 , a non-conductive extension  54 , and prongs  56 , with the non-conductive extension  54  forming a downward arching shape and making contact with the workpiece  14  at a rear bearing  58 . The non-conductive extension  54  can be made of non-conductive materials of various compositions, and can be configured in many different forms as needed. The purpose of the non-conductive extension  54  is to stabilize the grounding assembly  44  about the workpiece  14 . Though the present embodiment illustrates the non-conductive extension  54  as having a long rectangular shape extending away from the prongs  56  in a downward arching configuration, it could have a number of different shapes and sizes and be oriented about the workpiece  14  in different ways. Utilizing the non-conductive extension  54  is one means of stabilizing the grounding assembly  44  about the workpiece  14  among others. There may be some embodiments where the nonconductive extension  54  is not used, but the prongs or contact structure is urged into engagement with workpiece by other means (e.g., a strap, a weight, etc.). 
         [0018]    In the present embodiment, the grounding assembly  44  includes a compression assembly  60 , which compromises a magnet  62 , an adjustment assembly  64 , and a knob  66 , wherein the knob  66  is coupled to the adjustment assembly  64 , and the adjustment assembly  64  is coupled to the magnet  62  on the opposing end as more effectively illustrated in  FIG. 2 . The magnet  62  is generally in stable magnetic contact with the surface of the workpiece  14 . The purpose of the compression assembly  60  is to secure the grounding assembly onto the workpiece  14 , specifically to ensure that the grounding assembly  44  is in robust conductive contact with the workpiece. The purpose of the adjustment assembly  64  is to raise, lower, or otherwise move the grounding assembly  44  with respect to the workpiece  14  so that the grounding assembly  44  is properly secured to the workpiece and in reliable electrical contact with the workpiece. In this embodiment, the compression assembly  60  is generally perpendicularly integrated into the body  52  as illustrated in  FIG. 2 . The compression assembly  60  and the body  52  are generally fixed at their intersection. Specifically, the adjustment assembly  64  may contain threads such that the body  52  may be pulled displaced by the threads as the knob  66  is turned, moving the body either up or down the adjustment assembly, effectively determining the vertical location of the body  52  and the contact force of the grounding assembly  44  on the workpiece  14  (the entire assembly acting as a beam that exerts an increased contact force on the workpiece as the body is moved downwardly). As noted above, while the compression assembly  60  in this embodiment utilizes a magnet  62  and knob  66  mechanism, other means of attaching or holding the grounding assembly  44  in place relative to the workpiece  14  may be used in some other embodiments. These include but are not limited to other supports, clamps, wraps, human operators, external means of support, and so forth. The present configuration, including the compression assembly  60  and non-conductive extension  54 , is one embodiment of many different reasonable configurations that preserve the essence of the present invention. 
         [0019]    As illustrated in  FIG. 2  and the present embodiment, the prongs  56  are coupled to the body  52  of the grounding assembly  44 , and comprise tips  68  as shown. The prongs can be configured in various forms, including a wide range of shapes and sizes. The prongs  56  may be a separate part attached to the body  52  through various attachment methods, or they may be manufactured as one piece with the body  52 .  FIG. 3  illustrates the present embodiment as having two prongs. However, in some embodiments, there may only be one prong  56  present, while some embodiments may utilize two or more prongs  56 . Additionally, one or more embodiments may comprise a grounding assembly  44  with one or a plurality of prongs  56  receptacles on the body  52 , such that the operator can define how many prongs  56  are to be used by attaching or detaching prongs from the prong receptacles. For example, if an operator requires only one prong, the operator may detach all prongs  56  except for one so that the other prongs are not in the way. Conversely, if an operator is welding a large or oddly shaped workpiece  14 , the operator may attach a plurality of prongs  56  to ensure a solid ground. In embodiments where a plurality of prongs  56  is utilized, the prongs  56  may or may not be identical. However, in the presently contemplated embodiment, these of two prongs, or more generally, two grounding contacts, allows for measurement and indication of the quality of the ground, as discussed below. 
         [0020]    The prongs  56  direct the tips  68  to the desired grounding point on the workpiece  14 , generally but not necessarily being the joint  12 . Accordingly, in some embodiments, the prongs  56  may be absent, wherein the conductive tips  68  are coupled directly to the body  52 , bypassing the prongs  56 . Alternatively, some embodiments may utilize “tip holders” of shapes and configurations other than the generally shape of the prongs  56 . The prongs  56  may or may not be made of conductive material, insulated on the outside or not. In the case the prongs  56  are not made of conductive materials, there may be some other conductive path such as a wire or conductive core that runs along the prongs conductively coupling the tips  68  to the body  52  of the grounding assembly  44 . The prongs may or may not also be pliable. In applications where two workpieces are spaced from one another in the fit-up of the joint, it will generally be desired to have the contacts of the assembly form a ground with both workpieces such that the welding arc may be maintained as the process progresses between the workpieces. 
         [0021]      FIG. 2  shows the tips  68  being in intimate contact with the workpiece  14  at the joint  12 , coupling the workpiece  14  with ground. The tips  68  are configured so that they can be well-situated on the joint  12  or elsewhere on the workpiece  14 , establishing a stable ground connection. In order to accommodate joints  12  and workpieces  14  of different configurations, the tips  68  may be configured in different shapes, sizes, from different materials, and so forth. Additionally, the tips  68  may also be removable and interchangeable with respect to the prongs  56  to accommodate different joint  12  configurations. The tip  68  can also be easily removed from the prongs  56  and discarded if damaged or worn without needing to replace the entire grounding assembly  44 . When use, the tip  68  may be made removable and interchangeable through various means of attachment to the prongs  56 , such as but not limited to having threads, magnets, snapping mechanisms, and various other attachment methods. 
         [0022]    The tips  68 , being in contact with the workpiece, ground the workpiece  14  via a ground cable  42 . The ground cable  42  is conductively coupled to the prongs  56  at the base or terminal  70 . This completes a grounding circuit through the workpiece  14 , the ground cable  42 , and the ground terminal of the power supply  16  of the welding system  10 . In some embodiments, the ground lead  56  of the grounding assembly can be configured to also contain a communication cable so that data can be transmitted and received between the grounding assembly and the power supply  10 . Additional forms of communication are possible such as through communication lines elsewhere on the grounding assembly  44  or via Bluetooth, and so forth. The data may be sent and received from the power supply  10  as shown in  FIG. 1  or some other type of processing unit such as but not limited to a computer. 
         [0023]    In addition to providing a secure grounding method, the grounding assembly  44  also provides a means of sensing characteristic measurements, including but not limited to some indication of the quality of the ground connection.  FIG. 4  diagrammatically illustrates the sensing and indication circuit  72  of one embodiment, which comprises an indication module  74 , and a transformer circuit  76 , the transformer circuit comprising an oscillator  78 , a primary winding  80 , and a set of secondary windings  82 . In the particular embodiment shown, the oscillator  78  is coupled to the transformer  76  which features a primary winding  80  and a pair of secondary windings  82 . The secondary windings  82  each comprises one end  84  which is coupled to the prongs  56 . The secondary windings  82  are connected to each other on the sides opposite the ends  84  which are coupled to the prongs. The junction of the two secondary windings  82  is also the centertap ground cable terminal  86  as more clearly shown in  FIG. 4 . At the centertap ground cable terminal  86 , the ground cable  42  is coupled to the ends  84  of the transformer circuit  76 , thus grounding the workpiece via the prongs  56  and tips  68 . Additionally, the ends  84  also act as sensor leads going to the prongs  56  of the grounding assembly  44  where they are conductively coupled to the tips  68  and the workpiece  14 . In the present embodiment, the two tips, tip  1   96  and tip  2   98  now function as the sensor leads. A measurement circuit is completed through the workpiece  14  as current flows from the centertap transformer  76  to one tip  68 , through the workpiece  14  to the other tip  68 , and then back into the centertap transformer  76 . The signal then passes through a sensor  88  which feeds the measurement data to a processing circuit  90 , where measured data is stored and processed. 
         [0024]    The processing circuit  90  can be configured in many different ways in accordance with a wide range of possible functions as known to one skilled in the art. The processing circuit  90  may carry out tasks such as calibrating and digitizing sensor values, storing data, and controlling the indication module  74 . The processing circuit  90  is coupled to a power supply  92 , which may be a battery, capacitor, or some other appropriate power source to drive the power consuming components of the circuit, Additionally, there may also be an indication module  74  coupled to the processing circuit  90 . The indication module  74  may be configured to output readouts, sounds, lights, any combination of these and other types of output indication signals. These indications may give a direct numerical representation of the measurements, in which case the operator will know how to interpret the numerical representation with respect to quality of ground. In other embodiments, the indication  74  in conjunction with the processing circuit  90  may be preprogrammed so that it references the measured value with threshold values, effectively making a decision about the quality of the ground and outputting a qualitative indication of the quality of the ground connection or other parameters. For example, there may be a green LED, a yellow LED, and a red LED such that the green LED lights up when a solid ground connection has been made, the yellow LED lights up when an unstable ground connection is detected, and the red LED lights up when the ground connection is absent. In some embodiments, there may only be two degrees of ground quality: present or absent. The processing and indication function may not always need to be used and is not necessary for the grounding function of the grounding assembly  44 . Additionally, as mentioned above, the type and degree of indication may be configured to meet a wide range of desired functions and formats. Some embodiments may include a push to test button  94  coupled to the measurement circuit to turn the function on and off. 
         [0025]    The processing circuit  90  may also be coupled to an input controls interface  96  in some embodiments. The interface  96  allows the operator to select different functions and indication types. For example, the operator may want to see data from a previous measurement or turn an alarm on or off. Accordingly, the interface may include controls such as but not limited to buttons, touchscreens, knobs, keypads, and any combination of these and other types of existing or new input controls. The physical location of the output signals and input controls can be in various locations on the grounding assembly  44 . 
         [0026]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.