Cathode interface for a plasma gun and method of making and using the same

Interchangeable or standard electrode interface for a thermal spray plasma gun includes an interchangeable electrode having a first connecting section and a first annular coupling surface. A second connecting section is arranged in a plasma gun and includes a second annular coupling surface. An annular seal is spaced or axially spaced from an annular interface formed between the first and second annular coupling surfaces.

Not applicable.

REFERENCE TO A COMPACT DISK APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to equipment for the thermal spraying of powdered materials. More specifically, the present invention relates to a cathode interface for use with a thermal spray plasma gun.

2. Description of Related Art

A variety of thermal spray coatings have been used to protect various types of components. Coatings may provide various benefits such as to resist wear, retard corrosion, control clearances, salvage worn components, resist high temperatures and/or enhance electrical properties. These benefits can differ based on the coating material type and how those materials are applied. One group of spray coatings to which the subject matter of the present invention pertains in particular are those applied via the plasma spray process. This process has been used to apply many different types of coatings in numerous industries.

Each material coating specification requires a specific range of velocity and temperature transferred to the powder particle to achieve the required material properties on the part Improved consistency and efficiency in the delivery of thermal spray coatings remains an industry-wide goal.

The plasma gun has been used as a process tool in the spray coatings industry due to the wide range of parameters that are achievable with this basic tool. A key element of any plasma gun is the cathode geometry. Variations in cathode geometry can allow a plasma gun to provide coating properties at a different temperatures and velocities from the same base equipment. During repeat use, cathode exhibit wear which leads to replacement of the part. Thus a single plasma gun typically required replacement of the cathode. Prior art configurations were such that replacement of the cathode was difficult and took a long time, leading to long down times when the part needed to be replaced.

However, there are a number of factors that can prove challenging in replacing the a plasma gun cathode. Plasma spray guns must perform several different functions in order to achieve a successful coating process. Those functions include proper alignment of the cathode as well as cooling of the gun cathode during the spray process to prevent overheating. Accordingly proper flow of coolant sealing around the cathode area and adequate sealing of the cooling path is needed. An electrical connection between the cathode and the plasma gun is also required to serve as the return path for the plasma arc current flow. Precise orientation of mechanical location, electrical connections and water chamber seals must be achieved to obtain the desired gun operation and gun characteristics.

FIGS. 1 and 2show one example of a known plasma gun1(only the certain main portions of the gun are shown for purposes of illustration) that has a replaceable cathode10. As can be readily seen, the cathode10has a mounting portion20and a tip30from whose front end32a plasma arc discharges in a continuous manner during plasma spraying. The tip30typically has a rear portion31that is fixed to and extends into a receiving zone24of the mounting portion20. The mounting portion20includes a main internal space21which is sized and configured to receive therein cooling fluid and accommodates therein a front portion of a cooling tube40. Cooling fluid passes through the tube40via a main cooling passage70of the plasma gun1. The mounting portion20also includes an external thread22which threads into comparable internal threads of the component50and functions to axially mechanically fix and electrically connect the cathode10to a main internal component50of the plasma gun1. However, to provide sealing between the cathode10and the component50to among other things, prevent cooling fluid (typically pressurized) from escaping from the space21, a seal or O-ring60is typically provided in an area of an annular connecting interface23. Owing to its position in the interface23, the O-ring60is subjected to relatively high temperatures. Additionally, its location in the interface23is not ideal from the standpoint of providing maximum electrical conductivity between the cathode10and the component50. As such, providing a standardized interface which would offer significant improvement over known connecting interfaces between these components should take these considerations into account.

Utilizing a standard interface in a plasma gun has been utilized in areas such as the nozzle interface. U.S. Pat. No. 7,759,599 to HAWLEY et al., for example, describes one such arrangement, the disclosure of which is hereby expressly incorporated by reference thereto in its entirety. However, providing a standard interface for a cathode of a plasma gun has unique challenges which are not addressed by this document.

A standard interface for each cathode that would assure proper orientation of all plasma gun components with each interchangeable cathode, while minimizing the risk of human error would be beneficial to the spray coating industry. Optimal orientation could extend the range of performance for a single thermal spray plasma gun. Thus, there remains a need in the art for a standard cathode interface for a thermal spray plasma gun that provides an optimal, efficient and repeatable cathode connection for a wide range of cathode geometries.

SUMMARY OF THE INVENTION

The present invention provides a standard interface that takes into account one or more of the noted deficiencies and provides an interface that is better or improved from a mechanical location and orientation standpoint, provides for an improved electrical connection, and also improves sealing integrity and life. Such an arrangement can be used for a variety of plasma forming electrodes. The flexibility of the connecting interface is believed to offer a marked improvement over known designs.

The interface arrangement in accordance with the invention can ideally serve as a common mechanical interface for mating an interchangeable cathode to a thermal spray plasma gun body. In the assembled configuration, water flow may be carried between the gun body, through the cathode, and back out to a return water flow channel. Also, the interface provides sufficient capability to passing an electrical current of up to about 800 amps at up to about 300 volts between gun body (or components thereof) and the cathode. The actual power through the interface will, of course, vary depending upon the specific materials to be sprayed with the gun and the desired coating characteristics.

According to one non-limiting embodiment of the invention, there is provided an interchangeable or standard electrode interface for a thermal spray plasma gun, comprising an interchangeable electrode comprising a first connecting section and a first annular coupling surface, a second connecting section arranged in a plasma gun and comprising a second annular coupling surface, and an annular seal axially spaced from an annular interface formed between the first and second annular coupling surfaces. The annular seal can be at least one of axially spaced from an annular interface, located outside of an annular interface and/or can provide sealing in a sealing zone separated from an annular interface.

In embodiments, the interchangeable electrode is a cathode electrode.

In embodiments, the interchangeable electrode comprises a mounting portion and a different material arc discharge portion.

In embodiments, the first connecting section comprises an external thread and the second connecting section comprises an internal thread.

In embodiments, in an installed condition, the first and second annular coupling surfaces electrically and mechanically contact one another and/or the first and second annular coupling surfaces electrically and mechanically contact one another and form a main electrical interface without any non-metallic or non-electrically conductive seal interposed therein.

In embodiments, the annular seal is an O-ring.

In embodiments, the annular seal is arranged in an outer circumferential groove of the interchangeable electrode.

In embodiments, the annular seal is located axially in front of the first and second annular coupling surfaces.

In embodiments, the annular seal is arranged to provide sealing between inner and outer circumferential surfaces.

In embodiments, the second connecting section is arranged at least one of on a main internal component of the plasma gun and on a non-interchangeable internal component of the plasma gun.

In embodiments, the interchangeable electrode is a cathode electrode having an internal cooling space.

The invention also provides for an interchangeable or standard electrode interface for a thermal spray plasma gun, comprising an interchangeable electrode comprising a first connecting section and a first annular coupling surface and a second connecting section arranged in a plasma gun and comprising a second annular coupling surface. The first and second annular coupling surfaces are arranged generally perpendicular to a center longitudinal axis of the interchangeable electrode. An annular seal is arranged in a circumferential groove and being axially spaced from an annular interface formed between the first and second annular coupling surfaces.

In embodiments, the interchangeable electrode is a cathode electrode.

In embodiments, the interchangeable electrode comprises a mounting portion and a different material arc discharge portion.

In embodiments, the first connecting section comprises an external thread and the second connecting section comprises an internal thread.

In embodiments, in an installed condition, the first and second annular coupling surfaces electrically and mechanically contact one another.

In embodiments, the annular seal is an O-ring.

In embodiments, the circumferential groove is an outer circumferential groove arranged on the interchangeable electrode.

In embodiments, the annular seal is located axially in front of the first and second annular coupling surfaces.

In embodiments, the annular seal is arranged to provide sealing between inner and outer circumferential surfaces.

In embodiments, the second connecting section is arranged at least one of an a main internal component of the plasma gun and on a non-interchangeable internal component of the plasma gun.

In embodiments, the interchangeable electrode is a cathode electrode having an internal cooling space.

The invention also provides for an interchangeable or standard cathode electrode interface for a thermal spray plasma gun, comprising an interchangeable cathode comprising a first connecting section and a first annular coupling surface. a second connecting section arranged in a plasma gun and comprising a second annular coupling surface and an annular seal arranged in a circumferential groove and being axially spaced from an annular interface formed between the first and second annular coupling surfaces.

In embodiments, the interchangeable cathode comprises a mounting portion and a different material arc discharge portion.

In embodiments, the first connecting section comprises an external thread and the second connecting section comprises an internal thread.

In embodiments, in an installed condition, the first and second annular coupling surfaces electrically and mechanically contact one another.

In embodiments, the annular seal is an O-ring.

In embodiments, the circumferential groove is an outer circumferential groove arranged on the interchangeable cathode.

In embodiments, the annular seal is located axially in front of the first and second annular coupling surfaces and the first and second annular coupling surfaces are arranged generally perpendicular to a center longitudinal axis of the interchangeable cathode.

In embodiments, the annular seal is arranged to provide sealing between inner and outer circumferential surfaces.

In embodiments, the second connecting section is arranged at least one of on a main internal component of the plasma gun and on a non-interchangeable internal component of the plasma gun.

The invention also provides for a method of making a plasma gun comprising installing, in the plasma gun, an interchangeable electrode having the interchangeable interface in accordance with anyone of the above-noted embodiments.

The invention also provides for a method of replacing an interchangeable electrode of a plasma gun comprising removing a used interchangeable electrode from the plasma gun and installing a new interchangeable electrode having the interchangeable interface in accordance with anyone of the above-noted embodiments.

Additional features of the invention will be set forth in the figures and any description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features of the invention may be realized and obtained by way of the features, instrumentalities and/or feature combinations particularly pointed out hereinafter.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 3 and 4show one non-limiting example of a plasma gun100(only the certain main portions of the gun are shown for purposes of illustration) that has an interchangeable and replaceable cathode110in accordance with the invention. As can be readily seen when compared to the known arrangement10/50shown inFIGS. 1 and 2, the cathode110is mechanically and electrically connected to a main portion150of the plasma gun100via an interface but which lacks any seal, i.e., the interface lacks any non-metallic or non-electrically conductive seal as will be described in detail below. Instead, a seal160is axially spaced from this interface.

Thus, in the embodiment ofFIGS. 3 and 4, the cathode110has a mounting portion120and a tip130from whose front end132a plasma arc discharges in a continuous manner during plasma spraying. The tip130has a rear portion131that is fixed to and extends into a receiving zone124of the mounting portion120. The mounting portion120includes a main internal space121which is sized and configured to receive therein cooling fluid and accommodates therein a front portion of a cooling tube140. Cooling fluid passes through the tube140via a main cooling passage170of the plasma gun100. The mounting portion120also includes an external thread122which threads into comparable internal threads151of the component150and functions to axially mechanically fix and electrically connect the cathode110to a main internal component150of the plasma gun100. However, to provide sealing between the cathode110and the component150to among other things, prevent cooling fluid (typically pressurized) from escaping from the space121, a seal or O-ring160at a location other than an area of an annular connecting interface formed between the interface coupling surface123of the cathode110and the interface coupling surface152of the internal component150. In the embodiment ofFIGS. 3 and 4, the O-ring160is spaced from the interface123/152and is instead arranged in a generally circumferential groove125. The groove125can be arranged on the cathode110as an outer circumferential groove as shown inFIGS. 3 and 4or alternatively as an inner circumferential groove arranged on the internal component150. Owing to its position spaced from the interface123/152, the O-ring160is not subjected to relatively high temperatures as in the prior art. Additionally, its location spaced from the interface is more ideal from the standpoint of providing maximum electrical conductivity between the cathode110and the component150. This is because surfaces of the interface which were previously spaced apart (seeFIGS. 1 and 2) and which served to define a space for receiving therein an O-ring or seal can now be brought into electrical contact with one another. As a result of the configuration shown inFIGS. 3 and 4, a standardized interface is provided which offers significant improvement over known connecting interfaces between the components110and150.

Referring now toFIGS. 5-8, it can be seen that an exemplary cathode110has a generally cylindrical mounting portion120and a generally cylindrical tip130from whose front end132a plasma arc discharges in a continuous manner during plasma spraying. The mounting portion120includes a generally cylindrical main internal space121which is sized and configured to receive therein cooling fluid and accommodates therein a front portion of a cooling tube140(seeFIG. 4). The mounting portion120also includes an external thread122arranged on a rear end of the portion120as well as hex-shaped portion arranged adjacent the tip130. The hex-shaped portion is sized and configured so that an operator can remove the cathode110using a suitable tool such as a wrench or socket wrench, and, in this way, unthread the external threads122from the internal threads151of the internal component150during cathode110removal. The same hex-shaped portion allows an operator to install the cathode110using a suitable tool such as a wrench or socket wrench, and, in this way, thread the external threads122into the internal threads of the internal component150during cathode110installation. As can be seen inFIG. 7, a groove125can be arranged on the cathode110as an outer circumferential groove and this groove125is axially spaced from an interface coupling surface123of the cathode110.

In embodiments, the threaded connecting sections122and151can be of any type and are not limited to, for example, machine threads. Moreover, either the thread122or thread151need not be completely circumferential and can be in the form of intermittent threads. Non-limiting examples include ⅝-18 UNF thread. The interface123/152need not be limited to that shown inFIGS. 3 and 4and can additionally also function as a stop for the threading on of the cathode110. In embodiments, the O-ring160can be of any type, i.e., generally circular, square or rectangular in cross-section, and preferably functions to provide sealing for the cooling fluid circuit. The materials for certain components such as components150,120and130can be the same as those used for comparable component utilized in conventional plasma guns such as that shown inFIGS. 1 and 2.

FIGS. 9-11show one non-limiting plasma gun100′ that can utilize the interchangeable interface shown inFIGS. 3 and 4. Here, a Sulzer Metco SinplexPro-90 Plasma Gun is provided with an interchangeable cathode (seeFIG. 11) utilizing the interchangeable interface of the type exemplified inFIGS. 3 and 4.

FIGS. 12-14show another non-limiting plasma gun100″ that can utilize the interchangeable interface shown inFIGS. 3 and 4. Here, a Sulzer Metco SinplexPro-180 Plasma Gun is provided with an interchangeable cathode (seeFIG. 14) utilizing the interchangeable interface of the type exemplified inFIGS. 3 and 4.