Patent Application
20160360603
Devices, systems, and methods consistent with the invention relate to cutting, and more specifically to devices, systems and methods related to plasma arc cutting torches and components thereof, including a multi-component electrode for use in an arc plasma cutting torch.
In many cutting, spraying and welding operations, plasma arc torches are utilized. With these torches a plasma gas jet is emitted into the ambient atmosphere at a high temperature. The jets are emitted from a nozzle and as they leave the nozzle the jets are highly under-expanded and very focused. However, because of the high temperatures associated with the ionized plasma jet many of the components of the torch are susceptible to failure. This failure can significantly interfere with the operation of the torch and prevent proper arc ignition at the start of a cutting operation. Some torches utilize copper electrodes having an insert, in addition to a hafnium insert, in an effort to address these problems. An example of this is disclosed in U.S. Pat. No. 5,097,111, the entire disclosure of which is incorporated herein by reference. This patent explains the use of an additional insert within the electrode. However, this solution still does not alleviate the failure issues discussed above.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.
An exemplary embodiment of the present invention is an electrode assembly and a plasma torch containing the same, where the electrode assembly contains an emissive insert (e.g., hafnium) and a thermally conductive wrap surrounding the insert. The wrap is made from a high thermally conductive material or a composite of materials to aid in the cooling of the insert and prevent the jumping of an arc from the insert to the electrode body.
The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which:
Reference will now be made in detail to various and alternative exemplary embodiments and to the accompanying drawings, with like numerals representing substantially identical structural elements. Each example is provided by way of explanation, and not as a limitation. In fact, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope or spirit of the disclosure and claims. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure includes modifications and variations as come within the scope of the appended claims and their equivalents.
The present disclosure is generally directed to both air and liquid cooled plasma arc torches useful various cutting, welding and spraying operations. The construction and operation of these torches are generally known, and thus their detailed construction and operation will not be discussed herein. Further, embodiments of the present invention can be used in either handheld or mechanized plasma cutting operations. It should be noted that for purposes of brevity of clarity, the following discussion will be directed to exemplary embodiments of the present invention which are liquid cooled and can be used for both mechanized and hand geld cutting operations. However, embodiments of the present invention are not limited in this regard and embodiments of the present invention can be used in other types of welding and spraying torches without departing from the spirit or scope of the present invention. Further, various types and sizes of torches are possible at varying power levels if desired. The torches and components described herein could be used for marking, cutting or metal removal. Additionally, exemplary embodiments of the present invention, can be used with varying currents and varying power levels. The construction and utilization of coolant systems of the type that can be used with embodiments of the present invention are known and need not be discussed in detail herein.
Turning now to
As mentioned above, the electrode 100 includes a high thermionic emissive insert 103. During cutting, the plasma jet emits from this insert. Often this insert 103 is made from hafnium, but other materials such as zirconium and tungsten (and other similar materials) can be used. Typically, the usable life of the electrode 100 depends on the usable life of the insert 103, which tends to erode during operation. Further, the erosion of the insert 103 can be accelerated if the cooling of the insert 103 and the electrode body 101 is not optimal. Also, the generated plasma jet can have a tendency to jump from the insert 103 and make contact with the distal end of the electrode body 101. This can cause damage to the electrode body 101 and accelerate its failure.
Therefore, embodiments of the present invention utilize an insert wrap 105 which is wrapped around an exterior of the insert 103 and is inserted into the distal end of the electrode body 101 as shown. In exemplary embodiments of the present invention, the wrap 105 is made from a high heat transfer material, and can be a composite material. By having a high heat transfer rate the wrap 105 aids in optimizing the cooling of the insert 103. Thus, embodiments of the present invention have improved operating life over known electrodes.
The wrap 105 can be made from a number of high heat transfer rate materials, and composites thereof. For example, in some exemplary embodiments the wrap can be made of a material having a very high thermally conductivity, or can have a matrix material of either copper or silver which is impregnated with another material of high thermal conductivity. Each of copper and silver have a relatively good thermal conductivity. Copper has a thermal conductivity of about 401 W/mK at 20° C., and silver has a conductivity of about 429 W/mK at 20° C. While these are acceptable for some applications, it is desirable to have considerably higher conductivity to aid in removing heat from the insert 103. Therefore, in exemplary embodiments, the wrap 105 is made from a material having a thermally conductivity of at least 700 W/mK at 20° C. In further exemplary embodiments, the wrap 105 is made from a material having a thermal conductivity of at least 1,000 W/mK at 20° C. In further exemplary embodiments, the material has a thermal conductivity in the range of 1,000 to 2,500 W/mK at 20° C. It is noted that, because exemplary embodiments of the present invention can use a composition or matrix of materials (as discussed in more detail below) the above thermal conductivity discussion is directed to the overall thermal conductivity of the wrap 105. That is, the wrap 105 can be made up of a matrix of materials having thermal conductivity characteristics above or below the numbers but the overall conductivity is as described above. Additionally, because heat can affect the thermal conductivity of materials (e.g., the thermal conductivity can increase at higher temperatures), materials contemplated by embodiments of the present invention also have a higher thermal conductivity than silver even at higher temperatures. That is, the thermally conductive material contemplated by embodiments of the present invention, will have a higher thermal conductivity than silver throughout the operational temperature range experienced during cutting operations, which can range from 100 to 1600° C. For example, some exemplary embodiments can use a wrap 105 which is made from carbon chain materials, such as diamonds, nano-tube or nano-fibers and graphene. These types of carbon chain materials can have a very high thermal conductivity—higher than 2,000 W/mK—and can be placed on the hafnium insert 103 via a deposition process, such as vapor deposition. For example, a DLC (diamond like carbon) coating can be placed on the insert 103 via vapor deposition before the insert 103 is coupled to the electrode body 101. This layer/wrap 105 greatly aids in the cooling of the insert 103 as its thermal conductivity is much higher than copper or silver. Further, some of these materials, such as graphene, also have a relatively high electrical conductivity, which aids in allowing the cutting current to pass from the electrode body 101 to the insert 103. In exemplary embodiments, the wrap 105 of the carbon chain material can have a thickness in the range of 10 to 50 microns. In other exemplary embodiments, the thickness of the wrap 105 can be thicker. Thus, in exemplary embodiments of the present invention, the wrap 105 is made from high thermal conductivity materials. In further exemplary embodiments, the wrap 105 material can also have low thermal expansion—to maintain dimensional integrity, and can be electrically conductive. His will aid in optimizing the performance of the electrodes contemplated herein.
In exemplary embodiments of the present invention, the wrap can be press-fit with the insert 103 and the electrode body 101, where a crimping force is applied to the electrode body 101 so as to squeeze the insert 103 and the wrap 105 to secure the components in the body 101. However, exemplary embodiments are not limited to this and other methods of securing the components can be used. For example, the wrap 105 can have a metallurgical connection with the insert and/or the body 101. Examples of such connections can be via soldering.
In additional exemplary embodiments, the wrap 105 can be made of a composite material, having a base matrix material—which can be copper or silver, for example—and a high thermal conductivity material suspended in the matrix. Again, the suspended material can be a carbon based material, such as diamonds, etc. In other exemplary embodiments, the suspended material can be thermal pyrolytic graphite (TPG). TPG is a form of pyrolytic graphite manufactured from thermal decomposition of hydrocarbon gas in a high temperature chemical vapor deposition reactor. Materials such as TPG can have a thermal conductivity of at least 1,500 W/mK at 20° C. Further, these materials can be suspended in a silver or copper matrix via processes, such as sintering, and create a composite material wrap 105 that greatly improves the thermal performance of the insert 103. The composite wrap 105, again, is placed on an outer surface of the insert 103, and is positioned between the insert 103 and the electrode body 101. Because a matrix material of copper or silver is used—each having a relatively high electrical conductivity—the wrap 105 can fully cover the insert 103 within the body 101. In
In further exemplary embodiments, the material of the wrap 105 can be made from metallurgical alloys which provide the desired thermal and electrical performance. For example, an alloy comprising copper, chromium, zinc and titanium can be used. In further exemplary embodiments a powder sintering process can be used to create a metal matrix composite of materials which provide the desired thermal and electrical properties. An example of such a composite would be a metal-diamond composite material can be used to achieve the desired thermal and electrical properties. The metal can be any of the materials, alloys referenced herein, as well as others that have the desired properties. Additionally, a nano-fiber enforced composite process can be used to create a wrap 105 of the present invention. For example a carbon or graphene enforced composite can be used.
In further exemplary embodiments of the present invention, the electrode body 101 itself is a composite material. For example, the electrode body can be made of a copper or silver matrix material having a carbon based material impregnated within it—such as diamonds—which improves the overall thermal conductivity of the electrode body. Again, the carbon material can be impregnated with a process such as sintering. Of course, other manufacturing processes can be used to create a composite material electrode body 101. Further, in other exemplary embodiments, only the cavity 121 in which the insert 103 is inserted can be impregnated with carbon materials, such as diamonds. That is, in some embodiments, the majority of the electrode body 101 is a solid material, such as copper or silver, but the walls of the cavity 121 on the distal end of the electrode 100 are impregnated with diamonds, or some of the other materials discussed above, such that the thermal conductivity electrode body 101 in the area of the of the cavity 121 is increased over the remainder of the electrode body 101. In exemplary embodiments of the present invention, the thermal conductivity of the impregnated portions of the electrode body 101 have a thermal conductivity in the range of 500 to 1,000 W/mK at 20° C. In some of such embodiments, the wrap 105 is not needed and thus not used, such that the insert 103 makes direct contact with the composite walls of the cavity 121. In further exemplary embodiments, each of a wrap 105 and a composite material cavity 121 is used.
Further, in the embodiment shown, the wrap 105 has a constant thickness T, so that the cavity 121 is generally cylindrical. However, as further discussed below, in some embodiments, the thickness T can vary. Further, depending on the materials used for the wrap, the thickness T of the wrap 105 can range from 10 to 50 microns. However, in other exemplary embodiments, the thickness T can be much larger and can be in the range of 0.04 to 0.2 inches. Of course, other thickness can be used as well, and will be a function of the size constraints of the electrode body 101 and the desired thermal conductivity performance.
Additionally, as shown, the wrap 105 has an outside diameter d—as measured on the distal face 112 of the body 101—where the diameter d is in the range of 35 to 95% of the diameter D of the distal end face 112 of the body 101. In other embodiments, the diameter d is in the range of 45 to 85% of the diameter D. It is noted that the diameter D is the diameter of the flat end face surface 112 of the distal end of the body 101.
It should be noted that embodiments of the present invention can be used with cutting torches and systems that vary widely in the current and power levels. That is, embodiments of the present invention can be used in cutting system from below 100 amps to higher than 400 amps. However, because of the thermal attributes of exemplary embodiments of the present invention, many of the benefits of embodiments disclosed herein will be more appreciated in cutting applications which have higher current levels. For example, electrodes discussed herein can be used in cutting applications in the range of 275 to 400 amps. Further, because of the different demands put on consumables when operating at different current levels, the dimensional relationships of some of the components discussed herein can be optimized for different current levels.
When assembling/manufacturing exemplary embodiments of the electrode 100, as shown, the insert 103 and the wrap 105 (if present) is inserted into the cavity 121. Then a radially directed compressive force is applied on the sides the electrode body 101 at the distal end such that the wrap 105 and insert 103 are crimped into the electrode body 101 and held in place by this crimp force. The radial crimping force is applied such that the outside diameter of the electrode body 101 at the crimp force location is reduced by about 3 to 8%.
Additionally, while
Further, in exemplary embodiments of the present invention the electrode body 101 is made from an oxygen-free high thermal conductivity copper. Such copper alloys typically are 99.99% pure copper with a low oxygen content of no more than 0.0005% by weight. An example of such a copper alloy is C10100. A copper of this alloy provides the heat transfer characteristics that are desirable but is also susceptible to machining and crimping—so as to be crimped with the grooves in the shell.
Turning now to
The operation of the torch assembly 400, using the exemplary electrode assembly 100 is no different than the operation of known torches. However, because of the attributes discussed above, the electrode assembly 100 will have a longer life than known electrodes. Therefore, embodiments of the present invention provide significant improvements over known electrodes.
While the claimed subject matter of the present application has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the claimed subject matter. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the claimed subject matter without departing from its scope. Therefore, it is intended that the claimed subject matter not be limited to the particular embodiment disclosed, but that the claimed subject matter will include all embodiments falling within the scope of the appended claims.
