Electric heating – Metal heating – Nonatmospheric environment at hot spot
Reexamination Certificate
2002-09-10
2004-07-06
Stoner, Kiley (Department: 1725)
Electric heating
Metal heating
Nonatmospheric environment at hot spot
C219S137610, C219S137620
Reexamination Certificate
active
06759623
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a welding machine for performing welding by shielding a weld part with a gas, and more particularly to a welding process which uses a consumable or non-consumable electrode in a specially designed torch head having a diameter smaller than conventional torch heads.
The welding torch can be used in a wide variety of welding processes, such as, but not limited to MIG, MAG, STT, and TIG welding. In a MIG, MAG or STT welding process, a consumable electrode wire is fed to a workpiece in which current is applied to the electrode to melt a consumable electrode and transfer the melted portion of the electrode to a workpiece. MIG, MAG and STT welding employs a continuously fed consumable electrode which is shielded by a shielding gas. An arc is formed between the workpiece and the consumable electrode which causes the electrode to melt and transfer to the workpiece in the form of a welding pool. The shielding gas typically employed is an inert gas which is supplied through the torch to protect the weld from oxidation and provide the desired arc characteristics during welding.
Several drawbacks exist with using existing welding apparatus for MIG, MAG and STT welding. During MIG, MAG and STT welding, a short circuit develops between the electrode and the workpiece during transfer of the molten metal to the workpiece. This short circuit occurrence typically results in spattering of the weld metal about the workpiece. This spatter can result in reduced quality weld beads and damage to the torch head or clogging of the torch head. In order to reduce the amount of spatter produced during the welding process, various control techniques have been devised. One such control technique for MIG welding to reduce spattering is the use of a pulse MIG process which is disclosed in U.S. Pat. No. 4,647,754, entitled “Consumable Electrode-type Pulse Arc Welding Machine.” A control technique to reduce spatter for STT welding is disclosed in U.S. Pat. No. 5,148,001, entitled “System and Method of Short Circuit Arc Welding.” U.S. Pat. Nos. 4,647,754 and 5,140,001 are incorporated herein by reference.
Another problem associated with MIG, MAG, STT, and TIG welding is that the torch head is too large for use in the welding of narrowly spaced areas. The torch head is generally a cylindrical design with a fresco-conical tip which has a cylindrical central passageway for the electrode, and one or more passageways formed about the electrode to accommodate shielding gases and/or cooling liquids. The incorporation of the passageways for the shielding gas and/or the cooling liquid results in a significantly increased diameter of the torch head.
Various torch head designs have been developed for use in narrower regions. Several of these torch head designs are shown in U.S. Pat. Nos. 3,992,603; 4,254,322; 5,900,167; and 5,981,897. In U.S. Pat. Nos. 3,992,603; 4,253,322 and 5,900,167, the torch head is formed as a linear torch head. In the '603 patent, the torch head only includes an electrode opening and a cooling passageway positioned at one side of the electrode opening. The cooling passageway is linearly spaced from the electrode opening. The '322 patent discloses a torch head design that includes an electrode opening, shielding gas passageways positioned on both sides of the electrode opening, and two cooling liquid passageways positioned on one side of the electrode opening. The shielding gas, cooling passageways and electrode opening are all linearly aligned with one another. The '167 patent discloses a torch head that includes an electrode opening and two shielding gas tubes spaced from and positioned on both sides of the electrode opening.
Although these welding torch designs reduce one dimension of the torch head, i.e., the width, the length of the torch head is significantly increased. As a result, these torch heads can only be used in limited applications. Furthermore, due to the linear torch head design, the torch head is susceptible to bending when the torch head contacts the workpiece or other objects, thus resulting in improper welding and/or low quality weld bead formation. Furthermore, these torch head designs are highly susceptible to clogging due to spattering of the weld metal. Due to the narrow passageways of the tubes of these torch heads, spattering during the welding process can easily clog one or more of the tubes during the welding process. Furthermore, due to the design of the weld head, cleaning of the components of the weld head are very difficult, thus resulting in frequently replacing the components of the weld head. The linear design of these torch heads also does not provide uniform cooling of the torch head or uniform distribution of shielding gas about the electrode and weld metal. The proper cooling of the torch head facilitates in preventing damage to the components of the weld of the torch head. The proper distribution of shielding gas about the electrode and weld metal ensure proper arc characteristics during the welding process and facilitates in ensuring that a high quality weld bead is formed.
In view of the existing torch head designs, there is a need for a torch head design that has a smaller diameter than the present torch head designs and a torch head that provides adequate cooling to the torch head during welding and provides a uniformed and controlled distribution of shielding gas about the electrode and weld metal.
SUMMARY OF THE INVENTION
The present invention pertains to an improved welding torch head and more particularly to a welding torch head used in MIG, MAG or STT welding in which such welding torch head has a smaller torch head diameter than past torch heads to allow for welding in narrow workpiece regions. As can be appreciated, the invention has broader applications that can be used in other types of short circuit welding such as plasma arc welding, or TIG welding. However, the invention is particularly applicable to MIG, MAG and STT welding and will be described with particular relationship thereto.
In accordance with the principal aspect of the present invention, there is provided a welder that includes a torch head. In one embodiment, the welder includes a power supply to supply current to the electrode in the torch head. In another embodiment, the welder includes a welding circuit which controls one or more electrical or power parameters of the electrode during the welding process. In still another embodiment, one or more shielding gas sources are used with the welder to provide shielding gas about the electrode and/or to protect the weld metal during the welding process. Shielding gases also can be used to obtain the desired electric arc characteristics during a welding process. In still yet another embodiment, the welder includes a wire feeder to feed a consumable electrode through the torch head. In one specific aspect of this embodiment, the wire feeder includes a controller to feed the desired amount of electrode through the torch head during the welding process. The specially designed torch head of the present invention includes a base section and a body section connected to the base section. In a further embodiment, the base section includes one or more openings or connectors to enable one or more shielding gases and/or cooling fluids to be connected to the base section. When a consumable electrode is used, the base section also includes an opening to enable the consumable electrode to pass through the base section and into the body section of the torch head. In yet a further embodiment, the base section includes one or more electrical connectors to provide voltage and current to the electrode in the torch head. The body section of the torch head includes a uniquely designed arrangement of rods or tubes. These rods or tubes are arranged with respect to one another to form an inner chamber between the rods. In yet still a further embodiment, at least one of the rods includes an inner passageway to allow one or more shielding gases to pass there through. The passageway in the
Lincoln Global Inc.
McHenry Kevin L
Stoner Kiley
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