Electric heating – Metal heating – By arc
Reexamination Certificate
2000-06-23
2002-07-02
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S136000
Reexamination Certificate
active
06414268
ABSTRACT:
OBJECT OF THE INVENTION
The present invention, as expressed in the title of this descriptive statement refers to a torch for welding systems in automatic processes. This provides some important and advantageous characteristics in relation to those characteristics that currently exist for the same purpose and that could be considered as pertaining to its type.
Basically, welding is understood to be the union of two or more materials to achieve a single body.
There are may types of welds, but for the case in hand, we shall only mention arc welding with a filler material.
Arc welding with a filler requires strict operating conditions if the welding process is to be performed correctly. Although we are going to focus on explaining how the torch works, it is necessary to be aware of the whose process in order to understand the problems faced. As shall be seen later in relation with the figures, a typical machine incorporates the pertinent components, which are:
Rectifier unit. This produces the voltage and current necessary to fuse the wire. It is a continuous current and the negative pole is connected to the machine chassis or to the support system for the parts to be welded.
Wire feed unit or spool. This is responsible for supplying the electrode wire at a constant speed. This is important in order to guarantee the stability of the arc.
Hose. Through this element are channelled the wire, the current generated in the rectifier (positive pole) and the gas, to the welding gun.
Gas. The gas produces a neutral field or atmosphere around the welding arc. If the arc is not shielded by inert gas, then the oxygen present in the air would react with the electrode wire and with the materials to be welded, causing combustion and the end result would be porosity in the weld fillet.
Cooling unit. This is an independent cooling system composed of a motor pump, a radiator, a ventilator and a small tank of distilled water. If the welding gun requires cooling, these must also include two water tubes.
Welding torch or gun. The wire and gas come out of this element and this is where the arc is produced. Inside the gun, and to be more specific, in the tip, contact occurs between the positive pole of the rectifier unit and the wire.
The position of the gun is essential since, in order to achieve a good weld it is necessary to consider parameters such as the distance to the welding point, the angle and the capacity to resist high temperatures, as well as the correct amount of gas.
This is the element that directly supports the effects of the welding operation, such as high temperatures, spatter, knocks, etc.
Torch support. These are metallic clamps that are built into the machine chassis, they support the torch and are connected to the negative pole of the rectifier. They cannot be made of plastic since, as explained above, the position of the gun is essential, and a high degree of rigidity is required to prevent unwanted movements that could modify the points to be welded.
When the system is enabled, the gas valve located in the wire feed opens and after a certain time, the rectifier and wire feed are put into operation.
When the wire comes into contact with the part, the wire melts and an arc is produced. The wire feed unit must maintain a constant travel speed to ensure the uniformity of the arc generated. As the wire leaves the gun it is melted by the arc, depositing the molten material on the elements to be welded. The gas that also flows out of the gun, shields the arc to prevent oxygen from entering and causing material oxidation.
BACKGROUND TO THE INVENTION
In current automated systems, all the problems inherent in welding are aggravated by the fact that there are many repetitive cycles, with the subsequent non-productiveness caused by cleaning, fine tuning or break downs. This should be reduced to a minimum. Amongst these problems, the following should be highlighted:
Spatter. Once the arc has been generated, part of the molten material is projected, as droplets, due to the effect of the electromagnetic fields. These droplets are termed spatter and are projected at random, dirtying the surroundings. Many of these droplets get into the gun nozzle and end up stuck to the inside. This means that the nozzles must be cleaned frequently to permit the gas to exit correctly.
Impacts. Although, in principle the torches ought not to be knocked about, this is not so in practice. Knocks occur either because the parts are incorrectly placed in the tooling, or because the torches are mounted on height control cylinders, or also because the operator knocks them when he sees that some welding point has moved for an unknown reason. This could lead to a short circuit occurring in the gun as a result of the interior insulation breaking.
Temperature. The fact that the gun is very close to an arc directly affects its components. If the gun is not adequately cooled its conductivity will increase and this will negatively affect the current flow through the gun. This in turn increase the temperature of the gun and offers an even greater resistance to the current flow. This leads to greater energy consumption or the destruction of the gun.
Any of the above mentioned problems can cause an internal short circuit within the gun, putting it out of action.
With the general lay-out for a conventional torch, the following deficiencies occur.
The nozzle support or the gun body is metallic, bronze to be more specific, end its construction is very simple, this gives rise to continual deformations.
The gun tube is made from copper piping with an internal water cooling chamber, which means that it is not every rigid.
The insulating material between the gun tube and nozzle support is excessively thin, which means that there is very little insulation and causing short-circuiting amongst the metallic elements.
As the clamp body is made from bronze, it is susceptible to deformations and, moreover, it is oversized in comparison to the rest of the torch.
Given the fact that these elements, by their very construction, have no rigidity or heat dissipation capacity. It becomes necessary to cool them by water passing through the interior gun tube, adding yet another control parameter (levels, flow meters, thermostats, etc.).
It is not possible to attach a blower to eliminate spatter sticking to the nozzles and tips.
DESCRIPTION OF THE INVENTION
In general, the torch for welding systems in automatic processes, the object of this invention, consists of a tip where the wire comes in contact with the current, like those of the previous technique. It offers a special lay-out since it is screwed into the tip holder and this is then screwed into the gas distributor. There is also a gun hose carrying the gas, wire and power. There is a nozzle to direct the gas at the point to be welded and, similarly, the gun is connected to the hose.
The gun nozzle or body support is made of a highly heat resistant material, it is perfectly dielectric and very resistant to deformations caused by knocks and high temperatures.
The gun tube is made from solid copper. This reduces its resistively and therefore less heat is generated by the high frequency current flow. It is possible to operate with currents of up to 400 Amps without any cooling being required.
Its very structure means that no interior short circuiting is ever possible since the body of the gun itself acts as the insulator.
Thanks to the nylon washer built into the gun support or on the outside of the actual gun body, these is a better fit in the machine supporting clamp.
The cooling required with the current technique is eliminated, when working below 400 Amps, with the subsequent reduction in costs both for new equipment as well as for maintenance.
It is also possible, by eliminating an O-ring present in an annular slot in the gun tube, blocking off the gun support or gun body, and using the relative cooling conducts, to inject air through the body to eliminate spatter inside the nozzle, reducing the normal cleaning times in usual continuous automatic processes.
The invention proposes a torch that
Equiza Equiza Joaquin
Gorriz Elia Ramón
AP Amortiguadores, S.A.
Klauber & Jackson
Shaw Clifford C.
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