Electric heating – Metal heating – By arc
Reexamination Certificate
1999-07-19
2001-02-06
Ryan, Patrick (Department: 1725)
Electric heating
Metal heating
By arc
C219S070000
Reexamination Certificate
active
06184492
ABSTRACT:
The invention relates to a welding electrode holder for coated electrodes comprising an electrically conducting electrode holder body with positioning seats of electrodes and welding cable connection position, an electrically and thermally insulating handle of tubular shape where the back part of the electrode holder body is encaged, a lever pivotably assembled with the electrode holder body and having the lever arm electrically—thermally insulated, a compression spring seated on the electrode holder body or on the handle and pushing the lever arm thus forcing the lever to be turned and to exert force onto the positioning seats of electrodes, and an electrically—thermally insulating head covering the parts of the electrode holder body and those of the lever located in front of the handle or even covering and part of the handle and allowing the clamping of electrodes onto the electrode holder body.
Welding electrode holders for coated electrodes are known in several designers with differences focused mainly in the clamping mechanism of electrodes, in the geometry and the orientation of the positioning seat or seats of electrodes, in the connection of the welding cable to the electrode holder body and in the assembly of the insulating parts with the electrically conducting parts.
Common feature of the known electrode holders for coated electrodes is that the part of the electrode holder body with the welding cable connection position is located inside the handle and it is in contact with the inside wall of the longitudinal through hole of the handle.
The conduction of electric current from the welding cable to the electrode, through the electrode holder body, generates inevitably heat in the electrode holder body. The heat is generated due to the contact resistance between the bare end of the welding cable and the electrode holder body at the welding cable connection position, due to the electric resistance of the electrode holder body, and due to the contact resistance between the positioning seats of electrodes at the electrode holder body and the electrode.
A part of this heat is transferred from that section of the electrode holder body located inside the longitudinal through hole of the handle onto the inside wall of the handle and from there to the external surface of the handle which is held by the welder.
If the temperature on the external surface of the handle rises at a high value, it is not easy for the welder to hold and to manipulate the electrode holder. Overheating of the electrode holder not only makes it uncomfortable for the welder, but it can also cause excessive voltage drop in the welding circuit. Therefore, it can impair the performance of the welder and reduce the quality of the welds.
According to the standard DIN 8569 Part 1: 1974—Rod Electrode Holders for Metal Arc Welding—“the temperature of the rod electrode holder in the area held by the hand above the welding cable connection may exceed the ambient temperature by not more than 40 K”. This standard has been replaced by DIN EN 60974-11: 1996—Electrode holders—which states that “the temperature rise caused by the rated current passing through the electrode holder, . . . , shall not exceed 40 K at the hottest spot of the external surface of the handle”.
If the welding current, required for welding a size (diameter) of electrode, causes overheating of the electrode holder, it is necessary the electrode holder to be replaced by a bigger one. The bigger size electrode holder has a bigger body with bigger cross section in particular, resulting in reduction of the electric resistance. Consequently, the generated heat is reduced in relation to the heat generated in a smaller size (cross section) electrode holder body during the same time interval and by the same electric current intensity.
On the other hand, increasing the size of the electrode holder its weight is increased too, resulting in sooner fatigue of the welder's hand and rendering the electrode holder less comfortable and more awkward to use.
The invention as described herein aims at the reduction of the temperature developed on the external surface of the handle held by the welder and moreover at the reduction of the electrode holder weight in relation to the known electrode holders, for the same welding current intensity and for the same duty cycle.
The solution is achieved by transferring the welding cable connection position outside the handle and inside the insulating head of the electrode holder, behind or/and underneath the positioning seats of electrodes and by encaging the back part of the electrode holder body, i.e. the part behind the welding cable connection position, in a seperate receptacle located at the front part of the handle, above the longitudinal through hole of the handle and outside or inside the insulating head.
The transfer of the welding cable connection position outside the handle and behind or/and underneath the positioning seats of electrodes, i.e. its transfer closer to the positioning seats of electrodes, shortens the distance travelled by the welding current in the electrode holder body. A result of this is the reduction of the generated heat in relation to the heat generated in an electrode holder body of the same cross section, having the welding cable connected at the rear end of the electrode holder body, i.e. further from the positioning seats of electrodes.
Moreover, the weight of the electrode holder is reduced mainly due to the shorter length of the electrode holder body.
Furthermore, the transfer of the welding cable connection position outside the handle keeps the heat generating parts of the electrode holder body away from the hand of the welder. A result of this is the reduction of the temperature on the surface of the handle held by the welder in relation to the temperature developed at the same surface, when the welding cable connection position is located inside the handle and underneath the surface held by the welder.
The rest part of the electrode holder body, being inserted into a separate receptacle at the front part of the handle, is kept away from the surface of the handle held by the welder and in particular away from the downward part of this surface, due to the intervention of the longitudinal through hole of the handle. The hand of the welder can be kept further away from the back part of the electrode holder body, which is inserted in the separate receptacle of the handle, by one way of materialization of the invention, in which the front part of the handle with the separate receptacle is extended inside the insulating head and the whole electrode holder body is covered by the insulating head.
The lower temperature on the external surface of the handle held by the welder in relation to the temperature on the corresponding surface of the handle of the known electrode holders, when the electrode holder body is of the same cross section, as well as the the lower weight of the electrode holder, provide more comfortable working conditions to the welder. Consequently, the work efficiency is increased.
The invention is hereinafter described by two ways of materialization, as examples, without these examples to restrict the possible ways of its materialization. The differences between these two ways are focused mainly in the location of the welding cable connection position in relation to the positioning seats of electrodes and also in the assemblage of the electrode holder body with the handle.
REFERENCES:
patent: 3140386 (1964-07-01), Cartright
patent: 3654421 (1972-04-01), Streetman et al.
patent: 4761531 (1988-08-01), Moss
Dey Anjan
Ryan Patrick
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