Directional Arc-generating Device

Abstract

An arc-generating device comprising a plurality of electrode members each of which has the discharge surface sloped toward the inner and lower part thereof from the upper peripheral edge, said electrode members being assembled as an electrode assembly so that a conically concaved discharge space is formed by the discharge surfaces of all electrode members, and a longitudinal narrow gap is established between adjacent electrode members of each pair, whereby an electric arc is made to generate along said discharge space successively per two opposite discharge surfaces, thus establishing a directional arc stream along a common axis of the discharge surfaces, and respective pairs of the electrode members of said arc-generating device being supplied successively with pulse-shaped DC or AC voltage or a polyphase voltage.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a directional arc-generating device which can effectively eject a directional arc stream. Hitherto, in the conventional arc-ejecting devices used in arc welding and the like, generation of a concentrated and stable directional arc has been very difficult, and such generation could not be realized without entailing very complicated and expensive construction. Furthermore, in the conventional arc-generating devices, when electrode members made of a consumable material are used as the electrode members, it is necessary to adjust the discharge gap with consumption of the electrode members during the period of use, this adjustment being very troublesome and causing high complexity of the construction.

SUMMARY OF THE INVENTION

An essential object of the present invention is to provide a directional arc-generating device which can eject a concentrated and stable directional arc in spite of relatively simple and easily manageable construction of the device.

Another object of the present invention is to provide a directional arc-generating device which can effectively maintain a concentrated and stable directional arc without necessitating electrode adjustment irrespective of consumption of the electrode members.

The above and other objects of the invention have been attained, according to the present invention, by a device comprising a plurality of electrode members each of which has a discharge surface slanted toward the inner and lower part thereof from its upper peripheral edge, said electrode members being assembled as an electrode assembly so that a conically concaved discharge space is formed by the discharge surfaces of all electrode members and a longitudinal narrow gap is established between angular-shaped longitudinally sectioned surfaces of adjacent electrode members, whereby an electric arc stream is generated along said discharge space successively per two opposite discharge surfaces, thus establishing a directional arc along the common axis of the discharge surfaces.

The foregoing and other objects as well as detailed features of the invention will become more apparent and more readily, understandable by the following description when read in conjunction with the accompanying drawings, in which the same or equivalent members are designated by same numerals and characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an electrode assembly illustrating the device of the invention;

FIG. 2 is a taken view, sectional vertically, along line (II--II) in FIG. 1;

FIG. 3 is a plan view of another example of the invention, said view corresponding to FIG. 1;

FIG. 4 is a sectional view along line (IV--IV) in FIG. 3;

FIG. 5 is a schematic side view of a directionally ejected arc stream generated by the electrode assembly illustrated in FIG. 1;

FIG. 6 is a circuit diagram showing connection of a two-phase voltage with the electrode members in the case when said voltage is applied to the electrode assembly illustrated in FIG. 1 or FIG. 3;

FIG. 7 is a plan view of another example of the electrode assembly of the invention;

FIG. 8 is a sectional view along line (VII--VII) in FIG. 7;

FIG. 9 is a side view showing the electrode assembly illustrated in FIGS. 7 and 8; and

FIG. 10 is a circuit diagram showing an example of connection of a three-phase voltage with the electrode members in the case when said voltage is applied to the electrode assembly illustrated in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

The invention is based on the fact that when an expansion pressure produced by any electric arc is directed toward an axis of a restricted space of conical configuration within said space and said arc is successively generated along said space, the electric arc is directionally ejected along the axis of said space.

In the following, the invention will be described in detail in connection with the drawings. Referring to FIGS. 1 and 2; 1, 1a, 2 and 2a are respectively electrode members each having a form corresponding to an assembly obtained by cutting vertically a short cylinder into four symmetrical members. Each of the electrode members is sloped at its upper portion from its upper peripheral edge toward the inner and lower portion thereof, said sloped surface forming a discharge surface. Four electrode members 1, 1.sub.a, 2 and 2.sub.a are assembled as an electrode assembly having a short cylindrical form as shown in FIG. 2, whereby a conically concave discharge space is formed by the discharge surfaces of all electrode members, and a longitudinal narrow gap 3 is established between each pair of adjacent electrode members.

In the electrode assembly as illustrated in FIGS. 1 and 2, if a pulse-shaped DC or AC voltage is applied for a moment, to any pair of the electrode members, an arc discharge occurs between the electrode members of said pair, whereby a violent thermal expansion pressure is produced in the discharge space. This pressure presses forcibly the circumferential surface of the conically concave discharge space, whereby a reaction force is generated toward the central axis of the discharge space, thus causing intentional ejection of the arc stream along said axis of the discharge space. However, since in the above case an instantaneous voltage is applied, arc ejection is established for a moment only. For the purpose of securing a continuous ejection of the discharge arc in the discharge space, it is only necessary to generate an arc between electrode members in a successive and wavy manner. In this case, the successively generated elemental arcs are continuously ejected toward the central axis of the discharge space, whereby an assembled arc stream directed along said axis is continuously ejected, said assembled arc being shown in FIG. 5, in which l corresponds to length of the ejected arc stream. In this case, the length l can be extremely lengthened by providing a large discharge capacity, but since increases in expansion pressure leakage passing through the longitudinal gap 3 will increase with said discharge capacity, said gap 3 should be narrowed as much as possible within the range capable of suppressing short circuits between adjacent electrode members. As described above, only intermittent switching of the voltage applied to each pair of the electrode members is necessary in order to generate intermittently successive discharge arc. However, for the purpose of obtaining a stable arc, it is preferable to use an electrode assembly consisting of electrode members of even number, said members being grouped into two groups each consisting of every other electrode members, and to apply one and other phases of a two-phase voltage to said groups, respectively. According to such construction as described above, a well-balanced arc will be generated successively in the concave-shaped discharge space and the arc stream is concentrated on the axial line of the discharge space. A connection diagram for applying a two-phase voltage to the electrode assembly is shown in FIG. 6, in which U- and V-phase voltages are applied, respectively, to the electrode members 2, 2.sub.a and 1, 1.sub.a through respective transformers T.sub.1 and T.sub.2.

The example of FIGS. 3 and 4 is merely different from that of FIGS. 1 and 2 in the form of the longitudinally sectioned surface of each electrode member, and the number and arrangement of the pairs (4, 4.sub.a and 5, 5.sub.a) of the electrode members; and, the form of the conically concave discharge space, and the narrow gaps 3 are substantially equal to those in the example of FIGS. 1 and 2.

In the examples of FIGS. 1, 2 and 3, 4, the concave discharge space is formed to provide a conically-concave discharge surface, but said space may be formed to provide a pyramidally concave discharge surface with same effect.

When the above-illustrated concave discharge space according to this invention is utilized, there is an apprehension that the generated arc will sink down into the narrow gap 3 between the adjacent electrode members, but in practice expansion pressure of the successively generating arc ejects the arc upward along the axial direction of the assembled discharge surface. However, when the inclination of the discharge surface is abrupt, the upward ejection of the generated arc becomes very difficult. Therefore, it is preferable to select the inclination angle of the discharge surface at the central point of the discharge space so as to be at the most 60.degree., and more particularly about 40.degree..

The longest allowable intermittent "off" period of the arc is determined depending upon electrode material, discharge gap, atmosphere and the like. Accordingly, the intermittent period of time should be selected so that the "off" period of the arc may be always shorter than the allowable longest "off" period. As a result of the inventor's experiments, it has been confirmed that the limit of the "off" period corresponds to the period obtained when the discharge is intermitted twice or 1 time per second in the case where each of the electrode members is made of a graphite material having a large thermal inertia, said electrode members being assembled to establish a longitudinal narrow gap of about 1.8 mm. between adjacent electrode members to form a concaved discharge space, and the discharge is made to occur in the air, the discharge period and "off" period being made to be substantially equal to each other. Although the above-mentioned limit is somewhat different in the case of an electrode member made of a metal, in the case of electrode member made of graphite material, even when arc circuit under discharge condition is manually opened, it is possible to continue reproduction of the arc by again closing said circuit within the allowable cease period. Accordingly, in the case of reclosing of the arc circuit, it is possible without fail in spite of transient stoppage of the power source, to connect said circuit with another power source having different current and waveform thereby to switch the arc circuit on a different ejecting condition. Accordingly, it is possible to generate alternately long and short arc streams by repetition of rapid switching of the arc circuit thereby to vary the height of the directional arc stream. For the purpose of causing starting of a directional arc at the concaved discharge space, any conventional method can be adopted, for example, it may be possible to apply a high-frequency voltage across the electrode members thereby to generate a high-frequency arc therebetween or it may be possible to operate a short-circuiting graphite piece to cause a temporary contact thereof with the bottom portion of the concaved discharge space thereby to generate a short circuit arc at the central portion of the discharge surface of said space.

In embodying the present invention, if the electrode members are made of an arc-resisting material, a directional arc can be ejected for a long period of time. Of course, even when the electrode members are made of a consumable material, ejection of a directional arc can be attained for a long period of time so far as said electrode members are enclosed in an inert atmosphere.

However, the arc-generating device according to the invention can particularly exhibit its characteristic properties in the case when the consumable electrode members are used.

The example shown in FIGS. 7, 8 and 9 relates to a case in which consumable electrode members are used. In this example, an elongated cylinder made of a consumable electrode material is symmetrically split into six longitudinal electrode rods 6, 6.sub.a, 7, 7.sub.a, 8, and 8.sub.a each of which is worked at its upper portion to form a discharge surface as in the case of the example of FIG. 1. These electrode rods are bundled by mutually clamping the electrode rods by means of a heat-resisting insulator 9 so that a longitudinal narrow gap 3 is established between adjacent electrode rods of each pair. Of course, although there is no indication in the drawing, the electrode rods may be mechanically bundled into an electrode bundle through a heat-resisting insulator having thickness corresponding to the above-mentioned gap 3 and inserted between adjacent electrode rods of each pair.

Actual bundling of the electrode rods is carried out in such a manner that lower portion of each of the electrode rods is coated with an inorganic refractory material selected from plastic clay and heated to a temperature just below the temperature adapted to convert said material to unglazed pottery, and then the electrode rods treated as above are bundled as an electrode assembly.

Upper portion of each of the electrode rods is sloped, as in the case of the example shown in FIGS. 1 and 3, from its upper periphery toward its lower and inner portion thereby to form a discharge surface, and all discharge surfaces of the electrode rods are assembled to form a concaved discharge space.

Referring to the example shown in FIGS. 7, 8 and 9, as shown in FIG. 10, if the electrode rods (7, 7.sub.a), (8.sub.a, 8) and (6.sub.a, 6) are connected, respectively, to phases U, W, and V of secondary coils of a three-phase transformer primary coils of which are connected to three-phase voltage U, V and W, three-phase arc are successively generated across opposite discharge surfaces of each pair in accordance with phase rotation and this generated arc is continuously ejected along the central axis of the concaved discharge space as described in connection with the example of FIGS. 1 and 3.

Polarities of the electrode rods of each pair, for example, polarities of the electrode rods 7 and 7.sub.a may be reversed by varying their connection, but for the purpose of concentrating polyphase arc along axial direction of the concaved discharge space it is necessary to make each phase arc generate successively onto successively adjacent electrodes so as to cause succession crossing of the arcs.

According to the example of FIGS. 7, 8 and 9, arc stream is symmetric with respect to axial direction of the discharge space and stable as shown in FIG. 5, and furthermore arc discharge is uniformly generated successively along the discharge surfaces forming the discharge space. Accordingly, consumption of the discharge surfaces is strippingly carried out, so that only successive shortening of the electrode rods occurs while maintaining shapes of their discharge surface as they are in spite of consumption of the electrode surfaces. As a result, the gap between adjacent electrode rods is left as it is, so that it is possible to continue ejection of a directional arc stream for a long period of time, without requiring any adjustment of the electric voltage applied thereto.

When one device of this invention is operated by utilizing a single-phase power source, the electrode members of even number are used to form a concaved discharge space and said members are grouped into two groups each having the electrode members of half number, said groups being connected in parallel, one of said groups containing a capacitor or reactor therein, and a single-phase voltage being applied across said two groups.

According to the device illustrated in FIGS. 7, 8 and 9, since it is not necessary to adjust electrodes in accordance with consumption thereof, it is possible to obtain a very convenient portable arc-generating device having a handle, which can carry out point heating by ejecting an arc stream onto a member to be heated or carry out a linear continuous heating by transferring the device along surface of a member to be heated while ejecting arc stream along said surface. Furthermore, according to the device of this invention, heating degree can be easily adjusted by adjusting the distance between the member to be heated and the arc stream.

In practice, the device according to the invention is provided with means for feeding an arc voltage to the electrode members. These means may be realized according to any conventional system applicable for conventional arc welding devices and the like. For example, a metal wire conductor is embeded in each of the electrode members along the axis of the electrode assembly.

The following table relates to the results of an actual experiment carried out in connection with the case in which a device as illustrated in FIG. 9 was adopted and an arc discharge was continued without electrode adjustment. The ejection distance l of the ejected arc stream was about 60--70 mm., and each of the electrode members made of a graphite material was coated with a heat-resisting material. ##SPC1##

Claims

I claim:

1. A directional arc-generating device comprising an electrode assembly having an even number of at least four or more electrode members arranged in an adjacent spaced relation, each said electrode member having a longitudinal planar sidewall disposed in parallel face-to-face relation with a said sidewall of each adjacent said electrode member in said assembly, and each said electrode member having an arc-producing end which slants inwardly to define a conical concave arc-producing end of said assembly which provides a cavity having gaps between said electrode members, said electrode members being arranged in opposed pairs, means engaging said electrode members for maintaining said spaced relation of said electrode members, and means connected to said electrode members for supplying a varying arc-producing voltage successively to said opposed pairs of electrode members to produce intermittent successive arcs between said opposed pairs of electrode members, said arcs being directed outwardly of said cavity.

2. A directional arc-generating device as claimed in claim 1 in which each said electrode member consists of an elongated member made of a consumable electrode material, and in which said means maintaining said electrode members in said spaced relation comprises a heat-resistant insulating device fixedly engaging each said electrode member.

3. A directional arc-generating device as claimed in claim 1, in which said means for supplying a varying voltage includes AC polyphase voltage source means having a pair of terminals for each phase, and means connecting said pairs of terminals, respectively, to said opposing pairs of electrode members.

4. A directional arc-generating device as claimed in claim 1, in which said means for supplying a varying voltage includes pulsed DC voltage source means, and means connecting said voltage source means to said electrode members for successively applying DC pulses to different opposed pairs of electrode members.

5. A directional arc-generating device as claimed in claim 1, in which said means for supplying a varying voltage includes AC voltage source means, and means connecting said voltage source means to said electrode members for successively applying AC voltage to different opposed pairs of electrode members.