US2242894A - Control system - Google Patents

Description

, May 20, 1941- F. w. LYLE 2,242,894

CONTROL SYSTEM Filed June zo, 1939 Patented May 20, 1941 CONTROL `SYSTEM Frederick W. Lyle, Wlkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 30, 1939, Serial No. 282,174

(Cl. Z50- 27) 15 Claims.

My invention relates to control systems and it has particular relation to control systems utilizing electric discharge apparatus for controlling the ilow of power from a source to a work circuit,

An object of my invention is to provide a system of simple structure incorporating a minimum of auxiliary discharge devices for controlling the current flow through a pair of main electric discharge devices.

Another object of my invention is to provide a system of simple structure incorporating a minimum of auxiliary discharge devices for controlling current flow through a pair of main electric discharge devices of the immersed-ignition-electrode type connected in anti-parallel.

A more general object of my invention is to provide a novel circuit for controlling an electric discharge device of the immersed-ignition-electrode type.

A further object of my invention is to provide a simple, efcient, and inexpensive system for controlling the current ow from a source to a load.

An ancillary object of my invention is to provide a resistance, spot and seam welding system of simple construction that shall operate reliably and eiliciently.

In accordance with my invention, power is supplied to the material to be welded, or to any other suitable load, from an alternating-current source through electric discharge devices of the arc-like type. The main discharge devices are controlled by an auxiliary discharge device of the arc-like type. When the latter is rendered conductive, current flows through the main discharge devices and the load, and when the auxiliary discharge device is non-conductive, the current ilow through the main discharge devices is interrupted. The auxiliary discharge device is rendered conductive and maintained conductive for a predetermined time interval by control and timing means.

The control system for a pair of electric discharge devices of the immersed-ignition-electrode type connected in anti-parallel is simplied, in accordance with my invention, by interconnecting the ignition electrodes of the discharge devices through a high impedance network made up of relatively low impedance elements, and supplying ignition current to the discharge devices through the 10W impedance elements. In particular, the ignition electrodes are interconnected by a network comprising a plurality of rectiers. To supply ignition current, the impedance of the network is controlled by means of the auxiliary discharge device referred to hereinabove.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a speciiic embodiment when read in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic View of an embodiment of my invention;

Fig. 2 is a partial diagrammatic view showing a modification of my invention; and

Fig. 3 is a diagrammatic view showing another modification of my invention.

The apparatus shown in Figure 1 comprises a welding transformer 3, to the terminals of the secondary 5 of which a pair of Welding electrodes 1 are connected. The electrodes engage the material 9 to be welded and when current is transmitted through a primary of the transformer, welding current iiows through the material.

The primary of the transformer is supplied from an alternating-current source I3, which may be of the usual 60-cycle commercial type, through conductors l5, |1 and I9, and a pair of electric discharge devices 2| and 23 connected in anti-parallel. The discharge devices are of the immersed-ignition-electrode type. The discharge device 2| has an anode 25, a mercury pool cathode 21, and an ignition electrode 29. Similarly, the discharge device 23 has an anode 3|, a mercury pool cathode 33 and an ignition electrode 35.

The discharge devices 2| and 23 may be replaced by grid-controlled discharge devices Dro- Vided a proper resistor, and if desired, a source of biasing potential, are shunted between the control electrode and one of the principal electrodes of each such substituted grid-controlled discharge device.

The ignition electrodes 29 and 35 of the discharge devices are interconnected by a pair of back-to- back rectiers 31 and 39, each rectifier having an anode 4| and a cathode 43. The anodes 4| are connected to a common junction 45 and the cathodes 43 of rectiers 31 and 39 are connected to starting electrodes 29 and 35, respectively. A second pair of rectiers 41 and 49, each having an anode 5| and a cathode 53, are connected back-to-back between the cathodes 21 and 33 of the main discharge devices 2| and 23, so that the cathodes 53 are connected to a common junction While the rectiiiers 3l, 39, il and i9 are preferably of the dry type, it will be understood that rectiers of the electronic type may be utilized.

To control the flow of ignition current through the starting electrodes 29 and 35, an auxiliary discharge device 5i is provided. The latter is preferably of the arc-liketype and comprises an anode 59, a hot cathode Si, and a control electrode 63 and a gaseous medium at a suitable pressure. The cathode tl of the auxiliary clharge device 5l is connected to the junction d5 of rectiers 3l and 3Q. The anode E@ of the auxiliary discharge device is connected to the junction 55 of rectiiiers 4l and d.

To control the energization of the auxiliary discharge device 5l, control potential is impressed between the control electrode 63 and the cathode 6| by control and timing means It will be understood that conventional starters or timers, many o which are well 1noi/vn in the art, may be utilized for controlling the auxiliary discharge device 5l. 4

To initiate a welding operation, a circuit con troller 61| which is preferably manually operated and may be a foot switch oi a push-button, is closed to thus initiate the operation of the control and timing means d5 and because of the potential thereby impressed on control electrode 53, the auxiliary discharge device 5l is rendered conductive.

Assume that at the instant under consideration, the polarity of the source i3 is such that the anode of the left-hand discharge device 2| and the cathode 33 of the right discharge device 23 are positive relative to the cathode 2li of the left-hand discharge device and the anode 3| of the right-hand discharge device. Ignition current will then flow through a circuit which extends from the energized conductor i5 through rectiiier 49, anode 59 and cathode Si of auxiliary discharge device 51, rectier 3l, ignition electrode 29, cathode 2l to the energized conductor il. This ignition current causes discharge device 2| to be rendered conductive and current to flow from source i3 through the left-hand discharge device 2| and primary l of the Welding transformer 3. Current does not flow through the right-hand discharge device because at this time its anode 3| is negative relative to its cathode 33, and starting electrode is deenergized.

When the potential of the source i3 reverses, the ignition current flows from energized conductor |'i through rectifier d?, auxiliary discharge device 5l, rectifier 39, control electrode cathode 33 to energized conductor iii. However, at this time, the anode potential of the righthand discharge device 23 is positive and the latter is rendered conductive, While the left-hand discharge device 2| is not conductive. It is to be noted that as soon as one or the other of the main discharge devices 2l or 23 is rendered conductive and this occurs immediately after the initiation of current flow through the associated electrodes, the rectifiers di and 3l or rectiers 4l and 3?, respectively, and auxiliary discharge device 5l are short-circuited by the main discharge `device and the current iiow through the ignition electrodes 29 and 35 is discontinued for the remainder of the half cycle. In this manner, power loss and the other disadvantages arising from the continuous current iiow through the ignition electrodes, is avoided.

After a time interval predetermined by 'the operation oi the control and timing means 65, the auxiliary discharge device 5l is rendered nonconductive. Thus ignition current no longer flows through ignition electrodes 29 and S5 and the rectiiiers 3Q, ill and lit. The main dis-- charge devices 2| and 23 become non-conductive and remain non-conductive and the current ow through the welding transformer 3 is discontinued. The auxiliary discharge device 5l remains non-conductive until the ner: cycle of operation is initiated by the closing ol` switch 84 or automatically reinitiated after a predetermined time by the control and timing means The rectiers 3l and 3S connected between the starting electrodes 29 and may be replaced by a network 5i' comprising an inductor 69 shunted by a capacitor li, as shown in Fig. 2. The cathode El or auxiliary discharge device 5'.' is connected to an intermediate tap 'i3 on the inductor E9. The inductor 69 and the capacitor 1| are preferably tuned to the alternating-current supply frequency to constitute an antiresonant circuit, but this is merely an ancillary feature as capacitor 'i may be omitted, or a resistor substituted for inductor Gil. rihe operation of the system modified as shown in Fig. 2 is substantially the same as the operation hereinabove described with reference to 1Iig. l.

The modification shown in Fig. 3 is the same as that shown in Fig. 1 except that the rectiers di and (5f-l and the auxiliary discharge device 5l have been omitted. An auxiliary electric discharge device having a plurality of iilamentary electrodes or hot filaments l1, 'i9 and 8| and control electrodes 83 and 85, is connected be tween the cathodes 2l and 33 of the main discharge devices El and 23, so that electrode 11 is connected ythrough an impedance Sl to cathode [l and electrode i9 is connected through an impedance t9 to cathode 33. The electrode 8| is connected to the junction i5 of rectiiiers 31 and Batteries il and 93 each having a terminal voltage greater than half the peak alternating potential of the source i3, or any other suitable source or" control potential, are connected between the control electrodes 33 and 85 and the electrode 8l. To control the operation of the system a control device S5 having stationary contact members and S9 and moving contact members iti is utilised. When the control circuit is closed through contact members 9T and the auxiliary device is maintained in the deenergized condition. When the control circuit is closed through contact members 9G and IGI, the auxiliary device becomes energized and alternating-current from source it passes through the discharge device iii through a circuit which eX- tends from the energized conductor l5, impedance d3, lectrode i9, electrode il, impedance 3l, to energized conductor l2. When the polarity of the source is such that anode 25 is positive relative to cathode 2l, ignition current will flow through a circuit which extends from the energized conductor i5, through impedance 83, electrode electrode iii, rectier 3l, ignition electrode to the energized conductor Il'. Discharge device 2i is then rendered conductive while discharge device 28 remains non-conductive as hereinabove described with respect to l. Similarly, when the polarity of the source I3 is reversed, discharge device 23 is rendered conductive while discharge device 2| is nonconductive It will be recognized that the control device 95 of Fig. 3 or the control and timing means 65 of Fig. 1 may be replaced by a conventional timing device, many of which are well known in the art. Timing means of the type described in a copending application Serial No. 34,003` of John W. Dawson, filed July 31, 1935, and assigned to the Westinghouse Electric & Manufacturing Company may be utilized. The addition of the Itiming means to systems constructed according to my invention will be apparent to persons skilled in this art. For example, in applying the timer shown in Fig. 1 of Dawson in place ofY control device 95, the operating coil of relay 58 and switch 51 are connected in series across the source I3, The primary winding of transformer 43 is also connected across the source I3. The negative terminal of battery 34 is connected to the control electrodes 83 and 85 and the conductor 39 is connected to junction 45.

It is to be noted that while the discharge devices I and I6 are illustrated as separate valves, they may, under certain circumstances, be replaced by a single double-polarity discharge device comprisng a pair of mercury pool electrodes in each of which an ignition electrode is immersed.

I do not wish to be restricted to the specic structural details, arrangement of parts or circuit connections herein set forthy as various modiflcations thereof may be effected without departing from the spirit and scope of my invention.

I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

l. In combination, a pair of electric discharge devices connected in anti-parallel, each discharge device having a plurality of principal electrodes and an ignition electrode in contact with one of the principal electrodes, means for impressing an alternating potential between said principal electrodes, a pair of rectiers having like terminals connected together, said first pair of recti* ers being connected in parallel with said discharge devices, a second pair of rectiers having like terminals connected together, said second pair of rectiiiers being connected between the said ignition electrodes, and a common circuit, including an auxiliary discharge device, connected between the said pairs of rectiers for controlling the ignition current through said ignition electrodes.

2. In combination, a pair of electric discharge devices connected in anti-parallel for controlling the supply of power from a source to a work circuit, each discharge device having an anode, a mercury pool carthode and an ignition electrode in contact with said cathode, a network comprising a first pair of rectiers having like poles connected together, said rst pair of rectiers being connected between the said control electrodes, a second pair of rectifiers having like poles connected together, said second pair of rectifiers being connected between the said anodes of the said pair of discharge devices and an auxiliary electric discharge device connected between the common junction of the first pair of rectiers and the common junction of the said second pair of rectifiers, and control means associalted with the said auxiliary discharge device for controlling the energization of the said pair of discharge devices.

3. In combination, a pair of electric discharge devices connected in anti-parallel for controlling the supply of power from a source to a work circuit, each discharge device having an anode, a

cathode, and an ignition electrode immersed in said cathode, a parallel-tuned network consisting of a plurality of impedances and tuned to the frequency of said source, connected between the ignition electrodes of said valves, one of said impedances having an intermediate tap, a pair of back-to-back rectifiers connected between the anodes of said pair of discharge devices, an asymmetrically conductive auxiliary discharge device having a plurality of principal electrodes, means for connecting one of the principal electrodes of said auxiliary discharge device to the intermediate tap of said one impedance, means for connecting the other principal electrode to the common junction of said rectifiers, and means associated with the said auxiliary discharge device for controlling the energization of the said pair of discharge devices.

4. In combination, a pair of electric discharge devices connected in anti-parallel for controlling the supply of power from a source to a work circuit, each discharge device having a plurality of principal electrodes and a control electrode, a network having one portion comprising a first pair of rectifiers and an auxiliary electric discharge device connected between the said control electrode and one of the principal electrodes of one of the said pairs of discharge devices, and having another portion comprising a second pair of rectiers and the said auxiliary discharge device connected between the said control electrode and one of the principal electrodes of the other of the said pair of discharge devices and control means associated with the said auxiliary discharge device for controlling the energization of the said pair of discharge devices.

5. For use in supplying an alternating current load from a source of alternating current, the combination comprising a pair of electric discharge devices of the immersed ignition electrode type connected in anti-parallel between said source and said load, each of said discharge devices having an anode, a cathode, and an ignition electrode immersed in said cathode, a first pair of rectiers connected between the anode and the ignition electrode of one of said discharge devices, a second pair of rectiiiers connected between the anode and the ignition electrode of the other of said discharge devices, and a common circuit interconnecting the said first pair of rectiers and the said second pair of rectiers, the said common circuit including means for controlling the ow of current through said rectiers and said ignition electrodes to render the said discharge devices conductive.

6. For use in controlling the supply of power from a source of periodically pulsating potential to a load, the combination comprising a pair of electric discharge devices each having a plurality of principal electrodes and a control electrode, a rrst pair of rectiiiers connected between the control electrode and one of the principal electrodes of one of the said discharge devices, and a second pair of rectiiers connected between the control eiectrode and one of the principal electrodes of the other of said discharge devices, the said rectiers being interconnected by a common circuit including means for controlling the ow of current through the said rectiers to control the energization of the said discharge devices.

7. For use in supplying an alternating current load from a source of alternating current, the combination comprising a pair of electric discharge devices of the immersed-ignition electrode type connected in anti-parallel between said source and said load, each of said discharge devices having an anode, a cathode, and an ignition electrode immersed in said cathode, a rst pair of rectifiers having like poles connected together, said first pair oi rectiers being connected between the said ignition electrodes, a second pair ci rectifiers having like poles connected together, said second pair ol rectifiers being connected in parallel with said discharge devices, and means for transmitting current through the said rectiners and said ignition electrodes to render said discharge devices conductive.

8. in combination, an alternating current supply having two line conductors, two electric discharge devices each having an anode, a cathode and a control electrode, said discharge devices being connected to deliver current to opposite conductors of said supply, two unilaterally-conductive current paths having a rst set oi like terminals connected together and a second set of like terminals connected respectively to the opposite conductors oi said supply, a network having a neutral point, said network being connected in series with the control electrodes of said two discharge devices across said two conductors, and means including a control electrode to control current flow between said neutral point and said set of like terminals.

9. In combination, an alternating current supply having two line conductors, a pair of electric discharge devices oi' the immersed ignition electrode type connected in antiparallel to deliver vcurrent to opposite conductors oi said supply,

each discharge device having an anode, a cathode and an ignition electrode immersed in said cathode, two unilaterally-conductive current paths having a nist set of like terminals connected together and a second set of like terminals connected respectively to the opposite conductors of said supply, a network having an intermediate terminal, said network being connected in series with the ignition electrodes and cathodes oi said two discharge devices across said two conductors, and means including a control electrode to control current iiow between said intermediate terminal and said first set or" terminals.

10. In combination, an alternating current supply having two line con-ductors, two electric discharge devices each having an anode, a cathode and a control electrode, said discharge devices being connected to deliver current to opposite conductors or said supply, two unilaterally conductive current paths having a common junction and a pair of terminals, said terminals being connected respectively to opposite conductors of said supply, a network comprising a pair of unilaterally conductive current paths having a set of like terminals connected together, said network being connected in series with the control electrodes oi said two discharge devices across said two conductors, and control means comprising a single current path for controlling the current iicw between said junction and said set of like terminals.

ll.. 1n combination, an alternating current supply having two line conductors, two main electric discharge devices each having an anode, a cathode and a control electrode, said main devices being connected to deliver current to opposite conductors of said supply, an auxiliary electric discharge device having three principal electrodes arranged to constitute two unidirectional discharge paths, one oi said principal electrodes being common to both discharge paths, means for connecting the other two electrodes respectively to said two conductors, a network comprising two unilaterally conducting paths having a set of like terminals connected together to sai-d one principal electrode of said auxiliary device, said network being connected in series with the control electrodes of said two main devices across said two conductors, and control electrode means for said auxiliary discharge device.

l2. In combination, a rst and a second main electric discharge device of the immersed-ignition-electrode type connected in antiparallel for controlling the supply of power from a source to a work circuit, each main discharge device having an anode, a cathode, and an ignition electrode immersed in said cathode, a rst control circuit for said first main discharge device, said first control circuit comprising a rst and a second rectifier, an auxiliary discharge device and the ignition electrode and the cathode of said first main discharge device connected in series circuit relation to be energized from said source, a second control circuit for said second main discharge device, said second control circuit comprising a third and a fourth rectifier, the said auxiliary discharge device and the ignition electrode and the cathode of Said second main device connected in series circuit relation to be energized from said source, and control means for said auX- iliary discharge device.

i3. For use in supplying an alternating current load from a source of alternating current, the combination comprising a pair of main electric discharge devices cl the immersed-ignitionelectrode type connected in anti-parallel between said source and said load, each of said main discharge devices having an anode, a cathode, and an ignition electrode immersed in said cathode, a pair of back-touback rectiiiers connected between the ignition electrodes, the said iecticrs having a common junction, an auxiliary discharge device having a pair of anodes, a cathode, and a control electrode, means connecting the anodes of said auxiliary discharge device to the cathodes of said main discharge devices, means for connecting the cathode of said auxiliary discha ge device to the junction of said rectiiiers and means connected between the control electrode and the cathode of said auxiliary discharge device or rendering said auxiliary discharge device conductive.

14. In combination, a pair of electric discharge devices of the immersed-ignition-electrode type connected in anti-parallel for controlling the supply of power from a source to a work circuit, each discharge device having a pair of principal electrodes and a starting electrode immersed in said cathode, two unilaterally conductive current paths having a common junction and a set of like terminals connected respectively to opposite principal electrodes of said discharge devices, a network having an intermediate terminal, said network being connected between the starting electrodes of said discharge devices and means including a control electrode to control current flow between said set of like terminals and said intermediate terminal through said common junction.

15. In a system for controlling the supply of power from a source to a work circuit, in combination, a pair oi? main electric discharge devices connected loetween said source and said work circuit, each of said main discharge devices having a pair of principal electrodes and a starting electrode, a pair of rectifiers having a 'first set of like terminals connected together and having one terminal of a second set of like terminals connected to a principal electrode of one of said main discharge devices and another terminal of said second set of like terminals con nected to a principal electrode of the other of said main discharge devices, a network having an intermediate terminal, said network being connected between the starting electrodes of said discharge `devices and means including an auxiliary electric discharge device having a plurality of principal electrodes and a control electrode connected between the junction of said first set of like terminals of said rectifiers and the said intermediate terminal of said network for controlling the ignition of said main discharge devices.

FREDERICK W, LYLE.

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