US2798187A - Device for controlling the welding times and intervals in resistance welding apparatus - Google Patents

Description

July 2, 1957 K. w. HESS ET AL 2,798,187 DEVICE FOR CONTROLLING THE WELDING TIMES AND INTERVALS IN RESISTANCE WELDING APPARATUS Filed May 13, 1954 INVENT I FRANS HENDRIK DE ,JONG LAMBERTUS WILHELMUS ROOSENDAAL KARL WALTER HESS AGENT DEVICE FOR CONTROLLING THE WELDENG TIMES AND INTERVALS 1N RESHSTANCE WELDING APPARATUS Karl Walter Hess, Frans Hendrik De long, and Larnhertns Wilhelmus Roosendaal, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc, New York, N. Y., a corporation of Delaware Application May 13, 1954, Serial No. 429,626

Claims priority, application Netherlands May 18, 1953 3 Claims. (Cl. 315-166) The invention relates to a device for controlling the welding times and intervals in resistance welding apparatus. This is accomplished by means of a capacitor which is charged from a direct current source through a resistor and is discharged through a controllable gas or vapor-filled auxiliary discharge tube. The auxiliary discharge tube-capacitor-circuit includes means, for example a transformer, which transmits the discharge pulses as control pulses to one or more controllable gas or vapor-filled discharge tubes and the auxiliary discharge tube is controlled by means of a voltage derived from the combination capacitor-resistor in series with two series-connected voltage sources one of which provides control pulses of large amplitude. The time between two of said successive pulses is controllable and also determines the sum of a welding time and an interval, whereas the second voltage source provides small amplitude pulses at power supply frequency determining a welding-time. Moreover, the control electrode of the auxiliary discharge tube after a small amplitude power supply frequency ignition pulse has an additional negative bias voltage applied to it.

According to a further feature of the invention the said control pulses are supplied to the interconnected control electrodes of two gas or vapor-filled discharge tubes which in a relaxation circuit are connected in parallel to a direct voltage source. A quenching capacitor is provided between the two anode-cathode-circuits, while a resistor included in one of the anode circuits of the relaxation circuit provides control pulses of rectangular form for determining a weld time and an interval.

The above and other features, objects and advantages of the present invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings, wherein:

Fig. 1 is a schematic diagram of the device embodying the present invention for controlling welding intervals; and

Figs. 2, 3, 4, 5, and 6 are graphic representations of the operation of the present device.

Referring now to Fig. 1, a gas or vapor-filled discharge tube 1 is connected through a transformer 2 and a resistor 3 to a direct current source 4. The grid circuit of the tube 1 includes a peak voltage transformer 5 which is connected to the alternating current power supply lines, if desired, through a phase-shifting device. After a capacitor 6 has been sufiiciently charged through the resistor 3, with the result that the cathode assumes substantially the potential of the negative terminal of the direct voltage source, the tube 1 ignites due to the voltage peaks from the transformer 5 so that the capacitor 6 is discharged through this tube and a voltage pulse is transmitted to the secondary 7 of the transformer 2.

This will be more fully appreciated by reference to Fig. 2. The anode voltage relative to the cathode is Fatented July 2, 1957 designated 8 and corresponds with the increasingly rising voltage across the capacitor during the charging process. The grid voltage 9 also varies in accordance with the charging curve of the capacitor, however, the grid voltage curve 9 also has the voltage peaks 10 from the transformer 5 superposed on it. The line 4 represents the voltage of the direct current source 4. At the instant t1 the grid voltage exceeds the ignition characteristic 11 with the result that at this instant the tube 1 ignites and the capacitor 6 is discharged. As a result a voltage pulse of large amplitude is set up at the secondary 7 of the transformer 2, which pulse is designated 12 in Fig. 3. This is repeated, so that each time after a period (x+y) a voltage peak 12, 12', and so on, occurs. The period (x-l-y) is adjustable by varying the capacitor 6 (or the resistor 3) with the result that the period of time weld-time interval is adjustable.

Fig. 1 further shows an auxiliary discharge tube 13 which is connected to a second direct voltage source 14 in series with the direct voltage source 4. The anodecathode-circuit includes a capacitor 15 and a transformer 16. The capacitor 15 is connected through a resistor 17 to the negative terminal of the direct voltage source 14. When the capacitor 15 is sufficiently charged from the voltage source 14 through the resistor 17 and a control pulse causes the tube 13 to ignite, the capacitor 15 will be discharged through the tube and the transformer 16. This results in a voltage pulse being set up at the secondary of the transformer 16 which pulse is transmitted to the two interconnected grids 18 and 19 of the two gas or vapor-filled discharge tubes 20 and 21. These tubes are connected in parallel to the direct voltage source 4 in a relaxation circuit. A quenching capacitor 22 is provided between the anodes of the two tubes, the anode circuits also including resistors 23 and 24 and the common cathode lead including a resistor 25 for the negative grid voltage of the two tubes.

The control circuit of the tube 13 is constituted by the grid of this tube, the secondary '7, the secondary 26 of the peak voltage transformer 27, the primary of which is connected to the power supply lines, the resistors 24 and 17, the primary of the transformer 16 and the cathode of the tube 13.

The device to which rectangular control pulses are supplied is designated 28 and is connected to the anode resistor 24.

it is assumed that the capacitor 15 is sufiiciently charged through the resistor 17 according to the curve 29 (see Fig. 4) and that at the instant t the voltage peak 12 of great amplitude is supplied through the secondary 7 to the grid of the tube 13. Thereupon the tube ignites, with the result that the capacitor 15 is discharged and the transformer 16 transmits a control pulse 30 (see Fig. 5) to the two tubes 2% and 21 at the instant t Assuming that prior to the instant t, the tube 21 passed current, at the instant t the tube 20 will be ignited by the control pulse 30 and the tube 21 will be extinguished (see Fig. 6).

After the capacitor 15 has been discharged, it will be recharged through the resistor 17 from the voltage source 14 (see29 of Pig. 4) in which case the negative bias voltage 14 of the tube 13 initially is equal to the voltage of the voltage source 14 (as is shown in Fig. 4) since the resistor 24 does not pass current. The grid voltage increases according to the curve 31 which has the voltage peaks 32 of small amplitude supplied from the transformer winding 26 superposed on it. At the instant t the ignition characteristic of the tube 13 is exceeded and this tube is re-ignited. As a result a control pulse 36 (see Fig. 5) is again supplied from the transformer 16 to the two tubes 20 and 21 so that the tube 21 is ignited and the tube 20 is extinguished (see Fig. 6). The voltage drop across the resistor 24 is transmitted to the device 28 in the form of a rectangular voltage 33.

However, the negative grid voltage of the tube 13 has increased by a value equal to the voltage drop across the resistor 24, which increase is designated 34 in Fig. 4.

The capacitor 15 is again charged but the grid voltage curve of the tube 13 now varies according to the curve 31 having the voltage peaks 32 of small amplitude superposed on it with the result that within a definite period of time the ignition characteristic cannot be exceeded. This is only the case when a voltage peak 12' of great amplitude (see Figs. 3 and 4) is supplied by the transformer winding 7 at the instant t,. The tube 13 is reignited and a control pulse 30 (see Fig. is supplied to the tubes 20 and 21 with the result that the first one is ignited and the second one is extinguished (see Fig. 6).

Thus the period (x+y) can be divided into a period x and a period y the duration of which determines a weld time or an interval, or vice versa. The rectangular voltages 33 (see Fig. 1) may in addition have voltage peaks 35, for example for igniting additional discharge tubes, superposed on them.

While we have shown and described the preferred embodiment of our invention, it will be understood that the latter may be embodied otherwise than as herein specifically illustrated or described and that in the illustrated embodiment certain changes in the details of construction and in the arrangement of parts may 'be made without departing from the underlying idea of principle of the invention within the scope of the appended claims.

What is claimed is:

l. A device for controlling the duration of a cycle of welding and non-welding intervals of time in resistance welding apparatus, said device comprising a first capacitor, a first resistor, means for charging said capacitor through said resistor, a first discharge tube having an ionizable medium and a control electrode, said capacitor being connected to said tube to discharge therethrough during predetermined intervals to produce discharge pulses therein, circuit means for applying control voltages to said tube for discharging said capacitor, said circuit means comprising two series connected pulse voltage sources, one of said two series connected voltage sources producing voltage pulses having a magnitude considerably greater than the pulses produced by the other of said two sources, the duration between successive greater pulses being adjustable and determining the duration of said cycle, the pulses of the other of said two sources determining said welding interval of time, said circuit means further including means for applying a negative bias voltage to said control electrode during said welding interval of time, a controllable discharge tube assembly having an ionizable medium, and means for applying said discharge pulses to said assembly to control same.

2. A device as set forth in claim 1 wherein said controllable discharge tube assembly includes two discharge tubes each having an ionizable medium, a cathode, a control electrode and an anode and circuits therefor, said control electrodes being interconnected, and further comprising a relaxation circuit including a direct voltage source, said two discharge tubes connected in parallel to said direct voltage source, a second resistor connected in the anode circuit of one of said two tubes, at quench capacitor connected between the anode-cathode circuits of said two tubes, and means for applying said discharge pulses to said interconnected control electrodes, whereby control pulses of rectangular form for determining the weld and non-weld intervals of time are produced across said second resistor.

3. A device as set forth in claim 2 wherein said means for applying a negative bias voltage includes said second resistor connected to the control electrode of said first discharge tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,128,367 Kock Aug. 30, 1938 2,573,360 Rockafellow Oct. 30, 1951 2,605,305 Stadum July 29, 1952

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