US1085266A - Switching device for electric circuits. - Google Patents

Description

M. KALLMANN, DIEGD.

P. KAI-LEARN, ADMINISTRATRIX. SWITCHING DEVICE FOR ELECTRIC CIRCUITS.

APPLICATION FILED JUNE 26, 1906.

Patented Jan. 27, 1914.

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COLUMBIA ILANOCIRAPH CO.,WASHINUTON, D. c.

UNITED STATES T OFFICE.

MARTIN KALLMANN, OF BERLIN, GERMANY; PAULA KALLMANN, OF BERLIN, GERMANY, ADMINISTRATRIX OF SAID MAR-TIN KALLMANN, DECEASED.

SWITCHING DEVICE FOR ELECTRIC CIRCUITS.

Specification of Letters Patent.

Application filed June 26, 1906.

Patented Jan. 27, 1 914. Serial No. 323,538.

To all "Iii/L01 it may concern Be it known that I, Dr. MARTIN KALL- MANN, a subject of the Emperor of Germany, residing at new and useful Improvements in Switching Devices for Electric Circuits; and I do hereby declare the following to be a full, clear, and exact description of the lnvention, such as will enable others skilled in the art to which it appertains to make and use the;

same.

My invention relates to devices in cutouts, reversing-switches, automatic contactbreakers, cell-switches, and the like, and has for its object the prevention of violent breaksparks and flashing at the contacts, though it can also be employed with advantage to prevent extra-currents on the interruption of circuits with high self induction. This is attained by inserting in the circuit at the contact point or place of break or reversal a resistance of high temperature coefficient, especially iron, which on passage of current increases, on being heated to red-heat, many times in resistance and thus weakens the currentto such an extent that the final interruption of the circuit takes place almost without sparking and, any extra-currents remain but small.

Figures 1 and 2 show the changes in cur- I l l Kurfiirstendaunn 4-0/4], 5 Berlin, Germany, have invented certam l l l l I rent strength in a. circuit during the oper i ation of cuttlng off the current through a 1 self-acting resistance as in my improved switch. Fig. 3 shows a single pole switch and the connections between the supplementary switch and the self-actlng resistances.

Fig. I shows a bipol.ar switch with the acconnnlnymg resistance and supplementary switch. Fig. shows means for controlling t the supplementary switch by means of which the current is short circuited through the re- 5 sistance. Fig. 6, shows a device in which an excess of current causes the breaking of the main circuit and the opening of a bypath through the special form of resistance which I I provide. Fig. 7 shows another device for accomplishing the same result. Fig. 8 shows the switch as applied to an accumulator.

The resistance, in order to insure as small 5 a capacity for heat as possible, may be made of very thin iron wire which for the purpose oi preventing oxidation may, like incandescent lamp filaments, be inclosed in a.

vacuum, for instance a glass box or better in an atmosphere of hydrogen or other indifi'ercnt gas. If for example, the resistance is calculated for a currentof 2 amperes. the voltage at its ends increases rapidly with this current strength by reason of the heatmg, while the current remains almost constant, provided that the iron resistance forms the main portion oil the circuit resistance. for example if the increase is from 10 to :30 volts. It is only when a higher ten'lperature is reached that the essential increase in resistance ceases and the current-strength then increases further. In an iron wire for instance, 036 nnn. thick there is 2 volts fall of potential for ampere current, that is 4 ohms resistance; for 1 ampere and mode-rate heating. correspondingly 5 volts and 5 ohms: tor 2 amperes and dark red heat, correspond ingly 22 volts and 11 ohms; for amperes and medium red heat 50 volts and ohms: For 2.3 amperes and bright red heat 75 volts and about 33 ohms. Thus if in a circuit of 220 volts there is a load of 20 amperes corresponding to 11 ohms resistance of the lamps or the like, and it this load were cut out direct, there would be very considerable sparking caused. lt' however, there is introduced at the place of break, in suitable manner, a. reducing resistance, which in working is short-circuited, then on, opening the switch the current at the first moment, (if this resistance when cold is about 4 ohms.) will be 22m ....1amperes.

The break spark with this small change oi current (from 20 to 14.7) is naturally but trifling. Vithin a few seconds the thin iron wire will now become incandescent and increase in resistance to for instance, 33 ohms. The current-strength of the circuit then sinks to 220 r m a amperes.

and these remaining 5 amperes can likewise be interrupted without any considerable sparking. The case is similar on direct short circuiting taking place, where for instance, som Ir} amperes current only have still to be interrupted. This process can be used without dilliculty by simple bridging of the place of break either by a single or multiplepole switch, two breaks or it necessary more stages, being thus employed. In the latter case there are several sections of the reducing resistance to be cut out in stages.

Any form of switch, such as lever, rotary l ture, so that the entire circuit is broken.

or reversing switches with several contacts may be used. lf extremely thin iron wires of say l/ lO mm. thickness be used the redu ing resistance will under certain circumstances be heated to red heat in less than a second, so that a switch may be employed in which the main and shunt circuits are opened in rapid succession.

The use of the reducing resistance is particularly important for automatically opening the circuit. This automatic operation may be applied either only for the shunt switch, while the main switch is opened by hand, or the entire switching operation may be effected wholly automatically. In the first case, as long as the main switch is closed (preferably positively), the shunt switch is also closed, and the reduciru resistance thus short circuited. As soon as the main switch is opened the reducing resistance is cut into the place of break and the working current will flow through it. The current now falls again, as already explained, within a few seconds, by reason of the heating of the reducing resistance, and when it has reached a suitably small value, for example in the above case 5 amperes, an electromagnet, which is traversed either wholly or partly by the main current, releases its armature, which now interrupts the remaining current by cutting out the shunt (reducing resistance).' Thus the electromagnet armature falls of itself shortly after opening of the main switch. This can naturally also be done gradually in several stages if necessary by means of several electromagnets or electromagnetic armatures. For the circuit however, the danger of too great currentstrength is removed immediately on opening of the main switch, since the rapidly increasing reducing resistance the intensity. lVith entirely automatic switching the matter is similar. The reduc ing resistance is combined with an automatic device of suitable construction. 'Whcn the current is excessive the main contact is opened by the operation of a solenoid and the iron resistance is interposed in the path of the current, causing the latter to fall, and. the circuit is then fully opened by the operation of the supplementary switch. The lirst electromagnet would thus soon effect the first interruption in well known manner on too strong a current passing, while tie second electromagnet would release its armature on a sufficiently weak current flowing, thus operating similarly to a Zero automatic switch or a minimum-current cut-out. the maximum and minimum switching may be done simply by single electromagnet which first with too strong a current attracts an armature, thus cutting in the reducing quickly diminishes resistance, and then when the current is sullicienl'ly weakened again, releases the armaln this case suitable double lever switches and the like are necessary for the contacts (a main and a secondary contact).

The combination of the electro-magnet with one or more armatures may be varied as desired corresponding to the construction of the automatic device, the modern electroniagncts of pot or other shape, boxed in as far as possible, being preferably employed.

ln the same manner distance switches, rerersing-switches, double pole switching devices, etc., with the aid of reducers enable practically sparkless break. Similarly circuits with high self-induction (for instance magnetic fields of dynamos or motors) can be broken in this manner without strong extra currents being caused. The action of the reducer when applied to cell-switches ol': accumulators is similar. Here the iron wire reducer is inserted in. well known manner between the two-part cell-switch crank, 0]; Elle. sliding contact, instead of the usual constant resistance. As soon as tle contact bridges a cell, a strong current will llow through the iron resistance and the value of the latter will rapidly increase, so that the discharging current of the cell is quickly den'eased. The advantage here attained is that both the initial spark on closing the cell on the initially very small (cold) resistance. and the subsequent spark on cessation of closin by reason of the then very weak discharging current (since the resistance is in highly incandescent state) are but very small, smaller than when for instance nickeline-resistance, as usually employed for bridging in cell switch contacts, is used. This is of special importance when two cells have to be connected to each contact, for instance with 440 volt installations.

One form of device for carrying out the ab ve described invention is illustrated diagrammatically in 3.

When opening the switch 1 the secondarv switch 2 is still closed, so that the whole current to be consumed, which undergoes a. proportionately small weakening in conse quence of the still cold reductionsresistancc 3. flows through the lamps 4, or the like, and the said reduction-rcsistance. After a few seconds, the resistance 3 has become red-hot. and has consequently been greatly increased. llow the switch 2 can be opened without much sparking, as the current has in the meantime been reduced autou'iatically to a sm: ll fraction of its initial value. Serious sparking is thus avoided, on opening the main switch and also on opening the supplementary switch. On closing the circuit. the switcn 2, or the switch 1, may at will be closed first, or both may be closed at the same time. On opening them, the secondary switch of the reduction-resistance must always follow the main switch, for this secondary switch causes the interruption of the rest of the current.

Fig. 4 represents the system applied to a bipolar switch. Only one reduction-resistance is needed, but it is better to use two r sistances, shown at 3, which are connected both to a branch lead, and the two switches are then made bipolar in the usual way for reducing the break-spark. The working will, at once be seen from the preceding description. The circuit containing an inductive load 5 is in the first place broken by means of the switch 1 and then finally by the switch 2. If very thin iron spirals of an exceedingly small heating capacity are used, the reduction-resistance, which is considerably overloaded by high currents to be broken, or extra currents, becomes red-hot in some cases in less than one second, so that a single quick break switch may be used instead of two switches.

The opehing of the secondary circuit can also be effected automatically in a very simple manner, especially by using reductionresistances which do not become incandescent instantaneously, but only after a few seconds, as illustrated in Fig. 5. Here the current flows from the positive pole in the first place through a coil of a small electromagnet 11, passes over the pivot 12 into the knife of the lever-switch 1, and would, if the circuit were closed, flow in the direction of the arrow over contact 14 into the outer circuit, and from here to the negative pole. If resistance is intercalated, the electromagnet- 11 is excited and attracts its armature 15, against the action of the spring 17, so that the secondary contact 19, 20, and through the same reduction resistance 3 are likewise connected, but in consequence of the short-circuiting by the main lever only a weak current fiows through them. During the switching off of the lamps or motors, the armature 15 would keep the contact 19, 2O closed for an adjusting screw 21 of the main lever insures the mechanical closing of the secondary contact, as long as the main lever is closed. If the main lever switch 1 is opened and the contact broken at 14, the whole current then flows over the armature 15 of the electroi agnet through 19 and 20, and the reduction-resistance 3, and from here over the outer circuit to the minus pole. The breakspark at the main contact 14 is only small on account of the by-path over the reduction-resistance, which offers only a small resistance. After the interruption at 14, the armature 15 of the electromagnet is still held attracted by the electron'zagnet 11, as a strong current still flows through the windings 10. During the increased heating of the reduction-resistance this current sinks,

r l l l l 1 I however, within a few seconds to a fraction of the initial value, for instance, as shown by figures at the beginning, from about 15 to 5 amperes. Armature 15 is released by a spring 17, the contact 19, 20 is broken, and the circuit therefore fully opened. The secondary contact thus ii'ollows automatically the main contact, according to the load on the circuit, for if the strength of the current is very small, the armature 15, after the opening oi the main lever, drops at once otl' the electromagnet. The greater the load is the longer it takes until the current has been weakened suiiiciently, whereupon the secondary circuit is likewise broken. By closing the main switch 1, that is to say, by connecting the load, the contact 19, 20 is mechanically and automatically closed by means of the adjustable screw 21, so that the secondary circuit is always ready to prevent the break-spark as long as the main switch is closed. This form may in the same manner also be adapted for bipolar switches.

Fig. 6 shows in a diagrammatic view the same system for a selfacting switch, which. on a certain strength of current being reached, is intended to break a circuit, while Fig. 7 shows a practical form of construction of a self-acting switch. In Fig. 6 the main contact 23, 24 is closed by a hooked lever 26, pivoted at 27. Contact 23 is connected with a spring 28. The path of the current over the reduction resistance 3 is broken by the contact and 31. If the current in the releasing electromagnet reaches a certain strength it attracts the armature 33, the lever 26 releases the contact 23 (pivoted at 34) from 24, the main contact is opened, and the current flows at the other end of the two-armed lever, which at 35 contains an insulating-piece (the secondary CO11- tact 30, 31 being closed) and through the reduction-resistance 3, into the outer circuit. Here the current is only slightly reduced. as the resistance is still cold. In a very short time, however, for instance after 1 to 2 seconds, the resistance becomes red-hot and in consequence the resistance of the circuit consisting of the lamps or other loads and the reduction-resistance, rises so high that the strength of the current in the electromagnct sinks very considerably, for instance down to about the eighth part. In consequence of this the armature 33 drops oil from the electromagnet under the influence of the spring 30. and thereby the whole circuit, inclusive of the rechlotion-resistance, is opened.

W hile in Fig. 6 the operation of the main lever is effected directly by an ordinary electromagnet, the effect is produced. in Fig. 7 in a different way, which allows of in creasing the sensibility of the electromagnet. Here a special form of the electromagnct shunted to a resistance 3, which may either be formed after the usual manner of the main current resistances or of a resistance of a high temperature coetficient (for instance, iron) for increasing its sensibility. The current therefore flows, if the main switch 1 is closed, through this into the resistance 3 of the main circuit, and through the coil of the electromagnet a0, branching off from the same, into the outer circuit. it the current rises above a certain intensity, the iron core 41 is drawn into the coil of the electromagnet and releases the pawl 42 from the hook as, whereby the main switch 1 standing under the action of the spring at and pivoted to L5 is released from the contact 4L6. Hereby the secondary contacts 47, t8 are also released by the adjusting screw 4:9 but remain still in contact, in consequence of being stopped by pawl 42 and hook 43. This keeps the secondary circuit closed through the reduction-resistance 3. Only when the intensity of the current, in consequence of the increased heating of 3, has sunk considerably, the iron core 4-.1 drops down into the coil of the magnet t0 (the switch being mounted vertically) and strikes against pawl 42, which new releases the hook 13 of the lever 51, so that the latter under the influence ot the spring 52, opens th secondary contact and completely breaks the circuit. According to the preceding calcu lations and examples, the opening of the main contact, as well as of the secondary contact, takes place without much sparking. In the same manner, distance-switches, reversing-switches, double pole switching devices, etc., with the aid of reducers, produce a practically sparkless break. Similarly circuits with high self-induction (for instance magnetic fields of dynamos or motors) can be broken in this in anncr without strong extra currents being caused. The action of the reducer when applied to cell-switches ol accumulators is similar, as shown in Fig. 8. This is of special importance when, for example, two cells have to be connected to each contact, for instance with &0 volt installations. Here is intercalated instead of the usual constant re stance, which consists. as a rule, of some windings of nickeline wire, or the like, a reduction-resistance 3 of iron, or the like, inclosed it necessary in a glass reservoir with hydrogen, between the crank ot the cell-switch formed of two parts 60 and 61. The secondary contact 61 is insulated in the usual manner fr m the main contact and from the axle (32. or the current supply, by an insulated piece (55. In the position shown in the drawing, the currentwould on moving the eell-switch flow from contact 6?) over 60, 3, 61, (34L. As the resistance 3 was thus far still cold, there does not take place during this movement of the crank oi": the cell-switch any noticeable weakening of the outer circuit, and theretore no reduction of the tension. Now the reduction-resistance 3 is heated until it becomes red-hot, and its ohmic value is thereby considerably increased and the rate of discharge of the cell or cells of the accumulator is thereby lessened. ll ithin one second the cell-switch may now be moved one cell farther on, in consequence of which the short-circuiting of the cell. by the reduction resistance ceases, without the formation of any considerable break-spark, for the current to be broken is then only very weak. T he same operation is repeated and the spark is very small on the succeeding contacts, in consequence of the described properties of the reduction-resistance, which during its movement from cell to cell must have suiticient time to alternately cool down and get hot. In this way all other devices for the arresting of sparks can be entirely dispensed with, while violent shocks of current during the movement of the cell-switches and reactions upon the tension of the system are reduced to a minimum, in consequence (it the described properties.

Having thus described my invention. what 1 claim as new is: i

l. The combination of: an electric circuit. a switch therein, a second circuit, a supplementary switch and a resistance of a high positive temperature coetticient in the second circuit and means whereby the latter switch is operated by the operation of the main switch in one direction, said supple nientary switch being mechanically indc' pendent of the operation of the main switch in the other direction, means operated by an excess of current for opening the main switch, and a member also operated by such means for releasing the supplen'ientarv switch. I

The combination of an electric circuit, a switch therein, a second circuit, a supplementary switch therein, the latter being me chanically independent of the operation oil the main switch during the opening operation. and electrical and mechanical means autmnatically operated tor opening the supplementary switch at an interval after open ing the main switch, such electrical means including a conductor having a high positive temperature coetlicient connected with the supplementary switch, the duration oi said interval. being determined, by the effect of the current on such conductor.

3. In. an electric switch the combination et a main switch, a supplementary switch 'acent thereto, mechanical means for closthe supplementary switch by the operaon of the main switch, and electrical and mechanical means ii or automatically opening the supplementary switch at an interval utter the opening ot the main switch, such electrical means including a conductor having a high positive temperature co-eflicient connected with the supplementary switch, the duration of said interval being determined by the effect of the current on such conductor.

4-. In an electric switch the combination of a main switch, a supplementary switch adjacent thereto, adjustable mechanical means for closing the supplementary switch by the operation of the main switch, and electrical and mechanical means for auto matieally opening the supplementary switch at an interval after the opening of the main switch, such electrical means including conductor having a high positive temperatune eo-eflicient connected with the supplementary switch, the duration of said interval being determined by the effect of the current on such conductor.

The combination of a main electric cir" cuit, a switch therein, a second circuit, a supplementary switch therein, a device on said main switch adapted to contact with said supplementary switch, a resistance of a high positive temperature coefficient in the second circuit, a solenoid, a pawl actuated by the armature thereof for releasing the main switch, and means engaging the supple inentary switch and holding it closed until the current passing through the solenoid is sufliciently reduced to cause the armature to return to its normal position.

6. The combination of a main electric cireuit, a switch therein, a second circuit, a supplementary switch therein, hooks on each of said switches, a solenoid, a pawl engaged by the armature thereof when an excess of ciurrent is caused to pass through said solenoid, said pawl when operated releasing and openin the main switch, a second pawl simultaneously engaging the hook on the suppleineutary switch and holding it closed while the excess of current is passing through the solenoid, means connected with the main switch adapted to contact with the supplementary switch and a resistance of a high positive temperature coefficient in said second circuit.

7. The combination of an electric circuit, a switch therein, a second circuit, supplementary switch therein, and a resistancehaving a, high positive temperature coefficient in the second circuit, the latter switch remaining closed after opening the main switch. and means for effecting in connection with the resistance the automatic release of the supplementary switch after an interval following the opening of the main switch.

In testimony whereof, I afliX my signature, in presence of two witnesses.

Du. MARTIN KALLMANN. lVitnesses lVoLDnrmR IIAUPT, HENRY HAsPER.

Copies 01' this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C.

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