US2926298A - Electric switching arrangements - Google Patents

Description

V.L. NEWHOUSE ELECTRIC SWITCI-IING ARRANGEMENTS Feb.l23, 1960 4 Sheets-Sheet 1 Filed 061". 26. 1953 I Il TA CS ATTORNEYS.

Feb- 23, 1950 v. l.. NEwHousE 2,926,298

ELECTRIC swr'rcHING ARRANGEMENTS Filed Oct. 26, 1953 E 4 Sheets-Sheet 2 4| wa/ 4o V1 33\| wH l Il', I@ i 6 I I l conm-NED swlTcHlNs sHo oEvlcE awRlTE HEAD. 32

lo |713/ 40/\ & 4| v 33 L A coMBlEo swncHmc' sm 32 DEVICE awR| TE HEAD.

le lm/ 45d HT coMBNED swrTcHlNs' SH3 32 oEvlcE EwRlTE HEA INVENToR,

VERNON L. NEWHOUSEA BY Mmphew m ATTORNEYS Feb. 23, 1960 v. L. NEwHousE 2,925,298

ELECTRIC 'swITcRING ARRANGEMENTS Filed oct. 2e, 1953 4 sheets-sheet s L@ L@ m L@ m LEE L@ L@ COMBINED SWITCHING RITE Devices Aun w 52 HEADS. /sl s so I7/ F1' mvENToR.

VERNON L. NEWHOUSE Feb. 23, 1960 v. L.. NEwHoUsE 2,926,298

ELECTRIC swITcHING ARRANGEMENTS Filed oct. 26. 1953 4 sheets-sheet 4 VERNON L. NEWHOUSE BY Shanna, ,Mw

ATTORNEYS nited States ELECTRIC SWITCHING ARRANGEMENTS Vernon Leopold Newhouse, Didsbury, England, assignor to National Research Development Corporation, London, England, a corporation `of Great Britain Application October 26, 1953, Serial No. 38\8,232

Claims priority, application Great Britain October 29, 1952 4 Claims. (c1. 323-50) effective energization is meant energization sufficient to cause the utilization device properly to perform its required function. -fThe utilization device may, for example, form part of some signalling system or part of an electronic computing machine and may consume an appreciable amount ofrenergy. f

The invention `has useful but not exclusive application to the switching of the alternating current which serves to energize individually the writing heads of a magnetic drum store of the kind described incopending patent application Serial No. 146,446 of F. C. Williams, now Patent No. 2,734,186, issued February 7, 195-6. In such an application the energy consumed by each utiliza- `tion device, i.e. each writing head, .may be of the order of 10 watts and the speed of switching may have to be Vas rapid as 1 microsecond.

Several known methods are available for switching with such rapidity. -.For example, a separate amplifier valve may be provided for each writing head and the alternating current switched on by applying to the con -trol grid of suchvalve a voltage derived from the unidirectional current.

This arrangement has, however, the disadvantage of requiring a separate valve for each head and as the number of writing heads -is usually fairly large (as many as 256 in one particular case) thenumber The object ofthe present invention is to provide an telectric switching arrangement for the purpose previously stated and which is particularly suitable for operation at high speed but in which the disadvantages of the known arrangements mentioned above are either ob- Aviatecl or materially reduced.

In accordance with the present invention an electric 'switching arrangement for enabling a unidirectional current to cause an alternating current to energize effectively a utilization device includes an inductive component connected as part of the energizing channel between a source of energy and said utilization device, a control winding inductively coupled to` said inductive component and connected across the alternating current terminals of a 'rectifier network and selective means for passngsaid uniice directional current lin the low resistance direction bel tween the direct current terminals of such network,

Vthereby eifectively short-circuiting said inductive component to said alternating current and so causing saidv utilization device to be effectively energized.

Said inductive component may be a choke coil con nected in series with, or effectively in series with, said utilization device and having anv impedance to prevent the effective energization of said utilization device. Alternatively said inductive component may be a iirst transformer one of the windings of whichfis connected in phase opposition with the corresponding winding of a second and substantially similar transformer also forming part of said channel. The aforesaid rectifying network may be a full wave bridge network.

In order that the nature of the invention may be more readily understood a number of constructional embodiments thereof will now be described with reference to the accompanying drawings in which:

Fig. l is a circuit diagram illustrating one arrangement according to the invention for controlling the individual energization of any required' one of a plurality of writing head devices in a magnetic drum store for an electronic computing machine.

Fig. 2 is a circuit diagram, similar to part of Fig. 1, but showing an alternative arrangement.

Fig. 3 is a block schematic diagram, resembling Fig. 1 but illustrating the application of the modification of Fig. 2.

Fig. 4 is a detailed circuit diagram showing an alternative form of certain parts of the diagrams of Figs. 1, 2 or 3. Y -Y Fig. 5 is another detailed circuit diagram showing yet i 114, 1952, by Harry Malbon et al., now Patent No.

2,790,966, issued April 30, 1957, but as the actual construction of such writing head devices is of no relevance to the present invention they will not be further described. RT indicates the recording track of magnetic recording material. The input terminals 10 of each device are connected through terminals 11 to the sec- -ondary winding 12 of a head transformer HTG, HTI,

HT2 HTS individual thereto. Such head transformers are usually mounted immediately adjacent the 4writing head which is associated therewith. The primary winding 13 of each of said head transformers has one end connected to earth and its other end connected by Way of terminal 14 to the output terminal 15 of an associated switching means indicated generically at SMG, SM1, SM2 SMS Each `switching means has an input terminal 16 which is connected to a common busbar 17 which carries the alternating current for energizing the required Writing head. This busbar 17 is connected to the output terminal 18 of Va source of such Yenergizing alternating current indicated generally at ACS.

The alternating current source is shown as comprising a pair of pentode type thermionic vacuum tubes 20, 21 whose cathodes are interconnected and joined to earth by way of a, preferably variable, bias resistor 22. The screen grids of the two tubes are connected in parallel vand supplied with a suitable operating potential from a source of positive potential +300 v., by way of resistor 23 while the suppressor grids of the tubes are connected directly to the common cathodes. The anode of the first tube is connected to one end of Va centre-tapped primary winding 24 of a transformer 25 while the anode of the other tube 21 is connected to the opposite end of such primary winding. The centre tap 26 of the winding 24 is connected directly to the source of positive potential +300 v. The two control grids of the tubes 20,21 are connected respectively to input terminals 27, 28 supplied respectively with the recording control or modulation waveforms which are similar to each other but of anti-phase relationship. in the example shown the control waveforms are of square pulse form whereby one tube only at a time is made conductive, the opposite tube being then cut off. The secondary Winding 29 of transformer is shunted by a variable resistor 30 for balancing purposes and has one terminal thereof joined to output terminal 18 and the other terminal is earthed.

The controlling wave inputs to the control grids of the two tubes 20, 21 are, in the embodiment being described, assumed to emanate from the associated computing machine and to be significant of binary digital information which is to be recorded in different tracks RT on the magnetic drum through the intermediary of a chosen one of the plurality of writing head devices WH. The output from transformer 25, although continuously available on busbar 17, is not capable of passing to any of the writing head devices WH owing to the internal impedance of the associated switching device SM but any required one of such switching devices can be caused to assume a much lower impedance by the application of a unidirectional current to terminals 32 and 33 thereof. The selective application of such undirectional current to the required one of the switching devices is effected with the aid of a matrix arrangement of switching tubes which will now be described.

Each tube of a first set of n tubes V1, V2, V3 has its cathode connected to an individual busbar 361, 362, 363 while the anode of each of such tubes is connected to a source of suitable positive potential, +ve. The tubes are shown, for simplicity, as triodes but other types may be used. The control grid of tube V1 is connected to a source S1 of control potential. Such source S1 is shown symbolically as being a key switch which has two positions one of which, the normal position, serves to connect the control grid to a source of negative potential sufficient to cut off the tube V1 whereas in its alternative operated position such switching means S1 provides a positive voltage for the control grid of the tube whereby it is rendered fully conductive. The tubes V2 and V3 are likewise connected to sources S2 and S3 of control potential. j

Each tube of a second set of n thermionic vacuum tubes Va, Vb, Vc is arranged with its anode connected to an individual busbar 37a, 37b, 37e. The cathodes of such tubes, also shown as triodes for simplicity, are each connected to a source of suitable potential which is negative with respect to that connected to the anodes of tubes V1, V2, V3, e.g. to earth, while their control grids are connected respectively'to Vsources Sa, Sb, Sc of control potentials which, in a manner similar to that of sources S1, S2, S3, are shown as key switches arranged so that, when the switch is in its normal position the associated tube Va, Vb or Vc is cut-off whereas when such switch is altered to its operated position the control grid of the related tube is supplied With a positive bias potential suicient to turn the tube fully on.

The terminals 33 of the various switching devices are connected to one or other of the busbars 361, 362, 363 and the terminals 32 of such devices to one or other of the busbars 37o, 37b, 37e the connections the same pair of busbars. Thus device SMO is connected between busbars 361 and 37a, device SM1 between busbars 361 and 37b and so on.

By selectively applying a suitable positive bias potential to any one of the first set of tubes V1, V2, V3 and by similarly supplying a positive bias potential to any selected one of the second set of tubes Va, Vb, Vc unidirectional current will be caused to ow through one only of the plurality of separate switching devices SM thereby to alter the impedance of such device to a much lower value. When such impedance is thus lowered the alternating current output from the transformer 25 of source ASC can pass from the busbar 17 to the head transformer HT of the required writing head WH whereby such head is energized in accordance with the input control voltages applied to the tubes 20, 21 to cause recording in the required selected track RT on the magnetic recording drum.

In Fig. 1 the form of each switching device SM is similar and has been shown in detail once only for device SM2 at the intersection of busbars 361 and 37e which are associated with the tubes V1 and Vc. Such switching device SM2 comprises an inductive component 40 in the form of a choke coil whose winding 41 is connected between the terminals 15 and 16. The core of such choke coil is surrounded also by a control winding 42 whose opposite ends are connected respectively to the two alternating input current terminals 43 and 44 of a bridge type rectifier network indicated generally at 45 and comprising four rectiiers connected in the conventional manner to provide +ve and -ve D.C. output terminals 46 and 47. These output terminals are connected respectively to the terminals 32 and 33 of the device whereby the +ve terminal 46 of the rectifier network is that joined to the busbar 37e which is connected to an anode of the tube Vc in the second set of tubes Va, Vb, Vc and the -ve terminal 47 of such rectifier network is that joined to the busbar 361 which is connected to the cathode of the tube V1 in the first set of tubes V1, V2, V3.

In the operation of such an arrangement no alternating current available from the output terminal 18 of the source ACS can pass to any one of the head transformers HT and the associated writing heads WH owing to the impedance of the winding 41 of the choke coil 40 within each switching device VSM. Selection of a required writing head is effected by closing one of the switches S1, S2, S3 associated with the first set of tubes V1, V2, V3. and one of the switches Sa, Sb, lSc associated with the second set of tubes Va, Vb, Vc When such switch closure is effected one tube only in each set, say tube V71 in the first set and tube Vc in the second set, is rendered conductive where; by a unidirectional current can flow through those tubes by way of the intersection connection afforded by the associated switching device SM2. The direction of current ow through the associated rectifier network 45 of such switching device is in the low resistance direction and the effect of it is to short circuit to alternating currents below a certain amplitude maximum the control winding 42 connected across the A.C. terminals 43, 44 of that network, with the result that the gating choke coil A40 is elfectvely short'circuited to the energizing alternating current from the source ACS provided such current is below a corresponding amplitude maximum. By effectively short-circuited is meant that 'the impedance of the choke coil is reduced sufficiently to allow the energy applied to the writing head to rise to a level sufficient to effect proper recording. The alternating current on busbar 17 from source ACS is now enabled to pass through the winding 41 of the choke coil 40 in the selected switching device and thus to the reiqiuired writing head WH by way of its head transformer T.

-At the end of the `period required 'for making the record the tubes in the two sets V1, V2 and Va.

a i the flow;` of unidirectional current ceases` andtherestored normal yimpedance of the choke-coil 40 reduces the A.C. energy to a value below thatnecessary to'operate the writing head.-

It will be understood that in practice within, say, an electronic computing machine the controlling switch devices Sl, S2, S3 and Sa, Sb, Sc will ynot be manually operated key switches butwill be some suit- .able source of control potential derived, for instance, from the instructionstaticisor device of the computing machine whereby different combinations of digits in an vinstruction signal which lis of serial pulse train form can ,be caused to select one of the tubes` in each set for operation to its conductive state. As the manner of deriva- :tion o'f such control voltages is wellV known and asitA also forms no part of the present invention itl will-not be further described. 4.

VThe switching action of the arrangement described is kvery rapid, the required writing head being in practice energized sufficiently to operate properly within 1 microsecond of the instant of, application of the control signal to the two tubes concerned. Care must be taken in the design of the transformer-likev element'constituted by each v choke coil and its control winding to ensure thatsuch device has the minimum of leakage-flux since such leakage fiux delays the rise to short-.circuit value of the currents in its windings. .Y Y

Such an arrangement as shownin Fig. 1 provides for the selective effective energization of n2 utilization devices, e.g. recording heads, with the aid of two sets of therrnionic tubes havingn tubes in each set. Thus 2n or 6 tubes are required to deal with 9 heads as actually shown while two sets each of 16 tubes, i`.e. 32 tubes in all, would be required to select any one of 256 writing heads in the particular practical examplel mentioned previously. t v l By adopting agmodified arrangement the number of tubes required may be reduced still further.r In such modified arrangement each pair ftubes (i.e. one tube in one -setla'nd another tube in -the other set) include between them notY one switching device with its associated, rectifying network but a plurality of switching delvices with their rectifier networks connected as'a series chain, the particular switching device of the selected chain which is required being itself selected by control of the energization current supply to all of the devices of the chains through a like array of inductive ponents and rectifying networks. 1 f

Such a modified arrangement vwill.nowbe described with reference toV Figs.2 and 3. Fig. 2 shows the manner of connecting a chain of networks in series between any one busbar 36 associated with a tube of the Afirst Vset and any one busbar 37 associated with a tube of the second set. Thus between the busbar 36 connected to the cathode of tube V1 of the first set and the busbar 37 connected to the anode of tube Va of thesecond set, there is arranged a total of four rectifier networks 45a, 45b, 45e and 45d in series, the cathode of tube V1 being connected to what isnormally the negative output ter- Vrninal of the first rectifier network 45a, the positive terminal of such network beingv connected to thenega- `ftive terminal of the next network 45b and so on .with the positive terminal of the fourth network 45d con- ;nected to the anode of the tube Va.

Each rectifier network is associated,A exactly as in the nating current through further' switching devices o'f ,wsimilar nature to the devices SM already described.

Fig. 3 shows in block schematic form a complete lay- :are rendered nbn-conductiveta'gin wherebyv "abscess ou'tfforthe control of energizing current tofa total 'of 36 heads by means of 10 tubes. Insuch arrangement vthe first and second sets of tubes V1', V2, V3 and Va,

Vb, Vc serve to select one series chain of rectifier net- ,works within the complete switching device and write tively feed energizing alternating current from the comend of winding 64 is connected to terminal 15 while the mon busbar 17 which is connected vto the source ACSI.,

-to the first, second, third and fourth switchingdevicein eachchain. Each of such busbars includes afurther choke coil 50 whose core 51 is associated with-a control winding 52 connected to a rectifiernetwork 53. Such arrangement is substantially identical rwith that already described in connection with the switching devices SM Aof the first and second sets of tubes V115. and Va Each rectifier network 53 is' connected between a lcathode of a tube in a third set of tubes VI, 'VH and the anode of a tube ina fourth set oftubes Va, V,g with an arrangement substantially identical with that already described in connection with Fig. l whereby no two vnetworks are connected betweenthe same pair of tubes. The Ycontrol grids of the tubes of such third and fourth sets of tubes are, in a manner similar to that already described, supplied with., appropriate control potentials which are. such that the tubes, normally cut-off and non- .conductive, can be made conductive when required.

Thus with the arrangement shown in Fig. 3 byfapplyingan-appropriate positive-going control potentialtotube V2 in the first set andfto tube Vb in the second set and to tube Vn in the third set and to tube VB in thefourth set,' the particular writing head in device SH19 alone will be supplied with energizing alternating current since only the four series-connected rectifier networks of switching devices SH16, SHN, SH18, SH19 will be rendered operative while onlythe busbar 17d of the group which feeds such series will be supplied with energizing alternating current from the source ACS.

It will be understood -that ythe arrangement shown using three tubes in each' of the first-,and second sets of tubes and two tubes only in keach of the third and fourth sets is purposely simplified to preserve clarity of the drawing. In practice the advantage of the second ernbodiment becomes more manifest as the number of utilization devices is increased. Thus by employing chainseach of sixteen switching devices in conjunction A.with four tubes in eachof the four sets 'of .tubes a total ofV 256 utilization devices may be controlled by only 16 component takes the form of a first transformer 60 whose i primary winding 61 is connected in series with the primary winding 62 of a second and like transformer 63 across the energizing channel. of winding 61 is connected to input terminal 16 while the other end of winding 62 is earthed. The secondary windings 64, 65 of the two transformers are connected in series and arranged to supply the primary winding of the associated head transformer. For this purpose one other end of winding 65 is earthe'd. By suitable arrangement of either the primary or secondary winding connections, the two transformers are placed in phase opposition with the result that the arrangement so far described For this purpose one end u assegna wll provide output voltages which counteract each other whereby'the voltage applied to the head transformer is zero or substantially so. On the first transformer 60 there is provided additionally in inductively coupled relationship, a control winding 4'2 which is connected across the alternating current terminals of a reetifying network 45, the directA current terminals of such network being connected to terminals 32 and 33 which are equivalent lto those having similar reference numerals in the embodiment of Fig. 1.

Inl the operation of this modification, the effective short-circuiting ofthe control winding 42 in turn effectively short-circuits the first transformer 60 with fthe result that the output of the second transformer 63 is no longer counteracted by that of the first and the energy applied Y through terminal 15 to the writing head accordingly rises to'a value suicient to cause the head to operate. Other variants of lthe form 'of the inductive component may Vreadily be devised.

In another modified arrangement the rectifier network Yis simplified by the use of a centre-tapped control winding. Referring toFig. 5 the control winding 421, which is associated with the inductive component winding indicated schematically at IC, is centre-tapped at `67 and connected to terminal 32while its two opposite endVVV terminals are connected through half-wave rectifier elelfrnents 45x to terminal 33. The terminals 32 and 33 vother purposes involving the control of the alternating current energization of some I claim:

1-. An electric switching arrangement. for enabling a unidirectional current to cause an alternating current to energize effectively a utilization device which comprises an input terminal for connection to a source of energizing alternating current, an output terminal for connection to a utilization device to be operated by said energizing alternating current, anenergizing channel between said input and output'terrninals, said energizing channel including a serially connected Yinductive winding, a control winding separate from but inductively coupled to said inductive winding, a four arm bridge network withl each arm including a half-wave rectifier, said rectifiers being arranged to provide a high resistance to either direction of current ow across one diagonal and a low resistance to one form of utilization device.

direction of current 'flow across 'the' opposite diagonal, circuit means connecting said control winding-across said high resistance diagonal of said bridge network, two control input terminals for connection to a source of unidirectional current and circuit means connecting said control input terminals across said low resistance diagonal of said bridge network. y v

2. An electric switching arrangement according to claim 1 wherein said inductive winding comprises a choke coil connected between said input terminal and said output terminal, said choke coil having an impedance sufficient to prevent effective energization of said utilization device.

3. An electric switching arrangement according to claim 2 wherein said rectifier network comprises a full wave bridge-type network.

4. An electric switching arrangement according to claim 1 wherein said inductivewinding forms part yof a first transformer and wherein the arrangement includes a second transformer, means for connecting said first and second transformer primary windings in series and to said input terminal, further means connecting said secondary windings of said two transformers in series and to said output terminal, said series connections of said transformer windings being such that the output from the second transformer is in phase opposition to said first transformer and of a lvalue such that the resultant output to said utilization device connected to said output terminal is normally below that required to effect energization thereof.

References Cited` in the file of this patent y UNITED STATES PATENTS l1,920,618 Zierdt Aug. l, 1933 2,129,920 Fitz Gerald Sept. 13, 1938 2,136,441y Karolus Nov. l5, 1938 2,514,935 Clapp July 11, 1950 2,611,025 Iankowski Sept. 16, 1952 2,655,605 Hartley et al Oct. 13, 1953 l2,686,299 Eckert'y Aug. l0, 1954 2,691,151 Toulon Oct. 5, 1954 2,730,694 Williamson Ian. 10, 1956 2,734,942 Heald Feb. 14 1956 2,817,057 Hollman Dec. 17, 195,7

OTHER REFERENCES l ,Static Magnetic Matrix Memory and Switching Circuits (Rajchman), R.C.A. Review, volume 13, June 1952, page 190, Fig. 4 of interest.

Radar Electronic Fundamentals, Navships 900,016, published by Navy Dept., .lune 1, 1944 (pp. 771-81 relied on).

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