US2573076A - Electric sign circuit - Google Patents

Description

T. R. WELCH ELECTRIC SIGN CIRCUIT Oct. 30, 1951 2 SHEETS-SHEET 1 Filed Feb. 11, 1949 r m I INVENTOR.

THoMAs R055 Wu CH F/GJ A TrokNEY Oct. 30, 1951 T. R. WELCH ELECTRIC SIGN CIRCUIT 2 SHEETS-SHEET 2 Filed Feb. 11; 1949 INVENTOR. THOMAS ROSS WEZCH Patented Oct. 30, 1951 UNITED STATES PATENT OFFICE 2,573,076 ELECTRIC? SIGN omom'r Thomas Ross Welch, Los Angeles, Calif.

Application February 11, 1949, Serial No. 75,850 13 Claims (01. 177-350) This invention relates to electric circuits, and particularly to a circuit and controls therefor for use in the operation of flashing changeable message electric signs, this application being-a continuation in part of applicants copending application for Electric sign circuit, Serial No. 5,241, filed January 30, 1948, now abandoned.

The invention has especial application, and is so disclosed, as an improvement upon the apparatus of my prior application, Serial No. 718,433, filed December 26, 1946, now Patent No. 2,481,269, for Control system for electric sign. It is, accordingly, concerned with a sign and control system wherein a number of symbol formers are arranged in side by side relation for the display of a desired message or portion of a message consisting of words, letters or numerals which may appear on the symbol formers'in any combination desired and in a predetermined order of succession.

Energizing of the symbol formers is controlled by the presetting of a plurality of symbol selectors electrically connected by commonconductors to each symbol former. Undesired current flow in a reverse direction through portions of the common conductors and symbol selectors, not being used to condition the symbol formers for display, is prevented by incorporating in the system one way valves or rectifiers in such manner as to confine current flow to a direction toward the symbol formers.

The prior application contemplates the reforming of damaged rectifier valves or the preventing of such damage to valves by applying a current of inverse polarity in the system, which current is continuous with respect to those connected circuits not being used for th'econtrol of display by the symbol formers. The controls there disclosed satisfactorily perform their intended function, but it is contemplated by this invention to improve upon the system of the prior application by making the action of reforming or healing the rectifier valves a more efficient operation. Some loss of efliciency heretofore resulted from the fact that the circuits through which the current of inverse polarity is passed includes the coils of electromagnetic relays, these relays being used in the symbol former to condition the former for selected display of a desired character or numeral. The electrical resistance imposed by the relay coils is such as materially to reduce the value of the current flowing to the rectifier valves. By this invention a bypassing of the electromagnetic relay coils is made possible by means serving the dual function of providing a low impedance shunt path for the current of reverse polarity and of providing for the dissipation of energyat the contacts of a relay in the circuit and consequent suppression of arcing in the making and breaking of such contacts.

An object of the invention, thus, is to improve upon the control system of my prior, aboveidentified, application to the end that such system may operate with greater efiiciency.

More specifically, it is an object of the invention to incorporate in a control system of a kind heretofore known bypass means arranged in parallel with electromagnetic relays in the circuit, the bypass means having the form of unidirectional valves and serving the additional function of arc suppression connectors for inhibiting arcing in the circuit.

Other objects and structural details of the invention Will appear from the following description when read in connection with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of a sign control system embodying the arc suppression valves of the present invention, and showing one form of control for applying inverse potential in the system;

Fig. 2 is a view similar to Fig. 1 showing a second form of control for applying inverse potential in a system characterized by are suppression valves as shown in Fig. 1; and

Fig. 3 is a partial schematic diagram of an alternative arrangement.

Referring to the drawings, the sign and its controls are here shown schematically, a detailed illustrattion of the actual construction and location of the parts being not essential to an understanding of the invention.

Thus, a single symbol former is shown in Fig. 1 hereof within the dotted frame [0, and it will be understood that in a sign as actually constructed there is a plurality of such symbol formers arranged in side by side relation. Further, within a dotted frame ll there is here represented the symbol selector unit of the sign apparatus which in actual embodiment comprises a plurality of horizontal rows of plug receptacles, thecorresponding receptacles or plug positions of the several rows having a common electrical connection to a respective symbol former. In Fig. 1 there is shown three corresponding plug positions of different rows, such corresponding positions being referred to as a bank.

Within the dotted frame l2 are the control and actuating elements of the system.

The parts H], H and I2 of the system may be located relatively remotely from one another and interconnected electrically. Thus, the symbol formers may be mounted on a building or other exposed place while the selector unit Il may be placed within the building or other source of control and the control unit |2 may be placed adjacent the symbol former or adjacent the selector unit or in some other location.

For the present purposes, it is thought to be sufiicient to point out that the symbol former of unit I!) comprises a number of electromagnetic relays including coils |3 variably arrangedto permit and to prevent bypassing of sections of neon tubing making up the symbol former.w

selective pattern to condition the symbol former for illumination of a selected letter or .character when electric potential is applied, as through a transformer M. The coils |3 representing the electro-magnetic relays are connected to a common conductor I5 and to individual conductors l6. The conductors |6 for the symbol former are carried through a common cable I! 'to the symbol selector unit The plug positions of the symbol selector comprise a number of contacts l8, each contact l8 in each corresponding plug position of a bank being connected to a respective conductor I5. The plugs received in the plug positions of the selector unit include a number of prongs equal in number to the number of contacts l8, and the contacts l8 are constructed as recesses or sockets physically receiving the prongs of the plugs. The prongs of the plugs are variably connected by jumper elements indicated at |9 herein so that current supplied to a plug position will be directed to certain of the contacts I8 and to corresponding conductors l6 for the selective energization of coils IS in the symbol former. The sockets comprised in contacts l8 are divided into two groups, one of which is provided with valves 2| for limiting the direction of flow of current through their associated sockets in one direction only from the current supply conductor common ..to each. horizontal row of plug positions.

Current for the energization of the operating coils |3 of each symbol formeris supplied from abridgeconnected rectifier 22. Provision is made for selectively connecting the common conductors 23, 24 and25 of each horizontal row of plug positions to the positive polarity side of. the. rectifier 22. The selected conductor is simultaneously connected to the side of another rectifier 26, the rectifiers 22 and 26 being series connected and interconnected to common conductor |5. This is. accomplished by means including a plurality of electrically actuated switches 27, each switch having normally closed contacts 28 for connecting the common supply conductors 23, 24 and 25 of the symbol selectors to the negative side of the rectifier 26, and normally open contacts 29 operableto connect the common conductor to the positive side of the rectifier 22 when the operating coil 3| com-- prised in the switch assembly is energized.

Provision is made for successively energizing the operating coils 3| of switches 21 in timed sequence. One side of the coils 3| are commonly connected to a conductor 32 of an alternating current supply circuit further including conductor 33. The other side of the coils 3| are respectively connected with stationary contacts 34 of a stepping switch 35. The switch 35 is pro- -15 The electromagnetic relays are energized in..a..

vided with a rotating contact arm 36 constructed and arranged to move in step by step fashion over the contacts 34. The rotating contact 36 has electrical connection with conductor 33 representing the other side of the alternating supply circuit. Intermittent movement of the contact 36 is accomplished by means of a pawl and ratchet mechanism 31 operatively associated with an actuating coil 38 "having one terminal thereof connected to the-conductor 32 and its other terminal connected to the conductor 33 of 'the supply circuit through the contacts 39 of a cam switch 4|. The cam switch 4| is driven at a constant speed by a suitable motor 42 having its. terminals; connected to the circuit conductors 32 and 33.

The primary winding of the transformer I4 is supplied over a pair of conductors 43 connected to circuit conductor 33 and to circuit conductor 32 through a cam actuated switch 44 by means of a selector switch 45. The switch 44 is normally closed and is arranged to open in predetermined timed relation to the actuation of the switch 39, the cam acting on switch 44 being also driven by motor 42. According to the sequence of operation of the switches, the switch 44 opens to de-energize the sign before the switch 39 closes to cause stepping switch 36 toadmit current to the next successive row of plug posi-' tions of the selector unit. When contactor arm 36 of the stepping switch has so moved and when as a result thereof a pattern of selected coils I3 in each symbol former has been energized, the switch 44 is again caused to close, whereupon a high voltage potential is impressed across the sign through transformer M to illuminate the selected portions of the neon tubing.

and so to form lighted characters or symbols. The sign will remain illuminated for the time necessary for motor 42 to drive the cam controlling switch 44 to a position again opening such switch whereupon the sign will be momentarily extinguished while contactor arm 36 of the stepping switch'moves to the next row of plug positions in the selector unit.

Starting and stopping of the sign and its control system is accomplished through a main switch 46 which is: provided for connecting the circuit conductors 32 and- 33 with a main electric supply source at the opposite terminals of conductors 41. The switch 46 may be manually operable or may be arranged as shown with an operating coil 48 having. one-side connected. through a pair of. control conductors 49 leading from a push-button 5| preferably located at the symbol selector unit.

With further reference to the switches 21 which are successivelyenergized by stepping switch 35, it will be noted that when a coil 3| is energized, the switch and the common conductor 23 or 24 or 25 is connected through con-- tacts 29 and a common lead 52-to thepositive side of bridge rectifier 22.- Accordingly, currentis supplied through each symbol. selector of the row associated with the selected conductor 23, 24 or 25 in flow paths comprising the rectifiers or valves 2| and jumpers l9 to contacts l8 and thence by way of conductors Hi t selected ones of the electro-magnetic relay coils l3.

From the opposite side of coils- |3 the current flows by way of common conductor IE to the negative side of bridge rectifier 22.- Under such conditions, and as determined by the jumpers I9 in the symbol selector, a particular character will be displayed by the symbol former.

It has been recognized, however, that 'due to the fact that the contacts [8 of the plug positions in each vertical bank are connected to the same conductors I6, occasions may arise when a feed back through jumpers of another. plug position would result in misoperation of the system, exhibited by improper energization of the operating coils I3 of the symbol former associated with the affected bank of plug positions. It is for this reason that valves 2| are utilized. These valves are in the form of dry disc selenium rectifiers characterized by the ability to pass current without appreciable impedance in one direction, but substantially to inhibit a reverse flow of current. In the present instance, therefore, the valves in thesymbol selectors of a connected row will operate to permit the passage of current in anormal direction, that is, toward coils l3 and at the same time the valves of the other rows of plug positions will prevent passage of current in a reverse direction such as would be necessary for improper energization of the coils l3.

The valves 21 thus have a particular utility which is to some degree impaired by the fact that dry disc selenium rectifiers of this type are subject to occasional breakdown or to the creation of defects therein resulting in inability to inhibit reverse or inverse current flow. It further is a characteristic of such valves, however, that defects of this type can be healed or corrected by the deliberate application of a reverse current flow across the valves.

It has heretofore been proposed, in application Serial No. 718,433, to guard against breakdown of the valves 2| as well as to restore them to operative condition by applying a reverse polarity in the system, which reverse polarity is continuous with respect to the rows of symbol selector plug positions not connected to the positive side of rectifier 22. This is accomplished by the contacts 28 in switches 21. As previously explained, the contacts 29 operate to connect the selected row of symbol selectors to the positive side of rectifier 22. It is to be noted, however, that in the rows of symbol selector positions not selected by stepping switch 35, the contacts 28 of switches 21 are closed. The conductors 23, 24 or 25 not connected through closed contacts 29 are thus connected through contacts 28 and a common lead 53 to the negative side of bridge rectifier 26. Accordingly, a reverse potential is applied, extending from the positive side of rectifier 26 through conductor l5 and electro-magnetic coils l3 and conductors l6, back to contacts l8, jumpers l9, valves 21 and common conductor 23, 24 or 25.

Such a system presents the advantage of carrying on a continuous protection of the valves 2l against breakdown and the healing of any defective valves. It has been discovered, however, that the protective and healing action is best performed when an electrical current of relatively high value is permitted to reach the valves 25. In applying the reverse polarity across the electromagnetic relay coils I3, it is not always possible to maintain a current of sufficientmagnitude due to the resistance interposed by the coils. It would be possible to step up the voltage of the inverse current, but this is undesirable for a number of reasons. In accordance with the conception of the present invention, it is contemplated to bypass the coils IS in applying the inverse potential. This is accomplished by connecting the common conductor IE to the individual con ductors I6 by valves 54 arranged in parallel with I the coils l3. The valves 54 are similar to the valves 2| and permit current fiow thereby only in the direction of the inverse potential. Application of current in the opposite direction, as is used in energizingthe coils I 3 for illumination of the sign, acts on the valves 54 in a corrective manner similar to the correction contemplated for valves 2|. Through the use of the valves 54, therefore, current of sufiiciently high voltage may reach the valves 21 in the application of inverse potential in the system adequate to cure any defects in such valves.

The valves 54 perform a second function relating to arc suppression. The circuit from contact 29 through 23, 2|, I9, IS, IS and H includes the coil I3 having an inductance capacity. In the opening of inductance circuits such as when contact 29 is opened, it is possible for harmful contact conditions to arise. This is due to the fact that the el-ectro-magnetic field surrounding the inductive coil I 3, representing an appreciable amount of energy, collapses. This collapse of the magnetic field generates a voltage which appears across coil H31 and tends to maintain the fiow of current across the now open contacts 29. This continuation of current fiow due to the collapsing field is usually dissipated in the form of an,

arc across the contacts, the duration and severity of which is determined by theamount of energy stored in the magnetic field surrounding the coil. Through provision of the valves 54 in the present circuit, a low impedance shunt path is establishedacross the coils [3 so that the current produced by the collapsing magnetic field of coils I3 is dissipated through the valve and produces very little or no arcing at the contacts 29 which break the circuit. By reducing or eliminating the arcing across these contacts, their life is increased many times.

The system of Fig. 2 is the same as Fig. 1 insofar as the interposition of low impedance arc suppression valves in parallel relation to the electric coils of the symbol formers is concerned. Thus, in Fig. 2 these coils are indicated at I310, and the arc suppression valves associated therewith indicated at 54a. The circuit shown in Fig. 2 is basically the same as that of Fig. 1 and includes substantially all the same elements. Accordingly, the description of Fig. 2 will be limited to the features of distinction from Fig. l and only those parts will be described which'are new or which cooperate with the new parts. Elements which are the same in Fig. 2 as in Fig. 1 are here indicated by the same reference character with the addition thereto of the letter a.

According to the modification of Fig. 2, switches 21A are provided which correspond to the switches 21 of Fig. 1 and which, like the previously described switches, include normally closed contacts 28a and normally open contacts 29a. Unlike the circuit of Fig. 1, however, an inverse potential is not continuously applied in the system by reason of the closed contacts 28a since conductor 53a common to the closed contacts 28a is interrupted by a switch 55. The conductor 53a extends beyond switch 55 to the negative side of a source of current 56 which replaces the rectifiers 22 and 26 of the system of Fig. l. The positive side of source 56 is connected by a conductor 52a to the several switch-es 210: on the side of the normally open contacts 29a. Thus, when one of the coils 3| a is energized, the associated switch- 21a is actuated to open contacts 28a and to close contacts 2911, Current then will flow from the positive side .of source 56 through conductor 52.

and closed contacts 29a to-common conductor- 23a, 24a, or 25a and then past valves 2 la, jumpers We and contacts i8a to conductors Mia and coils 13a. From the opposite sides of coils l3a the current continues on through common conductor l5a. to the negative side of source 56. Further; in accordance with themodification of Fig. 2, common conductor I511. is interrupted by a switch 5'l'comprising normally closed contacts 58 and. normally open contacts 59. The normally closed. contacts 58 connect line 15a to the negative sideof source 56, while normally open contacts 59 connect line I511, to conductor 52a on the positive side of source 56 by means of branch lead line 6 l.

The modification of Fig. 2 is distinguished not only in structure, but in manner of operation from-the system of Fig. 1. In the Fig. 2 circuit it is contemplated that the application of an inverse potential for the reforming of valves 2 lashall not be a continuous operation, but rather shall be a periodic one. In the illustrative embodiment, the frequency of the inverse potential application is once for every 11 steps of the stepping switch 35a. The mode of operation contemplated is that the step of applying inverse potential in the system willtake place after each series of flashes representing a .full message and before the start of the repetition of such message. Thus, in the illustrative sign apparatus, the stepping switch 35a is provided with 10 contacts 34a, each connected to a respective row of plug positions in the symbol selector unit. The stepping switch additionally includes an 11th contact 52 upon which the stepping switch arm 36a rests after leaving the 10th contact 35a and before reaching the first contact 34a. This interval represents a pause 'in the illumination of the sign and it is during this pause that inverse potential is applied in the system.

Switch 55 in conductor 53a is a normally open switch controlled by a coil 63. Similarly, switch 5'! is controlled by a coil 64. Coils 63 and 64 are adapted to be energized simultaneously, being arranged in parallel in a conductor 65 connected to the 11th contact 62 in stepping switch 35a. The arrangement is such, therefore, that when stepping switch arm 36a reaches contact 62, current flows from one side 33a of the alternating current supply circuit through arm-36a to contact 62 and through conductor 65 to coils 63 and 64 and from thence back to the other side 32a of the alternating current supply circuit. Inasmuch as the stepping switch arm 36a is out of engagement with all of the contacts 3411, the several switches 21a will be set with the contacts 28a closed and contacts 29a open. The system, accordingly, is conditioned for the application of inverse potential and this is permitted as coils 63 and 64 act respectively to close switch 55 and to operate switch 51 to close the normally open contacts 59.- In this position of the parts, current flows from the positive side of source 56Zto conductor 52a. Because contacts 29a are open, the current cannot cross switches 21a and so is compelled to follow conductor 6| andcross contacts 59 to. commonconductor [5a and flow through this conductor in an inverse direction to electromagnetic coils [3a of the symbol formers. The inverse current is allowed to flow without substantial .impedance across coils. 13a by reason of the arc suppression valves 54a arranged in parallel relation thereto, and the circuit then continues on through conductors 16a to contacts 18a, jumpers l9a and valves :2la. to the common conductors23a, 24a and 25a. From the common conductors the current flows through the closed contacts28a of switches 21a to conductor 53a. Conductor 53a completes the circuit through closed contacts55 back to the negative side of source 56.

In the foregoing arrangements the relays or coils l3 (Fig. 1) and [3a (Fig. 2) operate high voltage switches controlling the circuits to the symbol formers for providing selected letters or characters and/or the like, and it is to be understood that said relays may also function to operate other devices for producing selected letters, characters, and the like.

The present invention is not to be limited to electric signs and their circuits, but is useful in many other devices including automatic machine tools, et cetera. In fact, the arrangement may be used in connection with any circuit that runs in sequence or cycles, whether or not the sequence or circuit arrangement of the cycles is to-be capable of being changed as is done in the present invention, by means of the jumpers I9.

Another arrangement of the invention is shown in Fig. 3. In this figure elements which are the same as in Fig. 1, are indicated by the samereference characters with the addition thereto of the letter b, and the description of said Fig. 3 will be limited to the features of distinction from Figs. 1 and 2.

In the arrangement of Fig. 3 groups of electric lights 15 or the like, are suitably arranged for visible display and are connected to the common conductor 15b and to the individual conductors [619, so that illumination of the sign is effected directly rather than through the medium of the relays l3 (Fig. 1) or l3a (Fig. 2).

Thus, by variously illuminating or energizing respective selected lights 15 of a group, various letters, characters or the like, are formed.

In connection with the present invention, it is to be noted that the coils I3 (Fig. 1), [3a (Fig. 2), and the lights 2'5, may be considered as a load or loads.

It will be apparent that further modified forms of the invention are possible, particularly in respect of the means for applying an inverse potential in the system. Two such means have been here shown by way of illustration only.

In addition, it will be understood that insofar as the invention resides broadly in a selenium rectifier'reforming circuit, including electromagnetic coil bypass means, it is applicable to sign systems other than as shown in application, Serial No; 718,433, and may, in fact, be used in electric circuits generally.

I claim:

1. In a changeable sign apparatus, the combination of a source of electrical energy; means for controlling the illumination of portions of said sign selectively to display characters, each of said means including an operating coil connected on one side to said source of energy; individual supply conductors connected to the other sides of said coils; individual current bypass means arranged in parallel relation to each saidoperating coils; valves in said bypass means limiting current flow therethrough to one direction; a plurality of symbol selectors connected to each of said individual supply conductors and having preselectable current fiow paths therethroughfrom a common connection with the other side of said source of energy; valves in said paths for limiting current flow to one direction therethrough, said last mentioned valves being oppositely arranged with respect to said first mentioned valves; and switch means operable to reverse the polarity applied to said common connections by said source of energy.

2. In a changeable sign apparatus, the combination of a source of electrical energy; means for controlling the illumination of parts of the sign to display characters, each of said means including an operating coil connected on one side I to said source of energy? individual supply conductors connected to the other sides of said coils; bypass means for conducting current in bypassing relation to each of said coils; valves in said bypassing means for limiting the flow of current therethrough to one direction; a plurality of symbol selectors connected with each of said supply conductors and having preselectable current flow paths therethrough from a common conductor; valves in said paths for limiting current flow to one direction therethrough, said last mentioned valves being oppositely arranged with respect to said first mentioned valves; transfer switches having one position normally connecting the common conductors to one side of said ing said common connectors to the other side of said source of energy; and means for actuating said switches from one position to the other in timed sequence.

3. In a changeable display sign having a plurality of electro-magnetically operated relays selectively actuated to condition the sign for the display of a selected character; a source of electrical energy, a common conductor connecting one side of the coils of said relays to said source of electrical energy, a plurality of control conductors individually connected to the opposite sides of said coils, a plurality of selectors each source of energy and another position connectconnected with said control conductors and operable to preselect current flow paths to one or more of said control conductors from an energy source, valves in the flow paths of each selector permitting unidirectional current 'flow to said conductors, means for successively connecting the flow paths of each selector to the energy source for normal current flow, means for subjecting valves of the selectors to reversed polarity during periods in which there is no normal current flow therethrough, and means for conducting said reverse polarity in'bypassing relation to the coils of said electromagnetic relays.

4. A changeable display sign according to claim 3, characterized in that said last named means has the form of rectifier valves serving the dual function of limiting current flow thereby to one direction and of dissipating energy to inhibit arcing.

5. In a changeable display sign having a plurality of electromagnetic relays including coils selectively energizable to condition the sign for display of a selected character, a source of electrical ener y, a common conductor connecting one side of said energy source to one side of said coils, individual conductors connected to the opposite sides of said coils, a current flow path interconnecting said common conductor and each said individual conductors in bypassing relation to said coils, valves in said fiow paths inhibiting current flow therethrough from said individual conductors to. said. common conductor, but permitting flow in an inverse direction, a plurality of selectors, each comprising contacts connected to respective individual conductors, a common supply conductor for the contacts of each said selector connected to the other side of the electrical energy source, unidirectional valves interposed between each said common conductors and the contacts of an associated selector permitting flow through said individual conductors toward said coils, but inhibiting universe flow, and means for applying an inverse polarity to said circuit.

6. In a changeable display sign having a plurality of electromagnetic relays including coils selectively energizable to condition the sign for display of a selected character, a source of electrical energy, a common conductor connecting one side of said energy source to one side of said coils, individual conductors connected to the opposite sides of said coils, a current flow path interconnecting said common conductor and each said individual conductors in bypassing relation to said coils, valves in said flow paths inhibiting current flow therethrough from saidindividual conductors to said common conductor, but permitting flow in an inverse direction, a plurality of selectors each comprising contacts connected to respective individual conductors, a common supply conductor for the contacts of each said selector connected to the other side of the electrical energy source, unidirectional valves interposed between each said common conductors and the contacts of an associated selector permitting flow through said individual conductors toward said coils, but inhibiting inverse flow, normally open switches operable when closed to reverse the circuit for application of inverse polarity, electrically energizable means for closing said switches, and timer means for directing current successively to said common supply conductors and intermittently to said electrically energizable means.

'7. A changeable display sign according to claim 6, characterized in that said timer means includes a stepping switch operable to connect said common supply conductors successively to the electrical energy source and after each series of such connections to connect said electrical energizable means to said energy source. 7

8. In an electric circuit, the combination of a plurality of electromagnetic coils arranged in a pattern for selective energization, a source of energy connected to one side of each said coils, individual supply conductors connected to the other sides of said coils, a plurality of selectors connected to each of the conductors and having preselectable current flow paths therethrough from a common connection connected to said source 'of energy, valves in said paths for limiting current flow to one direction therethrough, means for applying inverse polarity in the system to reform damaged valves, and bypass valves in parallel relation to said electromagnetic coils and arranged to pass current only in the direction of the inverse polarity.

9. In an electric circuit for connection to a source of energy: a plurality of electrical devices arranged for selective energization, one side of said devices being connected to said source of energy; individual supply conductors connected to the other side of said devices; a plurality of selectors connected to each of the conductors and having preselectable current flow paths therethrough from a common connection connected to said source of energy; valves in said paths for limiting current flow to one direction therethrough; means for supplying inverse polarity in 1 1 thesystemato -reform damaged'valves; and bypass valves in parallel relation to said devices and arranged to pass current only in the direction of inverse polarity.

L10. In an electric circuit for connection to a source of electrical energy: a plurality of electrical devices arranged inla pattern for selective energization, one side of said devices being adapted to be connected to said source of energy;

individual supply conductors connected to the 1 other Side of. said; devices; a plurality'of selectors connected to .eachvof the conductors and having preselectable. current flow paths therethrough from a-lcommon connection adapted to be connected to said source of energy; valves in iSaidMI- K paths for limiting current flowto one direction therethrough; .means for applying inverse polar- "ity in the system'to reform damaged valves; and bypass valves in: parallel relation to saidldevices and arranged to pass current only in the direc-pgg tion ofinverse polarity.

11; In an electric circuit for connection'with a source of electrical energy: a plurality of electric lights arranged for :selective energization,

one :side of said electric lightsbeing connected. 2

to said source of energy; individual supply conductors connected to the other sides of said lights; a plurality of selectors connected to each of the conductors and having preselectable current flow paths therethrough from a common 30 connection adapted to be connected to saidsource of energy; valves in said paths for limiting currentaifiow to" one direction therethroughymeans for applying: inverse polarity in the system to reform damaged valves; and bypass valves in par- 35 allel relation to said electric lights and arranged topass' current only in thewdirection of inverse polarity.

12. Inan electric: circuit for connection with a source of electrical energy: a plurality of; elec- 40 tric lights arranged in a pattern for selective energization, one side of said electric lightsbeing connected to said source of energyyiindividual supply conductors connected to the other sides of said lights; a plurality of selectors connected to'each of the conductors and having preselectable current flow paths therethrough fromna common connection adapted to'be connected to said .source of energy; valves in said paths for 12 limitingcurrent flow" to one direction therethrough; means for applying inverse polarity in the system to reform damaged valves; and bypass valves-in parallel relation to said electric lights and arranged to pass current only in the nected-to the opposite sides of said lights; a current flow path interconnecting said common coniductor and each of said individual conductors-in bypassing relation to said lights; valves in said fiowpaths inhibiting current flow therethrough .from said individual conductors to said common conductor, but permitting-flow in an inverse direction; a plurality of selectors each comprising contacts connected to respective individual con- .ductors; a common supply conductor for the contacts of each selector adapted to be connected to the other side of the electrical energy source;

unidirectional valves interposed between each said common conductor and the contacts of an associated selector permitting flow through said individual conductors toward said lights, but inhibiting inverse flow; normal open switches operable when closed to reverse the circuit for applicationof inverse polarity; electrically energizable means for closing said switches; and timer ,means for directing current successively to said common supply conductors and intermittently to said electrically energizable means.

THOMAS ROSS WELCH.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,346,493 Hammond July 13, 1920 3,356,094 Saslaw Aug. 15, 1944 FOREIGN PATENTS Number Country Date 192,390 Switzerland Jan. 3, 1938

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