US3508237A - Lamp outage indicating circuits - Google Patents

Description

April 21, 1970 3,508,237

S. KIMMELMAN LAMP OUTAGE INDICATING CIRCUITS Filed Dec. 1967 2 Sheets-Sheet 1 FIG. I.

l JJ w 4 FROM STOP LIGHT CONTROL SWITCH IN VENTOR SAMUEL KIMMELMAN BY ATTORNEY April 21, 1970 s. KIMMELMAN LAMP OUTAGE INDICATING CIRCUITS Filed Dec. 1, 1967 2 Sheets-Sheet 2 FIG. 5. 6 f i ,m

| l T 1 2 I) 0) 6) 6) 6) 6) E 15 1 .1 /7 l 2/ 22l 1 zas FROM ac. SOURCE TO LOAD LAMPS FIG. 6. L2;

INVENTOR SAMUEL K/MMELMAN AT TORNE Y United States Patent York Filed Dec. 1, 1967, Ser. No. 687,356 Int. Cl. G081) 21/00 US. Cl. 340251 9 Claims ABSTRACT OF THE DISCLOSURE A lamp outage indicating circuit for energizing from a variable voltage DC. current source a group of parallel connected lamps includes an electrical signal device controlled by relay contacts positionable by the ampere turn values of first and second coils of the relay, current flow from the source through the lamp group being directed through the first coil in series therewith, and the second coil receiving current flow from the source separately from the lamp group so that the flows of current through the coils vary similarly with changes in the source voltage and only the current flow through the first coil changes with outage of a lamp to give rise to the relationship of the respective ampere turn values by which the relay contacts are positioned to cause the signal device to give a lamp outage indication.

This invention relates to a direct current electric circuit for flashing a plurality of signal lamps, at least some rf which are connected in parallel, and having an electrical signal device, such as a pilot lamp, for indicating it one or more of the signal lamps is out.

The invention is especially suited for the flashing lamp systems of motor vehicles, such as turn-signal systems. In these systems it is important for safety reasons that the operator of the vehicle be made aware if one or more of the signal lamps is not functioning.

In motor vehicle flashing lamp turn-signal systems, the direction of a turn to be made is indicated by lamps mounted on the corresponding side of the vehicle at the front and back, and such lamps, when energized, flash intermittently due to the action of a flasher switch in the circuit leading to the lamps. A pilot lamp on the dashboard of the vehicle normally flashes with the signal lamps. The circuit for operating the pilot lamp should be reliably sensitive to indicate to the operator the failure of even one lamp in the system, for danger could arise if a signal lamp was not functioning.

In a known motor vehicle flashing lamp circuit, the pilot lamp is energized by a single coil relay which is sensitive to the level of current therethrough to the signal lamps. This relay is actuated at the higher current level which exists when all the lamps are functioning, but does not similarly respond to the lower current level existing when one or more of the lamps is out. Thus, the relay ordinarily operates to flash the pilot lamp in time with the flashing of the signal lamps so long as all the lamps are operative; but if one or more of the signal lamps fails, the pilot lamp remains on or off, depending on whether the relay is normally open or normally closed.

Since the voltage of the usual motor vehicle power supply is subject to variations, the current flow through the relay coil to the lamps is subject to corresponding variations. The greater the range of voltage variation the more ditficult it is to discern the change in current level that occurs when one lamp fails. In fact, when more than a very few signal lamps are in the circuit, the current change expectable from voltage variations may be equal to or greater than the change occurring when one of 3,508,237 Patented Apr. 21, 1970 the lamps fails. For example, in the 12 volt direct current systems now generally employed in automobiles, the actual voltage fluctuates between about 10 and 15 volts. If such a system has four parallel connected signal lamps which, for example, provide a circuit current of 4.0 amperes at an applied voltage of 12.8 volts, the reduction of the applied voltage to 10 volts will drop the circuit current to 3.52 amperes with all lamps operating, as compared with a decrease of the circuit current to 3.30 amperes if one lamp fails at a time when the actual applied voltage is 15 volts. Thus, in a system with only four such signal lamps, the relay for controlling energizing of the pilot lamp has to discriminate between circuit currents of 3.52 and 3.30 amperes, that is, a difference of only 6.25%, if the pilot lamp is to indicate only a lamp failure and not an allowable voltage fluctuation. If the number of such lamps is greater than four, the circuit current with all lamps operating at an applied voltage of 10 volts is less than or equal to the circuit current resulting from an applied voltage of 15 volts upon the failure of one lamp, so that the relay cannot discriminate between the allowable voltage fluctuation and a lamp failure.

Therefore, the known circuit for operating motor vehicle signal lamps will not give a true indication of lamp outages if used with more than four active lamps and is not suitably reliable for more than three active lamps. Yet many motor vehicles are now equipped with four turn-signal lamps on each side, and turn-signal systems having more than four lamps to a side could be desirable and may be required in the future.

Accordingly, it is an object of this invention to provide a circuit for energizing a group of parallel connected lamps from a variable voltage source of direct current, which circuit includes an electrical signal device or indicator, such as a pilot lamp, and is effective to indicate reliably by such signal device if one or more of the lamps is out when the number of lamps served is greater than that employed in known lamp outage indicating systems.

Another object is to provide such a circuit which will reliably indicate the failure of even a single lamp irrespective of the number of lamps in the circuit and of the voltage variations at the source.

Still another object is to provide a lamp outage indicating circuit having the foregoing characteristics and which is especially suitable for the flashing lamp systems of motor vehicles, such as turn-signal systems.

According to this invention, a lamp outage indicating circuit for energizing from a variable voltage DC. current source a group of parallel connected lamps includes an electrical signal device, such as a pilot lamp, controlled by relay contacts positionable by the ampere turn values of first and second coils of the relay which may be wound to buck or oppose each other on a common core, current flow from the source through the lamp group being directed through the first or load coil in series therewith and the second or bucking coil receiving current flow from the source separately from the lamp group so that the flows of current through the coils vary similarly with changes in the source voltage and only the current flow through the first or load coil changes with outage of a lamp of the group to give rise to a re lationship of the respective ampere turn values of the coils by which the relay contacts are positioned to cause the signal device to give a lamp outage indication.

In cases where the parallel connected lamps of the group are to be intermittently energized or flashed, for example, as in flashing lamp systems of motor vehicles, the load coil through which current flows to the lamps is connected in series with a flasher switch for receiving such current through the latter, and the other or bucking coil may be connected in parallel with the series connected flasher switch, load coil and lamp group, or in parallel with the load coil and lamp group, or in parallel with only the lamp group.

In preferred circuits according to this invention, reliable indications of lamp outage are obtained, irrespective of the number of lamps in the circuit and irrespective of the number of such lamps that may be out, by con meeting the bucking coil of the relay in series with the relay contacts and the signal device, and in such preferred circuits the relay contacts may be either normally open or normally closed.

In circuits according to this invention for indicating lamp outage in flashing turn-signal system of motor vehicles, the signal device may be constituted by a single pilot lamp for indicating a lamp outage in either of the groups of signal lamps for signaling turns in the left and right directions, or two pilot lamps may be provided for indicating a lamp outage in the respective groups of turn signal lamps.

Further, in circuits according to this invention, the relay with a load coil and a bucking coil may have normally open and normally closed contacts connected to respective pilot lamps to indicate the proper operations of all of the load lamps or the failure or outage of one or more of the load lamps. In such circuits, the two pilot lamps for respectively indicating proper operation and outage of the load lamps may be mounted behind differently colored lenses or mounted behind a common lens and be of different colors to provide correspondingly colored indications of proper lamp operation and of lamp failure or outage.

The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of a motor vehicle flashing turn-signal system having a lamp outage indicating circuit according to this invention;

FIG. 2 is a schematic diagram showing a modification of a portion of the system illustrated by FIG. 1;

FIGS. 3 and 4 are views similar to that of FIG. 1, but showing other embodiments of this invention provided with separate pilot lamps to indicate outage of a signal lamp in the groups of lamps for signaling turns in the right and left directions;

.FIG. 5 is a schematic diagram showing the application of a lamp outage indicating circuit in accordance with this invention to a simple system for energizing a number of parallel connected lamps; and

FIG. 6 is a schematic diagram illustrating a modification of a portion of the circuit shown by FIG. 5.

Referring to FIG. 1 in detail, it will be seen that, in the flashing turn-signal system for a motor vehicle, as there shown, the direction of a turn to be made is signaled by the selective flashing or intermittent energization of a plurality of lamps 10A and 10'A mounted on the right side of the vehicle at the front and back thereof, or of a plurality of lamps 10B and 10B similarly located on the left side of the vehicle, which lamps all have given or predetermined resistances so as to pass currents dependent on the voltage imposed thereon.

The selection of the group of signal lamps to be energized for signaling a turn is effected by a turn-signal switch 11 of conventional design having movable contacts 12A and 12B that are alternately movable, by selective manual actuation of the switch, from the rest positions shown in full lines on FIG. 1 to the actuated positions shown in broken lines. As is known. each of movable contacts 12A and 12B may be automatically returned to its rest position in response to rotation of the steering wheel upon completion of a turn in the direction corresponding to the contact 12A or 12B. When in their rest positions, movable contacts 12A and 12B establish conductive bridges between fixed contacts 13A and 14A and fixed contacts 13B and 143, respectively. Signal lamps 10'A at the right-rear of the vehicle are connected in parallel between contact 14A and ground, and signal lamps 10'B at the left-rear are similarly connected in parallel between contact 14B and ground. Contacts 13A and 13B are both connected through a brake actuated switch 15 and, if desired, through a series connected ignition switch 16 to one terminal of a D.C. current source 17 having its other terminal connected to ground The source 17 may be the usual storage battery of the motor vehicle, which source has a variable voltage, for example, a voltage varying between 10 volts and 15 volts for a 12 volt D.C. current system. Thus, whenever the vehicle brakes are applied to close switch 15, the rear signal lamp 10A and/or 10'B having the associated movable contact 12A or 123 at its rest position are energized to provide a stop signal.

When in their actuated positions, contacts 12A and 12B establish conductive bridges from fixed contacts 18A and 18B to fixed contacts 19A and 19B and also contacts 14A and 14B. Signal lamp 10A at the right-front of the vehicle is connected between contact 19A and ground, and signal lamp 10B at the left-front is similarly connected between contact 19B and ground. Thus, when contact 12A is actuated, all of the lamps 10A and 10A at the right side of the vehicle are connected in parallel to contact 18A and, when contact 12B is actuated, all of the lamps 10B and 10'B at the left side of the vehicle are connected in parallel to contact 18B.

Contacts 18A and 18B are connected through a flasher switch 20, and also if desired through ignition switch 16, to D.C. current source 17. The flasher switch 20 may be of the type disclosed in US. Patent No. 3,090,851 or in US. Patent No. 3,153,125, both issused to L. Strauss et 2.1., or of any other type of switching device adapted to pass discrete intervals or pulses of current when connected to a D.C. current source. In the embodiment shown on FIG. 1, flasher switch 20 is of a type having normally open contacts with a parallel connected heating resistance 29 which periodically causes closing of the contacts. Thus, when either contact 12A or contact 12B is moved to its actuated position, the associated signal lamps 10A and 10'A at the right side of the vehicle or the associated signal lamps 10B and 10'B at the left side of the vehicle are flashed or intermittently energized to signal turn in the corresponding direction.

In order to indicate outage or failure of any of the turn-signal lamps when turn signal switch 11 is actuated to cause flashing of such lamps, the circuit shown on FIG. 1 further generally comprises an electrical signal device 21, which may be in the form of a pliot lamp, as shown, and a relay 22 for controlling operation of pilot lamp 21.

In accordance with this invention, relay 22 includes a first or load coil 23, a second or bucking coil 24, and contacts 25 and 26 which are positionable relative to each other by the respective ampere turn values of coils 23 and 24 and interposed in a circuit for energizing pilot lamp 21. Load coil 23 is interposed between contacts 18A and 18B and flasher switch 20 so as to be connected in series with the group of parallel connected signal lamps 10A and 10'A or 10B and 10'B to be flashed or intermittently energized from source 17 upon actuation of turnsignal switch 11. Thus, the flow of current through coil 23, when flasher switch 20 is closed, is the sum of the flows of current through the parallel connected signal lamps 10A and 10A or 10B and 10'B which are then connected in the circuit by actuation of switch 11. Obviously, outage or failure of a lamp or lamps in the group of signal lamps connected in the circuit by actuation of switch 11 will correspondingly reduce the flow of current through coil 23.

The other or bucking coil 24 of relay 22 is, in accordance with this invention, connected to have a flow of current from source 17 conducted through such coil 24 sepa rately from the signal lamps A and 10'A or 10B and 10'B which are connected to the energizing circuit therefor by actuation of switch 11. Thus, the flow of current through coil 24 is not affected by outage of a lamp or lamps in either group of signal lamps. However, the flow of current through bucking coil 24 and the flow of current through load coil 23 are similarly affected by variations in the voltage at source 17.

In the arrangement of FIG. 1 which illustrates one of the preferred embodiments of the invention, bucking coil 24 is connected in a series circuit with relay contacts 25, 26 and signal lamp 21, which series circuit extends from a junction 27 between ignition switch 16* and flasher switch 20 to ground, and contacts 25, 26 are normally open. Thus, current flows through coil 24 and pilot lamp 21 is energized only when movable contact 25, which may be carried by a biased armature of relay 22, is displaced from the position shown to engage fixed contact 26.

Coils 23 and 24 are arranged, for example, by being oppositely wound on a common core 28, so that their respective ampere turn values, that is, the magnetic fluxes resulting from the flows of current through coils 23 and 24, will oppose or buck each other. Accordingly, contacts 25 and 26 will be closed or retained in a closed position for energizing pilot lamp 21 only when the difference between, or the net ampere turn value of, the ampere turn value of load coil 23 (hereinafter referred to as AT and the ampere turn value of bucking coil 24 (hereinafter referred to as AT is at least as large as the minimum magnetic flux (K) required to pull in the biased armature carrying contact 25. The condition required for closing of normally open contacts 25, 26 and for maintaining such contacts in closed position may be expressed as:

The number of turns T in load coil 23 and the number of turns T in bucking coil 24 are selected so that condition (I) is achieved upon closing of contacts 25, 26 only if all of the signal lamps 10A and 10A or 10B and 10B then connected in the flashing circuit are functional, and so that ATL-ATB K when the flow of current through load coil 23 is reduced in response to outage or failure of even one, or some other selected minimum number of the signal lamps in the group thereof then connected in the flashing circuit. Obviously, in selecting the numbers of turns T and T consideration must be given to the ratio of the current flow through the load coil 23 to the current flow through the bucking coil, which ratio is dependent, at least in part, on the number of parallel connected signal lamps in each group thereof to be connected in the flashing circuit by actuation of switch 11. For example, if each of such groups of signal lamps contains four lamps, as in the embodiment of FIGS. 1, and if the current flow through pilot lamp 21 is assumed to be equal to that through each signal lamp, then, so long as flasher switch 20 is in its closed condition with one of the groups of signal lamps connected in the flashing circuit, the flow of current through coil 23 to the four parallel signal lamps 10A and 10A or 10B and 10'B will be approximately four times as great as the flow of current through coil 24 to the single pilot lamp 21 upon closing of relay contacts 25 and 26.

If the signal lamps and the pilot lamp are assumed to be types each having a current flow therethrough of 1 ampere when a voltage of 12.85 volts is impressed thereon, the current flow through each lamp will vary between .88 amperes and 1.1 amperes, that is a difference of .22 amperes, for voltage variations between 10 and 15 volts, respectively. Thus, in the case where four signal lamps are included in each group to be connected to the flasher circuit, the flow of current through load coil 23 to such signal lamps will vary by .88 amperes for a voltage variation between 10 and 15 volts, while the same voltage variation will produce a similar, but smaller variation of .22 ampere in the flow of current through bucking coil 24 to the single pilot lamp 21. Since, for

any voltage variation at the source of DC. current, the change in the flow of current through load coil 23 is greater than the change in current through bucking coil 24 by a factor substantially equal to the number of lamps, the numbers of turns T and T must further be selected in relation to the number of signal lamps to ensure that an allowable decrease in source voltage does not decrease AT -AT B to less than K, while all signal lamps are functional and thereby cause an erroneous indication of lamp outage. Thus, AT AT with one which can be solved to give T /T +5 N or N T /T +5 Further, it is desirable that AT AT result in positive net values, that is, AT AT when all signal lamps are functional. This condition is satisfied when (IV). It is even desirable that AT AT when one signal lamp is out, and this condition is satisfied by making N T /T +l (V).

For the illustrated example having four signal lamps (N=4) in each group to be connected to the flashing circuit, T /T should be less than 4 (Equation IV) and preferably less than 3 (Equation V). Further, the exact turns ratio should be selected, or a suitable resistance should be interposed in series with either the coil 23 or the coil 24, or the resistance or bias of the relay armature against being pulled-in to close contacts 25, 26 should be selected so that, for actual source voltages varying between 10 volts and 15 volts, as expected, the condition of Equation I above is always satisfied with all signal lamps functioning and the condition of Equation II above is satisfied whenever one, or some other selected minimum number of the signal lamps is out.

Of course, if the pilot lamp has current characteristic different from the current characteristics of the signal lamps, Equations III, IV and V will be be correspondingly changed.

The operation of the circuit of FIG. 1 is as follows:

Assuming that ignition or master switch 16 is closed, manipulation of switch 11, for example, to move contact 12A to its actuated position, will cause a flow of current to occur through heating resistance 29 of flasher switch 20. After a predetermined period of such heating, the flasher switch contacts close to pass a flow of current through the closed contacts and to signal lamp 10A and 10A to light the latter or as many of them as are functional. Since relay contacts 25, 26 in series with coil 24- are normally open, initially there is no current flow through coil 24, and the ampere turn value of coil 23 is not bucked at all. If the number of signal lamps that are functional is sufllcient to result in a value of AT greater than K, the relay armature is pulled-in to close contacts 25, 26, with the result that a flow of current passes through coil 24 to pilot lamp 21 for lighting the latter. If all signal lamps are functional the simultaneous flows of current through coils 23 and 24 result in the condition AT =AT ZK, so that the relay contacts 25, 26 remain closed so long as the contacts of flasher switch 20 are closed. When the flasher switch contacts are closed, relatively little current passes through the high, parallel resistance of heater 29 so that progressive cooling occurs until the flasher contacts again open. When the flasher switch opens to deenergize signal lamps 10A and 10'A, current flow through coil 23 is interrupted and the initially continued flow of current through coil 24 would tend to cause a reversal of the polarity of the net magnetic flux, but in effecting such reversal of polarity the net flux drops toward a zero value so that relay contacts 25, 26 open to deenergize pilot lamp 21. Thus, so long as all signal lamps connected in the flashing circuit are functional, pilot lamp 21 will flash substantially in time with the flashing signal lamps.

If one signal lamp is out, relay contacts 25, 26 are closed in response to the initial flow of current through load coil 23. However, when contacts 25, 26 close, the resulting flow of current through bucking coil 24 to pilot lamp 21 achieves the condition AT =AT K, so that contacts 25, 26 will again open even though the contacts of flasher switch remain closed. Thus, in response to outage of a single signal lamp, pilot lamp 21 will be made to flicker and thereby indicate such outage.

If several of the signal lamps are out, either one of two conditions may be encountered. Firstly, the number of signal lamps remaining functional may be so small as to result in an initial flow of current through coil 23 that is insufficient to create the condition AT K necessary for even momentary closing of contacts 25, 26 and the described flickering illumination of pilot lamp 21, so that the latter will remain dark. Secondly, if the initial flow of current through coil 23 is sufficient to cause closing of contacts 25, 26, it may still be of such small magnitude that AT -AT occurring on closing of contacts 25, 26 tends to result in a negative net value greater than K. However, in tending to effect reversal of the polarity of the net flux, the latter drops toward a value of zero and thereby causes opening of contacts 25, 26 to interrupt the circuit through coil 24 to pilot lamp 21. Thus, flickering of pilot lamp 21 again occurs to indicate outage of more than one signal lamp, even though coils 23 and 24 are wound on the same core 28 and the net flux resulting from AT being greater than AT may be larger than the net flux required to pull in the armature and close contacts 25, 26.

It should be noted that, with the flasher switch 20 having normally open contacts, as shown on FIG. 1, the resistance of heater 29 must be sufficiently large in relation to the number of signal lamps 10A and 10'A or 10B and 10'B to ensure that, when the flasher contacts are open, the flow of current through heating resistance 29, and hence which is divided among the paralleled signal lamps, will be substantially less than that required to light such lamps. Of course, upon closing of the contacts of the flasher switch, such resistance 29 is shunted by the closed contacts and thus effectively removed from the circult of the signal lamps which have substantially the full source voltage impressed thereon to light the same.

If desired, the flasher switch 20 and relay 22 can be conveniently embodied in one assembly, as represented by the enclosing box in broken lines on FIG. 1, which assembly has terminals X, Y and Z respectively adapted for connection to the source 17 through ignition or master switch 16, to the turn signal switch 11, and to the pilot lamp 21. Although the assembly 30 employs a conventional flasher switch 20 with normally open contacts, a flasher switch with normally closed contacts may be substituted therefor, in which case current flows therethrough immediately upon actuation of the turn signal switch connected to terminal Y and, after a predetermined period, the normally closed contacts of the flasher switch are opened for another predetermined period, with the periodic opening and closing of the contacts being repeated cyclically to flash the signal lamps so long as the latter are connected to the flashing circuit.

It is also to be noted that the relay 22 having normally open contacts 25, 26 may be replaced by a similar relay having normally closed contacts, for example, as in the case of the relay 22a shown on FIG. 2. As before, the relay 22a has a load coil 23a for connection in series with the parallel connected signal lamps so that the flow of current through coil 23a is determined by the sum of the currents flowing through the signal lamps, and a bucking coil 24a, which may be oppositely wound on the same core 28a as coil 23a and is connected in a series circuit with normally closed contacts 25a, 26a and the pilot lamp. Such series circuit extends from a junction 27a located intermediate the normally open contacts of flasher switch 20 and coil 23a so that coil 24a also receives a pulsing or intermittent flow of current in response to the opening and closing of the flasher switch contacts. It will be apparent that the flow of current through coil 24a will be separate from the flow of current through the signal lamps and thus not influenced by outage of a signal lamp, and that the flows of current through coils 23a and 24a will be similarly influenced by variations of the source voltage.

In the case of the relay 22a, the number of turns T in load coil 23a and the number of turns T in bucking coil 24a may be selected so that, when all signal lamps are functional, the ampere turn value AT of load coil 23a is substantially balanced by the ampere turn value AT of bucking coil 24a, or at least so that in which K is the net ampere turn value or magnetic flux required to open the normally closed contacts 25a, 26a. Further, the respective numbers of turns in coils 23a and 24a are selected so that upon outage of one, or some other predetermined minimum number of the signal lamps, there will be obtained the condition ATE-A TL K1 (VI thereby to open the contacts 25a, 26a.

As in the case of the relay 22, the numbers of turns in coils 23a and 24a, or the resistance to relative movement of contacts 25a, 26a to their open position, that is, the value of K are selected so that the conditions of Equations VI and VII are respectively satisfied when all signal lamps are functional and when one or more signal lamps are out, irrespective of the acceptable variations of the source voltage. Further, the value of resistance 29 is selected so that, when turn selector switch 11 is in its neutral or non-actuated position, the current through resistance 29, coil 24a, contacts 25a, 26a and pilot lamp 21 to ground will be limited by resistance 29 and the resistance of lamp 21 to a value which cannot cause heating of the flasher switch 20 to a temperature at which the latters normally open contacts are made to close. Further, such limited current through coil 24a will result in an ampere turn value AT K that is, in a magnetic flux that is less than that required to overcome the spring bias of contacts 25a, 26a to their normall closed position. Thus, so long as turn signal or selector switch 11 remains in its neutral position, the contacts of flasher switch 20 remain open and contacts 25a, 26a of relay 22a remain in their normal closed position.

When turn signal switch 11 is actuated, the parallel connected signal lamps 10A and IO'A or 10B and 10B provide relatively lower resistance path from junction 27a to ground and accordingly increase the current flow through resistance 29 to a value that raises the temperature sufliciently to close the contacts of flasher switch 20. The increased current flow through resistance 29, and

the correspondingly increased voltage drop across resistance 29, decreases the voltage impressed on pilot lamp 21 so that the latter is not brightly illuminated until the contacts of flasher switch 20 are closed.

Upon closing of the contacts of flasher switch 20, the battery voltage is impressed at junction 27a. If all of the connected signal lamps are functional, the ampere turn values of coils 23a and 24a are equal and opposite, that is, AT AT K so that contacts 25a and 26a remain closed and the pilot lamp 21 connected to terminal Z is flashed in timed relation to the flashing of the signal lamps. If one or more of the signal lamps are out, the resulting decrease of the flow of current through coil 23a, without corresponding decrease in the current flow through coil 24a, causes AT -AT K with the result that contacts 25a, 26a are opened to extinguish pilot lamp 21. The opening of contacts 25a, 26a also decreases the ampere turn value of coil 24a to zero and, before the contacts 250:, 26a can close in the course of the decrease of the ampere turn value of coil 24a, the ampere turn value or flux of coil 23a becomes controlling, that is, AT K to maintain contacts 25a, 26a in open condition, thereby to keep pilot lamp 21 in its extinguished condition.

In FIG. 1, the outage indicating circuit in accordance with this invention is associated with a single pilot lamp 21 which serves to indicate the proper functioning or outage of lamps in the two groups of signal lamp 10A and 10'A, and 10B and 10'B provided for signaling turns in the right and left directions, respectively. However, outage indicating circuits in accordance with this invention may be incorporated in flashing turn-signal systems for motor vehicles which have two pilot lamps for respectively indicating outage of lamps in the groups of signal lamps provided for signaling turns in the right and left directions.

For example, as shown on FIG. 3, there is provided an assembly 30b of a normally open flasher switch and a relay 22b which is similar to the relay 22 in that it has a load coil 23b connected in series between the flasher switch and contacts 18A, 18B of turn signal switch 11, a bucking coil 24b and normally open contacts B, 268 which are closed only when AT A T ZK. However, in the circuit shown in FIG. 3, bucking co-il 24b is connected in series with contacts 25b, 26b and with two parallel branches having pilot lamps 21A and 21B in series with diodes 31A and 318, respectively, in a circuit that extends from contacts 19A and 19B of turn signal switch 11 to ground. It will be apparent that, when switch 11 is manipulated to move either contact 12A or 12B to its actuated position and thereby connect signal lamp 10A and 10B or 10B and 10'B to the flashing circuit, the pulsing current flowing through load coil 23b is divided, at either contact 19A or 1913, and a portion thereof can flow through either pilot lamp 21A or 21B, respectively, and bucking coil 24b to ground upon closing of relay contacts 25b, 26b. Thus, the flow of current through bucking coil 24b is separate from the flows of current through the parallel connected signal lamps 10A and 10A or 10B and 10'B, is not influenced by outage of such signal lamps. On the other hand, the flow of current through load coil 23b is dependent on the number of functioning signal lamps, and the flows of current through coils 23b and 24b are similarly influenced by variations in the voltage at source 17.

As in the case if relay 22, the numbers of turns in coils 23b and 24b of relay 22b and the resistance to closing of its contacts 25b, 26b are selected so that A TL'A T B=K when all signal lamps are functional irrespective of variations in the source voltage, and so that whenever one, or some other predetermined minimum number of the signal lamps is out.

The arrangement of FIG. 3 operates as follows:

Upon manipulation of switch 11, for example, to move its contact 12B to its actuated position, as shown in broken lines, left turn signaling lamps 10B and 10'B are connected in parallel to contact 18B and hence to the flashing circuit, and simultaneously the series circuit containing pilot lamp 218, bucking coil 24b and relay contacts 25b, 26b is connected to contact 183 by way of engaged contacts 12B and 19B. When flasher switch 20 closes, there is an initial flow of current through load coil 23b to signal lamps 10B and 10B, which initial flow of current results in AT K so that contacts 25b, 26b are closed and current flow passes from contact 19B through pilot lamp 21B, diode 31B, coil 24b and the closed relay contacts to be ground. If all signal lamps are functional, AT AT =K so that contacts 25b, 26b remain closed for so long as flasher switch 20 is closed, whereby pilot lamp 21B is flashed in time with signal lamps 10B and 10'B to indicate that a left turn is being signaled and that all of the signal lamps provided for that purpose are functional.

It should be noted that flow of current through pilot lamp 21A and signal lamp 10A to ground is blocked by diode 31A, thereby to prevent lighting of pilot lamp 21A or of the signal lamp 10A in series therewith when contact 12A is in its rest position.

If one of signal lamps 10B and 10'B is out, the initial flow of current through coil 23b is suflicient to close relay contacts 25b, 26b and temporarily light pilot lamp 213. However, when the bucking flow of current through coil 24b occurs, AT AT K so that contacts 25b, 26b open and pilot lamp 21B goes out. Thus, so long as flasher switch 20 is closed, pilot lamp 21B is made to flicker, thereby indicating outage of a lamp in the group of lamps for signaling a left turn. If more than one signal lamp is out, the result is again flickering of pilot lamp 21B, as described above with respect to the arrangement of FIG. 1, unless the number of inoperative signal lamps is so large as to result in an initial flow of current through coil 23b that is to small to cause initial closing of contacts 25b, 26b, in which case, pilot lamp 21B remains dark. Diodes 31A and 31B further ensure that, when contacts 25b, 26!; are open in response to lamp outage, current cannot flow from contact 19B through lamps 21B, 21A and 10A to ground for even dimly illuminating lamps 21A and 21B simultaneously.

When switch .11 is manipulated to signal a right turn by lamps 10A and 10'A, the operation of pilot lamp 21A is similar to that described above with respect to pilot lamp 21B.

Referring now to FIG. 4, there is shown another circuit according to this invention employing two pilot lamps 21'A and 21' B for indicating proper operation or outage of the lamps provided for signaling turns in the right and left directions, respectively. The circuit of FIG. 4 includes an assembly 30 which, as shown, may be of the same type as that employed in FIG. 1, and thus includes a normally open flasher switch 20 and a two coil relay 22 having normally open contacts.

In FIG. 4, the terminals X and Y of assembly 30 are connected in the same manner as shown on FIG. 1, and the terminal Z, rather than being connected through a single pilot lamp to ground, as previously disclosed, is connected through a diode 31A and pilot lamp 21'A, and a diode 31B and pilot lamp 21'B, in parallel, to contacts 19B and 19A, respectively, of switch 11.

The operation of the circuit shown on FIG. 4 is as follows:

When switch 11 is manipulated, for example, to move its contact 12B to the actuated position for signaling a left turn, and assuming that all of signal lamps 10B and ltl'B are functional, closing of flasher switch 20 results in a flow of current through coil 23 to light signal lamps 10B and 10B and to close relay contacts 25, 26- so that current also flows through coil 24, contacts 25, 26, pilot lamp 21'B and signal lamp A to ground. Since all of signal lamps 10B and 10B are functional, contacts 25, 26 remain closed so long as flasher switch is closed, and thus pilot lamp 2.1B is flashed in time with signal lamps 10B and 10'B. Since the voltage drops across coils 23 and 24 are relatively small, approximately equal voltages are applied to opposite sides of pilot lamp 21A upon movement of contact 12B to its actuated position and closing of relay contacts 25, 26, and thus pilot lamp 21'A is not illuminated. Further, pilot lamps 21'A and 21B are selected to be lit or rendered incandescent by substantially smaller flows of current therethrough than are necessary to light signal lamps 10A and -10A or 103 and -10B. Thus, although pilot lamp 21'B is in series with signal lamp 10A, the reduced current flow through that series circuit can light lamp 21B but not lamp 10A.

If one or more of signal lamps 10B and 10B is out, such outage is indicated either by flickering of pilot lamp 21'B or by the failure of that pilot lamp to light, as described above with reference to FIG. 1. Of course, if switch 11 is manipulated to signal a right turn by flashing of signal lamps 10A and 10A, then the pilot lamp 21-A is either flashed in time with such signal lamps to indicate that they are all functional, or pilot lamp 21'A is made to flicker or not lit at all to indicate outage of one or more of the respective signal lamps.

The diodes 31'A and 31B ensure that, when contacts 25, 26 are open by reason of the outage of signal lamps upon the actuation of turn signal switch 11, current will not flow from contact 19B through lamp 21'A, lamp 21'B and lamp 10A to ground, or from contact 19A through lamp 21B, lamp 21'A and lamp 10B to ground, to even dimly illuminate both pilot lamps simultaneously.

In all of the above described embodiments of the invention, the circuits for indicating lamp outage have been associated with flashing signal lamp systems, specifically flashing turn-signal systems for motor vehicles. However, as shown on FIG. 5, a relay 22 such as has been described above with reference to FIG. 1 may be employed with a pilot lamp 21 to indicate lamp outage in a simple circuit for energizing parallel connected load lamps 10 from a variable voltage source 17 of DO. current upon closing of a master switch 16. As before, upon closing of switch 16, the flow of current to lamps 10 passes load coil 23 of the relay so that the current flow through coil 23 is dependent on the number of functioning lamps 10. The flow of current through bucking coil 24 is separate from the current flows through lamps .10 and thus is not influenced by outage of any of such lamps. However, the flows of current through both coils 23 and 24 are similarly varied in response to variations of the source voltage.

When switch 16 is closed, the initial flow of current through coil 23 to lamp 10 causes contacts 25, 26 to close. If all lamps 10 are functioning so that AT AT 2 K, contacts remain closed and pilot lamp 21 is lighted continuously to indicate that all lamps are functioning. If one of lamps 10 is out, so that, after the initial closing of contacts 25, 26 AT --AT K, contacts 25, 26 then open and there results a flickering of pilot lamp 21 to indicate the lamp outage. If the number of lamps that is out is so large that the flow of current through load coil 23 while contacts 25, 26 are open does not result in AT K, there is not even momentary closing of contacts 25, 26 and pilot lamp 21 remains dark. If the outage of several of lamps '10 results in AT being greater than AT by at least the value of K, then the polarity of the net flux resulting from AT AT K is reversed relative to the polarity of the initial flux when contacts 25, 26 are open and AT K, and in the course of such reversal of polarity the net flux becomes less than K to again open the contacts. Thus, even when several lamps are out, pilot lamp 21 is made to flicker and reliably indicates such lamp outage.

Refering now to FIG. 6, there is shown a relay 220 in accordance with this invention which may be employed in a system, for example, of the type shown in FIG. 5, for lighting a pilot lamp 21C when all of the load lamps are functional and for lighting a pilot lamp 21D upon outage of one or more of the load lamps. Such pilot lamps 21C and 21D may be mounted behind differently colored lenses or be themselves of different colors and mounted behind a common lens to provide characteristic color indications of the functioning of all load lamps and the outage of one or more of the load lamps.

As shown, relay 220 includes a load coil 23c connected in series with the paralleled load lamps to the variable voltage source of DC. current so that the flow of current through coil 230 is dependent upon the number of load lamps that are functioning. Relay 220 further has a bucking coil 240 connected in series with pilot lamp 210 between a fixed relay contact 26c and ground, and a movable relay contact 25c connected in parallel with coil 23c and normally engaging a fixed contact 1260 which is connected through pilot lamp 21D to ground. The numbers of turns T and T in coils 23c and 24c and the magnitude of the net magnetic flux (K) required to move contact 250 from the position shown into engagement with contact 260 are selected so that AT A T =K when all the load lamps are functional, and AT -A T K when one, or some other minimum number of load lamps is out.

If all load lamps are functional when the same are connected to the DC. current source through coil 23c, then the initial current flow through coil 23c obviously results in AT K and contact 250 is moved to engage contact 260 and thereby light pilot lamp 210 by current flowing through coil 24c. Thereafter, AT AT =K so that contact 250 remains in engagement with contact 26c to continue the illumination of pilot lamp 21C for indicating the proper functioning of all load lamps. However, if one or some other predetermined minimum number of the load lamps is out, AT A T K so that, after the initial movement of contact 250 to contact 260, contact returns to its normal position against contact 1260, whereby there is obtained a flickering of both pilot lamps 21C and 21D. If many of the load lamps are out, so that AT K, the initial current flow through coil 230 with contact 250 spaced from contact 260 cannot cause movement of contact 250 away from contact 126050 that pilot lamp 21D is continuously lighted to indicate outage of many load lamps.

All of the above described embodiments of the invention have the bucking coil of the relay arranged in series with a pilot lamp and contacts of the relay. Such arrangement is advantageous in that, even though the bucking and load coils are wound on a common core, in which case the movable relay contact may be displaced or pulled-in whenever a suitable difference exists between the ampere turn values 'of the bucking and load coils, whichever is larger, the failure of several lamps will not result in a false indication of all lamps being functional.

In all of the above described circuits according to this invention, pilot lamps have been provided for giving characteristic indications of the proper functioning and outage of the associated signal or load lamps. However, it is obvious that such pilot lamps may be readily re placed by other types of electrical signal devices operative to give visual or audible indication of the condition or the signal or load lamps.

What is claimed is:

1. In a lamp outage indicating circuit for energizing from a DC. current source of variable voltage at least one group of several lamps having given resistances to current flow and at least some of which are connected in parallel, including means for connecting said lamps to said source and an electrical signal device for indicating a lamp outage, the combination of a relay having first and second coils which generate counteracting electromagnetic forces and having contact means positioned according to the relative ampere turn values of said coils and connected with said signal device for controlling the operation of said device, and respective means in said circuit for conducting current from said connecting means through said first coil and said group of lamps, in series, and through said second coil in series with said contact means and said signal device, but separately from said lamps, so that current will flow through said second coil only when said contact means is closed, and so that flows of current through said coils will vary similarly with variations of the voltage of said source and so that the current fiow through said first coil, but not any current flow through said second coil, is reduced by outage of a lamp of said group, the respective ampere turn values of said coils generated by flows of current therethrough at any of the normal voltages of said source being such that said contact means is held in closed position when said group of lamps is energized and all lamps of said groups are functional yet such that the force of said second coil overcomes the force of said first coil so as to switch said contact means to open position thereby causing a lamp outage indication by said signal device if a lamp of said group is not functional.

2. A lamp outage indicating circuit according to claim 1, said contact means being normally open, so that the force of said first coil will switch said contact means to closed position when said group of lamps is energized, said respective ampere turn values being such that if a lamp of said group is not functional said contact means will be opened by overriding force of said second coil to interrupt current flow through said second coil and cause a flickering of said signal device by ensuing alternating sections of said coils.

3. A lamp outage indicating circuit according to claim 1, said contact means being normally closed and said respective ampere turn values being such that they cause said contact means to remain in closed position so as to energize said signal device when all lamps of said group are functional, yet such that the force of said second coil will switch said contact means to open position to deenergize said signal device, and the force of said first coil will then hold said contact means in open position, if a lamp of said group is not functional.

4. A lamp outage indicating circuit according to claim -1, in which said connecting means includes flasher switch means operative to pass discrete pulses of DC. current from said source to the lamps for flashing the latter.

5. A lamp outage indicating circuit according to claim 1, in which first and second groups of said lamps are provided for alternate energization from said source, and said current conducting means in the circuit includes selector switch means actuatable to connect either group of said lamps in series with said first coil.

6. A lamp outage indicating circuit according to claim 5, in which said signal device includes a pilot lamp energizable through said contact means when either of said groups of lamps is connected with said first coil.

7. A lamp outage indicating circuit according to claim 5, in which said signal device includes first and second pilot lamps respectively corresponding to said first and second groups of lamps, and said pilot lamps are connected in parallel with the respective grou s of lamps and in parallel with each other in a series connection with said second coil and said contact means so that, upon actuation of said selector switch means, any lamp outage in the group of lamps thereby connected with said first coil is indicated by the respective pilot lamp.

8. A lamp outage indicating circuit according to claim 5, in which said signal device includes first and second pilot lamps respectively corresponding to said first and second groups of lamps, said pilot lamps being connected in parallel with each other in a series circuit with said second coil and said contact means so as to have substantially the voltage at said source impressed at one side of each of said pilot lamps when said contact means is in closed position, and means for impressing substantially the voltage at said source is impressed selectively at the other side of said first pilot lamp and at the other side of said second pilot lamp upon actuation of said selector switch means to connect said second lamp group and said first lamp group, respectively, in series with said first coil.

9. A lamp outage indicating circuit according to claim 1, in which said signal device includes first and second pilot lamps energizable to indicate the functioning of all of said lamps and the outage of a lamp, respectively, and said contact means includes normally closed contacts in series with said second pilot lamp to energize the latter in said closed position of the contact means and means for impressing normally open contacts in series with said first pilot lamp and which are closed in said open position of said contact means.

References Cited UNITED STATES PATENTS 1,726,423 8/1929 Churcher 340-251 XR 2,127,887 8/1938 Rayburn 340--251 XR 3,171,096 2/1965 Murray et a1. 340-251 XR 3,250,950 5/1966 Reiche 340251 XR JOHN W. CALDWELL, Primary Examiner D. MYER, Assistant Examiner US. Cl. X.R. 31582; 340

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