US3179847A - Electrical potential indicator - Google Patents

Description

A ril 20, 1965 Filed Jan. 25, 1960 R. E. DE MOTT 3,179,847

' ELECTRICAL POTENTIAL INDICATOR 2 Sheets-Sheet .l

f 5 .INVENTOR.

April 20, 1965 R. E. DE MOTT 3,179,847

ELECTRICAL POTENTIAL INDICATOR Filed Jan. 25. 1960 2 Sheets-Sheet 2 INVENTOR. FQQIeT/F DE/Yarr United. States Patent 3,1'7,847 ELECTRICAL POTENTIAL INDECATGR Robert E. De Mott, Delia, Alberta, Canada Filed Jan. 25, 1966, Ser. No. 4,327 1 Claim. (Cl. 315-185) My invention relates to new and useful improvements in electrical potential indicators, more specifically to indicators adapted to be used with incandescent bulbs and the like either individually or connected in a series, the principal object and essence of my invention being to provide a device of the character herewithin described wherein a predetermined amount of potential may be indicated when such potential has been applied across the lamp filament.

In the past, particularly when it is desired to ascertain which of a plurality of series-connected incandescent lamps have failed, it is necessary to remove each lamp independently and replace same with a lamp which is known to operate until the burned out lamp is located.

I have overcome this disadvantage by providing a potential indicator incorporated in parallel with the filament of the said lamp whereby a visual inspection of the lamp enables the user to ascertain which of the lamps has failed. I accomplish this either by a color change substance associated with the said lamp together with a heat generating impedance or by a deposit forming substance also activated by a heat generating impedance, or by the provision of two evacuated, sealed and joined envelopes, each one having a filament mounted therein, said filaments being connected in parallel. One of these filaments is the main illuminating filament and the other is an auxiliary filament adapted to have a longer operating life and to operate at a lower temperature thereby acting as an indicator.

It can therefore be said that the present invention relates to improvements in electrical potential indicators and more particularly to such indicators for denoting a predetermined amount of potential, and further to improvements in such indicators for denoting when a predetermined amount of potential has been applied across an incandescent lamp or across any specific electrical device. With such a lamp theextinguishing of same may be caused by the failure of its filament or by the interruption of the line potential.

One object of this invention, when in connection with incandescent lamps or electrical devices, is for denoting when either such a lamp or device is defective.

Another object of my invention is to utilize same in connection with an associated means for indicating when such a lamp or device in series with a plurality of lamps or devices has failed, and to indicate which particular lamp or device has failed.

A further object of my invention is to provide a device of the character herewithin described which is adapted to be used in connection with electrical fuses whereby the fuse concerned may be isolated readily if same has failed.

Certain types of electric lamps and devices are frequently operated in series, whereby the combined poten- In my invention an indicator will show which of the lamps or devices in series has failed, without having to test each lamp or device in the circuit. However, it is to be understood that the present invention is not limited to use With series connections only, nor to use in lamp and tube circuits only. Also it is to be understood that two filaments in parallel have conventionally been employed sealed within the same lamp envelope, one filament supplying the normal illumination, and the other auxiliary filament operating at a lower temperature, and having a longer operating life, and acting as an indicator filament. In this conventional arrangement should the lamp envelope develop a crack, voiding its vacuum, the said indicator filament and said main filament and said main filament would burn out, whereas with my improved invention this disadvantage is overcome.

As an advantage I provide an inexpensive indicator in association with various electrical apparatus, said indicator being mounted on the exterior, in the interior, or other locations in connection with such lamps of devices, said indicator being electrically connected in parallel with a currenhcarrying element of said device Where indication is desired, upon the application of a predetermined potential in the particular circuit, said potential being greater than normal operational potential.

As a further advantage I provide an inexpensive indicator in association with a source of electrical potential where indication is desired, upon tr e application of a predetermined increase in the amount of potential and Where said increased potential results in an increase of said indicators temperature.

As a means of mechanical and safety protection shielda heat responsive color change substance to be employed as an indicator, associated with a heat generating electrical resistor, and electric power source and an incandescent lamp filament or a current-carrying element or" an electrical device. Said heater resistor being associated with said color change substance to be electrically connected in parallel with the lamp filament or said currentcarrying element, or across said source or" electrical potential.

in another embodiment my invention comprises a fusible and visible depositable substance to :be employed as an indicator instead of a color change substance associated with the heat generating resistor. In the case of each of the above embodiments the color change and the fusing and visible deposit occurs only When said substance is subjected to a predetermined increase in temperature as the result of said heater resistor being subjected to a predetermined increase in the amount of applied electrical potential.

Sustained surge potential on a supply line is inlicated either by a change in color of said associated color change substance, or by a fused condition and a visible deposit of said associated fusible and visible depositable substance.

In a series circuit, failure of a filamentof one lamp or a current-carrying element of one electrical device is indicated by an inoperative arrangement together with either a change in color of said associated color change substance, or a fused condition and a visible deposit of said associated fusible and visible deposit-leaving substance.

In a series circuit, failure of line potential isindicated by an inoperative arrangement together with either unchanged color of all said associated color change substances or of unfused condition, in which case there re mains no visible deposit of any of said associated fusible and visible depositable substances. t

In a further embodiment thereof, my invention comprises, in combination, two evacuated sealed and joined .9 envelopes, each one having a filament mounted therein, the two filaments being connected in parallel one of which is the main illumination filament, and the other an auxiliary filament to be employed as an indicator. Said auxiliary filament emits light of a lower intensity than said main filament, and in comparison has a longer operating life, so that failure of the main filament is indicated by this lower intensity light emitted by said associated auxiliary filament.

A series circuit failure of the main filament of such a lamp is here indicated by the extinguishing of this main filament and an above normal intensity of light emitted by said associated auxiliary filament. At the same time less than normal intensity of light is emitted by the intact filaments of the other lamps of the series arrangement, and of course failure of line potential in such a series circuitextinguishes all the lamps.

With the foregoing objects in view, and such other objects and advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:

FIGURE 1 is a side elevation of a lamp illustrating one embodiment of the invention mounted in the interior of the lamp envelope.

FIGURE 2 is a fragmentary elevation of the top half of a lamp envelope showing a further embodiment of my device mounted externally of the envelope.

FIGURE 3 is a fragmentary elevation of the lower portion of a lamp illustrating a further embodiment of my invention mounted within an elongated, transparent lamp base assembly.

FIGURE 4 is a perspective view illustrating the associated color change or fusible and visible deposit substance applied on the heater resistor per se.

FIGURE 5 is a top plan section taken along the lines 5-5 of FIGURE. 1.

FIGURE 6 is a diagrammatic representation illustrating a plurality of lamps in series.

FIGURE 7 is a top plan view of FIGURE 2 along the lines 77 thereof.

FIGURE 7A is a side elevation of the cover per se of FIGURES 2 and 7.

FIGURE 8 is a side elevation of a lamp illustrating a further embodiment of my device.

FIGURE 9 is a side elevation of a lamp in phantom showing a yet further embodiment of my device.

' FIGURE 10 is a side elevation of the lower half of a lamp shown in phantom as illustrated in FIGURE 9 showing only the position of the transparent area through V which the indicator may be viewed.

FIGURE 11 shows a side elevation of the upper portion of a lamp with a further embodiment of my invention mounted externally thereof.

FIGURE 12 is a diagrammatic representation of a plurality of lamps mounted in series with the associated lamp indicators enclosed within separate evacuated envelopes placed upon the main evacuated envelopes.

In the drawings like characters of reference indicate corresponding parts in the different figures:

Proceeding therefore to describe my invention in detail, reference should be made to the accompanying drawings inwhich I have indicated a lamp 1 having an evacuated and sealed envelope 2 and an incandescent filament 3 supported by conventionally sealed-in lead wires 4. The envelope Z has a conventional base 5 attached thereto and is provided with contact elements 6 and 7 therein to which contact elements, the wires 4- are connected conventionally. The wires 4- are also connected to opposite ends of said filament 3 and are maintained in the desired spaced relationship by means of vitreous head 8.

Dealing now specifically with the embodiment illustrated in FIGURE 1, I have provided a further pair of all lead wires 4' extending upwardly from the lead wires 4, being maintained in spaced relationship by vitreous bead 9. Adjacent the tip 2' of the envelope, these extended lead wires 4' are connected to the terminals of a heat generating electrical bleeder resistor 10 which is associated with a heat responsive color change substance 11 supported upon a wafer 13. This substance 11 acts as the indicator and is capable of undergoing a change in color only when subjected to a predetermined amount of heat, said predetermined amount of heat being produced by the heat generated by said resistor 10 and only when this resistor is subjected to a predetermined increase of potential thereacross.

The design and proportion of said heater resistor 1t) and said color change substance 11 should be such that the former assumes heat generating qualities, and the latter undergoes its color change only as a result of a predetermined temperature being generated as mentioned, as a consequence of a predetermined electrical potential being applied across said resistor 10. The amount of said predetermined temperature for this color change should be somewhat greater than the temperature generated by said resistor 10 when it is subjected to only the normal potential of said filament 3. As a result the amount of said predetermined electrical potential required for this color change will also be somewhat greater than the normal potential of said filament 3.

Said color change substance 11 thus will be under the control of the heat generated by resistor It and should be such that a resultant color change will occur only when resistor 10 becomes suliiciently energized to assume heat generating qualities and thus the generation of su'ificient heat will occur only when resistor 10 is subjected to a predetermined greater than normal amount of electrical potential to therefore indicate the condition of said associated lamp 1 as for instance when filament 3 fails.

To provide a window through which said color change substance 11 can be observed directly opposite same, the tip of said envelope 2 is transparent as indicated at 12. It said lamp l is to receive a decorative coating, said transparent area 12 should be left uncoated.

To determine the condition of said lamp 1 it is only necessary to look at this area 12 to observe the condition of said associated color change substance 11. The heater resistor lit) should be of low wattage, and relatively high resistance and consists of any suitable type, such as printed, impregnated, carbon, metallized, sprayed, painted, wirewound or in filament form, and the like. The color change substance 11 to be composed of any suitable substance, such as paint, invisible ink, dye, lacquer, a mixture of an oxidizing agent with a reducing agent and the like, any of which would be capable of undergoing a change in color only when subjected to a predetermined increase in temperature. This color change substance is to be'applied in any suitable manner, such as by coating, by impregnating or by mixing with said resistor material, etc. Said color change coating may be applied by any suitable process, such as by dipping, spraying, printing, painting and the like.

It is to be understood that the heater resistor It) and said color change substance 11 could conveniently be mounted on a wafer 13 (as illustrated in FIGURE 5) by printing, spraying, painting and the like in a similar manner to that employed in conventional printed circuits.

A Wafer such as this would consist of any suitable heat resisting material, such as ceramic, mica or the like, and would be supported on the interior surface of said envelope 2 near the tip at 14, similarly as electronic vacuum tube electrode assembly mica support-wafers are conventionally supported. This wafer 13 also serves as a shield, preventing the normal heat generated by said filament 3 from producing a 'color change in said substance 11. If preferred, the edge of wafer 13 may be attached and bonded to the interior surface of envelope 2 at 14 similarly as an incandescent lamp base is attached and bonded to its lamp envelope.

FIGURE 6 shows diagrammatically a number of lamps in series, each similar to those illustrated in FIGURE 1 and embodying the principles of the present invention, with lead wires connecting with a source of potential.

When said filaments 3 are intact the high resistance paths of said resistors it are in parallel with the relatively low resistance paths of said filaments 3. As a result of this a small fraction of the line potential which is insuflicient to cause color change is applied across each of said resistors 10. However, when filament 16 of one of the lamps in FIGURE 6 is ruptured a change in color 17 of substance 11 associated with resistor it of that lamp is effected, as a consequence of said resistor it? and said lead wires 4' being subjected to the resultant increased potential incident to said filament failure, to indicate the condition of said associated lamp 1. The amount of potential impressed across the intact filaments 3 of the remaining lamps in the series is inappreciable, due to the small amount of current flowing through said resistor lit which produces said color change 17. Consequently filaments 3 of said remaining lamps are inoperative, as there is no appreciable heating of their filaments.

It is therefore, obvious that to determine the defective lamp 1, when said series of lamps cease to function, it is only necessary, to observe through the transparent area at 12 of each lamp it to discover the one with said changed color substance 17.

Although said heater resistors it? are at all times connected in parallel with the filaments 3 in said series arrangement their relatively high ohmic value and low wattage, together with their heat generating qualities only i (when under abnormal conditions) would result in a minimum amount of current flowing therethrough. The wattage of each said resistor ill may be approximately in the realm of A Watt as a maximum. Hence the energy consumed by the bleeder circuit is inappreciable, and may be further reduced by employing types of resistors It which have a negative resistance temperature coefiicient. The form and color change embodiment of the invention as illustrated in FIGURES 2, 4, 5 and 7 is the same as that previously described with relation to FIGURES l and 6 except that here the resistor iii and color change substance ll, are mounted on the exterior of lamp 1 and on the tip of said envelope 2. In this location the resistor Ill may be electrically connected across extended lead wires 4 which are held together by a vitreous bead 9 as stated, and which sealably extend through the wall of said envelope 2 to the exterior of same.

As a means of safety and mechanical protection a cover It; is attachable as indicated at 19 over said associated color change substance ill and heater resistor it) to said envelope 2. This cover 13 as seen in FIGURES 7 anl 7A has the aforementioned transparent observation area 22 directly registering over color change substance ill and must withstand the heat generated by resistor lit) when at full line potential, and is preferably attached (as at 19) as a lamp base and lamp envelope are conventionally attached. In order that cover 13 and envelope 2 may be securely bonded together, the cover may be attached to the envelope prior to any decorative coating being ap plied to the exterior or" such an envelope.

The form and color change embodiment of the invention as illustrated in FIGURE 3 is the same as the other embodiments except that in this instance the heater resistor lit and color change substance iii are located in the transparent part 23 of an elongated base assembly 21 veniently be attached to said base (as at 22) as a lamp base and lamp envelope are conveniently attached.

Said resistor 10 and color change substance 11 could be mounted on the transparent internal surface of said thimble 23 similar to the wafer mounting illustrated in FIGURE 5. Said color change substance 11 is to be applied on the transparent internal surface of the thimble 23, and heater resistor it is to be mounted on that surface of substance U. that is non-adjacent to the internal surface of thimble 23. The resistor It) is electrically connected across said lead wires 4 as at 24, similar to the conventional printed circuit technique.

Alternatively, instead of consisting of a thimble 23 joined to base 5 as described, said base assembly 21 could be composed of a transparent sleeve with said base 5 being crirnped about the exterior circumference of same similar to the conventional manner employed in household fuse technique.

It is further suggested that the heater resistor iii with the color change substance 11 could be mechanically suspended from and electrically connected across said lead wires 4, internally within the space occupied by transparent part 23. at the bottom of said envelope 2 and prior to the mounting of the assembey in envelope 2. Said transparent part 23 of the assembly 21 is to serve for attachment of base 5 to same as at 22, and also for attachment of base assembly 21 to said envelope 2. This could be accomplished, following the assembly of the mount and envelope 2;, by properly positioning the envelope and base 5 for placement in a mould and filling the intervening space between the bottom of the envelope and the top of the base with a transparent plastic so that base 5 is joined to part 23 as at 22.

Instead of being suspended from lead wires 4, said heater resistor lit and color change substance 11 could be internally mounted within transparent part 23 on a stem extension of the amount at the bottom of envelope 2.

The form and color change embodiment of the invention as illustrated in FIGURE 8 is the same as those previously described except that here the heater resistor it? and color change substance 11 are mounted on the tip of a heat resisting insulating stem 25, in the interior of envelope 2 and near the tip of said lamp 1.

The resistor 16 could as Well consist of any suitable conventional type of printed, sprayed, painted or the like conductor, and could be electrically connected across extended lead wires 4 with resistor lit and color change substance lllbein mounted on the tip of said stem 25 in a similar manner to the wafer mounting illustrated in FIGURE 5. The extended lead wires 4' could also be of the printed type and impressed on the surface of stem 25 and electrically connected to said lead wires 4 as at 24, as in conventional printed circuit technique.

The form and color change embodiment of the invention as illustrated in FIGURES 9 and 10 is the same as the previously described embodiments except that in this instance the heater resistor 1i? and said color change substance iii are mounted on the internal surface of the glass of envelope 2 itself, similar to the wafer mounting illustrated in FIGURE 5.

In this case as seen in FIGURE 10 the envelope 2 has the aforementioned transparent observation area 12 disposed on the sideof same and the color change substance 11 would be mounted directly on the internal surface of said envelope 2 and registering over said area 12. The resistor Ill would be mounted on that surface of said substance ii that is non-adjacent to the internal sur ace of envelope 2. The resistor lit), as aforementioned, is electrically connected across said leadwires 4 at 24, similar to the conventional printed circuit technique.

' The form of the invention illustrated in FIGURE. 4 comprising heater hesistor It and said color change substance Il can be electrically connected by leads denoted by 5 across the tcrminalsJlS of a source of electrical potential, where indication is desired upon the applica- 7 tion of a predetermined increase in the amount of the applied potential. In order to determine the condition of said source of potential it is only necessary to observe the condition of said associated color change substance 11.

In the embodiments of the invention employing a fusible and visible depositable substance, it is to be understood that the same drawings and specifications employed for the color change embodiments also apply to the fusible and visible depositable embodiments. However, in this latter case a substance is employed that is capable of fusing at a low temperature and leaving a visible deposit similar to the deposit left by the conventional household fuse when same burns out. This fusible and visible deposit-leaving substance would consist of any suitable material, such as wax, paint, celluloid, plastic, plastic cement, lacquer, bismuth, solder, fuse metal or the like, that is capable of fusing at a low andpractical degree of temperature and leaving a visible deposit. This substance is to be applied to said heater resistor It? in any suitable manner, such as by coating, by impregnating or by mixing with said resistor material or in like manner. Said coating may be applied by any suitable process, such as by dipping, spraying, printing, painting, etc.

In the two evacuated and sealed envelopes form and embodiment as illustrated in FIGURES 11 and 12, said potential indicator comprises a lamp I having an evacuated and sealed envelope 2, an incandescent filament 3 supported by lead wires 4, and mounted and sealed therein the the conventional manner.

A pair of similar lead wires 4' which are joined to said lead wires 4 are held together by a vitreous head 9, and extend upwardly through lamp 1 and sealably extend exteriorly through the wall of said envelope 2. In this location, said extended lead wires 4' are electrically connectedto lead wires 29 and 30 that pass sealably into a separate evacuated and sealed envelope 311. In the interior of .this envelope 31, lead wire 29 is electrically connected to one terminal of a small low wattage currentlimiting resistor 32. The other terminal of this resistor 32 is electrically connected to one terminal of a small low wattage auxiliary indicator filament 33. The other terminal of this filament 33 is electrically connected to said lead wire 30. Thus the series connected combination (resistor 32 and filament 33) is electrically connected in parallel with said filament 3. The resistor 32 and filament 33 are supported by said lead wires 29 and 36). The filament 33 will emit a substantial intensity of light when said series connected combination of resistor 32 and filament 33 is subjected to any predetermined increase in the amount of potential. As for example, if filament fails.

To be positively efiective the predetermined potential increase and the design of said resistor 32 and filament 33 should be such that filament 33 has a longer life than filament 3. The filament 33 should be such as to assume light emitting qualities only, when a predetermined amount of potential is applied across the combination comprising resistor 32 and filament 33, and hence only when a predetermined degree of temperature is generated by resistor 32. At the threshold of light emission by said filament 33 said predetermined degree of temperature, as generated by resistor 32, would be greater than the degree of temperature generated by the resistor itself when said resistor and filament combination is subjected to only the normal operational potential of the filament 3. Hence,

at the threshold of light emission by said filament 33 said predetermined amount of potential applied across said combination of 32 and 33 would be greater than the normal operational potential of the filaments.

To still further this accomplishment, resistor 32 and filament 33 should preferably comprise substances having negative resistance temperature co-efficients. The filament 33 would, therefore, be of such low wattage and low potential as to be only a fraction of that of said filament 3, together with relatively heavy cross sectional LI) area. Thus filament 33 would have a longer operating life than filament 3.

It follows that light is emitted by said'filament 33 when resistor 32 and filament 33 combination become sufiiciently energized for the said filament to assumelight emitting qualities. This occurs as a consequence of said combination being subjected to greater than normal operational potential of a predetermined amount thereby indicating the condition of said associated lamp 1. Under normal operating conditions, only the normal amount of operational potential of said filament 3 is applied, across said combination of said elements, which would beinsufiicient to cause a substantial intensity of light emission by filament 33.

To determine the conditionof said lamp 1, it is only necessary to observe the amount of intensity of light emitted by said auxiliary filament 33. When in a series circuit, failure of the main illumination filament 3 is indicated by an increase in the amount of intensity of the light above the normal amount of operational intensity as emitted by said filament 33. Failure of line potential is indicated by the total extinguishment of both of said filaments 3 and 33.

Said current-limiting resistor 32 may be of low wattage and relatively high ohmic value, providing it has a negative resistance temperature co-efiicient. It may consist of any suitable type conductor such as printed, carbon, metallized, impregnated, sprayed, painted, wire-wound or the like. Instead of mounting resistor 32 in envelope 31, same could conveniently be mounted along with said'main illumination filament 3 in envelope 2. I

If desired, a transparent area 12 may be disposed on the tip of said envelope 31, so that the light emitted by said filament 33 can be detected more readily.

This type of indicator may also be in the form of a unitary part of said lamp 1 by having the envelope 31 attached to the envelope 2 as at 34 in the same way that an incandescent lamp base is attached to its lamp envelope.

Any decorative exterior coating of lamp 1 could be applied following this attachment so as to ensure proper bonding between envelopes 2 and 31.

In FIGURE 12 the lamps are identical to that illustrated in FIGURE 11, and similarly embody the principles of the present invention, and are connected in series to wires 15 leading to a source of potential. One of these lamps in FIGURE 12 shows a ruptured filament 16, which results in an increased amount of intensity of light emission being apparent in envelope 31 of that lamp. This is caused by the combined resistor 32 and filament 33, with lead wires 29 and 36, being subjected to the resultant increased amount of potential incident to the failure of this filament 16, which indicates the condition of said associated lamp 1. The amount of potental impressed across the intact filaments of the remaining lamps is small, as a result of the small amount of current flowing through said combination, all of which has produced increased intensity of light emission. Therefore, said remaining lamps are inoperative as there is no appreciable heating of their filaments.

To determine the defective lamp 1, when said series circuit becomes inoperative and said lamps 1 cease to function, it is only necessary, to observe the amount of intensity of light emitted by said associated auxiliary filament 33 of each lamp 1, until the one with said increased intensity of light emission 35 is found.

As mentioned, the current-limiting resistors 32 and auxiliary filaments 33 are at all times connected in parallel with said lamps 1 in said series arrangement. As a result of the relatively high ohmic value of these elements when cold, together with low wattage and with said filaments 33 assuming light emitting qualities only (when under abnormal conditions) there would normally be'only a minimum amount of current flowing theretthr-ough. Hence, the energy consumed by the bleeder circuit is small, and may be further reduced by employing types of resistors 32 and filaments 3-3 which have negative resistance temperature co-efiicients.

Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made Within the spirit and scope of the claim without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

'In an incandescent lamp, the combination of an envelope, a filament, a heat generating impedance element connected in parallel with said filament to a source of current, said filament and said impedance element located within said envelope, said impedance element generating a relatively small amount of heat when said filament is in operation but generating a relatively large amount of heat when said filament is inoperative and current passes through the impedance element only, and a heat-responsive color-changeable indicating member disposed adjacent said impedance element, said indicating member having a predetermined color which is unaffected'by the relatively small amount of heat generated by said impedance element when said filament is in operation, but which color is permanently changed by the relatively large amount of heat generated by the impedance element when the filament is inoperative.

References Cited by the Examiner UNITED STATES PATENTS 1,838,716 12/1311 Stone 313-40 1,972,125 9/34 Anderson 315 1s5 2,152,228 3/39 Waters "315-185 2,461,962 2/49 Carlson s15 -1s5 2,489,649 11/49 Kuever 315-1s5 2,870,377 11/59 Ovrevik 315--185X ARTHUR GAUSS, Primary Examiner. RAL-PH NILSON, DAVID J. GALVIN, Examiners.

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