US3385999A - Discharge lamp transformer coil form having winding on insulated flange thereof - Google Patents

Description

May 28, 1968 DISCHARGE LAMP TRANSFORMER COIL FORM HAVING Filed Sept. 14, 1965 FIG. 3.

WITNESS s: W

A. R. CORNELL ET AL WINDING ON INSULATED FLANGE THEREOF 3 Sheets-Sheet 1 FIG.|.

FIG. 4.

INVENTOR$ ATTORNEY y 23, 8 A. R. CORNELL ET AL 3,385,999

DISCHARGE LAMP TRANSFORMER COIL FORM HAVING WINDING ON INSULATED FLANGE THEREOF 5 Sheegs-Sheet Filed Sept. 14, 1965 FIG.6.

y 1968 A. R. CORNELL ET AL 3,385,999

DISCHARGE LAMP TRANSFORMER CQIL FORM HAVING WINDING ON INSULATED FLANGE THEREOF Filed Sept. 14, 1965 a Sheets-Sheet :3

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United States Patent ABSTRACT OF THE DISCLOSURE A coil form for operating a gaseous discharge device which has spaced cathodes requiring cathode heating voltages thereacross, and which coil form includes a core having at least one primary winding thereon and an insulating flange secured to each end of the core. Each insulating flange contains heater coil windings thereon which may be in the form of printed circuit windings and which are connected to the cathodes of the discharge device. The heater windings are disposed in a magnetically coupled relationship with the primary winding and in conjunction serve to provide the cathode heater voltages.

This application is a continuation-impart of a copending application Ser. No. 153,955, filed Nov. 21, 1961, by the present inventors and assigned to the present assignee.

This invention relates generally to ballast transformers for lighting systems for rapid-start discharge devices and, more particularly, to the location of cathode heater windings mounted in the transformer for heating the lamp cathodes.

Rapid start fluorescent lamps require separate cathode heater voltages which heat the cathodes. In addition, these lamps require the usual high open circuit starting voltage which cause the initial lamp ionization or breakdown. For proper operation the lamps require a lower operating voltage and a current limiting ballast.

Heretofore, the cathode heater voltages were provided by small windings wound over the primary and/ or secondary. The heating windings generally had from 6 to turns depending on the ballast design and the lamp size. This position of the heating windings requires winding time on the transformer winding machines, in additon to that already required by the primary and secondary. Further, the heater windings are required to be insulated from the primary and/ or secondary by an insulation layer which also has to be machine wound. This insulation tends to break down due to the high electric field established between the heater windings and the primary winding during start-up.

It is, therefore, an object of this invention to provide improved structures for obtaining the required cathode heating voltage which simplifies the winding operation during transformer fabrication.

It is an additional object of this invention to provide a more practical and less expensive structure which provides the cathode heater voltage in a fluorescent lamp ballast.

Another object of the present invention is to provide a coil form or bobbin containing cathode heater windings integrally formed thereon.

A further object of the present invention is to provide a coil form adapted to receive primary and/ or secondary windings with the cathode heater windings integrally formed as printed circuits on the coil form.

Another object of the present invention is to provide 3,385,999 Patented May 28, 1968 a novel coil form wherein parts of the form are used for integrally containing printed cathode heater windings of a fluorescent lamp ballast.

Still another object of the present invention is to provide a plurality of arrangements wherein end flanges of a coil form provide for a plurality of windings integral therewith.

A, further object of this invention is to provide a coil form having cathode heater windings mounted thereon which can function in a variety of ballast transformers.

Briefly, these and other objects are achieved by providing a coil form around which are wrapped the primary and/or the secondary transformer windings. End flanges containing printed circuit windings are then mounted adjacent to the transformer windings so as to be magnetically coupled with the primary. These printed windings, which provide the cathode heater voltages, are insulated from the transformer windings by an insulating water or disk placed over the printed winding. The metal core is then inserted through the coil form. The printed circuit windings are also insulated from the metal core. The fabrication of the cathode heater windings is thus greatly simplified. More reliable service is obtained because of the position of the windings in conjunction with the improved insulation. This invention may be employed with a variety of transformers including the conventional ballast transformers of the bridged-gap, metal-shunt, or winding-separation type.

In practicing this invention in its broader aspects, it will occur to those skilled in the art that the coil form itself may have various configurations, and that the principles disclosed herein are equally applicable to all such variations. The above and other objects, features and advantages will become more apparent upon consideration of the following detailed description of the invention incorporating various modifications in accordance with the principles thereof, when taken in connection with the following accompanying drawings, in which:

FIGURE 1 is a fragmentary cross-sectional view of a round coil form having end flanges provided with printed circuit heater windings taken along the reference line II of FIG. 2 in the direction of the arrows;

FIG. 2 is an end view of the round coil form taken along the reference line II-II of FIG. 1 in the direction of the arrows;

FIG. 3 is an end view of the round coil form taken along the reference line III-III of FIG. 1 in the direction of the arrows;

FIG. 4 is a fragmentary cross sectional view of a round coil for-m having a modified end flange;

FIG. 5 is a cross sectional view of a rectangular coil form having end flanges provided with printed circuit heater windings;

FIG. 6 is an end view of the rectangular coil form taken generally along the reference line VIVI of FIG. 5 in the direction of the arrows;

FIG. 7 is an end view of the rectangular coil form taken along the reference line VIIVII of FIG. 5 in the direction of the arrows;

FIG. 8 is a schematic of a conventional low frequency lighting circuit used in connection with the rectangular coil form of FIGS. 5 to 7;

FIG. 9 is a cross sectional view of a bridged-gap ballast transformer employing the rectangular coil forms;

FIG. 10 is a cross sectional view of a metallic shunt ballast transformer employing the rectangular coil forms; and

FIG. 11 is a cross sectional view of a ballast transformer using separated windings and employing the rectangular coil forms.

With the specific reference to the drawings, FIG. 1

shows a round coil form 10 comprised of a spool body 12, made of an electrical insulating material, such as an epoxy resin, nylon or the like. The coil form 10 has end flanges 14 and 16 attached to or integral with the spool body 12. In the embodiment illustrated in FIGS. 2 and 3 the flanges 14 and 16 each have a circular aperture 17 cut from the center thereof. The flanges 14 and 16 can be fixed to the coil spool 12 in any manner or may be integral therewith; however, it is preferred that the apertures 17 will be of such a size as to make a force fit around the end of the coil spool 12.

The end flanges 14 and 16 are made of insulating material 18 such as nylon or epoxy resin. FIG. 2 shows the insulating material 18 with printed circuit conductive Windings 22 embedded or extending thereon. The printed winding 22 is made of copper or its equivalent, to form the necessary electrical conducting paths. An insulating disk 20 covers the printed winding 22 to prevent its contact with any other metallic elements forming part of the ballast, such as the conventional ballast casing, not shown.

FIG. 3 shows two printed windings 24 and 26 on the flange 16 similar to the single printed winding 22. on the flange 14. Wrapped around the spool 12 is the primary winding 28 and/or the secondary winding 30 wrapped over the primary as is Well known in the art. The printed windings 22, 24 and 26 are disposed in the central portions of the flanges proximate the primary 28 to insure good magnetic coupling therebetween. The ends 27 of the printed winding 22. are connected in the circuit by way of lead-in connections 29 which can be anchored to the flange 14, by way of solder 31, to the lead-ins 33 which are in turn connected to the other electrical components, such as the primary 28. Y

The round embodiment of the coil form 10 shown in FIGS. 1 to 3 is concerned primarily with high-frequency lighting applications. The usual core material (not shown) is a powdered ferrite substance pressed into cylindrical form and then inserted into the spool body 12 of the coil form 10.

FIG. 4 shows a modification of the round coil form 10 shown in FIGS. 1 to 3. Like reference numerals have been employed to illustrate like components of the two embodiments. The spool body 12 and the end flange 14 of this modification are identical to that illustrated previously. The difference lies in the other end flange 72. The flange 72 carries two printed windings 24 and 26, just as the flange 16 in the prior modification, but does so in a different manner. The end flange 72, instead of carrying both the heater windings 24 and 26 on the same side of the insulating material 18, carries one on each side thereof. The end flange 72 is somewhat thicker than the flange 16 to accommodate the depth of the two embedded printed windings. An insulating disk 20 is preferably used on each side of the insulating material 18 to prevent contact with other electric conducting materials. The inner insulating disk 20 is necessary to prevent contact between the primary and/ or secondary windings 28 and 30 and the printed winding 26.

FIG. shows a rectangular modification 74 of the round coil form 10. This modification is concerned primarily with low frequency or 60 c.p.s. lighting systems. The transformer is made of laminated sheets which form a rectangular core portion. The primary 28a and secondary 30a are mounted adjacent each other and are separated by flange 78. This configuration provides leakage reactance which forms a current-limiting ballast for the lamps.

FIG. 6 shows a rectangular coil form 74 and spool body 76 for containing three heater windings 22a, 24a and 26a. The end flanges 78 and 80 are generally rectangular shaped and have rectangular shaped openings 82. for fitting snugly around the ends of the rectangular spool body 76.

FIG. 6 shows flange 78 which differs from the previously described flange 14 in that the printed winding 22a is printed on the inside rather than on the outside surface of the insulating material 18a. Insulating disk 20a is located on the inside to cover the winding 22a preventing electrical contact with the primary winding 28a.

FIG. 7 shows flange which differs from the previously described flanges 16 and 72 shown in FIGS. 14 in that it is comprised of a pair of sections of material 18a abutting one another and each containing one of the heater windings 24a and 26a on its inner surface. In this m-odifi cation, only one insulating disk 20a is necessary to cover the heater winding 26a because the back of the material 18a containing the heater winding 26a covers the front of the material 18a containing the heater winding 24a to provide insulating therefor. The heater windings 24a and 26a may be placed on the opposite surface of the support material 18a used for each and accomplish the same purpose providing, of course, that an insulating disk is located on the outside surface of the flange 80 rather than the inside surface thereof.

It is to be understood that the modifications of the round coil form 10 of FIGS. 1 and 4 could work equally well with the rectangular coil form 74 of FIG. 5 and vice versa, the choice depending on the particular use to be made thereof.

FIG. 8 shows a conventional circuit for lighting systems of the low frequency variety. The circuit may be employed with the rectangular coil embodiment of FIGS. 5 to 7 and is generally of the high reactance stepped up autotransformer type circuit, The circuit includes a primary winding 28a and an adjacent secondary winding 30a, as illustrated physically in FIG. 5. The primary 28 is provided with suitable input leads 36 and 36' by which it can be connected to a suitable source of single phase alternating current such as indicated by the supply lines 38 and 38'. The secondary 39a is connected to the primary 28a so that the two windings are placed in a voltage additive relationship. As shown, the autotransformer connection is made at the lead 36.

Besides being connected in an autotransformer relation to the primary 28a, the circuit secondary 30a is also connected in series relation to a capacitor 40 to form a lead circuit for energizing the gaseous discharge lamps 32 and 34 with leading current. As shown, the secondary 30a is connected to the capacitor 40 by a lead 42 and, from the other side of the capacitor, an output lead 44 extends out of the ballast for connection to the upper cathode 46 of the gaseous discharge lamp 32. The other output lead for the circuit comprises the lead 48 which is connected to the other end of the primary of the autotransformer and extends out of the ballast for connection to the lower cathode 50' of the lamp 34. The remaining two cathodes 52 and 54 of the lamps 32 and 34, respectively, are parallel connected by means of the leads 56 and 58 to complete the circuit for the lamps. It will be noted that in this circuit the primary 28a, the secondary 30a, the capacitor 40 and the lamps 32 and 34 are all connected in series circuit relation.

The lamps 32 and 34 are gaseous discharge devices such as rapid start fluorescent lamps including cathodes which require cathode heater windings 22a, 24a and 2611 which are printed on the end flanges as described above. Accordingly, the need for placing these heater windings directly over the primary 28a or the secondary 30a wound upon a spool body 12a is eliminated by this invention. The first heater winding 22a is connected across the cathode 46 by means of the leads 44 and 60 so that it continuously supplies the heater current to cathode 46 during the lamp operation. The second heater winding 24a supplies heater current to the cathodes 52 and 54 through the leads 62, 64, 56 and 58. As shown, the cathodes 52 and 54 are connected in parallel across the heater winding 24a for heating purposes. The final heater winding 26a is connected across the cathode 50 by leads 48 and 66 so as to pass heater current therethrough.

As shown, heater winding 26a may form an extension of the primary 28a.

In order to start the lamps 32 and 34 sequentially, a starting capacitor 68 is connected between the leads 44 and 62 so that it is in parallel withthe lamp 32. When the ballast apparatus is first placed in operation, i.e., when the primary 28a is first energized, the combined voltages of the primary 28a and the secondary 30a are applied across the lamp 34. This causes the lamp 34 to ignite. Once the lamp 34 ignites, current flows through the-capacitor 68 which is of much greater impedance than the lamp 34 so that most of the voltage in the lead circuit then appears across it. This places a great enough voltage across the lamp 32 to cause it to ignite and this action occurs very rapidly. After the lamp 32 ignites, the lamps 32 and 34 are then operated in series effectively forming a low impedance bypass around the starting capacitor 68. Due to the capacitor 40 in the series circuit, the circuit draws a leading current to the lamps 32 and 34. -The circuit lamps 32 and 34, therefore, comprise what is known as a lead circuit. The leakage reactance of .the primary 28a and the secondary 30a combined with the reactance of capacitor 40 acts as a current limiting ballast as explained in reference to FIG. 9. As is well known, to start, the lamps require a high energizing voltage.- When operating, the lamps require less voltage and a higher leakage flux is desirable to limit the current in the lamps. The conventional ways of providing leakage flux are the bridged-gap, the metal-shunt, and the windingseparation type ballast transformers.

FIG. 9 shows a bridged-gap type ballast transformer 82 having a center leg 84 and two outer shell legs 86. Coil form 74 is shown mounted on the center leg 84 with a primary winding 28a and a secondary winding 30a adjacently positioned thereon. A bridged gap 85 is provided in the center leg 84 proximate the secondary winding 30a for establishing a high reluctance path through the secondary portion of the center leg 84. The gap 85 is especially effective under lamp operating conditions when a great deal of flux is established in the center leg 84 by the current in the primary 28a. The leakage flux lines are forced out of the center leg 84 and across'the Windows 88 by the high reluctance of the secondary portion.

FIG. shows a metalshunt type ballast transformer 90 which has many components identical in appearance and function to the components in the bridged-gap embodiment. These components are numbered the same as their corresponding components of FIG. 9. The leakage flux in this embodiment is established through the metal shunts 92 which extend across the window 88 and separate the primary 28a and the secondary 30a. A small air gap 94 is left proximate the center of the center leg 84. Under operating conditions flux is established by the primary 28a out of the center leg 84 and across the window 88 through the metal shunt 92. This type of ballast may also employ a bridged gap as in FIG. 9.

FIG. 11 shows a winding-separation type ballast trans former 96 with the identical components numbered the same as described above. Here the leakage flux path is provided by a substantial space 98 between the primary 28a and the secondary 30a. This embodiment shows only two printed heater windings indicating that the invention can be employed in a one-lamp circuit. The type of ballast transformer and the number of printed windings depends on the particular application. This type of ballast may also employ a bridged gap as in: FIG. 9.

While the present circuit is preferably used in conjunction with two-lamp circuits and has been so illustrated and described, it should be understood that the present circuit is equally applicable to circuits used to actuate more than two lamps, such as described in US. Patent No. 2,730,656 dated Ian. 10, 1956, or in single-lamp circuits.

It will be apparent to those skilled in the art that the objects of this invention have been achieved by providing cathode heater windings mounted or printed on the end flange members of a ballast transformer coil form. These heater windings can be fabricated and mounted on the transformer cheaper than winding them over the coil form as are the primary and secondary. Improved insulation is provided by this invention because of the spaced position of the heater winding from the primary and secondary windings. Because of the simple construction, the invention is adaptable to many types of ballast transformers.

Since it is clear that the invention can be embodied in other forms and constructions within the spirit and scope thereof, as would be apparent to one skilled in the art, it is to be understood that the particular forms shown are but a few of many such embodiments. Accordingly, with various modifications and changes being possible, the invention is not limited in any way with respect thereto, Moreover, it is to be understood that certain features of the invention can be employed without a corresponding use of other features thereof.

We claim as our invention:

1. A coil form comprising: an elongated spool body having at least one coil winding disposed thereon, flanges adjacent the opposite ends of said spool body, said flanges comprising an electric insulating material, an electric conducting material forming a discharge device heater coil and embedded in one of said flanges, a pair of dis charge device electric conducting heater coils embedded in the other of said flanges, and insulating means covering the exposed coil embedded surfaces of said flanges; and means for electrically connecting said heater coils to the coil windings disposed on said spool body.

2. The combination of a coil form and coil windings, said coil form comprising an elongated spool body, flanges adjacent the opposite ends of said spool body, said flanges including a base material which is electrically insulating and presenting opposite surfaces, an electrically conductive printed coil formed in each of the surfaces of one of said flanges, an electrically conductive coil formed in a surfaceof the other of said flanges, electric insulating means covering each of said printed coils, coil windings located on said spool body, means electrically connecting said printed coils in series to said coil windings, and means for electrically connecting said coil windings to a source of alternating electric potential.

3. The combination of a coil form and coil windings, said coil form comprising an elongated spool body, flanges adjacent the opposite ends of said spool body, said flanges including a base material which is electrically insulating and presenting opposite surfaces, an electrically conductive printed coil located on each of the opposed surfaces of one of said flanges, an additional electrically conductive printed coil formed in a surface of the other of said flanges, electric insulating means covering said printed coil, coil windings located on said spool body, means electrically connecting said printed coils in series to said coil windings, and means for electically connecting said coil windings to a source of alternating electric potential.

4. A coil form adapted to operate at least one gaseous discharge device having spaced cathodes, which device requires for proper starting, cathode heating voltages across each of said cathodes, said coil form comprising;

a body and at least one primary winding disposed thereon and adapted to be connected to an AC voltage source;

an insulating flange aflixed to said body; and

at least two cathode heater windings mounted on said flange, said heater windings adapted to be connected to the cathodes of said discharge device and disposed in magnetically coupled relationship with respect to said primary winding, and said heater windings and said primary winding operable to provide said cathode heater voltages.

5. The combination as specified in claim 4, wherein said heater windings are'printed circuit windings printed on said flange.

6. The combination 'as specified in claim 4, wherein an insulator means is provided over each of said heater windings.

'7. A coil form adapted to operate at least one gaseous discharge device which requires for proper starting, cathode heating voltages across each of two cathodes therein and a starting voltage applied between the cathodes, and which device requires for proper operation an operating voltage applied between said cathodes, said coil form comp an elongated body and at least one primary winding and at least one secondary winding disposed thereon in magnetically coupled relationship, said primary winding adapted to be connected across an operatin AC voltage source, said secondary winding adapted to be connected across said discharge device, said windings operable to provide the starting and operating voltages required for proper starting and operating of said discharge device,

insulating flange means afiixed to said elongated body,

at least two cathode heater windings mounted on said flange means, said heater windings adapted to be connected to the cathodes of said discharge devices and disposed in magnetically coupled relationship with respect to said primary winding, and said heater windings 'and said primary winding operable to provide said cathode heater voltages.

8. The combination as specified in claim 7, wherein said heater windings are printed circuit windings printed on at least one insulating flange.

9. The combination as specified in claim 7, wherein an insulator means is provided over each of said heater windings.

10. A coil form adapted to operate at least one gaseous discharge device means which requires for proper starting cathode heating voltages across each of two cathodes in Said discharge device means, and a starting voltage applied between the cathodes, and which device means requires for proper operation an operating voltage applied across said discharge device means and a current limiting ballast means, said coil form comprising;

an elongated body and at least one primary winding and at least one secondary winding adjacently disposed thereon in magnetically coupled relationship, said primary winding adapted to be connected across an operating AC voltage source, said secondary winding adapted to be connected across said discharge device means, said windings operable to provide the starting and operating voltages required for proper starting and operating said device means,

at least one insulating flange aflixed to said elongated body,

at least two cathode heater windings mounted on at least one flange, said heater windings adapted to be connected to the cathodes of said discharge device and disposed in magnetically coupled relationship with respect to said primary winding, and said heater windings and said primary winding operable to provide said cathode heater voltages, and

a magnetic core for magnetically coupling said primary and said secondary, said core having substantial leakage flux during device means operation which provides at least in part the required current limiting ballast.

11. The combination as specified in claim 10, wherein said magnetic core is of the bridged-gap type.

12. The combination as specified in claim 10, wherein 30 said magnetic core is of the magnetic-shunt type.

13. The combination as specified in claim 10, wherein said magnetic core is of the winding-separation type.

References Cited UNITED STATES PATENTS 2,786,187 3/1957 Nims 336-200 2,971,124 2/1961 Feinberg et a1. 31s-97 2,982,889 5/1961 Whearley 336-2O5X 3,089,106 5/1963 Saaty 336-200 DAVID I GALVIN, Primary Examiner.

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