Integral fluorescent-incandescent lamp structure
United States Patent Roche et al.  
 [ Apr. 15, 1975 INTEGRAL FLUORESCENT-INCANDESCENT LAMP STRUCTURE [75] Inventors: William J. Roche, Merrimac;  
 Theodore Wroblewski, Danvers, both of Mass.  
 [73] Assignee: GTE Sylvania Incorporated,  
 Danvers, Mass.  
 [22] Filed: Dec. 5, 1973 21 Appl. No.: 421,979  
 Primary ExaminerRudolph V. Rolinec Assistant Examiner-Darwin R. Hostetter Attorney, Agent, or Firm-Edward .l. Coleman [57] ABSTRACT A fluorescent-incandescent lamp structure comprising a phosphor coated tubular glass envelope containing a pair of arc discharge electrodes and having a base attached to one end and an incandescent lamp attached to the other end and connected as a ballast. A single mount structure is sealed within the tubular envelope at the base end and includes means for supporting one of the electrodes at the base end, a rigid glass tube projecting from the base end toward the other end, the second electrode being supported at the remote end of the glass tube, and an ignition coil with an emissive coating connected between the electrodes and suspended away from the arc discharge path by support wires projecting from the glass tube. The incandescent lamp is connected as a ballast for the fluorescent lamp by a first lead-in wire running from the base along the exterior of the tubular envelope to the incandescent lamp, and a second lead-in wire running from the incandescent lamp along the exterior of the envelope to the electrode at the base end of the fluorescent lamp. The second electrode is connected to the base by a third lead-in wire passing coaxially through the glass tube.  
 2 Claims, 5 Drawing Figures PATENTEDAPR 1 5191s 3878.416  
 sum 1 q 2 I II 5 &#34;II I 9 TOELECTRODE FIG. I Fit-1 2 FIG .3  
 INTEGRAL FLUORESCENT-INCANDESCENT LAMP STRUCTURE BACKGROUND OF THE INVENTION This invention relates generally to electric lamp structures and more particularly to an integral fluorescent-incandescent lamp structure.  
  The present invention provides a composite lamp structure in which the component light sources cooperate to provide efficient operation over an extremely long life without requiring external ballast and starting circuitry. For example, the lamp structure may be operated in a conventional incandescent lamp fixture. The composite lamp is particularly suited to numerous dec orative schemes and, with appropriate fixture design, can provide innovative illumination arrangements combining both direct and indirect lighting.  
 SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved electric lamp structure.  
  A principal object is to provide a fluorescentincandescent lamp structure having a single base and which requires no external ballast.  
  A further object is to provide a fluorescent incandescent lamp structure which is self-igniting and requires no external ballast.  
  Briefly, these objects are attained in a fluorescentincandescent lamp structure comprising an hermetically sealed, tubular glass envelope having an internal phosphor coating, mercury and a rare gas contained within the tubular envelope, first and second electrodes disposed at opposite ends of the tubular envelope, a base attached to one end of the tubular envelope, and an incandescent lamp attached to the other end thereof. A first lead-in wire connects a first terminal of the base to a first terminal of the incandescent lamp; a second lead-in wire connects a second terminal of the incandescent lamp to the first electrode in the tubular envelope; and a third lead-in connects the second electrode to the base. The attached incandescent lamp is selected to ballast an arc discharge across the electrodes within the phosphor coated tubular envelope, whereby no external ballasting is required.  
  In a preferred embodiment which provides a selfignition feature, the tubular envelope includes a mount structure sealed in the base end and comprising: means for supporting the first electrode at the base end of the envelope; a rigid insulating tube projecting from the base end toward the other end of the tubular envelope, the second electrode being supported by the remote end of the tube and the third lead-in wire passing through the insulating tube; an ignition coil with an emissive coating connected between the first and second electrodes; and support means projecting from the insulating tube and suspending the ignition coil away from the arc discharge path.  
 BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more fully described hereinafter in conjunction with the accompanying drawings, in which:  
  FIG. 1 is an elevation view of a composite fluorescent-incandescent lamp structure according to the invention;  
  FIG. 2 is a simplified wiring diagram representation of the lamp structure of FIG. 1;  
  FIG. 3 is an elevation, partly in section, of one embodiment of a fluorescent lamp useful in the lamp structure of FIG. 1;  
  FIG. 4 is a volt-ampere characteristic curve, together with load line, for a typical lamp structure according to FIGS. 1-3; and  
  FIG. 5 illustrates an alternative mount structure for the lamp of FIG. 3.  
 DESCRIPTION OF PREFERRED EMBODIMENT A fluorescent-incandescent lamp structure according to one embodiment of the invention is illustrated in FIGS. 1-3. In this instance, the composite lamp structure comprises a tubular fluorescent lamp 1 having a threaded base 6 attached to one end and a flameshaped incandescent lamp 3 removably attached to the other end, the fluorescent lamp thereby providing the effect of an illuminated candle stick when in operation. Incandescent lamp 3 has a threaded base 5 which is screwed into a threaded receptacle 7 attached to the end of the fluorescent lamp opposite that to which base 6 is attached. Of course. a number of alternative connecting arrangements may be employed: for example. base 6 may be a bi-pin type. and incandescent lamp 3 may have a plug-in base or be permanently wired in and attached to the end of the fluorescent lamp.  
  Referring to the wiring diagram representation of FIG. 2, incandescent lamp 3 is selected and connected as the sole ballast element for the fluorescent lamp. A first lead-in wire 28 is electrically connected from a first terminal (center contact 12) of lamp base 6 to a first terminal 9 of the incandescent lamp 3. In the present embodiment, of course, terminal 9 is actually the center terminal of the threaded receptacle 7 which is in electrically conductive engagement with the center contact of incandescent lamp base 5. A second lead-in wire 29 is then connected from a second terminal 11 of incandescent lamp 3 to a first electrode of the fluorescent lamp. Again, in this instance terminal 11 represents the threaded portion of receptacle 7 in electrically conductive engagement with the threaded shell of incandescent lampbase 5. A third lead-in wire 34 is then connected from the second electrode of the fluorescent lamp to a second terminal (threaded shell 10) of lamp base 6.  
  A fluorescent lamp particularly suitable for use as lamp 1 of the present composite structure is the single base, self-igniting lamp described in copending application Ser. No. 421,980, filed on even date herewith and assigned to the present assignee. FIG. 3 illustrates one embodiment of this self-igniting lamp as employed in the present composite structure. Referring to FIG. 3, the fluorescent lamp 1 has an hermetically sealed tubular glass envelope 2 containing a suitable rare gas filling such as for example percent argon. In addition, a charge of mercury is introduced into the envelope prior to sealing to yield the necessary mercury vapor pressure for operation of lamp 1. On the inside surface of the glass envelope 2 there is a coating of phosphor 4 which may be, for example, any suitable fluorescent lamp phosphor.  
  Attached to one end of the glass envelope 2 is the previously mentioned base 6, which comprises a cylindrical shoulder portion 8, an externally threaded shell 10 secured to shoulder 8 by a body of insulating means and projecting therefrom, and a second contact 12 separated by a body of insulating material 14 from the shell 10. Shoulder 8 is secured to the end of the glass envelope 2 by a suitable basing cement l6, and the threaded shell 10 and center contact 12 provide a screw-in base compatible with conventional screw-type incandescent lamp sockets.  
  Lamp 1 contains a single mount structure 18 which is sealed in the end of the envelope to which the base 6 is attached, while the other end of the envelope has a flat seal 20. The threaded receptacle 7 (not shown in FIG. 3) is secured. for example by a basing cement, to the flat seal end of the tubular glass envelope 2. Mount structure 18 includes a glass flare portion 22 having an exhaust tube 24 and a rigid glass insulating tube 26 projecting from the flare at the base end of the envelope toward the flat seal end of the envelope. Leadin wire 29 sealed through the flare 22 supports a first electrode 30 at the base end of the lamp; and a second electrode 32 is supported by the glass tube 26 at the flat seal end of the envelope. The second electrode 32 is connected to the base by the lead-in wire 34, which coaxially passes through the length of the glass tube 26 and is sealed through the flare 22.  
  To facilitate self-starting, an ignition coil 36, which may comprise a coiled-coil of tungsten wire with an electron emissive coating over substantially its entire length. is located with the envelope 2 and connected between the ends of the lead-in wires 29 and 34 disposed therein. The electron emissive coating on coil 36 may be of a conventional type such as a mixture of barium, strontium and calcium carbonates, which are reduced during lamp processing to their oxide forms. Electrode 30 includes a cathode element, which comprises a portion of the ignition coil at the junction 38 of the ignition coil 36 and lead-in wire 29, and an anode element 40 comprising a strip of metal electrically attached to junction 38, such as by welding. In like manner. electrode 32 includes a cathode element, which comprises a portion of the ignition coil at the junction 42 of the ignition coil 36 and the lead-in wire 34, and an anode element 44 comprisinga strip of metal electrically attached to junction 42, such as by welding. The anode elements may be in the form of other configurations, such as discs, suitable for the electron collecting function, and may comprise any of the materials typically employed for anode flags in fluorescent lamps, such as strips of nickel or nickel plated stainless steel.  
  As briefly described hereinbefore, electrode 32 is electrically connected to base 6 by the lead-in wire 34, which proceeds from clamped junction 42 through the insulating glass tube 26 and flare 22 to a solder connection to the threaded metal-shell l0. Electrode 30 is electrically connected to terminal 11 of the incandescent lamp 3 (FlG. 2) by the lead-in wire 29, which at one end is clamped to the electrode at junction 38, and at the other end (terminal 11) may be soldered to the threaded portion of receptacle 7 (FIG. 1). The other terminal of the incandescent lamp 3, represented by the numeral 9, is connected to a terminal of base 6 by lead-in wire 28, which at one end (terminal 9) may be soldered to the center contact of receptacle 7 (FIG. 1) and at the other end soldered to center contact 12. In order to extend from base 6 to the incandescent lamp receptacle 7, the lead-in wires 28 and 29 are secured to the exterior of the tubular glass envelope 2 and disposed to lie along the length thereof, the otherwise exposed portions of these wires being covered with an insulating means 45. For example, the lead-in wires may be both covered and secured to the tubular glass envelope by a clear insulating epoxy or a clear strip of insulating adhesive tape; or, the wires may be embedded in a clear adhesive tape which is secured along the length of the envelope. Of course, the wires 28 and 29 must also be isolated from each other by proper spacing or the use of insulating material.  
 When lamp 1 is ignited, as will be described hereinafter, the arc discharge path is formed essentially between junctions 38 and 42 and may be appropriately located by suitably shaping the portion of lead-in wire 29 projecting into the envelope from flare 22, and by forming a bend in the remote end of glass tube 26 supporting junction 42. The ignition coil 36 connected between junctions 38 and 42 is then suspended away from the arc discharge path between electrodes 30 and 32 by a plurality of support wires 46 projecting from the glass insulating tube 26. To stabilize and support the remote end of the glass tube 26, a resilient wire support structure 48 may be located at the flat seal end of the lamp in engagement with the lamp walls and the bent remote end of the glass tube. Generally, the wire support structure 48 is only required for longer are lengths, such as those described hereinafter in connection with FIG. 5.  
  The lamp structure of FIGS. 1-3 has both selfignition and self-ballasting capabilities. The ignition coil 36 shunts the are between electrodes 30 and 32 and develops the starting voltage required by fluorescent lamp I, while incandescent lamp 3 serves as a ballast for the arc discharge in lamp 1. Accordingly, this composite lamp structure may be mounted in a conventional incandescent lamp fixture and operated from a standard 60 cycle, volt AC line source.  
  In operation, a current is established in the lamp ignition coil 36, prior to ignition. The current path commences at the lead-in wire 34 and continues through the glass-to-metal seal in the flare 22, up through the glass insulating tube 26 to the remote end of the mount where it enters the ignition coil 36 at junction 42. Proceeding through the coil 36, the current path exits at As previously described the entire ignition coil is coated with a conventional electron emissive coating reduced to the oxide form. The current established in the ignition coil raises the oxide coating temperature to an emissive state (e.g., 800900C), at which time an electron cloud encircles the coil along its entire length. The electron cloud is accelerated by the longitudinal electric field generated in the coil by the coil current. The electron cloud is accelerated back and forth along the coil at the frequency of the lamp supply voltage (typically 60 cycles per second), resulting in collisions with mercury and rare gas atoms. The by-products of these collisions are excited and ionized atoms which increase very rapidly in number until they are of sufficient quantity tomaintain conduction between points 42 and 38 without the aid of the oxide coated ignition coil 36. Once conduction is established in this manner,  
 the voltage between points 42 and 38 will drop as the discharge current increases resulting from the negative volt-ampere characteristics of the discharge. At the same time. the current in the ignition coil will decrease since the coil has a positive volt-ampere characteristic. This will lower the temperature of the coil below the emissive level and the arc current will not have a tendency to originate at points along the coil body. The only emissive points on the coil during lamp operation are in the proximity of junctions 42 and 38, which are heated by the arc current.  
  The anode elements 44 and 40 serve to increase the efficiency and extend the life of the lamp by functioning as electron collectors during anode half cycle operation. The emissive coil is suspended away from the longitudinal axis of the discharge by the support wires 46 anchored to the glass insulating tube, this refinement further isolates the ignition coil from the are discharge current after the lamp has started. The glass tube 26, therefore, serves a dual function in that it electrically insulates the conducting wire 34 from the plasma and also serves as an anchorage for the ignition coil support wires.  
  As described in a relatively detailed theoretical discussion in the aforementioned copending application Ser. No. 421,980, it may be summarized that ignition coil 36 performs two functions to aid in lamp starting. (1) The electron emission along the length of the coil 36 serves to favorably distort the lamp field above the coil to a degree not attainable in a conventional lamp. (2) The field so generated satisfies locally the condition for a self-sustaining discharge over a small section of the coil 36 which will gradually increase in length until it fills the tube. The action of the ignition coil 36 can be likened to an electron emissive internal ground plane. Accordingly, the ignition coil eliminates the requirement that the lamp be mounted next to a conducting surface, thus freeing the lamp from the confines of a metal reflecting fixture.  
  With respect to design considerations. the resistance of the ignition coil is of particular importance since this will affect the efficiency of lamp operation. This can be seen in FIG. 4 where the V-] characteristic of a typical single-base fluorescent lamp 1 is shown together with the non-linear resistive ballast load line provided by the attached incandescent lamp. After ignition, the rms operating point will be located at point (v ,1 The bypass current through the ignition coil is determined by the lamp voltage intercept on the positive sloped ignition section of the fluorescent lamp characteristic at point (V I For maximum efficiency it is desirable to reduce the bypass current to a minimum by use of a high resistance coil. There exists a practical limit, however, on how high this resistance can be since the coil must pass sufficient preheat current at a relatively low voltage to result in an ignition point (V,-,I,-) which lies well below the incandescent ballast load line. Another requirement for the ignition coil is that it be able to carry the arc current at its terminal points without overheating.  
  In lamps made according to FIGS. 1-3 an arc-to-coil current ratio of 3.5:1 has been achieved for an are current of 350 ma. I have also found it desirable to coat the entire coil length with emissive material since this will increase the avalanche current considerably.  
  The impedance of the ballast selected for use with the lamp 1 must be such that the load line will pass above the ignition point (V,-,l,-) in FIG. 4 and intersect the lamp characteristic atthe desired operating point (V.,,I,,). In the present case of the non-linear incandescent-lamp 3 ballast. the ballast impedance required for lamp operation is best determined empirically.  
  For purposes of example, one specific implementation of the composite lamp structure of FIGS. 1-3, including a watt, I20 incandescent lamp 3 attached as a ballast to one end of a single threaded-base fluorescent lamp 1 (12WTI2) having an overall length of 25 cm. (9.75in.), an arc length of 18cm. (7 in.) and an envelope diameter of 3.8cm. (l.5in.). exhibited the following performance characteristics when operated from a ()0 cycle, 120 volt supply in a standard incandescent lamp fixture:  
 Fluorescent Lamp Overall System Starting Voltage 58 volts (min) volts Starting Current I30 milliamps I30 milliamps Lamp Voltage 30 volts I20 volts Lamp Current 450 milliamps 450 milliamps Lamp Power 12 watts 55 watts Arc Current 350 milliamps n/a Arc Power 9 watts n/a Ignition coil current I00 milliamps n/a Ignition coil power 3 watts n/a Lumens 315 685 Lumens per watt 26.2 125 When an incandescent lamp is used for ballast purposes. the life of the fluorescent-incandescent system is extremely long since the incandescent coil is operating below rated voltage. However, the use ofa 60 watt, 120 volt lamp as a ballast element, although convenient. does not represent an optimum ballast lamp since the resulting filament voltage in 25 percent below the rated value yielding a filament temperature which will reduce overall system efficiency. A much higher efficiency than that shown in the foregoing table can be obtained if a volt, 50 watt filament were used.  
  The specific lamp 1 construction of FIG. 3, however, is generally suitable only for fluorescent lamps having an arc lengthof less than ten inches. For longer length lamps, the electron cloud generated along the oxide coated ignition coil cannot be excited to a sufficient degree by the coil field to cause the sustained excitation and ionization of fill gas required to provide lamp ignition. In accordance with an alternative embodiment of the invention, this difficulty is overcome by the inclusion of a V-shaped ionization coil in the center of the main ignition coil. This lamp construction is illustrated by the alternative mount structure 18 shown in FIG. 5. As indicated, the V-shaped ionization coil structure 50 may be formed from the ignition coil 36&#39; at approximately the center of the length thereof and supported from the glass insulating tube 26 by projecting wires 52, the apex ofthe V being secured to the glass tube at a point 54. The remainder of the ignition coil 36, except for the two end portions, is suspended linearly between the ends of the insulating tube.  
  Electrical connections are made to a lamp employing the mount structure of FIG. 5 as described for FIG. 3, and current is established through the oxide coated ignition coil and V-shaped ionization coil 50 in the same manner described for the operation of the lamp of FIG. 3. An electron cloud is generated along the length of the ignition coil and along the V-shaped ionization coil 50. The coil 36 field accelerates the electron cloud of the main ignition coil 36 at the line frequency rate (e.g., 60 cycles per second), but is ineffective at maintaining sustained excitation and ionization. The field produced in the V-shaped zone. however, is effective in establishing a discharge between the legs of the V- shaped coil structure 50. The discharge initiated in this manner then proceeds to migrate symmetrically along the main oxide coated ignition coil, terminating atjunctions 42 and 38, at which point the discharge will fill the tube.  
  Although the invention has been described with respect to specific embodiments, it will be appreciated that modifications and changes may be made by those skilled in the art without departing from the true spirit and scope of the invention.  
 What we claim is:  
  l. A fluorescent-incandescent lamp structure conr prising in combination. an elongated tubular glass envelope which is hermetically sealed; a phosphor coating on the inside surface of said tubular envelope; mercury and a rare gas contained in said tubular envelope; first and second electrodes disposed within and at opposite ends of said tubular envelope; at base attached to one end of said tubular envelope; a threaded receptacle attached to the other end of said tubular envelope; an incandescent lamp removably attached to the receptacle end of said tubular envelope, said incandescent lamp including a threaded base which is screwed into said threaded receptacle;&#39; a first lead-in wire electrically connecting a first terminal of said base to a first terminal of said receptacle; a second lead-in wire electrically connecting a second terminal of said receptacle to said first electrode in said tubular envelope; and a third lead-in wire electrically connecting said second electrode in said tubular envelope to a second terminal of said base; said incandescent lamp being selected to provide ballasting for an arc discharge across said first and second electrodes.  
  2. A lamp structure according to claim 1 wherein said base of the tubular envelope is a threaded-type base, said first electrode is disposed toward the base end of said tubular envelope, and said first and second lead-in wires are secured to the exterior of said tubular envelope and disposed to lie along the length thereof, and further including transparent insulating means covering said first and second lead-in wires.