Filament lamp

Abstract: Reduced power consumption is achieved in a filament quartz lamp by encasing the filament in an inner envelope having an elliptical portion. An IR coating is provided on the outer surface of the elliptical portion to reflect selected wavelengths of the emitted light toward the filament. A fill gas is also maintained at a reduced pressure therein. A second or outer envelope defines a cavity with the inner envelope. It is filled with an inert gas to limit oxidation associated with the leads extending from the inner envelope. The outer envelope is sealed in the base portion, and the alumina silicate glass provides UV protection. This lamp arrangement provides for decreased power consumption without adversely affecting the lumen output, lamp life, or dimensional characteristics of the lamp.

Description: Background of the Invention This invention pertains to the art of electrical lamps and more particularly to incandescent lamps. The invention is particularly applicable to an incandescent lamp using a filament that generates light in response to electrical current applied thereto within an enclosed, pressurized vitreous first envelope. The first envelope is contained within a second or outer envelope and the cavity defined between the envelopes filled with an inert gas. This arrangement allows the lamp to be used in a wide variety of applications since it eliminates the potential for electrical safety hazard, reduces the probability of a non-passive failure, and can be used in non-hermetically, sealed lamp products. FIGURE 1 illustrates a quartz lamp A currently on the market. This lamp has a substantially cylindrical envelope or outer jacket B preferably formed from quartz or a similar vitreous material. A first or outer end C of the envelope is sealed and the second or inner end D is received in a lamp base E. Centrally supported within the envelope is a light generating filament F. As apparent in FIGURE 1, the filament F is generally aligned with a longitudinal axis of the envelope and maintained in position by first and second support members G, H. The first support member G provides both mechanical support and electrical connection between a first end of the filament and a first electrical lead. The first lead terminates in an externally threaded shell J received over a portion of the base member. The second support member H likewise supports a second end of the filament. It is electrically connected via a second lead with a solder connection K at the end of a central passage that extends generally axially through the base member E. Thus, the solder connection and the shell establish electrical contact with a female socket that receives the lamp base therein. These lamps may also employ an infrared coating represented by the letter L on the envelope B. The coating is intended to reflect a portion of the emitted light toward the filament and increase the efficacy of the lamp operation. Unfortunately, and as will become more apparent below, this lamp configuration is not ideal for achieving desired higher efficacies. A filament lamp having a filament within a generally elliptically shaped chamber is described in EP-A-0,562,871. A double-bulb halogen lamp, in which an inner bulb containing a filament is supported within an outer bulb, is described in EP-A-0,590,602. The high cost of energy, particularly in selected countries, requires that this type of lamp achieve significantly higher efficacies without any decrease in performance. For example, equivalent performance is desired and can be measured in lumen output and lamp life, while still meeting size requirements for lamps of this type. Accordingly, lower power consumption, high lumens, and extended lamp life ultimate goals in this particular application and substantial changes are required with known arrangements to achieve same. For example, currently manufactured versions as illustrated in FIGURE 1 operating at 110 volts have wattages of 65, 85, and 130 watts. It is believed that modifying the infrared coating provided on the envelope with known coatings could result in an efficacy gain of between 2% and 4% over lamps with prior infrared coatings. However, significantly higher efficacies are still required. Summary of the Invention The present invention contemplates a new and improved lamp that overcomes all of the above-referenced problems and others and provides decreased power consumption without adversely affecting lumen output, lamp life, or materially altering the size of the lamp. A lamp according to the invention is defined in claim 1. Advantageous modifications of this lamp are defined in the dependent claims. According to one aspect of the invention, the lamp is comprised of an inner envelope that contains a light generating filament within an elliptical portion of the inner envelope. A coating on the elliptical portion of the envelope reflects selected wavelengths of the generated light toward the filament. A substantially cylindrical outer envelope surrounds the inner envelope and defines a cavity there-between. The cavity is filled with an inert gas to limit oxidation of first and second leads extending from the filament through the inner envelope. According to another aspect of the invention, the temperature of the inner envelope is regulated through the use of a desired fill gas and fill pressure within the cavity to achieve optimal performance with regard to lumen output and lamp life. A principal advantage of the invention results from the significantly lower power consumption with this lamp construction with respect to known arrangements. Another advantage resides in the maintenance of the lumen output, lamp life, and satisfying dimensional requirements relative to presently manufactured quartz lamps of this type. Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description. Brief Description of the Drawings The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof, and wherein: FIGURE 1 is an elevational view of a prior art lamp with selected portions shown in cross-section; FIGURE 2 is an elevational view of the subject new lamp with selected portions shown in cross-section in a manner similar to FIGURE 1; FIGURE 3 is an elevational view of the support member used to mount the inner envelope in the outer envelope; and FIGURE 4 is an elevational view illustrating how the hooked end of the support member guides and orients the inner envelope into the outer envelope in the subject new lamp. Detailed Description of the Preferred Embodiment Referring now to the drawings wherein the showings are for the purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same, FIGURES 2 - 4 show a modified filament lamp 10 having improved performance. Particularly, reduced power consumption is achieved without sacrificing lumen output, lamp life, or dimensional requirements in comparison with the prior art assembly of FIGURE 1. The lamp 10 includes a light generating member, preferably a filament 12 . In this embodiment, the filament is a coiled coil as commonly used in the industry. However, other filament configurations such as a single coil, triple coil, etc., may be used without departing from the scope and intent of the invention. First and second ends 14, 16 of the filament are generally aligned along an axis that closely coincides with a longitudinal axis of inner envelope 20 . The inner envelope is formed of a vitreous material, for example quartz, and is sealed at its opposite ends in a manner to be described in greater detail below. The inner envelope 20 includes a central, substantially elliptical portion 22 in which the foci of the elliptical configuration are preferably located on the longitudinal axis that coincides with the filament axis. At least the outer surface of the elliptical portion includes a coating intended to reflect selected wavelengths of the generated light toward the filament. The coating is represented by numeral 24 in the drawings and it will be understood that it preferably comprises an infrared coating intended to permit other wavelengths of light to pass therethrough while reflecting the infrared portion of the emitted light spectrum toward the filament. The reflected infrared portion of the emitted light contributes to temperature elevation of the filament thereby resulting in increase efficiency of light emission since at least a portion of the reflected infrared radiation is converted to visible light radiation. The coating used on the Halogen-IR™ lamp available from General Electric Company is an example of one type of infrared reflective coating used in the industry. Preferably, the coating is comprised of multiple layers of refractory metal oxides having alternating high and low indexes of refraction. Chamber 26 formed in the envelope and housing the filament is preferably filled with a pressurized noble gas, such as xenon, krypton, argon, or nitrogen may be added to suppress arcing in high voltage products in an amount of 5% to 10%. A reduced cold pressure on the order of 3.3·10 5 Pa (2500 Torr) can be achieved and is significantly less than prior art cold pressures on the order of 5.3·10 4 Pa (4000 Torr.) The first end of the inner envelope has a reduced cross-section and is adapted to receive one end of a first inner lead 30 . Likewise, a second end of the inner envelope has a reduced cross-section and is adapted to receive an end of a second inner lead 32 . The inner leads are connected to the ends 14, 16, respectively, of the filament, exit the chamber 26 , and are sealingly received within the reduced cross-sectional portions of the sealed quartz at opposite ends of the inner envelope. The leads are, in turn, electrically connected to thin metal foils, typically formed of molybdenum and which are commonly referred to as moly foils. Thus, a pair of moly foils 34, 36 are sealed in the reduced diameter ends of the inner envelope by any well known or conventional seal arrangement. Extending generally axially outward from outer ends of the foils 34, 36 are first and second outer leads 40, 42, respectively. Outer terminal ends of the first and second outer leads 40, 42 protrude from the quartz inner envelope and are connected to support members in a manner to be described in greater detail below. The first outer lead 40 extends from the inner envelope and is connected to a first support member or wire 50 , particularly along a first end 52 of the support member. Any suitable mechanical interconnection between the first support member and the first outer lead 40 can be used. A second end 54 of the first support member is embedded or otherwise secured to lamp base 60 . Preferably the lamp base is a ceramic material, although other materials can be used without departing from the scope and content of the subject invention. A second support member 70 interconnects the second outer lead 42 with the lamp base 60 . It, too, is preferably embedded into the base to provide an electrically insulated, stable support for the inner envelope. First and second lead wires 72, 74 are connected to the bases of the first and second support members 50 , 70 , respectively. A first lead wire extends through an axially directed opening in the base. The opening is radially spaced from the longitudinal axis of the filament and the lamp. The first lead wire proceeds through the opening and is connected with an externally threaded shell 80 received around the base. The second lead wire 74 proceeds generally axially along the longitudinal axis, exiting the base through central opening 78 . A solder connection represented by numeral 82 is applied to the terminal end of the second lead wire so that the soldered end is axially and radially spaced from the shell 80 . The axial and radial spacing between the shell 80 and the solder connection 82 cooperates with suitable contacts in a lamp receiving socket (not shown) to provide electrical current to the filament through the lead wires, support members, outer leads, moly foils, and inner leads. A second or outer envelope 90 has a first or closed end 92 and a second end 94 received in a recess 96 of the base. A cementitious material 98 secures the second end 94 of the outer envelope in the base and rigidly supports the outer envelope relative to the base. Thus, the support members are secured in a reduced cross-section of the outer envelope where the support members extend outwardly from the outer envelope. The support members are further secured by the cement 98 in the base. The outer envelope is spaced along its length from the inner envelope 20 to define a sealed cavity 100. The cavity is preferably filled with an inert gas to prevent oxidation of the outer lead. If oxidation of the outer leads takes place, the seal between the outer leads and the inner envelope is potentially breached as a wedging action can occur as a result of the oxidation. The inert gas can also be advantageously maintained at a relatively low pressure of approximately 5.3·10 4 Pa (400 Torr). This low pressure provides a number of benefits. In addition to preventing oxidation of the outer leads, the use of a fill gas with varying degrees of thermal conductivity modifies the inner envelope wall temperature to achieve optimal performance with regard to lumen maintenance and lamp life. Additionally, the reduced pressure in the inner envelope reduces the probability of a non-passive failure. Moreover, the use of a sealed outer envelope formed from an alumina silicate glass reduces the amount of ultraviolet light (wavelengths in the range of 200-400 nanometers) radiated from the lamp. It also allows the lamp to be used in a non-hermetic outer jacket. That is, prior lamp arrangements operating at comparable temperatures (400°-500°C)require a hermetically sealed outer jacket or housing because of the concern with oxidation of the outer leads that results in eventual leakage at the seal interface and reduced lamp life. By providing the outer envelope over the inner envelope, the subject new lamp can be used in non-hermetically sealed outer jacket products. The outer envelope also eliminates potential problems with an exposed electrical lead wire. As is apparent from a review of FIGURE 2, all of the lead wires are contained within the outer envelope. With continued reference to FIGURE 2, and additional reference to FIGURES 3 and 4, the support members are illustrated in greater detail. As originally manufactured, a continuous wire member is provided having a generally hooked or U-shaped configuration 52 at a first end. The hooked configuration facilitates guiding and centering of the support member, and likewise the inner envelope, upon insertion into the outer envelope as shown in FIGURE 4. Expected results with the new lamp as shown and described with reference to FIGURES 2-4 are to reduce the power consumption from sixty-five to fifty watts, eighty-five to sixty-five watts, and one hundred thirty to ninety watts. This achieves a wattage reduction on the order of 23% to 31% over presently manufactured lamps of this type. The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.

Claims: A lamp (10) comprising: a light transmissive, inner elongated envelope (20) having a generally elliptical portion (22); an elongated light generating filament (12) disposed in the elliptical portion (22); first and second inner leads (30,32) connecting first and second ends (14,16) of the filament, respectively, to first and second outer leads (40,42) respectively which have terminal ends extending from the inner envelope; an infrared coating (24) disposed on the elliptical portion (22) of the envelope for reflecting selected wavelengths of the generated light toward the filament; a substantially cylindrical outer envelope (90) disposed about the inner envelope and defining a cavity (100) therebetween; an inert fill gas received in the cavity for limiting oxidation of the first and second outer leads (40,42); and first and second support members (50,70) connected to the terminal ends of the first and second outer leads, respectively, and orienting the inner envelope (20) within the outer envelope (90). The lamp as defined in claim 1 wherein the filament (12) is a coiled coil. The lamp as defined in claim 1 or 2 wherein the filament is substantially aligned with longitudinal axes of the inner and outer envelope. The lamp as defined in claim 1, 2 or 3, further comprising first and second thin metal foils (34,36) sealed in ends of the inner envelope, the metal foils interconnecting the first and second inner leads (30,32) to the first and second outer leads (40,42), respectively. The lamp as defined in claim 1, 2, 3 or 4, wherein the infrared coating (24) has layers of refractory metal oxides having alternating high and low indexes of refraction. The lamp as defined in any preceding claim, wherein the inner envelope (20) includes a reduced pressure fill. The lamp as defined in claim 6 wherein the inner envelope fill is pressurized to approximately 3.3·10 5 Pa (2500 Torr). The lamp as defined in any preceding claim, wherein the fill gas in the cavity is pressurized to approximately 5.3·10 4 Pa (400 Torr). The lamp as defined in any preceding claim, wherein the first support member (50) includes a generally hook-shaped end (52) facilitating assembly and location of the inner envelope within the outer envelope.

Inventors: OLWERT RONALD JAMES, PAGE TIMOTHY D, OLWERT, RONALD JAMES, PAGE, TIMOTHY D.
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1995
Main classification: H01K1
IPC codes: H01K1