WO2007116921A2

WO2007116921A2 - Incandescent lamp, reflector incandescent lamp, and lighting apparatus

Info

Publication number: WO2007116921A2
Application number: PCT/JP2007/057609
Authority: WO
Inventors: Shinya Kawagoe; Naotaka Hashimoto; Taku Ikeda; Toshiyasu Kojima
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2006-03-30
Filing date: 2007-03-29
Publication date: 2007-10-18
Also published as: WO2007116921A3; JP2007294394A

Abstract

Disclosed is an incandescent lamp for use while mounted within a reflector having a concave reflective surface that contains a hermetically sealed bulb storing a filament assembly (60) therein. The filament assembly (60) includes a primary light-emitting portion (64A) that is a single coil wound in a cylindrical shape with a short axis (SX) and a long axis (LX) in a cross sectional plane, the primary light-emitting portion (64A) intersecting an optical axis (R) of the reflector. The primary light-emitting portion (64) intersects the optical axis (R) in such a way that a central axis (CX) thereof, which is substantially perpendicular to the short axis (SX) and the long axis (LX), is tilted with respect to the optical axis (R) at least in a direction perpendicular to the optical axis (R) and the long axis (LX).

Description

DESCRIPTION

INCANDESCENT LAMP, REFLECTOR INCANDESCENT LAMP,

AND LIGHTING APPARATUS

Technical Field

The present invention relates to an incandescent lamp, a reflector incandescent lamp, and a lighting apparatus. More particularly, the present invention relates to a technology for improving a filament assembly used for an incandescent lamp. Background Art

A reflector halogen lamp, which is a type of a reflector incandescent lamp, is constructed froma reflectorhaving a concave reflective surface in combination with a halogen lamp. The reflector halogen lamp, for example, is used as a spotlight in stores and other places .

The halogen lamp contains a hermetically sealed bulb storing a filament assembly therein. When used in combination, the halogen lamp^'and the reflector can increase a light collecting efficiency thereof, by utilizing the filament assembly that is downsized as small as possible, and by concentrating a luminous area of the filament assembly on a focal point of the reflector to the greatest extent possible. Here, it is known that downsizing the luminous area of the filament assembly, especially in a direction of the reflector's optical axis (hereinafter merely referred to as optical axis) , has an effect of increasing the light collecting efficiency.

However, generally speaking, a rated voltage [V] , rated power [W] and rated life (e.g., 3000 hours) of the halogen lamp practically determine diameter and length of a tungsten wire that forms the filament assembly. It is hence difficult to downsize the filament assembly by, for instance, simply shortening the tungsten wire.

In a practically-used halogen lamp with a rated voltage of 100 [V] or more, a coiled coil is generally used for downsizing ^v the filament assembly. To further downsize the filament assembly, Japanese Laid-OpenPatentApplicationPublicationNo.2001-345077 discloses a halogen lamp utilizing a triple coil for the filament assembly. According to Japanese Laid-Open Patent Application PublicationNo. 2001-345077, an entire length of the triple coil is shorter than that of the coiled coil in the optical axis direction, provided the triple coil and the coiled coil aremade of the tungsten wires of the same length. Consequently, the light collecting efficiency will increase with use of the triple coil. However, the more the coil is wound, the greater oscillation the coil will have when an external force (impact) is applied to the halogen lamp . This greater coil oscillationproblematically causes the coil to be easily broken.

Japanese Laid-Open Patent Application Publication No. 6-510881 discloses a halogen lamp that not only solves the above problem, but also contains a compaqt filament assemblywhose length is shorter in the optical axis direction. Here, a plurality of single coils are positioned parallel to the optical axis, and at the same time, in radial symmetry with respect to the optical axis. The filament assembly constructed from the plurality of single coils is shorter than that constructed from one single coil in the optical axis direction, and therefore has a higher light collecting efficiency. Here, with each coil being a single coil, the above problem regarding the oscillation can be reduced as well.

In further improving the above halogen lamp, Japanese Laid-Open Patent Application Publication No.2002-63869 provides a halogen lamp in which one of the plurality of single coils is positioned parallel to and on the optical axis. This is because ahalogenlamp that contains acoil (i.e., alight-emittingportion) positioned on -the optical axis provides far greater illuminance than a halogen lamp that does not .

As illumination techniques for store presentation have become more diverse than ever, there has been an increasing use of a reflector halogen lamp. Accordingly, especially with the recent trend of energy conservation, a demand for a reflector halogen lamp with higher light collecting efficiency has been increasing as well.

Given the above factors, inventors of the present invention (hereinafter referred to as inventors) have invented a filament assembly constructed from a plurality of single coils, wherein (i) one of the plurality of single coils is positioned on the optical axis, (ii) the rest of the single coils are positioned at intervals on a line that intersects the optical axis, (iii) the plurality of single coils are each positioned substantially parallel to the optical axis, and (iv) the plurality of single coils are each made of a coil wire that has been wound in a flat cylindrical shape.

In the above invention, the coil wire makes a longer loop per turn than a coil wire of a conventional single coil that has been wound in a cylindrical shape (provided a short axis of the flat cylindrical shape and a diameter of the cylindrical shape are equal) . As the above invention allows a tungsten wire to form a shorter coil, a filament assembly, accordingly, can be further shortened in the optical axis direction. Naturally, the above inventionwas expected to increase the light collecting efficiency. It should be noted here that the flat cylindrical coils are longer than the cylindrical coils in a direction of the line that intersects the optical axis. This is not a drawback, however, as the light collecting efficiency is increased more efficiently when the filament assembly is shortened in the optical axis direction than in the direction intersecting the optical axis.

On the other hand, in the case where the filament assembly is constructed from the plurality of single coils, these single coils each have a smaller diameter than the previously-mentioned, practically-used coiled coil. In consequence, the single coil that is supposed to be positioned on the optical axis may get deviated therefrom by merely shifting, even to a small extent, in the direction intersecting the optical axis for manufacturing reasons. It is true that the above filament assembly invented by the inventors increases an allowable range of the coil shift (allowable displacement of the coil) in the coil's long axis direction, by having a coil formed in the flat cylindrical shape. However, when the coil (light-emitting portion) shifts in the short axis direction even to a small extent, the coil gets deviated from the optical axis, resulting in an extreme reduction in the lamp illuminance.

In the light of the above, the present invention aims to provide an incandescent lamp having a light-emitting portion that stays on a reflector's optical axis. Another aim of the present invention is toprovide areflector incandescent lamp anda lighting apparatus that incorporate the above incandescent lamp. Disclosure of the Invention

In order to achieve the above aims, the present invention provides an incandescent lamp for use while mounted within a reflector having a concave reflective surface, the incandescent lamp comprising: a bulb that is hermetically sealed; and a filament assembly stored in the bulb. The filament assembly includes a primary light-emitting portion that is a single coil wound in a cylindrical shape with a short axis and a long axis in a cross sectional plane, the primary light-emitting portion intersecting an optical axis of the reflector. The primary light-emitting portion intersects the optical axis in such a way that a central axis thereof, which is substantially perpendicular to the short axis and the long axis, is tilted with respect to the optical axis at least in a direction, perpendicular to the optical axis and the long axis. Here, the sentence "at least in a direction perpendicular to the optical axis and the long axis" implies that the central axis of the primary light-emitting portion may be tilted in the long axis direction, in addition to the direction perpendicular to the optical axis and the long axis. In the above-described incandescent lamp, the filament assembly includes the primary light-emitting portion that is the single coil wound in the cylindrical shape with the short axis and the long axis in a cross sectional plane, the primary light-emitting portion intersecting the optical axis of the reflector. Here, the primary light-emitting portion intersects the optical axis in such a way that the central axis thereof, which is substantially perpendicular to the short axis and the long axis, is tilted with respect to the optical axis at least in the direction perpendicular to the optical axis and the long axis. This construction advantageously increases an allowable displacement of the primary light-emitting portion, preventing the deviation of the primary light-emitting portion from the optical axis . Therefore, the incandescent lamp can stablymaintain its illuminance and provide the illuminance as much as needed. In order to achieve the above aims, the present invention also provides a reflector incandescent lamp that includes: a reflector; and the above-described incandescent lamp, the incandescent lamp being mounted within the reflector.

In order to achieve the above aims, the present invention further provides a lighting apparatus that includes: a lighting fixture having a reflector; and the above-described incandescent lamp, the incandescent lamp being mounted within the reflector.

In order to achieve the above aims, the present invention yet furtherprovides a lightingapparatus that includes : a lighting fixture; and the above-described reflector incandescent lamp, the reflector incandescent lamp being mounted within the lighting fixture .

In the above construction, the reflector incandescent lamp and the lighting apparatus employ the above incandescent lamp, and therebyyield the same advantage that is previously described.

In the present invention, "a cylindrical shape with a short axis and a long axis in a cross sectional plane" includes cylindrical shapes having the following cross sections, which are described with reference to FIGs. 9A-9E. Note that in FIGs. 9A-9E, short axes, long axes, and central axes (coil axes) that are substantially perpendicular to the short and long axes are each labeled as: "SX," "LX^Λ and "CX."

(i) FIG. 9A: A racetrack-shaped cross section as viewed in a coil axis (CX) direction. The racetrack shape consists of two parallel lines, wherein one line has each end connected to a corresponding end of the other line by an approximate semicircle, (ii) FIG. 9B: A cross section that has a distorted but an approximately circular shape as viewed in the coil axis (CX) direction. (iii) FIG. 9C: A substantially elliptic cross section as viewed in the coil axis (CX) direction. (iv) FIG. 9D: A substantially rectangular cross section as viewed in the coil axis (CX) direction, wherein four corners of the rectangle are rounded during a manufacturing process, (v) Any other cross sections that resemble the above ( (i) through (iv) ) . For example, a cross section shown in FIG. 9E, in which the cross section of (i) has two incurved lines instead of two parallel lines, is considered to resemble that of (i) . Deformed versions of the above cross sections ( (i) through (iv) ) due to manufacturing variations are included herein. Brief Description of the Drawing

FIG. 1 is a partially cut-away view showing an overall structure of a lighting apparatus of a first embodiment.

FIG. 2 shows a halogen lamp that constitutes the lighting apparatus . FIG. 3 is a perspective view showing a support structure operable to support a filament assembly of the halogen lamp.

FIG. 4 is a perspective view showing the filament assembly being supported by the support structure.

FIG. 5 illustrates a method of forming a filament coil that constitutes the filament assembly.

FIG. 6 schematically illustrates a plan view (top) and a front view (bottom) of a filament coil.

FIG. 7 schematically illustrates a plan view (top) and a front view (bottom) of the filament assembly. FIG. 8 illustrates an overall structure of a reflector halogen lamp of a second embodiment.

FIGs. 9A-9E show examples of cross sections of flat cylinders .

Best Mode for Carrying Out the Invention The followingdescribes embodiments of thepresent invention with use of the drawings . <First Embodiment>

FIG. 1 is a partially cut-away view showing an overall structure of a lighting apparatus 10 of the first embodiment. Elements shown in all the drawings, including FIG. 1, are shown in various degrees of scale.

For example, the lighting apparatus 10 is used as a spotlight in suchplaces as homes, stores and studios . The lighting apparatus 10 contains a lighting fixture 12 and a halogen lamp 14 which is represented here as an example of an incandescent lamp.

The lighting fixture 12 includes a body 16 formed in a cylindrical shape having a bottom, and a reflector 18 stored in the body 16. ^"

The bottom of the body 16 has a non-illustrated receiver attached thereto for mounting a base 30 (see FIG.2) of the halogen lamp 14. Note that the body 16 may be formed in any well-known shapes other than the cylinder.

The reflector 18 is detachable from the body 16, so as to make the halogen lamp 14 replaceable. The reflector 18 includes a funnel-shaped outer envelope 20 made of hard glass. The outer envelope 20 has a concave surface 2OA curved in a spheroidal or paraboloidal shape and the like. The concave surface 2OA is coated with a multilayer interference film 22 that constitutes a reflective surface of the reflector. The multilayer interference film 22 is constructed from metal films (e.g., aluminum and chrome), silicon dioxide (SiO₂), titanium dioxide (TiO₂) , magnesium fluoride (MgF) , zinc sulfide (ZnS) , and so on. An aperture diameter (mirror diameter) of the reflector 18 is 100 [mm] . If necessary, the reflective surface of the reflector may be faceted.

The reflector 18 further includes a front glass 24 that covers an opening of the outer envelope 20. In the present embodiment, the front glass 24 is firmly attached to the outer envelope 20, while the outer envelope 20 is detachable from the body 16 so as to make the halogen lamp 14 replaceable. However, the structure of the lighting apparatus should not be limited to such. Instead, the outer envelope may be firmly attached to the body, and the front glass may be made detachable from the body.

The halogen lamp 14 is used while mounted on the non-illustrated receiver and held into place within the reflector

18. During this state, a central axis B of an after-mentioned bulb 26, which constitutes thehalogenlamp 14, is aligned coaxially with an optical axis R of the reflector 18. The halogen lamp 14 has a rated voltage ranging from 100 [V] to 150 [V] , and a rated wattage of 100 [W] or less.

FIG. 2 is a partially cut-away front view of the halogen lamp 14.

The halogen lamp 14 includes a hermetically sealed bulb 26 and the base 30 (e.g., an Edison screw) which is attached by an adhesive 28 to an after-mentioned sealing portion 38 of the bulb 26.

The bulb 26 is comprised primarily of the following members that are disposed in listed order: a chip-off portion 32 that is a remnant of a bulb cutting operation for sealing the bulb; a filament housing portion 34 for storing therein an after-mentioned filament assembly 60' and the like; a cylindrical portion 36 that has an approximately cylindrical shape; and a sealing portion 38 formed by a heretofore known pinch seal method.

As shown in FIG. 2, the filament housing portion 34 has an approximately spheroidal shape. Here, "an approximately spheroidal shape" refers not only to a perfect spheroidal shape, but also to imperfect spheroidal shapes that are deformed due to manufacturing variations that occur during the glass manufacturingprocess. It is not requiredthat the filament housing portion be in the above-described shapes; the filament housing portionmaybe in a shape of an approximate cylinder, an approximate globe, or a combination of a plurality of approximate ellipses.

Likewise, the constitution of the bulb is not limited to the above. The bulb may instead be comprised primarily of the following members that are disposed in listed order: the chip-off portion, the filament housing portion, and the sealing portion.

The chip-off portion may be excluded from the bulb depending on circumstances .

An outer wall of the filament housing portion 34 is coated with an infrared-reflective coating. The infrared-reflective coating is not a necessity, but may be incorporated at discretion.

The bulb 26 is filled with a certain amount of halogen substance and noble gas. The bulb 26 may be additionally filled with nitrogen gas .

When the filament assembly is giving off light, tungsten that constitutes the filament assembly 60 is evaporated from the filament assembly 60. The halogen substance redeposits the evaporated tungsten into the filament assembly 60 throughaprocess called a halogen cycle, which prevents blackening of the bulb

26. Preferably, the halogen substance has a concentration ranging from 10 [ppm] to 300 [ppm] . In order to activate the halogen cycle, it is desired that the coldest spot of an inner wall of the bulb

26 maintains a temperature of 200 [⁰C] or more. Furthermore, a concentration of oxygen contained in the bulb 26 should be preferably set to 100 [ppm] or less; with this oxygen concentration, the halogen cycle operates in an appropriate manner.

It is desired that noble gas used here includes krypton gas. As will be discussed later, for the purpose of increasing the lamp's light collecting efficiency, light-emitting portions are placed adjacently from one another to downsize the filament assembly 60. At any area between these adjacent light-emitting portions, an arc discharge may occur while the filament assembly 60 is giving off light, leading to a breakdown of the filament assembly 60. Krypton gas, however, has an effect of restraining such a breakdown, and thus should preferably be included in noble gas . Especially, a filler gas should contain krypton gas as well as nitrogen gas and the halogen substance, with krypton gas being a major component thereof. A gas pressure in the bulb 26 at room

^• temperature is preferably set between 2 [atm] and 10 [atm] . If the bulb 26 breaks when the gas pressure is over 10 [atm] , fragments of the broken bulb 26 may scatter and further break the lighting fixture 12. Meanwhile, if the gas pressure is below 2 [atm] , the tungsten of the filament assembly evaporates more easily. This will result ina shorter lamp life . In otherwords, the gas pressure, if set within the stated range, will be adequately kept under control. Here, even if the bulb 26 breaks, the fragments thereof do not scatter violently enough to break the lighting fixture 12. The stated range of the gas pressure, which is adequately high, further makes the tungsten of the filament assembly 60 evaporation-resistant. This will result in a longer lamp life. The stated range of the gas pressure yet further restrains the breakdown of the filament assembly 60, which is caused by the arc discharge that occurs at any area between the adjacent light-emitting portions while the filament assembly 60 is giving off light. Ina case where the filler gas includes nitrogengas , nitrogen gas preferably makes up from 8 [%] to 40 [%] of the filler gas. If nitrogen gas accounts for more than 40 [%] of the filler gas, there is a chance the lamp's light collecting efficiency will decrease . This is because a heat , which is generatedby the filament assembly 60 while giving off light, is excessively emitted by means of nitrogen gas. On the other hand, whennitrogen gas accounts for less than 8 [%] of the filler gas, the arc discharge is prone to occur between the adjacent light-emitting portions while the filament assembly 60 is giving off light, making the filament assembly 60 breakdown-prone. In other words, if provided in the stated proportion, the nitrogen gas will be adequately kept under control,^" and therefore prevents the decrease of the lamp's light collecting efficiency due to the excessive emission of the heat

(generated by the filament assembly 60 while giving off light) by means of nitrogen gas . The stated proportion of nitrogen gas further restrains the breakdown of the filament assembly 60 , which is caused by the arc discharge that occurs at any area between the adjacent light-emitting portions while the filament assembly 60 is giving off light.

The sealing portion 38 contains therein a pair of metal foils 40 and 42 that are made of molybdenum and that are attached thereto. Here, the metal foils 40 and 42 may overheat and consequently get oxidized, causing the bulb 26 to lose its air tightness. To prevent such a situation, it is desired to improve heat radiation of the sealing portion 38 by providing thereto a concavo-convex surface for increasing a surface area thereof.

One ends of the metal foils 40 and 42 join and make electrical connections to one ends of external leads 44 and 46, respectively.

The external leads 44 and 46 are made of tungsten. The other ends of the external leads 44 and 46 go outside of the bulb 26 and are electrically connected, respectively, to terminals 48 and 50 of the base 30. Here, it is desired to place a fuse (not illustrated) in such a way that at least one of the external leads 44 and 46 is respectively connected, via the fuse, to the terminal 48 or 50 that corresponds to a base 116. When the light-emitting portion breaks and creates the arc discharge, the fuse will instantly melt, extinguishing the arc discharge. Therefore, by placing the fuse, breaking of and other damages on the bulb 26 triggered by an impact of the arc discharge can be avoided. Especially in a case where a plurality of light-emitting portions are placed adjacently from one another, the arc discharge may not occur due to the breaking of the light-emitting portion; however, there is a chance that the arc discharge occurs between the adjacent light-emitting portions. For this reason, it is preferable in this case to place a fuse both between the external lead 44 and the terminal 48, and between the external lead 46 and the terminal 50.

The other ends of the metal foils 40 and 42 join and make electrical connections to one ends of internal leads 52 and 54, respectively. The internal leads 52 and 54 are made of tungsten. Said one ends of the internal leads 52 and 54 are supported by the sealing portion 38 of the bulb 26. The internal leads 52 and 54 receive utility power via the base 30, and supply the utility power to the filament assembly 60. The internal leads 52 and 54 further function as support members operable to directly support part of the filament assembly 60.

FIG. 3 is a perspective view showing a support structure operable to support the filament assembly 60. FIG. 4 is a perspective view showing the filament assembly 60 being supported by the support structure . As shown in FIG. 3, support wires 56 and 58 are also support members operable to directly support part of the filament assembly 60. The support wires 56 and 58 are made of tungsten.

The internal leads 52 and 54 and the support wires 56 and 58 are braced by and between a pair of cylindrical glass stems

57 and 59. This structure not only supports the support wires 56 and 58, but also maintains relative positions of the internal leads 52 and 54 and the support wires 56 and 58.

As shown in FIG. 4, the filament assembly 60 is constructed from a plurality of filament coils. In the present embodiment, the filament assembly 60 is constructed from three filament coils 62, 64 and 66, which are each made with a tungsten wire that has been wound in a manner that will be described hereinafter.

The internal leads 52 and 54 and the support wires 56 and

58 are each inserted through at least one end of the filament coils 62, 64 and 66. Each of the internal leads 52 and 54 and the support wires 56 and 58 further has one or two "coil support portions" for supporting at least one of the filament coils 62,64 and 66. The coil support portion is bent to form a shape of a square with one side thereof missing.

Here, the filament coil 62 is supported by a coil support portion 52A of the internal lead 52 and a coil support portion 56A of the support wire 56.

The filament coil 64 is supported by a coil support portion 56B of the support wire 56 and a coil support portion 58A of the support wire 58. The filament coil 66 is supported by a coil support portion 58B of the support wire 58 and a coil support portion 54A of the internal lead 54.

As the support wires 56 and 58 are each made by bending a tungsten wire, the coil support portions 56A and 56B of the support wire 56are connected to each other, while the coil support portions 58A and 58B of the support wire 58 are connected to each other. That is to say, the filament coils 62, 64 and 66 are electrically wired in series to one another, with the internal leads 52 and 54 and the support wire 56 and 58 inserted therethrough.

When electric power is supplied via the internal leads 52 and 54 as shown in FIG. 4, there are some parts in the filament coils 62, 64 and 66 through which the coil support portions are inserted, and these parts do not emit light (nonluminous parts) .

At the same time, there are some parts in the filament coils 62,

64 and 66 through which no coil support portions are inserted (i.e., the parts between the coil support portions), and these parts emit light. Here, these light-emitting parts of the filament coils 62, 64 and 66 are referred to as light-emitting portions 62A, 64A and 66A, respectively. That is to say, the filament assembly 60 has a plurality of light-emitting portions (three light-emittingportions 62A, 64Aand 66A in thepresent embodiment) that are each constructed from a single coil.

Assuming that the light-emitting portions, as a whole, are in a shape of a cylinder, the light-emitting portions 62A, 64A and 66A of the present embodiment, as a whole, are in a shape of a prism with four corners thereof connected. Here, the area represented by this prism is referred to as LA, a luminous area of the filament assembly 60. The luminous area LA is indicated by chain lines in FIG. 3 instead of FIG. 4, as FIG. 4 would look complicated with an illustration of the luminous area LA. Shape and size of each component are determined (designed) so that, when the halogen lamp 14 is mounted within the lighting fixture 12 (see FIG. 1) , a central point of the luminous area LA (i.e., the light-emitting portion 64A) is placed approximately on a focal point of the reflector 18. From here on, there are occasions where the filament coil 64 is referred to as a primary filament coil 64, while the filament coils 62 and 66, which are positioned at either side of the primary filament coil 64, are referred to as secondary filament coils 62 and 66,- respectively.

Similarly, from here on, the light-emitting portion 64A of the primary filament coil 64 may be referred to as a primary light-emitting portion 64A, whereas the light-emitting portions

62Aand66Aof the secondary filament coils 62 and 66 may be referred to as secondary light-emittingportions 62Aand66A, respectively.

As stated earlier, in order to increase the lamp's light collecting efficiency, it is important to concentrate the luminous area of the filament assembly on the reflector's focal point by downsizing the luminous area as small as possible. However, a rated voltage [V], rated power [W] and rated life (e.g., 3000 hours) of the halogen lamp practically determine diameter and length of a tungsten wire that constitutes each of the filament coils. It is hence difficult to downsize the luminous area by simply shortening the tungsten wire.

In sum, to determine the rated voltage and rater power of the halogen lamp is none other than to determine the diameter and an effective length of the tungsten wire. Here, the effective length means a total length of the tungsten wires that constitute the light-emitting portions 62A, 64A and 66A. For example, the rated voltage and rated power of the halogen lamp and the length and diameter of the tungsten wire are related to one another as follows . (i) HO[V] , 65[W] : 0.04-006 [mm] , 400-500 [mm]

(ii) HO[V] , 40[W] : 0.03-0.05 [mm] , 380-480 [mm] ^" (iii) 120[V] , 65[W] : 0.035-0.055 [mm] , 450-550 [mm] (iv) 120[V] , 40[W] : 0.025-0.-045 [mm] , 430-530 [mm]

Since the effective length of the tungsten wire is inevitably determined as previously explained, the inventors have constructed the filament coils 62, 64 and 66 (light-emitting portions 62A, 64A and 66A) from single coils that have each been wound in a flat cylindrical shape (hereinafter referred to as flat coils) as shown in FIG. 4. In the above implementation, each wire of the flat coils make a longer loop per turn than a wire of a conventional single coil (hereinafter referred to as a cylindrical coil) which has been wound in a cylindrical shape

(provided a short axis of the flat cylindrical shape and a diameter of the cylindrical shape are equal) . As the tungsten wire can forma shorter coil, the luminous area, accordingly, canbe further narrowed in the optical axis direction. Naturally, the above implementation can increase the light collecting efficiency. Here , the flat coils are longer, ina direction of the line that intersects the optical axis, than the cylindrical coils . This is not a drawback, however, as the light collecting efficiency is increased more efficiently when the luminous area is narrowed in the direction of the optical axis than the direction intersecting the optical axis .

The filament coils (flat coils) 62, 64 and 66 are constructed as follows . FIG. 5 shows a plurality of cylindrical cores (mandrels) 68 that are aligned closely and parallel to each other. Two cores are used in FIG. 5 as an example. First, a tungsten wire 70 is wound around the cores. The cores 68 are then removed by getting pulled out of the wound tungsten wire 70, or by getting melted. A top part of FIG. 6 schematically illustrates a plan view of the filament coil 62 as viewed in the coil axis (CX) direction. A bottom part of FIG. 6 schematically illustrates a front view of the filament coil 62.

As the filament coils 64 and 66 each have almost a same shape as the filament coil 62, the illustration of the filament coil 62 in FIG. 6 represents the filament coils 64 and 66 as well. _.

As shown in the top part of FIG. 6, the filament coil 62, as viewed in the coil axis (CX) direction, has two parallel lines, wherein one line has each end connected to the corresponding end of the other line by a semicircle. Or specifically, the filament coil 62 is in a shape of a racetrack used for athletic events, a shape that originates from the coil-winding method described above. The more the cores 68 are, the flatter the racetrack shape gets. That is to say, a flatness of the filament coil 62 can be controlled by the number of the core 68. It is regarded that the flatness of the filament coil 62 can be obtained by dividing a long axis LX by a short axis SX of an inner circumference of the filament coil 62. With the above coil-winding method of the present embodiment, the flatness of the filament coil 62 is an integer. As previously described, the filament coil 62 shown in the bottom part of FIG. 6 has nonluminous parts 62B and the light-emitting portion 62A. The nonluminous parts 62B are both ends of the filament coil 62, which are supported by the coil support portions 52A and 56A (see FIG. 4) . The light-emitting portion 62A is a part between the coil support portions 52A and 56A.

Each of the filament coils does not need to have the previously-described racetrack shape, but may instead have any other shapes, including an ellipse. That is to say, the filament coils can be in any shape, as long as the shape has a long axis and short axis that run at right angles to each other, and as long as the shape is symmetrical with respect to its long and short axes. Viewed in this light, the filament coils may be in a shape of a rectangle as well. Accordingly, a flatness of the filament coils is not necessarily an integer but could be any decimal number. A top part of FIG. 7 schematically illustrates a plan view of the filament coils 62, 64 and 66 as viewed in the optical axis direction while the filament coils are coupled to the internal leads 52 and 54 and the support wires 56 and 58. A bottom part of FIG. 7 schematically illustrates a front view of the above filament coils 62, 64, and 66. FIG. 7 is mainly intended to illustrate relative positions of the filament coils 62, 64 and 66. In FIG. 7, illustrations of the internal leads 52 and 54 are thereby omitted, while the support wires 56 and 58 are each drawn as a line to show how the filament coils are electrically wired to one another. In the bottom part of FIG. 7 (the front view of the filament coils 62, 64 and 66) , the light-emitting portions 62A, 64A and 66A are shown as solid lines, whereas the nonluminous parts 62B, 64B and 66B are shown as two-dot chain lines. As shown in FIG. 7, the secondary filament coils 62 and 66 (secondary light-emitting portions 62Aand 66A) are separately positioned at either side of the primary filament coil 64 in the direction perpendicular to the optical axis and the long axis . That is, the secondary filament coils 62 and 66 align themselves with the primary filament coil 64, with the primary filament coil 64 being centrally located. The secondary filament coils 62 and 66 (secondary light-emitting portions 62A and 66A) are also positioned in such a way that, when viewed in the optical axis direction, the short axes SX thereof are aligned coaxially with the short axis SX of the primary filament coil 64.

The secondary filament coils 62 and 66 (secondary light-emitting portions 62A and 66A) are further positioned in such a way that the coil axes CX thereof run parallel to the optical axis R. On the other hand, the primary filament coil 64 (primary light-emitting portion 64A) intersects the optical axis R in such a way that the coil axis CX thereof is tilted with respect to the optical axis R at least in the direction perpendicular to the optical axis R and the long axis. A reason for tilting the primary filament coil 64 (primary light-emitting portion 64A) in the direction perpendicular to the optical axis R and the long axis will be discussed below.

Although the size of each component is designed to allow the optical axis to intersect the primary light-emitting portion 64A, there are cases where the primary light-emitting portion 64 gets deviated from an ideal position for manufacturing reasons , with the halogen lamp 14 still being mounted within the lighting fixture 12. For example, after getting coupled to the filament coils 62, 64 and 66, the internal leads 52 and 54 and the support wires 56 and 58 are braced by and between the cylindrical glass stems 57 and 59. During this bracing process, each component may get shifted from its original position relative to other components . There are also cases where, during a pinch seal process for forming the sealing portion 38, the internal leads 52 and 54 get shifted from their ideal, predetermined positions relative to the bulb 26.

A traditional, common filament assembly is constructed from a coiled coil with a coil diameter of 1.4-2 [mm] . On the contrary, a flat single coil of the present embodiment has a short axis of 0.1-0.7 [mm] . Therefore, if the flat single coil of the present embodiment is positioned such that the coil axis thereof runs

^■ parallel to the optical axis, the primary light-emitting portion thereof may stray from the optical axis by shifting, even to a small extent, in the coil's short axis direction. The primary light-emitting portion that has been strayed completely off the optical axis provides extremely low illuminance compared with the primary light-emitting portion that intersects, even if only partially, the optical, axis .

Given the above factors, the present embodiment has positioned the primary light-emitting portion 64A in such a way that the coil axis CX thereof is tilted in the direction^' perpendicular to the optical axis and the long axis . This avoids a situation as much as possible where the primary light-emitting portion 64A strays completely off the optical axis when shifting in directions intersecting the optical axis at a 90 degree angle. In other words, in the above design, an allowable displacement of the primary light-emitting portion 64A is greater in the direction perpendicular to the optical axis and the long axis. Here, the coil axis CX of the primary light-emitting portion 64A is preferably tilted only in the direction perpendicular to the optical axis and the long axis. However, it is acceptable that the coil axis CX of the primary light-emitting portion 64A is tilted in the long axis LX direction, in addition to the direction perpendicular to the optical axis and the long axis. As long as the coil axis CX of the primary light-emitting portion 64A is tilted at least in the direction perpendicular to the optical axis and the long axis , the above-mentioned advantage is obtained.

As shown in the bottom part of FIG. 7, the primary light-emitting portion 64A has one end electrically wired to one end of the adjacent secondary light-emitting portion 62A, and the other end electrically wired to one end of the adjacent secondary light-emitting portion 66A. Preferably, the primary light-emitting portion 64A is tilted in such a way that both ends thereof are positioned closely to, or located within a short distance from, their wired counterparts (i.e., the one end each of the secondary light-emitting portions 62A and 66A) . That is to say, the primary light-emitting portion 64A is tilted so that an end 64C2 (the one end of the primary light-emitting portion 64A) is closely positioned and electrically wired, via the support wire 56, to an end 62C (the one end of the secondary light-emitting portion 62A) , whereas an end 64Cl (the other end of the primary light-emitting portion 64A) is closely positioned and electrically wired, via the support wire 58, to an end 66C (the one end of the secondary light-emitting portion 66A) .

To put it another way, the primary light-emitting portion 64A is tilted in such a way that both ends thereof are positioned away from, or located distantly from, their unwired counterparts (i.e., the other end each of the secondary light-emitting portions 62A and 66A) . That is to say, the primary light-emitting portion 64A is tilted so that the end^'s 64Cl and 64C2 are positioned away from ends 62D and 66D, respectively.

While the filament assembly is giving off light, potential differences between the ends 64Cl and 62D, as well as between the ends 64C2 and 66D, are fairly large. If the ends 64Cl and 64C2 are closely positioned to the ends 62D and 66D respectively, these closely positioned ends will have more chance of developing the arc discharge in between, and consequently, more chance of the filament breakdown. On the other hand, there is almost no difference in electric potential between the ends 64Cl and 66C, as well as between the ends 64C2 and 62C. Therefore, the ends 64Cl and 66C, as well as the ends 64C2 and 62C, do not create the above problem and thus can be closely positioned to each other. In sum, tilting the primary light-emitting portion 64A in the above-described manner has an effect of preventing the arc discharge between the light-emitting portions (filament coils) , and consequently, the filament breakdown.

The top part of FIG. 7 is the plan view of the filament assembly 60 as viewed in the optical axis R direction. Here, the primary light-emitting portion has one end Pl and the other end P2 that are collinear on a line perpendicular to^* the optical axis and the long axis . Preferably, the primary light-emitting portion

64Ais tiltedto suchanextent that, whenviewedinacross sectional

^■ plane in the optical axis direction, (i) a maximum end-to-end distance thereof (a distance between Pl and P2, namely D_Cχ) in a direction perpendicular to the optical axis and the long axis and (ii) a maximum end-to-end distance thereof in the direction of the long axis (namely D_LX) are substantially equal. This way the allowable displacement of the primary light-emitting portion S4A in the direction perpendicular to the optical axis and the long axis becomes almost the same as that in the long axis direction. <Second Embodiment>

FIG. 8 is a vertical cross-sectional view that illustrates an overall structure of a reflector halogen lamp of the second embodiment .

A reflector halogen lamp 100 is a halogen lamp having a built-inreflector. Ahalogen lamp 102 used in the reflectorhalogen lamp 100 is basically constructed the same as the halogen lamp 14 (see FIG. 2) of the first embodiment, except that the halogen lamp 102 has a different base.

Made of hard glass or fused quartz, a reflector 104 has a funnel-shaped outer envelope 106. The outer envelope 106 has a concave surface 106A curved in a spheroidal or paraboloidal shape and the like. The concave surface 106A is coated with a multilayer interference film 108 that constitutes a reflective surface of the reflector. -The multilayer interference film 108 is constructed from metal films (e.g., aluminum and chrome), silicon dioxide (SiO₂) , titanium dioxide (Tio₂) , magnesium fluoride (MgF) , zinc sulfide (ZnS) , and so on. An aperture diameter (mirror diameter) of the reflector 104 is 100 [mm] . If necessary, the reflective surface of the reflector may be faceted. The reflector 104 further includes a front glass 110 that covers an opening of the outer envelope 106. The front glass 110 is held into place on the outer envelope 106 by a heretofore known clip 112, or may instead be firmly attached by an adhesive to the outer envelope 106. The clip 112 may be used in combination with the adhesive to hold the front glass 110 in place. The front glass is a nonessential component of the reflector halogen lamp, and thus may be excluded from the reflector halogen lamp.

The outer envelope 106 has its neck 106B fitted for, and attached by an adhesive 124 to, an outer envelope receiver 122. The outer envelope receiver 122 is placed on opposite side of terminals 116 and 118 of a base 114 in the halogen lamp 102.

The bulb 26 is attached to the base 114 in advance of a mounting of the base 114 within the outer envelope 106. The present invention has been described hereinbefore based on, but is not limited to, its embodiments. The present invention can be achieved by the following embodiments as well . (1) According to the first embodiment, the lighting apparatus contains the halogen lamp and the lighting fixture having the reflector. The lighting apparatus, however, may instead contain the halogen lamp and the lighting fixture having no reflector. For instance, the reflector 18 and the halogen lamp 14 contained in the lighting apparatus of FIG. 1 may be replaced by the halogen lamp 100 as shown in FIG. 8. (2) The above embodiments employ the halogen lamp as one form of incandescent lamp. However, the present invention can be achieved by utilizing an incandescent lamp other than the halogen lamp. That is, the present invention can utilize any light source that feeds electrical current through the filament assembly and gives off light by incandescence . Industrial Appl icabi I ity

The incandescent lamp of the present invention can be used while mounted within a reflector, and is suitable for use as an incandescent lamp withhigh light collecting efficiency and impact resistance.

Claims

CLAIMS l.An incandescent lamp for use while mounted within a reflector having a concave reflective surface, the incandescent lamp comprising: a bulb that is hermetically sealed; and

■a filament assembly stored in the bulb, wherein the filament assembly includes a primary light-emitting portion that is a single coil wound in a cylindrical shape with a short axis and a long axis in a cross sectional plane, the primary light-emitting portion intersecting an optical axis of the reflector, and the primary light-emitting portion intersects the optical axis in such a way that a central axis thereof, which is substantially perpendicular to the short axis and the long axis, is tilted with respect to the optical axis at least in a direction perpendicular to the optical axis and the long axis.

2. The incandescent lamp of Claim 1, wherein the filament assembly further includes a 1st secondary light-emittingportionanda 2nd secondary light-emitting portion that each have almost a same shape as the primary light-emitting portion, the 1st and 2nd secondary light-emitting portions are separatelypositioned at either side of the primary light-emitting portion in the direction of the short axis, so that the 1st and

2nd secondary light-emitting portions each have a central axis substantially parallel to the optical axis, the 1st secondary light-emitting portion, the primary light-emitting portion, and the 2nd secondary light-emitting portion are electrically wired in series to one another in this order, and the primary light-emitting portion is tilted in such a way that bothends thereof are eachpositionedaway froma corresponding, unwired end of the 1st or 2nd secondary light-emitting portion.

3. The incandescent lamp of Claim 2 , wherein when viewed in a cross sectional plane in a direction of the optical axis, (i) a maximum end-to-end distance of the primary light-emitting portion in the direction perpendicular to the optical axis and the long axis and (ii) a maximum end-to-end distance thereof in a direction of the long axis are substantially equal .

4. The incandescent lamp of Claim 1, wherein when viewed in a cross sectional plane in a direction of the optical axis, (i) a maximum end-to-end distance of the primary light-emitting portion in the direction perpendicular to the optical axis and the long axis and (ii) a maximum end-to-end distance thereof in a direction of the long axis are substantially equal .

5. .A reflector incandescent lamp comprising: a reflector; and an incandescent lamp of one of Claims 1 through 4 , the incandescent lamp being mounted within the reflector.

6. A lighting apparatus comprising: a lighting fixture having a reflector; and an incandescent lamp of one of Claims 1 through 4 , the incandescent lamp being mounted within the reflector.

7. A lighting apparatus comprising: a lighting fixture; and a reflector incandescent lamp of Claim 5, the reflector incandescent lamp being mounted within the lighting fixture.