US2148314A

US2148314A - Electric lamp

Info

Publication number: US2148314A
Application number: US143504A
Authority: US
Inventors: Daniel K Wright
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1937-05-19
Filing date: 1937-05-19
Publication date: 1939-02-21
Anticipated expiration: 1956-02-21

Description

D. K. WRIGHT ELECTRIC LAMP Feb. 21, 1939.

3 Sheets-Sheet 1 Filed May 19, 1937 t :h V rm 6 Or n tW m m ut elxwm vm m m/ m D y b D. K. WRIGHT Feb. 21, 1939.

ELECTR I C LAMP Filed May 19, 1937 5 Sheets-Sheet 2 Fig-5.

Imventorx Daniel K Wrigh D. K. WRIGHT ELECTRIC LAMP Feb. 21, 1939.

Filed May 19, 1937 3 Sheets-Sheet 3 Inventor Daniel K.Wr*ight,

His Attorney.

Patented Feb. 21, 1939 UNITED STATES PATENT OFFICE ELECTRIC LAMP tion of New York Application May 19, 1937, Serial No. 143,504

15 Claims.

My invention relates to an electric light projecting device which comprises a bulb or envelope at least a portion of which is reflective of light. More particularly, my invention relates to a device of the type disclosed and claimed in my copending application Serial No. 68,713, filed March 13, 1936, of which the present application is a continuation-in-part. The said device comprises a bulb which is composed of at least two sections of vitreous material united together at their edges by fusion, at least one of said sections being of pressed material and forming a wall which constitutes a comparatively large proportion of the bulb wall. In the preferred form of my invention, both sections are pressed or preformed and united at their edges by fusion. This allows ready access to the inner surfaces of said sections so that they may be properly shaped or coated, and at the same time the union by fusion insures a hermetic seal which will resist gas pressure or a vacuum.

My invention may be embodied in light projecting devices in which the light source is fixed at a definite point, such as the focal point of a reflector or other device for projecting the light. More particularly my invention may be embodied in light projecting devices of the type'in which a portion of the enclosure for the light source has a concave light-concentrating surface, preferably paraboloidal, at the focus of which is located the filament or other light source. One of the advantages of such light projectors is that they may be made in small sizes for use as headlamps on vehicles such as automobiles and airplanes where the small sized projector may be effectively incorporated in the streamlined design of the vehicle. Another advantage is the possibility of extremely accurate location of the light source with respect to the reflecting surface whereby a beam of the correct dimensions and directions may always be secured.

Light projectors have heretofore been proposed in which a bulb was blown with a portion thereof shaped like a paraboloid, this portion being subsequently silvered on the interior or exterior. However, the silvering of the exterior surface is objectionable because of the reflection of the light by the glass of the bulb. On the other hand it is difllcult or impractical in such a case to silver the interior of the paraboloidal portion while maintaining the remainder of the bulb free from silver. Another disadvantage of such a construction lies in the locating of the filament with respect to the reflecting surface since the seal between the stem on which the filament is mounted and the bulb must be kept plastic while the filament is being located because of inaccessibility to the filament and its supporting wires. If, on the other hand, an attempt is made to silver the paraboloidal portion of the bulb after the fila- 5 ment is mounted, there is a likelihood of depositing some of the silvering material on the filament or of forming a bridge of the material across the leading-in wires and thus short-circuiting the filament. Furthermore, it is very in difficult to prevent deposition of the silvering material on the remainder of the bulb in a practical manner.

One of the objects of my invention is to provide a construction for light projectors of the type 18 described in which the above-mentioned disadvantages will be obviated. Another object is to provide a construction which is commercially practicable. One of the features of my invention is the provision of a glass reflector portion, pref- 20 erably pressed glass, and a separate cover glass or lens portion sealed thereto. The concave glass or parabolic portion may be made with extreme accuracy by pressing, particularly when made of a glass having a low coemcient of expansion, such 25 as that commercially known as Pyrex. By making the bulb or enclosure of separate sections, the reflector section may be conveniently coated internally with a reflecting material before the filament or other light source is mounted therein. 30 The said light source may then be located at the focus of the reflecting portion by optical means as, for example, by placing the unit in a hydrogen or other non-oxidizing atmosphere, energizing the light source, and observing the beam produced 35 thereby on a screen.

While the above referred to co-pending application discloses the general construction and arrangement of my light projecting device, the present application includes in addition certain 40 specific features of the same, such as the construction of the sealing surfaces of the reflector and cover glass sections, and the construction of various means on the reflector section for accurately mounting the device in a suitable holder 45 and for accurately positioning the filament with respect to the reflecting surface during the manufacture of the projection device.

Another object of my invention is the provision of suitable sealing surfaces on the two pressed glass sections-comprising the bulb or envelope of my light projecting device, which surfaces may be readily sealed without impairing the reflecting coating on the reflector section, and without cracking the glass at and adjacent the seal.

Another object of my invention is the provision of positioning means on the reflector and cover glass sections of the projection device whereby said sections maybe correctly positioned and locked in predetermined relationship with respect to each other preparatory to the sealing of the same.

Still another object of my invention is the provision of an annular reference or mounting shoulder on the outer surface of the reflector section of. the projection device, said shoulder being accurately located with respect to the axis of the paraboloidal reflecting surface of such section.

A further object of my invention is the provision of a positioning and locking lug or projection on said annular reference or mounting shoulder which is adapted to extend into a recess in the mounting seat for the projection device to thereby position and lock said device in correct relationship with respect to the holder or mounting and associated supporting structure.

A still further object of my invention is the provision of an annular reference or filamentlocating shoulder on the inner surface of the reflector section of the projection device, said shoulder being accurately located with respect to the axis of, and also accurately located with respect to the focal point of, the reflecting surface of such section. This inner reference shoulder presents a surface against which a filament feeding jig is adapted to abut during the filament mounting operation to thereby accurately position the filament at the focalpoint of the reflecting surface, in which position the filament may then be clamped or secured in place in its support members. 1

Another object of my invention is the provision of a light projecting device having a cover glass section provided with an inner light difiusing surface, which may be obtained by forming said surface with light refracting media such as facets, or by frosting the same. The diffusing surface thus provided spreads or difiuses the beam of light projected by the reflector portion.

Other objects and advantages of my invention will appear from the following detailed description of species thereof and from the accompanying drawings, in which:

Fig. 1 is a horizontal sectional view of a light projecting device comprising my invention, and holding or mounting means therefor; Fig. 2 is a vertical sectional view taken on the line 2-2 of Fig. 1; Fig. 3 is an enlarged fragmentary sectional view of the reflector and cover glass sections adjacent their sealing surfaces, prior to the sealing thereof; Fig. 4 is a front elevation of the reflector section of the projection device; Fig. 5 is an enlarged fragmentary sectional view of the reflector andcover glass sections taken on the line 5-5 of Fig. 4; Fig. 6 is an elevation in section showing a method of providing the reflecting coating on the reflector section of the bulb or enclosure; Fig. 7 is a fragmentary sectional view at an enlarged scale of portions of the reflector and cover glass sections of the bulb illustrating the method of sealing them together; and Fig. 8 is a horizontal sectional view of a modified form of my projection device in which the cover glass section is provided with a light diffusing inner surface.

Referring to the drawings, particularly Figs. 1 and 2, the projection device comprisesa bulb or envelope Ill consisting of a preformed reflector section or member H made of pressed glass and a coverglass section or. member l2, also made of pressed glass. It will be, apparentfrom'the drawings that the cup or-bowl-shaped reflector section II is of substantially uniform thickness throughout. These two sections l I, I2, are sealed together at their peripheries to form the bulb or envelope Ill. The cover glass section may be plain, or it may be a lens having flutes and prisms on the inner surface thereof "as shown in Figs. 1 and 2, or it may be provided with an inner light diffusing surface such as is produced by facets formed thereon, as indicated in Fig. 8, or by frosting the same. It is possible to use such a lens because of the fact that it is made as a separate part from the remainderv of the enclosure, whereas with blown glass enclosures or bulbs of the type heretofore proposed a suitable lens could not be formed. The said reflector and cover glass sections ii and I2 respectively are preferably made of low-expansion glass, such as that com.- mercially known as Pyrex and described and claimed in United States Patent No. 1,304,623, Sullivan et al., issued May 2'7, 1919. Greater accuracy is obtained with a low expansion glass due to the fact that there is very little contraction of the glass upon cooling. The interior surface I3 of the reflector section Il may be of paraboloidal or any other suitable shape and is covered with a metallic coating l5 constituting a reflecting surface. By pressing the reflector section rather than blowing the same, the interior surface i3 can be made with extreme accuracy, much more so than is possible with the conventional stamped metal reflectors or with blown glass reflectors since the plastic glass conforms precisely to the curvature of the accurately formed surface of the plunger of the pressing apparatus. The metallic coating iii is preferably of aluminum, although any other suitable material may be employed. The said coating I4 is preferably applied to the interior surface 13 by vaporization of the coating metal in a vacuum, as described and claimed in the United States patent application of R. F. Strickland, Serial No. 104,241, filed October 6, 1936.

The reflector section H is formed with a pair of openings I5, 15 adjacent the apex thereof, and a central opening it at the said apex through which the bulb or envelope I is adapted to be exhausted. For conveying current to the device,

' I have shown a pair of terminal members 11, H

of the type described and claimed in my co-pending United States patent application Serial No. 57,196, filed January 2, 1936 now Patent No. 2,098,080, although other suitable forms may be employed if desired. The said terminal members H, H consist of cylindrical prongs which may be made of ordinary steel, and have reduced inner end portions l8, 18 extending into the reflector section it through the openings l5, I therein. Enlarged outer portions l9, 19 of said prongs form

shoulders

20, 20, preferably tapered, with the reduced inner end portions l8, I8. Comparatively thin metal cups or thimbles 2!, 2| are united, preferably by brazing, to the tapered

shoulders

20, 20 of said prongs, and have their edges or rims sealed and embedded in the

bosses

22, 22 provided at the outer edges of the openings i5, i5. I prefer to seal the metal cups or thimbles 2|, 2i to the

glass bosses

22, 22 according to the method disclosed and claimed in the copending United States patent application Serial No. 85,516, filed June 16, 1936, by A. Greiner, .E. Westerlund and the applicant herein. The metal cups 2!, 2| should be made of a metal to which expansion heat-resistant glass of the character,

hereinbefore indicated, I prefer to make the metal cups 2|, 2| of an alloy of iron, nickel and cobalt commercially known as "Fernicoi and disclosed and claimed in United States Patent No. 1,942,260, issued January 2, 1934, to H. Scott. I have found that this particular alloy effectively fulfills the above-mentioned requirements or conditions.

The inner surface I3 of the reflector section I I is preferably coated in the following manner. The said section II may be placed in a bell jar or, as shown in Fig. 6, it may be placed on a flat surface 44 having a rubber gasket 45 therein and the interior thereof exhausted through a pipe 46. The exhaust tube 41 must, of course, in this case be closed ofl, as by a stopper 4!, or by sealing the end thereof which must in that event be subsequently cut off to evacuate the lamp. A filament 49 is located within the reflector section I I and is mounted on

conductors

50, 5|] which are connected to a suitable source of electrical energy. Hairpin-shaped loops 5| of the metal with which the surface is to be coated (preferably aluminum) are placed on the filament 49 which is then heated to incandescence, thereby causing the metal 5I to be vaporized and deposited in an even coating I I on the surface I3.

A filament 23 is mounted on

leads

24, 24, which are in turn secured to the inner ends I8, I8 of the terminal members l1, II. The filament is accurately located at the focus of the paraboloidal reflecting surface by being held in such position in a suitable jig during the attachment of

leads

24, 24 to the prong ends I8, I8, as later described. The filament 23 3 also located in a definite position angularly with respect to the terminal members l1, II, the said filament and terminal members being preferably positioned in substantially the same plane. After exhaustion of the bulb or enclosure III through the opening I6, the same may be filled with an inert gas such as argon, nitrogen, or a mixture thereof. If desired, this gas fllling may be under a pressure such as, for example, two atmospheres.

As mentioned above, the cover glass and reflector sections of the projection device are made separately, being pressed from low-expansion glass, and are then sealed together at their peripheries by means of a 'pin point flame from a burner 52 (Fig. 7) to form the bulb or envelope III of the device. In order to prevent the heat attending this sealing operation from impairing the reflecting coating I4 which has been previously applied to the interior surface I3 of the reflector section II, and further, to prevent cracking of the glass at and adjacent such seal, I have found it highly desirable to construct the sealing surfaces of said reflector and cover glass sections in the particular manner indicated in the accompanying drawings. Referring particularly to Fig. 3, a. sealing surface 25 is provided at the periphery of the reflector section II, the plane of which surface is accurately located perpendicularly to the axis of the paraboloidal reflecting surface I4. A similar sealing surface 26 is provided on the cover glass section I2. To prevent cracking of the glass at and adjacent the seal, it is desirable that the extent of the surfaces in contact be disposed substantially along one line, and that the seal extend clear through or along the entire contact width of the two sealing surfaces. Under this requirement, if the reflecting surface were continued on up to the plane of the sealing surface 25, the heat attending the sealing operation would be apt to impair the same. However, by recessing the inner extremity of the sealing surface 25 to form the cut-away portion 21, the reflecting surface I4 is removed or maintained a suflicient distance away from the point of the seal to prevent deterioration of the same by the heat attending such sealing operation.

Preparatory to the sealing of the reflector and cover glass sections II and I2 respectively, the

same must be positioned in correct predetermined relationship with respect to each other transversely or radially of the reflector axis. In addition, where the cover glass section is in the form of a lens having flutes and prisms thereon, it is further necessary to rotate the said two sections relative to each other on their sealing surfaces until the correct rotative or angular relationship of said flutes and prisms with respect to the reflector section II is arrived at. To effect this preliminary positioning of the reflector and cover glass sections, I have provided positioning and locking means therebetween in the form of an annular ridge or protuberance 23 (Fig. 3) on the sealing surface 26 of the cover glass section I2 and a cooperating annular groove 29 In the sealing surface 25 of the reflector section II into which the annular ridge 28 is adapted to flt. This interlocking ridge and groove thus provide means for positioning the reflector and cover glass sections in correct predetermined relationship with respect to each other transversely or radially of the reflector axis. It should be understood that, while I have shown the annular groove 29 and ridge 28 on the reflector and cover glass sections respectively, the same may of course be reversed. Thus, the annular groove 29 may be provided on the cover glass section I2 and the annular ridge 28 on the reflector section, if desired.

To position the reflector and cover glass sections in correct rotative or angular relationship with respect to each other, I have provided additional positioning means comprising a recess or gap 30 (Fig. 5) in the annular ridge 2! on the cover glass section, forming shoulders 3|, 3I, and a locking lug 32 formed by an interruption or break in the annular groove 29 in the reflector section, and presenting

shoulders

33, 33. The recess 30 is adapted to snugly receive the locking lug 32 so that the shoulders 3I and 33 abut each other to thereby lock the reflector and cover glass sections in correct angular relationshipwith respect to each other preparatory to the sealing together of the same. Thus, where the cover glass section I2 is in the form of a lens having prisms and flutes thereon, as shown in Figs. 1 and 2, the recess 30 may be so located on such lens with respect to the said flutes and prisms as to properly position the same with respect to the reflector section I I and the filament 23.

In mounting my light projecting device in a supporting fixture or holder of the type disclosed and claimed in my co-pending application Serial No. 143,505, of even date, it is desirable to provide means for properly positioning the said device in such holder so as to be held in the correct plane to give the desired direction to the projected beam of light. For this purpose, I have provided an annular mounting shoulder 34 on the outer surface of the reflector section II adjacent the periphery thereof, the plane of which shoulder is accurately disposed perpendicularly to the axis of the paraboloidal reflecting surface I 4.

This annular shoulder 34 is adapted to be clamped or held against an annular mounting seat 36 provided on the holder 35 by means of a retaining ring 31. Since the plane of the annular mounting shoulder 34 is perpendicular to the reflector axis, the latter will accordingly be disposed perpendicularly to the plane of the mounting seat 36 on the holder 35 whenever the mounting shoulder 34 is properly seated thereagainst. By adjusting the plane of the mounting seat 36 with respect to the supporting structure 38, through suitable adjustment means 39 spaced around the periphery of the holder 35, the reflector axis, and consequently the projected beam of light can be aimed in the desired direction with respect to the supporting structure 38. Once the plane of the mounting seat 36 has been initially set in the desired position, any replacement of the original projection device will be automatically located in the same exact position as the original, so that the beam of light will be projected in the same direction as before.

To position the projection device in the correct rotative or angular position with respect to the holder 35, I have provided a lug or protuberance 40 (Figs. 1 and 2) extending rearwardly from the annular mounting shoulder 34, which lug 40 is adapted to project into, and be snugly received by an opening or recess 4| in the annular mounting seat 36. By locating the lug 40 at the proper point on the annular mounting shoulder 34 of the projection device, the latter will be thereby positioned and locked in the correct rotative or angular position with respect to the holder 35 and associated supporting structure 38 when said lug 40 is received in the recess 4!.

In the manufacture of my light projecting device, it is highly desirable that the filament 23 be accurately located with respect to the focal point of the paraboloidal reflecting surface H. To accomplish this object, I may provide an annular filament-locating shoulder 42 on the inner surface l3 of the reflector section II adjacent the periphery thereof. The plane of this shoulder 42 is disposed perpendicularly to the reflector axis, and in addition, is accurately located with respect to the focal point of the paraboloidal inner surface I3. In the filament mounting operation, a filament feeding jig is adapted to abut against this locating shoulder 42 to thereby accurately position the filament 23 at the exact focal point of the paraboloidal inner surface 13, in which position the filament is then clamped or secured in place in the reduced inner end portions l8, iii of the terminal members l1, II.

In order to more accurately locate the filament or check its location, the unit with the filament 23 mounted in place but without the cover glass l2, may be' placed in a bottle or other vessel having a hydrogen or other non-oxidizing atmosphere therein, and the terminals I1, I? connected to a source of current supply to render the said filament incandescent. The beam projected thereby may then be observed on a screen, and in case the location of the filament is not correct, an operator may reach into the bottle and bend the

leads

24, 24 to properly position the filament.

While I have shown the pressed glass cover section l2 in the form of a lens having flutes and prisms on the inner surface thereof (Figs. 1 and 2), it may be desirable to use other forms of cover glass construction for certain purposes. Thus, for general illumination, where a concentrated beam of light is not required, the cover glass section I2 may be provided with an inner light that various changes may be made therein with-- out departing from the spirit of my invention. For example, the lamp may, if desired, be mounted by its terminal members I'l in a socket of thetype shown in my hereinbefore referred to Patent No. 2,098,080. The said terminal members I! may be replaced by other forms of terminals or bases, such, for instance, as those shown in my Patent No, 1,988,290, of January 15, 1935.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A light-projecting device comprising a concave glass reflector portion having a pressed inner surface with a reflecting coating thereon, a cover glass sealed by fusion to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source mounted in said enclosure in definite optical relation to said reflecting surface.

2. A vehicle headlamp comprising a concave glass reflector portion having a pressed inner surface with a reflecting coating thereon, a cover glass sealed by fusion to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source mounted in said enclosure in definite optical relation to said reflecting surface.

3. A light-projecting device comprising a preformed concave glass reflector portion having a pressed inner surface with-a reflecting coating thereon and having a plurality of openings therein, a plurality of metal terminal and mounting members having portions thereof sealed around the said openings, a cover glass sealed to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, a light source in said enclosure located in definite optical relation to saidrefiecting surface, and conductors supporting said light source and connected with said terminal members through the said openings in said reflector portion.

4. In a light-projecting device, an enclosure consisting of a concave glass reflector portion with an outwardly extending flange at its rim and having a pressed inner surface with a reflecting coating thereon and a cover glass sealed by fusion at its periphery to the periphery only of said flange on said reflector portion, and a. light source mounted in said enclosure in definite optical relation to said reflecting surface.

5. A light-projecting. device comprising a concave reflector portion of low expansion glass having a pressed inner surface with a reflecting coating thereon, a cover glass sealed by fusion to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source mounted in said enclosure in definite optical relation to said reflecting surface.

6. A light-projecting device comprising a con-'- 7. A vehicle headlamp comprising a concave glass reflector portion having a pressed paraboloidal inner surface with a reflecting coating thereon, a lens having light-refracting protuberances thereon, said lens being fused to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source mounted in said enclosure in definite relation to the focus of said reflecting surface.

8. A light-projecting device comprising a preformed concave glass reflector portion having a pressed inner surface with a reflecting coating thereon and having a plurality of openings therein, a plurality of leads extending through and spaced from the edges of said openings, means at the outer side of said glass reflector portion sealing the openings between said leads and said reflector portion, a cover glass sealed to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source in said enclosure mounted on said leads and located in deflnite optical relation to said reflecting surface.

9. A light-projecting device comprising a concave glass reflector portion having a pressed inner surface with a reflecting coating of aluminum thereon, a cover glass sealed by fusion to the rim of said reflector portion and forming a hermetically sealed enclosure therewith, and a light source mounted in said enclosure in definite optical relation to said reflecting surface.

10. A light-giving electrical device comprising a light source, a reflector bulb of vitreous material comprising at least two pressed sections united together by fusion so that said bulb is sealed, the pressed inner surface of at least one of said sections having a reflecting coating thereon, and terminal connections sealed to said bulb and electrically connected to said light source.

11. A light-generating electrical device including a reflector bulb comprising at least two portions of vitreous material, one of which has a pressed inner surface with a reflecting coating thereon and forms a .wall which constitutes a comparatively large proportion of the bulb wall, said last-named portion being united to .terminal members sealed through the wall of said cup, a cover glass sealed by fusion to therim of said cup and forming a hermetically sealed enclosure therewith, conductive support members extending from said terminal members, and a light source mounted on said support members in definite optical relation to the surface of said reflector and positioned intermediate the bottom and the rim of said cup.

13. In a light-projecting device, a bulb comprising a concave glass reflector section having a pressed inner surface with a reflecting coating thereon and a pressed glass cover section sealed by fusion to the rim of said reflector section, the inner surface of said cover glass section being provided with light retracting media, and a light source mounted within said bulb.

14. In a vehicle headlamp, a bulb comprising a concave glass reflector section having a pressed inner surface with a reflecting coating thereon and a pressed glass cover section sealed by fusion to the rim of said reflector section, the inner surface of said cover glass section being provided with light refracting media, and a light source mounted within said bulb.

15. A pressed glass reflector member for a two-piece pressed glass enclosure, said member comprising a reflector portion and a sealing flange at the periphery of said reflector portion, the inner surface of said reflector portion being provided with a reflecting coating, and means on said inner surface for co-operating with a filament-feeding jig to accurately position a filament at the focus of said reflecting surface, said means comprising an annular fllament-locating shoulder adjacent said sealing flange and accurately located with respect to the axis and focus of said reflecting surface.

DANIEL K. WRIGHT.