US2144521A

US2144521A - Electric lamp

Info

Publication number: US2144521A
Application number: US178382A
Authority: US
Inventors: Bergmans Jan; Veen Hendrik Van Der; Wilhelmus L Vervest
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1936-12-18
Filing date: 1937-12-06
Publication date: 1939-01-17
Anticipated expiration: 1956-01-17
Also published as: BE425306A; NL51560C; FR830957A; GB513249A; CH205355A; DE718520C

Description

Jan. 17, 1939. JBER MAN HA 2,144,521

ELECTRIC LAMP Filed Dec. 6, 1957 2 Sheets-Sheet 1 Di I 7 'lnvehtors z Jan Bergmans, Hendrik v. oLVeen',

Wilhelmus L. Verve'st,

Their Attorney- Jan. 17, 1939. J. EFiGMANs ET AL 2,144,521 ELECTRIC LAMP Filed Dec. 6, 1937 2 Sheets-Sheet 2.

Inventors: Jan Bergmans', Hendrik v d. Veen Wilhelmus L,.\/eT"ves1";-,

Thel'f Attorney.

object of our invention is Patented Jan. '17, "1939 UNITED STATE ELECTRIC LAMP,

Jan Bergmans',

helmus L. Vervest, Elndhoven,

to General Electric Company, a corposlgnors ration of. New York Hendrik van der Veen. and Wil- Netherlands, as-

App cation December 6, 1937, Serial No. 178,382 In the Netherlands December 18, 1936 '8 Claims.

Our invention relates to electric lamps comprising an electric energy translation element, such as a filament, sealed within a bulb or envelope. More particularly, our invention relates to lamps in which a portion of the bulb is provided with a reflecting surface for the purpose of projecting the light rays from thefilament into a beam of light. Such a lamp is particularly suitable for recessed lighting systems wherein a surface or ceiling is illuminated by light sources which are installed in a cove or recess. 5 Heretofore, the lamps which have been generally used for recessed lighting systems have consisted of a bulb having a neck located in the continuation of the longitudinal axis of the bulb body or bulbous portion of the bulb. When the length of the bulb body of such a lamp is particularly large with respect to the diameter of the bulb body, a. recess of rather large dimensions is necessary in order to permit installation of the lamp, together with its holder and fitting, within such recess. This is a real disadvantage, preferable that the recess be as small as possible.

. In addiwn', the usual fittings, together with standard lamps, do not provide a good efiect, since-- the illumination of the surface or ceiling is not uniform while the lateral distribution of the light is not all that. could. be desired.

- One'object of our invention is to provide an electric incandescent lampsuitable for recessed lighting systems which will permit the use of a lamp recess of minimum dimensional Another to provide an electric incandescent lamp, for ,such systems, which will provide a uniform illumination' of the surface to be lighted. Still another object of our invention is to provide an electric incandescent lamp, for recessed lighting systems, of such construction as to permit the use of a minimum number of lighting units to provide the desired uniform illumination of the surface to be lighted. I

According to the invention, the bulb is shaped .so that the axis of the of more than '75 degrees, and degrees, with the longitudinal axis of the bulb body, thereby permitting the use of a lamp recess of small dimensions. is provided with a reflecting coating, so that no separate reflector member or-fittlng is necessary. Accordingly, no space is forthe accommodation of such reflectors and fittings. By means of a suitable shaping of the reflecting portion of the lamp bulb, and the mounting of the filament in a meridian plane of since it is recessed lightingbulb neck'forms an angle preferably of 90 I A portion of the bulb itself required -in-- the recess I such bulb, the requirements of uniform nation are completely satisfied.

Further objects and advantages of our invention will appear from the following description,

of species thereof and from the accompanying 5 drawings, in which: I Fig. l is a perspective view of a lamp COmPI1S ing our invention; Fig. 21s a transverse sectional view taken along the plane V-V of Fig. 1; Fig. 3

is atop or plan view of the lamp shown in Fig. 1; 10

Fig. 4 is a. top or plan view of a modified form of lamp according to our invention; Figs. 5 and 6 are side and top views respectively ofv a recessed lighting system provided with a lamp according to Figs. 1-3; Fig. "7 is atop view of a recessed. l5 lighting system provided with the modified form of lamp shown in Fig. 4; and Figs. 8 and 9 show the polar light distribution curves for a lamp comprising our invention according to the horizontal plane passing through the axis 3-]; of the lamp 20 (Fig. 5) and according to'the vertical or meridian plane of symmetry X-X of the, reflecting portion of the-lamp (Fig. 6), respectively.-

a first-requirement for the illumination of a plane surface, such as the. ceiling of a hall or 25 room, by means of a recessed illuminating system, the luminous intensity should beas uniform as possible over the entire surface, In order to satisfy this requirement, the candle power of the light source must be the greatest in the directions 30 in which the part of the ceiling to be illuminated is the farthest away from the light source. To permit the use of a minimum number of lighting units, it is advantageous to let the light distribution in the lateral direction enclose the largest 35 possible angle. These various requirements for the production of uniform illumination are effectively fulfilled by a lamp constructed in accordance with our invention and described hereinafter.

Referring to the drawings, the lamp i comprises a filament 2 sealed within a glass bulb or envelope 3 and connected to a base 4 secured to said bulb. The bulb 8 consists of a bulbous or bulb body portion 5, and a neck portion 6 the axis D-D of 45 which forms an angle a: of more than '75 degrees and preferably of 91) degrees with the longitudinal axisC-C of th bulbous portion 5, as shown in Fig. l. The sald'bulbous portion 5 is ovoid in shape and is formed as a body of rotation, the 50 longitudinal axis (2-0 of said bulbous portion constituting the axis of rotation. The said body of rotation or bulb body 5 is preferably formed so that a cross-section thereof, according to a meridian plane, will conform in contour to two illumiparts of a parabola, i. e., an upper parabola EF (Fig. 2) and a lower parabola F-G, the foci of which coincide, at least approximately, with each other, as shown at L. The locus of the coinciding foci L is preferably formed by a circle (Fig. 3)

the plane I--I of which is perpendicular to the axis of rotation CC of the bulb body portion 5, as shown in Fig. 2. The top and bottom ends or poles of the body of rotation are rounded off spherically, as indicated at H-E and G-J in Fig. 2.

The location of the two axes K-L and M-L I of the upper and lower parabolas, respectively,

depends on the direction and on the spread of the desired beam of light. From experiments it has been found that when a lamp, according to the invention, is placed -lna recess and. is used erably located in such a way as to form an angle W of an order of magnitude of 80 degrees with the axis of rotation CC of the bulb body 5. The

connection point of the upper and lower parabolas E-F and FG, respectively, is located on the axis M-L of the lower parabola.

The bulb body 5 is partially provided with a reflecting surface or portion 8, as indicated by cross-sectioning in Figs. 1-4. This reflecting surface i comprises approximately one-half of the bulb body 5, neglecting the small interruption at the point of connection of the bulb body 5 and bulb neck 5. The limiting plane AA (Fig. 3) of the reflecting surface] coincides approximately with the meridian plane of the bulb body 5 extending parallel to the axis DD of the bulb neck 5. As a result, the meridian plane of symmetry XX of the reflecting surface I extends perpendicularly to said axis D-D of the bulb neck. As shown in Fig. 2, the said limiting plane AA of the reflecting surface i, while extending parallel to the bulb neck axis DD, is preferably located-at a slight angle 1' to the axis of rotation CC of the bulb body portion 5 so as to extend approximately perpendicularly to the axes K-L and lVi-L of the upper and lower parabolas E--F and F-G respectively.

It is desirable, in order to obtain a light distribution which is uniform and almost entirely symmetrical, that the refiecting surface 1 have no interruptions such as would occur at the point of connection of the bulb body portion 5 and the bulb neck 6 in a bulb of conventional construction. Toobviate such ahiatus in the reflecting surface, an indentation 8 (Fig. 3) is provided at the point of connection of the bulb body 5 and the bulb neck 5 and in radial alignment, according to the bulb neck axis D-D, with such reflecting surface, whereby the hiatus or interruption therein is considerably reduced.

Within the bulb 3 the filament 2 is mounted on a stems in such a way as to lie in a meridian plane which may form at most an angle of 30 degrees (said angle being 15 degrees in Fig. 4) with the meridian plane of symmetry X-X ofthe reflecting surface I. The filament 2 is prefment lies. The end N of the filament is preferably located in the axis of rotation CC of the bulb body 5, as indicated in Fig. 2.

By-means of a suitable shaping of the bulb body 5 and of the bulb neck 6, the stem tube 9 sealed in the neck of the lamp may be of standard construction,.similar to that used in standard incandescent lamps. Excellent results are obtained with a. standard single or multiple coil filament mounted on such a standard stem tube, so that expensive projection lamp filaments are unnecessary.

As it is desirable, for manufacturing reasons, to-employ a stem tube and filament of such standard construction, it is necessary, in order to place the filament in the proper position with respect to the coinciding foci L, that the axis D-D of the bulb neck 6 extend perpendicularly to but slightly offset from the axis of rotation CC of the bulb body 5. The amount of such offset is indicated at c in Figs. 2 to 4.

While the indentation 8 in the bulb neck 6 is the preferred method of preventing the previously referred to interruptions in the reflecting surface I, a different solution is disclosed in the modification shown in Fig. 4. In this case, the meridian plane of symmetry XX of the reflecting surface I does not extend perpendicularly to the axis DD of the bulb neck, as in the previous form of the invention, but instead forms an angle 1; therewith of 105 degrees. Accordingly, the limiting plane A=A of the reflecting I surface 1 lies closely adjacent the conventional connection point between the bulb body portion 5 and the bulb neck 6, thereby resulting in very little interruption in the reflecting surface. Even though the filament 2 be not positioned exactly in the meridian plane of symmetry XX of the reflecting surface, excellent results are nevertheless obtained.

Figs. 5-7 are diagrammatic illustrations showing the manner in which a lamp I according to our invention may be mounted within a cove orrecess to provide a recessed indirect lighting system for a room or hallway. The lamp I is mounted within a cove fastened to a side wall I adjacent the ceiling or surface I I to be illuminated. The said cove consists of a horizontal shelf or ledge i2 provided with an inclined baffle I3 at its outer end .to thereby render the lamp or light source I, mounted in such cove, invisible. The lamp I is mounted in a socket I carried by a bracket'I5 secured to the horizontal ledge I2. As shown in Fig. 6, the socket It is so fastened to the bracket I5 as to position the axis D-D of the bulb neck 6 horizontally and parallel to the side wall Ill. The lamp I is mounted in the socket It in such a manner as to position the axes K-L and ML (indicated approximately by the line B-B in Figs. 2 and 5), of the two parabolas E-F and F-G, at an'angle e of approximately 15 degrees with respect to the ceiling I I. This angle may be varied as desired, de-

the arrow in Fig. 5.

Where the lamp I is of the modified form shown in Fig. 4, the same must'be mounted in the .cove I 2-I3 so that the axis D-D of the bulb neck 5 forms an angle (1 of approximately 15 degrees with respect to the side wall I0, as shown in Fig. 7. This is necessary in order to position the meridian plane of symmetry X-X 0f the reflecting surface I perpendicular to the side wall has in the case of the lamp shown the meridian plane of in Figs. 1-3.

As a result of the previously described loca-. tion of the filament 2 in the lamp, and of the peculiar reflecting characteristics of the reflecting surface I, two beams are formed in the previously mentioned meridian plane of symmetry x-x of such reflecting surface. One of these beams, which is formed by the co-action of the upper parabolic reflecting portion E-F, is subaxis K-L of such stantially parallel to the portion, while the other beam is substantially parallel to the axis M-L of the lower parabola F-G- Since the lamp i is arranged within the cove Ii -i3 with its axis of rotation C-C substantially vertically, as shown in Fig. 5, the

light beam parallel to the axis K-L therefore illuminates those portions of the ceiling farthest away while the beam parallel to the axisM-L illuminates those portions located nearer the lamp. The other portions of the reflecting surface I, i. e., those portions lying at either side of symmetry XX, provide 'the illumination extending; transversely of such plane. The spherical lower part G--J of the bulb illuminates the portion of the ceiling located directly above the lamp.

As a consequence of the indicated location of the filament! within the bulb 3, whereby the apparent length 'of such filament is smaller with respect to the upper reflecting portion E-F than for the lower portion F-G, the beam produced by the lower portion will have a greater dispersion in the lateral direction than the beam formed by the upper portion E-li. This is desirable in order to obtain a uniform illumination of the ceiling, as the ceiling portions illuminated by the lower portion F-G of the reflecting surface are located closer to the lamp i than those portions which are illuminated by the upper portion Eli-F. 1

Referring to Fig. d, showing the polarv light distribution curve, in the horizontal plane passing through the axis B-BiFig. 5), of a lamp constructed according to our invention,-it is apparent that the width b of the beam is of considerable extent, being much greater than that of the lamps heretofore employed. As a result, the lighting units can be placed at a much greater distance apart than before, while still maintaining uniform illumination, and therefore, fewer units are required. Furthermore, the points removed from the meridianplane of sym metry X- X of the reflecting surface which are illuminated. from the light source 0, for instance the points P and Q, are illuminated by a larger candle power than the point B. lying vertical or meridian plane of symmetry X-X H of the reflecting portion 8 of the lamp. Referring to this curve, it is seen that the ceiling from the point S, which is the farthest removed from the light source 0, to the point T, which lies approximately above the lightsource 0, is illuminated with a uniformly decreasing candle power,

thereby satisfying again the above-mentioned requirements for uniform illumination.

As a result of the fact that the axis D-D of the bulb neck 6 forms an angle of more than provided with a reflecting the lamp may beof different types.

I Letters Patent. of

75 degrees and preferably of 90 degrees with the longitudinal axis -43 of the bulb body 5, the advantage occurs that the recess may be made of minimum dimensions. Since the bulb itself is portion, a separate reflector member is-unnecessary, so that no space need be-provided in the cove or recess i2i3 to accommodate such a reflector member. The width of the recess or cove l2-i3 can be made of small dimensions due to the special construction of our lamp, which permits the mounting of such a lamp within the cove in such a manner that the axis D-D of the bulb neck, and consequently of the socket, is (parallel to the side wall- III, or forms an angle of a rather small value therewith, at most 30 degrees, in the case of the modified form of lamp shown in Fig. 4. The result is that the dimension a of the cove, as indicated in Figs. -7, can be made illumination. 'Even though the said filament be located somewhat 3 asymmetrically with respect to the reflecting surface 'I, no detrimental influence on the reflecting characteristics results.

It should be understood that a construction in which alight source, such as a conventional lamp, is placed in'a reflector having a shape similar to that of a lamp according to our inventlon, by means of which it is also possible to obtain good'results, is also included within the scope of the invention. Furthermore, the light emitting element or filament employed in Thus, in-

stead of anormal single or multiple coil filament,

it is 'possible'to use a discharge tube. -'Although the bulbous portion 5 is preferably paraboloidal in shape, other suitable shapes, such as ellipsoidal, may be advantageously employed if desired.

What we claim as new and desire to secure by the United States is:

1. An electric lamp comprising a glass envelope having an ovoid bulbous portion and a neck portion, the axis of said neck portion forming an angle of approximately 90 degrees with the longitudinal axis of said bulbous portion, said bulbous portion being provided with a. reflecting surface the limiting plane of which coincides approximately with a meridian'plane of said bulbous portion, and a light source within said bulb posi ianed approximately in the meridian plane of symmetry of said reflecting surface.

2. An electric lamp comprising a glass envelope having a bulbous portion and a neck portion, said bulbous portion being formed as a body of rotation the contour of which, according to a meridian plane, is substantially defined by the curve of two different parabolas the foci of which approximately coincide, said bulbous portion being provided with a reflecting surface the limit ing plane of which coincides approximately with a meridian-plane of said bulbous portion, and a light source within said bulb positioned approximately in the meridian plane of symmetry of said reflecting surface.

3. An electric lamp comprising a glass envelope having a bulbous portion and a neck portion, said bulbous portion being formed as a body of rotation consisting of two different and substantially paraboloidal halves, the locus of. the foci of which is defined by a circle the plane of which is perpendicular to the axis of rotation of said bulbous portion, said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of said bulbous portion, and a -light source within said bulb positioned approximately inthe meridian plane of symmetry of said reflecting surface. V

An electric lamp comprising a glass envelope having a bulbous portion and a neck por tion, said bulbous portion being formed as a body of rotation the contour of which, according to a meridian plane, is substantially defined by the curve of twodifierent parabolas the axes of which form a small angle with each other. said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of said bulbous portion, and a light source within said bulb positioned approximately in the meridian plane of symmetryof said reflecting surface.

5. An electric lamp comprising a glass envelope having a bulbous portion and a neck portion, said bulbous portion being formed as'a body of rotation the contour of'which, according to a meridian plane, 'is substantially defined by the curve of two diflerent parabolas the-axes of which form an angle of an order of magnitude of 80 degrees with the axis of rotation of said bulbous portion, said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of .said bulbous portion, and a light source within said bulb positioned approximately in the meridian planeof symmetry of said reflecting surface.

6. An electric lamp comprising a glass envelope-having a bulbous portion and a neck portion, said bulbous portion being formed as a body of rotation the contour of which, according to a meridian plane, is substantially defined by the curve of two diiferent parabolas the foci of 4 which approximately coincide, said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of said bulbous portion, and a semi-circular filament sealed within said bulb and positioned approximately in the meridian plane of symmetry of said reflecting surface with its center of gravity approximately coinciding with the common focus of the parabolas defined by that meridian plane in which said filament lies.

7. An electric lamp comprising a glass envelope having an ovoid bulbous portion and a neck portion, said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of said bulbous portion which is substantially parallel to the axis of said bulb neck, said bulb neck being provided with an indentation at its point of connection with said bulbous portion and in radial alignment, according to the bulb neck axis, with said reflecting surface, and a light source within said bulb positioned approximately in the meridian plane of symmetry of said reflecting surface.

8. An electric lamp comprising a glass envelope having an ovoid bulbous portion and a neck portion, said bulbous portion being provided with a reflecting surface the limiting plane of which coincides approximately with a meridian plane of said bulbous portion which forms an angle of approximately 15 degrees with the axis of said bulb neck, and a light source within said bulb positioned approximately in the meridian plane of symmetry of said reflecting surface.

JAN BERGMANS. I-IENDRJK VAN nan VEEN. wmnnmos L. VERVEST.