US3652892A - Illuminating lamp having concave segments on exterior bulb surface - Google Patents

Abstract

An illuminating lamp wherein the bulb is fabricated into a complicated form characterized by a large number of surface irregularities so as to disperse light from a luminous source without losing its original brilliance and afford comfortable ornamental illumination by projecting light over a broad area from the various convex and concave segments of the bulb surface utilizing the primary refraction caused by the lenticular and prismatic action of said segments.

Description

United States Patent 9 Nameda et a1.

ILLUMINATING LAMP HAVING CONCAVE SEGMENTS ON EXTERIOR BULB SURFACE Naoyoshl Nameda; Tetsuhlro Kano, both of Yokohama-shi, Japan Inventors:

Assignee: Tokyo Shibaura Electric 00., Ltd.,

Kawasaki-shi, Japan Filed: Nov. 3, 1969 Appl. No.: 873,517

Foreign Application Priority Data Nov. 4, 1968 Japan ..43/80252 Nov. 11, 1968 Japan ..43/97517 U.S.Cl ..3l3/1l6,3l3/111 Int. Cl. .1101] 5/16, H011: l/30 Field ofSearch ..313/1l0, 116

1 51 Mar. 28, 1972 Q] N References Cited 7 UNITED STATES PATENTS 2,973,451 2/1961 Plishker ..313/1l6 X FOREIGN PATENTS OR APPLICATIONS 421,040 2/1911 France ..313/ll6 X 3/1935 Great Britain...

Great Britain ..313/1 16 Primary Examiner-Robert Segal Attorney-George B. Oujevolk [57] ABSTRACT An illuminating lamp wherein the bulb is fabricated into a complicated fon'n characterized by a large number of surface irregularities so as to disperse light from a luminous source without losing its original brilliance and afford comfortable ornamental illumination by projecting light over a broad area from the various convex and concave segments of the bulb surface utilizing the primary refraction caused by the lenticu- A lar and prismatic action of said segments.

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- I y r/ V 2b 30 4o 50 60-. B DISTANCE BETWEEN FI'LAMENT AND INNER SURFACE OF BULB (L) m 0.. mm a 9 25 A O I. My A 0 3 b m E W 0O O O O 4 3 2 PATENTEDHAR28 1972 I 1 l l l I I I x |L ILLUMINATING LAMP HAVING CONCAVE SEGMENTS ON EXTERIOR BULB SURFACE The present invention relates to improvements in an illuminating lamp whereby light from a luminous source is dispersed over a broad area from the various segments of a bulb surface without losing the original brilliance of light, thereby affording comfortable ornamental illumination.

With a luminous source lacking a dispersing function, for example, a transparent bulb lamp, there is the problem that illumination therefrom has an intense glare and dazzles the naked eye, causing discomfort. To resolve this problem, therefore, there has heretofore been practised a process of frosting a bulb or globe covering the luminous source. In the case where the lamp member is frosted, light is dispersed after being subjected to complicated refraction, so that the bulb or globe as a whole looks bright, or the luminous source appears to grow large. Since, however, the original brilliance of light decreases, use of a bulb having complicated surface irregularities only results in beauty of form and not beauty of brilliance rendering such type of lamp suitable for ornamental illumination. Again, with an ordinary lamp for ornamental illumination, light from a source is simply allowed to be transmitted through the bulb surface or is subjected to reflection and refraction several times. In the former case, brightness is undesirably intense or excessively dazzling to the naked eye to cause discomfort, while, in the latter case, effective illumination decreases too much to afford a pleasant visual appeal. Moreover, in either case, the shape of an element constituting a luminous source, for example, a filament is easily recognized from the outside, resulting in the loss of ornamental beauty of a lamp. i

In view of the aforementioned drawbacks, the present invention uses a novel type of bulb having a complicated shape with surface irregularities in covering a luminous source, disperses the source light only by primary refraction without subjecting it to complicated refraction as is the case with the prior art lamps, and makes an apparent luminous source look large, bright and beautiful without dazzling the naked eye.

The present invention is characterized in that a luminous source is covered with a bulb, there are formed in the outer surface of the bulb a large number of convex and concave segments so as to disperse the source light, both end portions of each segment have a plane inclined at an angle of about 8 [8 1 (1r/2 A)] (where 1; represents the angle of incidence of the source light and A denotes the critical angle of said light refracting through the segment) and the area defined between said end portions is formed into a curved or flat plane.

The lenticular and prismatic action of the aforesaid numerous convex and concave segments enables the source light to be dispersed over as broad an area as possible simply by primary refraction without causing it to lose its original brilliance.

The main object of the present invention is to provide an illuminating lamp free from a dazzling effect and adapted for ornamental illumination wherein the aforesaid lenticular and prismatic action of the segments of the bulb surface affords brilliance as if from numerous dot-like luminous sources.

This invention can be more fully understood from the following detailed description when taken in connection with reference to the accompanying drawings, in which:

FIGS. 1A to 5C are optical illustrations of the principle underlying the present invention;

FIGS. 6A to 6K are perspective views of various modifications of the bulb segments used in the present invention;

FIGS. 7A and 7B are the side and bottom views respectively of an illuminating lamp according to an embodiment of the invention;

FIGS. 8A to 8C are enlarged views of the main part of said embodiment;

FIG. 9 is an elevation, with part broken away, of an illuminating lamp according to another embodiment;

FIG. l0'shows the related positions of the filament and segments of the lamp shown in FIG. 9;

FIG. 11 is a cross sectional view, with part enlarged, of the bulb used in the lamp of FIG. 9;

FIG. 12 is a longitudinal sectional view, with part enlarged, of the bulb used in the lamp of FIG. 9;

FIG. 13 is a diagram of the relationship between the ratio of the lengthwise to the crosswise length of each segment and the ratio of the filament length to the bulb radius; and

FIG. 14 is a diagram of the relationship of the angle of inclination of the prescribed plane of each segment versus the distance between the filament and the inner wall surface of the bulb.

If the source light is to be dispersed simply by primary refraction, then it is only necessary to form, by customary process, on the outer surface of a bulb covering a luminous source, a plurality of segments capable of performing a lenticular and prismatic action. Where, however, an illuminating lamp is desired which will display a more advanced effect which fully meets the aforesaid object, then it is necessary that the source light be subjected to refraction and dispersion over a broad area by each segment and that even when the bulb is looked at from a position or angle involved in a broader area than has been possible with the prior art, and the lights are recognized from a larger number of segments, namely, a larger number of segments are made to look bright.

In this connection let it be assumed that as shown in FIG. 1, there is placed a transparent glass plate Q at a certain distance from a luminous source P, and that the angle of incidence of the source light at point A on the outer surface S of said transparent glass plate Q is shown as 1 and the angle of refraction corresponding thereto is 8. If, in case of the aforesaid angle of incidence 6, a plane S passing point A is so inclined as to permit an angle of incidence defined with said plane S to be regarded as equivalent to a critical angle A, then it will be apparent that an angle of refraction corresponding to said angle of incidence can be made as large as possible. The aforementioned angle 1; of incidence and angle 6 of refraction as used in this specification respectively denote angles of inclination with respect to an axis 1 perpendicular to a plane passing point A before inclined as described above, namely, the plane S represented by the outer surface of the glass plate Q. If, in this case, the angle 8 of refraction or the angle of inclination defined by the plane S passing point A with the aforementioned axis 1 is designated as positive when it rotates leftward and as negative when it rotates rightward, then said angle 8 of refraction may be given by the following equation:

Where, therefore, the degree of inclination of the upper and lower end portions of each segment of the bulb surface is defined in accordance with the above equation (I) and the area between said upper and lower end portions has a flat and/or curved plane, then said segment can disperse the source light over as broad a range as possible in the vertical direction.

There will now be outlined the process of actually designing the bulb surface segments on the basis of the above-mentioned consideration. It will be noted that this typical example of design is associated with segments formed on a cylindrical glass bulb Q, 5 mm thick and mm. in inner diameter having a refractive index n 1.47 in a manner to surround a luminous source P. There will be first discussed the vertical longitudinal sectional form of the segment. In this connection, let us determine the angles n and 1 of incidence at the upper end a and lower end b of the segment as shown in FIG. 2. Since the angles 0,, and 0 of incidence from the luminous source P to the bulb Q are 3l and 2150 respectively, and the refractive index is 1.47, the angles 1; and 11 of incidence at points a and b are 2030 and 1440 respectively. Accordingly, it is seen from the above equation (1) that it is only required to set the angle 1 of inclination at point a at 6730 when the source light refracts upward and at --2630' in the case of downward refraction, and the angle 17 of inclination at point b at 5740 when the source light refracts upward and at 3620 in the case of downward refraction. In this connection, therefore,

with the vertical sectional form of the segment, there may be contemplated, as shown in FIGS. 3A to 3F, various types of surface segments having straight and/or curved line with the above-mentioned angles of inclination so as to refract lights in opposite directions to each other through tangentially contacting said flat planes covered with fiat and/or curved planes therebetween.

There will now be discussed the transverse sectional form of the segment. As shown in FIG. 4, light from the luminous source P goes straight through the bulb Q, so that the angles 1 and 1 of incidence at the right end c and left end d of the segment are equivalent to the angles (:7 and 0,, of incidence from the illuminating source P to the bulb Q. Since said angles 0,, and 0,, of incidence are 1 130 alike, it is only required to set the angle of inclination at point and d in accordance with the aforementioned equation (1), namely, for point c at 5830 when the light is refracted leftward and at 3530 in the case of rightward refraction, and for point d at 3530 when the light is refracted leftward and at 5830' in the case of rightward refraction. In connection, therefore, with the horizontal transverse sectional form of the segment, there may be contemplated, as shown in FIGS. A to SC, various types having fiat and/or curved planes tangentially contacting at the segment ends with the aforementioned angles of inclination, of which to refract light in opposite directions widely as possible.

With respect to the entire form of the segment, there may be considered various types having the vertical and horizontal section as shown in FIGS. 3 and 5, for example, those illustrated in FIGS. 7A and 78.

There will now be described an embodiment of the present invention by reference to the appended drawings. Referring to FIG. 7A, numeral 1 represents a transparent cylindrical bulb 5 mm. thick made of soda lime glass. One end of the bulb l is sealed flat to form a bottom section 2 and the other end is sealed to form a conical section 3 open at the end. To the open end of the conical section 3 is sealed a stem 5, which supports by means of a conductor 6 a filament 7 presenting a color temperature of 2,700 K. at the time of lighting, for example, with 100 v., 40 w. Said filament 7 is positioned at the center of the bulb 1. The sealed part of the stem 5 is covered with a base cap. All over the outer surface 9 of the bulb 1 are spatially arranged a large number of segments 10, 11 and 12, whose end portions are inclined as illustrated in FIGS. 8A and 8B in accordance with the aforementioned equation (1) and design plan, in vertically symmetrical relationship with respect to the segment 10 immediately facing the filament 7. Also on the outer surface of the bottom section 2 of the bulb 1 are spatially formed a large number of similar segments 11 and 12 in concentric relationship.

The above-mentioned arrangement disperses the light given forth by the filament 7 (a luminous source) over a broad area after it is subjected to primary refraction. Accordingly, larger number of segments formed all over the outer surface of the bulb l are beautifully illuminated, or appear to form luminous sources by themselves, thus affording optimum illumination for ornamental purposes without a dazzling, uncomfortable effect on the naked eye. Moreover, since dispersion can be carried out over a broadest possible area, the image of a filament as a luminous source is concealed from view.

There will now be described an illuminating lamp according to another embodiment of the present invention. Namely, the lamp of FIG. 9 is characterized in that where the length l of the filament is relatively larger to the radius L of the bulb, the length (a) of each segment parallel to the lengthwise plane of the filament and its width (b) in a perpendicular direction thereto bear a ratio (a/b) of more than 1.2, and that there are formed segments whose inclined plane defines an angle 0 of more than 30 with the outer surface of the bulb. The bulb 21 is made of, for example, light transmissive material such as glass. Within the bulb 21, there are embedded in a stem 24 lead-in wires 23. Between the mutually facing ends of the leadin wires 23 is fixed a filament 22, for example, by welding. One

of the ends of the stem 24 is sealed in the open part of the bulb 21. The other ends (not shown) of the lead-in wires 23 are extended to be electrically connected to the base cap 25 so as to form terminals. The interior of the bulb 21 is evacuated, filled with inert gas and sealed airtight. On the outer surface of the bulb 21 are formed a plurality of segments 28 having such surface irregularities as illustrated. These irregularities eliminate the dazzling effect of the filament 22 and conceal its shape from view, thus offering a pleasant visual appeal.

There will now be described the segment 28. The same parts of FIG. 10 as those of FIG. 9 are denoted by the same numerals. The length of the filament 22 is designated as l, the

distance between the central axis of the filament 22 and the outer surface of the bulb 21 as L, the length of the segment 28 parallel to the lengthwise plane of the filament 22 as (a) and the width thereof in a perpendicular direction thereto as (b). Let us consider the case where the filament 22 is linearly mounted in the axial direction of the bulb 21.

If, in this case, the filament has a length of more than about 5 mm. and the ratio l/L is more than l/ 10, and in consequence the ratio all; is more than 1.2 and the angle of inclination defined by the end portion of the segment at the lengthwise portion thereof with the assumed fiat plane of the outer surface of the bulb which would be presented if there were not formed any segments thereon, namely, the angle of inclination 0 is more than 30,then it has been experimentally confirmed that there can be prevented the dazzling effect of the filament 22 and light therefrom is dispersed over a broad area, to give good illumination.

There will now be described the results of said experiments. To expect the glass wall of the bulb to present a Ienticular effect, it is required that the glass wall be largely depressed or projected. However, from the standpoint of the techniques of manufacturing bulb glass, the thickness of the bulb wall is limited to about 5 mm. and the degree of said depression or projection is restricted to about half said bulb wall thickness. Accordingly, study of an electric bulb whose wall is 5 mm. thick and depressed by half said thickness will give a broad outline of such bulb. FIG. 11 shows a lamp as viewed in the direction of the central axis of the bulb. The width (b) of the segment may be determined in consideration of the bulb radius L, bulb thickness t, depth of depression (At t/2),

aforementioned critical angle to allow light to be dispersed over abroad area and desired number of segments to be formed in the bulb surface (at t, At const.).

FIG. 12 shows a lamp as viewed in a horizontal direction. The longitudinal length a of the segment may be determined from the bulb radius L, filament length l, I, At and other factors mentioned before (at 2, At const.). FIG. 13 indicates the relationship of a/b and l/L derived from the aforementioned conditions in FIGS. 11 and 12. Practical application is obtainable in hatched scope of FIG. 13.

If the ratio l/L is more than H10 and in consequence the ratio a/b' is smaller than 1.2 the segment will assume a shape approximating a square or horizontally elongated rectangle. Then no matter how the angle of inclination 0 at the end portion of the segment is varied, the broadened image of a filament will be readily projected outside of the bulb. The broadened width of the image corresponds to the degree of the angle 0 because a prismatic effect increases with the angle 0. A decreased angle 0 will lead to the occurrence of a striped pattern, whereas an increased angle 6 will lead to a continuous luminous area on the bulb surface. And in both cases, the object of the present invention can not be attained. If the ratio U1. is smaller than l/ 10, the filament may be regarded approxi mately as a dot-like luminous source, so that the size of the segment or a/b need not be more than 1.2. The length of a straight filament is defined within the range of 3 to 50 mm. from the standpoint of the construction of a mount. Accordingly, if the ratio l/L of more than l/lO is employed in practical application, then the ratio a/b more than 1.2 of the longitudinal to the transverse length of the segment is the range required for the case where the length of the filament can not be overlooked.

FIG. 14 represents the relationship of the angle of the inclined plane of the segment and the distance L between the inner wall surface of the bulb and the filament. It is necessary from the standpoint of manufacturing a lamp that the distance L between the filament and bulb be more than 7 to 8 mm. Further, the angle 0 of the inclined plane of the segment is required to be more than 30", because if said angle is smaller than 30 then light will fail to be effectively dispersed from the filament and in consequence tend to be dazzling to the naked eye. FIG. 14 indicates the relationship of L and 0 in case At and t are defined in the same way as described above. The refractive index of bulb glass in practical use is from 1.45 to 1.50 or almost the same as the aforementioned value. The foregoing embodiment has an effect of dispersing without a reflector the source light over a broad area, preventing the filament image from being directly projected and offering beautiful and comfortable illumination free from glare.

The present invention is not confined to the aforesaid embodiment. For example, some of the segments may be frosted as an exception to the rule of the previously mentioned equation (1) so as partly to remove brilliance. Further, the bulb may assume a spherical or square pyramidic form. Where the segments formed on a bulb of such particular shape are desired to display a lenticular and prismatic action, the segments may be so formed for working convenience as to allow tangential lines at both ends of the segment to have an equal angle of inclination or such an angle of inclination as has been averaged from the normally different angles defined by said tangential lines.

What we claim is:

1. An illuminating lamp comprising: a light bulb having a substantially cylindrical sidewall and a circular bottom endwall; a (substantially point-shaped) filament, mounted in said bulb and located on the longitudinal axis of said bulb; a large number of (convex and/or) concave segments formed on the outer surface of the bulb covering the filament) and located on lines parallel to said filament on the cylindrical portion of said bulb and as rays disposed radially from the bulb axis on the bottom portion of said bulb, so as to disperse light therefrom wherein at least part of each end of the segment is inclined at an angle of approximately 8 [8='n: (-A)] (wherein n denotes the angle of incidence defined by the source of light beam with the outer surface of the bulb at said segment end and A represents the critical angle of light in said segment) with respect to an axis perpendicular to the outer surface of the bulb; thereby dispersing light passing through the segment over a broad range and eliminating a dazzling effect.

2. The illuminating lamp according to claim 1, wherein some of the segments are frosted.

3. The illuminating lamp according to claim I, wherein the segments are topped with at least a minor segment.

4. The illuminating lamp according to claim 3, wherein the minor segment assumes the same form as the segment of claim 1.

5. The illuminating lamp according to claim 1, wherein the planes at both ends of the segment are inclined at an angle averaged from the normally different angles defined by said planes.

6. The illuminating lamp according to claim 1, wherein each of the segments formed at least in one portion of the bulb surface is partly frosted.

Claims (6)

1. An illuminating lamp comprising: a light bulb having a substantially cylindrical sidewall and a circular bottom endwall; a (substantially point-shaped) filament, mounted in said bulb and located on the longitudinal axis of said bulb; a large number of (convex and/or) concave segments formed on the outer surface of the bulb (, covering the filament) and located on lines parallel to said filament on the cylindrical portion of said bulb and as rays disposed radially from the bulb axis on the bottom portion of said bulb, so as to disperse light therefrom wherein at least part of each end of the segment is inclined at an angle of approximately delta ( delta Eta + OR - (90- Delta )) (wherein Eta denotes the angle of incidence defined by the source of light beam with the outer surface of the bulb at said segment end and Delta represents the critical angle of light in said segment) with respect to an axis perpendicular to the outer surface of the bulb; thereby dispersing light passing through the segment over a broad range and eliminating a dazzling effect.

2. The illuminating lamp according to claim 1, wherein some of the segments are frosted.

3. The illuminating lamp according to claim 1, wherein the segments are topped with at least a minor segment.

4. The illuminating lamp according to claim 3, wherein the minor segment assumes the same form as the segment of claim 1.

5. The illuminating lamp according to claim 1, wherein the planes at both ends of the segment are inclined at an angle averaged from the normally different angles defined by said planes.

6. The illuminating lamp according to claim 1, wherein each of the segments formed at least in one portion of the bulb surface is partly frosted.

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