US1786371A - Lighting fixture - Google Patents

Description

W. J. D. VAN DIJCK LIGHTING FIXTURE Dec. 23, 1930.

Filed Feb, 15, 1929 2 Sheets-Sheet l 930- w. J. D. VAN DIJCK 1,785,371

LIGHTING FIXTURE Filed Feb. 15. 1929 2 Sheets-Sheet 2 ivziuem Jbhcuuzas Dominica: 0011179618,

Patented. Dec. 23, 1 930 UNITED STATES- PATENT OFFICE l TO NA AMIQOOZE VENNOQTSCHAP: GLASFABRIEK VLEERDAM VOORHEEN JEEKEL, MI-TNSSEN 8a 00., OF LEERDAM, NETHERLANDS I i i V LIGHTING FIXTURE Application filed February 15, 1929, Serial No. 340,135, and in the Netherlandsl ebruary 13, 1928.

The present invention relates to lighting fixtures and has for its purpose'to meet all requirements for obtaining an economical illumination, restful to the eye and not fatiguing. r

To obtain a good illumination, it is essential, first of all, that the rays'of light of great intensity be prevented from striking the eye, particularly if the direction of these rays nearly, coincides with rays coming from the object to be viewed.

These difliculties are for the greater part overcome by the application of indirect illumination, but this manner of illumination is monotonous as a consequence of the lack of shade, and its luminous efliciency is small.

Though sharp contrasts must be avoided, it is desirable, for the elficiency of the eye, to give the location ofthe object to be viewed a greater intensity of light than the other parts of the lighted room.

, Refractive and totally reflective prisms have also been used, bringingabout, however, an inconvenient glittering of these prism-s; and moreover the light-distribution does not meet all requirements. A further drawback is that the prisms very soon get dirty, which impairs the efliciency.

By applying reflecting screens which surround the source of light, a good eflect on the eye has been obtained in some cases, with the disadvantage, however, that intense changes of light arise, while the efliciency of the lighting. fixture is generally insufficient.

Further, as a result of irregularities in the fixture, dark and light spots may appear in the range to be illuminated, whiletroublesome light-reflections often occur on-shining objects.

The considerations, on which the invention is based, so as to avoid the above mentioned disadvantages are the following:

,1. Obtaining a high efliciency of the light 2. Obtaining a high eificiency of the eye,

i. e. those parts ofthe room, which must be seen most clearly,,shouldhave the most intense illumination, whereas blinding must be entirely prevented; i V

3. The room must be illuminated locally I WiLLEi/i JO'HANNES noJuINIoUs VAN 11mm or THEHAGUE, NETHERLANDS, assien'on a uniform manner, so as to avoid intense changes to light;

4. As far asindirectillumination is applied, some shade-action should be obtained.

Ithas beenattempted to avoid thezappearance of abrupt changes in light-intensity by placing an opal or dulled plate under the reflector which, however, causes the disadvantage of undesired absorption, while rendering it" difficult, if not'impossible, to control the direction of the light.

The lighting fixture, according to the invention, is in the first place characterized by the specific shape of the casing or screen surrounding the source of light. This shape is so chosen that the rays either emanate from the source or, coming directly from the source, pass the openings of the fixture, or after having only once been reflected by a reflector, pass these openings or the space between the source of light and the reflectors, or both the openings and the aforesaid space. V

The shape of the casing or screen may be calculated mathematically or can be fixed in a geometrical constructive way. This problem has no special difficulties for one skilled in the art.

It is thus possible to accommodate the shape of the casing or screen to the shape of the room or space to'be illuminated, so that it is not necessary that the screen be shaped as arotati-on-body.

In this manner a lighting fixture is obtained which renders an intense and at the same time agreeable illumination, even if provided with a source of light less strong than might be expected, so that the great elii- V ciency of the modern incandescent lamp manifests itself completely, as practically no light is lost on account of rays returning to the source, or on'account of rays decreasing in intensity by repeated reflection, or on account of absorptlon or in another way.

. Another characteristic of the invention is to be seen in the way in. which sharp changes are avoided between regions to be illuminated with different intensities. To this end, the surfaces ofthe reflectors are provided with unevennesses of a very small curvature which, at the same time, must preferably be finely divided.

in this manner an elt'ect is obtained which, according to the i rention. is indicated by the t rm directed (n .sion and consists in that small incident beam of light is reflected as a. cone with only a small top angle.

T his must be distinguished from the known inanner of difiusing by a reflecting surface, for example, the known dulled glass, for in that case the rays falling on the mirror are reflected to all sides, owing to which the special shape and sizes of the reflecting casin or screen would loose their special effect, since a part of these reflected rays would fall back on the source of lightor on the mirror.

The directed diffusion produces therefore a. new technical effect, while re iining the efiect obtained by the principal charactcri lC.

When the shape of the casing or screen is fixed according to the principal characteristic in an analytic or gra ic way, suiiicient liberty is still left for giving these parts of the casing or screen which throw light on a plane serving for indirect illumination, such a. form that an ii'nportant part of the light, falling on the said plane, is concentrated on a small part thereof.

Hence it follows that some shade-action still occurs in that part oi? the room which is indirectly illuminated, giving a relief ellec and being agreeable to the eye. 7

These cnaracteristics and some other features will be better understood from the following description, taken in connection with the accompanying drawings, in which, by way of example, an embodiment according to the invention is illustrated.

Fig. 1 is a diagrammatic top-view of a table, indicating the light-distribution obtained with the lighting fixture of the invention;

Fig. shows a general View of the course of the beams of light with the device according to the invention;

Fig. 3 shows the light-distribution;

Fig. 4 shows a fixture for indirect illumination, of which Fig. 5 represents the light-distributioncurve.

With the illumination of the table-plane according to Fig. 1, the light is divided in such a manner that the middle part of the table is less intensely illuminated than a ringshaped part 3 around it. 1 is the lighting lixtnre suspended above the table; 2 is the t part of the table, which is less intensely illuminated than the ring-shaped part 3, where the light-intensity has reached a maximum, and extending over the table.

Besides the principal illun'iination of part 3, a faint general-illumination must be obtained. The way in which thelight-distribu: tion is obtained, is indicated in Fig.2, in

which the fixture is indicate l in section. The adjacent parts of the fixture are indicated at 9 and 10, 8 is the source of light, and 11 is the table. The middle part of the table 11 exclusively illuminated by rays directly originating from tne source of light 8, which part is limited by the cone 1212.

Inside this cone the ra s fall, directly originating from the source of light, as well as reflected rays, and therefore the strongest light intensity prevails therein. Such a reflected ray is indicated here at 14.

Outside the area limited by the cone- 12, liesan annular part or surface, exclusively illuminated by the rays, such as 15, reflected by the part 9, and not by direct rays. In case directed diffusion is utilized, a ray is emitted from each point of the casing or screen. This is indicated in the drawing by the rays 14, 15, 16 and 17, also to be indicated as bundles of rays 1 l1l, 15 15, 16'16 and 17-17.

From Fig. 2 it follows that the rays reflected by the casing no longer strike the source of light from which absorption might arise, as said rays are only once reflected.

The shape of the fixture is such that more light is reflected in downward than in upward direction, since the part 9 is larger than the part 10. The downwardly reflected rays principally strike the bright ring 3 (Fig. 1) on and around the table, whereas the upwardly reflected rays for the greater part fall on a small spot of the Ceiling situated vertically above the fixture (sec for example the 16 and 17) The light distribution-curves are represented in Fig. 3, measured in a room of 3.35 X 5 meters by 3.30 meters high. The source of light is a lamp of watts. In this figure, 1 is the fixture, 11 the table, 18 the bright spoton the ceiling above the fixture, and 19 an object on one of the walls which a cone of shade 20.

The light intensity amounts to 160 lux on the middle part of the table 11, whereas the intensity amounts to over 200 lux in the brighter illuminated ring 3, represented in Fig. 1.

A lax-meter (not shown), mounted horizontally, indicates about 14 luX-on the wall. The height of the fixture is 26 cm.; the lower part or bottom side of said fixture is cm. above the table surface, while latter is 75 cm. above the floor.

As there are no light-losses, other than on the reflecting planes, which can give an elliciency of 80%, Whereas other light losses at the utmost occur on account of small constructional imperfect-ions, for example, along the line on which the two bent planes meet or in the edges, an exceptional high etliciency of the source of light is obtained.

As only about half of the light is reflected here and the other half is emitted directly, an etficiency of nearly of the source of light may be obtained, the illumination being very steady and not fatiguing. 7

From Figures 2 and 3 it is clearly to be seen that the eyes of a person in the room, either standing or sitting at the table, can

never be struck by a direct ray or ray re-v fiected by the casing or screen. The illumination of 1 1 lux on the wall appears to be sufficient. For the rest, these light-intensities may be varied by altering the dimensions of the casing or screen.

The fixture according to the invention may I ing the direction of the rays a bit less sharp,

without the light dispersion becoming such, however, that the light-direction can no longer be controlled. r

The construction can also be difierent, provided that the required conditions be satisfied. In general, the casing or screen may be made of a transparent material, reflecting the light at the outside, whereas the material is dulled at one or at both sides or treated in such a manner that it also has the property that each point of the surface diffuses the rays.

In Fig. 4a fixture according to the invention is illustrated, serving for indirect illumination of a room.

On the side wall three parts in section 18, 19 and 20 are to be distinguished, which become merged. The part'20 closes the fixture at its lower end. The source of light 8 first of all emits a direct cone, limited by the lines 21, illuminating the middle part of the ceiling 22. Rays are reflected by the part 19, a bundle of these rays being indicated at 23, whereas the bottom part 20 reflects rays, indicated by 24, illuminating an annular portion or area of the ceiling 22'; rays coming from the side part 19 also partly illuminate the same. 7

The upper part 18 is a little more bent than the part 19 under it and reflects the bundle25.

Thus the effect is again obtained that the light intensity is strongest in the middle of the ceiling and decreases toward the sides, practically ending in zero, while no sharp changes occur.

The light distribution-curve is indicated in Fig. 5. r

The middle part 26 of the ceiling has the best luminous surface and gives the objects in the room some shade, whereas the screen itself causes a half shade cone, indicated by the lines 27 With a view to reduce the shade of this cone, the light is not concentrated in a very small spot, e. g. about the size of the casing,

but over a plane larger than the casing itself and divided indicated by the dotted lightdistribution curve. In order to avoid the disadvantage'of less sharp shade-action, it is possible to eliminate this action by making the part 20 of the fixture transparent, so that a direct cone 28 28 is formed, practically c0- inciding with the half-shadecone 2727.

In that case the form of the casing must be altered a little, so that from 1918 a little more flattened part arises and the light is concentrated more straight above the lamp. In that case a light-distribution curve occurs as indicated in a full line.

Finally, it should be observed that, accord ing to the invention, the phenomenon by which the rays coming from acertain point of the mirror are all situated inside a cone with a small top angle, the axis of which is located in the normal reflecting-direction, may also be obtained in another way.

As explained above, the directed diffusion was obtained by providing the surface of the eflecting casings or screens with unevenn-esses of very small curvature, which unevennesses must preferably be finely divided.

ii claim r 1. A llghting fixture comprlsing an incandescent lamp, and a light-reflecting casing surrounding the same and provided with a top opening; said casing embodying distinct upper and lower, convene-concave ellipsoidal portions disposed with their concave surfaces turned toward each other, so that the rays emitted by the lamp and impinging against the surface of the bottom portion will be reflected by the latter a single time only and will pass through said opening, while avoiding the lamp; one focus of the ellipsoidal parts being disposed at the center of the incandescent lamp.

2. A lighting fixture comprising an incandescent lamp, and a light-reflecting casing surrounding the same and provided with oppositely-located top and bottom openings; said casing embodying distinct upper and lower convex-concave portions disposed with their concave surfaces turned toward each other, so that the rays emitted by the lamp and. impinging against said surfaces will bereflected by the latter a singletime and will pass through both openings, While avoiding the lamp.

3. Alighting fixture according to claim 2, in which the convexo-concave portions of the casing embody ellipsoidal parts, one focus of which is disposed at the center of the incandescent lamp, while the other focus is located near one of'the casing openings. I V

In testimony whereof I aiiix my signature.

WILLEM JOHANNES DOMINICUS van DUCK.

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