Reflector for accommodating an electric lamp

Abstract

 The reflector (1) of metal sheet has a concave, reflecting surface (2) having an optical axis (3), and a light emission window (4) transverse to the axis (3). The reflecting surface (2) shows a plurality of flat lanes (5) which approach the axis (3) from the window (4) curves and gives the reflector (1) polygonal sections transverse to the axis. In an area adjacent the window (4) the lanes (5) are divided into flat sublanes (51-55), which sublanes have in sections transverse to the axis (3) mutually similar directions, and are located adjacent a circumscribed curve (6). The reflector is easy to manufacture.

Description

[0001] The invention relates to a reflector for accommodating an electric lamp, provided with:
   a concave reflecting surface having an optical axis,
   a light emission window transverse to the optical axis,
   which reflecting surface has a plurality of flat lanes which run from the light emission window in a curved manner towards the axis and which give the reflecting surface cross-sections transverse to the axis which are polygons whose vertices lie on a circumscribed curve.

[0002] Such a reflector is known from US-4 914 557.

[0003] The reflector is suitable for forming the light of an electric lamp accommodated therein into a beam and producing an evenly illuminated field. The width of the beam formed and the size of the illuminated field are greater in proportion as the number of lanes is smaller.

[0004] It is attractive if the width of the light beam may be set at will in that the number of lanes of the reflector is chosen. It is also attractive if the reflector is formed from metal sheeting in that the latter is forced into the desired shape. A comparatively light reflector is then obtained in a short time.

[0005] It was has been, however, that the reflectors cannot always be obtained from metal sheeting in the desired shape, or that reflectors of a correct basic shape have reflecting surfaces which show damage.

[0006] The invention has for its object to provide a reflector of the kind described in the opening paragraph which is of a shape which can be more easily realised.

[0007] This object, according to the invention, is realised in that the reflector is formed from metal sheeting and that the lanes in a region adjoining the light emission window are each subdivided into flat sublanes which in sections transverse to the axis have mutually similar directions and which are located adjacent the circumscribed curve.

[0008] In the known reflector, each cross-section between the vertices of the polygon in this cross-section deviates from the imaginary circumscribed curve. These deviations are greater in cross-sections near the light emission window than at a distance from this window. These deviations are also greater if a reflector with a given light emission window has a smaller number of lanes, and also if a reflector having a given number of lanes has a greater light emission window.

[0009] The deviations are smaller in the reflector according to the invention thanks to the subdivision of the lanes into sublanes. It has been found that as a result the reflector can be readily realised with a good quality of the reflecting surface. The deviations can be made smaller, for example, down to a value of 0,25 mm or less, in that the number of sublanes of a lane is increased as desired, in dependence on the dimension of the light emission window and the number of lanes. If a reflector is formed from a comparatively thick metal sheet, the said deviations may be chosen to be greater than if a comparatively thin sheet is used. Following the reduction of the said deviations between cross-section and circumscribed curve, the degree to which the points of the reflector in the direction perpendicular to the surface of the reflector at the location of each point deviate from the imaginary enveloping curved body of the reflector is also smaller, for example, smaller than 0,25 mm. This degree of deviation may change with the distance to the light emission window.

[0010] Since the sublanes of a lane have a similar direction in cross-sections transverse to the axis, and thus a similar three-dimensional shape, the subdivision of a lane has only a slight influence on the optical characteristics of the reflector. It is favourable if this influence is minimum in that the adjoining sublanes of each lane have an interconnection which in cross-sections transverse to the axis runs substantially in radial direction. As a result, these connections are not hit by light rays coming from the optical axis of the reflector.

[0011] Generally, the circumscribed curve is essentially a circle, but this curve may alternatively be, for example, an oval shape.

[0012] The reflector may comprise a holder for the exchangeable accommodation of an electric lamp on its axis. Alternatively, an electric lamp may be indetachably connected to the reflector, with its light source, for example an incandescent body or a discharge path between a pair of electrodes, on the axis.

[0013] This and other aspects of the invention will be explained in more detail in the ensuing description with reference to an embodiment of the reflector as shown in the drawing.

[0014] In the drawing:

Fig. 1 is an interior view;

Fig. 2 shows an enlarged detail of a light emission window;

Figs. 3, 4 show the reflector of Fig. 1 partly in side elevation, partly in longitudinal section with an electric lamp.

[0015] In Fig. 1, the reflector 1 for accommodating an electric lamp has a concave reflecting surface 2 (see also Fig. 3) with an optical axis 3 and a light emission window 4 transverse to this axis. The reflecting surface 2 has a plurality of flat lanes 5, twenty-one in the Figure, which run from the light emission window 4 in a curved manner towards the axis 3 and which give the reflecting surface cross-sections transverse to the axis which are polygons whose vertices 8 (Fig. 2) lie on a circumscribed curve 6.

[0016] The reflector 1 is formed from metal sheeting by forcing. The lanes 5 are each subdivided in a region adjoining the light emission window 4 into flat sublanes 51-55, which in cross-sections transverse to the axis 3 have mutually similar directions and which are located adjacent the circumscribed curve 6.

[0017] In Fig. 2, a number of flat lanes 5 are depicted in the light emission window 4 in the way in which they would touch this window without the measure according to the invention. The vertices 8 of the polygon which the lanes would form lie on a circumscribed curve 6. The inscribed curve 7 shows how far the innermost points of the reflector would be removed from the outermost points in the light emission window 4.

[0018] The measure according to the invention is illustrated in one lane 5, which lane is subdivided into an odd number, i.e. five, flat sublanes 51-55. These sublanes all have the same direction in cross-sections transverse to the axis. They have the same direction which the corresponding lane 5 would have had. The measure according to the invention has the result that the innermost points of the reflector lie on an inscribed curve 9 in the light emission plane which lies close to the circumscribed curve 6. As a result, only small diameter differences exist along the reflector circumference. The sublanes 51-55 lie near the circumscribed curve 6. The sublanes 52-54 are shifted to the outside compared with the sublanes 51, 55 and touch the circumscribed curve 6 in the Figure.

[0019] Fig. 2 also shows that adjoining sublanes 51, 52 and 53, 54 have interconnections 56 and 57, respectively, which in the cross-section shown transverse to the axis 3 run substantially in radial direction and are accordingly not visible from the axis 3.

[0020] The reflector has a smaller diameter in cross-sections remote from the light emission window 4 owing to its concave shape, so that the lanes there are narrower and deviate less from the circumscribed curve. As a result, a subdivision into a smaller number of sublanes, i.e. three, is sufficient there. Still further away from the light emission window, the lanes are so narrow that no subdivision is required.

[0021] In Fig. 3, the reflector 1 has a holder 11 for an electric lamp 12 on the axis 3. The lamp has a pair of electrodes 13 in an ionizable gas with a discharge path between them forming a light source on the axis 3. The pair of electrodes 13 is present in a discharge vessel 14 which is enclosed in an outer bulb 15 which carries a lamp cap 16. A screen cap 17 is present on the outer bulb, which cap prevents the radiation through the window 4 of non-reflected light. The lamp is a high-pressure sodium discharge lamp which emits white light during operation.

[0022] The electric lamp assembly of Fig. 4 has an electric lamp 22 at the reflector 1 with an incandescent body 23 on the axis 3 as the light source. A lamp cap 26 is present at the lamp, while the reflector 1 is closed by a glass disc 28 which is fixed by means of a flanged ring 29.

[0023] Examples of the reflector according to the invention are given in Table 1. The x and y coordinates given are those of the sublanes 51, 55.

TABLE 1

reflector 1		reflector 2		reflector 3		reflector 4
x	y	x	y	x	y	x	y
0.0	16.0	0.0	16.0	0.0	16.0	0.0	16.0
1.5	20.3	1.5	23.3	1.5	26.3	6.0	25.8
4.0	26.2	4.0	30.4	4.0	34.6	14.2	34.9
7.6	32.4	7.6	37.0	7.6	41.6	22.0	42.2
12.9	37.6	12.9	42.8	12.9	48.0	30.0	48.3
18.9	43.7	18.9	46.7	18.9	49.7	32.0	49.7
25.3	48.4	25.3	50.6	25.3	52.8	36.1	52.2
32.0	52.6	32.0	54.0	32.0	55.4	42.1	55.8
38.9	56.3	38.9	57.1	38.9	57.9	46.1	57.9
45.8	59.4	45.8	59.8	45.8	60.2	52.1	61.0
53.0	62.1	53.0	62.2	53.0	62.3	54.1	61.9
54.1	62.5	54.1	62.5	54.1	62.5	55.3	62.5

Claims

1. A reflector (1) for accommodating an electric lamp, provided with:
   a concave reflecting surface (2) having an optical axis (3),
   a light emission window (4) transverse to the optical axis,
   which reflecting surface (2) has a plurality of flat lanes (5) which run from the light emission (4) window in a curved manner towards the axis (3) and which give the reflecting surface (2) cross-sections transverse to the axis which are polygons whose vertices (8) lie on a circumscribed curve (6), characterized in that the reflector (1) is formed from metal sheeting and that the lanes (5) in a region adjoining the light emission window (4) are each subdivided into flat sublanes (51-52) which in sections transverse to the axis (3) have mutually similar directions and which are located adjacent the circumscribed curve (6).

2. A reflector as claimed in Claim 1, characterized in that the adjoining sublanes (51,52;53,54) of each lane (5) have an interconnection (56,57) which in cross-sections transverse to the axis runs substantially in radial direction.

3. A reflector as claimed in Claim 1 or 2, characterized in that a holder (11) for an electric lamp (12) is present on the axis (3).

4. A reflector as claimed in Claim 1 or 2, characterized in that an electric lamp (22) is fastened to the reflector, with a light source (23) on the axis (3).

Drawing