In the case of motor vehicle instruments in particular, it is desirable that at least some of the instruments are clearly visible in the dark, without the illumination of such instru- ments impairing the night vision of the driver. Accordingly, background illuminated instruments have begun to be used to greater extents, where digits or other signs on the dials of the instruments are illuminated from the rear side of the instrument. In such cases, it is also usual to achieve such rear side illumination of the instrument, by providing illu- mination behind the central part of the indicator and by providing the indicator with a transparent hub that enables the light to spread up through the hub to a diffuser, which in turn spreads the light in the indicator needle.

In the case of pointers or indicators of this kind, it is difficult to obtain uniform and effective illumination of the indicator needle. An unevenly illuminated indicator needle is tiresome to look at and also causes indicator precision.

Hitherto known pointers or indicators are also so complicated as to necessitate their manufacture in a number of different parts, such as indicator needle, light conductor, diffuser, cap, shaft and possible a counterweight, that must be assem- bled in order to obtain a complete indicator. Because of the small sizes of these components, it is obvious that assembly is both laborious and expensive.

In order to obtain sufficient illumination with the aid of light-emitting diodes, it has hitherto required the use of several diodes, normally from five to six diodes.

An object of the present invention is to provide a pointer or an indicator of the aforesaid kind with which at least some of the aforesaid drawbacks associated with known indicators have been overcome.

This object is achieved with an inventive pointer or indica- tor that includes a needle carried by a hub part, wherein said hub part includes a cap that forms a light conductor which extends from the bottom of the hub part to said needle.

According to another object of the invention, the needle and the hub part have the form of a one-piece structure.

According to one particular embodiment of the invention, the cap includes a surface that presents an exponential horn shape.

The invention will now be described in more detail with ref- erence to a non-limiting embodiment thereof and also with reference to the accompanying drawings, in which Fig. 1 is a side view of an inventive pointer or indicator; Fig. 2 illus- trates the indicator from its rear end, as seen from the right in Fig. 1; Fig. 3 is a plan view of the indicator shown in Fig. 1; Fig. 4 is a side view corresponding to the view of Fig. 1 but with the top casing removed; and Fig. 5 shows the indicator in Fig. 4 from beneath.

The inventive pointer or indicator includes a needle 1 car- ried by a hub 2. The needle 1 has a front part la which ex-

tends radially from the hub 2 through a considerable dis- tance, and an end part lb which extends radially from a cen- tre section lc through a short distance and in a direction opposite to the direction of the front part la, said centre section lc being located above the hub 2. A top casing 3 is f itted around the needle 1 on the hub 2, so as to cover the end surface of the hub 2 in the vicinity of the needle. As will be seen from Fig. 5, a fastener hole 5 is provided in the other end of the hub, for fastening the indicator to an outwardly projecting rotatable shaft (not shown) of the in- strument in which the indicator is used.

The indicator, including the needle 1 and hub 2, is conven- iently made in one piece, preferably injection-moulded, from a transparent plastic material through which light can be spread.

The hub 2 includes a generally cylindrical centre part 2a, in which the fastener hole 4 is provided. The hub also includes a cab or jacket 2b that extends from the centre part 2a. The cap 2b has a circular-sector cross-sectional shape and its size varies along the height of the hub. The greatest cross- sectional area of the cap 2b is located at that end of the hub which lies distal from the indicator 1. The surface of the cap 2b that faces in the same direction as the front part la of the needle is arcuate in shape, a single curved sur- face, whereas those surfaces 2c of the cap 2b that face in the same direction as the end part lb of the needle have a double-curved surface, these surfaces between the single- curved surface of the cap forming particularly a surface that has an exponential horn shape. This embodiment of the cap 2b and its surface 2c enables the cap to take up light from light diodes and lead the light to essentially the same point

in the centre section lc of the needle, regardless of the point at which the light impinges on the underside of the cap 2b.

In the case of the aforedescribed embodiment of the cap 2b, it normally suffices to place only two light diodes in the instrument dial, at positions corresponding to about 10 o'clock and 2 o'clock respectively, in respect of an indica- tor that has roughly equal deflections on both sides of the 12 o'clock point. In the case of the illustrated embodiment of the bottom surface of the cap 2b, at least one of the light-emitting diodes will always be positioned so that its light will impinge on the cap 2b and therewith be led up to the indicator 1. This enables a deflection angle of at least about 270 with respect to the indicator 1 to be achieved with solely two light-emitting diodes.

Provided in the central section lc of the needle 1, in the cross-direction of said needle, is a generally triangular opening 5 that is delimited by a front reflection surface 6a, a rear reflection surface 6b, and an upper surface 6c located slightly beneath the surface of the needle in the centre section lc. Both the front reflection surface 6a and the rear reflection surface 6b are single-curved surfaces, preferably parabolically curved surfaces. The two reflection surfaces 6a, 6b are designed to give total reflection of the light impinging thereon.

When light is transmitted by a light-emitting diode situated in the instrument dial and impinging on the underside of the cap 2b, light will thus be transmitted up to the needle 1 with the aid of the cap and will impinge on the reflection surfaces 6a, 6b. The light is reflected by the front reflec-

tion surface 6a as a planar wave, forwardly to the tip of the front part la of the needle. When the front reflection sur- face 6a is a parabolic surface, the front part of the needle may have a planar surface and still obtain uniform illumina- tion from the light directed onto the underside of the front part la of the needle surface by the front reflection surface 6a. The reflected light is directed from the rear reflection surface 6b onto the rear surface of the end part lb of the needle. This rear surface has a conic cross-sectional shape, preferably global, and therewith reflects the light forwards onto the underside of the surface of the end part lb of the needle and onto the underside of the surface of the centre section lc of said needle, so as to provide uniform illumina- tion.

The thickness of the bridge formed between the surface of the centre section lc of the needle and the upper surface 6c of the opening 5 is not uniform, but decreases forwardly so that the internal illumination of this part will also be uniform.

The aforementioned top casing 3 is adapted to prevent any spreading of stray light, particularly should the cap 2b be located outside one of the light diodes. The top casing 3 conveniently has a divided upper surface, so that the entire upper surface of the needle 1 will be visible, even in the centre section lc, therewith enabling the needle to be illu- minated throughout the whole of its length, from the tip of the needle to its end.

As a result of the particular geometrical design of the dif- ferent mutually co-acting parts of the needle, internal illu- mination of the needle can be made so uniform that no varia- tions in light intensity can be observed. Intensity varia-

tions in the order of 10-20% are insufficient to disturb the eye and will not therefore influence the driver.

It is mentioned above that two light-emitting diodes are used, although it will be understood that more or fewer light-emitting diodes may be used depending on the desired deflection of the indicator and also depending on how the cap is constructed.

The invention thus enables an internally illuminated indica- tor to be produced in one single piece, therewith requiring the minimum of assembly work. All that is required with re- spect to assembly is to fit the top casing, when such a cas- ing is used. The invention also enables fewer light-emitting diodes to be used in effecting illumination. Although cost savings in respect to each unit may seem to be small, the combined savings in costs is considerable with regard to mass-produced units.