The present invention relates to a searchlight.

Searchlights are used in many different contexts, for instance on ships, helicopters and also in permanent loca¬ tions for watching and searching purposes.

Searchlights on ships and helicopters are used to search for persons or objects over wide areas and over relatively large distances.

Known searchlights are very large and are very powerful. Despite this, they do not always give satisfactory illu ina- tion over long distances. Because of their size, it is not always possible to find sufficient space in which the searchlight can be easily maneuvered.

Another problem is that known searchlights are so constructed that when the focal distance shall be changed in order to illuminate a larger area, the light source is displaced relative to the reflector out of its focal position. The light is therewith scattered widely and unevenly, resulting in losses.

The present invention solves these problems and provides a searchlight that is considerably smaller in depth and which provides stronger illumination at a given distance for a given power input.

The present invention thus relates to a searchlight which transmits directional light with the aid of a reflector and a light source and which is characterized in that the searchlight includes at least three lamps, each having its respective light source and being fixed mechanically in relation to one another by means of a carrier device; in that each of the light sources is comprised of a gas discharge

lamp having an electrode distance of less than 5 millimeters; and in that the opening diameter of each reflector lies within a range exceeding approximately 100 millimeters and less than approximately 250 millimeters.

The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings, in which

- Figure 1 is a front view of an inventive searchlight;

Figure 2 is a sectional view taken on the line A-A in

Figure 1;

Figures 3a and 3b illustrate two different positions of a carrier plate; - Figure 4 illustrates another embodiment of the invention; - Figure 5 illustrates a further embodiment of the inven¬ tion; and

Figures 6a and 6b illustrate two positions of a carrier plate.

Figure 1 illustrates an inventive searchlight as seen immediately from the front. The searchlight is designed to transmit directional light with the aid of a reflector and a light source.

The inventive searchlight 1 includes at least three mutually separate lamps 3, each having its respective light source 4. The Figure 1 embodiment has ten lamps 3. The lamps 3 are mechanically fixed relative to one another with the aid of a carrier device. Each of the light sources 4 is comprised of a gas discharge lamp having an,electrode distance of less than 5 millimeters. The diameter of the opening 6 of each lamp reflector 5 is smaller than about 250 millimeters.

This means that each light beam can be directed very effec¬ tively, i.e. the light rays will have a high degree of parallelism owing to the fact that the spread of the light

source is small in relation to the size of the reflector. The use of several such lamps in coaction with one another provides a much stronger light for a given power input than a much larger conventional searchlight with the same power input.

The opening should not be smaller than 100 millimeters in the case of a gas discharge lamp having said electrode distance, since the parallelism of the light rays would then be impaired to an undesirable extent.

It is not possible at present to produce high power gas discharge lamps with short electrode distances. According to one preferred embodiment of the invention, the light sources are designed for a power input of from 25 to 75 W.

One commercially available light source is a gas discharge lamp manufactured by PHILIPS and marketed under the name Microdischarge-lamp or Micro powerlight. This lamp has an electrode distance of 4.2 millimeters.

The searchlight may include a varying number of lamps 3, the number used being contingent on the desired light power. According to one preferred embodiment, the inventive search- light comprises three to twenty lamps.

Practical comparison tests have been carried out with an inventive searchlight and a conventional searchlight.

Certain comparison data is given in the Table below.

Norselight SH 370 Searchlight accord¬ ing to the invention

Power input 1000 300

Voltage 24 V- •230 V 24 V-230 V

Divergence 8.3 degrees 8.5 degrees

Range at 1 Lux/m ² 1500 3000

Illuminance at:

250 m 39 Lux 80 Lux

500 m 6 Lux 15 Lux

1000 m 2 Lux 10 Lux

The known searchlight was a Norselight SH 370. This search¬ light had a halogen lamp which gave 30 Lumen/ . The inventive searchlight included ten lamps, each supplied with 30 . These discharge lamps gave approximately 90 Lumen/W. The values given in the Table show that the inventive searchlight was much more effective than a conventional searchlight having only one large reflector and using one large light source.

As before mentioned, the light source used in the aforesaid Norselight was a halogen lamp having a filament length of about 25 millimeters. A filament of this length produces a relatively large amount of ineffective stray light, i.e. light which is not parallel with the light transmitted by the reflector from that part of the light source located in the focus of the reflector.

It will be noted that despite the power supplied to the inventive searchlight being only about a third of the power supplied to the Norselight, the light sources gave roughly the same light flux due to the more effective discharge lamp. It will also be noted that despite the light sources giving

roughly the same light flux, the illuminance provided by the inventive searchlight was five times greater at a distance of 1000 m.

It is quite evident that the inventive searchlight is markedly superior to a conventional searchlight.

Furthermore, the use of a number of smaller mutually coacting lamps enables the depth dimension of the searchlight, i.e. the dimension from left to right in Figure 2, to be made much smaller than when using only one large reflector. The inventive searchlight therefore requires far less space and can be positioned much more easily than a conventional searchlight, for instance in a helicopter, and is also easier to maneuver.

The aforesaid carrier device may have any suitable construc¬ tion. For instance, the carrier device may include a frame¬ work of metal rods to which each lamp is attached.

However, according to one preferred embodiment of the invention, the lamp carrier device 7 comprises an elastically deformable plate which is common to the lamps 3 and to which each of said lamps 3 is attached, this attachment preferably being made in the vicinity of respective lamp openings.

The plate 7 may be made of a plastic material or formed by a thin metal sheet, for instance.

The plate is carried by a lamp housing 8. According to a much preferred embodiment of the invention, there is provided between the housing 8 and the plate 7 a pull-and-push device 9 which functions to deform the plate 7 elastically between a flat state and a curved state.

The pull-and-push device 9 may, e.g., include an electric stepping motor 10 which is mounted in the housing 8 and which

functions to turn a threaded screw 11 so as to move the front end 12 of said screw 11 towards and away from the motor respectively, as indicated by the arrow 13, when the motor is driven in respective appropriate directions. The front part of the screw 11 is attached to the carrier device, i.e. the plate 7.

The pull-and-push device 9 functions to deform the plate elastically between a first end state, illustrated in Figure 3b, in which the plate 7 curves convexly outwards in relation to said housing 8, and a second end state, illustrated in Figure 3a, in which the plate 7 curves convexly inwards in relation to the housing 8.

Thus, in combination with the pressure force or pulling force that the motor 10 is able to generate, the elasticity of the plate 7 shall be such that the plate will be curved in one or the other of said directions by means of the screw 11.

The curved states of the plate 7 have been exaggerated in Figures 3a and 3b. For instance, when the lamp housing has a diameter of 700 millimeters, it suffices to move the plate through only a few millimeters, for instance at most 5 millimeters, at the point on the plate at which the pulling or pressing force is exerted, i.e. at the point where the screw is attached to the plate, in order to change the light pattern or picture sufficiently for practical needs.

It is evident that when the plate is curved as illustrated in Figure 3a, the optical axes 14, 15 of the lamps will converge and therewith illuminate a relatively close spot. This plate state can be used when wishing to illuminate with strong light a limited area at a given distance, e.g. 250 metres. It is also evident that when the plate is curved as illustrated in Figure 3b, the optical axes 14, 15 of the lamps will diverge. When the plate 7 is curved in this direction, the lamps will naturally illuminate a wider area.

Thus, the invention enables the spread of light to be changed while maintaining the position of each light source relative to its associated reflector, thereby eliminating useless or ineffective light spread resulting from the light source being moved out of the focus of the reflector. Thus, in accordance with the invention, the area illuminated by the searchlight can be set while retaining a high and uniform light yield.

The pull-and-push device 9 will preferably engage the plate 7 at a point which is located symmetrically in relation to the lamps 3. This causes the curvature of the plate to become symmetrical with respect to the optical axes of the lamps.

According to another preferred embodiment of the invention, the searchlight 2 is provided with a round plate 16 (Figure 4) so as to further increase the symmetry between the angling of the optical axes of the lamps when the plate is curved. In this case, the plate is supported by the housing around the plate periphery. The push-and-pull device engages the centre of the plate and acts in a direction perpendicular to the plane thereof. The lamps 3 are placed symmetrically, so that their optical axes lie on concentrical circles, the centres of all of which coincide with the centre of the plate.

According to another preferred embodiment of the invention, the pull-and-push device 9 functions to elastically deform the plate 17 between a flat state and a state in which the plate 17 forms a single-curved surface which curves about a first axis X and between said flat state to a state in which the plate 17 forms a single-curved surface about a second axis Y which is perpendicular to the first axis X.

This latter embodiment is exemplified schematically in Figures 5, 6a and 6b. In the case of this embodiment, several pull-and-push devices 9 are placed between a carrier device

17 and the searchlight housing in the same way as that illustrated in Figure 2. The carrier device 17 is in the form of an elastically deformable plate and the push-and-pull devices engage the carrier device at points 19-27, as shown in Figure 5. By moving the push-and-pull devices at points 19, 21, 22, 24 and 26, 27 in opposite directions relative to the push-and-pull devices at points 20, 25 and 23, the carrier device 17 will be arched so that lines that extend along the carrier device parallel with the X-axis will be straight lines, whereas lines that are parallel with the Y- axis will be curved lines; see Figure 6a. Figures 6a and 6b illustrate schematically only a few lamps 3. Correspondingly, by moving the push-and-pull devices at points 19-21 and 22-24 in opposite directions in relation to the push-and-pull devices at points 25-26, the carrier device 17 will be arched so that all lines parallel with the Y-axis are straight lines, whereas lines parallel with the X-axis are curved lines; see Figure 6b.

It will be understood that movement of the push-and-pull devices in directions opposite to those mentioned in the above paragraph will cause the carrier device to arch in opposite directions.

This enables the spread of the light cone to be expanded or contracted in two mutually perpendicular directions, for instance in horizontal and vertical directions.

It is also conceivable to use a larger number of push-and- pull devices and to control these devices in a manner to curve the carrier device so as to form a double-curved surface.

The present invention thus solves the aforesaid problems associated with known searchlights and provides a searchlight of much greater efficiency in respect of luminance at a given distance in relation to the electrical power input.

It will be understood that modification and changes can be made. For instance, the carrier device may have some other mechanical design. Furthermore, the push-and-pull device may be constructed differently to that described. For instance, this device can be replaced with a hydraulic cylinder for arching or curving the plate.

Furthermore, the carrier device may be comprised of a frame structure which carries a separate attachment means for each lamp. This attachment means may be constructed to adjust or set each lamp individually in accordance with a predetermined pattern, so that the lamps will be directed relative to one another in the manner illustrated in Figures 3a, 3b, 6a and 6b. In this regard, the attachment means of each lamp may be of a known kind used to electrically adjust the position of a rear view mirror of an automobile.

The invention is thus not restricted to the aforedescribed and illustrated exemplifying embodiments thereof and can be varied within the scope of the following Claims.