OPTICAL DISTRESS SIGNAL TRANSMITTER

Abstract: An optical distress signal transmitter has a number of light emitting diodes (14) on a dome-shaped diode socket (18) whose surface (19) is coated with a retroreflective material, the light emitting diodes (14) projecting from this surface and being so arranged that at least two of them are visible when the distress signal transmitter is viewed from the side or from a higher elevation with respect to the base plane of the socket holding the light emitting diodes.

Description: OPTICAL DISTRESS SIGNAL TRANSMITTER The present invention relates to an optical dist¬ ress signal transmitter having a source of current, a light emitter, an electric circuitry for supplying current pulses to the light emitter, and switch means. In connection with life-saving operations at sea, there is always a need to be able quickly to locate the persons in distress, since, the time of survival in water is very short. Hence, it has been proposed to use optical distress signal transmitters emitting a flashlight. However, the distress signal transmitters used hitherto suffer from shortcomings in respect of current supply and light intensity. The object of the present invention, therefore, is to improve the prior art optical distress signal transmitters and provide a small-size, handy transmitter which, despite its small size, emits a strong and intense light which can be perceived from a great distance. This and other objects of the invention will be achieved by means of a distress signal transmitter which is characterized by the features stated in the claims. The invention will be described in greater detail hereinbelow with reference to the accompanying drawings. Fig. 1 is a side view of one embodiment of a distress signal transmitter according to the invention. Fig. 2 is a top plan view of the same transmitter. Fig. 3 sche¬ matically illustrates the principle of the optical per¬ formance of the transmitter. Fig. 4, in perspective, illustrates another embodiment of a distress signal transmitter according to the invention. The distress signal transmitter 10 shown in Figs. 1 and 2 has a housing 11 which accommodates batteries (not shown) and which may also hold switch means for initiating the transmitter. The housing has a spring- biased clip 12 by means of which the distress signal transmitter can be clamped on e.g. a life-jacket or a rucksack, if it is to be used in connection with rescue operations in mountain areas or elsewhere on land. The distress signal transmitter according to the inven- tion has a dome-shaped holder or socket 13 for a number of light emitting diodes 14 which, according to the invention, are provided in such a number and disposed in such a geometric arrangement that at least two light emitting diodes t are visible at the same time when the socket 13 is viewed from the side or from a higher elevation with respect to the base plane of the socket. In the illustrated embodiment, there are thus provided five light emitting diodes 14 which are arranged in a ring and with an angle at centre of approximately 30° with respect to the base plane of the dome. At the top of the dome, there is a sixth light emitting diode. The light emitting diodes are supplied with current from an electric circuitry (not shown) which emits such current pulses to the light emitting diodes that these will emit light pulses of an intensity of about 2 cd. at current pulses with a peak value of about 180 mA. According to the invention, the dome-shaped socket 13 is provided with a surface coating in the form of a retroreflective material of the type sold by e.g. Minnesota Mining and Manufacturing Company. The effect of this coating of retroreflective material is twofold, as will be explained in connection with Fig. 3. Fig. 3 thus is a " principle outline where a portion of the socket 13 and some of the light emitting diodes 14 are shown. In this instance, the line 15 represents a water surface which may as well be located further down, as counted from the base plane of the socket. Light rays 16 from the diode 14 will be totally reflec- ted in the water surface 15 because of the low angle of incidence, whereby, when searching is conducted from an air-craft, the small distress signal transmitter will be perceived as a large luminous area on the water, the light scattering angle being very large. By the use of the retroreflective coating on the dome surface, light rays 17 emitted by the diode 14 towards this surface will be reflected back through the light emitting diode and thus form part of the light rays 16. Hence, the retroreflective coating entails a substantial increase in the light intensity of the light rays 16. Also, the retroreflective coating is advantageous since it will reflect with high light density the searchlight from e.g. helicopters. The effect of the retroreflective surface increas¬ ing the light density of the light rays 16 can be further enhanced if the dome-shaped diode socket according to the invention is designed substantially as a prismatic body 18 with approximately planar surfaces 19 around at least most of the light emitting diodes 14. Such an embodiment of the invention is shown in Fig. 4 where also the housing 11 has been given a different design. The switch means incorporated in the distress signal transmitter has not been shown in more detail since it can be designed in many different ways. In the embodiment shown in Fig. 4, the dome-shaped light emitting diode socket 18 has been designed as a separate body which is mountable by means of a bayo¬ net catch and is sealed with respect to the housing 11 by suitable sealing means, so as to make the distress signal transmitter waterproof. OMPI

Claims: CLAIMS 1. An optical distress signal transmitter having a source of current, a light emitter (14) , an electric circuitry for supplying current pulses to the light emitter, and switch means, c h a r a c t e r i z e d in that it has a dome-shaped light emitting diode socket (13, 18) disposed at one end of a housing (11) for said source of current and having a surface (19) which is coated with a retroreflective material and from which a plurality of light emitting diodes (14) serving as light emitters protrude and on which the light emitting diodes (14) are provided in such a number and in such a geometric arrangement that at least two light emitting diodes are visible at the same time when the dome (13, 18) is viewed from the side or from a higher elevation with respect to the base plane of the dome. 2. Distress signal transmitter as claimed in claim 1, c h a r a c t e r i z e d in that the dome (18) is shaped substantially as a prismatic body with planar surfaces (19) around at least most of the light emitting diodes (14). 3. Distress signal transmitter as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the dome (13, 18) has a central light emitting diode (14) disposed at the top of the.dome, and five light emitting diodes (14) disposed in a ring and with an angle at centre of approximately 30 with respect to the base^ plane of the dome.

Inventors: FORSBERG OWE RENE, FORSBERG, OWE, RENE
Applicants: FORSBERG OWE RENE, FORSBERG, OWE, RENE
Application year: 1982
Main classification: G08B5
IPC codes: B63C9, G08B5