GB2090956A - Signal Light - Google Patents

Abstract

A signal device comprises a manually graspable closed container (1) having an impact-resistant transparent end region (2) sealed thereto surrounding a xenon flash tube (8), the closed container containing electronic circuitry (7) whereby the flash tube is caused to flash intermittently, electricity storage means (10) to operate the circuitry, and switch means (11) operable from outside of the sealed container. <IMAGE>

Description

SPECIFICATION Signal Light This invention relates to signal lights.

It is known to provide survival, rescue and warning equipment, such as life-jackets or liferafts, with a signal light These are batteryoperated and the operation of the batteries is activated by immersion in sea water. Once immersed such batteries cannot be readily deactivated to conserve battery life. Such batteries have an operating time of relatively few hours.

Another characteristic of such prior art systems is that there is a connecting wire between the battery and the lamp, since the lamp must be prominently visible while the battery must be immersed. Also, since equipment is typically stored for long periods it must allow of testing.

Testing of the prior art systems is done on a sampling basis since it is necessarily destructive testing. It cannot be carried out on an individual item-by-item basis.

We have now discovered that a suitable signal light system can be embodied as a single graspable unit movable if and when desired to a more prominent location, selectively operable, and capable of non-destructive testing.

In one aspect, the invention consists in a manually graspable closed container having an impact-resistant transparent end region sealed thereto surrounding a xenon tube, the closed container containing electronic circuitry whereby said flash tube is caused to flash intermittently, electricity storage means to operate said circuitry, and switch means operable from outside of the sealed container.

The closed container is preferably a generally cylindrical body, usually not exceeding 150 mm in length or 75 mm in transverse dimension.

Typically it does not exceed 225 grams in weight.

It may possess at one end a screw-fitting cap with a suitable sealing gasket, but more preferably it is permanently sealed with the electricity storage means and circuitry in place. The container can be made of suitably shock-resistant material such as resilient thermo-plastic polymer.

The impact-resistant transparent end region can also be made of an impact-resistant polymeric material, such as a polycarbonate polymer. It is usually generally domed in shape so that it is visible not only from all angles around the axis of the device but also from one end of the device.

The xenon flash tube is a device known in itself. Typically, it is formed as a U-shaped sturdy glass tube containing xenon gas which, when a high-voltage pulse (produced electronically from suitable circuitry) is applied gives a brilliant flash of white light of short duration. It is thus to be contrasted with the construction and operation of an incandescent bulb. The filament in such a bulb takes an appreciable time to heat up and an appreciable time to cool. Nat only does repeated application of electrical current tend to burn out such filaments so that reliable operation cannot be achieved, but also the relatively long pulse time means that the current is applied over a number of 30 millisecond periods.Since the eye integrates the signals it receives every 50 milliseconds, the visible light signal, received by the eye for a given amount of electrical energy is considerably less than that yielded by the device of the present invention. According to the present invention, the very brief pulse of light (which is normally effectively less than 50 milliseconds and often much less) ensures that all of the light energy emitted is received within one integration period and thus is much more noticeable to the observer. In practical terms, this means that a given battery can operate a flashing xenon tube for a longer period than it can operate a bulb with continuous or intermittent activation of a hot filament.Although the Applicants do not wish to be limited by any discussion as to the theory of the device, incandescent lamps typically operate at 10 percent efficiency and seldom more than 30 or 40 percent, so that the greatest proportion of the energy used is being used to produce heat instead of light. Xenon flash tubes can readily be fabricated to give 50 percent efficient or more whereby they can either be used to give a brighter flash for the same power consumption or to give a longer period of use for the same brightness.

The electronic circuitry used to operate the xenon flash tube is of the general nature known in the fabrication of larger units, such as for example are incorporated into aircraft wing tips. In the device according to the invention such circuitry is encapsulated in epoxy resin and immobilised in relation to the container. Thus, a robust structure is achieved, with the sealed container and the sturdy glass xenon flash tube being fixed in relation to the electronic circuit components.

The circuitry is preferably such that the light provides between 50 and 70 flashes per minute of operation. The optimum is to provide flashes per minute and as already stated the duration of each flash is normally less than 50 milliseconds.

The electricity storage means is normally a battery producing 3 or 6 volts. While conventional batteries can be used, long-life batteries for example of the lithium-sulphur dioxide type are more preferred. The closed and preferably sealed environment of the container protects such batteries from deterioration during the storage period.

The switch means according to the invention is preferably a reed switch towards one edge of the body of encapsulated electronic circuitry, so that it lies adjacent to the container wall. Magnetic operating (such as a cylindrical metallic button slidable in a groove or channel) can be located to slide along the outer surface of the wall so that, although there is no physical interconnection between the magnetic operating means and the reed switch, sliding of the operating means to and fro will cause the reed switch to make or break and thereby operate the electronic circuitry so that a period of intermittent flashing light is achieved.

The device according to the invention is itself a separate article of commerce, and can be provided for use by divers, mountaineers, or persons engaged in other hazardous activities. It has-the advantages that it can be held high for visual prominence, or can be combined with a number of other devices to increase overall visibility. Also, its robust and compact construction permits of use in hostile environments and permits of extended storage periods and of resistance to damage in an accident. Moreover, if the device is sealed but operated with a magnetic switch, it can be briefly tested at whatever intervals are specified by regulation without destruction of the battery. For example, a complete aircraft complement of lifejacket light can be individually tested instead of sample destruction testing a random percentage of such lights.

While the device as described above constitutes a major aspect of the invention, the invention also extends to an article of survival equipment such as a life jacket or life raft having attached thereto a device as described above in a position such that the switch means is operable by the user. For example, the device can be arranged on or towards the upper shoulder portion of a life jacket, for example sewn in to a suitable special pocket. Such pocket can possess a gap through which the switch can be operated.

Alternatively, the device can be incorporated into the structure of a life raft, needing no trailing wires or water-immersion batteries which can be subject to damage when the life raft is used.

The invention will be further described with reference to the accompanying drawing which shows a longitudinal section through such a signal device.

In the drawing a container generally indicated at 1 has a transparent end 2 and a body portion 3.

Transparent end 2 is a polycarbonate dome sealed at 4 to the body portion 3. This body portion though not transparent is also formed of polycarbonate and has an end cap 5 meeting the main part of the body at 6. Within the container is a conventional electronic circuit region generally indicated at 7, encapsulated in an epoxy resin which immobilises it in relation to the body portion and provides resistance to impact and to deterioration on storage. At one end of this region 7 is located a U-shaped xenon flash tube 8 with electrodes 9, attached to electronic circuitry such that a brief flash of effective duration less than 50 milliseconds is given 60 times a minute.

Towards the other end of the container is located lithium-sulphur oxide battery 10 for actuating the electronic circuitry. Such a battery not only gives an extended operating life but also gives a voltage which is essentially uniform over the greater part of that life, whereby the flash rate remains in the acceptable 50-70 flashes per minute range.

To one side of the encapsulated circuitry is provided a reed switch diagrammatically shown at 11. The internal operating member of the reed switch is located inside the sealed envelope and is shown diagrammatically at 12. On the outer surface of the container is located an integral protrusion 13 of generally channel-shaped nature with end regions 14 and having located generally within the channel (by virtue of inwardly turned channel edges, not shown) a magnetised metallic button 15. It is possible to slide the button 15 to one end or other of the channel, so that it attacts the internal operating member 12 of the reed switch and switches the electronic circuitry on or off accordingly.

The device as shown in the drawing can be cylindrical in nature and securely located in relation to a life jacket or life raft, for example within a sewn-in pocket in which pocket from the protrusion 13 is accessible by means of a suitable opening.

Claims (9)

Claims

1. A signal device comprising a manually graspable closed container having an impactresistant transparent end region sealed thereto surrounding a xenon flash tube, the closed container containing electronic circuitry whereby the said flash tube is caused to flash intermittently, electricity storage means to operate the said circuitry, and switch means operable from outside of the sealed container.

2. A signal device as claimed in Claim 1, wherein the closed container is a generally cylindrical body permanently sealed with the electricity storage means and circuitry in place.

3. A signal device as claimed in Claim 1 or Claim 2, wherein the impact-resistant end region is domed in shape and made of a polycarbonate polymer.

4. A signal device as claimed in any of Claims 1 to 3, wherein the said circuitry is encapsulated in epoxy resin and immobilised in relation to the container.

5. A signal device as claimed in any of Claims 1 to 4, wherein the said circuitry is such as to provide 50 to 70 light flashes per minute of operation.

6. A signal device as claimed in any of Claims 1 to 5, wherein the electricity storage means is a battery of the lithium-sulphur dioxide type.

7. A signal device as claimed in any of Claims 1 to 6, wherein the switch means is a reed switch.

8. A signal device according to Claim 1, substantially as herein described with reference to, and as shown in, the accompanying drawing.

9. An article of survival equipment such as a life jacket or life raft having attached thereto a device as claimed in any of Claims 1 to 8.