An optical warning arrangement

Abstract: The present invention relates to a method and to an arrangement for optically indicating that the gas pressure of a gas reservoir connected to a consumer has reached a predetermined value. This value is indicated by an acoustic signal within a predetermined frequency range and at a given lowest sound level. The method is characterized by listening for sound within the predetermined frequency range and above the lowest sound level with the aid of an active listening device, and activating a light source in response to the sound heard by this device. The arrangement for optically indicating that the gas pressure of a gas reservoir connected to a consumer has reached a predetermined value includes the gas reservoir, a gas delivery line which connects the gas reservoir with the consumer, and means for delivering an acoustic signal within a predetermined frequency range and at a sound level which exceeds a predetermined lowest value, and a sound detecting unit which actively listens for sound within the predetermined frequency range and at the sound level exceeding the lowest value, and a light source which is connected to the sound detecting unit.

Description: The present invention relates to a method of producing an optical indication that the gas pressure in a gas reservoir connected to a consumer has reached a predetermined value, this pressure value being indicated by an acoustic signal within a predetermined frequency range and at a given sound level. The invention also relates to a device for optically indicating that the gas pressure of a consumer-connected gas reservoir has reached a predetermined value. According to current standards applied in many countries with regard to breathing apparatus intended for use in contaminated environments and in fire environments, such apparatus shall be provided with a suitable warning device which will warn the wearer of the apparatus that the pressure in the gas reservoir has reached a predetermined value. For instance, in current European standards for body-carried breathing apparatus operating with compressed air, the aforesaid predetermined pressure level is given as 50 to 60 bars or when at least 200 liters free inhalation gas remains in the gas bottle or gas reservoir. Other pressure values apply in U.S. standards (U.S.A.) for instance. The majority of commercially available breathing apparatus of the kind intended are provided with an acoustic warning device which at the applicable predetermined warning pressure activates a whistle which is operated by the gas from the gas reservoir. Different standards specify the frequency and sound level of the acoustic warning signal produced. Since it is possible that the person wearing the breathing apparatus is located in a high sound level environment and may, in certain cases, wear a head guard, such as a helmet and/or a protective hood which restricts the ability of the wearer to hear the acoustic warning signal, or the hearing of the wearer may be impaired, it is possible that the wearer will fail to hear the acoustic warning. When the person concerned is working in a contaminated environment or a fire environment, his/her failure to hear the acoustic warning may prevent the person from stopping work in time to ensure a safe return. Conversely, the aforesaid person may misinterpret some other sound, such as an acoustic fire warning signal, and prematurely interrupt a life-saving operation in the belief that the acoustic warning of his/her breathing apparatus has been activated. In EP-A-182 985, there is disclosed an arrangement for optically indicating that the gas pressure in a gas reservoir being connected to a breathing apparatus has reached a predetermined value, said arrangement including the gas reservoir, a gas delivery line which connects breathing apparatus with the gas reservoir, and means for producing an acoustic signal within a predetermined frequency range and at a sound level which lies above a predetermined lowest value. US-A-4 432 041 discloses an escape light to be used in conjunction with fire and/or smoke detectors. Such detectors emit a shrill alarm when activated. The lightening unit has a piezo-ceramic transducer that detects sound waves and automatically turns the escape lightning unit on if the sound that is detected by the unit is within a predetermined frequency range and is sufficiently loud. This escape light is to be used when a fire and/or smoke detector is activated. It is not intended to augment the warning of the fire and/or smoke detector but to envisage an escape way by lightening up that part of the location towards which the light is directed, especially in darkness and smoke filled rooms. The object of the present invention is to provide a complement to the acoustic warning given by the breathing apparatus with the intention of increasing the certainty of identifying the warning signal produced. In accordance with the present invention, this object is achieved with a device according to the preamble of Claim 1 which is characterized by a sound detecting unit which listens for sound within the aforesaid frequency range and at a sound level which exceeds said predetermined lowest value, and by a light source which is connected to the sound detecting unit and mounted in a visor of a protective mask of the breating apparatus. Advantageous embodiments of the invention are set forth in the Claims subsidiary to Claim 1. The present invention will now be described in more detail with reference to the accompanying drawing, the single Figure of which is a block schematic illustrating the principles of an inventive optical warning system. When the apparatus produces an acoustic signal, there is activated at the same time a light source which indicates to the wearer of the breathing apparatus that the warning signal has been sounded by his/her apparatus and which also constitutes an optical complement to the acoustic system by increasing the certainty of the warning being noticed in a highly noisy environment in which there is a risk that the person carrying the apparatus will not hear the acoustic signal. In order to activate the optical signal and the acoustic warning precisely at one and the same time, there is used a sound detecting device, e.g. a piezo electric crystal, which listens actively or passively on the sound frequency and at the sound level applicable. When the pressure in a gas reservoir has fallen to the aforesaid predetermined level at which the warning signal shall be activated, the acoustic device will produce an acoustic signal within a predetermined frequency range, e.g. 2,000-4,000 Hertz, and at a sound intensity which exceeds a predetermined strength. According to the present invention, a sound detecting device 1 is placed adjacent the source of the acoustic signal. The device 1 is connected by a line 6 to an operational amplifier 2, or may be connected directly to a flashing unit 4 by means of a line 10. A voltage U is applied across the operational amplifier 2, which amplifies the signal from the sound detecting device, said voltage being produced by a power source 3, e.g. a battery. The operational amplifier 2 is connected to the power source 3 by means of lines 7 and 8. The signal produced by the operational amplifier 2 is delivered to a flashing unit 4, for instance an IC-circuit, along a line 10. The flashing unit 4 is connected to a light source 5 by means of lines 11 and 12. The light source 5 is, for instance, a light-emitting diode (LED). According to one embodiment of the invention, the operational amplifier 2 may be connected directly to the light source 5 by lines 10, 12 and the light source 5 connected to the power source 3 by the lines 7, 11. The flashing unit 4 is omitted in this embodiment. An acoustic signal is produced when the pressure in the gas bottle has fallen to a predetermined value at which a warning shall be sounded. The described electronic device which listens, either actively or passively, for the presence of sound from the gas reservoir detects the acoustic signal and, in response thereto, the sound detecting device activates an operational amplifier (OP) which in turn activates the light source. When the operational amplifier is permitted to open a flashing circuit, the light source, e.g. a light-emitting diode, can be caused to produce an optical, flashing signal. In other cases a fixed light is obtained. The electronics are suitably embodied together with a power source in an explosion-proof housing which is screened against external sound sources by partially surrounding the acoustic warning arrangement. Suitable sound frequency and sound level are determined when constructing the warning device. The light source 5 is positioned where it can be seen by the wearer of the apparatus and also preferably where it can be seen by other people that may be present nearby. When the warning system is used together with protective equipment, the light source is preferably mounted in the visor of the protective mask worn by the person wearing the apparatus.

Claims: An arrangement for optically indicating that the gas pressure in a gas reservoir being connected to a breathing apparatus has reached a predetermined value, said arrangement including the gas reservoir, a gas delivery line which connects breathing apparatus with the gas reservoir, and means for producing an acoustic signal within a predetermined frequency range and at a sound level which lies above a predetermined lowest value, characterized by a sound detecting unit (1) which listens for sound within the aforesaid frequency range and at a sound level which exceeds said predetermined lowest value, and by a light source (5) which is connected to the sound detecting unit (1) and mounted in a visor of a protective mask of the breating apparatus. An arrangement according to Claim 1 characterized in that the light source (5) is a light-emitting diode (LED). An arrangement according to Claim 1 or 2, characterized in that the sound detecting unit (1) is a piezo electric crystal. An arrangement according to one or more of Claims 1-3, characterized in that the arrangement includes an operational amplifier (2) mounted between the sound detecting unit (1) and the light source (5). An arrangement according to one or more of Claims 1-4, characterized in that the arrangement includes a flashing unit (4) which causes the light source (5) to produce an intermittently flashing light.

Inventors: LUNDBERG MATS, LUNDBERG, MATS
Applicants: INTERSPIRO AB
Application year: 1993
Main classification: A62B9
IPC codes: A62B9