Abstract:
The present invention relates to a gas-detecting unit for detection of CO 2  and an alarming unit, said gas-detecting unit and said alarming unit being integrated to comprise one device, and wherein said device is adapted to withstand harsh environments and cleaning of the device.

Description:
TECHNICAL FIELD 
     The present invention relates to a device adapted to detect and warn of the presence of CO 2 . 
     PRIOR ART 
     CO 2  alarm systems of the prior art are produced in compliance with German law, with a pre-alarm and a main alarm, where the pre-alarm issues a warning at 1.5% Short Time Exposure Limit (STEL), and the main alarm issues a warning at 3% STEL. This type of life-saving alarm warns that it is not advisable, or even fatal, for a person to enter the room. 
     Normally, a sensor is placed in the room where CO 2  may occur, such as in a beer cellar, and a central unit is placed outside the room. The central unit warns of the presence of CO 2  in the room so that a person may know whether or not the premises can be entered without the risk of exposure to CO 2 . 
     Because CO 2  is heavier than the normal mixture of gases in the air, the alarm is placed in a non ventilated closed room, such as a wine or beer cellar. In such a room, the sensor is to be placed near the ground. Under German law, the sensor is to be placed 30 cm from the floor. Some manufacturers recommend placement 1 m from the floor. It is normally placed such that it is not damaged by activity in the room, such as damage by beer kegs in a beer cellar, where it might be placed 50 cm from the floor for this reason. 
     It is also known that during the kerosene combustion process, for example for heating, CO production starts at 9000 ppm CO 2  as combustion deteriorates at higher CO 2  concentrations. 
     SUMMARY OF THE PRESENT INVENTION 
     Technical Problems 
     Considering the prior art, such as it has been described above, there is a technical problem to provide a device for the detection and warning of CO 2  in harsh environments, such as environments with abundant water, grease or other substances that may affect the device. 
     There is a technical problem to provide a device for detection and warning of CO 2  that can easily be cleaned, without the device being thereby adversely affected. 
     There is a technical problem to provide a device for detection and warning of CO 2  which emits with simple means a strong audible signal in conjunction with a warning. 
     There is a technical problem to provide detection and warning of the presence of CO 2  in rooms continuously used as a working environment. 
     There is a technical problem to measure the presence of CO 2  in a room with ventilation, open windows or doors, and where people move in and through the room. 
     There is also a technical problem to simplify a device and thereby make it more economically affordable so that it can be practically useful for the public as a device or system for the detection of CO 2 . 
     There is also a technical problem to provide an economically affordable device that is practically useful for the public as a device or system for the detection of CO. 
     The Solution 
     With the intention of solving one or more of the aforesaid technical problems, the present invention provides that a system for monitoring the CO 2  is placed in the immediate work environment, meaning adapted for e.g. the kitchen, meaning directly in the room where occupants work with CO 2  and adapted for the environment. 
     It is proposed that a device according to the present invention is an integrated unit in which both the gas-detecting unit with gas cell for detection of CO 2  and the alarming unit are integrated in one device. The alarming unit may comprise a light-emitting means for generating a flashing light and an audible means for generating an audible signal. 
     A device according to the present invention has an exterior casing which faces the room and is sealed to withstand fluid exposure in conjunction with cleaning or liquids present in the environment, as well as grease or oil. In order to allow for gas exchange into the gas cell active inside the unit, a portion of the casing which faces the unit&#39;s base opens for gas exchange but closes by means of interacting diagonal wall portions to prevent liquid from entering the unit. 
     According to one proposed embodiment of the present invention, these interacting wall portions are truncated cones of different sizes which face one another to form a system of wall portions through which no fluid can pass, while forming a sound amplification system of cones that produces a megaphone-like effect for the audible signal, and whereby gas flows easily for gas exchange in the gas cell. 
     A system of interacting truncated cones may, for example, comprise one first cone with its smaller opening facing in towards the device, the gas cell and the audible means; and its larger opening facing the base of the unit and a second cone, the second cone being larger than the first cone. This second cone may be open at its larger opening, which faces the first cone, and closed at its smaller opening, which faces the base of the unit. This closed portion creates a seal towards the base and a surface for a fastener for the unit. A third cone which is larger than the first and second cones is located above the first cone, with its larger opening facing, like the first cone, towards the second truncated cone. The smaller part of the third cone is closed by means of sealing between the third cone and the first cone. 
     The three cones overlap one another somewhat on the outer edge on the large end of the three cones, so that together they form inclined wall portions which prevent the possibility of liquid entering the gas cell, allow for gas exchange in the gas cell, and form the sound amplification system for the audible signal. 
     The first and third cones are integrated in the sealed casing of the device, while the other cone forms part of the attachment of the device to a base. 
     A first fastener is adapted to provide a fixed but removable attachment between the second cone and the sealed casing. The first fastener may comprise for example a screw joint in which the second cone is allocated a number of lug holes through which screws can be screwed and connect to threaded bores in the sealing casing. These threaded bores can, for example, be located on the first cone, the third cone, or on the sealing between the first and third cones. 
     The second cone can be allocated a second fastener adapted for interaction with a fastening plate, wherein the fastening plate is adapted to be secured to the base, and wherein the second fastener is adapted to a fixed but easily removable interaction between the second cone and the fastening plate. The second fastener may consist, for example, of a bayonet mount. 
     It is proposed that at least one portion of the casing which faces away from the base be transparent in order to let the flashing light through inside the casing; and that the transparent portion be of a colour which gives the warning light a colour appropriate for a warning signal. 
     In this way, both an audible signal and a light signal can be easily generated by the device according to the present invention. 
     This device can be adapted to issue various levels of alarm which can be determined by local legislation, for example, or ACGIH recommendations, which are accepted in the majority of countries in the world. 
     For example, a first level may be of the order of 5000 ppm Time Weighted Average (TWA) and a second level of the order of 1 to 3% STEL, where the first level warns of danger after prolonged exposure, but where the first level may be harmless in the event of short-term exposure; and where the second level warns of danger even in the event of short-term exposure. There might be, of course, only one or more than two levels of alarm. 
     An example of an additional alarm level is a third level that may be relevant in rooms where some form of kerosene combustion takes place, for example for heating or cooking. The present invention provides a third level set at 9000 ppm CO 2 , since kerosene combustion deteriorates at higher concentrations of CO 2 , resulting in CO accumulation. This third level is thus intended as a warning of CO accumulation. 
     An alarm system according to the present invention is a leak alarm, unlike life-saving alarms of the prior art, whereby the leak alarm warns of a change in the room environment. Such a room can be a working or living environment where there is a need to monitor dangerous levels of CO 2  and/or CO. The present invention can be adapted for use in various industrial premises and in workplaces such as restaurant kitchens, and also for private use, such as in homes, holiday homes, caravans and boats. 
     The invention thus provides that the sensor and warning indicator must be integrated in one unit, unlike the prior art where the sensor is located in one room while the alarming unit is located in another room. The device according to the present invention is to be placed and is to operate in an environment meeting statutory requirements for ventilation where air movement is created by human motion. It is therefore proposed that the device be installed at head height of the occupants of the room, and it is possible for a plurality of devices to be connected and installed in the same room. 
     It is proposed that a warning at the first alarm level could consist of the integrated flashing light, and that the warning at the second alarm level could consist of an audible signal from the integrated siren, which can also emit a unique clicking sound that would be less disruptive to surrounding rooms than the siren. 
     Prior art systems for CO 2  measurement are large, and if they are to be integrated into a device and installed according to the present invention, they would be very large and bulky. In order to provide an integrated unit that can easily be installed at head height in a working environment without being bulky, a CO 2  detector adapted to be of sufficiently small size for such an integration is required. It is proposed that a gas sensor be used that is adapted for CO 2  detection through absorption of infrared light, a so-called infrared sensor. A possible sensor unit which is sufficiently small to be used with the present invention is described and illustrated in the Swedish patent application SE 0901378-0, entitled “A Measuring Cell Adapted to Spectral Analysis” by the applicant SenseAir AB. 
     The device according to the present invention can be adapted for fixed installation, preferably against a wall. 
     The device according to the present invention includes components which are normally operated at 12 to 24 volts. Such an operating voltage can be obtained by connecting the device to the public grid and by the device also comprising an integrated transformer which supplies the necessary voltage. It is also possible to use an external transformer connected to the public grid that supplies the required voltage to the device. No matter which voltage supply method is chosen, it is proposed that the connection to the public grid be secured with some type of lock, such as a “plug-lock” so that the operating voltage to the device is not disconnected accidentally. It is also possible to use internal battery operation, such as a so-called ultracapacitor, in the device. It is also possible to operate a device according to the present invention, or charge the ultracapacitor for a device according to the present invention, with light cells. 
     A method according to the present invention consists of measuring CO 2  in the room in which persons/people are working and of the alarming unit being placed in this room to directly issue the alarm to the occupants of the room. 
     It is also possible to provide a first interface for communication, wherein an external alarm signal can be issued to the areas outside the monitored room. It is also possible to provide a second interface for communication, an interface for digital communications, whereby it is possible to communicate with the device for service purposes and if one wishes to keep a log of the measured gas concentrations. Both the first and the second interfaces for communication may consist of a wired or a wireless interface. There is nothing to prevent the first and second interfaces from consisting of a shared interface, such that only the second interface exists, but that it is also adapted for communication of an external alarm signal. The device according to the present invention can thus be included in a system of a plurality of devices where various rooms can be monitored from a central position from which it is possible to communicate with devices comprised by the system. 
     Advantages 
     The advantages that foremost may be regarded as characteristic of a method and device according to the present invention is that in this way, the CO 2  concentration can be measured continuously in a room/working environment occupied by people working or living, and this with one or more small, simple integrated devices that comprise both a gas-measuring unit and an alarming unit. The device is simple to manufacture, can be manufactured in a cost effective manner and can also easily be installed in rooms where it is important to monitor the CO 2  concentration to thereby monitor the working or living environment of the room. There is also a possibility to monitor dangerous levels of CO in rooms where incomplete combustion of kerosene, for example, takes place with small devices adapted to both industrial use and private use such as in homes, holiday homes, caravans and boats. 
    
    
     
       FIGURE DESCRIPTION 
       A device and method having characteristics associated with the present invention are shown schematically in the accompanying drawing in which: 
         FIG. 1  schematically and in a greatly simplified manner shows an alarm system for CO 2  according to the prior art, 
         FIG. 2  schematically and in a greatly simplified manner shows a device according to the present invention, 
         FIG. 3  shows a cross section of a device according to the present invention; 
         FIG. 4  shows a perspective representation of the device according to the present invention, and 
         FIG. 5  shows schematically and in a greatly simplified manner a system of interacting devices. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference being made to the figures, a device according to the present invention will now be described. 
       FIG. 1  shows schematically and in a greatly simplified manner an alarm system for CO 2  according to the prior art whereby the sensor  11  is located inside a room A and the alarm unit  12  is located outside the room A to warn of the danger of entering the room A due to the presence of CO 2  in the room A. 
       FIG. 2  shows schematically and in a greatly simplified manner a device  21  according to the present invention comprising a gas-detecting unit  22  for the detection of CO 2  and an alarming device  23  integrated into device  21 . The device  21  is located in room A′ and thus can measure the environment in room A′ and warn the persons  24  who are occupying and working or living in room A′. 
       FIG. 3  shows a cross section of the exterior casing  32  which faces the room and belongs to device  31 . Casing  32  is sealed to withstand exposure to liquids. In order to allow an exchange of gas  33  to the gas cell  34  active within the unit, a portion of the casing  32  which faces the base  35  of the device is open for gas exchange, but closed by means of interacting inclined wall portions  36 ,  37  and  38  which prevent liquid from entering the unit. 
     These interacting wall sections may consist of truncated cones of different sizes which face one another to form a system of wall portions through which no fluid can pass, while forming a sound amplification system of cones that produces a megaphone-like effect for the audible signal, and whereby gas flows easily for gas exchange in the gas cell. 
     In the embodiment according to figure there are a first  36 , a second  37  and a third  38  interacting cones. 
       FIG. 4  shows schematically a first fastener  41  adapted to provide a fixed but removable attachment between the second cone  42  and the sealed casing  43 . This first fastener  41  consists in the exemplary figure of a screw joint whereby the second cone  42  is allocated a number of lug holes  41   a ,  41   b ,  41   c  through which screws can be screwed and connected to threaded bores in the sealing casing  43 . These threaded bores can, for example, be located on the first cone, the third cone, or, as is shown more clearly in  FIG. 3 , such that the threaded bore is located in a mount  39 ′ which in turn is located in the seal  39  between the first and third cones  36 ,  38 . 
       FIG. 4  also shows that the second cone  42  may be allocated a second fastener  44  adapted for interaction with a fastening plate  45 , where the fastening plate is adapted to be attached to the base. The second fastener  44  is adapted for a firm but easily removable interaction between the second cone  42  and fastening plate  45 . The second fastener may, for example, as is shown in the figure, comprise a bayonet mount with a first bayonet section  44   a  and a second bayonet section  44   b  adapted for interaction, whereby an interacting fastener  35   a  is shown in  FIG. 3 . 
       FIG. 5  shows that a device  51  according to the present invention can be adapted to communicate using a first communication interface  52  and/or a second communication interface  53 , whereby the first interface  52  is adapted to transmit an external alarm signal to the area A 2  outside of the monitored room A 1 . 
     The second interface for communication  53 , an interface for digital communication, through which it is possible to communicate with the device  51  for service purposes and, if one wishes, to keep a log of the measured gas concentrations. 
     Both the first and the second interface  52 ,  53  for communication may comprise a wired interface or a wireless interface  54 . There is nothing to prevent the first and second interfaces from consisting of a shared interface, such that only the second interface exists, but that it is also adapted for communication of an external alarm signal. 
     The device according to the present invention can thus be included in a system of a plurality of devices  51 ,  55  in which different rooms A 1 , A 2  can be monitored from a central position  56  from which it is possible to communicate with the devices  51 ,  55  comprised by the system. 
     The invention is of course not limited to the above exemplary embodiments, but may undergo modifications within the scope of the concept according to the present invention as defined by the following claims.