EP1307683A1

EP1307683A1 - Carbon dioxide fire extinguishing device

Info

Publication number: EP1307683A1
Application number: EP01969584A
Authority: EP
Inventors: Thomas Andreas
Original assignee: Luxembourg Patent Co SA
Current assignee: Luxembourg Patent Co SA
Priority date: 2000-08-10
Filing date: 2001-08-10
Publication date: 2003-05-07
Anticipated expiration: 2021-08-10
Also published as: US6836217B2; DE50102278D1; US20040164868A1; JP2004505699A; EP1307683B1; RU2266464C2; LU90629B1; CN1446296A; AU2001289797A1; JP4751007B2; WO2002012781A1; CN1230647C

Abstract

The invention relates to a carbon dioxide fire extinguishing device comprising a capacitive measuring device (11) which is calibrated for a temperature range above and below the critical temperature of carbon dioxide and which is used to detect the amount of gas loss from a carbon dioxide pressure tank (10). The carbon dioxide fire extinguishing device comprises an outlet valve in which the capacitive measuring probe (12) is integrated in such an advantageous way that the outflow resistance of the extinguishing gas is hardly increased at all.

Description

Carbon dioxide fire extinguishing device.

The present invention relates to a carbon dioxide fire extinguisher.

State of the art

For fire extinguishing devices with gaseous extinguishing media, it is mandatory that the pressure vessel in which the extinguishing medium is stored under pressure is checked for gas losses. With carbon dioxide pressure cylinders, it must be ensured that a gas loss of more than 10% of the filling weight is reliably detected. Portable carbon dioxide fire extinguishers are weighed during their periodic inspection using a calibrated scale. Between two checks, a gas loss therefore goes unnoticed. In stationary carbon dioxide fire extinguishing systems, the carbon dioxide pressure bottles hang individually in a weighing device so that the weight of each individual carbon dioxide pressure bottle is continuously monitored. If the weight falls below a specified value, an alarm is triggered. Such weighing devices for hanging the carbon dioxide pressure bottles make the stationary fire extinguishing devices significantly more expensive. They must also be calibrated at regular intervals.

So far, there has been no satisfactory alternative to weighing the carbon dioxide pressure bottles.

Pressure monitors are completely unsuitable for determining a gas loss from a carbon dioxide pressure bottle, with a usual fill ratio of 1: 1.50 (ie a fill weight of 0.666 kg carbon dioxide per liter bottle volume), a gas loss below a temperature of 27 ° C 10% no longer causes a significant drop in pressure in the bottle (with a filling ratio of 1: 1, 34, ie a filling weight of 0.746 kg carbon dioxide per liter bottle volume, this lower temperature limit is even around 22 ° C). In addition, the pressure in the carbon dioxide pressure bottle is strongly temperature-dependent. Even level gauges with floating bodies have not been able to establish themselves as an alternative to weighing the carbon dioxide pressure containers, at least in the case of fire extinguishing devices. A valve with an integrated level meter with a float, as is known, for example, from the patent specification US-A-4,580,450 for a carbon dioxide pressure bottle, cannot be used in carbon dioxide fire extinguishing systems because accommodating the rod of the level meter in the valve base takes up a lot of space and as a result the inlet hole for the gas in the valve base must be relatively small. In this context, it should indeed be noted that carbon dioxide pressure cylinders for stationary carbon dioxide fire extinguishing devices only have an internal thread W 28.8 x 1/14 "according to DIN 477 in their bottle neck. A valve base must be screwed into this internal thread should have an inlet hole for the extinguishing agent with a diameter of at least 12 mm so that the carbon dioxide can flow into the valve with a low pressure loss after the fire extinguishing device has been triggered.

From US-A-5,701,932, for gas cylinders with high-purity gases, a gas cylinder valve with a built-in capacitive level measuring device is known as an alternative to a mechanical level measurement with a float. The capacitive level measurement described in US Pat. No. 5,701,932 is based on the principle that the liquid phase of a gas has a dielectric constant which is far higher than the gaseous phase, so that a decrease in the liquid level in the pressure bottle results in a reduction in the capacity of the Precipitates the probe. This measuring principle therefore presupposes that the measurement is carried out at a predetermined ambient temperature, at which it is ensured that there are two separate phases in the pressure bottle and that the liquid level in the pressure bottle decreases if gas is removed from the pressure bottle. In contrast to the application for high-purity gases described in US Pat. No. 5,701,932, however, this is by no means always the case with a carbon dioxide pressure bottle for the fire extinguishing area. Indeed, in fire extinguishers, carbon dioxide pressure bottles are used, among other things, in machine rooms for object protection, with ambient temperatures easily reaching over 40 ° C can be. Now with a filling ratio of the carbon dioxide pressure bottle of 1: 1.50 (ie 0.666 kg carbon dioxide per liter bottle volume), the liquid phase of the carbon dioxide takes up the entire bottle volume from a temperature of 27.2 ° C, so that above this temperature a gas loss no longer necessarily causes a change in the liquid level in the pressure bottle. In addition, the critical temperature of the carbon dioxide, from which the carbon dioxide forms a supercritical fluid, since there is no longer any difference between a gaseous and a liquid phase, is already at 31 ° C. Furthermore, it should be noted about the valve with the capacitive level measuring device from US Pat. No. 5,701,932 that it is also unsuitable for carbon dioxide pressure bottles in fire extinguishing devices, also for fluidic reasons. In fact, in a valve base with a W 28.8 x 1/14 "screw-in thread, the installation of the capacitive measuring probe takes up so much space that there is no space left for an inlet bore of at least 12 mm in diameter for the carbon dioxide extinguishing gas Obtaining space for such a 12 mm inlet bore in the valve base could of course reduce the diameter of the capacitive measuring probe, but one would have to accept stability problems of the measuring probe, which are not the responsibility of a safety-relevant element.

Object of the invention

The present invention is therefore based on the object in a carbon dioxide fire extinguishing device to reliably check the carbon dioxide pressure container for gas losses, both at low and at high ambient temperatures, without weighing. This object is achieved according to the invention by a device according to claim 1.

General description of the invention

In a carbon dioxide fire extinguishing device according to the invention Detecting a gas loss from the carbon dioxide pressure vessel uses a capacitive measuring device that is calibrated for a temperature range below and above the critical temperature of the carbon dioxide. In other words, the present invention is based on the surprising finding that a capacitive measuring device can measure changes in the liquid level in the pressure vessel not only in a known manner, but also above the critical temperature of the carbon dioxide, ie when there is no longer any physical difference between the gaseous and the liquid phase of the carbon dioxide, a measurable change in capacity can be clearly assigned to a gas loss from the pressure vessel. In this way, a simple solution for detecting gas loss from a carbon dioxide pressure container of a fire extinguishing device is provided, which can also be used at high ambient temperatures (ie temperatures above 30 ° C.) and makes complex weighing of the pressure container unnecessary.

Such a capacitive measuring device preferably comprises: a capacitive measuring probe which extends over the entire height of the pressure container, a measuring module for measuring the capacitance of the capacitive measuring probe, a microprocessor for processing the measured capacitance measured values, which assigns a corresponding gas loss to a measured capacitance change, and means for Generate an alarm message if the gas loss determined by the microprocessor exceeds a specified value.

Calibration is preferably carried out electronically, e.g. a temperature sensor and a memory with calibration values for a temperature range below and above the critical temperature of the carbon dioxide are used. Depending on the temperature, the microprocessor uses the calibration values in the memory to assign a corresponding gas loss to a measured change in capacity. If the calculated gas loss exceeds a specified value, the microprocessor generates an alarm.

Such a device is ideal for checking the gas content of carbon dioxide pressure bottles, both at high and at low ambient temperatures. It is therefore particularly suitable for use in carbon dioxide fire extinguishing devices where the ambient temperature can be between -20 ° C and + 60 ° C. In order that this device can also be used in a carbon dioxide fire extinguishing device in combination with a carbon dioxide pressure bottle, the present invention has additionally solved the problem of introducing the capacitive measuring probe into the carbon dioxide pressure bottle so cheaply through the narrow bottle neck that the outflow resistance of the extinguishing gas is hardly enlarged from the pressure bottle. For this purpose, the present invention has created an outlet valve for a carbon dioxide pressure bottle with an integrated capacitive measuring probe, a first measuring electrode being formed by a riser pipe which opens into the valve base and a second measuring electrode being formed by an electrode pipe which connects the riser pipe to a Intermediate gap surrounds along its entire length. This outlet valve finally provides a simple, reliable and inexpensive way to check portable carbon dioxide fire extinguishers for gas loss more easily and more often, or to avoid complex weighing devices for carbon dioxide pressure bottles in stationary carbon dioxide fire extinguishing devices. It should be emphasized in particular that such an outlet valve with a measuring probe can have approximately the same outflow resistance as a flow-optimized outlet valve without a measuring probe. The capacitive measuring probe, in which the riser tube forms an inner measuring electrode, is characterized by excellent stability even with large pressure cylinders.

Versions of this valve are also presented, in which the electrical connection to the capacitive measuring probe is solved in a particularly space-saving and trouble-free manner.

In a first embodiment, an insulating sleeve surrounds the first end of the riser pipe in the inlet bore of the valve base and electrically isolates it from the conductive valve base. Is in the inlet bore of the valve base this first end of the riser pipe is then in electrical contact with a contact element which is electrically insulated from the conductive valve base. The outer electrode tube, on the other hand, is in electrical contact with the conductive valve base and is electrically connected via the latter. The first end of the riser pipe advantageously has an annular end face as a contact surface for the insulated contact element, so that to establish a reliable electrical connection between the insulated contact element and the riser pipe, the latter only has to be pressed axially onto the contact element in the inlet bore of the valve base , An insulated contact element suitable for this first embodiment advantageously comprises a contact ring with approximately the same inside and outside diameter as the ring-shaped contact surface of the riser pipe, and an insulating ring with a larger outside diameter than the contact ring. This insulating ring lies with an end face on a shoulder face in the inlet bore and has a recess in the other end face into which the contact ring is fitted. In this version, a large-area, trouble-free contact between the riser pipe and the contact element is guaranteed, while at the same time an electrical short circuit is reliably prevented.

In this first embodiment, the valve base advantageously has a connection channel, which forms an opening in the aforementioned shoulder surface, against which the insulating ring lies in the inlet bore. The insulating ring then in turn has an annular groove in the end face, which rests on this shoulder surface, the opening of the channel in the shoulder surface opening into this annular groove, and a through-bore of the insulating ring extending from the annular groove to the contact ring. In this embodiment, an insulated connecting wire is then firmly connected with a first end to the contact ring and is inserted into the connecting channel through the through-hole and the annular groove of the insulating ring. The ring groove prevents the connecting wire from being sheared off if the contact element is twisted in the inlet bore. The second end of the aforementioned connecting wire is firmly connected to an externally accessible connecting element, the latter being sealed and inserted in an electrically insulated manner in a bore in the valve base. The conductive valve base makes electrical contact with the outer electrode tube. The electrical contact between the outer electrode tube and the valve base can then be established via an annular end face of the outer electrode tube, which is pressed against an annular end face of the valve base.

In this first embodiment, one end of the insulating sleeve preferably protrudes from the bore of the valve base and is used to fasten the outer electrode tube. In an advantageous embodiment, this electrode tube is e.g. screwed onto this end of the insulating sleeve such that its annular end face is firmly pressed against the annular end face of the valve base. Here, the insulating sleeve thus fulfills the function of an electrical insulator between the riser pipe and valve base, an insulating spacer between the riser pipe and the outer electrode tube and a fastening and pressing device for the outer electrode pipe. Due to this multifunctional sleeve, a minimum of individual parts is required for the installation of the two measuring electrodes. The insulating sleeve can furthermore have an electrically conductive outer wall, via which the valve base and the outer electrode tube are electrically connected to one another. This further improves the electrical contact between the valve base and the outer electrode tube.

In an alternative embodiment of the measuring electrode, the upper end of the riser pipe is screwed into the inlet bore of the valve base. An upper insulation sleeve is pushed onto the upper end of the riser pipe. A lower fastening sleeve is screwed onto the lower end of the riser pipe, the screwed fastening sleeve axially pressing the outer electrode tube against the upper insulation sleeve. The upper insulation sleeve is advantageously pressed against an end face of the valve base. A preferred embodiment of the lower fastening sleeve comprises a metallic core body which is screwed onto the lower end of the riser tube and an insulator which is arranged between the metallic core body and the outer electrode tube. Description based on the figures

An embodiment of the invention will now be described below with reference to the accompanying figures. Show it:

1: a block diagram of an exemplary structure of a carbon dioxide fire extinguishing device according to the invention; 2 shows a longitudinal section through an outlet valve of a carbon dioxide fire extinguishing device with an integrated device for determining a gas loss from the connected carbon dioxide pressure bottle, a first embodiment of a riser pipe being shown as a capacitive measuring probe; 3 shows an enlargement of the framed detail I from FIG. 2; and FIG. 4: an enlargement of the framed detail II from FIG. 2. FIG. 5: a longitudinal section through a further embodiment of a riser pipe which is designed as a capacitive measuring probe; and FIG. 6: a longitudinal section along section line 6-6 through the riser pipe of FIG. 5.

In Fig. 1, reference numeral 10 denotes a carbon dioxide pressure bottle of a carbon dioxide fire extinguishing device. This carbon dioxide pressure bottle is filled, for example, with a filling ratio of 1: 1.50 with carbon dioxide, which corresponds to a filling weight of 0.666 kg carbon dioxide per liter bottle volume. At a temperature of -20 ° C, the pressure bottle 10 is 62.8% filled with liquid carbon dioxide. At a temperature of + 20 ° C, the volume fraction of the liquid phase is 82%. At a temperature of 27.2 C, the pressure bottle is finally 100% filled with liquid carbon dioxide. From a temperature of 31 ° C (= critical temperature of carbon dioxide) there is no longer any physical difference between liquid and gaseous carbon dioxide, ie there is no longer a transition between a gaseous and liquid phase of carbon dioxide. It should be noted that the pressure in the pressure bottle increases from 19 bar at -20 ° C to 170 bar at + 60 ° C. 1 shows the carbon dioxide pressure bottle 10 with a essen device for detecting a gas loss from the pressure bottle 10, which is globally designated by the reference numeral 11. This device 11 comprises a capacitive measuring probe 12, which is composed of two electrodes. The latter extend over the entire height of the pressure bottle 10 and are separated from one another by an intermediate gap in which the carbon dioxide forms a dielectric. Note that: (1) at temperatures below 27.2 ° C, the dielectric in the upper part of the gap is formed by gaseous carbon dioxide (at 20 ° C, the measuring probe 10 is, for example, 82% immersed in liquid carbon dioxide, while the remaining 18 % are surrounded by gaseous carbon dioxide); (2) at temperatures between 27.2 ° C and 31 ° C the dielectric is formed in the entire intermediate gap by liquid carbon dioxide; and (3) at temperatures above 31 ° C, the dielectric is formed in the entire intermediate gap by supercritical carbon dioxide. The principle of operation of the device 11 is based on the surprising one

Recognition that a capacitive measuring device can not only measure changes in the liquid level in the pressure vessel 10 in a known manner, but that a measurable change in capacitance of the measuring probe 12 can also be clearly assigned to a gas loss of a few percent from the pressure vessel 10 if: a) the pressure vessel 10 is filled 100% with liquid carbon dioxide, and thus a gas loss of a few percent no longer necessarily causes a change in the liquid level in the pressure bottle; and b) the critical temperature of the carbon dioxide (31 ° C) is exceeded, and the carbon dioxide thus forms a supercritical fluid by not forming one

Difference more between a gaseous and a liquid phase there.

This functional principle of the device 11 is preferably implemented as follows. The capacitive measuring probe 12 is connected to a measuring module 14, which measures the capacitance of the capacitive measuring probe 12 and forwards its measured values to a microprocessor 16. In a memory module 20, on that the microprocessor 16 has access, calibration values for a temperature range below and above the critical temperature of the carbon dioxide are stored. The ambient temperature is recorded by means of a temperature probe 18. The microprocessor 16 calculates, based on the measured temperature and the calibration value for this temperature, the carbon dioxide content of the pressure bottle 10 and compares this calculated carbon dioxide content with the target content of the pressure bottle. If a gas loss is detected that exceeds a predetermined value, the microprocessor 16 generates an alarm message which is displayed, for example, by means of an optical and / or acoustic alarm module 22. In this way, a simple device for detecting gas loss from a carbon dioxide pressure vessel is created, which can also be used at high ambient temperatures.

2 shows an outlet valve 30 of a stationary carbon dioxide fire extinguishing device into which a capacitive measuring probe 12 is integrated. The upper part 31 of the outlet valve 30, which comprises a triggering device, is only indicated in FIG. 2, since it is not important for the understanding of the present invention.

The outlet valve 30 comprises a valve body 31 with a valve base 32 with an external thread 34, with which it is screwed into the bottle neck of a carbon dioxide pressure bottle. It should be noted here that the carbon dioxide pressure bottles used in stationary fire extinguishing devices only have a W 28.8 x 1/14 "thread according to DIN 477 in their bottle neck for screwing in the valve base 32, ie that the valve base 32 has relatively limited space An inlet bore 36 is arranged within the valve base 32, into which a riser pipe 38 axially opens, and this riser pipe 38 extends into the vicinity of the bottle bottom. Note that in a stationary carbon dioxide fire extinguishing device, the inlet bore 36 in the valve pedestal 32 and the like Riser pipe 38 must have at least an inner diameter of 12 mm, so that it is ensured that after the fire extinguishing device has been triggered, the extinguishing gas has a sufficiently low pressure loss via the riser pipe 38 into the Exhaust valve 30 can flow.

The capacitive measuring probe 12 is formed in the outlet valve 30 of FIG. 2 by the riser pipe 38 and by an outer electrode pipe 40 which surrounds the riser pipe 38 with an intermediate gap 42. In other words, the capacitive measuring probe 12 comprises two coaxial tubular electrodes, the riser tube 38 forming the inner electrode and the electrode tube 40 forming the outer electrode. The annular intermediate gap 42 between the two electrodes 38 and 40 is occupied by liquid, gaseous or supercritical carbon dioxide, which forms a dielectric between the two electrodes 38 and 40.

Annular spacers 44, 44 'made of an insulating material, the wall thickness of which corresponds to the width of the intermediate gap 42, are each attached to the riser 38 by means of a pair of locking rings 46, 46' and ensure that the annular intermediate gap 42 between the two electrodes over the entire length the measuring probe 12 remains constant. It should be noted that the spacers 44, 44 'have local flats 45, 45' so that the carbon dioxide can flow along the spacers 44, 44 'into the intermediate gap 42. Reference number 48 denotes a ventilation opening at the upper end of the outer electrode tube 40, which ensures that the liquid level and the pressure in the intermediate gap 42 and the pressure bottle always match.

The installation of the measuring probe 12 in the valve base 32 is now described in more detail with reference to FIG. 3. An insulating sleeve 50 is screwed onto the upper end of the riser 38. This insulating sleeve 50 comprises at its upper end a first external thread 52 with which it is screwed into an internal thread 52 ′ in a bore in the valve base 32. The lower end of the insulating sleeve 50 protrudes from the bore of the valve base 32 and is provided with a second external thread 54. The upper end of the outer electrode raw rs 40 is screwed onto this second external thread 54 in such a way that its end face 56 is pressed firmly against an end face 58 of the electrically conductive valve base 32 and thus in electrical contact with it stands. It should be emphasized that the insulating sleeve 50 consequently fulfills the function of an electrical insulator between the riser pipe 38 and the valve base 32, an insulating spacer between the riser pipe 38 and the outer electrode pipe 40 and a fastening and pressing device for the outer electrode pipe 40. Due to this multifunctional sleeve, a minimum of individual parts is required for the installation of the two measuring electrodes 38, 40. It should also be noted that the insulating sleeve 50 can also have an electrically conductive outer wall, via which the valve base 32 and the outer electrode tube 40 are electrically connected to one another. This further improves the electrical contact between valve base 32 and outer electrode tube 40.

The reference numeral 60 designates a contact ring which has approximately the same inside and outside diameter as the end face 62 of the riser pipe 38. This contact ring 60 is fitted into a recess in a first end face of an insulating ring 64. The latter has the same inside diameter, but a larger outside diameter than the contact ring 60 and lies with its second end face on a shoulder face 66 in the inlet bore 36. By screwing the riser pipe 38 into the valve base 32 using the insulating sleeve 50, the end face of the riser pipe 38 is pressed firmly against the contact ring 60, so that a reliable electrical connection between the riser pipe 38 and the contact ring 60 is established. In summary, it remains to be seen that the riser pipe 38 is in extensive contact with the contact ring 60 in the inlet bore 36 of the valve base 32, the contact ring 60 being reliably isolated from the conductive valve boss 32 by the insulating ring 64.

The reference numeral 70 denotes a connection channel in the valve base 32, which forms an opening in the shoulder surface 66, against which the insulating ring 64 rests in the inlet bore 36. The insulating ring 64 has an annular groove 72 in the end face, which rests on the shoulder surface 66, the opening of the connecting channel 70 opening into this annular groove 72. A through hole 74 of the insulating ring 64 extends from the annular groove 72 to the contact ring 60. An insulated connecting wire 76 is connected to the contact with a first end. ring 60 firmly connected and inserted through the through hole 74 and the annular groove 72 of the insulating ring 64 into the connection channel 70. The annular groove 72 prevents the connecting wire 76 from being sheared off if the contact ring 60 is rotated in the inlet bore 36. The description will now be continued with reference to FIG. 4. The connecting wire 76 is firmly connected to a rod-shaped connecting element 78. The latter is inserted in a sealed manner into a conical insulating sleeve 80, which in turn is pressed into a conical bore 84 in the valve body in a sealed manner by means of a clamping screw 82. 4, a circuit board with an electronic circuit is shown, which is fitted into a chamber 92 of the valve body. A screw plug 94 closes the chamber 92 and at the same time fixes the circuit board 90 in the chamber 92. The circuit board 90 is connected to the riser pipe 38 via the connecting element 78, which, as is known, forms the first electrode of the capacitive measuring probe 12. The circuit board 90 is connected to the outer electrode tube 40 via the electrically conductive valve housing, which, as is known, forms the second electrode of the capacitive measuring probe 12. A plug 96, which is inserted in a sealed manner into a connecting socket in the screw plug 94, enables the circuit board 90 to be connected to external circuits or external current sources via a connecting line 98.

The measuring module 14, the microprocessor 16, the temperature probe 18 and the memory module 20 are accommodated on the board 90. An alarm message is either forwarded to an external alarm module or a central monitoring network via the connection line 98. 5 and 6, the riser 38 'is screwed at one end into the inlet bore 36 of the valve base 32, whereby the electrical contact between the valve base 32 and the riser 38' is made directly. The reference numeral 110 denotes an upper insulation sleeve which is pushed onto the riser pipe 38 'and abuts the end face 58 of the valve base 32 via an end face 112. One end of the outer electrode tube 40 'is placed on the lower end of the upper insulation sleeve 110. pushed and rests with its upper end face on a shoulder surface 114 of the upper insulation sleeve 110. A fastening sleeve 116 is screwed onto the lower end of the riser pipe 38 '. The latter has a cylindrical end 118 which is inserted into the lower end of the outer electrode tube 40 '. When tightening the fastening sleeve 116, an annular pressing surface 120 is supported on the lower end face of the electrode tube 40 'in order to axially press the latter with its upper end face onto the shoulder surface 114 of the upper insulation sleeve 110, which in turn has its end face 112 against the end face 58 of the valve base 32 is pressed. The lower fastening sleeve 116 advantageously comprises a metallic one

Core body 122, in which the internal thread for screwing onto the riser pipe 38 ′ is formed, and an insulation sleeve 124, which is placed on the metallic core body 122 and avoids electrical contact between the outer electrode tube 40 and the metallic core body 122. As an alternative to the insulation sleeve 124, the metallic core body 122 can also be coated with an insulating material. As a further alternative to the insulation sleeve 124, a fastening sleeve can be used which is made entirely of an insulating material. However, the solution with a metallic core body 122 is characterized by greater mechanical strength in the event of large temperature fluctuations and is therefore preferred. As in the embodiment of FIG. 2, at least one annular spacer 44 made of an insulating material ensures that the annular intermediate gap 42 between the two tubes remains constant over the entire length. Reference numeral 130 in Fig. 5 denotes a locking pin which in one

Bore is screwed into the end face 58 of the valve base 32 and engages in a recess in the upper insulation sleeve 110 in such a way that it blocks the latter against rotation. A pierced locking pin 132 is advantageously used as a cable entry. Here, an insulated connection cable 134 is inserted through a cable duct 136 in the valve base 32 through the pierced locking pin 132 into an outer recess 138 of the insulation sleeve 110, where it is connected in an electrically conductive manner to the outer electrode tube 40 '. that is.

Reference numerals 140, 142 in FIG. 5 denote lateral openings in the lower and upper ends of the outer electrode tube 40 '. These openings 140, 142 ensure that the intermediate gap 42 is in direct connection with the interior of the bottle.

It should be noted that although the present invention has only been described in connection with the detection of gas loss from a carbon dioxide pressure vessel, it is of course also applicable to other gases which have properties similar to carbon dioxide.

Claims

claims

A carbon dioxide fire extinguishing device comprising: a carbon dioxide pressure bottle (12) for storing extinguishing agent; a device for detecting gas loss from the carbon dioxide pressure bottle (12); characterized in that the device for determining a gas loss from the carbon dioxide pressure bottle (12) comprises a capacitive measuring device (11) which is calibrated for a temperature range below and above the critical temperature of the carbon dioxide.

2. The apparatus of claim 1, comprising: a capacitive measuring probe (12) which extends over the entire height of the pressure vessel (10); a measuring module (14) for measuring the capacitance of the capacitive measuring probe (12); a microprocessor (16) which assigns a corresponding gas loss to a measured change in capacity; and

Means for generating an alarm message if the gas loss determined by the microprocessor exceeds a predetermined value.

3. The apparatus of claim 2, comprising: a temperature sensor (18); and a memory module (20) with calibration values for a temperature range below and above the critical temperature of the carbon dioxide, the microprocessor (16) depending on the temperature using these calibration values in order to assign a corresponding gas loss to a measured change in capacity.

4. The apparatus of claim 1, 2 or 3 comprising: an outlet valve (30) with a valve base (32) for screwing onto a carbon dioxide pressure bottle (10), this valve base (32) having an inlet bore (36); a riser pipe (38) which opens into the inlet bore (36) of the valve base (32) so that the carbon dioxide gas flows into the outlet valve (30) via the riser pipe (38) after the fire extinguishing device has been triggered; and a capacitive measuring probe (12) comprising two coaxial electrodes, the riser tube (38) forming the first electrode, and the second electrode being formed by an outer electrode tube (40) which connects the riser tube (38) with an intermediate gap ( 42) surrounds.

5. The device according to claim 4, characterized by: an insulating sleeve (50) which surrounds the end of the riser pipe (38) in the inlet bore (36) and electrically insulates it from the conductive valve base (32); a contact member (60, 64) in the inlet bore (36) of the valve base (32) that is electrically isolated from the conductive valve base (32) and is in electrical contact with the first end of the riser tube (38); the outer electrode tube (40) being in electrical contact with the conductive valve base (32).

6. The device according to claim 5, characterized in that the riser pipe (38) has an annular end face (62) as a contact surface for the insulated

Contact element (60, 64).

7. The device according to claim 6, characterized in that the insulated contact element (60, 64) comprises the following parts: a contact ring (60) with approximately the same inside and outside diameter as the ring-shaped contact surface (62) of the riser pipe (38); and an insulating ring (64) with a larger outer diameter than the contact ring (60), which rests with one end face on a shoulder face (66) of the inlet bore (36) and has a recess in the other end face into which the contact ring (60) is fitted.

8. The device according to claim 7, characterized by: a connecting channel (70) in the valve base (32) which forms an opening in the shoulder surface (66) on which the insulating ring (64) rests; an annular groove (72) in the end face of the insulating ring (64) which rests on this shoulder surface (66), the opening of the connecting channel (70) opening in the shoulder surface (66) opening into this annular groove (72); a through bore (74) of the insulating ring (64) from the annular groove (72) to the contact ring (60); and an insulated connecting wire (76) which is fixedly connected with a first end to the contact ring (60) and is inserted into the connecting channel (70) through the through-hole (74) and the annular groove (72) of the insulating ring (64).

9. The device according to claim 8, characterized by an externally accessible first connection element (78), which is inserted in a sealed and electrically insulated manner in a bore in the valve base (32) and to which the second end of the connection wire (76) is firmly connected.

10. Device according to one of claims 5 to 9, characterized in that the outer electrode tube (40) has an annular end face (56) which is pressed onto an annular end face (58) of the valve base (32).

11. The device according to claim 10, characterized in that one end of the insulating sleeve (50) protrudes from the bore of the valve base (32) and the electrode tube (40) is screwed onto this end of the insulating sleeve (50) such that its annular end face is firmly pressed onto the annular end face of the valve base (32).

12. Device according to one of claims 5 to 11, characterized in that the insulating sleeve (50) is screwed into the inlet bore (36).

13. The device according to claim 10, characterized in that a first end of the insulating sleeve (50) is inserted into the inlet bore (36). is screwed and the second end of the insulating sleeve (50) protrudes from the inlet bore (36); that the outer electrode tube (40) is screwed onto the second end of the insulating sleeve (50); and that the insulating sleeve (50) has an electrically conductive outer wall, via which the valve base (32) and the outer electrode tube (40) are electrically connected to one another.

14. Device according to one of claims 5 to 13, characterized in that the riser pipe (38) is screwed into the insulating sleeve (50).

15. The apparatus according to claim 4, characterized in that: the riser pipe (38) is screwed with its upper end into the inlet bore (36) of the valve base (32); an upper insulation sleeve (110) is pushed onto the upper end of the riser pipe (38 '); a lower mounting sleeve (116) on the lower end of the riser

(38 ') is screwed on, the screwed fastening sleeve (116) axially pressing the outer electrode tube (40') against the upper insulation sleeve (110).

16. The apparatus according to claim 15, characterized in that: the upper insulation sleeve (110) is pressed against an end face (58) of the valve base (32).

17. The apparatus of claim 15 or 16, characterized in that the lower fastening sleeve (116) comprises: a metallic core body (122) which is screwed onto the lower end of the riser pipe (38 '); and an insulator disposed between the metallic core body (122) and the outer electrode tube (40 ').