CHECKING THE OPERATION OF BREATHING EQUIPMENT

Abstract: The invention relates to a method of checking the working and/or the state of breathing equipment prior to its use, and also to an arrangement for carrying out the method. The breathing equipment includes a control circuit which, in turn, includes a programmed microprocessor (7), a sensor (10) mounted in the breathing equipment and connected to the microprocessor, and an indicating arrangement (11) connected to the microprocessor (7). The inventive method is characterized by activating the control circuit and therewith measuring or determining at least one functional or state parameter, comparing the measured parameter value with a control value, and indicating an acceptable or unacceptable value in the indicating arrangement (11).

Description: CHECKING THE OPERATION OF BREATHING EQUIPMENT The present invention relates to a method of checking the working and/or the operational state of breathing equipment prior to its use, and also to breath- ing equipment which includes an arrangement for checking at least one working or state parameter of the equipment. It is absolutely necessary to ensure that the breathing equipment used by a diver or a fireman, for instance, is fully serviceable and faultless prior to enter¬ ing non-breathable atmospheres, for instance when diving or when working in smoke-filled or toxic environment for instance. Among other things, it is necessary to check that the system gas-supply is completely full and therewith contains the amount of breathing gas that can be expected to be consumed, that the hoses leading to the breathing mask are tightly sealed, i.e. will not leak to the surroundings and therewith reduce the amount of gas available for breathing, that gas is able to flow from the gas res¬ ervoir freely and without hinder and will arrive at the breathing mask in sufficient volumes, i.e. that there is practically no resistance to the air flow and that the pressure prevailing in the breathing mask is higher than ambient pressure. The gas reservoir carried by the person concerned will normally have the form of a gas cylinder which contains breathing gas at a pressure of normally 300 bars, when the cylinder is full. The breathing gas is normally air, although under special circumstances may often contain at least 20 percent by volume oxygen and an inert gas, most often nitrogen and perhaps also helium. In some cases, for instance for diving to great depths, the breathing gas contains less than 20 percent oxygen by volume. Since the gas reservoir has a relatively small volume, it is important that the reservoir pressure is sufficiently high to supply the user with an anticipated maximum gas volume. It is also important that the hoses or lines leading from the gas reservoir are tight and that the flow resistance presented thereby is sufficiently small for the gas reservoir to deliver to the user a quantity of gas which is large enough to satisfy the user's requirements, even in the case of an extreme need, is extreme. Another important safety problem concerns the gas pressure in the mask when the mask is in place. The mask pressure must be greater than the ambient pressure, so that non-breathable atmosphere, particularly toxic atmosphere, is unable to penetrate into the mask. One object of the present invention is to provide a method whereby these functions and/or states can be checked prior to using breathing equipment. Another object of the invention is to provide an arrangement by means of which at least one functional parameter or state parameter of breathing equip¬ ment can be checked prior to use. The first of these methods is achieved in accordance with the invention with a method which is characterized by activating a control circuit which meas¬ ures at least one functional parameter or state parameter, comparing the meas¬ ured parameter value with a control value and indicating acceptable or insuffi¬ cient values respectively when the set criterion is fulfilled or when it is not ful¬ filled. The second object is achieved with an arrangement which includes breathing equipment, a programmed microprocessor, a sensor which is included in the breathing equipment and connected to the microprocessor, and an indicat¬ ing arrangement connected to the microprocessor. Advantageous embodiments of the present invention are set forth in the dependent Claims. According to the present invention, the control circuit is activated either by sensing intermittently a functional parameter or a state parameter of the breathing equipment, comparing the sensed parameter value with the latest measured parameter value, and activating the control circuit when there is a significant difference between these values. Another method to activate the control circuit is to intermittently sense a functional parameter or a state parame¬ ter of the breathing equipment, to compare the sensed parameter value with a predetermined value, e. g. 10 percent, of the maximum value of said parameter and to activate the control circuit when the sensed parameter is equal to or greater then the predetermined value. Alternatively, the control circuit is acti¬ vated manually, by pressing a start button for instance. The present invention will now be described in more detail with reference to the accompanying drawing, in which Fig. 1 is a block schematic illustrating breathing equipment provided with a control circuit for carrying out a functional test; and Fig. 2 is a diagram which illustrates primary pressure as a function of time when carrying out a functional test. The breathing equipment 16 includes a gas reservoir, which is usually a gas cylinder or gas container 1 containing breathing gas, for instance air or an oxygen-containing gas which includes most frequently at least 20 percent by volume oxygen and an inert gas, for instance nitrogen or helium, at a pressure of normally 300 bars when the container is completely full. The gas container 1 includes an outlet opening in which there is mounted a closure valve 2. The gas container 1 is connected to a primary pressure regulator 4, through the medium of the closure valve 2. A line 3 extends from the primary pressure regulator 4 to a secondary pressure regulator 5 which is located immediately upstream of a breathing mask 6. The pressure regulator 4 is set to reduce the pressure in the gas con¬ tainer 1 to typically about 7 bars in the line 3 downstream of the primary pressure regulator, i.e. the first regulator 4, and the second pressure regulator 5 is set to reduce the pressure of the gas passing to the breathing mask 6 still further, to a pressure of about 25 mm water column, i.e. to a pressure suitable for use in the mask 6. As the wearer breathes, the pressure in the mask will oscillate around this value during a breathing phase, therewith constantly maintaining an overpressure. The pressure regulator 5 is normally a requirement-controlled regulator which is closed prior to putting on the mask 6 and is opened by the subpressure that is generated when the wearer first inhales. The regulator 5 is opened when the relative pressure in the mask 6 falls beneath a preset value. It is necessary to activate other similar regulators manually, through separate activating means. A pressure sensor 10 is mounted in a space 12 formed between the clo¬ sure valve and the primary pressure regulator 4. This sensor 10 measures the pressure in the space 12 and is connected to a microprocessor 7 by means of a line 8. Lines 9 extend from the microprocessor 7 to an indicating arrangement 11 which is preferably, but not necessarily, mounted in the breathing mask 6. The indicating arrangement 11 includes at least one indicating device. Preferably, at least one indicating device is provided for each function included in the functional test. The indicating device is preferably a light-emitting diode (LED). The indicating arrangement 11 provided in the breathing mask 6 is preferably visible to the user, both when the mask 6 is worn and when removed, and will also be visible to people in the vicinity of the user. The breathing mask 6 included in the breathing equipment is preferably also provided with a differential pressure meter 14, which is connected to the microprocessor 7 by means of a line 15. The measured differential pressure is indicated in an indicating device by the indicating arrangement 11. Accordingly, the mask 6 of the illustrated breathing equipment is provided with a differential pressure meter 14 which is connected microprocessor 7 by a line 15. The measured differential pressure is indicated in the indicating arrangement 11 , visible to the user with the mask 6 fitted. According to the present invention, the lines 9 and 15 may be replaced with cordless connections between the microprocessor 7 and the indicating ar- rangement 11 and between the microprocessor and the differential pressure meter 14 respectively. The microprocessor 7 is programmed to carry out some or all of the func¬ tions described below. According to a third embodiment, the microprocessor senses the pressure in the space 12 intermittently, for instance every second or at some other chosen frequency, through the medium of the sensor 10, and compares the sensed pressure with the pressure that was last sensed. Alterna¬ tively, the microprocessor senses the pressure in the space 12 intermittently, for instance every second or at some other chosen frequency, through the medium of the sensor 10, and compares the sensed pressure value with a predetermined pressure value, for example 10 percent of the maximum pressure in the gas container 1. According to the invention, before testing the breathing equipment, the closure valve 2 is opened to an extent at which the space 12 is under the same pressure as the container 1 , whereafter the valve 2 is closed. The pressure in the space 12 increases as gas from the container 1 flows into the space. As the valve 2 is opened, the sensor 10 will deliver a much higher pressure value to the microprocessor 7. The microprocessor 7 receives the start signal required to carry out the functional diagnosis and state diagnosis in accordance with the in- vention in conjunction with the pressure comparison that automatically takes place. According to another embodiment, the microprocessor is fitted with a start button which replaces the start signal obtained when a marked pressure in¬ crease is obtained after each alternate sensed pressure value when the closure valve 2 is opened. It is also necessary in this case to open the closure valve to an extent in which the pressure in the space 12 will at least substantially equal the gas pressure in the container 1 , whereafter the valve is closed. In order for the test to provide the information required, it is necessary for the primary pressure valve 4 to be set so that a suitable pressure will be ob- tained in the line 3. Furthermore, the secondary pressure regulator 5 must be closed prior to opening the valve 2. Figure 2 illustrates the gas pressure in the proximity of the sensor 10 as a function of the time at which the test was carried out. None of the axes is graduated. Position 0 shows the relative pressure at the sensor 10 prior to starting the test. When the closure valve 2 is opened, the pressure in the space 12 will rise to the pressure of the gas reservoir, as illustrated at position 1 , and there is obtained in the line 3 a pressure which is contingent on the setting of the regulator 4, this pressure being 7 bars in the illustrated case. The valve 2 is then closed. The pressure that now prevails in the line 3 is not shown in Figure 2. The microprocessor 7 senses the pressure prevailing in the space 12 after a maximum pressure has been reached, i.e. after position 1 , for instance at posi¬ tion 2. If the pressure is below a first control value, for instance a value within the range of 97 to 80 percent, particularly a value in the vicinity of 90%, for instance a value in the range of 95% to 85%, particularly about 90% of the full pressure in the gas reservoir 1 , the microprocessor will understand this to mean that the gas supply does not fulfil the necessary pressure criterion and indicate in the indicating arrangement 11 an insufficiency value, said arrangement preferably being mounted in the mask 6. The indicating arrangement 11 indicates an acceptable value, when the pressure exceeds or is equal to the control value. The present functional test also includes ensuring that the line leading to the mask 6, i.e. the second pressure regulator 5, is tight and will not leak gas to the surroundings. To this end, the sensor 10 measures the pressure after a pre- determined time period, for instance 3-20 seconds, from the time at which pres¬ sure was measured in position 2 in Figure 2. The duration of this time lapse will depend on the level of accuracy desired. This pressure is measured before po¬ sition 3. When the pressure difference between the pressure measured at posi¬ tion 2 and the pressure measured before position 3 is greater than a second control value, the indicating arrangement 11 will indicate an insufficiency value. When the pressure difference is lower than or equal to the control value, the in¬ dicating arrangement will indicate that the value is acceptable. After testing the equipment for tightness, i.e. leakage, a check is made to ensure that the line 3 to the mask 6 is not blocked or that the supply of gas to the mask 6 through the regulator 5 is not hindered in some other way. To this end, the regulator 5 is opened with the mask 6 removed, so that the gas present between the closure valve 2 and the regulator 5 is able to flow freely to atmo¬ sphere, the valve 2 still being closed, and the pressure decrease in the space 12 is measured as a function of time, with the aid of the sensor 10. One criterion of acceptable outflow or function is found in the time taken for the pressure to fall to a% of the original pressure, for instance the pressure that prevailed prior to opening the second regulator, from (b-a)%, where b is a value greater than a. and equal or less than 100, for example 50, and a may be 10 for instance. When this time duration is equal to or smaller than a third control value, the indicating arrangement 11 will indicate an acceptable value; in other cases, an unacceptable value will be indicated. This is shown in Figure 2, where position 3 indicates that the second regulator 5 is open so that the gas content of the equipment downstream of the closure valve is able to flow freely from the system. Position 4 indicates that the pressure has fallen to a value of (100 -a)% of the pressure prevailing at position 3. Position 5 indicates that the pressure has fallen to a%. When the time, t5-t4, is shorter than or equal to the third control value, the function of the equipment with regard to gas supply is considered to be fully acceptable. Another criterion for acceptable gas outflow, or function, is one in which the pressure that prevails after opening the second regulator 5 is measured after a predetermined time interval. If, when measured, it is found that the pressure has fallen to the same value as a predetermined highest value or to a lower value, during this time period, the microprocessor 7 will indicate, via the indicat¬ ing arrangement 11 , that the supply of gas to the mask 6 is acceptable. Other¬ wise, the indicating arrangement 11 will indicate that the equipment is faulty. This second criterion is also shown in Figure 2. In this case, the pressure is measured from the time of opening the second regulator 5, i.e. at position 3, and is compared with a fourth control value, for instance at position 5 for the sake of simplicity. If the pressure at time point t5 exceeds a predetermined pres¬ sure, P5, the ordinate at position 5, the indicating arrangement 11 will indicate a malfunction. Naturally, the pressure decrease as a function of time can be measured in other ways. For instance, the derivative of the pressure curve can be measured as a function of time at the curve inflection point. The derivative, i.e. the directional coefficient of the curve, is then a measurement of the outflow rate. Another important function of the equipment resides in checking that the control circuit (10, 7, 8, 9, 11 ) works satisfactorily. Accordingly, the indicating ar- rangement 11 will indicate the functional state of the control circuit (10, 7, 8, 9, 11) when measuring the pressure after having changed the pressure in the re¬ gion where the sensor 10 acts. A malfunction is indicated if this does not take place. Another important function is that the face mask 6 fits tightly to the user's face and that when breathing with the closure valve 2 open a relative overpres¬ sure with regard to ambient atmosphere is maintained in the space between the mask 6 and the wearer's face. Accordingly, the closure valve 2 is opened after carrying out the aforedescribed tests, and a check is optionally made to ensure that the primary pressure regulator 4 is set to the correct setting. After having put on the mask 6, the regulator will open automatically as the user breathes in, or is opened manually if the regulator should be closed or switched-off. The breathing mask 6 includes a sensor 14 which measures the differ¬ ence between the pressures that prevail inside and outside the mask 6. Should the pressure between the mask 6 and the face of the wearer be greater than the pressure prevailing outside the mask during at least one breathing cycle, the indicating arrangement 11 will indicate a positive pressure, i.e. a fully acceptable function. Otherwise, the indicating arrangement will indicate a non-acceptable function. According to one preferred embodiment, serviceable equipment is indicat¬ ed when all tests have shown an acceptable result. The use of the equipment is prevented when one or more tests show an unacceptable result. However, according to one preferred embodiment, the equipment can be used when the gas reservoir has been filled to a higher pressure than a predetermined lowest pressure, wherein the indicating arrangement 11 will indicate that the reservoir pressure is lower than the lowest recommended value for a full gas reservoir. However, use of the equipment is prevented, or blocked, when the pressure in the gas reservoir is lower than a lowest predetermined pressure value, for instance 20 percent of maximum pressure. The microprocessor is powered by a small source of electric current, for instance by one or more batteries. The indicating arrangement will also preferably indicate the remaining operational time or useful life of the current source. If the remaining operational time is lower than a predetermined operational time, this is indicated in the indicating arrangement. According to another preferred em¬ bodiment, the equipment includes a registering device which is associated with the control circuit. This device registers each activation of the control circuit and the results of the tests and functional checks carried out after each activation. An active or a passive memory unit connected to the microprocessor is one ex- ample of such registering devices. This registration enables subsequent checks to be made to ascertain the number of times the equipment has been tested and the results obtained in conjunction therewith.

Claims: Claims 1. A method of checking the function and/or state of breathing equipment (16) prior to its use, characterized by activating a control circuit (7-11 , 14, 15) which measures or determines at least one functional or state parameter of the equipment, comparing the measured parameter value with a control value, and indicating an acceptable or unacceptable value. 2. A method according to Claim 1 , characterized by registering each acti- . vation of the control circuit and the result derived thereby. 3. A method according to Claim 1 or 2, characterized by sensing intermit- tently a functional parameter or state parameter of the breathing equipment (16), comparing the sensed value with a latest measured value, and activating the control circuit (7-11 , 14, 15) when a significant difference exists between the values. 4. A method according to Claim 1 or 2, characterized by sensing intermit- tently a functional parameter or state parameter of the breathing equipment (16), comparing the sensed value with a predetermined value, and activating the con¬ trol circuit (7-11 , 14, 15) when a significant difference exists between the values. 5. A method according to Claim 3 or 4, wherein the breathing equipment (16) includes a gas reservoir (1 ) provided with an outlet opening, a closure valve (2) mounted in the reservoir outlet opening, a line (3) in which there is included sequentially, as seen from the closure valve (2), a primary pressure regulator (4), a second regulator (5) and a breathing mask (6), characterized by measuring the pressure between the closure valve (2) and the first pressure regulator (4) as a first functional or state parameter. 6. A method according to Claim 5, wherein the second pressure regulator (5) is closed and the closure valve (2) is then opened and then closed, character¬ ized by measuring the pressure between the closure valve (2) and the first pressure regulator (4) over a predetermined time interval, determining the pres¬ sure decrease during said time interval, and indicating an acceptable value when the pressure decrease is smaller than a first control value or an unacceptable value when the pressure decrease is equal to or greater than a first control value respectively. 7. A method according to Claim 5, wherein the second pressure regulator (5) is closed and the closure valve (2) is thereafter opened and then closed, characterized by opening the second pressure regulator (5) after closing the closure valve (2) so as to empty the space (12) between the closure valve (2) and the first pressure regulator (4) of gas, measuring the pressure in the space (12) as a function of time, and indicating an acceptable or an unacceptable value when, after a predetermined time period, the pressure decrease (negative slope) is greater than a second control value and equal to or smaller than a second control value, respectively. 8. A method according to Claim 5, wherein the second pressure regulator (5) is closed and the closure valve (2) is thereafter opened and then closed, characterized by opening the second pressure regulator (5) after closing the closure valve (2) so as to empty the space (12) between the closure valve (2) and the first pressure regulator (4) of gas, measuring the pressure in the space (12) a second predetermined time period after opening the second pressure regulator (5), and indicating an acceptable or an unacceptable value when the pressure value less than a third control value and equal to or smaller than a third control value, respectively. 9. A method according to one or more of Claims 1 -8, characterized by indicating functioning of the control circuit (7-11 , 14, 15) when said circuit is activated in response to opening the closure valve (2). 10. A method according to one or more Claims 1-9, characterized by indi¬ cating an acceptable result when all tests have resulted in fully acceptable values, or by indicating an unacceptable result when at least one test has shown an unacceptable value. 11. A method according to Claim 5, characterized by indicating a fully acceptable result when the pressure is equal to or higher than a predetermined pressure value within the range of 97 to 80 percent of maximum pressure, pref¬ erably within the range of 95 to 85 percent of maximum pressure. 12. An arrangement for checking at least one functional parameter or state parameter of breathing equipment (16), characterized by a programmed microprocessor (7), a sensor (10) which is included in the breathing equipment (16) and connected to the microprocessor (7), and an indicating arrangement (11) connected to the microprocessor (7). 13. An arrangement according to Claim 12, characterized in that the arrangement also includes a registering device which registers each activation of the control circuit and the results that derive from checks carried out in response to this activation. 14. An arrangement according to Claim 12 or 13, in which the breathing equipment (16) includes a gas reservoir (1) having an outlet opening, a closure valve (2) mounted in the reservoir outlet opening, a line (3) which includes sequentially, as seen from the closure valve (2), a first or a primary pressure regulator (4), a second pressure regulator (5), and a breathing mask (6), char- acterized in that the sensor (10) is mounted in the space (12) between the closure valve (2) and the primary pressure regulator (4). 15. An arrangement according to Claim 12, 13 or 14, characterized in that the indicating arrangement (11 ) is mounted in the breathing mask (6) and is visible to the user and also to people in the vicinity of the user; and in that the indicating arrangement (11) includes at least one light-emitting diode (LED). 16. An arrangement according to one or more of Claims 12-15, character¬ ized in that the breathing equipment (16) includes a second pressure sensor (14) which measures the difference in pressure between the pressures prevailing inside and outside the mask (6); and in that the second sensor (14) is connected to the indicating arrangement (1 1 ) through the microprocessor (7).

Inventors: LUNDBERG MATS, LUNDBERG, MATS
Applicants: COMASEC INTERNATIONAL SA, LUNDBERG MATS, COMASEC INTERNATIONAL S.A., LUNDBERG, MATS
Application year: 1995
Main classification: A61M16
IPC codes: A61M16, A62B27, B63C11