Gas shutoff apparatus

Abstract: A flow rate of a gas is measured by a flow rate measurement means, and when the flow rate exceeds a predetermined reference value, occurrence of an abnormal state such as escape of the gas is detected and a shutoff means is automatically closed by control of a micro-­ computer, furthermore, "a gas consumption pattern" showing combination of an amount of gas consumption, maximum flow rate and continuous consumption time of a consumer is observed in a predetermined time period, and a reference value of the gas consumption pattern is decided on the basis of the consumption state, moreover, a decision level of abnormal state is varied and set as a new reference values corresponding to the gas consumption pattern.

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates generally to a gas shutoff apparatus for a gas equipment using a town gas or liquefied petroleum gas, and more particularly to a gas shutoff apparatus for preventing gas explosion or gas poisoning due to a gas escape from a gas supply tube or gas equipment. 2. DESCRIPTION OF THE RELATED ART The greater part of gas accidents are caused by escape of an unburned gas such as town gas or liquefied petroleum gas (hereinafter is referred to as the gas). The gas escapes when a main cock for supplying the gas to a gas equipment is opened without burning of the gas, when unexpected disconnection of a rubber tube supplying the gas to the gas equipment occurs or the rubber tube has cracks thereon and the like. In order to prevent escape of the gas in the prior art, an automatic shutoff valve, a reinforced tube, an alarm to detect the escaped gas and an automatic gas shutoff system which is connected to the alarm are, etc., used. However, the automatic shutoff valve usually cannot be activated under a small flow rate of the escaping gas, and the escape of the gas cannot be interrupted. On the other hand, in the gas alarm, it only generates an alarm, therefore if a person is absent from there or fails to notice it, the main cock cannot be shut, and dangerous escape of the gas cannot be interrupted. Furthermore, with regard to the automatic gas shutoff system connected to the alarm, diffusion thereof to existing houses is difficult owing to its high cost and necessity of connecting construction. Moreover, the above-mentioned conventional countermeasures are not effective to gas suicide which is liable to cause gas explosion. In order to improve these defects, recently, a gas shutoff apparatus for preventing the gas explosion or gas suicide is manufactured. In such gas shutoff apparatus, a flow rate of the gas is detected, and constant and continuous flow of a lot of gas for a long time is recognized as an abnormal state by a microcomputer, for example. In the above-mentioned conventional gas shutoff apparatus, when the flow rate exceeds a predetermined total flow rate of gas equipments of a consumer, occurrence of an abnormal state is detected and supply of the gas is interrupted (shutoff function at excess of a predetermined total flow rate). In another conventional apparatus, when the flow rate greatly increases and it is detected by a gas meter, that when the increased amount is significantly larger than a predetermined flow rate increase of a gas equipment which is maximum in gas consumption an abnormal state is detected, and supply of the gas is interrupted (shutoff function at excess of a predetermined limit of increase of flow rate). In still another conventional apparatus, when the gas equipment continuously consumes gas without variation of the flow rate, and the time of continuous gas consumption with the flow rate by the gas equipment exceeds a predetermined time period which is decided corresponding to average normal consumption rate thereof, the state is detected as an abnormal state and supply of the gas is interrupted (gas shutoff function at excess of a predetermined continuous use time). The respective predetermined reference values of these "total flow rates", "limit of increase of flow rate" and "continuous use time" are decided, for example, corresponding to a rated measurement capacity in the respective gas meters (Example 1). In other example, a gas meter is designed to have plural reference values, whereby a suitable reference value selected corresponding to a flow rate of a consumer is selected (Example 2). In the above-mentioned gas shutoff apparatus, the predetermined reference value of the flow rate and the consumption time must be decided on the basis of estimation or result of investigation with respect to a total flow rate of the gas equipments and a consuming pattern of the consumer provided with the gas meter. However, such deciding of the predetermined reference values in the gas meter has problems mentioned below. 1. In gas meters having predetermined reference values of the flow rate and/or use time, it is important to select an appropriate gas meter having suitable reference values for the consumers among a number of gas meters of different characteristics, in installing the gas meter. If a gas meter of under-capacity is selected, wherein the reference values are smaller for that consumer, gas is liable to be uselessly interrupted though usage is in normal flow rate. On the contrary, if a gas meter of over-capacity of the reference values is installed, wherein the respective reference values are larger than suitable reference values for the consumer, the gas is liable to fail to be interrupted even when the interruption of the gas is required. Therefore, there is a grove problem in safety aspect. On the other hand, for manufacturer of the gas meter, in fabrication of the gas meters many designs of gas meters corresponding to the various reference values are necessary, and therefore the fabrication cost is expensive and the consumers are forced to buy expensive apparatus. Furthermore, even if a suitable gas meter has been installed, in case that an additional gas equipment is introduced by the consumer after the installation of the gas meter, the gas meter must be replaced by a suitable one. Such change of the gas meter is very troublesome to the consumers. 2. There is a proposal that a gas meter is equipped with a switch for changing over for selecting suitable reference values by switching plurality of programs having various reference values for a consumer grouped in a consuming pattern showing a type of gas consumption. In such system, an operation for selecting a program is necessary, and the respective flow rates of all gas equipments of the consumer must be measured. Classifying into many subdivisions of the consuming pattern results in that the most suitable gas meter can be mounted to each consumer. However, a large memory for memorizing many programs of the subdivided consuming patterns is required for such system, and such large capacity memory can not be satisfied by that of a microcomputer which is driven by a battery. Furthermore, a lot of switches for switching the subdivided consuming patterns are required and the switching operation thereof becomes complicated, and it is liable to be maloperated or have switch failure for a long time. Therefore, the subdivided number of the consuming patterns is to be restricted to three patterns or so in the conventional meters. GB-A-1182786 describes a method and apparatus for preventing the accumulation of an explosive amount of a gas in a chemical reactor to which the gas is fed as a reactant. The flow rate of the gas is measured and compared with a delayed flow rate signal. Reduction of flow or shut-off occurs when a predetermined difference occurs. Patent Abstracts of Japan vol. 7 no.47 (M-196)(1192) 24th February 1983 & JP-A-57195978 describes apparatus to control discharge of unburnt gas by measuring flow rate, determining average flow rate at intervals, and comparing with a standard average value, or a duration time, to issue a shut off signal when necessary. US-A-4589435 discloses a water shut-off valve which shuts off if water flows for more than a predetermined time. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to provide a gas shutoff apparatus which is adaptable to various consumers of a town gas or liquefied petorleum gas. The gas shutoff apparatus in accordance with the present invention is defined in claim 1 In the gas shutoff apparatus in accordance with the present invention, when a flow rate of the gas during an operation of the timer exceeds the maximum value memorized in advance, data in the consumption-state memory is rewritten. Furthermore, when the operation of the timer has finished, the reference value of the flow rate is changed to a new reference value corresponding to the maximum value of a flow rate memorized in the consumption-state memory. In the similar manner, the reference value of the use time period is changed to a value corresponding to data obtained in the time period of the timer. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a principle of an embodiment of a gas shutoff apparatus in accordance with present invention; FIG. 2 is a block diagram of a controller in a first embodiment; FIG. 3 is a circuitry of the controller in the first embodiment; FIG. 4(a), FIG.4(b) and FIG.4(c) show a flow chart showing an operation of the controller wherein FIG.4(c) show disposition of FIG.4(a) and FIG.4(b); FIG. 5 is a timing chart showing an operation of a timer as shown in FIG. 2; FIG. 6 is a block diagram of a controller in a second embodiment; FIG. 7 is a graph showing a relation between a time and a flow rate of the gas; FIG. 8 is a graph showing a relation between ranks of the flow rate and allowable continuous times of gas consumption in the second embodiment; FIG. 9 is a flow chart showing an operation of the controller in the second embodiment; FIG. 10 is a block diagram of a controller in a third embodiment; FIG. 11 is a block diagram of a controller in a forth embodiment; FIG. 12 is a circuitry of the controller of the forth embodiment; FIG. 13(a), FIG.13(b) and FIG.13(c) show a flow chart showing an operation of the controller of the forth embodiment wherein FIG.13(c) shows disposition of FIG.13(a) and FIG.13(b); FIG. 14 is a block diagram of a controller in a fifth embodiment; FIG. 15(a), FIG.15(b) and FIG.13(c) shown a flow chart showing an operation of the controller of the fifth embodiment wherein FIG.15(c) shows disposition of FIG.15(a) and FIG.15(b); FIG. 16 is a block diagram of a controller in a sixth embodiment; FIG. 17 is a graph showing a relation between a margin rate and a time in the sixth embodiment; FIG. 18 is a block diagram of a controller in a seventh embodiment in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.1 is a block diagram showing a principle of a constitution of a gas shutoff apparatus in accordance with the present invention. A gas equipment 33 such as a gas range or gas heater is connected to a gas supply tube 1 through a shutoff means 4 and a gas meter 2 containing flow rate measurement means 3 such as a belows type digital gas flow rate meter therein. The shutoff means such as known electromagnetic gas shutoff valve 4 is disposed between the gas supply tube 1 and the gas meter 2, and is controlled by a controller 5 such as an electronic circuit or a microcomputer receiving a flow rate signal from the flow rate measurement means 3. FIG.2 is a block diagram of a first embodiment comprising a controller 51 in the present invention. Referring to FIG.2, the flow rate measurement means 3 detects flow rate of a town gas or liquefied petroleum gas (hereinafter is referred to as the gas) flowing from the gas supply tube 1 to the gas equipment 33, and generates a flow rate signal corresponding to the flow rate. A consumption state detection means 6 detects "a consumption state" as shown from a flow rate and consumption time of the gas on the basis of the flow rate signal. "A normal condition of gas consumption" showing reference values of the flow rate and consumption time of the gas is set in an initial condition setting means 7 such as manual ten-key input device as an initial value thereof. Then, the normal condition of gas consumption is inputted in a varying means 12 of normal condition of gas consumption and is set therein. A normal condition decision means of gas consumption 8 which is e.g. a comparator or value comparation step of microcomputer outputs a shutoff signal by decision of abnormal condition when an output signal of the consumption state detection means 6 deviates from the normal condition of gas consumption. A timer 9 measures a predetermined time period by a starting signal from a starting signal generating means 10. A consumption-state memory 11 memorizes the consumption state on the basis of the flow rate signal from the flow rate measurement means 3 during an operating period of the timer 9. The varying means 12 of normal condition of gas consumption varies the normal condition of gas consumption set therein corresponding to data of the consumption-state memory 11. A shutoff signal output means 13 outputs a closing signal for closing to the shutoff means 4 on the basis of a shutoff signal from the normal condition decision means of gas consumption 8. When the timer 9 receives a starting signal by operation of the starting signal generating means 10, for example a push-button switch or an input signal from an outer device (not shown), the timer 9 starts measurement of a time period. The timer period is selected two weeks or one month, for example. Then an amount of the gas consumption, maximum flow rates of the respective gas equipments and a continuous time of the gas consumption which are measured by the flow rate signal of the flow rate measurement means 3 are memorized in the consumption-state memory 11 from start of the timer 9. A combination of the amount of gas consumption, the maximum flow rates and the continuous consumption time is commonly called as "a gas consumption pattern". Memorized data in the consumption-state memory 11 gives the gas consumption pattern. The maximum value of the gas consumption pattern is memorized in the varying means 12 of normal condition of gas consumption. The memorized data is compared with the data of the initial condition set in the initial condition setting means 7 in the varying means 12 of normal condition of gas consumption, when the counting operation of the timer 9 has finished. As a result, either smaller one of both data is elected and is set in the varying means 12 of normal condition of gas consumption as a new normal condition of gas consumption. Namely, during the counting operation of the timer 9, a consumption state showing a value of the flow rate and consumption time of the gas in the present time is monitored, comparing the consumption state with the initial condition in the normal condition decision means of gas consumption 8. After once setting of the new normal condition of gas consumption in the varying means 12 of normal condition of gas consumption, the consumption state is compared with the new normal condition of gas consumption. When a gas consumption pattern exceeds the normal condition of gas consumption, the shutoff signal is output from the normal condition decision means of gas consumption 8, and the closing signal output means 13 outputs the closing signal to the shutoff means 4. The shutoff means 4 is driven so as to interrupt the gas by the closing signal. The controller 51 is preferably constituted by a microcomputer. A detailed circuit of the controller 51 is shown in FIG. 3. Referring to FIG.3, the flow rate signal from the flow rate measurement means 3 is inputted to the interruption input terminal INT1 of the microcomputer 14. The shutoff signal is output from an output terminal O₁ and is inputted into the shutoff means 4 through a driver circuit 15. Since a battery 16 is used as a power source in the embodiment, a shutoff valve of a one shot holding type is used as the shutoff means 4. Since the shutoff valve of the one shot holding type consumes little electric power in operation thereof. A system clock oscillator 17 is connected to terminals X1 and X2 of the microcomputer 14. FIG.4(a) and FIG.4(b) show a flow chart of the microcomputer 14. The flow rate is measured by the flow rate measurement means 3 (Step A). The consumption state is detected by the consumption state detection means 6 (Step B). Operation of the timer 9 is examined by the starting signal generating means 10 (Step C). When the timer 9 is in operation, the consumption state is memorized in the consumption-state memory 11, and the consumption state is replaced with a new maximum consumption state (Step E). When the starting signal generating means 10 is not operated and the timer 9 is also out of operation, the consumption state detected by the consumption state detection means 6 is compared with the normal condition of gas consumption in the normal condition decision means of gas consumption 8 (Step D). As a result, when the consumption state is over a predetermined normal condition of gas consumption, a closing signal is output from the closing signal output means 13 (Step F and G). Meanwhile, when the consumption state is within the normal condition of gas consumption, if the varying means 12 of normal condition of gas consumption is operated (Step H), the operation of the program is returned to the Step A, and measurement of the flow rate is repeated. In case the varying means 12 of normal condition of gas consumption is not operated in the normal condition of the gas consumption, when the counting operation of the timer 9 finished, the varying means 12 of normal condition of gas consumption is operated (Steps I and J). Furthermore, the maximum value of the consumption state memorized in the memory means of consumption state 11 is compared with the initial condition of the initial condition setting means 7, and either smaller one thereof is memorized in the varying means 12 of normal condition of gas consumption (Step K). The maximum values of the consumption state are multiplied by a predetermined safety factor in an actual apparatus. After the above-mentioned varying process of the normal condition of gas consumption, a consumption state detected by the consumption state detection means 6 is compared with the modified new normal condition of gas consumption (Step D). Then, finish of the counting operation of the counter 9 is examined (Step L). When the timer 9 is in the counting operation, the flow of the flow chart is returned to the Step D through the Step M. Meanwhile, when the timer 9 has finished the time counting operation, input of a starting signal is examined (Step N). The time counting operation of the timer 9 is started by input of the starting signal (Step O). When the starting signal is not inputted, the flow of the flow chart is returned to the Step A. FIG.5 is a timing chart showing the operation of the timer 9. Referring to FIG.5, abscissa is graduated by time, and the ordinate is graduated by the normal condition of gas consumption. A starting signal is inputted to the timer 9 at a time t S , and a counting operation starts. Then, the counting operation finishes at a time t E . The gas consumption pattern is observed in the time period from the time t S to time t E as shown by hatching. The initial condition set in the initial condition setting means 7 is referred as a reference value until the time t E . After the time t E , as mentioned above, the normal condition of gas consumption is renewed in the varying means 12 of normal condition of gas consumption. The technical advantages of the embodiment in accordance with the present invention are mentioned below. The consumption state is always monitored and is compared with the normal condition of gas consumption. Therefore, when the consumption state deviates from the normal condition of gas consumption by escape of the gas or forgetting extinction of a gas stove, for example, supply of the gas is interrupted by the operation of the shutoff means. As a result, gas explosion or gas poisoning can be prevented in a preliminary stage. Furthermore, since an actual gas consumption pattern of a consumer is observed during a predetermined time period, and the consumption state is renewed by the observation data, a specific gas consumption pattern of the consumer is introduced into the gas shutoff apparatus. And safety in use of a gas equipment is further improved. FIG.6 is a block diagram of a second embodiment of the present invention. Referring to FIG.6, means having the same reference numerals as shown in FIG.2 are identical with that of FIG.2, and hence the same descriptions thereof are applied. A consumption state detection means 6 further comprises a rank discriminator 18 and a continuous operation time measurement means 19 for measuring time of nonstop operation of a gas equipment. In the embodiment, a range of flow rates of the gas is divided into plural ranks, and the rank of a flow rate is decided by the rank discriminator 18. Furthermore, the continuous operation times with respect to the respective ranks of flow rate are measured by the continuous operation time measurement means 19. Respective allowable times for continuous operation with respect to the respective ranks of flow rate are set in the initial condition setting means 7 as initial conditions. A maximum value of the continuous operation times of the respective ranks of flow rate during operation of the timer 9 are memorized in the consumption-state memory 11. When the counting operation of the timer 9 has finished, the maximum value of the respective continuous operation times with respect to the respective ranks of flow rate memorized in the consumption-state memory 11 are given to the continuous operation time measurement means 19 as data. The data of the respective ranks of the flow rate are compared with the respective allowable time set in the initial condition setting means 7, and either shorter times in respective ranks of flow rate are elected in the continuous operation time measurement means 19. The resultant continuous operation times elected as mentioned above are set in the continuous operation time measurement means 19, as new total operation times with respect to the respective ranks of flow rate. Thereafter, signal from the rank discriminator 18 is decided on the basis of the new continuous operation time. In an actual operation of the gas shutoff apparatus, the continuous operation time can be multiplied by a predetermined safety factor. FIG.7 is a graph showing a gas consumption in an actual consumer using a plurality of gas equipments. Flow rates of the respective gas equipments such as a gas heater or a gas range are generally different from each other. Referring to FIG.7, the abscissa is graduated by time and the ordinate is graduated by a flow rate. Times t₀, t₁, ... t₉ are sampling times having a predetermined constant time interval. No gas equipment is used at time t₁, and the flow rate is zero. A flow rate QA is detected at the time t₂ in the consumption state detection means 6. Then, a rank of the flow rate QA is decided and the operation time with respect to the flow rate QA is measured. Subsequently, the flow rate increases is sampled at the sampling time t₃ and the increment of flow rate QB is detected, and then an operation time with respect to the increment of flow rate QB is measured. In the similar manner, measurement of operation time with respect to the flow rate QC is commenced at the sampling time t₄. On the contrary, the flow rate decreases was measured at the sampling time t₇, and decrease by QB of a flow rate is detected. From the graph of FIG.7, it is detected that a gas equipment having the flow rate QB is operated during a time period from the time t₃ to time t₆. The respective operation time periods with regard to the uses of equipment of flow rates QA and QC are measured in the similar manner. An examples of the ranks of flow rate ranked in the rank discriminator 18 are shown in Table 1. Referring to the Table 1, the flow rate is ranked from rank 1 to rank n. The flow rate of the rank 1 is 0--21 liters per hour, and that of the rank 2 is from 21 to 210 liters per hour. Furthermore, predetermined allowable continuous consumption times with regard to the respective ranks of the flow rate are set in the initial condition setting means 7, as shown in Table 2. FIG.8 is a graph showing the allowable continuous gas consumption time periods with regard to the respective ranks of flow rate. Referring to FIG.8, ranks of flow rate are graduated on the abscissa and allowable continuous gas consumption time periods are graduated on ordinate. Horizontal lines L1 show the allowable continuous gas consumption time periods set in the initial condition setting means 7. Horizontal lines L2 show new allowable continuous gas consumption time periods, which are renewed in the varying means 12 of normal condition of gas consumption. FIG.9 is a flow chart showing operation of the second embodiment as shown in FIG.6. Referring to the flow chart, initial allowable continuous gas consumption time periods are set in the initial condition setting means 7 (Step A). A flow rate of the gas is detected (Step B). Continuous gas consumption times with respect to the respective ranks of flow rate are measured (Step C). Counting operation of the timer 9 is examined (Step D), and when the timer 9 is in counting operation, the continuous gas consumption times with respect to the respective ranks of flow rate are memorized (Step E). Then, continuous gas consumption time periods of every ranks of flow rate are measured (Step F). When the continuous gas consumption time period exceeds the allowable continuous gas consumption time period (abnormal state), the shutoff signal is output (Steps G and H). When the continuous gas consumption time period is under the allowable continuous gas consumption time period (normal state), operation of the varying means 12 of normal condition of gas consumption is examined (Step I). If the operation is finished, the step of the operation return to the Step B. If the operation of the varying means 12 of normal condition of gas consumption does not finish, finish of the counting operation of the timer 9 is examined (Step J). When the counting operation of the timer 9 has finished, the gas consumption is compared with the initial condition set the initial condition setting means 7 (Step K), and the allowable continuous gas consumption time period is refreshed (Step L). After then, the value of allowable continuous gas consumption time period which has been set in the Step L is used in the next successive continuous gas consumption time measurement in Step F. Furthermore, the step of the flow chart returns to the Step B during the while the timer continues counting operation (Steps J and M). If the timer 9 is not making counting operation, input of a starting signal is examined (Step O). When the starting signal is inputted, the timer 9 starts counting operation (Step P). Meanwhile, the step returns to Step B in the absence of the starting signal. FIG.10 is a block diagram of a third embodiment of the present invention. Referring to FIG.10, means having the same reference numerals as shown in FIG.2 are identical with that as shown in FIG.2, and hence the same descriptions thereof are applied. A threshold flow rate detecting means 20 outputs a signal when the flow rate exceeds a predetermined value. An AND gate 21 outputs a signal to the timer 9 when both the signal of the threshold flow rate detecting means 20 and the starting signal from the starting signal generating means 10 are inputted therein. The counting operation of the timer 9 is started by the output signal of the AND gate 21. The threshold flow rate is a minimum flow rate of a gas equipment provided for the consumer. In the embodiment, the counting operation of the timer 9 starts on the basis of start of operation of the gas equipment. FIG.11 is a block diagram of a fourth embodiment of the present invention. Referring to FIG.11, means having the same reference numerals as shown in FIG.2 are identical with what is shown in FIG.2, and hence the same descriptions thereof are applied. In the embodiment, after shutoff of the gas supply in the tube 1 by operation of the gas shutoff means 4, when the shutoff means 4 is opened by manual operation, a reset signal is issued from the shutoff means 4. A shutoff-means-reset-signal-detector 22 detects the reset signal. An output signal of the shutoff-means-reset-signal-detector 22 is inputted to the timer 9 through an OR gate 23. Therefore, when the shutoff means 4 is operated during counting operation of the timer 9, count of the timer 9 is cleared and operation of the consumption-state memory 11 is interrupted by the signal from the shutoff-means-reset-signal-detector 22. The signal also acts to start the timer 9 like the starting signal of the starting signal generating means 10. FIG.12 is a detailed circuitry of the controller 54 as shown in FIG.11. Referring to FIG.12, means having the same reference numerals as shown in FIG.3 are identical with what is shown in FIG.3. The shutoff-means-reset-signal-detector 22 comprises a resistor and an N-channel FET 24. A shutoff device having a permanent magnet, a magnetic coil and a spring for holding its opening state are used as the shutoff means 4, for example. In the shutoff operation of the shutoff device, an electric pulse is applied to the magnetic coil so as to generate a magnetic force having reverse magnetic pole to that of the permanent magnet. Then, the shutoff state of the shutoff device is held by the force of the spring. Reopening of the shutoff device is accomplished by manual operation, for example. In the operation, a counter electromotive force is generated in the magnetic coil, and an electric potential owing to the counter electromotive force is applied to the gate of the conjunction type N-channel FET 24 of the shutoff-means-reset-signal-detector 22. The FET 24 is in OFF state during the while the electric potential is smaller than the cutoff voltage of the N-channel FET 24. Then, an input voltage is applied to the input terminal INT 2 of the microcomputer 14, since electric potential of the output terminal O₃ of the microcomputer 14 is at high level. FIG.13(a), FIG.13(b) and FIG.13(c) show a flow chart showing an operation of the controller 54 as shown in FIG.11. Description of the steps which are identical with what is made on FIG.4 is omitted. When an abnormal state wherein a consumption state exceeds the normal condition of gas consumption is detected in Step F, the closing signal is output to the shutoff means 1 (Step O). Subsequently, the counting operation of the timer 9 is examined (Step P). When the timer 9 is in counting operation, the count of the timer 9 is cleared (Step Q). Furthermore, operation of the consumption-state memory 11 is interrupted (Step R). When the timer 9 is not in the counting operation (Step P), the Step Q and R are skipped. Subsequently, input of the reset signal is examined (Step S) and, when the reset signal is not exist the gas consumption is examined (Step U). In this state, flow in the gas supply tube 1 is closed by operation of the shutoff means 4 (Step G). But, when the flow rate is detected in spite of close operation of the shutoff means 4, the shutoff signal is issued again (Step G). Then when the flow rate is not detected, input of the reset signal is monitored (Step S). In case the reset signal has been issued, if it is examined whether the operation of the consumption-state memory 11 is interrupted or not (Step T). And when the operation of the state 11 is interrupted, the timer 9 again starts counting operation is started (Steps O). If the consumption-state memory 11 is in continuous operation, the step returns to step A and the flow rate is measured (Step A). FIG.14 is a block diagram of a fifth embodiment of the present invention. Referring to FIG.14, means having the same reference numerals as shown in FIG.2 are identical with what are shown in FIG.2, and hence the same descriptions thereof are applied. In the embodiment, a counting means 25 memorizes numbers of occurrences of the abnormal state caused at operation of the shutoff means 4, classifying with respect to the flow rate and continuous time period, respectively, after reset of a normal condition of gas consumption in the varying means 12 of normal condition of gas consumption. Furthermore, a initial condition renewing means 26 renews the initial condition in the initial condition setting means 7 on the basis of a flow rate and continuous time period in the abnormal state, when numbers counted by the counting means 25 reach a predetermined number, and operation of the timer 9 starts. FIG.15(a), FIG.15(b) and FIG.15(c) shows a flow chart showing operation of the controller 55 as shown in FIG.14. The flow rate is measured by the flow rate measurement means 3 (Step A). The consumption state is detected by the consumption state detection means 6 (Step B). The operation of the timer 9 is examined by the starter signal generating means 10 (Step C). When the timer 9 is in counting operation, the consumption state is memorized in the consumption-state memory 11, and the consumption state is always replaced with a new maximum consumption state (Step E). When the starting signal generating means 10 is not operated and the timer 9 is also not operated, the consumption state detected by the consumption state detection means 6 is compared with the normal condition of gas consumption in the normal condition decision means of gas consumption 8 (Step D). As a result, when the consumption state is over a predetermined normal condition of gas consumption, the consumption state is recognized as an abnormal state (Step F), and occurrence of the abnormal state is counted with respect to the flow rate and the continuous time period, respectively (Step P). When the consumption state is within the normal condition of gas consumption, if the varying means 12 of normal condition gas consumption is operated (Step H), the flow of the flow chart is returned to the Step A, and measurement of the flow rate is repeated. When the varying means 12 of normal condition of gas consumption is not operated in the normal condition of the gas consumption, if the counting operation of the timer 9 is finished, the varying means 12 of normal condition of gas consumption is operated (Steps I and J). Furthermore, the maximum value of the consumption state memorized in the consumption-state memory 11 is compared with the initial condition of the initial condition setting means 7, and a smaller one thereof is memorized in the varying means 12 of normal condition of gas consumption (Step K). After the above-mentioned varying process of the normal condition of gas consumption, a consumption state detected by the consumption state detection means 6 is compared with the new normal condition of gas consumption (Step D). Subsequently, finish of the counting operation of the timer 9 is examined (Step L). When the timer 9 is in the counting operation, the flow of the flow chart is returned to the Step A through the Step M. When the timer 9 has finished the counting operation, input of a starting signal is examined (Step N). The counting operation of the timer 9 is started by input of the starting signal (Step O). When the starting signal not inputted, the flow of operation is returned to the Step A. Once a decision of abnormal is made, numbers of occurrence of the abnormal states of the flow rate and continuous time is counted (Step P), and reach to a predetermined number of the occurrence is counted (Step Q). Furthermore, the initial condition set in the initial condition setting means 7 is changed by the initial condition renewing means 26 (Step S), and the closing signal is given to the shutoff means 4 in order to interrupt flow of the gas (Step G). On the other hand, when the respective numbers of occurrence of the abnormal states are far from the predetermined number, the closing signal is issued (Step G). Then, input of a reset signal is examined (Step T), when the reset signal is not inputted, the flow rate of the gas is detected (Step U). When the flow rate is not zero, the closing signal is output. When the flow rate is zero, input of the reset signal is examined (Step T). When the reset signal is output, change of the initial condition is examined (Step V), and when the initial condition has changed, the timer 9 is cleared (Step W). Moreover, the initial condition is set in the initial setting condition means 7 (Step X), and subsequently, counting operation of the timer 9 starts (Step O). When the initial condition is not set in Step V, the flow of the flow rate returns to measurement of the flow rate (Step A). As mentioned above, after setting of the new normal condition of gas consumption by operation of the initial condition renewing means 26, when the predetermined number of shutoff operations due to the same abnormal states of the flow rate and continuous time occur, a new gas consumption pattern is automatically formed, as a result of decision that the preceding normal condition of gas consumption changed by the initial condition renewing means 26 is out of order in practical use. In this manner, the embodiment of the gas shutoff apparatus is capable of coping with change of gas consumption because of addition of a gas equipment. FIG.16 is a block diagram of a controller 56 of a sixth embodiment. Referring to FIG.16, means having the same reference numerals as shown in FIG.2 are identical with that of FIG.2, and hence the same descriptions thereof are applied. The controller 56 in the sixth embodiment comprises a margin rate detector for detecting a margin rate which shown by a ratio the normal condition of gas consumption to a consumption state. When an output signal of the margin rate detector 27 deviates from a predetermined range, the timer 9 is started to observe the gas consumption pattern corresponding to the consumption state. FIG.17 is a graph showing a relation between the margin rate and lapse time. In the graph, the abscissa is graduated by a lapse time and the ordinate is graduated by the margin rate. At time t0, the normal condition of gas consumption is set, and operation of the margin rate detector 27 starts. A predetermined margin rate m is plotted by a horizontal dotted line. The margin rate is higher than the predetermined margin rate m from t0 to t1. After the time t1, the margin rate is lower than the predetermined margin rate m. The starting signal generating means 10 is operated again at the time t1, or after lapse of a predetermined time period wherein the margin rate is under the predetermined margin rate m, thereby a new gas consumption pattern is set in the varying means 12 of normal condition of gas consumption. In the above-mentioned example, the margin rate is selected to be lower than the predetermined margin rate m. But, the present invention is applicable in such a case that, on the contrary, the margin rate is exceeding a predetermined margin rate, also by using the margin rate detector 27 in accordance with the present invention. For instance, when one of the gas equipments is abandoned, the normal condition of gas consumption is reduced by the initial condition renewing means 26. As mentioned above, the normal condition of gas consumption which is suitable to an actual use can be set before operation of the shutoff means by mean of the initial condition renewing means 26 on the basis of operation of the margin rate detector 27. As a result, the consumer of the gas shutoff apparatus in accordance with the present invention can add or decrease gas equipments without occurrence of gas interruption. Furthermore, safety is assured and convenience is improved. FIG.18 is a block diagram of a controller 57 of a seventh embodiment. Referring to FIG.18, means having the same reference numerals as shown in FIG.2 are identical with that of FIG.2, and hence the same descriptions thereof are applied. In the embodiment, the controller 57 comprises an initial condition reset means 28 for returning the condition of gas consumption set by the varying means 12 of normal condition of gas consumption to the initial condition. The initial condition reset means 28 comprises a switch, for example, and is controlled by a microcomputer. Then, in case that a lot of the gas is temporarily consumed, the gas shutoff apparatus is operable without unexpected shutoff by holding the reference value, which is larger than the consumption state and reset by the initial condition reset means 28 in a predetermined time period by a timer.

Claims: A gas shutoff apparatus comprising: flow rate measurement means (3) for generating a flow rate signal corresponding to a flow rate of a gas in a gas supply tube, consumption state detection means (6) for detecting particular consumption parameters, including the current flow rate and the time elapsed since consumption of gas has commenced, on the basis of said flow rate signal, normal condition decision means (8) of gas consumption for deciding whether or not the currently detected consumption parameter is normal and for generating a shutoff signal if said consumption parameter deviates unallowably from normal consumption, initial condition setting means (7) for setting an initial normal condition of gas consumption in said normal condition decision means (8), i.e. a normal allowable maximum flow rate signal and a normal allowable maximum period of consumption, shutoff means (4) for interrupting said gas supplying pipe line by said shutoff signal, timer means (9) for measuring a predetermined time period, during which a consumption pattern is to be monitored, said pattern comprising data as to maximum flow rate occurring during said period and longest time of consumption during said period, starting signal generating means (10) for starting said timer, consumption-state memory (11) for memorizing said consumption pattern on the basis of said flow rate signal during operation of the timer, and varying means (12) for varying said normal condition of gas consumption in said normal condition decision means (8) if said consumption parameter is larger than the initially stored value. A gas shutoff apparatus in accordance with claim 1, wherein said consumption state detection means (6) detects an amount delivered by of one or more gas equipments, and a value corresponding to an allowable total amount is set in the initial condition setting means as an initial value, and furthermore said consumption-state memory (11) also memorizes the current total amount delivered. A gas shutoff apparatus in accordance with claim 1, wherein the data of the flow rate stored in said consumption-state memory (11) is renewed with a flow rate of the gas equipment consuming a maximum amount of gas detected by said consumption state detection means (6) during operation of said timer (9). A gas shutoff apparatus in accordance with claim 1, wherein said consumption state detection means (6) further comprises a rank discriminator (18) for dividing a predetermined range of said flow rate into plural ranks and deciding a rank of a flow rate, and continuous gas consumption time measurement means (19) for measuring continuous using times with respect to the respective ranks, and allowable continuous gas consumption time periods with respect to the respective ranks are set in the initial condition setting means as initial conditions, and said continuous consumption time periods with regard to the respective ranks are memorized in the consumption-state memory during operation of the timer. A gas shutoff apparatus in accordance with claim 4, wherein said consumption-state memory (11) memories simultaneously the continuous consumption time periods of the respective ranks of the flow rate. A gas shutoff apparatus in accordance with claim 1, wherein said timer (9) starts counting operation when a flow rate signal exceeding a predetermined value is inputted after input of a starting signal of said starting signal generating means (10). A gas shutoff apparatus in accordance with claim 1 further comprising: a shutoff-means-reset-signal-detector (22) for detecting opening operation of the shutoff means (4) closed by shutoff signal, wherein; when the shutoff means (4) is closed during counting operation of the timer (9), the timer (9) is cleared and operation of the consumption-state memory (11) is stopped and a signal of the shutoff-means-reset-signal-detector is given to the timer (9) as a starting signal. A gas shutoff apparatus in accordance with claim 1 further comprising; counting means (25) for memorizing a number of occurrence of abnormal states with respect to the respective flow rates and continuous times after reset of normal condition of gas consumption in the varying means of normal condition of gas consumption, and initial condition renewing means (26) for starting said timer and resetting an initial condition on the basis of said respective flow rates and continuous times. A gas shutoff apparatus in accordance with claim 1 further comprising; margin rate detector (27) for detecting a margin rate showing a ratio said normal condition of gas consumption to a consumption state, wherein; said timer (9) is started to observe a gas consumption pattern corresponding to said respective flow rates and continuous time periods when output signal of said margin rate detector deviates from a predetermined range. A gas shutoff apparatus in accordance with claim 1 further comprising; initial condition reset means (28) for changing the consumption state set in the varying means of normal condition of gas consumption to said initial condition.

Inventors: ASANO KAZUTAKA, NAKANE SHINICHI, UNO TAKASHI, ASANO, KAZUTAKA, NAKANE, SHINICHI, UNO, TAKASHI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1987
Main classification: G01F1
IPC codes: G01F15, F23N5, G08B17