GB1592506A - Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere - Google Patents
Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere Download PDFInfo
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- GB1592506A GB1592506A GB50355/77A GB5035577A GB1592506A GB 1592506 A GB1592506 A GB 1592506A GB 50355/77 A GB50355/77 A GB 50355/77A GB 5035577 A GB5035577 A GB 5035577A GB 1592506 A GB1592506 A GB 1592506A
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- 239000000203 mixture Substances 0.000 title claims description 45
- 230000000712 assembly Effects 0.000 claims description 38
- 238000000429 assembly Methods 0.000 claims description 38
- 238000012544 monitoring process Methods 0.000 claims description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 12
- 229910052710 silicon Inorganic materials 0.000 claims description 12
- 239000010703 silicon Substances 0.000 claims description 12
- 230000007257 malfunction Effects 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 49
- 239000004020 conductor Substances 0.000 description 16
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 230000000007 visual effect Effects 0.000 description 3
- 206010065929 Cardiovascular insufficiency Diseases 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display
- G01N33/0063—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display using a threshold to release an alarm or displaying means
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
- G08B17/117—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means by using a detection device for specific gases, e.g. combustion products, produced by the fire
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Combustion & Propulsion (AREA)
- Food Science & Technology (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Emergency Alarm Devices (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Description
(54) ELECTRICAL CIRCUITRY FOR DETECTING A COMBUSTIBLE MIXTURE
OF GAS IN A MINE ATMOSPHERE
(71) We, CONSOLIDATION COAL
COMPANY, a corporation organised and existing under the laws of the State of Delaware, United
States of America, of One Oliver Plaza,
Pittsburgh, Pennsylvania 15222, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
This invention relates to electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere.
In underground mining operations solid material is dislodged from the mine face by the operation of cutting machines and as a consequence methane gas is emitted from the rock strata. The gases may accumulate in pockets in the mine presenting a threat of explosion in the presence of a spark. Only by monitoring the concentration of the mixture of gases in the mine atmosphere is it possible to determine whether the mixture of gases has reached a critical concentration.
One method of monitoring the mixture of combustible gases in the mine atmosphere involves the use of a conventional flame safety lamp. The accuracy of a flame safety lamp, however, is dependent on the skill of the operator and only the most skilled operator can detect combustible mixtures in a concentration of less than 1% with a flame safety lamp. Even though such a concentration may not be deemed critical, detecting a combustible mixture at this level of concentration is essential in order to determine the source of the gas emission for possible accumulation to a critical level. Another disadvantage of the flame safety lamp as an indicator of combustible gas in the mine atmosphere is the difficulty in using the device within one foot of the mine face where the concentration of gases is generally the greatest and the threat of explosion the most severe.In fact, in many cases the operator is exposed to a greater hazard, such as from a roof fall, if he is required to sample the concentration of methane gas within one foot of the mine face.
Electronic devices for monitoring combustible gases are known in the art and include a single sensing head that transmits a signal through a change in electrical resistance that is proportional to the gas/air ratio. The signals are amplified and transmitted to indicator and alarm circuits which when actuated alert the operator to hazardous gas concentrations. Such devices, however, have not proved to be acceptably accurate, particularly in a mine atmosphere.
There is need for apparatus for continuously monitoring the atmosphere of a mine for the presence of a combustible mixture of gases that are emitted from the face during the mining operation. The apparatus must be capable of accuracy to below 1% concentration in air for extended intervals. The apparatus must also be capable of being positioned at selected points in the mine, particularly at the mine face and on operating equipment.
According to the present invention there is provided electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere, the circuitry comprising sensor means for continuously monitoring the level of combustible gas in the mine atmosphere and operable to supply a plurality of output signals proportional to the concentration of a combustible mixture of gas in the mine atmosphere, power means for actuating the sensor means, regulator means for maintaining a preselected voltage across said sensor means, the regulator means having detector means for comparing the output signals of said sensor means with a preselected signal and generating signals proportional to said output signals from said sensor means, an alarm device for actuating an alarm signal to indicate the presence of a combustible mixture of gas in the mine atmosphere, the alarm device being arranged to receive an output signal from the detector means for actuaing the alarm signal when the output signals of said sensor means exceed a preselected value indicating the presence of a combustible mixture of gas in the mine atmosphere, comparator means connected to the detector means and the power means and operable to receive said signals proportional to said sensor means output signals from said regulator means and to generate a corresponding output signal responsive to the greater input signal received, meter means connected to the power means and the comparator means for recording the greater value of said signals received by the comparator means from the detector means, and a signal deviation detector for receiving input signals from the detector means and operable to actuate the alarm device and thereby indicate an excess deviation between the output signals of the sensor means.
The circuitry preferably comprises a time delay mechanism that receives amplified output signals from the detector means and the signal deviation detector. If the condition of the presence of combustible gas in the mine atmosphere or of an excess deviation between the output signals of the sensor means (which preferably comprises two sensor assemblies) occurs, the time delay mechanism is preferably actuated to stop the preselected voltage being maintained across the sensor means and thereby deenergise the sensor means after a preselected time interval. In addition, the time delay mechanism may generate a latch signal which is transmitted to the alarm device to indicate the undesirable condition.
Electrical circuitry embodying the invention may operate continuously at selected locations in the mine for a selected time interval to generate output signals that are proportional to the concentration of combustible gas in the mine atmosphere and actuate the alarm device when an undesirable condition occurs.
Circuitry embodying the present invention is preferably capable of detecting a 1.0% mixture of combustible gas in a mine atmosphere; and of providing a continuous readout of the concentration of combustible gas in the mine atmosphere.
The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a block diagram illustrating the elements of electrical circuitry embodying the invention for detecting a combustible mixture of gas in a mine atmosphere;
Figure 2 is an electrical schematic illustrating a voltage regulator for sensor elements including a level detector circuit for indicating the presence of a combustible mixture of gas in the mine atmosphere;
Figure 3 is an electrical schematic illustrating comparator and switch apparatus for monitoring output signals generated by sensor assemblies and for indicating the greater sensor output signal received;;
Figure 4 is an electrical schematic illustrating a signal deviation detector for monitoring the output signals generated by the sensor assemblies to detect an excess deviation between the sensor output signals;
Figure 5 is an electrical schematic illustrating an alarm device for indicating the presence of a combustible mixture of gas in the mine atmosphere and an excess deviation between the output signals of the sensor assemblies;
Figure 6 is an electrical schematic illustrating apparatus for supplying power to the sensor assemblies;
Figure 7 is a schematic diagram illustrating circuitry for selectively recording the output signals generated by the sensor assembly; and
Figure 8 is an electrical schematic illustrating a time delay mechanism for terminating the supply of power to the sensor assemblies and actuating an alarm signal when a combustible mixture of gas has been detected in the mine atmosphere and when an excess deviation between the output signals of the sensor assemblies has been recorded.
Referring to the drawings and particularly to Figure 1, this illustrates a block diagram of elements provided in electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere. The elements include a source of power 10, such as a battery pack, that supplies power to a pair of independent sensor elements or assemblies 12 and 14 that are connected to the power source 10 through regulators 16 and 18 respectively. The regulators 16 and 18 maintain a preselected voltage across the sensor assemblies 12 and 14 regardless of any variation that may occur in the power supply voltage or a change in the resistance of the sensor assemblies.The sensor assemblies 12 and 14 may be suitably mounted at preselected points in a mine or on machinery operating in the mine to continuously monitor the mine atmosphere for the presence of a combustible mixture of gas, specifically methane gas.
The sensor assemblies 12 and 14 generate output signals that are received by the regulators 16 and 18 and the magnitude of the signals are compared by a level detector of the regulators with a preselected signal voltage. In the event the output signals generated by the sensor assemblies 12 and 14 exceed said preselected signal, the regulators generate a responsive signal that is transmitted to an alarm device 20 that is actuated to thereby indicate the presence of a combustible mixture of gas in the mine atmosphere. The alarm device may comprise both audible and visual alarm signals.
The regulators 16 and 18 supply input signals to a comparator and switch assembly 22 in which the input signal received is proportional to the output signals generated by the sensor assemblies 12 and 14. The input signals from the regulators 16 and 18 are compared by the comparator 22 and the greater of the input signals is selected for readout by a meter 24 that receives current from the comparator and switch assembly 22. In this manner, a continuous readout of the greater output signal generated by the sensor assemblies 12 and 14 is provided. In addition, the operation of the switch of the comparator 22 momentarily interrupts the output to the meter 24 to provide a reading of the lower value of the output signals received by the comparator 22 from the sensor assemblies 12 and 14.
The outputs of the regulators 16 and 18, responsive to the output signals generated by the sensor assemblies 12 and 14, are also transmitted as input signals to a signal deviation detector 26. The signal deviation detector 26 compares the magnitude of the input signals from the regulators 16 and 18, which input signals are proportional to the respective signals received from the sensor assemblies 12 and 14.
If an excess deviation of preferably greater than 7.5% is recorded between the inputs from the regulators 16 and 18, the detector 26 generates an output signal that is transmitted to the alarm device 20. In this manner the operator is alerted to a possible malfunction of the sensor assemblies as indicated by the undesirable deviation between the output signals of the sensor assemblies recorded by the regulators 16 and 18.
In the event a combustible mixture of gas is detected by the sensor assemblies 12 and 14 a corresponding output signal is transmitted to the detectors of the current regulators 16 and 18. The regulators will transmit a corresponding output signal to a time delay mechanism or timer 28. After having received the output signal from either one of the regulators 16 and 18, indicating a dangerous condition as a result of combustible mixture in the mine atmosphere, the timer 28 will apply a signal to the regulators 16 and 18. This terminates current flow through the monitoring circuits of the regulators to cease operation of the sensor assemblies 12 and 14.
In an alarm condition the timer 28 is also operable to actuate the alarm device 20 to generate a continuous signal indicating the presence of a combustible mixture of gas in the mine atmosphere. Furthermore, the timer 28 is operable to receive the output from the signal deviation detector 26 when an excess deviation is recorded between the output signals of the sensor assemblies 12 and 14. In a similar manner the timer 28 will terminate operation of the sensor assemblies 12 and 14 by transmitting an input signal to the regulators 16 and 18 and also actuate the alarm device 20.
Referring to Figure 2, there is illustrated circuitry 30 for each of the regulators 16 and 18 of Figure 1 that includes a terminal 32, which is connected to a terminal 33 of the battery pack 10, illustrated in Figure 6, and also includes terminals 34, 36 and 38 that are connected to a terminal 40 of the battery pack 10, illustrated in Figure 6. Referring to Figure 6, the terminal 40 is connected by a switch 42 and a resistor 44 to the positive terminal 46 of a battery 47 to supply positive voltage to the terminal 40. A terminal 48 of circuitry 30 in
Figure 2 is connected via a terminal 50 to the electrical ground 52 of the battery pack 10.
The terminal 33 is connected through a resistor 53 to the negative terminal 49 of a battery 51 so that negative voltage is supplied to the terminal 33 and hence to the terminal 32 of
Figure 2.
Each of the regulators 16 and 18 is connected by terminals 56 and 58 to one of the respective sensor assemblies. Each of the sensor assemblies as illustrated in Figure 2 includes an active element 60 and an inactive element 62.
The electrical resistance of the active sensor element, 60 which is temperature sensitive, will change when exposed to a mixture of combustible gas. The inactive sensor element 62 is similar to the active element 60 but does not respond to being exposed to the gas. The element 62 may compensate for ambient changes in temperature, humidity, and atmospheric pressure in the mine.
The regulators 16 and 18 are operable to function as voltage regulators as illustrated in
Figure 2. In this manner a constant voltage is maintained across the respective sensor elements regardless of a variation in the power supply voltage from the power pack 10 or variations in the resistance of the sensor elements. Sensor element 60 is connected by terminal 54 to ground. Resistors 65 and 66 are connected between ground and the terminal 58 of the sensor element 62. The voltage appearing between resistors 65 and 66 at terminal 63 is compared by an operational amplifier 67 with a preselected reference voltage. The reference voltage received by the amplifier 67 is controlled by a Zener diode 69 connected by a resistor 68 and terminal 38 to the positive voltage of the battery pack 10. The voltage supply is adjustable by potentiometer 70.With this arrangement an increase in the voltage across the sensor elements 60 and 62 will accordingly increase the voltage at terminal 63 and the voltage input to the operational amplifier to a more positive state.
A transistor 72 is connected by a voltage divider comprising resistors 74 and 76 to the operational amplifier 67. Switching the output of the amplifier 67 to a more positive state as a consequence of an increase in the input signal to the sensor elements 60 and 62 correspondingly increases the base current of the transistor 72 through the voltage dividers 74 and 76 and resistor 78 connecting the emitter of transistor 72 to ground. An increase in base current of the transistor 72 also increases the collector current supplied through a resistor 80 and a conductor 82. This reduces the base voltage of and current bid to a regulator transistor 84 having an emitter connected to terminal 58 of the sensor element 62. A reduction in the current to the regulator transistor 84 reduces the input signal to the sensor elements 60 and 62 to the preselected level.
In the event the input signal to the sensor elements 60 and 62 should fall below the preselected level, the voltage across the resistor 66 and applied to the operational amplifier 67 will accordingly decrease thus switching the operational amplifier 67 to a more negative state.
This has the effect of decreasing the base current of the transistor 72. A decrease in the transistor base current also decreases the collector current supplied through the resistor 80 and conductor 82. Thus, the base voltage and current to the regulator transistor 84 is increased to increase the input signal to the sensor element 60 and 62 to the preselected value.
A capacitor 86 and resistor 88 form a feedback loop for the operational amplifier 67 so that the output thereof is an amplified sum of the input signal regulated by the Zener diode 69 and resistor 68 and an integral thereof. In this manner, undesirable oscillations in the output of the operational amplifier 67 are prevented to improve the performance thereof.
A silicon controlled rectifier 90 is included in the circuitry 30 and has an anode connected to the conductor 82 and a cathode connected to a ground conductor 92. A gate terminal 94 of the rectifier 90 is connected by a limiting resistor 96 to a terminal 98. The terminal 98 is connected to the time delay mechanism 28 and the alarm device 20. The silicon controlled rectifier 90 is normally retained in a nonconductive state in the absence of current flowing from the terminal 98 through the resistor 96 to the gate terminal 94. The application, however, of a high voltage signal at the gate terminal 94 from the terminal 98 actuates the rectifier 90 to become conductive between the anode and cathode and thereby direct current flow from the transistor 72 through the conductor 82 to the ground conductor 92.Thus, the regulator transistor 84 is maintained in a nonconducting state by interrupting base current flow through the transistor 84 by actuation of the silicon controlled rectifier 90. In this manner, the rectifier 90 is utilized to latch the regulator transistor 84 in a non-conducting state to terminate current flow through the sensor assemblies 12 and 14 under conditions where there exists a prolonged combustible mixture of gas in the mine atmosphere or an excess deviation between the magnitude of the output signals of each of the sensor assemblies 12 and 14.
The sensor elements 60 and 62 of eachof the sensor assemblies 12 and 14, illustrated in
Figure 1, generate an output signal that varies with a change in resistance of the respective sensor elements as a consequence of the concentration of combustible gases in the mine atmosphere. The output signals are transmitted through the terminal 56 to a level detector circuit 100 of the regulator and level detector. The sensor output signal is transmitted through a resistor 102 to an operational amplifier 104.
The operational amplifier 104 is connected by a resistor 106 to a voltage regulating apparatus 108 that includes a resistor 110 and Zener diode 112 connected to the terminal 32 which, as mentioned above, is connected to the terminal 33 of the power pack 10. In this manner, a pre-selected voltage level regulated by a potentiometer 114 is applied to the operational amplifier 104 to generate an equal but opposite current flow to that of the sensor assembly output signal through the resistor 102. In this manner, a zero net voltage appears at the input of the operational amplifier 104. With the above described arrangement the output of the operational amplifier 104 may be adjusted to a preselected value. A portion of the amplifier output is fed back to the input through a resistor 116 and is combined with the input through a resistor 118 to preset the gain of operational amplifier 104.The output of the operational amplifier 104 is transmitted to a potentiometer 120 so that the output voltage may be adjusted for readout and comparison purposes.
The adjusted output voltage of the operational amplifier 104 is transmitted to a terminal 122 that is connected to the comparator and switch assembly 22 and the signal deviation detector 26. The adjusted output signal is also transmitted from the potentiometer 120 through a conductor 124 to a comparator 126.
The comparator 126 compares the adjusted output of the operational amplifier 104, which is responsive to the output signals generated by the sensor elements 60 and 62, with the input received from the terminal 34 connected to the power pack 10 through a potentiometer 128. If the adjusted voltage from the amplifier 104 is greater than the preset input from the terminal 34, the comparator 126 switches to a positive state to generate an output signal of a positive voltage that is transmitted through a terminal 130 to activate the alarm device 20 and the time delay mechanism 28. The presence of a positive output voltage at the terminal 130 indicates the existence of a combustible mixture of gas in the mine atmosphere.
The adjusted output signals transmitted from the operational amplifier 104 of each of the regulators 16 and 18 is transmitted to terminals 132 and 134 of the comparator and switch assembly 22 illustrated in Figure 3. The comparator and switch assembly 22 is operable to compare the magnitude of the adjusted output signals received from the regulators and indicate quantitatively the greater value of the output signals received from the sensor assemblies 12 and 14 and also provide an indication as to which sensor assembly generates the greater output signal.
The regulator 16 supplies an amplified signal which is proportional to the output signal generated by the sensor assembly 12 to the terminal 132. Accordingly, the regulator 18 supplies an amplified signal which is proportional to the output signal generated by the sensor assembly 14 to the terminal 134. The respective signals from the terminals 132 and 134 are transmitted by conductors 136 and 138 as inputs to an operational amplifier 140.
The resultant output of the operational amplifier 140 is positive when the amplified signal from terminal 132 is greater than the amplified signal from terminal 134. With the operational amplifier 140 switched to a high output state, a positive voltage appears across a voltage divider 142 that includes a resistor 144 and a resistor 146. The positive voltage generated from the amplifier 140 actuates a relay 148 to close normally open contacts 149 to permit current flow from the terminal 132 through a conductor 152 to a terminal 154. The terminal 154 is connected to the analog meter 24. In this manner the meter 24 is actuated to provide a quantitative indication of the output signal generated by the sensor assembly as and thus an indication of the concentration of combustible gases in the mine atmosphere as recorded by the sensor assembly 12.
If the amplified signal generated by the regulator 18 in response to the output signal of the sensor assembly 14 is greater than the amplified signal from the terminal 132, the output of the operational amplifier 140 is switched to a negative state and the current flow to the resistor 144 is blocked by a diode 155. Consequently, the amplified signal from the terminal 134 passes through a conductor 151 and normally closed contacts 153 of the relay 148 to the terminal 154. The output from the terminal 154 generated by the amplified signal from the terminal 134 provides a quantitative readout of the output signal generated by the sensor assembly 14 in response to the concentration of combustible gases in the mine atmosphere.
When the operational amplifier 140 is switched to a high output state, base current is supplied to a transistor 156 through a conductor 158 and a resistor 160. The transistor 156 is actuated when the amplified signal from the terminal 132 exceeds the amplified signal from the terminal 134, and current flows through the collector of the transistor 156 to an indicator 158 that is connected by a terminal 159 to the positive voltage of the power source 10. The indicator 158 is actuated to thereby indicate that the sensor assembly 12 is being monitored for readout by the meter 24. With the operational amplifier 140 in a high output state, current flow to the base of a transistor 162 connected by a resistor 164 to the transistor 156 is terminated to thereby cease operation of an indicator 166. The indicator 166 is connected by a terminal 167 to the positive voltage of the power source 10.If the amplified signal from the terminal 134 exceeds the signal from the terminal 132, the amplifier 140 switches to a low output state and current flows through the resistor 164 to the base of the transistor 162 to activate the transistor 162 and the indicator 166. In this manner, monitoring of the sensor assembly 14 for readout by the meter 24 is indicated.
An inverter circuit 168 is connected across the operational amplifier 140 and transistors 156 and 162 by conductors 170 and a switch 172 respectively. The inverter circuit 168 is operable to override the output signal of the amplifier 140 to momentarily provide an indication of the lower value of the amplified signals received from the detectors of regulators 16 and 18. An inverter transistor 174 receives the output from the amplifier 140 through a diode 176 and a resistor 178 to provide a base current for the transistor 174. The emitter of the transistor 174 is connected to the negative terminal of the power source 10 through a terminal 175 and to ground.
With the operational amplifier 140 in a high output state, the inverter transistor 174 is actuated resulting in current flow through a resistor 180 and a low voltage condition at the collector of the transistor 174. The resistor 180 is connected by a terminal 181 to the positive voltage of the power source 10. With this arrangement the collector of the transistor 174 is at a low output stage when the amplifier
140 is at a high output state. Accordingly, when the output of the operational amplifier
140 is low, the collector of the transistor 174 is high.
A manual switch 172 connects the conductor 158 with the collector of the transistor
174. By manually actuating the switch 172 to close the circuit between the collector of the transistor 174 and the relay 148, a voltage level opposite to that of the output of the amplifier 140 is imposed on inputs to the relay
148 and the transistor 156. This effects a
change of state of the transistor 156 and the relay 148 to thereby override the output signal
transmitted by the amplifier 140 so that the lower value of the amplified signals received by the comparator 22 may be momentarily monitored by the meter 24.
The meter 24 illustrated in detail in Figure
7 receives current from the terminal 154 of the
comparator and switch assembly 22, which
current is proportional to the higher value of
the voltages transmitted by the regulators 14
and 16 to the terminals 132 and 134 respec
tively of Figure 3. The circuitry of the meter
24 illustrated in Figure 2 includes a conven
tional calibrated meter 182 connected by a
conductor 184 to the terminal 154. The meter
182 is driven by current received from a ter
minal 186 connected to the power pack 10,
the current being supplied via a resistor divider
network comprising resistors 188 and 190 and
a limiting resistor 192. The resistor 190 is
connected to the electrical ground of the
battery pack 10 by a terminal 191.The
resistor 192 limits the current flow to the meter 182 from the power pack 10, and the resistor network permits zero calibration of the meter 182.
Referring to Figure 4, there is illustrated the circuitry for the signal deviation detector 26 which is operable to record an excess deviation between the output signals of the sensor assemblies 12 and 14. Amplified signals from the respective terminals of the regulators 16 and 18 are received at terminals 194 and 196. The amplified signals from the detector circuits 100 are compared to each other by detector operational amplifiers 198 and 200. The amplifiers 198 and 200 are connected by conductors 202, 204, 206 and 208 to the terminals 194 and 196 respectively. A voltage divider network comprising resistors 210 and 212 connects the terminal 196 with the operational amplifier 198.With this arrangement amplified input from terminal 194 is transmitted through a resistor 213 and is received by the amplifier 198 which compares the input to a percentage of the input received from the terminal 196 through the voltage divider network. If the amplified input from the terminal 194 is lower than a percentage of the amplified input of the terminal 196, the operational amplifier 198 switches to a high output state. In a similar arrangement the operational amplifier 200 is connected by a resistor 216 to the terminal 196 and a voltage divider network comprising resistors 218 and 220 to the terminal 194. If the amplified signal from the terminal 196 is lower than the preset percentage of amplified signal from the terminal 194, the amplifier 200 switches to a high output state.Therefore, as long as the voltage levels of the amplified signals from the terminals 194 and 196 remain within a selected percentage of each other, the amplifiers 198 and 200 remain in a low output state.
If a deviation occurs between the respective amplified signals and the corresponding preset percentage thereof either the amplifier 198 or the amplifier 200 will switch to a high output state. In a high output state the switched amplifier supplies current through either of diodes 222 or 224 to the base of a transistor 226 after a preselected time delay as determined by a resistor 228 and a capacitor 230. The collector of the transistor 226 is connected by a diode 229 to a transistor 231. The emitter of the transistor 226 is connected to the base of a transistor 232 that is connected to the ground connection of the power source 10 at a terminal 233.
Current flow through the transistor 226 supplies base current to the transistor 232 to actuate the transistor 232. With this arrangement current does not flow to the base of the transistor 231, and consequently it remains inactive.
If no excess deviation exists between the voltages of amplified signals from the terminals 194 and 196, then the transistors 226 and 232 remain nonconductive to thus allow the base current of the transistor 231 to flow through a resistor 234 and diode 229 to actuate the transistor 231. Actuating the transistor 231 generates current flow therethrough and a resistor 236 connecting the collector of the transistor 231 with a terminal 238 connected to the positive voltage of power pack 10. With the transistor 231 actuated the collector thereof switches to a low level. When an excess deviation of voltage exists between the amplified signals of the sensor assemblies 12 and 14, a high voltage signal is transmitted from the collector of the transistor 231 to a terminal 240 that is connected to the alarm device 20 and the time delay mechanism 28.
If the output signals received at the terminals 194 and 196 from the operational amplifier 104 (Figure 2) of the regulator and level detectors 16 and 18 become negative because of damage to the sensor elements 60 and/or 62 because of damage to the conductors which connect the regulator terminals 54, 56 and 58 to the respective sensor assemblies diodes 195 and/or 197 conduct to supply base current to a transistor 203 through a base resistor 199 of a trouble circuit generally designated by the numeral 193. Current to the transistor 203 actuates the transistor 203 so that the collector thereof switches to ground to terminate the flow of base current to a transistor 209.For a normal condition where the trouble circuit 193 is not actuated, current flows from a terminal 219 connected to the negative terminal 33 (Figure 6) of the power pack 10 through a resistor 201, a Zener diode 205 and a resistor 207 to the base of the transistor 209.
The transistor 209 is actuated to direct the current through a resistor 213 to ground and to the base of a transistor 215 and therefrom to ground. Also, in a normal condition current from a terminal 221 connected to the positive terminal 40 (Figure 6) of the power pack 10 is directed through a resistor 217 to the actuated transistor 215 and to ground. The terminal 221 is connected through a resistor 211 to the emitter of the transistor 209.
In the event of a malfunction, as above described, current flow to the transistor 209 is terminated, subsequently, the transistors 209 and 215 are turned off. Current from the terminal 221 is directed through the resistor 217 and a diode 225 to the base of the transistor 226 after a preselected time delay as determined by the resistor 228 and capacitor 230.
As above described, actuation of the transistor 226 actuates the alarm device 20. In this manner, a malfunction of the sensor elements is brought to the attention of the operator.
The alarm device 20 is illustrated in detail in Figure 5. Each of the sensor assemblies 12 and 14 transmits an output signal to the associated one of the regulators 16 and 18 and for conditions in which a combustible mixture of gas is detected in the mine atmosphere by the level detector circuit of each of the regula tors, a high voltage alarm signal is transmitted either from the sensor assembly 12 to a terminal 242 or from the sensor assembly 14 to a terminal 244. The signals received by the alarm device 20 at the terminals 242 and 244 are pro- portional to the amplified signals received from the respective regulators 16 and 18.A high voltage alarm signal received at the terminal 242 is transmitted through a resistor 246 to supply base current for a transistor 248 to, in turn, actuate the transistor 248 and illuminate an indicator 250 that is connected by a terminal 251 to the positive terminal of the power source 10. In this manner the operator is informed as to the dangerous condition presented by the mixture of combustible gas in the mine atmosphere and the source of the respective alarm signal. Similarly, the high voltage alarm signal received from the regulator 18 for the sensor assembly 14 supplies current through a resistor 252 to the base of a transistor 254.In this fashion the transistor 254 is actuated to supply current to an indicator 256, connected by a terminal 257 to the positive terminal of the power source 10, and thereby actuate the indicator to indicate the presence of a combustible mixture of gas as recorded by the regulator 18 of the sensor assembly 14.
When an excess deviation exists between the output signals of the sensor assemblies 12 and 14, the signal deviation detector 26 is actuated to generate a high voltage level alarm signal that is transmitted to a terminal 258 of the alarm device 20. The alarm signal supplies a current to the base of a transistor 260 through a resistor 262 to actuate the transistor 260 and an indicator 264 in a similar manner as above described for the transistors 248 and 254. The indicator 264 is connected by a terminal 265 to the positive terminal of the power source 10. Each of the alarm signals received by the terminals 242, 244, and 258 are transmitted through diodes 226, 268, and 270 respectively for actuation of transistors 272 and 274. In this manner, the alarm signals provide base current for the transistors 272 and 274 through resistors 276 and 278.Thus, actuation of the transistor 272, in turn, actuates a visual alarm 280 and actuation of the transistor 274 actuates an audible alarm 282. The alarms 280 and 282 are connected by terminals 281 and 283 respectively to the positive terminal of the power source 10. The emitter of the transistor 274 is connected by a terminal 275 to the negative terminal of the power source 10 and to ground.
Under normal conditions base current is supplied from a terminal 284 that is connected to the positive voltage of battery pack 10 to supply current through a resistor 286 to a transistor 288. Thus, in the absence of a high voltage level alarm signal from the regulators 16 and 18 and the signal deviation detector 26 at the terminal 258, the transistor 288 remains actuated with the collector thereof maintained in a low voltage state. A silicon controlled rectifier 290 is connected by a terminal 285 and a limiting resistor 287 to the time delay mechanism 28 and is maintained in a normally non-conductive mode. However, the occurrence of an alarm signal to actuate the time delay mechanism 28 and generate a latch signal after a preselected time interval, applies a high voltage signal through the limiting resistor 287 to a gate terminal 289 of the rectifier 290.The application of a high voltage signal at the gate terminal 289 actuates the silicon controlled rectifier 290 to switch to a conductive state and terminate flow of the base current of the transistor 288, deenergizing the transistor 288.
Current then flows from a terminal 292 connected to the positive voltage of the battery pack 10 through a resistor 294, a diode 296 and resistors 276 and 278 to actuate the visual and audible alarms 280 and 282.
As explained hereinabove a high voltage alarm signal from either of the regulators 16 or 18 indicating the existence of a combustible mixture of gas in the mine atmosphere actuates the time delay mechanism 28. As illustrated in
Figure 8 the high voltage alarm signals from the regulators 16 and 18 are received at terminals 298 and 300 respectively of the time delay mechanism 28. In a similar manner the signal deviation detector 26 supplies a high voltage alarm signal to terminal 302 when the difference between the output signals of the sensor elements 12 and 14 exceeds a preselected value.
Respective alarm signals received at the terminals 298, 300, and 302 supply base current through diodes 304, 306 and 308 to a transistor 310 after a preselected time interval as determined by a resistor 312 and a capacitor 314.
The collector of the transistor 310 is connected to the power source 10 through a resistor 316 by a terminal 318. A transistor 320 is connected to the collector of the transistor 310 by a diode 322. Actuating the transistor 310 by supplying base current thereto provides base current for a transistor 323 to actuate the transistor 323.
The base current of the transistor 320 is terminated to thereby deenergize the transistor 320 and switch the collector thereof to a high voltage level. The collector of the transistor 320 is connected to the power source at a terminal 324 through a resistor 326. The emitter of the transistor 320 is connected to the electrical ground of the power source at a terminal 328. Thus, switching the collector of the transistor 320 to a high voltage level generates a latch signal to a terminal 330 that is connected to the terminal 285 of the alarm device illustrated in Figure 5 and to the terminal 98 of each of the regulators 16 and 18 as illustrated in Figure 2.In this manner the alarms 280 and 282 are actuated and current through the monitoring circuit 64 of the regulators is terminated to deenergize the sensor assemblies 12 and 14 when an alarm condition continues to exist for a preselected time interval.
In a non-alarm condition the transistors 310 and 323 remain in a nonconductive mode. Base current from the terminal 318 through the resistor 316 and the diode 322 maintains the transistor 320 in a conductive mode so that current flows from the terminal 324 through the resistor 326 and the transistor 320. Current flow through the transistor 320 switches the collector thereof to a low voltage level to prevent generation of a latch signal to the terminal 330 and a corresponding deenerization of the monitoring circuit 64.
WHAT WE CLAIM IS:
1. Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere, the circuitry comprising sensor means for continuously monitoring the level of combustible gas in the mine atmosphere and operable to supply a plurality of output signals proportional to the concentration of a combustible mixture of gas in the mine atmosphere, power means for actuating the sensor means, regulator means for maintaining a preselected voltage across said sensor means, the regulator means having detector means for comparing the output signals of said sensor means with a preselected signal and generating signals proportional to said output signals from said sensor means, an alarm device for actuating an alarm signal to indicate the presence of a combustible mixture of gas in the mine atmosphere, the alarm device being arranged to receive an output signal from the detector means for actuating the alarm signal when the output signals of said sensor means exceed a presence of a combustible mixture of gas in the mine atmosphere, comparator means connected to the detector means and the power means and operable to receive said signals proportional to said sensor means output signals from said regulator means and to generate a corresponding output signal responsive to the greater input signal received, meter means connected to the power means and the comparator means for recording the greater value of said signals received by the comparator means from the detector means, and a signal deviation detector for receiving input signals from the detector means and operable to actuate the alarm device and thereby indicate an excess deviation between the output signals of the sensor means.
2. Electrical circuitry according to claim 1, which includes a time delay mechanism arranged to receive input signals from the detector means and the signal deviation detector and to transmit responsive output signals after a preselected delay interval to the regulator means and the alarm device to stop said preselected voltage being maintained across the sensor means to interrupt operation thereof and actuate said alarm device for continuous operation.
3, Electrical circuitry according to claim 1 or claim 2, in which the regulator means includes a first series regulator connected to the sensor means and operable to maintain the preselected voltage across the sensor means, a first amplifier connected to the sensor means for comparing the voltage across said sensor means with a preselected signal, the first amplifier being operable to generate an output signal proportional to the voltage across the sensor means, and a second series regulator connected to the first amplifier and the first series regulator, the second series regulator being responsive to the output signal of said first amplifier to supply a corresponding output signal to said first series regulator for adjusting same to maintain the preselected voltage across the sensor means.
4. Electrical circuitry according to claim 3, in which the regulator means is operable as a voltage regulator to maintain the preselected voltage across the sensor means, the first amplifier is operable to compare the voltage appearing across the sensor means to a preselected reference voltage, and the first amplifier is further operable to generate in response to a change in the voltage appearing across the sensor means an output signal to said regulator means for maintaining the preselected voltage across the sensor means.
5. Electrical circuitry according to claim 3 or claim 4, which includes means for stopping first series regulator from maintaining a preselected voltage across the sensor means.
6. Electrical circuitry according to any one of the preceding claims, which includes a silicon controlled rectifier having a gate terminal connected to the alarm device and an anode and a cathode connected across the power means, and a resistor for limiting the gate current to said silicon controlled rectifier, the silicon controlled rectifier being operable upon actuation to terminate supply of power to the sensor means upon actuation of the alarm device.
7. Electrical circuitry according to any one of the preceding claims, in which the detector means includes a detector amplifier for receiving said output signals from the sensor means and transmitting a responsive output signal, feedback means for adjusting the output signal and the detector amplifier to a preselected magnitude proportional to the output signals received from the sensor means, and a comparator amplifier for receiving the output signals of the detector amplifier, the comparator amplifier being operable to compare said output signals from the detector amplifier with a preselected voltage applied thereto and to actuate said alarm device when said detector amplifier output signal exceeds such preselected voltage.
8. Electrical circuitry according to any one of the preceding claims, in which the sensor means includes a pair of sensor assemblies each having a pair of sensor elements connected to the regulator means to have the preselected
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (15)
1. Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere, the circuitry comprising sensor means for continuously monitoring the level of combustible gas in the mine atmosphere and operable to supply a plurality of output signals proportional to the concentration of a combustible mixture of gas in the mine atmosphere, power means for actuating the sensor means, regulator means for maintaining a preselected voltage across said sensor means, the regulator means having detector means for comparing the output signals of said sensor means with a preselected signal and generating signals proportional to said output signals from said sensor means, an alarm device for actuating an alarm signal to indicate the presence of a combustible mixture of gas in the mine atmosphere, the alarm device being arranged to receive an output signal from the detector means for actuating the alarm signal when the output signals of said sensor means exceed a presence of a combustible mixture of gas in the mine atmosphere, comparator means connected to the detector means and the power means and operable to receive said signals proportional to said sensor means output signals from said regulator means and to generate a corresponding output signal responsive to the greater input signal received, meter means connected to the power means and the comparator means for recording the greater value of said signals received by the comparator means from the detector means, and a signal deviation detector for receiving input signals from the detector means and operable to actuate the alarm device and thereby indicate an excess deviation between the output signals of the sensor means.
2. Electrical circuitry according to claim 1, which includes a time delay mechanism arranged to receive input signals from the detector means and the signal deviation detector and to transmit responsive output signals after a preselected delay interval to the regulator means and the alarm device to stop said preselected voltage being maintained across the sensor means to interrupt operation thereof and actuate said alarm device for continuous operation.
3, Electrical circuitry according to claim 1 or claim 2, in which the regulator means includes a first series regulator connected to the sensor means and operable to maintain the preselected voltage across the sensor means, a first amplifier connected to the sensor means for comparing the voltage across said sensor means with a preselected signal, the first amplifier being operable to generate an output signal proportional to the voltage across the sensor means, and a second series regulator connected to the first amplifier and the first series regulator, the second series regulator being responsive to the output signal of said first amplifier to supply a corresponding output signal to said first series regulator for adjusting same to maintain the preselected voltage across the sensor means.
4. Electrical circuitry according to claim 3, in which the regulator means is operable as a voltage regulator to maintain the preselected voltage across the sensor means, the first amplifier is operable to compare the voltage appearing across the sensor means to a preselected reference voltage, and the first amplifier is further operable to generate in response to a change in the voltage appearing across the sensor means an output signal to said regulator means for maintaining the preselected voltage across the sensor means.
5. Electrical circuitry according to claim 3 or claim 4, which includes means for stopping first series regulator from maintaining a preselected voltage across the sensor means.
6. Electrical circuitry according to any one of the preceding claims, which includes a silicon controlled rectifier having a gate terminal connected to the alarm device and an anode and a cathode connected across the power means, and a resistor for limiting the gate current to said silicon controlled rectifier, the silicon controlled rectifier being operable upon actuation to terminate supply of power to the sensor means upon actuation of the alarm device.
7. Electrical circuitry according to any one of the preceding claims, in which the detector means includes a detector amplifier for receiving said output signals from the sensor means and transmitting a responsive output signal, feedback means for adjusting the output signal and the detector amplifier to a preselected magnitude proportional to the output signals received from the sensor means, and a comparator amplifier for receiving the output signals of the detector amplifier, the comparator amplifier being operable to compare said output signals from the detector amplifier with a preselected voltage applied thereto and to actuate said alarm device when said detector amplifier output signal exceeds such preselected voltage.
8. Electrical circuitry according to any one of the preceding claims, in which the sensor means includes a pair of sensor assemblies each having a pair of sensor elements connected to the regulator means to have the preselected
voltage maintained across it and one of the sensor elements has a preselected electrical resistance and is temperature sensitive such that the temperature of said sensor element changes when exposed to a combustible mixture of gas in the mine atmosphere resulting in a change in the electrical resistance of said sensor element.
9. Electrical circuitry according to any one of the preceding claims, in which the comparator means includes an amplifier for receiving the output signals from the sensor means, the amplifier being connected to the meter means such that the greater output signal received by said amplifier from the sensor means is recorded by the meter means.
10. Electrical circuitry according to claim 9, in which said amplifier is operable to transmit an output signal responsive to the greater output signal received from the sensor means and including transistor means having an indicator device connected thereto such that the output from the transistor means actuates the indicator device to indicate the greater output signals received from the sensor means.
11. Electrical circuitry according to any one of the preceding claims, in which the signal deviation detector includes a first operational amplifier operable to compare a first output signal of the sensor means with a selected percentage of a second output signal of the sensor means, the first operational amplifier being operable to switch to a high output state when the first output signal exceeds the selected percentage of the second output signal and thereby supply a corresponding alarm signal for indicating an excess deviation between the first and second output signals of the sensor means, and a second operational amplifier operable to compare the second output signal of the sensor means with a selected percentage of the first output signal of the sensor means, the second operational amplifier being operable to switch to a high output state when the second output signals exceeds the selected percentage of the first output signal and supply a corresponding alarm signal indicating an excess deviation between the first and second output signals of the sensor means.
12. Electrical circuitry according to claim 11, which includes a trouble circuit for detecting a negative signal generated by the regulator means as indicating a malfunction of the sensor means and the regulator means, the trouble circuit being operable upon detecting a negative signal from the regulator means to actuate the alarm device and generate an alarm signal.
13. Electrical circuitry according to any one of the preceding claims, which includes a timer for terminating the supply of power to the sensor means when the sensor means records an undesirable mixture of combustible gas in the mine after a preselected time delay, the timer being operable to continue actuation of the alarm device when an excess mixture of combustible gas is recorded in the mine atmosphere, and the timer being connected to the signal deviation detector and to the regulator means.
14. Electrical circuitry according to any one of the preceding claims, in which the alarm device includes a plurality of transistor devices connected to the sensor means and the detector means for receiving output signals therefrom, an audio-visual alarm mechanism arranged to receive output from the transistor devices to indicate the presence of a combustible mixture of gas in the mine, and a silicon controlled rectifier connected to the transistor devices and operable upon actuation to supply an output signal to maintain continuous actuation of the audio-visual alarm mechanism when a combustible mixture of gas exists in the mine atmosphere.
15. Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere, the circuitry being substantially as herein described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/750,877 US4064498A (en) | 1975-10-28 | 1976-12-15 | Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1592506A true GB1592506A (en) | 1981-07-08 |
Family
ID=25019511
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB50355/77A Expired GB1592506A (en) | 1976-12-15 | 1977-12-02 | Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU510944B2 (en) |
| DE (1) | DE2755337A1 (en) |
| FR (1) | FR2374637A2 (en) |
| GB (1) | GB1592506A (en) |
| ZA (1) | ZA777399B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3126864C2 (en) * | 1981-07-08 | 1986-01-02 | Rheinische Braunkohlenwerke AG, 5000 Köln | Process for the early detection of smoldering fires in containers containing lignite dust |
| DE3132297C2 (en) * | 1981-08-12 | 1985-05-15 | Auergesellschaft Gmbh, 1000 Berlin | Circuit arrangement for a device for measuring and displaying the concentration of flammable gases and vapors contained in air |
| US4465318A (en) * | 1981-10-13 | 1984-08-14 | Coal Industry (Patents) Limited | Rotary cutting head for mining machines with means for inducing airflow and sensing thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1579535A (en) * | 1968-03-21 | 1969-08-29 | ||
| BE762753A (en) * | 1971-02-10 | 1971-07-16 | Inst Tekhn Teplofiziki Akademi | Measurement of combustible gas and vapour concentration |
| GB1419361A (en) * | 1974-03-26 | 1975-12-31 | Gen Monitors | Multi-channel combustible gas detector |
| DE2457650A1 (en) * | 1974-12-06 | 1976-06-10 | Bosch Gmbh Robert | DEVICE FOR CHECKING GASES |
-
1977
- 1977-12-02 GB GB50355/77A patent/GB1592506A/en not_active Expired
- 1977-12-05 AU AU31248/77A patent/AU510944B2/en not_active Expired
- 1977-12-12 DE DE19772755337 patent/DE2755337A1/en not_active Withdrawn
- 1977-12-12 ZA ZA00777399A patent/ZA777399B/en unknown
- 1977-12-14 FR FR7737718A patent/FR2374637A2/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2374637A2 (en) | 1978-07-13 |
| DE2755337A1 (en) | 1978-06-22 |
| FR2374637B2 (en) | 1984-09-14 |
| AU510944B2 (en) | 1980-07-24 |
| ZA777399B (en) | 1978-10-25 |
| AU3124877A (en) | 1979-06-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |