GB2127556A

GB2127556A - Sensing changes in the filtering effects of gaseous filters

Info

Publication number: GB2127556A
Application number: GB08325278A
Authority: GB
Inventors: Bill Peter Philip Nederman
Original assignee: NEDERMAN BILL P PH
Current assignee: NEDERMAN BILL P PH
Priority date: 1982-09-22
Filing date: 1983-09-21
Publication date: 1984-04-11
Also published as: DE3334162C2; IT8322962A0; SE8205417D0; IT8322963A1; CA1212162A; FI74881C; IT8324095V0; JPH0353700Y2; JPS5976515A; DK431283A; IT215131Z2; GB2127556B; FI833380A0; SE435577B; JPS6436024U; SE8205417L; FR2533140B1; IT8322963A0; DE3334162A1; GB8325278D0

Abstract

In a method and device for sensing changes in the filtering effect of electrostatic filtering devices (2) for separation of contaminants from gaseous streams, changes in voltage between filtering means (5) of the filtering device (2) are sensed, and signals are emitted (at 8) when a certain change in voltage takes place. The resonance voltage from filter cells (5) of the filtering device (2) are applied to a plurality of comparators (Figure 3) (not shown) set at different threshold levels. The outputs of the comparators control a pulse circuit which feeds means for emitting light, sound and control signals in dependance on changes in voltage between two filter cells (5). <IMAGE>

Description

SPECIFICATION Method and apparatus for sensing changes in the filtering effects of gaseous filters The present invention refers to a method for sensing changes in the filtering effect of filtering devices for separating contaminants from gaseous streams and to a device for carrying out the method in question.

Sensing principles known in the art to sense the degree of blockage of air filtering devices are not sufficiently sensitive. This means that the filtering device is allowed to be filled with contaminants to a relatively high degree before a warning signal is emitted. This means that the filtering device at times runs with a reduced filtering effect.

An object of the present invention is to eliminate this problem and to achieve a method by means of which a more sensitive sensing function is obtained. Another object of the invention is to provide a simple and reliable device to carry out the method according to the invention.

According to one aspect of the invention there is provided a method for sensing changes in the filtering effect of filtering devices for the separation of contaminants from gaseous streams with indication of the changes by means of signal emittance, wherein changes of voltage between different filtering means of the filtering device are sensed and that signals are emitted at a certain change in the voltage.

According to another aspect of the invention there is provided a device for carrying out the method for sensing changes in the filtering effect of filtering devices for separation of contaminants from gaseous streams with indication by means of signal emittance, comprising a control circuit in which voltage differences between filter cells of the filtering device influences signal emitting comparators for emittance of light, sound or control signals in dependence upon changes in voltage between the filter cells.

The invention will now be explained with reference to the accompanying drawings, of which: Figure 1 schematically shows a filtering device with a device according to the invention; Figure 2 schematically shows conditions for different voltage differences in the device of Figure 1; and Figure 3 illustrates a circuit diagram of a coupling forming part of the device according to the invention; The device illustrated in Figure 1 consists of a voltage transformer 1 and a filtering device 2 for separation of contaminants from gas, preferably harmful substances from smoke from welding apparatus. The filtering device 2 comprises an authormatically driven fan 3 and one or several removable filters 4 including filtering cells 5.The fan 3 is intended to suck in contaminated air 6 in an ionized sector 7 of the filtering device 2, where contamined particles in the air stream are charged positively to ensure that these particles will be deposited on the filter cells, which are of negative charge.

With a continuing deposit of particles on the filter cells 5 the capability of the latter to receive more particles increases such that the filtering effect of the filtering device will be unsatisfactory after some time of use.

In order to indicate a reduced filtering function before the filtering device 2 is blocked too much, the filter cells 5 are supervised by a sensing and signal emitting device 8. This has a electronic control circuit 9 (see Figure 3) with inputs 10 and 11 for indicating the voltage (the so called resonance voltage) between the filter cells 5. By normal filtering effect the voltage between the filter cells 5 is within the range 1 10124V (see Figure 2) and the control circuit 9 does not give any voltage to buzzer 12 and lamp 1 3 but continues to give voltage to a relay to the motor of the fan 3.If the voltage sinks below 11 OV or rises above over 1 24V by filling the filter cells 5 with contaminants and/or by short circuit effects in the filter cells 5, caused by damage on collector plates thereof (not shown) and/or as a consequence of disruption of ionizing cords (not shown) in the ionized sector 7, the following takes place:: Voltage Signal emittance < 108.5 constant buzzer sound constant light contactor to fan motor breaks within for example 1 2 seconds 108.5-11 1 OVintermittent buzzer sound intermittent light contactor does not break 1 10-124V no buzzer sound no light contactor does not break 124--1 25.5Vintermittent buzzer sound intermittent light contactor does not break < 125.5V constant buzzer sound constant light contactor to fan motor breaks within for example 1 2 seconds The breaking of the contactor to the fan motor, i.e. shut off fan 3, is preferably delayed by some seconds, for example 6-20 seconds, such that the fan 3 will not stop as a consequence of temporary passage of metal objects which temporarily reduces the voltage between the filter cells 5. If, however, the voltage remains below 108.5V or exceeds 1 25.5V the fan 3 is stopped and can only be re-started after removal or cleaning or dirty filter cells 5.

The values of the voltage/signal emittance chart above, can of course vary in dependence of the style and so forth of the parts of the sensing and signal emitting device 8 or other parts of the system.

The construction of the control circuit 9 can vary but in Figure 3 a practically useful and functionally correct device is illustrated. It may be mentioned that the input resonance voltage is rectified, voltage divided and filtered. The level is regulated by means of the trimmer potentiometer 1 4 and constitutes a value of the purity of the filter.

The voltage is transmitted to the comparators 1 5-1 8 and reference voltages are formed by stabilized 24V from the unit 1 9.

The comparator 1 6 and 17 are set at 1 24V and 1 10V respectively and the comparators 15 and 1 8 are set at 1 25.5V and 1 08.5V respectively.

The comparators 16 and 17 activate the pulse circuit 20 which feeds the buzzer 12 and triac 21, which ignites the signal lamp 13. An intermittent light and sound signal is obtained when one of the comparator 16 or 17 is activated.

The comparators 1 5 and 18 block the pulse circuit in an active condition and star the time circuit 22 which after about 1 2 seconds breaks the control current to triac 23, which causes the power supply contactor to drop out. The unit 24 works as a drive circuit for triac 23 and the resistors 25 and 26 cause a hysteresis of about 1 V at the levels 124V and 1 1 OV respectively to give a distinct on/off function.

The method and the device according to the invention are not limited to the embodiments described above but may be varied within the scope of the claims. Thus, signal emittance can take place in any form-for example, simply a light signal, a sound signal, an automatic cut-off signal or any appropriate combination thereof.

The limit values at which optical and/or sound signals are given and those which a fan cut-off signal is given may be the same or different.

Claims

1. A method for sensing changes in the filtering effect of filtering devices for the separation of contaminants from gaseous streams with indication of the changes by means of signal emittance, wherein changes of voltage.between different filtering means of the filtering device are sensed and that signals are emitted at a certain change in the voltage.

2. A method as claimed in claim 1 wherein signal emittance takes place in form of light and/or sound signals when the voltage exceeds or falls below a certain limit values and that signal emittance in form of a stop signal to a fan for gas transport through the filtering device takes place when the voltage is higher or lower than said limit values or other limit values.

3. A method as claimed in claim 2 wherein the stop signal is released with a certain time lag from the time when the voltage has reached any of the stop signal values.

4. A method as claimed in any of the preceding claims, wherein signal emittance takes place in form of an intermittent light and/or sound signal and in form of a constant light and/or sound signal if the voltage reaches higher or lower values than those necessary for releasing the intermittent light and/or sound signal.

5. A device for carrying out the method for sensing changes in the filtering effect of filtering devices for separation of contaminants from gaseous streams with indication by means of signal emittance, comprising a control circuit in which voltage differences between filter cells of the filtering device influences signal emitting comparators for emittance of light, sound or control signals in dependence upon changes in voltage between the filter cells.

6. A device as claimed in claim 5 wherein the control circuit is responsive to the resonance voltage between the cells.

7. A method as claimed in any of claims 1 to 4 and substantially as hereinbefore described with reference to the accompanying drawings.

8. A device substantially as hereinbefore described with reference to Figures 1 and 3 of the accompanying drawings.