This application represents the first application for a patent directed towards the invention and the subject matter.
1. Field of the Invention
The present invention relates to the control of smoke and heat evacuation and ventilation (SHEV) devices. The present invention also relates to SHEV control apparatus that is compatible with fire alarm systems.
2. Description of the Related Art
In many regions around the world, regulations are being put in place for the introduction of smoke and heat evacuation and ventilation devices into buildings. In particular, these regulations often relate to relatively large buildings and buildings that may be described as being of multiple occupancy. Thus, in many applications, it is necessary to include smoke and heat evacuation and ventilation apparatus in order to provide more time for residents to be evacuated when a fire has been detected.
In buildings of multiple occupancy, smoke may be vented naturally by opening windows and for a specified room volume, it is possible to calculate the size of window that is required. Windows of this type are usually positioned just below ceiling height, given that this is where the combustible gases collect. Thus, upon fire detection, the system is configured to exhaust this gas as quickly as possible from regions close to the ceiling. Windows can be louvered or opened from a hinge on their bottoms edge. The removal of smoke allows residents to escape and facilitates fire extinguishing activities.
Regulations are being developed in which all of the wires must be monitored and the detection circuits must also be monitored. While solutions are available, problems exist in that a substantial degree of wiring is required. Thus, it becomes necessary to have a pair of wires for detection with another pair of wires for actuation. This not only adds to installation costs but also creates additional problems in that the smoke and heat evacuation and ventilation system will operate in a substantially different manner to existing fire alarm systems.
Fire detection and alarm systems are known in which detection devices and alarm generating devices are connected across a single pair of wires. This field wiring may pass in and out of each device and an end of line device is connected across the field wiring at the last device. At the controller, resistors form a voltage divider and in a quiescent condition, a steady voltage may be measured. When a detector operates, a switch closes resulting in a comparator at the controller measuring a lower voltage, which in turns causes an alarm to sound.
Sounder circuits are also monitored for short circuit faults. Each sounder includes a blocking diode so as to ensure that current cannot actually flow through them during the quiescent condition. When the alarm is triggered, the current to the sounder circuits is reversed such that current can now flow through the blocking diodes and the alarm sounds. Thus, current flows in a first direction during the detection mode and then flows in the opposite direction during the activation mode. Such a situation is acceptable for alarm devices which, once current is removed, return to their original state; because, an alarm is either sounding or it is not sounding.
The situation with smoke and heat evacuation and ventilation (SHEV) systems is somewhat different. The scenario outlined above for alarm systems would be adequate for the SHEV devices were it only necessary to open them. However, in addition to alarm systems being operational when required, it is also necessary to conduct routine tests such that a test signal is generated to test the ventilation systems which would in turn result in them opening. However, at the completion of the test, it is also necessary for the system to return to its initial state. Thus, a problem exists in that not only is it necessary to open the ventilation devices but, thereafter, it is also necessary to close the ventilation devices. Thus, the ventilation devices not only require power in a first direction, to effect an opening, they also require power to be supplied in the opposite direction so as to ensure that the ventilation devices are closed again, thereby allowing the system to return to a quiescent monitoring state.
According to an aspect of the present invention, there is provided an interface circuit for a smoke and heat evacuation and ventilation device as set out in claim 1.
According to a second aspect of the present invention there is provided a controller for a plurality of smoke and heat evacuation and ventilation devices as set out in claim 11.
According to a third aspect of the present invention, there is provided a method of controlling a plurality of smoke and heat evacuation and ventilation devices as set out in claim 16.
A building 101 of multiple occupancy is illustrated in
The main front door 104 provides access to shared areas, including central elevators and staircases which provide access to the higher floors.
At each floor of the shared access area, there are provided smoke and heat evacuation and ventilation devices, located substantially just below ceiling level. Thus, for the first floor a group of devices 105 are provided, for the second floor there is a group of devices 106, for the third floor there is a group of devices 107, for the fourth floor there is a group of devices 108, for the fifth floor there is a group of devices 109 and for the sixth floor there is a group of devices 110.
The smoke and heat evacuation and ventilation device (SHEV) 110 identified in
Window 204 is shown in greater detail in
In order to close the SHEV, the polarity of a drive current supplied to the actuator 301, from the controller 302, is reversed, resulting in chain 303 being retracted back into the actuator 301, thereby closing window 204.
In an embodiment, chain 303 is configured to be of an optimum length to achieve appropriate opening and closing of the window 204. However, in a further embodiment, it is possible for the SHEV controller 302 to include a timer such that the extent to which chain 303 is extended and then retracted may be controlled accurately so as to ensure precise opening and closing without causing damage.
A schematic representation of the smoke and heat evacuation and ventilation system is illustrated in
In addition to the SHEV controller, each floor also includes a fire alarm and a fire detector. Thus, on the uppermost floor there is provided a detector 406 and an alarm 407. Similarly, on the ground floor there is provided a detector 408 and an alarm 409. On the remaining floors, detectors 410, 412, 414 and 416 are provided with alarms 411, 413, 415 and 417 respectively.
The detectors, alarms and SHEV controllers may be referred to as ancillary devices and as such are connected across field wires 418 and 419 for the first zone, or across field wires 420 and 421 for the second zone. At their ends, the field wires 418, 419 for the first zone are terminated by a first end of line device 422 and field wires 420, 421 of the second zone are terminated by a second end of line device 423.
The field wires communicate with a control circuit 424 which, in an embodiment, is housed behind a control panel located at an accessible position to facilitate testing and resetting thereof. In this example, control panel 424 is capable of supporting two zones as illustrated in
The arrangement shown in
For detection purposes, current limiting is provided to facilitate accurate voltage measurement for the detection of device activation. During alarm activation, the current is reversed and the current limiting devices are taken out of circuit. Similarly, it is possible for the current to be returned to its primary direction (as used in detection) but again with the current limiting devices taken out of circuit so as to facilitate SHEV closure and thereby establishing a reset condition.
Control panel 424 is shown in
In order to active the SHEVs it is necessary to supply sufficient current. Thus, in an example, it may be necessary to pass three to ten amps down two wires that are normally limited to, say, 100 mA in the forward direction. Systems of this type may be configured to provide between one and two amps in the reverse direction in order to operate the alarms.
In an embodiment, the SHEVs open when there is an alarm condition and then close in response to a reset condition. However, in an embodiment, compatibility is maintained with fire detection components.
In an embodiment, the current limit is bypassed for a set duration, during which time twenty-four volts (24 v) are applied to power the SHEVs. However, upon reset, the fire detection components are returned back to their normal operation. Thus, the current limit is bypassed so as to supply enough power to close the SHEVs. However after a period of time, the current limit is reintroduced thereby limiting the current to typically 30 mA.
The control circuit 424 includes a micro controller 425 configured to control the timing of SHEV operation. Thus, typically, SHEVs may be powered for between twenty to thirty seconds, during which time monitoring of the fire detectors is not available. However, after this timeout period, the current limit is brought back into play such that there is a voltage drop across the end of the line. When a detector is triggered, it pulls the voltage down to typically twelve volts and this can be detected at the control panel.
For the alarm condition, the polarity is reversed and in an embodiment, twenty four volts (of opposite polarity) is made available for a period of thirty seconds so as to open the SHEVs. In an embodiment, the alarms will sound due to the current being reversed. In an embodiment, the end of line device 422 includes a diode thereby placing it out of circuit during this reverse mode of operation.
The controller may be for a plurality of smoke and heat evacuation and ventilation devices connected to field wiring but the system also includes fire detection devices and alarms. A first driving circuit 426 provides a constant limited current in a first direction 427 through the field wiring. The first driving circuit also includes detection capability for detecting alarm conditions in response to voltage changes when the constant limited current is applied.
A second driving circuit 428 is configured to supply an opposite polarity voltage to the field wiring in order to activate the alarms and to open the SHEV devices. Furthermore, a third driving circuit 429 is configured to apply a non-limited voltage to the field wiring to provide a current in the first direction in order to close the SHEV devices.
In an embodiment, the controller 424 also includes a fourth driving circuit 430 for modifying the operation of the second driving circuit 428 to indicate that SHEV devices are to close during an alarm condition, in response to the operation of a switch 431. In an embodiment, the fourth driving circuit 430 introduces a step change to the opposite polarity voltage, as detailed with reference to
In the embodiment of
Many approaches to embodying the circuits of
After, say, sixty seconds, the micro controller may turn off the bypass transistor and disable the bridge. Thus, the current limiting operation resumes and the voltages are monitored by an analog to digital converter which provides feed-back to the micro controller 425.
An interface circuit for a smoke and heat evacuation and ventilation device connectable to field wiring that is compatible with a fire detection and alarm system is illustrated in
In the interface device, a switching circuit 603 is provided for supplying an opening current or a closing current to the SHEV device from the field wiring circuit. Furthermore, a control circuit 604 controls the switching circuit 603 in response to control conditions detected in the field current.
An actuator 605 receives current from switching circuit 603. In an embodiment, the actuator 605 controls the opening and closing of windows, of the type illustrated in
In a quiescent monitoring mode, that is to say when a current is flowing in the direction of arrow 601, this current is limited and, in some embodiments, may also be intermittent in order to conserve power. In an embodiment, the current limiting device is bypassed when SHEV closing current is required.
As illustrated in
In the embodiment of
In addition to edge detection, a first rectifier 613 provides a signal to switching logic 612 when current is flowing in the direction of arrow 601. Similarly, a second rectifier 614 provides an input signal to switching logic 612 when current flows in the direction of arrow 612. Consequently, operations performed within the switching logic 612, and subsequently the operation of switches 606 to 609, will be influenced by the direction of current flow. Thus, with this combination of detectors, the control circuit 604 responds to sudden changes in applied voltage and voltage polarity.
The switching logic 612 is configured to operate switches 606 to 609 in response to inputs from circuit 611, 613 and 614. The operation of this logic will be described with reference to
A graph shown in
At time 704, for the purposes of this example, an alarm condition is detected resulting in the voltage drop across the loop being reduced to 706, typically a drop of 12 volts down to 5 volts. There is a short reaction time from time 704 to time 707, whereafter the control panel recognises this voltage drop as an alarm condition and therefore takes action in order to sound the alarms. This action involves reversing the flow of current (from direction 601 to direction 602) while taking current limiting devices out of circuit. Thus, at time 707 the voltage across the loop is changed from voltage 706 (plus 5 volts) to voltage 708, typically minus 24 volts. This alarm condition, for the purposes of this example, is sustained from a time 707 to a time 709.
At time 707, the step change on the field loop (a falling edge) is detected by edge detection circuit 610. Furthermore, polarity detector 614 will subsequently identify the flow of current as being in the direction of arrow 602. This condition is recognised by the switching logic 612 such that, in this example, switch 609 and switch 606 are closed resulting in a voltage being applied across actuator 605 in order to open the SHEV device. Under the control of timer 611, this drive power to the SHEV is maintained until time 710, whereafter, a timeout occurs and no further power is conveyed to the SHEV controller. Thus, at time 710 the SHEV has been fully opened and the SHEV remains open until time 709.
At time 709 a reset condition occurs to the effect that the system may be put back to its monitoring condition. The reset condition is initiated at time 709 and in a conventional fire detection system, the system would return to a monitoring state at time 709. However, in the present embodiment, it is necessary to close the SHEV devices before quiescent monitoring may be re-adopted.
In order to close the SHEV devices, the current limiting circuitry at the control panel remains out of circuit and a voltage 712 of typically 20 volts is applied until time 713. The edge at time 709 is detected by edge detection circuit 710. After time 709, current flows in the direction of arrow 601, therefore a positive indication is provided by detector 613. The polarity has reversed therefore the closing of switches 606 and 609 results in the actuator operating in the reverse direction, thereby closing the windows. The closing operation may take place for the full duration from time 711 to time 713. However, the timer 611 may reduce this period such that the window closes without causing damage. At time 713, the current limiting devices are brought back into circuit and the monitoring operation is resumed, with the field loop voltage back to level 705.
In an embodiment, it is also possible for the SHEV devices to be closed while in the alarm condition. Such an operation is required in order to allow fire officers to manually control the SHEVs while maintaining the alarm condition. As illustrated in
In the example shown in
For the purposes of this example, it is assumed that the SHEV devices are opened again at time 809. This is achieved by returning the loop voltage to level 803 (minus 24 volt), resulting in falling edge 810 being detected at edge detector 610. As a result of this, an activating signal is again generated at time 809 which is maintained until time 810, resulting in the SHEV devices opening again.
Thus, with the device open, the generation of a rising edge with a current of negative polarity, results in the SHEV closing. In this way, it is possible to close the device for fire officer access even when the system is in an alarm condition. The alarm is preserved because the SHEV controller is looking for the edge.
In an embodiment, a 250 millisecond delay is introduced and by using the edge detection and polarity sensing it is possible to determine the state required for the SHEV device. This is used in combination with timer 611 so as to control the duration of activation up to a maximum of 60 seconds, in an embodiment.
Number | Date | Country | Kind |
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1110410.6 | Jun 2011 | GB | national |