APPARATUS FOR ACTUATING A SAFETY DEVICE

This invention relates to apparatus for actuating a safety device, and more particularly for actuating a door release arrangement on a device for holding open doors such as fire doors in the event of a fire alarm being raised. Such a holding device is referred to herein as a "door holder". The invention also relates to apparatus for releasing or closing a closure (such as a door).

Door holders are available in several forms. A simple hook and eye is most popular, with other devices using friction between the floor and a rubbing surface. There are magnetic types available that consist of two parts with attracting polarities, one being fixed to the door and the other to an adjacent surface.

Some such magnetic types are electromagnetic with the supply current being connected via an appropriate fire alarm system. The door release arrangement is hard-wired into the system in such a way that it acts to cut the electric supply to the electromagnet on activation of the fire alarm. Hence the door is allowed to close and thus form part of a safety fire break.

Electromagnetic door holders including such a door release arrangement are, however, expensive and complicated to fit, especially retrospectively. Consequently many fire doors are permanently held open with any suitable object that may be to hand. This is often, ironically, a fire extinguisher.

It is known from US-A-4520503 to provide a tone discrimination circuit for use with audible smoke or fire detectors or similar audible devices, which automatically emits an output electronic alarm signal, for notification of persons at remote locations, upon input of a proper audio tone from the smoke detector or other audible device. The circuit contains in series a microphone, a two stage audio amplifier, a frequency detector, and a time discrimination circuit. The circuit emits an output electronic alarm signal if and only if the audio input signal has sufficient amplitude, the desired frequency, and the desired duration. In the preferred example the duration must be 20 seconds or longer, though the circuit allows the audio input to cease for a period less than 0.25 seconds, without

loss of the output signal. The timing periods are adjustable.

The present invention seeks to solve these problems.

According to the present invention, there is provided a control unit for controlling an actuating means, wherein the control unit comprises a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and means coupled to the sensor for transmitting a signal to the actuating means in response to the alarm signal to actuate the actuating means; further comprising a timing control unit coupled to the transmitting means for outputting a timing control signal to the transmitting means for transmission to the actuating means to actuate the actuating means.

Preferably the signal is transmitted to the actuating means to actuate the actuating means on detection of the alarm signal. In preferred arrangements, the control unit transmits a signal for effecting actuation in response to the alarm signal only when an alarm condition is detected.

According to a further aspect of the invention there is provided a control unit for controlling an actuating means, wherein the control unit comprises a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and means coupled to the sensor for transmitting a signal to the actuating means for controlling the actuation of the actuating means, the conrol unit further comprising a timing control unit coupled to the transmitting means for outputting a timing control signal, wherein the unit is adapted such that the signal is transmitted to the actuating means in dependence on the alarm signal and the timing control signal.

Preferably a signal is transmitted to the actuating means to actuate the actuating means on detection of the alarm signal. In preferred arrangements, the control unit transmits a signal for effecting actuation of the actuator only when an alarm condition is detected. However, it is envisaged that the control unit might be arranged to send signals to the actuating means such that the nature of the signals, for example the presence or absence or some other characteristic (for example frequency) of the signals, determines

whether or not the actuation of the actuator is effected. In some arrangements, the detection of an alarm condition and/or the outputting of a timing control signal, for example, preferably effects a change in the nature of the signals sent to the actuating means. For example, the control unit may be adapted to send periodic signals having first characteristics to the actuation means, on detection of an alarm condition or under control of the timing control unit signals having second characteristics (or no signals) are sent to the actuation means to effect actuation.

Preferably the transmitting means is adapted to transmit the timing control signal to the actuating means to actuate the actuating means.

Preferably the control unit is adapted to be remote from the actuating means.

Preferably the control unit includes a memory for storing information relating to the pre- set time. Alternatively, or in addition, information relating to the pre-set time may be stored at the actuating means.

Preferably, where the control unit is adapted to transmit a signal to a plurality of actuating means, the same signal controls actuation of the plurality of actuating means. Alternatively, a plurality of different signals could be transmitted, each for a different actuating means.

Preferably the transmitting means is adapted to transmit a radio signal to the actuating means. Preferably the transmitting means is adapted to transmit a signal to the actuating means through the ambient medium.

Thus in preferred arrangements, the connection between the control unit and the actuating means is a wireless connection. Any suitable wireless connection means could be used. By providing a wireless connection, the installation of the control unit and actuating means can be simplified. The signal may be a radio frequency signal.

The alarm signal may comprise an acoustic signal, and/or might comprise another type

of signal, for example a radio frequency signal as emitted by some alarm systems.

Preferably the control unit further comprises a battery holder arranged to supply battery power to at least one component of the control unit. In some arrangements, preferably the power supply to the control unit is not mains power. In this way, easier installation may be possible. In many cases, the only power supply will be battery power, but in some cases other power supplies may be provided as an alternative or in addition to battery power. For example the control unit could include a solar power supply.

The control unit may further include a battery condition sensor, the control unit being adapted to transmit a signal to the actuating means in response to the detection of a battery condition.

This feature can provide a fail to safe mode for the control unit. For example, should the batteries be tampered with or removed then a signal is sent to the actuating device, for example to release the door. For example the battery condition sensor may monitor electronically for a drop in battery voltage which might occur if the batteries were tampered with or removed. Alternatively a switch system might be used, similar to that used for the actuating device.

The actuating means may be adapted to actuate a retaining means between a retaining state and a release state. The retaining means may be actuated by any suitable mechanism, for example magnetically, electromechanically, or any other mechanism or combination thereof.

According to the present invention, there is provided an actuating means adapted to be controlled by a timing control signal from a control unit via the ambient medium.

It is envisaged that in some arrangements, the control unit may be hardwired to an alarm device or system. The control unit may be adapted to receive the alarm signal other than through the ambient medium.

Thus a broad aspect of the present invention provides a control unit for controlling an actuating means, wherein the control unit comprises means for detecting an alarm condition, and means for transmitting a signal to the actuating means for controlling the actuation of the actuating means, the control unit further comprising a timing control unit coupled to the transmitting means for outputting a timing control signal, wherein the unit is adapted such that the signal is transmitted to the actuating means in dependence on the detection of the alarm condition and the timing control signal.

The means for detecting an alarm condition may comprise means for receiving an alarm signal. Thus the alarm signal may be received from the ambient medium as described further herein and/or may be received at the control unit via a wired link to an alarm system. The control unit may be incorporated into the alarm system itself.

The means for detecting an alarm condition may comprise, for example, a smoke detector.

In preferred arrangements described herein, the connection between the control unit and the actuating means is wireless, for ease of installation. In some arrangements, however, it is envisaged that a physical link may be present.

Further features of the present invention are set out in the dependent claims.

According to the present invention, there is provided apparatus for retaining and releasing a closure, comprising retaining means actuable between a retaining state in which it can retain the closure open and a release state in which it ceases to retain the closure and hence releases it, a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and means coupled to the sensor for actuating the retaining means to release the closure in response to the alarm signal.

According to a closely related aspect of the present invention, there is provided apparatus comprising a valve, a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and actuating means coupled to the sensor

for closing the valve in response to the alarm signal.

According to the present invention, there is provided apparatus for actuating a safety device, comprising an acoustic sensor and means coupled to the sensor for actuating the safety device in response to sound of a predetermined character.

Thus, in the case of a fire alarm system, for example, by actuating the safety device in response to sound of a predetermined character (typically the sound of fire alarm), a hard-wired link with the fire alarm system can be avoided. Hence the apparatus can be relatively cheap to install and relatively easily fitted to react to existing fire alarm systems.

Preferably, the actuating means is adapted to actuate the safety device only in response to sound in one or more predetermined frequency ranges, of a predetermined continuous duration and above a predetermined intensity threshold. If the above characteristics are carefully chosen, the apparatus can be highly discriminatory against sounds (even loud sounds) which do not emanate from fire alarms, and highly selective of sounds which do emanate from such alarms.

The invention extends to the aforesaid apparatus in combination with the safety device. The safety device may be or be part of a door holder or door closer and is hence conveniently actuable to permit release of a closure (for example, fire door). Again, the safety device may be actuable to close a valve, such as a valve on a gas line. Again, it may be an electrical switch, such as could turn off a mains electricity supply.

Preferably, the apparatus includes means for overriding the actuating means to permit actuation of the safety device at will. This feature has the advantage not only of convenience but also of safety. In the event of failure of the actuating means, it may be important, for example, to be able to close a closure by hand.

If, as is preferred, the safety device includes an engagement formation for holding a closure open and being actuable by the actuating means to permit release of the closure, the override means is preferably adapted to permit actuation of the safety device in

response to force applied to the engagement formation. This can afford a particularly simple way of permitting actuation of the safety device at will, since the closure need only be pushed open or closed for the safety device to be actuated.

Preferably, the override means is adapted to permit actuation of the safety device both in response to an opening force and in response to a closing force applied to the engagement formation in respective mutually opposed directions. This is an important safety feature. Whichever way the door is moved (open or closed), the safety device can be actuated. Thus, for example, a person could not inadvertently become locked in a room by the safety device.

In the preferred example, the override means is adapted to permit retraction of the engagement formation towards the body of the apparatus in response to force applied to the formation. More preferably, the engagement formation is pivotable, pivoting of the formation being arranged to cause its retraction. These features are a simple and convenient way of putting the invention into practice.

The apparatus may include a battery holder arranged to supply battery power to the actuating means. If so, and if an access door to the battery holder is provided, preferably the actuating means is arranged to actuate the safety device on opening of the access door. This is an anti-tamper feature. The apparatus also preferably includes a battery condition sensor (such as a voltage sensor); the actuating means being arranged to actuate the safety device if a low battery condition is sensed. This is a fail-safe safety feature, which can, for example, permit release of the closure if a low battery condition is sensed. The apparatus further preferably includes means for switching off power to the actuating means once the safety device has been actuated. This can conserve battery power, even in circumstances when the fire alarm (for example) is continuing to sound.

Another preferred feature that can conserve battery power is the inclusion in the actuating means of a bi-stable, preferably electro-mechanical, actuator. Whether it is on (actuating) or off (actuating), it does not consume power (or only consumes negligible amounts). Power is only consumed in changing the actuator from one state to the other.

The safety device may include an engagement formation for holding the closure open and being actuable by the actuation means to permit release of the closure.

In one preferred example the engagement formation is capable of engagement with a cooperating engagement formation. The cooperating formation could be mounted on the closure, whilst the main body of the apparatus could be mounted adjacent the closure. This obviates the need to mount the entire apparatus on the door. The apparatus could be mounted at a significant height above the floor, which would have the advantage that it could not be easily broken or tampered with.

In another preferred example, the engagement formation is capable of frictional engagement with the ground. This example is suitable for door-mounted use. In this example, preferably the engagement formation has an adjustable reach. Hence the clearance of the apparatus above the ground need not be critical.

The invention extends to apparatus as aforesaid in combination with the closure. It may also extend to a method of actuating a safety device; the method comprising features analogous to the apparatus features described above.

According to another aspect this invention provides a door holder that has an integral remotely released mechanism. The holder is manually operated to maintain a door in an open position by friction pressure between the holder stay and the floor. A clasp and spring provide both hold and release function. Connected to the clasp is an electro- mechanical device which when energized moves the clasp and allows the stay to release whereby the door may swing to close.

The power is provided from a battery within the holder, via a switch that is activated remotely by the fire alarm being sounded. The electro-mechanical device may be a solenoid or motor (for example, a servo or stepper motor). The switch may be activated by sound and/or radio waves. The invention could either form part of or be independent from a door closer.

The integral power of the unit may be switched by an Audio and/or a Radio Signal switching device. The holder may form an integral part of a door self closing device.

It will be appreciated that many of the above features may be provided independently, where appropriate.

Preferred features of the invention are now described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a first example of door holder mounted on a door, the door being closed and the door holder being viewed in front elevation;

Figure 2 is a view similar to that of Figure 1, but showing the door open and the door holder viewed in perspective; Figure 3 is a plan view of the holder, again mounted on the door;

Figure 4 is a scrap front elevational view of the holder showing the interior of the holder;

Figure 5 is a block diagram of the holder, showing particularly an actuating means; Figure 6 is an end view of a second example of door holder;

Figure 7 is a view of the second example similar to that of Figure 4; Figure 8 is a perspective view of a third example of door holder mounted at three different possible positions on a door;

Figure 9 is a scrap side view of the holder showing the interior of the holder; Figure 10 is a scrap perspective view of a fourth example of door holder showing the interior of the holder;

Figure 11 is a scrap sectional view showing a detail of the holder; Figure 12 is a block diagram of an arrangement incorporating a door holder as well as a control unit for the door holder; and Figure 13 is a block diagram of an arrangement like that shown in Figure 12 but incorporating a plurality of door holders.

Referring first to Figures 1 and 2, a first example of door holder 100 includes generally a body 102 (only the casing of which is visible in Figures 1 and 2) affixed to a door 10, a microphone 104, a plunger 106 including on one end a foot 108 for engaging the ground and at the other end a push knob 110, a holding arrangement (not shown in Figures 1 and 2) for keeping the plunger engaged with the ground and hence for holding the door, a release arrangement (also not shown) for releasing the plunger and hence the door, and means (again not shown) for actuating the door release arrangement in response to sound of a predetermined character sensed by the microphone 104. References to the actuating means are to be taken to include reference to the holding and release arrangements where the context so demands.

In use the door is held open by depressing the plunger 106 using the push knob 110 to engage firmly with the ground. The plunger is maintained automatically in position by the holding arrangement. If a fire alarm sounds, this sound is sensed by the microphone 104 and passed to the actuating means that actuates the release arrangement to release the plunger. If, as is invariably the case with fire doors, the door is biased towards the closed position, the door then automatically closes.

The door holder is now discussed in more detail with reference to Figures 3 and 4. The holding arrangement includes a clasp 120 and a retaining bracket 122 about which the clasp is free to pivot in all directions (as shown by the respective arrows in Figures 3 and

4). Pivoting of the clasp is limited both in the horizontal and in the vertical planes by abutment member 124, one end of the clasp riding over a shaped surface on this member. The plunger 106 is slidable in upper and lower guide brackets 126 and 128, and is biased upwardly by coil spring 130 which is attached to the plunger at its upper end with pin 132 and bears at its lower end against the lower guide bracket 128. Upward travel of the plunger is limited by stop 134. The shank of the plunger, which is hexagonal in cross-section, fits though a hexagonal hole 136 in the clasp 120 slightly larger than the shank cross-section.

It will be understood that the clasp 120 can grip or release the plunger 106 according to its angle relative to the plunger. Hence, when the plunger is depressed, the portion of

the clasp adjacent the hole 136 is moved slightly downwardly, and the plunger is free to continue to move downwardly. When pressure on the plunger is released, the spring 130 moves the plunger and the relevant portion of the clasp slightly upwardly, so that the plunger is then locked in position.

It will be appreciated that the holding arrangement described above allows the plunger to be adjustable for reach, so that different heights of door holder relative to the ground can be easily accommodated.

In this example, release of the plunger can be effected not only via the actuating means but also, by way of overriding the actuating means, by opening or closing the door. This is achieved as follows. The lower guide bracket 128 has a guide hole nearly the same size as the cross-section of the plunger 106 and hence acts as a fulcrum for the plunger. On the other hand, the upper guide bracket 126 has a rectangular slot, the narrow sides of which are parallel to the direction of movement of the door holder as the door is opened or closed. The narrow sides form a close fit with the plunger. Hence the plunger is free to rock somewhat when the door is opened or closed via an opening or closing force applied to the foot 108. Rocking movement of the plunger in turn causes the clasp 120 to pivot about a vertical axis. The shaped surface on the abutment member 124 curves upwardly towards each end. Hence pivoting of the clasp to an off-centre position causes that end of the clasp engaged with the abutment member to rise somewhat, which releases the plunger. The plunger then rises under the action of the spring 130. In this way movement of the door releases the plunger.

In a variant of the first example, the abutment member 124 includes a slit. The clearance between the upper and lower surfaces of the slit in the abutment member is screw-adjustable in order that the sensitivity of triggering of the clasp may be adjusted.

Referring to Figure 4, the release arrangement (actuated by the actuating means) includes a motor 150, powered by the actuating means, driving a threaded rod 152 via a reduction gearing mechanism 154. The threaded rod screws into and out of a corresponding threaded sleeve 156 which abuts the clasp 120 and is restrained from

rotating, so that the clasp 120 pivots about a horizontal axis. Hence rotation of the motor 150 causes the clasp to hold or release the plunger 106 according to its direction of rotation. If the plunger is released by the clasp, the spring 130 acts to retract the plunger back to its release position at which in turn releases the door.

The actuating means is arranged to supply electrical pulses to the motor 150 of sufficient duration that it can drive the threaded sleeve 156 from one extreme of travel to the other. For the remainder of the time, power is not supplied to the motor.

In an alternative example of the release arrangement, instead of including an electric motor, the arrangement comprises a permanent magnet (possibly of the rare earth type) on the clasp and a permanent magnet of a type that can have its polarity switched by an electrical pulse of only modest power. Such a magnet may suitably be made of Strontium, Barium Ferrite, Neodymium-lron-Boron, or Samarium Ferrite. The permanent magnet is so located on the clasp that it is moveable with the clasp between the poles of the switchable permanent magnet. Thus the permanent magnet on the clasp and hence the clasp can be attracted to one or other of the poles of the switchable magnet according to its polarisation at any particular time. The movement of the clasp produced by switching the permanent magnet is arranged to hold or release the plunger as appropriate.

In another alternative example of the release arrangement, the arrangement includes a bi-stable latch of the type found on retractable ballpoint pens or on catches for loft doors, to hold the clasp selectively in its hold and release states. The latch would be powered by a solenoid.

In fact, it will be apparent that any suitable kind of bi-stable electro-mechanical device would be advantageous, in that it is advantageous not to consume power in performing the hold or release functions, but only to consume it in changing state from one function to the other. Other suitable types of bi-stable actuators would be remanence solenoid, latching solenoid or opposed solenoid actuators.

The actuating means is now described with reference to Figures 3 to 5. It is shown as 160 in Figure 4 and includes various components mounted on a Printed Circuit Board.

In one part of the actuating means, the output from microphone 104 is amplified in amplifier 162 and then passed to a means for determining whether the alarm signal (sound) is of the predetermined character. This means comprises a rectifier and filter circuit 164 and a comparator 166. The rectifier and filter circuit filters out any signals outside the range 500-1000 Hertz. The filtered signal is then passed to the comparator 166 and compared with a threshold duration (5 seconds) and a threshold intensity (65 decibels) stored in threshold storage 168. Any signal that exceeds these thresholds is passed through OR gate 170 to the positive drive of monostable 172, and thence via bridge driver 174 to the motor 150. Hence any sound of the predetermined character described above triggers the actuating means to actuate the release arrangement to release the plunger 106 and thus release the door.

The characteristics of the sound which are tested for may be varied according to what sound it is intended that the door holder should respond to. For example, fire alarms in many countries are required by law to produce sound of a particular type. The characteristics that are tested for may need to be varied accordingly. As a guideline, the frequency of a conventional fire alarm sound is usually between 100 and 3000 Hz, the duration at least two seconds, and the intensity at least 55 or 60 decibels, although higher intensities are most usual. Other values of these parameters are naturally possible. If the alarm sound has two fundamental frequencies, the number of false positives may be reduced by testing separately at both frequencies.

As is clear from Figure 5, power is only supplied to the major components of the actuating means and to the motor 150 when main micro-switch 176 is closed. As can be seen from Figure 4, this switch is open unless formation 178 on the plunger 106 closes the switch, which occurs only when the plunger is depressed. Hence the depressed position of the plunger is effectively the "standby" state for the actuating means, whilst the release position is effectively the "off' state. Thus after an appropriate sound has caused the actuating means to actuate the motor the actuating means and motor will be

turned off even if the sound persists, so that current drain then falls to nil or some negligible quiescent value (typically 30 μA).

After actuation, the motor 150 resets the clasp 120 when the plunger 106 is depressed. Depression closes the switch 176, which in turn triggers monostable 180 and hence drives the motor in reverse via the negative drive of monostable 172. The reset clasp can then again hold the plunger in the depressed position.

The actuating means 160 is battery-powered and includes a battery holder 182. The door holder is designed to function on a single set of batteries for at least a year. Also provided is a battery voltage monitor 184 that produces an output signal if the battery voltage falls below a preset fail-safe threshold. The output of the monitor 184 is fed via the OR gate 170 to the positive drive of the monostable 172. Hence if a low battery voltage signal is produced the plunger 106 is released, so that the door is free to close. Furthermore, the low battery voltage signal is passed to the "B" (inverting) input of AND gate 186, whose other input "A" is coupled to the switch 176. The AND gate output goes active when A is active and B is inactive. Thus a low battery voltage signal will disable the negative drive of the monostable 172 and thereby prevent resetting of the clasp 120.

Therefore once a low battery voltage condition has been detected, the actuating means acts to release and keep released the plunger 106. The door holder remains inoperational until fresh batteries have been inserted. This is a fail-safe feature.

Another safety feature is that the clasp 120 is released if the access door 188 to the battery compartment is tampered with. To open the access door it is necessary to unscrew screw 190. However, unscrewing of this screw is arranged to turn access door micro-switch 192 on. This triggers monostable 194, which acts to release the plunger 106. The door holder cannot be operated again until the access door is replaced (and the batteries are in place).

A second example of door holder is now described with reference to Figures 6 and 7. Like parts to those in the first example are represented by like reference numerals. The second example is similar to the first example in many fundamental ways.

The basic features of the second example are as follows. The door holder 200 comprises a box 202 that is fixed to a door 10. Removal of lid 203 reveals a battery 281 , a Printed Circuit Board 261 , and micro-switch 276, which is closed when manual pressure is applied to stay pad (plunger push knob 210). This allows electrical power to flow to the switch 260 (actuating means) and thus put it to "stand-by". When a local independent fire alarm is sounded, the switch 260 closes and allows power to flow and energize solenoid/motor 250 which releases clasp 220 and allows the stay (plunger 206) to retract by pressure from spring 230. This in turn puts the micro-switch 276 back to "open" and stops the power supply to the solenoid/motor 250. The fire alarm may still be sounding, but as the stay has been released, current drain is essentially nil.

The battery 281 is again calculated to have a life in excess of one year. Piezo transducer 296 sounds a warning when potential in the battery 281 is insufficient to operate the solenoid/motor 250.

LED 298 glows when the switch 260 is energized and therefore at stand-by.

Manual release of the door holder is possible by moving the exposed end of the clasp 220.

Specific features of note in the second example are firstly that (as shown in Figure 7) the release arrangement in this example suitably includes a solenoid rather than a motor. Secondly, the spring 230 is in a different location to its location in the first example. Thirdly, the shank of the plunger 206 tapers from a broader to a narrower cross-section in order that depression of the plunger can activate the switch 276.

In a variant of the second example, the body 202 of the door holder is hingedly attached to the door. Thus if, for example, the holder is attached to the outside of the door, the door can be opened (but not closed) even if the plunger is being held depressed.

In another variant, the plunger 206 is provided with a foot that is hingedly attached to the

plunger (for example, by a flap of rubber if the foot is made of rubber). This again allows the door to be opened even if the plunger is being held depressed.

In summary, the door holder of the second example has a remotely operated release system. All the constituent parts are within a box that is fixed to a fire door. The sound of the local zone fire alarm activates a switch, which allows current from a battery to energise an electro-mechanical device to release a stay.

A third example of door holder is now described with reference to Figures 8 and 9. Again, like parts to those in the first example are represented by like reference numerals. In this example, the body 302 of the door holder 300 is wall-mounted rather than door- mounted. Three possible alternative mounting positions are shown. The door holder includes a tilt-adjustable mounting 301 for versatility.

In the third example, the plunger 306 is completely separable from the body 302 and is door-mounted. It will be understood that the plunger and body need to be aligned on installation. In analogous fashion to the second example, the plunger is engageable with the body and is retained in the body by a clasp and spring forming part of the holding arrangement.

This is explained in more detail with reference to Figure 9. In the third example, the actuating means is as described previously in relation to the first or second examples. A solenoid 350, with a return spring 351 , which is in compression, is used as the release arrangement, together with actuating arm 353. The holding arrangement includes a clasp 320 that is engageable in a location groove 307 in the plunger 306 to hold or release the plunger. The actuating arm 353 is so shaped that it can engage with the tail of the clasp to lift the clasp into and out of engagement with the location groove 307. Hence the actuating means can effect holding or release of the plunger.

The plunger 306 is arranged to be engaged in the body 302 against the action of coil spring 330 that is mounted in a fixed spring housing 329 and engages against a spring pad 331, which is slideable in the housing. Thus, when the clasp 320 releases the

plunger 306, the plunger, and hence the door, are forced away from the body of the holder by the action of the spring.

The actuating means can also be overridden either by opening or by closing the door. Firstly, the engagement between the clasp 320 and the groove 307 in the plunger is sufficiently weak to allow the door to be pulled away from the body 302 against the action of the clasp. Secondly, if the door is pushed further towards the body against the action of the clasp, the spring pad 331 abuts against a second plunger 333, which is slideable with respect to the spring housing 329 to cause the actuating arm 353 to release the clasp 320. The strength of the spring 330 is sufficient to force the groove in the plunger beyond the reach of the clasp before the clasp has had time to engage with the plunger. It will be understood that this second feature has the advantage of preventing the user slamming the door against the body 302 of the holder, since if the door is slammed too hard the clasp will not engage with the groove 307.

Since the plunger 306 is tapered between the groove 307 and its proximal end, pushing of the door against the body 302 can be arranged to release the door without the use of the second plunger 333.

The plunger 306 has a hole 309 for receiving a bar to turn it to screw it into the door.

In a variant of the third example, a fixed plunger with a male helical thread engages a corresponding female threaded rotatable socket in the body 302 and rotates this socket as the door is pushed against the body. The socket is arranged to be held by the holding arrangement and released in response to the sound of a fire alarm.

The actuating means may be overridden by pulling the door towards the closed position, away from the body. The socket is longitudinally slotted, the arms formed by the slots being retained by a resilient ring around the socket.

A fourth example of door holder is now described with reference to Figures 10 and 11. In this example, the actuating means is as described in relation to the first and second

examples. The workings of the holder are covered with a lid 403. The release arrangement comprises a solenoid 450, which drives a pivotable ratchet lever 420. The holding arrangement includes a foot operable carrier plate 421 , which is attached to back plate 423 of the holder by long pins 425. Bushes 427 are slideable along the pins against the action of springs 429. As shown in Figure 11 , the bushes are shaped to be slideable in elongate grooves 431 in the carrier plate. The carrier plate is biased upwardly by further springs 433. The ratchet lever 420 is engageable in a slot 435 in the carrier plate to hold the carrier plate. More than one slot may be provided.

A plunger 406 biased by coil spring 430 is attached to the carrier plate 421 by upper and lower guide brackets 426 and 428. The plunger includes a hinged foot 408.

Operation of the holder in this example is similar to operation of the holder in the first two examples. The door holder is set by pressing down with the foot on the carrier plate, which engages the ratchet lever 420 in the slot 435. This downward movement of the carrier plate engages the foot 408 of the plunger 406 with the ground. The loading of spring 430 creates the necessary friction to hold the door in place. Release of the door is effected by release of the ratchet lever 420.

The actuating means can be overridden by opening or closing the door. Movement of the door in one direction (say, to close it) pivots the foot 408 so that the door holder offers no resistance to movement of the door. Movement of the door in the other direction (say, to open it) cannot cause pivoting of the foot, but instead causes pivoting of the entire assembly of carrier plate 421 and plunger 406 against the bias of the springs 429 so that ratchet lever 420 disengages from the slot 435.

Figures 12 and 13 illustrate an arrangement incorporating a door holder 1000 generally as described above as holder 100, together with a control unit 1200 for the door holder. The control unit incorporates some of the functionality that the door holder would otherwise incorporate. In particular, it incorporates the microphone 104 the output from which is amplified in the amplifier 162 and then passed to a means 1202 for determining whether the alarm signal (sound) is of the predetermined character. This means is as

described hitherto with reference to the door holder 100.

The output from means 1202 is transmitted to the holder 1000 via a TX unit 1204 and radio transmitter aerial 1206 on the control unit.

The control unit 1200 also includes a timing control unit 1210 coupled to the TX unit 1204 and to an input device (such as a keypad) 1212 for inputting timing control commands. The control unit 1200 comprises a control chip 1224 and a storage chip 1236. The control chip 1224 comprises a clock chip and a comparator chip.

A radio receive aerial 1002 and RX unit 1004 on the holder 1000 receive signals from the control unit 1200. The remainder of the door closer 1000 is as hitherto described with reference to holder 100 except that the closer includes a timing unit 1006 coupled to an actuating means 1008 as described hitherto. The timing unit 1006 is adapted to receive timing commands from the control unit 1200 and to operate the holder 1000 in dependence on those timing commands. The timing unit 1006 comprises a storage chip 1012 and a comparator chip 1024.

In use of the arrangement illustrated in Figure 12, the operator installs a control unit 1200 near to, preferably adjacent to, the source of the alarm signal, such as a fire alarm. The operator installs a door holder 1000 on a door that is to be closed when an alarm signal is detected, such as a fire door. Thus, the control unit and door holder are installed distant from each other.

The operator sets the clock chip to the local time. The operator then uses the controls on the input device (eg. keypad) 1212 of the control unit 1200 to input timing control commands. The timer can be set at any point up to the required time of operation. In particular, the operator inputs a pre-set time for actuating the door release mechanism in response to a signal transmitted from the control unit 1200, thereby closing the door. Since the clock chip maintains the local time, this allows the comparator chip to determine when the local time is the same as the pre-set time.

The signal may be transmitted from the control unit 1200 to the door holder 1000 at the time at which the operator inputs the command, and then stored in the RX unit 1004 of the holder 1000. Once the pre-set time is reached, the stored signal actuates the door release mechanism and closes the door.

Alternatively, the pre-set time may be stored in storage chip 1224. When the pre-set time matches the local time (maintained by the clock chip) the storage chip 1224 instructs the TX unit 1204 to transmit a signal to the door holder 1000. When the signal is received at the RX unit 1004 of the holder 1000, the door release mechanism is actuated and the door is closed.

The operator also uses the controls on the input device (eg. keypad) 1212 of the control unit 1200 to input a later pre-set time for deactivating or enabling overriding of the action of the door release mechanism actuator - thus enabling the door to be held open again by the holder 1000. The action of the actuator is deactivated or is able to be overridden in response to a signal transmitted from the control unit 1200 to the door holder 1000.

As discussed above with respect to the signal for actuating the door release mechanism, the signal for deactivating or enabling overriding of the actuator may be transmitted from the control unit 1200 to the door holder 1000 at the time at which the operator inputs the command, and then stored at the RX unit 1004 of the holder 1000 until the pre-set time is reached. Once the pre-set time is reached, the stored signal deactivates or enables overriding of the actuator of the door release mechanism and allows the door to be opened.

Alternatively, the signal may be transmitted from the control unit 1200 to the door holder 1000 only once the pre-set time is reached. When the signal is received at the RX unit 1004 of the holder 1000, the actuator of door release mechanism is deactivated or is able to be overridden, thus allowing the door to be opened.

The arrangement illustrated in Figure 12 allows a fire door to be shut at night, when most buildings are unoccupied and the risk of fire spreading undetected is greatest. By

actuating the door release mechanism at a pre-set time during the night, in response to a first timed signal, the operator ensures that the fire door closes during the night and cannot be held open using the door holder 1000 until the action of the actuator is deactivated or is able to be overridden in response to a second timed signal (eg. the following morning). During the period between the first and second signals, the action of the actuator cannot be deactivated or overridden.

By way of example, the first timed signal may actuate the door release mechanism to close the door at a pre-set time from 8pm to 2am, preferably at a time from 9pm to 1am, more preferably at a time from 10pm to 12 midnight, most preferably at about 11pm.

By way of example, the second timed signal may deactivate or enable overriding of the actuator, thereby allowing the door to be opened, at a pre-set time from 4am to 10am, preferably at a time from 5am to 9am, more preferably at a time from 6am to 8am, most preferably at about 7am.

If required, the operator can set a number of timed closure commands, allowing for a number of time periods (ie. two or more time periods) to be programmed when a door holder 1000 is actuated and the door is therefore closed.

By way of example, using the input device (eg. keypad) 1212, an operator inputs a first pre-set time at which the door release mechanism is to be actuated in response to a first timing control signal, thereby closing the door. The operator inputs a second, later time at which the door release actuator is to be deactivated or is able to be overridden in response to a second timing control signal to allow the door to be held open again. The operator inputs a third, still later, time at which the door release mechanism is to be actuated in response to a third timing control signal, to close the door. The operator then inputs a fourth, yet later, time at which the door release actuator is to be deactivated or is able to be overridden in response to a second timing control signal, thereby allowing the door to be opened for a second time.

The signals from the control unit 1200 may be transmitted to the door holder 1000 at the

time at which the operator inputs the command, and then stored at the RX unit 1004 of the holder 1000 until the pre-set time is reached. Alternatively, the signal may be transmitted from the control unit 1200 to the door holder 1000 only once the pre-set time is reached.

Referring now to Figure 13, an arrangement is illustrated that incorporates a control unit 1200, generally as described above, together with one, two or more door holders 1000, each of which as generally as described above (in Figure 13, three door holders are illustrated).

The time-controlled signal from the control unit 1200 is transmitted to each of the holders 1000 and is received by the aerial 1002 and RX unit 1004 of each holder 1000. The timing unit 1006 of each holder 1000 is adapted to receive the timing commands from control unit 1200 and to operate the holder in dependence on those commands. Thus, the actuation of the one, two or more door holders 1000 may be coordinated, and one, two or more doors may be closed simultaneously in response to a single time-controlled signal from the control unit 1200.

In use of the arrangement illustrated in Figure 13, the operator installs a control unit 1200 near to, preferably adjacent to, the source of the alarm signal, as discussed above. The operator installs door holders 1000 on each door that is to be closed when an alarm signal is detected. Thus, the control unit and door holders are installed distant from each other.

Using the input device (eg. keypad) 1212 as discussed above, the operator inputs timing control commands. In particular, the operator inputs a pre-set time for actuating the door release mechanisms in response to a signal transmitted from the control unit 1200, thereby closing the doors. The operator also inputs a pre-set time at which the actuator of the door release mechanism is to be deactivated or is able to be overridden in response to a signal transmitted from the control unit 1200, thereby allowing the doors to be opened.

The signals from the control unit 1200 may be transmitted to the door holders 1000 at the time at which the operator inputs the command, and then stored at the RX unit 1004 of the holders 1000 until the pre-set time is reached. Alternatively, the signal may be transmitted from the control unit 1200 to the door holders 1000 only once the pre-set time is reached.

As discussed above, an operator may input multiple timed closure commands, allowing for a number of time periods to be programmed when door holders 1000 are actuated and the doors are therefore closed.

In order to eliminate signal interference problems where multiple systems A, B and C are situated closely together (eg. on different floors of a building), it may be necessary use different signal identifiers - for example, different signal frequencies - in each of the systems.

In this regard, with reference to the arrangement illustrated in Figures 12 and 13, the input device (eg. keypad) 1212 of the control unit 1200 comprises an identifier set-up control 1208 linked to the TX unit. The holder 1000 comprises an identifier set-up control 1010 linked to the RX unit.

The identifier set-up control 1208 of the control unit 1200 allows an operator to input the identifier for system A (eg. the frequency at which the TX unit 1204 transmits a signal). In use, the operator inputs a selected identifier, which is stored in the storage chip 1236. The operator then transmits a signal - having the selected identifier - from the control unit 1200 to the door holder 1000. The operator then programs the RX unit 1004 of the holder 1000, via the identifier set-up control 1010, to recognise the received signal identifier and to respond only to signals that have the selected identifier. The received signal identifier is stored in the storage chip 1012 of the holder 1000.

The operator repeats this initialisation process for each system A, B and C, selecting a different identifier for each system and storing this identifier in the storage chip of the holder(s) 1000. By way of example, the operator may select a different frequency for

each system. Thus, the RX unit(s) associated with each system respond only to signals at the frequency transmitted by their respective TX unit, avoiding interference between systems.

In more detail, when the RX unit 1004 of a holder 1000 receives a signal from control unit 1200, the signal is passed to the comparator chip 1024 to determine whether the signal identifier (eg. frequency) matches the signal identifier stored in the storage chip 1012. If the signal identifiers match (eg. the frequencies are the same), then the door holder 1000 responds to the signal by actuates the door release mechanism, thereby closing the door; or by overriding the actuator, thereby allowing the door to be opened.

The control unit 1200 may be powered using any convenient power source. In preferred examples, the control unit 1200 includes a battery holder for holding one or more batteries or other power sources. In the preferred example, the control unit fails to safe in that, should the battery or other power source be tampered with, removed or if the power supply becomes low, a radio signal is sent to the actuating device to release the door. In one example, this is done by monitoring electronically for a drop in battery voltage, but a switch system could be used such as that described above in relation to the actuating device.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

For example, instead of the apparatus being used to release a door, it may be used to cut off a gas supply by turning off a gas valve in response to the warning sound of a gas alarm. This aspect may have particular applicability in boats or caravans.

The holding and release functions on the valve can be achieved with any of the holding and release arrangements described above (with suitable modification where appropriate). Alternatively the valve may be driven directly by an electric motor. The apparatus may be powered by mains electricity rather than batteries if it is mounted in

the home, for example.

In one form of this aspect, a gas alarm system may be provided comprising two main parts. The first part is a gas warning device that makes a specific special warning sound, whilst the second is the apparatus referred to in the preceding paragraph. In this example, the apparatus would only be responsive to the particular sound made by the gas warning device. This would prevent it from triggering due to a different alarm sounding.

As another example, the apparatus may be used to actuate the mains electrical switch for a building if a fire alarm is sensed. This has the advantage that fire-fighters entering a blazing building fitted with this apparatus would not receive any electric shocks. Also, the apparatus may be used to turn off the mains gas supply for the same reasons.

As another example of possible modifications of the invention, if a low battery condition is sensed the apparatus may fail-safe via mechanical rather than electrical means.

As yet another example, the apparatus may be incorporated into any appropriate type of door closing mechanism, such as a Perko (trade mark) door closer.

Again, instead of the holding arrangement including a plunger held in place under frictional engagement with a clasp, a ratchet could be arranged to engage with teeth on the plunger. Release of the plunger could be effected by solenoid actuated release of the ratchet.

Again, the safety device could be a roller driven by a clockwork mechanism that is wound up when the door is opened. The mechanism could be actuated to close the door in response to sound of the predetermined character.

Again, deliberate redundancy could be built into the apparatus by providing, for example, two or more actuating means.

Again, instead of being triggered by sound of the predetermined character, the apparatus could be triggered by radio-frequency radiation of a predetermined character such as is emitted by certain types of fire control centres on sensing a fire.

Again, the actuating means might include a timer for actuating the safety device after a predetermined period of time, say, six or eight hours. Thus in the case of a door holder, for example, the door might be opened at the beginning of a day. After the predetermined period (perhaps at night time), the door holder would be actuated automatically to release the door. This is an additional safety feature. The timer could be electrical or mechanical (for example, a clockwork mechanism).

Alternatively or additionally, the actuating means might include a light-sensitive device for actuating the safety device when the ambient light level falls below a predetermined value. Thus, for example, all the fire doors in a building could be arranged to close after dark.