Field of the invention The present invention relates to a safety device. More particularly the present invention relates to a safety device which is arranged to switch off electric power of an appliance in a case when smoke or heat is detected.

Background of the invention

Overheating of domestic appliances, for example televisions or washing machines, causes a great amount of fires at homes. This is usually caused by misuse of said appliances, such as leaving an electrical stove on unattended. Also appliances such as televisions or computers may overheat because of dust piled up inside the device.

In many cases the fire is detected only after a fire alarm device has been activated in a room and significant damages have already been caused by the fire. There are no safety devices available which could be attached to any existing domestic appliance to control and protect them from overheating.

Therefore, there exists a need for a device, which could be attached to any domestic appliance having a risk for overheating and causing a fire, wherein the overheating would be detected before any damages have occurred and further overheating would be prevented.

Summary of the invention

The present invention provides a safety device having an input and an output for an electrical receptacle, wherein the electric power from the input is arranged to pass through the device through a switch unit to the output, said switch unit having means for switching off said passing power by breaking the electrical continuity, and a detector unit having means for detecting smoke and/or heat operably connected to the switch unit, wherein the detector unit, in case of detecting smoke and/or heat, is arranged to signal the switch unit to switch off the power. Operably connected" as used herein refers to a functional linkage between different elements which are joined so as to operate in a functional manner, for example joined electronically. One advantage of the present invention is that the power of said appliance can be automatically switched off to prevent further overheating and fire. This can be achieved by detecting smoke and/or heat which are detectable even before any fire has set on.

Another advantage of the device of the present invention is that it is preferably portable and it can be attached to any existing domestic appliance, i.e. in practice by plugging in to an electric receptacle or the like.

Further advantage of the present invention is that the smoke and/or heat detector can be placed in any suitable place i.e. it does not have to be attached to the device itself. Still further advantage of the present invention is that any additional devices may be connected to the safety device, such as a fire extinguisher or a fire alarm.

Brief description of the drawings Figure 1 shows an embodiment of an arrangement of the safety device Figure 2 shows a circuit diagram of the safety device

Figure 3 shows an embodiment of the safety device including an additional fire extinguisher

Figure 4 shows an embodiment of an arrangement of the safety device wherein the switch unit is located in the safety device unit Figure 5 shows an implementation of the safety device having a casing containing the safety device itself and a casing containing the detector unit

Detailed description of the invention

The present invention provides a safety device having an input and an output for an electrical receptacle. This means that the device may be connected between a regular wall socket or the like and the domestic appliance to be protected. The "electrical receptacle" as used herein includes, in addition to regular one-phase power wall sockets, other suitable electrical connection types, such as three-phase electric power connections. Examples of electrical receptacles include general 1 10V or 240V electrical receptacle outlets wherein a corresponding inlet can be plugged. The safety device is generally equipped with a plug to be plugged to a wall socket.

Preferably the safety device is portable i.e. it can be placed in any suitable place and connected to any suitable appliance, and it can be removed and placed to another place.

The electric power from the input is arranged to pass through the device through a switch unit to the output, said switch unit having means for switching off said passing power by breaking the electrical continuity. This will prevent the overheating of the appliance as the feeding power has been switched off at the output. The means for switching off the power may comprise any known suitable means, such as a relay (one or more) or any suitable electrical circuit. In one embodiment the device itself contains the switch unit. In another embodiment the detector unit contains the switch unit.

The device may also contain a control unit arranged to control the operation of the switch unit i.e. the control unit may receive a signal from the detector unit in case of fire and/or smoke and control the switch unit to break the electrical continuity. In one embodiment the detector unit contains the control unit i.e. they are in the same physical casing which is connected to the switch unit and can operate it. In another embodiment the control unit is located in the casing of the safety device. In the device arrangement there is also a detector unit having means for detecting smoke and/or heat operably connected to the switch unit, wherein the detector unit, in case of detecting smoke and/or heat, is arranged to signal the switch unit to switch off the power, for example by using a control unit to receive the signal and operate the switch unit. In one embodiment there are more than one detecting units which can be different or of the same type. They can also be in the same or separate casings. In general, the device may have means (for example sockets) for connecting more than one of such detecting units, and therefore more detecting units may be added if needed. The safety device arrangement is arranged to monitor predefined temperature limits, i.e. to recognize when the temperature is too high and there is a risk of fire, or to monitor predefined smoke limits in the same manner. This may be carried out by the detector unit, by the control unit or by any other suitable arrangement.

In one embodiment the detector unit is connected to the safety device by wire. In another embodiment the detector unit is wirelessly connected to the safety device. In such case the wireless connection may be any suitable radio frequency wireless connection, such as Bluetooth, WLAN or the like, or it can be some other wireless connection, such as light based connection (e.g. infrared), or audible connection. In general the detector unit may be placed in a suitable place for detecting the heat and/or smoke, such as above or near the appliance itself. The detector unit may be arranged to be fastened with fastening means to the appliance to be monitored or to a furniture above it. In one embodiment, where appropriate, the detector unit is arranged to be placed inside the appliance to be monitored.

In one embodiment the detector unit comprises a smoke detector. Smoke detector may be of any suitable type, such as an optical detector, an ionization detector, an air-sampling detector, such as aspirating smoke detector, or a carbon dioxide or carbon monoxide sensor.

An optical detector is a light sensor. When used as a smoke detector, it includes a light source (incandescent bulb or infrared LED), a lens to collimate the light into a beam, and a photodiode or other photoelectric sensor at an angle to the beam as a light detector. In the absence of smoke, the light passes in front of the detector in a straight line. When smoke enters the optical chamber across the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus triggering the alarm (Wikipedia).

An ionization detector can detect particles of smoke that are too small to be visible. It includes about 37 kBq or 1 μθί of radioactive americium-241 ( ²⁴¹ Am), corresponding to about 0.3 μg of the isotope. The radiation passes through an ionization chamber, an air-filled space between two electrodes, and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm (Wikipedia). An air-sampling smoke detector is capable of detecting microscopic particles of smoke. Most air-sampling detectors are aspirating smoke detectors, which work by actively drawing air through a network of small-bore pipes laid out above or below a ceiling in parallel runs covering a protected area. Small holes drilled into each pipe form a matrix of holes (sampling points), providing an even distribution across the pipe network. Air samples are drawn past a sensitive optical device, often a solid-state laser, tuned to detect the extremely small particles of combustion (Wikipedia). In one embodiment the detector unit comprises a heat detector. Heat detector is a fire alarm device designed to respond when the convected thermal energy of a fire increases the temperature of a heat sensitive element. The thermal mass and conductivity of the element regulate the rate flow of heat into the element. All heat detectors have this thermal lag (Wikipedia). The heat detector may be a fixed temperature heat detector or a rate-of-rise heat detector.

Fixed temperature heat detector is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive element reaches a set operating temperature. Thermal lag delays the accumulation of heat at the sensitive element so that a fixed-temperature device will reach its operating temperature sometime after the surrounding air temperature exceeds that temperature. The most common fixed temperature point for electrically connected heat detectors is 58 °C. Technological developments have enabled the perfection of detectors that activate at a temperature of 47 °C, increasing the available reaction time and margin of safety (Wikipedia).

Rate-of-Rise (ROR) heat detectors operate on a rapid rise in element temperature of 6.7° to 8.3°C increase per minute, irrespective of the starting temperature. This type of heat detector can operate at a lower temperature fire condition than would be possible if the threshold were fixed. Rate of rise detectors may not respond to low energy release rates of slowly developing fires. To detect slowly developing fires combination detectors add a fixed temperature element that will ultimately respond when the fixed temperature element reaches the design threshold (Wikipedia).

In one embodiment the safety device of the invention has means for controlling a fire extinguisher operably linked to the device wherein the detector unit, in case of detecting smoke and/or heat, is arranged to signal the device to switch on the fire extinguisher. This may be carried out by using a control unit to receive the signal and operate the fire extinguisher. The fire extinguisher may be connected to the safety device by wire or by wireless connection, such as by radio transmission. In one embodiment the safety device of the invention has means for controlling a fire alarm operably linked to the device. The alarm may be integrated to the safety device or it can be remote and connected to the safety device by wire or by wireless connection. The fire alarm may use audible or visible alarm signal, or both.

The safety device of the invention is now described by some non-limiting examples with references to the attached figures.

Exam les

Figure 1 shows an exemplary arrangement of the safety device attached to a television set. In the safety device there are the device unit 1 and the detector unit 2. The switch unit 1 is located in the middle of the connecting cable 3, wherein the first end of the cable 3 is connected to the source of the power 4 (wall socket) and the second end of the cable 3 is connected to the power cord 5 of the television set 8. The connecting cable is an electric cable containing two or more electrical wires. One of the wires is connected to the wires 6 of the detector unit 2 so that the electric power travels through the detector unit 2 having the switch unit 7. !n this embodiment the detector unit and the switch unit are integrated in the same casing located at the close proximity of the television set 8.

The detector unit 2 may contain a heat detector or a smoke detector or both. The switch (relay) is closed in the normal state (when the temperature of the television is normal) allowing electric power to travel through the safety device. If smoke or rise of the temperature to a predefined safety limit is detected, for example when the television is overheated, the switch will open and the feed current to the television will be cut off. This will turn off the television and prevent further overheating and even the breaking out of fire. The detector unit may be installed close to the appliance, for example with any suitable fastening means, or inside the appliance if possible. Figure 2 shows an exemplary arrangement of the safety device attached to a television set as a switch diagram. The diagram shows the operating principle of the switch unit 7 of the detector unit 2. In the situation of Figure 2 the temperature of the television set has risen over the predefined safety limit or the smoke detector has detected smoke, and the switch unit 7 of the detector unit 7 has opened the circuit thus shutting down the television. One wire 13 of the electric cable goes continuously through the device (not shown in the figure). Another wire 14 of the electric cable goes through the switch unit 7. Figure 3 shows an embodiment wherein the safety device 1 is connected to a fire extinguisher. The extinguisher unit 1 1 , such as a carbon dioxide fire extinguisher, has been placed on the television set, close to the ventilation holes. The extinguisher unit has been connected to the detector unit 2 with a cable. If smoke or rise of the temperature to a predefined safety limit is detected, for example when the television is overheated, the extinguisher unit 1 1 will switch on, the switch will be opened, the feed current to the television will be cut off, and the fire in the television will be extinguished.

Figure 4 shows an embodiment where the main power does not go through the detector unit(s), but the detector(s) signal the switch unit 7 to switch off the power. This is safe as the detector unit(s) do(es) not operate with the main power, but may be use only minute current for signaling. In one embodiment the device arrangement contains a separate temperature detector unit 15 and a separate smoke detector unit 16. In one embodiment they are located in the same casing. These units may be connected with a cable to the safety device 1 , which contains the switch unit 7. Such an arrangement may also be implemented wirelessly, wherein the detector unit will control the safety device for example with radio transmitter. Figure 5 shows an implementation of the safety device having a casing containing the safety device 1 itself and a casing containing the detector unit 2, connected together with a cable 6. In the safety device there are lights indicating the operation thereof and a push button for testing the operation of the device. It will be appreciated that the devices of the present invention can be incorporated in the form of a variety of embodiments, only a few of which are disclosed herein. It will be apparent for the expert skilled in the field that other embodiments exist and do not depart from the scope of the invention. Thus, the described embodiments are illustrative and should not be construed as restrictive.