WO2000062581A1

WO2000062581A1 - Floor heater controlled by a presence detector

Info

Publication number: WO2000062581A1
Application number: PCT/SE2000/000656
Authority: WO
Inventors: Stefan BÄCKFORS
Original assignee: Baeckfors Stefan
Priority date: 1999-04-13
Filing date: 2000-04-06
Publication date: 2000-10-19
Also published as: SE9901305D0; AU4443500A; SE9901305L

Abstract

A floor protecting device includes a floor protecting cover in turn including a heating element and means for turning the heat on or off in dependence of the presence or absence, respectively, of a person on the floor protecting cover. A method of controlling the heating function in a floor protecting cover including a heating element is also disclosed, said method including the following steps: detecting the presence of a person on the floor protecting cover; if a person is detected on the floor protecting cover, turning or keeping the heating function on; if a person is not detected on the floor protecting cover, turning or keeping the heating function off. Hence, the device according to the invention provides a heating source which only consumes energy when it is actually being used thus saving energy without reducing the comfort of the person or animal using it.

Description

FLOOR HEATER CONTROLLED BY A PRESENCE DETECTOR

Technical Field

The present invention relates to a floor protecting device comprising a floor cover which in turn comprises a heating element.

Background

Such floor protecting covers are known, for example, from US Patents US 2, 619, 580, US 2, 845, 519, and US 4 247 756. The floor protecting covers disclosed in these documents consist of a relatively rigid plastic or rubber sheet on which a chair, and possibly other furniture, may be placed.

US 2, 845, 519 and US 2, 619, 580 disclose portable heating floor covers in which standard resistive heating elements are placed between two electrically insulating sheets.

US 4, 247,756 discloses an electrically heated floor mat comprising outer layers and an inner, electrically resistive layer, said layers being vulcanized together. The heat may be controlled by a thermostat. The selection of materials etc. making the mat fit for normal use is discussed.

Except for the thermostat control disclosed in US 4, 247, 756 none of the documents describe how the heating function can be controlled.

Object of the Invention

It is an object of the present invention to provide a more energy-efficient heated floor protector than what is known in the art. Summary of the Invention

This object is achieved according to the invention by a floor protecting device including a floor protecting cover in turn including a heating element and means for turning the heat on or off in dependence of the presence or absence, respectively, of a person on the floor protecting cover.

The object is also achieved by a method of controlling the heating function in a floor protecting cover including a heating element, said method including the following steps: - detecting the presence of a person on the floor protecting cover;

- if a person is detected on the floor protecting cover, liirning or keeping the heating function on; if a person is not detected on the floor protecting cover, taming or keeping the heating function off.

Hence, the device according to the invention provides a heating source which only consumes energy when it is actually being used thus saving energy without reducing the comfort of the person or animal using it.

Preferably, said heating element is a heating foil or ribbon placed between a first and a second sheet of the floor protecting cover. Alternatively, only one sheet may be used, or the heating element may be incorporated in the cover.

Alternatively a type of self-regulating electrically conductive plastic material com- prising soot particles may be used instead of the heating foil or ribbon. This has the advantage that the soot particles expand with heat, thereby effectively setting an upper limit for the temperature of the cover.

The means for detecting presence and/or absence can for example be any type of sensor adapted to detect movements, for example, an infrared (IR) detector. Alternatively, the sensor for detecting presence and/or absence may be a sensor adapted to detect weight, or changes in weight, such as a strain gauge sensor.

In yet another embodiment the sensor for detecting presence and/or absence is a sensor adapted to detect the conductivity of its surroundings.

A combination of sensors may of course be used. In addition to the sensor or sensors a thermostat or similar control device may be used to ensure that the cover never becomes too hot.

Preferably, the device according to the invention also includes a mains connector and/or a transformer for transforming a mains voltage to a lower voltage on which the heating element will operate. This will enable adaptation to security standards if the voltage source delivers a voltage higher than what is allowed with this type of device.

Alternatively, the device may be powered from another source, for example, a low- voltage source such as a battery. This will eliminate the need for a transformer if security regulations prohibit the use of mains voltage with the device according to the invention.

Advantageously, the device according to the invention further includes means for turning the power on and/or off manually.

According to one embodiment, if a person is not detected on the floor protecting cover, the heating function is turned off after a certain delay.

Some detectors, for example, the ones based on movement, may not detect a person^'s presence all the time. The delay function will prevent the heating function from being turned off while the person is still present. Brief Description of the Drawings

The present invention will be described in more detail in the following, by way of preferred embodiments and with particular reference to the drawings, in which: Figure 1 illustrates an embodiment of a floor cover according to the invention, comprising a heating element, seen from above;

Figure 2 is cross-sectional view of a floor cover through the line A-A in Fig. 1 Figure 3 shows a floor cover according to one embodiment of the invention, in use; Figure 4 shows a floor cover according to another embodiment of the invention, in use;

Figure 5 is an exemplary connection diagram of a floor cover according to an embodiment of the invention; Figure 6 shows another embodiment of the floor cover.

Detailed Description of Embodiments

Figure 1 shows an embodiment of a floor protecting device according to the invention. The device comprises a floor protecting cover 1. As can be seen, a part of the cover comprises a heating element 3, shown as a shaded area. It should be understood that the rectangular shape and size of the floor cover 1 and of the heating ele- ment 3 are only intended as an example. The shape and size may be selected freely, as may the relative size of the cover 1 and the heating element 3. The heating element 3 may have substantially the same size as the cover 1 , or may be located in only a part of the cover 1.

The heating element 3 may be any type of heating element known in the art, for example, a heating foil or cables. The heating element is powered from the mains, through a cable 5 and a mains connector 6. On the cable 5 there may be a transformer 7 for transforming the voltage down to a voltage that fulfils safety standards for this kind of electric equipment. These standards vary between different countries so that in some countries the transformer mav not be needed. Of course, the heating element 3 may be powered from another source, such as a battery or a power generator. The transformer 7 is not necessary for the heating function, but for security reasons a lower voltage than the mains voltage should be used. In most countries there are security rules for electric equipment that will require the voltage to be transformed down to a lower voltage. In Sweden the voltage must be lower than 50V. If a lower voltage than this is applied, of electric safety regulations are fulfilled in other ways, no transformer is needed.

On the cable there is also a presence detector 9. In this embodiment the presence detector is an IR detector of a kind well known in the art. The IR detector registers movement in a certain area, depending on how it is located and directed. The IR detector registers movement and is preferably mounted in such a way that it registers movement of a person's legs near the floor cover. How to locate and adjust the IR detector will be discussed in more detail below. When the IR detector registers the presence of a person in the area covered by it, the heat is turned on in the floor cover. In order to prevent the heating from being turned off if the person does not move for a while, a delay function should be implemented. A connection diagram for the floor cover is shown in Figure 5.

In Figure 1 the transformer 7 and the IR detector 9 are mounted on the cable in the same position. Of course, they could be mounted in different locations, based on practical considerations.

Other components may be present. Figure 1 also shows an optional on/off or auto/off switch 11 located between the transformer 7 and the floor cover 1. It could of course be located between the transformer 7 and the mains connector 6. A timer may be used together with the switch 1 1, so that the heating can be turned on manually but will be automatically turned off after a certain period of time. A thermostat (not shown) or similar control device may also be used, to prevent overheating of the cover, which may occur, for example, if the cover is accidentally covered by something.

Figure 2 shows a cross-section through the floor cover shown in Figure 1. The floor cover 1 comprises an upper la and a lower sheet lb of a material, such as a plastic or rubber material. The material should be relatively rigid, but still slightly pliant so that the cover does not become too hard. The material should also be strong enough that there is practically no risk that normal wear and tear, for example from chair wheels or legs, or shoes, will destroy it. Between the two sheets la, lb, the heating element 3 is placed. The units associated with power supply and presence detection are not shown in this Figure.

Preferably the upper and lower sides of the floor cover should be identical, so that it can be turned easily, for example, so that the cable 5 can be located as near a mains outlet as possible.

The cable 5 has to extent into the cover 1 to reach the heating element 3. The part of the cable 5 (see Fig. 1) between the transformer 7 and the heating element 3, that is, the low- voltage part should as thin as the security regulations will allow, so that the part of the cover through which the cable runs does not make the cover 1 significantly thicker. It would be possible to make a groove in one or both sheets la, lb of the cover through which the cable could run, but this will probably be difficult since the sheets la, lb should be quite thin. The cable 5 must also be fixed to the cover in a secure way, for example using an adhesive, so that there is no risk that the connection will be damaged by, for example, a strong pull of the cable.

The heating element may be implemented in any way known in the art. For example, a metal foil may be used. Such foils are available in any size and with a wide range of electric properties, such as output power, resistance, etc. One or more electrically resistive ribbon strips, laid out in a suitable way may also be used.

Instead of an IR sensor, another type of sensor may be used. For example, a sensor registering the weight placed on the floor cover may be used to register the presence of a person on the floor cover. This sensor may work in different ways: It may register the weight in the part of the cover in which the heating element is located, the weight in another part of the cover or the total weight on the cover. In the two latter cases, the weight sensor must be adjusted to the weight of the furniture and other things normally placed on the cover, or the relevant part of it, so that it will register the change in weight when a person sits down on the chair, or stands on the cover. The change in weight to which the sensor will react should be adjusted to match the change that can reasonably be expected. The sensor in these cases should react only to relatively large changes, for example 40 kg or more. In the prior case, the sensor should react to the smaller change caused by the feet of a person sitting down. This has the disadvantage that other things may cause a relatively small weight increase, for example, a pet, or a waste-paper basket, if displaced.

Strain gauge sensors may be used as one type of weight detectors. They should be integrated into the cover and be arranged to measure the strain in at least one direction. A number of different patterns are available, and which pattern to choose is a matter of size and economic consideration. One great advantage of strain gauge sensors is that they can be made fairly thin and can easily be fixed inside the cover, for example, by use of an adhesive.

A photocell or a combination of photocells could also be used to detect the presence of a person on the cover.

Yet another type of sensor that may advantageously be used with the invention in a sensor registering the conductivity of its environment. The principle of conductivity sensors is based on the fact that the human body is 70% fluid and therefore has a high conductivity. Conductivity sensors are used, for example, in security systems in art galleries, to detect a person coming too close to a work of art. Conductivity sensors are extremely well suited for use with the invention in that instead of movement, it registers the properties of its surroundings, which means that a person sitting or standing still will still be registered as present by the sensor. The conductivity sensor may register a person at a particular distance, which may be set to an adequate value, for example 10 cm.

The sensor or sensors may be used to detect both presence and movement, to obtain a more reliable indication of whether a person is actually present. In this case, each time movement is detected, the heating will be turned on for a given period of time. After this period the heating will be turned off and the reference set to zero. The heating will be turned on again when another movement is detected.

Figure 3 shows a floor cover 21 like the one shown in Figure 1, placed in a normal working situation, that is, behind a desk 23 and with a chair 25 placed on it. A person is sitting on the chair 25. Preferably, only part of the cover 21 is heated, so that the person's feet may be located on the heated portion of the floor cover while the chair is placed on a part that is not heated. An IR sensor 27 is mounted on one leg of the desk and directed so that it covers essentially the heated portion of the floor cover 21. The IR sensor 27 should cover an angular area wide enough that the presence of feet or legs above the heated portion of the cover 21, but not much wider. A suitable angular area is indicated with dotted lines in Figure 3. Preferably, the IR sensor 27 is mounted so that the beam does not reach too far away from the floor cover 21, since this would cause the heating to be turned on by movements in other places.

Instead of the IR sensor, a light beam might be used. Assuming that a person work- ing at a desk does not sit still, a light beam and a sensor could be placed in such a way that the light beam would be broken by the person^'s legs, constantly, or once in a while when the person moved. For example, they could be mounted on the two legs of the table between which the person's legs will be placed when sitting at the table. Of course, a delay function would have to be implemented so that the heat would be on for a certain period of time after the light beam was broken.

Figure 4 shows another embodiment of a floor cover 41 in a working situation. This floor cover 41 is preferably smaller than the ones shown in the previous figures, and is used in work spaces where a person works standing up. It therefore only has to be slightly bigger than the person's feet, and comprise a heating element extending over essentially the whole surface of the cover. In Figure 4 the cover 41 is placed in front of a working table. The materials used are the same as described above. The types of sensor described above may be used in this embodiment, and the same factors regarding voltage and orientation of the sensor as described above should be considered. Figure 4 shows a transformer 45 and an IR sensor 47, directed so that it registers the feet of the person standing on the floor cover. If a weight sensor is used instead, it should react only to relatively large changes of weight.

Figure 5 shows a connection diagram of the device according to the invention. A floor protecting cover 51 comprises a heating element 53, as described above. The heating element is power fed through a cable 55, connectable to the mains through a mains connector 56. On the cable 55 a presence indicator 57 is mounted. The presence indicator 57 comprises a relay 58 and a delay function that will delay the turning off of the heating. A switch 59 may also be mounted on the cable. The switch 59 may enable manual auto/off.

Mounted on the cable there is also a transformer 61 suitable for converting the mains voltage to a lower voltage that is allowed in an apparatus such as a floor mat. A power indicator 63 may also be included, which will indicate, for example, by a light, if the heating is on. In Figure 5, the switch 59, the transformer 61, and the power indicator 63 are placed between the presence detector 57 and the heating element 53.

The presence detector 57, transformer 61 , switch 59 (if present) and any other electric components may be integrated in a housing 65 as indicated by the dashed lines.

As mentioned above, the heating element is preferably integrated in the cover between two sheets of a suitable material constituting the cover. These sheets, and the heating element, may be assembled in a number of ways. The sheets may be glued together, or vulcanized together. The heating foil or ribbon strips of the heating element can be integrated integrated in a plastic or rubber sheet, on which a similar sheet without a heating element is fastened, for example with glue or heat treatment.

Figure 6 shows a connection diagram for a floor protecting device 71 in which a conductivity sensor is used to detect presence, and a connection diagram for this invention. The floor protecting device in this embodiment comprises a heating element 72 and a conductivity sensor 73. The conductivity sensor 73 is connected to a transmitter 74 which transmits a signal to a relay 75. When the relay 75 is open, the heating element 72 is not heated. When the relay 75 is closed, the heating element 72 is heated. The transmitter shown in the Figure is powered from the same voltage source 76 as the heating element 72. Connected between the power source 76 and the heating element 72 is an auto/off switch. There may also be a transformer 78 for adapting to security regulations, if necessary. The transformer 78 may comprise a selector 79 for selecting high or low power.

The shape and size of the heating element and the conductivity sensor may vary, but it is feasible for them to be about the same size and overlapping, since the conductivity sensor will control the heating function based on the presence of a person's feet near itself. The invention is of course not limited to the embodiments shown. As will be understood, elements from all the embodiments described above may be combined. For example, any type of sensor may be used with any size cover, and with or without a transformer, depending on the voltage source used. If desired two or more sensors could be combined. Any type of heating element known in the art may be used with any of the embodiments shown.

An indication that the heating function is turned on may be given, for example by means of a sound signal or a visual indication. Alternatively, an indication may be given that the floor protecting cover has a higher temperature than the surroundings. For example, the floor protecting cover may be made from a material that changes colour with temperature, preferably so that it changes colour at a temperature slightly over normal room temperature.

Power control means may be provided to enable the user to select a suitable power.

Information from the presence detectors may also be transmitted to a control unit through another network, for example the power supply network, the telecommuni- cations network or a short-range communications network, in ways common in the art.

Claims

1. A floor protecting device including a floor protecting cover in turn comprising a heating element, characterized in that it includes detecting means for detecting the presence and/or absence of a live being on the floor protecting cover, said detecting means cooperating with the heating element.

2. A floor protecting device according to claim 1 including switch means for taming the heat on or off in dependence of the detected presence or absence, respectively, of a person on the floor protecting cover.

3. A floor protecting device according to claim 1 or 2 wherein the detecting means is adapted to react to movements.

4. A floor protecting device according to any one of the preceding claims, further including a mains connector and a transformer connected to the mains connector for transforming a mains voltage to a voltage lower than the mains voltage and supply said lower voltage to the heating element.

5. A floor protecting device according to any one of the claims 2-4,wherein the switch means is adapted wait a predetermined period of time before taming the heating element off after detecting the non-presence of a live being.

6. A method of controlling the heating function in a floor protecting cover including a heating element, said method including the following steps:

- detecting the presence of a person on the floor protecting cover

- if a person is detected on the floor protecting cover, taming or keeping the heating function on - if a person is not detected on the floor protecting cover, taming or keeping the heating function off.

7. A method according to claim 6, wherein, if a person is not detected on the floor protecting cover, the heating function is tamed off after a certain delay.

8. A method according to claim 6 or 7, wherein the presence of a person is detected using a movement detecting sensor.