WO2001063190A1

WO2001063190A1 - Method and system for detection

Info

Publication number: WO2001063190A1
Application number: PCT/SE2001/000396
Authority: WO
Inventors: Patrik GRANSTRÖM
Original assignee: Vattenfall Ab
Priority date: 2000-02-25
Filing date: 2001-02-23
Publication date: 2001-08-30
Also published as: SE0000626L; SE0000626D0; AU2001236295A1

Abstract

The present invention relates to a method, a system and a device for detecting a change of state of a household appliance, such as a refrigerator or a freezer, comprising a temperature-controlled space. For the space, a first parameter is detected which is representative of a change of pressure in said space, and a second parameter, a message being given if a parameter value deviates by a predetermined size from an initial value, and determining that detection of a change of state has occurred.

Description

METHOD AND SYSTEM FOR DETECTION

Technical Field

The present invention relates to a method, a system and a device for detecting a change of state of a house- hold appliance, such as a refrigerator or a freezer, which comprises a temperature-controlled space.

Technical Background

In housekeeping, in the food and catering business it is important to be able to keep products, such as foods and beverages, at an adequate temperature in order to favour their shelf-life. This is usually carried out in cooled spaces, for example in refrigerators and freezers. However, it easily happens that in a stressful situation, the door of a refrigerator or a corresponding door is accidentally left open, which may result in an increase of temperature and, consequently, the products becoming unfit for food. On such occasions, it is desirable to be informed about what has occurred, so that the necessary measures may be taken.

However, in certain situations, the door of a refrigerator may be allowed to be open during a predetermined period of time without the user desiring to be informed thereof, if this does not significantly affect the products. If, on the other hand, the conditions would change so as to be disadvantageous to the keeping of products, it is desirable for the user to be informed about the occurrence .

On the other hand, there is another problem, that is the temperature, for example, in a refrigerator does not necessarily increase, although the door of the refrigerator is open. Instead the compressor of the refrigerator works harder in order to keep a constant temperature, and if this is allowed to go on, the compressor may start burning .

There is thus a need for monitoring, preferably remote monitoring, of household appliances, so that a user or a consumer can continuously be informed if something unforeseen occurs, such as the door of a refrigerator being left open. The installation of a monitoring device must not be complicated and should be possible in a few simple operations. Moreover, such a device should be in- expensive.

Summary of the Invention

The object of the present invention is to provide a solution of the above-mentioned problem of giving desired information, on a desired occasion, about the status of a cooled space, the solution being applicable in the different situations and also uncomplicated and inexpensive.

This is achieved by a method, a system and a device which are defined in the independent claims 1, 14 and 18, respectively, by obtaining information which relates to two parameters characteristic of the temperature- controlled space. According the invention, one parameter is representative of a change of pressure in the temperature-controlled space. The invention is thus based on the understanding that opening of a previously closed temperature- controlled space, for example, in a refrigerator or a freezer, leads to a change of pressure in the space, and that a safe detection of an open space may be obtained by detecting the pressure in the space. Such a change of pressure can essentially be detected from an arbitrary location in the space. This flexibility means great advantages in respect of mounting, as will be described below in this application. The invention is also based on the understanding that safety may be increased considerably by monitoring both a first parameter in the form of a change of pressure in said space and a second parameter, for instance a parameter which is representative of the temperature in the space. The combination of detecting these two parameters is a great help in fault tracing, as will be evident from the following. The parameter which is representative of a change of pressure may, for example, be detected in order to discover if an essentially constant state has changed in some way, irrespective of to what extent. It is thus a binary parameter state which reflects an unchanged and a changed state, respectively. The use of pressure sensors has several advantages . In contrast to mechanical sensors, a pressure sensor may be placed at an essentially arbitrary location in the temperature-controlled space. A pressure sensor functions independently of external con- ditions, such as light. Unlike a light sensor, a pressure sensor thus makes it possible to detect an open door of a refrigerator, whether there is complete darkness, or the refrigerator space is defined by a transparent glass door. Besides, a pressure sensor functions very well without any need for calibration.

The second parameter may, for example, be continuous and detected in order to obtain a value thereof . The combination of detecting a change of pressure and a continuous parameter gives many options and possibilities of an accurate monitoring of temperature-controlled spaces.

Sensors for detection of the two parameters may advantageously be placed in one and the same unit, which further points to the already mentioned flexibility of the invention. The binary parameter state is thus representative of a change of pressure. When the door of a refrigerator or a freezer is opened, the pressure in the temperature- controlled space is changed. A message about this can then be sent to the user, so that the user becomes aware of that occurred. Preferably, the user should be able to decide after how much time such a message is to be sent. If someone in the household (or the restaurant, grocery shop, etc.) temporarily opens the door of a refrigerator to take out or put in products, the user should not need to receive a message. However, if the door is open for a longer period of time predetermined by the user, the mes- sage will be sent.

After a change of pressure has been detected in the temperature-controlled space, an alarm is preferably not sent immediately. First the second parameter is checked, such as a parameter which is representative of the tem- perature . If the temperature is then changed so as to reach outside a predetermined temperature range, an alarm is given. On the other hand, if the temperature is kept within the range and the change of pressure has lasted for a long time, an alarm can be sent since this may in- dicate that the compressor has to work harder than usual . However, if the temperature sensor detects an elevated or continuously increasing temperature and the pressure sensor indicates that the door is closed, this is none the less interpreted as abnormal, and, therefore, an alarm is given. This may occur, for instance, in connection with a power failure.

The combination of the detection of these two parameters thus allows the user a better monitoring of the temperature-controlled space and a better indication of where to find a potential problem.

The second, continuous parameter which is detected is, as mentioned earlier, preferably the temperature in the temperature-controlled space. If the temperature during a predetermined period of time deviates from a prede- termined temperature range, a message can thus be sent to the user.

As already mentioned, the compressor may be forced to work harder if the door of a refrigerator is open, in order to prevent the temperature in the refrigerator from increasing. One of the two parameters may thus advantageously be the electricity consumption of the compressor or the temperature of the compressor. Another possible parameter is the presence of the amount of moisture. If, for instance, the moisture content exceeds a predetermined moisture content in the refrigerator, a message can be given in order to indicate an abnormal state .

The user should preferably himself or herself be able to indicate what conditions should be fulfilled as regards the two parameters for a message to be sent. Preferably, the user should also be able to choose the contents of the message, such as information that detection, owing to for example a change of pressure, of an open door of a refrigerator has occurred, and what temperature the refrigerator space has. Thus, it is possible to get a quick confirmation that something actually has occurred and at the same time have a continuous and accurate monitoring of the continuous change of state (increase of temperature) , whereby it is possible to determine within what space of time the necessary measures should be taken. It is also possible to detect more than two parameters if it is desirable to obtain further information, in which case conditions can be made that detection of a change of state in the refrigerator has occurred if, for instance, at least one message related to a parameter has been sent.

In order to monitor the temperature-controlled space, a simple small sensor unit is advantageously used, comprising, for instance, a temperature sensor and a pressure sensor. A user may easily attach the sensor unit in the space. In, for example, a refrigerator it is possible to attach the sensor unit to the wall, on the inside of the door or in another suitable location, for instance, with double-stick tape, and lay signal lines through a hole available in the wall of the refrigerator. The signal lines are connected to an intermediate unit which processes the information obtained from the sensor unit and which via, for example, the electric mains com- municates with a central processing unit which can inform the user about the state of the temperature-controlled space. The monitoring will be described in more detail in the following.

Brief Description of the Drawings

Fig. 1 schematically shows a preferred embodiment of a system for detecting a change of state in a refrigerator in accordance with the present invention, Fig. 2 schematically shows a preferred embodiment of an intermediate unit for use in the present invention,

Figs 3A-3C show flow charts for an intermediate unit for detecting a state of change in a refrigerator in accordance with the invention, and Figs 4A-4C show flow charts for a server for detecting a change of state in a refrigerator in accordance with the present invention.

Description of Preferred Embodiments Fig. 1 schematically shows a preferred embodiment of a system for detecting a change of state in a refrigerator in accordance with the present invention.

The figure should illustrate only how the system may be formed and is not intended for representing a picture of reality according to scale, but only a schematic picture .

In the refrigerator 2, a sensor unit 4 is placed on the wall of the refrigerator for detecting at least two parameters which are representative of the environment in the refrigerator 2. The figure shows that the sensor unit

4 has two sensors 6 and 8, a pressure sensor and, for example, a temperature sensor.

From the sensor unit 4 runs wires in a cable 10 to an intermediate unit 12. The sensor unit 4 is conven- iently located on one wall of the refrigerator 2, for example by means of double-stick tape and the cable 10 may be drawn through the rear wall of the refrigerator 2. The intermediate unit 12 further communicates with a server 16 via the electric mains (illustrated by a plug 14) , the server, in its turn, also communicating with a computer 18 or a telephone 20. A chip in the intermediate unit 12 is programmed for communicating with the sensors 6,8. The software in the chip determines how often the sensors 6,8 should be polled. In this software, it is also possible to supply a certain logic in such a manner that the intermediate unit 12 itself can come to decisions. By doing so, unnecessary traffic on the electric mains is minimised, to which the intermediate unit 12 is connected via a standard type plug 14. The intermediate unit 12 communicates, for instance, via LonWorks (a standardised technique which is suitable for electric mains communication) . The protocol which is used is LonTalk®.

The program in the server 16 polls the intermediate unit 12 about what values it has obtained from the sensors 6, 8 and stored. If the server 16 discovers such a value which according to the predetermined adjustments is considered to be an unfavourable change of state in the refrigerator 2, an alarm is given. The alarm may, for instance, by means of prior-art computer networks technique be sent to the computer 18 or the telephone 20. Although the system in Fig. 1 has been illustrated with wires in a cable, it is also possible to bring about communication between, for example, the sensor unit and the intermediate unit in a wireless manner, for instance by means of a radio interface, such as Bluetooth™ or an IR interface etc.

Fig. 1 shows that the intermediate unit 12 comprises a plug of male type. However, it is practical to also provide the unit with a plug of female type, in which the plug of the refrigerator may be inserted. The obvious ad- vantage of this is that the user only needs to use one wall socket, instead of two. Fig. 2 schematically shows a preferred embodiment of an intermediate unit 12 and its main components for use in the present invention. The intermediate unit 12 obtains its power supply from the electric mains (illus- trated with a plug 14) via a power supply unit 22 (transformer circuit) which is built in the intermediate unit 12. The power supply unit 22 communicates with a chip 24 through two wires: a power supply wire 26 and a signal line 28. The chip 24 has software in order to obtain pa- rameter values and store them in a memory for forwarding to a server via the signal line 28 (the signal overlays the power supply signal) . By the signal line 28 the server may also poll the intermediate unit 12. The chip has two temperature inputs T_x, T₂ for connection of one temperature sensor each, which measure the temperature in a refrigerator and a freezer, respectively. In a corresponding manner there are two pressure inputs Pi, P₂ for connecting one pressure sensor each. Moreover, an input W of a moisture sensor which can measure the moisture, for example, in the refrigerator is shown in the figure.

Fig. 3A shows a flow chart for an intermediate unit for detection of a change of state in a refrigerator in accordance with the invention. The intermediate unit has a sensor unit connected to it that comprises a pressure sensor according to the invention. In this preferred embodiment, after the intermediate unit has been installed and configured (start) , the intermediate unit polls the sensor unit in a polling step 302 what status or what value the pressure sensor has, i.e. if it has detected a change of pressure, value 1, or if not, value 0. The current value of the pressure sensor is acquired in an acquiring step 304 to the intermediate unit and is stored in a storing step 306 in its memory. The current pressure value is available to be acquired by the software of the server from the memory. Subsequently, a determining step 308 follows, in which it is determined if the acquiring of values has reached its end or if a new value is to be acquired. In normal cases, it is desirable to acquire new values, the steps 302-308 being repeated with predetermined ranges and a new value overlays an old value in the storing step 306. However, it is also possible to intro- duce a limitation of a certain number of loops, after which the acquiring is stopped.

Fig. 3B shows yet another flow chart for an intermediate unit. In this case, measuring of temperature is illustrated when a connected sensor unit comprises a tem- perature sensor. This flow chart is essentially analogous to that shown in Fig. 3A, the reference numerals for the respective corresponding steps have been added by ten. The only difference between the two flows is that in Fig. 3B in the polling step 312 the temperature in the refrigerator is polled, the temperature possibly assuming continuous values.

Fig. 4A shows how the superordinate system, i.e. the server works with respect to the pressure parameter. After the server has been configured (start) , the server polls the intermediate unit what current pressure value is stored (step 402) . If the value is 0, i.e. no change of pressure has been detected (the pressure in the space is normal) , this step is repeated after a predetermined period of time which conveniently is at least so long that the intermediate unit has had time to obtain a new value. However, if the value is 1, i.e. a change of pressure has been detected, a clock suitably starts in a time-measuring step 404. A consumer may accept that the door of the refrigerator is open for a certain number of minutes. But if this time is exceeded, an alarm in an alarm step 406 is given, regardless of the temperature being acceptable or not, for instance to a computer or a telephone. In a subsequent determining step 408, it is decided whether the loop should be repeated or finished in accordance with adjustments chosen beforehand.

Fig. 4B shows how the superordinate system, i.e. the server works with respect to the temperature parameter. After the server has been configured (start) , the server polls the intermediate unit what value of the temperature it has stored in the memory (step 412) . If the value is within the allowed, normal temperature range, this step is repeated after a predetermined period of time which suitably is at least so long that the intermediate unit has had time to acquire a new value. However, if the value is outside the normal temperature range, the server gives an alarm in an alarm step 416, for example, to a computer or telephone. In a subsequent determining step 418, it is decided whether the loop is to be repeated or finished in accordance with adjustments chosen in advance .

The server may be programmed to work in different ways. According to a preferred embodiment, the server may work in accordance with the flow chart in Fig. 4A, and if a change of pressure is detected (step 402) at the same time carry out the steps according to Fig. 4B . When the door of the refrigerator is open, a change of pressure is thus detected, the clock starting (step 404) at the same time as the temperature value is controlled (step 412) . An alarm is given if the changed, new pressure has been detected a predetermined period of time, and at the same time information about what temperature prevails be ob- tained, irrespective of if it is within the normal range or not. This may be an advantage when determining how acute necessary measures should be taken. Another advantage of this embodiment is that a method with an increased safety in relation to prior-art technique is pro- vided. A supplementary control occurs before an alarm is sent out. When a change of pressure has been detected, the alarm is not given until the door of the refrigerator has been open "too long", or if the temperature earlier has had time to assume a value outside that allowed. Naturally, the server may be programmed to work without time-measuring if it is desirable only to note that someone has opened the refrigerator, information thereof possibly being sent directly to a computer or telephone. The temperature loop can, of course, be carried out at the same time in order to obtain more information. According to yet another embodiment of the invention, the software of the server acquires available, current pressure value and temperature value, respectively, from the memory of the intermediate unit . This means that the steps in the flow charts shown in Figs 4A and 4B are carried out parallelly. Thus, this means that detection of a change of pressure in order to control the temperature is not a condition. If there is space and capacity in the connections between the parts comprised in the system, this embodiment allows that an alarm may be given faster than in the earlier mentioned embodiment. Consequently, an alarm is given either if the temperature is outside a predetermined temperature range or if the pressure deviates for a time exceeding the predetermined time. Fig. 3C shows yet another flow chart for an intermediate unit. In this case, measuring of the power consumption of the compressor of a refrigerator is illustrated when a connected sensor unit comprises a power sensor. This flow chart is essentially analogous with those shown in Figs 3A and 3B, the reference numerals for the respective corresponding steps being added by twenty and ten, respectively. The only difference between the flows is that in Fig. 3C, in the polling step 322, it is polled for the power consumption of the compressor of the re- frigerator, the consumption being able to assume continuous values .

Fig. 4C shows how the superordinate system, i.e. the server works with respect to the consumption parameter according to a preferred embodiment of the invention. Af- ter the server has been configured (start) , the server asks the intermediate unit what value of the power consumption that it has stored in the memory (step 422) . If the value is within what is to be considered normal power consumption, this step is repeated after a predetermined period of time which conveniently is at least so long that the intermediate unit has had time to acquire a new value. If the value, on the other hand, is outside

(probably greater than) a predetermined allowed normal consumption, the server is to ask the intermediate unit for the current status of temperature and pressure. These are stored (according to Figs 3A and 3B) and are avail- able for the server from the memory of the intermediate unit . The temperature sensor is in this embodiment conveniently located adjacent to the compressor. The server thus acquires in an acquiring step 424 current values which are stored in the memory of the intermediate unit in order to obtain the current temperature at the compressor and in order to determine whether the door is open, i.e. if the pressure has deviated from the normal. Subsequently, the server gives an alarm in an alarm step 426 to, for instance, a telephone or a computer. Thus, the consumer may obtain information if

1. the compressor is about to be damaged, for example, owing to the fact that it is old, defect etc. since the temperature is very high, or

2. the compressor works at high pressure and becomes overheated owing to the door of the refrigerator being open. This conclusion may be drawn if the pressure sensor has registered a change of pressure.

In a subsequent determining step 428, it is determined if the loop is to be repeated or finished in accor- dance with settings chosen in advance.

It should be noted that an alarm also could be given immediately after abnormal power consumption has been registered and, thus, the step 424 could be left out. However, this step gives the consumer further information of where the error is to be found.

Another compressor parameter that is possible to monitor is the time that the compressor works. If the compressor works for a longer period of time than what has in advance been defined as normal, there may be an abnormal state.

Although certain preferred embodiments have been de- scribed above, the invention is not limited thereto. It is thus possible to use other parameter combinations than those described. Furthermore, the invention is not limited to be used in refrigerators or freezers, but may also be used in other temperature-controlled spaces, such as in stoves. It should thus be understood that a plurality of modifications and variations may be provided without abandoning the scope of the present invention which is defined in the appended claims.

Claims

1. A method for detecting a change of state of a household appliance, which comprises a temperature- controlled space, comprising the steps of detecting a first parameter in said space, the parameter being representative of a change of pressure in said space, a first message being given if the parameter value deviates by a predetermined size from an initial value, detecting a second parameter which is related to a state in said space, a second message being given if the parameter value deviates by a predetermined size from an initial value, and determining that detection of the change of state has occurred if at least one of said first message and said second message has been given.

2. A method for detecting a change of state as claimed in claim 1, in which the detection of said first parameter and said second parameter is carried out in a cooling device, such as a refrigerator or a freezer, a deviation of said first parameter value preferably repre- senting that a door of the cooling device is open.

3. A method for detecting a change of state as claimed in any one of the preceding claims, in which a first value of the first parameter is a predetermined pressure range, and a second value is a deviation from the pressure range, a message being given if the pressure deviation lasts a predetermined period of time.

4. A method for detecting a change of state as claimed in any one of the preceding claims, wherein the second parameter is representative of continuous values.

5. A method for detecting a change of state as claimed in claim 4, in which the second parameter is detected in said space and is representative of a temperature change .

6. A method for detecting a change of state as claimed in claim 5, in which said initial value is a predetermined temperature range, a message being given if the temperature deviates from the temperature range by a predetermined number of degrees, the message preferably comprising information about the current temperature in said space.

7. A method for detecting a change of state as claimed in claim 6, in which said first parameter and said second parameter are detected from essentially the same location in said space.

8. A method for detecting a change of state as claimed in claim 4, in which the second parameter is representative of a parameter of a compressor belonging to the temperature-controlled space, such as the temperature of the compressor or the power consumption of the compressor.

9. A method for detecting a change of state as claimed in claim 4, in which the second parameter is detected in said space and is representative of the moisture content in the temperature-controlled space.

10. A method for detecting a change of state as claimed in any one of the preceding claims, wherein the second parameter is detected after the value of the first detected parameter has deviated by said predetermined size from said initial value.

11. A method for detecting a change of state as claimed in any one of the preceding claims 1-9, the first parameter being detected after the value of the second detected parameter has deviated by said predetermined size from said initial value.

12. A method for detecting a change of state as claimed in any one of claims 1-9, wherein the first and the second parameter are detected, preferably in parallel with one another, independently of one another's values.

13. A method for detecting a change of state as claimed in any one of the preceding claims, which comprises detecting at least one more parameter in said space, a further message being given if its parameter value deviates by a predetermined size from an initial value, and detection of the change of state being determined having occurred if at least one of said first message, said second message and said further message has been given.

14. A system for detecting a change of state of a household appliance which comprises a temperature-controlled space, comprising - a) a sensor arrangement which, in said space, is adapted to detect at least two parameters and comprises a pressure sensor, one of said parameters being representative of a change of pressure in said space,

- b) an intermediate unit which is adapted to be in communication with the sensor unit and is adapted to receive information from the sensor unit and thus determine the parameter values, and

- c) an alarm unit which is adapted to be in communication with the intermediate unit, the alarm unit being adapted to receive the parameter values determined by the intermediate unit, at least if any one of these deviates from predetermined values, and being adapted to give an alarm if such a deviation occurs .

15. A system as claimed in claim 14, which further comprises a polling/conveying unit, via which the intermediate unit is adapted to communicate with the alarm unit, the polling/conveying unit being adapted to poll the intermediate unit and convey the response to the alarm unit .

16. A system as claimed in any one of claims 14-15, in which the sensor arrangement comprises, apart from the pressure sensor, a temperature sensor for detecting the temperature in said space .

17. A system as claimed in claim 16, in which the pressure sensor and the temperature sensor are comprised in a common sensor unit .

18. A device for detecting a change of state for a household appliance which comprises a temperature-controlled space, comprising first means for detecting, in said space, a first parameter which is representative of a change of pressure in said space, said first means being adapted to give a first message if the parameter value deviates by a predetermined size from an initial value during a predetermined period of time, second means for detecting, in said space, a second parameter, said second means giving a second message if the parameter value deviates by a predetermined size from an initial value, and third means for determining that detection of the change of state has occurred if at least one of said first message and said second message has been given.

19. A use of a method, system or device as claimed in any one of the preceding claims, in a cooling device, such as a refrigerator or a freezer, in order to derive the reason for a possible error, such as an open door of the cooling device, power failure or compressor error.