IRONING APPLIANCE COMPRISING A SAFETY DEVICE AND METHOD OF MAKING AN IRONING APPLIANCE SAFE.

Abstract

Ironing appliance comprising a heating element (1) controlled by means of a thermostat (2), the appliance having a safety device comprising motion detection means (5) and a safety relay (3) connected in series with the heating element (1) to interrupt the supply to said heating element (1) when the appliance is left stationary for too long, said appliance being characterized in that said safety device comprises means (2a) for determining the state of opening of the thermostat (2) and in that the safety device opens said safety relay (3) when, simultaneously, the determining means (2a) indicate that the thermostat (2) is open and the motion detection means (5) detect that the appliance has not been moved for a time t greater than a warning threshold t1.

Description

The present invention relates to an ironing appliance composed of a heating element controlled by means of a thermostat and more particularly to an appliance provided with a safety device comprising means for detection of movement and a relay assembled in series with the heating element so as to interrupt the supply of power to the heating element when the appliance remains motionless for too long a time.

There is known, from the U.S. Pat. No. 4,661,685, a domestic iron composed of a heating element and a safety device controlling the opening of a relay assembled in series with the heating element to interrupt the supply of power to the latter when the iron remains motionless too long on its soleplate. This safety device also contributes to limit the electric consumption of the iron by stopping the power supply when the iron remains motionless too long on its heel.

Such a safety device controls the opening of the relay only according to the time during which the iron is motionless, or immobile, so that the opening of the relay is generally carried out when current for supplying the heating element passes through the relay. The relay must thus be dimensioned to support a large number of openings while it is being supplied with voltage, which leads to choosing a relay that is expensive to manufacture.

The invention which follows aims at providing an ironing appliance composed of a safety device that is more economical to implement. The invention in particular aims at providing a safety method for a domestic iron that makes it possible to use a safety relay that is less expensive to manufacture.

The goal of the invention is reached by an ironing appliance composed of a heating element controlled by means of a thermostat, the appliance being provided with a safety device comprising means for detection of movement and a safety relay mounted in series with the heating element making it possible to interrupt the supply of power to the heating element when the appliance remains motionless too long, wherein the safety device is composed of means for determining the opening state of the thermostat and the safety device controls the opening of the safety relay when, simultaneously, the means for determining indicate that the thermostat is open and the means for detection of movement detect an immobilization of the appliance during a time t longer than an alarm threshold t₁.

Such a characteristic makes it possible to control the opening of the safety relay when current is not flowing through the latter so that wear of the safety relay is greatly reduced.

According to another characteristic of the invention, the safety device controls, at the latest, the opening of the safety relay when the appliance is motionless during a time t longer than a critical threshold t₂, the critical threshold t₂ being longer than the alarm threshold t₁.

Such a characteristic makes it possible to ensure maximum safety by ensuring cutting of the power to the heating element when the time during which the appliance is motionless exceeds the critical threshold t₂.

According to another characteristic of the invention, the safety device monitors the state of the thermostat when the time during which the appliance is motionless is comprised between the alarm threshold t₁ and the critical threshold t₂ and controls the opening of the safety relay as soon as the thermostat is detected to be in an open state by the means for determining the state of opening.

According to still another characteristic of the invention, the appliance comprises a heel on which it can rest at the time of the inactive phases of ironing and an ironing soleplate, in thermal communication with the heating element, on which it can rest for the active phases of ironing, the appliance comprising position detecting means making it possible to determine if the appliance rests or not on its heel and the values of the alarm threshold t₁ and the critical threshold t₂ are a function of the position of the iron detected by the position detecting means.

According to another characteristic of the invention, the values of the alarm threshold t_1r and critical threshold t_2r when the iron rests on its heel are respectively longer than the values of the alarm threshold t_1s and critical threshold t_2s when the appliance rests on its soleplate.

The invention also relates to a safety method for an ironing appliance provided with a heating element controlled by means of a thermostat in which a safety relay, disposed in series with the heating element, is open when the appliance remains motionless too long, wherein the safety relay is open when the thermostat is in an open state and the appliance is motionless during a time t longer than an alarm threshold t₁.

According to another characteristic of the invention, the safety relay is opened, at the latest, when the appliance is motionless during a time t longer than a critical threshold t₂, the critical threshold t₂ being longer than the alarm threshold t₁.

According to another characteristic of the invention, the state of opening of the thermostat is monitored over a time period of immobilization of the appliance ranging between the alarm threshold t₁ and the critical threshold t₂ and the safety relay is opened as soon as the thermostat is detected in an open state in the immobilization time period.

One will better understand the goals, aspects and advantages of the present invention, from the description given hereafter of a particular embodiment of the invention, presented as a non-limiting example, while referring to the annexed drawings in which:

FIG. 1 is a schematic representation of the supply circuit for the heating element of a domestic iron according to a particular embodiment of the invention;

FIG. 2 represents an example of an algorithm of operation of the safety method according to the invention.

Only the elements necessary for an understanding of the invention have been shown.

FIG. 1 represents schematically, the supply circuit for a heating resistance 1 of a domestic iron composed of a soleplate in thermal communication with heating resistance 1 and a heel on which the iron can rest substantially vertically. Heating resistance 1 is connected in series with a thermostat 2 whose assigned temperature is controlled by the user and the supply circuit comprises two terminals L, N which are subjected to a supply voltage when the iron is connected to the electrical supply network.

In order to limit fire hazards, the iron is provided with a safety device composed of a safety relay 3 controlled by a control module 4, the safety relay 3 being mounted in series with heating resistance 1 so that the opening of the safety relay 3 interrupts electric supply to heating resistance 1.

The control module 4 receives, in a manner known per se, information from a motion detector 5 and a position sensor 6 making it possible to determine if the iron rests or not on its heel. The position sensor 6 is preferentially disposed to detect that the iron rests on its heel while the soleplate of the iron is tilted by more than 20° relative to the horizontal. Thus, the iron is considered to be placed on its heel when it is placed on an independent iron rest, such as the iron rest integrated into an ironing board, these iron rests generally having an inclination of about 45°. In an advantageous way, the control module 4 is constituted by an ASIC or by an electronic circuit carried on a printed circuit also supporting the whole of the other elements 3, 5, 6 of the safety device.

More particularly according to the invention, the control module 4 controlling the opening of the safety relay 3 incorporates or is connected to means 2a for determining the state of opening or closing of thermostat 2. As an example, these means 2a determine the state of opening of thermostat 2 by measuring the terminal voltage of a voltage divider disposed between the heating element 1 and thermostat 2 or by measuring the current passing through the safety relay 3 using a shunt.

The safety device can thus control the opening of the safety relay 3 by taking account of the state of opening of thermostat 2 so that the opening of the safety relay 3 can be carried out preferentially when thermostat 2 is open. One thus avoids the accelerated wear of the safety relay 3 generated in particular by the appearance of electric arcs when the safety relay 3 is open when it is under tension.

A particular embodiment of the safety method for a domestic iron according to the invention now will be described in relation to FIG. 2.

According to this figure, in a first step 101 of the method, the control module 4 determines if the iron is motionless, or immobile, using information coming from the motion detector 5.

When the iron is regarded as motionless, the control module 4 carries out step 102 of the method in which the control module 4 determines, with the assistance of the position sensor 6, whether the iron is immobilized on its heel or its soleplate.

If the iron rests on its heel, the control module 4 passes then to step 103A of the method in which it measures the time t that has elapsed since the last moment to when the iron was determined to be motionless. This time t of immobilization of the iron is compared with a predetermined alarm threshold t_1r, for example of about 8 minutes, then according to the result, the following operations are carried out:

if the elapsed time t is less than the alarm threshold t_1r, the method is returned to step 101. The control module 4 thus continues to monitor the time t of immobilization of the iron and to compare it with the threshold t_1r.

if the time t of immobilization of the iron exceeds the alarm threshold t_1r, then the method passes to step 104A.

During step 104A, the control module 4 monitors the state of opening or closing of thermostat 2 and carries out the following operations:

if thermostat 2 is in an open state, the control module 4 then immediately carries out step 106 of the method in which the control module 4 controls the opening of the safety relay 3. Such an opening of the safety relay 3 is carried out when the latter is not traversed by a current so that the wear of the safety relay is extremely low.

inversely, when thermostat 2 is in a closed state, the control module 4 carries out the intermediate step 105A of the method.

During step 105A, the control module 4 checks if the time t of immobilization of the iron exceeds a critical threshold t_2r, longer than the alarm threshold t_1r. As an example, the value of the critical threshold t_2r could be selected so that t_2r=t_1r+20 seconds.

The control module 4 then carries out the following operations:

if the time t of immobilization of the iron does not exceed the value of the critical threshold t_2r, the safety method is returned at step 101 and control module 4 again carries out the operations associated with steps 101 and following.

when the time t of immobilization of the iron exceeds the critical threshold t_2r, the control module 4 immediately carries out step 106 of the method in which the control module 4 controls the opening of the safety relay 3. This opening of the safety relay 3 beyond the critical threshold t_2r of immobilization is carried out while the safety relay is under tension.

Once the opening of the safety relay 3 is carried out, the control module 4 again carries out the various operations associated with steps 101 and those that follow of the method.

In particular, if detector 5 detects a movement of the iron at the time of step 101 of the method, the control module 4 then carries out the step 110, which consists in controlling the closing of the safety relay 3.

Lastly, if during step 102, the position sensor 6 sends to the control module 4 the information according to which the iron is resting on its soleplate, the control module 4 then carries out the steps 103B and those that follow of the method. These steps 103B, 104B and 105B of the method are on all points similar to the steps 103A, 104A and 105A previously described but with threshold values t_1s and t_2s in place of the thresholds t_1r and t_2r.

As an example, the alarm threshold t_1s is about 30 seconds and the critical threshold t_2s is about 40 seconds so that the closing of the safety relay 3 by the safety method intervenes much more quickly when the iron rests on its soleplate that when it rests on its heel.

Such a method of security of a domestic iron, by controlling the opening of the safety relay when the thermostat is in an open state over a range of immobilization time of the iron comprised between an alarm threshold t_1r, t_1s and a critical threshold t_2r, t_2s, has the advantage of allowing in the majority of the cases the opening of the safety relay when current is not flowing through this latter. In particular, when the iron rests a long time on its heel, the thermostat starts to cycle rapidly so that the probability that the thermostat is found in an open state over the range of time comprised between t_1r and t_2r is very high.

Such a safety method thus makes it possible to reduce the use of the safety relay, which makes it possible to increase its lifespan considerably and thus to reduce the dimensioning of the relays. There results a less expensive safety device.

In an advantageous manner, the safety method can also control the activation of one or more indicators to inform the user when the immobilization time of the iron exceeds the alarm threshold and the critical threshold, respectively.

Of course, the invention is by no means limited to the embodiment described and illustrated, which was given only as an example. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without leaving for all that the field of protection of the invention.

Thus, in an alternative embodiment, the safety device could have only one sensor which, by an analysis of the signals, will make it possible to determine at the same time the position of the iron and it being placed in movement. As an example, this sensor could be a sensor providing a signal relating to the position of the iron, the detection of movement of the iron being then carried out by obtaining the time derivative of the signal provided by this sensor.

Thus, in an alternative embodiment not represented, the invention could also be applied to a vertical smoothing appliance.

Claims

1. Ironing appliance composed of a heating element (1) controlled by means of a thermostat (2), the appliance being provided with a safety device comprising means for detection of movement (5) and a safety relay (3) assembled in series with the heating element (1) allowing to interrupt the supply of power to said heating element (1) when the appliance remains motionless too long, wherein said safety device comprises means (2a) for determining the state of opening of the thermostat (2) and the safety device controls the opening of said safety relay (3) when, simultaneously, the means (2a) for determining indicate that the thermostat (2) is open and the means for detection of movement (5) detect an immobilization of the appliance during a time t longer than an alarm threshold t1.

2. Ironing appliance according to claim 1, wherein the safety device controls, at the latest, the opening of the safety relay (3) when the appliance is motionless during a time t longer than a critical threshold t2, the critical threshold t2 being longer than the alarm threshold t1.

3. Ironing appliance according to claim 2, wherein the safety device monitors the state of the thermostat (2) when the time during which the appliance is motionless is comprised between the alarm threshold t1 and the critical threshold t2 and controls the opening of the safety relay (3) as soon as the thermostat is detected to be in an open state by the means (2a) for determining the state of opening.

4. Ironing appliance according to claim 3, wherein it is composed of a heel on which it can rest during inactive phases of ironing and an ironing soleplate in thermal communication with the heating element, on which it can rest during active phases of ironing, the appliance comprising position detecting means (6) making it possible to determine if the appliance rests or not on its heel and in that values of the alarm threshold t1 and the critical threshold t2 are a function of the position of the iron detected by the position detecting means (6).

5. Ironing appliance according to claim 4, wherein the values of the alarm threshold t1r and critical threshold t2r when the iron rests on its heel are respectively longer than the values of the alarm threshold t1s and critical threshold t2s when the appliance rests on its soleplate.

6. Safe operating method for an ironing appliance provided with a heating element (1) and a safety relay (3) disposed in series with the heating element (1), said method comprising: controlling supply of power to the heating element by means of a thermostat (2); and opening the safety relay when the thermostat (2) is in an open state and the appliance remains motionless for a time t longer than an alarm threshold t1.

7. Safe operating method according to claim 6, wherein said step of opening the safety relay (3) is performed, at the latest, when the appliance remains motionless for a time t longer than a critical threshold t2, the critical threshold t2 being longer than the alarm threshold t1.

8. Safe operating method for an ironing appliance according to claim 7, wherein the state of opening of the thermostat (2) is monitored over a range of immobilization time of the appliance comprised between the alarm threshold t1 and the critical threshold t2 and the safety relay (3) is at opened as soon as the thermostat is detected in an open state in said range of immobilization time.

9. Ironing appliance according to claim 2, wherein it is composed of a heel on which it can rest during inactive phases of ironing and an ironing soleplate in thermal communication with the heating element, on which it can rest during active phases of ironing, the appliance comprising position detecting means (6) making it possible to determine if the appliance rests or not on its heel and in that values of the alarm threshold t1 and the critical threshold t2 are a function of the position of the iron detected by the position detecting means (6).

10. Ironing appliance according to claim 9, wherein the values of the alarm threshold t1r and critical threshold t2r when the iron rests on its heel are respectively longer than the values of the alarm threshold t1s and critical threshold t2s when the appliance rests on its soleplate.

11. Ironing appliance according to claim 1, wherein it is composed of a heel on which it can rest during inactive phases of ironing and an ironing soleplate in thermal communication with the heating element, on which it can rest during active phases of ironing, the appliance comprising position detecting means (6) making it possible to determine if the appliance rests or not on its heel and in that values of the alarm threshold t1 and the critical threshold t2 are a function of the position of the iron detected by the position detecting means (6).

12. Ironing appliance according to claim 11, wherein the values of the alarm threshold t1r and critical threshold t2r when the iron rests on its heel are respectively longer than the values of the alarm threshold t1s and critical threshold t2s when the appliance rests on its soleplate.