EP1306481B1 - Method for regulating the humidity of the laundry exiting a drying and ironing machine and such a machine using this method - Google Patents

Abstract

The system includes a humidity detector in contact with the linen leaving an ironing machine. The output from this detector is applied to an amplifier with automatic gain control, providing a signal which is then used to effect control of a heating element. <??>In order to control the humidity of linen emerging from an ironing machine, the humidity is measured with a sensor (18). The measurement signal is transmitted to a variable gain amplifier (30). An automatic gain control circuit (32) controls the output of this circuit so that it is not saturated. An element (12) within the ironing machine is then controlled in response to this output signal. The gain of the automatic control circuit is kept constant for a given period of time, if there is no humidity signal information being provided.

Description

Technical area

The invention relates primarily to a method of controlling the moisture content of ironed clothes leaving a dryer ironer.

The invention also relates to a ironing dryer using this method, that is to say a dryer ironing integrating means able to maintain the moisture content of the ironed iron to a set value. When the linen comes, for example, from hospitals, the set value is low enough to ensure good microbial quality of ironed linen, regardless of the moisture content of the laundry introduced into the machine.

State of the art

In a ironing dryer, the clothes to be ironed are introduced between a rotating ironing cylinder and a complementary member which matches the shape of a portion of the circumference of the cylinder. Heating means ensure the vaporization of the water contained in the laundry pressed between these organs.

Ironing dryers can be divided into two categories: ironing dryers "calender" and "heated cylinder" ironers.

In ironers with a calender, the rotating ironing cylinder is lined and internally provided with means for recovering the vapor and gases released by the laundry. The pieces of laundry then circulate between the lining carried by the cylinder and a metal bowl called "calender". The heating means are generally integrated in this metal bowl.

In heating rollers with heating rollers, the heating means are placed inside the metal cylinder, whose outer surface is smooth and in direct contact with the laundry. The pieces of laundry then circulate between the cylinder and endless textile webs which are pressed against the outer surface of the cylinder over part of its circumference. Suction means are provided behind the endless belts to recover vapors and gases.

Regardless of the type of ironing dryer used, the moisture content of the ironed iron coming out of the machine depends on many factors such as the nature of the textile, its moisture content when it is introduced into the machine, its speed scrolling inside the machine, the heating temperature of the laundry, etc.

When ironing linen comes, for example, from hospitals, it may contain bacteria. These bacteria will then grow all the faster as the moisture content of the dried and ironed laundry will be high. To guarantee a good microbial quality of laundry leaving a dryer ironer, so it is highly desirable that its moisture content as low as possible.

Conversely, it must be ensured that the heating of the laundry does not exceed a certain value, beyond which the clothes may be burned.

In most existing machines, there is no device to control the moisture content of ironed linen. The users of these machines must then manually adjust the speed of movement of the laundry and that of the heating temperature depending on the nature of the textile and its moisture content at the entrance of the machine. For practical reasons, the setting thus made at the beginning of an ironing cycle of sometimes important duration is generally not modified until the end of this cycle.

It is understood that such a single manual adjustment does not ensure a good microbial quality of all the pieces of laundry coming out of the machine. Indeed, to avoid burning the laundry, the user naturally tends to adjust so that only the small items of laundry and synthetic textiles have a satisfactory moisture content from this point of view.

The document DE-A-34 36 553 describes a ironing dryer in which the pieces of laundry circulate between a plurality of calender cylinder sets placed in series. Each of the cylinders is rotated at an adjustable speed and includes steam suction means having an opening throttle valve adjustable. At the output of the machine, the laundry items are deposited on a metal plate and their residual moisture content, between said plate and a point contact member, is measured by means of a resistance bridge. The humidity level thus measured is compared with an adjustable set point.

If the measured moisture content is higher than the set value, the throttle valve of the suction means of the first calender cylinder assembly, in the direction of the scrolling of the laundry, is opened one by one, and that of the means suction of the second calender cylinder assembly and so on, until the desired moisture content. If the humidity level is still too high after the complete opening of all the throttle valves, then the speed of rotation of all the cylinders is reduced.

Conversely, if the measured moisture content is lower than the set value, it closes the throttle valve of the last set of calender cylinder, in the direction of scroll of the laundry, then that of the penultimate and so on until the desired humidity level is reached. If the humidity measured remains below the set point after closing all the throttle valves, then the speed of rotation of all the cylinders is increased.

The means for controlling the drying rate of the laundry described in this document raise problems which make these control means ineffective in practice.

A first problem has its origin in the appearance of the curve illustrated in Figure 1 of the accompanying drawings, showing the variations of the equivalent electrical resistance (in Ohms) of a piece of laundry, depending on the moisture content that it contains. It can be seen from this curve that very small variations in this rate result in very large variations in the equivalent electrical resistance when the laundry is not very moist (moisture content below 6%). Conversely, when the laundry is very wet (moisture content above 15%), the equivalent electrical resistance of the laundry is almost constant. Under these conditions, it appears that it is not practically possible to control the moisture content of the laundry at the exit of the machine directly on the basis of a measurement made by a resistance bridge of invariable characteristics, such as teaches the document DE-A-34 36 553.

Another disadvantage of the drying control means described in this document arises from the fact that the resistance of each piece of laundry is measured by passing it between a metal plate and a point contact member. The measurement is therefore subject to considerable variations, in particular because of the total or partial electrical contact losses between the contact member and the laundry. These losses of contact make the measurement thus carried out practically unusable.

Yet another disadvantage of the control means described in DE-A-34 36 553 is that the adjustment of the moisture content is performed primarily by controlling the suction of the steam. This results in a relatively long response time, incompatible with a good microbial quality of the laundry leaving the machine.

Presentation of the invention

The subject of the invention is precisely a method for controlling the moisture content of pieces of laundry leaving a ironing dryer, making it possible at least in part to solve the problems of the ironing dryers of the prior art and in particular ensuring effective control of the ironing machine. Moisture content of the ironed laundry, even when this rate undergoes significant variations during the same ironing cycle.

According to the invention, this problem is solved by means of a method for controlling the moisture content of ironed clothes coming out of a ironing dryer, according to which the humidity level of the ironed clothes pieces is measured, then at least one element of the ironing dryer is controlled according to the measured humidity level, in order to move it to a set point, characterized in that the measured humidity level is amplified with an instantaneous optimized gain of such that the measured moisture content thus amplified has an unsaturated value, which is used to control said ironing dryer element.

With this method, the amplification gain is adjusted automatically according to the value of the measurement signal, to obtain an unsaturated output signal, which can then be used to correct the moisture content of the laundry that comes out. of the machine. A effective and virtually instantaneous adjustment of this rate is thus obtained regardless of the state of the laundry that is introduced into the ironing dryer.

Advantageously, the gain is initially given a maximum value, then the gain is divided by a given factor, as many times as necessary, until the measured and amplified moisture content has said unsaturated value. Preferably, the divisor factor is then given a value substantially equal to two.

In the absence of a measurement of the moisture content of a piece of ironed linen, that is to say when no piece of laundry leaves the machine, the optimized instantaneous gain is advantageously kept unchanged for a period of time. predetermined time after the end of the measurement of the moisture content of the last piece of linen ironed previously. This characteristic makes it possible not to repeat the measurements using the maximum value of the gain when several pieces of laundry are ironed after each other.

Advantageously, several measurements of the humidity level are successively carried out, the measurement signals are smoothed and the average is calculated before amplifying them with said optimized instantaneous gain. This characteristic makes it possible to ignore any aberrant measurements to control the moisture content of the laundry.

The invention also relates to a dryer ironer comprising means for measuring the moisture content of ironed clothes leaving the ironing dryer, said measuring means being capable of delivering a measurement signal in the presence of a piece of laundry, and control means responsive to the measurement signal for modifying the humidity level by acting on at least one element of the ironing dryer, characterized in that the control means comprise means for amplifying, with variable gain, the measurement signal and automatic gain control means, able to give the gain of the amplification means an optimized value, such that the amplification means emit a unsaturated output signal.

According to a preferred embodiment of the invention, the element on which the control means act is a means for adjusting the speed of travel of the clothes in the ironing dryer. This adjustment means can in particular vary the speed of rotation of the ironing cylinder of the machine.

Preferably, the means for measuring the moisture content comprise two electrically conductive members, each comprising at least two (preferably five) flexible tabs capable of being simultaneously in contact with the pieces of laundry leaving the ironing dryer, the flexible tongues. the two members being arranged alternately, so as to form as many elementary sensors as pairs arranged in parallel.

Advantageously, the machine further comprises means for measuring the moisture content of the clothes to be ironed entering the ironing dryer.

Preferably, the machine further comprises means for recording the measurement signal, which provide maximum traceability to the ironed linen.

Brief description of the drawings

• la figure 1, déjà décrite, représente l'évolution de la résistance équivalente d'une pièce de linge (en Ohms) en fonction du taux d'humidité de celle-ci (en %), pour une valeur donnée du gain d'amplification du signal représentatif de cette résistance ; et
• la figure 2 représente de façon très schématique une sécheuse repasseuse conforme à l'invention, équipée de moyens de contrôle du taux d'humidité du linge repassé ;
• la figure 3 est une vue en perspective qui représente à plus grande échelle les moyens de mesure du taux d'humidité à la sortie de la machine ; et
• la figure 4 représente schématiquement les moyens de contrôle qui équipent la machine de la figure 2.

A preferred embodiment of the invention will now be described by way of nonlimiting illustration, with reference to the accompanying drawings, in which:

• FIG. 1, already described, represents the evolution of the equivalent resistance of a piece of laundry (in Ohms) as a function of the moisture content thereof (in%), for a given value of the gain of amplification. the signal representative of this resistance; and
• FIG. 2 very schematically represents a ironer dryer according to the invention, equipped with means for controlling the moisture content of the ironed laundry;
• Figure 3 is a perspective view showing on a larger scale the means for measuring the moisture content at the output of the machine; and
• FIG. 4 diagrammatically represents the control means which equip the machine of FIG. 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 2 very schematically shows a drying ironer with a heating roller equipped, in accordance with the invention, with means for controlling the moisture content of the pieces of ironed clothes coming out of this machine. However, it will be understood by those skilled in the art that the invention is not limited to this type of machine and also relates to ironers with a calender.

In the case represented by a drying ironer with a heating cylinder, FIG. 2 shows an ironing cylinder 10, of horizontal axis, means 12 (such as an electric motor) making it possible to drive the cylinder 10 in rotation. around its axis, at an adjustable speed, and endless textile belts 14, in contact with a portion of the circumference of the cylinder 10. The endless textile belts are mounted on rollers such as 16, whose axes are parallel to that of the cylinder 10.

To facilitate the reading of Figure 2, some components of the ironer dryer well known to those skilled in the art have not been represented. Among these components, there are in particular heating means placed inside the cylinder 10 and suction means gases and steam released by the laundry, through the textile strips 14.

The clothes are ironed by introducing them between the cylinder 10 and the textile strips 14, in a direction corresponding to the direction of rotation of the cylinder 10 (arrow F). The ironed and dried linen pieces leave the machine on a cylindrical and substantially horizontal portion 14a of the textile strips 14.

According to the invention, the ironing dryer illustrated schematically in FIG. 2 incorporates a device making it possible to control continuously the instantaneous moisture content of the clothes that come out of it, so that this rate is kept permanently at a set point, regardless of the moisture content of the clothes at the entrance of the machine. Specifically, the set value is chosen low enough to ensure good microbial quality of ironed linen, especially when it comes from a hospital.

As will be described later in more detail with reference to FIG. 4, the device for controlling the moisture content of the ironed articles comprises mainly means 18 for measuring this moisture content and control means for controlling the humidity. at least one ironing dryer element capable of modifying said rate.

The measuring means 18 are situated at the outlet of the ironing dryer, precisely above the cylindrical and substantially horizontal portion 14a of the textile strips 14, in the embodiment shown. They are designed to deliver a measurement signal representative of the moisture content of the ironed clothes that come out of the machine.

In the preferred embodiment of the invention illustrated in FIG. 3, the measuring means 18 comprise two electrically conductive members 21 and 22, electrically insulated from one another by an insulating block 24.

More specifically, the electrically conductive members 21 and 22 are metal plates. These plates comprise substantially planar base portions 21a and 22a, which are mounted on a fixed portion 26 of the machine, above the cylindrical portion 14a and substantially horizontal, so as to be substantially parallel to each other.

Each of the metal plates forming the electrically conductive members 21 and 22 also includes at least two flexible tabs 21b and 22b, which protrude from the base plates 21a and 22a. The flexible tabs 21b and 22b are arranged parallel to each other and alternately, equidistant from each other. They have end portions folded in the same plane, tangential to the cylindrical portion 14a and substantially horizontal on which the ironed clothes pieces. Thus, the ironed clothes that come out of the machine are simultaneously in contact with all the end portions of the flexible tongues 21b and 22b.

In the preferred embodiment of the invention illustrated in Figure 3, each of the metal plates forming the electrically conductive members 21 and 22 comprises five flexible tabs 21b and 22b.

The arrangement of the measuring means 18 which has just been described amounts to forming at least two and, preferably, five humidity sensors arranged in parallel. The sensitivity of the measuring means is thus given a relatively low value, well suited to the measurement of the very low humidity levels generally found at the outlet of the ironers.

As illustrated in FIG. 4, electrical conductors 28 connect the two electrically conductive members 21 and 22 of the measuring means 18 to the means 20. These electrical conductors 28 convey an electrical measurement signal, representative of the electrical resistance between the electrically conductive members 21 and 22 and, therefore, the moisture content present in a piece of laundry possibly in contact with the tongues. 21b and 22b.

According to the invention, the control means 20 comprise amplification means 30, with variable gain, of the measurement signal coming from the measuring means 18.

According to the invention, the control means 20 also comprise means 32 for automatically adjusting the gain of the amplification means 30. These automatic gain adjusting means 32 are arranged to automatically give the gain amplification means 30. an optimized instantaneous value, such that the output signal emitted by the amplification means 30 is unsaturated, irrespective of the humidity level of the pieces of laundry coming out of the machine.

In other words, the automatic gain control means 32 determine at each instant an optimized instantaneous gain for which the output signal delivered by the amplification means always has a usable value, that is to say distinct from the saturation limits for which changes in the moisture content of the laundry do not vary the signal coming out of the amplification means.

The control means 20 thus deliver, at the output of the amplification means 30, a signal which is permanently the image of the humidity contained in the pieces of laundry coming out of the machine, whatever the value of this humidity.

In practice, the automatic gain control means 32 may include an algorithm that calculates the optimized instantaneous gain from the measurement signal delivered by the measuring means 18.

In the preferred embodiment of the invention, but in a nonlimiting manner, the automatic gain adjustment means initially give the gain of the amplification means 30 its maximum value.

If the output signal thereof is unsaturated, this gain value is taken as the optimized instantaneous value and is maintained as long as the output signal remains unsaturated.

Conversely, if the output signal of the amplification means is saturated, the automatic gain adjustment means 32 divide the maximum value of the gain by a predetermined factor, for example substantially equal to two in the preferred embodiment of FIG. the invention.

We then examine again whether the output signal of the amplification means 30 is saturated or not. If not, the maximum value of the gain divided by the factor is taken as the optimized instantaneous value, as long as the output signal remains unsaturated. In the opposite case, the last value of the gain is again divided by the said factor, and so on until an unsaturated output signal is obtained.

The unsaturated output signal thus obtained according to the invention is then compared in 33 to a moisture content recorded and used to control one or more elements of the ironer dryer capable of modifying said rate. In the preferred embodiment of the invention illustrated in the figures, this element is constituted by the means 12 for rotating the cylinder 10. More specifically, the drive means 12 are then actuated so as to modify the speed of advance of the pieces of laundry in the machine. This modification has the effect of bringing very quickly to the desired value the moisture content of the piece of laundry coming out of the machine.

To complete the description, it will be noted that before being injected into the amplification means 30, the measurement signal preferably undergoes a smoothing operation in a smoothing circuit 34 and an averaging operation in an averaging circuit 36. Thus, the measurement signal that is transmitted to the amplification means 30 does not take into account possible erratic measurements and represents the average of a determined number of consecutive measurements.

In addition, in the preferred embodiment of the invention, the algorithm of the automatic gain control means 32 is designed so as to avoid systematically restarting the amplification with a maximum value gain when several pieces of laundry. the same batch, having substantially the same moisture content, are ironed continuously after each other.

For this purpose, when the measuring means 18 emit no measurement signal indicating the presence of a piece of laundry on the cylindrical portion 14a and substantially horizontal, the algorithm maintains unchanged the last value of the instantaneous gain optimized for a predetermined period of time, after the end of the previous measurement signal indicating the presence of a piece of laundry on the portion 14a.

Advantageously, the ironing dryer according to the invention is also equipped with means 38 for measuring the moisture content of the clothes to be ironed which are introduced into the ironing dryer (Figure 2). These measuring means 38 can be made in the same manner as the measuring means 18 described above. They are mounted on another fixed part 40, above another cylindrical portion 14b and substantially horizontal endless belts 14, located where the textile parts are introduced into the machine.

The signal delivered by the measuring means 38 is also transmitted to the automatic gain control means 32 (FIG. 4). It can in particular be used to detect the introduction of a piece of laundry in the ironing dryer.

As shown diagrammatically in FIG. 4, the measurement signal delivered by the measuring means 18 placed at the output of the machine is advantageously recorded in recording means 42, with other information notably enabling identify the ironed clothes. This arrangement makes it possible to ensure the traceability of the operations carried out on the machine and more precisely to guarantee the good microbial quality of the ironed linen.

Of course, the invention is not limited to the embodiment which has just been described by way of example. Thus, the algorithm for automatically adjusting the gain of the amplification means 30 to the optimum instantaneous value may be substantially different from that which has been described. This algorithm can in particular initially give the gain its lowest value or a pre-established average value. On the other hand, the humidity measurement means may in certain cases be replaced by existing means, without departing from the scope of the invention.

Claims (12)

1. Method for controlling the moisture content of ironed linen items leaving a drying ironer, according to which the moisture content of the ironed linen items is measured, then at least one element of the drying ironer is monitored according to the measured moisture content, so that it can be moved to a set value, wherein the measured moisture content is amplified with an instant optimised gain so that the measured moisture content so amplified shows a non-saturated value, which is used to monitor said element of the drying ironer.
2. Method according to claim 1, in which the gain is initially given a maximum value, then the gain is divided by a given factor, as many times as necessary until the measured, amplified moisture content shows said non-saturated value.
3. Method according to claim 1, in which, if no measurement is made of the moisture content of an ironed item of linen, the instant optimised gain is kept unchanged for a predetermined length of time after the end of the measurement of the moisture content of the last item of linen ironed.
4. Method according to claim 1, in which successive measurements of the moisture content are taken, the measurement signals are smoothed and their average is calculated before they are amplified with said instant optimised gain.
5. Drying ironer comprising means for measuring the moisture content of ironed linen items leaving the drying ironer, said measuring means being able to deliver a measurement signal in the presence of an item of linen, and control means sensitive to the measurement signal so as to adjust the moisture content by acting on at least one element of the drying ironer, wherein the control means comprise variable gain amplification means for amplifying the measurement signal, and means for automatic gain adjustment able to give an optimised value to the gain of the amplification means so that the amplifications means emit a non-saturated output signal.
6. Drying ironer according to claim 5, in which the automatic adjustment means initially give the gain a maximum value, then divide the gain by a given factor, as many times as is necessary, until said optimised value is obtained.
7. Drying ironer according to claim 5 in which, in the absence of a measurement signal, the automatic adjustment means maintain the gain at said optimised value for a predetermined length of time after the end of the last measurement signal.
8. Drying ironer according to claim 5, in which the control means comprise smoothing means and averaging means.
9. Drying ironer according to claim 5, in which the element on which the control means act are means for adjusting the conveying speed of the linen items in the drying ironer.
10. Drying ironer according to claim 5, in which the means for measuring moisture content comprise two electrically conductive parts each comprising at least two flexible tongues able to contact simultaneously the items of linen leaving the drying ironer, the flexible tongues of the two conductive parts being arranged in alternate manner so as to form as many element sensors as there are pairs arranged in parallel.
11. Drying ironer according to claim 5, also comprising means for measuring the moisture content of linen items to be ironed entering the drying ironer.
12. Drying ironer according to claim 5, also comprising means for recording the measurement signal.

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