EP0312467A1 - Controlbox for a deep-freezer - Google Patents

Abstract

Automatic defrosting device for deep-freezer, comprising a clock (3), a double switch for defrosting (5, 7), heating resistors (16) and a battery thermostat (22). The thermostat (22) has two triggering levels, a high one (+8 DEG C) and a low one (-28 DEG C). The high triggering level stops heating (16) and restarts cold production (12). The low triggering level also restarts ventilation (13). <IMAGE>

Description

The present invention relates to a control cabinet for freezing and preservation apparatus of the type comprising a single enclosure.

The cold technique is more and more often applied to food products such as pastry and ready meals, allowing the realization of the products in a massive way or in the best conditions, then their conservation without any degradation until the period of their sale and of their consumption.

In order for the products to be preserved in the best conditions, without modification of their texture, of their initial appearance, and without drying, it is advantageous to proceed in two stages, namely: freezing followed by conservation.

Freezing consists of a very rapid freezing operation at the heart of the product. This operation must be carried out in a device called deep-freezer, the refrigerating power of which is high, at a low temperature of the order of - 40 ° C. At the end of freezing, which does not exceed a few hours, the products are transferred to a preservative, inside which there is a temperature of the order of - 25 ° C.

There is currently a freezing and preservation device comprising a single enclosure. An appliance of this type, called a freezer-preservative, is for example described in the document FR-A-2,468,314. This device includes a single enclosure containing:
- the evaporator, or battery, of a refrigeration installation over which the air contained in the enclosure passes under the action of a fan,
- a deep-freezing compartment, in permanent communication with the compartment containing the evaporator and generally placed under it, and,
- at least one storage compartment capable of being placed in communication and isolated the freezing compartment.

The refrigeration installation is capable of several operating regimes, namely: at least one regime where it ensures the maintenance of a storage temperature of the order of - 25 ° C and one regime where it provides a freezing temperature of the order of - 40 ° C. Since the device is used as a simple preservative, the various compartments which it comprises, namely the compartment containing the battery of the refrigerating unit, the deep-freezing compartment and the storage compartments, communicate with each other, the temperature being the same, of the order of - 25 ° C throughout the device.

Insofar as products have to be deep-frozen, the storage compartments are isolated, by operating closing flaps, from the deep-freezing compartment. As frigories are only supplied in the deep-freezing compartment, the temperature in this freezer then reaches approximately - 40 ° C. At the end of the deep-freezing period, the flaps are reopened and the various compartments are put back in communication so that, taking into account this new distribution, the average temperature of the whole is of the order of - 25 ° C.

A shutter is also often provided, normally open when the aforementioned shutters are closed, and vice versa, which has the role of opening, during freezing, a wide passage between the upper downstream part of the freezing compartment and the part lower upstream of the compartment containing the evaporator of the refrigeration installation: this passage is open during freezing, allowing air to circulate massively from the freezing compartment to the evaporator, and it is however closed during conservation, the all of this air flow then passing through the storage compartments, as it should be.

Generally, the control means of the various flaps are coupled and driven by a single geared motor itself controlled by a clock for programming the operating regime of the device.

When the user wishes to freeze a certain quantity of products, it suffices to display the freezing time on the clock and to control the start of freezing, which activates a gear motor causing the tilting of the aforementioned flaps. . At the end of freezing, the clock automatically controls the return to the initial conservation regime, these flaps tilting back to their initial position.

Like all refrigeration systems, a freezer-freezer must be defrosted at regular intervals. Its command and control device therefore necessarily comprises a part responsible for controlling, at predetermined times, a sequence defrost. This defrosting is carried out in this type of installation by stopping the production of cold and ventilation, while heating resistances of the battery, that is to say of the evaporator, are put into service.

The appended FIG. 1 represents, in the form of a block diagram, the portion of a conventional regulator which is responsible for controlling the sequences of automatic defrosting.

This known regulator comprises, connected to the supply terminals 1 and 2, a programming and control clock 3. This clock controls, at predetermined times, for example every 6 hours, by a connection 4, the timed switching of a first two-way switch 5, and by a connection 6 the timed switching of a second two-way switch 7.

Before the start of the defrosting sequence, the positions of the two switches 5 and 7 are such that their input terminal, respectively 8 and 9, is connected to their first output terminal, respectively 10 and 11. Terminal 10 then supplies the cold production device 12, which is connected between this terminal 10 and the second line wire 2, the first line wire 1 being itself connected to terminals 8 and 9. Terminal 11 in turn supplies the ventilation 13 which is connected between this terminal and the second line wire 2.

After the switchover triggered by the defrosting programming clock 3, the input terminals 8 and 9 of these two switches 5 and 7 are each connected to their second output terminal, respectively 14 and 15. Between terminal 14 and the second line wire 2 are connected in series the defrost resistors 16, responsible for heating the battery to carry out the defrost, and a battery thermostat 17, placed against the latter and adjusted to open its contact at a temperature slightly above 0 ° C, for example 8 ° C, this contact can then be closed only by energizing an incorporated relay, connected between wire 2 and, via link 18, terminal 10. Clock 3 is set to maintain contact between 8 and 14 for a predetermined time, for example 30 minutes. This time having elapsed, the contactor 5 switches back to its initial position 8-10.

Between the terminal 15 of the second switch and the wire 2 is connected a device 19 for controlling the forced closing of the flaps, the latter reopening naturally when the terminal 15 is no longer supplied. Clock 3 is set to maintain contact between 9 and 15 for a predetermined duration, greater than d₁. For example, d₂ is 35 minutes. This time having elapsed, the switch 7 switches back to its initial position 9-11.

It appears from the diagram in FIG. 1 that the operation, for defrosting, of this known device is as follows:

At the start of the defrost start, the clock 3 controls, by connections 4 and 6, the switching to the right of the switches 5 and 7. The cold production 12 and ventilation 13 devices, being no longer supplied, s 'stop instantly. The resistors 16 are supplied and begin to heat the battery, and the flaps are closed by the device 19, which is also supplied.

When the battery has risen to a temperature above 0 ° C, that is to say that it is completely defrosted, the thermostat 17 triggers and cuts off the electrical supply to the resistors 16. A time has then elapsed d₃, less than d₁ and dependent on the frost charge of the battery. For example, d₃ is equal to 20 minutes.

During the 10 minutes remaining to reach d₁, the resistors, due to their thermal inertia, continue to heat the compartment containing the battery. We then observe a release of water vapor which comes to condense on the surrounding cold parts to deposit ice there: there is creation of ice blocks which can no longer be absorbed by the battery, these ice blocks being able to in the long run take proportions such that they manage to block the fan or even the air circuit.

At the end of the time d₁, the switch 5 having returned, the production of cold is reset while, the position of the switch 7 remaining unchanged for the moment, the shutters are always closed and the ventilation always stopped. During this time interval, equal to d₂-d₁, in our example therefore equal to 5 minutes, the battery absorbs the water vapor which surrounds it then, at time d₂, the switch 7 returns to its initial position, so that the ventilation starts again while the shutters open again. In certain cases, in particular when the frost load is high, the battery has not completely absorbed, at the end of the time d₃, all this water vapor, so that ventilation, when restarting, causes sending a breath of air into the storage compartments relatively hot and humid, which in particular causes a deposit of frost or ice on the product.

The invention aims to remedy these drawbacks by means of a deicing control and regulation device which is adapted to the effective frost charge of the battery. To this end, it relates to a regulating box for freezer-freezer which comprises a device for automatically controlling the defrost of the battery, under the control of a control clock which supplies, at a predetermined instant, a start command signal. defrost, this signal causing on the one hand the stopping of the cold production device and the ventilation device, and on the other hand the starting of a battery heating device. According to the invention, this automatic control device is associated with a thermostatically controlled device placed on the battery which has on the one hand a high switching point, set at a temperature slightly above 0 ° C, for example between 5 and 10 ° C, and on the other hand a low switching point, set at a temperature substantially equal to slightly lower than the storage temperature, therefore for example between - 25 ° C and - 30 ° C. The device is equipped with means so that the switching of the thermostat contact corresponding to the high point of this thermostatically controlled command results in the restarting of the cold production device, and so that, the temperature of the battery having consequently dropped considerably, the switchover of the thermostat contact corresponding to the low point of this thermostatically controlled control then causes the ventilation device to start up again.

Advantageously, in the case of a device for which said start-of-defrost signal also causes the closing of the shutter (s) of separation, this second switchover of thermostat contact at the low point also causes the reopening of this (these) shutter (s) s).

• Figure 2 est une représentation schématique, par schéma-blocs, de ce dispositif ;
• Figure 3 est un diagramme représentant les courbes de variation de la température de la batterie en fonction du temps, relatives à deux séquences de dégivrage pour des charges en givre différentes de la batterie.

In any case, the invention will be well understood, and its advantages and other characteristics will emerge during the following description of a non-limiting example of embodiment of this controlled defrost control device, with reference to the appended drawings in which:

• Figure 2 is a schematic representation, by block diagram, of this device;
• Figure 3 is a diagram representing the curves of variation of the temperature of the battery as a function of time, relating to two defrosting sequences for frost loads different from the battery.

We recognize in FIG. 2 the programming and control clock 3, connected between the two supply lines 1 and 2, as well as the two-way switches 5 and 7 which are however here controlled together and simultaneously by a common connection 20 coming from the clock 3. The cold production device 12 is always connected between the terminal 10 of the contactor 5 and the line wire 2, while the ventilation device 13 is connected, as for the device in FIG. 1 , between terminal 11 of the other contactor 7 and this same line wire 2.

The device 19 for forced closing of the shutters is always connected between the terminal 15 of the switch 7 and the line wire 2, but it is this time through a series contactor 21, which is the opening contactor "point bottom "of a thermostat 22 with two tilting points, the probe of which is placed on the battery of the cold production device: the contact 21 opens when the temperature of the battery has dropped until reaching a value below the temperature this conservation, for example it opens to - 28 ° C. This contact 21 is provided so that, once it is opened, it can only be closed by a signal from the clock 3, routed by the electrical connections 23 and 24.

The heating resistors 16 of the battery are always connected between the terminal 14 of the switch 5 and the line wire 2, but this time they are connected through a series contactor 25, which is the "high point" opening contactor. "of the above-mentioned thermostat 22. Thermostat 22 is set to open this contact when the temperature of the battery has risen until it reaches, after total defrost, a temperature slightly above 0 ° C: for example, it opens at + 8 ° C. As with the other contact of this thermostat, this contact 25, once opened, can only be closed by sending the aforementioned electrical signal, by the connections 23 and 26 coming from the clock 3.

Between the line wire 1 and the terminal 10 (connected to the cold production device 12) is placed a controlled contactor 27, the closing of which is controlled, through the connection 28, by the signal "high point" of the thermostat 22 ( it is the same signal which simultaneously controls the opening of 25 and the closing of 27), and whose reopening is controlled, via connection 29, by clock 3: the high point signal of thermostat 22 therefore leads to both stopping the feeding of resistors 16 (by opening contact 25) and restarting cold production 12 (by closing contact 27).

Between the line wire 1 and the terminal 11 (connected to the ventilation device 13) is placed a controlled contactor 30, the closing of which is controlled, through the connection 31, by the "low point" signal from the thermostat 22 (it is the same signal which simultaneously controls the opening of 21 and the closing of 30), and the reopening of which is controlled, via connection 32, by clock 3: the low point signal from thermostat 22 therefore causes both opening the shutters (by opening contact 21) and restarting the ventilation (by closing contact 30).

Referring to all of Figures 2 and 3, the operation of this automatic defrosting device is as follows:

By first taking the case, shown in curve A (FIG. 3), of a relatively low charge of frost from the battery, the clock 3 sends, at the predetermined time, a command signal to start defrosting on wire 20 (Figure 2). Switches 5 and 7 then toggle together to the right, changing connections 8-10 and 9-11 to 8-14 and 9-15 respectively. At this stage, the contactors 25 and 21 are closed and the contactors 27 and 30 open.

This switching of switches 5 and 7 consequently leads to:
- stopping the production of cold and ventilation, since 12 and 13 are no longer supplied,
- closing the shutters and starting the heating resistors of the battery, 19 and 6 being supplied.

The freezing and deep-freezing compartments are not substantially affected by the heating of the resistors, since the shutters are closed and the ventilation stopped, and the temperature of the battery rises regularly up to 0 ° C (part a of curve A ).

The temperature of the battery then remains at 0 ° C (level b) as long as the defrosting lasts. When the battery is defrosted, the temperature increases, faster than previously (portion c), until reaching at d the high trigger point (8 ° C) of thermostat 22.

The thermostat 22 then simultaneously controls the opening of 25 and the closing of 27, which cuts the heating of the resistors 16 and re-triggers the production of cold 12. The heating of the battery then ceases rapidly and, the trend reversing, we attend a rapid fall in temperature (portion of curve e).

When the temperature of the battery has dropped to the temperature (- 28 ° C) which corresponds to the low point of tripping of the double thermostat 22 (point f on curve A), this thermostat 22 simultaneously controls the closing of the contactor 30 ( which causes the ventilation 13 to start up again) and the contactor 21 to open (which causes the shutters to reopen). It follows that the freezer-freezer is then restarted in its normal working position, the temperature of the battery then stabilizing at the temperature of - 25 ° C, which was that before the start of the defrost. .

When a certain predetermined time has elapsed after the start of the defrosting sequence, this time being fixed at a maximum possible value for this sequence (for example one hour), the clock 3 sends an end of operation signal defrost on wires 20,23,29 and 32. As a result:
- switches 5 and 7 switch back to the right, re-establishing connections 8-10 and 9-11,
the contactor 21 closes,
- the contactors 27 and 30 reopen,
so that all the initial conditions are restored, the device being ready for a new subsequent defrosting.

In FIG. 3, there has been shown by a dashed section g the temperature variation of the battery which was previously obtained with the same frost charge, after point d, with the device of FIG. 1.

Curve B shows the evolution, with the device of FIG. 2, of the temperature of the battery with a relatively large frost charge. The references on this curve: a ′, b ′, c ′, ..., g ′ correspond to the references a, b, c, ..., g relating to curve A.

These curves show that the total duration of the defrosting operation (T₁ for curve A, T₂ for curve B) varies with the frost load and is perfectly suited to the latter. The cooling of the battery begins as soon as it is defrosted, and the storage facility is restarted as soon as the temperature of the battery has dropped to its normal operating point.

The device which has just been described can be subject, like all the devices, to damage. If such damage occurs, it appears necessary, however, to have the possibility of defrosting the battery of the freezer-conservator. According to another advantageous aspect of the invention, the control unit is furthermore provided with an "emergency" defrosting device, which is drawn in dashed lines in FIG. 2.

This backup device includes a start-up and delay timer 33, which is engaged by a simple pressure of the finger on a push button 34. This engagement causes the sending, by the connections 35 and 36, of a signal of closing two contactors 38, 39, which connects the resistors 16 between the supply terminals 1 and 2, and the sending, by connection 37, of an opening signal of a contactor 40 which opens the ventilation supply circuit 13, so that it stops. A battery thermostat 41 acts, when the latter has exceeded its defrosting temperature, on a contactor 42 which opens and then cuts the heating of the resistors. After a predefined time delay, the clock 33 emits a signal which returns the four contactors 38, 39, 40 and 42 to their initial state (38 and 39 open, 40 and 42 closed).

The invention is, of course, not limited to the embodiment which has just been described, and is on the contrary capable of being carried out in different equivalent ways, comprising for example fewer elements, such as double contactors or reversing contactors. The different phases of the sequence are advantageously indicated by indicator lights placed on the front panel of the cabinet. Preferably, to avoid any addition of intensity, the tilting to the right of switches 5 and 7 causes the opening of a contactor which cuts the supply of the refrigeration compressor of the device 12, this contactor then being closed by action of the thermostat. of battery (high point at 8 ° C).

Claims (4)

1 - Regulation unit for freezer-conservator, comprising an automatic device for controlling and regulating the defrosting of the battery, or condenser, of the cold production device (12), under the control of a control clock (3) and a thermostatically controlled device (22) whose probe is placed on this battery, the clock (3) providing, at a predetermined instant, a command signal to start defrosting which on the one hand causes the stopping of the production of cold (12) and ventilation (13), and on the other hand the start-up of a heating device (16) of the battery, characterized:
- in that the thermostatically controlled device (22) has on the one hand a high switching point (d) adjusted to a temperature slightly above 0 ° C, and on the other hand a low switching point (f), set at a temperature substantially equal to slightly lower than the storage temperature,
- in that it is equipped with means (27.30) so that the triggering of the thermostat (22) corresponding to its high point (d) results in the restarting of the cold production device (12) and so that, after the temperature of the battery has consequently dropped considerably, the triggering of the thermostat (22) corresponding to its low point (f) also causes the ventilation device (13) to be restarted. 2 - Control unit according to claim 1, of the type according to which said control signal for the start of defrosting also causes the closing of one or more separation flaps, characterized in that it is equipped with means (21) for that said triggering at the low point (f) of the thermostat (22) also causes the opening of this or these separation flaps. 3 - Control unit according to claim 1 or claim 2, characterized in that it is further equipped with an emergency defrosting device (33 to 42) which, for a predetermined time, cuts the ventilation (13) and turns on the heater (16) of the battery. 4 - Control unit according to one of claims 1 to 3, characterized in that it is equipped with means for stopping the refrigeration compressor of the cold production device (12) during the actuation of the heating device (16) drums.

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