FR2587098A1 - REFRIGERATION APPARATUS HAVING AN IMPROVED DEFROST DEVICE - Google Patents

Abstract

THIS REFRIGERANT APPLIANCE IS EQUIPPED WITH AN DEFROST DEVICE INCLUDING AN ELECTRIC RESISTOR 6 WHICH IS SWITCHED ON AFTER A PREDETERMINED TIME HAS ELAPSED BY MEANS OF A TIMER 17. THIS TIMER IS STOPPED WHEN ELECTRIC RESISTANCE 6 IS ON AND IT IS ON. IS TURNED ON WHEN THIS RESISTOR IS SWITCHED OFF BY A THERMOSTATIC PROBE 7 WHICH RESPONDS TO THE EVAPORATOR TEMPERATURE 3. IN THIS WAY THE ADVANTAGE OF KEEPING THE TIME INTERVALS CONSTANT BETWEEN TWO TANDING DEFROST CYCLES SUCCESSFUL THAT THE DURATION OF EACH DEFROST CYCLE IS MADE VARIABLE.

Description

The present invention relates to an apparatus

  type of refrigeration that includes an electric compressor

  that, an evaporator, an electrical resistance provided for the defrosting of the evaporator, a timer which, after expiration of a predetermined time, switches on the electrical resistance and stops the compressor, and a thermostatic probe which responds to the temperature

  of the evaporator by putting said resistance out of circuit

  cooked when a predetermined thermal level is reached

on the evaporator.

  During the defrost cycle of a fri-

  gorific, it is important, on the one hand, that the evapora-

  teur is completely rid of the accumulation of frost but, on the other hand, it is equally important to avoid the rise in the thermal level of the preserved products.

  The defrost cycle of a refrigerator is de-

  finished by three main moments: a first instant,

  intervention of the electrical resistance with interrup-

  tion of the refrigeration cycle, a second instant, of switching off the electrical resistance, and a

  third instant, to restart the cooling cycle

  management. The command parameter used to determine

  the first and third moments are usual-

  time. According to the known technique, a timer is used for this purpose which, at intervals fixed in advance, stops the compressor and sets the resistance of

defrost in circuit.

  The second moment of the defrost cycle is

  on the contrary controlled according to the temperature at-

  tinted by the evaporator, using thermostat probes

  that switch off the electric defrost resistor. The timer remains in action for

  the operation of the defrost resistor.

  Since the control parameters of these times (temperature) are not homogeneous

  between them, the defrost cycle of a refrigerating appliance

  that necessarily have mismatches compared to

  compliance with the requirements set out above.

  Indeed, to guarantee a total defrosting of the evaporator, it is necessary to provide between the first instant and the third instant an interval of

  time greater than the normal intervention time for the

  sistance. If, on the contrary, we opt for a refurbishment

  immediate operation of the compressor at the end of operation

  defrost resistance, there will be no gain

  proud to have completely freed the frost evaporator.

  The problem underlying this present in-

  vention consists in producing a refrigeration appliance which is capable, by its structure and its functioning, of

  overcoming the disadvantages of technology

known aforementioned pic.

  This problem is solved by a refrigerator

  fique of the aforementioned type, which is characterized in that it comprises means which stop said timer when said resistor is on and restart it when the resistor is switched off

by said probe.

  Other features and advantages of the

  vention will be better understood on reading the description

  tion which will follow from an exemplary embodiment and with reference to the accompanying drawing which schematically represents an electrical supply and defrost circuit for a refrigeration appliance according to the invention. In this drawing, the whole of the electrical circuit diagram of a refrigerating apparatus according to the invention has been designated by 1.

  In diagram 1, a line L of ali-

  electrical information including branches Ll and L2 en-

  which are the potential differences of the network, for example 220 V.

  In diagram 1, we have indicated in 2 a

  electric sister, which is usually communica-

  tion for the fluid flow with an evaporator 3 and with a condenser not shown.

  An electric fan 5 is provided for

  complete forced air circulation on the surface of

the evaporator 3.

  An electric resistance is also provided

  than 6, placed near the evaporator 3 to provo-

  defrost this evaporator at preset intervals

  completed, as will be explained below.

  On the evaporator 3, a probe 7 is placed

  keen to capture the temperature. Probe 7 is connected

  ted to an actuator 8 belonging to a first switch

9.

  The switch 9 has a movable contact assembly 10 which is connected to the branch L2 of the line L and which can move between a first and a second contact terminal designated respectively by

11 and 12.

  Terminal 11 is connected to the moving element 13 of a second switch 14, also provided with first and second designated contact terminals

15 and 16 respectively.

  An electromechanical type timer 17 is connected to line L in series with the resistor

  6; timer 17 and resistor 6 are connected

  to each other on terminal 15 of the second switch

14.

  Terminal 16 of this switch 14 is in turn connected to terminal 12 of the first switch 9 and, by this terminal, to a terminal 20 of the power supply of the

compressor 2.

  A second terminal 21 for supplying the compressor

  sor 2 is connected to branch L1 of line 'L.

  In addition, terminals 16 and 22 are connected

  the moving element 22 of a switch 23 which can inter

  cut off the power supply to fan 5 of the

as described below.

  The moving parts 13 and 22 of the second switch 14 and of the switch 23 are actuated by a

  classic way in itself by the timer 17, for example-

ple, by cams.

  The actuator 8 constitutes, with the probe 7, a device for thermal control of the evaporator 3. This device has two intervention thresholds, which are

  respectively an upper threshold for which one indicates-

  ra, only as an example, a value of 7 C, and a lower threshold for which we will indicate, here also at

  as an example, a value of -25 C.

  When the signal from the probe 7 reaches these thresholds, the actuator 8 switches the position of the moving element 10 of the switch 9 from the first terminal 11 to the second terminal 12, or vice versa, as will be

set out below.

  During normal operation of the device

  refrigerator, during which, in this example, the temperature

  erection of the evaporator 3 is between +7 C and -25 C, the moving element 10 of the first switch is

  closes on contact terminal 12 by determining the supply

  electric compressor 2.

  The moving element 13 of the second switch 14 is closed on terminal 16 and the switch 23 determines

  the fan power supply 5.

  Timer 17 has an appreciable internal electrical resistance, greater than that of resistance 6. The effect of resistance 6 on the current flowing

  in timer 17 is therefore negligible and this cost

  rant is low enough not to cause overheating

  resistance appreciably 6. At an instant

  determined, the timer 17 intervenes on the interrupt

  23, by removing the electrical supply from the

tiler 5.

  The evaporator 5, which is no longer traversed by

  forced air circulation, undergoes a temperature drop.

  which is detected by probe 7. When the lower threshold is reached, the signal

  sent by probe 7 activates actuator 8, which

  mutates the moving part 10 of the first switch 9 to

the contact terminal 11.

  The compressor 2 remains on, owing to the fact that it is supplied through the second switch 14, the moving assembly 13 of which is closed on the contact terminal 16.

  After the expiration of a predefined time interval

  completed after the fan 5 has been stopped, the timer 17 intervenes on the moving element 13 of the second switch 14, passing the contact

  this switch from terminal 16 to terminal 15.

  The timer 17 is stopped because it is short-circuited on the branch L2 of the line L and, at the same time, the defrost resistor 6 is switched on. Resistor 6 determines a heating of

  evaporator 3, the temperature of which is always controlled

linked by probe 7.

  When the temperature of the evaporator 3 exceeds

  the upper threshold level programmed by the action-

  neur 8, the moving element 10 of the first switch 9 is again moved from the contact terminal 11 to the

contact terminal 12.

  This interrupts the power supply to the

  resistance 6 while that of compressor 2 and time

Poriser 7 is restored.

  When it has been restarted, the timer

  tor 17 switches over the moving part 13 of the second

  th switch 14 to place it in the closed position

  re on contact terminal 16 and, after an interval of

  predetermined time after restarting the compressor

  sor 2, it intervenes on switch 23 to reset

be fan 5 on.

  A first advantage of the refrigeration appliance

  according to the invention consists in that it maintains the

  unchanged compressor 2 operating time

  independent of the duration of the defrost cycle. A

  another advantage of the invention is that it guarantees

  tit that at the end of each defrost cycle, the evaporator

  t '3-- is e - firstly rid of its frost and ready

  for immediate restarting of compressor 2.

  Another important advantage brought by the app

  reil refrigerant according to the invention consists in that it cools the products placed in the immediate vicinity of

  the evaporator at a temperature lower than the temperature

  speed before each defrost cycle, due to the fact that it interrupts fan operation

  ahead of the compressor shutdown

  sister. In addition, the predetermined delay in starting

  of the fan in relation to restarting the

  compressor allows the evaporator to reach fast-

  the operating temperature and avoid circulating

  inside the refrigeration unit

  heated by the defrost cycle which has just ended

  ner. Of course, various modifications may be made by those skilled in the art to the device which

  has just been described only by way of non-binding example

  mitative without departing from the scope of the invention.

Claims (3)

RESELL I C AT IONS   1 - Refrigerating appliance comprising a compressor   electric heater (2), evaporator (3), resistance   electric (6) provided for defrosting the evaporator   timer, a timer (17) which, after a predetermined time has elapsed, switches on said resistor and stops the compressor, and a thermostatic probe (7) which responds to the temperature of the evaporator by putting said resistor (6) off when a predetermined thermal level is reached on the evaporator, this device being characterized in that it comprises means which stop the timer (17) when the resistor (6) is in circuit and which restart it when this resistor is switched off by the probe (7).   2 - Apparatus according to claim 1, character-   in that the timer (17) and the resistor (6) are connected in series with each other between the branches (L1, L2) of an electrical supply line and in that said means comprise a first switch   (9) and a second switch (14), the first switch   tor having a mobile contact equipment (10) which is supplied by the branch (L2) of said line (L) to which the timer (17) is also connected, and this mobile equipment alternately closing on a   compressor supply contact (12) and on the equi-   mobile page (13) of the second switch (14) and the equi-   mobile page (13) of this second switch closing alternately on the contact (16) supplying the   compressor and on said resistor (6), the first   mutator (9) being controlled by the thermostatic probe   (7) and the second switch (14) being controlled by the- said timer (17).   3 - Apparatus according to claim 1, character-   laughed at in that it includes an electric fan (5)   associated with the evaporator (3) and whose electrical supply   plate is controlled by a switch (23), itself controlled by the timer (17), so that the fan stops with a predetermined advance time relative to the stop of the compressor and is returned to   walking with a predetermined delay compared to delivery of this compressor.