US3675438A

US3675438A - Refrigerator with fluid amplifier means

Info

Publication number: US3675438A
Application number: US62106A
Authority: US
Inventors: Kazuo Takemasa; Hitoshi Komada
Original assignee: Tokyo Sanyo Electric Co Ltd; Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1969-08-11
Filing date: 1970-08-07
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11

Abstract

A refrigerator includes a first and second storage compartments evaporator means for refrigerating air, means for circulating the refrigerated air to both of the compartments and means for defrosting the evaporator. A fluid amplifier is provided in the refrigerated air circulating passage between air circulating means and the first compartment. The fluid amplifier includes a single inlet for receiving the refrigerated air from the outlet of air circulating means, a first outlet communicated with the first compartment and a second outlet communicated with the second compartment, and a control port communicated with the refrigerated air circulating passage downstream of evaporator means. The control port operates in response to a predetermined pressure drop in the refrigerated air flow to divert the flow of refrigerated air through the amplifier normally directed to the first outlet to the second outlet. Means is also provided which is responsive to the flow of refrigerated air from the second outlet of the fluid amplifier to initiate defrost operation by defrost means.

Description

United States Patent Takemasa et al. [451 July 11, 1972 [541 REFRIGERATOR WITH FLUID 3,487,654 1/1910 borenz "62/140 AMPLIFIER MEANS inventors: Tak both Primary Examiner-Meyer Perhn of Gunma, Japan Assignees: Sauyo Electric Co.. Ltd., Osaka; Tokyo Sanyo Electric Co., Ltd., Gunma, Japan Filed: Aug. 7, 1970 Appl. No.: 62,106

Attorney-Darby & Darby [57] ABSTRACT A refrigerator includes a first and second storage compartments evaporator means for refrigerating air, means for circulating the refrigerated air to both of the compartments and means for defrosting the evaporator. A fluid amplifier is provided in the refrigerated air circulating passage between air [30] F i A u u p i D m circulating means and the first compartment. The fluid ampli- A I fier includes a single inlet for receiving the refrigerated air Aug l ll 3, 1199??) Japan ..44/63426 M the outlet of air circulating means, a first outle commw pn Japan l 394 nicated the first compamncni and a second ouuet municated with the second compartment, and a control port [52] U.S.Cl .62/l56,62/l80,654222776 communicamd with Lhe refrigerated circulating passage 51] In Cl Fzsd 24/06 downstream of evaporator means. The control port operates [58] He. 0.. 209 180 in response 0 a predeermined pressure dlrop in he 5 6 refrigerated air flow to divert the flow of refrigerated air through the amplifier normally directed to the first outlet to the second outlet. Means is also provided which is responsive 6 [5 1 References cued to the flow of refrigerated air from the second outlet of the n- STATES PATENTS fluid amplifier to initiate defrost operation by defrost means. 3,309,887 3/1967 .lacobus .62/l4O l3Clallm,3DrawlngHgures 26 '2 26b 28 F F- "T I FREEZER LIZ l I L30 36 l 260 l 26: i l 002% I 0 3 4 MEANS I| com a r msm I B. r fifififiifl L I i MEANS 1 l I 1 [3* 38 ls l COMPRESSOR 2o CONTROL SWITCH 42 P'A'TENTEUJUL 1 1 1972 sum 20! 2 FIG. 3

FREEZER FOOD COMPARTMENT B DEFROST INITIATION MEANS COMPRESSOR CONTROL SWITCH DEFROST CONTROLLER DEVICE BACKGROUND OF THE INVENTION This invention relates to refrigerators and in particular to a combination refrigerator having automatic defrosting means.

Combination refrigerators generally include two storage compartments known as a freezer compartment and a fresh food compartment which are operated at different temperatures, a single evaporator for refrigerating air, and means for circulating refrigerated air to both of the compartments in order to keep the desired temperatures therein.

During cooling operation of such refrigerator, moisture containing air is circulated from the two storage compartments through the evaporator. Substantially all of the moisture in the recirculated air then condenses to form layers of frost on the evaporator. As is clear to those skilled in the art, the frost accumulation on the evaporator reduces greatly the refrigeration capacity of the evaporator, and thus of the refrigerator itself. In order to avoid a decrease in the refrigeration capacity, it is necessary to remove the frost from the evaporator.

In conventional refrigerators, the defrost operation of the evaporator is periodically initiated, for example, by timer means to be continued for a predetermined period of time regardless of the amount of the accumulated frost on the evaporator. Since the frost accumulation depends primarily on the moisture content of the recirculated air and does not necessarily depend on the time elapsed between two defrost cycles, the periodic defrosting more often than not proves to be inefficient and unsatisfactory.

Accordingly, it is an object of this invention to provide a new and improved refrigerator including defrost means which successfully avoids the above mentioned disadvantages.

It is other object of this invention to provide a new and improved refrigerator having means for removing frost from the evaporator which automatically operates in response to the accumulation of a predetermined amount of the frost,

It is another object of this invention to provide a new and improved defrost means of the type described having an inexpensive and reliable fluid amplifier associated therewith.

SUMMARY OF THE INVENTION In accordance with a preferred form of this invention, there is provided a refrigerator having separate freezer and fresh food compartments, an evaporator for refrigerating air, means for circulating the refrigerated air from the evaporator to both of the compartments and defrost means for removing the frost from the evaporator. A fluid amplifier means is disposed downstream of the air circulating means between the freezer compartment and air circulating means. The fluid amplifier means includes a single inlet for receiving the refrigerated air from the outlet of the air circulating means, a first outlet connected to the freezer compartment, a second outlet connected to defrost initiation means and a control port for directing the flow of refrigerated air through one or the other of the outlets. The control port of the fluid amplifier communicates with refrigerator air passage means so as to be responsive to a pressure change in the passage downstream of the evaporator.

During normal operation of the refrigerator, the control port directs the refrigerated air entering the fluid amplifier means through the first outlet into the freezer compartment. While on the other hand, as the air pressure in the refrigerated air passage decreases to a predetermined level due to a blockage of effective flow space in the evaporator by a predetermined amount of collected frost, the control port operates to divert the refrigerated air through the second outlet to the defrost initiation means. Upon receiving a supply of the refrigerated air, the defrost initiation means functions to start a defrost operation of the evaporator. The defrost operation is automatically terminated by suitable defrost termination means.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be better understood from the following description taken in conjunction with the accompanying drawings.

FIG. I is a diagrammatic illustration of a refrigerator having an improved defrost arrangement according to form of this invention;

FIG. 2 is a diagrammatic illustration of a typical control circuit for the defrost operation of the refrigerator as shown in FIG. I; and

FIG. 3 is a diagrammatic illustration of a refrigerator according to another form of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Refen'ing now to the drawings, in particular to FIG. I, there is diagrammatically illustrated a combination refrigerator and its associated refrigeration system embodying one preferred form of this invention. A refrigerator cabinet 10 defines a freezer compartment [2 designed to be maintained at a temperature below freezing and a fresh food compartment 14 adapted to operate at a temperature above freezing. The two compartments are separated by a heat insulating partition (not shown). A refrigeration system of the combination refrigerator includes an evaporator Id of fin-on-tube type for providing refrigerated air and a motor fan 18 for circulating refrigerated air to the freezer and fresh food compartments [2 and 14. As is well known, a fin-on-tube type evaporator l6 generally comprises a serpentine refrigerant tubing having a plurality of turns which are provided with a plurality of plate fins extending transversely of the turns in a direction generally parallel to the direction of flow of air over the evaporator. A condenser 20, a motor compressor 22 for supplying liquid refrigerant to the evaporator and a flow restricting capillary tube 24 are connected by suitable conduits to the evaporator l6 in closed series flow relationship to form a closed refrigerant circuit.

In accordance with the present invention a monostable fluid amplifier 26 is provided downstream of the motor fan 18. More specifically, as shown in FIG. 1 the monostable fluid amplifier includes an inlet 26a for receiving the refrigerated air from the outlet of motor fan 18 and a first or freezer outlet 26b connected through a first pamage 28 to the freezer compartment and a second or fresh food outlet 26c connected through a second passage 30 to the fresh food compartment. ln accordance with the usual fluid amplifier practice, the fluid amplifier 26 also includes a control port 26d for directing the refrigerated air through one or the other of the

outlets

26d and 26c. The control port 26d communicates with the inlet side of the motor fan 18 for receiving a portion of the refrigerated air flowing from the evaporator 16.

There is provided in the second passage 30 leading from the second outlet port 26c to the fresh food compartment 14 a defrost initiation means 32 for initiating a defrost operation of the evaporator in response to a predetermined temperature or pressure condition in the passage as will be fully described hereinafter. In the illustrated embodiment, the defrost initiation means 32 may comprise a suitable temperature responsive element such as a thermistor, a gas-filled thermostat or a pressure sensitive element.

A fresh food passage 34 is provided to place the outlet of the motor fan 18 in direct communication with the fresh food compartment 14 for diverting a portion of the refrigerated air from the outlet of the motor fan into the fresh food compartment 1. A control or valve means 36 is inserted in the fresh food passage 34 which functions to selectively open and close the passage in response to a temperature change within the compartment 14 thereby to keep the temperature therein within a predetermined range. Flow control means 36 may comprise a suitable gas-filled thermostatic mechanism or a magnetically operated flow controller such as a valve or air damper. The inlet or upstream side of the evaporator 16 is communicated via a return path 38 with both the freezer and fresh food compartments, l2 and I4.

For the pur ose of automatically controlling the temperature in the freezer compartment 12, a temperature sensing unit 40 is positioned within the compartment and is operatively connected to a control switch 42 for selectively energin'ng and deenergizing the motor fan [8 and compressor 22 in response to predetermined temperature conditions within the freezer compartment.

in order to remove the frost layer that has been formed on the evaporator 16, a radiant heater 44 is positioned in heat transfer relation with the fin-on-tube structure of the evaporator. The heater 44 is electrically connected to the defrosting controller device 46 which simultaneously energizes the defrost heater and deenergizes the motor fan 18 and compressor 16 upon receipt of a defrost initiation signal or output from defrost initiation means 32. A defrost termination means 48 in the form of a suitable thermally responsive element is also provided on the evaporator in heat transfer relation for producing and supplying a defrost termination signal to the defrost controller device 46 upon receipt of which the controller device deenergizes the defrost heater 44 and simultaneously energizes again the compressor 22 and motor fan 18 into another cooling operation.

with the above described refrigeration system, during normal operation motor fan 18 draws air from both freezer and fresh food compartments l2 and 14 through the return path 38 and through the evaporator 16. As the air passes over the evaporator, it is sufficiently cooled down. The cooled refrigerated air flowing from the evaporator is circulated by the motor fan through fluid amplifier 26 into the freezer compartment 12 on one hand and through fresh food passage 34 directly into the fresh food compartment 14 on the other. The fluid amplifier is designed to permit inlet fluid through the inlet port 260 to flow out through the first outlet port 26b dur ing the normal cooling operation of the refrigerator. The refrigerated air cools the spaces and food stuffs in the freezer and fresh food compartments l2 and 14. Thereafter, it is recirculated through return line 38 back to the evaporator to be refrigerated again. in this manner, forced circulation of the refrigerated air through the evaporator and both compartments is continued. As this forced circulation of the refrigerated air goes on, the freezer and fresh food compartments are gradually cooled down to their respective predetermined iower temperature.

When the desired minimum temperature in the fresh food compartment 14 is attained, the flow controller 36 in the fresh food passage 34 operates to shut off the flow of refrigerated air into the fresh food compartment. Upon closure of the air passage substantially all of the refrigerated air is circulated by the motor fan 18 to the freezer compartment 12.

On the other hand, as the temperature within the fresh food compartment [4 rises to a predetermined upper value the temperature responsive flow controller 36 opens the passage 34 thereby permitting the flow of refrigerated air into the fresh food compartment.

The temperature control of the freezer compartment 12 is effected by means of temperature sensing means 40 disposed within the freezer compartment. More specifically, when the temperature within the freezer compartment 12 reaches a predetermined lower value, the temperature sensing unit 40 operates the control switch 42 to open thereby deenergizing both the motor fan 18 and compressor 22.

Thus, the cooling operation of the refrigerator is stopped until such time as the temperature within the freezer compartment rises to a predetermined upper level, when the temperature sensor unit 40 operates the control switch 42 to energize the motor fan and compressor into cooling operation. in this manner, the temperatures within the fresh food compartment l2 and freezer compartment 14 are automatically maintained within the desired ranges.

lt is to be understood that during normal cooling operations of the refrigerator a relatively small proportion of air within the fresh food compartment 14 is drawn through the passage 30 into the fluid amplifier 26 through the second outlet port 260 thereof due to entrainment by the refrigerated air flowing from the inlet port 26a through the first outlet port 26b. Thus, temperature responsive means 32 is normally kept at a temperature within the predetermined temperature range set for the fresh food compartment, for example, in the order of several degrees centigrade.

As the cooling cycle of operation proceeds, moisture laden air from the freezer and fresh food compartments l2 and l4 comes in contact with the plate type fins of the evaporator 16 and substantially all of the moisture in the air condenses to form layers of frost on the evaporator. The frost gradually collects on the evaporator to such extent that the accumulating frost closes or plugs the relatively small spaces between the fins substantially reducing the effective air passage area within the evaporator. As the result, the flow of recirculated air through the evaporator is largely blocked and the air pressure at the inlet side, or upstream, of the motor fan unit 18 decreases in comparison with the air pressure at the outlet side, or downstream thereof. This reduction in the air pressure in turn causes a corresponding reduction in pressure in the control port 264' of the fluid amplifier 26. The fluid amplifier is so designed that when the pressure in the control port 26d decreases to a predetermined lower level the flow of refrigerated air through the amplifier is switched over from the first outlet port 2611 to second outlet port 260. Thus, the refrigerated air of about 20 C. flows through the second outlet port 260 into the air passage 30 and comes in contact with the temperature responsive defrost initiation means 32 Upon contact with the refrigerated air of an abnormally lower temperature, temperature responsive means 32 operates the defrosting controller device 46 to simultaneously energize the radiant heater 44 and deenergize the motor compressor 22 and motor fan unit 18 thereby initiating a defrost operation of the evaporator [6.

During defrost operation, the radiant heater 44 warms up to the evaporator to defrost temperature and the frost layer is removed from the evaporator. The end of the desired defrost operation is sensed by the defrost termination means 48 which operates in response to a predetermined high temperature in the evaporator to deenergize the heater 44 and energize the compressor 22 and motor fan 18 at the same time. Thus, the defrost operation is terminated and another cooling cycle is started once again. A complete defrosting of the evaporator 16 permits a free and uninterrupted passage of recirculated air from the refrigerator compartments l2 and 14 through the evaporator. This substantially reduces the pressure difference between the upstream and downstream sides of the motor fan unit 18 and the air pressure in the control port returns to the normal range so that the refrigerated air flow through the amplifier is diverted from the second outlet 26c and flows out through the first outlet 26b into the freezer compartment 12 as normally expected. The cooling cycle of operation is repeated until the air flow space in the evaporator is again blocked by the accumulated frost to such extent as to cause the switching over of the refrigerated air flow through the amplifier 26 from the first outlet 26!: to the second outlet 26c and into the passage 30, when defrost initiation means again operates to start the defrost operation as explained above.

With this arrangement, the desired defrosting of the evaporator is automatically effected as the frost layer on the evaporator accumulates to a predetermined amount and is automatically discontinued after a complete defrosting of the evaporator.

A typical example of the control circuitry for the defrosting operation is illustrated in FIG. 2 of the drawings, wherein like reference numerals are used to designate like component parts. Motor fan unit 18 and motor compressor 22 are connected in parallel across the power supply lines 50 and 52 through control switch 42 and a selector switch 46a of defrost controlling device 46. The defrost controlling device, which is shown in the form of a magnetically operated switch, further includes a magnetic coil 46b positioned in magnetically operative relation with the selector switch 46a. The magnetic coil 46b is connected in series with a normally open, defrost initiating, temperature responsive bimetal switch 32 and a defrost termination, temperature responsive switching element 48, across the power supply lines 50 and 52. Defrost heater 44 is connected in parallel to the magnetic coil 46b of the defrost controller device.

In the normal cooling operation, the control switch 42 operates to open and close the circuit to fan l8 and compressor 22 in response to the temperature within the freezer compartment as detected by the temperature sensing unit 40, thereby maintaining the temperature in the freezer and fresh food compartments within the predetermined range as described above. As the frost accumulation on the evaporator reaches the predetermined amount, the normally open temperature responsive bimetal switch 32 operates in response to the temperature of the refrigerated air through the passage 30 to close and complete an electric circuit to the defrost heater 44 and magnetic coil 46b and both heater and coil are energized. Upon energization of the magnetic coil 46!: it magnetically operates the switch 460 out of engagement with the contact S to keep the selector switch open. Thus, the circuit to the fan and compressor is open at the same time as the defrost operation is initiated by the heater and kept open while the defrosting continues. At the termination of the defrost operation, which is indicated by the temperature rise in the evaporator, the normally closed temperature responsive defrost termination switch 48 opens the circuit to the defrost heater 44 and magnetic coil 46b thereby deenergizing the heater and coil. Upon deenergization of the magnetic coil, the selector switch moves back into engagement with the switch contact S to close the circuit to the fan 18 and compressor 22. Thus, the defrost operation is automatically tenninated and the cooling operation is again started. As the cooling cycle starts, relative- 1y warm air from the fresh food compartment comes in contact with the defrost initiation bimetal switch 32 while the defrost termination switch 44 is subject to a relatively lower temperature. Under this condition, the defrost initiation switch 32 returns to its normally open position and the the defrost termination switch 48 moves back to its normally closed position making the defrost circuit ready for another defrosting operation if it is called for.

In FIG. 3, there is illustrated diagramatically a combination refrigerator embodying another form of this invention. The refrigerator of this invention is substantially identical in construction with the one described above except that instead of using the mechanical flow controller 36 another monostable fluid amplifier is employed to automatically control the temperature in the fresh food compartment [4. As shown in FIG. 3, wherein like component parts are designated by like reference numerals to those used in F IG. 1, a second monostable fluid amplifier 60 is provided downstream of the motor fan unit 18. The fluid amplifier has a single inlet port 600 for receiving the refrigerated air from the outlet of the motor fan 18, a single control port 60d for controlling the flow of refrigerated air through the amplifier and a pair of outlet ports 60b and 60c. The first and second outlet ports 60!: and 600 communicate through

air passageways

62 and 64 with the fresh food compartment 14 and the freezer compartment 12, respectively. The control port 604 of the amplifier is connected to the passage 62 and includes valve means 66 designed to selectively open through a path which close the control port to the pressure in the passage 62 in response to a temperature change within the fresh food compartment 14.

in operation, refrigerated air is drawn from the evaporator 16 and circulated to the first and second

fluid amplifiers

26 and 60 by the motor fan unit 18. The portion of refrigerated air circulated to the first fluid amplifier 26 usually flows from the inlet port 26a through the first outlet port 26!: and enters the freezer compartment 12 to cool the spaced therein. During cooling operation of the fresh food compartment, the con trol port 60d of the second fluid amplifier 60 is closed by the temperature responsive valve means 66 until such time as the temperature within the fresh food compartment 14 reaches a predetermined lower value. The fluid amplifier is so designed that when the control port 604 is closed substantially all of the refrigerated air entering the fluid amplifier 60 from the inlet port flows through the first outlet 60b into the fresh food compartment l4 thereby to cool down the space within the compartment. When the desired minimum temperature in the fresh food compartment is attained, the temperature responsive valve 66 opens the control port 60d to the pressure in the flow passage 62 to divert or switch over the flow of refrigerated air from the first outlet 6% port to the second outlet port 60c. As the result of this switchover, all or substantially all of the refrigerated air flow from the outlet of motor fan 18 is supplied to the freezer compartment 12 through

flow passages

28 and 64. While on the other hand, when the temperature within the fresh food compartment rises to a predetermined upper level the temperature responsive valve 66 closes the control port 604 and the refrigerated air flowing through the second outlet port 60c is again switched backed to the first control port 60b and flows into the fresh food compartment 14.

When the temperature within the freezer compartment reaches a predetermined lower level, the temperature sensing unit 40 operates the control switch to deenergize the motor fan l8 and the compressor 22 bringing the cooling operation to a temperary standstill. On the other hand, when the temperature within the freezer compartment rises to a predetermined upper level the temperature sensing unit 40 operates to energize the motor fan and compressor. The cooling operation is then started again as described above. The above mentioned fluid amplifier arrangement enables an automatic and effer: tive control of the temperature conditions within the freezer and fresh food compartments.

The defrost mechanism of this second embodiment and its operation being substantially identical with the first embodiment shown in FIGS. 1 and 2, no detailed explanation is given.

in the above illustrated embodiments of the this invention the control port of the fluid amplifier 26 is connected to the refrigerated air passage between the evaporator and the motor fan. in other words, the control port communicates with the circulating refrigerated air passage at a point downstream of the evaporator and upstream of the motor fan. However, the control port may suitably be connected to the circulating air passage at a point downstream of the motor fan in so much as the control port may provide the desired flow controlling action.

From the foregoing description, it will be appreciated that the present invention provides a new defrost arrangement for automatically removing the frost collected on the evaporator of refrigerators whenever the frost thereon reaches the predetermined amount. For the automatic defrost initiation, a fluid amplifier is inserted in the refrigerated air circulating passage. The fluid amplifier supplies the refrigerated air to defrost initiation means in response to the preselected pressure drop in the air circulating passage caused by the blocade of the passage by the frost formed on the evaporator to the predetermined amount. Defrost initiation means functions to initiate the defrost operation in response to the predetermined lower temperature of the supplied refrigerated air. As is apparent from the foregoing discussion, the initiation of the desired defrosting operation of the evaporator by the present defrost arrangement is strictly and solely dependent on or commanded by the amount of frost collected on the evaporator. Phrased differently, the defrosting of the evaporator is started whenever and only when the frost on the evaporator collects to the predetermined amount. Thus, in contrast with the conventional periodic defrost operation whenin the defrosting of the evaporator is periodically effected regardless of the amount of frost accumulated on the evaporator, the defrost arrangement of the present refrigerator carries out more eflicient and economical defrost operation in that it initiates the defrost operation only when it is essentially called for. Moreover, the above mentioned distinctive advantage of the present defrost arrangement is economically accomplished by employing a conventionally known, inexpensive fluid amplifier. The fluid amplifier is especially advantageous in that it is extremely simple, rigid in construction and operates dependably under varied surroundning temperatures. This assures a high reliability in the operation of the defrost arrangement.

While the present invention has been described in connection with details of illustrative embodiments, it is to be understood that this invention is not limited to the particular embodiments disclosed and that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What we claim is:

1. in a refrigerator including first and second compartments, an evaporator for refrigerating air, means for circulating refrigerated air to both of said compartments and means for defrosting said evaporator, the improvement which comprises a fluid amplifier in the air flow path estabiished by said air circulating means; said fluid amplifier including an inlet for refrigerated air, a first outlet communicating with said first compartment, a second outlet communicating with said second compartment and a control port for switching over the flow of refrigerated air normally directed to said first outlet toward said second outlet, said control port being responsive to a predetermined change in the pressure of the circulating refrigerated air, means responsive to the flow of the refrigerated air through said second outlet to said second compartment to initiate the defrosting operation by said defrosting means, and means responsive to a predetermined condition for terminating the defrosting operation.

2. A refrigerator as defined in claim 1, in which said responsive means comprises temperature first named responsive means provided in air flow passage between said second outlet of said fluid amplifier and said second compartment.

3. A refrigerator as defined in claim 2, in which said temperature responsive means comprises semiconductor means, inserted in air flow passage between said second outlet of said fluid amplifier and said second compartment.

4. A refrigerator as defined in claim 1, in which said first named responsive means is subject to the temperature of the air entrained from said second compartment to said fluid amplifier through said second outlet under normal operating condition.

5. A refrigerator as defined in claim I, in which said control port is responsive to a predetermined change in the pressure of the circulating refrigerated air at a point between said evaporator and said air circulating means.

6. A refrigerator as defined in claim 1, in which said evaporator comprises a fin-on-tube evaporator.

7. A refrigerator as defined in claim I, in which said first compartment comprises a freezer compartment and said second compartment comprises a fresh food compartment adapted to be maintained at a temperature higher than that of the freezer compartment.

8. A refrigerator as defined in claim 1, in which a refrigerated air passage is provided between the outlet of said air circulating means and said second compartment, the flow of refrigerated air through the passage being controlled by flow controlling means in response to a predetermined temperature within said second compartment.

9. A refrigerator as defined in claim I wherein the pressure change in the circulated refrigerated air is caused by the formation of a frost layer on said evaporator, said means for terminating the defrosting operation comprising means for sensing the temperature of said evaporator.

10. A refrigerator as defined in claim I wherein said means for initiating the defrosting operation includes means for deenergin'ng said refrigerated air circulating means while operating means for removing accumulated frost from said evaporator, and said means for terminating the defrosting operation includes means for energin'ng said refrigerated air circulating means while disabling said frost removing means.

ll. A refrigerator as defined in claim I0 wherein said frost removing means includes a heater for supplying heat to said eva rator. 4

l A refrigerator as defined in claim l1 wherein the pressure change in the circulated refrigerated air is caused by the formation of a frost layer on said evaporator, said means for terminating the defrosting operation comprising means for sensing the temperature of said evaporator.

13. A refrigerator as defined in claim 12, in which said control port is responsive to a predetermined change in the pressure of the circulating refrigerated air at a point between said evaporator and said air circulating means.

i U i U

Claims

1. In a refrigerator including first and second compartments, an evaporator for refrigerating air, means for circulating refrigerated air to both of said compartments and means for defrosting said evaporator, the improvement which comprises a fluid amplifieR in the air flow path established by said air circulating means; said fluid amplifier including an inlet for refrigerated air, a first outlet communicating with said first compartment, a second outlet communicating with said second compartment and a control port for switching over the flow of refrigerated air normally directed to said first outlet toward said second outlet, said control port being responsive to a predetermined change in the pressure of the circulating refrigerated air, means responsive to the flow of the refrigerated air through said second outlet to said second compartment to initiate the defrosting operation by said defrosting means, and means responsive to a predetermined condition for terminating the defrosting operation.

5. A refrigerator as defined in claim 1, in which said control port is responsive to a predetermined change in the pressure of the circulating refrigerated air at a point between said evaporator and said air circulating means.

7. A refrigerator as defined in claim 1, in which said first compartment comprises a freezer compartment and said second compartment comprises a fresh food compartment adapted to be maintained at a temperature higher than that of the freezer compartment.

9. A refrigerator as defined in claim 1 wherein the pressure change in the circulated refrigerated air is caused by the formation of a frost layer on said evaporator, said means for terminating the defrosting operation comprising means for sensing the temperature of said evaporator.

10. A refrigerator as defined in claim 1 wherein said means for initiating the defrosting operation includes means for deenergizing said refrigerated air circulating means while operating means for removing accumulated frost from said evaporator, and said means for terminating the defrosting operation includes means for energizing said refrigerated air circulating means while disabling said frost removing means.

11. A refrigerator as defined in claim 10 wherein said frost removing means includes a heater for supplying heat to said evaporator.

12. A refrigerator as defined in claim 11 wherein the pressure change in the circulated refrigerated air is caused by the formation of a frost layer on said evaporator, said means for terminating the defrosting operation comprising means for sensing the temperature of said evaporator.