US2085867A - Refrigerating apparatus - Google Patents

Description

July 6,1937.

' E. PICK REFRIGERATING APPARATUS Original Filed Sept. 9, 1933 NORMAL OPERA r/o/v AVERAGE //v CAB/NET TEMPERATURE REJPOMS/VE ELEMENT Patented July 6, i937 REFRIGERATING APPARATUS Eric Pick, New York, N. Y., assignor to Servel,

Inc., New York, N. Y., a corporation of Dela- Ware Application September 9, 1933, Serial-No. 688,733 Renewed'May 21, 1937 Claims.

This invention relates to improvements in refrigerating apparatus and method of operation thereof; and it comprises a temperature responsive element so placed in relation to a cooler of a refrigerating apparatus that said temperature responsive element is subjected to a drop in temperature upon formation of frost on the cooler, thereby being adapted to serve either as a guide in manually controlled defrosting of the cooler, or as automatic control means in automatically controlled defrosting; all as more fully hereinafter set forth and as claimed. 7

Refrigerating apparatus usually has a. cooler maintained at a temperature below the freezing temperature of water. Atmospheric air frequently carries a proportion of water vapor corresponding to a dew point considerably higher than the temperature of the cooler. When such air comes in contact with the cooler condensation takes place, and the moisture condensed on the cooler freezes. When the cooler is installed in a closed cabinet every opening of the cabinet door admits outside air while some of the chilled air escapes from the cabinet. Thus, additional water vapor is introduced into the cabinet and eventually deposited on the cooler in the form of frost.

A further source of moisture is in the cabinet itself in foodstuffs or other moist substances placed therein for safekeeping. The cooler is customarily placed near the top of the cabinet. Air near the cooler is chilled whereby its density is increased causing it to fall to the bottom of the cabinet. Upon its travel away from the cooler the air increases in temperature and again picks up moisture when it comes in contact with moist substances. The warmer and moisture laden air rises back to the top of the cabinet due to its decreased density, and part of its moisture content is condensed and deposited on the cooler. Due to this air circulation within a cabinet containing moist substances as well as due to the occasional opening of the cabinet door the thickness of the coating of frost or ice on the cooler gradually increases.

It is customary to defrost the cooler periodically, i e. to interrupt the flow of heat from the cooler either by interrupting the operation of the device abstracting heat from the refrigerating fluid or by interrupting the circulation of the refrigerating fluid. Such interruption of the refrigerating effect causes a gradual rise in temperature of the cooler and when its temperature exceeds the freezing temperature of water the frost melts and drips off as water. When all frost or ice has been removed from thecooler in this manner the refrigerating effect is re-established whereby the apparatus is placed in normaloperation once more.

Users find the task of defrosting a cumbersome one, and are apt to postpone it until an excessive coating of frost has formed. The greater the thickness of the frost layer the greater is the resistance to the flow of heat towards the cooler. Thus, an excessive coating of frost on the cooler decreases the efficiency of the apparatus and increases the energy consumption for 'a given refrigerating effect.

frost coating, and since, during a substantial portion of the defrosting period the temperature within the cabinet is higher than that required to avoid rapid deterioration of food or the like.

Furthermore, a longer period of defrosting is required to remove a heavier placed in the cabinet, a long defrosting period is l defrosting period unnecessarily, thereby carry- 5 ing an undesirably high temperature for an excessive period of time which causes an accelerated deterioration of food within the cabinet.

It is an object of this invention to provide novel control means for the initiation and termination of the defrosting period.

Another object of this invention is the provision of novel control means which permit initiation and termination of defrosting at the most desirable respective times.,

A further object of this invention is a novel method of operating a refrigerating apparatus by carrying out defrosting under precise control, thereby making for greater efficiency, economy and convenience.

Still other objects of this invention will become apparent from the following disclosure which shows the manner in which I attain the aforementioned objects.

I have found that atemperature responsive element placed in close proximity to, but spaced from, the cooler of a refrigerating apparatus constitutes excellent means for controlling defrosting. Such element is subjected to a. gradual drop in temperature as the frost coating on the cooler increases in. thickness. As will be shown on the basis of observed conditions, it is a. simple matter to establish the relationship between temperature of the element and thickness of the frost frost corresponds to a. certain high temperature at which the defrosting is terminated.

The temperature responsive element may be operatively connected to a mechanism for automatically controlling defrosting. This may beaccomplished by the automatic opening and closing of a switch which controls the flow of energy or the temperature responsive element may actumined low and high temperatures, respectively;

ate a valve controlling the circulation of the refrigerating fluid. Frequently, thermostatic means are used for controlling the temperature f a refrigerating apparatus during normal refrigerating operation. The aforementioned temperature responsive element does not take the place of such thermostatic means, but may be used in addition thereto, and for the sole purpose of controlling defrosting.

The temperature responsive element may also be operatively connected to indicating or alarm means such as, indicator and dial, or signal lights or bells, remotely located if desired. These means furnish to the user the necessary information to guide him in the initiating and terminating of the defrosting period by interrupting and reestablishing, respectively, the refrigerating effect.

In the accompanying drawing, wherein similar numerals refer to similar parts throughout the several views.

Figure 1 is a diagrammatic view of my invention as applied to an absorption system;

Figure 2 is a similar view of my invention as applied to a compression system; I

Figure 3 is a view similar to that of Figure 1 as applied to a unit of a central cooling system;

Figure 4 is a diagrammatic view of my invention showing a temperature: responsive element connected to indicating and signal means;

Figure 5 is a detail sectional elevation on an enlarged scale of one form of the temperature responsive element, taken in the plane of Figure 1;

Figure 6 is a detail sectional elevation on an enlarged scale of another form of temperature responsive element, taken in the plane of Figure 3; and

Figure 7 is a diagram showing variations in temperature in the course of an operating cycle comprising a period of normal operation and a period of defrosting.

Referring now to Figure 1, a cooler l0 within a cabinet II is part of a refrigerating system including a generator l2, a condenser I3 and an absorber Hi, all interconnected by pipe connections l5. This type of refrigerating apparatus is more fully described in the patent to von Platen et al. No. 1,609,334, dated December '7, 1926. The generator I2 is heated by a burner l6 which is supplied with gasthrough a pipe I] controlled by a manually operable valve l8. A pipe l9 with a valve 20 forms a by-pass around valve I8. A tray 2| underneath the cooler I 0 is connected by means of a conduit 22 to an open tank 23 which is located adjacent to burner I6. The tank 23 may be in the shape of an annular trough surrounding the burner I6.

A temperature responsive element in the cabinet H is connected by means of a conduit 8| with a valve 82 in gas supply pipe l1 and this arrangement controls the supply of gas -in such manner as to maintain normally the temperature in cabinet between predetermined limits for instance 42 to 47 F., as is well known in the- 2,085,867 -to the refrigerating apparatus, at the predetersulating material, is placed around the container 25. The guard 28 is open at the top as at 29, and terminates at 30 a short distance from the cooler II). The container 25 is filled with a fluid 3| whose thermal expansion and contraction are communicated through a pipe 32 to a rapid action valve operating mechanism 33 (see Figure 1) which is adapted to quickly close valve 20 at a predetermined low temperature of the fluid 3|, and again to quickly open valve 20 at a predeter- 'mined high temperature of the fluid 3|.

The valve -I8 is initially so adjusted that, with valve 20 closed, gas is supplied to the burner H5 at a rate of flow sufllcient to maintain combustion but not high enough to produce any substantial refrigerating effect in the cooler ll).

When the apparatus illustrated in Figure 1 is first placed in operation the cooler I0 is free from any frost coating. At this stage the air'circulation within the cabinet previously referred to causes warm air to enter the top opening 29 of the guard 28 whereupon it becomes chilled due to its proximity to the cooler III; the cooled air then flows downwardly through the space between the edge 30 and the cooler l0. The space within the guard 28 is filled with comparatively warm air and there is a comparatively high temperature gradient available for forcing heat through the insulation 21 to the container 25 while the down current of partly chilled air through the space between the face 25 and the cooler l0 obstructs the free flow of heat from the face 26 to the cooler I0. As a result, the fluid 3| is maintained at a certain temperature somewhere between the temperature of the cooler Ill and the average temperature within the cabinet ll.

As frost is gradually deposited on -the cooler I0 the air space between the face 26 and the frost on cooler I0 becomes smaller. The flow of air within this space is thereby reduced and this air is chilled more thoroughly. This tends to'promote the flow of heat from the face 26 towards the cooler I 0, so that the temperature of the fluid 3| is gradually lowered as the frost coating increases in thickness. Finally the spaces between the face 26 and the cooler III as well as between the edge 30 and the cooler l0 become filled with frost. Thereupon the air within the guard 28 is trapped and lowered in temperature which reduces the flow of heat from the air through insulation 21 to the container 25. The frost in the space between the face 26 and the cooler I0 on the other hand promotes the flow of heat from the face 26 to the cooler l0, and as a result there is a substantial drop in temperature of the fluid 3| which thereby is caused to contract in volume or reduce in pressure, respectively.

The valve operating mechanism 33 is so adjusted that it is actuated by the temperature responsive element 24, when the last described condition prevails, to close the valve 20, thereby interrupting the refrigerating effect. The cooler l0 then warms up and the frost on it melts. The

resulting water drips into the tray 2| whence it flows by gravity through the conduit 22 into the tank 23. During defrosting the temperature of element 24 rises, the melting of all frost corresponding to a certain high temperature at which it again actuates the mechanism 33 to open the valve 20, thereby increasing the flow of gas to .the burner l6 and returning the apparatus to normal operation. This cycle of operations repeats itself in intervals the duration of which depends on how fast frost is collected on the cooler As soon as the normal refrigerating operation is reestablished some of the heat produced by the burner I6 heats the water in the tank 23 causing it to evaporate whereby it is disposed of in a most convenient manner. The heating of tank 23 may be dispensed with if its area is large enough and if provision for the renewal of the air above it is made so that the water in it may evaporate between successive defrosting opera tions.

In Figure 2, a refrigerant such as S02 is circulated by a compressor 40, via pipe connections l5 through a condenser 3, a pressure reducing valve 4|, the cooler I0 and back to the compressor 40 which is driven by an electric motor 42. Underneath the cooler lll'is a tray 2| with an overflow ture in cabinet normally between predetermined limits.

In normal operation of the apparatus illustrated in Figure 2, frost collecting on the cooler rupt the supply of current to the motor 42.

perature indicator 60 having a pointer 6| Ill causes a gradual drop in temperature of element 24 which, at a predetermined low temperature, causes the switch mechanism 43 to inter- I'hereupon the cooler 0 warms up, and the frost melts and drips as water into the tray 2| whence it is discharged vto'waste through connection 22. When all frost is melted the element 24 reaches a predetermined high temperature at which it actuates the mechanism 43 to re-establish the supply of electric current to the motor 42, thereby returning the apparatus to normal operation.

In Figure 3 a cooling fluid of constant temperature is circulated through the cooler l0 and pipe connections l5. by a remotely located refrigerating machine (not shown) which may be of any suitable type or construction. The circulation of the cooling fluid is controlled by a valve 50 operable by a solenoid 5| which is supplied with electricity through the conductors 52'under' control of a snap action switch mechanism 43 governed by the temperature responsive element 24.

In operation, defrosting is initiated by the element 24 actuating, at a low temperature, the switch mechanism 43 to establish a circuit through the solencid.5l causing it to close valve 56. the opening of valve 50 whenthe element 24 actuates, at a high temperature, the switch mechanism 43 again to de-energize the solenoid 5|.

In Figure 4 the temperature responsive element 24 has an operating connection 32 with a tem- Expansion and contraction of the fluid in element 24, for instance mercury, through conduit 32 with a Bourdon tube (not shown) contained in the casing of. indicator 60 and communicating its motion to pointer 6|. Since under given conditions a definite relationship exists between the temperature of element 24 and the thickness of frost coating on the cooler In the dial of indicator 60 may he graduated in Defrosting is automatically terminated by.

is communicated terms of temperature or thickness of frost coating, or both. High and low contacts 62 and 63 are connected by conductors 64 and 65 to signal lights 66 and 67, respectively, and thence to a conductor 68. The pointer 6| is connected to a conductor 69. The conductors 68 and 69 are connected to a source of electrical energy (not shown). The circulation of cooling fluid through the cooler II) is controlled by the valve 50.

The need for initiation of defrosting is indicated by signal light 61 when contact is established between pointer 6| and contact 63. The need for termination of defrosting is indicated by signal light 66 when a circuit is completed by the pointer 6| and contact 62. The signal lights may be remotely located and furnish convenient guidance for manual control. Defrosting is initiated by closing valve 50, and terminated by again opening it. If desired, a recording instrument may be employed in place of indicator 60 to furnish a permanent record of the operation of the refrigerating apparatus.

In order to eliminate the need for highly sensitive control means adjusted with great accuracy, as great as possible a drop in temperature of the temperature responsive element 24 is desirable from the condition when there is no frost on the cooler to the condition when defrosting is in order. Ifthe temperature responsive element is placed at a great distance from the cooler it will assume substantially the temperature within the cabinet, usually 40 to 50 R, which temperature has a tendency to increase as a frost coating forms on the cooler. On the other hand, if the element is placed so that it touches the cooler it will assume a-temperature close to that of the cooler which is often substantially constant during normal operation. Neither of thesetwo locatached to the container 25 and the guard 28.

The hub portion ll of the arm 10 is slidable on the post 12 which is screwed at 13 into the cooler l6. away from the cooler l0, and an adjusting nut 15 permits to force the arm 10 towards the cooler l0 against the action of spring 14. By turning the adjusting nut-l5 the distance between the face 26 of the container 25 as well as the edge 30 of the guard 28 on the one hand, and the wall of cooler ill on the other hand, may be adjusted as" desired. Separate adjustments similar in principle to that shown in Figure 6 may be provided for both the container 25 and the guard 23 so that either may be adjusted independently of the other.

Figure 7 shows typical variations in temperature in the course of an operating cycle when using my control. Upon placing the refrigerating apparatus in operation (point A) the temperature of the temperature responsive element drops rapidly to about 32 F. (point B). Thereafter there is a gradual drop in temperature,

slow at first, but somewhat faster whenthe frost coating on thec'ooler has increased in thickness. When the temperature .has dropped to about 26 F. (point C) defrosting-is initiated whereupon a .rapid rise in temperature takes place. At about 45 F. (point D) all frost is melted but a. margin of safety is allowed and the defrosting A spring 14 tends to push the arm 10' 4 period is terminated at 48" F. (point A) whereupon the cycle is repeated.

For the purpose. of automatic control of coordinated alternating normal operation and defrosting the temperature responsive element (80) controlling normal operation is adjusted to interrupt the supply of energy at 42 F. and to ture responsive element and in the adjustment of the temperature range.

It is to be noted that in interest of clarity of presentation the scale of abscissas has been somewhat distorted in Figure 7, the duration of the period of normal operation having been in fact' considerably longer with reference to the illustrated duration of the defrosting period.

Whenever the ,cabinet door is opened, and especially when warm substances are placed in the cabinet, the temperature rises abruptly a few degrees, as illustrated at E in Figure 7, and then again drops substantially to the value existing before. This does not interfere with my system of control.

The results shown in Figure 7 have been obtained with a temperature responsive element arranged as shown in Figure 6, with a distance between the element and the cooler of about one eighth inch. A shortening of this distance, other conditions being equal, causes a lowering of the temperature of the element and vice versa, but the character of the temperature curve remains substantially the same so long as the distance is not made too long or'too short.

Some refrigerating apparatus is equipped with thermostatic controls tending to mair tain a con- ,stant air temperature within the cabinet, for instance, by lowering the temperature of the cooler as the frost coating increases thereby compensating for-the increased resistance to the flow of heat. In such cases the temperature responsive element may be so placed as to measure the coating of frost. Thus, the average thickness of frost is smaller than with haphazard manual control, and improved efficiency of the apparatus results. initiation of defrosting is relatively thin, requir ing a comparatively short time to melt it, and since, furthermore, defrosting is terminated substantially at the time when all frost has melted,

the refrigerating effect is interrupted for a minimum length of time only. This results in improved operation and better food preservation.

Since the coating of frost at the convenience is evident when it is considered that most refrigerating apparatus, once allowed to warm up appreciably by unnecessarily prolonged defrosting, requires about half a day after having been placed in operation again, to produce a supply of ice cubes.

While I have shown several forms of my invention," it will be understood that various changes may be made therein, particularly in the type and arrangement of temperature responsive element. Other modifications in the details of construction and arrangement of parts will readily occur to those skilled in the art. Reference is, therefore, made to the appended claims for a definition of the limits of my invention.

What I claim is:

1. In a refrigerating apparatus having a cooler subjected to formation of frost thereon, a duct terminating a short distance from the cooler, and 2 temperature responsive element in-said duct, differences in temperature of air near the cooler being adapted to induce flow of air from the duct toward the cooler, and frost formed on the cooler being adapted to act as a valve and interrupt said air flow.

2. A refrigerating apparatus comprising a cooler, circulation means to induce a flow of heat from the cooler, means to control the rate of flow of heat from the cooler, a temperature responsive element located close to but spaced from the cooler, the said temperature responsive element being so arranged as to permit a flow of heat from the element towards the cooler, heat insulating material arranged to retard the flow of heat towards the temperatm'e responsive element, and means operatively connected to the temperature responsive element for actuating said control means.

3. A refrigerating apparatus comprising a cooler, circulation means to induce a flow of heat from the cooler, means to control the rate of flow of heat from the cooler, a temperature responsive element located close to but spaced from the cooler, a guard surrounding the temperature responsive element, said guard terminating a short distance from the cooler. and means operatively connected to the temperature responsive element for actuating said control means.

4. In a refrigerating apparatus comprising a heating element and a cooler subjected to the formation of frost thereon, a tray underneath the cooler and adapted to receive water resulting from the melting of frost on the cooler, a tank located at an elevation lower than the elevation of said tray, said tank being exposed to heat generated by said heating element, and a conduit connecting said tray with said tank.

5. In a refrigerating apparatus of the absorption type comprising a generator heated by a burner, a cold storage space and a cooler located within said space, collecting means within said cold storage space and adapted. to receive water dripping from the cooler, and a conduit having its one end in communication with said collecting means and its other end terminating outside of said cold storage space at a place of disposal for the collected water, said place of disposal being exposed to hot gases discharged by said burner.

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