US2494512A - Milk cooler having automatic control means - Google Patents

Description

Jan, l0, 1950 c. H. KAFER ET AL 2,494,512

MILK COOLER HAVING AUTOMATIC CONTROL MEANS Filed June l1, 1946 5 Sheets-Sheet l Jan. 10, 1950 c. H. KAFER ETAL. 2,494,52

MILK COOLER HAVING AUTOMATIC` CONTROL MEANS Filed June 11, 1946 5 Sheets-SheetZ @MQE Jan. 10, 1950 2,494,512

C. H. KAFER ET AL MILK COOLER HAVING AUTOMATIC CONTROL MEANS Filed June 11, 1946 5 Sheets-Sheet 5 Jan. l0, 1950 c, H. KAFER ETAL 2,494,512

MILK cooLER HAVING AU'roNATTc CONTROL MEANS Filed June 1l, 1946 5 Sheets-Sheet 4 YTIL/nbas 47g' SIEHE #Ka ER 7175-7 .Hau/'asd -ZL/hzle Jam w, 1950 c. H. KAFER ET AL 2,494,512

MILK COOLER HAVING AUTOMATIC CONTROL MEANS TEMH DEEE' .4II fans Fernel/ect' 1 2 5 4 5 6 '7 9 lo /2/3/4/5 /6 /7 //s 2oz/272324 ZIME HOURS fig-5 finan Patented Jan. 10, 1950 MILK COOLER HAVING AUTOMATIC CONTROL MEANS Clare H. Kater and Howard D. White, Adrian,

Mich., Mich.

assignors to Revco,

Inc., Deerfield,

Application June 1l, 1946, Serial No. 675,943

12 Claims. (Cl. 62-7) i This invention relates to refrigerating apparatus of the type wherein cold water is employed as the direct refrigerating medium, which water in turn is chilled by means of volatile refrigerant owing through an expansion coil submerged in the water. The invention may be embodied in the form of a tank of such size as to receive a number of cans of freshly procured milk, which is to be cooled to a low temperature before shipment to the creamery or other processing point, although the invention is of course applicable to other cooling problems.

One object of the invention is to provide an improved refrigerating apparatus, including a tank or receptacle for the articles to be cooled, wherein provision is made for the forced circulation of the cooling liquid when the apparatus is subjected to its heaviest load.

Another object of the invention is generally to provide improvements in coolers of this nature, whereby the same will be more durable and less susceptible to service diiiiculties, and may be manufactured economically.

Another object of the invention is to provide for the regulation of the temperature of the cooling medium within such close limits that there is maintained in the tank a bank of ice in contact with the circulated water, and wherein the formation of excessive amounts of ice, or the freezing up of the bath, isprevented.

Other objects of the invention, and the best means now known to attain the same, will become apparent as this description proceeds, and the novel subject matter will be pointed out in the subjoined claims.

It may be noted prefatorily that it has heretofore been proposed to provide a tank containing water, to cool the water in the tank by means of the well-known compressor-condenser-expander type of electric refrigeration machine, and to employ the cold water bath as the medium for chilling freshly procured milk or other substances. In any such apparatus, the refrigerant volatilizing in the expansion coil cools the water to below its normal freezing point of 32 Fahrenheit, with the result that the coil gradually becomes coated with ice. The process of converting the water into ice proceeds as the refrigeration machine is operated, and accordingly, unless the water is supplied with heat from some extraneous source, the whole bath tends to freeze. Stated otherwise, the condition in the tank is one of unstable equilibrium. tending to convert the two-component system of water and ice into a single phase system of ice when no extraneous perature of anywhere between 32 and 34.

heat load is imposed, and tending to convert the system into the single component system of water when the tank is loaded with cans of warm milk.

In order to function satisfactorily for the cooling of fresh milk, it is also necessary that the refrigerating machine have sulcient capacity, as compared to the amount of milk to be treated, to cool the Warm milk to a low temperature in the shortest interval of time. It is generally assumed that fresh milk has a temperature of about Fahr., and that to inhibit bacteriological growth to a satisfactory extent the milk should be cooled to a temperature below 50 Fahr. within an hour. A refrigerating machine large enough to absorb this heat load obviously has such capacity as to freeze increasing amounts of Water when the apparatus is not being utilized, thus leading to excessive ice formation.

In many applications of refrigerating machines, it has been found possible to control the refrigerating effect within satisfactory limits by employing an automatically operative valve controlling the admission of refrigerant to the expansion coil, and a pressure or temperature responsive means to govern the operation of a switch for the electric motor of the compressor. The systems heretofore proposed have not, however, been found adequate for the regulation of apparatus of the type herein contemplated. As previously indicated, the rapid reduction of temperature of the milk dictates that the cooling water should be as close as possible to its freezing point of 32, yet at that temperature it has been heretofore practically impossible to prevent the conversion of excess amounts of water into ice, or to maintain a reasonable equilibrium in the relative amounts of ice and water.

Certain uncontrollable conditions may now be stated which augment the diii'culties inherent in the problem. There is first the wide variation in atmospheric temperature, which acts to change the amount of heat leaking into the apparatus, and therefore the amount of work required from the machine. There is also the matter of changes in barometric pressure, which aect the calibration of pressure-responsive control elements. Normal changes in atmospheric pressure are suicient to vary the settings of such instruments as much as two degrees, thus a control set to maintain a bath temperature of 33 may operate to establish a bath tem- This is sumcient to destroy the approximate state of equilibrium desired. Again, the control instruments themselves cannot be made economically with a closer calibration tolerance than plus or minus one degree, or with a differential of less than four to live degrees. It will therefore be understood that, using the customary and available type of equipment in the usual way, the uncontrollable influences tend to preclude the regulation of the equilibrium of the system, icewater, in such manner as to prevent that system from transforming itself to solid ice, on the one hand, or water at undesirably high temperature on the other.

According to the present invention, and among other things, regulation is nevertheless eil'ected, and equilibrium is maintained within close and satisfactory limits, by utilizing the inherent property of water sometimes referred to as its anomalous or negative coeicient of thermal expansion. In common with most substances, warm water expands when heated, and contracts as It is Fahr., at which temperature Water has its maximum density of 1.000 grams per cubic centimeter.

At 32 Fahr., or the normal freezing temperature, the density is sufiiciently less that the colder water will be found at the top, and conversely the warmer water will be at the bottom of the system. This temperature differential of some six or seven degrees between the freezing point and the maximum density point is of the same order of magnitude as the uncontrollable variations in the instruments. We have discovered that we can utilize the temperature variation and its concomitant density change in regulating the system, ice-water, so as to maintain it in a state of practical equilibrium, independent of the uncontrollable factors just noted.

The invention will be more fully understood from the following detailed description of a typical embodiment, illustrated in the accompanying drawings, wherein:

Fig. 1 is a perspective, with portions broken away, of a cabinet adapted to cool cans of milk or other articles;

Fig. 2 is a top plan view showing milk cans positioned in the cooler;

Fig. 3 is an enlarged transverse section through the cabinetlooking toward the ends of the expansion coil, and also showing details of the guard plates;

Fig. 4 is an enlarged `fragmentary section along the back Wall of the cabinet, showing the thermal control bulb connected to the expansion coil;

Fig. 5 is a detail, on an enlarged scale, along the line 5-5 of Fig. 4, and particularly showing how the thermal control element is spaced from the coil, and the relative amounts of ice formed thereon;

Fig. 6 is a section through the circulator pump and casing;

Fig. 7 is a detail showing the means for maintaining the Water level in the bath;

. Fig. 8 is a diagram illustrating a typical performance curve of the refrigerating machine; and

Fig. 9 is a diagram illustrating a typical day's operation in the cooling of milk.

Referring first to Figs. l and 2, there is i1- lustrated a cabinet having external upright side walls Il, top cover sections I2 and I3 respectively positioned at the rear and one end, and a hinged lid I li provided with lifting handles I5 and a supporting rod I6. The cover section i 3 is removably positioned over a machinery compartment, divided from the space beneath the lid I4 by an internal wall I1 (see Fig. 4) wherei there is located the refrigeration compressor ani condenser (not. shown). To provide for air cir culation over the machinery, the front wall o the cabinet adjacent the machinery compari ment may be provided with a grilled opening I I and the detachable cover I3 may also be pro vided with a grilled opening I9. Inasmuch a any standard type of compressor and condense may be employed, it is deemed unnecessary t illustrate or further describe these elements.

The space within the cabinet beneath the lil I4 and cover section l2 may be denominated th cooling compartment. It is defined by interna walls Ila and 2l, respectively spaced from th wall Il and the front, back, and opposite em wall II, to provide for insulating material 22 The bottom of the cooling compartment, the cover section I2, and the lid I,may also be of doubll wall and insulation construction, so as to mint mize heat losses. Sheet metal is preferred fol the wall structure, although obviously other ma terials of construction may be employed if desired. The cooling space may well be of sucl size as to receive four or six standard size mill cans 23, such as are employed on a dairy farm although obviously the cabinet may be made o: any size desired.

Referring further to Figs. 3 and 4, the space: walls II and Ila are provided with a bushing ZI through which yextends a refrigerant supply tube 25, extending to an automatic pressure responsivf valve 26 which may be of any desired make. Inasmuch as such valves are well known, it will bi unnecessary to illustrate the same more fully, o1 to describe their mode of operation beyond recalling that, as the refrigerant pressure build: up in the expansion coil, the valve is closec` against atmospheric and spring pressure whici normally tends to open the valve. Refrigerani iiuid passing the valve enters an expansion coi consisting of a vertical section 21 which is turned at right angles to form a coil composed of successive descending loops 28, 28a, 2817, 28o, etc. arranged in helical fashion adjacent the internal side walls I 1a and 2|, to a region close to the bottom of the compartment. The final turn ol tubing, herein denoted by the reference numeral 28o, is then bent to provide a riser 29 leading tc a high point in the compartment, and which merges into a final loop 3i encircling the walls and nally leading through the bushing 24 tc the compressor.

As shown in Figs. l, 4, and 5, the several turns of tubing 28-28c are supported within the cooling compartment by uprights 32, spaced several inches from the walls 2i, and pipe hangers 3l connected to the supports and encircling the tubing. The lowermost length -of tubing 28o, adjacent the riser 29, is also provided with a clamp 35 having a tube engaging portion 36 merging into two straight portions 3l which in turn are formed into a bulb engaging section 38 for the bulb 39 of a conventional type of thermostatic motor control element. The control element itself is located in the machinery compartment, and therefore is not illustrated. However, it will be understood by those skilled in the art that it is of the type wherein changes in pressure of refrigerant contained in the bulb 39 are transmitted through a conduit 4I to cause the opening and closing of a snap switch connected in the circuit for the compressor motor. When the pressure in the bulb 39 increases to an approximately predetermined value, the switch is closed to start the motor. and thereby exhaust refrigerant from the expansion coil. When a sumcient degree of evacuation has been attained, and the bulb temperature drops, the switch opens, thereby shutting oi the motor.

Usually, the pressure of the refrigerant in a control bulb or power element, such as the bulb 39 corresponds closely to the pressure (and therefore temperature) of the refrigerant in the expansion coil. In the present invention, some significant differences obtain, and these will be discussed hereinafter. It will here simply be noted that the straight sections 3l space the bulb 39 from the coil, about three-eighths of an inch for the unit herein illustrated.

The helical turns of the expansion coil are located in the lower half of the cooling compartment, which is adapted to contain suicient water to submerge the uppermost loop 28. Guard rails i3 of channel shaped sections are secured to the rear wall and the back portions of the end walls 2l, to overlie the coil and thereby protect it from damage when the milk cans are inserted or removed. The front wall, over which access is customarily had, is provided with an inclined guard plate dd which not only protects the tubing but also serves as a skid for the milk cans. Similar inclined skid or bang plates 45 are framed at the forward portions of the end walls, for the same purpose.

Inasmuch as the insertion and removal of the cans will cause a change in the level of the water, an overow pipe 41 (Figs. 1 and '1) is positioned in the cooling compartment, rising to such height as may be desired, but terminating below the expansion coil loop 3l, which serves as a refrigerant drying coil section, wherein any residual liquid refrigerant will be vaporized. The pipe di is quickly detachable, so that it may be removed readily when the cabinet is drained and cleaned. To this end, an internally threaded pipe elbow d8 is embedded in the insulation at the bottom of the cabinet, where it is held in position by a depending ange portion formed on the bottom internal wall or liner 49. The outwardly ex= tending portion of the elbow receives a nipple El passing through the side wall of the cabinet, where it receives a supporting washer 50 connected tothe outer wall Il. The upwardly extending portion of the elbow d@ receives a iianged reducer 52 which, when tightened, compresses a rubber gasket 53 against the liner t9, thereby making a -water tight joint. The central bore of the reducer is provided with a circumferential groove 5d in which is positioned a rubber ring 55, of such size as to engage the end of the pipe il snugly when the pipe is thrust into the bore. A tight joint is accordingly provided around the pipe 41, which nevertheless can be quickly removed by an upward tug, thereby avoiding the necessity of applying a wrench.

The water contained in the cooling compartment is circulated during milk cooling periods by means of a pump located at the rear central portion, as shown in Fig. 1, and constructed as best shown in Fig. 6. The cover section l2 is provided with an opening through which extends a cylindrical cup member 6|, having a rim 62 for supporting the cup on the cover, and an open bottoni 63. The bottom in turn supports an annular soft rubber gasket 64, from which is suspended a tube 65 by means of an annular ange 66. Rubber footings 61 are connected in spaced relation around the periphery of the ange 63 by bolts 68, and from them inwardly extend brackets 69 to support an electric motor 7l. A rubber diaphragm l0 is also extended over the ange 66 and is secured by the bolts, in order to prevent moisture from the cabinet reaching the motor.

The opening in the cover section l2 is covered by a perforated cap 'i2 formed with depending lugs 'i3 and an annular ange 'I4 Vwhich respectively f rictionally engage the internal wall of the cup 6| and the housing of the motor li. The cap is perfectly curved, as shown, to preclude any tendency on the part of the user to place some object on it. When the motor is running. an induced current of air iiows through the perforations between the lugs 73 and ange M, around the motor, and then outwardly, thereby removing the heat generated by operation. It will be observed that the cap l2 may be readily removed and that the entire unit may then be withdrawn for inspection or cleaning, inasmuch as the motor Il and tube S5 are interconnected through the footings 67.

The shaft 'i5 of the motor il is connected, lthrough a iiexible coupling i6, to an impeller shaft 'il extending downwardly in the tube 65, where there is provided a radial bearing it mounted on a spider 1d. An impeller 8l, herein shown as of the screw propeller type,is secured to the shaft 'il above the bearing. The lower end of the tube 65 is open, and in service it is intended to be spaced from the bottom liner t9 a slight distance, to provide for admission of water from the lower part of the cooling compartment. The tube 65 is also provided with a discharge opening 82, located at about the level of the upper coil loop 2li, and so positioned that the discharged water is expelled along the length of the coil. A dee'ctor d3, mounted 'm the tube above the discharge opening, serves to direct the water in its intended path, and an opening M above the deiiector provides access to the coupling 56.

The motor may be connected to operate in any desired manner, but it is preferred to include in its circuit an electric timer, set to run for a period of say one hour, after which the circuit is auto matically opened and forced circulation of the water therefore discontinued.

From the foregoing description, it Will be seen that thereis provided a novel cooling cabinet or tank adapted to receive a'body of liquid which may be circulated around the articles placed in the cabinet. The apparatus is compact, selfcontained, easily cleaned, and the working parts are protected against injury. Such a cabinet may be utilized for many cooling problems, and

among them, as heretofore noted, is the cooling of fresh milk.

A typical and common practice on the farm is to take the evening milk to the cooler, place the cans in the water bath,Y and start the pump motor so as to circulate the water over the evapo. rator coils and around the cans. As previously noted, the milk temperature should be reduced to below 50 within an hour after this operation has been instituted. The cans may then stand in the bath until the morning's milking has been completed, the new batch of milk is then similarly cooled, and the entire days production may then be set out for shipment to the creamery. The following explanatory description'of operation will proceed on the assumption that such practice is to be followed, although of course it will be apparent that other procedures may be used.

According to one practice of the present invention, the interval between milk cooling periods is utilized to convert some of the water in the bath into ice, which form on and adheres to the submerged expansion coil. During these intervals, the refrigeration machine operates in the usual fashion. That is to say, the expansion valve admits compressed refrigerant to the coil, the refrigerant expands in the coil and builds up pressure, this pressure closes the valve automatically and the refrigerant expands still further as it absorbs heat. A pressure-temperature condition is then reached, reflected by the bulb for the motor control switch, which causes the switch to close and start the compressor. The expanded refrigerant is thus withdrawn for recompression, the expansion valve opens and admits more refrigerant, the coil becomes colder and the temperature drop is ultimately refiected by contraction of the fluid in the thermostatic control, causing the motor switch to open. The cycle then repeats itself.

During this interval, the ice tends to form in increasing amounts, and situations have been experienced with prior coolers when so much ice formed that it has been impossible to place the cans in the cooling compartment. On the other hand, if no ice is formed, the cooling water does not reach its optimum temperature to cool the milk rapidly when the cans are inserted and the pump is operated. What is really desired is the formation of a quantity of ice which can be mostly melted by the circulating water during the actual cooling period, and that quantity of ice which is suicient to chill the circulated water to very close to its freezing point of 32. Accordingly, provision is made, by this invention, to regulate the amount of ice, and to maintain it at a quantity which is neither excessive nor insulcient.

Referring again to Figs. 1, 4, and 5, it will be noted that the thermostatic bulbi 39 for the motor control switch is located close to the bottom of the cabinet, or in that region where the density of the water in contact with the ice on the coils approaches a maximum. This may be taken as corresponding to a temperature of about 38 or 39 Fahr. It has also been noted that the bulb is not in direct contact with the coil, although a good thermal path between the coil and bulb is provided by the metallic clamping member 35. A second thermal path also exists-namely, between the water itself and the bulb. It will also be seen that the bulb is located near the discharge end of the submerged portion of the expansion coil, but nevertheless at a position in which saturated vapor is present, the long coil section 3| being the region-.wherein the refrigerant may become superheated.

Let it next be assumed that the expansion valve and the motor switch control are so set as to admit refrigerant to the coil in such amount, and under such pressure, as to establish a coil surface temperature of say Fahr. Ice accordingly will be formed around the coils, and the formation will be progressive as long as this coil temperature is below 32. However, since the densest water is at the bottom of the compartment, and as this water is also the warmest, the formation of ice around the bulb 39 will proceed more slowly. This is because the warm water tends to melt the ice as it is formed, the resulting cooling causes such water to rise where its freezing is more readily effected, and the thermosyphonic or self-induced circulation promptly replaces such chilled water with more dense and relatively warm liquid.

. irreducible manufacturing tolerances.

Eventually. however, a nlm of ice will form around the bulb 39, thus reducing the rate of heat transfer to it from the dense water, and causing the bulb to be chilled preferentially by the metallic path through the clamp I5. It may further be assumed that the motor control switch is set to open some five or six degrees in temperature above the actual coil temperature. Accordingly, before the bulb 39 can be fully chilled, the motor switch opens and the entire system begins to warm up.

Due to the comparatively thin film of ice which may have formed on the bulb, because of the conditions just explained, the ensuing melting of the ice will proceed preferentially around the bulb. The water there is warmer, and the ice lm is thinner. Accordingly, the bulb temperature will increase more rapidly than the coil temperature, until a point is reached, say 33 to 37 Fahr., at which the motor control will again close. The cooling action, and the formation of additional amounts of ice around the coil, will now be resumed until the cut-ou or open switch .condition again occurs.

In Fig. 5, the dot and dash line I illustrates the way in which the ice bank is formed around the coils. Beginning with a bare coil, a. small casingof ice is formed on each length of tubing during the first cycle, these gradually increase in size until they merge, but the amount of ice at any time around the bulb 39 is limited. For the six-can sized cabinet upon which the present drawings are based, the thickness of the ice bank shown in Fig. 5 may be assumed to be approximately three inches, which has been found adequate for the loads to be handled. By mounting the bulb so that it is influenced alternately by the 20 coil temperature and the 38 water temperature, there is available a change in temperature of 18 to operate the control while the coil and ice bank average temperature is held closeto 32. To explain the matter in other language, and by way of analogy. the coll 28 is operated on a freezing cycle, while the bulb 39 is subjected to the conditions of a defrosting cycle by reason of its relation to the coil and the dense water.

As noted above, valves and controls such as may be utilized in this invention are well known, but they are not sensitive within several degrees of temperature (and corresponding pressure) due to uncontrollable atmospheric changes and According to this invention, these factors are substantially ignored by establishing, with the aid of the water itself, a working range in which a few degrecs change has no effect on the ultimate result. Hence, whether the refrigerant temperature and pressure varies, or the control switch becomes slightly erratic, there is automatic regulation of the formation of the ice during the periods between milk cooling operation.

A typical cycle chart of the operation of the refrigeration system is illustrated in Fig. 8. The thermostatic switch control has been set to have a normal cut-in point. of 331/2". As the chart is laid out, this temperature was reached at the bulb at zero minutes, at which time the ice nlm around the bulb had so melted as to produce this temperature by heat transfer from the dense water. On the ensuing pull-down, which required eight minutes, enough refrigerant was admitted to the coil to provide a surface coil temperature of nineteen degrees, as measured by carefully located thermocouples. Because of the dual thermal path into the bulb 39however, this element had then reached a temperature of only 26, at which point the switch is opened. The progress of warming and expansion is then reected by the rising branches of the chart, a period of relative equilibrium being maintained at both coil and bulb surface for approximately fteen minutes. As the ice disappeared from the bulb, however, its temperature rose rapidly, due to contact with 38 water, while the coil temperature remained at freezing. Upon regaining the cut-in point, the cycle was repeated.

It will be seen from this diagram that the bulb temperatures, and therefore the cut-in and cutout points, and also the actual refrigerant preseures and temperatures, may be varied considerably without other effect than to change the length of the cycles. For most service, the settings reflected by Fig. 8 will be found satisfactory, although Variations of several degrees either Way, as may be imposed by exsting conditions, do not interfere with the positive and limited formation of ice.

Fig. 9 similarly illustrates a days operation in the cooling of milk. The cooler was operated to provide the nominal three-inch ice bank as just described, and was charged at zero hours with three cans filled with milk at 90, and with air temperature between 90 and 95. At the same time, the motor li was started to operate the water pump for one hour. At starting, the mean bath temperature was 34, at the end of the hour the bath temperature at the point of reading was only 36, but the milk itself had been cooled to 47, which is entirely satisfactory.

During the ensuing eleven hours; the refrigeration machine operated again to renew the icebank, and the mean water temperature again dropped to 34, or very close to the freezing temperature. Three more cans of fresh milk were then inserted, and were cooled to 45 in an hour. During the remainder of the twenty-four hour period, ice was formed, and the water chilled, as already explained. It is to be noted that the bath temperature was maintained very close to the minimum temperature for water, and yet the regulation effected through the bulb 39 precluded conversion of too much water into ice.

From the foregoing description, it will be seen that the invention moreover provides e, novel means for effectively regulating the temperature of a liquid bath close to its freezing point, and at the same time preventing conversionof excess liquid into the solid phase over long periods of time. Thus, reverting again to the conditions reflected in Figs. 8 and 9, it has been established that failure to impose an extraneous load of warm milk in the bath every twelve hours does not lead to solidlcation, but merely the formation of more ice than will be required during the next cooling. It is moreover to be understood that While the principles of the invention have been presented in connection with one specic embodiment thereof, and have been explained by reference to certain detailed operating data, the invention is not limited thereto, but is susceptible of numerous modiiications and variations. Accordingly, it is intended that the invention be construed as having a scope commensurate with the following claims.

We claim:

l. Cooling apparatus comprising a cabinet having a relatively xed cover section and a removable lid, a refrigerating coil in the cabinet disposed around the walls thereof and in the lower portion of the cabinet, said coil terminating in a `suction line loop positioned adjacent the upper portion of the cabinet, inclined guard and skid plates positioned at the front portion of the cabinet over said suction line loop and having a iiange portion disposed over the coil in the lower portion, an overflow drain pipe mounted in the cabinet and adapted to maintain a body of liquid therein at about the level of said flange portion, thereby to submerge the coil except for said suction line loop, and a liquid circulating pump extending downwardly from said fixed cover section to nearly the bottom of the cabinet and adapted to circulate said liquid from the bottom alon said submerged coil.

2. Cooling apparatus comprising a cabinet having upright side walls, a cover section for a portion of the top of the cabinet, a lid for the balance ing a relatively xed cover section and a removable lid, a refrigerating coil in the cabinet clisposed around the vertical walls thereof and in spaced relation thereto, said cabinet being adapted to contain a body of liquid submerging said coil, an opening formed in said xed cover section, a cup supported in said opening, a tube supported from said cup, a motor mounted in said cup, said motor having a shaft extending into said tube and an extension on the shaft, an impeller carried by the extension, said tube being formed with a bottom inlet opening and a side discharge opening to permit circulation of liquid from the bottom of the cabinet along the sides of said coil, a removable guard cover for the cup adapted to be positioned on the surface of said xed cover section, said guard cover being perforated to admit cooling air to said motor, said motor, tube, and impeller being bodily and removably mounted in said opening, said removable cover engaging said motor to retain the same in position.

4. In cooling apparatus having upright side walls and a cover, an opening formed in said cover, a cup in the opening, a motor driven impeller mounted in said cup, a tube suspended from the cup and shielding the impeller, a cooling coil in the cabinet disposed around said side walls below the cover, an inlet in the tube at the bottom thereof, an outlet from the tube adjacent the upper portion of the cooling coil, a defiector plate above the outlet to direct eiliuent from the impeller along the coil, and a diaphragm above said plate to preclude the passage of moisture into said cup. y

5. Cooling apparatus having upright side walls and a covered top, a cooling coil disposed around said side walls below the top, a circulating pump positioned in said cabinet to circulate liquid along said coil and throughout the cabinet, refrigerating means for'admitting volatile refrigerant to the' coil and withdrawing expended refrigerant therefrom, said last named means including a pressure responsive expansion valve and a thermostaticswitch control, said switch control including a feeler bulb, positioned in the bottom of the cabinet adjacent said coil but in spaced relation thereto, and a metallic clamp interconnecting said bulb and coil, whereby good heat transl1 fer is effected between the coil and bulb and heat transfer can also occur directly between fluid in the cabinet and said bulb whether or not said circulating pump is operated.

6. Cooling apparatus comprising a cabinet having upright side walls, a partition dividing the cabinet into a machinery compartment and a cooling compartment, a cover for the machinery compartment, a second cover for a portion of the cooling compartment, a bushing positioned in said partition to provide an aperture therethrough, a refrlgerating coil leading from the machinery compartment through said bushing, said bushing being positioned at a relatively high point in said partition, said coil being bent downwardly and thence in helical form around the side walls of the cooling compartment and in spaced relation thereto, the suction end of said coil being bent upwardly and around said side walls to form a section wherein refrigerant may become superheated, said suction end passing through said bushing to return to the machinery compartment, upright supporting members disposed in the cooling compartment for supporting the helical portion of said refrigerating coil, guard plates positioned around the side walls over said supporting members and helical portion, a circulating pump mounted on and depending from said second cover portion into said cooling compartment, said pump being positioned adjacent a portion of said helical coil portion, said cooling compartment being adapted to contain a bath of water to submerge said helical portion, an overflow pipe for removing displaced water when articles are placed in the cooling compartment, a refrigerant valve for admitting volatile refrigerant to the refrigerating coil, and a thermostatic control feeler bulb mechanically and thermally connected in spaced relation to said helical coil portion adjacent the bottom of the cooling compartment, said bulb also being positioned for direct contact with said Water.

7. Refrigerating apparatus comprising a cooling compartment having a lower portion adapted to contain a body of water, a refrigerant expansion coil disposed around the walls of said lower portion and adapted to be submerged in the water, said coil having its discharge end positioned at a low point in the said lower portion of the compartment, said discharge end being connected to a refrigerant suction line, a clamp on the coil at said low point, said clamp having extensions and a bulb holding section spaced from the coil, a control bulb for a thermostatic control switch in said section, said bulb also being positioned for contact with said water, means for cyclically supplying refrigerant to the coil to maintain a surface temperature therefor below the freezing point of water, thereby to form an ice bank over the coil, said bulb being so spaced from the coil that the dense water surrounding the bulb precludes the attainment thereof of the minimum coil temperature and heats the bulb more rapidly than the coil during successive periods of operation, whereby the formation of ice on the coil proceeds preferentially to the formation of ice on the bulb and the water in contact with the ice may be maintained near freezing temperature without excessive conversion into ice.

8. Rcirigerating apparatus including a cabinet having a lower portion adapted to contain a bath of water, a refrigerating expansion coil positioned in said lower portion and adapted to be submerged in the bath adjacent the walls of the cabinet, an inlet for the coil above said lower portion, a discharge erid of the coil positioned at a low point in said lower portion, said discharge end merging into a riser and suction conduit above said lower portion, whereby superheating of refrigerant in the coil may be confined to the portion thereof above the bath, an automatic pressure responsive expansion valve for admitting refrigerant to the coll, a clamp on the coil adiacent the bottom of the cabinet, said clamp having extensions thereon, a thermostatic control switch feeler bulb connected to the extensions of said clamp, whereby said bulb may be conjointly subjected to temperatures of said coil and dense water at the bottom of the bath, and whereby when said coil is supplied with refrigerant to maintain a coil surface temperature below freezing said dense water will produce at said bulb a temperature several degrees above the coil surface temperature.

9. Refrigerating apparatus adapted to periodically form a bank of ice in substantial equilibrium with cold water comprising a tank adapted to contain a bath of water, an expansion coil disposed around the walls oi' the tank in spaced relation thereto and adapted to be submerged in the water, a pressure responsive expansion valve for admitting volatile refrigerant to the coil. said valve being adapted to admit sufficient refrigerant to maintain a surface coil temperature below freezing, whereby water in contact with the coil will be converted into ice on the coil, a feeler bulb for a thermostatic control positioned at a low point in the tank and adjacent the coil, a metallic clamp interconnecting the bulb and coil in spaced relation, whereby said bulb will be conjointly sub- `iected to temperature effects on the coil surface and dense water gravitating to the bottom of the bath and the temperature of said dense water will tend to produce a temperature dierential of several degrees between said coil temperature and said bulb temperature, thereby enabling said bulb to respond to defrosting conditions while said coil is maintained at frosting condition.

10. In a refrigeration system of the compressor-condenser-expander type having an automatic expansion valve interposed between the condenser and expander and a thermally controlled switch for governing the operation oi the compressor, a tank in which the expander is located, said tank being adapted to contain a body oi water, the discharge end of said expander being disposed at a low point in said tank and thereby at the region of maximum density oi water contained in said tank, said discharge end merging into a suction line disposed at a relatively high point in said cabinet and above the normal level of the bath, a thermal switch for the compressor motor, a control element for said switch positioned adjacent the discharge end of the expander and thereby in the region of maximum density of the water, and a clamp connecting said control element to said vdischarge end in spaced relation to the expander, said clamp providing a heat transfer path from the expander to both the control element and the water, whereby, when said valve and switch are so adjusted as to cause the formation of a body of ice on said expander, a much thinner nlm of ice may form on said control element, and whereby when said thinner illm of ice is melted by contact with high density water said control element may actuate said switch to start the compressor motor prior to melting of the entire body of ice on the inlet portions of said expander.

il. In the regulation of a cooling bath of water wherein the water is cooled by volatile refrigerant contained in a coil submerged in the bath. the process which comprises periodically admitting and withdrawing volatile refrigerant into and from the coil in suilicient quantity to maintain a coil surface temperature at or below freezing, and controlling said withdrawing of refrigerant by means disposed at the bottom of the bath and conjointly subjected to the temperature eiect of said coil surface temperature and dense water gravitating to the bottom of the bath, whereby the formation of ice on the coil may proceed in limited fashion independently of adventitious variations in heat leakage, external temperature, and barometric pressure.

12. In a process of cooling a water bath and removable material adapted tobe placed in the water bath, and wherein the water bath is cooled by volatile refrigerant contained in a coil submerged in the bath; the steps comprising periodically admitting and withdrawing volatile refrigerant into and from the coil in sucient quantity to maintain a coil surface temperature at or below freezing, controlling said withdrawing of refrigerant by means disposed at the bottom of the bath and conjointly subjected to the temperature effect of said coil surface temperature and dense water gravitating to the bottom of l to maintain the temperature at or below freezing4 and thereby renew the limited formation of ice.

CLARE H. KAFER. HOWARD D. WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED -STATES PATENTS Number Name y Date 1,982,570 Cann. Nov. 27, 1934 2,192,851 Tobey Mar. 5, 1940 2,217,253 Hughes Oct. 8, 1940 2,364,154 Markley Dec. 5, 1944 2,419,377 Shaw Apr. 22, 1947

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