US2329746A - Refrigerating apparatus - Google Patents

Description

Sept. 21, 1943. s. M. DAVISON REFRIGERATING APPARATUS Filed April 3, 1940 6 Sheets-Sheet l Se t. 21, 1943. s. M. DAVIS N REFRIGERATING APPARATUS '6 Sheets-Sheet 2 Filed April 3, 1940 Sept. 21, 1943. s. M. DAVISON REFRIGERATING APPARATUS 6 Sheets-Sheet 5 Filed April 3, 1940 Sept. 21, 1943.

s. M. DAVISON REFRIGERATING APPARATUS Filed April 3, 1940 6 Sheets-Sheet 4 Sept. 21, 1943. s DAVISQN 2,329,746

REFRIGERATING APPARATUS Filed April 5, 1940 6 Sheets-Sheet 5 FLO. IO.

Sept. 21, 1943.

FLQ'. 11.

s. M. DAVISON REFRIGERATING APPARATUS Filed April 3, 1940 6 Sheets-Sheet 6 Patented Sept. 21, 1943 REFBJGERATING APPARATUS Sidney M Davison, Annisquam, Mass, assignor to General Foods Corporation, New York, N. Y., a corporation of Delaware Application April 3, 1940, Serial N0. 327,717

23 Claims.

This invention relates to refrigerating apparatus of the refrigerant evaporator type, and more particularly to devices of the character commonly known as plate frosters" which embody a plurality of plate-like evaporator elements connected in parallel in a volatile refrigerant circuit and movable relatively to one another so as to receive and compress therebetween comestibles to be quick-frozen.

In the plate frosters of the prior art, one example of which is shown in the patent to Birdseye and Hall, No. 1,905,131, dated April 25, 1933, a plurality of refrigerant evaporators in the form of substantially rectangular, hollow plates are mounted one above the other in relativelymovable relationship in such manner that the plates may be separated to permit the loading of comestibles therebetween and then brought toward one another in order to efiect a controlled pressure contact with the upper and lower surfaces of the comestibles and to quick-freeze the latter by ex traction of heat therefrom through the medium of a volatile refrigerant circulated through the plates. Located above the stack of plates is a source of liquid refrigerant, customarily designated a surge drum, to which the refrigerant is supplied through a suitable float valve intended to automatically maintain a desired level of refrigerant within the drum. Leading downwardly from the surge drum is a liquid refrigerant supply header to w ch all of the plates of the froster are connected parallel by means of flexible conduits, such as hoses. As the liquid refrigerant in the plates absorbs heat from the product being frozen, some of it evaporates, and in order to maintain an eflicient transfer of heat, it is necessary to quickly discharge from the plates the vapor thus formed. To this end, each plate is also provided with a second flexible conduit or hose which connects to a common vapor discharge header, the latter in turn discharging into the vapor space in the top of the surge drum whence the vapor may be withdrawn and passed through a circuit including a compressor and a condenser whereby it is again reduced to liquid form and then returned to the drum.

In the plate frosters in general use prior to the present invention, the liquid supply and vapor discharge hoses of each plate are connected to their respective headers at approximately the same level, the hoses of the top plate of the froster being connected to the headers at approximately the same level as the plate and with very little slack therein, while the hoses of the other plates are connected to the headers equidistantly below the top connections, but with smaller intervals therebetween than exist between the 'plates when the latter are in fully separated position, the result being that the hoses of the bottom plate connect to the supply and discharge headers at approximately the same level as that occupied by the middle plate of the froster when the plates are separated.

With this construction, when the plates are closed in freezing position upon relative; thin products, both the liquid supply and vapor discharge hoses of the plates in the lower portion of the froster sag or dip below their respective plates, the amount of dip increasing toward the bottom plate. It has been discovered that, under these conditions, any substantial dip in a vapor discharge hose below its plate tends to produce erratic performance by that plate because the vapor produced therein cannot flow freely, due solely to its buoyancy, outwardly from the plate and up through the vapor discharge hose and header, but must be forced downwardly through the liquid in that portion of the hose which sags below the plate before it can flow upwardly and out of the hose into the header in the desired manner.

When the doors of the insulated froster hous-- ing are opened to unload the product already frozen, or when the froster is to receive its first load of the day, the plates are usually flooded, or nearly flooded, with the liquid refrigerant. As soon as the doors are opened, the plate surfaces exposed to the relatively warm air absorb heat and vapor is formed inside the plates, and as the warm product is loaded onto the plates, the rate of evaporation is increased. When the stations, as the spaces between the plates are designated, are all loaded with the product to be frozen, the plates are moved toward one another so as to effect a controlled pressure contact against both the top and bottom surfaces of the product, whereupon the heat load on the plates is again greatly increased in a very short time and at a time when the product is at its highest temperature. It has been found that the extreme heat load thus impressed on the plates causes the refrigerant to evaporate at such a rapid rate that the vapor forces a large percentage of the liquid refrigerant out of the plates and itself attempts to escape through both the liquid supply and vapor discharge hoses.

Because of the fact that the two hoses of each plate of these prior frosters are connected to their respective headers at the same level, the vapor tends to escape as easily through the liquid supply hose as through the vapor discharge hose. Furthermore, when the two headers are full of liquid, there is a lower static head on the plate nipple to which the liquid supply hose is connected than there is on the vapor discharge nipple because the outlet of the vapor discharge header in the surge drum is located above the level of the liquid refrigerant therein. Because of this and the hose arrangement previously mentioned, considerable difliculty has been experienced in attempting to cause the vapor, particularly that formed in the upper plates, to discharge through the conduits intended for this purpose, and it has been observed that the vapor often escapes from the plates more easily through the liquid supply hoses than it does through the vapor discharge lines. This condition is undesirable for a number of reasons, particularly because the backflow of vapor through the liquid supply hoses and header resists the flow of liquid refrigerant to the plates and thus tends to cause some of the plates to become gas bound. The presence in the plates of a high percentage of gas is, of course, objectionable because the gas is a very much less efiicient heat absorbing medium than the liquid refrigerant.

The discharge of vapor through both the liquid supply and vapor discharge hoses also causes an unstable condition in the plates, and excessive superheating of the refrigerant at certain locations because of the manner in which the hoses are arranged as hereinbefore described.

It is therefore one of the objects of the present invention to so improve the structure and mode of operation of refrigerating devices of the plate froster type that all of the vapor generated in the plates passes out of the latter through the vapor discharge conduits, and that there is maintained a unidirectional flow of the liquid refrigerant and its vapor through the froster at all times during normal operation.

Another object is to provide a plate froster of novel construction wherein the liquid upply and vapor discharge hoses and the means by which the vapor is discharged into the surge drum are so constructed and arranged that the static head on the vapor discharge lines is reduced to a minimum and the flow of the vapor in only one direction is insured, thereby materially increasing the eificiency of the froster.

In plate frosters of the known type wherein all of the plates are provided with hoses connecting to a common supply and discharge headers as previously described, it has been discovered that another undesirable condition arises because of the fact that there is an upward flow of vapor in each of the headers past the ends of all of the hose nipples, except the lowermost one. Assuming that an equal volume of vapor is generated in each plate and that the vapor leaves each plate through both plate nipples, it is obvious that there will be a very much greater quantity of vapor passing through the upper portion of each header than there will be in the lower end thereof. This situation gives rise to unequal velocities of vapor fiow past the header connections of the difierent hoses, and thereby causes erratic operation and undesirable conditions in the plates, particularly in the upper plates where the velocities past the header connections are high and the static head of the liquid refrigerant is low.

It is therefore a further object of the invention to so arrange the vapor discharge conduits of a plate froster that there will be a rapid, uniform velocity of outflow of vapor from each plate, and that the discharge from any one plate will not interfere with that from any other, at all Operati positions of the plates.

Still another object is to provide a refrigerating apparatus of the type embodying a plurality of volatile refrigerant evaporators mounted in parallel, relatively movable relationship with liquid refrigerant supply and vapor discharge hoses for each evaporator so constructed and arranged as to insure a unidirectional flow of the refrigerant and its vapor throughout the system under ordinary operating conditions and for all operating positions of the plates, the discharge outlets from said plates being so located that the vapor leaving the lower plates will not exert any undesirable effect upon the operation of the upper plates.

A still further object is to provide a refrigerating apparatus of the character described wherein each evaporator element of the froster is provided with an individual vapor discharge conduit opening directly into the surge drum, the outlets of said conduits and the other elements within the drum being so devised that entry of liquid refrigerant into the main vapor suction line leading from the drum to the compressor is minimized.

A sudden increase in the heat load on the plates of a froster in the manner previously mentioned also causes a surge of liquid into the surge drum with a consequent temporary increase in the height of the liquid level in said drum. For example, in existing frosters embodying ten stations, this periodic rise of the liquid level above normal may be as much as five or six inches. The liquid in the drum may also rise above the desired normal level due to defective operation of the automatic valve in the liquid refrigerant supply line leading to the drum. Increases in the liquid level of this character are, in certain case objectionable because of the resulting submergence of the vapor discharge opening into the drum, especially in frosters where said opening is located only slightly above the normal liquid level for the purpose of reducing to a minimum the static head on the vapor discharge lines from the various plates. The increase in liquid depth may also be undesirable if the decrease in volume of the vapor space within the surge drum produced thereby unduly retards drying of the vapor entering the drum and thus increases the amount of liquid which is carried by the vapor into the main suction line leading to the compressor.

It is therefore still another object of the present invention to provide a refrigerating device of the plate froster type with means which are efiective to maintain the liquid refrigerant in the surge drum at an approximately constant level in spite of surges of refrigerant into the drum which might otherwise raise the liquid level an excessive amount above normal.

These and other objects, including a general desire to remedy the various defects existing in plate frosters of the character heretofore known and to thereby produce an improved refrigerating device of increased efliciency, will appear more fully upon a consideration of the detailed description of certain embodiments of the invention which follows. Although four specific forms of plate froster refrigerating apparatus have been disclosed in the accompanying drawings, it is to be expressly understood that these drawings are for the purpose of illustration only and are not to be construed as defining the scope of the ininvention, reference being had for the latter purpose to the appended claims.

In the drawings, wherein like reference characters indicate like parts throughout the several views:

Fig. 1 is a side elevation of one form of refrigerating device of the plate froster type embodying the present invention, the view being taken from the refrigerant supply side of the plates with the door of the insulated housing removed and other parts omitted in order to better disclose the construction to which the invention more directly relates, and showing the plates in relatively close, freezing position;

Fig. 2 is a side elevation of the apparatus of Fig. 1 taken from the opposite, or vapor discharge, side of the plates;

Fig. 3 is a side elevation, on an enlarged scale, of the surge drum and associated equipment of the apparatus shown in Figs. 1 and 2;

Fig. 4 is a transverse vertical section of the surge drum taken substantially on line 44 of Fig. 3;

Fig. 5 is a horizontal section through the upper ends of the vapor discharge pipes of the surge drum taken substantially on line 5--5 of Fig. 3;

Figs. 6, 7 and 8 are a front elevation, an axial vertical section and a transverse horizontal section, respectively, of the upper end of one of the vapor discharge pipes of Fig. 3, all on a further enlarged scale;

Fig. 9 is a side elevation, similar to Fig. l, of asecond form or froster embodying the invention;

Figs. 10 and 11 are side elevations, also similar to Fig. l but omitting the surge drum and associated equipment mounted on top of the froster housing, of two additional embodiments of the invention, .Fig. 11 showing the latest preferred construction of the liquid supply lines; and

Fig. 12 is a fragmentary horizontal sectional view, on an enlarged scale, taken substantially on the line I2l2'of Fig. 11, showing the novel arrangement of the conduits which supply liquid refrigerant to the lowermost plates of the froster.

Referring first to Figs. 1-8, inclusive, there is disclosed therein an improved form of refrigerating apparatus-of the plate froster type wherein the flexible conduits or hoses through which the liquid refrigerant and its vapor are supplied to and discharged from the various plates are so constructed and arranged as to insure a unidirectional flow of the liquid and vapor through the plates with none of the vapor escaping to the surge drum through the liquid supply hoses, when the froster is operating under normal heat .load conditions, and wherein each plate is provided with an individual vapor discharge pipe leading directly into the vapor space of the surge drum, the outlets of these latter pipes being so devised that the velocity of the vapor outflow from all plates is uniform. The arrangement of the elements within the surge drum is also such that entry of liquid into the main suction line from the drum to the compressor is reduced to a minimum.

As shown best in Figs. 1 and 2, the froster of the present invention is similar in general construction to those already known in that it comprises a plurality of horizontally disposed, rectangular, hollow metallic plates H mounted one above the other in a stack Within an insulated housing I2, which plates are adapted to be moved vertically with respect to one another in any suitable manner, as by a hydraulic ram I 3, to compress therebetween under controllable pressure comestibles to be quick-frozen, the freezing being accomplished through the medium of a volatile liquid refrigerant circulatel within the plates. The spacing between the adjacent surfaces of the plates may be varied as desired to accommodate products of diiferent thicknesses by a mechanism which forms no part of the present invention and has therefore been omitted from the drawings in the interest of clarity. For example, the froster shown in Figs. 1 and 2 consists of eleven plates forming ten comestible receiving spaces or stations therebetween, each plate being approximately two inches thick and the space between adjacent plate surfaces being about one and one half inches when they are in their most tightly closed freezing position, as shown. There is also indicated in broken lines in these two figures the position of the lowermost plate when the plates are in fully separated position, at which time the spaces therebetween are approximately three and one quarter inches in height. This particular embodiment of the invention, as well as that illustrated in Fig. 9, is adapted to operate most eificiently and to attain the desired results to the maximum degree when freezing products having a thickness of approximately two inches or less.

Mounted on top of the froster housing I2 is a tank or surge drum M, which may be provided with an insulated casing as indicated in broken lines in the drawings, wherein is contained a supply of a suitable volatile liquid refrigerant, such as ammonia, the amount of the liquid in the drum being maintained at a predetermined level L by means of an automatically controlled float valve (not shown) in the liquid supply line l5. Liquid refrigerant from the surge drum I4 is supplied to the plates ll through a vertical supply header l6 which is connected to the bottom of the drum near one end thereof by means of a pipe l1, and extends downwardly inside the housing l2 adjacent one corner of the stack of plates H. The 'bottom'end of header l6 passes through the floor iii of the freezing chamber within the housing l2 and into the space I!) between said floor and the base 20 of the froster, the lower extremity of the header being provided with a suitable valve 2| which is normally closed but may be opened for the purpose of draining the system by gravity when desired.

The plates I l are connected in parallel to liquid supply header l6 by a plurality of flexible conduits or hoses 22, each hose being connected at one end to one of the plates by means of a nipple 23 fixed to the plate adjacent one corner thereof, while the other end is connected to a second nipple 24 leading into the header IS. The refrig-v erant thus supplied to the plates circulates therein through a plurality of passageways or tubes arranged in series, series-parallel or parallel in a manner already known to the art, the vapor discharge ends of the tubes of each plate communicating with an outwardly extending discharge nipple 25 preferably located adjacent the corner of the plate diagonally opposite that at which the supply nipple 23 is positioned. In order to remove from the plates the vapor generated therein when the liquid refrigerant absorbs heat through the walls thereof, each plate discharge nipple 25 is connected to one end of a second flexible conduit or nose 26 which extends upwardly and connects at its opposite. end with the bottom end of a vapor discharge pipe 21 at a point within and just below the top of the froster housing I2. The vapor discharge pipes 21 are supported in any suitable manner, as by a plate 28, with their upper ends extending into the surge drum I4 a predetermined distance above the normal level L of the liquid refrigerant therein so as to discharge into the vapor space in the upper portion of the drum.

In the embodiment illustrated in Figs. 1-8, the outlets at the upper ends of the vapor discharge pipes 21 are positioned at approximately the center line of the surge drum. Assuming that the drum is fourteen inches in diameter, the normal level of the liquid refrigerant would preferably be approximately four inches from the bottom of the drum and three inches below the plane of the outlets of the vapor discharge pipes 21. With such a construction, it is obvious that the cross sectional area of the vapor space within the drum is several times as great as the combined area of the outlets of the pipes; for example, a ratio between said areas of approximately to 1 has been found to be quite satisfactorv in practice.

The vapor discharged into the vapor space of the surge drum M from the pipes 21 may be withdrawn from the drum through a suction connection 29 which extends vertically downwardly into the drum closely adjacent the same end thereof as that at which the header supply pipe I! is connected, the vapor passing from the suction connection 29 through a suitable pipe 30 to a compressor 3| and thence into a condenser 32 wherein it is returned to liquid form under relatively high pressure. From the condenser 32 the liquid refrigerant may be returned to the surge drum l4 through supply line 45 and the previously mentioned, but not illustrated, automatically controlled float valve.

In order to attain the desired objective of maintaining a unidirectional flow of liquid refrigerant and vapor through the plates and preventing the escape of vapor by backfiow through the liquid supply hoses and header, the present invention contemplates a novel arrangement of the liquid supply header and hoses and the vapor discharge lines such that the lowermost point in the path of flow of the liquid refrigerant between the surge drum and each plate is a substantial distance below its associated plate at all operating positions of the latter. Although it is also preferable that each of the discharge hoses have no portion thereof appreciably lower than its associated plate at any operating position, satisfactory operation will be obtained as long as the drop below each plate in the liquid supply line leading thereto is substantially greater than that in the vapor discharge line leading therefrom. For example, in a froster of the size and characteristics described in the preceding paragraphs, it has been found that the desired results will be attained by providing a drop of approximately twenty-four inches in the liquid supply line leading to each plate when the plates are in freezing position, even though some of the vapor discharge hoses might then sag as much as six inches below their respective plate That is, a difference of from about eighteen to twenty-four inches or more between what might be termed the negative heads" of the liquid supply and vapor discharge lines of each plate is adequate for the purposes of the present invention, the higher the position of a plate in the stack the greater is the drop in its liquid supply line required for most efficient operation.

In the embodiment illustrated in Figs. 1 and 2, this end is accomplished by locating the supply hose nipples 24 as low down as convenient on the supply header l6, each nipple 24 being so positioned that it is below its corresponding plate nipple 23 even when the plates are in fully separated position. With this construction, the liquid refrigerant in those portions of the supply hoses 22 which lie below the levels of their associated plates ofl'ers sufficient resistance to the downward flow of vapor to prevent its escape from the plates into the surge drum through the liquid supply lines instead of through the vapor discharge lines. Similarly, by connecting the vapor discharge hoses 26 to individual vapor discharge pipes 21 leading directly into the surge drum and by making these connections at the top of the froster housing in the manner illustrated in Fig. 2, there is no appreciable sag or dip in the individual discharge hoses even when the plates are in their most tightly closed freezing position as shown in Fig. 2. The resistance offered to the free upward flow of the vapor by buoyancy alone through the vapor discharge lines, and to the discharge of the liquid refrigerant which is carried out of the plates with the vapor, is thus maintained at a minimum. This arrangement of the liquid supply and vapor discharge conduits also makes it possible to drain the entire system by gravity through valve 2| when the plates are raised to a position corresponding to one of their normal freezing positions; that is, when the plates of the embodi ment illustrated are closed upwardly to a spacing therebetween of approximately two inches or less.

The second major objective of the present inventionnamely, the insurance of a substantially uniform, rapid velocity of outflow of vapor from all of the plates-is attained both by providing each plate with an individual discharge line leading directly into the surge drum, and by so constructing and arranging the outlets of vapor discharge pipes 21 within the drum that the outflow from each pipe does not interfere with that from any of the others and is itself not obstructed by the adjacent pipes.

As is shown best in Figs. 3-8, the open upper end of each vapor discharge pipe 21 in the disclosed embodiments of the invention is cut off at an angle to the horizontal, two vertical cuts are made in the wall of the pipe downwardly from the thus beveled open end, symmetrically positioned with respect to the highest point thereof,

and then a horizontal cut is made to intersect with the lower ends of the two vertical cuts, whereupon removal of the metal bounded by the cuts provides an opening 33 of limited peripheral extent in the wall of the pipe. To complete the structure, the beveled open end of the pipe is capped by an elliptical deflecting plate 34. The openings 33 in adjacent pipes are directed alternately to different sides of the longitudinal axis of the drum, and all of said openings are formed in the sides of the pipes opposite to those which face the suction connection 29.

With this construction, the vapor and whatever liquid is carried along with it discharge from pipe 21 in substantially horizontal streams of limited width which are so directed as to avoid interference with one another and avoid impact against the next pipe in line. In this latter connection, it will also be noted that the liquid supply line I5 leading into the surge drum is offset from the longitudinal center line thereof so as to avoid interference with the discharge from the fourth pipe 21 from the right as viewed in Figs. 3 and 5. A further advantage of the arrangement disclosed is that a large part of the liquid refrigerant which issues with the vapor from the discharge pipes 21 will separate from the vapor and settle inthe bottom of the drum, particularly when it loses its velocity in the original direction of discharge and attempts to reverse its flow to reach the suction connection 29 leading to the compressor. Entry of liquid into the suction connection is also minimized by closing the lower end of the latter by a plate 35 and forming the inlet thereto by cutting away a semicylindrical section of the vertical wall thereof at the side opposite that facing the vapor discharge pipes 21, as indicated at 36, leaving the uncut portion of the wall to serve as a bafile.

A still further insurance against the possible spraying of liquid refrigerant into the suction connection if slugging occurs when an abnormally high heat load is placed on the plates, a baffle plate 31 may be provided extending angularly upwardly from the bottom of the tank between the inlet end of header supply pipe l1 and the inlet of suction connection 29, said baffle plate having a plurality of opening therethrough adjacent the lower edge thereof so as to permit circulation of liquid refrigerant the full length of the drum. The upper edge of baflie plate 31 is preferably located slightly below the plate 35 closing the lower end of the suction connection so as not to interfere with the flow of apor to the latter.

In some instances, it is desirable to place the outlets of the vapor discharge pipes in the surge drum as close as possible to the level of the liquid refrigerant in the drum in order to minimize the static head on the discharge lines of the froster and thereby assist in producing the desired unidirectional flow of refrigerant and vapor. However, when this is done there may be a danger of submergence of the vapor outlets due to sudden surges of liquid refrigerant into the drum, as when the froster is initially loaded with the warm product to be frozen. -To obviate this possible difliculty, a modified construction such as that shown in Fig. 9 may be employed.

The froster illustrated in Fig. 9 is of substan tially the same construction as that of Figs. 1-8

except for the relative location of the outlets of the vapor discharge pipes 2'1! and the addition of an overflow device which is adapted to maintain an approximately constant level of the liquid refrigerant in the surge drum, in spite of tendencies to raise the level above said vapor discharge outlets when the heat load on the plates is suddenly increased or in the event of defective operation of the automatic float valve.

As shown, the upper endsof the vapor discharge pipes 21 are so located that the lower edges of their openings 33 are positioned only slightly above the normal level L of the liquid refrigerant within the surge drum l4, and there is provided between the bafiie plate 37 and the adjacent end of the drum an overflow pipe 39 of approximately the same diameter as the head or supply pipe ll, the open upper end of the overflow pipe being positioned intermediate the normal refrigerant level L and the plane of the lower edges of the vapor discharge pipe openings 33. For example, again assuming a surge drum offourteen inches in diameter and a normal depth of liquid refrigerant of four inches, the lower edges of the discharge openings 33 may be positioned approximately one inch above the level L, and the inlet of the overflow pipe 39 about one half inch above said level. These distances are, of course, merely exemplary and may be varied, as desired, to suit different conditions.

The overflow pipe 39 is preferably connected to a low pressure liquid refrigerant accumulator through piping 40 and a suitable valve 4|, which is ordinarily left open during operation of the froster. If desired, the lower end of supply header l6 may also be connected to the piping 40 through a suitable pipe extension 42 and drain valve 43, the latter being closed at all times except when it is desired to drain the liquid out of the froster.

In order to provide sufilcient drop in the liquid supply lines, particularly those of the lower plates, to enable the froster to efliciently operate on products thicker than those which can be adequately handled by the arrangements shown in Figs. 1 and .9, constructions such as those illustrated in Figs. 10 and 11 have been provided, the latter showing the presently preferred form of liquid supply for a ten station froster capable of freezing products up to three inches or a little more in thickness.

In the embodiment of Fig. 10, which, except for the specific arrangement of the liquid supply lines, may be of substantially the same construction as the froster shown in Figs. 1-8, the lower extremity of the bottom portion of header I6 which passes through the floor l8 of the freezing chamber is suitably connected as by an elbow 44 to one end of a horizontal auxiliary header or manifold 45, the other end of which is provided with a suitable drain valve 46, corresponding to the valve 2| of Fig. 1. Instead of connecting all of the liquid supply hoses 22 to nipples 24 leading into the vertical header It, only seven such nipples are provided. in the present embodiment to which the hoses of the seven uppermost plates are connected, the supply lines of the four bottom plates of the stack being so arranged that these plates receive their liquid refrigerant from the horizontal auxiliary header 45.

As shown, the auxiliary header 45 is provided near its valved end with four vertical pipes or risers 41, 48, 49 and 50 which extend upwardly through the floor N3 of the froster and terminate at their upper ends in suitable nipples 5|, 52, 5t and 54 to which are connected flexible conduits leading to the tenth, eighth, ninth and eleventh plates of the stack, respectively, the eleventh plate being the lowermost one of the froster. While the connections between nipples 52 and 53 and the eighth and ninth plates, respectively, may be made by continuous flexible hoses 55, in the same manner as the upper seven'plates are connected to nipples 24, each of the connections between nipples 5i and 54 and the tenth and eleventh plates, respectively, is preferably made of two relatively straight sections of flexible hose 56 and 51, the left-hand ends (as viewed in Fig. 10) of these hoses being connected to the riser nipples 5i and 54 and plate nipples 23, while respectively, their right-hand ends are interconnected by means of U-shaped or return bend elbows 58. In this way, the flexibility of the com duits leading to the two lowermost plates is preserved Without requiring excessively sharp bends in the hoses.

With this construction, the lowermost point in the path of flow of the liquid refrigerant to each of the plates is sufiiciently far below its associated plate to prevent the vapor from escaping from the plate through the liquid supply line when the plates are in operating position for the freezing of products on the order of three inches in thickness, and even when the plates are in fully separated or loading position. Likewise, the location of valve 46' at the end of auxiliary header 45 enables draining of the entire system by gravity at any position of the plates.

In the embodiment of the invention illustrated in Figs. 11 and 12,,which is again substantially the same as that of Figs. 1-8 except for the arrangement of the liquid supply conduits of the various plates, the desired drop in the paths of flow of the liquid refrigerant to the plates, particularly those in the lower portion of the stack, is obtained by making the effective connection between the three bottommost plates and the supply header I6 at a point well below the floor I8 of the froster housing. which point is preferably at least eighteen inches below the position of the bottom plate when the plates are in fully separated position.

As illustrated, the lower end of the supply header I6 is provided with a manifold casting 59 located in the space 19 below the floor l8 closely adjacent the base 20 of the froster, which casting is also fitted with three vertically extending pipes or risers 60, GI and 62 which pass upwardly through floor 18 and terminate at different elevations within the froster housing in nipples 63, 64 and 65, respectively. A suitable drain valve 66, corresponding to the valves 2| and 46 of the embodiments previously described, is also connected to the bottom of manifold casting 59.

The top eight plates of the froster are connected to the supply header IS in the manner reviously described by means of plate nipples 23, flexible hoses 22 and header nipples 24, the latter nipples being located as low down on the supply header as is convenient. The plate nipples of the three lowermost plates, however, are connected by hoses B1, 68 and 69 to riser nipples 63, B4 and 65, respectively, the lowermost plate being connected to the shortest riser 60, and so on, as shown.

With this arrangement, which is the latest preferred construction for a ten station froster, the liquid refrigerant supplied to the lowermost plates of the stack must flow downwardly all the way to the manifold casting 59 and then upwardly through risers 60, BI and 62 before reaching the plates, thereby insuring a suflicient drop in the supply line of each plate to prevent anyescape of vapor from the plates by a reverse flow through the liquid supply side of the system. By thus supplying the lower plates from the manifold casting 59 through the risers 60, 6| and 62, it becomes possible to also lower the header nipples 24 of the upper plates, and thereby similarly increase the drop in the supply lines of these'plates to the desired extent.

It will be understood that, in all of the constructions illustrated in the drawings, sufiicient slack is provided in the various supply and discharge hoses t enable the same to reach the plates in whatever positions the latter may occupy, and that all portions of the liquid supply side of the system which are positioned outside of the froster housing are preferably insulated in any suitable manner in order to minimize vapor ization of the liquid refrigerant therein.

There is thus provided by the present invention improved refrigerating apparatus of a type particularly well adapted to the quick-freezing of comestibles which remedies a number of defects which have been discovered in the commercial operation of prior freezing devices of the same general character, and which embodies a more efilcient arrangement of elements than heretofore known for effecting a freezing operation by evaporation of a volatile liquid refrigerant, such as ammonia. By devising novel arrangements of the conduits through which the liquid refrigerant and its vapor are supplied to and discharged from the evaporator elements of a plate froster, a unidirectional flow through the system and a rapid, uniform velocity of vapor discharge from the plates are substantially assured, thereby reducing to a minimum the possibility of trapping large quantities of vapor in certain of the plates, a condition which is productive of erratic and unsatisfactory freezing operation. Another advantage of the improved arrangements of liquid supply and vapor discharge lines of the present invention, particularly that of the embodiment of Fig. 11, is that they facilitate drainage of the entire system by gravity. The construction and relative positioning of the various elements within the surge drum have also been materially improved, not only to assist in obtaining the advantages already mentioned, but also for the purpose of minimizing the amount of liquid refrigerant that is drawn into the vapor suction line leading to the compressor of the system. Means have also been provided for reducing to a minimum the static head on the vapor discharge side of the system, while at the same time avoiding the adverse effects upon vapor discharge lines of such reduced head which tend to result from sudden variations in the level of the liquid refrigerant in the surge drum. These and other features of the apparatus embodying the present invention characterize the latter as a substantial improvement over similar devices of the prior art.

Although four specifically different forms of apparatus have been described and illustrated in the accompanying drawings, it should be obvious that the invention is not limited to the particular structures shown, but is capable of a variety of mechanical embodiments. For example, although two different constructions have been disclosed whereby certain of the lowermost plates of the froster may be provided with connections to the liquid supply side of the system at points substantially below the floor of the freezing chamber, it. will be recognized that the same result may be attained by various other mechanical expedients, and that the number of plates so connected may also be varied as desired. Furthermore, while the invention finds particular usefulness in connection with devices of the plate froster type, its utility is not limited to this specific form of apparatus and certain of its features are readily susceptible of application to other types of refrigerating devices. It is also to be clearly understood that the dimensions and other statements of size, capacity, number of plates and the like set forth herein are intended for illustrative purposes only to assist in a better understanding of the underlying concepts of the invention, and that various changes, which will now suggest themselves to those skilled in the art, may be made in the form, details of construction and arrangement of the parts without departing from the spirit of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements mounted in parallel relation to one another and adapted to freeze comestibles while the latter are in heat exchanging contact therewith, a source of volatile liquid refrigerant, means providing a path of flow for said liquid refrigerant by gravity from said source to said elements and comprising a separate conduit for delivering refrigerant into each of said elements, and additional means communicating with the interior of each of said elements through which vapor generated within the latter is adapted to be discharged therefrom, the lowest point in each of said conduits being sufliciently far below its associated element to provide a negative liquid head effective to prevent the backflow of vapor from said associated element therethrough.

2. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated ele ments mounted in parallel relation to one another andadapted to freeze comestibles while' the latter are in heat exchanging contact therewith, a source of volatile liquid refrigerant, means providing a path of flow for said liquid refrigerant by gravity from said source to said elements and comprising a separate conduit for delivering refrigerant into each of said elements, and additional means communicating with the interior of each of said elements through which vapor generated within the latter is adapted to be discharged therefrom, the lowest point in each of said conduits being sufficiently far below the lowest point in the vapor discharge means communicating with the same element to effectively prevent backflow of vapor from said same element therethrough.

3. In a refrigerating apparatus of the plate froster type embodying a plurality of horizontally disposed, hollow metallic plates mounted one above the other through which a volatile liquid refrigerant is adapted to flow and which are vertically movable relatively to one another to receive and engage therebetween comestibles to be frozen, a gravity flow refrigerant circuit com-' prising a source of volatile liquid refrigerant, means including a series of conduits each delivering liquid refrigerant into one of said plates from said source, at least a portion of each of said supply conduits being positioned sufficiently far below its associated plate at all operating positions of the latter to effectively prevent vapor generated within said plate by absorption of heat through the walls thereof from escaping through said conduit under normal operating conditions,

and means including a second series of conduits each connected with one of said plates for discharging therefrom the refrigerant vapor generated therein, each of said discharge conduits being so constructed and arranged that no portion thereof occupies a position appreciably below its associated plate at any operating position of the latter.

4. In a refrigerating apparatus of the type embodying a plurality of horizontally disposed, hollow metallic plates mounted one above the other through which a volatile liquid refrigerant is adapted to flow and which are adapted to freeze comestibles while the latter are in heat exchanging contact therewith, a gravity flow refrigerant circuit comprising a vertically positioned header for supplying volatile liquid refrigerant to said plates, a series of conduits each delivering refrigerant into one of said plates from said header, and a second conduit communicating with the interior of each of said plates through which the 7 vapor generated within said plate is adapted to be discharged therefrom, the lowwt point in each of said first named conduits being sufficiently far below its associated plate at all operating positions of the latter to provide a negative liquid head effective to prevent the escape of vapor from said plate by backflow through said conduit.

5. In a refrigerating apparatus of the platefroster type embodying a plurality of horizontally disposed, hollow metallic plates mounted one above the other through which a volatile liquid refrigerant is adapted to flow and which are vertically movable relatively to one another to receiverand engage therebetween comestibles to be frozen, a gravity flow refrigerant circuit comprising a vertically positioned header for supplying volatile liquid refrigerant to said plates, a series of conduits flexible at least in part each delivering refrigerant into one of said plates from said header, the point of connection between each of said conduits and said header being sufficiently far below the lowermost operating position of they associated plate to prevent backflow of vapor from said associated plate therethrough,

, and a second series of conduits flexible at least in part each communicating with the interior of one of said plates through which the vapor generated within said plate by absorption of heat through the walls thereof is adapted to be discharged therefrom, each of said discharge conduits being so constructed and arranged that no portion thereof occupies a position appreciably below its associated plate at any operating position of the latter.

6. In a refrigerating apparatus-of the plate froster type embodying a plurality of horizontally disposed, hollow metallic plates mounted in an insulated housing one above the other through which a volatile liquid refrigerant is adapted to flow and which are vertically movable relatively -to one another to receive and engage therebetween comestibles to be frozen, a refrigerant circuit comprising a vertically positioned header for supplying volatile liquid refrigerant to said plates, the lower end of said header extending downwardly, through the floor of said housing a substantial distance below the lowermost position to which the bottom plate of the froster may be moved, conduits flexible at least in part connecting the interlors of a number of the uppermost plates of said froster with said header at points within said housing but substantially below the lowermost operating positions of the respective plates, a manifold connected to the lower end of said header, a plurality of' risers extending upwardly from said manifold through the floor of 7 ing a second conduit flexible at least in part communicating with the interior of each of said plates through which vapor is adapted to be discharged therefrom.

7. In a refrigerating apparatus of the plate froster' type embodying a plurality of horizontally disposed, hollow metallic plates mounted one above the other through which a volatile liquid refrigerant is adapted to flow and which are vertically movable relatively to one another to receive and engage therebetween comestibles to be frozen, a gravity flow refrigerant circuit comprising a source of volatile liquid refrigerant, means including a series of conduits each delivering refrigerant into one of said plates from said source, at least a portion of each of said upply conduits being positioned sufl'iciently far below its associated plate at all operating positions of the latter to 'efiectively prevent vapor generated within said plate by absorption of heat through the walls thereof from escaping through said conduit under normal operating conditions, and means including a second series of conduits each connected with one of said plates for discharging therefrom th refrigerant vapor generated therein, each of said discharge conduit having its outlet end located above the highest operating position of the uppermost plate and being so constructed and arranged that no portion thereof occupies a position appreciably below its associated plate at any operating position of the latter.

' 8. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a source of volatile liquid refrigerant, a conduit having a portion movable with each of said elements connecting the interior thereof with said source, a receiver for the vapor generated within the elements, and a second series of conduits each having a portion thereof movable with one of said elements connecting the interior thereof with said vapor receiver, the outlet ends of all of said second named conduits being so constructed and arranged within said receiver that vapor may discharge substantially horizontally from each without interference with that discharged from any other.

9. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a source of volatile liquid refrigerant, a series of conduits each having a portion thereof movable with one of said elements connecting the interior thereof with said source, at least a portion of each of said conduits being positioned sufliciently far. below its associated element at all operating positions of thelatter to effectively prevent vapor generated within said element from escaping through said conduit under normal operating conditions, a receiver for the vapor generated within the elements, and a second series of conduits each having a portion thereof movable with one of said elements connecting the interior thereof with said vapor receiver and having no portion appreciably below its associated element at any operating position of the latter, the outlet ends of all of said second named conduits being so constructed and arranged within said receiver that vapor may discharge from each without interference with that discharged from any other.

10. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a supply of volatile liquid refrigerant, conduit means flexible at least in part connected to each of said elements for supplying liquid refrigerant to the latter from said tank, at least a portion of each of said conduits being positioned sufllcienfly positions of the latter to effectively prevent vapor generated within said element from escaping through said conduit under normal operating conditions, and conduit means flexible at least in part connected to each of said elements for discharging the vapor from its associated element directly into the space within said tank above the level of the liquid refrigerant therein, each of said discharge conduits being so constructed and arranged that no portion thereof occupies a position appreciably below its associated element at any operating position of the latter.

11. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a supply of volatile liquid refrigerant, means including a series of conduits flexible at least in part each connected to one of said elements for supplying liquid refrigerant to the latter from said tank, at least a portion of each of said conduits beingpositioned sufllciently far below its associated element at all operating positions of the latter to effectively prevent vapor generated within said element from escaping through said conduit under normal operating conditions, and a second series of conduits flexible at least in part each connected to one of said elements for discharging the vapor from its associated element directly into the space within said tank above the level of the liquid refrigerant therein, the cross sectional area of said vapor space being at least several times the combined area of the outlets of all of said discharge conduits.

12. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latterare compressed therebetween, a tank positioned above all of said elements adapted to contain a supply of volatile liquid refrigerant, means including a series of conduits flexible at least in part each connected to one of said elements for supplying liquid refrigerant to the latter from said tank, and a second series of conduits flexible at least in part each connected to one of said elements for discharging the vapor generated in the latter directly into the space within said tank above the level of the liquid refrigerant therein, each of said discharge conduits having an outlet in said vapor space which is directed at an angle relatively to the outlets of the adjacent conduits so as to prevent interference between the discharges therefrom.

- 13. In a refrigerating apparatus of the type embodying a plurality of horizontally disposed, hollow refrigerated elements mounted one above the other and adapted to move vertically in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a source of volatile liquid refrigerant, a series of conduits each having a portion movable with one of said elements connecting the interior thereof with said source, a receiver for the vapor generated withinsaid elements, and a second series of conduits each having a portion movable with one of said elements connecting the interior thereof with said vapor receiver, all of said conduits being so constructed and arranged as to provide a unidirectional flow of liquid re- I frigerant and vapor through each of said elements at all operating positions of the latter, the outlet ends of said second'named conduits being located within said receiver and so disposed relatively to one another so as to prevent the vapor discharging from the lower elements from interfering with the vapor discharge from the upper elements.

14. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a supp y of volatile liquid refrigerant, means including a series of conduits flexible at least in part each connected to one of said elements for supplying liquid refrigerant to the latter from said tank, a second series of conduits flexible at least in part each connected to one of said elements for discharging the vapor generated in the latter directly into the space within said tank above the level of the liquid refrigerant therein, means including a compressor and a condenser for liquefying the vapor collected in said tank, and a vapor suction conduit leading from said vapor space to said compressor, the outlets of adjacent discharge conduits in said vapor space being directed in different directions to prevent interference with one another and all of said outlets being directed away from said vapor suction conduit.

15. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a supply of volatile liquid refrigerant, means including a conduit flexible at least in part connected to each of said elements for supplying liquid refrigerant to the latter from said tank, a second conduit flexible at least in part connected to each of said elements for discharging the Vapor generated in the latter directly into the space within said tank above the level of the liquid refrigerant therein, means including a compressor and a condenser for liquefying the vapor collected in said tank, a vapor suction conduit leading from said vapor space to said compressor, and bailie means for preventing the entry of liquid refrigerant into said suction conduit.

16. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated elements adapted to move in parallel relation to one another and to freeze comestibles While the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a supply of volatile liquid refrigerant, means including a series of conduits flexible at least .in part each connected to one of said-elements for supplying liquid refrigerant to the latter from said tank, and a second series of conduits flexible at least in part each connected to one of-said elements for discharging the vapor generated in the latter directly into the space within said.

tank above the level of the liquid refrigerant therein, each of said discharge conduits terminating in a vertically disposed section of pipe .having a deflecting plate secured to the open upper end thereof at an angle to the horizontal and an opening of limited peripheral extent in the wall of said pipe immediately beneath said plate.

ments adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a predetermined amount of volatile liquid refrigerant, means including a conduit flexible at least in part connected to each of said elements for supplying liquid refrigerant to the latter from said tank, a second conduit flexible at least in part connected to each of said elements for discharging the vapor generated in the latter directly into the space within said tank above the level of the liquid refrigerant therein, and an overflow pipe extending into said tank with its inlet end positioned slightly above the normal level of the liquid refrigerant which it is desired to maintain in the tank.

18. In a refrigerating apparatus of the type embodying a plurality of hollow refrigerated ele ments adapted to move in parallel relation to one another and to freeze comestibles while the latter are compressed therebetween, a tank positioned above all of said elements adapted to contain a predetermined amount of volatile liquid refrigerant, means including a conduit flexible at least in part connected to each of said elements for supplying liquid refrigerant to the latter from said tank, a second conduit flexible at least in part connected to each of said elements for discharging the vapor generated in the latter directly into the space within said tank above the level of the liquid refrigerant therein, and an overflow pipe extending into said tank with its inlet end positioned intermediate the normal level of the liquid refrigerant which it is desired to maintain in the tank and the level of the outlets of said discharge conduits.

19. In a refrigerating apparatus of the type embodying a plurality of refrigerant evaporators connected in parallel to a common source of vola-.

tile liquid refrigerant, a tank adapted to contain a supply of volatile liquid refrigerant, means for supplying refrigerant from said tank to said evaporators, and an individual vapor discharge conduit leading from each of said evaporators into said tank, the outlet ends of said conduits within said tank being so constructed and arranged as to discharge above the normal level of the liquid refrigerant in said tank in substantially horizontal streams of limited width so directed as not to interfere with one another.

20. In a refrigerating apparatus of the type embodying a plurality of refrigerant evaporators connected in parallel to a common source of volatile liquid refrigerant, a tank adapted to contain a supply of volatile liquid refrigerant, means for supplying refrigerant from said tank to said evaporators, and an individual vapor discharge conduit leading from each of said evaporators into said tank, each of said conduits having an outlet positioned above the normal level of the liquid refrigerant in said tank and directed at an angle relatively to the outlets of the adjacent conduits so as to prevent interference between the discharges therefrom.

21. In a refrigerating apparatus of the type embodying a plurality of refrigerant evaporators duit leading from each of said evaporators into said tank, means for liquefying the vapor collected in said tank, and a vapor suction conduit leading from said tank to said liquefying means, the outlet ends of said vapor discharge conduits being so constructed and arranged as to discharge above the normal level of the liquid refrigerant in said tank away from said vapor suction conduit, the outlets of adjacent conduits being directed in different directions relatively to one another to prevent interference therebe-' above the normal level of the liquid refrigerant in said tank and having a deflecting plate secured to the open upper end thereof at an angle to the horizontal and an opening of limited peripheral extent in the wall of said pipe immediately beneath said plate.

23. In a refrigerating apparatus of the type embodying a plurality of refrigerant evaporators connected in parallel to a common source of volatile liquid refrigerant, a tank adapted to contain a supply of volatile liquid refrigerant, means for supplying refrigerant from said tank to said evaporators, an individual vapor discharge conduit leading from each of said evaporators into said tank and having its outlet positioned above the normal level of the liquid refrigerant therein, and an overflow pipe extending into said tank with its inlet end positioned intermediate the normal level of the liquid refrigerant and the level of the outlets of said conduits.

A SIDNEY M. DAVISON.

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