US2043310A - Method and apparatus for cooking and cooling canned goods - Google Patents

Description

JumeQ, 1936.., A. R. THOMPSON METHOD ANDPPARATUS FOR COOKING AND COOLING CANNED GOODS Filed Oct. l0, 1952 d. mm n. mm N WM m Patented June 9, 1936 PATENT oFFlc'E.

METHOD AND APPARATUS FOR COOKING AND COOLING CANNED GOODS Albert B.. Thompson, San'Jose, Calif., assigner to Food Machinery Corporation, San Jose, Calif.,

a corporation of Delaware Application October 10, 1932,v Serial No. 637,141 27 Claims. (Cl.1-2`6272) My invention relates in general to the canning industry and has partlcularreference to a method and apparatus forcooking and cooling food stuffs in hermetically sealed cans, or other containers.

`According to present day methods of processing food stuifs inhermetically sealed cans to preserve them, it is the customary practice to subject the filled cans, after sealing, to a cooking operation, during which time the cans are subjected to a sufficient temperature for the proper length of time to eifect sterilization of their contents. Not all commodities require `the application of the same temperatures for sterilization, but in general, temperatures above 212 degrees F. are employed for this purpose, either because required for proper sterilization, or in order to l llimit the time required for its' accomplishment.

The application of such temperatures to the cans causes an increase in their internal pressures which may result in expanding the ends of -the cans beyond their elastic limit so that they remain permanently bulged outwardly', a condition not acceptable to the trade. In order to avoid this, it is the customary practice to apply a' pressure externally of the cans during the cooking sufficiently above atmospheric to counterbalance or partially counterbalance theA internal pressures developed iri the cans, thus relieving the strain on the can heads. Devices for carrying out the cooking un'der pressure are knownin the art as pressure cookers. y Upon the completion of the cookingl of the cans-they are transferred to a cooler, and it has been found necessary to maintain a pressure above atmospheric in the cooler also in order to prevent excessive outward bulging of the can heads by the force of internal pressure, which might 4otherwise occur from the -sudden shock if the cans were suddenly relieved of the external pressure applied in the cooker by delivering them into the atmosphere. Coolers of this char--v actor are known aspressure coolers.

Heretofore it has been the practice to maintain a uniform pressure throughout', the cooler to `which the cans were subjected during their entire travel'through the cooler, and I have dis-.- covered that this practice is directly account- 'able fora considerable proportion of the spoilage which has heretofore occurred in a certain percentage of the cans subsequent to processing.V I attribute this to the fact that as the cooling of the cans progresses their internal pressures decrease, and since the external pressure applied to them remains constant, the difference between the external and internal pressures progressively increases as the cooling progresses.

As is'well known, it is 'customary in many instances to subject the lled cans just prior to sealing to a heating, or exhausting, process, for the 4purpose of driving the air from the contents of the cans to produce a vacuus condition in the sealed cans when they are finally cooled. Consequently, it will be seen that at some point during the cooling process and prior to the time that the cooling is completed the internal pressure in the cans will have been reduced to atmospheric, and from this point on, as the cans are further cooled, they are subjected to the combined strain of both the internal and external pressures which may result in forcing some of the cooling liquid into the contents of the cans past the can seals which have not yet become fully set, thereby causing recontamination and subsequent spoilage of the can contents.

I have discovered that this spoilage can be substantially eliminated if the pressure' applied externally of the cans is reduced during cooling e so as to maintain the diiference between the internal and external pressures well within the strength of the can seals, and it is, accordingly, an

` object of this invention to provide amethod of cooling hermetically sealed, filled cans, subsequent to the cooking operation, by applying to them an initial external pressure suiiiciently above atmospheric to prevent overstraining of 5 the can heads by the internal pressure generated within the cans during the cooking process, and.

by reducing the pressure 'thus applied as the cansare cooled suiliciently to prevent the forcing of cooling liquid past the can seals by excessive differencesrof internal and external pressures.

It is also an object to provide a method of cooling the cans as above stated in which the external pressure is applied either wholly or in part by means o f a body of cooling -liquid beneath which the cans are introduced for cooling, and through which they are elevated so as to reduce the external pressure applied at a rate suiiicient to prevent .forcing of cooling liquid past the can seals by excessive differencesbetween,internal and external pressures.v

Another object is to provide a method of proc- Y essing foodstuffs in hermetically sealed cans, in t which the cans are cooked under pressure above atmospheric and then subjected to a cooling process in which the cans are elevated through a body of cooling liquid, the cans being transferred from the cooking zone to a point beneath the surface of the cooling liquid without loss of external pressure on the cans `suilicient to result in overstraining the can heads.

It is a further object to provide an apparatus for carrying out the above methods, and more particularly to provide an apparatus for cooling the cans under a diminishing external pressure, subsequent to the cooking operation, by the provision of means for introducing the cans directly into submergence beneath the surface of a body of cooling liquid and passing the cans upwardly through the liquid so as to diminish the pressure exerted externally of the cans as the cooling progresses.

A further object is to provide an apparatus for processing canned goods including a pressure cooker, a. cooler containing a body of cooling liquid beneath the surface of which the cans are introduced by a pocketed transfer valve, and means for preventing excessive loss of pressure in the 4transfer valve during transfer of the cans from the cooker to lthe cooler.

.A still further object is to provide an apparatus for processing canned goods including a cooker and a coolercontaining a body of cooling liquid, in which a pressure tight pocketed valve is utilized to transfer cans from the cooker into submergence beneath the cooling liquid, and means `is provided for freeing the valve pockets of liquid carried out of the cooler to prevent its introduction into the cooker.

Various other objects and advantages will hereinafter become apparent as the description progresses in connection with which attention is directed to the accompanying drawing, in which:

Figure 1 is a side elevation ofV a combined cooker and cooler, a portion of the shell of the cooler being broken away to illustrate certain features of its construction.

Figure 2 is a top plan view disclosed in Figure 1.

Figure 3 is a side elevation, partly broken away, of the top portion of a modied form of cooler.

Figure 4 is a fragmentary side elevation of the lower portion of a modified form of cooker.

Referring to Figures l and 2, the vertical cylindrical shell I of a pressure cooker A is supported by a base 2, and closed at its opposite ends as by heads 3 and 4 so as to provide a closed cooking chamber into which the cans are introduced by a rotary pressure tight valve 5, provided with can pockets 6, and from which they are discharged by a similar valve 1, having can pockets' 8. Since the construction and operation of such valves is well known in the art, it is not deemed necessary to illustrated further details of their construction. Live steam under pressure is introduced into the interior of the cooker by means of the steam pipe 9, and the condensate may be drained away by the drain pipe I controlled by valve II of a well known type which permits the passage of liquid but preventsthe passage of steam. 'Ihe steam admitted to the cooker provides the necessary cooking temperature, and being admitted under pressure also provides for the application of pressure above atmospheric externally of the cans so-as to prevent overstraining of their heads, from pressure generated within them during the cooking process.

The mechanism for advancing the cans through the cooker comprises the well-known reel and spiral construction which, being identical with that utilized in the cooler, has not been illustrated; reference being had to the cooler illustrated for its details of construction. The

of the apparatus cooker reel is driven in the direction indicated by the arrow by means of a gear I2, secured to the upper end of the reel shaft I3, and driven in turn from the shaft I4 through the train of reducing gears I5. The shaft may be driven from any suitable-source of power, applied to a pulley I6. The inlet valve 5 is driven by a gear I1, secured to the upper end of the valve shaft I8, and intermeshing with the gear I2. 'Ihe discharge valve 1 is driven from the Valve shaft I9 by means of the pinion 20 intermeshing with a gear 2 I, secured to the lower end of the reel shaft I3.

'Ihe cans are discharged from the cooker A directly into the shell 22 of the cooler B by means of the valve I which, as above noted, is pressure tight, whereby the transfer is effected ,without exposing the cans to the atmosphere and without interchange of pressures between the cooker and cooler.

In the embodiment shown in Figures l and 2, the cooler is closed at the bottom by the head 23, but its top is open to the atmosphere. Within the cooler shell 22 and extending around its inner circumference is a fixed helically directed rail or rcan track 24, forming a continuous shelf upon which thev cans are received and advanced upwardly through the cooler from the inlet valve 1 to the point of discharge, where they are removed from the cooler by the rotating star wheel 25, which need not be pressure tight since the interior of the cooler is open to the atmosphere. The cans are advanced upwardly along the can track 24 by a rotatable reel 26, supported by a reel shaft 21 and provided with a peripheral series of pusher bars 28, extending longitudinally of the reel axis and preferably formed of angle iron, so as to engage and advance the cans while simultaneously assisting to support them on the can track 24. The reel shaft 21 is driven in the direction indicated by means of the gear 29 interm'eshing with the valve p'inion 2U.

As the cans emerge from the valve 1 into the cooler shell 22, they are relieved from the external pressure to which they have theretofore been subjected in the cooker and, consequently', it is necessary that a pressure be applied' in the cooler which will suflciently oppose the internal pressure Within the cans to preclude overstraining the can heads.

It is contemplated that such pressure may be applied either by compressed air or by the hydrostatic pressure .of abody of cooling liquid, but` since it is necessary to provide for the application of diminishing pressuresto the cans during their progress through the cooler, it will be seen that if compressed air were to be used it would be necessary todivide up the cooler into a plurality of separate compartments and maintain a different air pressure in each one. By utilizing ,liquid pressure, however, such construction is not necessary as the diminishing pressure' required may be applied simply by elevating the cans through the liquid.

Preferably, therefore, the 'pressure is supplied by a body of cooling liquid'30 beneath the surface of which the cans are introduced by the valve 1, andr through which they are elevated as the cooling progresses, at such a rate as to prevent variation between the pressures internally and externally of the cans to a suicient extent to force cooling liquid into the cans past the can seals, the speed of the reel being suitable for this purpose.

I have found that when the steam filled pockets of the transfer valve are brought into communication with the cooling liquid in the cooler, the initial inrush of liquid in to the pockets causes the steam to be rapidly condensed, and under cer-y tain conditions, as for example where the apparatus is operating at reduced speed, this condensation may result in producing a vacuum in the valve pockets for a brief instant before the pocket completely fills with cooling liquid. This sudden decrease in external pressure,'even though only momentary may result in overstraining of the can heads by the internal pressures within the cans, and to avoid this I provide, as shown in Figs. l and 2, a` pipe 3| leading from any suitable source of air pressure, and communicating with the interior of the valve casing 32 so as to communicate with the valve pockets at an intermediate point intheir travel from the cooker to the cooler. By the introduction of sufficient air into the pockets by way oi the pipe 3| just prior to the time they are brought into communication with the cooling liquid, excessive loss of pressure due to steam condensation is avoided.

The proper amount of air to be introduced into the valve pockets by way of the pipe 3| will depend upon operating conditions, as for example, the steam pressure in the pockets, the temperature of the air introduced, the internal pressures in the cans, and the strength of the cans, but as an illustrative example, assuming that the internal pressure within the cans entering the transfer valve 'l to be 35 pounds per squareinch, the steam pressure in the cooker 15 pounds per square inch, and that the'can seals will safely withstand a pressure of not more than 30 pounds per square inch, then if the pipe 3| carries an air pressure of 25 pounds per square inch, sufficient air will be introduced into the valve pockets to raise the pressure within them from 15 pounds per square inch to 25 pounds per square inch. When the pockets are then presented to the cooler it has been found that the condensation of the steam in the pocket causes a momentary drop in pressure of only about 20 pounds, thus leaving` enough pressure externally of the cans to prevent overstrain inthe moment before the liquid from the cooler completely fills the pocket. Asksoon as the pocket is fllledwith liquid the pressure becomes the same as that in the cooler.

It will be understood that the particular nu-v merical example given above is illustrative only, and under some conditions the amount of air required to be introduced into the vlave pockets in order to prevent excessive loss of pressure from steam condensation when the pockets are/presented to the cooling liquid may not necessarily have to be suicient to increase the pressure in lthe valve pockets, depending upon particular operating conditions.

For example, under some conditions, the introduction of the air into the steam filled valve pockets may result in more or less condensation of steam, depending uA en the relative temperature of the air introduced, and the extent of such condensation may be' such ,that it would not be necessary to increase the pressure in the valve pockets i'n order to mix sufficient air with-the steam to prevent excessive loss of pressure in the valve pockets from steam condensation when the pockets are presented to the cooling liquid. It will thus be seen that the quantity of air required to be introduced by way of the pipe 3| will largely depend upon the operating conditions of .each individual case, the essential requirement being that sufficient air be mixed with the steam in the pockets to insure, that condensation of the steam when the pockets proper pressures to the incoming cans.

are presented to the cooling liquid will not result in sufficient loss of pressure to permit overstraining of the cans by force'of' internal pressures within them.

'I'he modification disclosed in Fig. 4 illustrates an alternative method of providing against loss of pressure in the transfer valve. Referring to that figure, the drain pipe Illa communicates with the interior of the cooker at'a point slightly above the top of the valve casing 32 so as to maintain a body of liquid in the bottom of the cooker to a level just above the valve. 'I'he liquid may be introduced as desired by a valve controlled pipe 33 although condensation of steam will materially assist in maintaining the liquid to the proper level. Overow is cared for by the pipe Illa controlled by a valve ||a similar to valve Il.

By the construction just described, as illustrated in Fig. 4, the air pipe 3| may be dispensed with since the pockets of thel valve 1 iillwith liquid from the cooker thereby maintaining the pressure externally of the cans during transfer without danger of the creation of the vacuum condition when the pockets open into the cooler as in the case when the pockets are filled with steam.

The proper depth of cooling liquid to be maintained within the lcooler will depend upon the circumstances of each individual case, but in any event the pressure exerted by the liquid at the point where the cans are introduced into the cooler must be at least sufficient to overcome the internal pressure of the cans to such an extent as to preclude overstraining of the can heads. It will be obvious that the pressure thus required duce a pressure on Vthe incoming cans suiicient to prevent overstraining the can heads, it will be -understood that it may be increased if desired without injury to the cans or heads up to a point where the pressure applied to the incoming cans equals their internal pressures, or even beyond this point, although preferably not far beyond. vSince it is desirable to maintain the lspeed of the cooler at a rate correspondingwith other machinery in the canning line, it will be seen that by varying the depth of liquid between the limits mentioned, a corresponding range of reel speeds is available, while at the same time applying The range of permissible reel speeds may also be increased to some extent by varying the rate of circulation of the cooling liquid, which -is introduced by means of the spray pipe 34 and overflows by way of the overflow pipe 35, thus varying the rate of cooling.

It will be noted that the cooler is constructed tall enough sothat a substantial portion of the travel of the cans will be above the average liquid level, and this is to provide for variations in liquid level according to requirements, and also to provide forla portion of the cooling by liquid sprays.

As heretofore pointed out, on account of the preliminary exhausting of the cans prior to sealing them, the pressure within the cans will be reduced to atmospheric at some time prior to completion of the cooling process and, Consequently,

CTI

if it can be avoided; since such pressure only adds to the strain on the can seals, to which they are thereafter subjected by the vacuum obtaining within them. For this reason, it is ordinarily desirable, if possible, to complete the cooling of the cans after they emerge from the cooling liquid under atmospheric pressure, and in the cooler illustrated in Figs. 1 and 2 this is accomplished by applying to the cans after they emerge from the cooling liquid, and during the balance of their travel through the cooler, sprays of cooling water directed downwardly onto the cans from the annular spray pipe 34 arranged at the top of the cooler directly over the can track 24.

As each pocket of the valve 1 comes into registry with the can inlet of the cooler and discharges its can therethrough, it will be seen that l the pocket lls with cooling liquid from the cooler,

which liquid would be carried around and discharged into the cooker unless some means were provided for its disposal. The continuous discharge of the cooling liquid into the cooker by the valve pockets would lower the cooker temperature and necessitate an excessive consumption of steam in order to keep the cooker interior at the desired temperature and pressure, and in order to avoid this a drain pipe 36 communicates with the lower portion of the valve casing 32. surrounding the valve 1 whereby to drain the valve pockets of liquid carried out of the cooler, and prevent its introduction into the cooker.

From the foregoing description it will be understood that in operation the cans of filled product, after being sealed, are successively delivered into the cooker A by the inlet valve 5, and after passing through thecooker, within which they are subjected to the required heat treatment under proper pressure, they are transferred, without detrimental relief of pressure, into the cooler B by the pressure tight valve 1.

Within the cooler a minimum depth of liquid will be maintained such as to apply suiicient pressure externally of the cans entering it from the valve 1 to preclude overstraining the can heads by internal pressure. For example, suppose the pressure within the cans entering the cooler to be 35 pounds per square inch above atmos pheric, and that the can seals will withstand a pressure of not more than 30 pounds per square inch with safety under such conditions, the minimum depth of liquid maintained in the cooler would be such as to exert a pressure of at least 5 pounds per square inch 4externally of the incoming cans, thus requiring a minimum depth of approximately 11% feet of water above the can inlet; assuming water weighs .433 pound per square inch per foot of head.

As hereinbefore noted, this depth may be increased if desired so as to allow for changes in reel speeds; although I prefer not to increase the depth materially beyond that which would apply a pressiu'e to the incoming cans equal to their internal pressures, for the reason that the can seals are generally more easily loosened by excessive external pressure than by excessive internal pressure, particularly before the seals have finally become set by cooling.

As the cans are passed into the cooler they are received upon thev helical can track 24 and advanced upwardly therealong by the pusher bars '28 at a rate such as to insure decrease ci the liquid pressure at a suiiicient rate to prevent such variation between internal and external pressures as would overstrain the cans. 'Ihat is to say, the cans should be elevated fast enough to decrease the liquid pressure to such extent that it cannot overstrain the can seals by reason of the decrease in internal pressures and thus force cooling liquid into the cans, and slow enough so that the liquid pressure will not be relieved 5 suiiciently to permit overstraining the can heads by force of internal pressures. The specic pressures represented by these limits will, of course, Vary according to conditions in each individual instance, being dependent upon the liquid depth, l the rate of cooling, and the strength of the cans and seals, and any speed between such limits may be selected as desired. Preferably, although not essentially, that speed should be selected between these limits which will bring the cans out of the l liquid into the atmosphere above at about the time the internal pressures reach atmospheric, and in practice it is also desirable to select a speed in accordance with the speeds of other machinery in the canning line. It will be seen that by regulating the depth of the liquid within the permissible limits above stated, or by varying thc rate of cooling as, for example, by varying the rate the fresh cooling'liquid is delivered by the spray pipe 34, a wide variety of speeds is 25 available to choose from, according to requirements.

After the cans emerge from the cooling liquid, and during the balance of their travel through the cooler, they are subjected to atmospheric pressure and the cooling is completed by the application of sprays of cooling liquid issuing from the spray pipe 34.

t is believed that the superiority of the above described method and apparatus over those previously known, as well as the many advantages resulting from their use will now be apparent. By providing for a reduction in the pressure applied externally of the cans during the cooling process it is possible to apply to the cans at the start of the cooling suilcient pressure to prevent overstraining their heads from internal pressures, while at the same time overstraining the seals during the latter part of the cooling process, with resultant spoilage, is avoided. Also, by applying the pressure medium in the form of a body of cooling medium, through which the cans are elevated during cooling, the proper reduction in pressure is readily and effectively accomplished, and makes possible the use of a greatly simplied cooling apparatus. As may be seen, where the pressure is applied by liquid instead of compressed air, a lighter cooler shell may be used, and the necessity of providing pressure tight bulkheads is dispensed with. Furthermore, no compressor mechanism or pressure control apparatus is required, and a pressure tight discharge valve is not necessary.

Although where possible I prefer to operate the cooler under atmospheric pressure, it should be understood that the principle of the invention is not limited thereto, but may be employed also to advantage in combination with the use of air pressure to augment the liquid pressure. Thus it may be found desirable in some instances to apply air under pressure to the surface of the cooling liquid as for example, where it is desired to increase the pressure applied to the cans entering the cooler without necessitating an increase in the height of the cooler to the extent which would be required if the increase in pressure were to be provided entirely by liquid pressure alone.

In the modication illustrated in Fig. 3, there is illustrated the tcp of a cooler 31 identical with that shown in Figs. 1 and 2, except that 75 Aso provision is made for operation either under atmospheric pressure or under pressure above atmospheric. The top of the cooler is closed by a head 38 so as to provide a closed cooling chamber, which may be opened to the atmosphere through the pipe 39 by opening the valve 40, or may be maintained under air pressure above atmospheric by closing the valve 40 and opening valve 4I to admit compressed air from the pipe 42. The discharge valve 43 is similarto the valves 5 and 1, being pressure tight for obvious reasons.

'Ihe operation of the1modiiied form' of cooler, when opened to the atmosphere through the pipe 39, is thesame as that illustrated in Figs. 1 and 2.

When it is desired, however, to increase the pressure applied to the incoming cans -to such an extent as would necessitate an increase in the height of the cooler, if the pressure were entirely supplied by liquid pressure, this may be done if desired by closing the cooler to the atmosphere and admitting compressed air from the pipe 42. In suchevent irais important thatthe maximum air,v pressure admitted be not more than may safely be applied to the cans when they have cooled suffciently for discharge from the cooler. For example, if it is desired to apply a pressure of 10 pounds per square inch to cans entering the cooler and such cans have been exhausted prior to sealing so as to provide a vacuum within them, after being cooled, of '7 pounds per square inch below atmospheric, the air pressure applied to the surface of the liquid should not be more than 3 pounds per square inch above atmospheric, assuming that the can seals will withstand not more than 10 pounds per square inch with safety. The minimum depth of liquid above the can inlet would thenbe that required to supply '1 pounds per square' inch pressure or approximatelyV 16 feet,

whereasif liquid pressure alone were to be used,'.

without the air pressure, the liquid depth required would be approximately 23 feet. The use of the air pressure to augment the liquid pressure thus makes it possible to use a cooler approximately 7 feet shorter than if liquid pressure alone were relied upon. A

As may be seen,..the rate of advance ofthe cans through the cooler, and the depth of liquid necessary, are determined in the same manner where the air pressure is used as in the case where the cooler is operated open to the atmosphere, except that the depth of liquid required may be reduced according to the air pressure utilized, and variation of reel speeds may be made` as before.

It should be noted that Where the cooler is operated under air pressure in the manner just described it is also advantageous to carry out the latter portion ofthe cooling by liquid sprays as it is when the cooler is operated under atmospheric pressure. This is for the reason that if for any reason any of the canfseams should temporarily weaken under the air pressure, there is less chance of recontamination by the spray liquid which, being taken from the city mainsfis relatively pure as compared with the body of cooling liquid in' which the cans are submerged. 1

It will be understood that the invention vis not limited to the employment of the particular numerical examples stated, which are given for pur-f posesof illustration only, but may be varied according to requirements'in accordance with the principle of the invention as hereinabove ex plained.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by. Letters Patent is:

1. The method of processing foodstuffs in sealed containers which comprises` sterilizing the same by heat treatment applied under pressure above atmospheric, then subjecting the containers to a cooling medium while exposing them to pressure above atmospheric, and reducing the external pressure on the containers during the initial portion of the cooling period at such a rate as to prevent overstraining of the container seals by such pressure.

2. The method of processing foodstuffs in sealed containers which comprises subjecting the containers to heat treatment under external pressure above atmospheric, then, transferring them while under pressure into a cooling medium having a pressure sumcient to prevent overstraining of the containers by differences of internal and external pressures, and graduallyreducing theA pressure of the cooling medium during the initial portion of the cooling period at a rate suiiicient to prevent overstraining of the can seals by differences between internal and external pressures.

3. 'The method of processing foodstuffs in sealed containers which. comprises subjecting the con-- tainers to heat treatment under external pressure 25 above atmospheric, then transferring them while under suchvexternal pressure intoa liquid cooling medium at a point sufficiently below the surface thereof so that the pressure applied by the liquid at such point will be sufficient to preventV overstraining of the containers by dierences of internal 'and external pressures, and gradually reducing the external pressure on the containers as i the cooling progresses by passing them through a path extending upwardly from the point of inlof the liquid at such a rate as toprevent overstraining the can seals by differences between internal and external pressures.

4. The method of processing foodstus in sealed troduction of the containers .toward the surface containers which comprises subjecting the containers to heat treatment under external pressure above atmospheric, then'transferring them while under such external pressure into aliquid cooling medium at a point sumciently below the surface thereof sovthat the pressure appliedby the liquid at such point will be suicient to preventv overstraining of the containers byforce of internal, pressure, and gradually reducing the external pressure on the containers as the cooling progresses by passing them through a path extending upwardly through the liquid from thejpoint of introductionof the containers toward the surface of the liquid.

5. The method of processing Afoodstuiis in sealedl containers which comprises subjecting the containers to heat treatment under steam pressure above atmospheric, thentransferring said containers while under steam pressure into -a body of cooling liquid at a pointl below the surface thereof, maintaining sufficient pressure externally of the containers during transfer to prelil der steam pressure into a liquid cooling medium at a point below the surface thereof, and mixing suiiicient air with the steam applied to the cans during transfer to prevent excessive loss of ex- -containers to heat treatment under steam pressure above atmospheric, isolating said containers from the heating zone and transferring them into a body of cooling liquid at a point below the surface thereof while maintaining them under steam pressure sufiicient to prevent overstraining the cans by differences between internal and external pressures, and mixing sufficient air with the steam applied tothe cans during transfer to prevent excessive loss ofvexternal pressure from steam condensation when the containers are presented to the cooling liquid.

8. The method of processing foodstuffs in sealed containers which comprises subjecting the containers to heat treatment under pressure above atmospheric, isolating said containers from the heating zone, and transferring them while so isolated into a body of cooling liquid at a point below the surface thereof and maintaining said containers under liquid pressure suicient to prevent overstraining of the cans by differences between internal and external pressures during the transfer.

9. The method of processing foodstuffs in sealed containers which comprises sterilizing the same by heat treatment applied under pressure above atmospheric, then subjecting the containers to a cooling medium while exposing them to pressure above atmospheric, partially cooling the containers, reducing the external pressure to atmospheric throughout the period of such partial cooling at such rate as to prevent overstraining of the container seals by the difference between internal and external pressures, and then continuing the cooling by the application of a cooling medium while exposing the containers to atmospheric pressure.

10. The method of processing foodstulfs in sealed containers which comprises subjecting the containers to heat treatment under pressure above atmospheric, then transferring them while under such pressure into a liquid cooling medium at a point sufficiently below the surface thereof so that the pressure ap- ,plied by the liquid at such point will be suiiicient to prevent overstraining of the containers by force of internal pressure, partially cooling the containers while gradually reducing the external pressure on them by passing them through a path extending upwardly from the point of introduction of the containers through and out of the liquid, and completing the cooling of the containers after they emerge from the liquid by the application of a cooling medium while exposing the containers to atmospheric pressure.

11. The method of processing foodstuffs in sealed containers which comprises sterilizing the same by heat treatment applied under pressure above atmospheric, then transferring them while under such pressure into a liquid cooling medium at a point sufiiciently below the surface thereof so that the pressure applied by the liquid at such point will be suicient to prevent overstraining of the containers by force of internall pressure,

partially cooling the containers while graduallyreducing the external pressure on them to at- `while exposing the containers to atmospheric pressure.

12. The method of processing foodstuifs in exhausted sealed containers which comprises sterilizing the same by heat treatment applied under pressure above atmospheric, then subjecting the containers to a cooling medium while exposing them to pressure above atmospheric, reducing the external pressure during cooling to reach atmospheric at approximately the time the internal pressures of the containers have been reduced to atmospheric, and then completing the cooling by the application of a cooling medium while exposing the containers to atmospheric pressure.

13. An apparatus for cooling canned goods comprising a shell, means for maintaining a body of cooling liquid in said shell, a can inlet in said shell below the level of the liquid, a can outlet in the shell above the inlet, and means within the shell for conveying cans along a path extending upwardly through the cooling liquid from the inlet to the outlet.

14. An apparatus for cooling canned goods comprising a vertical shell, means for maintaining a body of cooling liquid therein, a can inlet in said shell below the level of the liquid, a can outlet in the shell above the inlet, a helical can track within the shell extending upwardly through the cooling liquid from the can inlet to the can outlet, and means fon advancing a procession of cans upwardly along the can track from the inlet to the outlet.

15. An apparatus for cooling canned goods from the inlet to the outlet.

16. An apparatus for processing canned goods comprising a pressure cooker, a cooler having a can inlet in its lower portion, means for transferring cans from the cooker to the cooler inlet without relief from pressure, means for maintaining a body of cooling'liquid in the cooler of a depth above the inlet such as to exert suil'icient external pressure on cans introduced therethrough to prevent overstraining the cans from internal pressure, a can outlet in the cooler above the inlet, and means Within the cooler for conveying cans upwardly through the cooling liquid from the can inlet to the can outlet.

17. An apparatus for processing canned goods comprising a pressure cooker, a cooler having a can inlet in its lower portion, a pressure tight valve for transferring cans from the cooker to the cooler inlet while under pressure, means for maintaining a body of cooling liquid in said cooler to a depth 70 inlet, and means within the cooler for conveying 75 the cans upwardly through Ythecooling liquid from the can inlet to the can outlet at a rate suflicient ,t6 prevent overstrainingthe can seals by differences between internal and external pressures.

18. An apparatus for processing foodstuffs in sealedcontainers comprising a pressure tight cooking chamber, means for introducing steam under pressure into said chamber, a cooling chamber having acontainer inlet, means for maintaining a bodyv of cooling liquid in the cooling chamber to submerge the container inlet, a pressure tight pocketed valve for transferring containers under steam pressure from the cooking chamber to the container inlet of the cooling chamber, and means for introducing air under pressure into the'valve pockets as they trav'el from the cooker to the cooler.

19. An apparatus for processing foodstuffs in sealed containers comprising a cooking chamber having a container inlet and a container outlet, means for maintaining a body of liquid in said cooking chamber to submerge the container outlet, means for conveying cans through the cookA ing chamber from said inlet to said outlet, a cooling chamber having a lower container inlet and an upper container outlet, means for maintaining a body of cooling liquid in the cooling chamber to submerge its container inlet, means for conveying containers upwardly through the cooling chamber from its inlet to its outlet, and-a pressure tight valve for transferring containers from the outlet of the cooker to thev inlet of the cooling chamber.

20. An apparatus for cooling canned goods comprising a shell, means for maintaining a body of cooling liquid under atmospheric pressure therein, a can inlet in the shell below 4the level of the liquid, a can outlet in the shell above the surface of the liquid, means Within the shell for conveying cans upwardly through the cooling liquid from l the can inlet to the can outlet, 'and means for spraying cooling liquid against the cans during their passage from the surface of the liquid to the can outlet.

21. An apparatus for processing foodstuffs in sealed containers comprising a cooking chamber,

means for heating said chamber, a cooling chamber, means for maintaining a body of cooling liquid in said cooling chamber, a pocketed prese sure tight valve connecting said chambers whereby to transfer containers from the cooking chamber into the cooling chamber at a point below the surface of the cooling liquid, and means for freeing the valve pockets of liquid carried out of the cooling chamber to prevent its introduction into the cooking chamber.

22. The method of processing foodstuffs in sealed containers which comprises subjecting the the containers to heat treatment under external pressure above atmospheric, then transferring them while under such external pressure intova body of liquid cooling medium at a point below the surface thereof, and gradually reducing the pressure applied to said containers by said cooling liquid throughout the period of submergence of said containers therein by passing the containers through a path extending upwardly through the liquid from the point of introduction of the containers toward the surface .of the uquid. l v Y 23. In a method of processing hermetically sealed canned goods wherein the cans are subjected to heat treatment of such character as to generate pressures internally of the cans in exy, to reduce the pressures internally of the cans to within the normal strength of the can seals, and reducing the pressure applied externally of the cans during the said cooling period at such rate relative to the rate of reduction of the pressures internally of the cans as to maintain the difference between the internal and external pressures within the normal strength of the can seals.

24. In a method of processing hermetically sealed canned goods wherein the cans are subjected to heat treatment of such character as to generate pressures internally of the cans in excess of the normal strength of the can seals, while applying pressure externally of the cans sufficient to prevent overstrain of the can seals by internal pressures, the steps of maintaining such external 25 pressure on the cans while passing them into a liquid cooling medium at a point below thesurface thereof where the pressure applied to the cans by the liquid is sulcient to prevent overstrain of the can seals by internal pressures, subjecting the cans to the cooling effect of said liquid cooling medium for a sufficient length of time to reduce the pressures internally of the cans to within the normal strength of the can seals, and reducing the pressure applied externally of the cans during the said cooling period by passing the cans upwardly through the cooling liquid at such a rate relative to the rate of reduction of the pressures internally of the cans as to maintain the difference between the internal and external pressures within the normal strength of l the can seals.

25. In a method of processing hermetically sealed canned goods wherein the'cans are sub- 45 jected to heat treatment under externally applied pressure above atmospheric', thereby generating pressure internally of said cans, the steps of thereafter subjecting said cans to a cooling treatment under externally applied pressure above atmospheric, and progressively reducing the pressure applied externally of the cans during the cooling treatment at such rate as to prevent overstraining of the can seals by differences be tween the pressures internally and externally of the cans. A

26. In a method of processing hermetically sealed canned goods wherein the cans are subjected to heat treatment under externally applied pressure above atmospheric, thereby generating pressure internally of said cans, the steps of thereafter subjecting said cans to a cooling treatment under externally applied pressure above atmospheric,` and progressively reducing the pressure applied externally of the cans during the 65 cooling treatment in such relation to the 'reduction of pressure internally ofthe cans as to prevent overstraining of the can seals by differences between the pressure internally and externally of the cans;

27. In a method 'of processing hermetically sealed canned goods wherein the cans are subjected to heat treatment under externally applied pressureab'ove atmospheric, the steps of thereafter `transferring said cans while under such external pressure into a cooling liquid at a. point sufliciently below the surface thereof so that the pressure applied to the cans by such liquid is sufficient to prevent overstraining of the. can seals by differences between the pressures internally and externally of the cans, and progressively elevating the cans through said cooling liquid during cooling of the cans thereby to reduce the pressure applied to the cans by said liquid at such rate as to prevent overstraning of the can seals by differences between the pressures internally and externally of the cans.

ALBERT R. THOMPSON.

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