US2209315A - Method of canning - Google Patents

Description

July 30, 1940. c. o. BALI.

METHOD OF CANNING Filed May 26, 1938 2 Sheets-Sheet l Nw K mw E Aww w/ Q July 30, 1940. c. o. BALL METHOD OF CANNING Filed May 26, 1938 2 Sheets-Sheet 2 ATTORNEY a www mm ""y 3 94 A. 2,209,315

UNITED STATES PATENT GFFICE METHOD OF CANNING Charles 0. Ball, Oak Park, Ill., assignor to American Can Company, New York, N. Y., l. corporation of New Jersey Application May 26, 1938, Serial No. 210,281

s claims. (ci. 99-182) The present invention relates in general to an food products, for example, can be carried out improved method of canning and has particular without high temperatures where the treatment reference to protecting a product of liquiform takes place in a chamber having a sub-atmosor of discrete particle nature against bacterial phere. The eiective value oi heat at any re- 5 or other contamination while the same is being duced temperature, under such conditions, will 5 subjected to steps of treatment as for example depend upon the absolute pressure of the chamduring or following sterilization, storage, hanber pressure. This makes it possible to heat treat dling or other procedure incident to canning. a product by steam at a temperature lower than In some respects the invention is an improve- 212 F. which is the temperature of saturated Y ment upon my Patent 2,029,303, issued by the steam at normal atmospheric pressure. Some 10 United States Patent Oiiice on February 4, 1936. products Will retain their taste, color or other In my former patent which treats of sterilizing characteristics much better at the lower tema product, sterilizing a. can and also a cover and peratures of steam made possible by the reduced introducing the treated product into the can and chamber pressure.

l5 sealing the product in the can, provision is made An object of the present invention is the pro- 15 for handling the sterilized product and can parts vision of a method of treating a product under in an enclosed chamber or chambers the interiors sterile conditions by introducing it into an inner of which are maintained under a pressure greater sealed chamber `wherein there is maintained a than the atmospheric pressure outside of the chamber atmosphere of desired absolute pressure chambers so that contamination of the interior less than normal atmospheric pressure, there also 2o walls of the chamber as wen as contamination of being provided a Surrounding conned and concan orproduct passing therethrough will be pretrolled atmosphere of less preSSllre S0 that DOS- vented even though there may exist leaks in the sible contaminetiOn 0f the Dl'OduCt While Within apparatus. the inner chamber is entirely eliminated.

In the present invention provision is made for A further object is the provision of a method 25 utilizing an interior treating chamber pressure 0f treating a Sterile product which includes 00nless than normal or outside atmospheric pressure trol of a created atmosphere exterior to a treatand insuring at all times an additional controlled ing Chamber so that il.' there are any leaks in the surrounding atmosphere just exterior to the treating chamber walls no contamination from chamber. This controlled atmosphere is at less the outside will enter through the leaks because 3o pressure than any pressure existing within the gases, vapors, etc., will only pass through the treating chamber. With this condition prevailleaks outwardly from the treating chamber. ing at al1 times should there be leaks in the ap- Another Object 0f the inVeIltiOn iS the DIO- paratus, bacteria or other types of contamination vision of such a method wherein contamination could notenter the treating Chamber as any exfrom the Outside iS prevented in 8. manner which 35 change of pressure would always be outward, that permits a continuous stream or flow of the prodis, from the interior of the treating chamber to uct through the chamber.

the surrounding conned atmosphere and there- Still another Objectis the provision ot a method fore the outside normal atmosphere will not be 0f evaporating a liquid within a vammlmv cham- 4o involved. ber, the chamber being protected against cono This provision in addition to overcoming any tamination by a surrounding protecting conned evils which might occur by leaky chamber Walls chamber or jacket which is at 9,11 times held permits much more latitude of treatment within under a absolute pressure loss than that obtaim the chambers themselves. In other Words, the ing in the vaouum chamberpresent invention contemplates a treating cham- Yet another object is the provision of a method 5 ber, which may be subjected to a high vacuum of stemming and comme a produot by stormzmg instead of pressure, as in my patent referred to the product then mung it into cam either be above, and when cans and product are brought into or discharged from the vacuum chamber fore or after complete sterilization, then transporting the partially or fully sterilized product iglstiggldanger of entrance of bacterial con While within a can through a sealed ch r and Treatment o! a product is often desirable in hermetiCa-lly Sealing the een while Still Within a chamber having a sub-atmosphere, i. e., one the Chamber Which i8 Protected against Contamihaving an absolute pressure below atmospheric nation by enclosure of thachamber, the chamber pressure. Steam heat treatment of sterilized being entirely confined within a jacket mainu i tainedvat an absolute pressure less than the pressure existing within the chamber.

Anotherobject is the provision -of a method .of handling a food product after its sterilization and after its cooling whenl sterilized by heat,

which includes a treating chamber adapted to any tendency to equalize pressures Vas through wall leaks, entrance or discharge openings will ',result in an outward flow from the treating chamber and never an inward ilow into the chamber'thus preventing any entrance of contaminating elements.

A further object is the provision of a method o'f canning a discrete 'particle productl'by heat lsterilizing and cooling the product, sterilizing a can to receive the product, sterilizing a can cover, illling the product into the can and hermetically `sealing by uniting can and cover, the lling oi' the product into the sterilized can andits sealing being carried out within one or more treating chambers maintained at less thanA normal atmospheric pressure, the treating chambers be'- ing' surrounded by a protecting jacket 4which is at all times held under an absolute pressureless vthan the pressure within the treating chambers to prevent contamination of. the product at any stage of its treatmentwhile within the chambers.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which,

taken in connection with the accompanyingA drawings, discloses a preferred embodiment thereof.

vReferring to the drawings:

Figure l is a schematic view illustrating a series of interconnected mechanisms for performing various steps in the treatment of a product which in one case is of liquiform nature or as in another case of the discrete particle type and illustrating the manner of protecting the treating chambers by surrounding jackets coniining a space which is'maintained under vacuum;

Fig. 2 is an enlarged sectional view taken substantially along the line 2-2 in Fig. l parts being broken away;

'Fig 3 is av fanciful sectional view taken substantially along the line 3-3 in Fig. 1 and illustrating the means of protecting one of the valve openings associated with the can sterilizer; and

Fig. 4 is a transverse sectional view of the discharge valve of the apparatus illustrating the protection of the valve surfaces against contamination, this view being taken substantially along the line 4--4 in Fig. l.

The invention contemplates the passage oi a Vflood product or the like through a treating*l chamber, the drawings illustrating an initial step of sterilization and showing alternate treatments for a product of a liquiform nature and one consisting of discrete particles. When the sterilization of a discrete particle product is taking place some of the mechanism which applies only to liquiformv products is closed off from operation aaoasis L cans may receive the` product 'and the iilled cans. are shown as being hermetically sealedby double seamed covers. The drawings falsoV show, as exemplary of treating steps.. th'steriliz'ation o f the empty cans as'well as the covers. 'fIfhepresent`- invention is directed specifically to conditionsapplying to a treating chamber and "therefore lit is only incidental whether'a canisl'used'durln'gl the treatment. If the -product is not 'to be put into a can obviously the treating vchamber will be slightly changed to meet whateverconditions obtain. i

ioff' The connecting passageways betweenthe vvaril I ous chambers or sections'of. the same chamber provide for a sealed space for treatment of prod l uct as desired and provision is made for venclosing the walls of the chamber vor chambers with a. surrounding jacket. The `space within this jacket may be connected'with` a source of vacuum 1 so that the pressure obtained withinthe space can be held at all times under a less absolutev pressure than the pressure used in the treating chamber or chambers.

The enclosing jacket, as vwill be hereinaftermore definitely shown ln detail, is 'coextensive with any outside wall part of the treating chamber so that entrance of. contamination-from the For the purpose of more clearly illustrating the various steps of the present invention ref- 'erence should be had to Fig. 1 which represents schematically the principal parts ofran apparatus for carrying out these steps. In the description which follows consideration will rst be given to the treatment of a product of the discrete particle type.

The product is or may be iirst introduced'into a hopper 2| of a product sterilizing apparatus 22. In this consideration of a discrete product, garden peas will be taken as an example an these are designated by the numeral .23. This product passes from the hopper and through the sterilizing apparatus after which, if thesterilization consists of a heat treatment, the sterilized product moves downwardly from the sterilizing apparatus 22 and enters a cooling device 24. This device 24 discharges a sterilized and cooled product through a. passageway 25 which extends from one side of the cooling device. A manually operated gate valve 26 is introduced in the passageway 25 and is used to seal off the passageway when this part of the apparatus is not being used. The passageway 25 leads to a. viillingchamber 21 where it is introduced into cans preparatory to entering the treating chamber.

'I'he cooling device 2 4 is surrounded by'an outer spaced wall 28 which also extends'around the passageway 25 and furthermore encloses the gate valve 26. 'Ihis spaced Wall encloses a protecting jacket 29 and provides an enclosure for the entire cooling operation as well as thepassageway 25. Only the operating hand wheel-of the gate valve 26 extends outside of the jacket Wall 28 and provision is made for packing this joint so that there will never beany means of entrance of contamination into the cooling chamber or into the passageway 25.

aaoasis A The hopper section and the sterilizing device may be provided with live steam and steam pipes 35 are provided for this purpose. The protecting chamber 29 surrounding the cooling device 24. the gate valve 25 and the passageway 25 are adapted to be maintainedunder a desired vacuum low casing or series of casings 4|.

which at all times is less in absolute pressure from that existing inside the cooling chamber and inside the passageway 25. Vacuum pipes 3l may be used for this purpose.

'I'he filling chamber 21 is contained within an inner housing 32, and an outer spaced wall 33 surrounds the chamber in all directions so that a protecting space 34 is provided between thewalls 32, 33 and thisconstitutes a protecting jacket or chamber which is also adapted to be held under a vacuum so that the absolute pressure within the jacket will always be less than that existing in the filling chamber 21. A pipe 35 extends through the outer wall 33, where it is protected by a suitable stuiling box, and into the wall 32. 'I'his permits the entrance of steam into the filling chamber.

While the sterilized and cooled peas 23 are passing into the filling chamberv open ended cans 35 are conveyed along a runway 31 and pass intoA one of a plurality of pockets '33 of a rotary valve 39 mounted on a vertical shaft 45. 'Ihis valve i member constitutes a movable element of a can sterilizing apparatus and is surrounded by a hol- The rst casing, that is, the one through which thevrunway 31 extends, preferably encloses a vacuumizing chamber 42 and connects with a suitable source of vacuum as by means of a pipe 43. As the turret rotates in the direction of the arrow air is withdrawn from the rotary valve pockets 33 and from the empty cans therein as each pocket with its can passes along the chamber.

The casings 4I adjacent that which enclosesthe vacuum chamber 42 enclose steam chambers 44 receiving live steam through a pipe 45. The

4steam chambers 42 are preferably interconnected by means of a pipe 45. During the continued rotation of the valve 39 in the direction of the arrow the empty cans are successively subjected to the steam chambers 44 and upon completion of one rotation of the valve the cans carried thereby are sterilized. I'he chambers 44 may be provided with a drain pipe 41.

v The sterilized cans are thence thransferred from the valve pockets ofthe sterilizer and pass through a passageway 5| which connects with the filling'chamber 21 of the filling apparatus. Each can upon reaching the filling chamber is'engaged by a starwheel 52 which moves it through the filling chamber, putting it into lling position .to receive a charge of the product 23. This fill-` 'ing of the can in the sterile filling chamber takes place under completely aseptic conditions the walls of the chamber completely enclosing the apparatus.

'I'he spaced walls 33 which enclose the filling chamber are extended to the can sterilizer and adjacent the turret 39, these walls spreading out into a rotary turret seat casing 53. The protecting chamber 34 on the insidev of the walls thus extends into this turret seat wall 53 and terminates in an annular opening 54 (see also Fig. 3). 'Ihis opening completely encircles the end of the pasasgeway 5l which is adjacent the turret 39 and thus prevents the entrance of any contamination from the outside into the passageway or into the cans passing therethrough.

vThe lled and sterilized can with its sterilized product is thence transferred through a passageway 55 (Fig. 1) which opens at one end into the filling chamber 21. At the'opposite end the passageway communicates with a chamber 55 in which is located a starwheel 51. The can passing from the passageway 55 is received by one arm of the starwheel 51 and after being swept in a circular path of travel through the chamber 55 is introdu dinto a closing chamber 53.

'Ihe wall 2v which encloses the fillingchamber 21 continues as the enclosing wall for the of steam into these chambers. lWhere these pipes pass through the protecting jacket walls 33 provision is made for suitable stuiilng boxes to prevent any contamination from the outside along the surface of the pipes.

While the foregoing operations are taking place can covers 5I are advanced through a runway 52 and positioned successively into a plurality of pockets 53 of a valve member 54 mounted on a vertical shaft 55. This valve constitutes a movable element in a can cover sterilizing apparatus. The valve 54 is continuously rotated in the direction of the arrow and is completely .enclosed by a casing or a series of casings 55.

In the casing section through which runway 52 extends there is provided a vacuum chamber 51 and a pipe 55 provides a means for evacuating this chamber. As the cover 5I within the turret pocket 53 passesadjacent the chamber 51 air is removed from the pocket and from the surfaces of the cover.

Adjacent the casing containing the vacuum chamber 51 the casing sections 56 enclose steam chambers 59. Steam at a desired temperature may be circulated through the steam chambers 59 by means of pipes 15 the drawings illustrating two such chambers connected together by a suitable steam pipe connection 15.

By the time the turret 54 has made one complete rotation and the covers resting in the tur'- ret pockets have been subjected to the steam Within the steam chambers 59- these covers are in a sterile condition. 'I'he sterilized covers are thence removed through a passageway 1| and positioned into a chamber enclosed in a cover` cooling apparatus 12. The covers pass from the passageway 1I into a pocket of a starwheel 13 mounted on a vertical shaft 14. 'I'his starwheel carries the covers through the cooling chamber of the cooling apparatus.

The passageway 1l and the cooling chamber 12 are enclosed within suitable walls which may be a part of or connected with the chamber iso .into the sealing chamber.

ratus 12, the passageway 1l and extends into the casing 66 of the can cover sterilizer. An annular opening 15 joins with the end of the Jacket space 59 within the casing section 66 (as best illustrated in Figs. l and 3) and this annular space 15 completely surrounds the entrance opening to the passageway 1| adjacent the face of the turret 64.

A suitable cooling medium may be circulated through the cooling chamber of thecooling apparatus 12 as by means of pipes 16 which extend also through the wall 33 where they are suitably packed against contamination from the outside.

The step of cooling a can cover after sterilizing may in some cases be dispensed with but where a plastic sealing compound is used in the covers as a gasket for forming a hermetic seal between cover and can it may be desirable that the can cover be cooled prior to its introduction It is the heat of the steam used in the sterilizer that is extracted in this manner.

The sterilized and cooled covers 6|, in passing from the cooling apparatus 12, travel through a passageway 11 which is formed inside of the chamber walls 32 and which connects the cover cooling apparatus with the chamber 56. This permits introduction of the can covers into the starwheel 51 which loosely places a cover upon each can fed into the chamber 56 through passageway 55. It will be understood that the starwheel 51 may be of double construction so that the lower section of the starwheel will provide for transfer of the can from the passageway 55 into the chamber 58 and the upper part of the into one of the pockets and being conveyed by` starwheel will correspondingly handle the can cover.

The lled cans with their loosely applied covers upon leaving the starwheel chamber 56 pass into the can closing and sealing chamber 58. The numeral 18 designates a suitable closing machine, the seaming head or other part of this machine being fully enclosed within the sealing chamber 58. 'Ihe protecting chamber 59 also extends around the closing chamber 58 and around the sealing mechanism 18 so that at no time will there be any opportunity for contamination to enter into the sealing chamber. Suitable pipes 19 extending into the outer shell 33 of the protecting jacket 59 or its corresponding jacket 34 may provide for vacuumizing this protecting jacket at alltimes.

The filled and sterilized can with its superimposed sterilized cover upon passing into the sealing mechanism 18 within the sealing cham-` ber 58 is hermetically sealed. The hermetically sealed can is thence removed from the sealing chamber by a discharge valve 80 operating in an enclosing housing 8| which joins with the walls 32, 33. The valve 80 comprises a multiple pocket turret 82 mounted on a vertical shaft 83 (see also Fig. 4) the hermetically sealed can passing the valve into a discharge chamber.

Itl will be observed by reference to Figs. l and 4 i that the discharge end of the sealing chamber 58, where it contacts the turret valve 82, is. com- 1 pletely encircled with the protecting chamber 59 Vand the shaft 83 where it extends through thechamber walls is suitably provided with stuif- 1 ingboxes or other means of protection against contamination from the outside. i "The casing wall 8l extends into an elongated housing 85 which encloses the discharge chamthrough a steam pipe 88 and through pipes 89/ leading into both sides of the housing 85. 'The cans upon being brought successively to the plunger 81 are discharged by it from the chamber 88 in any suitable manner.

Consideration will now be given to the alternate phase of treatment of liquiform products and the sterilization and evaporation of milk will be given by way of example. 'I'he sterilized and evaporated milk after this treatment will be brought into the filling chamber 21 and following its receipt the further treatment of the milk will parallel the handling of the garden peas as has. already been fully described as exemplary of a. product of the discrete particle type. Description of this latter or further treatment of milk will therefore not be repeated.

Preparatory to sterilizing and evaporating milk in the apparatus the gate valve 26` (Fig. l) will be fully closed and this shuts off from use the various mechanisms specifically relating to discrete particle products that have already been previously described.

As best illustrated in Fig. 2 the milk may be pumped through a sterilizer 9| where the milk is sterilized as it is forced therethrough. The

milk is rst introduced into the apparatus through A form of sterilizer suitable for sterilization of the milk is herein shown as consisting of a series of circulating heating coils each coil comprising two concentric spaced pipe elements 95 located within a sealed housing 96 the milk being caused to traverse a sinuous path between each pair of concentric pipes. 'I'he pipe walls constitute in this instance heated surfaces. Header members are associated with the ends of the pipes 95 to insure proper transfer of the milk from one set of pipes `to the other. The milk is nally delivered at the top of the housing 98 through a pipe 91.

During the passage of milk through the pipes it is heated to a high temperature receiving its heat through the walls of the concentric pipes. These wall surfaces are preferably heated by steam which is introduced into the housing 96 and which circulates around the exterior of the outer pipe elements and also passes through the inside of the inner pipe of each pair of pipes.Y A pipe 98 leading into the top of the housing may be used for introducing the steam at the proper pressure and temperature to effect the required transfer of heat to the milk.

Since the milk is in a thin film-like form by reason of the close space between the concentric pipes, i. e.,-the pipe surfaces between which the milk passes, it picks up or rapidly absorbs the heat. The housing 96 is also provided with a drain pipe 99 from which condensate may be operates through the condenser.

the housing preferably near the top for venting the space surrounding the heating coils.

The heated milk is thus fully sterilized and is then passed through the pipe 31 into a vacuum pan |05. 'A manually controlled valve |06 may be located in the line 91 to control the amount of milk passing through the discharge pipe 91.

If desired the milk in its passage through the pipe 91 can be cooled to approximately its evap oration temperature before entering the vacuum pan.

'I'he vacuum pan |05 comprises a cylindrical housing |01 which is fitted with a dome-shaped top section |08 and a cylindrical bowl-like bottom |09. A baille plate may be secured to the inner wall of the vacuum pan and is preferably curved to extend over the outlet of the pipe 91. 'I'he milk owing through the pipe and entering the vacuum pan strikes against the baille plate and is caused to discharge properly into the vacuum pan. It will be understood that the milk entering the pan is subjected to the vacuum within and cooling and condensation take place.

'I'he evaporated milk which collects in the 4vacuum pan |05 is designated by the numeral 2. Heat is applied continuously to the body of milk while in the pan to maintain the temperature of the milk at a point where efllcient evaporation takes place. A heating coil ||3 is provided for this purpose which is submerged in the body of the milk on the inside of the vacuum pan, its terminal ends ||4, ||5 extending outside of the pan. Steam at suitable temperature and pressure may be circulated through the heating coi1 a'nd thus impart the required heat to the body of milk in the vacuum pan.

The dome top |08 of the vacuum pan iskconnected to a header pipe |2| which leads into a suitable condenser |22. Any suitable means of evacuating the condenser may be used as by a low vacuum pump 23 which connects with and By means of this pump a desired degree of vacuum may be maintained at all times in the condenser and by its connection with the vacuum pan the desired degree of vacuum will be maintained in the pan.

The evaporated milk'is adapted to be withdrawn from the vacuum pan through a discahrge pipe |25 which connects into a pump |26 by means of which the milk is forced into a filling pipe 21 (see also Fig. 1) which conveys the milk into the filling chamber 21. A hand operated valve |28 is located in the pipe |21 and this controls the amount of milk passing through the pipe.

During the treatment of a discrete particle product being run through the apparatus, the valve |28 would be closed. This valve thus provides the means for shutting off any connection between the filling chamber and the vacuum pan when this part of the apparatus is not in use.

From the time the milk leaves the sterilizer 9| through the pipe 91 and until it passes into the filling chamber 21 as evaporated milk all of the passageways are protected by a surrounding controlled and confined atmosphere. Thus provision is made for preventing any contamination of the product and any contaminating action to the interior of the pipes, vacuum pan, etc., which might be caused by leakage of the apparatus. To insure against such contamination the various pipes and vacuum pan condenser, etc., are enclosed within sealed jackets which may be maintained at an absolute pressure at all times less than the absolute pressure existing in any of the product conveying parts of the apparatus now under consideration.

The vacuum pan |05 is surrounded by a casing |3| (Fig, 2) the walls of which are spaced from the outer walls of the vacuum pan members |01, |08, |09- and an enclosing housing |32 is also provided around the pipe 91 adjacent the vacuum pan. This housing |32 is connected with the housing |3| and provides for intercommunication with a. protecting space |35 which surrounds the vacuum pan and with an auxiliary space |36 which surrounds the pipe 91. The manipulating handle of the valve |06 is extended through the wall of the housing |32 and the stem of the handle is properly packed in a sealed joint to prevent any leakage around the valve stem.

Atubular housing |31 is also provided to surround the header pipe |2| leading to the condenser |22 and this housing is bolted to the vacuum pan housing |3I. A protecting housing |38 is also provided for surrounding the condenser y |22 and this housing is hermetlcally secured to the end of the housing |31. This provides a jacket space |4| surrounding the pipe |2| and communicating on one side with the vacuum pan I outer spaced housing |46 which encloses the discharge pipe |25"and also the pump |28 and this housing provides a confined space |41 surrounding these parts and which communicates with the jacket space |35 of the vacuum pan.

In like manner an enclosing tubular housing 48 is connected with the housing |46 and surrounds the pipe |21. Housing |48 at its inner end is directly connected with the spaced jacket wall 33 surrounding the flllingchamber 21. 'I'he housing |48 encloses a confined jacket space |49 which communicates with the jacket' space |41 at one end and with the protecting space 34 of the filling chamber at the other end.

Where the heating coil \||3 passes into the vacuum chamber of the vacuum pan, the pipes ||4, ||5 are suitably packed and this also applies where they extend through the casing |3| surrounding the vacuum pan. In a similar manner the operating shaft of the pump |26, which is designated by the numeral |5|, is suitably packed where it extends through the wall |46 of the enclosing housing. l

The pump shaft |5| fmay carry a drive pulley |52 to which operating power may be applied in suitable manner as by a drive belt |53. The hand wheel of the valve |28 is located exterior of the housing |48 and where the valve stem extends through the housing wall a suitable packed joint is provided.

By reason of the intercommunication of the jacket chambers |35, |36, |4|, |42, |41 and |48, the entire space surrounding the various units of the evaporating apparatus are confined and may be maintained at a suitable diminished absolute pressure. This creation and maintenance of an artificially controlled atmosphere is ef-y indirectly from all of the other surrounding jacket spaces.

Thev amount of absolute pressure maintained in these jacket spaces is always less than that existing on the inside of the vacuum pan |05 or in the pipes or chambers connected therewith. Thus bacterial contamination is prevented from entering into the product or into the interior of the working parts of the apparatus concerned with heating or sterilization, with evaporation or condensation of the milk. This example of a treatment of milk, which requires a treating chamber at a reduced or sub-atmospheric pressure, emphasizes the advantages of having a confined and` controlled protecting casing surrounding the treating chamber.

It will be evident from the foregoing; that irrespective of whether a discrete particle product is being handled through the apparatus such as peas filled into sterile cans, or whether condensed milk or other liquiform products are being sterilized, evaporated or otherwise treated, that the entire process of any particular stage is such as to fully protect the product against outside contamination. From' a mechanical standpoint where it is necessary for some part to extend through a surrounding jacket wall of a protecting chamber, it will be seen that provision is also made for preventing entrance of bacterial contamination at such a point.

It' will also be evident that in order to insure the maintenance of aseptic operating conditions in the various chambers, passageways, etc., these chambers and other parts will be rendered completely sterile before operation begins. This may be done by treating the chambers with saturated steam under pressure. As an extreme safety measure, the surrounding jackets may also be sterilized before operation begins, although this is not an essential part of the procedure.

With a created, confined and regulated surrounding and protecting atmospher, any pressure desired in any treating chamber may be used irrespective of the normal outside atmosphere. In other words there are no limiting circumstances relating to a desired treatment which cannot be successfully adjusted and used where a protecting zone of controlled atmosphere is available according to the teachings of the present invention.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the steps of the process described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing allv ol.I

its'material advantages, the process hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. A method of canning which comprises passing a sterilized product to be canned into a sealed chamber for treating and sterilizing cans, maintaining about the product and in said chamber a sterile atmosphere having an absolute pressure not greater than that of the natural atmosphere outside of the apparatus, and surrounding said chamber with a confined controlled atmosphere of less absolute pressure than the pressure within said chamber.

2. A method of canning which comprises passchamber, sterilizing the product, passing the sterilized product into a can 'filling chamber, maintaining about the product and the can parts in said filling chamber a sterile atmosphere having absolute pressure not greater than that of the natural atmosphere outside of the apparatus, and surrounding said filling chamber with a confined atmosphere of less absolute pressure than that of said lling chamber during said product treatment.

3. A method of canning which comprises passing a sterile product to be canned into a sterile fillirg chamber, passing a sterile can into said filling chamber, filling the product into the can while in said filling chamber, transferring the filled can into a sterile can closing chamber, hermetically sealing the filled can, and surrounding said closing and filling chambers and the intercommunication therebetween with a confined sterile atmosphere of less absolute pressure than that in any of said chambers during said product treatment.

4. A method of canning which comprises passing a product to be canned into a heat treating chamber, passing said product into a cooling chamber, passing a can through a sterilizing chamber to sterilize the can, passing a can cover through a sterilizing chamber to sterilize the cover, transferring the sterilized can into a sterile filling chamber, transferring the cooled product into said filling chamber, filling the product into the can While in said lling chamber, transferring the filled can into a sterile can closing chamber, transferring the sterilized can cover into said closing chamber and hermetically uniting the sterilized cover with the filled sterilized can, maintaining about the product and the can parts in said sterile closing and filling chambers a sterile atmosphere having absolute pressure not greater than that of the natural atmosphere outside of the apparatus, and surrounding said cooling, filling and closing chambers and the inter-communication therebetween with an atmosphere of less absolute pressure than that in any of said chambers during said product treatment.

5. A method of canning which comprises passing a product to be canned into a sterilizing chamber, sterilizing said product therein, passing a can into a vacuumlzing chamber and thence into a sterilizing chamber, sterilizing the can while in said chamber, passing a can cover into a vacuumizing chamber and thence into a sterilizing chamber, sterilizing said cover, transferring the sterilized can into a sterile filling chamber, transferring the sterilized product into said filling chamber, filling the product into the can while in said filling chamber, transferring the filled can into a sterile can closing chamber, transferring the sterilized can cover into said closing chamber and hermetically uniting the sterilized coverwith the filled sterilized can, maintaining a sterile chamber atmosphere at a predetermined absolute pressure in said closing and filling chambers to which the product and can partsare subjected, the while surrounding said closing and filling chambers and the intercommunication therebetween with a confined atmosphere of less absolute pressure than that in any of said chambers.

6. The method of treating liquiform products which comprises sterilizing the product, passing the product into a vacuum pan while cooling it, maintaining a vacuum in the pan through the medium of a condenser, withdrawing the sterile and cool liquid from the vacuum pan, and pro 75 tecting the liquid against contamination by surrounding said vacuum pan and said condenser with a confined atmosphere of less absolute pressure than that obtaining within said elements.

'7. The method of treating liquiform products which comprises sterilizing the product, passing the product into a vacuum pan, maintaining a vacuum in the pan, withdrawing the sterile liquid from the vacuum pan, and protecting the liquid against contamination by surrounding the vacuum pan with a conned high vacuum which is in excess of the vacuum within the said pan.

8. The method of treating liquiform products which comprises sterilizing the product, passing the product into a vacuum pan, maintaining a. vacuum in the pan through the medium of a vacuum pump and a condenser thereby cooling the liquid, supplying heat to the cooled liquid in the said Vacuum pan to cause evaporation of water which passes into said condenser thereby condensing said liquid, withdrawing the sterile,

cooled and condenser liquid from the vacuumv pan', and protecting the liquid against contamination by surrounding said vacuum pan and said condenser with a conned atmosphere of less absolute pressure than that obtaining Within said elements.

CHARLES O. BALL.

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