US 2182383 A
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Dec. 5, 1939. o. w. LANG :1- AL MEANS AND METHOD OF PROCESSING CANNED FOODS Filed Sept. 28, 1936 2 Sheets-Sheet 1 CONDUC TING FLU/D s 1 m m H E v. W m r Z XM A 2 5 Q g a L 00 c T A W OH 2 u B M 7 7 2 Dec. 5, 1939. 1 o. w. LANG El" AL 1 2,182,333
MEANS AND METHOD OF PROCESSING CANNED FOODS Filed Sept. 28, 1936 2 Sheets-Sheet 2 INVENTORST OTTO W. LANG HAROLD C. EETTS BY Mfl W F ATTORNEYS.
Patented Dec. 5, 1939 MEANS AND METHOD or raocnssmo omen roons Otto W. Lang and Harold C. Betta; San Francisco, Calif.; said Betta assignor of fifteen per cent tosaidLang Application September 2a, 1936, Serial No. 102,855
Our invention relates to a means and method for processing materials designed to be packed and sold in metal containers, and more particularly to a means and method for pre-heating,
I pasteurizing or cooking foods packed and sold in tin plate containers commonly known as cans.
Among the objects of our invention are; -To provide a fast and economical method of heating food in cans during packing; to provide a simple 10 method of preheating, pasteurizing or cooking food stuits while being canned; to provide a means and method for heating canned food during processing so as to greatly reduce the space required in the processing plant; and to provide a simple and eifective means and method for electrically cooking canned foods, or other organic materials, wet or dry.
Our invention possesses numerous other obiects and features of advantage, some of which,=
together with the foregoing, will be set forth in the following description of specific apparatus embodying and utilizing our novel method. It is therefore to be understood that our method is applicable to other apparatus, and that we do not limit ourselves, in any way, to the apparatus of the present application, as we may adopt various other apparatus embodiments, utilizing the method, within the scope of the appended claims.
Referring to the drawings: Figure 1 is a longitudinal, sectional view, conventionalized, of one embodiment of our invention as applied to pre-heatlng canned food.
Figure 2 is a fragmentary, sectional view of an alternative method of making connection to the lower part of the can. Figure 3 is a fragmentary view in section of a top electrode as applied to a closed can.
Figure 4 is a view partl'y in section and partly in elevation of a can showing side contact electrodes.
' Figure 5 is a plan view of an oval can indicating electrode contact area.
Figure 6 is a diagrammatic sectional view showing the can of Figure 5 positioned between two electrodes.
Figure 7 is a schematic sectional view of a preheating turntable.
And Figure 8 is a plan view/partly in section look ng-down on the top of the turntable illustrated in Figure 7.
At the present time cannery practice consists broadly in placing food in cans which are fol'fiid from-tin plate; the latter being usually a thin iron sheet protected on both sides thereof by a ll film of pure tin. The cans have many shapes,
but are usually formed with the side walls in the shape of a cylinder, the top and bottom being rolled or crimped in place toform an airtight, seal.
Inasmuch as the majority of canned foods are ,5 cooked during the packing process, thecraw food is usually placed in the can and the can and its contained food are then pre-heated to definite temperatures to drive out gases and air contained therein, before closure. .The top is then put on, m spun into place, and the cans are given final cooking. The removal oithe gases before the final cooking step prevents the covers from being strained by expansion of gas. Sometimes, how= ever, as for example, in the case of condensed 5 milk or canned beer, the covers are spun on and the can is then given a pasteurimng heating without pre-heating.
In prior practice it has been customary, in the pro-heating, pasteurizing or cooking steps;, to as conduct the can into steam boxes on conveyor belts, so that continuous progression may be obtained during the heating step. This necessitates rather large steam volumes to accommodate the long length of conveyor belt so that the cans may remain in the box for the proper length of time. Furthermore, the live steam sup plied to these cabinetsv is continually escaping through the entrance and exit holes of the cabinet, and in order that evenpartial efiiciency may 30 be obtained the cabinets must be completely and rather heavily insulated.
Our invention, broadly, comprises eliminating the steam cabinet either for pre-heating, 'pas= teurizing or cooking and substituting therefor electrical heating of the contents of the can by utilizing the tin plate side walls of the can itself as a resistance element, and passingtherethrough electrical current of extremely high densities at low voltages until the desired heat is developed in the contents 'of the can. Our method is therefore not adapted to containers having insulating walls such as glass jars.
We are aware of the fact that it has previously been proposed to heat packaged foods by passing an electrical current through the food itself; and we are also aware of the fact that it has previously been proposed to place the food in speciai containers, such as graphite cooking pots," and pass a current through these containers'to heat '50 the food,'thereafter transferring the heated food to the can. We have found, however, that such prior practices do not produce the advantages herein to be set forth, as in many cases it is highly,v detrimental to the food to pass a current as through it, and, again, the food itself may be so non-conducting as to make such a procedure impossible. Furthermore, we do not have to provide any special crucibles or cooking pots; we utilize as a resistance element the identical container in which the food is later to be sold, and it never has to be removed from that container after heating. Consequently there is no chancefor the food, after sterilization, pasteurization or cooking, to become contaminated. Furthermore,we havefound thatbyutilizingthis electrical method of heating, temperatures can be very strictly controlled, there is a high eiiiciency v of energy conversion, and theheating may take place in a relatively short time and in a space which is relatively small compared to the steam cabinets heretofore deemed necessary.
There are several means by which we apply current to tin cans, several of which are'ilius ao trated' in the drawings to which-we will now refer.
In Figure 1 we have shown in a conventionalized manner a tin can comprising the usual cylindrical side wall I, closed at the bottom by bottom disc 2 with the 'usual rolled, seam 3. The top of the can, not yet being closed, is provided with a rolled edge 4 which will later enter into a top rolled seam similar to seam 3. We prefer to position the can in a depression 5 on a lower plate 301, which may well be a copper plate forming a portion of a traveling belt, or, as will later be described, the bed plate of a turntable. Depres sion 5 is so out thats central boss I projects upwardly to contact the raised can bottom 2, thus affording a wide electrical contact overthe entire bottom of the can.
The top of the can is contacted by a swinging electrode 8 hinged to a conductor bar 9, and
preferably provided with a flexible jumper id to do carry current around the bearing. Top electrode 8 is preferably provided with a central aperture il over the can to allow escape of gases from the contents l2 of the can, and on its under surface is provided with a circular channel II.
shaped'to fit the rolled edge 4 of the top of the can. We prefer to place considerable pressure between the top and bottom electrodes, and this pressure may be supplied by a spring ll or, if desired, by making electrode! of suflicient weight to provide pressure by gravity alone, or both. Base and conductor bar 9 are connected to the low voltage secondary I! of a step-down transformer It, whose primary i1 is connected to the alternating current mains in any convenient of the can and we have found in practice that I for a one-pound-tall can a current of 400 amperes as at .1 volt applied for! minutes develops sumcient heat in the exterior walls to heat a can filled with water to the boiling point.- Other foods or mate-- rials contained in the can may take longer or I .shorter periods of applied heat. The cans then pass from the cooker.
often happens,' however, that cans are lacqueredon their inner surface in order to better preserve the container walls from certain belt or turntable to theseiler' where the top is crimped on,'and thence to the corrosive actions of the contained food. In this case, standard practice is to thinly lacquer the cylinder l and the bottom 2 before the bottom is crimped to the cylinder. When the scam I is formed, we have found that under these circum- 5 stances a lacquer film may be included between the material of bottom 2 and cylinder I, there creating a high resistance path. It is obvious that inasmuch as low voltage current is used that such resistance will develop excessive heat- 10 mg with consequent loss of the seal at the seam, and .we have therefore provided, as shown in Figure 2, a different arrangement for the bottom of the can, where the recess I is filled with a good conductor, such as brine it, for example, which 15 will contact the can above the seam 3. The thin lacquered seams never form a totally insulating joint, and the conductivityof the brine is suflicient to prevent heating of the seam as a large portion ofthe current is passed into the can go through the brine contacting the side walls directly.
necessary within the can and an extremely high resistance is developed, I may prefer not to utilize 25 the top or bottom of the can for contact points, but to make contact directly to'the upper and lower portionsof' the side walls as shown in Figure 4. Here, lateral arms I! carry substantially semi-circular contacts, which may be moved radially toward the axis of the can to clamp the can immediately below the top rolled edge. Similarly, the bottom may be clamped by contact arms 2|, having contact electrodes 22 attached thereto in exactly the same manner as the upper set of electrodes. Inasmuch asthe contacting is done above and below the seam planes, it is obvious that a totally insulating seam could be used on both top and bottom of the can,
irrespective of theconductivity of the top and 0 bottom seams. It should be pointed out in this respect that the lateral seam 24 ofthe can, which joins the edges of theside walls so that the cylinder I may beformed, is not across the path of the current, as the current flows parallel to the a seam and therefore this seam is never damaged. In clamping the can tightly with the lateral type of clamps'it is obvious that the seam 24 may be positioned between two opposing electrodes so that the electrodes can contact the entire--oonbe omitted and channel i2 may be changed in contour to arecess-of the same shape as recess I on the bottom electrode, there being also in this case-a projection I so that the entire top. of
w So far we, have shown our new invention as applied to"tall cans, these cans being very satisfactory for heating because they provide a have shown an example of this type of can in 'Figure 5 and Figure 8, the example being the well known oval sardine can 23. In order to provide a longer pathfor the current we prefer to form a lower electrode II smallerthan the area of the is aisaaes bottom of the can but having the same contour, and pomtion it so that all current paths from this electrode to top electrode 8 will be substan- 4 tially the same length. Thus the current travels for a considerable extent through the bottom of the can as well as the side walls, and this extra extent provides the desired resistance. Furthermore, while in this case we have shown top electrode l as appliedto the entire top of the can, it
is obvious that the top electrode 8 may be made the same shape and size as lower electrode 25.
In Figures '1 and 8 we have shown, greatly conventionalized and simplified, a turntable on which the cans may be electrically heated. A
turntablebase 21 is mounted on a shaft 28, the latter being supported by bearing 29. Conductor bar 9 here is in the form of a ring concentric ,with the periphery of theturntable, and upper electrodes 8 are hinged to this conductor bar as before recited. The bottom of the cans are placed in depressions asdescribed in Figure '1. The cans are fed to the turntable from the conveyor line through entrance chute 30' by star wheel III and leave by exit chute 3|, the turn table rotating at a speed which will give the required heating between the time of entrance and exit. The conductor bar 9 and base 21 are energized from transformer l6, which in this case is mounted to rotate with the turntable so that the low voltage secondary leads will not have to be brushed. Brush rings 32 are mounted on insulating block 33, can'ied on shaft 28, and are con tacted by stationary brushes 34 which lead to the mains through a switch 36. Switch 36 is utilized to cut the current through the transformer at the instant the cans enter and leave the turntable so that the primary circuit may be broken when secondary contact across the can is made or-broken by the movements of electrodes 8 actuated by lifting cam 31. Switch 3|, of course, may be automatically operated, and those skilled in the art will easily understand proper connections. The intermittent excitation of the.
cans will, of course, lengthen somewhat the time the cans are on the turntable, but as the com nection and disconnection may be made rapidly the time is not greatly prolonged. In order that heat may be conserved we may prefer to cover the entire turntable with an insulating cover 38.
We have found that our system of can heating greatly reduces space in canning lines, re
duces heat losses, and provides an accuratelycontrollable heating for either open or closed cans for pre-heating, pasteurizing or cooking. We have found that the final product is in all ways fully equal to steam heated products and in tained with steam boxes. Steam boxes-are con-' tinually leaking stefam and thissteam condenses on every object surrounding the packing lin'e, providing ideal conditions-for the growth of bac-' term and fungus. Everything is continually wet, also leading to rust of machinery. The elimination of such leaking steam allows the sur- [I roundings and machinery to be dry, thus greatly reducing the chances of contamination of food and prolonging the life of the equipment.
Another extremely important advantage of our process lies in the fact that we are able to attain cooking temperatures which cannot be attained by the use of steam. For example, in packing sardines it-is highly desirable that the cooking be carried on to the point that the layer of fat directly under the skin is at least partially tried out. A temperature sufficiently high to do this, however, cannot be attained in steam boxes, because it is not possible to apply steam to the cans under pressure because of leakage. It is also impractical to retort the open cans, and therefore it has heretofore not been possible to process sardines as sardines grilled in the can. For example, even when-steam is admitted to a steam box under super-heated conditions, leakage prevents the applied temperature; from rising over 210. Our process, however, will pro.- vide a sufliciently high temperature so that the sardines may be fried or grilled in the can be- .fore the cover is placed upon it, and a superior product results. Other foods may be treated in the same manner with high temperatures.
It is to be distinctly understood that our process applies to any heating or the cans, whether open or closed, including cooking, pro-cooking, exhausting, processing, 'pasteurizing, sterilizing, blanching, concentrating foods or vegetables or liquids, frying, grilling or toasting, either wet or dry organicmaterials, and in this regard our process is applicable to the heat treatment of any organic material, wet or dry, whether or not it is being processed for human or animal consumption. Our process is, of course, equally adaptable for the heat treatment of liquids, as
exemplified by condensed milk and beer.
It is also to be distinctly understood that our .process is fully adapted for use in conjunction with containers formed of-materials other than tin plate. For example, certain novelty packs may be packaged and sold in special containers formed of thin walled metals such as, for example,
While in tinned iron containers known to the trade as the passage of said heating current.
2. The method of processing .relatively non- V conductive organic material processed and sold in tinned iron containers known to the trade as tin cans, having a side seam andan end seam, which comprises heating said container when filled by applying a heating current to the walls of said container across said end seam and parallel to said side seam, and providing an auxiliary current path around said end seam during the passage of said heating current.
conductive organic material processed and sold in tinned iron containers known to the trade as tin cans, which comprises filling said containers with said material, onveyingthe filled contain? ers over a predetermined path. applying a low .voltace heating current to top and bottom of said 7 2,188,888 ,3. The method or p relatively non-- containers ata predetermined point in said path to heat the entire side walls of said container, maintaining said current until said material is processed, and removing said containers from the end of said path.
. O'I'I'O W. LANG.
HAROLD C. BETTE.