DK141954B - Method and apparatus for after sterilization to reduce the volume and suppressed in sealed cans. - Google Patents

Description

U1984

The present invention relates to a method and apparatus for reducing, after sterilization, the volume and suppressed in closed canisters, the lids and / or bottom of the cans being provided with an annular deformation zone, during and during the sterilization process, the can can be filled and closed at elevated temperature. over a predetermined period of time, a sterilization temperature above the filling temperature is heated, after which the can can be cooled to room temperature.

The term "annular" is used herein in the sense of circumstantial, irrespective of whether the shape in question is circular.

For the preservation of products, there is known a method, which according to the inventor Nicolas Appert is called apertification, which consists in the products, after being enclosed within a tight container, being exposed to a sufficiently high temperature for a sufficiently long time. to ensure complete destruction of both enzymes and microorganisms that could alter the properties of the products.

20 It is also known in the preparation of preserved products in metal cans, after the can is filled, fitted with a lid and closed, to introduce it into either a bath of hot water, an autoclave or other suitable sterilizing apparatus, by which the can and its contents can is brought up to a temperature above 100 ° C, usually between 110 and 130 ° C, but which is also capable of achieving higher temperature levels.

The temperature and duration of sterilization are inseparable factors in the process, and the term "sterilization scale" denotes a table of required durations to achieve the desired sterilization effect at varying temperatures, the required time decreasing with increasing temperature, as determined by a mathematical formula. which includes the dimensions of the metal box and the nature and consistency of the perishable product.

35 A large number of experimental studies have shown that in the vast majority of cases there is an equal interest in preserving the original character of the product, as perceived by the senses, and in taking financial considerations so that scale values can be used with a short time at a high temperature during sterilization, which allows for a time saving in the operation, the use of devices of smaller dimensions for a particular production and a reduced energy consumption.

This, in bringing a can and its contents from the temperature at which the can was closed to a higher temperature, increases the pressure in the can, and it is necessary that the can provide an appropriate resistance to this pressure, without undergoing permanent deformations and without risk of leaks.

It is clear that the mechanical strength of the can against internal pressure consequently sets a limit on the temperature at which it is possible to perform the sterilization.

Various measures in the design of the can, as well as in the design of the sterilizers and in the sterilization process itself, make it possible to avoid this difficulty within certain limits. One of these measures is to ensure that the can and its contents at the instant of closure can be at the highest temperature possible, however, this temperature cannot exceed 100 ° C, where the contents of the can are highly water-containing, which can be filled into a can at atmospheric pressure, but which can exceed 100 ° C if the filling takes place at a pressure exceeding atmospheric pressure.

Closing the can in the hot state allows it to be brought to a higher sterilization temperature without exceeding the critical internal overpressure in the can; the maximum internal pressure that arises in the can is, among other things, a function of the relationship between the temperature of the can closing moment and the sterilization temperature.

However, this measure causes two disadvantages, the hot closure of the can causes a negative pressure of its size to increase in the interior of the can with its closure temperature, which in part gives rise to a risk of imprinting the can's cylindrical wall under 1A1954 3 influence of atmospheric pressure or even weak shocks, and partly increases the risk of contamination of the contents of the can, if it is not completely dense, which may be due to a failure of one of its false or may result from 5 deformation of a seam as a result of shock effects, although the seam was fine from the beginning *

U.S. Patent No. 3,103,089 discloses an invention whose purpose is to prevent unwanted deformation of cans or other containers as a result of reducing internal pressure. This is achieved by vacuum or, optionally, by magnetically acting means which are used to induce a temporary elastic deformation of the end wall of the can.

From Belgian Patent Specification No. 532,675, it is known to subject canned cans to a deformation of the end walls by means of pressure means, which deformation according to page 16, line 34 et seq., Serves to eliminate the voids in such cans. However, neither the US nor the Belgian invention allows the extent of the resulting deformation to be determined.

The object of the present invention is to avoid or reduce the risk of imprinting and contamination by closing the cans at a temperature of about 100 ° C or even higher if necessary so that the cans can be sterilized at a high temperature for a short time. the formation of an internal negative pressure of considerable size and the disadvantages which this causes, are avoided so that a general improvement in the quality of preserved products can be obtained, and more particularly the aim of the method and apparatus according to the invention is to as accurately as desired can determine to what extent the volume of the cans should be reduced.

This object is achieved by a method of the kind mentioned in the introduction, which according to the invention is characterized in that during the cooling to room temperature, the volume of the can can under the permanent, mechanical folding or discharge of the annular deformation zone U1954 4 of the lid and / or the bottom from the outside is permanently diminished depending on the falling temperature and before the room temperature is reached and that the difference between the internal and the external pressure is set below a predetermined limit value.

As to the apparatus, this is characterized by two mutually opposed, mutually opposite printing heads, each provided with a plunger which affects a surface at the bottom and / or the lid of a closed canister which can be inserted between the printing heads, at least of which 10, one is axially movable in the direction of another by means of a displacement device adapted to be actuated at adjustable pressure.

In an advantageous embodiment of the method according to the invention, the volume of the can can be reduced by 15 permanent deformation of the lid and / or bottom so that the internal pressure after cooling to room temperature does not deviate from the atmospheric pressure by - 0.15 bar at most. An accidental, permanent deformation e.g. of the can of the can of the can is safely excluded by the measures in connection with the new method. As a result, canned cans of very thin material can also be safely sterilized using very high filling temperatures and cooled to room temperature.

An appropriate embodiment of the method 25 is characterized in that the lid and / or the bottom are only permanently deformed when the temperature of 40 ° C or lower is reached.

In an advantageous embodiment of the apparatus according to the invention, each pressure piston has a lid or bottom engaging annular zone with a pressure surface formed in dependence on the lid 30 or the bottom zone. Furthermore, according to the invention, one or each printing piston may have a contact area cooperating with the edge of the canister to limit the relative movement between the edge of the canister and the printing surface.

By permanently reducing the volume of the can is meant a reduction which is obtained by a permanent deformation of at least one of the walls of the can. To provide such a volume reduction, the can is designed in such a way that at least one wall element 141954 is deformed.

The deformable wall element is generally a bottom or a lid, and in the most commonly used cans there are two such elements, namely a bottom and a lid, each of which, from the beginning, generally has a slightly concave shape. When a filled and then sealed can is subjected to sterilizing heating, the gradual increase in pressure will cause the deformable wall elements concerned to undergo a temporary outward deformation. During cooling, the lid and bottom will again assume their original, slightly concave shape, when the vacuum in the interior of the can has become sufficiently strong that the respective wall elements of the atmospheric pressure are pressed inward. The risk of imprinting the wall of the can and of renewed contamination of the contents of the can is present after the cooling phase, as it is linked to the internal negative pressure.

Thus, the practice of the method according to the invention, whereby the internal volume of the can is permanently reduced, can advantageously be done in such a way that the vacuum in the can is kept at a predetermined limit value.

The method according to the invention can be applied not only to normal endplates of tinplate or other types of steel, of aluminum etc., but also to end-bases of any other materials which have the necessary properties to be used as endplates in a can.

The invention, on the other hand, is not limited to the normal circular cylindrical can form, as it can also be applied to cylindrical or prismatic cans as well as to cone-stub and pyramid-stub cans of any cross-section.

In such cases, it is clear that the "annular pressure surface" of the pressure means is intended to mean a pressure surface which is constrained by a contour similar to the outline of the end bottom being pressed which leaves the middle portion of that end bottom free.

The invention will now be described in more detail with reference to the drawing, in which: FIG. 1 shows a normal, filled canned side view and partly in section.

6 1Α195Λ fig. 2 is a schematic sectional view of an apparatus for carrying out the method according to the invention; FIG. Fig. 3 is a schematic and side view of a machine adapted to be placed in a production line in which sterilization is performed and which serves to carry out the method according to the invention; 4 is a schematic sectional view taken along line IV-XV of FIG. 3

FIG. 5 on a larger scale, a partial section along the line V-V

10 in FIG. 4, FIG. Fig. 6 is a schematic partial view showing a traditional bottom; 7 is a view of FIG. 6 is a similar view showing an end bottom with a stiffening wave pattern 54 and with waves 55 increasing the flexibility shown in various positions taken during the execution of the method according to the invention; FIG. Fig. 7A is a larger-scale sectional view illustrating the deformations of an end bottom in the practice of the method of the invention; 8 is an explanatory diagram; FIG. 9 is a view illustrating the application of the invention to a can open-lid lid; and FIG. 10 is a view similar to FIG. 9, wherein a can is seen with a pressed bottom.

Considered first, FIG. 1, a conventional cylindrical can 10 can be seen which traditionally has a bottom 11 and a second bottom or a lid 12. The can is filled with a product 13 which fills it up to a certain height 14, whose exact position is 30 can vary from can to can, leaving behind a lid 12 some free space 15 containing air and steam. The product 13 to be preserved may be in solid state, in liquid form or may be a mixture of solid and liquid. The volumes occupied by the product, steam and air are each functions of temperature.

An increase in temperature causes an increase in these volumes by expansion of the product, by increasing the pressure of the steam and by expanding the trapped air and steam. In particular, the end bottoms 11 and 12 are intended to withstand the pressures arising from these volume increases, being deformed so that their initially slightly concave shape changes to a more or less convex or vaulted shape, whereby there is a significant increase in the internal volume, so that the volume, vapor, air and gases will remain sufficiently large over the product to keep the stresses resulting from the pressure within permissible limits.

During cooling, the contents will contract, and the end bottoms will thereby essentially occupy their original positions, being affected by the contraction produced by the contraction and, where appropriate, the pressure of certain sterilizers.

As already mentioned above, the underpressure that occurs in the can of the can reach so much the greater values when the can of filling and closing takes place at a high temperature relative to the surroundings. For the aforementioned reasons, it is prone to make the filling and closing at as high a temperature as possible, but is limited by the risk of compression resulting from the resulting underpressure. This risk depends on the shape of the can.

It can thus be cited as an example that the risk of compression is so low that it can be disregarded under the usual manufacturing conditions and conditions of use at 25 cans whose diameter does not exceed 71.5 mrn ^ and whose height is 115 mm, while a can with a diameter of 100 mm and a height of 118 mm can spontaneously develop bulges at relative pressures of 0.6 bar, and a can with a diameter of 153 mm and a height of 250 mm can spontaneously develop bulges from a relative vacuum 30 of 0.2 bar.

In FIG. 2, an example is shown which is arranged for carrying out such a method, two pressure means 21 and 22 each having a centering part with a tapered insertion surface 23, 24 which can guide a can 10 35 against two projecting parts 25 respectively. , 26, the profile of which is aligned with the profile of the corresponding bottom 11, 12 and having an active pressure surface 25A and 26A, respectively, which may advantageously be annular, leaving a cavity within. Although the thrust member 22 is in fixed communication with U1954 8 a portion 28 which is reciprocated, as indicated by a double arrow F, the second thrust member 21 is guided in a fixed guide 30 and this thrust member is provided by thrust bars 31 to abutment against a member 32 which restricts movement and, for example, functions with compressed air and is adapted to provide a predetermined resistance to the depression of the rods 31.

In the embodiment shown in FIG. 2, the pressure faces 25A, 26A are cone-shaped and inclined towards the interior.

10 In FIG. 3-5 are shown a machine known per se which is adapted to carry out the method according to the invention, the pressure against the end bottoms being exerted by a mechanical apparatus, which will be described in more detail with reference to FIG. 2nd

FIG. 3, 4 and 5 show a stand 32 and two brackets 33 and 34 supporting a shaft 35. Two fixed ridges 36 and 37 are firmly connected to each of brackets 33 and 34.

Two drums 38 and 39 are attached to shaft 35 so that they rotate therewith. Each of the drums has distributed along its circumference a plurality of heads 40, 41, which accompany the rotary movement of the drum, and each of which is firmly connected to a roller 42, 43, which follows the corresponding guide groove 36, 37. The heads 40, 41 are thus aligned two and two and approach or remove from one another during their rotation, the movement 25 being guided by the guide tracks 36, 37.

An apparatus such as that of FIG. 2 may be mounted on each pair of the heads thus facing each other. Each of the heads 40 may e.g. forming a support corresponding to the support 28 for a pressure means 22, 30 while each of the heads 41 carries a pressure means 21 with associated stroke-limiting means 32. This stroke-type limiting means is provided with a compressed air end mouth 45 shaft 35, which is hollow, at which point is inserted a pivot connection 35 which, by means of duct means not shown in detail, which radially enters the shaft, supplies compressed air to the stroke length limiting means 32 distributed on the drum 39 .

In FIG. 4, for a machine with a horizontal shaft, it is shown how cans 10 are fed from above using gravity by means of a gutter or slit 46, each can being received by a carousel 47 arranged 5 to guide them into a coaxial position with a pair of pressure heads. The fixed guides 36 and 37 are set in such a way as to induce a pushing operation within an angle 48, and the cans thus treated are passed from the lower portion along a path or slit 49.

The limiter for the stroke of the pushing means may also utilize a spring force or a hydraulic pressure. In addition, the pressure against the bottoms can be achieved by a pressure fluid acting directly on them.

FIG. 6 illustrates the course of the deformation 15 caused by a mechanical pressure P against a bottom of the usual type which is pressed into a position such as the position 12A. The maximum volume reduction that can be achieved in this way by permanent deformation of the bottoms in the vicinity of the folds is about 3%, namely 1.5% for each bottom.

For practicing the present invention, it is advantageous to use bottoms of the kind disclosed in French Patent Specification No. 1,533,259, which can be seen at 50 in FIG. 7. These bottoms are characterized by the application of an annular zone with stiffener rings 54 in the immediate vicinity of the seam and at least one resilient area 55 on the intermediate portion. Under the influence of a mechanical pressure P, such a bottom will tend to be unfolded permanently, transitioning to a position such as 50A which allows a substantially greater volume reduction, namely a reduction of about 8-10%, 4-5% for every bottom. Assuming position 50A, the middle region of the bottoms is still subject to elastic deformations, whereby under the influence of a residual internal negative pressure, they will move to a position as shown at 50B. With a dashed line 35 50C, on the other hand, an outward displacement is shown to which the bottom can be exposed at the beginning of sterilization under the influence of the internal overpressure, without permanent deformations and without the risk of roll-up of the seam.

U1954 10

FIG. Fig. 7A shows, on a larger scale, an example of the enduring deformations of an end bottom 50 in a can, which is deformed by means of a pressure means 126 having three annular pressure lips, 127A, 127B and 127C, located therein within each other; and which are axially displaced relative to each other. A dotted line A shows the profile of the bottom 50 after the first lip 127A exerts its pressure, while a dotted ^ line B shows the profile of the bottom after the second pressure lip 127B exerts its pressure, and a third dotted line C shows the bottom profile after the third pressure lip 127C exerts its pressure. In each of these cases, these are permanent deformations that are taken up - of the bottom, a dashed line B illustrating the elastic deformation in which one can still be found. the middle portion, of the bottom 50.

It is to be understood that the number of annular folding zones with which the bottom of the can is to be formed during these deformations depends on the volume of the contents of the can and the pressure of the pressure means, as well as the diameter of the can and the total number of pressure lips 20 on the pressure means used.

In any case, the mechanical deformation intended to reduce the can content of the can or its free space is according to the invention in an area along the perimeter where a permanent folding takes place, while the middle part is always resilient and follows volume changes and pressure changes for the can contents. This is why, after the cooling, which leads to a certain negative pressure in the can, the middle part of the bottom will resiliently move from position C to position D.

30 Experience has shown that, due to the normally occurring differences in the content level in different filled cans with the same product or between the different cans' temperature at the filling, it is desirable to have the possibility of a volume reduction of about 10%, 35 why in the vast majority of cases, preference should be given to the use of end bottoms which, in accordance with the aforementioned patent specification, are designed with the combination of an external tightening zone near the can of the can with resilient zones near the central region. However, by reducing the normally occurring differences, it is also possible within the scope of the invention to use less resilient end bundles of a traditional nature.

In the practice of the invention, a pressure limit is set which must not be exceeded in the finished cans, and which e.g. may be between -0.15 bar and +0.15 bar relative to atmospheric pressure. This condition determines the volume reduction to be used, which is otherwise a function of the filling temperature and the height to which it is filled, and partly of the amount of gases contained in the can, which in turn determines the expansion coefficient or contraction coefficient of the product.

Thus, as the size of the volume reduction to be used is determined, the moment at which the volume reduction is to take place can be determined.

15 Given the potential risk of re-contamination, it is unfortunate to reduce the volume after the can cool down, as the damage at this point may already have occurred. It is therefore clear that the pressure against the bottoms should be applied as soon as they have withdrawn, 20 ie. at a temperature sufficiently far below the filler temperature to allow the magnitude of the vapor pressure to provide sufficient suppression for the end bottoms to return to their original position by themselves.

However, if this operation takes place while the vapor pressure is still of considerable value, e.g. at 0.2 or 0.3 bar, the following cooling will still cause a vapor pressure drop and a contraction of the product and air, resulting in a renewed pressure drop which may be sufficient to cause the can wall to bulge inward.

30 These considerations lead to the fact that the operation whereby the volume is reduced should be placed during the cooling process at as high a temperature level as possible, but below which the vapor pressure changes become weak, and this level may e.g. lie at about 40 ° C, where the pressure of water vapor is 35 at 0.075 bar and below which the pressure decreases relatively slowly.

12

U195A

When this level of 40 ° C is determined, the filling temperature can be determined for each can type which can be allowed without the risk of compressing the can.

This is illustrated in diagram form in FIG. 8, which shows the course of the pressure variations as a function of the temperature T, the curve Pv showing the course of the vapor pressure variations, while the curve Pi shows the relative pressure variations in the interior of the can.

Out of the temperature axis T is indicated by To, the above-mentioned temperature level is about 40 ° C, the choice of which is determined by the corresponding size Po of the vapor pressure, e.g. can be 0.075 bar. Assuming this temperature level Two, where you have decided to make a volume reduction, you determine another temperature level T1, which is suitable for use in rinsing and closing the can. This temperature level is determined by a certain maximum size P of the negative pressure that the can type can withstand without the risk of bulging.

Thus, two cases may occur depending on whether this temperature T1 determined for the can closure is satisfactory or out of range. If it is insufficient, it is maintained to perform a can to reduce the volume of the can at this temperature, after which a new pressure difference / µ P 'is determined, which is now presumed to be satisfactory as the final level of sterilization after the can is closed. . This sterilization (indicated by an arrow S) consists in increasing the temperature to a certain level T3 (point A) which produces a certain relative pressure P3 in the can and a bulge of the end bottoms (to position 50C in Fig. 7). . During the subsequent cooling, the temperature will first return to the closing temperature T2 during a first stage R32, whereby the internal relative pressure is substantially equalized, so that the end of the can, under elastic deformation, will return to its original position (shown at 50 in FIG. 7). During a subsequent stage R21 of the cooling, the temperature reaches the level Ti (point B) with a corresponding pressure drop / \ P1 for the vapor pressure, which means that a certain negative pressure P2 will be developed, which will generally be larger than the pressure drop P 'as a result of the enclosed gases and the product itself.

13 1 Λ 1 954 At this level, a first volume reduction is induced which induces a certain compression K1 and causes the internal pressure to rise to a certain positive value P1, which determines the starting point C of the curve stretch R10, which represents a cooling stretch RIO leading to the temperature level Two (point D), where it is hypothetically established that a new volume reduction must occur. This operation leads to a new compression Ko, which in turn causes the pressure in the can to rise to a certain positive size 10 corresponding to the point E. The last cooling distance Ro, which leads the can to ambient temperature, changes the internal relative pressure to a value. that is very close to zero to ensure that the can maintains a proper appearance so that it can be negotiated, even though the climatic conditions under which it is stored will cause it to be at temperatures that are. eg. can fluctuate between 5 ° C and 40 ° C.

The size of the internal negative pressure Pi and P2 should, of course, be chosen below the limit where there is a 20 risk that the can itself can bulge inwards. In particular, this limit is a function of the thickness of the sheet material from which the sides of the can are made, which points to one of the important advantages of the present invention, namely the possibility of reducing this sheet thickness without deteriorating the quality of the packaging.

The force by which the can is pressed is, of course, limited to a value below the value at which the can or other parts of the can are ruptured and this restriction exerted by the force limiting means 30 32 (Fig. 2) is a function of the can size and construction.

The sides of a can generally can easily withstand a pressure of 3 bar, which makes it possible to use quite high pressures.

The technique of the invention for reducing the volume of the cans may be used against cans equipped with bottoms 35 of the said kind and which are adapted to be easily opened.

In these cases, the pressure means should take into account the fact that it is not necessary to press the bottom which is designed to be easily opened so that the other end bottom is pressed exclusively. An example of an apparatus adapted for this case is shown in FIG. 9, wherein said can 60 has a bottom 61 which is similar to that of FIG. 7, and a bottom 62 adapted to be readily opened. A pressure means 30 similar to that of FIG. 25 also rests here against the bottom 61. The pressure means 65 which rests on the bottom 62 differ from the pressure means 22 in FIG. 2, partly in that its protruding portion 66 abuts the end floor with a surface forming support over its entire area, except for an area along the circumference, 10 and partly in that the recess formed around the circumference of the member, at the circumference has an area 68 which serves to abut against the socket 69. This causes the pressure exerted against the bottom 62 to cause deformations which are limited to a small value which can in fact be set equal to zero if it is necessary and which is within the permissible deformation in its only zone 67 along the circumference.

In FIG. 10, there is shown an apparatus adapted to practice the present invention against a pressed can 70, e.g. may be provided with a lid-forming end bottom 71 of the kind which can be easily opened. Opposite to this end bottom is a pressure means 65 of the above-described type, while a head 72 adapted to press against the pressed end bottom 73 has a press drop 76, the abutment surface of which has a profile adapted to it. free edge 75 at which the end bottom is connected to the sides of the can. The center portion 74 presses against the entire middle portion of the base by means of springs 77 which prevent the base from being pressed. The clearance between the portion 74 and its guide 72 is greater than the maximum predicted value of the displacement of the thrust member, which is again determined by means of a pressure limiting member (not shown).

The axial pressure P exerted under these circumstances forces a movement in the form of an axial displacement of the assembly and of the supported portion of the bottom, with a ridge of the edge 75, which connects to the sides of the can. This displacement can occur over such a height as is necessary to achieve the optimum final volume reduction, which is again determined by the condition that a resultant internal pressure between -0.15 and +0 is obtained. , 15 bar, as described above. It is to be understood that when the lid-forming end-bottom used in conjunction with the pressed end-bottom is a normal end-bottom, i.e. not an end-end of the kind which can be easily opened, this end-end may, in turn, be provided with a region of volume reduction.

The present patent does not cover the use of the process in the manufacture of foodstuffs.

Claims (5)

A method of reducing the volume and suppressed in closed canisters after sterilization, the lids and / or bottom of the cans being provided with an annular deformation zone, the can being filled during the sterilization process 6g closed at elevated temperature and then over a predetermined period of time. heated to a sterilization temperature above the filling temperature, after which the can can be cooled to room temperature, know the e-10 character in that the volume of the can at the time of cooling to room temperature tends to stay, mechanical folding or unloading of the annular deformed or outwardly deformed zone of the lock and depending on the decreasing temperature and before the room temperature is reached and that the difference between the internal and the external pressure is set below a predetermined limit value. Process according to Claim 1, characterized in that the volume of the canning box during permanent deformation of the lid and / or bottom is reduced so much that the internal pressure after cooling to room temperature does not deviate from the atmospheric pressure by ~ 0.15 bar at most. 3. A method according to claim 2, characterized in that the lid and / or the bottom are only permanently deformed when the temperature of 40 ° C or lower is reached. Apparatus for carrying out the method according to claims 1-3 and arranged for the cooling section of a plant for hot filling and closing, and for sterilizing closed canning cans, wherein the sterilized canning boxes can be cooled to room temperature in the cooling section, known gently at two mutually flushing. , facing headers (21 and 22), each provided with a pressure piston (25 and 26) which affects a surface at the bottom and / or lid of a closed canister which can be inserted between the headers of which at least one is axially movable in the direction of another 35 by means of a displacement device (30, 32) arranged to be operable at adjustable pressure. Apparatus according to claim 4, characterized in that each pressure plunger has a lid or bottom attacking, annular zone with a dependency on the lid or