Method and installation for packaging a liquid product in a package

Abstract

To package liquids in thin-walled packages while at the same time conferring good mechanical strength upon these packages, an inert gas such as nitrogen and/or carbon dioxide, in the gaseous state is or are introduced into the liquid by means of an injector (22), the liquid becoming saturated or supersaturated with which gas(es); the product obtained is stored in a reservoir (14) at a constant level above which an overhead of the said gas is created at a raised pressure which is constant by virtue of regulating means (3). On demand, this product is transferred, by tapping means (4), to packages which are partially filled with product the surface of which is surmounted with an overhead of the said gas at a raised pressure after the package has been sealed.

Description

[0001] The invention relates to the packaging of liquid products in intrinsically deformable packages or containers.

[0002] It consists more particularly in a method and a plant for packaging liquid products allowing such products, for example liquid food products, to be packaged in packages or containers with thin walls, without increasing the risk of damage to the package and/or loss of product by comparison with the risks run with packages of greater thickness.

[0003] What is happening is that with a view to reducing the cost of packaging and the weight of such packages, the current trend is for liquids (cordials and other beverages) to be packaged in packages (metal tins known as cans, bottles made of synthetic materials, cartons, etc.) of increasingly thin wall thickness.

[0004] Because of the thinness of the wall, these packages are intrinsically deformable and are tricky to handle and to stack.

[0005] It is known practice for this disadvantage to be overcome by establishing a raised pressure inside the package while its contents are being packaged, this giving it good mechanical strength. This raised pressure may be obtained by injecting a small amount of inert gas in the liquid state, preferably nitrogen in the liquid state, onto the surface of the liquid, for example food liquid, while it is being packaged, between the operation of filling and the operation of sealing the package. The disadvantage of this technique is that it is relatively expensive.

[0006] It is an object of the invention to overcome this drawback and the invention therefore relates to a method for packaging liquid product in at least one package, characterized in that an inert gas such as nitrogen and/or carbon dioxide, in the gaseous state, is or are mixed with a liquid so as to form a product consisting of the liquid saturated or supersaturated with gas; this product is stored in a buffer reservoir which is partially filled with product up to a predetermined level; this level is kept approximately constant and, above this level, an overhead of the said gas in the gaseous state, due to the saturation or the supersaturation, at a predetermined approximately constant raised pressure; the said product is transferred on demand from the buffer reservoir to the package, open to atmospheric pressure, keeping the said predetermined level and the said predetermined raised pressure in the buffer reservoir so as to partially fill the package with the said product with an overhead of the said gas at a pressure the value of which is approximately equal to that of the overhead in the buffer reservoir, and the package is sealed.

[0007] By virtue of this technique, the cost of raising the pressure of the packages is appreciably reduced.

[0008] The method may further have one or more of the following features:

[0009] when, in the buffer reservoir, the raised pressure of the overhead of the said gas reaches the predetermined raised pressure, the excess gas is discharged;

[0010] in order to mix the inert gas and/or the carbon dioxide in the gaseous state into the liquid, this gas is injected into the liquid;

[0011] the raised pressure in the overhead of the buffer reservoir is set to a value lying in the range of 10 mbar to 3 bar;

[0012] the raised pressure is set to a value of about 50 mbar.

[0013] The invention also consists in a plant for packaging liquid product in at least one package, characterized in that it comprises a first circuit in at least part of which a liquid is circulated, a second circuit in at least part of which an inert gas such as nitrogen and/or carbon dioxide, is circulated under pressure in the gaseous state and which at outlet comprises an injector opening into an injection zone of the first circuit so as to form a product consisting of the liquid saturated or supersaturated with gas, the first circuit comprising a buffer reservoir into which the said product is introduced, means for keeping a predetermined level of liquid in this buffer reservoir, control and regulating means for maintaining a predetermined approximately constant raised pressure due to the saturation or supersaturation in the buffer reservoir, and means for tapping from the reservoir in order to transfer the said product from it into the package with an overhead at a pressure the value of which is approximately equal to that of the overhead in the buffer reservoir.

[0014] This simple plant combines good reliability with a modest cost.

[0015] The installation may also have one or more of the following features:

[0016] the first circuit comprises a transfer pump, the inlet of which is supplied with liquid to be saturated or supersaturated with gas, for circulating this liquid, and a filling line, the upstream end of which is connected to the outlet of the pump, an injector belonging to the second circuit opening into the line downstream of the pump for injecting the pressurized gas in the gaseous state thereinto;

[0017] the control and regulating means comprise a regulator, a pressure transducer measuring the pressure of the gas in the overhead of the reservoir and a level detector detecting the level of the said product in the reservoir, these being connected to the regulator, and a regulator exhaust valve, controlled by the regulator and connected to the overhead in the reservoir so as to discharge excess gas therefrom on the command of the regulator;

[0018] the second circuit comprises injection equipment supplying the injector, and the control and regulating means comprise a regulator electrically or pneumatically connected to the injection equipment in order to transmit to it a signal that regulates the injection; the

[0019] raised pressure kept approximately constant lies within the range from 10 mbar to 3 bar;

[0020] the raised pressure has a value of about 50 mbar;

[0021] the control and regulating means comprise a calibrated safety valve connected to the top of the reservoir.

[0022] Other features and advantages of the invention will become apparent from the description which will follow of one embodiment of the invention which is given by way of non-limiting example and illustrated in the appended single FIGURE, which shows a diagram of a plant according to the invention.

[0023] The plant depicted in this diagram is a plant for transferring nitrogen or some other inert gas and/or carbon dioxide in the gaseous state into an aqueous liquid, for example a food liquid intended to form a beverage; in such an application in the food industry, the gas has been filtered and sterilized beforehand, for example using the method in the French Patent Application published with the number 2 774 006.

[0024] This plant comprises a first circuit 1 comprising, from the upstream end downstream, a transfer pump 11, the inlet of which is supplied with liquid to be laden and here more specifically to be saturated or supersaturated with gas, a filling line 12, the upstream end of which is connected to the outlet of the pump, a valve 13 inserted in the filling line to allow or prevent flow through this line, and a buffer volume forming a reservoir 14 into which the downstream end of the line 12 opens.

[0025] The plant comprises a second circuit 2 supplied with inert gas such as nitrogen and/or carbon dioxide under pressure in the gaseous state; this circuit 2 comprises, at outlet, a gas-injecting device comprising injection equipment 21 such as that marketed under the name “coffret d'injection Carb'Eco” [Carb'Eco injection kit] by the company “Carboxyque Française” supplying an outlet injector 22 with a nonreturn valve opening into a zone situated between the transfer pump 11 and the valve 13 of the filling line 12 pressurized by the pump. The injection equipment 21 is connected electrically to the pump 11 to receive from it a signal authorizing injection slaving the injection equipment to the pump in such a way in particular that injection of gas is interrupted if operation of the pump is stopped.

[0026] The plant also comprises: means 3 for controlling and regulating the saturation or supersaturation of the liquid with gas, comprising a regulator 31, such as the one marketed under the name “coffret de régulation Carb'Eco” [Carb'Eco regulating kit] by the company “Carboxyque Française”; a pressure transducer 32 connected by a nozzle 321 to the top of the buffer reservoir 14 to measure the gas pressure therein and which is electrically connected to the regulator 31 to transmit a corresponding measured-pressure signal to it; a level detector 33 for detecting the level in the reservoir of the product consisting of the liquid saturated or supersaturated with gas and which is also electrically connected to the regulator 31 to transmit a corresponding measured-level signal to it; a regulation exhaust valve 34 connected by a pipe 341 to the top of the reservoir to discharge to the outside any excess gas and which is connected by a conductor 342 of electricity to the regulator 31 in order to receive a pressure-regulating signal therefrom; and a calibrated safety valve 35 connected by a pipe 351 also to the top of the reservoir so as to discharge to the outside any excess gas in the event of a malfunctioning of the regulation.

[0027] The regulator 31 is also electrically or pneumatically connected, on the one hand, to injection equipment 21 to transmit to it a signal that regulates injection as a function of the measured-pressure signal, and, on the other hand, to the pump 11 to transmit to it a level-regulating signal designed to modify the output of the pump according to the fluctuations of the level of the saturated or supersaturated liquid product in the reservoir.

[0028] The plant also comprises tapping means 4 for tapping off liquid product from the reservoir on demand so as to transfer this liquid product to the packages. These tapping means comprise at least one tapping line 41, in which at least one tapping control valve, not depicted, is inserted.

[0029] In this plant, the liquid supplied to the pump 11 is circulated thereby under pressure in the filling line 12, while the gas supplying the injection equipment 21 is circulated towards the injector 22 by which it is injected in the gaseous state into the injection zone of the line 12 so as to saturate or supersaturate with gas the liquid flowing through this line.

[0030] If the valve 13 is open, the product consisting of the liquid saturated or supersaturated with gas is transmitted to the buffer reservoir 14 where it is kept at a predetermined approximately constant level checked constantly by the level detector 33 by an appropriate command of the pump 11, so that the reservoir is never completely full and so that above the free surface of the liquid product there is an overhead of the gas in the gaseous state initially introduced into the liquid and which has been desorbed during the return to equilibrium of the gas which initially saturated or supersaturated the liquid in accordance with the part pressure of this gas in the buffer volume and its fraction dissolved in the liquid. This overhead consisting of inert gas such as nitrogen and/or of carbon dioxide, in the gaseous state, is kept at a predetermined approximately constant raised pressure checked constantly by the pressure transducer 32, by the regulator 31, by means of the exhaust valve 34 which discharges superfluous gas to outside the plant. If, however, in spite of the regulation, the raised pressure increases above a certain threshold beyond the raised pressure predetermined by the control and regulating means, the calibrated valve 35 opens and itself discharges the surplus gas to outside the plant.

[0031] Thus, the inert gas and/or the carbon dioxide, in the gaseous state, is or are mixed with the liquid flowing through the filling line 12 and a product consisting of the liquid saturated or supersaturated with gas is formed and stored in the buffer reservoir 14. However, this buffer reservoir is filled only partially, up to the predetermined level which is kept approximately constant by altering the flow rate through the line 12; an overhead consisting of the gas which results from the desorption of the gas previously injected into the line 12 and mixed with the liquid is obtained above the free surface of the product consisting of the liquid saturated or supersaturated with gas; this gaseous overhead is kept at the predetermined approximately constant raised pressure and liquid product is transferred on demand from the reservoir 14 to one or more packages open to atmospheric pressure, keeping the predetermined level and the predetermined pressure in the reservoir so that the packages are partially filled with product. After this, the packages are sealed and a gaseous overhead at a raised pressure close to the aforementioned predetermined raised pressure is obtained in these packages.

[0032] The choice of the flow rate of gas injected into the line 12 is dictated by the need to saturate or supersaturate the liquid with the desired predetermined constant pressure in the overhead of the reservoir 14. The relationship, at a given temperature, between the pressure P of the gas in the overhead of the reservoir and the concentration x of the gas in the liquid is governed by Henry's law whereby P=H.x where H is a coefficient specific to each gas known as “Henry's coefficient”.

[0033] In the case of the example described and depicted hereinabove, which is that of a food liquid, nitrogen and/or carbon dioxide in the gaseous state is or are injected into the line 12 by means of an injector 22 so as to obtain, in the overhead of the reservoir 14, a constant raised pressure at a value preferably lying in the range from 10 mbar to 3 bar, for example of more or less 50 mbar, this making it possible to obtain a raised pressure of a similar value in the packages; thanks to this injection of nitrogen and/or of carbon dioxide, not only is the package and its contents stiffened, but the amount of oxygen in contact with the product is also substantially reduced and the risks of the product oxidizing are diminished. In addition, the plant according to the invention is inexpensive and, in the current state of the art and of costs, the cost of such a plant is about one fifth or one sixth of the cost of a conventional plant by means of which liquid nitrogen is introduced into the packages before they are sealed.

Claims

1. Method for packaging liquid product in at least one package, characterized in that an inert gas such as nitrogen and/or carbon dioxide, in the gaseous state, is or are mixed with a liquid so as to form a product consisting of the liquid saturated or supersaturated with gas; this product is stored in a buffer reservoir (14) which is partially filled with product up to a predetermined level; this level is kept approximately constant and, above this level, an overhead of the said gas in the gaseous state, due to the saturation or the supersaturation, at a predetermined approximately constant raised pressure; the said product is transferred on demand from the buffer reservoir to the package, open to atmospheric pressure, keeping the said predetermined level and the said predetermined raised pressure in the buffer reservoir so as to partially fill the package with the said product with an overhead of the said gas at a pressure the value of which is approximately equal to that of the overhead in the buffer reservoir (14), and the package is sealed.

2. Method according to claim 1, characterized in that when, in the buffer reservoir (14), the raised pressure of the overhead of the said gas reaches the predetermined raised pressure, the excess gas is discharged.

3. Method according to either one of claims 1 and 2, characterized in that, in order to mix the inert gas and/or the carbon dioxide in the gaseous state into the liquid, this gas is injected into the liquid.

4. Method according to any one of claims 1 to 3, characterized in that the raised pressure in the overhead of the buffer reservoir (14) is set to a value lying in the range of 10 mbar to 3 bar.

5. Method according to claim 4, characterized in that the raised pressure is set to a value of about 50 mbar.

6. Plant for packaging liquid product in at least one package, characterized in that it comprises a first circuit (1) in at least part of which a liquid is circulated, a second circuit (2) in at least part of which an inert gas such as nitrogen and/or carbon dioxide, is circulated under pressure in the gaseous state and which at outlet comprises an injector (22) opening into an injection zone of the first circuit so as to form a product consisting of the liquid saturated or supersaturated with gas, the first circuit (1) comprising a buffer reservoir into which the said product is introduced, means for keeping a predetermined level of liquid in this buffer reservoir, control and regulating means (3) for maintaining a predetermined approximately constant raised pressure due to the saturation or supersaturation in the buffer reservoir, and means (4) for tapping from the reservoir in order to transfer the said product from it into the package with an overhead at a pressure the value of which is approximately equal to that of the overhead in the buffer reservoir (14).

7. Plant according to claim 6, characterized in that the first circuit (1) comprises a transfer pump (11), the inlet of which is supplied with liquid to be saturated or supersaturated with gas, for circulating this liquid, and a filling line (12), the upstream end of which is connected to the outlet of the pump, an injector belonging to the second circuit (2) opening into the line (2) downstream of the pump (11) for injecting the pressurized gas in the gaseous state thereinto.

8. Plant according to either one of claims 6 and 7, characterized in that the control and regulating means (3) comprise a regulator (31), a pressure transducer (32) measuring the pressure of the gas in the overhead of the reservoir (14) and a level detector (33) detecting the level of the said product in the reservoir (14), these being connected to the regulator, and a regulator exhaust valve (34), controlled by the regulator (31) and connected to the overhead in the reservoir (14) so as to discharge excess gas therefrom on the command of the regulator.

9. Plant according to any one of claims 6 to 8, characterized in that the second circuit (2) comprises injection equipment (21) supplying the injector (22), and the control and regulating means (3) comprise a regulator (31) electrically or pneumatically connected to the injection equipment in order to transmit to it a signal that regulates the injection.

10. Plant according to any one of claims 6 to 9, characterized in that the raised pressure kept approximately constant lies within the range from 10 mbar to 3 bar.

11. Plant according to claim 10, characterized in that the raised pressure has a value of about 50 mbar.

12. Plant according to any one of claims 6 to 11, characterized in that the control and regulating means (3) comprise a calibrated safety valve (35) connected to the top of the reservoir (14).