Process and a device for headspace foaming of containers filled with carbonated beverages

A process for the foaming of the headspace of containers filled with carbonated beverages, wherein, after the filling of the beverages into the containers, the containers are transferred to a foaming area, in which an electromagnetic beam, preferably a laser beam, is irradiated in a controlled way into the headspace of the container which is not filled with the beverage, whereby, due to the resultant foaming, the gas volume in the headspace is displaced from it, and the containers are subsequently sealed, as well as to a device for carrying out the process.

FIELD OF THE INVENTION
 The invention relates to a process for headspace foaming of containers
 filled with carbonated beverages, in which the beverage is foamed in the
 container after filling so that the volume previously contained in the
 headspace is displaced from it due to the ascending foam, and a device for
 carrying out this process.
 BACKGROUND OF THE INVENTION
 In bottling plants, beverages are filled into containers in such a way that
 a residual gas volume remains in the headspace of the containers. This
 residual volume is at first filled with carbon dioxide in the case of
 beverages containing CO.sub.2. Since the containers are exposed to ambient
 air during transfer form the bottling station to the sealing station,
 there is a risk of oxygen entering the headspace during this transfer,
 which promotes germ formation in such beverages and thus greatly reduces
 their storage stability.
 For the afore-mentioned reason, beverages are conventionally foamed during
 transfer from the bottling station to the sealing station by introducing a
 gaseous or liquid medium into the headspace onto the surface of the
 beverage so that the resultant foam expels the gas volume, and thus also
 the oxygen that has entered, from the headspace. Thus, the oxygen content
 in the headspace will be reduced at the moment the container is sealed.
 One example of such a foaming device is disclosed in German Utility Model
 No. 91 16 815 U1. A jet of liquid, here in particular water, is introduced
 into the headspace of the filled containers at a pressure of 40 bar by
 means of the device described therein. The pulse of the water jet can be
 regulated.
 It is in particular disadvantageous in such process and devices according
 to the prior art that after the high-pressure water injection the beverage
 foam has relatively large pores so that, despite large overfoam volumes (2
 to 5 ml/container), the average oxygen values that can be achieved in the
 headspace are not better than 0.018 to 0.12 mg per liter. The
 disadvantageously large overfoaming results in a high waste water
 pollutant load and thus substantial liquid waste disposal costs; also, the
 large overfoam volumes are equivalent to net beverages losses which, of
 course, are expensive per se.
 A further main disadvantage of this known foaming process resides in the
 fact that water, and thus foreign media, is injected into the beverage,
 thereby diluting it. There is danger of germs being injected into the
 beverage together with the water, while, to avoid this danger, special
 equipment for preparing germ-free water must be provided.
 SUMMARY OF THE INVENTION
 The object of the present invention is to create a method and a device for
 headspace foaming of containers filled with carbonated beverages, which
 overcome the aforementioned disadvantages of the prior art. In particular,
 the invention is intended to achieve a good storage stability of the
 contained beverages and very low foaming losses.
 The advantage of foaming the beverage according to the invention is first
 that the foam ascending from electromagnetic beam foaming has much finer
 pores than, for instance, foam resulting from water injection, and thus
 becomes substantially more gas-tight. The amount of oxygen remaining in
 the headspace after foaming with an electromagnetic beam is very low, and
 in a range that conventional high-pressure injection systems with
 comparable overfoaming losses cannot even approach.
 Another advantage is that the microporous foam arising from the irradiation
 with a controlled electromagnetic beam can be regulated very well with
 regard to the resultant foam quantity and therefore foaming losses can be
 minimized. Thus, the overfoam volumes, which are expensive and waste-water
 polluting per se, can be greatly reduced.
 A further advantage of the foaming according to the invention resides in
 the fact that special plant technologies for preparing germ-free water are
 no longer required since, as a matter of course, water is not used as a
 foaming agent. As a further result of the fact that the introduction of
 water can be dispensed with is that the beverage no longer experiences
 dilution or contamination with residual germs in the water.
 The electromagnetic beam may be, for example a micro wave beam or the like.
 According to a preferred embodiment of the invention, the electromagnetic
 beam comprises a laser beam.
 According to a preferred embodiment of the present invention, the
 containers pass along a bottling conveyor, a transfer conveyor and a
 sealing conveyor, with the point of foaming by means of laser irradiation
 being located immediately upstream of the point of sealing of the
 containers. According to such a development, the foaming of the beverage
 is carried out shortly before the sealing of the containers, i.e. there is
 little time for the oxygen-containing ambient air to enter the headspace
 after the foam has displaced the gas therein.
 In accordance with one embodiment of the present invention the laser beam
 is radiated into the headspace in a pulsed fashion, while it may
 preferably be triggered by a triggering means such as an ultrasonic switch
 or a light barrier at a triggering rate adapted to the speed of the
 containers that pass through. As an alternative to triggering by external
 triggering means, the laser beam may be pulsed per se.
 However, the laser beam may, alternatively, also be radiated into the
 headspace in a continuous fashion.
 The laser beam radiated onto the surface of the beverage may be adjusted in
 its intensity, pulse shape, length and/or frequency; according to the
 requirements of the specific application.
 According to a further embodiment of the invention, the level of foam in
 the headspace is measured or detected, respectively, by measuring means
 and the intensity, pulse shape, length and/or frequency are adjusted
 dependent on the detected level.
 By means of controlling devices as usually employed in laser technology the
 following parameters for the laser radiation may be set for a preferred
 embodiment of the invention.
 The average power of the laser beam irradiated onto the surface of the
 beverage may be adjusted in the range of about 10 to 20000 W; the
 frequency of the laser beam may be adjusted in the range of about 5 to
 about 2000 Hz, and the shutter opening time should be in the range of 5 ms
 to 2000 ms.
 The foaming of the beverage is induced by the energy of the laser beam.
 Since different beverages also foam differently, the power of the laser
 beam irradiated into the headspace can in each case be adjusted so
 accurately that foaming losses are minimized while, at the same time, the
 greatest possible amount of oxygen is expelled.
 Advantageously, the vicinity of the laser beam radiation point may be
 surrounded by a haze of an inert gas, provided by a corresponding
 apparatus, in order to avoid the entry of ambient air into the headspace.
 The device according to the invention preferably has a laser beam emitter
 comprising a CO.sub.2 laser with a maximum performance of 10 to 20000 W, a
 duty cycle of 5 to 100%, an optical guiding system for the laser beam, and
 a focusing means with a lens having a diameter of about 3.81 cm (1.5 in.)
 and focal point diameter of 300 to 500 .mu.m.

FIG. 1 shows an elevation of an embodiment of a device according to the
 invention for headspace inertization. The foaming means of this device is
 designated in general with the reference numeral 10. It comprises a
 CO.sub.2 laser 15 which is firmly anchored to the floor next to a transfer
 conveyor 33 indicated in dash-dotted lines. The transfer conveyor 33
 conveys containers 18, here bottles, already filled with beverage from a
 bottling conveyor 31 to a sealing conveyor 32 (cf. FIG. 3).
 The CO.sub.2 laser 15 provides a laser beam which is directed into an
 optical guiding system 16 for the laser beam. This system 16 is designed
 as an arm spanning the distance between the CO.sub.2 laser 15, the focus
 means 17 being placed directly above the mouth of the bottle 18 to be
 processed.
 The laser beam irradiated onto the surface of the beverage has a power of
 about 10 to about 20000 W, the frequency of the laser beam being adjusted
 to about 5 to about 2000 Hz, and the shutter opening time being about 5 ms
 to 2000 ms. The employed CO.sub.2 laser shows an average performance of
 about 10 to about 20000 W and has a duty cycle of about 5 to 100%.
 The above variable parameter are set by known control devices for laser
 beam technology and adjusted in such a way that, in any case, a suitable
 laser beam with a predetermined power is injected for a specific type of
 beverage with a predetermined carbonization and/or a predetermined
 CO.sub.2 contents which effects a foaming in the beverage, but does not
 result in high foaming losses. Thus, foaming is induced in a proportional
 relationship with the power of the laser beam. In the optimum case, the
 laser beam is radiated onto a black surface.
 The foaming of the beverage by a laser results in a highly microporous foam
 which displaces the gas volume contained in the bottle 18 up to then due
 to its ascension in the headspace of the containers 18. Because of its
 microporosity, the resultant foam is highly gas-tight and effects a type
 of plug flow in the container neck. Therefore, only a very small amount of
 the original gas volume remains in the headspace, the gas tightness of the
 microporous foam alone prevents air from the environment from entering the
 headspace.
 As a result of this process, the oxygen content in the headspace is at a
 very low value when the containers 18 are sealed, a result which
 conventional high pressure water injections in which large-pore foam is
 formed can not achieve. With such a small amount of oxygen in the
 headspace, the risk of germ formation is minimized. The storage stability
 of the filled beverage is greatly improved. Due to the exact adjustability
 of the parameters of the laser beam, an exactly controllable foaming takes
 place, and overfoaming losses are largely prevented so that high pollutant
 loads in the waste water can also be prevented.
 In FIG. 2 the focus means 17 is shown. It may be seen that the lens center
 is positioned at a short distance directly above the center of the bottle
 mouth such that the laser beam emitted therefrom directly hits the surface
 of the beverage without being deflected by any portion of the bottle neck.
 FIG. 2 further shows how the vicinity of the bottle mouth may be surrounded
 with a haze of gaseous nitrogen (GAN). Two streams of gaseous nitrogen are
 employed, namely one annular vertical stream 21 which may be supplied by
 an annular nozzle 20 surrounding the focus means 17, and a horizontal
 stream supplied by a nozzle 20. The vertical GAN stream prevents air from
 entering the bottle neck, while the horizontal stream and the vertical
 stream prevent foam ascending in the headspace of the bottle 18 from
 approaching the focus means and thereby contaminating it.
 The supply means for the GAN streams are described in FIG. 3 which shows a
 top view of the headspace inertization means according to the invention.
 The arrangement of the foaming means 10 with the CO.sub.2 laser 15, the
 arm 16 of the optical guiding system for the laser beam, and the focus
 means 17 in relation to the conveying facilities for the containers 18 is
 apparent from this view. Filled containers 18 are delivered by a bottling
 conveyor 31 that rotates clockwise, and is partially shown at the lefthand
 side, to a transfer conveyor 33 which rotates counterclockwise. Just
 before the sealing of the bottles 18 in the sealing conveyor 32, the laser
 beam is radiated into a container 18. This irradiation takes place just
 prior to the sealing of the container 18 so that as little ambient air as
 possible can enter the headspaces of the containers 18 before they are
 sealed.
 Upon irradiation by the laser beam the beverage liquid contained in the
 bottles 18 foams so that the gas in the headspace is expelled and no
 ambient air can enter the headspace of the containers 18 until they are
 sealed.
 Supply means 35 and 36 for the GAN hazing streams are also shown in FIG. 3.
 They may comprise pipes with valves incorporated, leading from a GAN
 reservoir to the annular nozzle providing a GAN stream 21 (FIG. 2) or to
 the nozzle 20 (FIG. 2) providing the horizontal GAN stream.
 The supply means 35 comprises a pipe which leads through the arm 16 to the
 focus means at the radiation point.
 A sensoring means 34 in connection with the triggering control of the laser
 15 is arranged near the radiation point. This sensoring means 34 supplies
 information about the frequency of the arriving bottles 18 so that the
 laser 15 may be triggered exactly in correspondence with said frequency.
 Although the invention has been described by means of an embodiment so far
 with regard to foaming of beverage in bottles, it is understood that the
 process and the device according to the invention can also be used for
 headspace foaming of other containers, e.g. cans, etc. and for the foaming
 of various beverages, e.g. beer, soft drinks, etc., in particular
 carbonated beverages.