The present invention relates to a plant for treatment of a liquid flowing through a tube of flexible material, which simultaneously is moving in the flow direction of the liquid through a liquid filled first zone and then a liquid filled second zone, which plant comprises means forming a closed tunnel having inlet and outlet at its ends for movement of the flexible tube into, through and out of the tunnel, different parts of the tunnel coupled in series constituting said first and second zones, respectively, first inlet means and first outlet means arranged for liquid flow through the first zone around the flexible tube in the move¬ ment direction thereof, and second inlet means and second outlet means arranged fo ^' r liquid flow through the second zone around the flexible tube in the movement direction thereof.

In the following the invention will be described in connection with a plant for heat treatment of a liquid, that is flowing through a tube of flexible material in the above described manner, by means of one or more different other liquids caused to flow around the flexible tube through the above said tunnel. However, the invention is not limited to a plant for particularly heat treatment of the liquid in the flexible tube or to the fact that the treatment of this liquid is accomplished by means of the liquids caused to flow around the flexble tube through the tunnel. Thus, the invention principally is applicable also in con¬ nection with a plant arranged for a different kind of treatment, such as radiation treatment, of a liquid in a flexible tube, which treatment per se does not concern the liquids flowing around the flexible tube.

A plant of the kind in question is described schematically in a report published by Mr Lennart Stenstrδm at a conference in Princeton, USA, in 1983, "First International Conference on Aseptic Packing - ASEPTIPAK '83". The plant described in the report is based on an invention according to US-A-3.913.299.

vertical part is conncected with a supply means in the form of a funnel 4, and the horizontal part through the transferring device 3 is connected to one end of the pipe 2, which in its entirety extends horizontally. The other end of the pipe 2 through a transferring device 5 is connected with a discharge means comprising a tubular discharge member 6.

The pipes 1 and 2 and the transferring devices 3 and 5 form a tunnel, the inlet of which is situated in the funnel 4 and the outlet of which is situated in the outlet member 6.

A tube of flexible material containing a liquid to be heat treated in the plant is to- be moved through said tunnel. Liquid is to flow through the flexible tub,e while this moves through the plant. The drawing shows rolls 7, 8 with belt-formed flexible material and means 9 for continuous welding together of the belts leaving the rolls, so that a tube 10 is formed. A supply pipe 11 for liquid to fill the tube and to flow there¬ through extends from above into the tube 10 thus formed.

At the outlet end of the discharge member 6, outside thereof, there is a device (not shown) for cross-sealing of the liquid-filled tube 10 at even intervals as this leaves the discharge member 6. By such a cross-sealing separate portions of liquid are obtained within the tube 10, as shown at 12.

During operation of the plant the whole tunnel, that is formed by the pipes 1 and 2 and by the transferring devices 3 and 5, should be filled up with liquid around the flexible tube 10. This liquid during the movement of the tube 10 through the tunnel should move in the same direction, as the tube 10. For this purpose the plant comprises a first pump 13 that with its suction side through a conduit 14 is connected to said transferring device 3 and that with its pressure side through a conduit 15 is connected to the funnel 4. Further, a second pump 16 is connected with its suction side through a conduit 17 to the transferring device 5 and with its pressure side through a conduit 18 to the transferring device 3.

In the transferring device 3 there is a passage connecting the interior of the pipe 1 with the interior of the pipe 2 and preferably having a smaller cross-sectional area than the interior of both pipes 1 and 2. The described conduits 14 and 18 are connected to the transferring device 3 one at each side of the passage therein.

Also the transferring device 5 may have a passage for the flexible tube 10, which passage has a smaller cross-sectional area than the interior of the pipe 2. If so, the conduit 17 is connected upstream of this passage.

The discharge member 6, the interior of which constitutes a continuation of the tunnel through the pipes 1 and 2, has a discharge opening 19, the size of which substantially coincides with that of the cross-section of the liquid-filled tube 10. Below the opening 19 there is a container 20 for receiving liquid leaking out through the discharge opening 19.

A third pump 21 with its suction side, through a conduit 22, communicates with the interior of the container 20 and with its pressure side, through a conduit 23, communicates with the interior of the discharge member 6. Through a conduit 24 also a container 25 containing liquid is connected to the discharge member 6. A free liquid surface in the container 25 is substantially larger than the cross-sectional area in said tunnel (around the tube 10) and is situated at a higher level than the outlet opening ^' 19 in the discharge member 6.

As indicated in the drawing there is maintained a free liquid surface at a certain level in the funnel 4 around the flexible tube 10. A free liquid surface is maintained at about the same level within the flexible tube 10 in the area of the opening of the supply pipe 11. The liquid surface in the container 25 is situated, during operation of the plant, at a lower level than the liquid surface in the funnel 4.

Thus, a liquid body is maintained in the funnel 4 at the tunnel inlet and a liquid body is maintained in the discharge member 6 at the tunnel outlet, the liquid pressure being larger at the tunnel inlet than at the tunnel outlet.

A sensing and control unit 26 is arranged to sense the position of the liquid surface in the funnel 4 and to control through a connection 27 the capacity of the pump 21 such that the liquid surface in the funnel 4 is maintained at a predetermined level.

The conduit 15 extends through a first heat exchanger 28, that has a supply conduit 29 and a discharge conduit 30 for a heating medium. The conduit 18 e tends through a second heat exchanger 31 having a supply conduit 32 and a discharge conduit 33 for a cooling medium.

Liquid being pumped through the conduit 15 by means of the pump 13 will thus be heated in the heat exchanger 28 and will then, while it flows further on through the pipe 1, heat liquid present within the flexible tube 10. The pipe 1 forms a heating zone Zl.

Correspondingly, the pipe 2 forms a cooling zone Z2, in which the liquid in the flexible tube 10 is again cooled. Liquid being circulated by means of the pump 16 through the pipe 2 and the conduits 17 and 18 will thus be cooled in the heat exchanger 31 and will then cool liquid within the flexible tube 10.

The plant operates in the following manner.

Liquid to be heat treated in the plant is supplied continuously through the inlet pipe 11. Within the flexible tube 10, which is continuously formed in a manner described before and is moved downwards in the funnel 4, a free liquid surface is formed in the area of the opening of the supply pipe 11.

Simultaneously, liquid is circulated by means of the pump 13 through the conduit 15, the heat exchanger 28, the pipe 1 and the conduit 14, so that the liquid-filled flexible tube 10 is surrounded by heating liquid all the time while it is moved through the pipe 1, i.e. the heating zone Zl. In the same way liquid is circulated by means of the pump 16 through the conduit 18, the heat exchanger 31, the pipe 2 and the conduit 17, so that the liquid-filled flexible tube 10 is surrounded by cooling liquid all the time while it is moved through the pipe 2, i.e. the cooling zone Z2.

Even the discharge member 6, through which the liquid-filled flexible tube 10 is moved, is filled with liquid. A continuous liquid body is formed by liquid in the discharge member 6 and the liquid in the con¬ tainer 25. Liquid in the discharge member 6 has in the shown embodiment of the invention no thermal function. If desired, it can be given such a function, however, for instance a cooling function.

Depending upon a desired heat treatment of the liquid supplied through the inlet pipe 11, the capacities of the pumps 13 and 16 are set at desired values, among other things with regard to chosen flows and tem- peratures in the conduits 29 and 32. In dependence of the set capaci¬ ties of the pumps 13 and 16 a free liquid surface is formed at a certain level in the funnel 4. This level is sensed by means of the sensing and control unit 26 that controls the capacity of the pump 21, so that a pre¬ determined liquid pressure is maintained in the discharge member 6. At an unchanged capacity of the pumps 13 and 16 an unchanged liquid pressure in the discharge member 6 means that the liquid surface in the funnel 4 is maintained at a desired level.

This means that the pump 21 constantly will supply to the discharge mem- ber the same amount of liquid that leaves the same through the outlet opening 19. In other words, despite the fact that liquid constantly accompanies the flexible tube 10 out through the outlet opening 19, an ^' unchanged liquid pressure may be maintained within the discharge member 6.

By the above described arrangement it is automatically achieved that the liquid pressure in the pipe 1 immediately upstream of the passage in the transferring device 3 becomes substantially the same as the liquid pressure in the pipe 2 immediately downstream of the passage in the transferring device 3. This means that substantially no liquid at all flows through the passage in the transferring device 3 outside the flexible tube 10.

Even on boths sides of the transferring device 5 the liquid pressures are maintained at the same value, so that substantially no liquid at all passes out or in through the opening of the pipe 2 in the discharge member 6.

In this way stable pressure conditions are obtained in both the zones Zl and Z2. Further, it is avoided that heating liquid from the zone Zl is mixed with cooling liquid from the zone Z2.

The purpose of the continer 25 is that undesired pressure variations in the discharge member 6 during operation of the plant should be as small as possible and rapidly be evened out.

Already in the discharge member 6 but above all outside thereof the flexible tube 10 is allowed to expand, before separate liquid portions are formed therein by the above-mentioned cross-sealing of the same. This means that the liquid within the flexible tube moves faster than the tube itself through the two heat treatment zones Zl and Z2.

The movement of the flexible tube 10 through the plant is accomplished substantially by the flow of liquid taking place within as well as outside of the tube 10 in the zones Zl and Z2. In other words, the flowing liquids entrain the flexible tube 10 forwards and through the plant. Upon need auxiliary transporting means may be arranged, for instance after the discharge member 6. Thus, the above said means for cross-sealing of the flexible tube 10 may for instance be arranged also to exert a traction thereon. At the plant shown in fig 1 the liquid flow

through the flexible tube 10 is accomplished only by means of gravity. For avoiding that the plant has to be made unnecessarily high only for accomplishing a desired liquid flow through the tube 10, the funnel 4., the rolls 7 and 8, the sealing means 9 and a part of the supply pipe 11 may be arranged in a closed space, in which a super-atmospheric pressure is created and allowed to act on the free liquid surfaces in the funnel 4 and the flexible tube 10.

Upon need the liquid flow through the flexible tube 10 may be accomp- lished by means of a hose pump of the kind shown in US-A-3.913.299.

At the plant described above the discharge member 6 has a discharge opening 19 for the flexible tube 10 situated such that liquid all the time leaks out around the tube 10. Alternatively, the discharge member 6 and the container 25 could be replaced by a large funnel, to the lower part of which the transferring device 5 would be connected. The funnel would then contain a liquid body having a free liquid surface, the flexible tube 10 being transported out of the plant by being moved upwardly through the funnel. In this case the flexible tube 10 would preferably be cross-sealed, such that separate liquid portions would be defined therein, already before the flexible tube would leave the liquid in the funnel.

Fig 2 shows a heat treatment plant very much resembling the plant in fig 1. For details which exactly correspond to each other in the two plants the same reference numerals have been used in fig 1 and fig 2.

As can be seen, there has been added to the plant in fig 2 a further transferring device 34, which connects a horizontal pipe section la with a vertical pipe section lb. The horizontal pipe section la forms a heat treatment zone Zla, which corresponds to the heat treatment zone Zl in fig 1. To the pipe section la there is connected a recirculation means ^" comprising a pump 13a, conduits 14a, 15a and a heat exchanger 28a having inlet and outlet conduits 29a and 30a, respectively.

To the vertical pipe section lb there is connected a recirculation means comprising an outlet conduit 14b, that is connected with the transferring device 34 and with the suction side of a pump 13b, and an inlet conduit 15b, that is connected with the pressure side of the pump 13b and with the funnel 4. There is no heat exchanger in this recirculation means.

In the plant according to fig 2 both of the heat treatment zones Zla and Z2 are situated in the horizontal pipe sections la and 2, whereas the vertical pipe section lb only has for its purpose to enable use of gravity for the obtainment of the desired liquid flow through the flexible tube 10. It is important in this connection that both liquids flowing through the vertical pipe section lb within and outside the flexible tube 10 have substantially the same density, so that the flexible tube 10 will not be compressed to a differnt degree at different levels in the pipe section lb. If the liquids are of substantially the same kind, this can be most easily accomplished if the two liquids have substantially the same temperature in the whole pipe section lb. Inde¬ pendent of which kind of liquid is used in the circulation circuit lb, 14b, 13b, 15b it may be necessary to heat or cool this liquid for main- taining of a desired temperature and, thereby, a desired density thereof. Possibly, it may be necessary to use one kind of liquid for the recircu¬ lation circuit lb, 14b, 13b, 15b and a different kind of liquid - having a different density — as a heat treatment liquid in the recirculation circuit la, 14a, 13a, 15a.

In the above described two embodiments of the plant according to the invention only two heat treatment zones are shown. Of course, any number of heat treatment zones may be arranged in the described tunnel. Further¬ more, the tunnel need not extend exactly horizontally. It may prove suitable to make the tunnel somewhat inclined, whereby it may be avoided that air is collected in the tunnel and in the flexible tube. In this case, the tunnel preferably is inclined such that possibly enclosed air moves in the same direction as the liquids in the tunnel and the flexible tube, respectively.