Drinking teat and device for watering animals, and method for production of said drinking teat

Abstract

The invention relates to a drinking teat for watering animals, comprising an adapter (11) configured for releasably connecting to a liquid reservoir (10) and a liquid line (12) which opens into a drinking opening (13) which is configured for the drawing of liquid by an animal, wherein the adapter (11) and the liquid line (12) form a fluid-conducting interior (14) and is characterised in that at least in a partial section of the liquid line (12) a liquid-impermeable conducting element (16) configured for guiding gas bubbles (15) is arranged in a stationary manner. The invention also relates to a device for watering animals, comprising a liquid reservoir (10) having a drinking teat with the aforementioned features. The invention also relates to a method for producing the drinking teat according to the invention.

Description

[0001] Drinking nipple and device for watering animals and method for its manufacture

[0002] The present invention relates to a drinking nipple for watering animals, in particular small animals, comprising an adapter designed for detachable connection to a liquid reservoir and a liquid line opening into a drinking opening designed for liquid extraction by an animal, wherein the adapter and the liquid line form a fluid-conducting interior space. Furthermore, the invention relates to a device for watering animals, comprising a liquid reservoir with a drinking nipple. Furthermore, the invention relates to a method for producing a drinking nipple designed for watering animals.

[0003] Such drinking nipples and devices are used particularly in the keeping of small laboratory animals, such as mice and rats. Such animals are usually kept in cages, whether for research purposes or privately. Drinking bottles according to the device mentioned above, equipped with the aforementioned drinking nipples, are used to ensure the animals' fluid supply.

[0004] These devices comprise a liquid reservoir, for example in the form of a drinking bottle, with a drinking nipple arranged on this liquid reservoir. The drinking nipple comprises a liquid line that surrounds a fluid-conducting interior, through which the liquid is guided from the liquid reservoir to the drinking opening from which the animal can draw the liquid. The device is usually arranged "upside down" on the cage so that the drinking nipple hangs downwards and the liquid reservoir is above it. Due to gravity, an increasing hydrostatic pressure is created in the interior towards the drinking opening. Atmospheric air pressure acts from the outside at the drinking opening against this. Due to the higher external air pressure compared to the hydrostatic pressure at the drinking opening, the liquid is prevented from leaking out as long as the drinking opening is not touched by the animal from the outside.

[0005] If an animal comes into contact with the drinking opening, a certain amount of liquid will either leak out or be actively drawn by the animal by licking the drinking opening. As a result, a negative pressure develops in the interior over time compared to the surrounding atmosphere. Previously, it was assumed that the negative pressure created in the liquid reservoir during the animal's withdrawal of liquid would cause an air bubble to form, which would rise in the liquid line and equalize the pressure in the reservoir. Such pressure equalization is always necessary to allow further withdrawal of liquid.

[0006] Contrary to the assumption that an air bubble forms in the fluid line over time as the animal consumes water, originating at the drinking opening. This air bubble expands, detaches after a while, and rises upwards, thus causing the aforementioned pressure equalization, something else actually occurs. In fact, it has been observed that this required pressure equalization does not occur reliably. Rather, it has been determined that on the inside of the drinking opening, in the area of ​​the interface between the liquid and the outside atmosphere, the surface tension steadily increases as an animal draws liquid, until this boundary layer or interface is suddenly breached and air suddenly flows into the drinking opening.

[0007] During this process, the air bubble takes up a significant portion of the space in the fluid line, displacing the fluid across its entire cross-section. Such bubbles in lines are known as Taylor bubbles. These bubbles are named after the British physicist Geoffrey Ingram Taylor. They form as gas bubbles in a fluid-filled line and always strive to fill the entire cross-section of such a line, completely displacing the fluid in this area. The space required by such a Taylor bubble prevents, or at least impedes, fluid from flowing downwards between the inner wall of the fluid line and the Taylor bubble.

[0008] However, the rise of gas bubbles in the liquid line is a prerequisite for an animal to always be able to extract liquid from the drinking opening.

[0009] A Taylor bladder that is "stuck" in the area of ​​the drinking opening effectively causes the drinking cap to fail, meaning the animal can no longer obtain any liquid from that moment on. The ascent of a Taylor bladder also depends on the fluid being able to move downwards past the contact surface between the Taylor bladder and the inner wall of the fluid line. However, since the Taylor bladder strives to fill the entire interior of the fluid line, only a very small area remains between the inner wall of the through-capillary and the Taylor bladder in which the fluid can flow downwards.

[0010] The mechanism of Taylor blister formation described above therefore poses a threat to animal welfare. Thirsty animals, dehydrated animals, and even deaths have been observed in considerable numbers. For example, in an animal facility with approximately 900 cages and 3,000 mice, an average of three to twelve cases of dehydrated, dead, or thirsty animals were observed per week. Entire groups of animals were also affected, so it can be ruled out that the lack of or undersupply of fluid is due to the drinking behavior of individual animals. Rather, there is reason to believe that this is a systematic underlying problem with the drinking nipples and caps currently available on the market, and that a large number of animals are regularly receiving insufficient fluid, unbeknownst to animal keepers.

[0011] It has been observed that the fluid supply of laboratory animals can regularly be compromised. This occurred particularly frequently when the air pressure remained almost static at one level for an extended period or increased constantly at a sufficient rate of change (usually in summer), presumably resulting in the formation of a trapped Taylor bladder behind the drinking opening. For the reasons described above, fluid extraction by licking the drinking opening is no longer possible.

[0012] An animal can only overcome such a "drying out" of a section of the fluid line by either shaking the drinking nipple or, as has been observed in rats, by blowing air into the fluid line with its nose, which expels the Taylor bladder(s) and subsequently completely fills the fluid line with fluid up to the drinking opening.

[0013] However, options such as shaking or blowing air into the cages are not feasible for most animals. Mice, in particular, are usually too small to perform such a feat of strength. Furthermore, the drinking systems are often completely fixed to the cages. Only external intervention, such as a sufficient change in air pressure or intervention by the animal caregiver, can clear the blockage. Such intervention by the animal caregiver would be time-consuming and costly, and given the large number of animals in the laboratory, is practically unfeasible.

[0014] In addition, the problem of the lack of fluid supply to test animals appears to occur entirely randomly, since the random initial position of the drinking system determines the further course of the scenario in the event of an unfavorable air pressure pattern. This means that, either on its own or in combination with a slight or static change in air pressure and the fact that the drinking nipple opening may not have been used by the test animal for an extended period, the drinking or dispensing opening subsequently extends a short distance into the fluid line, both externally and internally.

[0015] If, as described, a Taylor bladder has formed behind the drinking opening, extending deep into the fluid line, it is impossible for the animal to transport fluid forward to the drinking opening, and the drinking system thus ceases to function. It is assumed that the various influencing factors, viewed individually or in combination, are the reason why the undersupply or lack of supply does not occur simultaneously in a larger group of drinking bottles, but rather occurs sporadically and unpredictably.

[0016] The object of the present invention is therefore to propose a drinking nipple that always ensures a reliable supply of liquid to animals. Furthermore, the object is to propose a device with such a drinking nipple. Furthermore, the object of the present invention is to provide a method for producing such drinking nipples.

[0017] The drinking nipple with the features mentioned above achieves this objective by stationary mounting a fluid-impermeable guide element designed to guide gas bubbles at least in a portion of the liquid line. Advantageously, this reliably prevents gas bubbles, particularly Taylor bubbles, from spreading across the entire cross-section of the liquid line and / or causes these bubbles to rise. This ensures that bubbles forming or present in the liquid line always rise against gravity, while simultaneously allowing liquid to flow past the bubbles in the direction of gravity. This ensures that no gas or air bubble remains permanently in any portion of the liquid line.This ensures that the fluid line up to the drinking opening is always filled with fluid, ensuring that an animal can extract fluid from the drinking opening at any time. The fluid-impermeable guide element, which is neither permeable to liquid nor gas, thus represents an inhomogeneity in the generally regular internal cross-section of the fluid line.

[0018] The liquid line is preferably straight or angled over its entire length and has, for example, lengths between 25 mm and 80 mm. More preferably, the drinking nipple is cap-shaped. The drinking opening, which is also referred to as the dispensing opening, has, for example, a diameter of approximately 1.2 mm to 1.6 mm and preferably extends over a length of approximately 2 mm. An expedient embodiment of the invention is characterized in that the guide element is arranged so as to be adjacent to an inner wall of the liquid line. This offers the advantage that the guide element prevents any inhomogeneity or irregularities on the otherwise generally smooth surface of the inner wall of the liquid line.A disruption of the surface geometry is created, which reliably prevents both the formation and persistence of Taylor bubbles in one place. This is also achieved by always maintaining a path open for the fluid past the bubble, allowing it to flow downward to the extraction opening. This ensures that the animal can extract fluid at any time.

[0019] A preferred development of the invention is characterized in that the guide element is configured such that the inner surface formed by the inner wall of the liquid line and the guide element has at least one region of greater curvature compared to the greatest curvature of the inner wall of the liquid line. Particularly preferably, the region of greater curvature has such a large curvature that this curvature is abrupt compared to the greatest curvature of the inner wall. In this way, the smoothness of the overall inner surface is interrupted because the curvature changes unsteadily. This additionally counteracts the formation of otherwise adhering Taylor bubbles.

[0020] According to a further preferred embodiment, the regions of greater curvature are formed by projections, corners, or edges. It is also possible for the regions of greater curvature to be formed by raised material on the inside of the fluid line, for example, by knobs, bump-like elevations, or the like.

[0021] A further expedient embodiment of the invention is characterized in that the guide element is spiral-shaped. This offers the advantage that the spiral shape has a guiding function. Air bubbles are guided upwards against gravity by the helical shape of the spiral guide element. Alternatively, the guide element is designed as a perforated plate or in the form of a wire mesh. A further expedient embodiment of the invention is characterized in that the clear width of the guide element is at least substantially smaller than the inner diameter of the liquid line. In this way, it is possible to insert the guide element into the liquid line and arrange it therein. A particular advantage arises from the fact that conventional drinking nipples can be retrofitted to the advantageous drinking nipples according to the invention in a particularly simple manner by arranging the guide element in the liquid line.This makes it possible to retrofit drinking nipples that are available on the market as mass-produced goods in large quantities, either manually or automatically, with relatively little manufacturing effort.

[0022] A preferred development of the invention is characterized in that the clear width of the guide element, at least in one holding section, is selected to be larger than the inner diameter of the fluid line, such that the guide element is arranged in the fluid line in a clamped fit, supported by its inner wall. Advantageously, the guide element is thus designed to be self-retaining. This significantly simplifies the production of the drinking caps according to the invention, since the guide element only needs to be inserted into the fluid line and automatically transitions into the clamped fit.

[0023] A further advantageous embodiment of the invention is characterized in that the guide element length corresponds at least to the length of the liquid line. This ensures that gas or air bubbles are reliably prevented from remaining in all areas of the liquid line, thus actively counteracting the formation of Taylor bubbles.

[0024] According to a further preferred embodiment, the guide element is arranged extending from the drinking opening into the liquid line. This advantageously ensures that the area of ​​the drinking opening is always free of bubbles and thus filled with liquid. Only when this area is always filled with liquid can it be guaranteed that liquid can be drawn from the drinking opening. If there were a gas or air bubble in the area of ​​the drinking opening, licking by an animal looking for liquid would not result in any liquid being drawn. The initiation of liquid drawing from the drinking nipple is always accompanied by a certain amount of liquid being drawn through licking the drinking opening and air flowing into the liquid line to equalize the pressure so that more liquid can be drawn.Once a Taylor bladder becomes lodged in the area of ​​the drinking opening, it would permanently prevent the possibility of initiating fluid withdrawal.

[0025] A further advantageous embodiment of the invention is characterized in that at least a portion of the guide element is arranged so as to protrude into the drinking opening. This ensures that no gas or air bubbles become trapped directly in the drinking opening.

[0026] According to a further preferred embodiment of the invention, the guide element is wire-shaped. This allows the guide element to be manufactured simply and cost-effectively.

[0027] A further advantageous embodiment of the invention is characterized in that the guide element consists of a hydrophilic material or is at least coated with such a material. This offers the advantage of preventing the formation of a distinct interface layer. The use of a hydrophilic material improves wetting with liquid and thus the transport of the liquid, thus counteracting the adhesion and persistence of bubbles in one place. In other words, the bubbles are constantly detaching from the inner surface of the liquid line.

[0028] A suitable embodiment of the invention is characterized in that the guide element comprises, consists of, or is coated with a metal or metal alloy. Stainless steel, for example, type 1.4576, is preferably used. Gold or other precious metals, for example, are used as the coating material.

[0029] According to another preferred embodiment, the drinking nipple is formed in one piece. This offers the advantage that the guide element is firmly connected to the fluid line. The guide element is thus securely positioned in the fluid line and / or secured against loss and / or displacement.

[0030] A preferred development of the invention is characterized in that the drinking opening and / or the liquid line is designed without a valve. Advantageously, the drinking nipple according to the invention comprises no moving parts, so that it is maintenance-free and absolutely reliable in terms of its function. Furthermore, it is simple and cost-effective to manufacture. In principle, however, the present invention is also suitable for drinking nipples that comprise a drinking valve, for example those that comprise a ball closure as a drinking valve, i.e. comprise a movably mounted ball present in front of the drinking opening in the liquid line, which is displaced by the licking movement of an animal in such a way that liquid is withdrawn.

[0031] A further advantageous embodiment of the invention is characterized in that the drinking opening has a diameter that is smaller than the inner diameter of the liquid line. The reduced diameter of the drinking opening compared to the inner diameter of the liquid line prevents the tendency for liquid to leak, i.e., the unintentional escape of liquid without an animal licking the drinking opening. However, it is also possible for the diameter of the drinking opening to correspond to the inner diameter of the liquid line. For example, the diameter of the drinking opening is approximately 1.2 to 1.6 mm.

[0032] Furthermore, the object is achieved by a corresponding device which comprises a drinking nipple for watering animals comprising a liquid reservoir with a drinking nipple having the features described above.

[0033] Furthermore, the object is achieved by the method mentioned above for producing a drinking nipple with the aforementioned features by providing a drinking cap comprising an adapter configured for detachable connection to a liquid reservoir and a liquid line opening into a drinking opening configured for liquid extraction by an animal, wherein the adapter and the liquid line form a fluid-conducting interior, and by stationary arrangement of the fluid-impermeable guide element configured for guiding air bubbles in at least a partial section of the liquid line. Advantageously, the invention thus makes it possible to convert drinking caps already known from the prior art into the drinking nipple according to the invention extremely inexpensively with the least possible manufacturing effort.

[0034] Further preferred and / or expedient features and embodiments of the invention emerge from the dependent claims and the description. Particularly preferred embodiments are explained in more detail with reference to the accompanying drawings. The drawing shows:

[0035] Fig. 1 is a schematic representation of a drinking nipple known from the prior art,

[0036] Fig. 2 is a perspective view of a first embodiment of the drinking nipple according to the invention and of the device,

[0037] Fig.3 is a perspective view of a second embodiment of the drinking nipple according to the invention and of the device,

[0038] Fig. 4 is a schematic representation of a forming Taylor bubble,

[0039] Fig. 5 is a schematic representation of an enlarging and stuck Taylor bubble,

[0040] Fig. 6 is a schematic representation of a Taylor bubble rising in the liquid line,

[0041] Fig. 7 is a schematic representation of the drinking nipple according to the invention with a variant of the guide element,

[0042] Fig. 8 is a schematic representation of the operating principle of the drinking nipple according to the invention,

[0043] Fig. 9 is a schematic representation of a Taylor bladder filling the entire liquid line and Fig. 10 is a schematic representation of the beginning of inflowing air through the drinking opening.

[0044] Figure 1 schematically shows a drinking nipple as known from the prior art. This comprises an adapter 11 designed for detachable connection to a liquid reservoir 10 (not shown in Figure 1). The drinking nipple further comprises a liquid line 12 that opens into a drinking opening 13. The drinking opening 13 is designed for liquid extraction by an animal. The adapter 11 and the liquid line 12 form a fluid-conducting interior space 14.

[0045] Figure 1 schematically shows gas bubbles 15. These are intended to illustrate the current ideal of the functionality of the drinking nipple, drinking device, or drinking bottle known from the prior art. As already explained at the beginning, it was previously assumed that when liquid is drawn through the drinking opening 13, air enters the liquid line 12 via this opening, and several gas bubbles 15 rise in the liquid line 12 against gravity, thus leading to pressure equalization in the liquid reservoir 10 (not shown in Figure 1).

[0046] Figures 2 and 3 show two embodiments of the device according to the invention for watering animals. Each shows the liquid reservoir 10 with a drinking nipple according to the invention. The drinking nipple is detachably attached to the liquid reservoir 10 by means of its adapter 11, for example, by means of a screw, bayonet, or clamp fastening.

[0047] Figures 4 to 6 schematically show the actual behavior of gas bubbles 15 in such drinking nipples. Air entering via the drinking opening 13 does not form a bubble behind the drinking opening 13 - as shown in Figure 10 - but the tension between the outside atmosphere and the liquid in the liquid line 12 continues to increase until it is virtually explosively broken and a large amount of air flows into the liquid conductor 12. With increasing air entry, this increases, as shown in Fig. 5 and may even rise at least a short distance upwards in the liquid line 12. As already explained at the beginning, these gas bubbles 15 form as so-called Taylor bubbles, which remain stationary inside the liquid line 12 for long periods of time, even to the point of the liquid line 12 partially or completely drying out. In extreme cases, this can lead to - as shown in Fig.9 as an example – the entire fluid line 15 dries out. The consequences of such Taylor bubble formation and the associated disadvantages have already been explained in detail at the beginning.

[0048] According to the invention, a fluid-impermeable guide element 16 is provided in at least a partial section of the liquid line 12. The guide element 16 is thus designed such that it is impermeable to gases and / or liquids. In particular, the guide element 16 is configured such that it has no capillary conducting effect. The guide element 16 is arranged in the liquid line 12, in particular, in a stationary manner, i.e., immobile both within itself and relative to the liquid line 12.

[0049] Fig. 7 shows an example of the guide element 16 arranged in the liquid line 12. As shown in Fig. 7, the guide element 16 extends over the entire length of the liquid line 15. However, the present invention is not limited to this exemplary arrangement of the guide element 16. Rather, the guide element 16 is alternatively arranged only in a partial section of the liquid line 12. The guide element 16 is designed in particular to guide the gas bubbles 15.

[0050] As shown in Fig. 2, the liquid line 12 is preferably straight over its entire length, so that the guide element length corresponds at least to the length of the liquid line 12. It is also possible for the liquid line 12 to be angled, as shown in Fig. 3. These are preferably between 25 mm and 80 mm long.

[0051] Preferably, the guide element 16 is arranged adjacent to an inner wall 17 of the liquid line 12. Alternatively, the guide element 16 can also be attached point-by-point to the inner wall 17, for example, by a spot-welded connection. Further preferably, the guide element 16 is configured such that the inner surface formed by the inner wall 17 of the liquid line 12 and the guide element 16 has at least one region of greater curvature compared to the greatest curvature of the inner wall 17 of the liquid line 15.

[0052] The areas of greater or larger curvature are preferably formed by projections, corners, or edges (not shown in the drawing). It is also possible for the areas of greater curvature to be formed by material elevations on the inner side 17 or fluid line 15, for example by knobs, bump-like elevations, or the like (also not shown in the drawing).

[0053] More preferably, the guide element 16 is spiral-shaped—as illustrated by way of example in Figures 7 and 8. Preferably, the diameter of the spiral is smaller than the diameter of the fluid line 15. According to an alternative embodiment, the guide element 16 is designed as a perforated plate 18 or in the form of a wire mesh 19, as schematically illustrated in Figure 10. Preferably, the hole size of the perforated plate 18 or the mesh size of the wire mesh 19 is selected such that they do not form a capillary-acting guide structure.

[0054] Preferably, the inside diameter of the guide element 16 is at least substantially smaller than the inside diameter of the liquid line 15. According to a further advantageous embodiment of the invention, the inside diameter of the guide element 16 is selected to be larger than the inside diameter of the liquid line 15, at least in a holding section, such that the guide element 16 is arranged in a clamp fit in the liquid line 12, supported on its inside wall or inside wall 17.

[0055] More preferably, the guide element 16 is arranged extending from the drinking opening 13 into the liquid line 12. According to an alternative embodiment of the invention, at least a portion of the guide element 16 is arranged to protrude into the drinking opening 13. As shown in Figures 7 and 8, the guide element 16 is preferably wire-shaped. Advantageously, the guide element 16 comprises a hydrophilic material or is at least coated with such a material.

[0056] More preferably, the guide element 16 is made of a metal or metal alloy or is coated with one. Stainless steel, for example, type 1.4576, is preferably used. Gold or other precious metals, for example, are used as the coating material.

[0057] Preferably, the drinking nipple according to the invention is formed in one piece, ie the guide element 16 is integrally connected to the liquid line 12 or its inner wall 17.

[0058] More preferably, the drinking opening 13 and / or the liquid line 12 are designed without a valve. However, the present invention is not limited exclusively to such valve-free liquid lines 12, but is also suitable for liquid lines 12 with valves, which, for example, comprise a ball valve. As shown in the drawing, the drinking opening 13 preferably has a drinking opening diameter that is reduced compared to the inner diameter of the liquid line 12.

[0059] The present invention also encompasses the method mentioned above for producing a drinking nipple with the aforementioned features. According to the invention, a drinking cap, i.e., a drinking nipple known from the prior art, is provided for producing the drinking nipple according to the invention, which has an adapter 11 designed for detachable connection to a liquid reservoir 10. The method also involves arranging the fluid-permeable guide element 16 in a fixed position at least in a partial section of the liquid line 12.

Claims

1. Drinking nipple for watering animals, comprising an adapter (11) designed for detachable connection to a liquid reservoir (10) and a liquid line (12) opening into a drinking opening (13) designed for liquid extraction by an animal, wherein the adapter (11) and the liquid line (12) form a fluid-conducting interior (14), characterized in that a fluid-impermeable guide element (16) designed to guide gas bubbles (15) is arranged in a stationary manner at least in a partial section of the liquid line (12).

2. Drinking nipple according to claim 1, characterized in that the guide element (16) is arranged adjacent to an inner wall (17) of the liquid line (12).

3. Drinking nipple according to one of claims 1 or 2, characterized in that the guide element (16) is arranged in such a way that the inner wall (17) of the liquid line (12) and the guide element (16) has at least one region of greater curvature compared to the greatest curvature of the inner wall (17) of the liquid line (12).

4. Drinking nipple according to claim 3, characterized in that the regions of great curvature are formed by projections, corners or edges.

5. Drinking nipple according to one of claims 1 to 3, characterized in that the guide element (16) is spiral-shaped.

6. Drinking nipple according to one of claims 1 to 5, characterized in that the clear width of the guide element (16) is at least substantially smaller than the inner diameter of the liquid line (12).

7. Drinking nipple according to one of claims 1 to 6, characterized in that the clear width of the guide element (16) is selected at least in a holding section to be larger than the inner diameter of the liquid line (12) in such a way that the guide element (16) is arranged in the liquid line (12) with support on its inner wall (17) in a clamp fit.

8. Drinking nipple according to one of claims 1 to 7, characterized in that the guide element length corresponds at least to the length of the liquid line (12).

9. Drinking nipple according to one of claims 1 to 7, characterized in that the guide element (16) is arranged extending from the drinking opening (13) in the liquid line (12).

10. Drinking nipple according to claim 9, characterized in that at least a part of the guide element (16) is arranged to project into the drinking opening (13).

11. Drinking nipple according to one of claims 1 to 10, characterized in that the guide element (16) is wire-shaped.

12. Drinking nipple according to one of claims 1 to 11, characterized in that the guide element (16) consists of a hydrophilic material or is at least coated with such a material.

13. Drinking nipple according to one of claims 1 to 12, characterized in that the guide element (16) consists of a metal or a metal alloy.

14. Drinking nipple according to one of claims 1 to 13, characterized in that the drinking nipple is formed in one piece.

15. Drinking nipple according to one of claims 1 to 14, characterized in that the drinking opening (13) and / or the liquid line (12) is / are designed without a valve.

16. Drinking nipple according to one of claims 1 to 15, characterized in that the drinking opening (13) has a drinking opening diameter which is reduced compared to the inner diameter of the liquid line (12).

17. Device for watering animals comprising a liquid reservoir (10) with a drinking nipple according to one of claims 1 to 16.

18. A method for producing a drinking nipple designed for watering animals according to one of claims 1 to 16, characterized by Providing a drinking cap comprising an adapter configured for detachable connection to a liquid reservoir (10) and a liquid line (12) opening into a drinking opening (13) configured for liquid removal by an animal, wherein the adapter (11) and the liquid line (12) form a fluid-conducting interior space (14), and stationary arrangement of the fluid-impermeable guide element (16) designed to guide gas bubbles (15) in at least one partial section of the liquid line (12).

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