Ventilation unit for a freezer cabinet and method for operating a ventilation unit of this type

Abstract

Ventilation unit (10) for a freezer with a pipeline (20) and at least one heating element (30), wherein at least in sections an air-permeable filling material is arranged in the pipeline (20), as well as a freezer with such a ventilation unit and a method for operating such a ventilation unit (10).

Description

[0001] The invention relates to a ventilation unit for a freezer.

[0002] A well-known phenomenon in various types of refrigerators is that after closing a door, it initially cannot be opened again, or only with considerable force. This phenomenon can be attributed to the temperature dependence of air density. As temperature decreases, the air density increases, and the specific volume of the air decreases accordingly.

[0003] If an air exchange takes place between the interior of the refrigerator and the environment when the door is open and then closed, the warmer ambient air inside the refrigerator is cooled down. The specific volume of the air inside the refrigerator decreases as a result. This results in a pressure difference between the interior of the refrigerator and the environment. Until the pressure difference is equalized, the door is difficult or even impossible to open. This problem is particularly relevant for freezers, especially ultra-low temperature freezers, whose interiors can be cooled to as low as -90°C, as significant pressure differences can occur here due to the large temperature difference compared to the environment.

[0004] Various ventilation systems are known from the prior art to achieve pressure equalization between the interior and the environment when the door is closed. For example, US 4,662,270, US 3,680,329, US 2007 / 0 107 458 A1, and US 2016 / 0 327 328 A1 present systems that feature a heated pipe connecting the interior to the environment. US 2005 / 160754 A1 and US 2007 / 0 107 458 A1 also provide a timer for controlling the heating. All of these systems feature differently designed valves to separate the interior from the environment while maintaining equal pressure. DE 20 2014 008 327 U1, US 4 257 445, and US 4 569 208 provide examples of how such valves can be designed. Further prior art documents include US 6 374 620 B1, US 6 397 620 B1, and US 6 223 817 B1.

[0005] A disadvantage of current ventilation systems is that they feature valves with moving parts or assemblies. This results in wear and tear, which reduces the service life of the systems and increases maintenance costs. Furthermore, such systems are complex to manufacture.

[0006] The invention is therefore based on the object of providing a ventilation system for freezers that has a long service life and requires little maintenance, and is also preferably easy to manufacture. The invention is also based on the object of providing a freezer with a corresponding ventilation system and a method for controlling such a ventilation system in a freezer.

[0007] The object is achieved according to the invention by a ventilation unit for a freezer having the features of patent claim 1, by a freezer having the features of patent claim 5 and by a method according to the features of claim 9.

[0008] Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0009] The ventilation unit according to the invention for a freezer comprises a pipe and at least one heating element, wherein an air-permeable filling material is arranged in the pipe at least in sections.

[0010] The intended use of the ventilation unit is preferably to equalize pressure differences between two gas-filled, particularly air-filled, spaces. For this purpose, air can flow through the pipe when the ventilation unit is in use. The pipe preferably has a flow direction.

[0011] When the ventilation unit is used in a freezer, the piping and the filler material arranged therein can ice over due to the temperatures prevailing in the freezer. This icing occurs in particular when condensate from the air settles and freezes. This icing can reduce the cross-section of the piping or even completely close it. To completely close the piping, an ice plug is preferably arranged in the piping. This can reduce or completely stop the air flow through the ventilation unit. This can deliberately exploit this effect according to the invention, in particular to prevent undesired air flows through the ventilation unit when pressure conditions are balanced, and can be promoted by arranging the filler material in the piping.By activating the heating element, the ventilation unit can be defrosted, i.e. opened, or kept free of ice, i.e. kept open.

[0012] The pipe can be straight or at least have a bend. The pipe is preferably made of a material with high thermal conductivity, in particular a metallic material. The high thermal conductivity enables rapid defrosting of the ventilation unit. The pipe can, in particular, have a round, square, or polygonal cross-section. A square or polygonal cross-section, in particular, can be characterized by particularly low manufacturing costs.

[0013] The heating element can be designed as an electrical heating element. Alternatively, the heating element can be designed as a fluidic heating element, in which liquid substances such as coolant, water, or oil, or gaseous substances such as air, are used as the heat transfer medium.

[0014] The filler material is preferably arranged in the pipeline such that it completely fills the cross-section of the pipeline. The filler material preferably has good thermal conduction properties. Metallic materials are therefore particularly suitable as filler material. This allows rapid heat introduction into the filler material and rapid heat dissipation out of the filler material. The air permeability of the filler material is preferably achieved by having pore-like channels through which air flowing through the pipeline can flow. Water condensing from the air can precipitate on the filler material. The pore size is preferably selected to be small enough that the pores can freeze due to condensation water precipitating on the filler material.At the same time, the pore size is preferably selected to be large enough to allow a sufficiently large air flow through the filling material when the pores are open, i.e., not frozen. Thawing and thus opening the pores can occur by activating the at least one heating element. Filling materials that have a fine pore structure with a large number of small pores can be particularly advantageous. The large number of pores can enable a large air flow. At the same time, such a filling material can have a large surface area on which water can condense and settle. Furthermore, a fine pore structure can enable rapid thawing.

[0015] Preferably, the at least one heating element is arranged on the pipeline. The at least one heating element can be arranged on the inside and / or the outside of the pipeline. Preferably, the at least one heating element is arranged on the outside of the pipeline in the circumferential direction around the pipeline. By activating the at least one heating element, the pipeline can be heated from the outside. The heat can be introduced into the filler material via the pipeline. Particularly preferably, the at least one heating element is arranged in the section of the pipeline in which the filler material is arranged. In this way, the heat conduction path from the at least one heating element to the filler material can be kept short. As a result, the time delay between the activation of the at least one heating element and the heating of the filler material can be kept short. In this way, dynamic heating of the filler material can be achieved.This also allows the time delay between the activation of at least one heating element and the opening of the pores to be minimized.

[0016] The filling material is preferably in the form of a knitted wire fabric. A knitted wire fabric is any spatial structure made of wire in which spaces are arranged between the individual wires or wire strands. The spaces are referred to as pores. The structure can be ordered, for example in the form of a woven fabric, braid, or knitted fabric in the literal sense, or disordered in the form of a tangle. The knitted wire fabric can also be a mixture of ordered and disordered structures. The knitted wire fabric can be elastic. In particular, it can be designed as a sponge-like structure. The elasticity of the knitted wire fabric can be adjusted in particular by the size of the pores and the thickness of the wire used.Wire mesh made from low-gauge wire can be particularly advantageous for use in a ventilation unit, as it can create a very fine pore structure.

[0017] Alternatively, the filler material can be formed from bulk elements such as chips or spheres. The pores can be formed by the spaces between the individual elements. The pore size can preferably be adjusted by the size of the elements. Alternatively, the filler material can be formed from any open-pore structure. Foams, preferably metal foams, are particularly suitable for this purpose.

[0018] In a further development of the invention, the heating element is formed by the filler material. The heating element is preferably designed as an electrical heating element. The filler material can be designed as an electrical resistor. When the heating element is activated, the filler material can act as a heat source. This allows the heat to be generated directly in the filler material, where it is needed to thaw the pores. This avoids energy losses caused by heat conduction and reduces the number of components in the ventilation unit. Alternatively, the heating element can be formed, at least in sections, by the pipe. For this purpose, the pipe can be designed, at least in sections, as an electrical resistor. The pipe has at least one securing element to secure the filler material.The securing element can be used to prevent displacement of the filler material, particularly caused by air currents in the pipeline. The securing element establishes a positive and / or frictional connection to the filler material. The securing element itself is connected to the pipeline both materially and positively. Particularly preferably, the securing element is arranged downstream of the filler material in the flow direction.

[0019] According to the invention, the securing element is designed as a tab. The tab is preferably arranged transversely to a longitudinal axis of the pipeline. The tab is formed by a contour of the tab being cut out at least in sections from a wall of the pipeline, so that the contour has a cut-out section. The tab is bent into the cross-section of the pipeline at a non-cut-out section of the contour. The non-cut-out section is preferably perforated to facilitate bending in. The cutting out can be carried out in particular by laser cutting or punching. By designing it as a tab, the securing element can be manufactured particularly cost-effectively. The filling material can also be secured by reducing the cross-section of the pipeline at least in sections, in particular downstream of the filling material in the flow direction.A reduction in the cross-section of the pipeline, at least in sections, can be achieved, for example, using a retaining ring, which is preferably arranged in the pipeline. For this purpose, the pipeline can have a retaining groove.

[0020] A freezer according to the invention comprises a housing having an interior space, at least one door, and a ventilation unit according to the invention. A freezer can, in particular, be an ultra-low freezer. Ultra-low freezers preferably have a temperature control range of -90°C to -40°C. The interior space is, in particular, the space enclosed by the housing and the door when the door is closed.

[0021] Preferably, the at least one ventilation unit is arranged in the at least one door and / or the housing such that a first end of the pipe opens into the interior and a second end of the pipe opens into an environment. The environment preferably refers to the space arranged outside the freezer. Typically, the temperature in the interior is lower than the temperature in the environment. The pipe may be iced over and thus blocked by an ice plug. The ice plug is formed, for example, by condensation that has settled on the filling material. The environment and the interior can thus be separated by the housing and the at least one door of the freezer.

[0022] Particularly in an interior that is separated from the surroundings, a pressure difference can occur between the interior and the surroundings. This typically occurs when warm ambient air enters the interior, for example, due to the temporary opening of a door. There, the air is usually cooled, reducing its volume and the pressure in the interior compared to the surroundings. Typically, there is a connection between the opening of the door and the creation of a pressure difference. A pressure difference can be compensated for by allowing air from the surroundings to flow into the interior.

[0023] Because the pipe opens into the interior with its first end and into the environment with its second end, the ventilation unit can create a connection between the interior and the environment. The connection is preferably created by activating the at least one heating element, thereby defrosting the ice plug and opening the ventilation unit. This allows air to flow into the interior. The typical pressure gradient preferably results in a flow direction through the pipe from the environment to the interior. The pipe is preferably closed by deactivating the at least one heating element. As a result, the pipe and the filling material of the ventilation element in particular can be cooled by the low temperatures prevailing in the interior. Water can therefore condense on the pipe and the filling material from the air, in particular in the pipe, and form a new ice plug.

[0024] In a preferred embodiment of the invention, the heating element can be activated by opening the at least one door. In particular, the freezer can have an opening sensor, for example in the form of a switch or button, that can detect the opening of the door.

[0025] The invention is designed such that the heating element is deactivated after a specific period of time has elapsed after the at least one door has been closed. Deactivating the at least one heating element can prevent icing and thus closing of the ventilation unit. The time period is preferably selected to be long enough that the pressure difference between the ambient air and the interior caused by the opening and closing of the door is equalized after the door has been closed. This time period can particularly take into account the fact that the pressure difference does not occur at its maximum immediately after the door has been closed, but rather follows a temporal progression.The temporal progression depends, among other things, on how long the door was open, the interior volume, the amount of air exchanged between the interior and the surroundings while the door was open, and the temperature difference between the interior and the surroundings. Factors that can affect freezers include the interior volume, the freezer's performance, and its cooled mass. Especially if the door was not opened long enough ago, the last time the door was opened can also influence the temporal progression of the pressure difference.

[0026] The freezer can be designed such that the time period can be defined by presetting. A value of three minutes has proven particularly advantageous. The time period can preferably be set by a user of the freezer. The time period can also be determined or influenced by incorporating data entered by the user and / or determined by sensors. Such data can include, for example, the interior temperature, the ambient temperature, the pressure difference, and / or the temperature difference between the interior and the surroundings.

[0027] In a method according to the invention for operating a ventilation unit according to the invention in a freezer according to the invention, the opening of the at least one door is detected, the heating element is activated when the door is open, the closing of the at least one door is detected and the heating element is deactivated after the expiration of the specific period of time after the door is closed.

[0028] Preferably, the at least one heating element is activated simultaneously with the detection of the door opening. By activating the at least one heating element when the door is opened, the ventilation device can be opened when the door is subsequently closed, allowing pressure equalization between the environment and the interior. This allows, in particular, the fact that there is typically a connection between the opening of the door and the occurrence of a pressure difference between the interior and the environment to be taken into account.

[0029] In a further development of the invention, the temperature difference and / or the pressure difference between the interior and the surroundings are taken into account when determining the time period. For this purpose, the pressure difference and / or the temperature difference between the interior and the surroundings are preferably monitored. Large pressure and / or temperature differences preferably extend the time period. For small pressure and / or temperature differences, the method can be modified to shorten the time period accordingly.

[0030] The time period can be determined based on the interval time that has elapsed since the heating element was last deactivated and / or the last heating duration between the last activation and deactivation of the heating element. Heating the ventilation element during the time period preferably serves to keep the ventilation unit open, i.e. ice-free, for a sufficiently long time after the door has been closed in order to allow pressure equalization. If the last activity of the heating element was sufficiently recent, residual heat may still be present in the ventilation element, which can help keep the ventilation unit open. Typically, the shorter the time since the last activity of the heating element, the more residual heat is present. The operation of the ventilation unit can therefore be designed such that a short interval time allows the time period to be shortened.The duration of the last activity of the heating element, the last heating period, can also provide an indication of how much residual heat is present in the ventilation unit. Therefore, the method is preferably designed such that the last heating period, i.e., the duration of the last activity of the heating element, has a shortening effect on the time period.

[0031] Embodiments of the invention are explained with reference to the following figures. They show: Figure 1 shows a schematic representation of an embodiment of a ventilation unit arranged in a door, Figure 2 shows a schematic representation of an embodiment of a pipeline, Figure 3 shows a schematic representation of a further embodiment of a pipeline, Figure 4 shows a schematic representation of an embodiment of an ultra-low freezer with a ventilation unit, Figure 5 shows a flow diagram of a first method for operating a ventilation device in an ultra-low freezer, Figure 6 shows a flow diagram of a second method for operating a ventilation device in an ultra-low freezer.

[0032] The same reference symbols are used for identical and functionally equivalent parts. For clarity, not all reference symbols are used in every figure.

[0033] Figure 1shows a ventilation unit 10 arranged in a door 44 with a pipe 20 and a heating element 30. An air-permeable filling material, which can be designed as a wire mesh 12, is arranged in the pipe 20.

[0034] The intended use of the ventilation unit 10 is preferably to create a pressure difference 82 (see Fig. 3 ) between two spaces, in particular an interior space 46 and an environment 50 (see Fig. 2 ). For this purpose, air can flow through the pipe 20. For this purpose, the pipe 20 preferably has a flow direction 28.

[0035] Figure 4shows a freezer designed as an ultra-low freezer 40 with a ventilation unit 10. When the ventilation unit 10 is used in the ultra-low freezer 40, the pipe 20 and the wire mesh 12 arranged therein can ice over due to the temperatures prevailing in the ultra-low freezer 40. The icing occurs, for example, when condensate from the air precipitates and freezes. As a result of the icing, the cross-section of the pipe 20 can be reduced or even completely closed. To completely close the pipe 20, an ice plug is preferably arranged in the pipe 20. An air flow through the ventilation unit 10 can thus be reduced or completely stopped. This effect can be intentional, in particular to prevent undesired air flows through the ventilation unit 10, and can be promoted by arranging the wire mesh 12 in the pipe 20.By activating the heating element 30, the ventilation unit 10 can be defrosted, i.e. opened, or kept free of ice, i.e. kept open.

[0036] Figure 1 shows further details of the ventilation unit 10. The pipe 20 preferably has a first end 22, a second end 24, and a pipe longitudinal axis 26. The pipe 20 can be straight or at least have a bend. Preferably, the pipe 20 is made of a material with high thermal conductivity, in particular of a metallic material. The high thermal conductivity can, in particular, enable rapid de-icing of the ventilation unit 10. The pipe 20 can, for example, have a round cross-section 98 ( Figure 2 ) or a square cross-section 99 ( Figure 3 ).

[0037] The knitted wire mesh 12 is preferably arranged in the pipeline 20 such that it completely fills the cross-section of the pipeline 20. The knitted wire mesh 12 is preferably a spatial structure made of wire, in which gaps are arranged between the individual wires or wire strands. Water condensing from the air can precipitate on the wires or wire strands as well as on the pipeline 20. The gaps are referred to as pores and can ensure the air permeability of the knitted wire mesh 12. The size of the pores is preferably selected to be small enough that the pores can freeze due to condensation water precipitating on the knitted wire mesh 12. At the same time, the size of the pores is preferably selected to be large enough that a sufficiently large air flow through the knitted wire mesh 12 is possible when the pores are open, i.e., not frozen.

[0038] The wire mesh 12 can be elastic. In particular, it can be designed as a sponge-like structure. The elasticity of the wire mesh 12 can be adjusted, in particular, by the size of the pores and the thickness of the wire strands used. A wire mesh 12 made of thin wire strands can be particularly advantageous for use in a ventilation unit 10, since it allows for the creation of a very fine pore structure.

[0039] The heating element 30 can be designed as an electrical heating element. The heating element 30 is preferably supplied with energy via cable 32. The heating element 30 is preferably arranged on the outside of the pipeline 20 in the circumferential direction around the pipeline 20. Activating the heating element 30 allows the pipeline 20 to be heated from the outside. Heat can be introduced into the knitted wire fabric 12 via the pipeline 20. The heating element 30 is preferably arranged in the section of the pipeline 20 in which the knitted wire fabric 12 is arranged. In this way, the heat conduction path from the heating element 30 to the knitted wire fabric 12 can be kept short. As a result, the time delay between the activation of the heating element 30 and the heating of the knitted wire fabric 12 can be kept short. In this way, dynamic heating of the knitted wire fabric 12 can be realized.This also makes it possible to minimize the time delay between the activation of the at least one heating element 30 and the opening of the pores.

[0040] The pipeline 20 has a securing element for securing the wire mesh 12.

[0041] Figure 2 and Figure 3show exemplary embodiments of a pipeline 20 in which the securing element is formed by a tab 90 according to the invention. The tab 90 is formed by a contour of the tab 90 being cut out at least in sections from a wall 21 of the pipeline 20, so that the contour has a cut-out section 96. The tab 90 is bent into the cross section of the pipeline 20 at a non-cut-out section 94 of the contour in the bending direction 92. The non-cut-out section 94 is preferably perforated to facilitate bending. The cutting can be done in particular by laser cutting or punching. By forming it as a tab 90, the securing element can be manufactured particularly cost-effectively. The illustration in Figure 2 shows the pipeline 20 in a manufacturing step in which the tab 90 has already been cut out but not yet bent into the cross-section. Figure 3shows a pipeline 20 in which the tab 90 is bent into the cross section of the pipeline 20.

[0042] In Figure 4 Further details of the ultra-low temperature freezer 40 are shown. The ultra-low temperature freezer 40 preferably has a control range of -90°C to -40°C. The ultra-low temperature freezer has a housing 42 in which the interior space 46 is arranged. In addition, the ultra-low temperature freezer 40 has the door 44 and the ventilation unit 10. The interior space 46 is referred to in particular as the space enclosed by the housing 42 and the door 44 when the door 44 is closed. The ventilation unit 10 is preferably arranged in the door 44 such that the first end 22 of the pipe 20 opens into the interior space 46 when the door 44 is closed, and a second end 24 of the pipe 20 opens into the environment 50. The environment 50 is preferably formed by the space arranged outside the ultra-low temperature freezer 40.

[0043] Typically, the temperature in the interior 46 is below the temperature in the surroundings 50. The pipe 20 may be frozen and thus sealed by an ice plug. The ice plug is preferably formed by condensation that has settled on the wire mesh 12. The surroundings 50 and the interior 46 can thus be separated by the housing 42 and the door 44 of the ultra-low temperature freezer 40.

[0044] Particularly when the interior space 46 is separated from the surroundings 50, a pressure difference 82 can occur between the interior space 46 and the surroundings 50. This is typically the case when, for example, warm air from the surroundings 50 has entered the interior space 46 due to the temporary opening of the door 44. There, the air is usually cooled, whereby its volume decreases and the pressure in the interior space 46 drops compared to the surroundings 50. Typically, there is a connection between the opening of the door 44 and the creation of a pressure difference 82. A pressure difference 82 can be compensated for by allowing air from the surroundings 50 to flow into the interior space 46.

[0045] Because the pipe 20 opens with its first end 22 into the interior 46 and with its second end 24 into the environment 50, the ventilation unit 10 can establish a connection between the interior 46 and the environment 50. The connection is preferably established by activating the heating element 30, thus defrosting the ice plug and opening the ventilation unit 10. This allows air to flow into the interior 46. The typical pressure gradient preferably results in a flow direction 28 through the pipe 20 from the environment 50 to the interior 46. The pipe 20 is preferably closed by deactivating the heating element 30. As a result, in particular the pipe 20 and the wire mesh 12 of the ventilation element 10 can be cooled by the low temperatures prevailing in the interior 46.Water can thus condense from the air in the pipe 20 and the wire mesh 12 and form a new ice plug.

[0046] The heating element 30 is preferably activated by opening the door 44. The ultra-low temperature freezer 40 may have an opening sensor 48 that can detect the opening of the door 44. The heating element 30 is thereby activated after a certain period of time 66 (see Fig. 3 and 4) are deactivated after closing at least one door 44.

[0047] Figure 5 shows a flow diagram of a first method for operating the ventilation device 10 in the ultra-low freezer 40. As a result of a detection 60 of the opening of the door 44, an activation 62 of the heating element 30 takes place. After a subsequent detection 64 of the closing of the door 44 has taken place, a deactivation 68 of the heating element 30 takes place after the expiration of the specific time period 66.

[0048] Preferably, the activation 62 of the heating element 30 occurs without a time delay with the detection 60 of the opening of the door 44. This makes it possible to ensure that the ventilation device 10 is open when the door 44 is subsequently closed, so that pressure equalization can take place between the environment 50 and the interior 46. This makes it possible, in particular, to take into account the fact that there is typically a connection between the opening of the door 44 and the occurrence of a pressure difference 82 between the interior 46 and the environment 50.

[0049] The time period 66 is preferably selected to be long enough so that the pressure difference 82 between the environment 50 and the interior 46 caused by the opening and closing of the door 44 is equalized after the door 44 is closed. With the help of the time period 66, it is particularly possible to take into account the fact that the pressure difference 82 does not occur immediately in its maximum form after the door 44 is closed, but rather has a temporal progression.

[0050] The ultra-low freezer 40 can be configured such that the time period 66 can be defined by presetting. A value of three minutes has proven particularly advantageous. The time period 66 can also be determined or influenced by incorporating data entered by the user and / or determined by sensors. Such data can be the pressure difference 82 and / or a temperature difference 80 between the interior 46 and the surrounding area 50. Large pressure differences 82 and / or temperature differences 80 preferably extend the time period 66. In the case of small pressure differences 82 and / or temperature differences 80, the method can be modified such that the time period 66 is shortened accordingly.

[0051] As in Figure 6As shown, when determining the time period 66 of a current opening cycle 110, reference can be made to a most recently performed opening cycle, i.e., a most recent opening cycle 100. Thus, an interval time 70 that has elapsed since the last deactivation 68 of the heating element 30 and / or a last heating duration 72 between the last activation 62 and deactivation 68 of the heating element 30 can be taken into account in determining the time period 66. Heating the ventilation element 10 during the time period 66 preferably serves to keep the ventilation unit 10 open, i.e., ice-free, for a sufficiently long time after the door 44 has been closed in order to enable pressure equalization. If the last activity of the heating element 30 was sufficiently recent, residual heat may still be present in the ventilation element 10, which can assist in keeping the ventilation unit 10 open.Typically, the more residual heat is present, the shorter the last activity of the heating element, i.e., the shorter the interval time 70. The operation of the ventilation unit 10 can therefore be configured such that a short interval time 70 enables a shortening of the time period 66 of the current opening cycle 110. The duration of the last activity of the heating element 30, the last heating period 72, can also provide an indication of how much residual heat is present in the ventilation unit 10. Therefore, the method is preferably configured such that a long last heating period 72 has a shortening effect on the time period 66.

[0052] The method for operating the ventilation unit 10 can in particular be implemented as a combination of the first, in Figure 5 depicted, and the second, in Figure 6illustrated method, so that both the temperature difference 80 and / or the pressure difference 82 as well as the interval time 70 and / or the last heating duration 72 are taken into account when determining the time period 66. List of reference symbols

[0053] 10 Ventilation unit 12 Wire mesh 18 Pin 20 Pipe 21 Wall 22 First end 24 Second end 26 Longitudinal pipe axis 28 Flow direction 30 Heating element 32 Cable 40 Ultra-low freezer 42 Housing 44 Door 46 Interior 48 Opening sensor 50 Surroundings 60 Door opening detection 62 Heating element activation 64 Door closing detection 66 Time span 68 Heating element deactivation 70 Interval time 72 Last heating duration 80 Temperature difference 82 Pressure difference 90 Tab 92 Bending direction 94 Uncut section 96 Cut section 98 Round cross section 99 Square cross section 100 Last opening cycle 110 Current opening cycle

Claims

1. A ventilation unit for a freezer cabinet having a pipe (20) and at least one heating element (30), wherein an air-permeable filling material is arranged at least in sections in the pipe (20), and wherein the pipe (20) has at least one securing element for securing the filling material, characterized in that the securing element is designed as a tab (90), wherein the tab (90) is formed in that a contour of the tab (90) is cut out at least in sections from a wall (21) of the pipe (20) and the tab (90) is bent into the cross section of the pipe (20) at a non-cutout section (94).

2. The ventilation unit according to claim 1, characterized in that the at least one heating element (30) is arranged on the pipe (20).

3. The ventilation unit according to any one of the preceding claims, characterized in that the filling material is designed as a wire mesh (12).

4. The ventilation unit according to any one of the preceding claims, characterized in that the heating element (30) is formed by the filling material.

5. A freezer cabinet comprising a housing (42) having an interior (46) and at least one door (44), characterized in that the freezer cabinet has at least one ventilation unit (10) according to any one of the preceding claims.

6. The freezer cabinet according to claim 5, characterized in that the at least one ventilation unit (10) is arranged in the at least one door (44) and / or the housing (42) such that a first end (22) of the pipe (20) opens into the interior (46) and a second end (24) of the pipe (20) opens into a space outside the freezer cabinet.

7. The freezer cabinet according to one of claims 5 to 6, characterized in that the heating element (30) is activated by opening the at least one door (44).

8. The freezer cabinet according to one of claims 5 to 7, characterized in that the heating element (30) is deactivated after a certain period of time (66) has elapsed after the closing of the at least one door (44).

9. A method for operating a ventilation unit (10) according to any one of claims 1 to 4 in a freezer cabinet according to any one of claims 5 to 8, wherein • the opening of the at least one door (44) is detected (60), • the heating element (30) is activated (62) when the door (44) is open, • the closing of the at least one door (44) is detected (64), • the heating element (30) is deactivated (68) after a certain period of time (66) has elapsed after the closing of the door.

10. The method for operating a ventilation unit (10) according to claim 9, characterized in that the temperature difference (80) and / or the pressure difference (82) between the interior (46) and the environment (50) are incorporated in the determination of the period of time (66).

11. The method for operating a ventilation unit (10) according to one of claims 9 or 10, characterized in that an interval time (70) that has passed since the last deactivation of the heating element (30) and / or the last heating period (72) between the last activation and deactivation of the heating element (30) is incorporated in the determination of the period of time (66).

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