cooling device

Abstract

This application relates to a cooling device, comprising: a first cooling element, sleeved on the cylinder body of a hydraulic cylinder; the first cooling element having a first channel, and a first liquid inlet and a first liquid outlet communicating with the first channel; and a second cooling element, sleeved on the first cooling element; the second cooling element having a second channel, and a second liquid inlet and a second liquid outlet communicating with the second channel; wherein both the first and second cooling elements are configured to conduct heat; the first liquid inlet, the first channel, and the first liquid outlet together define a first heat exchange channel; the second liquid inlet, the second channel, and the second liquid outlet together define a second heat exchange channel; a heat exchange medium can flow through the first heat exchange channel and / or the second heat exchange channel to exchange heat with the cylinder body. In the above-mentioned cooling device, the heat exchange medium can exchange heat with the cylinder body to reduce the temperature of the piston rod, improve the plastic deformation and fracture of the piston rod, and increase the fatigue life of the piston rod.

Description

Technical Field

[0001] This application relates to the technical field of cooling devices for hydraulic cylinders, and in particular to a cooling device for cooling the cylinder body of a hydraulic cylinder. Background Technology

[0002] Hydraulic cylinders come in various structural forms, including piston type, plunger type, multi-stage telescopic sleeve type, and rack and pinion type. Piston-type hydraulic cylinders consist of a cylinder body and a piston rod. During operation, piston-type hydraulic cylinders generate a large amount of heat. Prolonged operation at high temperatures can cause the piston rod to undergo plastic deformation or even fracture due to excessive heat, thus reducing its fatigue life. Summary of the Invention

[0003] Therefore, it is necessary to provide a cooling device that can reduce the temperature of a piston-type hydraulic cylinder, thereby reducing the temperature of the piston rod, which is beneficial to improving the plastic deformation and fracture of the piston rod and increasing its fatigue life.

[0004] According to one aspect of this application, a cooling device is provided for cooling a hydraulic cylinder; the cooling device includes:

[0005] A first cooling component is sleeved on the cylinder body of the hydraulic cylinder; the first cooling component has a first channel, and a first liquid inlet and a first liquid outlet communicating with the first channel; and

[0006] The second cooling component is sleeved outside the first cooling component; the second cooling component is provided with a second channel, and a second liquid inlet and a second liquid outlet communicating with the second channel;

[0007] The first cooling element and the second cooling element are both configured to conduct heat; the first liquid inlet, the first channel and the first liquid outlet together define a first heat exchange channel; the second liquid inlet, the second channel and the second liquid outlet together define a second heat exchange channel; the heat exchange medium can flow through the first heat exchange channel and / or the second heat exchange channel to exchange heat with the cylinder.

[0008] The aforementioned cooling device, by forming a first heat exchange channel and a second heat exchange channel, and configuring both the first and second cooling components to be heat-conducting, allows the heat of the hydraulic cylinder body to be transferred to the first and second cooling components. This enables the heat exchange medium flowing through the first heat exchange channel to exchange heat with the hydraulic cylinder body, and simultaneously enables the heat exchange medium flowing through the second heat exchange channel to exchange heat with the hydraulic cylinder body. In this way, the temperature of the hydraulic cylinder can be reduced, thereby reducing the temperature of the piston rod. This is beneficial for improving the plastic deformation and fracture of the piston rod, and increasing the fatigue life of the piston rod.

[0009] In one embodiment, the first channel is constructed in a spiral shape, and the axis of the first channel is parallel to the axis of the first cooling element.

[0010] In one embodiment, the first channel is configured as a first groove on the inner wall surface of the first cooling element.

[0011] In one embodiment, the second channel is constructed in a spiral shape, and the axis of the second channel is parallel to the axis of the second cooling element.

[0012] In one embodiment, the second channel is disposed on the inner wall surface of the second cooling element.

[0013] In one embodiment, the inner wall surface of the second cooling element is provided with a second groove, and the outer wall surface of the first cooling element is provided with a third groove communicating with the second groove. The second groove and the third groove together define and form the second channel.

[0014] In one embodiment, both the second groove and the third groove are constructed in a spiral shape, with the edge of each turn of the second groove fitting against the edge of the corresponding turn of the third groove.

[0015] In one embodiment, the second groove and the third groove rotate in the same direction.

[0016] In one embodiment, the second cooling element is further provided with a third liquid outlet that communicates with the first liquid outlet.

[0017] In one embodiment, the cooling device further includes a temperature measuring element disposed on the first cooling element, the temperature measuring element being used to measure the temperature of the cylinder block.

[0018] In one embodiment, the first cooling element and the cylinder block are clearance-fitted.

[0019] In one embodiment, the second cooling element and the first cooling element are fitted with a clearance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the assembly of the cooling device and the hydraulic cylinder in one embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the structure of the first cooling element in one embodiment of this application.

[0022] Figure 3 This is a schematic diagram of the structure of the second cooling element in one embodiment of this application.

[0023] Explanation of icon numbers:

[0024] 10. Cooling device; 11. First cooling component; 111. First channel; 112. First liquid inlet; 113. First liquid outlet; 114. Third groove; 115. First section; 1151. First mounting hole; 1152. Second mounting hole; 1153. Fourth mounting hole; 116. Second section; 12. Second cooling component; 121. Second channel; 122. Second liquid inlet; 123. Second liquid outlet; 124. Third liquid outlet; 125. Second groove; 126. Third mounting hole; 127. Fifth mounting hole; 20. Hydraulic cylinder; 21. Cylinder body; 211. Inner cylinder; 212. Outer cylinder. Detailed Implementation

[0025] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0026] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0027] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0030] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0031] Figure 1 This is a schematic diagram of the assembly of the cooling device and the hydraulic cylinder in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of the first cooling element in one embodiment of this application; Figure 3 This is a schematic diagram of the structure of the second cooling element in one embodiment of this application.

[0032] See Figures 1 to 3 This application provides a cooling device 10 for cooling a hydraulic cylinder 20. The cooling device 10 includes a first cooling element 11 and a second cooling element 12. The first cooling element 11 is sleeved outside the cylinder body 21 of the hydraulic cylinder 20. The first cooling element 11 has a first channel 111, and a first liquid inlet 112 and a first liquid outlet 113 communicating with the first channel 111. The second cooling element 12 is sleeved outside the first cooling element 11. The second cooling element 12 has a second channel 121, and a second liquid inlet 122 and a second liquid outlet 123 communicating with the second channel 121.

[0033] The first cooling element 11 and the second cooling element 12 are both configured to conduct heat; the first liquid inlet 112, the first channel 111 and the first liquid outlet 113 together define the first heat exchange channel; the second liquid inlet 122, the second channel 121 and the second liquid outlet 123 together define the second heat exchange channel; the heat exchange medium can flow through the first heat exchange channel and / or the second heat exchange channel to exchange heat with the cylinder 21.

[0034] In this application, the heat exchange medium is cooling water. The heat exchange medium can also be coolant or other liquids with a temperature lower than that of the hydraulic cylinder 20, and no further restrictions are imposed here.

[0035] Thus, by forming a first heat exchange channel and a second heat exchange channel, and configuring both the first cooling element 11 and the second cooling element 12 to be heat-conducting, the heat of the cylinder body 21 of the hydraulic cylinder 20 can be transferred to the first cooling element 11 and the second cooling element 12. This allows the heat exchange medium flowing through the first heat exchange channel to exchange heat with the cylinder body 21 of the hydraulic cylinder 20, and also allows the heat exchange medium flowing through the second heat exchange channel to exchange heat with the cylinder body 21 of the hydraulic cylinder 20. In this way, by exchanging heat with the heat exchange medium, the temperature of the hydraulic cylinder 20 can be reduced, thereby reducing the temperature of the piston rod. This is beneficial for improving the plastic deformation and fracture of the piston rod and increasing the fatigue life of the piston rod.

[0036] See Figure 1 The hydraulic cylinder 20 includes a cylinder body 21 and a piston rod (not shown in the figure) disposed on the cylinder body 21. The cylinder body 21 includes an inner cylinder 211 and an outer cylinder 212. The piston rod is movably inserted into the inner cylinder 211, and the cooling device 10 is sleeved on the outer cylinder 212.

[0037] It should be noted that the cooling device 10 provided in this application is used in the pulse test system of the equipment for testing high-pressure common rail systems, which belongs to heavy-duty fuel engine systems. In other words, the piston rod is in a high-pressure and high-temperature working environment.

[0038] See Figure 1 and Figure 2 In some embodiments, the first cooling element 11 is configured as a rotating body, comprising a first segment 115 and a second segment 116 connected to one end of the first segment 115, wherein the radial dimension of the first segment 115 is greater than the radial dimension of the second segment 116. It is understood that the specific structure and dimensions of the first cooling element 11 can be set according to the model of the hydraulic cylinder 20.

[0039] In some embodiments, the first cooling element 11 is made of metal. Optionally, the first cooling element 11 is made of copper. It is understood that metal can conduct heat. Of course, the material of the first cooling element 11 is not limited to metal or copper; other heat-conducting materials can also be used to make the first cooling element 11. Furthermore, there are many forms of heat conduction, not limited to the materials used in this application. Heat from the hydraulic cylinder 20 can also be transferred to the first cooling element 11 in other ways. Moreover, the first cooling element 11 does not necessarily need to be entirely made of metal; only the parts directly in contact with the outer cylinder 212 and the parts directly in contact with the second cooling element 12 can be made of metal. In short, the first cooling element 11 only needs to conduct heat, and no further limitations are imposed here. Similarly, the heat conduction method of the second cooling element 12 is not limited and can refer to the heat conduction method of the first cooling element 11.

[0040] See Figure 1 and Figure 2 In some embodiments, the first channel 111 is configured as a spiral, and the axial direction of the first channel 111 is parallel to the axial direction of the first cooling element 11. It is understood that the first channel 111 can be configured as a left-handed spiral or a right-handed spiral. Optionally, in one embodiment of this application, the first channel 111 is configured as a left-handed spiral.

[0041] Thus, by constructing the first passage in a spiral shape to guide the flow of the heat exchange medium, compared to an annular structure, the spiral structure allows for more thorough heat exchange between the heat exchange medium and the cylinder 21, thereby improving the cooling effect on the cylinder 21, reducing the temperature of the piston rod, and thus improving the plastic deformation and fracture of the piston rod, and increasing the fatigue life of the piston rod.

[0042] See Figure 1 and Figure 2 In some embodiments, the first channel 111 is configured as a first groove on the inner wall surface of the first cooling element 11. It can be understood that the groove has an opening, which allows the heat exchange medium to directly contact the outer wall surface of the outer cylinder 212; the shape of the first groove can be annular or spiral, and is not limited in detail here.

[0043] Thus, by setting the first channel 111 on the inner wall surface of the first cooling element 11, the heat exchange medium flowing through the first channel 111 can directly contact the outer wall surface of the outer cylinder 212, thereby accelerating the heat exchange efficiency.

[0044] It should be noted that in this application, the heat exchange medium flowing through the first channel 111 can directly contact the outer wall surface of the outer cylinder 212. When the first channel 111 is located on the first cooling element 11 and the heat exchange medium does not directly contact the outer wall surface of the outer cylinder 212, the heat of the hydraulic cylinder 20 is transferred to the first cooling element 11 because the first cooling element 11 can conduct heat. The heat exchange medium flowing through the first channel 111 exchanges heat with the first cooling element 11, thereby indirectly reducing the temperature of the hydraulic cylinder 20, so as to reduce the temperature of the piston rod, thereby improving the plastic deformation and fracture of the piston rod and increasing the fatigue life of the piston rod.

[0045] See Figure 1 and Figure 3 In some embodiments, the second cooling element 12 is configured as a rotating body, and the second cooling element 12 is sleeved outside the second segment 116 of the first cooling element 11, and the radial dimension of the second cooling element 12 is between the radial dimension of the first segment 115 of the first cooling element 11 and the radial dimension of the second segment 116. It can be understood that the outer wall surface of the first cooling element 11 and the inner wall surface of the second cooling element 12 are in contact.

[0046] See Figure 1 and Figure 3 In some embodiments, the second channel 121 is configured as a spiral, and the axial direction of the second channel 121 is parallel to the axial direction of the second cooling element 12. It is understood that the second channel 121 can be configured as a left-handed spiral or a right-handed spiral. Optionally, in one embodiment of this application, the second channel 121 is configured as a right-handed spiral.

[0047] Thus, by constructing the second channel 121 in a spiral shape to guide the flow of the heat exchange medium, compared to an annular structure, the spiral structure helps to slow down the flow rate of the heat exchange medium, thereby making the heat exchange more complete, improving the cooling effect on the cylinder 21, reducing the temperature of the piston rod, and thus improving the plastic deformation and fracture of the piston rod, and increasing the fatigue life of the piston rod; furthermore, both the first channel 111 and the second channel 121 are set in a spiral shape, which helps to reduce the wall thickness between the first channel 111 and the second channel 121, thereby improving the heat exchange efficiency.

[0048] See Figure 1 and Figure 3 In some embodiments, the second channel 121 is disposed on the inner wall surface of the second cooling element 12.

[0049] See Figure 1 and Figure 3 In some embodiments, the inner wall surface of the second cooling member 12 is provided with a second groove 125, and the outer wall surface of the first cooling member 11 is provided with a third groove 114 communicating with the second groove 125. The second groove 125 and the third groove 114 together define and form a second channel 121.

[0050] It is understandable that the closer the position of the second channel 121 is to the axis of the cylinder 21 along the radial direction of the cylinder 21, the higher the heat exchange efficiency and the better the cooling effect on the cylinder 21. The first cooling element 11 and the second cooling element 12 are respectively provided with a connected second groove 125 and a third groove 114. The heat exchange medium flowing through the second channel 121 can directly contact the outer wall surface of the first cooling element 11, so that the heat exchange medium flowing through the second channel 121 can exchange heat with the first cooling element 11 more efficiently. The heat of the cylinder 21 will be transferred to the first cooling element 11. In this way, the temperature of the cylinder 21 can be reduced, thereby reducing the temperature of the piston rod, improving the plastic deformation and fracture of the piston rod, and increasing the fatigue life of the piston rod.

[0051] See Figure 1 and Figure 3 In some embodiments, both the second groove 125 and the third groove 114 are constructed in a spiral shape, with the edge of each turn of the second groove 125 fitting against the edge of the corresponding turn of the third groove 114.

[0052] See Figure 1 and Figure 3 In some embodiments, the second groove 125 and the third groove 114 have the same direction of rotation. Optionally, both the second groove 125 and the third groove 114 are left-handed.

[0053] Thus, by setting the second groove 125 and the third groove 114 to a spiral structure with the same direction of rotation, a closed second channel 121 is formed, so that the heat exchange medium passes through the second inlet hole 122 through the second channel 121 to exchange heat with the first cooling element 11, and then is discharged from the second outlet hole 123.

[0054] See Figure 1 and Figure 3 In some embodiments, the second cooling element 12 is further provided with a third liquid outlet 124 communicating with the first liquid outlet 113. Thus, by aligning the first liquid outlet 113 and the third liquid outlet 124, the installation position of the second cooling element 12 can be determined. Furthermore, since the second cooling element 12 is sleeved outside the first cooling element 11, the heat exchange medium flowing through the first liquid outlet 113 cannot be directly discharged and needs to be discharged through the third liquid outlet 124. Of course, the first liquid outlet 113 can also be configured to allow the heat exchange medium to be directly discharged from the first liquid outlet 113 by changing its position and shape; this is not a limitation here.

[0055] It should be noted that, in the embodiments of this application, the positions and shapes of the first liquid inlet 112, the first liquid outlet 113, the second liquid inlet 122, the second liquid outlet 123, and the third liquid outlet 124 can be correspondingly set according to the different positions and shapes of the first channel 111 and the second channel 121, in order to meet the usage requirements. Furthermore, in this application, the cross-sections of the first channel 111 and the second channel 121 (i.e., the second groove 125 and the third groove 114) are semi-elliptical; however, it is understood that other shapes can also be used. Moreover, in this application, the first heat exchange channel and the second heat exchange channel can be used individually or together, and the choice can be made as needed.

[0056] See Figure 1 and Figure 2 In some embodiments, the cooling device 10 further includes a temperature measuring element (not shown in the figure) disposed on the first cooling element 11, which is used to measure the temperature of the cylinder block 21.

[0057] See Figure 1 The first section 115 of the first cooling component 11 has a first mounting hole 1151, which extends through the first section 115 along the radial direction of the cylinder 21. A temperature measuring element is located in the first mounting hole 1151, and one end of the temperature measuring element can directly contact the outer wall surface of the outer cylinder 212 to improve the accuracy of the measurement. In this way, the temperature of the cylinder 21 can be monitored in real time, and the cooling method can be adjusted and selected according to the temperature of the cylinder 21.

[0058] See Figure 1 In some embodiments, the first cooling element 11 and the cylinder 21 are clearance-fitted, meaning there is a gap between the inner wall surface of the first cooling element 11 and the outer wall surface of the outer cylinder 212. Optionally, the fit tolerance is H7 / f6.

[0059] See Figure 1 In some embodiments, the second cooling element 12 and the first cooling element 11 are clearance-fitted, that is, there is a gap between the inner wall surface of the second cooling element 12 and the outer wall surface of the first cooling element 11. Optionally, the fit tolerance is H7 / f6.

[0060] See Figures 1 to 3 In some embodiments, the first segment 115 of the first cooling element 11 is further provided with a second mounting hole 1152, and the second cooling element 12 is provided with a third mounting hole 126 corresponding to the second mounting hole 1152, and the axes of the second mounting hole 1152 and the third mounting hole 126 are both parallel to the axis of the cylinder block 21. The cooling device 10 also includes fasteners (not shown in the figure), which extend sequentially into the second mounting hole 1152 and the third mounting hole 126 to connect the first cooling element 11 and the second cooling element 12.

[0061] See Figures 1 to 3In some embodiments, multiple second mounting holes 1152 are provided at circumferential intervals along the first segment 115, and multiple fasteners are also provided accordingly. Each fastener extends sequentially into one of the second mounting holes 1152 and a corresponding third mounting hole 126. This ensures a secure connection between the first cooling element 11 and the second cooling element 12.

[0062] See Figures 1 to 3 In some embodiments, the first segment 115 is further provided with a fourth mounting hole 1153, which is used to connect with the lifting ring when the cooling device 10 is hoisted. Optionally, multiple fourth mounting holes 1153 are provided at intervals along the circumference of the first segment 115, and the fourth mounting holes 1153 are spaced apart from the second mounting holes 1152.

[0063] See Figures 1 to 3 In some embodiments, the second cooling element 12 is provided with a fifth mounting hole 127 at the end of the cylinder body 21 away from the first segment 115 along the axial direction, and the second cooling element 12 is fixed to the mounting base (not shown in the figure) by means of the fifth mounting hole 127.

[0064] In summary, this application provides a cooling device 10 that forms a first heat exchange channel and a second heat exchange channel, and configures both the first cooling element 11 and the second cooling element 12 to be heat-conducting, so that the heat of the cylinder body 21 of the hydraulic cylinder 20 can be transferred to the first cooling element 11 and the second cooling element 12. This allows the heat exchange medium flowing through the first heat exchange channel to exchange heat with the cylinder body 21 of the hydraulic cylinder 20, and also allows the heat exchange medium flowing through the second heat exchange channel to exchange heat with the cylinder body 21 of the hydraulic cylinder 20. In this way, the temperature of the hydraulic cylinder 20 can be reduced, thereby reducing the temperature of the piston rod, which is beneficial to improving the plastic deformation and fracture of the piston rod and increasing the fatigue life of the piston rod.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A cooling device for cooling a hydraulic cylinder; characterized in that, The cooling device includes: A first cooling component is sleeved on the cylinder body of the hydraulic cylinder; the first cooling component has a first channel, and a first liquid inlet and a first liquid outlet communicating with the first channel; and The second cooling component is sleeved outside the first cooling component; the second cooling component is provided with a second channel, and a second liquid inlet and a second liquid outlet communicating with the second channel; The first channel is spiral in shape, and the axis of the first channel is parallel to the axis of the first cooling element; the first channel is a first groove provided on the inner wall surface of the first cooling element. The second channel is spiral-shaped, and its axial direction is parallel to that of the second cooling element. The second channel is located on the inner wall of the second cooling element. The inner wall of the second cooling element has a second groove, and the outer wall of the first cooling element has a third groove communicating with the second groove. The second groove and the third groove together define the second channel. Both the second groove and the third groove are spiral-shaped, with the edge of each turn of the second groove fitting against the edge of the corresponding turn of the third groove. The second groove and the third groove have the same spiral direction. The first cooling element and the second cooling element are both configured to conduct heat; the first liquid inlet, the first channel and the first liquid outlet together define a first heat exchange channel; the second liquid inlet, the second channel and the second liquid outlet together define a second heat exchange channel; the heat exchange medium can flow through the first heat exchange channel and / or the second heat exchange channel to exchange heat with the cylinder.

2. The cooling device according to claim 1, characterized in that, The second cooling component is also provided with a third liquid outlet that communicates with the first liquid outlet.

3. The cooling device according to any one of claims 1-2, characterized in that, The cooling device further includes a temperature measuring element disposed on the first cooling element, the temperature measuring element being used to measure the temperature of the cylinder block.

4. The cooling device according to any one of claims 1-2, characterized in that, The first cooling component and the cylinder block are fitted with a clearance.

5. The cooling device according to any one of claims 1-2, characterized in that, The second cooling element and the first cooling element are fitted with a clearance.

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