An automatic connection and expansion device for copper tubes and fins

Abstract

The present invention relates to an automatic connection and expansion device for a copper tube and a fin, belonging to the technical field of expansion connection of copper tubes and fins. The joint comprises a connecting pipe and a sleeve. The connecting pipe is divided into a connecting section a, a connecting section b and a sealing section along its own axial direction. The end face of the connecting section a is provided with a connecting hole a, the outer cylindrical surface of the sealing section is provided with a connecting hole b connected to the connecting hole a, the outside of the connecting section b is provided with external threads a, external threads b and external threads c, the outside of the sealing section is provided with a sealing plug, both open ends of the sealing plug are provided with sealing steps extending inward, and an interference fit is formed between the sealing plug and the inner wall of the pipe mouth of the copper tube, the closed end of the sleeve is coaxially provided with a threaded hole, and a sealing sleeve is provided inside, and an interference fit is formed between the sealing sleeve and the outer wall of the pipe mouth of the copper tube, and the joint further comprises a nut a corresponding to the external thread a, a nut b corresponding to the external thread c, a sealing ring a and a sealing ring b.

Description

Technical Field

[0001] The invention relates to the technical field of copper tube and fin expansion connection, and in particular to an automatic connection and expansion connection device for copper tubes and fins. Background Art

[0002] In the prior art, the connection between the copper tube and the fin of the radiator or heat exchanger is generally made by the tube expansion process, which relies on the metal deformation and expansion of the copper tube to generate a compressive force between the outer surface of the copper tube and the inner surface of the mounting hole on the fin to connect and seal the copper tube and the fin.

[0003] Common tube expansion methods include mechanical tube expansion and hydraulic tube expansion. Among them, the hydraulic tube expansion method can solve the shortcomings of the mechanical tube expansion method in terms of geometric shape limitations and easy damage to the threaded protrusion structure on the inner wall of the pipe, and achieve full expansion of the entire copper pipe. However, the hydraulic tube expansion method also has the following disadvantages:

[0004] 1. Since the internal pressure of the copper tube is high when it is deformed, the sealing performance between the copper tube and the hydraulic joint and the stability of the connection between the hydraulic connection and the copper tube are required to be high. The former leads to a complex structure of the hydraulic joint, high precision, and great processing difficulty. The latter makes the disassembly and assembly of the hydraulic joint more inconvenient, delaying the production progress.

[0005] 2. Metal deformation and expansion will also occur near the orifice of the copper tube. The part of the copper tube near the orifice will deform step by step, causing a gap to appear at the connection between the copper tube and the hydraulic joint. The gap will gradually expand. On the one hand, it further strengthens the requirements for the sealing performance and connection stability between the copper tube and the hydraulic joint. On the other hand, it causes local deformation of the copper tube orifice, which will affect the subsequent welding of the two adjacent groups of copper tubes.

[0006] To this end, the present invention provides an automatic connection and expansion device for copper tubes and fins. Summary of the Invention

[0007] In order to solve the problems mentioned in the above background, the present invention provides an automatic connection and expansion device for copper tubes and fins.

[0008] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows.

[0009] An automatic connection and expansion device for a copper tube and a fin comprises a copper tube and a joint. The joint is used to form a double-sealed connection with the tube mouth of the copper tube, and the sealing performance and connection stability between the joint and the copper tube are both proportional to the pressure change in the copper tube.

[0010] Furthermore, two groups of connectors are provided, one group of connectors has a liquid pipe a at its input end and a liquid pipe b at its output end, and the other group of connectors has a liquid pipe b at its output end and a liquid pipe a at its input end.

[0011] Furthermore, the end of the liquid pipe a is connected to the hydraulic system;

[0012] A pressure limiting valve is provided at the end of the liquid pipe b, a pressure gauge is provided on the liquid pipe b, a liquid discharge pipe is also provided on the liquid pipe b, and a control valve is provided on the liquid discharge pipe.

[0013] Furthermore, the connector includes a connecting pipe, the inner cavity of which is a liquid-filled hole;

[0014] The connecting pipe is divided into three sections along its axial direction: connecting section a, connecting section b and sealing section. The sealing section is located between connecting section a and connecting section b. The outer diameter of the sealing section is smaller than the outer diameter of connecting section a or connecting section b. The outer diameter of connecting section a is equal to the outer diameter of connecting section b. A shaft shoulder is formed between the sealing section and connecting section a or connecting section b.

[0015] Furthermore, the end surface of the communicating section a is provided with a connecting hole a, and the outer circumferential surface of the sealing section is provided with a connecting hole b communicating with the connecting hole a;

[0016] The outside of the connecting section b is provided with an external thread, and the external thread is provided with three groups, namely external thread a, external thread b and external thread c. External thread a is close to the sealing section, external thread b is located between external thread a and external thread c, and the thread rotation direction of external thread a and external thread c is the same, and the thread rotation direction of external thread b is opposite to that of external thread a or external thread c.

[0017] Furthermore, the joint also includes a nut a corresponding to the external thread a and a nut b corresponding to the external thread c.

[0018] Furthermore, a sealing plug is provided on the outside of the sealing section;

[0019] Both open ends of the sealing plug are provided with sealing steps extending inwards, and when the sealing plug is sleeved on the outside of the sealing section, the end faces of the two sets of sealing steps facing each other are respectively in contact with the two sets of shaft shoulders;

[0020] An interference fit is formed between the sealing plug and the inner wall of the pipe mouth of the copper pipe.

[0021] Furthermore, the joint also includes a sealing ring a and a sealing ring b.

[0022] Furthermore, the joint further comprises a sleeve;

[0023] The sleeve is a circular cylindrical structure with one end open and the other end closed. A threaded hole is coaxially opened at the closed end of the sleeve. The threaded hole corresponds to the external thread b and the sleeve is assembled to the pipe through the cooperation of the threaded hole and the external thread b.

[0024] Furthermore, a sealing sleeve is provided inside the sleeve, and an interference fit is formed between the sealing sleeve and the outer wall of the pipe mouth of the copper pipe.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In this solution, the structure of the joint is simple, and the sealing performance and connection stability between the joint and the copper tube increase with the increase of the pressure in the copper tube, showing a proportional relationship. Specifically:

[0027] The pressure in area a is consistent with that in the copper tube. As the pressure in the copper tube increases, the pressure in area a also increases.

[0028] The pressure in area a where the pressure changes gradually pushes the inner wall of the sealing plug to fit more closely to the inner wall of the copper tube, and pushes the sealing step to fit more closely to the shaft shoulder. In other words, the sealing performance and connection stability between the sealing plug and the copper tube are directly proportional to the pressure change in area a.

[0029] At the same time, the wall of the copper tube is pushed to fit more closely to the sealing sleeve. That is to say, the sealing performance and connection stability between the sealing sleeve and the copper tube are also directly proportional to the pressure change in area a.

[0030] 2. In this solution, the connector is directly inserted into the copper pipe mouth under normal pressure, and is also directly pulled out from the copper pipe mouth under normal pressure, making disassembly and assembly more convenient and quick.

[0031] 3. In this solution, the sealing plug and the sealing sleeve are sealing parts made of rubber material, which has a certain elasticity. Therefore, when the sealing plug is subjected to pressure, it can drive the copper tube mouth to expand. The expansion is restricted by the sealing sleeve and the sleeve, so the copper tube expands only slightly instead of deforming significantly, which is conducive to the subsequent U-shaped tube welding, so that all copper tubes are connected to form a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of the present invention when the connector is not plugged into the copper tube opening;

[0033] Figure 2 A schematic diagram of the structure of the present invention when the connector is plugged into the orifice of a copper tube;

[0034] Figure 3 Schematic diagram of the structure of the joint, liquid pipe a and liquid pipe b;

[0035] Figure 4 is a structural diagram of the joint;

[0036] Figure 5 is a cross-sectional view of the joint;

[0037] Figure 6 It is a cross-sectional view of the connecting pipe and the sealing plug;

[0038] Figure 7 It is a cross-sectional view of the connecting pipe and the sleeve;

[0039] Figure 8 is a cross-sectional view of the sleeve;

[0040] Figure 9 is an exploded view of the present invention;

[0041] Figure 10 It is a cross-sectional view of the sleeve, the annular mold and the sealing sleeve.

[0042] The reference numerals in the accompanying drawings are:

[0043] 1. Copper tube; 2. Fin; 3. Joint; 301. Connecting pipe; 302. Filling hole; 303. Connecting hole a; 304. Connecting hole b; 305. Sealing plug; 306. Sealing step; 307. Sleeve; 308. Nut a; 309. Sealing ring a; 310. Sealing ring b; 311. Nut b; 312. Sealing sleeve; 313. Threaded hole; 314. Ring mold; 4. Liquid pipe a; 5. Liquid pipe b; 501. Pressure limiting valve; 502. Pressure gauge; 503. Liquid drain pipe; 504. Control valve. DETAILED DESCRIPTION

[0044] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0045] In the prior art, the connection between the copper tube and the fin of the radiator or heat exchanger is generally made by the tube expansion process, which relies on the metal deformation and expansion of the copper tube to generate a compressive force between the outer surface of the copper tube and the inner surface of the mounting hole on the fin to connect and seal the copper tube and the fin.

[0046] Common tube expansion methods include mechanical tube expansion and hydraulic tube expansion. Among them, the hydraulic tube expansion method can solve the shortcomings of the mechanical tube expansion method in terms of geometric shape limitations and easy damage to the threaded protrusion structure on the inner wall of the pipe, and achieve full expansion of the entire copper pipe. However, the hydraulic tube expansion method also has the following disadvantages:

[0047] 1. Since the internal pressure of the copper tube is high when it is deformed, the sealing performance between the copper tube and the hydraulic joint and the stability of the connection between the hydraulic connection and the copper tube are required to be high. The former leads to a complex structure of the hydraulic joint, high precision, and great processing difficulty. The latter makes the disassembly and assembly of the hydraulic joint more inconvenient, delaying the production progress.

[0048] 2. Metal deformation and expansion will also occur near the orifice of the copper tube. The part of the copper tube near the orifice will deform step by step, causing a gap to appear at the connection between the copper tube and the hydraulic joint. The gap will gradually expand. On the one hand, it further strengthens the requirements for the sealing performance and connection stability between the copper tube and the hydraulic joint. On the other hand, it causes local deformation of the copper tube orifice, which will affect the subsequent welding of the two adjacent groups of copper tubes.

[0049] Therefore, the present invention proposes an automatic connection and expansion device for copper tubes and fins, which has a simple structure. The sealing performance and connection stability between the device and the copper tube increase with the increase of the pressure in the copper tube, and are directly proportional. During the expansion process of the copper tube, it can ensure that no large-scale metal deformation occurs at the tube mouth of the copper tube, and only a small expansion occurs, which is beneficial to subsequent welding.

[0050] like Figure 1-9 As shown, the present invention includes a connector 3, and two groups of connectors 3 are provided. The input end of one group of connectors 3 is provided with a liquid pipe a4, and the output end is used to connect with one pipe end of the copper pipe 1. The input end of the other group of connectors 3 is used to connect with the other pipe end of the copper pipe 1, and the output end is provided with a liquid pipe b5.

[0051] The end of the liquid pipe a4 is connected to the hydraulic system, which is used to supply hydraulic medium to the copper tube 1 through the liquid pipe a4 and the joint 3. The hydraulic medium can be hydraulic oil or compressed air. The hydraulic system can be implemented by existing conventional technical means and will not be described in detail.

[0052] A pressure-limiting valve 501 is provided at the end of the liquid pipe b5. The working pressure of the pressure-limiting valve 501 is adjustable. When the pressure in the copper tube 1 is higher than the working pressure of the pressure-limiting valve 501, the hydraulic medium will be discharged through the pressure-limiting valve 501. The working pressure of the pressure-limiting valve 501 corresponds to the metal deformation and expansion of the copper tube 1. The purpose of providing the pressure-limiting valve 501 is to prevent excessive filling of hydraulic medium into the copper tube 1, which may cause excessive expansion and deformation of the copper tube 1. The pressure-limiting valve 501 can be realized by existing conventional technical means and will not be described in detail.

[0053] A pressure gauge 502 is provided on the liquid pipe b5 for real-time monitoring and displaying the pressure value in the copper tube 1 for observation and judgment by the operator. The pressure gauge 502 can be realized by conventional technical means and will not be described in detail.

[0054] The liquid pipe b5 is also provided with a discharge pipe 503, and the discharge pipe 503 is provided with a control valve 504 for controlling the opening and closing of the discharge pipe 503. When the copper tube 1 is expanded, the control valve 504 is closed. After the expansion is completed, the control valve 504 is opened to discharge the hydraulic medium in the copper tube 1. The control valve 504 can be realized by existing conventional technical means and will not be described in detail.

[0055] The joint 3 is connected to the pipe mouth of the copper tube 1 in a double sealing manner. The sealing performance and connection stability between the joint 3 and the copper tube 1 are directly proportional to the pressure change in the copper tube 1. At the same time, the joint 3 can also ensure that during the expansion process, the pipe mouth of the copper tube 1 does not undergo significant deformation, and only a slight expansion occurs, which is beneficial to subsequent welding.

[0056] Specifically, such as Figure 4-9 As shown, the connector 3 includes a connecting pipe 301 , and the inner cavity of the connecting pipe 301 is a liquid-filling hole 302 .

[0057] The connecting pipe 301 is divided into three sections along its own axial direction: a connecting section a, a connecting section b and a sealing section. The sealing section is located between the connecting section a and the connecting section b. The outer diameter of the sealing section is smaller than the outer diameter of the connecting section a or the connecting section b. The outer diameter of the connecting section a is equal to the outer diameter of the connecting section b. Therefore, two sets of shaft shoulders are formed on the connecting pipe 301.

[0058] The end surface of the communicating section a is provided with a connecting hole a303, and the outer circumferential surface of the sealing section is provided with a connecting hole b304 communicating with the connecting hole a303.

[0059] The outside of the connecting section b is provided with an external thread, and the external thread is provided with three groups, namely external thread a, external thread b and external thread c, wherein the external thread a is close to the sealing section, the external thread b is located between the external thread a and the external thread c, and the thread rotation direction of the external thread a and the external thread c is the same, and the thread rotation direction of the external thread b is opposite to that of the external thread a or the external thread c.

[0060] The joint 3 further includes a nut a308 corresponding to the external thread a and a nut b311 corresponding to the external thread c.

[0061] like Figure 6 As shown, a sealing plug 305 is provided on the outside of the sealing section. Specifically, sealing steps 306 are extended inward at both open ends of the sealing plug 305, and when the sealing plug 305 is sleeved on the outside of the sealing section, the opposite end faces of the two sets of sealing steps 306 are respectively fitted with the two sets of shaft shoulders.

[0062] The sealing plug 305 and the sealing step 306 are generally made of rubber material, which has a certain elasticity, so the sealing plug 305 can be directly put on the outside of the sealing section.

[0063] The sealing plug 305 forms an interference fit with the inner wall of the tube mouth of the copper tube 1.

[0064] like Figure 7-9 As shown, the joint 3 further includes two sets of sealing rings: sealing ring a309 and sealing ring b310.

[0065] The joint 3 also includes a sleeve 307, which is a circular cylindrical structure with one end open and the other end closed. A threaded hole 313 is coaxially opened at the closed end of the sleeve 307. The threaded hole 313 corresponds to the external thread b, and the sleeve 307 is assembled to the connecting pipe 301 through the cooperation between the threaded hole 313 and the external thread b.

[0066] A sealing sleeve 312 is sleeved inside the sleeve 307 , and an interference fit is formed between the sealing sleeve 312 and the outer wall of the pipe mouth of the copper pipe 1 .

[0067] The assembly process of connector 3 is as follows:

[0068] First, the sealing plug 305 is placed on the outside of the sealing section. The opposite end surfaces of the two sets of sealing steps 306 are respectively in contact with the two sets of shaft shoulders. The area a formed by the inner wall of the sealing plug 305, the facing end surfaces of the two sets of sealing steps 306, and the outer wall of the sealing section is connected to the connecting hole b304.

[0069] Next, screw the nut a308 onto the external thread a, and the nut a308 fits tightly with the sealing plug 305;

[0070] Next, put the sealing ring a309 on the outside of the connecting section b and fit the sealing ring a309 with the nut a308;

[0071] Next, the sleeve 307 is assembled onto the external thread b through the cooperation between the threaded hole 313 and the external thread b, and the closed end of the sleeve 307 is tightly fitted with the sealing ring a309;

[0072] Next, the sealing sleeve 312 is placed inside the sleeve 307, and the sealing ring b310 is placed outside the connecting section b, with the sealing ring b310 fitting against the closed end of the sleeve 307;

[0073] Next, screw the nut a308 onto the external thread c and make the sealing ring b310 fit tightly against the closed end of the sleeve 307, and the assembly of the joint 3 is completed.

[0074] Working principle of the present invention:

[0075] Step 1: Assemble the copper tube 1 and fin 2;

[0076] Step 2: The sealing plug 305 and the sealing sleeve 312 are both made of rubber material. Therefore, the two assembled connectors 3 can be directly inserted into the mouth of the copper tube 1 until the mouth of the copper tube 1 contacts the sealing ring a309 and the connector 3 cannot be inserted further.

[0077] At this time, since the sealing plug 305 forms an interference fit with the inner wall of the tube opening of the copper tube 1, and the sealing sleeve 312 forms an interference fit with the outer wall of the tube opening of the copper tube 1, and the interior of the copper tube 1 is at normal pressure, the joint 3 and the copper tube 1 form a double sealing fit through: the sealing plug 305 and the inner wall of the tube opening of the copper tube 1, and the sealing sleeve 312 and the outer wall of the tube opening of the copper tube 1;

[0078] Step 3: Open the control valve 504 and arrange the liquid discharge pipe 503 vertically upward;

[0079] The hydraulic medium enters the copper tube 1 through the liquid pipe a4 and the filling hole 302 in sequence, and the air in the copper tube 1 is discharged through the liquid pipe b5 and the drain pipe 503 in sequence. When the air in the copper tube 1 is completely discharged, that is, when the hydraulic medium overflows through the drain pipe 503, the control valve 504 is closed.

[0080] Step 4: The hydraulic medium is continuously delivered into the copper tube 1, and the pressure inside the copper tube 1 increases gradually, causing the copper tube 1 to expand and deform;

[0081] During this process, since the area a formed by the inner wall of the sealing plug 305, the facing end surfaces of the two sets of sealing steps 306, and the outer wall of the sealing section is connected to the connecting hole b 304, that is, the pressure in area a is consistent with that in the copper tube 1, the pressure in area a also changes gradually;

[0082] The pressure in the region a where the pressure is increasing pushes the inner wall of the sealing plug 305 to fit more closely to the inner wall of the copper tube 1, and pushes the sealing step 306 to fit more closely to the shaft shoulder. In other words, the sealing performance and connection stability between the sealing plug 305 and the copper tube 1 are directly proportional to the pressure change in the region a. The connection stability increases because the pressure change causes the inner wall of the sealing plug 305 to be subjected to an increased pressure, which in turn increases the friction between the sealing plug 305 and the inner wall of the copper tube 1, and the increase in the friction is greater than the increase in the thrust force on the sealing plug 305 caused by the increased pressure in the copper tube 1.

[0083] At the same time, the wall of the copper tube 1 is pushed to fit more closely to the sealing sleeve 312. In other words, the sealing performance and connection stability between the sealing sleeve 312 and the copper tube 1 are also directly proportional to the pressure change in area a.

[0084] In addition, the cooperation between the sealing plug 305 and the sealing sleeve 312 can prevent the pipe opening of the copper tube 1 from being greatly deformed, so that the pipe opening of the copper tube 1 is only slightly expanded, which is conducive to the subsequent U-shaped tube welding, so that all copper tubes are connected to form a whole;

[0085] Step 5: After the expansion connection between the copper tube 1 and the fin 2 is completed, the control valve 504 is opened, and the hydraulic medium in the copper tube 1 is discharged through the drain pipe 503. The pressure in the copper tube 1 returns to normal pressure, and the sealing performance and connection stability between the copper tube 1 and the sealing plug 305 or the sealing sleeve 312 are also restored. At this time, the connector 3 can be directly pulled out.

[0086] In the fourth step, the reason why the friction between the sealing plug 305 and the inner wall of the copper tube 1 increases more than the thrust force on the sealing plug 305 due to the increased pressure in the copper tube 1 is that:

[0087] F1=P*S1;F2=P*S2*f;

[0088] When F2>F1, S2*f>S1;

[0089] Wherein, F1 is the thrust force exerted on the sealing plug 305 by the pressure inside the copper tube 1;

[0090] F2 is the friction force between the sealing plug 305 and the inner wall of the copper tube 1;

[0091] P is the pressure inside the copper tube 1;

[0092] S1 is the end surface area of ​​the sealing plug 305;

[0093] S2 is the inner wall area of ​​the sealing plug 305;

[0094] f is the coefficient of friction between rubber and copper.

[0095] Therefore, as long as S2*f>S1 is satisfied, it can be ensured that the ratio of the increase in the friction between the sealing plug 305 and the inner wall of the copper tube 1 is greater than the ratio of the increase in the thrust force generated by the increase in the pressure inside the copper tube 1 on the sealing plug 305. In other words, the stability of the connection between the sealing plug 305 and the copper tube 1 is directly proportional to the pressure change inside the copper tube 1.

[0096] In the above step four, area a is connected to the copper tube through the cooperation of connecting hole a and connecting hole b, rather than directly connected to the liquid filling hole through connecting hole b. This is because in the latter, hydraulic medium flows in the liquid filling hole. According to Bernoulli's principle, there is a negative pressure difference between area a and the liquid filling hole. Therefore, this solution chooses the former, and connects with the copper tube through the cooperation of connecting hole a and connecting hole b to ensure that the pressure changes in area a are consistent with those in the copper tube.

[0097] In a preferred embodiment, the sealing ring a309 and the sealing ring b310 are O-rings.

[0098] Preferred embodiments, such as Figure 5As shown, the circumscribed circle diameter of the nut a308 and the nut b311 is consistent with the inner diameter of the copper tube 1; its significance lies in that, during the hydraulic expansion process after the joint 3 is inserted into the pipe mouth of the copper tube 1, the circumscribed circle diameter of the nut is consistent with the inner diameter of the copper tube 1, which can better support and limit the sealing steps 306 set at both ends of the sealing plug 305, and the threaded connection rotation direction between the nut a308 and the external thread a, and the threaded connection rotation direction between the nut b311 and the external thread c are opposite to the threaded connection rotation direction between the threaded hole 313 and the external thread b, which can ensure that the threaded connection in this solution is more stable.

[0099] Preferred embodiments, such as Figure 10 As shown, an annular mold 314 is further provided between the sleeve 307 and the sealing sleeve 312 . Specifically, both ends of the annular mold 314 are open, and the outer diameter of the annular mold 314 matches the inner diameter of the sleeve 307 , so that the annular mold 314 can be sleeved in the sleeve 307 .

[0100] The inner cavity of the annular mold 314 is divided into two sections along the axial direction: a cylindrical section and a frustum section.

[0101] The shape of the sealing sleeve 312 matches the inner shape of the annular mold 314, and the sealing sleeve 312 can be sleeved in the annular mold 314; its significance lies in that after the joint 3 is inserted into the pipe mouth of the copper tube 1, the cylindrical part of the sealing sleeve 312 that matches the inner cavity of the cylindrical section of the annular mold 314 will form an interference fit with the outer wall of the copper tube 1, that is, a layer of sealing fit is formed. In the subsequent hydraulic expansion process, the pressure in area a drives the sealing plug 305 to undergo elastic deformation, and the part of the pipe mouth of the copper tube 1 located in the inner cavity of the frustum section of the annular mold 314 is expanded into a bell mouth. Of course, if the annular mold 314 is not added, the expansion at the pipe mouth of the copper tube 1 is a cup-shaped expansion.

[0102] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An automatic connection and expansion device for a copper tube and a fin, comprising a copper tube (1) and a joint (3), characterized in that: The joint (3) is used to form a double-sealed connection with the pipe mouth of the copper pipe (1), and the sealing performance and connection stability between the joint (3) and the copper pipe (1) are both proportional to the pressure change in the copper pipe (1); Two groups of connectors (3) are provided. The input end of one group of connectors (3) is provided with a liquid pipe a (4), and the output end is used to be connected to one pipe end of the copper pipe (1). The input end of the other group of connectors (3) is used to be connected to the other pipe end of the copper pipe (1), and the output end is provided with a liquid pipe b (5). The joint (3) includes a connecting pipe (301), and the inner cavity of the connecting pipe (301) is a liquid-filling hole (302); The connecting pipe (301) is divided into three sections along its own axial direction: a connecting section a, a connecting section b, and a sealing section. The sealing section is located between the connecting section a and the connecting section b. The outer diameter of the sealing section is smaller than the outer diameter of the connecting section a or the connecting section b. The outer diameter of the connecting section a is equal to the outer diameter of the connecting section b. A shaft shoulder is formed between the sealing section and the connecting section a or the connecting section b. The end surface of the communication section a is provided with a connection hole a (303), and the outer circumferential surface of the sealing section is provided with a connection hole b (304) communicating with the connection hole a (303); The connecting section b is provided with external threads on the outside. The external threads are provided in three groups and are respectively external threads a, external threads b and external threads c. External threads a are close to the sealing section, external threads b are located between external threads a and external threads c, and the thread rotation direction of external threads a and external threads c is the same, and the thread rotation direction of external threads b is opposite to that of external threads a or external threads c. The outer sleeve of the sealing section is provided with a sealing plug (305); Both open ends of the sealing plug (305) extend inwardly with sealing steps (306), and when the sealing plug (305) is sleeved on the outside of the sealing section, the end faces of the two sets of sealing steps (306) facing each other are respectively in contact with the two sets of shaft shoulders; An interference fit is formed between the sealing plug (305) and the inner wall of the tube mouth of the copper tube (1); S2*f>S1, S2 refers to the inner wall area of ​​the sealing plug (305), S1 refers to the end surface area of ​​the sealing plug (305), and f is the friction coefficient between rubber and copper.

2. The automatic connection and expansion device for copper tubes and fins according to claim 1, characterized in that: The end of the liquid pipe a (4) is connected to the hydraulic system; A pressure limiting valve (501) is provided at the end of the liquid pipe b (5), a pressure gauge (502) is provided on the liquid pipe b (5), a liquid discharge pipe (503) is provided on the liquid pipe b (5), and a control valve (504) is provided on the liquid discharge pipe (503).

3. The automatic connection and expansion device for copper tubes and fins according to claim 1, characterized in that: The joint (3) further comprises a nut a (308) corresponding to the external thread a and a nut b (311) corresponding to the external thread c.

4. The automatic connection and expansion device for copper tubes and fins according to claim 1, characterized in that: The joint (3) further comprises a sealing ring a (309) and a sealing ring b (310).

5. The automatic connection and expansion device for copper tubes and fins according to claim 1, characterized in that: The joint (3) further comprises a sleeve (307); The sleeve (307) is a circular cylindrical structure with one end open and the other end closed. A threaded hole (313) is coaxially opened at the closed end of the sleeve (307). The threaded hole (313) corresponds to the external thread b, and the sleeve (307) is assembled to the pipe (301) through the cooperation between the threaded hole (313) and the external thread b.

6. The automatic connection and expansion device for copper tubes and fins according to claim 5, characterized in that: A sealing sleeve (312) is provided inside the sleeve (307), and an interference fit is formed between the sealing sleeve (312) and the outer wall of the pipe mouth of the copper pipe (1).

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