FIELD OF THE INVENTION

The invention relates to a pipe connection for connecting pipes of dissimilar materials. In particular, the pipe connection is suitable for high pressure and high-temperature coolant line of a refrigerant circuit of an automotive air conditioning system.

BACKGROUND OF THE INVENTION

For many years air conditioning systems for motor vehicles have been operated with chlorofluorocarbon. Recently, because of environmental constraints, carbon dioxide is becoming popular as a coolant. Since carbon dioxide must be used in the liquid state, the coolant must be under high pressure. The known resin or elastomer hoses can no longer be applied. There is a need to use rigid, resilient pipes and corresponding connections. Thus, a vibration-absorbing stainless-steel hoses has been developed in place of the known composite hoses. The stainless-steel hose has a metal wall and has excellent gas permeability compared with known composite hoses formed of rubber and resins. Despite its excellent properties, the steel has a drawback - it is heavy. Thus, there is a need to use materials of lower weight. In order to reduce the weight of refrigerant circuits of automotive air conditioners the aluminum alloy pipes have been applied. However, there are some problems . The bellows of the vibration-absorbing hose must be composed of stainless steel in view of processability and strength. The refrigerant circuit piping needs to be composed of aluminum in view of a reduction in the weight. Thus, the hose made of steel needs to be connected with the aluminum pipe. It is difficult to obtain a joint with high strength and high hermeticity of these two materials . In order to solve this problem, various solutions have been proposed.

The European patent EP1903269 discloses a connection structure for connecting dissimilar metal tubes. A connection structure comprises a metal bellows tube made of stainless-steel being integrally connected to a metal tube made of aluminum. The bellow tube has a reinforcement portion disposed on the outer surface of the bellows. A connection section on the bellows tube side includes a straight tube portion of the bellows tube, a nipple, the reinforcement portion, and a fastening collar, being fitted and secured to each other in that order from the inside of the tube. The nipple has a base joined to the reinforcement portion and a connection end extending to the metal tube side farther than an end face of the fastening collar. The fastening collar has a small diameter portion located on the metal tube side and a large- diameter portion located on the bellows side of the metal bellows tube, the small-diameter portion being continuous with the large- diameter portion. A connection section on the metal tub side includes a connection end of the metal tube and a sleeve secured to the outer side of the connection end. The sleeve has a base joined to the connection end and a fitting end extending to the metal bellows tube side. The fitting end of the sleeve on the metal tube side is fitted on the small-diameter portion of the fastening collar on the metal bellows tube side. The outer surface of the connection end of the nipple is bonded and fixed to the inner surface of the connection end of the metal tube with a thermosetting resin while an end face of the reinforcement portion of the metal bellows tube and the end face of the fastening collar are in contact with or close to the end face of the connection end of the metal tube.

The application of a thermosetting resin for bonding the outer surface of the nipple of the metal bellows tube to the inner surface of the connection end of the aluminum tube constitutes some inconveniences. There is a need to use additional tools and steps to apply a resin onto the outer surface of the nipple. The resin is cured by heating. Thus, there is a need to provide a heat treatment. In result, a process of assembling a connection is complex and requires many steps with the use of different tools.

From the patent application EP3135976 is known a connection assembly for corrugated pipe hose lines. According to this invention a connecting arrangement for corrugated hose assemblies with aluminum pipes comprises at least one corrugated pipe made of stainless steel and a connection nipple made of stainless steel. The corrugated pipe and nipple are integrally connected to each other. The invention is characterized in that a fluid-tight connection is obtained via crimping of the pressure carrier tube directly to the tube has a fluid-tight connection. The aluminum tube widened in two sections at its end. The first stage of the aluminum tube, spaced from the end, fits over the nipple. The first stage of the expansion of the aluminum tube is crimped, so that the material of the aluminum tube in this area on the sealing area and the at least one circumferential sealing element of the nipple is pressed. The second section of the aluminum tube is wider than the first step. The second section has a diameter which can be pushed onto the end of the pressure-carrier tube. The second section of the aluminum tube is crimped, so that the holding profile of the nipple covering the end of the pressure-carrier tube is compressed and the pressure-carrier tube in the region of the holding profile of the nipple is pressed into this. Due to the crimping and the associated deformation of the aluminum tube, this tube and the pressure-carrier tube are positively and frictionally connected to each other. The pressure-carrier tube is also pressed into the profile of the connection nipple and thereby between connection nipple and the pressure-carrier tube also is a positive and frictional connection. Thus, all pressure carrying parts of the assembly are firmly and pressure-tightly connected .

The drawback of this solution is that the aluminum tube and its widened sections are one, integral element. This is not very practical. The end of the tube must be easy to the plastic formation - in order to form widened section. This introduces some limits with the thickness of the aluminum tube wall. Secondly, it is not very convenient to join together two long elements such as hoses, pipes, especially when there is a need to repair after assembling the line. SUMMARY OF THE INVENTION An object of the invention is to provide a pipe connection for connecting steel hose, absorbing vibration, to an aluminum pipe in the refrigerant circuit in an automotive air conditioning system. The pipe connection between dissimilar metal pipes should be high-pressure, high-temperature and leakages resistant. At the same time, the pipe connection should be simple to assemble, without using any adhesive materials, and to repair after assembling the line.

In order to achieve the objective mentioned above, the present invention provides a pipe connection which comprises a hose nipple, which is inseparably connected at one end to a corrugated tube, an outer composite hose covering the corrugated tube and a first part of the hose nipple, a sleeve clamped around the first part of the hose nipple and a part of the outer composite hose covering the first part of the hose nipple. The pipe connection comprises a tubular connector. The connector is inseparably connected to the second part of the hose nipple. A second part of the hose nipple is inserted into a cylindrical part of the connector. The cylindrical part of the connector is clamped around the second part of the hose nipple. The sleeve is clamped around the cylindrical part of the connector.

Preferably, the second part of the hose nipple contains, at its outer surface, two annular protrusions, which are configured to stab into inner surface of the connector, when the connector is clamped around the second part of the hose nipple.

Preferably, the sleeve contains, at its inner surface, three annular protrusions which are configured to stab into outer surface of the connector, when the sleeve is clamped around the connector .

Preferably, the connector is made of a less hard material than the hose nipple and the sleeve.

Preferably, the connector is made of aluminum.

Preferably, the hose nipple and the sleeve are made of steel. Preferably, the first part of the hose nipple contains, at its outer surface, three annular protrusions configured to stab into inner surface of the composite hose, and the sleeve contains, at its inner surface, three annular protrusions configured to stab into outer surface of the composite hose, which are arranged to overlap the hose nipple's protrusions, when the sleeve is clamped around the connector and the composite hose.

Preferably, between the hose nipple and the connector is placed a sealing, which is embedded in a groove arranged at the outer surface of the hose nipple.

Preferably, the hose nipple contains, at its one end, an extension which is inserted into the end of the corrugated tube.

Preferably, the connector contains, at its second end, an extension, which is arranged to connect with another pipe by welding or brazing.

Preferably, the connector contains at the second end, at its outer surface, an annular tenon protruding outward, which sets up the position of the sleeve in the longitudinal direction.

Preferably, the connector contains at the second end, at its inner surface, an annular tenon protruding inward, which sets up the position of the connector in relation to the hose nipple.

Preferably, the hose nipple is inseparably connected at one end to the corrugated tube by a weld.

Preferably, an outer surface of the corrugated tube is coated with an elastomer.

Preferably, junction of the annular tenon protruding outward from the outer surface of the connector with the sleeve is covered with an elastomer film.

ADVANTAGES OF THE INVENTION

Pipe connection according to the invention provides high-pressure, high-temperature and leakages resistant joint of corrugated steel tube, absorbing vibration, to an aluminum pipe of a refrigerant circuit. The connection does not use any adhesive material, such as resins in order to connect dissimilar metals. It is generally based on clamping particular elements and on taking advantage of different hardness of steel and aluminum when the steel protrusions stab into connector made of aluminum. Moreover, application of the additional element - aluminum connector to which aluminum tube is to be welded or brazed enable easier assembling of the pipe connection and further repairs.

BRIEF DESCRIPTION OF DRAWING

The invention is presented in its embodiments in the drawing, where :

Fig. 1 is a cross-sectional view of the pipe connection according to the present invention,

Fig. 2 is a cross-sectional view of a connector,

Fig. 3 is a cross-sectional view of a corrugated tube with an elastomer at its outer surface connected to a hose nipple,

Fig. 4 is a cross-sectional view of a sleeve,

Fig. 5 is a cross-sectional view of an outer composite hose,

Fig. 6 is a cross-sectional view of a corrugated tube with an elastomer at its outer surface,

Fig. 7 is a cross-sectional view of a corrugated tube without an elastomer at its outer surface.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Fig. 1 a pipe connection in accordance with a first embodiment of the present invention comprises a hose nipple

1, which is inseparably connected at one end to a corrugated tube

2, an outer composite hose covering the corrugated tube 2 and a first part la of the hose nipple 1, a sleeve 3 clamped around the first part la of the hose nipple 1 and a part of the outer composite hose 4 covering the first part la of the hose nipple 1. The pipe connection comprises also a tubular connector 5. The connector 5 is inseparably connected to the second part lb of the hose nipple 1.

According to the invention the connector 5 is made of aluminum, whereas the hose nipple 1 and the corrugated tube 2 are made of steel .

The hose nipple 1 is inseparably connected at one end to the corrugated tube 2 by a weld 6. To connect these elements the TIG orbital welding have been employed. In order to obtain welding connection, the hose nipple 1 contains, at its end, the annular flange 7, and the marginal ridge 8 of the corrugated tube 2 is flattened. The flange 7 serves to connect the hose nipple 1 to the marginal ridge 8 of the corrugated tube 2. The flattening of the marginal ridge 8, and the flange 7 makes the contact surface between the hose nipple 1 and the corrugated tube 2 bigger. In result, the weld 6 connecting these two elements is also bigger than it would be without applying the flange 7 and flattened the marginal ridge 8. The hose nipple 1 contains at its one end the extension 9 which is inserted into the end of the corrugated tube 2 for length of about two ridges. The inner diameter of the extension 9 is the same as the diameter of the corrugated tube 2. The extension 9 enables smooth passage between the inner surface of the hose nipple 1 and the inner surface of the corrugated tube 2.

According to the invention the connector 5 contains at its second end an extension 10, which is arranged to connect with another pipe by welding or brazing. Thanks to the extension 10 the connector 5 can be connected to the other pipe 11 made of aluminum. In order to connect the connector 5 with the pipe 11, the end of this pipe is inserted into the extension 10, and the border of the extension 10 is connected by a weld or brazed (e.g. filled weld) with the outer surface of the pipe 11.

The connector 5 contains, at its second end, at its inner surface, e the annular tenon 12 protruding inward. The tenon 12 is arranged to set up the position of the connector 5 in relation to the hose nipple 1. The annular tenon 12 contacts with the edge of the hose nipple preventing the end of the cylindrical part 5a of the connector 5 from contacting the edge of the composite hose 4. In result, there is the slot 13 between the end of the cylindrical part 5a of the connector 5 and end of the composite hose 4. The slot 13 serves as a dilatation. It helps to eliminate tensions which could appear between the composite hose 4 and the connector 5, which further could result in unsealing the connection.

The tenon 12 serves also to set up the position of the pipe 11. When the pipe 11 is inserted into the extension 10, the annular tenon 12 limits the length to which the pipe 11 can be inserted. It also prevents the pipe 11 to contact the hose nipple 1.

Thanks to the connector 5 the hose nipple 1 and the corrugated tube 2 do not directly connect with the aluminum pipe 11. Application of the additional, intermediary element - connector 5 in the pipe connection allows to easier and more convenient inseparably connection of two long parts : the corrugated tube 2 and the aluminum pipe 11. It is easier and more convenient, comparing to the known prior art, to assembly the pipe connection by connecting short aluminum connector 5 to the steel hose nipple 1 connected to the long corrugated tube 2, and next to connect the long aluminum pipe 11 to the connector 5. This arrangement also facilitates repairs of the pipe connection, after assembling the line .

Moreover, in the connection according to the invention, the aluminum pipe 11 does not have to be clamped around the hose nipple or is not clamped by a sleeve. Thus, the thickness and hardness of the wall of the connector 5 are not limited by parameters of the plastic forming.

In accordance with the embodiment of the present invention the connector 5 is inseparably connected to the second part lb of the hose nipple 1. This inseparable connection results from fixing of particular elements of the pipe connection. The arrangement of the elements is as follows . The second part lb of the hose nipple 1 is inserted into a cylindrical part 5a of the connector 5. The cylindrical part 5a of the connector 5 is clamped around the second part lb of the hose nipple 1. Further, the sleeve 3 is clamped around the cylindrical part 5a of the connector 5. The cylindrical part 5a of the connector 5 and the sleeve 3 are clamped in the longitudinal direction - parallel to the axis of the hose nipple 1.

However, fixing of the particular elements of the pipe connection only by clamping in the longitudinal direction does not suffice to provide firm, tight, high pressure, and high-temperature resistant connection. In order to achieve connection with such properties, additional technical features have been applied in the pipe connection according to the invention.

The second part lb of the hose nipple 1 contains, at its outer surface, two annular protrusions 14. The hose nipple 1 and the protrusions 14 form a monolithic structure. The protrusions 14 are made from the same material as the hose nipple 1 - the steel. This material has a higher hardness than aluminum. Thus, when the connector 5 is clamped around the second part lb of the hose nipple 1, the protrusions 14 stab into inner surface of the connector 5. The protrusions 14 are set transversal toward the axis of the connector 5 and the direction of the clamping. This setting of the protrusions results in the connection between the hose nipple 1 and the connector 5 that is stronger than in the case that there is only clamping in the longitudinal direction. Moreover, rectangular shape in the cross-section view of the protrusions 14 cause that they block the move of the connector 5 in the longitudinal direction more firmly than they would have rounded shape.

Furthermore, stronger connection between the connector 5 and the hose nipple 1 and the corrugated tube 2 results also from three annular protrusions 15 at the inner surface of the sleeve 3. These three protrusions 15 are configured to stab into outer surface of the connector 5, when the sleeve 3 is clamped around the connector 5. The sleeve 3 and the protrusions 15 form a non-lithic structure. The protrusions 15 are made from the same material as the sleeve 3 - the steel. This material has a higher hardness than aluminum. Thus, when the sleeve 3 is clamped around the connector 5, the protrusions 15 stab into the outer surface of the connector 5. The protrusions 15 also are set transversal toward the axis of the connector 5 and the direction of the clamping. They also have a rectangular shape in the cross-section view, similarly to the protrusions 14. The position of the protrusions 15 is that they overlap with protrusions 14. Thanks to this the wall's thickness of the cylindrical part 5a of the connector 5 is not too small. If the protrusions 14 and 15 would be coincident the wall of the cylindrical part 5a of the connector 5 could be too thin to bear the breaking force.

Thanks to the protrusions 14 and 15 which stab into aluminum connector 5 the connection with hose nipple 1 is strong, high- pressure, high-temperature and leakages resistant.

The outer composite hose 4, as it is shown in Fig. 5, consists of three layers 16a, 16b, 16c made of an elastomer material and the tubular metal mesh 17 situated between layers 16a and 16b. Layer 16a constitutes the outer layer of whole outer composite hose 4. Layer 16c constitutes the inner layer of whole outer composite hose 4. Layers 16a and 16b and have the same thickness. Layer 16c is thinner. The outer composite hose 4 thanks to its inner enforcement - tubular metal mesh 17 - helps to keep corrugated tube 2 resistant to the internal pressure.

Referring back to Fig. 1, the composite hose 4 is inseparably connected to the hose nipple 1 and the sleeve 3 by clamping. The sleeve 3 is clamped around the first part la of the hose nipple 1 pressing composite hose 4 to the outer surface of the hose nipple 1. In order to strengthen this connection the hose nipple 1 contains, at its outer surface, three annular protrusions 18. When the composite hose 4 is pressed to the outer surface of the first part la of the hose nipple 1 the protrusions 18 stab into inner surface of the composite hose 4. Moreover, also the sleeve 3 contains, at its inner surface, three annular protrusions 19. When the sleeve is clamped the protrusions 19 stab into outer surface of the composite hose 4. The protrusions 19 are arranged to overlap the protrusions 18, when the sleeve 3 is clamped around the connector 5 and the composite hose 4.

The protrusions 18 and 19 are set transversal toward the axis of the hose nipple 1 and the direction of the clamping. This setting of the protrusions results that the connection between the hose nipple 1, sleeve 3 and the composite hose 4 is stronger than in the case that there is only clamping in the longitudinal direction .

The pipe connection according to the invention, in order to achieve very high level of tightness comprises the sealing 20 which is placed between the hose nipple 1 and the connector 5. The sealing 20 is embedded in the groove 21 arranged at the outer surface of the hose nipple 1. The sealing 20 can be a D-ring seal made from elastomer.

In accordance with the invention the connector 5 contains at the second end, at its outer surface, the annular tenon 22 protruding outward. The tenon 22 serves to set up the position of the sleeve 3 in the longitudinal direction.

According to the invention junction of the annular tenon 22 protruding outward from the outer surface of the connector 5 with the sleeve 3 is covered with an elastomer film 23. This elastomer film 23 can be an heat-shrink band. The elastomer film 23 provides the protection of the junction from the galvanic corrosion. This corrosion can appear when different metals contact each other e.g aluminum and steel. The heat-shrink band keeps the junction off the oxygen.

Referring to Fig 6. the corrugated tube 2, in the first embodiment, is, at its outer surface, covered with the elastomer 24. The elastomer 24 helps to reduce the noise made by a coolant passing through the corrugated tube. According to the invention, the last four ridges 8 (counting with the last flattened ridge) at the end of the corrugated tube 2 are not coated with the elastomer 24. This helps to avoid burning the elastomer during welding.

In the alternative embodiment, shown in Fig. 7, the outer surface of the corrugated tube 2 is not covered with the elastomer. This keeps the tube more flexible.

Although the invention has been explained in relation to its preferred embodiment as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the present invention. Hence, the indicated embodiment of the invention relating to the pipe connection thereof cannot limit the scope of protection which is defined in the claims.