US20120211208A1

US20120211208A1 - Brazing joints

Info

Publication number: US20120211208A1
Application number: US13/029,242
Authority: US
Inventors: Dae-hyun Jin
Original assignee: Advanced Distributor Products LLC
Current assignee: Advanced Distributor Products LLC
Priority date: 2011-02-17
Filing date: 2011-02-17
Publication date: 2012-08-23

Abstract

One aspect provides a header tube and a refrigeration tube that have ends on which one or more coupling ends are integrally formed thereon. Methods of fabricating the header tube and refrigeration tube are also provided.

Description

TECHNICAL FIELD

This application is directed, in general, to a coupling end that can be used to braze joints in heating ventilation air conditioning (HVAC) systems.

BACKGROUND

Condensing or cooling coils are well known and have been used for decades in HVAC systems. Some coils are constructed of aluminum while other coils are constructed of copper. Typically, these coils are connected to the refrigerant delivery pipes that include brazed joints. As is well known, brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (known as wetting) and is then cooled to join the work pieces together. However, the price of copper metal has begun to experience a sharp increase in price due to growing world-wide demand. As such, manufacturers have not only been continually confronted with brazing problems in general, but have also begun to be confronted with problems associated with brazing two different metals, such as aluminum and copper together.

SUMMARY

One aspect provides a refrigerant coil. In this embodiment, the refrigerant coil comprises a header tube that has an integrally formed coupling end. The coupling end has a first non-flared section at an end of the header tube joined by a tapered shoulder to a second non-flared section wherein an internal diameter of the first section is less than an internal diameter of the second section.
In another aspect, there is provided a a method of manufacturing the refrigerant coil in which the method comprises cutting a refrigerant header tube to a predetermined length to have first and second ends and shaping at least one of said first and second ends to form a coupling end. The coupling end has first and second non-flared sections joined by a tapered shoulder wherein an internal diameter of the first section is less than an internal diameter of the second section.
In yet another embodiment, a refrigeration coil is provided. In this embodiment, a refrigeration tube has first and second longitudinal sections having a first rounded corner located therebetween and has first and second ends, respectively. At least one of the first and second ends comprises an integrally formed coupling end having a first flared section located adjacent the first end and having a first internal diameter that graduates from a first, smaller internal diameter to a second, larger internal diameter. A second non-flared section joins the first section and has a second internal diameter larger than the first smaller internal diameter. A third flared section joins the second section and has a third internal diameter that graduates from a third smaller diameter to a fourth internal diameter that is larger than the second internal diameter. This embodiment further comprises a header plate located adjacent the first and second ends and wherein the first and second longitudinal sections extend through openings located in the header plate.
A method of fabricating the refrigeration coil discussed above is also provided. This embodiment comprises forming the refrigeration tube to have first and second longitudinal sections joined by a first rounded corner. The first and second longitudinal sections have first and second ends, respectively. The first and second ends are positioned through openings in the header plate to a predetermined distance, and the ends are shaped to form a coupling end on each of the first and second ends. The coupling ends each have first flared section located at the first end and have a first internal diameter that graduates from a first, smaller internal diameter to a second, larger internal diameter. The second section joins the first section and has a second internal diameter larger than the first smaller internal diameter, and a third flared section joins the second section and has a third internal diameter that graduates from a third smaller diameter to a fourth internal diameter that is larger than the second internal diameter. This embodiment further comprises brazing a second rounded corner to each of the coupling ends.

BRIEF DESCRIPTION

Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1A illustrates an embodiment of a header tube having an integrally formed coupling end, as provided by this disclosure;

FIG. 1B illustrates the header tube of FIG. 1A coupled to a conventional refrigeration coil;

FIG. 2 illustrates a coupling end of the header tube of FIG. 1A having a connecting tube received therein;

FIG. 3 illustrates the embodiment of FIG. 2 subsequent to a brazing processes;

FIG. 4A-4B illustrate an embodiment of a refrigeration coil having at least one integrally formed coupling end that extends through a header plate;

FIG. 5 illustrates an enlarged view of an embodiment of the coupling end of the refrigeration coil of FIG. 4;

FIG. 6 illustrates the refrigeration coil of FIG. 4 having a return bend brazed thereto; and

FIG. 7 illustrates an enlarged view of the coupling end and return bend of FIG. 6, subsequent to a brazing process.

DETAILED DESCRIPTION

FIG. 1A illustrates one embodiment of a refrigeration tube 100 that may be used in a conventional refrigeration coil 103, as generally seen in FIG. 1B, including those employed in a refrigeration or condensing coil of a HVAC system. The refrigeration tube 100 is typically cut to a length 105, as may be required by design. In this particular embodiment, the refrigeration tube 100 may be a header tube to which other refrigeration tubes may be coupled at the points of openings 110 located along its length 105. The refrigeration tube 100 also includes an integrally formed coupling end 115 that may be located at one or both ends of the refrigeration tube 100. These integrally formed coupling ends 115 provide unique advantages over those of conventional design.
For example in conventional designs, a sweat coupling collar is typically used to join two different pieces of tubing, which typically have the same metallic composition, such as copper. In such applications, the collar must be brazed or soldered to the end of each tube that is to be joined. However, problems can arise when a copper based refrigeration coil is replaced with an aluminum base refrigeration coil. This exchange of coil types is beginning to happen with greater frequency given that the price of copper has risen significantly. Thus, conventional sweat joints must first be unsealed and then re-sweated after coils are exchanged. In such operations, the sweat joints can be prone to leaks or weak joints due to the characteristics of the brazing solder or the brazing filler metal for the joint brazing between dissimilar materials such as the connecting tube, which might be copper and the replaced coil, which might be aluminum. Unlike brazing between similar materials, subtle movements of dissimilar materials during brazing affect brazing quality. Uniform and smooth distribution of filler metal while positioning brazing materials without any movements, especially during a cooling down period is a key for the quality joint brazing between dissimilar materials. Therefore, a unique design for the coupling end is necessary.
FIG. 2 illustrates an enlarged view of the coupling end 115 having a connecting tube 205 positioned within the coupling end 115. In one embodiment, the header tube 100 and integral coupling end 115 and connecting tube 205 may be comprised of the same material, such as aluminum or copper. However, in another embodiment, the connecting tube 205 might be comprised of copper, while the header tube 100 and integral coupling end 115 might be comprised of aluminum. In this embodiment, the integral coupling end 115 is particularly advantageous by providing a superior brazed connection when compared to those of conventional design. For example, in the illustrated embodiment, the coupling end 115 is integrally formed with the refrigeration tube 100. As such, no brazing steps need be taken to attach the coupling end 115 on the end of the refrigeration tube 100, thereby reducing the chances of an inferior brazed joint. Moreover, the coupling end 115 has a first non-flared section 210 that has an internal diameter 215 which is less than an internal diameter 220 of a second non-flared section 225, the advantages of which as discussed below. The first section 210 and the second section 225 are joined by a shoulder 230. Also, the first section 210 is integrally formed with the header tube 100 at shoulder 235. In contrast, certain conventional designs have only one non-flared section or only one flared section, which provides a much tighter gap between the tube and the coupling end.
When positioned within the coupling end 115, the connecting tube 205, which has an external diameter 240 that is less than both the internal diameters 215 and 220, seats on the shoulder 235. In one advantageous embodiment, a ratio 245 of the internal diameter 215 to the internal diameter 220 is less than 1. For example, in one design, the internal diameter 215 may be 0.756 inches, while the internal diameter 220 may be 0.780 inches, thereby providing a ratio of about 0.97. The advantages of this general ratio are addressed below regarding FIG. 3.
FIG. 3 illustrates an embodiment where the connecting tube 205 is brazed to the coupling end 115. As seen here, due to the above-stated ratio 245 of the internal diameters 215, 225, the brazing solder 305 is substantially located only between the external diameter 240 of the connecting tube 205 and the internal diameter 220 of the second section 225; that is, typically, there is a small amount of solder located between the first section 210 and the connecting tube 205. In one embodiment, a difference between the internal diameter 215 of the first section 210 and the external diameter 240 of the connecting tube 205 ranges from about 0.002″ to about 0.006″. This provides a strong brazed connection between the header tube 100 and the connecting tube 205 and substantially isolates the solder to the area between the section 210 and the connecting tube 240. Further, the difference also allows a close enough fit between the section 210 and the connecting tube 205 that the connecting tube is held in a substantially planar position, which also allows for an improved brazed connection. Also, in one embodiment, a difference between the internal diameter 220 of the second section 225 and the external diameter 240 of the connecting tube 205 ranges from about 0.01″ to about 0.03″. This provides smooth and uniform distribution of brazing solder or brazing filler metal between the header tube 100 and the connecting tube 205 and especially between the second section of 225 and the external diameter 240 of the connecting tube 205. Since conventional designs typically have only one non-flared section or only one flared section, as mentioned above, it's very difficult, if not impossible, to meet both requirements of a tight fit and smooth and uniform distribution at the same time. In such conventional designs, given the decrease in the difference between the internal diameter of the coupling end and the external diameter of the connecting tube, it's not easy to feed the brazing solder or the brazing filler metal smoothly and uniformly due to the tight gap. Moreover, it's very likely, in such conventional designs for the brazing filler to flow into the interior of the header and it's very difficult to position the connecting tube in a substantially planar position.
In one embodiment, the header tube 100 may be fabricated by cutting it to a predetermined length as required by design, which forms first and second ends. A press and die, which may have a mirror configuration of the coupling end 115, can be used to shape at least one of the ends of the header tube 100 to form the integral coupling end 115, as described above in its various embodiments.
FIG. 4A illustrates another embodiment of a refrigeration coil as provided by this disclosure. This embodiment provides a refrigeration tube 400 having longitudinal sections 405, 410 that are joined by a rounded corner 415 located between them. The rounded corner 415 may be integrally formed with the tube 400, such as a bend in the tube, or it may be brazed onto the ends of the longitudinal sections 405, 410. The refrigeration tube 400 has a length 420 that extends from the rounded corner 415 to the ends 417, 419 of the longitudinal sections 405, 410, which include integrally formed coupling ends 425, 430, as shown in FIG. 45. The integrally formed coupling ends 425, 430 provide advantages over conventional coupling ends that must be individually brazed onto the ends of the tubes, which requires additional manufacturing or assembling steps and also increases the possibility that a weak or leaky joint may result. Though two coupling ends 425, 430 are shown, it should be noted that, in other embodiments, only one coupling end might be present. A press and a die having a mirror configuration of the coupling ends 425, 430 can be used of shape the ends 417, 419 into the coupling ends 425, 430.
The refrigeration coil further includes a header plate 435 that has openings through it and that is located adjacent the coupling ends 425, 430. Prior to the formation of the coupling ends 425, 430, the ends 417, 419 of the longitudinal sections 405, 410 are inserted through openings in the header plate 435 to a predetermined distance, as discussed below.
FIG. 5 illustrates an enlarged view of one of the coupling ends 425, generally shown in FIG. 4B. In this embodiment, the integrally formed coupling end 425 has a flared section 505 located adjacent an end of the longitudinal section 405. The flared section 505 has an internal diameter 510 that graduates from a smaller internal diameter 510 a to a larger internal diameter 510 b. The coupling end 425 further comprises a non-flared section 515 that joins the flared section 505 and that has an internal diameter 520 that is larger than the smaller internal diameter 510 a. Another flared section 530 joins the non-flared section 520 and also has an internal diameter 535 that graduates from a smaller diameter 535 a to an internal diameter that is larger than the internal diameter 520.
In one embodiment, the flared sections 505 and 530 each include an angled wall 505 a and 530 a, respectively, (further designated by the arcs) wherein a ratio of the angled wall 505 a of the flared section 505 to the angled wall 530 a of the flared section 530 ranges from about 0.71 to about 0.90. In one specific embodiment, the ratio may be 0.9. For example, the angled wall 505 a may have an angle of about 27° and the angled wall 530 a may have an angle of about 30°. It should be understood that other angles may be used to achieve the range of ratios and the specific ratio has noted above. These angles provide the benefits over conventional devices. For example, the ratio of the angled wall of many conventional designs is about 0.4 to about 0.6, which means the angled wall of the conventional designs is typically much greater than that for the embodiment illustrated in FIG. 5. However, problems such as a buckling issue and split cups can arise with these conventional designs when a copper based refrigeration coil is replaced with an aluminum base refrigeration coil because an aluminum base refrigeration coil requires much greater expansion force because of the thicker material thickness due to the lower tensile strength in order to maintain the required minimum internal burst pressure. Therefore, a unique design for the coupling ends 425, 430 is needed for a lower tensile strength material such as aluminum.
FIG. 6 illustrates the refrigeration tube 400 where another return bend 605 has been brazed to the coupling ends 425, 430. Conventional brazing techniques may be used to braze the return bend 605 to the coupling ends 425, 430. As seen in this embodiment, the coupling ends 425, 430 are formed a distance 610 from the header plate 435. In one embodiment, the refrigeration tube has the length 420 that extends from the rounded corner 415 to the coupling ends 425, 430, and the coupling ends 425, 430 extend from the header plate 435 the distance 610 is at least about 0.65 inches. In one advantageous embodiment, the distance ranges from about from 0.65 to about 0.75 inches. The above-mentioned distance advantageously provides greater distance between the header plate 435 and the brazing point, and thereby prevents excessive heating of the header plate 435 and reduces the possibility of the header plate 435 cracking due to excessive heat. Normally, aluminum header plates are being used for aluminum base refrigeration coils.
FIG. 7, illustrate a partial view of the coupling end 425 after brazing operations have been completed to braze the return bend 605 to the coupling end 425. As seen in this embodiment, due to general configuration as described above, the coupling end allows for the end of the return bend 605 (shown in dashed lines) to tightly seat on the shoulder at the junction of the flared section 505 and the non-flared section 515. In one embodiment, a difference between the internal diameter 515 of the non-flared section and the external diameter of the connecting return bend 605 ranges from about 0.001″ to about 0.003″. This tighter gap between the coupling end 425 and the connecting return bend 605 provides advantages such as improved brazing quality, higher brazing speed, and less damage of header plate 435 over the conventional designs. In addition, the flared section 530 allows solder 705 to uniformly seal about end of the coupling end 425 and the return bend 605, thereby providing an improved brazed joint over conventional coupling designs and processes.
A method of fabricating the refrigeration tube 400 is also provided. In one embodiment, the method may comprise forming longitudinal sections 405, 410 that are joined by the rounded corner 415. Ends 417, 419 of the longitudinal sections 405, 410 are positioned through openings in the header plate 435 to the predetermined distance 610. The ends 417, 419 are then shaped to form integral coupling ends 425, 430, as seen in FIG. 4. In one method embodiment, a press and die may be used to produce coupling ends 425, 430. Each of the coupling ends 425, 430 may be formed to have the flared sections 505, 515, 530, as described above. Once the coupling ends 425, 430 are formed; the round corner 605 can be brazed or soldered in place using conventional brazing processes.
Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.

Claims

1. A refrigerant coil, comprising:

a header tube, said header tube having an integrally formed coupling end, said coupling end having a first non-flared section at an end of said header tube joined by a tapered shoulder to a second non-flared section wherein an internal diameter of said first section is less than an internal diameter of said second section.

2. The refrigerant coil recited in claim 1, wherein a ratio of said internal diameter of said first section to said internal diameter of said second section is less than 1.

3. The refrigerant coil recited in claim 2, wherein said ratio is about 0.97.

4. The refrigerant coil recited in claim 1, wherein said coupling end comprises aluminum and further comprising a copper connecting tube having an end positioned within said coupling end, said copper connecting tube having an external diameter that is less than said internal diameter of said first section and said internal diameter of said second section and wherein said copper connecting tube seats on an internal shoulder of said first section at a junction point of said header tube and said coupling end.

5. The refrigerant coil recited in claim 4, wherein a brazing solder is located only between said external diameter of said copper connecting tube and said internal diameter of said second section.

6. The refrigerant coil recited in claim 4, wherein a difference between said internal diameter of said first section and said external diameter of said connecting tube ranges from about 0.002″ to about 0.006″.

7. A method of manufacturing a refrigerant coil, comprising:

cutting a refrigerant header tube to a predetermined length having first and second ends; and

shaping at least one of said first and second ends to form a coupling end, said coupling end having first and second non-flared sections joined by a tapered shoulder wherein an internal diameter of said first section is less than an internal diameter of said second section.

8. The method recited in claim 7, wherein shaping includes shaping said internal diameter of said first section and said internal diameter said second section such that a ratio of said internal diameter of said first section to said internal diameter of said second section is less than 1.

9. The method recited in claim 8, wherein said ratio is about 0.97.

10. The method recited in claim 7, wherein said coupling ends comprise aluminum and said method further comprising,

positioning an end of a connecting tube comprising copper within said coupling end such that said connecting tube seats on an internal should of said first section, said connecting tube having an external diameter that is less than said internal diameter of said first section and said internal diameter of said second section; and

brazing said connecting tube to said coupling end such that brazing solder is located only between said external diameter of said connecting tube and said internal diameter of said second section.

11. A refrigeration coil, comprising:

a refrigeration tube having first and second longitudinal sections having a first rounded corner located therebetween and having first and second ends, respectively, at least one of said first and second ends comprising an integrally formed coupling end having:

a first flared section located adjacent said first end and having a first internal diameter that graduates from a first, smaller internal diameter to a second, larger internal diameter;

a second non-flared section joining said first section and having a second internal diameter larger than said first smaller internal diameter;

a third flared section joining said second section and having a third internal diameter that graduates from a third smaller diameter to a fourth internal diameter that is larger than said second internal diameter; and

a header plate located adjacent said first and second ends and wherein said first and second longitudinal sections extend through openings located in said header plate.

12. The refrigeration coil recited in claim 11, wherein each of said first and second ends comprises said coupling end, and further comprising a second rounded corner that is brazed to each of said coupling ends.

13. The refrigeration coil recited in claim 11, wherein said first and third flared sections each include an angled wall, wherein a ratio of said angled wall of said first flared section to said angled wall of said third flared section ranges from about 0.71 to about 0.90.

14. The refrigeration coil recited in claim 13, wherein said ratio is about 0.9.

15. The refrigeration coil recited in claim 11, wherein said refrigeration tube has a length that extends from said first rounded corner to said coupling end, and wherein said coupling end extends from said header plate a distance, wherein said distance ranges from about 0.65 to about 0.75 inches.

16. The refrigeration coil recited in claim 11, wherein a difference between the internal diameter of the non-flared section and the external diameter of the connecting return bend ranges from about 0.001″ to about 0.003″.

17. The refrigeration coil recited in claim 15, wherein said distance is about 0.72 inches.

18. A method of fabricating a refrigeration coil, comprising:

forming a refrigeration tube having first and second longitudinal sections joined by a first rounded corner, said first and second longitudinal sections having first and second ends, respectively;

positioning said first and second ends through openings in a header plate to a predetermined distance;

shaping a coupling end on each of said first and second ends, said coupling ends each having a first flared section located at said first end and having a first internal diameter that graduates from a first, smaller internal diameter to a second, larger internal diameter, a second section joining said first section and having a second internal diameter larger than said first smaller internal diameter, and a third flared section joining said second section and having a third internal diameter that graduates from a third smaller diameter to a fourth internal diameter that is larger than said second internal diameter; and

brazing a second rounded corner to each of said coupling ends.

19. The method recited in claim 17, wherein shaping said first and third flared sections includes forming an angled wall, wherein a ratio of said angled wall of said first internal diameter to said angled wall of said third internal diameter ranges from about 0.71 to about 0.90.

20. The method recited in claim 17, wherein said refrigeration tube has a length extending from said first rounded corner to said coupling ends wherein said the distance is about from 0.65 to 0.75 inches.

21. The refrigeration coil recited in claim 17, wherein a difference between the internal diameter of the non-flared section and the external diameter of the connecting return bend ranges from about 0.001″ to about 0.003″.

22. The method recited in claim 20, wherein said distance is about 0.72 inches.