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(11) | EP 0 133 687 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and apparatus for expanding heat exchanger tubes |
| (57) A heat exchanger tube is expanded externally, for instance for connecting it with
a plate perimetrically of a hole in the plate through which it passes, by forcing
through the bore of the tube a series of at least two expanders of progressively larger
size. These expanders are secured on a tool steel rod so far apart from one another
than before a trailing expander engages in the bore of the tube, the expander which
led it has already emerged from the far end of the tube. |
FIELD OF THE INVENTION
[0001] The present invention relates to a method of expanding the width of a tube, and also to an expanding tool used for the expanding. The expanding method of present invention is useful for fixing tubes to fins in order to build a core of heat exchanger, for example.
DESCRIPTION OF THE PRIOR ART
[0002] A conventional method of expanding the tubes of a solderless type heat exchanger is described in relation to FIGURE 1 of the drawings, as follows:
At first, a set of expanding tools 14 is moved towards the tubes .2 so as to insert the expanding parts 15 into the tubes 2, as shown in FIGURE 1. Each expanding part 15 is located at the top end of a stem 14a and the outer width thereof is slightly wider than the inner width of the corresponding tube. Then, the expanding tools are forced toward the inside of tubes 2 in such manner that the front face 15a of each expanding part 15 contacts with the inner surface of the corresponding tube 12. Therefore, the width of each tube 12 is expanded in accordance with the progression of the expanding part 13.
[0003] On the other hand, the tubes 12 of the heat exchanger have a tendency that the coolant-passage area thereof has become small in order to reduce the weight of the heat exchanger. Therefore, the expanding tool 14 has also become small and thin in accordance with the tendency. The small and thin expanding tool, however, does not have enough strength to endure the pressing force when the expanding part is inserted into the tube. In other words, such a kind of the expanding tool is in danger because of the bending thereof.
BRIEF DESCRIPTION OF THE. DRAWINGS
[0004]
Figure 1 is a front elevation view of a conventional expanding tool and a core of a heat exchanger.
Figure 2 is a longitudinal sectional view of a part of a core of a heat exchanger.
Figures 3, 4 and 5 are sectional views of expanding tools and a core of a heat exchanger and show progressive steps in an expanding process of an embodiment of present invention.
Figure 6 shows a sectional shape of the tube.
Figures 7 and 8 are fragmentary front elevational views of an expanding part shown in Figure 3.
Figure 9 is a front elevation view of an expanding tool of another embodiment of the present invention.
Figure 10 is a fragmenting longitudinal sectional view of a stopper plate being used in this other embodiment of the present invention.
DETAILED DESCRIPTION OF
THE PREFERRED EMBODIMENT
[0005] In Figures 2, 3, 4 and 5, the numeral 1 shows an expanding tool having a finishing expanding part 3 at one end of a stem la, a preliminary expanding part 4 at the approximate center of the stem la and a guide portion lc at the other end of the stem la. The shape of the finishing expanding part 3 and the preliminary expanding part 4 is shown in Figures 7 and 8, respectively. Each of those parts 3 and 4 has a front face 3b and 4b, respectively. At this portion the sectional area of each expanding part 3 and 4 is increasing toward the center portion 3a and 4a. On the other hand, at the back face 3c and 4c located behind the center portion 3a and 4a the sectional area of each of the expanding parts 3e and 4e is decreasing toward the end point 3e and 4e, respectively.
[0006] The cross-sectional shape of each expanding part 3 and 4 is the same as the shape of a tube 2. As shown in Figure 6, the shape of the tube 2 is made up by two types circle which have a special relationship with one another, as designated by the following formula:
wherein Rl is a radius of the shorter circle, R2 is a radius of the longer circle, A is a longer width of the tube 2 and B is a shorter width of the tube 2.
[0007] The maximum width of the finishing expanding part 3 is the same as the inner width of designed tube 2. The maximum width of the preliminary expanding part 4 is intermediate in size between the inner width of the pre-expanded tube 2 and that of the designed tube 2. Both the expanding parts 3 and 4 are made of a tool steel treated by tempering and the surfaces of both parts 3 and 4 are plated with hard chrome after they have been polished. Both parts 3 and 4 are connected one to another with a first stem 1 a made of high tool steel and the length thereof is longer than that of the tube 2. Therefore, the distance between the finishing expanding part 3 and the preliminary expanding part 4 is longer than the axial length of the tube 2. -The preliminary expanding part 4 is connected with a second stem made also of a high tool steel by a pin. The guide portion lc is formed integrally at the end of the second stem lb. A holding groove-ld is formed in the second stem lb at the near edge of the guide portion lc. The holding groove ld is clamped by a clamp 9 when the expanding tools 1 are pulled out from the tubes 2. The clamp 9 can clamp all of the expanding tools 1 at one time and is moved by an oil cylinder (not shown).
[0008] The tube 2, through which a coolant flows in use, is made of an aluminum alloy (A3003-0) and the thickness thereof is 0.4 mm. A taper shape portion 2a, the inner width thereof being slightly (about 0.02 mm) larger than the maximum width of the finishing expanding part 3, is formed at the end of the tube 2.
[0009] Numeral 5 shows a plate fin made from an aluminum plate (A1050-H24) the thickness of which is 0.1 mm. The plate fin 5 has a plurality of holes provided therein for receiving tubes 2. Before the expanding of the tube 2, there is about a 0.1-0.15 mm gap between the outer surface of the tube 2 and the inner surface of the corresponding hole.
[0010] Numerals 6 and 7 show an upper header plate and a lower header plate, respectively. Those plates 6 and 7 are made of an aluminum alloy (A5052-0) and the thickness thereof is 1.2 mm. Both plates 6 and 7 have a plurality of holes for the tubes 2 therein, and the opening area thereof is slightly larger than that of the respective holes of the plate fin 5.
[0011] Numeral 8 shows a stopper plate having a guide groove 8a to which the upper header plate 6 fits and a plurality of holes 8b the inner width thereof is as long as that of the taper shape portion 2a of the tube 2. Numeral 10 shows a holding plate 10 supporting the lower header plate. The holder plate 10 has a plurality of holes 10a the inner width of which is slightly larger than the maximum width of the finishing expanding part 3. And the holes can support the preliminary expanding part 4. Numeral 11 shows a holder having a plurality of holding grooves lla (which is the same as the number of expanding tools 1) the inner width of which is slightly larger than the maximum width of the finishing part 3 and the depth thereof is as long as the height of the finishing expanding expanding part 3. Therefore, the holder 11 can hold the finishing expanding part 3 and also can make the expanding tools 1 be in order. Numeral 12 shows core-side holders located on both sides of a core 13 of a heat exchanger and between the upper and the lower header plates 6 and 7. The core-side holders 12 hold the core 13 of the heat exchanger in order to prevent the reduction of the core 13 even when the tubes 2 are reduced in their axial length by the progress of the expanding tool 1.
[0012] The heat exchanger is made up by the following process:
As first, a predetermined number of the tubes 2 is arranged in such manner that the taper shape portion 2a locates down side. Then the upper header plate 6, the predetermined numbers of plate fins and the lower header plate 7 are provided along the tubes 2 one after another so as to make the core 13 of the-heat exchanger as such process that the tube 2 is inserted into the hole of the upper header plate 6, the fins 5 and the lower header plate 7. After contracting the core 12 provisionally, the core 12 is turned upside down, as shown in Figure 2.
[0013] The expanding tools 1 end the same numbers of the tubes 2, which are arranged such that the guide lc locates upside, are held by the holder plate 10 and the holder 11.
[0014] The core 12 is moved toward the expanding tools 1 so as to insert the grid lc into the end of the tube 2 opposite side of the taper shape portion 2a. Then, the core is fixed by the core-side holder 12 in order to set up the height of the core, in other words, the distance between the upper and the lower header plate 6 and 7. After that, the upper surface of the upper header plate is fixed by the stopper plate 8, as shown in Figure 3. Then the clamp 9 clamps the holding groove ld of the expanding tools 1, as shown in Figure 4. Then the clamp 9 is moved upward so as to pull out the expanding tools 1 from the tubes 2, as shown in Figure 5. According to the upward progress of each expanding tool 1, the preliminary expanding part 4 moves through along the axis of the tube 2 and expands the inner width of the tube as large as the width thereof. Since the distance between the preliminary expanding part 4 and the finishing expanding part 3 is longer than the length of the tube 2, the finishing expanding part 3 enters the tube 2 after the preliminary expanding part 4 out of the tube 2, namely after expanding by the preliminary expanding part 4 has been completed.
[0016] Pl + P2 > PO wherein Pl is the needed load for the movement of the preliminary expanding part 4, P2 is the needed load for the movement of the finishing expanding part 3 after the preliminary expanding part 4 has expanded the tube 2 by its increment. P0 is the needed load for an expanding part when the expanding part expands the tube as wide as the width of the finishing part 3 in only one step. Therefore, if both the preliminary and the finishing expanding parts 4 and 3 move in the tube 2 at the same time, the expanding tool 1 needs more power for its movement than the power that is needed for the movement when only one expanding part at a time is in the tube.
[0017] However, the expanding tool 1 of this embodiment does not pull both the finishing and preliminary expanding parts 3 and 4 at the same time. Therefore, the expanding tool 1 can be pulled by small power.
[0018] During the expanding process, the tube 2 is forced upwardly because of friction between the tube 2 and the expanding parts 3 and 4. The tube 2, however, is not pulled out from the core 13 by the friction, since the taper shapcd portion 2a of the tube 2 is held by the stopper plate 8.
[0019] Though the expanding tool 1 of the above embodiment has two expanding parts 3 and 4, it is, however, clear that the expanding tool 1 of this invention can have a greater plurality of expanding parts, as shown in Figure 10. The inner widths of the expanding parts 41-4n become wider step by step, and the distance between each adjacent two expanding parts is longer than the length-of the tube 2.
inserting a stem of an expanding tool into one end of said tube;
urging said stem of said expanding tool axially along said tube; and
while conducting said urging step, causing a preliminary expanding part of said expanding tool provided on said stem to expand the internal width of said tube, then causing at least one next expanding part of said expanding tool provided on said stem to further expand said internal width of said tube after said preliminary expanding part has expanded said internal width of said tube and emerged therefrom.
a stem, the transverse cross-sectional area of which is smaller than the internal transverse cross-sectional area of the tube which is to be expanded and the length of which is longer than said tube;
a plurality of expanding parts provided on said stem, the transverse cross-sectional shape of each of which is similar to the internal transverse cross-sectional shape of said tube and the transverse cross-sectional area of which is slightly larger than the initial transverse cross-sectional area of said tube;
the transverse cross-sectional area of each one of said expanding parts being slightly larger than that of each respectively leading on of said expanding parts; and
the distance between each adjacent two of said expanding parts being longer than the length of said tube.