GB1593656A - Methods for the manufacture of heat exchangers - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO METHODS FOR THE MANUFACTURE OF HEAT EXCHANGERS (71) We, SOCIETE ANONYME DES USINES CHAUSSON, a company duly organized under the laws of France, of 35, rue Malakoff, 92 ASNIERES, France, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a method for the manufacture of a heat exchanger core which comprises tubes inserted through fins.

According to the present invention, there is provided a method for the manufacture of a heat exchanger core which comprises tubes inserted through fins, the tubes each being made by rolling a strip into substantially tubular form, the edges of the strip being brought close together and connected to one another by electric welding, which forms an outer longitudinal bead and an inner longitudinal bead along the welded edges, the tubes so formed then being engaged in apertures in the fins and into tube passages of tube end plates, a radial pressure being then exerted inside each tube on a major portion at least thereof to expand the tube by a plastic deformation to cause each tube positively to engage with the fins and end plates.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a diagrammatic cross-sectional elevation of a radiator core and of part of an apparatus for use in the manufacture of the core, Figure 2 is a diagrammatic, partly exploded, perspective view illustrating different operations for the manufacture of a tube in the radiator core of Figure 1, Figure 3 is an elevation of one form of a tool of the apparatus and shows how the tool is used to expand a tube mouth, Figure 4 is anelevation similar to Figure 3 but rotated by 90 , Figure 5 is a diagrammatic elevation, partly in section, illustrating a particular feature of the apparatus; Figure 6 is a view similar to Figure 5, showing a possible variation in the particular feature illustrated in that Figure, Figure 7 is an enlarged lateral elevation of another form of the tool shown in Figure 3 and 4, Figure 8 is an end elevation seen according to the line VIII-VIII in figure 7, and Figure 9 is a cross-sectional elevation similar to Figure 4 and shows yet another form of the tool.

Referring to the drawings, Figure 1 diagrammatically shows a core of a cooling radiator, which core is constituted by tubes 1 engaged in perforated apertures 2a of cooling fins 2. The tubes 1 are also engaged in tube passages 3a of tube end plates 3 and 31, respectively.

the tubes 1 are tubes with a circular crosssection of the type called electro-welded tubes, i.e. tubes which, as illustrated in Figure 2, are made by progressive rollin up of a strip forming a preliminary tubular shape 4, bringing together edges 5, Sa of the strip so rolled, the holding the edges 5, Sa close together or even tlght against one another and passing a welding element constituted, in the example shown, by a coil 6 supplied with a high frequency current which heats the edges 5, Sa; rollers (not shown) then ensure the forging and thus the welding of the edges 5, Sa.

The type of tube 1 so constructed is formed at the moment the edges 5, 5a are welded, with an outer longitudinal bead 7 and an inner longitudinal bead 8 right along the welded edges.

In order that the outer wall of the tube is made smooth and accurately dimensioned the outer bead 7 is removed with a cutting tool 7a (Figure 2) which is normally provided on the machine forming and welding tube.

Taking into consideration the small diameter of the tubes used in heat exchangers, particularly cooling radiators, the diameter of each tube being of about 5 mm, it is not possible to remove the inner bead 8 on the machine manufacturing the tube.

The tubes 1 manufactured as above explained are, after they have been positioned in the fins 2 and end plates 3, 31, submitted to a physical expansion operation performed by expansion tools 9 mounted at the ends of push rods 10 protruding from a plate 11 which can be moved in the direction of the arrow fi so that the tools 9 will be progressively inserted into the tubes 1 to produce a radial pressure which causes their expansion by plastic deformation which occurs when the resilient limit of the metal constituting the tubes is exceeded. These tubes are then permanently distorted while they are strongly pressed against the walls of the apertures 2a of the fins and against the walls of the tube passages 3a in the end plates 3 and 31, respectively. This obviates the need for welding of the tubes to the fins and end plates.

To prevent any motion of each tube 1 during insertion of the tools 9, the end la of each tube 1 is for example held to rest in the base of a respective recess 12, the recesses 12 being provided in a bearing plate 13. The tools 9 are inserted into the tubes 1 for example for at least half of their length and then they are removed. The radiator core is then rotated by 1800, and the tools 9 are re-inserted into the tubes 1, but from their other ends la. Other working methods can be envisaged.

To take into account the existence of the inner bead 8, the tools 9 carried by the rods 10 are each constituted for example as illustrated in Figure 3 and 4. As shown, the expansion tool comprises a core 14, for example of circular cross-section, but whose diameter is substantially smaller than that of the duct formed by each tube 1 in such a way that the core 14 can freely enter inside the tube whatever size the bead 8 may be.

The core 14 is connected to a corresponding push rod 10 which delimits, in the embodiment shown in Figure 3 and 4, a shoulder 15 at its lower end.

The core 14 is used as a support and a guide for a sheath 16 whose lower portion 16a is of a circular cross-section but is bevelled as illustrated at 17 in such a way that the lowest end of the portion 1 6a is reduced to a rounded line or rib 161. The diameter of the portion 16a is slightly smaller than the inner diameter of the tube 1, for example from 1 to 3/10th millimeters, in order that the portion 16a can freely enter the tube 1 when moved in the direction of the arrow fi. The portion 16a extends from the rib 161 beyond the end of the bevelled portion which, preferably, forms two helical ramps 171, 172.

The sheath forms a second portion 16b which is bulbous and whose maximum diameter corresponds to the internal diameter to which each tube has to be expanded.

The second portion 1 6b has an axial groove 18 whose depth is at least equal to the thickness of the bead 8, and the groove 18 extends down as far as the top of the bevelled portion 17 and over the whole length of the portion 16b.

The sheath 16 is preferably fixed onto the core 14 which is inserted in the rod 10 so that the sheath 16 will bear against the shoulder 15. In order that the core 14 and the sheath 16 be axially connected to the rod 10 while being able to rotate relatively to the rod 10, there is provided a retaining ring or any other equivalent means 19. It is important that the unit formed by the core 14 and the sheath 16 can freely rotate.

As illustrated in the drawings and particularly in Figures 3,4 and 5, when the plate 11 is moved in the direction of the arrowfi, the tools 9 are progressively brought to the level of the upper mouth of each tube 1 and, consequently, it is the rounded rim 161 of the sheath 16 which first enters the corresponding tube 1. If this end rim 161 meets the bead 8, it is deviated and turned by the bead 8 which thus comes progressively into abutment with one of the ramps 171 or 172 of the bevelled portion 17. It results therefrom that the sheath 16 and the core 14 are progressively rotated up to the moment when the groove 18 is aligned with the bead 8. The motion according to arrowfi continuing, the bead 8 is used as a guide for the sheath 16 which cannot rotate any longer and whose portion 16b causes the progressive expansion by plastic deformation of the tube 1.

The above disclosure shows that the initial angular position of the bead 8 with respect to the linear end 161 of the sheath has no detrimental influence. Actually there is no difference whether the bead will initially come into abutment with a part of the ramp 171 or 172 or whether the rim will directly enter the groove 18 without having ever been in contact with the ramps.

From the above, it can be seen that no particular care need be taken at the moment of positioning the tubes 1 into the fins 2 and possibly into the end plates 3, 31.

Fig. 6 shows a slight variation according to which the expansion tools 9, having the basic form as above described, are fixedly mounted at the end of the push rods 10, i.e.

without having the possibility to rotate with respect to the rods. In this case, the rods themselves are able to rotate with respect to the plate 11 and, for this purpose, housings 20 are for example provided in the plate 11, the housings 20 containing a ball 21 or other low friction abutment element provided to transmit the push of the plate 11 to the rods 10. A retaining component, for example a ring 22, is provided in order that each rod 10 will be held in the plate 11.

Figure 7 and 8 illustrate a variation of an embodiment of the sheath 16 mounted on the core 14. According to this variation, the sheath 16 is provided at its periphery with ribs 23 with a circular generatrix, these ribs forming grooves 181, 182 . . 18n therebetween.

Figure 7 shows that the above mentioned ribs and grooves extend over the whole length of a portion 16b of the sheath and are then extended along the periphery of a portion 16a with is shaped as a truncated cone.

Also, the ribs 23 are progressively made thinner to form a linear edge or rib 24 at their ends.

In this case, upon the motion in the direction of the arrow fi which is given to each expansion tool, the inner bead 8 of a tube 1 is automatically guided into one of the grooves 181, 182 or 1 8n, the bead 8 causing the sheath to rotate as above explained or causing both the sheath and the rod carrying it to rotate.

Fig. 9 shows another variation in which the same reference numbers designate the same parts as in Figures 3 and 4. As illustrated, a section 16c called a guiding section and having a circular cross-section is provided between the portions 16a and 16b. The portion 16a is bevelled to form the same ramps 17 as in Figs. 3 and 4, and these ramps lead as previously to the groove 18 which also extends in the guiding section 1 6c in forming a slot. The radius of the guiding section 16c is the same as that of the portion 16a, that is just a very little smaller than the inner diameter of the tube 1, or even equal to this diameter before expansion of the tube.

The upper portion of the groove 18 is closed by a cutting edge 25 which extends transversely to the groove 18 substantially at the level of the intersection of the guiding section 16a and of the bulbous portion 16b.

The cutting portion 25a of the cutting edge 25 is aligned with the periphery of the guiding section 16a.

When the cutting tool as above described is introduced into the tube 1, the inner bead 8 engages one of the ramps of the bevelled portion 17, which causes the expansion tool to rotate in either direction to bring the tool into an angular position at which the bead 8 of the tube 1 always enters the groove 18.

When the guiding section 16c enters the tube 1, it bears on the inner wall of this tube by its whole periphery which ensures a perfect centering of the tool inside the tube before the cutting device 25a of the cutting edge 25 reaches the bead 8. Then the cutting device 25 cuts off the bead 8 to level the corresponding portion, the tool continuing to be suitably centered by the guiding section 16c. The portion 16b produces its expanding effect on the smoothed-off portion of the tube, which means on the whole inner periphery, thus the expansion is then carried out exactly as it is done for a tube which has been obtained by a drawing out technique.

It is advantageous, as shown in Figure 9, that the core 14 be foreshortened to extend only as far as 14a, i.e. at the level of the cutting edge 25. Thus the portion 16a is hollow which enables the chips and swarf coming from the cutting of the bead 8 to fall inside the tube 1 as the tool advances without the chips etc. fouling the tool.

It will be appreciated that the core 14 and the sheath 16 can be constituted by only a single art.

twi will be further appreciated that, with the present method, it becomes possible to manufacture heat exchangers while using tubes of a cheaper construction, especially electrically-welded tubes which up to now could not be used in conjunction with expansion of the tube mouths as described because of the presence of the longitudinal beading.

The present method and apparatus is also described in co-pending Application No.

8018925 (Serial No. 15937),to which reference is accordingly directed.

WHAT WE CLAIM IS: 1. A method for the manufacture of a heat exchanger core which comprises tubes inserted through fins, the tubes each being made by rolling a strip into substantially tubular form, the edges of the strip being brought close together and connected to one another by electric welding, which forms an outer longitudinal bead and an inner longitudinal bead along the welded edges, the tubes so formed then being engaged in apertures in the fins and into tube passages of tube end plates, a radial pressure being then exerted inside each tube on a major portion at least thereof to expand the tube by a plastic deformation to cause each tube positively to engage with the fins and end plates.

2. A method as claimed in claim 1, wherein said inner longitudinal beads are cut-off the walls of the tubes just prior to exerting said radial pressure inside the tubes.

3. A method as claimed in claim 2, wherein, in order to cut-off said inner longitudinal beads, the position of said bead within each tube is detected, a cutting device

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   ribs 23 with a circular generatrix, these ribs forming grooves 181, 182 . . 18n therebetween.

   Figure 7 shows that the above mentioned ribs and grooves extend over the whole length of a portion 16b of the sheath and are then extended along the periphery of a portion 16a with is shaped as a truncated cone.

   Also, the ribs 23 are progressively made thinner to form a linear edge or rib 24 at their ends.

   In this case, upon the motion in the direction of the arrow fi which is given to each expansion tool, the inner bead 8 of a tube 1 is automatically guided into one of the grooves 181, 182 or 1 8n, the bead 8 causing the sheath to rotate as above explained or causing both the sheath and the rod carrying it to rotate.

   Fig. 9 shows another variation in which the same reference numbers designate the same parts as in Figures 3 and 4. As illustrated, a section 16c called a guiding section and having a circular cross-section is provided between the portions 16a and 16b. The portion 16a is bevelled to form the same ramps 17 as in Figs. 3 and 4, and these ramps lead as previously to the groove 18 which also extends in the guiding section 1 6c in forming a slot. The radius of the guiding section 16c is the same as that of the portion 16a, that is just a very little smaller than the inner diameter of the tube 1, or even equal to this diameter before expansion of the tube.

   The upper portion of the groove 18 is closed by a cutting edge 25 which extends transversely to the groove 18 substantially at the level of the intersection of the guiding section 16a and of the bulbous portion 16b.

   The cutting portion 25a of the cutting edge 25 is aligned with the periphery of the guiding section 16a.

   When the cutting tool as above described is introduced into the tube 1, the inner bead 8 engages one of the ramps of the bevelled portion 17, which causes the expansion tool to rotate in either direction to bring the tool into an angular position at which the bead 8 of the tube 1 always enters the groove 18.

   When the guiding section 16c enters the tube 1, it bears on the inner wall of this tube by its whole periphery which ensures a perfect centering of the tool inside the tube before the cutting device 25a of the cutting edge 25 reaches the bead 8. Then the cutting device 25 cuts off the bead 8 to level the corresponding portion, the tool continuing to be suitably centered by the guiding section 16c. The portion 16b produces its expanding effect on the smoothed-off portion of the tube, which means on the whole inner periphery, thus the expansion is then carried out exactly as it is done for a tube which has been obtained by a drawing out technique.

   It is advantageous, as shown in Figure 9, that the core 14 be foreshortened to extend only as far as 14a, i.e. at the level of the cutting edge 25. Thus the portion 16a is hollow which enables the chips and swarf coming from the cutting of the bead 8 to fall inside the tube 1 as the tool advances without the chips etc. fouling the tool.

   It will be appreciated that the core 14 and the sheath 16 can be constituted by only a single art.

   twi will be further appreciated that, with the present method, it becomes possible to manufacture heat exchangers while using tubes of a cheaper construction, especially electrically-welded tubes which up to now could not be used in conjunction with expansion of the tube mouths as described because of the presence of the longitudinal beading.

   The present method and apparatus is also described in co-pending Application No.

   8018925 (Serial No. 15937),to which reference is accordingly directed.

   WHAT WE CLAIM IS: 1. A method for the manufacture of a heat exchanger core which comprises tubes inserted through fins, the tubes each being made by rolling a strip into substantially tubular form, the edges of the strip being brought close together and connected to one another by electric welding, which forms an outer longitudinal bead and an inner longitudinal bead along the welded edges, the tubes so formed then being engaged in apertures in the fins and into tube passages of tube end plates, a radial pressure being then exerted inside each tube on a major portion at least thereof to expand the tube by a plastic deformation to cause each tube positively to engage with the fins and end plates.
2. 2. A method as claimed in claim 1, wherein said inner longitudinal beads are cut-off the walls of the tubes just prior to exerting said radial pressure inside the tubes.
3. 3. A method as claimed in claim 2, wherein, in order to cut-off said inner longitudinal beads, the position of said bead within each tube is detected, a cutting device

   for cutting the bead is aligned with the bead and said cutting device is moved along inside the tube to cut the bead off, whereafter said radial pressure is exerted.
4. 4. A method as claimed in any one of the preceding claims, wherein the outer longitudinal bead of each tube is cut-off the tube before the tubes are engaged into the apertures in the fins and into the tube passages.
5. 5. A method for the manufacture of a heat exchanger core which comprises tubes inserted through fins, substantially as hereinbefore described with reference to any one of the embodiments shown in the accompanying drawings.