Väkiparta, Tapio (Lähdekuja 2, Pori, FIN-28300, FI)
| 1. | A method for manufacturing ovalshaped metal tubes, where an essentially roundshaped metal tube is rolled both in the sideways direction and in the vertical direction of the tube, characterized in that the metal tube (11) is rolled at least in two steps (2,4), and that between said rolling steps (2,4), the metal tube is rolled at least once in a direction that is perpendicular to the rolling direction of the rolling steps (2,4). |
| 2. | A method according to claim 1, characterized in that in the rolling, the total degree of deformation of the metal tube (11) is essentially 35%. |
| 3. | A method according to claim 1 or 2, characterized in that the metal tube (11) is fed by means of at least two guiding feed rollers (10) into roughing (2). |
| 4. | A method according to claim 3, characterized in that the employed feed rollers (10) are rollers where the surface (17) that gets into contact with the metal tube conforms to the shape of the metal tube. |
| 5. | A method according to claim 3, characterized in that in the roughing step (2), the metal tube is rolled down by at least two roughing rollers (12), so that the degree of deformation of the metal tube is essentially 0.52%. |
| 6. | A method according to claim 5, characterized in that the employed roughing rollers (12) are rollers that are biradial on the surface (18) that gets into contact with the metal tube (11), in which case there are distinguished the radii R1 and R2 in the roughing roller. |
| 7. | A method according to claim 36, characterized in that after roughing (2), the metal tube (11) is rolled down in a direction perpendicular to the roughing direction at least by two side rollers (13), essentially to 18% of the width of the metal tube obtained from roughing. |
| 8. | A method according tOo claim 7, characterized in that the employed side rollers (13) are rollers that on the surface (19) that gets into contact with the metal tube (11) are straight. |
| 9. | A method according to any of the preceding claims, characterized in that the metal tube (11) is in the finishing rolling (4) rolled into an oval shape by at least two finishing rollers (14), so that the degree of deformation of the metal tube is essentially 23.5%. |
| 10. | A method according to claim 9, characterized in that on the surface (20) that gets into contact with the metal tube (11), the shape of the finishing rollers (14) corresponds to the shape of an oval. |
| 11. | A method according to any of the preceding claims, characterized in that the metal tube (11) is straightened at least in two mutually perpendicular directions by means of at least two straightening rollers (15,16). |
| 12. | A method according to claim 11, characterized in that the employed straightening rollers (15) are two rollers that are essentially vgrooved on the surface (21) that gets into contact with the metal tube (11), as well as six straightening rollers (16) that are arranged in a direction perpendicular to the straightening rollers (15) and have essentially monoradial surfaces (22). |
| 13. | A method according to claim 5,6, 9 or 10, characterized in that at least the roughing rollers (12) and the finishing rollers (14) are adjusted both in the radial and in the axial direction. |
| 14. | A method according to claim 13, characterized in that in the radial direction, the adjusting is realized by adjusting the mutual distance of the rollers by a separate adjusting mechanism (28). |
| 15. | A method according to claim 13, characterized in that in the axial direction the adjusting is realized by means of an adjustable locking plate (31) and a ring (32) made of a pneumatic material, both provided in connection with the roller. |
| 16. | A method according to claim 7 or 8, characterized in that at least the side rollers (13) are adjusted both by shape adjustment (36) and by straightening adjustment (35). |
| 17. | An apparatus for manufacturing ovalshaped metal tubes, said apparatus including, for rolling essentially roundshaped metal tube, rollers both in the sideways direction of the tube and in the vertical direction thereof, characterized in that the apparatus comprises at least two sets of rollers (12, 14) arranged on both sides of the metal tube, and at least one set of rollers (13) arranged on both sides of the metal tube (11), in a direction that is perpendicular to the rolling direction defined by the former set of rollers. |
Oval-shaped tubes are used for example in gas heaters, where the advantage is that the outer surface area of the tube is increased in comparison with the quantity of liquid contained in the tube, as well as a more advantageous circulation for the gas flame in between the tubes than when using round tubes. In the prior art oval-shaped metal tubes are manufactured so that a sheet is worked into a U-shaped profile, which is then closed into a tube by welding at the seam located on the side of the profile. An oval-shaped tube can also be manufactured by drawing the tube through an oval-shaped ring and by utilizing mold technique. When manufacturing an oval tube by rolling of a round tube, it is possible that on the side of the tube, at the seam of the top and bottom roll, there is left a mark along the whole length of the tube, which mark is harmful both in appearance and because of the properties required of the tube. In addition, the shorter radius of the oval tube may in some cases remain inadequate.
From the patent publication JP 9239438, there is known a method for manufacturing oval tubes of round tube by using the rolling technique. By means of the invention, a round tube is rolled into an oval-shaped tube so that the tube is rolled by a top and bottom roll as well as by two rolls located on both sides of the tube. However, the rolling power demand for the side rollers according to said method is too high for achieving the measures required of an oval tube.
The object of the present invention is to avoid drawbacks of the prior art and to introduce a novel solution for manufacturing an oval tube made of metal.
The invention is characterized by what is set forth in the characterizing parts of the independent claims. Other embodiments of the invention are characterized by what is set forth in the rest of the claims.
Remarkable advantages are achieved by using the method and apparatus according to the invention. The manufacturing of an oval tube can be carried out by rolling in a cost-effective way, and a high-quality product is obtained by following the method of the invention. According to the invention, oval-shaped metal tubes are manufactured by rolling an essentially round-shaped metal tube both in the transversal and lengthwise directions of the tube, which means that the metal tube is rolled at least in two steps, and in between said rolling steps, the metal tube is rolled at least once in a direction that is transversal to the rolling direction of said rolling steps.
Advantageously the total degree of deformation the metal tube is essentially 3-5%, which refers to the difference in meter weight (= weight/meter) between the initial tube and the ready-made oval tube. According to the invention, metal tube is fed into roughing by means of at least two feed rollers guiding the metal tube. The employed feed rollers are rollers which, on that surface that gets into contact with the metal tube, have the same shape as the metal tube to be rolled. By rolling the metal tube down in the roughing step by at least two roughing rollers, so that the degree of deformation of the tube is essentially 0.5-2%, the final measures are preferably affected. Advantageously the roughing rollers are biradial on that surface that gets into contact with the metal tube, in which case the formation of the smaller radius in the finishing rollers can preferably be enhanced. By rolling the metal tube down in a direction that is perpendicular to the roughing direction by using at least two side rollers, advantageously by 1-8% of the width of the metal tube obtained from roughing, the seam joint of the top and bottom rollers from the preceding roughing step is prevented from leaving a mark in the tube. The employed side rollers are rollers that are straight on the surface that gets into contact with the metal tube. In addition, the side rollers are used for adjusting the tube straightness in the direction of the larger diameter of the oval tube, and also the shape of the shorter radius of the oval tube is affected. In finishing, the metal tube is rolled into an oval shape at least by two finishing rollers, so that the degree of deformation of the tube is essentially 2- 3.5%. The shape of the finishing rollers essentially corresponds to the oval shape at the surface that gets into contact with the metal tube. According to a preferred
embodiment of the invention, the metal tube is straightened at least in two directions that are mutually perpendicular by means of at least two straightening rollers. This affects the straightness of the final oval tube. According to a preferred embodiment of the invention, the employed straightening rollers are two rollers that are essentially v- grooved on the surface that gets into contact with the metal tube, as well as six latter straightening rollers that are essentially monoradial in surfaces and perpendicular to the former straightening rollers. According to a preferred embodiment of the invention, at least the roughing rollers and the finishing rollers are adjusted both in the radial and axial directions. According to a preferred embodiment of the invention, the radial adjusting is realized by adjusting the mutual difference of the rollers by using a separate adjusting mechanism. In the axial direction, the adjusting is realized by means of an adjustable locking plate and a ring made of a pneumatic material, both arranged in connection with the roller. At least the side rollers are adjusted both by shape and straightening adjustments. By means of the adjusting mechanisms connected to the rollers, the measures of the oval tube are affected, and by means of said mechanisms, it also is possible to perform the adjusting operations for oval tubes of various sizes in a fast and precise fashion. The method according to the invention for manufacturing metallic oval tubes is realized by an apparatus that includes rollers for rolling an essentially round-shaped metal tube both in the sideways direction and in the vertical direction, which apparatus comprises at least two sets of rollers arranged on both sides of the metal tube, as well as another set of rollers arranged on both sides of the metal tube in a direction that is perpendicular to the rolling direction defined by the first two sets of rollers.
The invention is described in more detail below with reference to the appended drawings.
Figure 1 a A rolling apparatus according to the invention Figure 1 b Rolling apparatus rollers Figure 2 Adjusting mechanism of the rollers Figure 3 Adjusting mechanism of the side rollers
Figures 1 a and 1 b illustrate an apparatus according to the invention for manufacturing oval tube. Figure 1b shows the rollers illustrated in figure 1a in a cross-section seen from the direction of the arrow 23. A metal tube that is roundish in cross-section and is made of either hard or soft metal, for instance a copper tube, is fed in the rolling apparatus 9 through the feeding step 1, so that the two feed rollers 10 conforming to the shape of the metal tube 11 keep the metal tube in a given line for the rolling operation. The feed rollers may be located either above or underneath the metal tube, or at the sides thereof, and on their surface 17 that gets into contact with the metal tube, they have the same shape as the metal tube. The feed rollers 10 feed the metal tube 11 into roughing 2, where the round metal tube is flattened by two roughing rollers 12, so that the final measures of the tube are affected. The roughing rollers 12 are located both above and underneath the tube, and are biradial on the surface 18 that gets into contact with the metal tube, i. e. there are distinguished the radii R1 and R2. In the roughing step 2, the degree of deformation of the metal tube 11 is 0.5- 2%. This refers to the difference in weight per one meter between the original tube 8 and the worked metal tube. The thickness of the tube wall remains essentially the same throughout the whole roughing process, but the wall circumference is decreased.
After roughing 2, the metal tube 11 is transferred in the line to the next rolling step 3, in which the tube is rolled down in a direction perpendicular to the roughing direction by two side rollers 13 for essentially 1-8% of the metal tube width after roughing 2.
On the surfaces 19 that are in contact with the metal tube 11, the side rollers 13 are straight. The use of the side rollers ensures that the quality requirements for the shorter radius of the oval tube are fulfilled in the final rolling, and in the roughing step it prevents the seam joint of the top and bottom rollers from leaving a mark in the metal tube. The side rollers 13 also are used for adjusting the oval tube straightness in the direction of the larger diameter. In the next finishing step 4, the metal tube is rolled by two finishing rollers 14 located above and underneath the metal tube 11, so that the metal tube obtains an oval shape, in which case the degree of deformation of the metal tube is 2-3.5%. On the surface 20 that gets into contact with the metal tube, the shape of the finishing rollers 14 corresponds to the shape of an oval.
After the finishing step 4, the metal tube is transferred to the straightening units 5 and 6, where the metal tube 11 is straightened at least from two directions that are perpendicular to each other by means of straightening rollers 15,16. The straightening rollers guide and straighten the tube. The employed straightening rollers 15 are two rollers arranged on both sides of the metal tube, said rollers being essentially v-grooved on the surface 21 that gets into contact with the metal tube 11. as well as six latter straightening rollers 16 that are essentially monoradial on the surfaces 22. After the straightening units 5 and 6, there is obtained the end product, i. e. the oval tube 7.
Figure 2 illustrates how the roughing rollers 12 and the finishing rollers 14 are adjusted both in the radial and in the axial direction. The radial adjusting is realized by a rocking lever mechanism 25, which means that the housing element 26 belonging thereto is provided by a slot 27 that enables the moving of the housing element. By means of an adjusting mechanism 28 installed in connection with the housing element, the mutual distance of the rollers is adjusted in the vertical direction. The adjusting mechanism 28 comprises a wedge 29, a wedge transfer screw 37 and a locking screw 30. When the screws should be shifted nearer to each other, the locking screw 30 is opened, and the wedge 29 is shifted forward by the wedge transfer screw 29, whereafter the locking screw 30 is tightened. A given distance in the movement of the adjusting mechanism 28 corresponds to a given distance in the vertical movement of the rollers 14. Typically the adjusting demand is 0-0.2 millimeters, which means that the difference in the parallelism of the roller axes does not disturb the process. In the horizontal direction, the rollers 14 are moved by the axial adjustment. The axial adjustment is realized by an adjustable locking plate 31 and a ring 32 made of a pneumatic material, such as rubber, arranged in connection with the roller 14, and by moving said plate and ring, the roller grooves 33 are in the axial direction adjusted to match.
Figure 3 illustrates the adjusting of the side rollers 13. The side rollers 13 are adjusted both by shape adjustment 36 and by straightening adjustment 35. The shape adjustment of the side rollers means that the mutual positions of the side rollers can
be adjusted, and thus the tube can be worked when necessary. In the straightening adjustment 35, the side rollers are shifted together in the horizontal direction.
For a man skilled in the art, it is obvious that the various preferred embodiments of the invention are not restricted to the above described examples only, but may vary within the scope of the appended claims.
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