Apparatus and method for preforming metal strip for manufacturing roll formed and welded tubes

Abstract

An apparatus and method for preforming metal strips (40) for manufacturing roll-formed and welded tubes, comprising an embossing tool (20) and a strip edge chamfering tool (30), wherein the embossing tool comprises an embossing roller (1) having a cylindrical surface (2) with a central embossed portion (3, 3'), and the strip edge chamfering tool comprises an edge chamfering roller (31) and an anvil roller (32), the edge chamfering roller (31) comprising a recessed central section (34) and on each side of the central section... Side section (35), wherein the chamfering roller (31) and the anvil roller (32) are configured to receive and pass through the metal strip in a gap (33) formed between the rollers, wherein the gap (33) has a reduced height in the side section, the side section being located where the longitudinal side edge of the metal strip will pass, such that the longitudinal side edge on each side of the metal strip and on the embossed side of the metal strip becomes chamfered as it passes between the pair of rollers (31, 32).

Description

Technical Field

[0001] This disclosure relates to an apparatus for preforming metal strips for manufacturing roll-formed and welded tubes, and a method for preforming metal strips. Background Technology

[0002] Welded tubing and pipes are typically manufactured by longitudinally forming a flat strip of metal into a nearly complete tube and then welding the two edges together. Roll-formed tubing is used in numerous application areas, such as the HVAC&R market (heating, ventilation, air conditioning, and refrigeration). Within this technological field, environmental demands are driving the development of air conditioning and refrigeration appliances with increased efficiency. In response, efforts have been made to supply small-diameter tubes with a wide range of internal surface reinforcements, which increase their heat transfer coefficient compared to standard smooth solutions. Manufacturing methods for advanced products, such as small-diameter welded tubes with internal surface patterns for heat exchange applications, must produce products with minimal internal irregularities to achieve optimal flow properties and heat transfer. With increasing demand for cost reduction, there has been interest in providing alternatives to copper tubing, which has traditionally dominated air conditioning and refrigeration appliances, in the form of aluminum fittings. Therefore, it is desirable to find ways to manufacture aluminum tubing with properties that are competitive for applications such as those in the HVAC&R field. Summary of the Invention

[0003] This disclosure relates to an apparatus for preforming metal strips for manufacturing rolled and welded tubes, comprising an embossing tool and a strip edge chamfering tool. The embossing tool includes an embossing roller having a cylindrical surface with an embossed central portion. The strip edge chamfering tool includes an edge chamfering roller and an anvil roller, the edge chamfering roller including a recessed central section and side sections on each side of the central section, the edge chamfering roller and anvil roller being configured to receive and pass the metal strip through a gap formed between the rollers. The gap has a reduced height in the side sections, the side sections being located where the longitudinal side edges of the metal strip will pass, such that the longitudinal side edges on each side of the metal strip, and on the embossed side of the metal strip, become chamfered as they pass between the pair of rollers.

[0004] Preferably, the embossing tool includes the cylindrical surface of the embossing roller, and the surface includes the central embossing portion and side portions arranged on each side of the central portion, the central portion having an embossed pattern, and the side portions having no embossed pattern, and the central section of the strip edge chamfering tool is sized such that the embossed pattern of the metal strip passing through the edge chamfering gap between the pair of rollers is not affected by the rollers. The strip edge chamfering tool (30) is preferably separate from the embossing tool and is arranged downstream of the embossing tool in the travel direction (T) of the strip to be preformed.

[0005] Alternatively, the embossing tool and the strip edge chamfering tool can be integrated to include a combined embossing and edge chamfering roller, wherein the central embossing portion is included in the central section of the edge chamfering gap.

[0006] The first and second rollers are shaped such that the gap includes a central section, which is sized such that the pattern imprinted on the metal strip passing between the pair of rollers is unaffected by the rollers. The gap further includes side sections arranged on each side of the central section, the gap having a reduced height in the side sections. The side sections are located where the longitudinal side edges of the metal strip will pass, such that the longitudinal side edges on each side of the metal strip, on the side of the metal strip facing the imprinting rollers, are chamfered as they pass between the pair of rollers. This minimizes the height of the weld bead in the finished roll-formed and welded tube.

[0007] Advantageously, when the strip edge chamfering tool is arranged downstream of the embossing tool in the travel direction (T) of the strip to be preformed, the embossed pattern on the central portion of the embossing roller preferably includes a plurality of grooves arranged in the cylindrical surface of the central portion, and the cylindrical surface of each side portion is preferably flush with the cylindrical surface of the central portion between the grooves, which further helps to reduce the height of the inner weld seam. The embossing roller may consist of a central embossed pattern roller group and side rollers, wherein the side rollers are arranged on each side of the central embossed pattern roller group, and wherein the central embossed pattern roller group has a cylindrical surface forming the central portion, and the side rollers have cylindrical surfaces forming the side portions. This allows for flexibility in the selection of the embossed pattern. The cylindrical surface of the embossing roller preferably has a total width of 15 mm or more, and the central portion of the embossing roller suitably has a width that is 85-99% of the total width.

[0008] The central section of the gap between the first and second rollers of the strip edge chamfering tool has a width equal to or greater than the width of the central portion of the impression roller, to ensure that the pattern imprinted on the central portion of the strip is not affected by the edge chamfering tool. The first roller of the pair of rollers in the edge chamfering tool is preferably designed to include a recess extending (run) along a circumferential portion of the cylindrical surface of the first roller, the recess having outwardly sloping side edges on each side of the recess. The sloping side edges are suitably inclined at an angle of 30-60°, preferably 43-47°, to provide sufficient edge chamfering.

[0009] The side sections of the gap between the first and second rollers may suitably have a width equal to or greater than half the difference between the total width (W1) of the impression tool and the width (W2) of the central portion of the impression tool for each of the side sections.

[0010] This disclosure further relates to a method for preforming a metal strip, comprising: embossing a pattern in a central portion of the strip along its longitudinal direction, while rolling side portions on each side of the central portion of the strip without embossing the pattern; and chamfering the longitudinal side edges of the strip on the sides of the strip where the embossed pattern is disposed. During chamfering, strip material at the longitudinal side edges of the strip is pressed down by up to 20-60%, preferably 35-40%, of the strip thickness, thereby forming a beveled edge surface along the longitudinal side edges of the strip to minimize the internal weld seam of the finished welded tube. The embossed pattern provided on the strip includes protrusions, and during the embossing step, the side portions of the strip are suitably rolled to a strip thickness substantially flush with the strip thickness between the protrusions of the embossed pattern. Thus, the side portions of the strip will have a smaller thickness relative to the original metal strip thickness, resulting in a smaller internal weld seam in the tube. The chamfering of the opposite edges is preferably carried out in a subsequent step.

[0011] This disclosure will become apparent from the detailed embodiments given below. The detailed embodiments and specific examples disclose preferred embodiments of this disclosure only by way of illustration. Those skilled in the art will understand, based on the guidance in the detailed embodiments, that changes and modifications can be made within the scope of this disclosure. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a preferred preforming equipment; Figure 2 This is an exploded perspective view of an example of an impression roller according to a preferred embodiment of the present disclosure; Figure 3a yes Figure 2A cross-sectional view of the impression roller; Figure 3b yes Figure 3a The cross-sectional view showing the circled details; Figure 3c This is a cross-sectional view showing details of an alternative embodiment; Figure 4 The illustration schematically shows details of the imprinting portion of an impression roller according to an example of this disclosure; Figure 5 The illustration schematically shows details of the imprinting portion of an impression roller according to another example of this disclosure; Figure 6 A partial cross-sectional view of a tube with an internal embossed pattern is shown; Figure 7 The illustration schematically depicts the edge of a strip pre-formed by an impression roller according to the present disclosure.

[0013] Figure 8a A portion of the edge chamfering roller is shown; Figure 8b A portion of an edge chamfering tool is shown, with strips entering the tool; Figures 9a-9c The diagram schematically illustrates the seam section of a roll-formed strip during welding at its longitudinal side edges. Detailed Implementation

[0014] This disclosure relates to an apparatus for preforming metal strips for manufacturing rolled and welded tubes, comprising an embossing tool and a strip edge chamfering tool. The strip edge chamfering tool is preferably arranged downstream of the embossing tool in the direction of travel of the strip to be preformed. However, as an alternative, chamfering of the strip edge prior to embossing is conceivable, or the embossing and edge chamfering operations can be integrated into a single tool comprising a single combined embossing, edge chamfering, and anvil roller. In an apparatus in which the edge chamfering tool is arranged prior to the embossing tool in the direction of travel of the strip, the embossing roller and the edge chamfering roller may include the same features and configurations as described below for an embodiment in which the edge chamfering tool is arranged after the embossing tool in the direction of travel of the strip. In an apparatus comprising a combined embossing and edge beveling tool with a single combined embossing, an edge beveling roller, and an edge beveling tool, embossing and edge beveling are performed simultaneously. This means that the embossed pattern is arranged within a recess in a strip receiving gap, the recess being sized such that the central portion of the strip receives the embossed pattern on its surface, and the longitudinal side edges are beveled. Preferably, an unpatterned portion is provided on each side of the embossed central portion of the strip.

[0015] Regardless of the configuration of the strip preforming apparatus, the intended result is the production of preformed metal strips having an embossed surface pattern on their central portion and chamfered longitudinal side edge portions. This allows for the efficient manufacture of small-diameter tubes by roll forming and welding the preformed strips. In the following description, the apparatus is essentially based on a preferred embodiment in which the embossing tool and the edge chamfering tool are separate tools, each comprising a strip preforming roll and an anvil roll. However, it should be understood that the details described below apply to all such embodiments unless otherwise stated.

[0016] By implementing embossing and edge chamfering in separate subsequent steps, the strip preforming process becomes more flexible and allows for easier control over the properties of the resulting preformed strip. In this embodiment, the embossing tool includes an embossing roller with a cylindrical surface having a central portion and side portions disposed on each side of the central portion, the central portion having an embossed pattern and the side portions having no embossed pattern. The strip edge chamfering tool includes a pair of first and second rollers, wherein the first roller is an edge chamfering roller including a recessed central section and side sections on each side of the central section, and the second roller is an anvil roller. The edge chamfering roller and the anvil roller are configured to receive and pass the metal strip through a gap formed between the rollers. The first and second rollers are shaped such that the gap includes the central section, which is sized such that the embossed pattern of the metal strip passing between the pair of rollers is unaffected by the rollers. The gap further includes side sections disposed on each side of the central section, the gap having a reduced height in the side sections. The side section is located where the longitudinal side edge of the metal strip will pass, such that the longitudinal side edge on each side of the metal strip, on the side of the metal strip facing the impression roller, becomes chamfered as it passes between the pair of rollers. This minimizes the height of the weld seam in the finished roll-formed and welded tube, as will be described in more detail below. Therefore, by means of this apparatus, the metal strip can be pre-formed, thereby facilitating welding and producing a final tube product with improved weld quality.

[0017] The final tube product may suitably be an advanced small-diameter tube product made of aluminum or its alloys, having a diameter of 20 mm or less, preferably 5-10 mm. The tube product is preferably manufactured as a continuous coil with a length exceeding 500 m, preferably exceeding 1000 m. Such tube products find applications, for example, in the fields of heating, ventilation, air conditioning, and refrigeration.

[0018] The roll forming process for welded tubes involves rolling a pre-formed strip into a tubular shape and welding the longitudinal edges of the strip together, thereby obtaining a tube by means of high-frequency welding in an induction-heated welding coil. To achieve this, the strip is fed into a forming machine or apparatus that shapes the strip through different successive forming steps performed by a plurality of forming rolls. As the strip passes through the welding coil, an electromagnetic field is induced around the coil, inducing a current flowing through the strip, primarily concentrated at the edges to be joined. The resistance of the metal to the current at these edges generates the necessary thermal development to rapidly reach the melting point. While the edges are still molten, they are forged together due to interaction with the side extrusion rolls, thus applying force to the strip and therefore generating the desired pressure at the interface of the two edges. Upon passing through the welding rolls, oxidized and molten metal are extruded from the joint and combined with clean underlying metal. After welding, sizing rolls complete the process, giving the tube the desired final geometry.

[0019] The production of advanced tube products, such as small-diameter welded tubes with internal surface patterns, for heat exchange applications from metal strips involves a two-stage process, including a stage of preforming the strip and a stage of rolling the strip into a tubular shape and welding it into the tube.

[0020] In the manufacture of roll-formed and welded tubes from aluminum strips, it is important to mitigate potential problems arising from the properties of aluminum. To achieve the desired heat transfer properties, the tube has an internally embossed surface pattern. Variations in strip width should preferably be kept to a minimum to improve stability during the welding process and the quality of the finished tube product.

[0021] The strip is typically supplied to the preforming stage in the form of a preform strip roll, where it is prepared for use in the next stage of tube forming and welding. The preforming stage involves embossing the strip onto the inner surface of the tube to be formed, obtaining an embossed pattern that will form the internal grooves of the tube. After the preforming stage, the strip can be appropriately stored in rolls until it is rolled and welded into the form of a tube.

[0022] The embossing process performed in the embossing station includes a cold deformation process on a strip to obtain a surface pattern. The embossed pattern on the central portion of the embossing roller preferably comprises multiple elongated grooves of a certain depth arranged at an angle relative to the rotation direction of the embossing roller. The groove depth of the embossing roller pattern is preferably less than 0.35 mm. Various embossing patterns can be applied; for example, spiral patterns improve performance in evaporation applications, and herringbone patterns improve performance in condensation applications.

[0023] The cold roll forming process applies a desired pattern to the surface of a strip by imprinting, wherein a strip blank is fed into a system of coupling rolls (including an imprinting roll and an anvil roll) to apply the necessary forming pressure. The imprinting roll has a cylindrical surface comprising a central portion with an imprinted pattern and side portions arranged on each side of the central portion. The side portions have no imprinted pattern. The central portion of the imprinting roll is provided with a negative image of the desired strip pattern and is pressed onto the strip supported by the anvil roll, thereby cold roll forming and imprinting the strip. Providing an imprinted pattern on the imprinting roll results in the imprinting of a corresponding pattern onto the strip surface, wherein grooves in the imprinting roll pattern correspond to protruding ribs on the strip, such that a pattern of ribs is formed on the strip surface. The rib height corresponds to the maximum groove depth of the imprinting roll pattern.

[0024] The anvil roller can be fixed in a horizontal position, while the impression roller can be adjusted in the vertical direction, thereby changing the gap between the rollers and thus allowing trimming and optimal distribution of forming pressure on the strip.

[0025] The central portion of the impression roller can be composed of a central pattern roller assembly, and the side portions can be composed of side rollers arranged on each side of the central pattern roller assembly. The central pattern roller assembly has a cylindrical surface forming the central portion of the impression roller, and the side rollers have cylindrical surfaces forming the side portions of the impression roller. This provides flexibility regarding the impression pattern. Alternatively, the impression roller can be manufactured as a single piece.

[0026] The central embossing pattern roller assembly can consist of a single embossing pattern disk or two or more embossing pattern disks with or without spacers in between. The embossing pattern disks and optionally included smooth spacers may preferably have beveled edges at their interfaces, such that circumferential channels are formed at the interfaces through these beveled edges. This minimizes localized stress in the material and thus reduces the risk of tool breakage.

[0027] The central impression pattern roller assembly is responsible for pattern formation, and the side rollers are used to provide unpatterned side portions on the strip by pressing the outer portion of the strip, as described below. The two side rollers can be bolted to the central impression ring, which can be clamped to the central shaft and fixed in place within the impression station.

[0028] As mentioned, the side portions of the embossing roller are unpatterned. Therefore, the outer portion of the cold-rolled and embossed strip does not exhibit any embossed pattern, but rather has a smooth surface. By providing these unpatterned side portions along the length of the strip during the preforming stage, the risk of strip edge thickness variations can be minimized, the risk of uneven geometry at the strip edge at weld points can be reduced, and the risk of embossed ribs being welded together, resulting in large internal weld seams, can be avoided. Therefore, providing unpatterned side portions on the embossed strip achieves optimal control over the strip edge geometry (essential for ensuring optimal welding conditions) to improve process stability and post-weld tube quality.

[0029] The cylindrical surface of the impression roller may suitably have a total width of 15 mm or more, with the central portion having a width that is 85-99% of the total width. Strip widths of 15 mm or more are suitable for manufacturing heat exchanger tubes for HVAC&R applications, such as up to 64 mm.

[0030] The width of the unpatterned side portion of the imprinting roller is determined based on considerations related to weldability and the heat transfer performance of the finished tube. A wider unpatterned side portion will be easier to weld, as this will be closer to the standard procedure for smooth strip welding. However, an excessively wide unpatterned side portion may adversely affect the final heat transfer performance, since ideally, a continuous pattern around the inner circumferential portion of the tube would be desired. Therefore, the width of the unpatterned side portion should preferably be as small as possible, while still ensuring that the imprinted ribs are not included in the inner weld seam. It has been found that when the strip has a total width of 15 mm or more, the combined width of two unpatterned strip side portions should preferably be 1-15% of the total strip width.

[0031] The cylindrical surface of the side portion of the impression roller is preferably flush with the cylindrical surface of the central portion between the grooves of the impression roller pattern. This is particularly beneficial in conjunction with the edge chamfering of the strip that occurs in the subsequent preforming steps described below, as this further reduces the height of the inner weld seam in the finished welded tube. Therefore, during the impression stage, the strip in the unpatterned side portion is preferably rolled down to the nominal bottom wall thickness of the strip, i.e., flush with the grooves between the ribs of the imprinted surface pattern. Thus, the side portion remains smooth but is still rolled down to a thickness lower than the original side portion in blank form. This improves the performance of the final tube because the height of the inner weld seam can be reduced, resulting in less disturbance to the hydrodynamics within the final tube. The desired thickness of the unpatterned side portion can be obtained by selecting the outer diameter of the impression roller at the side portion to be the same as the outer diameter of the impression roller at the central portion.

[0032] During high-frequency welding of rolled tubes in induction heating welding coils, a weld seam is typically formed on the inside of the tube. The high-frequency welding process is a true hot forging process, during which molten portions of the tube edges are ejected from the welding areas inside and outside the tube. The internal ejection forms an inner weld seam after solidification. For larger diameter tubes, this weld seam is rarely problematic. However, internally reinforced tubes suitable for HVAC&R applications typically have a suitable small diameter of 20 mm or less, and therefore it is important that the inner weld seam be as small as possible. To ensure a minimum inner weld seam height while maintaining the tube burst pressure at the desired level, the shape of the strip edge of the incoming embossed strip is modified. During cold rolling, the strip edge is chamfered on the side surface that will form the inside of the tube. By adjusting the chamfer angle and length, which define the slope and size of the chamfer, the height of the inner weld seam can be kept low enough to be contained within the depth of the embossed surface pattern.

[0033] As mentioned, according to a preferred embodiment, the strip edge chamfering tool includes a pair of first and second rollers configured to receive and pass the metal strip through a gap formed between the rollers. The first and second rollers are shaped such that the gap includes a central section sized such that the imprinted pattern of the metal strip passing between the rollers is unaffected by the rollers. This ensures that the imprinted pattern remains intact on the strip that has been imprinted before entering the edge chamfering tool. The gap further includes side sections arranged on each side of the central section, the gap having a reduced height in the side sections. The side sections are located where the longitudinal side edges of the metal strip will pass, such that the longitudinal side edges of the metal strip on each side of the strip, on the side of the metal strip facing the imprinting rollers, are chamfered as they pass between the rollers. After the strip is rolled into a nearly finished tube form, the edges of the strip are welded together. Due to the edge chamfering, less material is present at the longitudinal edges of the strip. As described above, this is particularly evident when the unpatterned side portion of the strip has been rolled to be flush with the bottom of the embossed pattern. In this way, the inner weld seam is constructed on the inner surface of the tube starting from the bottom wall thickness height, rather than the higher original strip thickness. Less material is ejected from the weld area, and the chamfered edges create a space to accommodate a portion of the molten material. Thus, the height of the weld seam in the finished rolled and welded tube can be minimized while maintaining the finished product's ability to meet mechanical requirements.

[0034] The rollers of the edge chamfering tool can be designed in various ways. Preferably, the first roller of the pair of rollers in the edge chamfering tool is arranged such that the imprinted side of the strip faces the first roller, and is designed to include a recess extending along a circumferential portion of the cylindrical surface of the first roller, the recess having outwardly inclined side edges on each side of the recess. The inclined side edges are suitably inclined at an angle of 30-60°, preferably 43-47°, to provide sufficient edge chamfering. The side sections of the gap between the first and second rollers can each suitably have a width equal to or greater than half the difference between the total width (W1) of the imprinting tool and the width (W2) of the central portion of the imprinting tool for each of the side sections. Since the gap between the rollers of the edge chamfering tool is sized to have a height exceeding the maximum strip thickness without affecting the imprinted pattern, the outer edge of the strip is chamfered by the inclined side sections of the chamfering rollers, as... Figure 7 The diagram is schematically illustrated in the middle. Figure 7 This illustrates the edge beveling operation in a step following the imprinting step.

[0035] This disclosure further relates to a method for preforming a metal strip, comprising: embossing a pattern in a central portion of the strip along its longitudinal direction, while simultaneously rolling side portions on each side of the central portion of the strip without embossing the pattern; and chamfering the longitudinal side edges of the strip on the sides of the strip where the embossed pattern is provided. As mentioned above, embossing is preferably performed separately before edge chamfering, but may be performed after or simultaneously with edge chamfering if desired. During chamfering, strip material at the longitudinal side edges of the strip is pressed down by up to 20-60%, preferably 35-40%, of the strip thickness, thereby forming a sloping edge surface along the longitudinal side edges of the strip to minimize the internal weld seam of the finished welded tube. The embossed pattern provided on the strip includes protrusions, and during the embossing step, the side portions of the strip are suitably rolled to a strip thickness substantially flush with the strip thickness between the protrusions of the embossed pattern, which is particularly advantageous when embossing is performed before edge chamfering. Therefore, the side portion of the strip will have a lower thickness that results in a smaller internal weld in the tube.

[0036] Description of exemplary embodiments This disclosure will now be described with reference to the accompanying drawings, in which preferred exemplary embodiments of the disclosure are illustrated. However, this disclosure may be implemented in other forms and should not be construed as limited to the embodiments disclosed herein. The disclosed embodiments are provided to fully convey the scope of this disclosure to those skilled in the art.

[0037] Figure 1This is a schematic illustration of an apparatus 20 for preforming a metal strip 40. The apparatus includes an impression station with an impression roller 1 and an anvil roller 22, and an edge chamfering tool BO including a pair of rollers 31, 32. The strip 40 travels along the travel direction T through the preforming tool.

[0038] Figure 2 This is an exploded perspective view of an example of an impression roller, and Figure 3a It is a cross-sectional view of the same roller, and Figure 3b Details are shown. The impression roller 1 has a cylindrical surface 2, which includes a central portion 3 having an impression pattern 10 and side portions 4a, 4b arranged on each side of the central portion 3. The side portions 4a, 4b have no impression pattern, such as... Figure 3b As shown in the figure, the cylindrical surface of the impression roller has a total width W1, and the central portion has a width W2 that is 85-99% of the total width W1.

[0039] In the illustrated example, the central portion 3 of the impression roller 1 is composed of a central impression pattern roller 6, and the side portions 4a and 4b are composed of side rollers 7a and 7b. The side rollers are arranged on each side of the central impression roller. The impression pattern 10 on the central portion of the impression roller includes a plurality of elongated grooves 11 having a depth D1 and arranged at an angle relative to the rotation direction of the impression roller, wherein the groove depth D1 of the impression pattern is preferably less than 0.35 mm. Figures 3a-3b As shown, the cylindrical surfaces of the side portions 4a and 4b are flush with the cylindrical surface of the central portion 3 between the grooves.

[0040] Figure 3c This is a schematic cross-sectional view showing details of the combined embossing and edge-beveling rollers. In this case, the embossing portion 3' is arranged in the central section 34' of the recess 37'. The unpatterned side portion 4a' is also included in the central section 34'. The side section 35' includes the beveled edge-beveling side edge 36'.

[0041] The central impression roller can be in the form of an impression pattern roller group, including multiple impression pattern rollers. Therefore, the central portion 3 of the impression roller 1 can be composed of an impression pattern roller group, which includes one or more impression pattern disks 13a, 13b with cylindrical impression surfaces, on which the same or different impression patterns are provided. Figure 4 The illustration includes details of two pattern rollers, a metal strip 40 to be imprinted, and an imprinting roller assembly of anvil roller 22. In this case, the imprinting pattern roller assembly includes two imprinting pattern disks 13a and 13b, each having an imprinting pattern composed of angled grooves, but with a mirrored pattern, which together form a herringbone pattern on the imprinted strip. Figure 5The illustration shows details of an impression roller assembly including smooth spacer rings 15 between impression pattern disks 13a and 13b. In this case, the cylindrical surface of each spacer ring is flush with the cylindrical surface of the central portion 3 between the grooves. Figure 5 As shown, the embossed pattern disks 13a, 13b and the smooth spacer ring 15 have beveled edges 16, 17 at their interface. Figure 6 A partial cross-sectional view of a tube 18 with an internally embossed herringbone pattern 19 is shown.

[0042] Figure 7 A cross-section of a portion of the finished preformed strip is shown, which has been preformed by an impression roller according to this disclosure in a step following impression. The outline of the recess in the edge chamfering roller 31 is indicated by dashed lines. This includes a central section 34 and side sections 35 (in...). Figure 7 The recess (shown only one in the figure) together with the anvil roller (not shown) forms a strip receiving gap 33. The gap 33 is sized such that the ribs 44 of the embossed pattern in the central portion 41 of the strip are unaffected, and in this example, the side section 35, including the outwardly chamfered side edge 36, has a width greater than the width of the unpatterned side portion 42 of the strip. The outermost edge of the strip is chamfered up to the thickness indicated by the dashed line 43. The figure also shows how the surface of the side portion 42 is flush with the bottom of the recess formed between the ribs 44 in the central portion 41, providing an embossed pattern on the central portion 41 including a plurality of protruding ribs 44 (only one rib is shown in this figure). The ribs 44 correspond to the impression roller ( Figure 3b The groove 11 of the embossed pattern 10 on the surface.

[0043] Figure 8a A portion of an edge-chamfering roller 31 is shown, comprising a central section 34 sized such that the imprinted pattern of a metal strip passing between the pair of rollers is unaffected by rollers 31 and 32. Side sections 35 are arranged on each side of the central section, in which a gap 33 has a reduced height. The central section 34 and the side sections 35 together form a recess 37 extending circumferentially along the cylindrical surface of the first roller. The recess has outwardly sloping side edges 36 on each side formed at the side sections 35. Figure 8b This shows a portion of an edge-beveling tool configured to receive and pass through a metal strip 40 in a gap 33 formed between rollers 31 and 32. In this figure, the upper roller 31 corresponds to... Figure 8a The roller shown. The upper roller forms an edge chamfer on the inner side of the strip, which will be the finished tube. Roller 32 acts as an anvil roller.

[0044] Figures 9a-9cThe diagram illustrates the welding principle and shows the seam section during welding of a roll-formed strip at its longitudinal side edges. After pre-forming in an apparatus including an embossing tool and an edge-beveling tool, the strip is roll-formed until the beveled edges are brought close together. Figure 9a The nearly closed tube is subjected to high-frequency welding by passing it through a welding coil, in which the strip material begins to melt due to the energy induced by the high-frequency coil. Figure 9b During welding, molten material fills the space formed between the chamfered edges of the strip and forms a weld seam. Figure 9c Due to the low thickness of the strip in this space and the welding area, the height of the inner weld can be kept to a minimum.

[0045] Those skilled in the art will recognize that this disclosure is not limited to the preferred embodiments described above. They will further recognize that modifications and variations are possible within the scope of the appended claims. Furthermore, by studying the accompanying drawings, this disclosure, and the appended claims, those skilled in the art can understand and implement variations to the disclosed embodiments when carrying out the claimed disclosure.

Claims

1. An apparatus for preforming metal strips (40) for manufacturing roll-formed and high-frequency welded tubes with internal grooves for HVAC&R applications, comprising an embossing tool (20) and a strip edge chamfering tool (30), wherein - The embossing tool includes an embossing roller (1) having a cylindrical surface (2) with a central portion (3, 3') and side portions (4a, 4b) arranged on each side of the central portion, the central portion being provided with an embossed pattern (10), and the side portions being un-embossed. - The strip edge chamfering tool includes an edge chamfering roller (31) and an anvil roller (32), the edge chamfering roller (31) including a recessed central section (34) and side sections (35) on each side of the central section, wherein the edge chamfering roller (31) and the anvil roller (32) are configured to receive and pass the metal strip in a gap (33) formed between the edge chamfering roller (31) and the anvil roller (32), wherein the gap (33) has a reduced height in the side sections, the side sections being located where the longitudinal side edge of the metal strip will pass, such that the longitudinal side edge on each side of the metal strip and on the embossed side of the metal strip becomes chamfered as it passes between the edge chamfering roller (31) and the anvil roller (32). The embossed pattern (10) on the central portion includes a plurality of grooves (11) arranged in the cylindrical surface of the central portion (3), and The cylindrical surface of each side portion (4a, 4b) is flush with the cylindrical surface of the central portion (3) between the grooves.

2. The apparatus according to claim 1, wherein -The strip edge chamfering tool (30) is arranged downstream of the embossing tool in the travel direction (T) of the strip to be pre-formed, and - The central section (34) of the strip edge chamfering tool (30) is sized such that the pattern imprinted by the metal strip passing through the gap (33) between the edge chamfering roller (31) and the anvil roller (32) is not affected by the edge chamfering roller (31) and the anvil roller (32).

3. The apparatus of claim 1, wherein the embossing tool and the strip edge chamfering tool are integrated to include a combined embossing and edge chamfering roller, wherein the central portion (3') is included in the central section (34') of the gap (33).

4. The apparatus according to claim 1, wherein the impression roller (1) comprises a central impression pattern roller group (6) and side rollers (7a, 7b), the side rollers being arranged on each side of the central impression pattern roller group, wherein the central impression pattern roller group has a cylindrical surface forming the central portion (3), and the side rollers have cylindrical surfaces forming the side portions (4a, 4b).

5. The apparatus according to any one of claims 1-4, wherein the cylindrical surface of the impression roller has a total width (W1) equal to or greater than 15 mm, and the central portion of the impression roller has a width (W2) that is 85-99% of the total width (W1).

6. The apparatus according to any one of claims 1-4, wherein the central section (34) of the gap (33) between the edge chamfering roller (31) and the anvil roller (32) of the strip edge chamfering tool (30) has a width (W3) equal to or greater than the width (W2) of the central portion (3) of the impression roller (1).

7. The apparatus according to any one of claims 1-4, wherein the edge chamfering roller (31) in the edge chamfering tool includes a recess (37) extending along a circumferential portion of a cylindrical surface of the edge chamfering roller, the recess having outwardly inclined side edges (36) on each side of the recess.

8. The device according to claim 7, wherein the outwardly inclined side edge (36) is inclined at an angle of 30-60°.

9. The device according to claim 8, wherein the outwardly inclined side edge (36) is inclined at an angle of 43-47°.

10. The apparatus according to any one of claims 1-4, wherein the side section (35) of the gap (33) between the edge chamfering roller (31) and the anvil roller (32) each has a width equal to or greater than half the difference between the total width (W1) of the imprinting tool and the width (W2) of the central portion of the imprinting tool.

11. A method for preforming a metal strip (40) using the apparatus according to claim 1 for manufacturing a roll-formed and high-frequency welded tube with internal grooves, comprising: - A pattern is embossed along the longitudinal direction on the central portion (41) of the strip, while the side portions (42) on each side of the central portion of the strip are rolled without embossing the pattern, wherein the embossed pattern includes protrusions (44), and during the embossing step, the side portions of the strip are rolled to a strip thickness substantially flush with the strip thickness between the protrusions of the embossed pattern, and - The longitudinal side edge (43) of the strip is chamfered on the side of the strip where the pattern is embossed.

12. The method of claim 11, wherein, During the chamfering, the strip material at the longitudinal side edge (43) of the strip is pressed down by up to 20-60% of the strip thickness, thereby forming a sloping edge surface along the longitudinal side edge of the strip.

13. The method of claim 12, wherein, During the chamfering, the strip material at the longitudinal side edge (43) of the strip is pressed down by up to 35-40% of the strip thickness, thereby forming a sloping edge surface along the longitudinal side edge of the strip.

14. The method of claim 11 or 12, wherein, After the embossing step, the side edges are chamfered in a subsequent step.

15. The method of claim 11 or 12, wherein the embossing and edge chamfering are performed simultaneously in an integrated embossing and edge chamfering tool.

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