Method for producing a seamless metallic belt

Abstract: A method for producing a seamless metallic belt without a welded line and capable of being easily produced in high accuracy. A seamless belt material 21 having a defined length as a whole is placed on a core 11 and is held in a stretching state on the core 11 thermally expanded by heating, and further, in the above state, an outer circumference of the belt material 21 is cut to a predetermined thickness. The seamless metallic belt 20 is obtained by removing after the core 11 is cooled.

Description: This invention relates to a method for producing a seamless metallic belt, which is capable of using for a belt of a conveyor, a belt device for molding a material of a synthetic resin film or the like. Conventionally, an endless metallic belt, which is toroidally continued with thin-plane shaped metallic material, is used for a belt of a conveyor. Further, the endless metallic belt is used for a belt device for molding a synthetic resin film, a synthetic resin sheet, a synthetic resin board or the like. Particularly, a mirror belt finished to a mirror surface is used for producing an optical film, sheet, board or the like, required with evenness of the surface. As material of the aforementioned endless metallic belt, various metals are properly used in response to the use, especially, stainless material (SUS) inhabiting a generation of a rust and so on is heavily used for the mirror finished belt in order that evenness of the surface is not impaired. The aforementioned endless metallic belts are produced with, for example, a method in which a metallic plate processed with metal rolling is to be a banded shape and the endless belt is resulted by welding both of the ends of the banded metallic plate, a method in which a metallic pipe is processed with metal rolling and the thin endless belt is resulted by enlarging the diameter of a loop of the metallic pipe, and so on. The endless belt produced with metal rolling is called as a seamless metallic belt or the like in view of no joint line like end-welding. In the aforementioned conventional producing method, however, the following disadvantages are listed. Disadvantages of the producing method with end-welding for the banded metallic plate In the producing method with end-welding for the banded metallic plate; the mechanical strength of a welded portion is reduced to approximately 50-70 % as compared with another portions of the main body. Thereby allowing disadvantages in which the welded portion becomes expanded (necking) with the use, and further, degradation, weld crack, rupture and so on easily appear by repeatedly bending. In order to ensure endurance for the use of the endless belt with end-welding, it is required that the diameter of rollers run thereon with the endless belt is defined as more than 1,000 times of the thickness of the endless belt, curvature radius is defined to be larger so as not to concentrate large force on the welded portion, and so on. As a result, a disadvantage in which a device using the endless belt is not allowed to be a smaller size comes. On the endless belt with end-welding, the welded portion becomes changed as compared with another portions of the main body and brought about necking with time even on the minor finished belt, resulting in a disadvantage of faulty appearance, such as optical anisotropy and the like. Disadvantages of the producing method with pipe metal rolling In the producing method with pipe-metal rolling, there is a disadvantage of need of a large special apparatus in the manufacture. In view of manufacturing with metal rolling of the pipe, there is disadvantage in which it is difficult that the dimensional accuracy of the thickness of the belt and the like is increased, particularly, it is seriously difficult that all the circumferential length of the belt is produced in high accuracy. JP-A-06050391 discloses apparatus for forming a seamless belt in which a seamless metallic workpiece is firstly positioned inside a cylindrical jig which has been heated and which shrinks upon cooling onto the workpiece. The jig is then fitted to a lathe and the inner periphery of the workpiece is ground out before the jig is heated and the workpiece removed. The workpiece is then positioned around a cooled cylindrical jig which expands as it warms up to securely hold the workpiece while its outer periphery is then ground. It is an object of the present invention to provide a method for producing a seamless metallic belt without a welded line and capable of being easily produced in high accuracy. Accordingly, in a first aspect, the invention consists in a method for producing a seamless metallic belt from a thin walled metallic belt material comprising the steps of: placing the belt material on a flat circumferential outer surface of a core, wherein the outer diameter of the core is a predetermined amount smaller than the inner diameter of the belt material; thermally expanding the core to cause the inner circumference of the belt material to press against the outer circumference of the core; cutting the outer circumferential face of the belt material until a predetermined constant thickness of the belt is obtained; andremoving the belt material from the core by cooling and shrinking the core after said step of cutting to thereby create said seamless metallic belt; characterised in that said step of thermally expanding the core is achieved by using a cartridge type heater provided in the core. In the present invention as described above, the belt material results thinner by cutting the outer circumference of the metal-made belt material of a pipe-shape or the like, thus obtaining an endless belt. The endless belt is a seamless belt, because a seam does not appear on the original belt material. In the process, for example, the outer circumference of the belt material is rotating-cut while the inner circumference is retained in a perfect circle or in similar ways, thereby allowing thickness to be controlled with high accuracy. The whole circumferential length of the seamless belt has a dependence on the whole circumferential length of the belt material with high accuracy in the stage of the belt material. The whole inner circumferential length of the belt material is precisely found by cutting the inner circumferential face of the belt material or by similar ways. Therefore, the whole circumferential length of the seamless belt is also controlled with high accuracy. In view of above description, the seamless metallic belt having the accurate thickness and whole circumferential length without a seam is obtained, thus attaining the aforementioned object. As a result, the belt material of a predetermined length can be certainly held by using the thermal expansion and shrinkage of the core (namely, "tightfit"). At this point, insofar that the core is formed with a homogeneous material to have the outer circumference of a sectional perfect circle with high accuracy, roundness of the outer circumferential face is maintained even when the core thermally expands. Thereby allowing the inner circumference of the belt to be maintained in the perfect circle with high accuracy in the process that the belt material is cut, the structure and the placing process to be simple, and the accurate thickness to be achieved. It is advisable that the belt material is any one of stainless steel, carbon steel, precipitation hardening type steel and titanium alloy. When the above materials are used as the required high-function belt, effect of the present invention sufficiently comes into play. It is advisable that the belt material is a material obtained by using any one of extrusion molding, pultrusion molding, casting, centrifugal casting and forging. In view of the aforementioned processes, the even belt material without any seam on the whole circumference can be obtained, thus further improving quality of the seamless metallic belt produced by using the present invention. It is advisable that the belt material has a thickness from 50 microns to 2 mm after the cutting process. In a further aspect, the invention consists in apparatus for producing a seamless metallic belt from a thin walled metallic belt material, the apparatus including a core having a flat circumferential outer surface adapted to receive the belt material, wherein the outer diameter of the core is a predetermined amount smaller than the inner diameter of the belt material; means to thermally expand the core to cause the inner circumference of the belt material to press against the outer circumference of the core; means for cutting the outer circumferential face of the belt material until a predetermined constant thickness of the belt is obtained; and means to remove the belt material from the core by cooling and shrinking the core to thereby create said seamless metallic belt; characterised in that said means to thermally expand the core comprise a cartridge type heater provided in the core. In the accompanying drawings: Fig. 1 is a disintegrated perspective view showing the preferred embodiment of the present invention; Fig. 2 is a schematic side elevational view showing structure of a device for cutting the outer circumference on the preferred embodiment; Fig. 3 is a schematic view showing a tubular material of the preferred embodiment; Fig. 4 is a schematic view showing a belt material of the preferred embodiment; and Fig. 5 is a schematic view showing a seamless metallic belt of the preferred embodiment. The preferred embodiment according to the present invention will be explained below with reference to the attached drawings. In the embodiment, a seamless metallic belt 20 (see Fig. 5) is produced to adjust the thickness and the circumferential length in accuracy by the steps of forming a tubular belt material from metallic raw material of stainless steel or the like, and cutting the outer circumferential face of the belt material. Explanation of a device for cutting the outer circumferential face In Fig. 1, a core 11 is a metallic cylinder made of aluminium or the like and excellent in thermal conductivity, which is used as jig for forming the seamless metallic belt to cut the outer circumferetial face of a belt material 21. A cartridge type heater 12 is provided in the core 11 to be able to heat it to a required temperature, operating from the outside. The core 11 is a sectional perfect circle, in which has an outer diameter dc1 in a cooling state and an outer diameter dc2 in a heated state by the heater 12 in view of thermal expansion. Therefore, the belt material 21 having an inner diameter db1 (dc2>db1>dc1) can be fitted on the outer circumferential face of the core 11 when the core 11 is cooled. At this point, the core 11 expands through heating, whereupon the outer circumferential face of the core 11 completely touches the whole inner circumferential face of the belt material 21, thereby fittingly holding the belt material 21 in a stretching state. Incidentally, the core 11 may be cooled with air cooling, and also may be constructively cooled by providing a cooling means of a water-cooled type or the like in the core 11 or a cooling means of an air blow type in the proximity of the core 11. The known lathe or miller can be appropriately used for cutting the outer circumferential face, for example, a device 13 shown in Fig. 2 can be employed. In Fig. 2, the core 11 is mounted on a support shaft 131. The support shaft 131 is rotatably supported with a pair of bearings 132, in which the core 11 is sandwiched or passed through in the axial direction, thereby the axis of the core 11 is supported to agree with the support shaft 131. A gear 133 and a motor 134 are provided at an end of the support shaft 131, thereby the support shaft 131 and the core 11 are rotatably driven. At the other end of the support shaft 131, a slip ring 135 is provided, in which a power source line of the heater 12 integrated in the core 11 is connected to the slip ring 135. A slip brush 136 connected power source of the outside is slidably moved in the slip ring 135, thereby power supply for the heater 12 in the rotating core 11 is ensured. Adjacent to the core 11 located on the support shaft 131, a cutting tool 14 is located to allow to cut the outer circumferential face of the belt material 21 fittingly mounted on the outer circumference of the core 11. The cutting tool 14 is supported by a cutting-tool attached portion provided in the device 13 to be precisely moved relative to the core 11 by the moving system (the above structure is well-known and omitted to be shown in a drawing). Thereby allowing it to be proximate to and opened a space from the rotating core 11, with the result that the cut thickness of the belt material 21 is determined, and further, allowing it to be moved in the axial direction of the core 11 with a process of cutting, with the result that all the outer circumferential face of the belt material 21 mounted on the core 11 is allowed to be precisely cut. Explanation of producing steps When the seamless metallic belt 20 is produced by using the aforementioned device, the following steps are performed. First, metal raw-material, used for the seamless metallic belt 20, is processed to form the tubular material 22 (see Fig. 3). As the metal raw-material, it is advisable to use any one of stainless steel, carbon steel, precipitation hardening type steel, and titanium alloy. For forming the tubular material 22, a known process, such as forging, extrusion, pultrusion, casting, centrifugal casting or the like, which is capable of forming the tubular material 22 without a seam, can be used. The formed tubular material 22 is formed to have a sufficiently smaller inner diameter db2 than the outer diameter dc1 of the core 11 in cooling, and a predetermined thickness t2 a larger outer diameter db3 than the inner diameter db2. And, the belt material 21 is formed by cutting the inner circumferential face of the tubular material 22 to make a perfect circle of the inner diameter db1 (see Fig. 4). For cutting the inner circumferential face, a known process, such as a honing process, spinning process or the like, can be used. At this time, the inner diameter db1 of the belt material 21 is adjusted with precision to be a size which all the circumferential length of the inner circumferential face is to be all the circumferential length required as the seamless metallic belt 20. Continuously, the belt material 20 is mounted onto the core 11, and further, the core 11 is placed to the device 13 for cutting the outer circumference. When the belt material 21 is mounted onto the core 11, the core 11 is previously cooled, and the belt material 21 is passed from the upper end of the core 11 to be located on the outer circumferential face of the core 11. In the above state, the core 11 is heated by the heater 12 to be expanded, so that the belt material 21 is held on the outer circumferential face of the core 11 with a stretching state. After the belt material 21 is mounted, the device 13 is operated to rotate the core 11 and to cause the cutting tool 14 to touch onto the outer circumferential face of the belt material 21 mounted on the core 11, and then the outer circumferential face is uniformly and precisely cut across all the circumference and all the width. The cutting process is performed until the thickness of the belt material 21 is reaches t0, consequently, when the outer diameter db0 is formed; the seamless metallic belt 20 having the inner diameter db1 is also formed. After the cutting process, the core 11 is stopped rotating and cooled by turning off the heater 12 to release the stretched hold of the seamless metallic belt 20, and then the seamless metallic belt 20 is removed from the core 11. As a result, the seamless metallic belt 20 is produced with accuracy of the thickness and the whole circumferential length. Incidentally, the heater 12 used in the embodiment is not limited to the use of the electrothermal type, and may appropriately use, for example, a circulating type of hot-water or the like. Concrete experiment The following is an explanation as to an experiment for producing the seamless metallic belt 20 based on the aforementioned embodiment. (1) The tubular material 22 is formed with a precipitation hardening type steel (SUS630) by using a centrifugal casting method (the inner diameter db2 = 900 mm, the outer diameter db3 = 1,000 mm, the width of circumferential face (the length in the axial direction) = 1,000 mm). The formed tubular material 22 is resulted in the belt material 21 having the inner diameter db1 = 950.0 mm by undergoing the honing process for the inner circumferetial face. (2) The belt material 21 is placed on the core 11 having a room temperature. The core 11 is made of an aluminum alloy, in which has the outer diameter dc1 = 949.5 mm in a room temperature, and the part of the core 11, corresponding to the cartridge heater 12 provided therein, has the inner diameter 910 mm and the width of circumferential face 1,500 mm. The core 11 placed thereon with the belt material 21 is mounted on the lathe, and the surface temperature of the core 11 is defined as 80 °C by heating the heater 12 so as to cause the belt material 21 to be held on the outer circumference of the core 11 in a stretching state. (3) During the above state, the core 11 is rotated to cut the outer circumferential face of the belt material 21 until the outer diameter is 952.0 mm. While the surface temperature T of the core 11 is increased based on the following equation (Equation 1), the outer circumferential face of the belt material 21 is further cut, with result that the seamless metallic belt 20 having the thickness t0 = 0.54 mm is formed. Incidentally, in Equation 1, t means the thickness of the belt material 21 (t < 2 mm). Equation 1 T = -25t + 130 (4) The core 11 is cooled to a room temperature, and the seamless metallic belt 20 is removed. After that, the seamless metallic belt 20 is resulted in a mirror belt by performing abrasive polishing on the surface thereon with a conventional method. The obtained mirror finished seamless metallic belt 20 has a surface-roughness Ra of 0.007 micron and the thickness of 0.5 mm. (5) The mirror finished seamless metallic belt 20 undergoes an endurance test by being wound on a pair of rollers. In the test, two rollers each having the outer diameter of 250 mm are located in approximate 1,100 mm between both centers. The above rollers are wound thereon with the belt 20 and rotated, and further, one of the above rollers is added with tractive force by a hydraulic cylinder in a direction distance from the other roller. As a result, bending stress is repeatedly added to the power of ten raised to the seventh power, but degradation, weld crack and so on do not appear on the surface. (6) As comparison, the aforementioned material (SUS630) is formed to be a belt shape having the thickness of 0.55 mm with the metal rolling method, and then resulted in the endless belt by performing argon TIG welding on both of the ends of the material. The obtained endless belt is polished to have a mirror face and resulted in the surface-roughness Ra = 0.007 micron and the thickness of 0.5 mm. The above endless belt undergoes the aforementioned endurance test. As a result, weld crack appears on the end of the welded line by repeatedly adding stress in 29,000 times. And further, the welded line is extended and the mirror face is degenerated.

Claims: A method for producing a seamless metallic belt (20) from a thin walled metallic belt material (21) comprising the steps of: placing the belt material (21) on a flat circumferential outer surface of a core (11), wherein the outer diameter of the core (11) is a predetermined amount smaller than the inner diameter of the belt material (21); thermally expanding the core (11) to cause the inner circumference of the belt material (21) to press against the outer circumference of the core (11); cutting the outer circumferential face of the belt material (21) until a predetermined constant thickness (t0) of the belt is obtained; and removing the belt material (21) from the core (11) by cooling and shrinking the core after said step of cutting to thereby create said seamless metallic belt (20); characterised in that said step of thermally expanding the core is achieved by using a cartridge type heater (12) provided in the core. The method for producing a seamless metallic belt according to claim 1, wherein the belt material is any one of stainless steel, carbon steel, precipitation hardening type steel and titanium alloy. The method for producing a seamless metallic belt according to claim 1 or claim 2, wherein the belt material is obtained by using any one of extrusion molding, pultrusion molding, casting, centrifugal casting and forging. The method for producing a seamless metallic belt according to any one of the preceding claims, wherein the belt material has a thickness from 50 microns to 2 mm after said step for cutting. The method for producing a seamless metallic belt according to any one of the preceding claims, wherein the core is made of aluminum alloy. Apparatus for producing a seamless metallic belt (20) from a thin walled metallic belt material (21), the apparatus including a core (11) having a flat circumferential outer surface adapted to receive the belt material (21), wherein the outer diameter of the core (11) is a predetermined amount smaller than the inner diameter of the belt material (21); means to thermally expand the core (11) to cause the inner circumference of the belt material (21) to press against the outer circumference of the core (11); means (14) for cutting the outer circumferential face of the belt material (21) until a predetermined constant thickness (t0) of the belt is obtained; and means to remove the belt material (21) from the core (11) by cooling and shrinking the core to thereby create said seamless metallic belt (20); characterised in that said means to thermally expand the core (11) comprise a cartridge type heater (12) provided in the core. The apparatus for producing a seamless metallic belt according to claim 6, wherein the core (11) is made of aluminum alloy.

Inventors: FUJII ATSUSHI, FUNAKI AKIRA, MATSUZAWA KOUZABURO, FUJII, ATSUSHI, FUNAKI, AKIRA, MATSUZAWA, KOUZABURO, Matsuzawa, Kouzaburo, c/o Matsuzawa Co., Ltd.
Applicants: IDEMITSU PETROCHEMICAL CO, IDEMITSU PETROCHEMICAL CO., LTD.
Application year: 1997
Main classification: B23P15
IPC codes: B23P13, B23P15