Abstract: The invention relates to a device, comprising at least one flow chamber (20?) having an inlet opening and an outlet opening, said flow chamber being provided for the flow of a medium therethrough. The flow chamber (20?) is arranged in a single-piece block element (2) and is at least partly delimited by a diathermal wall in order to effect absorption or release of thermal energy through the wall by means of the medium. The at least one flow chamber (20?) is formed in the block element (2) from a plurality of first channels (22) spaced apart from each other, which extend straight and parallel to each other, and a plurality of second channels (23) spaced apart from each other, which extend straight and parallel to each other, the first and the second channels (22, 23) each having two ends and being closed at least at one (27) of the two ends. The second channels (23) are arranged at an angle to the first channels (22), the first channels and the second channels thus crossing.

Abstract: The present invention relates to a fault detectable sheet body fixed distance conveying and punching assembly, which may include a rack, a conveying trough seat, a feeding trough, a processing rack and a punching device. On the rack is provided a feed motor and a feed screw. The movable feeding block is sleeved on the feed screw and the movable feeding seat is fixedly connected to the movable feeding seat. On the movable feeding seat is provided a feed lifting cylinder and on the feed lifting cylinder is provided a feed lifting block. On the feed lifting cylinder are equally provided feed blocks which may go through the feeding trough. On the processing rack is also provided a position detecting device which may include a detecting lifting cylinder provided on the processing rack. Under the detecting lifting cylinder is connected the detecting block. On the both sides of the detecting block is provided an acoustic wave range finder.

Abstract: The present invention relates to a conveying accuracy related fault detectable integrated sheet body punching and grinding assembly, including frame, conveying trough seat and processing frame. The processing frame is provided with a punching device and a grinding device, the frame is provided with a feed motor and feed screw. The feed screw is sleeved with a movable feed block; the movable feed block is fixedly connected with a movable feed seat, and the movable feed seat is provided with a feed lift cylinder, the feed lift cylinder is provided with a feed lift block. The feed lift block is evenly disposed with feed blocks that are capable of passing through the feed conveying trough, and a vertically oriented beam emitter is disposed on the portion that the feed lift block corresponds with the grinding device.

Abstract: The present invention relates to an automatic fault diagnosable integrated sheet body punching and grinding assembly, including a frame and a conveying slot seat, a processing frame is provided on the conveying slot seat, the processing frame is sequentially provided with a punching device and a grinding device; the frame is provided with a feeding motor and a feeding screw cooperating with each other, the feeding screw is sleeved with a movable feeding block, and the movable feeding block is fixedly connected with a movable feeding seat, the movable feeding seat is provided with a feeding lift cylinder, the feeding lift cylinder is provided with a feeding lift block; the feeding lift block is evenly disposed with feeding blocks that can pass through the feeding slot, and the distance between the processing portion of the punching device and the grinding device is the same as that between the adjacent two feeding blocks.

Abstract: A first step of setting a steel material heated to a temperature not lower than an A1 transformation point on a forming table and a second step of punching a ring-form member from the steel material and thereafter forming and quenching the ring-form member on the forming table are included. A press die is constructed to be dividable into an inner cylinder and an outer cylinder. In the second step, the ring-form member is punched from a coil material by pressing a tip end portion of the inner cylinder and a tip end portion of the outer cylinder against the coil material. The punched ring-form member is formed and quenched by further pressing a tip end of the inner cylinder against the ring-form member while the ring-form member is held between the outer cylinder and a forming die.

Abstract: [Object] To provide a method of manufacturing a plate-like molded body having a thickened portion in a region spaced apart from an edge in a substantially flat plate-like portion. [Solution] Provided is a method of manufacturing a plate-like molded body having a plurality of thickened portions, including at least a drawing step of obtaining by a drawing process a cylindrical drawn molded body including a flat plate portion and a cylindrical drawn portion that swells in such a manner as to project from the flat plate portion and has a circular top portion.

Abstract: A fine blanking cam die for removing a slug from a workpiece includes an axially moveable punch, laterally moveable cam dies and a driver engaged with at least one of the cam dies. The laterally moveable cam dies define an aperture to receive the punch. Movement of the driver causes movement of at least one of the cam dies such that a side force is applied to a slug of material being formed as the punch travels through the workpiece.

Abstract: An upper die part includes an embossing bell, a stripper ring, and an inner shape embossing element. The stripper ring has an embossing surface with a corrugated profile on the embossing surface. A lower die part includes an embossing anvil having a corrugated profile on its embossing surface. The embossing bell and the inner shape embossing element each are provided with an embossing shoulder, which are disposed, with respect to the corrugated profile of the stripper ring, in the stroke direction in such a way that the shoulders can seize the burrs only alter the corrugating step. The corrugating step takes place prior to burr compression. The outer and inner contours of the disk are not able to change positions, but are able to change shapes on the burr side after the corrugating step.

Abstract: The method is for manufacturing a rotor core having a cylindrical boss section formed with an axial hole, a disc section radially extending from one end of the boss section, and a plurality of claw sections provided along an outer periphery of the disk section. A boss section-side hole as a part of the axial hole is formed by plastic deformation in a preliminary shaping step. The remaining part of the axial hole of the billet disposed on a die is punched through using a center hole punch having a diameter smaller than an inner diameter of the boss section-side hole to form the disk section-side hole in the flush/punch through step, so that the axial hole is constituted of the boss section-side hole, the disk section-side hole and a step portion between the boss section-side hole and the disk section-side hole.

Abstract: A system and method forming a ground bonding strap. A length of cable is measured to determine a segment of cable to stamp to form a pair of connectors. The segment is heated. The segment is stamped to form the pair of connectors. The pair of connectors defining an indentation and a pair of receptacles disposed through the cable. The pair of receptacles being each adjacent to and separated by an indentation. The indentations being positioned to allow a user to cut between the pair of connectors to form a ground bonding strap of a length selected by the user.

Abstract: One embodiment described herein is a sheet of material 200 formed into accurate and high value structures by implementing a plurality of elongated slots 202 that are obliquely placed along a fold line 204 which create one or more strips 206 consisting of a length w, a width s and an angle f to said fold line 204. The strips 206 are put into a state of plastic deformation through torsion which is controlled via the combination of said length w, width s, and angle f elements to create accurate, unique, complex and high value products or forms. The embodiments described allow for a greater degree of freedom of sheet material types, a greater degree of sheet material thicknesses, while simplifying implementation. This and other embodiments are also enclosed.

Abstract: A burring apparatus is provided, including a burring die having a top surface for a workpiece to be placed on, the burring die configured to be cylindrically symmetric with a burring hole formed concentrically therein to provide an inner surface, a burring punch having a tip end portion for punching the workpiece to cut off a metal piece and a tip portion for pressing a remaining portion of the workpiece warped in the burring hole to form a boss, and a scrap removing unit attached to the inner surface of the burring die, wherein the burring punch, the burring die and the scrap removing unit are configured to trap, push out and let fall by scraping off the metal piece as the burring punch is lowered into the burring hole and lifted.

Abstract: A lead hole is formed in a base material of an injection hole member with a straight punch, and then, a taper hole is formed in the base material by widening the lead hole with a taper punch. An intersection line between a virtual plane perpendicular to a central axis of the lead hole and an inner peripheral surface of the lead hole is elliptic in shape, whose major axis is directed along an intersection line between a virtual plane, which includes the central axis of the lead hole and a thickness direction axis of the base material, and the virtual plane perpendicular to the central axis of the lead hole. An intersection line between a virtual plane perpendicular to a central axis of the taper punch and an outer peripheral surface of the taper punch is round in shape.

Abstract: A hot forging press machine includes a fixed lower die, a vertically movable upper die, a punching blade for punching, and a deburring blade. The deburring blade includes a deburring upper blade and a deburring lower blade to perform deburring. The deburring upper blade is fixed to a lower portion of the upper die, and the lower blade is fixed to an upper portion of the lower die. A lower sweeping plate urged upward by a spring is slidably fitted to an outer circumference of the lower blade to perform deburring, and an upper sweeping plate of the upper die presses an entirety of an upper surface of a flange portion of a pressed product to perform the discharging.

Abstract: A system and method forming a ground bonding strap. A length of cable is measured to determine a segment of cable to stamp to form a pair of connectors. The segment is heated. The segment is stamped to form the pair of connectors. The pair of connectors defining an indentation and a pair of receptacles disposed through the cable. The pair of receptacles being each adjacent to and separated by an indentation. The indentations being positioned to allow a user to cut between the pair of connectors to form a ground bonding strap of a length selected by the user.

Abstract: A thin plate burring processing method includes a first step of forming a thin portion thinner than an original thickness in a target portion by performing crushing processing on the target portion of a plate-like workpiece, a second step of forming a circular through-hole in the thin portion by punching processing, and a third step of forming an annular portion rising from a surface of the workpiece by performing projection processing with burring processing around the through-hole formed in the thin portion.

Abstract: A system and method forming a ground bonding strap. A length of cable is measured to determine a segment of cable to stamp to form a pair of connectors. The segment is heated. The segment is stamped to form the pair of connectors. The pair of connectors defining an indentation and a pair of receptacles disposed through the cable. The pair of receptacles being each adjacent to and separated by an indentation. The indentations being positioned to allow a user to cut between the pair of connectors to form a ground bonding strap of a length selected by the user.

Abstract: The present invention is premised upon method of manufacturing rolled pierce nuts having a predetermined profile from a metal rod, more particularly to a method and apparatus delivering greater manufacturing flexibility through the use of multiple stations with flexible inputs and outputs.

Abstract: Disclosed herein is a method for processing an orifice capable of processing recessed portions and orifices, each having a unique hole diameter different from each other, to high positioning accuracy and in a short time. A press includes: a B-axis angle indexing device 3 disposed on a base 2b, the B-axis angle indexing device 3 including a table B; an A-axis angle indexing device 25 disposed on the table B, the A-axis angle indexing device 25 including a table A; a chuck 32 disposed on the table A, the chuck 32 for holding a work; a base Z 6 disposed on a base, the base Z 6 being operable in an axis Z-direction; a base X 8 disposed on the base Z, the base X 8 being operable in an axis X-direction; a punch holding portion 13 disposed on the base X, the punch holding portion 13 being operable vertically in an axis Y-direction; and a plurality of punches 19, 22 held on the punch holding portion in parallel with the axis Z.

Abstract: A method for processing a plate workpiece supported on a workpiece support. The method includes moving a tool die and a tool punch along a stroke axis and toward a processing position above a support plane of the workpiece support. The processing position corresponds to a region of the plate workpiece having a formed shape, which extends upwardly from the support plane of the workpiece support.

Abstract: There is a dry test strip holder having a test port and a retainer defining a well about the test port, and a sheet of test strip material. A test element that is 50% or less greater than the size of the test port is cut from the sheet using a die and punch. The punch drives the test element through a channel in the die while the cone-shaped outer surface of the die spreads the retainer, allowing the test element to drop into the well. A cap is snapped over the retainer to capture the test element.

Abstract: A method of manufacturing an outer retainer for a one-way clutch having an outward flange at one side edge thereof involves punching out a part of an annular portion having the outward flange by sliding a punch toward an axis of the outer retainer substantially in an axially inner direction from a retainer outer periphery-sided curve portion of the outward flange to a retainer inner periphery-sided curve portion thereof in a way that uses a die and the punch.

Abstract: Laminations to be stacked as magnetic cores are produced from a very thin amorphous metal strip, using a punch press with accurate punch/die clearance. The laminations are collected on conveyor spindles or a transport rod or pipe, in either case being arranged without the need for substantial handling. Heat annealing and anti-vibration treatments can be applied along a conveying path. The laminations are grouped in a stack to define a core and are packaged or encapsulated in electrically nonconductive coverings. The finished core has advantageous electrical characteristics and low cost.

Abstract: A plate workpiece processing machine includes a workpiece support, a tool punch holder, a tool die holder, a tool drive, multiple tool punches, and multiple tool dies. Various tool punches and tool dies have tool heads of differing heights. The tool punch holder is positionable based on the tool head height of a tool punch secured to the tool punch holder and/or the tool die holder is positionable based on the tool head height of a tool die secured to the tool die holder.

Abstract: A contact bending fixture includes a lower die slider, a positioning rod, a linear actuating mechanism, and an upper die slider. A lower die mounted on the lower die slider includes a die holder, a lower bending module, a contact holding stick, and a bearing roller. The lower bending module includes a smooth sustaining side surface facing the bearing roller for defining an insertion gap therebetween. An upper die mounted on the upper die slider opposes the lower die and includes a punch holder, a hold-down plate, an elastic component, and an upper bending module. The hold-down plate presses and holds down an end of an under-bending contact on the top surface of lower bending module with an opposite end of the contact suspending in the insertion gap. Therefore, the contact bending fixture is capable of bending a contact at a required angle in one step.

Abstract: A lead hole is formed in a base material of an injection hole member with a straight punch, and then, a taper hole is formed in the base material by widening the lead hole with a taper punch. An intersection line between a virtual plane perpendicular to a central axis of the lead hole and an inner peripheral surface of the lead hole is elliptic in shape, whose major axis is directed along an intersection line between a virtual plane, which includes the central axis of the lead hole and a thickness direction axis of the base material, and the virtual plane perpendicular to the central axis of the lead hole. An intersection line between a virtual plane perpendicular to a central axis of the taper punch and an outer peripheral surface of the taper punch is round in shape.

Abstract: A press forming apparatus comprises an upper die provided with an upper drawing die, a punch, an upper movable blank holder, and a trimming member and a lower die provided with a lower drawing die, a die, an outer periphery drawing die, and a lower movable blank holder. The upper die is lowered with respect to the lower dye, and the outer periphery portion of a blank is held by the trimming member and the upper blank holder. The central portion of the blank is drawn by the upper and lower drawing dies. The outer periphery portion of the blank is trimmed by the trimming member and the outer periphery drawing die, and drawing of the outer periphery portion of the blank is started by the upper drawing die and the outer periphery drawing die.

Abstract: Disclosed herein is a method for processing an orifice capable of processing recessed portions and orifices, each having a unique hole diameter different from each other, to high positioning accuracy and in a short time. A press includes: a B-axis angle indexing device 3 disposed on a base 2b, the B-axis angle indexing device 3 including a table B; an A-axis angle indexing device 25 disposed on the table B, the A-axis angle indexing device 25 including a table A; a chuck 32 disposed on the table A, the chuck 32 for holding a work; a base Z 6 disposed on a base, the base Z 6 being operable in an axis Z-direction; a base X 8 disposed on the base Z, the base X 8 being operable in an axis X-direction; a punch holding portion 13 disposed on the base X, the punch holding portion 13 being operable vertically in an axis Y-direction; and a plurality of punches 19, 22 held on the punch holding portion in parallel with the axis Z.

Abstract: A method of processing a sheet metal sheet with a combined punching and forming machine includes spraying a lubricant onto on a lower side of the sheet metal sheet in a first forming position on the sheet, forming the sheet metal sheet at the first forming position with a first forming tool, and forming the sheet metal sheet with the second forming tool at a second forming position on the sheet metal sheet after spraying the lubricant onto the first forming position and before forming the sheet metal sheet at the first forming position.

Abstract: A plate-like material is pressed and a middle concave portion centered on a center axis is formed in one axial surface of the material. Likely, an annular concave portion centered on a center axis and radially outwardly arranged is formed in one and/or the other axial surface of the material. The material is then cut along a radially outer rim of the middle concave portion, and between a radially outer rim and a radially inner rim of the annular concave portion. In this way, a thrust plate having indented portions at radially inside and outside portion of the one and/or the other axial surface thereof is manufactured. A burr formed in press working is accommodate within the indented portion and does not axially protrude from the one and/or the other axial surface of the thrust plate.

Abstract: A method of forming a chamfered through hole having a chamfered portion at each end thereof by: forming a prepared hole in a plate-like portion; forming a first chamfered portion by driving a first punch; forming a second chamfered portion by driving a second punch, which has a second tapered surface and a generally columnar central pressing portion protruding from the center of the second tapered surface and having an annular corner at a tip thereof, and thereby forming the second chamfered portion and a central recess recessed axially inward; and punching out an unnecessary portion protruding radially inward of the prepared hole by using a finishing punch having an outer diameter equal to or smaller than that of the corner of the central pressing portion. The punching out the unnecessary portion is performed by punching from the first chamfered portion toward the second chamfered portion using the finishing punch.

Abstract: There is provided a method for forming a hollow shaft with a flange directly in sheet metal. This method is a method for forming a hollow shaft having a flange portion 17 at the end thereof based on stamping performed on sheet metal 20. The method includes forming an upright portion 14 which is upright with respect to the surface of the sheet metal 20 by using a burring punch 320 and a burring die 310, and bending outward the free end portion of the upright portion 14 radially with respect to the central axis of the cylindrical portion by using a bending punch and a bending die. Here, the formed hollow shaft has the upright portion 14 protruding upright with respect to the surface and the flange portion 17 radially extending from the end of the upright portion.

Abstract: In a wheel bearing assembly, the length of an annular protrusion in an axis direction, or the oscillation angle through which the center axis of a calk jig is oscillatingly turned relative to the center axis of a constant-velocity joint outer ring is restricted so that the annular protrusion and the calk jig do not interfere with each other when the constant-velocity joint outer ring is calk-fixed to the calk fixation portion of the wheel hub by radially outwardly bending a tubular protrusion formed on an end surface of the center shaft portion through the oscillating turn of the calk jig after the center shaft portion of the constant-velocity joint outer ring has been fitted to the hollow hole of the wheel hub.

Abstract: A method and device for production of stampings with an almost smooth cutting and enlarged functional surface, especially fine blanking and/or forming a workpiece out of a flat strip, wherein flat strip is clamped between an upper part consisting of a shearing punch, a pressure pad, a V-shaped projection and an ejector arranged on the pressure pad, and a lower part consisting of cutting die, ejector and an inner form stamp. By adjusting the state of stress in the cutting zone to a position oriented compressive stress by movement slightly retarded with regard to movement of the shearing punch additionally pressing in material in a direction almost perpendicular to the cutting direction by a tool element acting with controlled force depending on the part geometry and thickness of the workpiece parallel to the cutting line between shearing punch and cutting die, tears at cutting and reduced rollover are achieved.

Abstract: A solder preform for use to attach an electronic component to a substrate. The preform is for placement by a pick-and-place machine using a vacuum nozzle which picks the preform from a preform holder. Each of the sides of the preform configured to function as a vacuum side pick up surface has an enlarged planar surface area. Methods for forming such solder preforms are also disclosed.

Abstract: A method of producing a light alloy wheel with a forging technique, aiming for producing the wheel having a large-diameter disk by use of a small-scale press device, comprising: heating an intermediate product that is formed by casting or forging and has a discoid and a cylindrical thick wall, which are to respectively become disk and rim at completion, to a plasticity temperature; then, rotating the intermediate product with stopping of the rotating at interval of a predetermined angle; pressing at least a portion of the to-be disk part by molds at time of said stopping, as to push out metal into recesses on the lower mold and to thereby form holes; repeating of such rotating, stopping and pressing as to give a pattern on whole of the to-be disk part; and further press processing and finish processing on the to-be disk and the to-be rim parts.

Abstract: A method of forming a chamfered through hole having a chamfered portion at each end thereof by: forming a prepared hole in a plate-like portion; forming a first chamfered portion by driving a first punch; forming a second chamfered portion by driving a second punch, which has a second tapered surface and a generally columnar central pressing portion protruding from the center of the second tapered surface and having an annular corner at a tip thereof, and thereby forming the second chamfered portion and a central recess recessed axially inward; and punching out an unnecessary portion protruding radially inward of the prepared hole by using a finishing punch having an outer diameter equal to or smaller than that of the corner of the central pressing portion. The punching out the unnecessary portion is performed by punching from the first chamfered portion toward the second chamfered portion using the finishing punch.

Abstract: A method is provided for processing a product formed by a punch press. The method includes leaving a micro joint connecting a workpiece to a raw material forming the product when forming a slit in the workpiece along an outer shape of the raw material. The method also includes forming the product by bending a bending process portion downward on the basis of a cooperation of an upper metal mold and a lower metal mold. The method further includes dropping the product by separating the connection between the product and the workpiece by the micro joint.

Abstract: A method and assembly for punching a hole in material provided. A magnetostrictive device 14 includes a coil 26, a magnetostrictive member 22, and a punch 28 operatively associated with the magnetostrictive member 22. The magnetostrictive member 22 is constructed and arranged to lengthen, when exposed to a magnetic field created by the coil 26, thereby moving the punch 28. Material 12 to be punched is associated with the punch 28. The coil is energized to create a magnetic field and thus lengthen the magnetostrictive member 22 so that the punch 28 moves through the material 12, creating a hole in the material 12.

Abstract: A pressing method by which through holes are formed using a punch in a target plate material that has a first face and a second face that is opposite to the first face, includes forming at least one first through hole by punching the target plate material from the second face with the punch in such an orientation that the first face of the target plate material is in contact with a base that is made of an elastic material, and forming at least one second through hole from the first face of the target plate material in a region, which is different from a region in which the at least one first through hole is formed, in such an orientation that the second face of the target plate material is in contact with the base.

Abstract: The invention involves a forming tool for a machine tool. The forming tool can be used, for example, to create various large forms in sheet metal or other workpieces.

Abstract: A hollow stepped article is formed from a solid blank to reduce the material cost, and cracking is prevented in a stepped portion of large diameter when a portion of the blank is deformed by its radial expansion.

Abstract: A method for perforating a sheet (1) with the aid of a stamp (3) and a matrix (2) is described, the sheet (1) being elongated before the hole punching in accordance with the setpoint diameter in the hole boundary area through bulging of the hole area. In order to be able to stamp flat perforated sheets, it is suggested that the sheet (1) be countersunk through embossing in the hole boundary area on the side diametrically opposite the matrix (2) after the hole punching to equalize internal tensions.

Abstract: It is an object of the present invention to provide a method of manufacturing a cylindrical part with a thin-walled portion at a lower cost, and according to the manufacturing method of the present invention, a base metal formed with thin-walled portion adjacent to its closed end can be easily detached from working jigs. According to the method, a thin-walled portion is at first formed by the ironing process on a cylindrical wall adjacent to the closed end, so that an outer-side step portion is formed on an outer peripheral surface of the cylindrical wall. Then the closed end is punched out and the thin-walled portion is enlarged in a radial and outward direction to form an inner-side step portion on an inner peripheral surface of the cylindrical part.

Abstract: A metal design panel is constituted by a surface decorative member and a thermoplastic resin member, which are firmly and integrally combined together. A plurality of through holes or dimples are formed at prescribed positions of a metal plate panel, which serves as a surface decorative member, in conformity with an outline of a product completed in manufacture. The metal plate panel is subjected to trimming to remove an unwanted peripheral portion, thus extracting a metal plate therefrom. The metal plate is arranged in a metal mold, into which a melted thermoplastic resin is injected to form a resin layer, which is firmly combined with the metal plate. Alternatively, a core member is formed and extracted from the metal plate panel and is combined with a resin layer upon injection molding.

Abstract: A number of holes (3) are formed in the outer circumferential wall (2) of a tubular metallic pipe (1) at regulator intervals in both circumferential and axial directions. Each of the holes (3) consists of a polygonal opening (4) and raised pieces (5) formed by bending the material from the peripheral edge surrounding the opening (3). This pipe may be used as an insert pipe in injection molding an article such as a lead screw, an optical fiber ferrule or the like. The raised pieces reinforce the part of the pipe surrounding each hole, and enhances the bonding between the molding material and insert pipe.

Abstract: Described is a method of manufacturing a crown-shaped component 3 having a plurality of axially extending protrusions 2 which are formed at an end of a cylindrical portion 1. The method comprises the steps of: upsetting the cylindrical portion into a cylindrical blank 10a having protrusions arrayed on and along the inner circumferential surface of a remaining part 12; annealing the cylindrical blank; removing the remaining part by cutting; and subjecting the resultant blank to a shot blasting process, whereby a magnetic characteristic of the resultant crown-shaped component is improved.

Abstract: A composite stripper for use in conjunction with an apparatus for joining multiple pieces of sheet metal or other sheet material is disclosed. The composite stripper is an elongated cylindrical member having a compliant distal engagement portion which is compressible to clamp sheet materials tightly together and a relatively hard proximate portion to provide an adequate interface between the punch assembly and the material to be joined.

Abstract: A punch and die tool for cutting a slug from a sheet of material that is retained in the opening of the die and does not adhere to or follow the punch on its upward stroke, and a method for retaining a slug in a die, are disclosed. The die is formed with one or more irregularities or grooves on the edge of the die face so that the slug cut by the operation of the punch and die will have a burr on its edge. The burr causes the slug to lodge in the inside surface of the die and prevents the slug from following the punch on its upward stroke.

Abstract: A seat belt anchorage plate for a seat belt device formed with a plate shaped member (base) 2 is provided with a slot 6 into which a belt (waist belt) 13 is inserted and which has long edge parts opposed with each other. The belt 13 is folded back along the one long edge part 691 of the opposed long edge parts in the slot 6 so that the one long edge part 691 bears the tension of the belt 13. The one long edge part 691 is formed so as to expand in the direction opposite to that of the tension of the belt 13 toward a central part from both ends in its longitudinal direction.