Abstract: The invention relates to a method for mounting elements when installing a wind turbine by hoisting to the nacelle, the hub inclusive the main bearing being mounted to the hub with fastening members such as bolts. The invention also relates to a nacelle for a wind turbine, said nacelle provided with a slot for accommodating a main bearing for the hub. The invention also relates to method for transporting elements of a wind turbine, said elements comprising a nacelle, a hub and a main bearing for the hub, and said method comprising assembling with fastening members, at the site of production or at another preliminary site of transportation, the hub and the main bearing.

Abstract: A method of manufacturing a rotor assembly in which a first impeller and a second impeller are fixed to a rotation shaft which is supported by a bearing so as to be rotatable, the method including: fixing the second impeller to the rotation shaft; fitting and fixing a sleeve to the rotation shaft after fixing the second impeller; fitting and fixing the bearing to the sleeve after fitting and fixing the sleeve; and fixing the first impeller after fitting and fixing the bearing.

Abstract: The invention relates to a device (1) and to a method associated with an assembly mechanism for a rotor system of an axial turbo engine having a central tension anchor, as is particularly known from engine technology. To this end, the invention provides a tensioning tool that pre-tensions or biases the tension anchor prior to and during the insertion of the anchor into the compound rotor assembly. After inserting the biased tension anchor in the compound rotor assembly, the tension anchor is relaxed, whereby the anchor exercises a compressive force on the compound rotor assembly. According to a preferred embodiment, the compound rotor assembly is also biased (compressed) and relaxed after assembling the tension anchor, so that a desired nominal bias Sigmanominal can be particularly easily achieved. The use of a shaft locking nut is no longer necessary in the device according to the invention, thus avoiding the difficulties that are associated with the use of this nut, such as complexity and safety problems.

Abstract: A method of manufacturing a steam turbine rotor which includes an ultra-high temperature side portion in which ultra-high temperature steam flows and a high temperature side portion in which high temperature steam flows, the manufacturing method including the steps of: preparing a first electrode having a chemical composition corresponding to a chemical composition of a heat resistant alloy making up the ultra-high temperature side portion and a second electrode having a chemical composition corresponding to a chemical composition of the high temperature side portion; tentatively joining together joints of the electrodes, with the joints of the electrodes made smaller in cross sectional area than other electrode portions; subjecting the tentatively joined first and second electrodes to an ESR process to obtain an ESR ingot and forging the ingot into a shape of a rotor to obtain a rotor forging; and heat-treating the rotor forging to obtain a rotor blank and manufacturing the steam turbine rotor from the rotor

Abstract: A method for erecting an offshore wind turbine at a wind turbine erection site is provided, wherein the wind turbine includes a rotor, which has, in a fully assembled condition, a predetermined number of rotor blades mounted to a rotor hub. The method comprises transporting the rotor hub to the erection site; transporting rotor blades to the erection site; and, mounting, on a vessel, rotor blades to the rotor hub so that the rotor is in the fully assembled condition. Further, a vessel having at least one flange for mounting a rotor hub is provided.

Abstract: The invention relates to a device for assembling a rotor of a wind turbine at sea. The device comprises a support structure that is provided with means for rotating the hub of a rotor around the hubs longitudinal axis. The support structure is further adapted to be connected to an offshore platform such that the rotating means may be positioned outside the periphery of the platform. The invention also relates to an assembly of an offshore platform and the device, connected thereto. The invention further relates to a method for assembling a rotor of a wind turbine at sea, and to a method of assembling a wind turbine at sea, using the device and assembly. The device and method provide a more efficient assemblage.

Abstract: A method of modifying an existing casting mold for a turbine moving blade having a shroud band segment with an initial coupling geometry for coupling with a further shroud band segment, the coupling geometry having an initial coupling angle of the shroud band segment relative to a circumferential direction of the turbine, includes calculating a modified coupling geometry for the shroud band segment, the modified coupling geometry including a modified coupling angle of the shroud band segment relative to the circumferential direction. The method further includes creating at least one of a removal zone and an application zone, wherein the creating of the removal zone includes removing a first amount of casting mold material from the removal zone and wherein the creating of the application zone includes applying a second amount of an additional casting mold material to the application zone, wherein the removing and the applying steps result in the casting mold having the modified coupling angle.

Abstract: The present invention relates to a Francis runner for a hydraulic machine that comprises a belt with a rotational symmetry about a central axis of the runner, a ceiling with a rotational symmetry about the axis, and a plurality of blades (21, 22) extending between the ceiling and the belt. The runner also includes at least two elements (41, 42, 43, 61, 62, 63) partially defining at least the belt and/or the ceiling while at least one edge (231, 232, 241, 242) of a blade (21, 22) is inserted between the two elements defining the belt and/or the ceiling.

Abstract: The present disclosure relates to a wind turbine (10) including: a rotor (18) including a rotatable hub (20) and a plurality of rotor blades (22), each of the plurality of rotor blades (22) being attached to the hub (20); and at least one airfoil body (120) including an aerodynamic profile (156) and an airfoil body root portion (122); wherein the aerodynamic profile (156) is configured for increasing aerodynamic lift of at least an inner portion of a rotor blade (22); and the at least one airfoil body (120) is attached to the hub (20) at the airfoil body root portion (122). In addition thereto, the present disclosure relates to an aerodynamic assembly (118) for a wind turbine (10) and a method of assembling a wind turbine (10).

Abstract: There is provided a method of manufacturing a rib for an aircraft wing, the method comprising providing a billet of material for forming the rib, machining away material from all sides of the billet to form a rib for use in an aircraft, the rib including a web that extends between first and second flanged portions, each flanged portion having a flange that facilitates fixing of the rib to another component of the aircraft, wherein the material that forms the web extends diagonally across the billet, the web having a first face on a first side and a second face on a second side opposite to the first side of the web, and the first flanged portion extends more to the first side of the web than to the second side and the second flanged portion extends more to the second side of the web than to the first side.

Abstract: The present invention relates to a service crane for a wind turbine comprising a nacelle and a hub. One or more wing blades is attached to the hub via a wing pitch bearing, and the service crane comprises an attachment foundation for connection to the hub. The service crane is adapted to be mounted on the wind turbine during operation and to be dismounted when not being used. The attachment foundation of the service crane is mounted on the hub of the wind turbine via the wing pitch bearing.

Abstract: A wind turbine blade assembly is provided. The assembly includes at least one wind turbine blade. The blade includes a blade root portion. The assembly also includes at least one blade root hub fitting coupled to the blade root portion. The blade root hub fitting is configured to couple to a rotatable hub.

Abstract: A shaped rotor wheel, a turbo machine including the rotor wheel, and a method for producing the same are disclosed. In an embodiment, a rotor wheel is provided which includes at least one disk member and at least one spacer member, and is a capable of carrying and axially spacing one or more stages of blades. Also disclosed is a method for producing such a rotor wheel using metal powders as a starting material, and processing the metal powder using powder metallurgy techniques.

Abstract: A clamp for clamping a blade for a wind turbine is provided. The clamp includes a first contact surface adapted to contact a portion of a surface of the blade and a second contact surface adapted to contact another portion of the surface of the blade. The second contact surface is displaceable relative to the first contact surface. The clamp also includes a bar connected in an adjustable orientation relative to the first contact surface. Further, a method of installing wind turbine blades at a hub rotatable around a rotation axis along a horizontal direction is provided.

Abstract: A method of manufacturing a turbine disk includes the steps of machining an initial slot using a cutting tool and machining intermediate and semi finished slot using a form tool that forms surfaces of the slot except for the bottom surface. A final finishing step utilizes a cutting tool that includes a shape that forms the bottom portion of the disk slot.

Abstract: A lock for constraining blades in a hub includes a flexible ring for constraining the blades from moving axially in the hub, a finger attached to the hub for preventing the ring from rotating relative to the hub and whereby the ring flexes about at least a partial circumference thereof if urged axially by the blades.

Abstract: A method for producing a rotor, particularly a turbine disk or a turbine ring for a turbine stage of a turbomachine, wherein at least the following steps are carried out: producing a blade ring (14) including a plurality of rotor blades (12), welding adapters (22) together which are disposed in the region of blade footings of the rotor blades (12), wherein at least substantially radial weld seams (30a) having predetermined welding depths are generated, disposing a rotor disk (32) or a rotor ring on the blade ring (14), and welding the rotor disk (32) or the rotor ring to the adapters (22) of the rotor blades (12), wherein at least one further weld seam (30b) is generated. A rotor, particularly a turbine disk or a turbine ring for a turbine stage of a turbomachine is also disclosed.

Abstract: A wind turbine includes a tower, a nacelle located adjacent a top of the tower, a rotor coupled to the nacelle, and a dynamic vibration damper coupled to the tower and configured to dampen vibrations induced in the tower in a torsional direction while negligibly effecting vibrations induced in the tower in bending directions. The dynamic vibration damper may be tuned to a resonant frequency of the wind turbine in the torsional direction. A method of retrofitting a wind turbine with a vibration damper is also disclosed.

Abstract: A turbine is described. The turbine includes: (i) a shaft capable of rotation along its longitudinal axis and capable of connecting to an electrical generator, and the shaft having disposed thereon at least one shaft hinge; (ii) a radial arm including a first end having disposed thereon at least one first hinge; and a hinge pin that fits inside a cavity formed when at least one the shaft hinge of the shaft is in an engaged position with at least one first hinge of the radial arm, and in the engaged position the hinge pin capable of connecting the radial arm to the shaft.

Abstract: A process of fabricating rotating hardware and rotating hardware formed thereby. The process includes fabricating at least two members that together define at least two portions of a component. Each member has an interface surface at which the members can be joined to locate a first of the portions in a radially outward direction from a second of the portions. The members are joined together so that the interface surfaces thereof form a joint interface located within a pad region that has a axial thickness that is greater than a contiguous region of the component. The joint interface is not perpendicular to the axial and radial directions of the component. The pad region is defined by embossments that are offset from each other in the radial direction of the component so as to partially but not completely overlap each other in the axial direction of the component.

Abstract: A method of attaching a labyrinth seal support to a turbine engine shaft is disclosed. The method includes inserting axial bolts to secure the labyrinth seal support, the shaft and a device for driving the turbine module with the shaft, and screwing tightening screws in extracting holes, for extracting the drive device with respect to the shaft, provided on the shaft to tighten the labyrinth seal support onto the shaft.

Abstract: A modular rotor blade hub for a wind turbine rotor includes a plurality of segments, wherein at least one segment includes at least one face abutting against at least one face of at least one adjacent segment, and wherein at least one of said faces extends from an outer periphery of the hub to a central region of the hub. Further, methods for mounting a wind turbine including a modular hub are provided.

Abstract: A method of assembling a rotor lock assembly for use in a wind turbine. The wind turbine includes a rotor rotatably coupled to a generator by the rotor shaft. The generator and the rotor shaft are supported from a bedplate frame. The rotor shaft includes a rotor lock disk. The method includes coupling a support frame to the bedplate frame. The support frame is positioned adjacent to the rotor lock disk. A plurality of lock pin housings are coupled to the support frame. Each lock pin housing of the plurality of lock pin housings is positioned with respect to the rotor lock disk. A plurality of lock pins is provided. Each lock pin of the plurality of lock pins is configured to engage the rotor lock disk. Each lock pin is coupled between a corresponding lock pin housing of the plurality of lock pin housings and the rotor lock disk to facilitate limiting a rotation of the rotor shaft.

Abstract: A wind turbine, tower and method for making same are provided. The wind turbine includes a rotor having one or more blades and a rotor radius distance approximately equal to the distance measured from a centerline of the rotor to a tip of one of the blades. The tower has one or more tower sections, including a first tower section having a generally cylindrical or frusto-conical shape. The first tower section has at least one first diameter. A reduced diameter tower section is connected to the first tower section, and has a waist portion with at least one second diameter that is smaller than the first diameter. At least a portion of the reduced diameter tower section having the second diameter is located about one rotor radius distance from the centerline of the rotor, and the reduced diameter section provides increased static clearance to the tip of the blades.

Abstract: An apparatus and method for a turbine wheel assembly for a pneumatic rotary vibrator that provides a selectable force output while being removably retained on a vibrator shaft member. The turbine wheel assembly is mounted inside of a generally circular interior chamber of a pneumatic vibrator housing. The turbine wheel assembly includes: (1) a turbine ring that has an outside diameter, an inside diameter and a face width, (2) a sleeve member that is round and tubular, (3) an intermediate weight ring assembly that has an outer circumference, an inner circumference, and a predetermined face width, The weight ring assembly is formed by a plurality of wedge shaped segments.

Abstract: The present invention relates to a method of generating tightly intermeshing, self-cleaning, co-rotating screw profiles, the use of the screw profiles in screw and transition elements, novel screw profiles which have been generated by the method and a computer program product for executing the method in a computer system.

Abstract: The present invention provides a manufacturing method for an impeller with which molding and high-quality finishing can be performed extremely easily and quickly through resin molding using a die, and an impeller manufactured by the impeller manufacturing method. A metallic bush is disposed in a die, whereupon a resin material is injected through a gate in the die. A connecting portion between an unnecessary resin portion formed from residual resin material in the gate and a resin impeller main body molded around the bush is formed to be thin, and the unnecessary resin portion is removed from the impeller main body using pushing or withdrawing means.

Abstract: A Pelton turbine is disclosed that includes at least one needle valve injector assembly and at least one high efficiency injector assembly. The high efficiency injector assembly provides a generally unimpeded flow path for water from a distributor to a runner of the turbine. The high efficiency injector assemblies and needle valve injector assemblies are operated in cooperation to provide the overall desired flow rate through the turbine and to increase the efficiency of the turbine. A high efficiency injector assembly may be retrofitted for a needle valve injector assembly to improve the efficiency of existing turbine systems.

Abstract: An apparatus and method for balancing a gas turbine engine rotor includes a plurality of balancing weights adapted to be selectively attached to at least one of inlets or outlets of a cooling passage of the rotor. The weights include cooling access which permits coolant to communicate with the cooling passage.

Abstract: A balancing weight clip with a mass adapted to balance a rotor assembly of a gas turbine engine, includes a weight portion, a first flange engaging portion and a second flange engaging portion extending from the weight portion, each being engageable with a sidewall of at least one recess located on an edge of a flange of a disc of the rotor assembly. Each flange engaging portion is provided with a hook engageable with a mating groove provided on a face of the flange. At least one of the first and second flange engaging portions is resiliently biased so that the first and second flange engaging portions are elastically moveable away from one another to removably secure the balancing weight clip to the flange and engage each hook with the mating groove.

Abstract: A method of making a multiple alloy, multi-section welded turbine rotor includes providing a forged multiple alloy rotor section having an integral microstructure, the rotor section comprising a first alloy having a first alloy composition and second alloy having a second alloy composition, a first weld face comprising the first alloy on a first end and an a second weld face comprising the second alloy on an opposed second end. The method also includes providing a first rotor section comprising the first alloy composition and a second rotor section comprising the second alloy composition. The method also includes welding the first rotor section to the first weld face and welding the second rotor section to the second weld face.

Abstract: A fan is disclosed herein. The fan includes a hub portion operable to rotate about an axis. The hub portion extends along the axis between forward and aft ends. The fan also includes at least one platform operably fixed with the hub portion. The at least one platform at least partially encircles the axis. The fan also includes at least one airfoil extending from the at least one platform radially outward relative to the axis between a base and a tip. The at least one platform terminates at forward and aft circumferential edges spaced from one another along the axis. At least one of the forward and aft circumferential edges extends about the axis and along the axis.

Abstract: The specification discloses a rotating turbine tower. The tower rotates to maintain the turbine facing into the wind. This allows structure optimization. The tower structure is comprised of a leading edge and a trailing edge, with joining panels between the edge structures. The tower edges are the main structural components of the tower. The separation of the edges tapers to follow the bending moment on the tower, reducing the need to taper material thickness. The tapering shape of the tower structure matches the primary edgewise moment distribution. The tower can be assembled on site from components, thereby facilitating transportation to the tower site. The material properties and shape can be selected based upon the tower maintaining a near constant orientation with the wind. This can save weight and costs. The tower architecture can be of differing shapes such as a triangle or a structure tapering at each end.

Abstract: A method of manufacturing an aerofoil structure to have a portion with an increased erosion resistance, the method comprising: providing one or more titanium elements (2, 4, 6) and a beta-stabilizing material (8); wherein the one or more elements (2, 4, 6) have an alpha-beta microstructure; assembling the one or more elements (2, 4, 6) and the beta-stabilizing material (8) such that the beta-stabilizing material (8) is adjacent to the one or more elements (2, 4, 6); and heating the assembly such that the beta-stabilizing material (8) diffuses into an adjacent portion of the one or more elements (2, 4, 6), causing the adjacent portion of the one or more elements (2, 4, 6) to have a beta microstructure which provides an increased erosion resistance.

Abstract: The invention relates to a process for manufacturing a blade connection of a rotor blade for a wind energy system which comprises fastening elements for fastening the blade connection to a hub, which fastening elements are provided on a circular arc, preferably equidistant from each other. Furthermore, the invention relates to a blade connection and a fastening element for a blade connection. The invention is based on the problem of improving the fastening of a rotor blade on the hub of a wind energy system as well as improving the manufacture and/or making a suitable blade connection available. The invention solves this problem as regards the process in that fastening elements formed in pieces are arranged on the circular arc and spaced from each other with spacer elements.

Abstract: A mobile wind power station includes a wind turbine secured to a tower. A base of the tower is coupled to a support, which includes a mobile, surface-mounted pedestal and a plurality of bolts. The plurality of bolts extend upwardly from the mobile, surface-mounted pedestal and are received in the base of the tower.

Abstract: A bushing (30, 31) in a hole (26) through a ceramic matrix composite structure (20) with a flange (34, 38) on each end of the bushing (30, 31) extending beyond and around the hole and pressing against opposed surfaces (22,24) of the CMC structure (20) with a preload that resists buckling of the composite structure fibers and resists internal CMC fiber separation. A connecting element (40), such as a bolt or pin, passes through the bushing (30, 31) for engagement with a supporting element (50). The bushing (31) may be formed in place as a single piece of ceramic, and cured along with the CMC structure (20), or it may be formed as two ceramic or metal parts (32, 36) that are joined together and preloaded by threads (33). The connecting element (40) may be a pin, or it may be a bolt with a shaft threaded into one part (32) of the bushing and a head (42) that pushes the second flange (38) toward the first flange (34).

Abstract: A method of making an ice dispense agitator of a type as may be used in ice and beverage dispensing machines is characterized by manufacturing the agitator as an integral unit by cutting the agitator from flat metal stock and then bending the agitator into a desired final shape.

Abstract: The invention proposes a process for producing components (10) or semi-finished products which contain intermetallic titanium aluminide alloys, which includes the following process steps: rough contouring of a plurality of plate-like bodies (11) so as to correspond to a desired final shape of the component (10) or semi-finished product, some of these plate-like bodies or all the plate-like bodies consisting of titanium aluminide alloys; carrying out surface-to-surface joins between the plurality of plate-like bodies (11) stacked on top of one another so as to form an overall body (10); and forming the desired final shape of the overall body (10). The invention also concerns a component, in particular for jet engines, which is produced using this process.

Abstract: A method for providing a disc of a bladed rotor for use in a gas turbine engine including the steps of determining the location of blade fixing slots to be formed on the disc to receive the roots of respective blades, determining a virtual profile of each slot on the disc, and forming, prior to the slots being formed in the disc, a narrow, axial pilot slot centrally of the virtual profile of each slot.

Abstract: Quick attachable and detachable mounting arms for ceiling fans. A first version has flat headed fasteners initially attached to one end of mounting arms, with key-hole slots in the endshield of the ceiling fan motor. The user raises the mounting arm so that the flat headed fasteners fits through the larger openings in the keyhole slots and then pulls the mounting arm outward until the arm locks in place by the smaller opening portions of the keyhole slots. Rubber type gaskets and washers help lock and hold the mounting arms in place. The flat headed fasteners can also be located on the endshields with the keyhole slots on mounting arms. A second embodiment includes inwardly deformable springably snapable fasteners that can be located on the ends of the mounting arms which can deform inwardly and expand after passing through slots on the endshield of the rotor. Alternatively, the fasteners can be located on the bottom of the endshield with the receiving slots on the ends of the mounting arms.

Abstract: An air cleaner including an improved airflow path is provided according to the invention. The air cleaner includes a duct extending between an air inlet of the air cleaner and an air outlet, with the duct being configured to conduct an airflow. The duct includes a shaped input region located downstream of one or more air cleaning components and upstream of an impeller, a curved transition region downstream of the shaped input region, with the curved transition region transitioning the airflow from an air inlet orientation to an air outlet orientation, and an expansion output region downstream of the curved transition region, with the expansion output region allowing the airflow to expand. The air cleaner further includes the impeller located in the curved transition region of the air duct. The airflow is smoothly conducted from the air inlet to the air outlet by the duct.

Abstract: A variable chord morphing helicopter rotor blade is disclosed. The variable chord morphing helicopter rotor blade includes an extensible quasi-static chord section connected to the rotor blade, an adjusted airfoil chord length of the rotor blade corresponding to extension of the quasi-static chord section relative to a baseline airfoil chord length, the adjusted airfoil chord length determined according to helicopter flight conditions.

Abstract: A fan includes a hub, several fan blades, and a motor that is operable to drive the hub. A motor controller is in communication with the motor, and is configured to select the rate of rotation at which the motor drives the hub. The fan is installed in a place having a floor and a ceiling. An upper temperature sensor is positioned near the ceiling. A lower temperature sensor is positioned near the floor. The temperature sensors communicate with the motor controller, which includes a processor configured to compare substantially contemporaneous temperature readings from the upper and lower temperature sensors. The motor controller is thus configured to automatically control the fan motor to minimize the differences between substantially contemporaneous temperature readings from the upper and lower temperature sensors. The fan system may thus substantially destratify air in an environment, to provide a substantially uniform temperature distribution within the environment.

Abstract: With a method for surface strengthening and smoothening of metallic components, in particular of rotors or rotor drums (7) with integral blading for aircraft engines, the components are loaded in a vessel (2) which is filled with strengthening elements (10). A tumbling movement is performed by which the metallic components are strengthened and smoothened by a relative movement between the workpiece surface and the strengthening elements in one process step. The strengthening elements (10) have a circumferential, rounded edge area, or compressive strengthening area (13) for strengthening the surface, and, extending therefrom on both sides, a flatly curved smoothening area (14) for smoothening the surface roughened by strengthening. With low time and apparatus investment, workpieces can be provided that feature high fatigue strength and advantageous aerodynamic properties.

Abstract: Method for establishing a wind turbine (1) on a foundation (7) where at least a part of the wind turbine rotor (4) means is attached to a wind turbine tower (2) by attachment means. Further the method comprises the steps of positioning said wind turbine tower including said at least a part of the wind turbine rotor means on the foundation, elevating a wind turbine nacelle (3) to a use position on said tower, and directly or indirectly connecting said nacelle to said at least a part of the wind turbine rotor means. The invention also relates to transport of a wind turbine tower, and a vessel (10) suitable for transporting a wind turbine tower.

Abstract: A vertical axis turbine and method of making same is disclosed. The device and method comprise a plurality of blades rotatably disposed around an axis of rotation at a plurality of blade locations, each blade being twisted at a first angle about its longitudinal axis, each blade having its distal ends located a predetermined distance from the axis of rotation, each blade being bent at one or more central locations along the longitudinal axis so the one or more central locations are the same predetermined distance from the axis of rotation as the distal ends, each blade having a foil cross section perpendicular to the axis of rotation for maintaining unidirectional rotation of that blade about the axis of rotation in a fluid flow, and each blade having its longitudinal axis tilted at a second angle with respect to the axis of rotation.

Abstract: Embodiments of the invention can provide systems, methods, and an apparatus for thermally isolating a turbine rotor wheel. According to one embodiment, a method for thermally isolating a turbine rotor wheel can be provided. The turbine rotor wheel can include a pair of blade posts, or shanks, supporting respective turbine rotor blades such that a shank cavity is formed between respective blade posts. To thermally isolate the turbine rotor wheel, at least one seal operable to partition the shank cavity into an upper region and a lower region can be provided. In addition, this seal can be inserted within the shank cavity to partition the shank cavity into an upper region and a lower region. In doing so, cooling air flow can be divided between the upper region and the lower region so that the lower region can be maintained at a lower temperature than the upper region.

Abstract: The invention relates to a rotor disk for the rotor of a non-positive displacement machine with at least one borehole extending in an axial direction. The aim of the invention is to provide a rotor disk for a non-positive displacement machine that has an increased serviceable life. To this end, the boring extends in an at least partially convex manner whereby having an enlarged diameter in the middle area in order to increase internal compressive stress an to reduce tangential stresses.

Abstract: A fan assembly comprises a frame and a securing element. The frame has a first end portion, a second end portion and a middle portion. The foam securing element comprises a positioning hole having a first hole having a shape corresponding to the first end portion, a second hole having a shape corresponding to the second end portion, and a third hole having a cross section larger than that of the second hole. When the second end portion is inserted into the first hole, the second end portion and the middle portion pass through the first hole and the first end portion urges against the periphery of the second hole to receive the second end portion in the third hole. The second end portion of the frame is stopped by a periphery of the positioning hole after rotating at a predetermined angle so that the frame is positioned.