WO 2012/015058 PCT/JP2011/067575 DESCRIPTION Backward Tension Applying Mechanism for Twisting Paired Electric Wires and Method for Fabricating Twisted Pair Cable by Employing 5 Backward Tension Applying Mechanism Technical Field The present invention relates to a backward tension applying mechanism for twisting paired electric wires at equal pitches without 10 any slack to make a twisted pair cable that is excel in signal protection against electrical noise, and a method for fabricating a twisted pair cable by employing the same mechanism. Background Art 15 Conventionally, there have been proposed various fabrication configurations for fabricating the twisted and paired electric wires (twisted pair cable) by twisting together paired electric wires. For example, PTL1 describes a twisted pair cable fabrication configuration in which connectors connected to ends of paired electric wires are 20 fixed to corresponding receiving jigs, the paired electric wires are respectively inserted into electric wire insertion grooves in a central driven gear, and the driven gear is rotated by a drive gear to twist together the paired electric wires. 25 In addition, PTL2 describes, as a conventional example, a 1 WO 2012/015058 PCT/JP2011/067575 twisted pair cable fabrication configuration in which terminals at one ends of paired electric wires are fixed to a stationary member, while terminals at the other ends are fixed to a rotary member, and the paired electric wires are twisted together by rotating the rotary 5 member. As one embodiment, a configuration is described in which paired electric wires are fed out towards the other end side of the paired electric wires while one end portion of each of the paired electric wires are twisted respectively within cylindrical portions, and a rotor at an intermediate portion is fed out towards the other end side 10 while being rotated in the same direction as the direction of the twisting at the one end portions so as to twist together the paired electric wires. Additionally, PTL3 describes a twisted pair cable fabrication 15 configuration in which one ends of paired electric wires are respectively fixed to corresponding clamps at the one end, the other ends of the paired electric wires are respectively connected to corresponding clamps at the other end, the clamps at the other end are respectively pulled by corresponding cylinders, and the clamps at 20 both the ends are respectively rotated in opposite directions by corresponding motors so as to form a twisted pair cable. In addition, PTL4 describes a twisted pair cable fabrication configuration which employs pairs of electric wires which are different 25 in length. One ends of the pairs of the electric wires are fixed to a 2 WO 2012/015058 PCT/JP2011/067575 common clamp, while the other ends of the long electric wire and short electric wire are respectively connected to corresponding clamps. The clamp for the short electric wire can move forwards and backwards. Then, the clamps connected to the other ends are rotated by motors to 5 form the pairs of electric wires which are different in length. Citation List Patent Literature [PTL 1] JP-A-2000-149684 (Fig. 1) 10 [PTL 2] JP-A-2007-227185 (Figs. 1 and 4) [PTL 3] JP-A-2005-149966 (Fig. 4) [PTL 41 JP-A-2004-362881 (Fig. 11) Summary of Invention 15 Technical Problem However, in the prior arts that are described in PTL1 to PTL4, in a case in which paired electric wires are twisted together as is shown in an example in Figs. 7(a) and (b), there would be caused the following possibility. In Fig. 7(a), one ends of paired electric wires 61 20 are connected together to a common clamp 62, while the other ends of the paired electric wires 61 are connected to corresponding clamps 63. Then, the paired electric wires 61 are twisted together by rotating an intermediate rotor 64, for example, in such a state that a backward tension (a tensile force) is applied to the paired electric wires 61 on 25 the common clamp 62 side. As this occurs, since there exists 3 WO 2012/015058 PCT/JP2011/067575 variation within a permitted tolerance in length to which the paired electric wires 61 were cut, the paired electric wires 61 are twisted together with the longer electric wire 611 being slackened slightly, and the variation in length of the paired electric wires 61 is absorbed in a 5 twisted portion as is shown in Fig. 7(b). This deteriorates the accuracy of pitch at which the electric wires 61 are twisted, and therefore, it has been unable to ascertain that twisted portions 61a are uniform in condition irrespective of their positions along the length of a completed twisted pair cable 61'. Because of this, the quality of the 10 completed twisted pair cable 61' needs to be guaranteed by measuring an inter-wire gap and characteristic impedance. In Fig. 7(b), reference numeral 65 denotes a terminal connected to both the ends of the paired electric wires 61. 15 Solution to Problem The present invention has been made in view of the situations that are described above, and it is an object of this invention to provide a backward tension applying mechanism for twisting paired electric wires, which can form a twisted pair cable with good quality 20 which is twisted at uniform pitches without involving any slack by devising the way to apply backward tension, even in a case in which there exists variation in length of paired electric wires and a method for fabricating the twisted pair cable by employing the same mechanism. 25 4 WO 2012/015058 PCT/JP2011/067575 In order to achieve the object, according to a first aspect of the present invention, there is provided a backward tension applying mechanism for twisting paired electric wires, comprising a pair of electric wire clamps, a pair of movable base plates to which the pair of 5 electric wire clamps are respectively fixed, a common stationary base plate with which the pair of movable base plates are brought into engagement so as to be slidable in a longitudinal direction of the electric wires along guide rails, and a pair of air cylinders which applies backward tension to connect the common stationary base 10 plate with the pair of movable base plates. According to the configuration, one ends of paired electric wires are connected to the pair of electric wire clamps, while the other ends of the paired electric wires are fixed to other electric wire clamps. 15 Then, the pair of air cylinders are actuated, and the pair of electric wire clamps are caused to move backwards respectively relative to the common stationary base plate by the pair of movable base plate, whereby the paired electric wires are pulled respectively relative to the other electric wire clamps so as to absorb slack therein. Then, in 20 this state, the paired electric wires are twisted together at equal pitches without involving any slack (looseness). According to a second aspect of the present invention, there is provided a method for fabricating a twisted pair cable by employing 25 the backward tension applying mechanism defined in the first aspect 5 WO 2012/015058 PCT/JP2011/067575 of the present invention, comprising the steps of fixing one end portions of paired electric wires by the pair of electric wire clamps, fixing the other end portions of the paired electric wires by the other electric wire clamps, actuating the pair of air cylinders so as to cause 5 the pair of electric wire clamps to move backwards respectively relative to the common stationary base plate by the pair of movable base plates and pull the paired electric wires respectively relative to the other electric wire clamps; and twisting the paired electric wires in that state. 10 According to the configuration, the one end portions of the paired electric wires are fixed by the pair of electric wire clamps, and the other end portions of the paired electric wires are fixed by the other electric wire clamps. Then, the pair of air cylinders are 15 actuated so that the pair of electric wire clamps caused to move backwards respectively relative the common stationary base plate by the pair of movable base plates so as to absorb slack in each of the paired electric wires. Then, in this state, the paired electric wires are twisted together at equal pitches without involving any slack 20 (looseness). The twisting of the paired electric wires is implemented, for example, by rotating the other electric wire clamps by a motor, by turning the paired electric wires by a rotor between the pair of electric wire clamps and the other electric wire clamps, or by rotating the other electric wire clamps by the motor, while rotating the rotor, in the same 25 direction and rotation speed as the rotor. The other electric wire 6 WO 2012/015058 PCT/JP2011/067575 clamps may be paired up with each other or a common electric wire clamp may be adopted to fix the other end portions of the paired electric wires. 5 Advantageous Effects of Invention According to the first aspect of the present invention, even though the paired electric wires have different lengths, the paired electric wires can be twisted together in such a state that the paired electric wires are stretched tight by absorbing slack therein by pulling 10 respectively the paired electric wires by the corresponding air cylinders. By adopting this configuration, even in a case in which there exists variation in length of paired electric wires, it is possible to form a twisted pair cable with good quality in which the paired electric wires are twisted together at uniform pitches without involving any 15 slack. According to the second aspect of the present invention, even though the paired electric wires have different lengths, the paired electric wires can be twisted together in such a state that the paired 20 electric wires are stretched tight by absorbing slack therein by pulling respectively the paired electric wires by the corresponding air cylinders. By adopting this configuration, even in a case in which there exists variation in length of paired electric wires, it is possible to form a twisted pair cable with good quality in which the paired electric 25 wires are twisted together at uniform pitches without involving any 7 WO 2012/015058 PCT/JP2011/067575 slack. Brief Description of the Drawings Fig. 1 is a perspective view showing an embodiment of a 5 backward tension applying mechanism according to the present invention. Fig. 2 is a perspective view showing electric wire clamps of the backward tension applying mechanism. Fig. 3 is a perspective view showing a state in which backward 10 tension is applied to electric wires in the backward tension applying mechanism. Fig. 4 is a perspective view showing one mode of other electric wire clamps which are disposed at an opposite side to the side where the backward tension applying mechanism is disposed. 15 Fig. 5(a) is a schematic plan view showing one mode of a method for fabricating a twisted pair cable, and Fig. 5(b) is a schematic plan view showing a completed twisted pair cable. Fig. 6 is a perspective view showing one mode of a twisted pair cable-fabrication-apparatus to which the backward tension applying 20 mechanism is applied. Fig. 7(a) is a schematic plan view showing one mode of a conventional method for fabricating the twisted pair cable, and Fig. 7(b) is a schematic plan view showing the completed twisted pair cable. 25 8 WO 2012/015058 PCT/JP2011/067575 Description of Embodiments Figs. 1 to 3 show one embodiment of a backward tension applying mechanism for twisting paired electric wires according to the present invention. 5 As shown in Fig. 1, a backward tension applying mechanism 1 for twisting paired electric wires includes a pair of left and right electric wire clamps 2, a pair of left and right strip-like movable base plates 3 on which the electric wire clamps 2 are installed respectively, 10 a rectangular common stationary base plate 5 having a pair of left and right guide rails 4 with which the movable base plates 3 are respectively brought into slidable engagement, and a pair of left and right long air cylinders 6 which are provided at left- and right-hand sides of the common stationary base plate 5 and of which distal ends 15 of rods 6a are fixed to front ends of the corresponding movable base plates 3 via corresponding brackets 7. The clamps 2, movable base plates 3, rails 4, air cylinders 6 and brackets 7 are each disposed symmetrically widthwise. Each of 20 the clamps 2 has a horizontal electric wire insertion groove 9 having a terminating end face (a rear end face) 9a which is disposed symmetrically widthwise with a terminating end face (a rear end face) 9a of a horizontal electric wire insertion groove 9 in the other clamp 2 and with which a distal end 8a of each of a pair of left and right electric 25 wires 8 is brought into abutment, a block portion 10 in an upper 9 WO 2012/015058 PCT/JP2011/067575 surface of which the electric wire insertion groove 9 is provided, a cutout portion 10c provided in an external vertical side-wall 10b of the block portion 10 at a front portion of the electric wire insertion groove 9, a vertically elongated movable electric wire holding plate 11 which 5 enters the cutout portion 10c so as to fixedly hold a distal end portion of the electric wire 8 between an inner surface of a vertical inner wall 10d of the block portion 10 and itself, a compression coil spring (a spring member) 12 which biases the electric wire holding plate 11 towards the internal wall 10d of the block portion 10, an operation 10 lever 13 which can move forwards and backwards and which is formed into an L-shape at a rear end thereof, and wedge-shaped portions 14 (refer to Fig. 2) which are formed integrally on a front portion of the operation lever 13 to press the electric wire holding plate 11 outwards against the biasing force of the coil spring 12 so as to form a gap 15 which is equal to or larger than a diameter of the electric wire between the electric wire holding plate 11 and the internal wall 1Od of the block portion 10. The movable base plates 3 are disposed so as to lie close 20 widthwise to each other, and the clamps 2 are disposed so as to lie close widthwise to each other. The movable base plates 3 and the clamps 2 are both separated widthwise from each other with respect to a central narrow gap 15 as a boundary. The clamp 2 is disposed on a front half of the corresponding movable base plate 3, and one of a pair 25 of left and right short air cylinders 16 is disposed on a rear half of the 10 WO 2012/015058 PCT/JP2011/067575 movable base plate 3 concerned. The pair of air cylinders 16 are designed to automatically release the fixing of the electric wires by the clamps 2. In a state shown in Fig. 1 in which the electric wires are fixed (set) in place, distal ends of rods 16a of the short air cylinders 16 5 are in abutment with rear end faces 13a of the operation levers 13 which has retreated. The air cylinders 16 are disposed so as to lie close widthwise to each other and are separated widthwise from each other with respect to a central gap 17 as a boundary. 10 The common stationary base plate 5 is formed wider than a total width of the pair of left and right movable base plates 3, and the pair of left and right guide rails 4 are disposed so as to extend from a rear end 5a to a position lying further forwards than a front end 5b of the common stationary base plate 5 by passing the front end 5b (with 15 front end portions of the guide rails 4 so extending denoted by reference numeral 4a). In addition, sliding engagement portions 18 are provided on respective rear surfaces of the movable base plates 3 so as to be brought into slidable engagement with the corresponding guide rails 4. A stopper plate 20 is erected at the rear end 5a of the 20 common stationary base plate 5, and this stopper plate 20 has a pair of left and right stopper projections 20 with which stopper projections 19 at rear ends of the movable base plates 3 are brought into abutment. 25 Cylinder main bodies 6b, having a hollow cylindrical shape, of 11 WO 2012/015058 PCT/JP2011/067575 the pair of left and right backward tension applying air cylinders 6 are fixedly disposed at left- and right-hand sides of a front surface of the common stationary base plate 5 in positions which lie further outwards widthwise than the pair of movable base plates 3 so as to extend 5 longitudinally from the rear end to the frontend of the common stationary base plate 5. The respective rods 6a of the air cylinders 6 project long towards the front and are then connected respectively to brackets 7 which project widthwise at respective front ends of the movable base plates 3. In a state shown in Fig. 1 in which the rods 10 6a of the air cylinders 6 are extended, no backward tension is applied to the electric wires 8, and therefore, the electric wires 8 hang down loosely. The clamps 2 are closed to hold the electric wires 8 side by side widthwise at the same height. 15 Fig. 2 shows a state in which the clamps 2 are each opened. In the state shown in Fig. 2, when the operator inserts one end portions of the electric wires 8 (See, Fig. 1) into the electric wire insertion grooves 9 in the clamps 2 and pulls the operation levers 13 backwards, the tapered wedge-shaped portions 14 retreat together 20 with the operation levers 13, whereby the gaps between the inner walls 10d and the holding plates 11 in the block portions 10 are narrowed down to a gap equal to or smaller than the diameter of the electric wire, and the electric wires 8 are fixedly held between the inner walls 10d and the holding plates 11 by virtue of the biasing 25 forces of the coil springs 12. 12 WO 2012/015058 PCT/JP2011/067575 The respective rods 6a of the air cylinders 6 are retracted into the corresponding cylinder main bodies 6b by virtue of respective air pressures of the air cylinders 6 as is shown in Fig. 3 from the state 5 shown in Fig. 1, whereby the movable base plates 3 move backwards along the corresponding guide rails 4 together with the corresponding rods 6a. Then, the clamps 2 move backwards together with the corresponding movable base plates 3, whereby backward tension is applied respectively to the electric wires 8 by the corresponding 10 clamps 2. Even though lengths of the electric wires 8 vary, by applying the backward tension respectively to the electric wires 8 in the way described above, tensile forces applied to the electric wires 8 are 15 made uniform (that is, the electric wires 8 are pulled with equal forces), whereby the generation of slack due to the difference in length between the electric wires 8 is prevented. Respective plugs 6c of the air cylinders 6 may be connected to a common air pressure hose. In Fig. 3, the respective rods 6a of the air cylinders 6 are not compressed 20 completely but still project leaving an extra stroke to some extent, so that backward tension can be applied to an electric wire 8 which is longer than expected. Fig. 3 shows a state in which the electric wires 8 are set at one 25 ends thereof. The other ends of the electric wires 8 are fixed 13 WO 2012/015058 PCT/JP2011/067575 separately by a pair of left and right cylindrical electric wire clamps (other electric wire clamps) 21, for example, as is shown in an example in Fig. 4. The clamps 2 shown in Fig. 4 each include a cylindrical wall 22, an electric wire insertion groove 23 provided in the 5 cylindrical wall 22 and having an electric wire abutment surface 23a at a terminating end, a holding portion 24 which holds an end portion of the electric wire 8 inserted in the electric wire insertion groove by virtue of a biasing force of a spring, and an L-shaped operation lever 25 which lies at right angles to the cylindrical wall and which opens the 10 holding portion 24 against the biasing force of the spring. The clamps 2 are fixed to a common rotary plate 26 while lying side by side widthwise, and the rotary plate 26 is connected, in turn, to a motor 27, whereby the clamps 2 and the rotary plate 26 rotate together by driving the motor 27. The motor 27 is fixed to a base plate 28 via 15 short strut 29. One mode of a method for fabricating a twisted pair cable by employing the backward tension applying mechanism described above is shown in Fig. 5(a). As shown Fig. 5(a), front and rear ends of a 20 long electric wire 81 and a short electric wire 82, which are eventually cut to different lengths which fall within a permitted cutting tolerance, are fixed in place respectively by the front and rear clamps 2, 21. The front (or other) clamps 21 are disposed side by side widthwise without being offset in a front-to-rear direction, whereby the front end 25 positions of the electric wires 8 are regulated equally by the clamps 21. 14 WO 2012/015058 PCT/JP2011/067575 The rear clamps 2 are caused to move slidingly backwards by the corresponding air cylinders 6 (See Fig. 3), and the rear clamp 2 holding the long electric wire 81 and the rear clamp 2 holding the short electric wire 82 are positioned so as to be spaced apart in the 5 front-to-rear direction from each other, with the former rear clamp 2 positioned rearwards and the latter rear clamp 2 positioned forwards, whereby backward tension is applied respectively to the electric wires 8 which are so fixed to the corresponding rear clamps 2. 10 In this state, for example, a rotor 30, which is disposed close to the clamps 2 at the rear ends of the electric wires 8, is caused to move towards the front clamps 21 at a constant speed while rotating in one direction as is indicated by an arrow. At the same time, the front clamps 21 are rotated by the motor 27 (See Fig. 4) in the same 15 direction and at the same speed as the rotor 31. Thus, the paired electric wires 8 are twisted together between the rear clamps 2 and the rotor 30. While twisting the paired electric wires 8, as is shown in Fig. 20 5(b), the permitted cutting tolerance between the paired electric wires 8 is absorbed at a non-twisted portion 8c on the side where the backward tension is loaded to the electric wires 8 (the side of the rear end portions of the electric wires 8). Then, since the long electric wire 81 has an extra longer length L than the short electric wire 82 at 25 the end portion, pitches P between twisted portions 8d of the paired 15 WO 2012/015058 PCT/JP2011/067575 electric wires 8 are made uniform, and therefore, there is completed a twisted pair cable which is twisted at uniform pitches P and in a neat fashion at every twisted portion 8d. 5 Thus, since the performance of a product (a twisted pair cable 8') can be guaranteed only by measuring pitches P by the operator, the conventionally performed measurement of inter-wire gap and characteristic impedance is made unnecessary. In Fig. 5(b), reference numeral 31 denotes a terminal which is electrically 10 connected to the front and rear ends of the electric wires 8 through press contact. In Fig. 3, although the lengths of the electric wires 8 are reduced while the paired electric wires 8 are being twisted, the value 15 (N) of backward tension being applied can be controlled by the air pressures of the backward tension applying air cylinders 6 by regulating (controlling) the air pressures of the air cylinders 6 by an air regulator. The rods 6a of the air cylinders 6 do not extend, and the value of backward tension is regulated by the air pressures. Air 20 pressures are applied to the air cylinders 6 so as to realize a value of backward tension which is predetermined depending upon the diameter or type of electric wires used, and the regulation is completed when a prescribed air pressure is reached. 25 After the paired electric wires 8 are twisted as desired, the rods 16 WO 2012/015058 PCT/JP2011/067575 6a of the air cylinders 6 are extended longest as is shown in Fig. 1, and the holding of the electric wires by the clamps 2 is released as is shown in Fig. 2, whereby the twisted pair cable 8' can be removed from the clamps 2. The clamps 2 can automatically be released by 5 extending the short air cylinders 16 shown in Fig. 1 so as to move the operation levers 13 to the front. Fig. 6 shows an example of a twisted pair cable fabrication apparatus 32 to which the backward tension applying mechanism 10 described above is applied. The backward tension applying mechanism 1 is provided equally on each of three circumferential surfaces of one (rear) intermittent rotary member 33 which are provided circumferentially at 15 equal intervals. In Fig. 6, reference numeral 2 denotes an electric wire clamp, reference numeral 16 denotes a clamp releasing cylinder, reference numeral 6 denotes a backward tension applying cylinder, reference numeral 3 denotes a movable base plate, and reference numeral 5 denotes a common stationary base plate. The three 20 circumferential surfaces are made up of three common stationary base plates 5. A pair of electric wire clamps (other electric wire clamps) 21 and a common motor 27, which are like those shown in Fig. 4, are 25 provided equally on three circumferential surfaces of the other (front) 17 WO 2012/015058 PCT/JP2011/067575 intermittent rotary member 34 which are disposed circumferentially at equal intervals. The three circumferential surfaces are made up of three base plates 28 which are like that shown in Fig. 4. The intermittent rotary members 33, 34 are supported rotatably on 5 corresponding struts 35, 36 and are rotated together through one thirds the full rotation at a time by an intermittent driving device (for example, an air cylinder 37 and a torque brake 38). In each of the intermittent rotary members 33, 34, the circumferential surface situated on a near side refers to an electric wires setting plane 5, 28, 10 the circumferential surface situated to face downwards refers to a paired electric wires twisting plane 52, 282, and the circumferential surface situated on a far side refers to a twisted pair cable discharge plane 53, 283. 15 Paired electric wires 8 (See Figs. 3, 4) are fixed in place by the front and rear clamps 2, 21 on the circumferential surfaces at the electric wires setting planes 5, 28, and backward tension is applied to the paired electric wires 8 by the horizontal cylinders 6. Then, when the circumferential surface rotates to the paired electric wires twisting 20 planes 52, 282, a rotor 30, which is cut to be opened in part of a circumference thereof so as to have a cutout opening portion 30a and which has a twisting rod 30b erected to face the cutout opening portion 30a as is shown in Fig. 5(a), is raised by a vertical air cylinder (not shown) so as to be set between the paired electric wires 8 (or the 25 paired electric wires 8 are inserted through the annular rotor 30). 18 WO 2012/015058 PCT/JP2011/067575 Then, the paired electric wires 8 are twisted together by rotating the rotor 30 and the motor 27 simultaneously. Then, when the circumferential surface rotates to the twisted pair cable discharge plane 53, 283, tapes are automatically wound around both front and 5 rear ends of a twisted pair cable 8' (See Fig. 5(b)), and a completed twisted pair cable is discharged. This cycle is automatically repeated to thereby fabricate twisted pair cables 8' with good efficiency. While the embodiment is described as employing the rotor 30, a 10 configuration employing no rotor 30 may be adopted in which the clamps 21 shown in Fig. 4 are rotated by the motor 27 in such a state that one ends of the paired electric wires 8 are fixed in place by the clamps 2 shown in Fig. 3, while the other ends of the paired electric wires 8 are fixed in place by the clamps 21 shown in Fig. 4, whereby 15 the paired electric wires 8 can be twisted between the clamps 2 and the clamps 21. The clamps 21 shown in Fig. 4 refer to an example of holding the paired electric wires 8, and therefore, any shapes or configurations can be set as required, provided that they can fixedly hold the paired electric wires 8' respectively and can be rotated by the 20 motor 27. In addition, the clamp assembly made up of the clamps 2, the cylinders 6, 16 and the base plates 3, 5, which are shown in Fig. 3, that is, the backward tension applying mechanism 1 can be rotated by 25 a motor (not shown). In this case, the clamps 21 shown in Fig. 4 can 19 WO 2012/015058 PCT/JP2011/067575 be made into a common clamp which clamps the electric wires 8 altogether. In addition, the paired electric wires 8 can be twisted together between the front and rear clamps 2, 21 by rotating the intermediate rotor 30 only without using the motor 27 on the clamp 5 side. Additionally, the clamps 3 shown in Fig. 3 refer to an example of holding the paired electric wires 8, and therefore, any shapes or configurations can be set as required, provided that they can fixedly hold the paired electric wires 8 respectively. 10 In addition, in Fig. 1, the cylinder main bodies 6b of the backward tension applying air cylinders 6 can be connected to front ends of the movable base plates 3, and the rods 6a of the air cylinders 6 can be connected to rear ends of the common stationary base plate 5. In short, the air cylinders 6 may only have to connect the movable 15 base plates 3 with the common stationary base plate 5. Industrial Applicability The backward tension applying mechanism and the twisted pair cable fabrication method which employs the same mechanism can be 20 applied to increase the performance of a twisted pair cable which is applied to a noise prevention signal wire etc. for motor vehicles by forming twisted portions at equal intervals without involving any slack (looseness) therein. 25 This application is based upon and claims the benefit of priority 20 WO 2012/015058 PCT/JP2011/067575 of Japanese Patent Application No. 2010-166699 filed on July 26, 2010, the contents of which are incorporated herein by reference. Reference Sign List 5 1 backward tension applying mechanism 2 electric wire clamp 3 movable base plate 4 guide rail 5 common stationary base plate 10 6 air cylinder 8 electric wire 21 other electric wire clamp 15 20 25 21